TY - JOUR
A1 - Miesner, Timon
A1 - Herzschuh, Ulrike
A1 - Pestryakova, Luidmila Agafyevna
A1 - Wieczorek, Mareike
A1 - Zakharov, Evgenii S.
A1 - Kolmogorov, Alexei I.
A1 - Davydova, Paraskovya V.
A1 - Kruse, Stefan
T1 - Forest structure and individual tree inventories of northeastern Siberia along climatic gradients
JF - Earth system science data : ESSD
N2 - We compile a data set of forest surveys from expeditions to the northeast of the Russian Federation, in Krasnoyarsk Krai, the Republic of Sakha (Yakutia), and the Chukotka Autonomous Okrug (59-73 degrees N, 97-169 degrees E), performed between the years 2011 and 2021. The region is characterized by permafrost soils and forests dominated by larch (Larix gmelinii Rupr. and Larix cajanderi Mayr).
Our data set consists of a plot database describing 226 georeferenced vegetation survey plots and a tree database with information about all the trees on these plots. The tree database, consisting of two tables with the same column names, contains information on the height, species, and vitality of 40 289 trees. A subset of the trees was subject to a more detailed inventory, which recorded the stem diameter at base and at breast height, crown diameter, and height of the beginning of the crown.
We recorded heights up to 28.5 m (median 2.5 m) and stand densities up to 120 000 trees per hectare (median 1197 ha(-1)), with both values tending to be higher in the more southerly areas. Observed taxa include Larix Mill., Pinus L., Picea A. Dietr., Abies Mill., Salix L., Betula L., Populus L., Alnus Mill., and Ulmus L.
In this study, we present the forest inventory data aggregated per plot. Additionally, we connect the data with different remote sensing data products to find out how accurately forest structure can be predicted from such products. Allometries were calculated to obtain the diameter from height measurements for every species group. For Larix, the most frequent of 10 species groups, allometries depended also on the stand density, as denser stands are characterized by thinner trees, relative to height. The remote sensing products used to compare against the inventory data include climate, forest biomass, canopy height, and forest loss or disturbance. We find that the forest metrics measured in the field can only be reconstructed from the remote sensing data to a limited extent, as they depend on local properties. This illustrates the need for ground inventories like those data we present here.
The data can be used for studying the forest structure of northeastern Siberia and for the calibration and validation of remotely sensed data.
Y1 - 2022
U6 - https://doi.org/10.5194/essd-14-5695-2022
SN - 1866-3508
SN - 1866-3516
VL - 14
IS - 12
SP - 5695
EP - 5716
PB - Copernicus
CY - Göttingen
ER -
TY - JOUR
A1 - Kruse, Stefan
A1 - Stünzi, Simone Maria
A1 - Boike, Julia
A1 - Langer, Moritz
A1 - Gloy, Josias
A1 - Herzschuh, Ulrike
T1 - Novel coupled permafrost-forest model (LAVESI-CryoGrid v1.0) revealing the interplay between permafrost, vegetation, and climate across eastern Siberia
JF - Geoscientific model development : GMD ; an interactive open access journal of the European Geosciences Union
N2 - Boreal forests of Siberia play a relevant role in the global carbon cycle. However, global warming threatens the existence of summergreen larch-dominated ecosystems, likely enabling a transition to evergreen tree taxa with deeper active layers. Complex permafrost-vegetation interactions make it uncertain whether these ecosystems could develop into a carbon source rather than continuing atmospheric carbon sequestration under global warming. Consequently, shedding light on the role of current and future active layer dynamics and the feedbacks with the apparent tree species is crucial to predict boreal forest transition dynamics and thus for aboveground forest biomass and carbon stock developments. Hence, we established a coupled model version amalgamating a one-dimensional permafrost multilayer forest land-surface model (CryoGrid) with LAVESI, an individual-based and spatially explicit forest model for larch species (Larix Mill.), extended for this study by including other relevant Siberian forest species and explicit terrain.
Following parameterization, we ran simulations with the coupled version to the near future to 2030 with a mild climate-warming scenario. We focus on three regions covering a gradient of summergreen forests in the east at Spasskaya Pad, mixed summergreen-evergreen forests close to Nyurba, and the warmest area at Lake Khamra in the southeast of Yakutia, Russia. Coupled simulations were run with the newly implemented boreal forest species and compared to runs allowing only one species at a time, as well as to simulations using just LAVESI. Results reveal that the coupled version corrects for overestimation of active layer thickness (ALT) and soil moisture, and large differences in established forests are simulated. We conclude that the coupled version can simulate the complex environment of eastern Siberia by reproducing vegetation patterns, making it an excellent tool to disentangle processes driving boreal forest dynamics.
Y1 - 2022
U6 - https://doi.org/10.5194/gmd-15-2395-2022
SN - 1991-959X
SN - 1991-9603
VL - 15
IS - 6
SP - 2395
EP - 2422
PB - Copernicus
CY - Göttingen
ER -
TY - JOUR
A1 - Radosavljevic, Boris
A1 - Lantuit, Hugues
A1 - Knoblauch, Christian
A1 - Couture, Nicole
A1 - Herzschuh, Ulrike
A1 - Fritz, Michael
T1 - Arctic nearshore sediment dynamics - an example from Herschel Island - Qikiqtaruk, Canada
JF - Journal of marine science and engineering
N2 - Increasing arctic coastal erosion rates imply a greater release of sediments and organic matter into the coastal zone. With 213 sediment samples taken around Herschel Island-Qikiqtaruk, Canadian Beaufort Sea, we aimed to gain new insights on sediment dynamics and geochemical properties of a shallow arctic nearshore zone. Spatial characteristics of nearshore sediment texture (moderately to poorly sorted silt) are dictated by hydrodynamic processes, but ice-related processes also play a role. We determined organic matter (OM) distribution and inferred the origin and quality of organic carbon by C/N ratios and stable carbon isotopes delta C-13. The carbon content was higher offshore and in sheltered areas (mean: 1.0 wt.%., S.D.: 0.9) and the C/N ratios also showed a similar spatial pattern (mean: 11.1, S.D.: 3.1), while the delta C-13 (mean: -26.4 parts per thousand VPDB, S.D.: 0.4) distribution was more complex. We compared the geochemical parameters of our study with terrestrial and marine samples from other studies using a bootstrap approach. Sediments of the current study contained 6.5 times and 1.8 times less total organic carbon than undisturbed and disturbed terrestrial sediments, respectively. Therefore, degradation of OM and separation of carbon pools take place on land and continue in the nearshore zone, where OM is leached, mineralized, or transported beyond the study area.
KW - permafrost
KW - Arctic Ocean
KW - stable carbon isotopes
KW - nitrogen
KW - sediment
KW - chemistry
KW - sediment dynamics
KW - Beaufort Sea
KW - grain size
Y1 - 2022
U6 - https://doi.org/10.3390/jmse10111589
SN - 2077-1312
VL - 10
IS - 11
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Dallmeyer, Anne
A1 - Kleinen, Thomas
A1 - Claussen, Martin
A1 - Weitzel, Nils
A1 - Cao, Xianyong
A1 - Herzschuh, Ulrike
T1 - The deglacial forest conundrum
JF - Nature Communications
N2 - How fast the Northern Hemisphere (NH) forest biome tracks strongly warming climates is largely unknown. Regional studies reveal lags between decades and millennia. Here we report a conundrum: Deglacial forest expansion in the NH extra-tropics occurs approximately 4000 years earlier in a transient MPI-ESM1.2 simulation than shown by pollen-based biome reconstructions. Shortcomings in the model and the reconstructions could both contribute to this mismatch, leaving the underlying causes unresolved. The simulated vegetation responds within decades to simulated climate changes, which agree with pollen-independent reconstructions. Thus, we can exclude climate biases as main driver for differences. Instead, the mismatch points at a multi-millennial disequilibrium of the NH forest biome to the climate signal. Therefore, the evaluation of time-slice simulations in strongly changing climates with pollen records should be critically reassessed. Our results imply that NH forests may be responding much slower to ongoing climate changes than Earth System Models predict.
Deglacial forest expansion in the Northern Hemisphere poses a conundrum: Model results agree with the climate signal but are several millennia ahead of reconstructed forest dynamics. The underlying causes remain unsolved.
Y1 - 2022
U6 - https://doi.org/10.1038/s41467-022-33646-6
SN - 2041-1723
VL - 13
IS - 1
PB - Nature Publishing Group UK
CY - [London]
ER -
TY - JOUR
A1 - Kruse, Stefan
A1 - Herzschuh, Ulrike
T1 - Regional opportunities for tundra conservation in the next 1000 years
JF - eLife
N2 - The biodiversity of tundra areas in northern high latitudes is threatened by invasion of forests under global warming. However, poorly understood nonlinear responses of the treeline ecotone mean the timing and extent of tundra losses are unclear, but policymakers need such information to optimize conservation efforts. Our individual-based model LAVESI, developed for the Siberian tundra-taiga ecotone, can help improve our understanding. Consequently, we simulated treeline migration trajectories until the end of the millennium, causing a loss of tundra area when advancing north. Our simulations reveal that the treeline follows climate warming with a severe, century-long time lag, which is overcompensated by infilling of stands in the long run even when temperatures cool again. Our simulations reveal that only under ambitious mitigation strategies (relative concentration pathway 2.6) will ~30% of original tundra areas remain in the north but separated into two disjunct refugia.
KW - Larix gmelinii
KW - Larix cajanderi
KW - nonlinear response
KW - treeline ecotone
KW - tundra
KW - Ecology
KW - Short Report
Y1 - 2022
U6 - https://doi.org/10.7554/eLife.75163
SN - 2050-084X
VL - 11
PB - eLife Sciences Publications
CY - Cambridge
ER -
TY - JOUR
A1 - Li, Chenzhi
A1 - Postl, Alexander K.
A1 - Böhmer, Thomas
A1 - Cao, Xianyong
A1 - Dolman, Andrew M.
A1 - Herzschuh, Ulrike
T1 - Harmonized chronologies of a global late Quaternary pollen dataset (LegacyAge 1.0)
JF - Earth system science data : ESSD
N2 - We present a chronology framework named LegacyAge 1.0 containing harmonized chronologies for 2831 pollen records (downloaded from the Neotoma Paleoecology Database and the supplementary Asian datasets) together with their age control points and metadata in machine-readable data formats.
All chronologies use the Bayesian framework implemented in Bacon version 2.5.3. Optimal parameter settings of priors (accumulation.shape, memory.strength, memory.mean, accumulation.rate, and thickness) were identified based on information in the original publication or iteratively after preliminary model inspection.
The most common control points for the chronologies are radiocarbon dates (86.1 %), calibrated by the latest calibration curves (IntCal20 and SHCal20 for the terrestrial radiocarbon dates in the Northern Hemisphere and Southern Hemisphere and Marine20 for marine materials).
The original publications were consulted when dealing with outliers and inconsistencies. Several major challenges when setting up the chronologies included the waterline issue (18.8% of records), reservoir effect (4.9 %), and sediment deposition discontinuity (4.4 %).
Finally, we numerically compare the LegacyAge 1.0 chronologies to those published in the original publications and show that the reliability of the chronologies of 95.4% of records could be improved according to our assessment.
Our chronology framework and revised chronologies provide the opportunity to make use of the ages and age uncertainties in synthesis studies of, for example, pollen-based vegetation and climate change.
The LegacyAge 1.0 dataset, including metadata, datings, harmonized chronologies, and R code used, is openaccess and available at PANGAEA (https://doi.org/10.1594/PANGAEA.933132; Li et al., 2021) and Zenodo (https://doi.org/10.5281/zenodo.5815192; Li et al., 2022), respectively.
Y1 - 2022
U6 - https://doi.org/10.5194/essd-14-1331-2022
SN - 1866-3508
SN - 1866-3516
VL - 14
IS - 3
SP - 1331
EP - 1343
PB - Copernics Publications
CY - Katlenburg-Lindau
ER -
TY - JOUR
A1 - Courtin, Jérémy
A1 - Andreev, Andrei
A1 - Raschke, Elena
A1 - Bala, Sarah
A1 - Biskaborn, Boris
A1 - Liu, Sisi
A1 - Zimmermann, Heike
A1 - Diekmann, Bernhard
A1 - Stoof-Leichsenring, Kathleen R.
A1 - Pestryakova, Luidmila Agafyevna
A1 - Herzschuh, Ulrike
T1 - Vegetation changes in Southeastern Siberia during the late pleistocene and the holocene
JF - Frontiers in Ecology and Evolution
N2 - Relationships between climate, species composition, and species richness are of particular importance for understanding how boreal ecosystems will respond to ongoing climate change. This study aims to reconstruct changes in terrestrial vegetation composition and taxa richness during the glacial Late Pleistocene and the interglacial Holocene in the sparsely studied southeastern Yakutia (Siberia) by using pollen and sedimentary ancient DNA (sedaDNA) records. Pollen and sedaDNA metabarcoding data using the trnL g and h markers were obtained from a sediment core from Lake Bolshoe Toko. Both proxies were used to reconstruct the vegetation composition, while metabarcoding data were also used to investigate changes in plant taxa richness. The combination of pollen and sedaDNA approaches allows a robust estimation of regional and local past terrestrial vegetation composition around Bolshoe Toko during the last similar to 35,000 years. Both proxies suggest that during the Late Pleistocene, southeastern Siberia was covered by open steppe-tundra dominated by graminoids and forbs with patches of shrubs, confirming that steppe-tundra extended far south in Siberia. Both proxies show disturbance at the transition between the Late Pleistocene and the Holocene suggesting a period with scarce vegetation, changes in the hydrochemical conditions in the lake, and in sedimentation rates. Both proxies document drastic changes in vegetation composition in the early Holocene with an increased number of trees and shrubs and the appearance of new tree taxa in the lake's vicinity. The sedaDNA method suggests that the Late Pleistocene steppe-tundra vegetation supported a higher number of terrestrial plant taxa than the forested Holocene. This could be explained, for example, by the "keystone herbivore" hypothesis, which suggests that Late Pleistocene megaherbivores were able to maintain a high plant diversity. This is discussed in the light of the data with the broadly accepted species-area hypothesis as steppe-tundra covered such an extensive area during the Late Pleistocene.
KW - last glacial
KW - Holocene
KW - Lake Bolshoe Toko
KW - paleoenvironments
KW - sedimentary ancient DNA
KW - metabarcoding
KW - trnL
KW - pollen
Y1 - 2021
U6 - https://doi.org/10.3389/fevo.2021.625096
SN - 2296-701X
VL - 9
PB - Frontiers Media
CY - Lausanne
ER -
TY - JOUR
A1 - Heim, Birgit
A1 - Lisovski, Simeon
A1 - Wieczorek, Mareike
A1 - Morgenstern, Anne
A1 - Juhls, Bennet
A1 - Shevtsova, Iuliia
A1 - Kruse, Stefan
A1 - Boike, Julia
A1 - Fedorova, Irina
A1 - Herzschuh, Ulrike
T1 - Spring snow cover duration and tundra greenness in the Lena Delta, Siberia
BT - two decades of MODIS satellite time series (2001-2021)
JF - Environmental research letters
N2 - The Lena Delta in Siberia is the largest delta in the Arctic and as a snow-dominated ecosystem particularly vulnerable to climate change.
Using the two decades of MODerate resolution Imaging Spectroradiometer satellite acquisitions, this study investigates interannual and spatial variability of snow-cover duration and summer vegetation vitality in the Lena Delta.
We approximated snow by the application of the normalized difference snow index and vegetation greenness by the normalized difference vegetation index (NDVI). We consolidated the analyses by integrating reanalysis products on air temperature from 2001 to 2021, and air temperature, ground temperature, and the date of snow-melt from time-lapse camera (TLC) observations from the Samoylov observatory located in the central delta.
We extracted spring snow-cover duration determined by a latitudinal gradient. The 'regular year' snow-melt is transgressing from mid-May to late May within a time window of 10 days across the delta.
We calculated yearly deviations per grid cell for two defined regions, one for the delta, and one focusing on the central delta. We identified an ensemble of early snow-melt years from 2012 to 2014, with snow-melt already starting in early May, and two late snow-melt years in 2004 and 2017, with snow-melt starting in June. In the times of TLC recording, the years of early and late snow-melt were confirmed.
In the three summers after early snow-melt, summer vegetation greenness showed neither positive nor negative deviations. Whereas, vegetation greenness was reduced in 2004 after late snow-melt together with the lowest June monthly air temperature of the time series record. Since 2005, vegetation greenness is rising, with maxima in 2018 and 2021.
The NDVI rise since 2018 is preceded by up to 4 degrees C warmer than average June air temperature. The ongoing operation of satellite missions allows to monitor a wide range of land surface properties and processes that will provide urgently needed data in times when logistical challenges lead to data gaps in land-based observations in the rapidly changing Arctic.
KW - Arctic vegetation
KW - tundra
KW - snow cover duration
KW - NDVI
KW - NDSI
KW - MODIS
KW - Lena Delta
Y1 - 2022
U6 - https://doi.org/10.1088/1748-9326/ac8066
SN - 1748-9326
VL - 17
IS - 8
PB - IOP Publ. Ltd.
CY - Bristol
ER -
TY - JOUR
A1 - Herzschuh, Ulrike
A1 - Li, Chenzhi
A1 - Boehmer, Thomas
A1 - Postl, Alexander K.
A1 - Heim, Birgit
A1 - Andreev, Andrei A.
A1 - Cao, Xianyong
A1 - Wieczorek, Mareike
A1 - Ni, Jian
T1 - LegacyPollen 1.0
BT - a taxonomically harmonized global late Quaternary pollen dataset of 2831 records with standardized chronologies
JF - Earth system science data : ESSD
N2 - Here we describe the LegacyPollen 1.0, a dataset of 2831 fossil pollen records with metadata, a harmonized taxonomy, and standardized chronologies.
A total of 1032 records originate from North America, 1075 from Europe, 488 from Asia, 150 from Latin America, 54 from Africa, and 32 from the Indo-Pacific.
The pollen data cover the late Quaternary (mostly the Holocene). The original 10 110 pollen taxa names (including variations in the notations) were harmonized to 1002 terrestrial taxa (including Cyperaceae), with woody taxa and major herbaceous taxa harmonized to genus level and other herbaceous taxa to family level.
The dataset is valuable for synthesis studies of, for example, taxa areal changes, vegetation dynamics, human impacts (e.g., deforestation), and climate change at global or continental scales.
The harmonized pollen and metadata as well as the harmonization table are available from PANGAEA (https://doi.org/10.1594/PANGAEA.929773; Herzschuh et al., 2021). R code for the harmonization is provided at Zenodo (https://doi.org/10.5281/zenodo.5910972; Herzschuh et al., 2022) so that datasets at a customized harmonization level can be easily established.
Y1 - 2022
U6 - https://doi.org/10.5194/essd-14-3213-2022
SN - 1866-3508
SN - 1866-3516
VL - 14
IS - 7
SP - 3213
EP - 3227
PB - Copernicus
CY - Göttingen
ER -
TY - JOUR
A1 - Weinelt, Ferdinand Anton
A1 - Stegemann, Miriam Songa
A1 - Theloe, Anja
A1 - Pfäfflin, Frieder
A1 - Achterberg, Stephan
A1 - Weber, Franz
A1 - Dübel, Lucas
A1 - Mikolajewska, Agata
A1 - Uhrig, Alexander
A1 - Kiessling, Peggy
A1 - Huisinga, Wilhelm
A1 - Michelet, Robin
A1 - Hennig, Stefanie
A1 - Kloft, Charlotte
T1 - Evaluation of a meropenem and piperacillin monitoring program in intensive care unit patients calls for the regular assessment of empirical targets and easy-to-use dosing decision tools
JF - Antibiotics : open access journal
N2 - The drug concentrations targeted in meropenem and piperacillin/tazobactam therapy also depend on the susceptibility of the pathogen. Yet, the pathogen is often unknown, and antibiotic therapy is guided by empirical targets. To reliably achieve the targeted concentrations, dosing needs to be adjusted for renal function. We aimed to evaluate a meropenem and piperacillin/tazobactam monitoring program in intensive care unit (ICU) patients by assessing (i) the adequacy of locally selected empirical targets, (ii) if dosing is adequately adjusted for renal function and individual target, and (iii) if dosing is adjusted in target attainment (TA) failure. In a prospective, observational clinical trial of drug concentrations, relevant patient characteristics and microbiological data (pathogen, minimum inhibitory concentration (MIC)) for patients receiving meropenem or piperacillin/tazobactam treatment were collected. If the MIC value was available, a target range of 1-5 x MIC was selected for minimum drug concentrations of both drugs. If the MIC value was not available, 8-40 mg/L and 16-80 mg/L were selected as empirical target ranges for meropenem and piperacillin, respectively. A total of 356 meropenem and 216 piperacillin samples were collected from 108 and 96 ICU patients, respectively. The vast majority of observed MIC values was lower than the empirical target (meropenem: 90.0%, piperacillin: 93.9%), suggesting empirical target value reductions. TA was found to be low (meropenem: 35.7%, piperacillin 50.5%) with the lowest TA for severely impaired renal function (meropenem: 13.9%, piperacillin: 29.2%), and observed drug concentrations did not significantly differ between patients with different targets, indicating dosing was not adequately adjusted for renal function or target. Dosing adjustments were rare for both drugs (meropenem: 6.13%, piperacillin: 4.78%) and for meropenem irrespective of TA, revealing that concentration monitoring alone was insufficient to guide dosing adjustment. Empirical targets should regularly be assessed and adjusted based on local susceptibility data. To improve TA, scientific knowledge should be translated into easy-to-use dosing strategies guiding antibiotic dosing.
KW - meropenem
KW - piperacillin/tazobactam
KW - antimicrobial stewardship
KW - critically ill
KW - antibiotics
KW - pharmacokinetic/pharmacodynamic
Y1 - 2022
U6 - https://doi.org/10.3390/antibiotics11060758
SN - 2079-6382
VL - 11
IS - 6
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Ehmann, Lisa
A1 - Zoller, Michael
A1 - Minichmayr, Iris K.
A1 - Scharf, Christina
A1 - Maier, Barbara
A1 - Schmitt, Maximilian V.
A1 - Hartung, Niklas
A1 - Huisinga, Wilhelm
A1 - Vogeser, Michael
A1 - Frey, Lorenz
A1 - Zander, Johannes
A1 - Kloft, Charlotte
T1 - Role of renal function in risk assessment of target non-attainment after standard dosing of meropenem in critically ill patients
BT - a prospective observational study
JF - Critical care
N2 - Background: Severe bacterial infections remain a major challenge in intensive care units because of their high prevalence and mortality. Adequate antibiotic exposure has been associated with clinical success in critically ill patients. The objective of this study was to investigate the target attainment of standard meropenem dosing in a heterogeneous critically ill population, to quantify the impact of the full renal function spectrum on meropenem exposure and target attainment, and ultimately to translate the findings into a tool for practical application. Methods: A prospective observational single-centre study was performed with critically ill patients with severe infections receiving standard dosing of meropenem. Serial blood samples were drawn over 4 study days to determine meropenem serum concentrations. Renal function was assessed by creatinine clearance according to the Cockcroft and Gault equation (CLCRCG). Variability in meropenem serum concentrations was quantified at the middle and end of each monitored dosing interval. The attainment of two pharmacokinetic/pharmacodynamic targets (100% T->MIC, 50% T->4xMIC) was evaluated for minimum inhibitory concentration (MIC) values of 2 mg/L and 8 mg/L and standard meropenem dosing (1000 mg, 30-minute infusion, every 8 h). Furthermore, we assessed the impact of CLCRCG on meropenem concentrations and target attainment and developed a tool for risk assessment of target non-attainment. Results: Large inter-and intra-patient variability in meropenem concentrations was observed in the critically ill population (n = 48). Attainment of the target 100% T->MIC was merely 48.4% and 20.6%, given MIC values of 2 mg/L and 8 mg/L, respectively, and similar for the target 50% T->4xMIC. A hyperbolic relationship between CLCRCG (25-255 ml/minute) and meropenem serum concentrations at the end of the dosing interval (C-8h) was derived. For infections with pathogens of MIC 2 mg/L, mild renal impairment up to augmented renal function was identified as a risk factor for target non-attainment (for MIC 8 mg/L, additionally, moderate renal impairment). Conclusions: The investigated standard meropenem dosing regimen appeared to result in insufficient meropenem exposure in a considerable fraction of critically ill patients. An easy-and free-to-use tool (the MeroRisk Calculator) for assessing the risk of target non-attainment for a given renal function and MIC value was developed.
KW - beta-Lactam
KW - Intensive care
KW - Pharmacokinetics/Pharmacodynamics
KW - Target attainment
KW - Renal function
KW - Risk assessment tool
KW - Continuous renal replacement therapy
Y1 - 2017
U6 - https://doi.org/10.1186/s13054-017-1829-4
SN - 1466-609X
SN - 1364-8535
VL - 21
PB - BioMed Central
CY - London
ER -
TY - JOUR
A1 - Stachanow, Viktoria
A1 - Neumann, Uta
A1 - Blankenstein, Oliver
A1 - Bindellini, Davide
A1 - Melin, Johanna
A1 - Ross, Richard
A1 - Whitaker, Martin J. J.
A1 - Huisinga, Wilhelm
A1 - Michelet, Robin
A1 - Kloft, Charlotte
T1 - Exploring dried blood spot cortisol concentrations as an alternative for monitoring pediatric adrenal insufficiency patients
BT - a model-based analysis
JF - Frontiers in pharmacology
N2 - Congenital adrenal hyperplasia (CAH) is the most common form of adrenal insufficiency in childhood; it requires cortisol replacement therapy with hydrocortisone (HC, synthetic cortisol) from birth and therapy monitoring for successful treatment. In children, the less invasive dried blood spot (DBS) sampling with whole blood including red blood cells (RBCs) provides an advantageous alternative to plasma sampling.
Potential differences in binding/association processes between plasma and DBS however need to be considered to correctly interpret DBS measurements for therapy monitoring. While capillary DBS samples would be used in clinical practice, venous cortisol DBS samples from children with adrenal insufficiency were analyzed due to data availability and to directly compare and thus understand potential differences between venous DBS and plasma. A previously published HC plasma pharmacokinetic (PK) model was extended by leveraging these DBS concentrations.
In addition to previously characterized binding of cortisol to albumin (linear process) and corticosteroid-binding globulin (CBG; saturable process), DBS data enabled the characterization of a linear cortisol association with RBCs, and thereby providing a quantitative link between DBS and plasma cortisol concentrations. The ratio between the observed cortisol plasma and DBS concentrations varies highly from 2 to 8. Deterministic simulations of the different cortisol binding/association fractions demonstrated that with higher blood cortisol concentrations, saturation of cortisol binding to CBG was observed, leading to an increase in all other cortisol binding fractions.
In conclusion, a mathematical PK model was developed which links DBS measurements to plasma exposure and thus allows for quantitative interpretation of measurements of DBS samples.
KW - adrenal insufficiency
KW - cortisol
KW - dried blood spots
KW - pediatrics
KW - pharmacokinetics
KW - binding
KW - association
KW - red blood cells
Y1 - 2022
U6 - https://doi.org/10.3389/fphar.2022.819590
SN - 1663-9812
VL - 13
PB - Frontiers Media
CY - Lausanne
ER -
TY - JOUR
A1 - Abiuso, Paolo
A1 - Holubec, Viktor
A1 - Anders, Janet
A1 - Ye, Zhuolin
A1 - Cerisola, Federico
A1 - Perarnau-Llobet, Marti
T1 - Thermodynamics and optimal protocols of multidimensional quadratic Brownian systems
JF - Journal of physics communications
N2 - We characterize finite-time thermodynamic processes of multidimensional quadratic overdamped systems.
Analytic expressions are provided for heat, work, and dissipation for any evolution of the system covariance matrix.
The Bures-Wasserstein metric between covariance matrices naturally emerges as the local quantifier of dissipation.
General principles of how to apply these geometric tools to identify optimal protocols are discussed.
Focusing on the relevant slow-driving limit, we show how these results can be used to analyze cases in which the experimental control over the system is partial.
KW - stochastic thermodynamics
KW - thermodynamic control
KW - thermodynamic length
KW - overdamped brownian systems
Y1 - 2022
U6 - https://doi.org/10.1088/2399-6528/ac72f8
SN - 2399-6528
VL - 6
IS - 6
PB - IOP Publ. Ltd.
CY - Bristol
ER -
TY - JOUR
A1 - Glückler, Ramesh
A1 - Herzschuh, Ulrike
A1 - Kruse, Stefan
A1 - Andreev, Andrei
A1 - Vyse, Stuart Andrew
A1 - Winkler, Bettina
A1 - Biskaborn, Boris
A1 - Pestryakova, Luidmila Agafyevna
A1 - Dietze, Elisabeth
T1 - Wildfire history of the boreal forest of south-western Yakutia (Siberia) over the last two millennia documented by a lake-sediment charcoal record
JF - Biogeosciences : BG / European Geosciences Union
N2 - Wildfires, as a key disturbance in forest ecosystems, are shaping the world's boreal landscapes. Changes in fire regimes are closely linked to a wide array of environmental factors, such as vegetation composition, climate change, and human activity. Arctic and boreal regions and, in particular, Siberian boreal forests are experiencing rising air and ground temperatures with the subsequent degradation of permafrost soils leading to shifts in tree cover and species composition. Compared to the boreal zones of North America or Europe, little is known about how such environmental changes might influence long-term fire regimes in Russia. The larch-dominated eastern Siberian deciduous boreal forests differ markedly from the composition of other boreal forests, yet data about past fire regimes remain sparse. Here, we present a high-resolution macroscopic charcoal record from lacustrine sediments of Lake Khamra (southwest Yakutia, Siberia) spanning the last ca. 2200 years, including information about charcoal particle sizes and morphotypes. Our results reveal a phase of increased charcoal accumulation between 600 and 900 CE, indicative of relatively high amounts of burnt biomass and high fire frequencies. This is followed by an almost 900-year-long period of low charcoal accumulation without significant peaks likely corresponding to cooler climate conditions. After 1750 CE fire frequencies and the relative amount of biomass burnt start to increase again, coinciding with a warming climate and increased anthropogenic land development after Russian colonization. In the 20th century, total charcoal accumulation decreases again to very low levels despite higher fire frequency, potentially reflecting a change in fire management strategies and/or a shift of the fire regime towards more frequent but smaller fires. A similar pattern for different charcoal morphotypes and comparison to a pollen and non-pollen palynomorph (NPP) record from the same sediment core indicate that broad-scale changes in vegetation composition were probably not a major driver of recorded fire regime changes. Instead, the fire regime of the last two millennia at Lake Khamra seems to be controlled mainly by a combination of short-term climate variability and anthropogenic fire ignition and suppression.
Y1 - 2021
U6 - https://doi.org/10.5194/bg-18-4185-2021
SN - 1726-4170
SN - 1726-4189
VL - 18
IS - 13
SP - 4185
EP - 4209
PB - Copernicus
CY - Göttingen
ER -
TY - JOUR
A1 - Glückler, Ramesh
A1 - Geng, Rongwei
A1 - Grimm, Lennart
A1 - Baisheva, Izabella
A1 - Herzschuh, Ulrike
A1 - Stoof-Leichsenring, Kathleen R.
A1 - Kruse, Stefan
A1 - Andreev, Andrej Aleksandrovic
A1 - Pestryakova, Luidmila
A1 - Dietze, Elisabeth
T1 - Holocene wildfire and vegetation dynamics in Central Yakutia, Siberia, reconstructed from lake-sediment proxies
JF - Frontiers in Ecology and Evolution
N2 - Wildfires play an essential role in the ecology of boreal forests.
In eastern Siberia, fire activity has been increasing in recent years, challenging the livelihoods of local communities. Intensifying fire regimes also increase disturbance pressure on the boreal forests, which currently protect the permafrost beneath from accelerated degradation.
However, long-term relationships between changes in fire regime and forest structure remain largely unknown.
We assess past fire-vegetation feedbacks using sedimentary proxy records from Lake Satagay, Central Yakutia, Siberia, covering the past c. 10,800 years.
Results from macroscopic and microscopic charcoal analyses indicate high amounts of burnt biomass during the Early Holocene, and that the present-day, low-severity surface fire regime has been in place since c. 4,500 years before present.
A pollen-based quantitative reconstruction of vegetation cover and a terrestrial plant record based on sedimentary ancient DNA metabarcoding suggest a pronounced shift in forest structure toward the Late Holocene.
Whereas the Early Holocene was characterized by postglacial open larch-birch woodlands, forest structure changed toward the modern, mixed larch-dominated closed-canopy forest during the Mid-Holocene.
We propose a potential relationship between open woodlands and high amounts of burnt biomass, as well as a mediating effect of dense larch forest on the climate-driven intensification of fire regimes.
Considering the anticipated increase in forest disturbances (droughts, insect invasions, and wildfires), higher tree mortality may force the modern state of the forest to shift toward an open woodland state comparable to the Early Holocene.
Such a shift in forest structure may result in a positive feedback on currently intensifying wildfires.
These new long-term data improve our understanding of millennial-scale fire regime changes and their relationships to changes of vegetation in Central Yakutia, where the local population is already being confronted with intensifying wildfire seasons.
KW - fire
KW - larch
KW - boreal
KW - forest
KW - Russia
KW - charcoal
KW - pollen
KW - ancient DNA
Y1 - 2022
U6 - https://doi.org/10.3389/fevo.2022.962906
SN - 2296-701X
VL - 10
PB - Frontiers Media
CY - Lausanne
ER -
TY - JOUR
A1 - Lehmann, Nico
A1 - Kuhn, Yves-Alain
A1 - Keller, Martin
A1 - Aye, Norman
A1 - Herold, Fabian
A1 - Draganski, Bogdan
A1 - Taube, Wolfgang
A1 - Taubert, Marco
T1 - Brain activation during active balancing and its behavioral relevance in younger and older adults
BT - a functional near-infrared spectroscopy (fNIRS) study
JF - Frontiers in Aging Neuroscience
N2 - Age-related deterioration of balance control is widely regarded as an important phenomenon influencing quality of life and longevity, such that a more comprehensive understanding of the neural mechanisms underlying this process is warranted.
Specifically, previous studies have reported that older adults typically show higher neural activity during balancing as compared to younger counterparts, but the implications of this finding on balance performance remain largely unclear.
Using functional near-infrared spectroscopy (fNIRS), differences in the cortical control of balance between healthy younger (n = 27) and older (n = 35) adults were explored.
More specifically, the association between cortical functional activity and balance performance across and within age groups was investigated. To this end, we measured hemodynamic responses (i.e., changes in oxygenated and deoxygenated hemoglobin) while participants balanced on an unstable device.
As criterion variables for brain-behavior-correlations, we also assessed postural sway while standing on a free-swinging platform and while balancing on wobble boards with different levels of difficulty.
We found that older compared to younger participants had higher activity in prefrontal and lower activity in postcentral regions.
Subsequent robust regression analyses revealed that lower prefrontal brain activity was related to improved balance performance across age groups, indicating that higher activity of the prefrontal cortex during balancing reflects neural inefficiency.
We also present evidence supporting that age serves as a moderator in the relationship between brain activity and balance, i.e., cortical hemodynamics generally appears to be a more important predictor of balance performance in the older than in the younger. Strikingly, we found that age differences in balance performance are mediated by balancing-induced activation of the superior frontal gyrus, thus suggesting that differential activation of this region reflects a mechanism involved in the aging process of the neural control of balance.
Our study suggests that differences in functional brain activity between age groups are not a mere by-product of aging, but instead of direct behavioral relevance for balance performance.
Potential implications of these findings in terms of early detection of fall-prone individuals and intervention strategies targeting balance and healthy aging are discussed.
KW - aging
KW - neuroimaging
KW - functional near-infrared spectroscopy (fNIRS)
KW - balance
KW - postural control
KW - prefrontal cortex
KW - neural inefficiency
Y1 - 2022
U6 - https://doi.org/10.3389/fnagi.2022.828474
SN - 1663-4365
VL - 14
PB - Frontiers Media
CY - Lausanne
ER -
TY - JOUR
A1 - Inceoglu, Fadil
A1 - Shprits, Yuri Y.
A1 - Heinemann, Stephan G.
A1 - Bianco, Stefano
T1 - Identification of coronal holes on AIA/SDO images using unsupervised machine learning
JF - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2 - Through its magnetic activity, the Sun governs the conditions in Earth's vicinity, creating space weather events, which have drastic effects on our space- and ground-based technology.
One of the most important solar magnetic features creating the space weather is the solar wind that originates from the coronal holes (CHs).
The identification of the CHs on the Sun as one of the source regions of the solar wind is therefore crucial to achieve predictive capabilities.
In this study, we used an unsupervised machine-learning method, k-means, to pixel-wise cluster the passband images of the Sun taken by the Atmospheric Imaging Assembly on the Solar Dynamics Observatory in 171, 193, and 211 angstrom in different combinations.
Our results show that the pixel-wise k-means clustering together with systematic pre- and postprocessing steps provides compatible results with those from complex methods, such as convolutional neural networks.
More importantly, our study shows that there is a need for a CH database where a consensus about the CH boundaries is reached by observers independently.
This database then can be used as the "ground truth," when using a supervised method or just to evaluate the goodness of the models.
Y1 - 2022
U6 - https://doi.org/10.3847/1538-4357/ac5f43
SN - 1538-4357
VL - 930
IS - 2
PB - IOP Publ. Ltd.
CY - Bristol
ER -
TY - JOUR
A1 - Chaabene, Helmi
A1 - Markov, Adrian
A1 - Prieske, Olaf
A1 - Moran, Jason
A1 - Behrens, Martin
A1 - Negra, Yassine
A1 - Ramirez-Campillo, Rodrigo
A1 - Koch, Ulrike
A1 - Mkaouer, Bessem
T1 - Effect of flywheel versus traditional resistance training on change of direction performance in male athletes
BT - a systematic review with meta-analysis
JF - International journal of environmental research and public health : IJERPH
N2 - Objective:
This study aimed to systematically review and meta-analyze the effect of flywheel resistance training (FRT) versus traditional resistance training (TRT) on change of direction (CoD) performance in male athletes.
Methods:
Five databases were screened up to December 2021.
Results:
Seven studies were included. The results indicated a significantly larger effect of FRT compared with TRT (standardized mean difference [SMD] = 0.64). A within-group comparison indicated a significant large effect of FRT on CoD performance (SMD = 1.63). For TRT, a significant moderate effect was observed (SMD = 0.62). FRT of <= 2 sessions/week resulted in a significant large effect (SMD = 1.33), whereas no significant effect was noted for >2 sessions/week. Additionally, a significant large effect of <= 12 FRT sessions (SMD = 1.83) was observed, with no effect of >12 sessions. Regarding TRT, no significant effects of any of the training factors were detected (p > 0.05).
Conclusions:
FRT appears to be more effective than TRT in improving CoD performance in male athletes. Independently computed single training factor analyses for FRT indicated that <= 2 sessions/week resulted in a larger effect on CoD performance than >2 sessions/week. Additionally, a total of <= 12 FRT sessions induced a larger effect than >12 training sessions. Practitioners in sports, in which accelerative and decelerative actions occur in quick succession to change direction, should regularly implement FRT.
KW - human physical conditioning
KW - eccentric training
KW - strength training
KW - athletes
KW - sports
KW - muscle strength
Y1 - 2022
U6 - https://doi.org/10.3390/ijerph19127061
SN - 1661-7827
SN - 1660-4601
VL - 19
IS - 12
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Liu, Sisi
A1 - Stoof-Leichsenring, Kathleen Rosemarie
A1 - Kruse, Stefan
A1 - Pestryakova, Luidmila Agafyevna
A1 - Herzschuh, Ulrike
T1 - Holocene vegetation and plant diversity changes in the north-eastern Siberian treeline region from pollen and sedimentary ancient DNA
JF - Frontiers in Ecology and Evolution
N2 - Although sedimentary ancient DNA (sedaDNA) has been increasingly used to study paleoecological dynamics (Schulte et al., 2020), the approach has rarely been compared with the traditional method of pollen analysis for investigating past changes in the vegetation composition and diversity of Arctic treeline areas. Here, we provide a history of latitudinal floristic composition and species diversity based on a comparison ofsedaDNA and pollen data archived in three Siberian lake sediment cores spanning the mid-Holocene to the present (7.6-0 cal ka BP), from northern typical tundra to southern open larch forest in the Omoloy region. Our results show that thesedaDNA approach identifies more plant taxa found in the local vegetation communities, while the corresponding pollen analysis mainly captures the regional vegetation development and has its limitations for plant diversity reconstruction. Measures of alpha diversity were calculated based onsedaDNA data recovered from along a tundra to forest tundra to open larch forest gradient. Across all sites,sedaDNA archives provide a complementary record of the vegetation transition within each lake's catchment, tracking a distinct latitudinal vegetation type range from larch tree/alder shrub (open larch forest site) to dwarf shrub-steppe (forest tundra) to wet sedge tundra (typical tundra site). By contrast, the pollen data reveal an open landscape, which cannot distinguish the temporal changes in compositional vegetation for the open larch forest site and forest-tundra site. IncreasingLarixpollen percentages were recorded in the forest-tundra site in the last millenium although noLarixDNA was detected, suggesting that thesedaDNA approach performs better for tracking the local establishment ofLarix. Highest species richness and diversity are found in the mid-Holocene (before 4.4 ka) at the typical tundra site with a diverse range of vegetational habitats, while lowest species richness is recorded for the forest tundra where dwarf-willow habitats dominated the lake's catchment. During the late Holocene, strong declines in species richness and diversity are found at the typical tundra site with the vegetation changing to relatively simple communities. Nevertheless, plant species richness is mostly higher than at the forest-tundra site, which shows a slightly decreasing trend. Plant species richness at the open larch forest site fluctuates through time and is higher than the other sites since around 2.5 ka. Taken together, there is no evidence to suggest that the latitudinal gradients in species diversity changes are present at a millennial scale. Additionally, a weak correlation between the principal component analysis (PCA) site scores ofsedaDNA and species richness suggests that climate may not be a direct driver of species turnover within a lake's catchment. Our data suggest thatsedaDNA and pollen have different but complementary abilities for reconstructing past vegetation and species diversity along a latitude.
KW - sedimentary ancient DNA
KW - metabarcoding
KW - pollen
KW - Siberia
KW - palaeovegetation
KW - plant diversity
KW - latitudinal gradient
Y1 - 2020
U6 - https://doi.org/10.3389/fevo.2020.560243
SN - 2296-701X
VL - 8
PB - Frontiers Media
CY - Lausanne
ER -
TY - JOUR
A1 - Huang, Sichao
A1 - Stoof-Leichsenring, Kathleen R.
A1 - Liu, Sisi
A1 - Courtin, Jeremy
A1 - Andreev, Andrej A.
A1 - Pestryakova, Luidmila. A.
A1 - Herzschuh, Ulrike
T1 - Plant sedimentary ancient DNA from Far East Russia covering the last 28,000 years reveals different assembly rules in cold and warm climates
JF - Frontiers in Ecology and Evolution
N2 - Woody plants are expanding into the Arctic in response to the warming climate. The impact on arctic plant communities is not well understood due to the limited knowledge about plant assembly rules.
Records of past plant diversity over long time series are rare. Here, we applied sedimentary ancient DNA metabarcoding targeting the P6 loop of the chloroplast trnL gene to a sediment record from Lake Ilirney (central Chukotka, Far Eastern Russia) covering the last 28 thousand years.
Our results show that forb-rich steppe-tundra and dwarf-shrub tundra dominated during the cold climate before 14 ka, while deciduous erect-shrub tundra was abundant during the warm period since 14 ka. Larix invasion during the late Holocene substantially lagged behind the likely warmest period between 10 and 6 ka, where the vegetation biomass could be highest.
We reveal highest richness during 28-23 ka and a second richness peak during 13-9 ka, with both periods being accompanied by low relative abundance of shrubs. During the cold period before 14 ka, rich plant assemblages were phylogenetically clustered, suggesting low genetic divergence in the assemblages despite the great number of species. This probably originates from environmental filtering along with niche differentiation due to limited resources under harsh environmental conditions. In contrast, during the warmer period after 14 ka, rich plant assemblages were phylogenetically overdispersed.
This results from a high number of species which were found to harbor high genetic divergence, likely originating from an erratic recruitment process in the course of warming. Some of our evidence may be of relevance for inferring future arctic plant assembly rules and diversity changes. By analogy to the past, we expect a lagged response of tree invasion. Plant richness might overshoot in the short term; in the long-term, however, the ongoing expansion of deciduous shrubs will eventually result in a phylogenetically more diverse community.
KW - sedimentary ancient DNA (sedaDNA)
KW - metabarcoding
KW - phylogenetic and taxonomic plant diversity
KW - Arctic Russia
KW - Siberia
KW - holocene
KW - glacial
KW - treeline
Y1 - 2021
U6 - https://doi.org/10.3389/fevo.2021.763747
SN - 2296-701X
VL - 9
PB - Frontiers Media
CY - Lausanne
ER -
TY - JOUR
A1 - Cao, Xianyong
A1 - Tian, Fang
A1 - Andreev, Andrei
A1 - Anderson, Patricia M.
A1 - Lozhkin, Anatoly V.
A1 - Bezrukova, Elena
A1 - Ni, Jian
A1 - Rudaya, Natalia
A1 - Stobbe, Astrid
A1 - Wieczorek, Mareike
A1 - Herzschuh, Ulrike
T1 - A taxonomically harmonized and temporally standardized fossil pollen dataset from Siberia covering the last 40 kyr
JF - Earth System Science Data
N2 - Pollen records from Siberia are mostly absent in global or Northern Hemisphere synthesis works. Here we present a taxonomically harmonized and temporally standardized pollen dataset that was synthesized using 173 palynological records from Siberia and adjacent areas (northeastern Asia, 42-75 degrees N, 50-180 degrees E). Pollen data were taxonomically harmonized, i.e. the original 437 taxa were assigned to 106 combined pollen taxa. Age-depth models for all records were revised by applying a constant Bayesian age-depth modelling routine. The pollen dataset is available as count data and percentage data in a table format (taxa vs. samples), with age information for each sample. The dataset has relatively few sites covering the last glacial period between 40 and 11.5 ka (calibrated thousands of years before 1950 CE) particularly from the central and western part of the study area. In the Holocene period, the dataset has many sites from most of the area, with the exception of the central part of Siberia. Of the 173 pollen records, 81 % of pollen counts were downloaded from open databases (GPD, EPD, PANGAEA) and 10 % were contributions by the original data gatherers, while a few were digitized from publications. Most of the pollen records originate from peatlands (48 %) and lake sediments (33 %). Most of the records (83 %) have >= 3 dates, allowing the establishment of reliable chronologies. The dataset can be used for various purposes, including pollen data mapping (example maps for Larix at selected time slices are shown) as well as quantitative climate and vegetation reconstructions. The datasets for pollen counts and pollen percentages are available at https://doi.org/10.1594/PANGAEA.898616 (Cao et al., 2019a), also including the site information, data source, original publication, dating data, and the plant functional type for each pollen taxa.
KW - Late Quaternary vegetation
KW - Holocene environmental history
KW - eastern continental Asia
KW - plant macrofossil data
KW - late pleistocene
KW - paleoenvironmental records
KW - Verkhoyansk mountains
KW - climate dynamics
KW - glacial maximum
KW - Northern Asia
Y1 - 2020
U6 - https://doi.org/10.5194/essd-12-119-2020
SN - 1866-3508
SN - 1866-3516
VL - 12
IS - 1
SP - 119
EP - 135
PB - Copernics Publications
CY - Katlenburg-Lindau
ER -
TY - JOUR
A1 - Steirou, Eva
A1 - Gerlitz, Lars
A1 - Sun, Xun
A1 - Apel, Heiko
A1 - Agarwal, Ankit
A1 - Totz, Sonja Juliana
A1 - Merz, Bruno
T1 - Towards seasonal forecasting of flood probabilities in Europe using climate and catchment information
JF - Scientific reports
N2 - We investigate whether the distribution of maximum seasonal streamflow is significantly affected by catchment or climate state of the season/month ahead. We fit the Generalized Extreme Value (GEV) distribution to extreme seasonal streamflow for around 600 stations across Europe by conditioning the GEV location and scale parameters on 14 indices, which represent the season-ahead climate or catchment state. The comparison of these climate-informed models with the classical GEV distribution, with time-constant parameters, suggests that there is a substantial potential for seasonal forecasting of flood probabilities. The potential varies between seasons and regions. Overall, the season-ahead catchment wetness shows the highest potential, although climate indices based on large-scale atmospheric circulation, sea surface temperature or sea ice concentration also show some skill for certain regions and seasons. Spatially coherent patterns and a substantial fraction of climate-informed models are promising signs towards early alerts to increase flood preparedness already a season ahead.
Y1 - 2022
U6 - https://doi.org/10.1038/s41598-022-16633-1
SN - 2045-2322
VL - 12
IS - 1
PB - Nature portfolio
CY - Berlin
ER -
TY - JOUR
A1 - Rothe, Martin
A1 - Zhao, Yuhang
A1 - Kewes, Günter
A1 - Kochovski, Zdravko
A1 - Sigle, Wilfried
A1 - van Aken, Peter A.
A1 - Koch, Christoph
A1 - Ballauff, Matthias
A1 - Lu, Yan
A1 - Benson, Oliver
T1 - Silver nanowires with optimized silica coating as versatile plasmonic resonators
JF - Scientific reports
N2 - Metal nanoparticles are the most frequently used nanostructures in plasmonics. However, besides nanoparticles, metal nanowires feature several advantages for applications. Their elongation offers a larger interaction volume, their resonances can reach higher quality factors, and their mode structure provides better coupling into integrated hybrid dielectric-plasmonic circuits. It is crucial though, to control the distance of the wire to a supporting substrate, to another metal layer or to active materials with sub-nanometer precision. A dielectric coating can be utilized for distance control, but it must not degrade the plasmonic properties. In this paper, we introduce a controlled synthesis and coating approach for silver nanowires to fulfill these demands. We synthesize and characterize silver nanowires of around 70 nm in diameter. These nanowires are coated with nm-sized silica shells using a modified Stober method to achieve a homogeneous and smooth surface quality. We use transmission electron microscopy, dark-field microscopy and electron-energy loss spectroscopy to study morphology and plasmonic resonances of individual nanowires and quantify the influence of the silica coating. Thorough numerical simulations support the experimental findings showing that the coating does not deteriorate the plasmonic properties and thus introduce silver nanowires as usable building blocks for integrated hybrid plasmonic systems.
Y1 - 2019
U6 - https://doi.org/10.1038/s41598-019-40380-5
SN - 2045-2322
VL - 9
PB - Nature Publ. Group
CY - London
ER -
TY - JOUR
A1 - de Gelder, Gino
A1 - Fernandez-Blanco, David
A1 - Melnick, Daniel
A1 - Duclaux, Guillaume
A1 - Bell, Rebecca E.
A1 - Jara Muñoz, Julius
A1 - Armijo, Rolando
A1 - Lacassin, Robin
T1 - Lithospheric flexure and rheology determined by climate cycle markers in the Corinth Rift
JF - Scientific reports
N2 - Geomorphic strain markers accumulating the effects of many earthquake cycles help to constrain the mechanical behaviour of continental rift systems as well as the related seismic hazards. In the Corinth Rift (Greece), the unique record of onshore and offshore markers of Pleistocene similar to 100-ka climate cycles provides an outstanding possibility to constrain rift mechanics over a range of timescales. Here we use high-resolution topography to analyse the 3D geometry of a sequence of Pleistocene emerged marine terraces associated with flexural rift-flank uplift. We integrate this onshore dataset with offshore seismic data to provide a synoptic view of the flexural deformation across the rift. This allows us to derive an average slip rate of 4.5-9.0 mm.yr(-1) on the master fault over the past similar to 610 ka and an uplift/ subsidence ratio of 1:1.1-2.4. We reproduce the observed flexure patterns, using 3 and 5-layered lithospheric scale finite element models. Modelling results imply that the observed elastic flexure is produced by coseismic slip along 40-60 degrees planar normal faults in the elastic upper crust, followed by postseismic viscous relaxation occurring within the basal lower crust or upper mantle. We suggest that such a mechanism may typify rapid localised extension of continental lithosphere.
Y1 - 2019
U6 - https://doi.org/10.1038/s41598-018-36377-1
SN - 2045-2322
VL - 9
PB - Nature Publ. Group
CY - London
ER -
TY - JOUR
A1 - Freisleben, Roland
A1 - Jara Muñoz, Julius
A1 - Melnick, Daniel
A1 - Miguel Martinez, Jose
A1 - Strecker, Manfred
T1 - Marine terraces of the last interglacial period along the Pacific coast of South America (1 degrees N-40 degrees S)
JF - Earth system science data : ESSD
N2 - Tectonically active coasts are dynamic environments characterized by the presence of multiple marine terraces formed by the combined effects of wave erosion, tectonic uplift, and sea-level oscillations at glacialcycle timescales. Well-preserved erosional terraces from the last interglacial sea-level highstand are ideal marker horizons for reconstructing past sea-level positions and calculating vertical displacement rates. We carried out an almost continuous mapping of the last interglacial marine terrace along similar to 5000 km of the western coast of South America between 1 degrees N and 40 degrees S. We used quantitatively replicable approaches constrained by published terrace-age estimates to ultimately compare elevations and patterns of uplifted terraces with tectonic and climatic parameters in order to evaluate the controlling mechanisms for the formation and preservation of marine terraces and crustal deformation. Uncertainties were estimated on the basis of measurement errors and the distance from referencing points. Overall, our results indicate a median elevation of 30.1 m, which would imply a median uplift rate of 0.22 m kyr(-1) averaged over the past similar to 125 kyr. The patterns of terrace elevation and uplift rate display high-amplitude (similar to 100-200 m) and long-wavelength (similar to 10(2) km) structures at the Manta Peninsula (Ecuador), the San Juan de Marcona area (central Peru), and the Arauco Peninsula (south-central Chile). Medium-wavelength structures occur at the Mejillones Peninsula and Topocalma in Chile, while short-wavelength (< 10 km) features are for instance located near Los Vilos, Valparaiso, and Carranza, Chile. We interpret the long-wavelength deformation to be controlled by deep-seated processes at the plate interface such as the subduction of major bathymetric anomalies like the Nazca and Carnegie ridges. In contrast, short-wavelength deformation may be primarily controlled by sources in the upper plate such as crustal faulting, which, however, may also be associated with the subduction of topographically less pronounced bathymetric anomalies. Latitudinal differences in climate additionally control the formation and preservation of marine terraces. Based on our synopsis we propose that increasing wave height and tidal range result in enhanced erosion and morphologically well-defined marine terraces in south-central Chile. Our study emphasizes the importance of using systematic measurements and uniform, quantitative methodologies to characterize and correctly interpret marine terraces at regional scales, especially if they are used to unravel the tectonic and climatic forcing mechanisms of their formation. This database is an integral part of the World Atlas of Last Interglacial Shorelines (WALIS), published online at https://doi.org/10.5281/zenodo.4309748 (Freisleben et al., 2020).
Y1 - 2021
U6 - https://doi.org/10.5194/essd-13-2487-2021
SN - 1866-3508
SN - 1866-3516
VL - 13
IS - 6
SP - 2487
EP - 2513
PB - Copernics Publications
CY - Katlenburg-Lindau
ER -
TY - JOUR
A1 - Adolfs, Marjolijn
A1 - Hoque, Mohammed Mainul
A1 - Shprits, Yuri Y.
T1 - Storm-time relative total electron content modelling using machine learning techniques
JF - Remote sensing
N2 - Accurately predicting total electron content (TEC) during geomagnetic storms is still a challenging task for ionospheric models. In this work, a neural-network (NN)-based model is proposed which predicts relative TEC with respect to the preceding 27-day median TEC, during storm time for the European region (with longitudes 30 degrees W-50 degrees E and latitudes 32.5 degrees N-70 degrees N). The 27-day median TEC (referred to as median TEC), latitude, longitude, universal time, storm time, solar radio flux index F10.7, global storm index SYM-H and geomagnetic activity index Hp30 are used as inputs and the output of the network is the relative TEC. The relative TEC can be converted to the actual TEC knowing the median TEC. The median TEC is calculated at each grid point over the European region considering data from the last 27 days before the storm using global ionosphere maps (GIMs) from international GNSS service (IGS) sources. A storm event is defined when the storm time disturbance index Dst drops below 50 nanotesla. The model was trained with storm-time relative TEC data from the time period of 1998 until 2019 (2015 is excluded) and contains 365 storms. Unseen storm data from 33 storm events during 2015 and 2020 were used to test the model. The UQRG GIMs were used because of their high temporal resolution (15 min) compared to other products from different analysis centers. The NN-based model predictions show the seasonal behavior of the storms including positive and negative storm phases during winter and summer, respectively, and show a mixture of both phases during equinoxes. The model's performance was also compared with the Neustrelitz TEC model (NTCM) and the NN-based quiet-time TEC model, both developed at the German Aerospace Agency (DLR). The storm model has a root mean squared error (RMSE) of 3.38 TEC units (TECU), which is an improvement by 1.87 TECU compared to the NTCM, where an RMSE of 5.25 TECU was found. This improvement corresponds to a performance increase by 35.6%. The storm-time model outperforms the quiet-time model by 1.34 TECU, which corresponds to a performance increase by 28.4% from 4.72 to 3.38 TECU. The quiet-time model was trained with Carrington averaged TEC and, therefore, is ideal to be used as an input instead of the GIM derived 27-day median. We found an improvement by 0.8 TECU which corresponds to a performance increase by 17% from 4.72 to 3.92 TECU for the storm-time model using the quiet-time-model predicted TEC as an input compared to solely using the quiet-time model.
KW - ionosphere
KW - relative total electron content
KW - geomagnetic storms
KW - neural
KW - networks
KW - NTCM
KW - European storm-time model
Y1 - 2022
U6 - https://doi.org/10.3390/rs14236155
SN - 2072-4292
VL - 14
IS - 23
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Smirnov, Artem
A1 - Shprits, Yuri Y.
A1 - Allison, Hayley
A1 - Aseev, Nikita
A1 - Drozdov, Alexander
A1 - Kollmann, Peter
A1 - Wang, Dedong
A1 - Saikin, Anthony
T1 - Storm-Time evolution of the Equatorial Electron Pitch Angle Distributions in Earth's Outer Radiation Belt
JF - Frontiers in astronomy and space sciences
N2 - In this study we analyze the storm-time evolution of equatorial electron pitch angle distributions (PADs) in the outer radiation belt region using observations from the Magnetic Electron Ion Spectrometer (MagEIS) instrument aboard the Van Allen Probes in 2012-2019. The PADs are approximated using a sum of the first, third and fifth sine harmonics. Different combinations of the respective coefficients refer to the main PAD shapes within the outer radiation belt, namely the pancake, flat-top, butterfly and cap PADs. We conduct a superposed epoch analysis of 129 geomagnetic storms and analyze the PAD evolution for day and night MLT sectors. PAD shapes exhibit a strong energy-dependent response. At energies of tens of keV, the PADs exhibit little variation throughout geomagnetic storms. Cap PADs are mainly observed at energies < 300 keV, and their extent in L shrinks with increasing energy. The cap distributions transform into the pancake PADs around the main phase of the storm on the nightside, and then come back to their original shapes during the recovery phase. At higher energies on the dayside, the PADs are mainly pancake during pre-storm conditions and become more anisotropic during the main phase. The quiet-time butterfly PADs can be observed on the nightside at L> 5.6. During the main phase, butterfly PADs have stronger 90 degrees-minima and can be observed at lower L-shells (down to L = 5), then transitioning into flat-top PADs at L similar to 4.5 - 5 and pancake PADs at L < 4.5. The resulting PAD coefficients for different energies, locations and storm epochs can be used to test the wave models and physics-based radiation belt codes in terms of pitch angle distributions.
KW - pitch angle
KW - pitch angle distributions
KW - electrons
KW - radiation belts
KW - magnetosphere
KW - van alien probes
Y1 - 2022
U6 - https://doi.org/10.3389/fspas.2022.836811
SN - 2296-987X
VL - 9
PB - Frontiers Media
CY - Lausanne
ER -
TY - JOUR
A1 - Haas, Bernhard
A1 - Shprits, Yuri Y.
A1 - Allison, Hayley
A1 - Wutzig, Michael
A1 - Wang, Dedong
T1 - Which parameter controls ring current electron dynamics
JF - Frontiers in astronomy and space sciences
N2 - Predicting the electron population of Earth's ring current during geomagnetic storms still remains a challenging task.
In this work, we investigate the sensitivity of 10 keV ring current electrons to different driving processes, parameterised by the Kp index, during several moderate and intense storms.
Results are validated against measurements from the Van Allen Probes satellites. Perturbing the Kp index allows us to identify the most dominant processes for moderate and intense storms respectively.
We find that during moderate storms (Kp < 6) the drift velocities mostly control the behaviour of low energy electrons, while loss from wave-particle interactions is the most critical parameter for quantifying the evolution of intense storms (Kp > 6). Perturbations of the Kp index used to drive the boundary conditions at GEO and set the plasmapause location only show a minimal effect on simulation results over a limited L range.
It is further shown that the flux at L & SIM; 3 is more sensitive to changes in the Kp index compared to higher L shells, making it a good proxy for validating the source-loss balance of a ring current model.
KW - ring current
KW - magnetosphere
KW - electron lifetimes
KW - electrons
KW - van allen probes (RBSP)
KW - ring current model
KW - verb
Y1 - 2022
U6 - https://doi.org/10.3389/fspas.2022.911002
SN - 2296-987X
VL - 9
PB - Frontiers Media
CY - Lausanne
ER -
TY - JOUR
A1 - Kühn, Danilo
A1 - Müller, Moritz
A1 - Sorgenfrei, Nomi
A1 - Giangrisostomi, Erika
A1 - Jay, Raphael Martin
A1 - Ovsyannikov, Ruslan
A1 - Martensson, Nils
A1 - Sanchez-Portal, Daniel
A1 - Föhlisch, Alexander
T1 - Directional sub-femtosecond charge transfer dynamics and the dimensionality of 1T-TaS2
JF - Scientific reports
N2 - For the layered transition metal dichalcogenide 1T-TaS2, we establish through a unique experimental approach and density functional theory, how ultrafast charge transfer in 1T-TaS2 takes on isotropic three-dimensional character or anisotropic two-dimensional character, depending on the commensurability of the charge density wave phases of 1T-TaS2. The X-ray spectroscopic core-hole-clock method prepares selectively in-and out-of-plane polarized sulfur 3p orbital occupation with respect to the 1T-TaS2 planes and monitors sub-femtosecond wave packet delocalization. Despite being a prototypical two-dimensional material, isotropic three-dimensional charge transfer is found in the commensurate charge density wave phase (CCDW), indicating strong coupling between layers. In contrast, anisotropic two-dimensional charge transfer occurs for the nearly commensurate phase (NCDW). In direct comparison, theory shows that interlayer interaction in the CCDW phase - not layer stacking variations - causes isotropic three-dimensional charge transfer. This is presumably a general mechanism for phase transitions and tailored properties of dichalcogenides with charge density waves.
Y1 - 2019
U6 - https://doi.org/10.1038/s41598-018-36637-0
SN - 2045-2322
VL - 9
IS - 488
PB - Nature Publ. Group
CY - London
ER -
TY - JOUR
A1 - Woodfield, Emma E.
A1 - Horne, Richard B.
A1 - Glauert, S. A.
A1 - Menietti, J. D.
A1 - Shprits, Yuri Y.
A1 - Kurth, William S.
T1 - Formation of electron radiation belts at Saturn by Z-mode wave acceleration
JF - Nature Communications
N2 - At Saturn electrons are trapped in the planet’s magnetic field and accelerated to relativistic energies to form the radiation belts, but how this dramatic increase in electron energy occurs is still unknown. Until now the mechanism of radial diffusion has been assumed but we show here that in-situ acceleration through wave particle interactions, which initial studies dismissed as ineffectual at Saturn, is in fact a vital part of the energetic particle dynamics there. We present evidence from numerical simulations based on Cassini spacecraft data that a particular plasma wave, known as Z-mode, accelerates electrons to MeV energies inside 4 RS (1 RS = 60,330 km) through a Doppler shifted cyclotron resonant interaction. Our results show that the Z-mode waves observed are not oblique as previously assumed and are much better accelerators than O-mode waves, resulting in an electron energy spectrum that closely approaches observed values without any transport effects included.
Y1 - 2018
U6 - https://doi.org/10.1038/s41467-018-07549-4
SN - 2041-1723
VL - 9
PB - Nature Publ. Group
CY - London
ER -
TY - JOUR
A1 - Smirnov, Artem G.
A1 - Kronberg, Elena A.
A1 - Daly, Patrick W.
A1 - Aseev, Nikita
A1 - Shprits, Yuri Y.
A1 - Kellerman, Adam C.
T1 - Adiabatic Invariants Calculations for Cluster Mission: A Long-Term Product for Radiation Belts Studies
JF - Journal of Geophysical Research: Space Physics
N2 - The Cluster mission has produced a large data set of electron flux measurements in the Earth's magnetosphere since its launch in late 2000. Electron fluxes are measured using Research with Adaptive Particle Imaging Detector (RAPID)/Imaging Electron Spectrometer (IES) detector as a function of energy, pitch angle, spacecraft position, and time. However, no adiabatic invariants have been calculated for Cluster so far. In this paper we present a step-by-step guide to calculations of adiabatic invariants and conversion of the electron flux to phase space density (PSD) in these coordinates. The electron flux is measured in two RAPID/IES energy channels providing pitch angle distribution at energies 39.2-50.5 and 68.1-94.5 keV in nominal mode since 2004. A fitting method allows to expand the conversion of the differential fluxes to the range from 40 to 150 keV. Best data coverage for phase space density in adiabatic invariant coordinates can be obtained for values of second adiabatic invariant, K, similar to 10(2), and values of the first adiabatic invariant mu in the range approximate to 5-20 MeV/G. Furthermore, we describe the production of a new data product "LSTAR," equivalent to the third adiabatic invariant, available through the Cluster Science Archive for years 2001-2018 with 1-min resolution. The produced data set adds to the availability of observations in Earth's radiation belts region and can be used for long-term statistical purposes.
KW - L-Asterisk
KW - magnetosphere
KW - electrons
KW - model
Y1 - 2019
VL - 125
IS - 2
PB - John Wiley & Sons, Inc.
CY - New Jersey
ER -
TY - JOUR
A1 - Jara Muñoz, Julius
A1 - Melnick, Daniel
A1 - Pedoja, Kevin
A1 - Strecker, Manfred
T1 - TerraceM-2: A MatlabR (R) Interface for Mapping and Modeling Marine and Lacustrine Terraces
JF - Frontiers in Earth Science
N2 - The morphology of marine and lacustrine terraces has been largely used to measure past sea- and lake-level positions and estimate vertical deformation in a wealth of studies focused on climate and tectonic processes. To obtain accurate morphometric assessments of terrace morphology we present TerraceM-2, an improved version of our MatlabR (R) graphic-user interface that provides new methodologies for morphometric analyses as well as landscape evolution and fault-dislocation modeling. The new version includes novel routines to map the elevation and spatial distribution of terraces, to model their formation and evolution, and to estimate fault-slip rates from terrace deformation patterns. TerraceM-2 has significantly improves its processing speed and mapping capabilities, and includes separate functions for developing customized workflows beyond the graphic-user interface. We illustrate these new mapping and modeling capabilities with three examples: mapping lacustrine shorelines in the Dead Sea to estimate deformation across the Dead Sea Fault, landscape evolution modeling to estimate a history of uplift rates in southern Peru, and dislocation modeling of deformed marine terraces in California. These examples also illustrate the need to use topographic data of different resolutions. The new modeling and mapping routines of TerraceM-2 highlight the advantages of an integrated joint mapping and modeling approach to improve the efficiency and precision of coastal terrace metrics in both marine and lacustrine environments.
KW - TerraceM
KW - marine terraces
KW - tectonic geomorphology
KW - geomorphic markers
KW - LiDAR
KW - coastal geomorphology
KW - neotectonics
KW - morphometry
Y1 - 2019
U6 - https://doi.org/10.3389/feart.2019.00255
SN - 2296-6463
VL - 7
PB - Frontiers Research Foundation
CY - Lausanne
ER -
TY - JOUR
A1 - Kühn, Danilo
A1 - Giangrisostomi, Erika
A1 - Jay, Raphael Martin
A1 - Sorgenfrei, Nomi
A1 - Föhlisch, Alexander
T1 - The influence of x-ray pulse length on space-charge effects in optical pump/x-ray probe photoemission
JF - New journal of physics : the open-access journal for physics
N2 - Pump-probe photoelectron spectroscopy (PES) is a versatile tool to investigate the dynamics of transient states of excited matter. Vacuum space-charge effects can mask these dynamics and complicate the interpretation of electron spectra. Here we report on space-charge effects in Au 4f photoemission from a polycrystalline gold surface, excited with moderately intense 90 ps (FWHM) soft x-ray probe pulses, under the influence of the Coulomb forces exerted by a pump electron cloud, which was produced by intense 40 fs laser pulses. The experimentally observed kinetic energy shift and spectral broadening of the Au 4f lines, measured with highly-efficient time-of-flight spectroscopy, are in good agreement with simulations utilizing a mean-field model of the electrostatic pump electron potential. This confirms that the line broadening is predominantly caused by variations in the take-off time of the probe electrons without appreciable influence of local scattering events. Our findings might be of general interest for pump-probe PES with picosecond-pulse-length sources.
KW - space-charge effects
KW - mean-field model
KW - x-ray photoemission
KW - electron spectroscopy
KW - pump-probe
KW - ARTOF
Y1 - 2019
U6 - https://doi.org/10.1088/1367-2630/ab2f5c
SN - 1367-2630
VL - 21
PB - IOP Publ. Ltd.
CY - Bristol
ER -
TY - JOUR
A1 - Busch, Aglaja
A1 - Bangerter, Christian
A1 - Mayer, Frank
A1 - Baur, Heiner
T1 - Reliability of the active knee joint position sense test and influence of limb dominance and sex
JF - Scientific reports
N2 - The output of a sensorimotor performance can be measured with the joint position sense (JPS) test. However, investigations of leg dominance, sex and quality measures on this test are limited. Therefore, these potential influencing factors as well as reliability and consistency measures were evaluated for angular reproduction performance and neuromuscular activity during the active knee JPS test in healthy participants. Twenty healthy participants (10 males; 10 females; age 29 +/- 8 years; height 165 +/- 39 cm; body mass 69 +/- 13 kg) performed a seated knee JPS test with a target angle of 50 degrees. Measurements were conducted in two sessions separated by two weeks and consisted of two blocks of continuous angular reproduction (three minutes each block). The difference between reproduced and target angle was identified as angular error measured by an electrogoniometer. During reproduction, the neuromuscular activity of the quadriceps muscle was assessed by surface electromyography. Neuromuscular activity was normalized to submaximal voluntary contraction (subMVC) and displayed per muscle and movement phase. Differences between leg dominance and sex were calculated using Friedman-test (alpha = 0.05). Reliability measures including intraclass correlation coefficient (ICC), Bland-Altman analysis (bias +/- limits of agreement (LoA)) and minimal detectable change (MDC) were analysed. No significant differences between leg dominance and sex were found in angular error and neuromuscular activity. Angular error demonstrated inter-session ICC scores of 0.424 with a bias of 2.4 degrees (+/- 2.4 degrees LoA) as well as MDC of 6.8 degrees and moderate intra-session ICC (0.723) with a bias of 1.4 degrees (+/- 1.65 degrees LoA) as well as MDC of 4.7 degrees. Neuromuscular activity for all muscles and movement phases illustrated inter-session ICC ranging from 0.432 to 0.809 with biases between - 2.5 and 13.6% subMVC and MDC from 13.4 to 63.9% subMVC. Intra-session ICC ranged from 0.705 to 0.987 with biases of - 7.7 to 2.4% subMVC and MDC of 2.7 to 46.5% subMVC. Leg dominance and sex seem not to influence angular reproduction performance and neuromuscular activity. Poor to excellent relative reliability paired with an acceptable consistency confirm findings of previous studies. Comparisons to pathological populations should be conducted with caution.
Y1 - 2023
U6 - https://doi.org/10.1038/s41598-022-26932-2
SN - 2045-2322
VL - 13
PB - Macmillan Publishers Limited, part of Springer Nature
CY - London
ER -
TY - JOUR
A1 - Dumont, Hanna
A1 - Ready, Douglas D. D.
T1 - On the promise of personalized learning for educational equity
JF - npj science of learning
N2 - Students enter school with a vast range of individual differences, resulting from the complex interplay between genetic dispositions and unequal environmental conditions. Schools thus face the challenge of organizing instruction and providing equal opportunities for students with diverse needs. Schools have traditionally managed student heterogeneity by sorting students both within and between schools according to their academic ability. However, empirical evidence suggests that such tracking approaches increase inequalities. In more recent years, driven largely by technological advances, there have been calls to embrace students' individual differences in the classroom and to personalize students' learning experiences. A central justification for personalized learning is its potential to improve educational equity. In this paper, we discuss whether and under which conditions personalized learning can indeed increase equity in K-12 education by bringing together empirical and theoretical insights from different fields, including the learning sciences, philosophy, psychology, and sociology. We distinguish between different conceptions of equity and argue that personalized learning is unlikely to result in "equality of outcomes" and, by definition, does not provide "equality of inputs". However, if implemented in a high-quality way, personalized learning is in line with "adequacy" notions of equity, which aim to equip all students with the basic competencies to participate in society as active members and to live meaningful lives.
KW - Education
KW - Psychology
KW - Sociology
Y1 - 2023
U6 - https://doi.org/10.1038/s41539-023-00174-x
SN - 2056-7936
VL - 8
IS - 1
PB - Nature Publishing Group
CY - London
ER -
TY - JOUR
A1 - Barra, Felipe
A1 - Hovhannisyan, Karen V.
A1 - Imparato, Alberto
T1 - Quantum batteries at the verge of a phase transition
JF - New journal of physics : the open-access journal for physics
N2 - Starting from the observation that the reduced state of a system strongly coupled to a bath is, in general, an athermal state, we introduce and study a cyclic battery-charger quantum device that is in thermal equilibrium, or in a ground state, during the charge storing stage. The cycle has four stages: the equilibrium storage stage is interrupted by disconnecting the battery from the charger, then work is extracted from the battery, and then the battery is reconnected with the charger; finally, the system is brought back to equilibrium. At no point during the cycle are the battery-charger correlations artificially erased. We study the case where the battery and charger together comprise a spin-1/2 Ising chain, and show that the main characteristics-the extracted energy and the thermodynamic efficiency-can be enhanced by operating the cycle close to the quantum phase transition point. When the battery is just a single spin, we find that the output work and efficiency show a scaling behavior at criticality and derive the corresponding critical exponents. Due to always present correlations between the battery and the charger, operations that are equivalent from the perspective of the battery can entail different energetic costs for switching the battery-charger coupling. This happens only when the coupling term does not commute with the battery's bare Hamiltonian, and we use this purely quantum leverage to further optimize the performance of the device.
KW - quantum batteries
KW - quantum thermodynamics
KW - quantum phase transition
Y1 - 2022
U6 - https://doi.org/10.1088/1367-2630/ac43ed
SN - 1367-2630
VL - 24
IS - 1
PB - IOP Publ. Ltd.
CY - Bristol
ER -
TY - JOUR
A1 - Mattern, Maximilian
A1 - Pudell, Jan-Etienne
A1 - Laskin, Gennadii
A1 - Reppert, Alexander von
A1 - Bargheer, Matias
T1 - Analysis of the temperature- and fluence-dependent magnetic stress in laser-excited SrRuO3
JF - Structural dynamics
N2 - We use ultrafast x-ray diffraction to investigate the effect of expansive phononic and contractive magnetic stress driving the picosecond strain response of a metallic perovskite SrRuO3 thin film upon femtosecond laser excitation. We exemplify how the anisotropic bulk equilibrium thermal expansion can be used to predict the response of the thin film to ultrafast deposition of energy. It is key to consider that the laterally homogeneous laser excitation changes the strain response compared to the near-equilibrium thermal expansion because the balanced in-plane stresses suppress the Poisson stress on the picosecond timescale. We find a very large negative Grüneisen constant describing the large contractive stress imposed by a small amount of energy in the spin system. The temperature and fluence dependence of the strain response for a double-pulse excitation scheme demonstrates the saturation of the magnetic stress in the high-fluence regime.
KW - Thin films
KW - Thermodynamic properties
KW - Bragg peak
KW - Ultrafast X-ray diffraction
KW - Thermal effects
KW - Phonons
KW - Magnetism
KW - Lattice dynamics
KW - Lasers
KW - Perovskites
Y1 - 2020
U6 - https://doi.org/10.1063/4.0000072
SN - 2329-7778
VL - 8
IS - 2
PB - AIP Publishing LLC
CY - Melville, NY
ER -
TY - JOUR
A1 - Warschburger, Petra
A1 - Gmeiner, Michaela Silvia
A1 - Bondü, Rebecca
A1 - Klein, Alexandra-Maria
A1 - Busching, Robert
A1 - Elsner, Birgit
T1 - Self-regulation as a resource for coping with developmental challenges during middle childhood and adolescence
BT - the prospective longitudinal PIER YOUTH-study
JF - BMC Psychology
N2 - Background
Self-regulation (SR) as the ability to regulate one's own physical state, emotions, cognitions, and behavior, is considered to play a pivotal role in the concurrent and subsequent mental and physical health of an individual. Although SR skills encompass numerous sub-facets, previous research has often focused on only one or a few of these sub-facets, and only rarely on adolescence. Therefore, little is known about the development of the sub-facets, their interplay, and their specific contributions to future developmental outcomes, particularly in adolescence. To fill these research gaps, this study aims to prospectively examine (1) the development of SR and (2) their influence on adolescent-specific developmental outcomes in a large community sample.
Methods/design
Based on previously collected data from the Potsdam Intrapersonal Developmental Risk (PIER) study with three measurement points, the present prospective, longitudinal study aims to add a fourth measurement point (PIERYOUTH). We aim to retain at least 1074 participants now between 16 and 23 years of the initially 1657 participants (6-11 years of age at the first measurement point in 2012/2013; 52.2% female). The study will continue to follow a multi-method (questionnaires, physiological assessments, performance-based computer tasks), multi-facet (assessing various domains of SR), and multi-rater (self-, parent-, and teacher-report) approach. In addition, a broad range of adolescent-specific developmental outcomes is considered. In doing so, we will cover the development of SR and relevant outcomes over the period of 10 years. In addition, we intend to conduct a fifth measurement point (given prolonged funding) to investigate development up to young adulthood.
Discussion
With its broad and multimethodological approach, PIERYOUTH aims to contribute to a deeper understanding of the development and role of various SR sub-facets from middle childhood to adolescence. The large sample size and low drop-out rates in the first three measurements points form a sound database for our present prospective research.Trial registration German Clinical Trials Register, registration number DRKS00030847.
KW - Self-regulation
KW - Adolescence
KW - Prospective longitudinal study
KW - Mental health
Y1 - 2023
U6 - https://doi.org/10.1186/s40359-023-01140-3
SN - 2050-7283
VL - 11
IS - 1
PB - Springer Nature
CY - London
ER -
TY - JOUR
A1 - Pranav, Manasi
A1 - Hultzsch, Thomas
A1 - Musiienko, Artem
A1 - Sun, Bowen
A1 - Shukla, Atul
A1 - Jaiser, Frank
A1 - Shoaee, Safa
A1 - Neher, Dieter
T1 - Anticorrelated photoluminescence and free charge generation proves field-assisted exciton dissociation in low-offset PM6:Y5 organic solar cells
JF - APL materials : high impact open access journal in functional materials science
N2 - Understanding the origin of inefficient photocurrent generation in organic solar cells with low energy offset remains key to realizing high-performance donor-acceptor systems. Here, we probe the origin of field-dependent free-charge generation and photoluminescence in wnon-fullereneacceptor (NFA)-based organic solar cells using the polymer PM6 and the NFA Y5-a non-halogenated sibling to Y6, with a smaller energetic offset to PM6. By performing time-delayed collection field (TDCF) measurements on a variety of samples with different electron transport layers and active layer thickness, we show that the fill factor and photocurrent are limited by field-dependent free charge generation in the bulk of the blend. We also introduce a new method of TDCF called m-TDCF to prove the absence of artifacts from non-geminate recombination of photogenerated and dark charge carriers near the electrodes. We then correlate free charge generation with steady-state photoluminescence intensity and find perfect anticorrelation between these two properties. Through this, we conclude that photocurrent generation in this low-offset system is entirely controlled by the field-dependent dissociation of local excitons into charge-transfer states. (c) 2023 Author(s).
Y1 - 2023
U6 - https://doi.org/10.1063/5.0151580
SN - 2166-532X
VL - 11
IS - 6
PB - AIP Publishing
CY - Melville
ER -
TY - JOUR
A1 - Bittmann, Frank
A1 - Dech, Silas
A1 - Schaefer, Laura
T1 - Another way to confuse motor control
BT - manual technique supposed to shorten muscle spindles reduces the muscular holding stability in the sense of adaptive force in male soccer players
JF - Brain Sciences
N2 - Sensorimotor control can be impaired by slacked muscle spindles. This was shown for reflex responses and, recently, also for muscular stability in the sense of Adaptive Force (AF). The slack in muscle spindles was generated by contracting the lengthened muscle followed by passive shortening. AF was suggested to specifically reflect sensorimotor control since it requires tension-length control in adaptation to an increasing load. This study investigated AF parameters in reaction to another, manually performed slack procedure in a preselected sample (n = 13). The AF of 11 elbow and 12 hip flexors was assessed by an objectified manual muscle test (MMT) using a handheld device. Maximal isometric AF was significantly reduced after manual spindle technique vs. regular MMT. Muscle lengthening started at 64.93 & PLUSMN; 12.46% of maximal voluntary isometric contraction (MVIC). During regular MMT, muscle length could be maintained stable until 92.53 & PLUSMN; 10.12% of MVIC. Hence, muscular stability measured by AF was impaired after spindle manipulation. Force oscillations arose at a significantly lower level for regular vs. spindle. This supports the assumption that they are a prerequisite for stable adaptation. Reduced muscular stability in reaction to slack procedures is considered physiological since sensory information is misled. It is proposed to use slack procedures to test the functionality of the neuromuscular system, which is relevant for clinical practice.
KW - maximal isometric Adaptive Force
KW - holding capacity
KW - muscle stability
KW - muscle instability
KW - neuromuscular functioning
KW - neuromuscular control
KW - motor control
KW - muscle spindle
KW - muscle physiology
KW - regulatory physiology
Y1 - 2023
U6 - https://doi.org/10.3390/brainsci13071105
SN - 2076-3425
VL - 13
IS - 7
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Hovhannisyan, Karen V.
A1 - Nemati, Somayyeh
A1 - Henkel, Carsten
A1 - Anders, Janet
T1 - Long-time equilibration can determine transient thermality
JF - PRX Quantum
N2 - When two initially thermal many-body systems start to interact strongly, their transient states quickly become non-Gibbsian, even if the systems eventually equilibrate. To see beyond this apparent lack of structure during the transient regime, we use a refined notion of thermality, which we call g-local. A system is g-locally thermal if the states of all its small subsystems are marginals of global thermal states. We numerically demonstrate for two harmonic lattices that whenever the total system equilibrates in the long run, each lattice remains g-locally thermal at all times, including the transient regime. This is true even when the lattices have long-range interactions within them. In all cases, we find that the equilibrium is described by the generalized Gibbs ensemble, with three-dimensional lattices requiring special treatment due to their extended set of conserved charges. We compare our findings with the well-known two-temperature model. While its standard form is not valid beyond weak coupling, we show that at strong coupling it can be partially salvaged by adopting the concept of a g-local temperature.
Y1 - 2023
U6 - https://doi.org/10.1103/PRXQuantum.4.030321
SN - 2691-3399
VL - 4
IS - 3
PB - American Physical Society
CY - College Park
ER -
TY - JOUR
A1 - Bittmann, Frank
A1 - Dech, Silas
A1 - Schaefer, Laura
T1 - How to confuse motor control
BT - passive muscle shortening after contraction in lengthened position reduces the muscular holding stability in the sense of adaptive force
JF - Life : open access journal
N2 - Adaptation to external forces relies on a well-functioning proprioceptive system including muscle spindle afferents. Muscle length and tension control in reaction to external forces is most important regarding the Adaptive Force (AF). This study investigated the effect of different procedures, which are assumed to influence the function of muscle spindles, on the AF. Elbow flexors of 12 healthy participants (n = 19 limbs) were assessed by an objectified manual muscle test (MMT) with different procedures: regular MMT, MMT after precontraction (self-estimated 20% MVIC) in lengthened position with passive return to test position (CL), and MMT after CL with a second precontraction in test position (CL-CT). During regular MMTs, muscles maintained their length up to 99.7% +/- 1.0% of the maximal AF (AF(max)). After CL, muscles started to lengthen at 53.0% +/- 22.5% of AF(max). For CL-CT, muscles were again able to maintain the static position up to 98.3% +/- 5.5% of AF(max). AFiso(max) differed highly significantly between CL vs. CL-CT and regular MMT. CL was assumed to generate a slack of muscle spindles, which led to a substantial reduction of the holding capacity. This was immediately erased by a precontraction in the test position. The results substantiate that muscle spindle sensitivity seems to play an important role for neuromuscular functioning and musculoskeletal stability.
KW - maximal isometric Adaptive Force
KW - holding capacity
KW - muscle stability
KW - neuromuscular functioning
KW - neuromuscular control
KW - motor control
KW - muscle spindle
KW - muscle physiology
KW - regulatory physiology
Y1 - 2023
U6 - https://doi.org/10.3390/life13040911
SN - 2075-1729
VL - 13
IS - 4
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Hijazi, Saddam
A1 - Freitag, Melina A.
A1 - Landwehr, Niels
T1 - POD-Galerkin reduced order models and physics-informed neural networks for solving inverse problems for the Navier-Stokes equations
JF - Advanced modeling and simulation in engineering sciences : AMSES
N2 - We present a Reduced Order Model (ROM) which exploits recent developments in Physics Informed Neural Networks (PINNs) for solving inverse problems for the Navier-Stokes equations (NSE). In the proposed approach, the presence of simulated data for the fluid dynamics fields is assumed. A POD-Galerkin ROM is then constructed by applying POD on the snapshots matrices of the fluid fields and performing a Galerkin projection of the NSE (or the modified equations in case of turbulence modeling) onto the POD reduced basis. A POD-Galerkin PINN ROM is then derived by introducing deep neural networks which approximate the reduced outputs with the input being time and/or parameters of the model. The neural networks incorporate the physical equations (the POD-Galerkin reduced equations) into their structure as part of the loss function. Using this approach, the reduced model is able to approximate unknown parameters such as physical constants or the boundary conditions. A demonstration of the applicability of the proposed ROM is illustrated by three cases which are the steady flow around a backward step, the flow around a circular cylinder and the unsteady turbulent flow around a surface mounted cubic obstacle.
KW - Proper orthogonal decomposition
KW - Inverse problems
KW - Physics-based machine learning
KW - Navier-Stokes equations
Y1 - 2023
U6 - https://doi.org/10.1186/s40323-023-00242-2
SN - 2213-7467
VL - 10
IS - 1
PB - SpringerOpen
CY - Berlin
ER -
TY - JOUR
A1 - Schmidt, Lena Katharina
A1 - Francke, Till
A1 - Grosse, Peter Martin
A1 - Mayer, Christoph
A1 - Bronstert, Axel
T1 - Reconstructing five decades of sediment export from two glacierized high-alpine catchments in Tyrol, Austria, using nonparametric regression
JF - Hydrology and earth system sciences : HESS
N2 - Knowledge on the response of sediment export to recent climate change in glacierized areas in the European Alps is limited, primarily because long-term records of suspended sediment concentrations (SSCs) are scarce. Here we tested the estimation of sediment export of the past five decades using quantile regression forest (QRF), a nonparametric, multivariate regression based on random forest. The regression builds on short-term records of SSCs and long records of the most important hydroclimatic drivers (discharge, precipitation and air temperature - QPT). We trained independent models for two nested and partially glacier-covered catchments, Vent (98 km(2)) and Vernagt (11.4 km(2)), in the upper otztal in Tyrol, Austria (1891 to 3772 m a.s.l.), where available QPT records start in 1967 and 1975. To assess temporal extrapolation ability, we used two 2-year SSC datasets at gauge Vernagt, which are almost 20 years apart, for a validation. For Vent, we performed a five-fold cross-validation on the 15 years of SSC measurements. Further, we quantified the number of days where predictors exceeded the range represented in the training dataset, as the inability to extrapolate beyond this range is a known limitation of QRF. Finally, we compared QRF performance to sediment rating curves (SRCs). We analyzed the modeled sediment export time series, the predictors and glacier mass balance data for trends (Mann-Kendall test and Sen's slope estimator) and step-like changes (using the widely applied Pettitt test and a complementary Bayesian approach).Our validation at gauge Vernagt demonstrated that QRF performs well in estimating past daily sediment export (Nash-Sutcliffe efficiency (NSE) of 0.73) and satisfactorily for SSCs (NSE of 0.51), despite the small training dataset. The temporal extrapolation ability of QRF was superior to SRCs, especially in periods with high-SSC events, which demonstrated the ability of QRF to model threshold effects. Days with high SSCs tended to be underestimated, but the effect on annual yields was small. Days with predictor exceedances were rare, indicating a good representativity of the training dataset. Finally, the QRF reconstruction models outperformed SRCs by about 20 percent points of the explained variance.Significant positive trends in the reconstructed annual suspended sediment yields were found at both gauges, with distinct step-like increases around 1981. This was linked to increased glacier melt, which became apparent through step-like increases in discharge at both gauges as well as change points in mass balances of the two largest glaciers in the Vent catchment. We identified exceptionally high July temperatures in 1982 and 1983 as a likely cause. In contrast, we did not find coinciding change points in precipitation. Opposing trends at the two gauges after 1981 suggest different timings of "peak sediment". We conclude that, given large-enough training datasets, the presented QRF approach is a promising tool with the ability to deepen our understanding of the response of high-alpine areas to decadal climate change.
Y1 - 2023
U6 - https://doi.org/10.5194/hess-27-1841-2023
SN - 1027-5606
SN - 1607-7938
VL - 27
IS - 9
SP - 1841
EP - 1863
PB - Copernicus
CY - Göttingen
ER -
TY - JOUR
A1 - Mazarei, Elham
A1 - Penschke, Christopher
A1 - Saalfrank, Peter
T1 - Band gap engineering in two-dimensional materials by functionalization
BT - Methylation of graphene and graphene bilayers
JF - ACS Omega
N2 - Graphene is well-knownfor its unique combination of electricaland mechanical properties. However, its vanishing band gap limitsthe use of graphene in microelectronics. Covalent functionalizationof graphene has been a common approach to address this critical issueand introduce a band gap. In this Article, we systematically analyzethe functionalization of single-layer graphene (SLG) and bilayer graphene(BLG) with methyl (CH3) using periodic density functionaltheory (DFT) at the PBE+D3 level of theory. We also include a comparisonof methylated single-layer and bilayer graphene, as well as a discussionof different methylation options (radicalic, cationic, and anionic).For SLG, methyl coverages ranging from 1/8 to 1/1, (i.e.,the fully methylated analogue of graphane) are considered. We findthat up to a coverage theta of 1/2, graphene readily accepts CH3, with neighbor CH3 groups preferring trans positions. Above theta = 1/2, the tendency to accept further CH3 weakens and the lattice constant increases. The band gapbehaves less regularly, but overall it increases with increasing methylcoverage. Thus, methylated graphene shows potential for developingband gap-tuned microelectronics devices and may offer further functionalizationoptions. To guide in the interpretation of methylation experiments,vibrational signatures of various species are characterized by normal-modeanalysis (NMA), their vibrational density of states (VDOS), and infrared(IR) spectra, the latter two are obtained from ab initio moleculardynamics (AIMD) in combination with a velocity-velocity autocorrelationfunction (VVAF) approach.
KW - Adsorption
KW - Alkyls
KW - Band structure
KW - Electrical conductivity
KW - Two dimensional materials
Y1 - 2023
U6 - https://doi.org/10.1021/acsomega.3c02068
SN - 2470-1343
VL - 8
IS - 24
SP - 22026
EP - 22041
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Adesina, Morenike O.
A1 - Block, Inga
A1 - Günter, Christina
A1 - Unuabonah, Emmanuel Iyayi
A1 - Taubert, Andreas
T1 - Efficient Removal of Tetracycline and Bisphenol A from Water with a New Hybrid Clay/TiO2 Composite
JF - ACS Omega
N2 - New TiO2 hybrid composites were prepared fromkaolinclay, predried and carbonized biomass, and titanium tetraisopropoxideand explored for tetracycline (TET) and bisphenol A (BPA) removalfrom water. Overall, the removal rate is 84% for TET and 51% for BPA.The maximum adsorption capacities (q (m))are 30 and 23 mg/g for TET and BPA, respectively. These capacitiesare far greater than those obtained for unmodified TiO2. Increasing the ionic strength of the solution does not change theadsorption capacity of the adsorbent. pH changes only slightly changeBPA adsorption, while a pH > 7 significantly reduces the adsorptionof TET on the material. The Brouers-Sotolongo fractal modelbest describes the kinetic data for both TET and BPA adsorption, predictingthat the adsorption process occurs via a complex mechanism involvingvarious forces of attraction. Temkin and Freundlich isotherms, whichbest fit the equilibrium adsorption data for TET and BPA, respectively,suggest that adsorption sites are heterogeneous in nature. Overall,the composite materials are much more effective for TET removal fromaqueous solution than for BPA. This phenomenon is assigned to a differencein the TET/adsorbent interactions vs the BPA/adsorbent interactions:the decisive factor appears to be favorable electrostatic interactionsfor TET yielding a more effective TET removal.
Y1 - 2023
U6 - https://doi.org/10.1021/acsomega.3c00184
SN - 2470-1343
VL - 8
IS - 24
SP - 21594
EP - 21604
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Erler, Alexander
A1 - Riebe, Daniel
A1 - Beitz, Toralf
A1 - Löhmannsröben, Hans-Gerd
A1 - Leenen, Mathias
A1 - Pätzold, Stefan
A1 - Ostermann, Markus
A1 - Wójcik, Michał
T1 - Mobile laser-induced breakdown spectroscopy for future application in precision agriculture
BT - a case study
JF - Sensors
N2 - In precision agriculture, the estimation of soil parameters via sensors and the creation of nutrient maps are a prerequisite for farmers to take targeted measures such as spatially resolved fertilization. In this work, 68 soil samples uniformly distributed over a field near Bonn are investigated using laser-induced breakdown spectroscopy (LIBS). These investigations include the determination of the total contents of macro- and micronutrients as well as further soil parameters such as soil pH, soil organic matter (SOM) content, and soil texture. The applied LIBS instruments are a handheld and a platform spectrometer, which potentially allows for the single-point measurement and scanning of whole fields, respectively. Their results are compared with a high-resolution lab spectrometer. The prediction of soil parameters was based on multivariate methods. Different feature selection methods and regression methods like PLS, PCR, SVM, Lasso, and Gaussian processes were tested and compared. While good predictions were obtained for Ca, Mg, P, Mn, Cu, and silt content, excellent predictions were obtained for K, Fe, and clay content. The comparison of the three different spectrometers showed that although the lab spectrometer gives the best results, measurements with both field spectrometers also yield good results. This allows for a method transfer to the in-field measurements.
KW - LIBS
KW - precision agriculture
KW - soil
KW - multivariate methods
KW - feature selection
Y1 - 2023
U6 - https://doi.org/10.3390/s23167178
SN - 1424-8220
VL - 23
IS - 16
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Schlappa, Stephanie
A1 - Bressel, Lena
A1 - Reich, Oliver
A1 - Münzberg, Marvin
T1 - Advanced particle size analysis in high-solid-content polymer dispersions using photon density wave spectroscopy
JF - Polymers
N2 - High-solid-content polystyrene and polyvinyl acetate dispersions of polymer particles with a 50 nm to 500 nm mean particle diameter and 12-55% (w/w) solid content have been produced via emulsion polymerization and characterized regarding their optical and physical properties. Both systems have been analyzed with common particle-size-measuring techniques like dynamic light scattering (DLS) and static light scattering (SLS) and compared to inline particle size distribution (PSD) measurements via photon density wave (PDW) spectroscopy in undiluted samples. It is shown that particle size measurements of undiluted polystyrene dispersions are in good agreement between analysis methods. However, for polyvinyl acetate particles, size determination is challenging due to bound water in the produced polymer. For the first time, water-swelling factors were determined via an iterative approach of PDW spectroscopy error (X-2) minimization. It is shown that water-swollen particles can be analyzed in high-solid-content solutions and their physical properties can be assumed to determine the refractive index, density, and volume fraction in dispersion. It was found that assumed water swelling improved the reduced scattering coefficient fit by PDW spectroscopy by up to ten times and particle size determination was refined and enabled. Particle size analysis of the water-swollen particles agreed well with offline-based state-of-the-art techniques.
KW - emulsion polymerization
KW - multiple light scattering
KW - photon density wave
KW - spectroscopy
KW - particle sizing
KW - swelling of polymers
Y1 - 2023
U6 - https://doi.org/10.3390/polym15153181
SN - 2073-4360
VL - 15
IS - 15
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Khalil, Samir
A1 - Kohler, Ulrich
A1 - Tjaden, Jasper Dag
T1 - Is There a Rural Penalty in Language Acquisition? Evidence From Germany's Refugee Allocation Policy
JF - Frontiers in Sociology
N2 - Emerging evidence has highlighted the important role of local contexts for integration trajectories of asylum seekers and refugees. Germany's policy of randomly allocating asylum seekers across Germany may advantage some and disadvantage others in terms of opportunities for equal participation in society. This study explores the question whether asylum seekers that have been allocated to rural areas experience disadvantages in terms of language acquisition compared to those allocated to urban areas. We derive testable assumptions using a Directed Acyclic Graph (DAG) which are then tested using large-N survey data (IAB-BAMF-SOEP refugee survey). We find that living in a rural area has no negative total effect on language skills. Further the findings suggest that the “null effect” is the result of two processes which offset each other: while asylum seekers in rural areas have slightly lower access for formal, federally organized language courses, they have more regular exposure to German speakers.
KW - refugees
KW - allocation policies
KW - rural
KW - language acquisition
KW - intergroup contacts
KW - language courses
KW - integration
Y1 - 2022
U6 - https://doi.org/10.3389/fsoc.2022.841775
SN - 2297-7775
VL - 7
SP - 1
EP - 11
PB - Frontiers
CY - Lausanne, Schweiz
ER -
TY - JOUR
A1 - Wolff, Martin
A1 - Gast, Klaus
A1 - Evers, Andreas
A1 - Kurz, Michael
A1 - Pfeiffer-Marek, Stefania
A1 - Schüler, Anja
A1 - Seckler, Robert
A1 - Thalhammer, Anja
T1 - A Conserved Hydrophobic Moiety and Helix-Helix Interactions Drive the Self-Assembly of the Incretin Analog Exendin-4
JF - Biomolecules
N2 - Exendin-4 is a pharmaceutical peptide used in the control of insulin secretion. Structural information on exendin-4 and related peptides especially on the level of quaternary structure is scarce. We present the first published association equilibria of exendin-4 directly measured by static and dynamic light scattering. We show that exendin-4 oligomerization is pH dependent and that these oligomers are of low compactness. We relate our experimental results to a structural hypothesis to describe molecular details of exendin-4 oligomers. Discussion of the validity of this hypothesis is based on NMR, circular dichroism and fluorescence spectroscopy, and light scattering data on exendin-4 and a set of exendin-4 derived peptides. The essential forces driving oligomerization of exendin-4 are helix–helix interactions and interactions of a conserved hydrophobic moiety. Our structural hypothesis suggests that key interactions of exendin-4 monomers in the experimentally supported trimer take place between a defined helical segment and a hydrophobic triangle constituted by the Phe22 residues of the three monomeric subunits. Our data rationalize that Val19 might function as an anchor in the N-terminus of the interacting helix-region and that Trp25 is partially shielded in the oligomer by C-terminal amino acids of the same monomer. Our structural hypothesis suggests that the Trp25 residues do not interact with each other, but with C-terminal Pro residues of their own monomers.
KW - biophysics
KW - diabetes
KW - peptides
KW - oligomerization
KW - conformational change
KW - molecular modeling
KW - static and dynamic light scattering
KW - spectroscopy
Y1 - 2021
U6 - https://doi.org/10.3390/biom11091305
SN - 2218-273X
VL - 11
IS - 9
PB - MDPI
CY - Basel
ER -