TY - JOUR A1 - Kihampa, Charles A1 - Joseph, Cosam C. A1 - Nkunya, Mayunga H. H. A1 - Magesa, Stephen M. T1 - Larvicidal and IGR activity of extract of Tanzanian plants against malaria vector mosquitoes N2 - Background & objectives: This paper reports the larvicidal activity of seventeen Tanzanian plant species against the malaria vector, Anopheles gambiae s.s. Giles larvae. Some of the plants are used traditionally as sources of insecticidal materials. Methods: The crude extracts from the leaves, stem and root barks of the investigated plants were obtained by solvent extraction and then bio-assayed following WHO protocols showed LC50 values 10 to 400 ppm after 24 h exposure. The structures were determined on interpretation of spectroscopic data. Results: The most active extracts were those from the stem and root barks of Annona squamosa, Uvaria faulknerae, U. kirkii and Uvariodendron pycnophyllum, all of which had LC50 values between 10 and 100 ppm. Long-term exposure beyond 24 h also showed more susceptibility of the larvae to the extracts. Larvae deformities by forming tail-like structures were observed for the methanol extracts of Tessmannia martiniana var pauloi. Interpretation & conclusion: The results suggest that the investigated plant extracts are promising as larvicides against An. gambiae s.s. Giles mosquitoes and could be useful leads in the search for new and biodegradable plant derived larvicide products. Y1 - 2009 UR - http://www.mrcindia.org/journal/ SN - 0972-9062 ER - TY - GEN A1 - Dietze, Elisabeth A1 - Mangelsdorf, Kai A1 - Andreev, Andrei A1 - Karger, Cornelia A1 - Schreuder, Laura T. A1 - Hopmans, Ellen C. A1 - Rach, Oliver A1 - Sachse, Dirk A1 - Wennrich, Volker A1 - Herzschuh, Ulrike T1 - Relationships between low-temperature fires, climate and vegetation during three late glacials and interglacials of the last 430 kyr in northeastern Siberia reconstructed from monosaccharide anhydrides in Lake El’gygytgyn sediments T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Landscapes in high northern latitudes are assumed to be highly sensitive to future global change, but the rates and long-term trajectories of changes are rather uncertain. In the boreal zone, fires are an important factor in climate-vegetation interactions and biogeochemical cycles. Fire regimes are characterized by small, frequent, low-intensity fires within summergreen boreal forests dominated by larch, whereas evergreen boreal forests dominated by spruce and pine burn large areas less frequently but at higher intensities. Here, we explore the potential of the monosaccharide anhydrides (MA) levoglucosan, mannosan and galactosan to serve as proxies of low-intensity biomass burning in glacial-to-interglacial lake sediments from the high northern latitudes. We use sediments from Lake El'gygytgyn (cores PG 1351 and ICDP 5011-1), located in the far north-east of Russia, and study glacial and interglacial samples of the last 430 kyr (marine isotope stages 5e, 6, 7e, 8, 11c and 12) that had different climate and biome configurations. Combined with pollen and non-pollen palynomorph records from the same samples, we assess how far the modern relationships between fire, climate and vegetation persisted during the past, on orbital to centennial timescales. We find that MAs attached to particulates were well-preserved in up to 430 kyr old sediments with higher influxes from low-intensity biomass burning in interglacials compared to glacials. MA influxes significantly increase when summergreen boreal forest spreads closer to the lake, whereas they decrease when tundra-steppe environments and, especially, Sphagnum peatlands spread. This suggests that low-temperature fires are a typical characteristic of Siberian larch forests also on long timescales. The results also suggest that low-intensity fires would be reduced by vegetation shifts towards very dry environments due to reduced biomass availability, as well as by shifts towards peatlands, which limits fuel dryness. In addition, we observed very low MA ratios, which we interpret as high contributions of galactosan and mannosan from biomass sources other than those currently monitored, such as the moss-lichen mats in the understorey of the summergreen boreal forest. Overall, sedimentary MAs can provide a powerful proxy for fire regime reconstructions and extend our knowledge of long-term natural fire-climate-vegetation feedbacks in the high northern latitudes. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1439 KW - molecular tracers KW - organic aerosols KW - emission factors KW - carbonaceous aerosols KW - pollen records KW - core PG1351 KW - biomass KW - holocene KW - levoglucosan KW - charcoal Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-516843 SN - 1866-8372 IS - 2 ER - TY - JOUR A1 - van Loon, Jacco Th. A1 - Bailey, M. A1 - Tatton, B. L. A1 - Apellaniz, Jesus Maiz A1 - Crowther, P. A. A1 - de Koter, A. A1 - Evans, C. J. A1 - Henault-Brunet, V. A1 - Howarth, I. D. A1 - Richter, Philipp A1 - Sana, Hugues A1 - Simon Díaz, Sergio A1 - Taylor, W. A1 - Walborn, N. R. T1 - The VLT-FLAMES tarantula survey IX. - the interstellar medium seen through diffuse interstellar bands and neutral sodium JF - Astronomy and astrophysics : an international weekly journal N2 - Context. The Tarantula Nebula (a.k.a. 30 Dor) is a spectacular star-forming region in the Large Magellanic Cloud (LMC), seen through gas in the Galactic disc and halo. Diffuse interstellar bands (DIBs) offer a unique probe of the diffuse, cool-warm gas in these regions. Aims. The aim is to use DIBs as diagnostics of the local interstellar conditions, whilst at the same time deriving properties of the yet-unknown carriers of these enigmatic spectral features. Methods. Spectra of over 800 early-type stars from the Very Large Telescope Flames Tarantula Survey (VFTS) were analysed. Maps were created, separately, for the Galactic and LMC absorption in the DIBs at 4428 and 6614 angstrom and - in a smaller region near the central cluster R 136 - neutral sodium (the Na ID doublet); we also measured the DIBs at 5780 and 5797 angstrom. Results. The maps show strong 4428 and 6614 angstrom DIBs in the quiescent cloud complex to the south of 30 Dor but weak absorption in the harsher environments to the north (bubbles) and near the OB associations. The Na maps show at least five kinematic components in the LMC and a shell-like structure surrounding R 136, and small-scale structure in the Milky Way. The strengths of the 4428, 5780, 5797 and 6614 angstrom DIBs are correlated, also with Na absorption and visual extinction. The strong 4428 angstrom DIB is present already at low Na column density but the 6614, 5780 and 5797 angstrom DIBs start to be detectable at subsequently larger Na column densities. Conclusions. The carriers of the 4428, 6614, 5780 and 5797 angstrom DIBs are increasingly prone to removal from irradiated gas. The relative strength of the 5780 and 5797 angstrom DIBs clearly confirm the Tarantula Nebula as well as Galactic high-latitude gas to represent a harsh radiation environment. The resilience of the 4428 angstrom DIB suggests its carrier is large, compact and neutral. Structure is detected in the distribution of cool-warm gas on scales between one and > 100 pc in the LMC and as little as 0.01 pc in the Sun's vicinity. Stellar winds from the central cluster R 136 have created an expanding shell; some infalling gas is also detected, reminiscent of a galactic "fountain". KW - ISM: individual objects: Tarantula Nebula (30 Doradus Nebula) KW - ISM: molecules KW - ISM: kinematics and dynamics KW - ISM: lines and bands KW - ISM: structure KW - local insterstellar matter Y1 - 2013 U6 - https://doi.org/10.1051/0004-6361/201220210 SN - 0004-6361 VL - 550 IS - 9 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Li, Tian-yi A1 - Benduhn, Johannes A1 - Qiao, Zhi A1 - Liu, Yuan A1 - Li, Yue A1 - Shivhare, Rishi A1 - Jaiser, Frank A1 - Wang, Pei A1 - Ma, Jie A1 - Zeika, Olaf A1 - Neher, Dieter A1 - Mannsfeld, Stefan C. B. A1 - Ma, Zaifei A1 - Vandewal, Koen A1 - Leo, Karl T1 - Effect of H- and J-Aggregation on the Photophysical and Voltage Loss of Boron Dipyrromethene Small Molecules in Vacuum-Deposited Organic Solar Cells JF - The journal of physical chemistry letters N2 - An understanding of the factors limiting the open-circuit voltage (V-oc) and related photon energy loss mechanisms is critical to increase the power conversion efficiency (PCE) of small-molecule organic solar cells (OSCs), especially those with near-infrared (NIR) absorbers. In this work, two NIR boron dipyrromethene (BODIPY) molecules are characterized for application in planar (PHJ) and bulk (BHJ) heterojunction OSCs. When two H atoms are substituted by F atoms on the peripheral phenyl rings of the molecules, the molecular aggregation type in the thin film changes from the H-type to J-type. For PHJ devices, the nonradiative voltage loss of 0.35 V in the J-aggregated BODIPY is lower than that of 0.49 V in the H-aggregated device. In BHJ devices with a nonradiative voltage loss of 0.35 V, a PCE of 5.5% is achieved with an external quantum efficiency (EQE) maximum of 68% at 700 nm. Y1 - 2019 U6 - https://doi.org/10.1021/acs.jpclett.9b01222 SN - 1948-7185 VL - 10 IS - 11 SP - 2684 EP - 2691 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Piro, Vitor C. A1 - Dadi, Temesgen H. A1 - Seiler, Enrico A1 - Reinert, Knut A1 - Renard, Bernhard Y. T1 - ganon BT - precise metagenomics classification against large and up-to-date sets of reference sequences JF - Bioinformatics N2 - Motivation: The exponential growth of assembled genome sequences greatly benefits metagenomics studies. However, currently available methods struggle to manage the increasing amount of sequences and their frequent updates. Indexing the current RefSeq can take days and hundreds of GB of memory on large servers. Few methods address these issues thus far, and even though many can theoretically handle large amounts of references, time/memory requirements are prohibitive in practice. As a result, many studies that require sequence classification use often outdated and almost never truly up-to-date indices. Results: Motivated by those limitations, we created ganon, a k-mer-based read classification tool that uses Interleaved Bloom Filters in conjunction with a taxonomic clustering and a k-mer counting/filtering scheme. Ganon provides an efficient method for indexing references, keeping them updated. It requires <55 min to index the complete RefSeq of bacteria, archaea, fungi and viruses. The tool can further keep these indices up-to-date in a fraction of the time necessary to create them. Ganon makes it possible to query against very large reference sets and therefore it classifies significantly more reads and identifies more species than similar methods. When classifying a high-complexity CAMI challenge dataset against complete genomes from RefSeq, ganon shows strongly increased precision with equal or better sensitivity compared with state-of-the-art tools. With the same dataset against the complete RefSeq, ganon improved the F1-score by 65% at the genus level. It supports taxonomy- and assembly-level classification, multiple indices and hierarchical classification. Y1 - 2020 U6 - https://doi.org/https://doi.org/10.1093/bioinformatics/btaa458 SN - 1367-4811 SN - 1367-4803 VL - 36 SP - 12 EP - 20 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Allan, Eric A1 - Weisser, Wolfgang W. A1 - Fischer, Markus A1 - Schulze, Ernst-Detlef A1 - Weigelt, Alexandra A1 - Roscher, Christiane A1 - Baade, Jussi A1 - Barnard, Romain L. A1 - Bessler, Holger A1 - Buchmann, Nina A1 - Ebeling, Anne A1 - Eisenhauer, Nico A1 - Engels, Christof A1 - Fergus, Alexander J. F. A1 - Gleixner, Gerd A1 - Gubsch, Marlen A1 - Halle, Stefan A1 - Klein, Alexandra-Maria A1 - Kertscher, Ilona A1 - Kuu, Annely A1 - Lange, Markus A1 - Le Roux, Xavier A1 - Meyer, Sebastian T. A1 - Migunova, Varvara D. A1 - Milcu, Alexandru A1 - Niklaus, Pascal A. A1 - Oelmann, Yvonne A1 - Pasalic, Esther A1 - Petermann, Jana S. A1 - Poly, Franck A1 - Rottstock, Tanja A1 - Sabais, Alexander C. W. A1 - Scherber, Christoph A1 - Scherer-Lorenzen, Michael A1 - Scheu, Stefan A1 - Steinbeiss, Sibylle A1 - Schwichtenberg, Guido A1 - Temperton, Vicky A1 - Tscharntke, Teja A1 - Voigt, Winfried A1 - Wilcke, Wolfgang A1 - Wirth, Christian A1 - Schmid, Bernhard T1 - A comparison of the strength of biodiversity effects across multiple functions JF - Oecologia N2 - In order to predict which ecosystem functions are most at risk from biodiversity loss, meta-analyses have generalised results from biodiversity experiments over different sites and ecosystem types. In contrast, comparing the strength of biodiversity effects across a large number of ecosystem processes measured in a single experiment permits more direct comparisons. Here, we present an analysis of 418 separate measures of 38 ecosystem processes. Overall, 45 % of processes were significantly affected by plant species richness, suggesting that, while diversity affects a large number of processes not all respond to biodiversity. We therefore compared the strength of plant diversity effects between different categories of ecosystem processes, grouping processes according to the year of measurement, their biogeochemical cycle, trophic level and compartment (above- or belowground) and according to whether they were measures of biodiversity or other ecosystem processes, biotic or abiotic and static or dynamic. Overall, and for several individual processes, we found that biodiversity effects became stronger over time. Measures of the carbon cycle were also affected more strongly by plant species richness than were the measures associated with the nitrogen cycle. Further, we found greater plant species richness effects on measures of biodiversity than on other processes. The differential effects of plant diversity on the various types of ecosystem processes indicate that future research and political effort should shift from a general debate about whether biodiversity loss impairs ecosystem functions to focussing on the specific functions of interest and ways to preserve them individually or in combination. KW - Bottom-up effects KW - Carbon cycling KW - Ecological synthesis KW - Ecosystem processes KW - Grasslands KW - Jena experiment KW - Nitrogen cycling Y1 - 2013 U6 - https://doi.org/10.1007/s00442-012-2589-0 SN - 0029-8549 VL - 173 IS - 1 SP - 223 EP - 237 PB - Springer CY - New York ER - TY - JOUR A1 - Manning, Pete A1 - Gossner, Martin M. A1 - Bossdorf, Oliver A1 - Allan, Eric A1 - Zhang, Yuan-Ye A1 - Prati, Daniel A1 - Blüthgen, Nico A1 - Boch, Steffen A1 - Böhm, Stefan A1 - Börschig, Carmen A1 - Hölzel, Norbert A1 - Jung, Kirsten A1 - Klaus, Valentin H. A1 - Klein, Alexandra-Maria A1 - Kleinebecker, Till A1 - Krauss, Jochen A1 - Lange, Markus A1 - Müller, Jörg A1 - Pasalic, Esther A1 - Socher, Stephanie A. A1 - Tschapka, Marco A1 - Türke, Manfred A1 - Weiner, Christiane A1 - Werner, Michael A1 - Gockel, Sonja A1 - Hemp, Andreas A1 - Renner, Swen C. A1 - Wells, Konstans A1 - Buscot, Francois A1 - Kalko, Elisabeth K. V. A1 - Linsenmair, Karl Eduard A1 - Weisser, Wolfgang W. A1 - Fischer, Markus T1 - Grassland management intensification weakens the associations among the diversities of multiple plant and animal taxa JF - Ecology : a publication of the Ecological Society of America N2 - Land-use intensification is a key driver of biodiversity change. However, little is known about how it alters relationships between the diversities of different taxonomic groups, which are often correlated due to shared environmental drivers and trophic interactions. Using data from 150 grassland sites, we examined how land-use intensification (increased fertilization, higher livestock densities, and increased mowing frequency) altered correlations between the species richness of 15 plant, invertebrate, and vertebrate taxa. We found that 54% of pairwise correlations between taxonomic groups were significant and positive among all grasslands, while only one was negative. Higher land-use intensity substantially weakened these correlations(35% decrease in rand 43% fewer significant pairwise correlations at high intensity), a pattern which may emerge as a result of biodiversity declines and the breakdown of specialized relationships in these conditions. Nevertheless, some groups (Coleoptera, Heteroptera, Hymenoptera and Orthoptera) were consistently correlated with multidiversity, an aggregate measure of total biodiversity comprised of the standardized diversities of multiple taxa, at both high and lowland-use intensity. The form of intensification was also important; increased fertilization and mowing frequency typically weakened plant-plant and plant-primary consumer correlations, whereas grazing intensification did not. This may reflect decreased habitat heterogeneity under mowing and fertilization and increased habitat heterogeneity under grazing. While these results urge caution in using certain taxonomic groups to monitor impacts of agricultural management on biodiversity, they also suggest that the diversities of some groups are reasonably robust indicators of total biodiversity across a range of conditions. KW - Biodiversity indicators KW - correlation KW - fertilization KW - grassland management KW - grazing KW - land-use change KW - land-use intensity KW - mowing KW - multidiversity KW - multitrophic interactions Y1 - 2015 U6 - https://doi.org/10.1890/14-1307.1 SN - 0012-9658 SN - 1939-9170 VL - 96 IS - 6 SP - 1492 EP - 1501 PB - Wiley CY - Washington ER - TY - JOUR A1 - Qu, J. Q. A1 - Zhang, J. Y. A1 - Grimsdale, A. C. A1 - Mullen, K. A1 - Jaiser, Frank A1 - Yang, X. H. A1 - Neher, Dieter T1 - Dendronized perylene diimide emitters : Synthesis, luminescence, and electron and energy transfer studies N2 - Aggregation of chromophores in the solid state commonly causes undesirable red shifts in the emission spectra and/or emission quenching. To overcome this problem, we have prepared soluble perylenetetracarboxidiimide dyes in which the chromophores are effectively shielded by polyphenylene dendrimers attached in the bay positions. Models show that attachment of the shielding units in the bay position should provide more efficient shielding than attaching them via the imide moieties. The dendrimers possess excellent film-forming properties due to alkyl substituents on their peripheries. The lack of a red shift in emission upon going from solution to the solid state indicates the dendrons suppress interaction of the emissive cores, leading to pure red-orange emission. Single-layer LEDs produce red-orange emission with relatively low efficiency especially for the higher generation dendrons, which is attributed to poor charge conduction. LEDs using blends of the dendrimers and the undendronized dye as a model compound in PVK have been investigated, and a model to extract relative charge injection rates through the dendritic scaffold from the spectral contributions in the EL spectra is developed Y1 - 2004 SN - 0024-9297 ER - TY - JOUR A1 - Steyrleuthner, Robert A1 - Schubert, Marcel A1 - Jaiser, Frank A1 - Blakesley, James C. A1 - Chen, Zhihua A1 - Facchetti, Antonio A1 - Neher, Dieter T1 - Bulk electron transport and charge injection in a high mobility n-type semiconducting polymer N2 - Bulk electron transport in a high mobility n-type polymer is studied by time-of-flight photocurrent measurements and electron-only devices. Bulk electron mobilities of similar to 5 x 10(-3) cm(2)/Vs are obtained. The analysis of the electron currents suggests the presence of an injection barrier for all conventionally used low workfunction cathodes. Y1 - 2010 UR - http://www3.interscience.wiley.com/cgi-bin/jhome/10008336 U6 - https://doi.org/10.1002/adma.201000232 SN - 0935-9648 ER - TY - JOUR A1 - Hagoort, Iris A1 - Vuillerme, Nicolas A1 - Hortobágyi, Tibor A1 - Lamoth, Claudine J. C. T1 - Outcome-dependent effects of walking speed and age on quantitative and qualitative gait measures JF - Gait & posture N2 - Background: Walking speed predicts many clinical outcomes in old age. However, a comprehensive assessment of how walking speed affects accelerometer based quantitative and qualitative gait measures in younger and older adults is lacking. Research question: What is the relationship between walking speed and quantitative and qualitative gait outcomes in younger and older adults? Methods: Younger (n = 27, age: 21.6) and older participants (n = 27, age: 69.5) completed 340 steps on a treadmill at speeds of 0.70 to a maximum of 1.75 m.s(-1). We used generalized additive mixed models to determine the relationship between walking speed and quantitative (stride length, stride time, stride frequency and their variability) and qualitative (stride regularity, stability, smoothness, symmetry, synchronization, predictability) gait measures extracted from trunk accelerations. Results: The type of relationship between walking speed and the majority of gait measures (quantitative and qualitative) was characterized as logarithmic, with more prominent speed-effects at speeds below 1.20 m.s(-1). Changes in quantitative measures included shorter strides, longer stride times, and a lower stride frequency, with more variability at lower speeds independent of age. For qualitative measures, we found a decrease in gait symmetry, stability and regularity in all directions with decreasing speeds, a decrease in gait predictability (Vertical, V, anterior-posterior, AP) and stronger gait synchronization (AP-mediolateral, ML, AP-V), and direction dependent effects of gait smoothness, which decreased in V direction, but increased in AP and ML directions with decreasing speeds. We found outcome-dependent effects of age on the quantitative and qualitative gait measures, with either no differences between age-groups, age-related differences that existed regardless of speed, and age-related differences in the type of relationship with walking speed. Significance: The relationship between walking speed and quantitative and qualitative gait measures, and the effects of age on this relationship, depends on the type of gait measure studied. KW - Gait quality and quantity KW - Aging KW - Walking speed KW - Treadmill KW - Generalized KW - additive mixed models Y1 - 2022 U6 - https://doi.org/10.1016/j.gaitpost.2022.01.001 SN - 0966-6362 SN - 1879-2219 VL - 93 SP - 39 EP - 46 PB - Elsevier CY - Clare ER - TY - JOUR A1 - Ullbrich, Sascha A1 - Benduhn, Johannes A1 - Jia, Xiangkun A1 - Nikolis, Vasileios C. A1 - Tvingstedt, Kristofer A1 - Piersimoni, Fortunato A1 - Roland, Steffen A1 - Liu, Yuan A1 - Wu, Jinhan A1 - Fischer, Axel A1 - Neher, Dieter A1 - Reineke, Sebastian A1 - Spoltore, Donato A1 - Vandewal, Koen T1 - Emissive and charge-generating donor-acceptor interfaces for organic optoelectronics with low voltage losses JF - Nature materials N2 - Intermolecular charge-transfer states at the interface between electron donating (D) and accepting (A) materials are crucial for the operation of organic solar cells but can also be exploited for organic light-emitting diodes(1,2). Non-radiative charge-transfer state decay is dominant in state-of-the-art D-A-based organic solar cells and is responsible for large voltage losses and relatively low power-conversion efficiencies as well as electroluminescence external quantum yields in the 0.01-0.0001% range(3,4). In contrast, the electroluminescence external quantum yield reaches up to 16% in D-A-based organic light-emitting diodes(5-7). Here, we show that proper control of charge-transfer state properties allows simultaneous occurrence of a high photovoltaic and emission quantum yield within a single, visible-light-emitting D-A system. This leads to ultralow-emission turn-on voltages as well as significantly reduced voltage losses upon solar illumination. These results unify the description of the electro-optical properties of charge-transfer states in organic optoelectronic devices and foster the use of organic D-A blends in energy conversion applications involving visible and ultraviolet photons(8-11). KW - Electronics, photonics and device physics KW - Optoelectronic devices and components KW - Photonic devices KW - Solar energy and photovoltaic technology Y1 - 2019 U6 - https://doi.org/10.1038/s41563-019-0324-5 SN - 1476-1122 SN - 1476-4660 VL - 18 IS - 5 SP - 459 EP - 464 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Kraffert, Felix A1 - Steyrleuthner, Robert A1 - Albrecht, Steve A1 - Neher, Dieter A1 - Scharber, Markus C. A1 - Bittl, Robert A1 - Behrends, Jan T1 - Charge Separation in PCPDTBT : PCBM Blends from an EPR Perspective JF - The journal of physical chemistry Y1 - 2014 U6 - https://doi.org/10.1021/jp509650v SN - 1932-7447 VL - 118 IS - 49 SP - 28482 EP - 28493 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Donges, Jonathan A1 - Schleussner, C. -F. A1 - Siegmund, Jonatan F. A1 - Donner, Reik Volker T1 - Event coincidence analysis for quantifying statistical interrelationships between event time series JF - European physical journal special topics N2 - Studying event time series is a powerful approach for analyzing the dynamics of complex dynamical systems in many fields of science. In this paper, we describe the method of event coincidence analysis to provide a framework for quantifying the strength, directionality and time lag of statistical interrelationships between event series. Event coincidence analysis allows to formulate and test null hypotheses on the origin of the observed interrelationships including tests based on Poisson processes or, more generally, stochastic point processes with a prescribed inter-event time distribution and other higher-order properties. Applying the framework to country-level observational data yields evidence that flood events have acted as triggers of epidemic outbreaks globally since the 1950s. Facing projected future changes in the statistics of climatic extreme events, statistical techniques such as event coincidence analysis will be relevant for investigating the impacts of anthropogenic climate change on human societies and ecosystems worldwide. Y1 - 2016 U6 - https://doi.org/10.1140/epjst/e2015-50233-y SN - 1951-6355 SN - 1951-6401 VL - 225 SP - 471 EP - 487 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Collado-Fregoso, Elisa A1 - Hood, Samantha N. A1 - Shoaee, Safa A1 - Schröder, Bob C. A1 - McCulloch, Iain A1 - Kassal, Ivan A1 - Neher, Dieter A1 - Durrant, James R. T1 - Intercalated vs Nonintercalated Morphologies in Donor-Acceptor Bulk Heterojunction Solar Cells: PBTTT:Fullerene Charge Generation and Recombination Revisited JF - The journal of physical chemistry letters N2 - In this Letter, we study the role of the donor:acceptor interface nanostructure upon charge separation and recombination in organic photovoltaic devices and blend films, using mixtures of PBTTT and two different fullerene derivatives (PC70BM and ICTA) as models for intercalated and nonintercalated morphologies, respectively. Thermodynamic simulations show that while the completely intercalated system exhibits a large free-energy barrier for charge separation, this barrier is significantly lower in the nonintercalated system and almost vanishes when energetic disorder is included in the model. Despite these differences, both femtosecond-resolved transient absorption spectroscopy (TAS) and time-delayed collection field (TDCF) exhibit extensive first-order losses in both systems, suggesting that geminate pairs are the primary product of photoexcitation. In contrast, the system that comprises a combination of fully intercalated polymer:fullerene areas and fullerene-aggregated domains (1:4 PBTTT:PC70BM) is the only one that shows slow, second-order recombination of free charges, resulting in devices with an overall higher short-circuit current and fill factor. This study therefore provides a novel consideration of the role of the interfacial nanostructure and the nature of bound charges and their impact upon charge generation and recombination. Y1 - 2017 U6 - https://doi.org/10.1021/acs.jpclett.7b01571 SN - 1948-7185 VL - 8 SP - 4061 EP - 4068 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Nikolis, Vasileios C. A1 - Benduhn, Johannes A1 - Holzmueller, Felix A1 - Piersimoni, Fortunato A1 - Lau, Matthias A1 - Zeika, Olaf A1 - Neher, Dieter A1 - Koerner, Christian A1 - Spoltore, Donato A1 - Vandewal, Koen T1 - Reducing Voltage Losses in Cascade Organic Solar Cells while Maintaining High External Quantum Efficiencies JF - dvanced energy materials N2 - High photon energy losses limit the open-circuit voltage (V-OC) and power conversion efficiency of organic solar cells (OSCs). In this work, an optimization route is presented which increases the V-OC by reducing the interfacial area between donor (D) and acceptor (A). This optimization route concerns a cascade device architecture in which the introduction of discontinuous interlayers between alpha-sexithiophene (alpha-6T) (D) and chloroboron subnaphthalocyanine (SubNc) (A) increases the V-OC of an alpha-6T/SubNc/SubPc fullerene-free cascade OSC from 0.98 V to 1.16 V. This increase of 0.18 V is attributed solely to the suppression of nonradiative recombination at the D-A interface. By accurately measuring the optical gap (E-opt) and the energy of the charge-transfer state (E-CT) of the studied OSC, a detailed analysis of the overall voltage losses is performed. E-opt - qV(OC) losses of 0.58 eV, which are among the lowest observed for OSCs, are obtained. Most importantly, for the V-OC-optimized devices, the low-energy (700 nm) external quantum efficiency (EQE) peak remains high at 79%, despite a minimal driving force for charge separation of less than 10 meV. This work shows that low-voltage losses can be combined with a high EQE in organic photovoltaic devices. KW - energy losses KW - nonradiative recombination KW - open-circuit voltage KW - organic solar cells KW - voltage losses Y1 - 2017 U6 - https://doi.org/10.1002/aenm.201700855 SN - 1614-6832 SN - 1614-6840 VL - 7 SP - 122 EP - 136 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Ryppa, C. A1 - Senge, Mathias O. A1 - Hatscher, S. S. A1 - Kleinpeter, Erich A1 - Wacker, Philipp A1 - Schilde, Uwe A1 - Wiehe, A. T1 - Synthesis of mono- and disubstituted porphyrins : A- and 5,10-A(2)-type systems N2 - General syntheses have been developed for meso-substituted porphyrins with one or two substituents in the 5,10- positions and no beta substituents. 5-Substituted porphyrins with only one meso substituent are easily prepared by an acid-catalyzed condensation of dipyrromethane, pyrrole-2-carbaldehyde. and an appropriate aldehyde using a "[2+1+1]" approach. Similarly, 5,10-disubstituted porphyrins are accessible by simple condensation of unsubstituted tripyrrane with pyrrole and various aldehydes using a "[3+1]" approach. The yields for these reactions are low to moderate and additional formation of either di- or mono-substituted porphyrins due to scrambling of the intermediates is observed. However, the reactions can be performed quite easily and the desired target compounds are easily removed due to large differences in solubility. A complementary and more selective synthesis involves the use of organolithium reagents for SNAr reactions. Reaction of in situ generated porphyrin (porphine) with 1.1-8 equivalents of RLi gave the monosubstituted porphyrins, while reaction with 3-6 equivalents of RLi gave the 5,10-disubstituted porphyrins in yields ranging from 43 to 90%. These hitherto almost inaccessible compounds complete the series of different homologues of A-, 5,15-A(2)-, 5,10-A(2)-, A(3)-, and A(4)-type porphyrin's and allow an investigation of the gradual influence of type, number, and regiochemical arrangement of substituents on the properties of meso-substituted porphyrins. They also present important starting materials for the synthesis of ABCD porphyrins and are potential synthons for supramolecular materials requiring specific substituent orientations Y1 - 2005 SN - 0947-6539 ER - TY - JOUR A1 - Blaum, Niels A1 - Schwager, Monika A1 - Wichmann, Matthias C. A1 - Rossmanith, Eva T1 - Climate induced changes in matrix suitability explain gene flow in a fragmented landscape - the effect of interannual rainfall variability JF - Ecography : pattern and diversity in ecology ; research papers forum N2 - In fragmented landscapes, the survival of species and the maintenance of populations with healthy genetic structures will largely depend on movement/dispersal of organisms across matrix areas. In this article, we highlight that effects of fragmentation and climate change occur simultaneously and may enhance or mitigate each other. We systematically analyzed the effect of increasing interannual variation in rainfall on the genetic structure of two neighbouring small mammal subpopulations in a fragmented savanna landscape. The effect of interannual rainfall variation is analyzed for two contrasting scenarios that differ in mean annual rainfall and are both close to a dispersal threshold. Scenario 1 (low mean annual rainfall) lies slightly below this threshold and scenario 2 (high mean annual rainfall) slightly above, i.e. the amount of rainfall in an average rainfall year prevents dispersal in scenario 1, but promotes gene flow in scenario 2. We show that the temporal dynamics of the matrix was crucial for gene flow and the genetic structure of the neighbouring small mammal subpopulations. The most important result is that the increase in rainfall variability could both increase and decrease the genetic difference between the subpopulations in a complex pattern, depending on the scenario and on the amount of variation in rainfall. Finally, we discuss that the relevance of the matrix as temporarily suitable habitat may become a key aspect for biodiversity conservation. We conclude to incorporate temporal changes in matrix suitability in metapopulation theory since local extinctions, gene flow and re-colonization are likely to be affected in fragmented landscapes with such dynamic matrix areas. Y1 - 2012 U6 - https://doi.org/10.1111/j.1600-0587.2011.07154.x SN - 0906-7590 VL - 35 IS - 7 SP - 650 EP - 660 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Dietze, Elisabeth A1 - Mangelsdorf, Kai A1 - Andreev, Andrei A1 - Karger, Cornelia A1 - Schreuder, Laura T. A1 - Hopmans, Ellen C. A1 - Rach, Oliver A1 - Sachse, Dirk A1 - Wennrich, Volker A1 - Herzschuh, Ulrike T1 - Relationships between low-temperature fires, climate and vegetation during three late glacials and interglacials of the last 430 kyr in northeastern Siberia reconstructed from monosaccharide anhydrides in Lake El’gygytgyn sediments JF - Climate of the Past N2 - Landscapes in high northern latitudes are assumed to be highly sensitive to future global change, but the rates and long-term trajectories of changes are rather uncertain. In the boreal zone, fires are an important factor in climate-vegetation interactions and biogeochemical cycles. Fire regimes are characterized by small, frequent, low-intensity fires within summergreen boreal forests dominated by larch, whereas evergreen boreal forests dominated by spruce and pine burn large areas less frequently but at higher intensities. Here, we explore the potential of the monosaccharide anhydrides (MA) levoglucosan, mannosan and galactosan to serve as proxies of low-intensity biomass burning in glacial-to-interglacial lake sediments from the high northern latitudes. We use sediments from Lake El'gygytgyn (cores PG 1351 and ICDP 5011-1), located in the far north-east of Russia, and study glacial and interglacial samples of the last 430 kyr (marine isotope stages 5e, 6, 7e, 8, 11c and 12) that had different climate and biome configurations. Combined with pollen and non-pollen palynomorph records from the same samples, we assess how far the modern relationships between fire, climate and vegetation persisted during the past, on orbital to centennial timescales. We find that MAs attached to particulates were well-preserved in up to 430 kyr old sediments with higher influxes from low-intensity biomass burning in interglacials compared to glacials. MA influxes significantly increase when summergreen boreal forest spreads closer to the lake, whereas they decrease when tundra-steppe environments and, especially, Sphagnum peatlands spread. This suggests that low-temperature fires are a typical characteristic of Siberian larch forests also on long timescales. The results also suggest that low-intensity fires would be reduced by vegetation shifts towards very dry environments due to reduced biomass availability, as well as by shifts towards peatlands, which limits fuel dryness. In addition, we observed very low MA ratios, which we interpret as high contributions of galactosan and mannosan from biomass sources other than those currently monitored, such as the moss-lichen mats in the understorey of the summergreen boreal forest. Overall, sedimentary MAs can provide a powerful proxy for fire regime reconstructions and extend our knowledge of long-term natural fire-climate-vegetation feedbacks in the high northern latitudes. KW - molecular tracers KW - organic aerosols KW - emission factors KW - carbonaceous aerosols KW - pollen records KW - core PG1351 KW - biomass KW - holocene KW - levoglucosan KW - charcoal Y1 - 2020 U6 - https://doi.org/10.5194/cp-16-799-2020 SN - 1814-9332 SN - 1814-9324 VL - 16 IS - 2 SP - 788 EP - 818 PB - Copernicus Publications CY - Göttingen ER - TY - JOUR A1 - Wang, Y. A1 - Herzschuh, Ulrike A1 - Shumilovskikh, L. S. A1 - Mischke, Steffen A1 - Birks, H. John B. A1 - Wischnewski, J. A1 - Böhner, Jürgen A1 - Schluetz, F. A1 - Lehmkuhl, F. A1 - Diekmann, Bernhard A1 - Wuennemann, B. A1 - Zhang, C. T1 - Open Access Quantitative reconstruction of precipitation changes on the NE Tibetan Plateau since the Last Glacial Maximum - extending the concept of pollen source area to pollen-based climate reconstructions from large lakes JF - Climate of the past : an interactive open access journal of the European Geosciences Union N2 - Pollen records from large lakes have been used for quantitative palaeoclimate reconstruction, but the influences that lake size (as a result of species-specific variations in pollen dispersal patterns that smaller pollen grains are more easily transported to lake centre) and taphonomy have on these climatic signals have not previously been systematically investigated. We introduce the concept of pollen source area to pollen-based climate calibration using the north-eastern Tibetan Plateau as our study area. We present a pollen data set collected from large lakes in the arid to semi-arid region of central Asia. The influences that lake size and the inferred pollen source areas have on pollen compositions have been investigated through comparisons with pollen assemblages in neighbouring lakes of various sizes. Modern pollen samples collected from different parts of Lake Donggi Cona (in the north-eastern part of the Tibetan Plateau) reveal variations in pollen assemblages within this large lake, which are interpreted in terms of the species-specific dispersal and depositional patterns for different types of pollen, and in terms of fluvial input components. We have estimated the pollen source area for each lake individually and used this information to infer modern climate data with which to then develop a modern calibration data set, using both the multivariate regression tree (MRT) and weighted-averaging partial least squares (WA-PLS) approaches. Fossil pollen data from Lake Donggi Cona have been used to reconstruct the climate history of the north-eastern part of the Tibetan Plateau since the Last Glacial Maximum (LGM). The meanannual precipitation was quantitatively reconstructed using WA-PLS: extremely dry conditions are found to have dominated the LGM, with annual precipitation of around 100 mm, which is only 32% of present-day precipitation. A gradually increasing trend in moisture conditions during the Late Glacial is terminated by an abrupt reversion to a dry phase that lasts for about 1000 yr and coincides with "Heinrich event 1" in the North Atlantic region. Subsequent periods corresponding to the Bolling/Allerod interstadial, with annual precipitation (P-ann) of about 350 mm, and the Younger Dryas event (about 270 mm P-ann) are followed by moist conditions in the early Holocene, with annual precipitation of up to 400 mm. A drier trend after 9 cal. ka BP is followed by a second wet phase in the middle Holocene, lasting until 4.5 cal. ka BP. Relatively steady conditions with only slight fluctuations then dominate the late Holocene, resulting in the present climatic conditions. The climate changes since the LGM have been primarily driven by deglaciation and fluctuations in the intensity of the Asian summer monsoon that resulted from changes in the Northern Hemisphere summer solar insolation, as well as from changes in the North Atlantic climate through variations in the circulation patterns and intensity of the westerlies. Y1 - 2014 U6 - https://doi.org/10.5194/cp-10-21-2014 SN - 1814-9324 SN - 1814-9332 VL - 10 IS - 1 SP - 21 EP - 39 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Al-Sa'di, Mahmoud A1 - Jaiser, Frank A1 - Bagnich, Sergey A. A1 - Unger, Thomas A1 - Blakesley, James C. A1 - Wilke, Andreas A1 - Neher, Dieter T1 - Electrical and optical simulations of a polymer-based phosphorescent organic light-emitting diode with high efficiency JF - Journal of polymer science : B, Polymer physics N2 - A comprehensive numerical device simulation of the electrical and optical characteristics accompanied with experimental measurements of a new highly efficient system for polymer-based light-emitting diodes doped with phosphorescent dyes is presented. The system under investigation comprises an electron transporter attached to a polymer backbone blended with an electronically inert small molecule and an iridium-based green phosphorescent dye which serves as both emitter and hole transporter. The device simulation combines an electrical and an optical model. Based on the known highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels of all components as well as the measured electrical and optical characteristics of the devices, we model the emissive layer as an effective medium using the dye's HOMO as hole transport level and the polymer LUMO as electron transport level. By fine-tuning the injection barriers at the electron and hole-injecting contact, respectively, in simulated devices, unipolar device characteristics were fitted to the experimental data. Simulations using the so-obtained set of parameters yielded very good agreement to the measured currentvoltage, luminancevoltage characteristics, and the emission profile of entire bipolar light-emitting diodes, without additional fitting parameters. The simulation was used to gain insight into the physical processes and the mechanisms governing the efficiency of the organic light-emitting diode, including the position and extent of the recombination zone, carrier concentration profiles, and field distribution inside the device. The simulations show that the device is severely limited by hole injection, and that a reduction of the hole-injection barrier would improve the device efficiency by almost 50%. KW - conjugated polymers KW - high performance polymers KW - organic electronics KW - organic light-emitting diode KW - simulations KW - TCAD Y1 - 2012 U6 - https://doi.org/10.1002/polb.23158 SN - 0887-6266 VL - 50 IS - 22 SP - 1567 EP - 1576 PB - Wiley-Blackwell CY - Hoboken ER -