Gold Open-Access
Refine
Year of publication
Document Type
- Article (2374)
- Review (84)
- Monograph/Edited Volume (73)
- Other (43)
- Part of Periodical (40)
- Conference Proceeding (29)
- Part of a Book (22)
- Master's Thesis (19)
- Doctoral Thesis (17)
- Report (12)
Language
- English (2088)
- German (587)
- Spanish (29)
- French (19)
- Multiple languages (4)
- Italian (3)
- Russian (3)
- Portuguese (2)
Keywords
- digital education (37)
- e-learning (37)
- MOOC (35)
- online course creation (33)
- online course design (33)
- Digitale Bildung (32)
- Kursdesign (32)
- Micro Degree (32)
- Online-Lehre (32)
- Onlinekurs (32)
Institute
- Institut für Biochemie und Biologie (413)
- Extern (367)
- Institut für Geowissenschaften (247)
- Institut für Physik und Astronomie (216)
- Institut für Romanistik (169)
- Institut für Umweltwissenschaften und Geographie (153)
- Historisches Institut (146)
- Hasso-Plattner-Institut für Digital Engineering GmbH (125)
- Department Sport- und Gesundheitswissenschaften (115)
- Institut für Ernährungswissenschaft (102)
Reference values and validation of the 1-minute sit-to-stand test in healthy 5-16-year-old youth
(2021)
Objectives:
It is essential to have simple, reliable and valid tests to measure children's functional capacity in schools or medical practice. The 1-minute sit-to-stand (STS) test is a quick fitness test requiring little equipment or space that is increasingly used in both healthy populations and those with chronic disease. We aimed to provide age-specific and sex-specific reference values of STS test in healthy children and adolescents and to evaluate its short-term reliability and construct validity.
Design setting and participants:
Cross-sectional convenience sample from six public schools and one science fair in central Europe. Overall, 587 healthy participants aged 5-16 years were recruited and divided into age groups of 3 years each.
Outcomes:
1-minute STS. To evaluate short-term reliability, some children performed the STS test twice. To evaluate construct validity, some children also performed a standing long jump (SLJ) and a maximal incremental exercise test.
Results:
Data from 547 youth aged 5-16 years were finally included in the analyses. The median number of repetitions in 1 min in males (females) ranged from 55 [95% CI: 38 to 72] (53 [95% CI: 35 to 76]) in 14-16-year olds to 59 [95% CI: 41 to 77] (60 [95% CI: 38 to 77]) in 8-10-year olds. Children who repeated STS showed a learning effect of on average 4.8 repetitions more than the first test (95% limits of agreement: -6.7 to 16.4). Moderate correlations were observed between the STS and the SLJ (r=0.48) tests and the maximal exercise test (r=0.43).
Conclusions:
The reported STS reference values can be used to interpret STS test performance in children and adolescents. The STS appears to have good test- retest reliability, but a learning effect of about 10%. The association of STS with other measures of physical fitness should be further explored in a larger study and technical standards for its conduct are needed.
The current paradigm of cosmic-ray (CR) origin states that the greater part of galactic CRs is produced by supernova remnants. The interaction of supernova ejecta with the interstellar medium after a supernova's explosions results in shocks responsible for CR acceleration via diffusive shock acceleration (DSA). We use particle-in-cell (PIC) simulations and a combined PIC-magnetohydrodynamic (PIC-MHD) technique to investigate whether DSA can occur in oblique high Mach number shocks. Using the PIC method, we follow the formation of the shock and determine the fraction of the particles that gets involved in DSA. With this result, we use PIC-MHD simulations to model the large-scale structure of the plasma and the magnetic field surrounding the shock and find out whether or not the reflected particles can generate upstream turbulence and trigger DSA. We find that the feasibility of this process in oblique shocks depends strongly on the Alfvenic Mach number, and the DSA process is more likely to be triggered at high Mach number shocks.
We present two new empirical models of radiation belt electron flux at geostationary orbit. GOES-15 measurements of 0.8 MeV electrons were used to train a Nonlinear Autoregressive with Exogenous input (NARX) neural network for both modeling GOES-15 flux values and an upper boundary condition scaling factor (BF). The GOES-15 flux model utilizes an input and feedback delay of 2 and 2 time steps (i.e., 5 min time steps) with the most efficient number of hidden layers set to 10. Magnetic local time, Dst, Kp, solar wind dynamic pressure, AE, and solar wind velocity were found to perform as predicative indicators of GOES-15 flux and therefore were used as the exogenous inputs. The NARX-derived upper boundary condition scaling factor was used in conjunction with the Versatile Electron Radiation Belt (VERB) code to produce reconstructions of the radiation belts during the period of July-November 1990, independent of in-situ observations. Here, Kp was chosen as the sole exogenous input to be more compatible with the VERB code. This Combined Release and Radiation Effects Satellite-era reconstruction showcases the potential to use these neural network-derived boundary conditions as a method of hindcasting the historical radiation belts. This study serves as a companion paper to another recently published study on reconstructing the radiation belts during Solar Cycles 17-24 (Saikin et al., 2021, ), for which the results featured in this paper were used.
Regional flood frequency analysis (RFFA) is a powerful method for interrogating hydrological series since it combines observational time series from several sites within a region to estimate risk-relevant statistical parameters with higher accuracy than from single-site series. Since RFFA extreme value estimates depend on the shape of the selected distribution of the data-generating stochastic process, there is need for a suitable goodness-of-distributional-fit measure in order to optimally utilize given data. Here we present a novel, least-squares-based measure to select the optimal fit from a set of five distributions, namely Generalized Extreme Value (GEV), Generalized Logistic, Gumbel, Log-Normal Type III and Log-Pearson Type III. The fit metric is applied to annual maximum discharge series from six hydrological stations along the Sava River in South-eastern Europe, spanning the years 1961 to 2020. Results reveal that (1) the Sava River basin can be assessed as hydrologically homogeneous and (2) the GEV distribution provides typically the best fit. We offer hydrological-meteorological insights into the differences among the six stations. For the period studied, almost all stations exhibit statistically insignificant trends, which renders the conclusions about flood risk as relevant for hydrological sciences and the design of regional flood protection infrastructure.
Climate Benefits of Cleaner Energy Transitions in East and South Asia Through Black Carbon Reduction
(2022)
The state of air pollution has historically been tightly linked to how we produce and use energy. Air pollutant emissions over Asia are now changing rapidly due to cleaner energy transitions; however, magnitudes of benefits for climate and air quality remain poorly quantified. The associated risks involve adverse health impacts, reduced agricultural yields, reduced freshwater availability, contributions to climate change, and economic costs. We focus particularly on climate benefits of energy transitions by making first-time use of two decades of high quality observations of atmospheric loading of light-absorbing black carbon (BC) over Kanpur (South Asia) and Beijing (East Asia) and relating these observations to changing energy, emissions, and economic trends in India and China. Our analysis reveals that absorption aerosol optical depth (AAOD) due to BC has decreased substantially, by 40% over Kanpur and 60% over Beijing between 2001 and 2017, and thus became decoupled from regional economic growth. Furthermore, the resultant decrease in BC emissions and BC AAOD over Asia is regionally coherent and occurs primarily due to transitions into cleaner energies (both renewables and fossil fuels) and not due to the decrease in primary energy supply or decrease in use of fossil use and biofuels and waste. Model simulations show that BC aerosols alone contribute about half of the surface temperature change (warming) of the total forcing due to greenhouse gases, natural and internal variability, and aerosols, thus clearly revealing the climate benefits due to a reduction in BC emissions, which would significantly reduce global warming. However, this modeling study excludes responses from natural variability, circulation, and sea ice responses, which cause relatively strong temperature fluctuations that may mask signals from BC aerosols. Our findings show additional benefits for climate (beyond benefits of CO2 reduction) and for several other issues of sustainability over South and East Asia, provide motivation for ongoing cleaner energy production, and consumption transitions, especially when they are associated with reduced emissions of air pollutants. Such an analysis connecting the trends in energy transitions and aerosol absorption loading, unavailable so far, is crucial for simulating the aerosol climate impacts over Asia which is quite uncertain.
The analysis of event time series is in general challenging. Most time series analysis tools are limited for the analysis of this kind of data. Recurrence analysis, a powerful concept from nonlinear time series analysis, provides several opportunities to work with event data and even for the most challenging task of comparing event time series with continuous time series. Here, the basic concept is introduced, the challenges are discussed, and the future perspectives are summarized.
A detailed investigation of the energy levels of perylene-3,4,9,10-tetracarboxylic tetraethylester as a representative compound for the whole family of perylene esters was performed. It was revealed via electrochemical measurements that one oxidation and two reductions take place. The bandgaps determined via the electrochemical approach are in good agreement with the optical bandgap obtained from the absorption spectra via a Tauc plot. In addition, absorption spectra in dependence of the electrochemical potential were the basis for extensive quantum-chemical calculations of the neutral, monoanionic, and dianionic molecules. For this purpose, calculations based on density functional theory were compared with post-Hartree-Fock methods and the CAM-B3LYP functional proved to be the most reliable choice for the calculation of absorption spectra. Furthermore, spectral features found experimentally could be reproduced with vibronic calculations and allowed to understand their origins. In particular, the two lowest energy absorption bands of the anion are not caused by absorption of two distinct electronic states, which might have been expected from vertical excitation calculations, but both states exhibit a strong vibronic progression resulting in contributions to both bands.
Elucidation of the reaction mechanism for the synthesis of ZnGeN2 through Zn2GeO4 ammonolysis
(2021)
Ternary II-IV-N-2 materials have been considered as a promising class of materials that combine photovoltaic performance with earth-abundance and low toxicity. When switching from binary III-V materials to ternary II-IV-N-2 materials, further structural complexity is added to the system that may influence its optoelectronic properties. Herein, we present a systematic study of the reaction of Zn2GeO4 with NH3 that produces zinc germanium oxide nitrides, and ultimately approach stoichiometric ZnGeN2, using a combination of chemical analyses, X-ray powder diffraction and DFT calculations. Elucidating the reaction mechanism as being dominated by Zn and O extrusion at the later reaction stages, we give an insight into studying structure-property relationships in this emerging class of materials.
This study deals with the facile synthesis of Fe1-xS nanoparticle-containing nitrogen-doped porous carbon membranes (denoted as Fe1-xS/N-PCMs) via vacuum carbonization of hybrid porous poly(ionic liquid) (PIL) membranes, and their successful use as a sulfur host material to mitigate the shuttle effect in lithium-sulfur (Li-S) batteries. The hybrid porous PIL membranes as the sacrificial template were prepared via ionic crosslinking of a cationic PIL with base-neutralized 1,1 '-ferrocenedicarboxylic acid, so that the iron source was molecularly incorporated into the template. The carbonization process was investigated in detail at different temperatures, and the chemical and porous structures of the carbon products were comprehensively analyzed. The Fe1-xS/N-PCMs prepared at 900 degrees C have a multimodal pore size distribution with a satisfactorily high surface area and well-dispersed iron sulfide nanoparticles to physically and chemically confine the LiPSs. The sulfur/Fe1-xS/N-PCM composites were then tested as electrodes in Li-S batteries, showing much improved capacity, rate performance and cycle stability, in comparison to iron sulfide-free, nitrogen-doped porous carbon membranes.
(1) Background:
Adaptive diversification of complex traits plays a pivotal role in the evolution of organismal diversity. In the freshwater snail genus Tylomelania, adaptive radiations were likely promoted by trophic specialization via diversification of their key foraging organ, the radula.
(2) Methods:
To investigate the molecular basis of radula diversification and its contribution to lineage divergence, we used tissue-specific transcriptomes of two sympatric Tylomelania sarasinorum ecomorphs.
(3) Results:
We show that ecomorphs are genetically divergent lineages with habitat-correlated abundances. Sequence divergence and the proportion of highly differentially expressed genes are significantly higher between radula transcriptomes compared to the mantle and foot. However, the same is not true when all differentially expressed genes or only non-synonymous SNPs are considered. Finally, putative homologs of some candidate genes for radula diversification (hh, arx, gbb) were also found to contribute to trophic specialization in cichlids and Darwin's finches.
(4) Conclusions:
Our results are in line with diversifying selection on the radula driving Tylomelania ecomorph divergence and indicate that some molecular pathways may be especially prone to adaptive diversification, even across phylogenetically distant animal groups.
About 15 years ago, the first Massive Open Online Courses (MOOCs) appeared and revolutionized online education with more interactive and engaging course designs. Yet, keeping learners motivated and ensuring high satisfaction is one of the challenges today's course designers face. Therefore, many MOOC providers employed gamification elements that only boost extrinsic motivation briefly and are limited to platform support. In this article, we introduce and evaluate a gameful learning design we used in several iterations on computer science education courses. For each of the courses on the fundamentals of the Java programming language, we developed a self-contained, continuous story that accompanies learners through their learning journey and helps visualize key concepts. Furthermore, we share our approach to creating the surrounding story in our MOOCs and provide a guideline for educators to develop their own stories. Our data and the long-term evaluation spanning over four Java courses between 2017 and 2021 indicates the openness of learners toward storified programming courses in general and highlights those elements that had the highest impact. While only a few learners did not like the story at all, most learners consumed the additional story elements we provided. However, learners' interest in influencing the story through majority voting was negligible and did not show a considerable positive impact, so we continued with a fixed story instead. We did not find evidence that learners just participated in the narrative because they worked on all materials. Instead, for 10-16% of learners, the story was their main course motivation. We also investigated differences in the presentation format and concluded that several longer audio-book style videos were most preferred by learners in comparison to animated videos or different textual formats. Surprisingly, the availability of a coherent story embedding examples and providing a context for the practical programming exercises also led to a slightly higher ranking in the perceived quality of the learning material (by 4%). With our research in the context of storified MOOCs, we advance gameful learning designs, foster learner engagement and satisfaction in online courses, and help educators ease knowledge transfer for their learners.
Editorial
(2023)
Phytoliths in particulate matter released by wind erosion on arable land in La Pampa, Argentina
(2022)
Silicon (Si) is considered a beneficial element in plant nutrition, but its importance on ecosystems goes far beyond that. Various forms of silicon are found in soils, of which the phytogenic pool plays a decisive role due to its good availability. This Si returns to the soil through the decomposition of plant residues, where they then participate in the further cycle as biogenic amorphous silica (bASi) or so-called phytoliths. These have a high affinity for water, so that the water holding capacity and water availability of soils can be increased even by small amounts of ASi. Agricultural land is a considerable global dust source, and dust samples from arable land have shown in cloud formation experiments a several times higher ice nucleation activity than pure mineral dust. Here, particle sizes in the particulate matter fractions (PM) are important, which can travel long distances and reach high altitudes in the atmosphere. Based on this, the research question was whether phytoliths could be detected in PM samples from wind erosion events, what are the main particle sizes of phytoliths and whether an initial quantification was possible.Measurements of PM concentrations were carried out at a wind erosion measuring field in the province La Pampa, Argentina. PM were sampled during five erosion events with Environmental Dust Monitors (EDM). After counting and classifying all particles with diameters between 0.3 and 32 mu m in the EDMs, they are collected on filters. The filters were analyzed by Scanning Electron Microscopy and Energy Dispersive X-Ray analysis (SEM-EDX) to investigate single or ensembles of particles regarding composition and possible origins.The analyses showed up to 8.3 per cent being phytoliths in the emitted dust and up to 25 per cent of organic origin. Particles of organic origin are mostly in the coarse dust fraction, whereas phytoliths are predominately transported in the finer dust fractions. Since phytoliths are both an important source of Si as a plant nutrient and are also involved in soil C fixation, their losses from arable land via dust emissions should be considered and its specific influence on atmospheric processes should be studied in detail in the future.
Comprehensive untargeted and targeted analysis of root exudate composition has advanced our understanding of rhizosphere processes. However, little is known about exudate spatial distribution and regulation. We studied the specific metabolite signatures of asparagus root exudates, root outer (epidermis and exodermis), and root inner tissues (cortex and vasculature). The greatest differences were found between exudates and root tissues. In total, 263 non-redundant metabolites were identified as significantly differentially abundant between the three root fractions, with the majority being enriched in the root exudate and/or outer tissue and annotated as 'lipids and lipid-like molecules' or 'phenylpropanoids and polyketides'. Spatial distribution was verified for three selected compounds using MALDI-TOF mass spectrometry imaging. Tissue-specific proteome analysis related root tissue-specific metabolite distributions and rhizodeposition with underlying biosynthetic pathways and transport mechanisms. The proteomes of root outer and inner tissues were spatially very distinct, in agreement with the fundamental differences between their functions and structures. According to KEGG pathway analysis, the outer tissue proteome was characterized by a high abundance of proteins related to 'lipid metabolism', 'biosynthesis of other secondary metabolites' and 'transport and catabolism', reflecting its main functions of providing a hydrophobic barrier, secreting secondary metabolites, and mediating water and nutrient uptake. Proteins more abundant in the inner tissue related to 'transcription', 'translation' and 'folding, sorting and degradation', in accord with the high activity of cortical and vasculature cell layers in growth- and development-related processes. In summary, asparagus root fractions accumulate specific metabolites. This expands our knowledge of tissue-specific plant cell function.
Keine Reform für die Zukunft
(2021)
Am 1. Januar 2021 trat die jüngste Reform des Erneuerbare-Energien-Gesetzes (EEG) in Kraft. Sie führte mit der finanziellen Beteiligung der Gemeinden an den Erträgen der Windenergie klammheimlich eine verfassungswidrige Abgabe ein: Durch das Zusammenspiel des neuen § 36k EEG 2021 mit der altbekannten EEG-Umlage fließt eine bei den Strom-Endverbrauchern erhobene Abgabe in die kommunalen Haushalte. Das kann auf keine Gesetzgebungskompetenz gestützt werden. Darüber hinaus führt die Deckelung der EEG-Umlage in den Jahren 2021 und 2022 in Verbindung mit § 36k EEG 2021 dazu, dass in verfassungswidriger Weise Bundesmittel den Gemeinden zur freien Verfügung gestellt werden.
Restrictive means to reduce the spread of the COVID-19 pandemic have not only imposed broad challenges on mental health but might also affect cognitive health. Here we asked how restriction-related changes influence cognitive performance and how age, perceived loneliness, depressiveness and affectedness by restrictions contribute to these effects. 51 Germans completed three assessments of an online based study during the first lockdown in Germany (April 2020), a month later, and during the beginning of the second lockdown (November 2020). Participants completed nine online cognitive tasks of the MyBrainTraining and online questionnaires about their perceived strain and impact on lifestyle factors by the situation (affectedness), perceived loneliness, depressiveness as well as subjective cognitive performance. The results suggested a possible negative impact of depressiveness and affectedness on objective cognitive performance within the course of the lockdown. The younger the participants, the more pronounced these effects were. Loneliness and depressiveness moreover contributed to a worse evaluation of subjective cognition. In addition, especially younger individuals reported increased distress. As important educational and social input has partly been scarce during this pandemic and mental health problems have increased, future research should also assess cognitive long-term consequences.
Major international organizations (IOs) are heavily contested, but they are rarely dissolved. Scholars have focused on their longevity, making institutional arguments about replacement costs and institutional assets as well as IO agency to adapt and resist challenges. This article analyzes the limits of institutional stickiness by focusing on outlier cases. While major IOs are dissolved at considerably lower rates than minor IOs, the article nevertheless identifies twenty-one cases where major IOs have died since 1815. These are tough cases as they do not conform to our institutionalist expectations. To better understand these rare but important events, the article provides case illustrations from the League of Nations and International Refugee Organization, which were dissolved due to their perceived underperformance and a disappearing demand for cooperation. These cases show the limits of the institutional theories of IO stickiness: sometimes member states find high replacement costs justified or consider assets as sunk costs, and IOs may lack agency to strategically respond. This article refines theories of institutional stickiness and contributes to the institutional theory of the life and death of IOs.
Les principales organisations internationales (OI) sont fortement contestées, mais rarement dissoutes. Pour expliquer leur longévité, les chercheurs ont avancé des arguments institutionnels concernant les coûts de remplacement et les actifs de l'institution, mais aussi la capacité des OI à s'adapter et à résister aux défis. Cet article analyse les limites de la persistance des institutions en se concentrant sur des cas particuliers. Tandis que les principales OI sont dissoutes bien moins fréquemment que des OI moins importantes, cet article identifie néanmoins 21 cas de disparition d'OI principales depuis 1815. Ces derniers sont particulièrement difficiles, car ils ne correspondent pas à nos attentes en termes d'institutions. Afin de mieux comprendre ces événements rares, mais non moins importants, l'article propose comme illustrations de cas la Société des Nations et l'Organisation internationale pour les réfugiés, qui ont été dissoutes à cause de leur manque apparent de résultats et de la disparition de la demande de coopération. Ces cas mettent en évidence les limites des théories institutionnelles de persistance des OI : parfois, les États membres considèrent les coûts de remplacement élevés justifiés ou les actifs comme des coûts irrécupérables, et les OI n'ont peut-être pas la capacité de leur répondre de manière stratégique. Le présent article affine les théories de persistance institutionnelle et contribue à la théorie institutionnelle de vie et de mort des OI.
Las organizaciones internacionales (OI) más importantes son muy cuestionadas, pero rara vez se disuelven. Los investigadores se han centrado en la longevidad de las IO, formulando argumentos institucionales sobre los costes de sustitución y los activos institucionales, así como sobre la capacidad de adaptación y resistencia de las organizaciones internacionales. Este artículo analiza los límites de la rigidez institucional centrándose en casos atípicos. Aunque las OI más importantes se disuelven en proporciones considerablemente menores que las OI de menor importancia, el artículo identifica 21 casos en los que OI más importantes desaparecieron desde 1815. Se trata de casos difíciles, ya que no se ajustan a nuestras expectativas institucionalistas. Para comprender mejor estos raros pero importantes acontecimientos, el artículo ofrece ejemplos de casos de la Sociedad de Naciones y de la, Organización Internacional para los Refugiados que se disolvieron debido a su bajo desempeño percibido y a la desaparición de la demanda de cooperación. Estos casos muestran los límites de las teorías institucionales sobre la rigidez de las OI: En ocasiones, los Estados miembros consideran justificados los elevados costes de sustitución o consideran que los activos son costes irrecuperables, y las OI pueden no disponer de capacidad de respuesta estratégica. Este artículo profundiza en las teorías de la rigidez institucional y contribuye a la teoría institucional de la vida y la muerte de las organizaciones internacionales.
AUKUS und die strukturellen Veränderungen der sicherheitspolitischen Lage im indo-pazifischen Raum
(2022)
Vienna
(2021)
This book explores and debates the urban transformations that have taken place in Vienna over the past 30 years and their consequences in policy fields such as labour and housing, political and social participation and the environment. Historically, European cities have been characterised by a strong association between social cohesion, quality of life, economic ambition and a robust State. Vienna is an excellent example for that. In more recent years, however, cities were pressured to change policy principles and mechanisms in the context of demographic shifts, post-industrial transformations and welfare recalibration which have led to worsened social conditions in many cities. Each chapter in this volume discusses Vienna's responses to these pressures in key policy arenas, looking at outcomes from the context-specific local arrangements. Against a theoretical framework debating the European city as a model of inclusion and social justice, authors explore the local capacity to innovate urban policies and to address new social risks, while paying attention to potential trade-offs.
The book questions and assesses the city's resilience using time series and an institutional analysis of four key dimensions that characterise the European city model within the context of post-industrial transition: redistribution, recognition, representation and sustainability. It offers a multiscalar perspective of urban governance through labour, housing, participatory and environmental policies, bringing together different levels and public policy types.