Lunar impact basins are critical markers to understand the early bombardment history. This study focuses on isostatic compensation processes at 16 lunar farside basins, exploring how long-term alteration processes affect estimates of impactor sizes and timing. Using a lithospheric flexure model, we analyze the isostatically compensated gravity signature of these basins. Our approach is based on previously published basin formation models using the iSALE-2D shock physics code. Here we investigate how isostatic compensation processes alter the gravity signature using models of basin formation as initial conditions. We compare our results with the present day observed gravity data. We assume that isostatic compensation is the result of flexural deformation of the crust-mantle boundary with varying lithospheric elastic thicknesses. Our results indicate that the effect of isostatic compensation on the gravity signature varies depending on the thermal conditions at the time of impact. We find that despite this variability, the overall influence of isostatic compensation on the gravity signature is generally moderate to minor. Additionally, our analysis is consistent with previous studies that have shown that the elastic thickness varies across the Moon. Our findings contribute to our understanding of the relationship between basin formation and the thermal evolution of the Moon. The variations in elastic thickness found provide nuanced insights into lunar geological processes and improve our understanding of the early history of the Moon.
Weniger anzeigenThe study of environmental ancient DNA provides us with the unique opportunity to link environmental with ecosystem change over a millennial timescale. Paleorecords such as lake sediments contain genetic pools of past living organisms that are a valuable source of information to reconstruct how ecosystems were and how they changed in response to climate in the past. Here, we report on paleometagenomics of a sedimentary record in northern Siberia covering the past 6700 years. We integrated taxonomic with functional gene analysis, which enabled to shed light not only on community compositions but also on eco-physiological adaptations and ecosystem functioning. We reconstructed the presence of an open boreal forest 6700 years ago that over time was gradually replaced by tundra. This vegetation change had major consequences on the environmental microbiome, primarily enriching bacterial and archaeal ammonia oxidizers (e.g., Nitrospira, Nitrosopumilus, and Ca. Nitrosocosmicus) in the tundra ecosystem. We identified a core microbiome conserved through time and largely consisting of heterotrophic bacteria of the Bacteroidetes phylum (e.g., Mucilaginibacter) harboring numerous functional genes for degradation of plant-biomass and abiotic and biotic stress resistance. Archaea were also a key functional guild, involved in nitrogen and carbon cycling, not only methanogenesis but possibly also degradation of plant material via enzymes such as cellulases and amylases. Overall, the paleo-perspective offered by our study can have a profound impact on modern climate change biology, by helping to explain and predict the ecological interplay among multiple ecosystem levels based on past experiences.
Weniger anzeigenIn this work, we analyzed trifluoromethyl fluorosulfonate (CF3OSO2F) and trifluoromethoxy sulfur pentafluoride (CF3OSF5) regarding their potential use as dielectrics by investigating some of their intrinsic and extrinsic properties. Both compounds show a higher breakdown voltage than SF6 with averaged relative breakdown voltages of 1.3±0.2 for CF3OSO2F and 1.4±0.2 for CF3OSF5 compared to SF6 with 1.0. Like the dielectric (CF3)2CFCN, both compounds decompose during the breakdown process. The decomposition products were analyzed by IR spectroscopy and GCIR methods. Furthermore, the molecular structures of both gaseous compounds CF3OSO2F and CF3OSF5 have been determined by in situ crystallization, and their physical properties were determined as well.
Weniger anzeigenDecreased long-range temporal correlations (LRTC) in brain signals can be used to measure cognitive effort during task execution. Here, we examined how learning a motor sequence affects long-range temporal memory within resting-state functional magnetic resonance imaging signal. Using the Hurst exponent (HE), we estimated voxel-wise LRTC and assessed changes over 5 consecutive days of training, followed by a retention scan 12 days later. The experimental group learned a complex visuomotor sequence while a complementary control group performed tightly matched movements. An interaction analysis revealed that HE decreases were specific to the complex sequence and occurred in well-known motor sequence learning associated regions including left supplementary motor area, left premotor cortex, left M1, left pars opercularis, bilateral thalamus, and right striatum. Five regions exhibited moderate to strong negative correlations with overall behavioral performance improvements. Following learning, HE values returned to pretraining levels in some regions, whereas in others, they remained decreased even 2 weeks after training. Our study presents new evidence of HE's possible relevance for functional plasticity during the resting-state and suggests that a cortical subset of sequence-specific regions may continue to represent a functional signature of learning reflected in decreased long-range temporal dependence after a period of inactivity.
Weniger anzeigenWater tanks as traditional rainwater harvesting systems for agriculture are widely distributed in South India. They have a strong impact on hydrological processes, affecting streamflow in rivers as well as evapotranspiration. This study aims at an accurate representation of water harvesting systems in a hydrologic model to improve model performance and assessment of the catchment water balance. To this end, spatio-temporal variations of water bodies between the years 2016 and 2018 and the months of January and May 2017 were derived from Sentinel-2 satellite data to parameterize the water tanks (reservoir) parameters in the Soil and Water Assessment Tool (SWAT+) model of the Adyar basin, Chennai, India. Approximately 16% of the basin is covered by water tanks. The initial model performance was evaluated for two model setups, with and without water tanks. The best model run was selected with a multi-metric approach comparing observed and modelled monthly streamflow for 5000 model runs. The final model evaluation was carried out by comparing estimated water body areas by the model and remote sensing observations for January to May 2017. The results showed that representing water tanks in the hydrologic model led to an improvement in the representation of the seasonal variations of streamflow for the whole simulation period (2004–2018). The model performance was classified as good and very good for the calibration (2004–2011) and validation (2012–2018) periods as NSE varies between 0.67 and 0.85, KGE varies between 0.65 and 0.72, PBIAS varies between −24.1 and −23.6, and RSR varies between 0.57 and 0.39. The best fit was shown for the high and middle flow segments of the hydrograph where the coefficient of determination (R2) ranges from 0.81 to 0.97 and 0.75 to 0.81, respectively. The monthly variation of water body areas in 2017 estimated by the hydrologic model was consistent with changes observed in remote sensing surveys. In summary, the water tank parametrization using remote sensing techniques enhanced the hydrologic model's efficiency and applicability for future studies.
Weniger anzeigenhe adoption of COVID-19 contact tracing apps (CTAs) has been proposed as an important measure to contain the spread of COVID-19. Based on a cross-national dataset, this article analyzes public perceptions toward CTAs and the factors that drive CTA acceptance in China, Germany, and the United States. We find that public acceptance of CTAs is significantly higher in China as compared with Germany and the United States. Despite very different sociopolitical contexts, there are striking similarities in the factors that drive CTA acceptance in all three countries. Citizens are willing to accept digital contact tracing despite concerns about privacy infringement and government surveillance, as long as the apps are perceived as effective in lowering infection rates and providing health information. This creates a chicken-and-egg problem for CTAs in Germany and the United States where CTAs are voluntary: a high citizen adoption rate is necessary for CTAs to be effective, but CTAs are only effective if adoption rates are high.
Weniger anzeigenSituational judgment tests (SJTs) are popular instruments in selection and assessment. However, the application of SJTs to non-Western cultural contexts remains scarce. In this study, we investigated whether an SJT on personal initiative, developed in Germany and translated into Cuban Spanish, had similar psychometric properties in Cuba. Second, there is an ongoing debate about the extent to which the situation description plays an important role for SJTs. We supposed that the impact of situation descriptions might depend on test takers’ familiarity with the culture in which the SJT was developed. Hence, we tested whether the omission of situation descriptions had larger effects in a Cuban than in a German sample. We applied a 2 (with vs. without situation description in the item stem) × 2 (cultural background: Cuba vs. Germany) between-subjects design (NCuba = 192, NGermany = 213). The results revealed similar psychometric properties between Cuban and German test takers concerning measurement invariance, construct-related validity, and reliability. In addition, we examined whether samples differ regarding applicant perceptions: Notably, for four of six applicant perception scales, the Cuban sample reported a more positive view of the SJT. Furthermore, we found that the effect of situation availability on SJT performance did not substantially depend on the test takers’ cultural background. Implications for cross-cultural generalizability are discussed.
Weniger anzeigenCompanionship is related to better affect and relationship satisfaction, but few studies have examined both partners' perspectives over time and the link between companionship and health. In three intensive longitudinal studies (Study 1: 57 community couples; Study 2: 99 smoker–nonsmoker couples; Study 3: 83 dual-smoker couples), both partners reported daily companionship, affect, relationship satisfaction, and a health behavior (smoking in Studies 2 and 3). We proposed a dyadic score model that focuses on the couple level for companionship as a dyadic predictor with considerable shared variance. On days with higher companionship, couples reported better affect and relationship satisfaction. When partners differed in companionship, they also differed in affect and relationship satisfaction. For smoking, a different picture emerged: Whereas smokers with nonsmoking partners smoked less on average with higher companionship, smokers with smoking partners smoked more on days with higher companionship. Findings show companionship as a consequential relationship construct deserving further study. Using the dyadic score model acknowledged both partners' perspectives on companionship. It demonstrated higher precision for detecting effects of partner averages in a dyadic predictor compared with traditional approaches, tests for effects of partner differences in a dyadic predictor and in outcome while maintaining the focus on the dyad.
Weniger anzeigenOver the past 3 years, employees have constantly witnessed how their organizations have responded to the challenges posed by the COVID-19 pandemic. Here, we hypothesize that employees' perceptions of the COVID-19 safety climate of their organization positively affect their vaccine readiness. To examine the underlying mechanisms of this effect, we use a self-perception theory lens. Thus, we hypothesize that an organization's COVID-19 safety climate affects employees' COVID-19 vaccine readiness through employees' adherence to COVID-19 guidelines. We conducted a time-lagged study over the time span of 1 year (N = 351) to test our hypotheses. In general, results support our hypotheses. In particular, results showed that perceived COVID-19 safety climate assessed at an early stage of the pandemic (April 2020, when no vaccines were available) predicted employees' COVID-19 vaccine readiness more than a year later. In line with self-perception theory, this effect was mediated by employees' adherence to COVID-19 guidelines. The present study provides theoretical insight into the underlying mechanisms of organizational climate on employees' attitudes. From a practical perspective, our results suggest that organizations are a powerful lever for promoting vaccine readiness.
Weniger anzeigenA layer of laminins, assembled on a thin sheet of collagen type IV (Col-IV) forms the backbone of the basal lamina, which controls biological processes such as embryogenesis, tissue homeostasis, and development. Here, the dynamic functions of laminin-111 (Lam-111) in ultrathin films at the air–water interface are investigated. It is shown that the 2D confinement induces polymerization and that expansion via adlayer formation occurs only with extended growth time. The highly robust self-assembly enables the functionalization of surfaces with cross-linked 2D Lam-111 networks of defined thickness using little more than a beaker. The 2D laminin material also displays two dynamic functions required for the maintenance of tissues – the capability for self-renewal and self-healing. By assembling Lam-111 2D networks at the surface of Col-IV sheets, freestanding bilayers closely mimicking the basal lamina can be produced in vitro. There is a marked difference in miPSC spreading and adhesion force between Lam-111 sheets assembled in the presence or absence of Col-IV. These fundamental studies highlight the importance of dynamic functions, encoded into the molecular structure of the building blocks, for the assembly, maintenance, and functioning of the complex material systems found in natural tissues and can provide cues for the molecular design of resilient technical systems.
Weniger anzeigenOne of the most natural connections between quantum and classical machine learning has been established in the context of kernel methods. Kernel methods rely on kernels, which are inner products of feature vectors living in large feature spaces. Quantum kernels are typically evaluated by explicitly constructing quantum feature states and then taking their inner product, here called embedding quantum kernels. Since classical kernels are usually evaluated without using the feature vectors explicitly, we wonder how expressive embedding quantum kernels are. In this work, we raise the fundamental question: can all quantum kernels be expressed as the inner product of quantum feature states? Our first result is positive: Invoking computational universality, we find that for any kernel function there always exists a corresponding quantum feature map and an embedding quantum kernel. The more operational reading of the question is concerned with efficient constructions, however. In a second part, we formalize the question of universality of efficient embedding quantum kernels. For shift-invariant kernels, we use the technique of random Fourier features to show that they are universal within the broad class of all kernels which allow a variant of efficient Fourier sampling. We then extend this result to a new class of so-called composition kernels, which we show also contains projected quantum kernels introduced in recent works. After proving the universality of embedding quantum kernels for both shift-invariant and composition kernels, we identify the directions towards new, more exotic, and unexplored quantum kernel families, for which it still remains open whether they correspond to efficient embedding quantum kernels.
Weniger anzeigenCompartmentalization by membranes is a common feature of eukaryotic cells and serves to spatiotemporally confine biochemical reactions to control physiology. Membrane‐bound organelles such as the endoplasmic reticulum (ER), the Golgi complex, endosomes and lysosomes, and the plasma membrane, continuously exchange material via vesicular carriers. In addition to vesicular trafficking entailing budding, fission, and fusion processes, organelles can form membrane contact sites (MCSs) that enable the nonvesicular exchange of lipids, ions, and metabolites, or the secretion of neurotransmitters via subsequent membrane fusion. Recent data suggest that biomolecule and information transfer via vesicular carriers and via MCSs share common organizational principles and are often mediated by proteins with intrinsically disordered regions (IDRs). Intrinsically disordered proteins (IDPs) can assemble via low‐affinity, multivalent interactions to facilitate membrane tethering, deformation, fission, or fusion. Here, we review our current understanding of how IDPs drive the formation of multivalent protein assemblies and protein condensates to orchestrate vesicular and nonvesicular transport with a special focus on presynaptic neurotransmission. We further discuss how dysfunction of IDPs causes disease and outline perspectives for future research.
Weniger anzeigenOne of the most challenging endeavors for students is choosing a career path that best fits their interests, wills and skills, and setting their professional goals accordingly. Such decisions are often made from within the culture of academia, in which mentors and peers are mainly familiar with the academic job market and lack the knowledge necessary to consult about other types of careers. We aimed to address this gap for ecology and related fields by creating an engaging and effective tool to help students and professionals to familiarize themselves with the diversity of potential career paths available to ecologists. The tool is an applied card game – the Ecologist's Career Compass – which is provided here freely. The game is played as a trump card game and includes 33 cards, each representing a combination of one of four job-market sectors and one of nine types of positions. Each card indicates the level of seven skill categories required to likely be hired and succeed in the focal position at the focal sector, as well as more specific examples for typical jobs in the focal combination. The information in the game largely relies on input from a global survey we conducted among 315 ecologists from 35 countries. While the challenges faced by early-career ecologists in developing their professional path are substantial and diverse, this game can assist in gaining a broad comparative overview of the whole ecology job market and the skills required to likely excel in different paths. We hope this applied game will act as a conversation starter about the diversity of aspirations and opportunities in ecology classrooms and labs.
Weniger anzeigenThe structure-based design of antigens holds promise for developing vaccines with higher efficacy and improved safety profiles. We postulate that abrogation of host receptor interaction bears potential for the improvement of vaccines by preventing antigen-induced modification of receptor function as well as the displacement or masking of the immunogen. Antigen modifications may yet destroy epitopes crucial for antibody neutralization. Here, we present a methodology that integrates deep mutational scans to identify and score SARS-CoV-2 receptor binding domain variants that maintain immunogenicity, but lack interaction with the widely expressed host receptor. Single point mutations were scored in silico, validated in vitro, and applied in vivo. Our top-scoring variant receptor binding domain-G502E prevented spike-induced cell-to-cell fusion, receptor internalization, and improved neutralizing antibody responses by 3.3-fold in rabbit immunizations. We name our strategy BIBAX for body-inert, B-cell-activating vaccines, which in the future may be applied beyond SARS-CoV-2 for the improvement of vaccines by design.
Weniger anzeigenAmines are a very important class of compounds and the selective synthesis of differently substituted primary, secondary and tertiary alkyl amines is challenging. Here we present the synthesis of primary, secondary, and tertiary alkyl amines from ammonia and alcohols, aldehydes, ketones and hydrogen by combining borrowing hydrogen or hydrogen autotransfer and reductive amination with hydrogen. The key is a nanostructured, bimetallic Co/Sc catalyst able to mediate both reactions or concepts efficiently. We observe a broad product scope, a very good functional group tolerance, upscaling is easily accomplished and our catalyst is reusable.
Weniger anzeigenUsing unnatural amino acid mutagenesis, we made a mutant of CaMKII that forms a covalent linkage to Calmodulin upon illumination by UV light. Like wild-type CaMKII, the L308BzF mutant stoichiometrically binds to Calmodulin, in a calcium-dependent manner. Using this construct, we demonstrate that Calmodulin binding to CaMKII, even under these stochiometric conditions, does not perturb the CaMKII oligomeric state. Furthermore, we were able to achieve activation of CaMKII L308BzF by UV-induced binding of Calmodulin, which, once established, is further insensitive to calcium depletion. In addition to the canonical auto-inhibitory role of the regulatory segment, inter-subunit crosslinking in the absence of CaM indicates that kinase domains and regulatory segments are substantially mobile in basal conditions. Characterization of CaMKIIL308BzF in vitro, and its expression in mammalian cells, suggests it could be a promising candidate for control of CaMKII activity in mammalian cells with light.
Weniger anzeigenWe predict a novel metallic state of matter that emerges in a Weyl-semimetal superstructure with spatially varying Weyl-node positions. In the new state, the Weyl nodes are stretched into extended, anisotropic Fermi surfaces, which can be understood as being built from Fermi arclike states. This “Fermi-arc metal” exhibits the chiral anomaly of the parental Weyl semimetal. However, unlike in the parental Weyl semimetal, in the Fermi-arc metal the “ultraquantum state,” in which the anomalous chiral Landau level is the only state at the Fermi energy, is already reached for a finite energy window at zero magnetic field. The dominance of the ultraquantum state implies a universal low-field ballistic magnetoconductance and the absence of quantum oscillations, making the Fermi surface “invisible” to de Haas–van Alphen and Shubnikov–de Haas effects, although it signifies its presence in other response properties.
Weniger anzeigenComplex non-linear systems biology models comprise relevant knowledge on processes of pharmacological interest. They are, however, too complex to be used in inferential settings, for example, to allow for the estimation of patient-specific parameters for individual dose optimisation. Thus, there is a need for simple models with interpretable components to infer the drug effect in a clinical setting. In particular, it is essential to accurately quantify and simulate the interindividual variability in the drug response in order to account for covariates like body weight, age and genetic disposition. To this end, non-linear model order reduction and simplification methods can be used if they maintain model interpretability during reduction and consider an entire population rather than just a single reference individual. We present a sample-based approach for robust model order reduction and propose two improvements for efficiency. In particular, we introduce a new sampling method to generate the virtual population based on transformed latin hypercube sampling. Thereby, the sample is stratified in the relevant parameter-space directions, which are identified using empirical observability Gramians. We illustrate our approach in application to a blood coagulation pathway model, where we reduce the complexity from a 62-dimensional highly non-linear to a six-dimensional and a nine-dimensional system of ordinary differential equations for two scenarios, respectively.
Weniger anzeigenThe topological classification of gapped band structures depends on the particular definition of topological equivalence. For translation-invariant systems, stable equivalence is defined by a lack of restrictions on the numbers of occupied and unoccupied bands, while imposing restrictions on one or both leads to “fragile” and “delicate” topology, respectively. In this article, we describe a homotopic classification of band structures—which captures the topology beyond the stable equivalence—in the presence of additional lattice symmetries. As examples, we present complete homotopic classifications for spinless band structures with twofold rotation, fourfold rotation and fourfold dihedral symmetries, both in presence and absence of time-reversal symmetry. Whereas the rules of delicate and fragile topology do not admit a bulk-boundary correspondence, we identify a version of stable topology, which restricts the representations of bands, but not their numbers, which does allow for anomalous states at symmetry-preserving boundaries, which are associated with nontrivial bulk topology.
Weniger anzeigenThe phase before an extreme weather event is crucial for the actual reaction to the impacts of such an event. In this phase, professionals in the field of civil protection and emergency management anticipate the intensity and impact of the event and use these expectations for action. We argue that anticipation is—beyond others—shaped by the organizations’ shared narratives of past crisis that resulted from extreme weather events. The findings focus on the frame of ‘blame’ in the narration and are based on two fields of study, road maintenance services and forest fire control. Qualitative group discussions and semistructured interviews show two very different views on blame depending on the organization: human factors and fate. This contrast can be traced back to the character of the weather events itself, but also with the self-image of the organization and perceived external expectations. Depending on the narrative plot and threshold of the event, narratives can affect and alter practices of anticipation through narrations of renewal. Findings contribute to the understanding of organizational sensemaking through narratives of blame and consequences.
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