Showing papers by "University of Nebraska–Lincoln published in 2016"
TL;DR: In this paper, the authors present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macro-autophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes.
Abstract: In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes.
For example, a key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process versus those that measure flux through the autophagy pathway (i.e., the complete process including the amount and rate of cargo sequestered and degraded). In particular, a block in macroautophagy that results in autophagosome accumulation must be differentiated from stimuli that increase autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. It is worth emphasizing here that lysosomal digestion is a stage of autophagy and evaluating its competence is a crucial part of the evaluation of autophagic flux, or complete autophagy.
Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. Along these lines, because of the potential for pleiotropic effects due to blocking autophagy through genetic manipulation, it is imperative to target by gene knockout or RNA interference more than one autophagy-related protein. In addition, some individual Atg proteins, or groups of proteins, are involved in other cellular pathways implying that not all Atg proteins can be used as a specific marker for an autophagic process. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular assays, we hope to encourage technical innovation in the field.
5,187 citations
TL;DR: This Account critically review the recent progress in understanding the fundamental science on ion migration in OTP based solar cells and raises some questions that need to be understood and addressed in the future.
Abstract: ConspectusOrganometal trihalide perovskites (OTPs) are emerging as very promising photovoltaic materials because the power conversion efficiency (PCE) of OTP solar cells quickly rises and now rivals with that of single crystal silicon solar cells after only five-years research. Their prospects to replace silicon photovoltaics to reduce the cost of renewable clean energy are boosted by the low-temperature solution processing as well as the very low-cost raw materials and relative insensitivity to defects. The flexibility, semitransparency, and vivid colors of perovskite solar cells are attractive for niche applications such as built-in photovoltaics and portable lightweight chargers. However, the low stability of current hybrid perovskite solar cells remains a serious issue to be solved before their broad application. Among all those factors that affect the stability of perovskite solar cells, ion migration in OTPs may be intrinsic and cannot be taken away by device encapsulation.The presence of ion migrat...
1,237 citations
TL;DR: In this paper, single-crystal perovskite devices 2-3 mm thick exhibit 16.4% X-ray detection efficiency with sensitivity four times higher than α-Se detectors.
Abstract: Single-crystal perovskite devices 2–3 mm thick exhibit 16.4% X-ray detection efficiency with sensitivity four times higher than α-Se X-ray detectors.
1,136 citations
TL;DR: In this article, a modified synthetic method is reported for producing high-quality monolayer 2D transition metal carbide Ti3C2Tx flakes, and their electronic properties are measured.
Abstract: 2D transition metal carbide Ti3C2Tx (T stands for surface termination), the most widely studied MXene, has shown outstanding electrochemical properties and promise for a number of bulk applications. However, electronic properties of individual MXene flakes, which are important for understanding the potential of these materials, remain largely unexplored. Herein, a modified synthetic method is reported for producing high-quality monolayer Ti3C2Tx flakes. Field-effect transistors (FETs) based on monolayer Ti3C2Tx flakes are fabricated and their electronic properties are measured. Individual Ti3C2Tx flakes exhibit a high conductivity of 4600 ± 1100 S cm−1 and field-effect electron mobility of 2.6 ± 0.7 cm2 V−1 s−1. The resistivity of multilayer Ti3C2Tx films is only one order of magnitude higher than the resistivity of individual flakes, which indicates a surprisingly good electron transport through the surface terminations of different flakes, unlike in many other 2D materials. Finally, the fabricated FETs are used to investigate the environmental stability and kinetics of oxidation of Ti3C2Tx flakes in humid air. The high-quality Ti3C2Tx flakes are reasonably stable and remain highly conductive even after their exposure to air for more than 24 h. It is demonstrated that after the initial exponential decay the conductivity of Ti3C2Tx flakes linearly decreases with time, which is consistent with their edge oxidation.
981 citations
TL;DR: In this paper, a combination of nanoscopic and macroscopic level measurements was used to show that ion migration in polycrystalline perovskites dominates through grain boundary (GBs).
Abstract: The efficiency of perovskite solar cells is approaching that of single-crystalline silicon solar cells despite the presence of a large grain boundary (GB) area in the polycrystalline thin films. Here, by using a combination of nanoscopic and macroscopic level measurements, we show that ion migration in polycrystalline perovskites dominates through GBs. Atomic force microscopy measurements reveal much stronger hysteresis both for photocurrent and dark-current at the GBs than on the grain interiors, which can be explained by faster ion migration at the GBs. The dramatically enhanced ion migration results in the redistribution of ions along the GBs after electric poling, in contrast to the intact grain area. The perovskite single-crystal devices without GBs show negligible current hysteresis and no ion-migration signal. The discovery of dominating ion migration through GBs in perovskites can lead to broad applications in many types of devices including photovoltaics, memristors, and ion batteries.
846 citations
TL;DR: Numerical approaches were reviewed and implemented for depicting the cellular mechanics within the hydrogel as well as for prediction of mechanical properties to achieve the desired hydrogels construct considering cell density, distribution and material-cell interaction.
Abstract: Bioprinting is a process based on additive manufacturing from materials containing living cells. These materials, often referred to as bioink, are based on cytocompatible hydrogel precursor formulations, which gel in a manner compatible with different bioprinting approaches. The bioink properties before, during and after gelation are essential for its printability, comprising such features as achievable structural resolution, shape fidelity and cell survival. However, it is the final properties of the matured bioprinted tissue construct that are crucial for the end application. During tissue formation these properties are influenced by the amount of cells present in the construct, their proliferation, migration and interaction with the material. A calibrated computational framework is able to predict the tissue development and maturation and to optimize the bioprinting input parameters such as the starting material, the initial cell loading and the construct geometry. In this contribution relevant bioink properties are reviewed and discussed on the example of most popular bioprinting approaches. The effect of cells on hydrogel processing and vice versa is highlighted. Furthermore, numerical approaches were reviewed and implemented for depicting the cellular mechanics within the hydrogel as well as for prediction of mechanical properties to achieve the desired hydrogel construct considering cell density, distribution and material-cell interaction.
737 citations
Vardan Khachatryan1, Albert M. Sirunyan1, Armen Tumasyan1, Wolfgang Adam +2283 more•Institutions (141)
TL;DR: Combined fits to CMS UE proton–proton data at 7TeV and to UEProton–antiproton data from the CDF experiment at lower s, are used to study the UE models and constrain their parameters, providing thereby improved predictions for proton-proton collisions at 13.
Abstract: New sets of parameters ("tunes") for the underlying-event (UE) modeling of the PYTHIA8, PYTHIA6 and HERWIG++ Monte Carlo event generators are constructed using different parton distribution functions. Combined fits to CMS UE data at sqrt(s) = 7 TeV and to UE data from the CDF experiment at lower sqrt(s), are used to study the UE models and constrain their parameters, providing thereby improved predictions for proton-proton collisions at 13 TeV. In addition, it is investigated whether the values of the parameters obtained from fits to UE observables are consistent with the values determined from fitting observables sensitive to double-parton scattering processes. Finally, comparisons of the UE tunes to "minimum bias" (MB) events, multijet, and Drell-Yan (q q-bar to Z / gamma* to lepton-antilepton + jets) observables at 7 and 8 TeV are presented, as well as predictions of MB and UE observables at 13 TeV.
686 citations
TL;DR: In this paper, the structural order of the electron transport layers of perovskite solar cells has been shown to have a significant impact on solar cell performance, and the power conversion efficiency of CH3NH3PbII3 planar heterojunction photovoltaic cells increases from 17.1% to 19.4%.
Abstract: Organometal trihalide perovskites have been demonstrated as excellent light absorbers for high-efficiency photovoltaic applications. Previous approaches to increasing the solar cell efficiency have focused on optimization of the grain morphology of perovskite thin films. Here, we show that the structural order of the electron transport layers also has a significant impact on solar cell performance. We demonstrate that the power conversion efficiency of CH3NH3PbI3 planar heterojunction photovoltaic cells increases from 17.1 to 19.4% when the energy disorder in the fullerene electron transport layer is reduced by a simple solvent annealing process. The increase in efficiency is the result of the enhancement in open-circuit voltage from 1.04 to 1.13 V without sacrificing the short-circuit current and fill factor. These results shed light on the origin of open-circuit voltage in perovskite solar cells, and provide a path to further increase their efficiency. Ongoing efforts are devoted to raising the efficiency of solar cells in converting energy from solar radiation. Now, improved structural order in the charge transport layers of perovskite solar cells is shown to increase the efficiency from 17.1% to 19.4%.
620 citations
Wageningen University and Research Centre1, University of Nebraska–Lincoln2, International Crops Research Institute for the Semi-Arid Tropics3, International Food Policy Research Institute4, Africa Rice Center5, Jomo Kenyatta University of Agriculture and Technology6, International Institute of Tropical Agriculture7, Federal University of Technology Minna8, University of Zimbabwe9, International Maize and Wheat Improvement Center10
TL;DR: In this article, a robust yield gap analysis for 10 countries in sub-Saharan Africa using location-specific data and a spatial upscaling approach reveals that, in addition to yield gap closure, other more complex and uncertain components of intensification are also needed, i.e., increasing cropping intensity and sustainable expansion of irrigated production area.
Abstract: Although global food demand is expected to increase 60% by 2050 compared with 2005/2007, the rise will be much greater in sub-Saharan Africa (SSA). Indeed, SSA is the region at greatest food security risk because by 2050 its population will increase 2.5-fold and demand for cereals approximately triple, whereas current levels of cereal consumption already depend on substantial imports. At issue is whether SSA can meet this vast increase in cereal demand without greater reliance on cereal imports or major expansion of agricultural area and associated biodiversity loss and greenhouse gas emissions. Recent studies indicate that the global increase in food demand by 2050 can be met through closing the gap between current farm yield and yield potential on existing cropland. Here, however, we estimate it will not be feasible to meet future SSA cereal demand on existing production area by yield gap closure alone. Our agronomically robust yield gap analysis for 10 countries in SSA using location-specific data and a spatial upscaling approach reveals that, in addition to yield gap closure, other more complex and uncertain components of intensification are also needed, i.e., increasing cropping intensity (the number of crops grown per 12 mo on the same field) and sustainable expansion of irrigated production area. If intensification is not successful and massive cropland land expansion is to be avoided, SSA will depend much more on imports of cereals than it does today.
581 citations
TL;DR: In this paper, the authors describe carbazolyl dicyanobenzene (CDCB)-based donor-acceptor (D-A) fluorophores as a class of cheap, easily accessible, and efficient metal-free photoredox catalysts for organic synthesis.
Abstract: We describe carbazolyl dicyanobenzene (CDCB)-based donor–acceptor (D–A) fluorophores as a class of cheap, easily accessible, and efficient metal-free photoredox catalysts for organic synthesis. By changing the number and position of carbazolyl and cyano groups on the center benzene ring, CDCBs with a wide range of photoredox potentials are obtained to effectively drive the energetically demanding C(sp3)–C(sp2) cross-coupling of carboxylic acids and alkyltrifluoroborates with aryl halides via a photoredox/Ni dual catalysis mechanism. This work validates the utility of D–A fluorophores in guiding the rational design of metal-free photoredox catalysts for visible-light-promoted organic synthesis.
526 citations
TL;DR: Tunneling contacts made of any insulating polymers, a champion technology in silicon solar cells, are shown to increase the stabilized efficiency of perovskite solar cells (PSCs), and significantly enhance the resistance of PSCs to water-caused damage.
Abstract: Tunneling contacts made of any insulating polymers, a champion technology in silicon solar cells, are shown to increase the stabilized efficiency of perovskite solar cells (PSCs) to 20.3%. The tunneling layers spatially separate photo-generated electrons and holes at the perovskite-cathode interface and reduce charge recombination. The tunneling layers made of hydrophobic polymers also significantly enhance the resistance of PSCs to water-caused damage.
University of Birmingham1, University of Victoria2, Australian National University3, University of Freiburg4, Uppsala University5, Wageningen University and Research Centre6, University of Oslo7, Princeton University8, University of Nebraska–Lincoln9, Vrije Universiteit Brussel10, University of Bristol11
TL;DR: In this human-influenced era, we need to rethink the concept of "drought" to include the human role in mitigating and enhancing drought as mentioned in this paper, which is not fully understood.
Abstract: Drought management is inefficient because feedbacks between drought and people are not fully understood. In this human-influenced era, we need to rethink the concept of drought to include the human role in mitigating and enhancing drought.
United States Geological Survey1, Wake Forest University2, University of Minnesota3, Utah State University4, Martin Luther University of Halle-Wittenberg5, Utrecht University6, University of Oldenburg7, University of Tartu8, University of Washington9, Trinity College, Dublin10, Imperial College London11, University of Wisconsin-Madison12, University of Colorado Boulder13, United States Department of Agriculture14, Queensland University of Technology15, University of Maryland, College Park16, University of Oxford17, University of Nebraska–Lincoln18, University of Guelph19, La Trobe University20, Commonwealth Scientific and Industrial Research Organisation21, Colorado State University22
TL;DR: It is found that an integrative model has substantially higher explanatory power than traditional bivariate analyses and several surprising findings that conflict with classical models are revealed.
Abstract: How ecosystem productivity and species richness are interrelated is one of the most debated subjects in the history of ecology. Decades of intensive study have yet to discern the actual mechanisms behind observed global patterns. Here, by integrating the predictions from multiple theories into a single model and using data from 1,126 grassland plots spanning five continents, we detect the clear signals of numerous underlying mechanisms linking productivity and richness. We find that an integrative model has substantially higher explanatory power than traditional bivariate analyses. In addition, the specific results unveil several surprising findings that conflict with classical models. These include the isolation of a strong and consistent enhancement of productivity by richness, an effect in striking contrast with superficial data patterns. Also revealed is a consistent importance of competition across the full range of productivity values, in direct conflict with some (but not all) proposed models. The promotion of local richness by macroecological gradients in climatic favourability, generally seen as a competing hypothesis, is also found to be important in our analysis. The results demonstrate that an integrative modelling approach leads to a major advance in our ability to discern the underlying processes operating in ecological systems.
TL;DR: First-principles calculation evidence is shown that the GeS and GeSe monolayers as well as bulk SnS and SnSe can maintain their ferroelasticity and ferroelectricity (anti-ferro electricity) beyond the room temperature, suggesting high potential for practical device application.
Abstract: Phosphorene and phosphorene analogues such as SnS and SnSe monolayers are promising nanoelectronic materials with desired bandgap, high carrier mobility, and anisotropic structures. Here, we show first-principles calculation evidence that these monolayers are potentially the long-sought two-dimensional (2D) materials that can combine electronic transistor characteristic with nonvolatile memory readable/writeable capability at ambient condition. Specifically, phosphorene is predicted to be a 2D intrinsic ferroelastic material with ultrahigh reversible strain, whereas SnS, SnSe, GeS, and GeSe monolayers are multiferroic with coupled ferroelectricity and ferroelasticity. Moreover, their low-switching barriers render room-temperature nonvolatile memory accessible, and their notable structural anisotropy enables ferroelastic or ferroelectric switching readily readable via electrical, thermal, optical, mechanical, or even spintronic detection upon the swapping of the zigzag and armchair direction. In addition, ...
TL;DR: This review summarizes typical structures of perovskite solar cells and comments on novel device structures, and the applications of perOVskiteSolar cells are discussed.
Abstract: Organolead halide perovskite materials possess a combination of remarkable optoelectronic properties, such as steep optical absorption edge and high absorption coefficients, long charge carrier diffusion lengths and lifetimes. Taken together with the ability for low temperature preparation, also from solution, perovskite-based devices, especially photovoltaic (PV) cells have been studied intensively, with remarkable progress in performance, over the past few years. The combination of high efficiency, low cost and additional (non-PV) applications provides great potential for commercialization. Performance and applications of perovskite solar cells often correlate with their device structures. Many innovative device structures were developed, aiming at large-scale fabrication, reducing fabrication cost, enhancing the power conversion efficiency and thus broadening potential future applications. This review summarizes typical structures of perovskite solar cells and comments on novel device structures. The applications of perovskite solar cells are discussed.
TL;DR: In this paper, the effects of oxygen and water in contact with black phosphorus (BP) have been investigated and it was shown that the reaction with oxygen is primarily responsible for changing properties of BP.
Abstract: Black phosphorus (BP) has attracted significant interest as a monolayer or few-layer material with extraordinary electrical and optoelectronic properties. Chemical reactions with different ambient species, notably oxygen and water, are important as they govern key properties such as stability in air, electronic structure and charge transport, wetting by aqueous solutions, and so on. Here, we report experiments combined with ab initio calculations that address the effects of oxygen and water in contact with BP. Our results show that the reaction with oxygen is primarily responsible for changing properties of BP. Oxidation involving the dissociative chemisorption of O2 causes the decomposition of BP and continuously lowers the conductance of BP field-effect transistors (FETs). In contrast, BP is stable in contact with deaerated (i.e., O2 depleted) water and the carrier mobility in BP FETs gated by H2O increases significantly due to efficient dielectric screening of scattering centers by the high-k dielectri...
TL;DR: The environmental fate ofDCF in different compartments such as soil and water has been addressed with an overview of current treatment methods and the toxicity concerns regarding DCF in aquatic as well as terrestrial environment along with an introduction to the metabolites of DCF through consumption and abiotic degradation routes are discussed.
TL;DR: A 16-item version of the Difficulties in Emotion Regulation Scale is developed – the DERS-16, which shows minimal differences in its convergent and discriminant validity with relevant measures when compared to the original DERS.
Abstract: The Difficulties in Emotion Regulation Scale (DERS) is a widely-used, theoretically-driven, and psychometrically-sound self-report measure of emotion regulation difficulties. However, at 36-items, the DERS may be challenging to administer in some situations or settings (e.g., in the course of patient care or large-scale epidemiological studies). Consequently, there is a need a briefer version of the DERS. The goal of the present studies was to develop and evaluate a 16-item version of the DERS - the DERS-16. The reliability and validity of the DERS-16 were examined in a clinical sample (N = 96) and two large community samples (Ns = 102 and 482). The validity of the DERS-16 was evaluated comparing the relative strength of the association of the two versions of the DERS with measures of emotion regulation and related constructs, psychopathology, and clinically-relevant behaviors theorized to stem from emotion regulation deficits. Results demonstrate that the DERS-16 has retained excellent internal consistency, good test-retest reliability, and good convergent and discriminant validity. Further, the DERS-16 showed minimal differences in its convergent and discriminant validity with relevant measures when compared to the original DERS. In conclusion, the DERS-16 offers a valid and brief method for the assessment of overall emotion regulation difficulties.
TL;DR: A large-scale gene expression atlas composed of 62,547 messenger RNAs, 17,862 nonmodified proteins, and 6227 phosphoproteins harboring 31,595 phosphorylation sites quantified across maize development reveals patterns of developmental regulation within tissues for the transcriptome, proteome, and phosphoburden.
Abstract: Coexpression networks and gene regulatory networks (GRNs) are emerging as important tools for predicting functional roles of individual genes at a system-wide scale. To enable network reconstructions, we built a large-scale gene expression atlas composed of 62,547 messenger RNAs (mRNAs), 17,862 nonmodified proteins, and 6227 phosphoproteins harboring 31,595 phosphorylation sites quantified across maize development. Networks in which nodes are genes connected on the basis of highly correlated expression patterns of mRNAs were very different from networks that were based on coexpression of proteins. Roughly 85% of highly interconnected hubs were not conserved in expression between RNA and protein networks. However, networks from either data type were enriched in similar ontological categories and were effective in predicting known regulatory relationships. Integration of mRNA, protein, and phosphoprotein data sets greatly improved the predictive power of GRNs.
TL;DR: A facile strategy is reported that can simultaneously enhance the stability and efficiency of p–i–n planar heterojunction-structure perovskite devices and enhances the water and moisture stability of the non-sealed perovkite devices by retaining nearly 90% of their original efficiencies after 30 days' exposure in an ambient environment.
Abstract: The instability of hybrid perovskite materials due to water and moisture arises as one major challenge to be addressed before any practical application of the demonstrated high efficiency perovskite solar cells Here we report a facile strategy that can simultaneously enhance the stability and efficiency of p-i-n planar heterojunction-structure perovskite devices Crosslinkable silane molecules with hydrophobic functional groups are bonded onto fullerene to make the fullerene layer highly water-resistant Methylammonium iodide is introduced in the fullerene layer for n-doping via anion-induced electron transfer, resulting in dramatically increased conductivity over 100-fold With crosslinkable silane-functionalized and doped fullerene electron transport layer, the perovskite devices deliver an efficiency of 195% with a high fill factor of 806% A crosslinked silane-modified fullerene layer also enhances the water and moisture stability of the non-sealed perovskite devices by retaining nearly 90% of their original efficiencies after 30 days' exposure in an ambient environment
TL;DR: The scaling-down approach to estimate the contribution of non-symbiotic N2 fixation is robust because it focuses on global quantities of N in sources and sinks that are easier to estimate, in contrast to estimating N losses per se, because losses are highly soil-, climate-, and crop-specific.
Abstract: Industrially produced N-fertilizer is essential to the production of cereals that supports current and projected human populations. We constructed a top-down global N budget for maize, rice and wheat for a 50-year period (1961 to 2010). Cereals harvested a total of 1551 Tg of N, of which 48% was supplied through fertilizer-N and 4% came from net soil depletion. An estimated 48% (737 Tg) of crop N, equal to 29, 38 and 25 kg ha−1 yr−1 for maize, rice and wheat, respectively, is contributed by sources other than fertilizer- or soil-N. Non-symbiotic N2 fixation appears to be the major source of this N, which is 370 Tg or 24% of total N in the crop, corresponding to 13, 22 and 13 kg ha−1 yr−1 for maize, rice and wheat, respectively. Manure (217 Tg or 14%) and atmospheric deposition (96 Tg or 6%) are the other sources of N. Crop residues and seed contribute marginally. Our scaling-down approach to estimate the contribution of non-symbiotic N2 fixation is robust because it focuses on global quantities of N in sources and sinks that are easier to estimate, in contrast to estimating N losses per se, because losses are highly soil-, climate- and crop-specific.
Arizona State University1, East China Normal University2, Chinese Academy of Sciences3, University of Western Australia4, Zhejiang University5, University of Florida6, University of California, Davis7, Zhejiang University of Science and Technology8, Georgia Institute of Technology9, James Cook University10, Duke University11, University of Nebraska–Lincoln12, Princeton University13
TL;DR: The International Workshop on Habitat Fragmentation and Biodiversity Conservation, held at the Thousand Island Lake, Zhejiang, China, discussed threats to biodiversity in fragmented landscapes and how fragmentation research can identify and help mitigate these threats as mentioned in this paper.
Abstract: Habitat loss and fragmentation has long been considered the primary cause for biodiversity loss and ecosystem degradation worldwide, and is a key research topic in landscape ecology (Wu 2013). Habitat fragmentation often refers to the reduction of continuous tracts of habitat to smaller, spatially distinct remnant patches, and habitat loss typically occurs concurrently with habitat fragmentation (Collinge 2009). Although some habitats are naturally patchy in terms of abiotic and biotic conditions (Wu and Loucks 1995), human actions have profoundly fragmented landscapes across the word (Haddad et al. 2015), altering the quality and connectivity of habitats. Therefore, understanding the causes and consequences of habitat fragmentation is critical to preserving biodiversity and ecosystem functioning.
From May 4th to 10th, 2015, an International Workshop on Habitat Fragmentation and Biodiversity Conservation, held at the Thousand Island Lake, Zhejiang, China, discussed threats to biodiversity in fragmented landscapes and how fragmentation research can identify and help mitigate these threats. To meet these challenges, the Workshop had three goals. The first was to synthesize key findings in fragmentation science. Second was to identify important remaining research questions concerning the relationships between habitat fragmentation, biodiversity, and ecosystem functioning at local, regional, and global scales. Finally, we examined the unique roles of field-based fragmentation experiments in addressing these questions. The Workshop’s findings are relevant to the broader ecological community, and we present them here to stimulate research that will advance landscape ecology and conservation biology.
TL;DR: The breadth of IR boundary shifts in land plants is explored and it is demonstrated that synonymous substitution rates are, on average, 3.7 times slower in IR genes than in SC genes, which provides strong evidence that the duplicative nature of the IR reduces the substitution rate within this region.
Abstract: Rates of nucleotide substitution were previously shown to be several times slower in the plastid inverted repeat (IR) compared with single-copy (SC) regions, suggesting that the IR provides enhanced copy-correction activity. To examine the generality of this synonymous rate dependence on the IR, we compared plastomes from 69 pairs of closely related species representing 52 families of angiosperms, gymnosperms, and ferns. We explored the breadth of IR boundary shifts in land plants and demonstrate that synonymous substitution rates are, on average, 3.7 times slower in IR genes than in SC genes. In addition, genes moved from the SC into the IR exhibit lower synonymous rates consistent with other IR genes, while genes moved from the IR into the SC exhibit higher rates consistent with other SC genes. Surprisingly, however, several plastid genes from Pelargonium, Plantago, and Silene have highly accelerated synonymous rates despite their IR localization. Together, these results provide strong evidence that the duplicative nature of the IR reduces the substitution rate within this region. The anomalously fast-evolving genes in Pelargonium, Plantago, and Silene indicate localized hypermutation, potentially induced by a higher level of error-prone double-strand break repair in these regions, which generates substitutional rate variation.
TL;DR: In this article, the authors explored how academic achievement relates to two main components of self-regulated learning for students in elementary and secondary school and found that average correlations significantly differed based on the specific process or strategy, academic subject, grade level, type of selfregulated learning measure, and type of achievement measure.
Abstract: This research synthesis explores how academic achievement relates to two main components of self-regulated learning for students in elementary and secondary school. Two meta-analyses integrated previous findings on (1) the defining metacognitive processes of self-regulated learning and (2) students’ use of cognitive strategies. Overall correlations were small (metacognitive processes, r = 0.20; cognitive strategies, r = 0.11), but there was systematic variation around both of them. Five moderator analyses were conducted to explain this variation. Average correlations significantly differed based on the specific process or strategy, academic subject, grade level, type of self-regulated learning measure, and type of achievement measure. Follow-up tests explored the nature of these differences and largely support the hypotheses. Theoretical, methodological, and practical implications of these findings are discussed.
TL;DR: Developments in community-wide sequencing and glycomics have revealed that more complex interactions occur between putative prebiotic substrates and the gut microbiota than previously considered.
TL;DR: It is found that, when orally administered to humans, Bifidobacterium longum AH1206 stably persists in the gut of 30% of individuals for at least 6 months without causing gastrointestinal symptoms or impacting the composition of the resident gut microbiota.
TL;DR: A surface-chemistry strategy to achieve metallic Ni(OH)2 nanosheets by engineering their electronic structure, representing a first metallic configuration of transition-metal hydroxides, giving rise to greatly enhanced performance for UOR.
Abstract: The direct urea fuel cell (DUFC) is an important but challenging renewable energy production technology, it offers great promise for energy-sustainable developments and mitigating water contamination. However, DUFCs still suffer from the sluggish kinetics of the urea oxidation reaction (UOR) owing to a 6 e(-) transfer process, which poses a severe hindrance to their practical use. Herein, taking β-Ni(OH)2 nanosheets as the proof-of-concept study, we demonstrated a surface-chemistry strategy to achieve metallic Ni(OH)2 nanosheets by engineering their electronic structure, representing a first metallic configuration of transition-metal hydroxides. Surface sulfur incorporation successfully brings synergetic effects of more exposed active sites, good wetting behavior, and effective electron transport, giving rise to greatly enhanced performance for UOR. Metallic nanosheets exhibited a much higher current density, smaller onset potential and stronger durability.
TL;DR: The demonstration of energy‐efficient OTP synaptic devices opens a new plausible application of OTP materials into neuromorphic devices, which offer the high connectivity and high density required for biomimic computing.
Abstract: New parallel computing architectures based on neuromorphic computing are needed due to their advantages over conventional computation with regards to real-time processing of unstructured sensory data such as image, video, or voice. However, developing artificial neuromorphic system remains a challenge due to the lack of electronic synaptic devices, which can mimic all the functions of biological synapses with low energy consumption. Here it is reported that two-terminal organometal trihalide perovskite (OTP) synaptic devices can mimic the neuromorphic learning and remembering process. Various functions known in biological synapses are demonstrated in OTP synaptic devices including four forms of spike-timing-dependent plasticity (STDP), spike-rate-dependent plasticity (SRDP), short-term plasticity (STP) and long-term potentiation (LTP)), and learning-experience behavior. The excellent photovoltaic property of the OTP devices also enables photo-read synaptic functions. The perovskite synapse has the potential of low energy consumption of femto-Joule/(100 nm)2 per event, which is close to the energy consumption of biological synapses. The demonstration of energy-efficient OTP synaptic devices opens a new plausible application of OTP materials into neuromorphic devices, which offer the high connectivity and high density required for biomimic computing.
TL;DR: It is demonstrated that the surface recombination rate (or surface trap state density) in methylammonium lead tribromide (MAPbBr3) single crystals can be fully and reversibly controlled by the physisorption of oxygen and water molecules, leading to a modulation of the photoluminescence intensity by over two orders of magnitude.
Abstract: One of the limiting factors to high device performance in photovoltaics is the presence of surface traps. Hence, the understanding and control of carrier recombination at the surface of organic-inorganic hybrid perovskite is critical for the design and optimization of devices with this material as the active layer. We demonstrate that the surface recombination rate (or surface trap state density) in methylammonium lead tribromide (MAPbBr3) single crystals can be fully and reversibly controlled by the physisorption of oxygen and water molecules, leading to a modulation of the photoluminescence intensity by over two orders of magnitude. We report an unusually low surface recombination velocity of 4 cm/s (corresponding to a surface trap state density of 108 cm−2) in this material, which is the lowest value ever reported for hybrid perovskites. In addition, a consistent modulation of the transport properties in single crystal devices is evidenced. Our findings highlight the importance of environmental conditions on the investigation and fabrication of high-quality, perovskite-based devices and offer a new potential application of these materials to detect oxygen and water vapor.
TL;DR: In this article, the authors present a direct evidence for the macroscopic migration of V I • in MAPbI 3 perovskite devices at an elevated temperature of 330 K.
Abstract: DOI: 10.1002/aenm.201501803 device effi ciency. [ 34 ] On the other hand, migration of the iodine vacancies (V I • ) has not been yet experimentally observed. Theoretical calculations suggest that the V I • might be even more mobile than MA + ions, although the activation energy values for V I • migration calculated by different methods vary from 0.08 to 0.58 eV. [ 35,36 ] In view of the widely observed oxygen vacancies migration in many oxide perovskite materials, the assumption of V I • migration in MAPbI 3 materials is quite reasonable. In this contribution, we present a direct evidence for the macroscopic migration of V I • in MAPbI 3 perovskite fi lms at an elevated temperature of 330 K. Most interestingly, we report a reversible conversion between MAPbI 3 and lead iodide (PbI 2 ) phases under a small electric fi eld at the elevated temperature as a result of a set of solid-state chemical reactions, and show that the conversion of MAPbI 3 to PbI 2 is slower than the conversion of PbI 2 to MAPbI 3 at room temperature (RT). The MAPbI 3 lateral devices were fabricated on glass substrates to enable observation of ion migration process by an optical microscope or a charge-coupled device (CCD) camera. Figure 1 a shows the working area of a fresh MAPbI 3 device at 330 K in vacuum taken with the CCD camera. The cross-sectional structure of the device is illustrated in Figure 1 b. After applying a constant electrical fi eld of ≈3 V μm −1 for 20–60 s, a thread formed near the anode region, and then gradually moved toward the cathode along the applied electric fi eld direction. Figure 1 c,e show the snapshot optical images obtained during the migration of this thread under the applied electric fi eld. Sketches in Figure 1 b,d,f illustrate a change in the device crosssection due to the formation of the thread (red region) and its subsequent motion across the channel from the anode to the cathode. (The process of thread formation and its motion can be seen in Video S1, Supporting Information). The thread appears darker than the neighboring regions due to the scattering of light incident at an angle of 50°–60°. When observed with vertical incident light in refl ection mode, the thread (region B) has a similar color with the neighboring regions (Figure 1 g). The optical microscopy image in transmission mode in Figure 1 h shows that this thread has higher transparency than the neighboring regions. To determine composition of the formed thread, we conducted energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction analysis (XRD) measurements. The scanning electron microscope (SEM) ( Figure 2 a) and EDX images (Figure 2 c–h) show the distributions of gold (Au), I and lead (Pb) elements in a device poled by an applied electric fi eld of 3 V μm −1 for 1 min. The quantitative distribution of these elements along the Solution-processed solar cells based on organolead trihalide perovskite (OTP) materials are emerging as a new generation of photovoltaic devices due to their low cost and superior performance. [ 1–17 ] The power conversion effi ciency (PCE) of the perovskite solar cells increased dramatically from 3.8% to over 20% after only a few years of research. [ 1–7,9–16,18–22 ] The advances in low-cost, high-throughput processing methods, such as doctor-blading and spray coating, are also fast, which allowed fabrication of high-effi ciency large-scale devices. [ 23–28 ] One of the remaining issues is whether the OTP materials and devices have suffi cient stability that is needed for the commercialization of the OTP solar cells. [ 3,29,30 ] Among all factors that cause the instability of the hybrid perovskites, ion migration has been recently been identifi ed to be intrinsic to the hybrid perovskite polycrystalline fi lms and cannot be removed by device encapsulation. To solve the instability problem of the OTP-based devices, a deeper insight into the ion migration effect is necessary, since it might provide hints for the development of new materials with better stability. [ 30,31 ]