bluuebunny/crossref_metadata_2025_split huggingface dataset:
Air‐Stable Symmetric Ambipolar Field‐Effect Transistors Based on Reduced Graphene Oxide‐OTS Self‐Assembled Monolayer Heterostructure
Authors: Peng Peng , Liu Hongtao , Wu Bin , Tang Qingxin , Liu Yunqi 
Published: January 2019

AbstractGraphene has attracted great interest in the past decade due to its unique band structure and physical properties such as quantum electronic transport, extremely high mobility, high elasticity and optical properties. Graphene is generally obtained by mechanical exfoliation, epitaxial growth, chemical vapor deposition and chemical synthesis approaches, wherein the reduction of graphene oxide (GO) is a practical approach to synthesize large‐scale graphene. Via reduction, highly conductive reduced graphene oxide (RGO) can be obtained, which has electrical and optical properties analogous to those of graphene. However, Field‐effect transistors (FETs) based RGO typically exhibit p‐type in ambient rather than the ambipolar behavior of intrinsic graphene, due to the doping effect induced by substrate and the air. Meanwhile, large hysteresis accompanies with the p‐type transistor. Here, a self‐assembled monolayer (SAM) of octadecyltrichlorosilane (OTS)‐RGO heterostructure is developed, in which RGO is sandwiched between OTS SAMs. The heterostructure passivates the RGO device and eliminates the doping of graphene from the surroundings. The obtained RGO FETs exhibit air‐stable symmetric ambipolar behavior with Dirac point at 0 V gate voltage and negligible hysteresis. This approach will also be applicable to pristine graphene and other two‐dimensional materials to obtain the intrinsic properties under ambient conditions, thereby promoting the research and applications of two‐dimensional materials.
Organic Two‐Dimensional Assembly with Rectification Property Mediated by Cucurbit[8]uril
Authors: Zhang Zhi‐Yuan , Chen Yong , Qi Ji‐Wei , Liu Yu 
Published: January 2019

AbstractWe report a highly regular organic two‐dimensional assembly made of cucurbit[8]uril and aromatic units that shows peculiar optoelectronic properties. We found that this individual self‐assembled microplate displayed a good conductivity under forward bias but nearly no current was detected under reverse bias along the stacking direction. This unique phenomenon is due to the coordination assembly of cucurbit[8]uril with aromatic units and aromatic stacking between layers. Moreover, the fluorescent properties are maintained in the solid state. Our result might show advantages in fabricating optoelectronic devices and help others to design organic two‐dimensional materials with specific functions.
Conducting a Reproducible Mendelian Randomization Analysis Using the R Analytic Statistical Environment
Authors: Rasooly Danielle , Patel Chirag J. 
Published: January 2019

AbstractMendelian randomization (MR) is defined as the utilization of genetic variants as instrumental variables to assess the causal relationship between an exposure and an outcome. By leveraging genetic polymorphisms as proxy for an exposure, the causal effect of an exposure on an outcome can be assessed while addressing susceptibility to biases prone to conventional observational studies, including confounding and reverse causation, where the outcome causes the exposure. Analogous to a randomized controlled trial where patients are randomly assigned to subgroups based on different treatments, in an MR analysis, the random allocation of alleles during meiosis from parent to offspring assigns individuals to different subgroups based on genetic variants. Recent methods use summary statistics from genome‐wide association studies to perform MR, bypassing the need for individual‐level data. Here, we provide a straightforward protocol for using summary‐level data to perform MR and provide guidance for utilizing available software. © 2019 by John Wiley & Sons, Inc.
Visible‐Light‐Driven Photocatalytic Z‐Scheme Overall Water Splitting in La5Ti2AgS5O7‐based Powder‐Suspension System
Authors: Song Zhimin , Hisatomi Takashi , Chen Shanshan , Wang Qian , Ma Guijun , Li Shikuo , Zhu Xiaodi , Sun Song , Domen Kazunari 
Published: January 2019

AbstractLa5Ti2CuxAg1−xS5O7 (x=0–1) is a type of long‐wavelength‐responsive oxysulfide photocatalysts for hydrogen evolution and has been demonstrated to enable the Z‐scheme water‐splitting coupling with oxygen evolution photocatalysts (OEPs) in the particulate sheet. Among La5Ti2CuxAg1−xS5O7 materials, La5Ti2AgS5O7 was found to have the highest performance on Z‐scheme overall water splitting in conjunction with PtOx‐WO3 as an OEP and a triiodide/iodide (I3−/I−) redox couple as a shuttle electron mediator in a powder‐suspension system. Loading Pt/NiS on La5Ti2AgS5O7 benefitted the Z‐scheme to achieve an apparent quantum yield of 0.12 % at 420 nm. The results for this powder‐suspension system differ from earlier studies on photocatalyst sheet configurations, in which p‐type doping and the formation of a solid solution could effectively enhance the water‐splitting activity. This work not only demonstrates a La5Ti2AgS5O7‐based Z‐scheme water‐splitting photocatalyst but also improves the understanding of the difference between particulate sheets and a powder‐suspension system available in an optimal strategy for water splitting.
Kinetic Competition between Water‐Splitting and Photocorrosion Reactions in Photoelectrochemical Devices
Authors: Nandjou Fredy , Haussener Sophia 
Published: January 2019

AbstractSemiconductor photocorrosion is a major challenge for the stability of photoelectrochemical water‐splitting devices. Usually, photocorrosion is studied on the basis of thermodynamic aspects, by comparing the redox potentials of water to the self‐decomposition potentials of the semiconductor or analyzing the equilibrium phases at given electrolyte conditions. However, that approach does not allow for a prediction of the decomposition rate of the semiconductor or the branching ratio with the redox reaction. A kinetic model has been developed to describe detailed reaction mechanisms and investigate competition between water‐splitting and photocorrosion reactions. It is observed that some thermodynamically unstable semiconductors should photocorrode in a few minutes, whereas others are expected to operate over a period of years as a result of their extremely low photocorrosion current. The photostability of the semiconductor is mainly found to depend on surface chemical properties, catalyst activity, charge carrier density, and electrolyte acidity.
Selective Hydrogenation of CO2 to CH3OH on Supported Cu Nanoparticles Promoted by Isolated TiIV Surface Sites on SiO2
Authors: Noh Gina , Lam Erwin , Alfke Jan Lucas , Larmier Kim , Searles Keith , Wolf Patrick , Copéret Christophe 
Published: January 2019

AbstractSmall and narrowly distributed Cu nanoparticles, supported on SiO2 decorated with isolated TiIV sites, prepared through surface organometallic chemistry, showed significantly improved CO2 hydrogenation activity and CH3OH selectivity compared to the corresponding Cu nanoparticles supported on SiO2. These isolated Lewis acid TiIV sites, evidenced by UV/Vis spectroscopy, are proposed to stabilize surface intermediates at the interface between Cu nanoparticles and the support.
Geographic patterns of the climate sensitivity of lakes
Authors: McCullough Ian M. , Cheruvelil Kendra Spence , Collins Sarah M. , Soranno Patricia A. 
Published: January 2019

AbstractClimate change is a well‐recognized threat to lake ecosystems and, although there likely exists geographic variation in the sensitivity of lakes to climate, broad‐scale, long‐term studies are needed to understand this variation. Further, the potential mediating role of local to regional ecological context on these responses is not well documented. In this study, we examined relationships between climate and water clarity in 365 lakes from 1981 to 2010 in two distinct regions in the northeastern and midwestern United States. We asked (1) How do climate–water‐clarity relationships vary across watersheds and between two geographic regions? and (2) Do certain characteristics make some lakes more climate sensitive than others? We found strong differences in climate–water‐clarity relationships both within and across the two regions. For example, in the northeastern region, water clarity was often negatively correlated with summer precipitation (median correlation = −0.32,n = 160 lakes), but was not correlated with summer average maximum temperature (median correlation = 0.09,n = 205 lakes). In the midwestern region, water clarity was not related to summer precipitation (median correlation = −0.04), but was often negatively correlated with summer average maximum temperature (median correlation = −0.18). There were few strong relationships between local and sub‐regional ecological context and a lake's sensitivity to climate. For example, ecological context variables explained just 16–18% of variation in summer precipitation sensitivity, which was most related to total phosphorus, chlorophylla, lake depth, and hydrology in both regions. Sensitivity to summer maximum temperature was even less predictable in both regions, with 4% or less of variation explained using all ecological context variables. Overall, we identified differences in the climate sensitivity of lakes across regions and found that local and sub‐regional ecological context weakly influences the sensitivity of lakes to climate. Our findings suggest that local to regional drivers may combine to influence the sensitivity of lake ecosystems to climate change, and that sensitivities among lakes are highly variable within and across regions. This variability suggests that lakes are sensitive to different aspects of climate change (temperature vs. precipitation) and that responses of lakes to climate are heterogeneous and complex.
Species‐level biodiversity assessment using marine environmental DNA metabarcoding requires protocol optimization and standardization
Authors: Jeunen Gert‐Jan , Knapp Michael , Spencer Hamish G. , Taylor Helen R. , Lamare Miles D. , Stat Michael , Bunce Michael , Gemmell Neil J. 
Published: January 2019

AbstractDNA extraction from environmental samples (environmental DNA; eDNA) for metabarcoding‐based biodiversity studies is gaining popularity as a noninvasive, time‐efficient, and cost‐effective monitoring tool. The potential benefits are promising for marine conservation, as the marine biome is frequently under‐surveyed due to its inaccessibility and the consequent high costs involved. With increasing numbers of eDNA‐related publications have come a wide array of capture and extraction methods. Without visual species confirmation, inconsistent use of laboratory protocols hinders comparability between studies because the efficiency of target DNA isolation may vary. We determined an optimal protocol (capture and extraction) for marine eDNA research based on total DNA yield measurements by comparing commonly employed methods of seawater filtering and DNA isolation. We compared metabarcoding results of both targeted (small taxonomic group with species‐level assignment) and universal (broad taxonomic group with genus/family‐level assignment) approaches obtained from replicates treated with the optimal and a low‐performance capture and extraction protocol to determine the impact of protocol choice and DNA yield on biodiversity detection. Filtration through cellulose‐nitrate membranes and extraction with Qiagen's DNeasy Blood & Tissue Kit outperformed other combinations of capture and extraction methods, showing a ninefold improvement in DNA yield over the poorest performing methods. Use of optimized protocols resulted in a significant increase in OTU and species richness for targeted metabarcoding assays. However, changing protocols made little difference to the OTU and taxon richness obtained using universal metabarcoding assays. Our results demonstrate an increased risk of false‐negative species detection for targeted eDNA approaches when protocols with poor DNA isolation efficacy are employed. Appropriate optimization is therefore essential for eDNA monitoring to remain a powerful, efficient, and relatively cheap method for biodiversity assessments. For seawater, we advocate filtration through cellulose‐nitrate membranes and extraction with Qiagen's DNeasy Blood & Tissue Kit or phenol‐chloroform‐isoamyl for successful implementation of eDNA multi‐marker metabarcoding surveys.
Drawdown flushing in a chain of reservoirs—Effects on grayling populations and implications for sediment management
Authors: Reckendorfer Walter , Badura Hannes , Schütz Claudia 
Published: January 2019

AbstractWe used an information theoretic approach to assess the effects of an ecologically adjusted sediment management scheme on grayling (Thymallus thymallus L. 1758) populations. Additionally to reservoir operation, candidate models included a variety of parameters and processes that may influence grayling populations such as flow, temperature, density dependence, and bird predation. Population parameters analyzed included total densities, young of the year numbers, and larval densities. These analyses were supplemented by a characterization of sediments and sedimentation patterns in the reach. Investigations were carried out in six sites affected by flushing and in one control site. A total of thirteen flushing operations have been undertaken within the study period leading to considerable remobilization of fine sediments and gravel. Due to seasonal and hydrological restrictions, not every flood could be used for flushing. These limitations led to an interrupted management throughout the chain of reservoirs as well as to long time intervals between flushing events with possible effects on spawning habitat quality. None of the investigated population parameters was affected by flushing, and thus, the study generally supports the current reservoir management scheme. Our analyses revealed the magnitude and timing of high water events, temperature, and density‐dependent effects, that is, population densities the year before, as the most influential variables for grayling population dynamics in the investigated stretch. The siltation of reservoirs is a significant problem for reservoir storage, flood protection, river deltas, and coastal zones. Its management—which is inevitable to safeguard river deltas and secure flood protection—poses also the challenge to safeguard riverine ecosystems below reservoirs. Based on our experience, we propose a periodic flushing regime in concordance with the hydrograph thereby mimicking the timing, magnitude, frequency, and duration of natural SSC pulses and gravel transport. This flushing regime minimizes adverse downstream environmental impacts and maximizes benefits.
Fruit production is influenced by tree size and size‐asymmetric crowding in a wet tropical forest
Authors: Minor David M. , Kobe Richard K. 
Published: January 2019

AbstractIn tropical forest communities, seedling recruitment can be limited by the number of fruit produced by adults. Fruit production tends to be highly unequal among trees of the same species, which may be due to environmental factors. We observed fruit production for ~2,000 trees of 17 species across 3 years in a wet tropical forest in Costa Rica. Fruit production was modeled as a function of tree size, nutrient availability, and neighborhood crowding. Following model selection, tree size and neighborhood crowding predicted both the probability of reproduction and the number of fruit produced. Nutrient availability only predicted only the probability of reproduction. In all species, larger trees were more likely to be reproductive and produce more fruit. In addition, number of fruit was strongly negatively related to presence of larger neighboring trees in 13 species; presence of all neighboring trees had a weak‐to‐moderate negative influence on reproductive status in 16 species. Among various metrics of soil nutrient availability, only sum of base cations was positively associated with reproductive status, and for only four species.SynthesisOverall, these results suggest that direct influences on fruit production tend to be mediated through tree size and crowding from neighboring trees, rather than soil nutrients. However, we found variation in the effects of neighbors and nutrients among species; mechanistic studies of allocation to fruit production are needed to explain these differences.
Characterizing neutral and adaptive genomic differentiation in a changing climate: The most northerly freshwater fish as a model
Authors: O'Malley Kathleen G. , Vaux Felix , Black Andrew N. 
Published: January 2019

AbstractArctic freshwater ecosystems have been profoundly affected by climate change. Given that the Arctic charr (Salvelinus alpinus) is often the only fish species inhabiting these ecosystems, it represents a valuable model for studying the impacts of climate change on species life‐history diversity and adaptability. Using a genotyping‐by‐sequencing approach, we identified 5,976 neutral single nucleotide polymorphisms and found evidence for reduced gene flow between allopatric morphs from two high Arctic lakes, Linne'vatn (Anadromous, Normal, and Dwarf) and Ellasjøen (Littoral and Pelagic). Within each lake, the degree of genetic differentiation ranged from low (Pelagic vs. Littoral) to moderate (Anadromous and Normal vs. Dwarf). We identified 17 highly diagnostic, putatively adaptive SNPs that differentiated the allopatric morphs. Although we found no evidence for adaptive differences between morphs within Ellasjøen, we found evidence for moderate (Anadromous vs. Normal) to high genetic differentiation (Anadromous and Normal vs. Dwarf) among morphs within Linne'vatn based on two adaptive loci. As these freshwater ecosystems become more productive, the frequency of sympatric morphs in Ellasjøen will likely shift based on foraging opportunities, whereas the propensity to migrate may decrease in Linne'vatn, increasing the frequency of the Normal morph. The Dwarf charr was the most genetically distinct group. Identifying the biological basis for small body size should elucidate the potential for increased growth and subsequent interbreeding with sympatric morphs. Overall, neutral and adaptive genomic differentiation between allopatric and some sympatric morphs suggests that the response of Arctic charr to climate change will be variable across freshwater ecosystems.
Assessing the long‐term carbon‐sequestration potential of the semi‐natural salt marshes in the European Wadden Sea
Authors: Mueller Peter , Ladiges Nils , Jack Alexander , Schmiedl Gerhard , Kutzbach Lars , Jensen Kai , Nolte Stefanie 
Published: January 2019

AbstractSalt marshes and other blue carbon ecosystems have been increasingly recognized for their carbon (C)‐sink function. Yet, an improved assessment of organic carbon (OC) stocks and C‐sequestration rates is still required to include blue C in C‐crediting programs. Particularly, factors inducing variability in the permanence of sequestration and allochthonous contributions to soil OC stocks require an improved understanding. This study evaluates the potential for long‐term C sequestration in the semi‐natural salt marshes of the European Wadden Sea (WS), conducting deep (1.3 m) down‐core OC‐density assessments in sites with known site histories and accretion records. Because these young marshes have developed from tidal‐flat ecosystems and have undergone rapid succession during the last 80–120 yr, the identification of different ecosystem stages down‐core was crucial to interpret possible changes in OC density. This was conducted based on the down‐core distribution of different foraminiferal taxa and grain sizes. Comparisons of historic and recent accretion rates were conducted to understand possible effects of accretion rate on down‐core changes in OC density. δ13C in OC was used to assess the origin of accumulated OC (autochthonous vs. allochthonous sources). We show that large amounts of short‐term accumulated OC are lost down‐core in the well‐aerated marsh soils of the WS region and thus emphasize the importance of deep sampling to avoid overestimation of C sequestration. Despite steep declines in OC‐density down‐core, minimum values of OC density in the salt‐marsh soils were considerably higher than those of the former tidal‐flat sediments that the marshes were converted from, illustrating the greater C‐sequestration potential of the vegetated ecosystem. However, our data also suggest that marine‐derived allochthonous OC makes up a large fraction of the effectively, long‐term preserved OC stock, whereas atmospheric CO2 removal by marsh vegetation contributes relatively little. The implication of this finding for C‐crediting approaches in blue C ecosystems has yet to be clarified.
Climate will increasingly determine post‐fire tree regeneration success in low‐elevation forests, Northern Rockies,USA
Authors: Kemp Kerry B. , Higuera Philip E. , Morgan Penelope , Abatzoglou John T. 
Published: January 2019

AbstractClimate change is expected to cause widespread shifts in the distribution and abundance of plant species through direct impacts on mortality, regeneration, and survival. At landscape scales, climate impacts will be strongly mediated by disturbances, such as wildfire, which catalyze shifts in species distributions through widespread mortality and by shaping the post‐disturbance environment. We examined the potential for regional shifts in low‐elevation tree species in response to wildfire and climate warming in low‐elevation, dry mixed‐conifer forests of the northern Rocky Mountains,USA. We analyzed interactions among climate and wildfire on post‐fire tree seedling regeneration 5–13 yr post‐fire at 177 sites burned in 21 large wildfires during two years with widespread regional burning. We used generalized additive mixed models to quantify how the density of Douglas‐fir and ponderosa pine seedlings varied as a function of climate normals (30‐yr mean temperature, precipitation, soil moisture, and evapotranspiration) and fire (tree survivorship, burn severity, and seed source availability). Mean summer temperature was the most important predictor of post‐fire seedling densities for both ponderosa pine and Douglas‐fir. Seed availability was also important in determining Douglas‐fir regeneration. As mean summer temperature continues to increase, however, seed availability will become less important for determining post‐fire regeneration. Above a mean summer temperature of 17°C, Douglas‐fir regeneration is predicted to be minimal regardless of how close a seed source is to a site. The majority (82%) of our sampled sites are predicted to exceed a mean summer temperature of 17°C by mid‐century, suggesting significant declines in seedling densities and potential forest loss. Our results highlight mechanisms linking climate change to shifts in the distribution of two widely dominant tree species in western North America. Under a warming climate, we expect post‐fire tree regeneration in these low‐elevation forests to become increasingly unsuccessful. Such widespread regeneration failures would have important implications for ecosystem processes and forest resilience, particularly as wildfires increase in response to climate warming.