SNAPSHOT USA 2019 : a coordinated national camera trap survey of the United States

This article is protected by copyright. All rights reserved.With the accelerating pace of global change, it is imperative that we obtain rapid inventories of the status and distribution of wildlife for ecological inferences and conservation planning. To address this challenge, we launched the SNAPSHOT USA project, a collaborative survey of terrestrial wildlife populations using camera traps across the United States. For our first annual survey, we compiled data across all 50 states during a 14-week period (17 August - 24 November of 2019). We sampled wildlife at 1509 camera trap sites from 110 camera trap arrays covering 12 different ecoregions across four development zones. This effort resulted in 166,036 unique detections of 83 species of mammals and 17 species of birds. All images were processed through the Smithsonian's eMammal camera trap data repository and included an expert review phase to ensure taxonomic accuracy of data, resulting in each picture being reviewed at least twice. The results represent a timely and standardized camera trap survey of the USA. All of the 2019 survey data are made available herein. We are currently repeating surveys in fall 2020, opening up the opportunity to other institutions and cooperators to expand coverage of all the urban-wild gradients and ecophysiographic regions of the country. Future data will be available as the database is updated at eMammal.si.edu/snapshot-usa, as well as future data paper submissions. These data will be useful for local and macroecological research including the examination of community assembly, effects of environmental and anthropogenic landscape variables, effects of fragmentation and extinction debt dynamics, as well as species-specific population dynamics and conservation action plans. There are no copyright restrictions; please cite this paper when using the data for publication.Publisher PDFPeer reviewe

Mammal responses to global changes in human activity vary by trophic group and landscape

Wildlife must adapt to human presence to survive in the Anthropocene, so it is critical to understand species responses to humans in different contexts. We used camera trapping as a lens to view mammal responses to changes in human activity during the COVID-19 pandemic. Across 163 species sampled in 102 projects around the world, changes in the amount and timing of animal activity varied widely. Under higher human activity, mammals were less active in undeveloped areas but unexpectedly more active in developed areas while exhibiting greater nocturnality. Carnivores were most sensitive, showing the strongest decreases in activity and greatest increases in nocturnality. Wildlife managers must consider how habituation and uneven sensitivity across species may cause fundamental differences in human–wildlife interactions along gradients of human influence.Peer reviewe

Fixed-target serial femtosecond crystallography using in cellulo grown microcrystals

The crystallization of recombinant proteins in living cells is an exciting new approach in structural biology. Recent success has highlighted the need for fast and efficient diffraction data collection, optimally directly exposing intact crystal-containing cells to the X-ray beam, thus protecting the in cellulo crystals from environmental challenges. Serial femtosecond crystallography (SFX) at free-electron lasers (XFELs) allows the collection of detectable diffraction even from tiny protein crystals, but requires very fast sample exchange to utilize each XFEL pulse. Here, an efficient approach is presented for high-resolution structure elucidation using serial femtosecond in cellulo diffraction of micometre-sized crystals of the protein HEX-1 from the fungus Neurospora crassa on a fixed target. Employing the fast and highly accurate Roadrunner II translation-stage system allowed efficient raster scanning of the pores of micro-patterned, single-crystalline silicon chips loaded with living, crystal-containing insect cells. Compared with liquid-jet and LCP injection systems, the increased hit rates of up to 30% and reduced background scattering enabled elucidation of the HEX-1 structure. Using diffraction data from only a single chip collected within 12 min at the Linac Coherent Light Source, a 1.8 Å resolution structure was obtained with significantly reduced sample consumption compared with previous SFX experiments using liquid-jet injection. This HEX-1 structure is almost superimposable with that previously determined using synchrotron radiation from single HEX-1 crystals grown by sitting-drop vapour diffusion, validating the approach. This study demonstrates that fixed-target SFX using micro-patterned silicon chips is ideally suited for efficient in cellulo diffraction data collection using living, crystal-containing cells, and offers huge potential for the straightforward structure elucidation of proteins that form intracellular crystals at both XFELs and synchrotron sources

Fabrication and characterization of a focused ion beam milled lanthanum hexaboride based cold field electron emitter source

We report on a method of fabricating lanthanum hexaboride (LaB$_6$) cold field emission tips with sub-100-nm apices by using a combination of electrochemical etching and focused ion beam milling. The primary advantage of combining the two methods is rapid fabrication while maintaining reproducibility. The LaB6 tips have low work functions and high mechanical stabilities and are chemically inert to residual gases. Field emission characterization was performed on three tips, with apex sizes of 15, 85, and 80 nm yielding 10 nA cold field emission currents at 0.76, 3.9, and 3.6 kV extraction potentials, respectively. All three tips showed excellent emission current stability for periods exceeding 30 min in a 5 × 10$^{−9}$ mbar vacuum

Fabrication and characterization of a focused ion beam milled lanthanum hexaboride based cold field electron emitter source

We report on a method of fabricating lanthanum hexaboride (LaB$_6$) cold field emission tips with sub-100-nm apices by using a combination of electrochemical etching and focused ion beam milling. The primary advantage of combining the two methods is rapid fabrication while maintaining reproducibility. The LaB6 tips have low work functions and high mechanical stabilities and are chemically inert to residual gases. Field emission characterization was performed on three tips, with apex sizes of 15, 85, and 80 nm yielding 10 nA cold field emission currents at 0.76, 3.9, and 3.6 kV extraction potentials, respectively. All three tips showed excellent emission current stability for periods exceeding 30 min in a 5 × 10$^{−9}$ mbar vacuum

Coherent x-ray diffraction of a semiregular Pt nanodot array

Structural insight into nano-objects down to the atomic scale is one of the most important prerequisites tounderstand the properties of functional materials and will ultimately permit one to relate the size and shape ofnanoparticles to their catalytic activity. We elucidate the potential of extracting structural information abouta small ensemble of nanoparticles that are semiregularly arranged on a periodic array from coherent x-rayBragg diffraction. The observed fringe pattern in the Pt(111) Bragg peak obviously originates from the mutualinterference of the Bragg scattered wave field from individual nanoparticles in the nanoarray. Despite the absenceof a symmetry center in the Bragg peak of the nanoarray, we identify the most prominent in-plane spatialfrequencies of the latter by applying a Patterson map analysis to the Bragg peak superstructure. Integrationalong the in-plane reciprocal space direction over the relevant in-plane regions of interest results in Laueoscillations that arise from nanoparticle sets of similar heights in real space. A one-to-one comparison withreal-space microscopic information obtained from scanning electron microscopy and atomic force microscopysuggests potential nanoparticle subsets as the origin for the x-ray intensity in these regions of interest by the goodagreement in their height and direction-dependent in-plane interparticle distances, as also further supported bysimulations. Nanoparticle arrays with well-defined tunable sizes and lateral distances may serve in the future totrack structural changes in, e.g., sizes, relative positions, and tilts of smallest’ catalysis-relevant nanoparticlesduring operando heterogeneous catalysis experiments in the 10-nm-size regime

Single-particle structure determination by correlations of snapshot X-ray diffraction patterns

Diffractive imaging with free-electron lasers allows structure determination from ensembles of weakly scattering identical nanoparticles. The ultra-short, ultra-bright X-ray pulses provide snapshots of the randomly oriented particles frozen in time, and terminate before the onset of structural damage. As signal strength diminishes for small particles, the synthesis of a three-dimensional diffraction volume requires simultaneous involvement of all data. Here we report the first application of a three-dimensional spatial frequency correlation analysis to carry out this synthesis from noisy single-particle femtosecond X-ray diffraction patterns of nearly identical samples in random and unknown orientations, collected at the Linac Coherent Light Source. Our demonstration uses unsupported test particles created via aerosol self-assembly, and composed of two polystyrene spheres of equal diameter. The correlation analysis avoids the need for orientation determination entirely. This method may be applied to the structural determination of biological macromolecules in solution