418 research outputs found
Increasing Spatial Fidelity and SNR of 4D-STEM using Multi-frame Data Fusion
4D-STEM, in which the 2D diffraction plane is captured for each 2D scan
position in the scanning transmission electron microscope (STEM) using a
pixelated detector, is complementing and increasingly replacing existing
imaging approaches. However, at present the speed of those detectors, although
having drastically improved in the recent years, is still 100 to 1,000 times
slower than the current PMT technology operators are used to. Regrettably, this
means environmental scanning-distortion often limits the overall performance of
the recorded 4D data. Here we present an extension of existing STEM distortion
correction techniques for the treatment of 4D-data series. Although applicable
to 4D-data in general, we use electron ptychography and electric-field mapping
as model cases and demonstrate an improvement in spatial-fidelity,
signal-to-noise ratio (SNR), phase-precision and spatial-resolution
Lossy Compression of Electron Diffraction Patterns for Ptychography via Change of Basis
Ptychography is a computational imaging technique that has risen in
popularity in the x-ray and electron microscopy communities in the past half
decade. One of the reasons for this success is the development of new high
performance electron detectors with increased dynamic range and readout speed,
both of which are necessary for a successful application of this technique.
Despite the advances made in computing power, processing the recorded data
remains a challenging task, and the growth in data rate has made the size of
the resulting datasets a bottleneck for the whole process. Here we present an
investigation into lossy compression methods for electron diffraction patterns
that retain the necessary information for ptychographic reconstructions, yet
lead to a decrease in data set size by three or four orders of magnitude. We
apply several compression methods to both simulated and experimental data - all
with promising results
Atomic resolution mapping of localized phonon modes at grain boundaries
Phonon scattering at grain boundaries (GBs) is significant in controlling
nanoscale device thermal conductivity. However, GBs could also act as
waveguides for selected modes. To measure localized GB phonon modes, meV energy
resolution is needed with sub-nm spatial resolution. Using monochromated
electron energy loss spectroscopy (EELS) in the scanning transmission electron
microscope (STEM) we have mapped the 60 meV optic mode across GBs in silicon at
atomic resolution and compared it to calculated phonon densities of states
(DOS). The intensity is strongly reduced at GBs characterised by the presence
of five- and seven-fold rings where bond angles differ from the bulk. The
excellent agreement between theory and experiment strongly supports the
existence of localized phonon modes and thus of GBs acting as waveguides
ResearchSherlock: Toward a seamless integration of printed books into the digital academic workflow
With the increase of digital information practices (e.g. online search, desktop
publishing, electronic reference management, etc.) in the academic context,
printed books are sometimes cumbersome to integrate into the digital workflow.
We present ResearchSherlock, an Android app that allows the user to
quickly gather bibliographic information for a printed book by scanning its
shelfmark or ISBN. The application also provides recommenddations for
thematically related books, to promote the discovery of other relevant books
that are available in the local library
Nanoparticle Exsolution from Nanoporous Perovskites for Highly Active and Stable Catalysts
Nanoporosity is clearly beneficial for the performance of heterogeneous catalysts. Although exsolution is a modern method to design innovative catalysts, thus far it is predominantly studied for sintered matrices. A quantitative description of the exsolution of Ni nanoparticles from nanoporous perovskite oxides and their effective application in the biogas dry reforming is here presented. The exsolution process is studied between 500 and 900 °C in nanoporous and sintered LaSrTiNiO. Using temperature-programmed reduction (TPR) and X-ray absorption spectroscopy (XAS), it is shown that the faster and larger oxygen release in the nanoporous material is responsible for twice as high Ni reduction than in the sintered system. For the nanoporous material, the nanoparticle formation mechanism, studied by in situ TEM and small-angle X-ray scattering (SAXS), follows the classical nucleation theory, while on sintered systems also small endogenous nanoparticles form despite the low Ni concentration. Biogas dry reforming tests demonstrate that nanoporous exsolved catalysts are up to 18 times more active than sintered ones with 90% of CO conversion at 800 °C. Time-on-stream tests exhibit superior long-term stability (only 3% activity loss in 8 h) and full regenerability (over three cycles) of the nanoporous exsolved materials in comparison to a commercial Ni/AlO catalyst
SARS-CoV-2 Omicron variants BA.1 and BA.2 both show similarly reduced disease severity of COVID-19 compared to Delta, Germany, 2021 to 2022
German national surveillance data analysis shows that hospitalisation odds associated with Omicron lineage BA.1 or BA.2 infections are up to 80% lower than with Delta infection, primarily in ≥ 35-year-olds. Hospitalised vaccinated Omicron cases’ proportions (2.3% for both lineages) seemed lower than those of the unvaccinated (4.4% for both lineages). Independent of vaccination status, the hospitalisation frequency among cases with Delta seemed nearly threefold higher (8.3%) than with Omicron (3.0% for both lineages), suggesting that Omicron inherently causes less severe disease.Peer Reviewe
Composition Analysis of III-Nitrides at the Nanometer Scale: Comparison of Energy Dispersive X-ray Spectroscopy and Atom Probe Tomography
International audienc
Temporal transcriptomic analysis of the Listeria monocytogenes EGD-e σB regulon
<p>Abstract</p> <p>Background</p> <p>The opportunistic food-borne gram-positive pathogen <it>Listeria monocytogenes </it>can exist as a free-living microorganism in the environment and grow in the cytoplasm of vertebrate and invertebrate cells following infection. The general stress response, controlled by the alternative sigma factor, σ<sup>B</sup>, has an important role for bacterial survival both in the environment and during infection. We used quantitative real-time PCR analysis and immuno-blot analysis to examine σ<sup>B </sup>expression during growth of <it>L. monocytogenes </it>EGD-e. Whole genome-based transcriptional profiling was used to identify σ<sup>B</sup>-dependent genes at different growth phases.</p> <p>Results</p> <p>We detected 105 σ<sup>B</sup>-positively regulated genes and 111 genes which appeared to be under negative control of σ<sup>B </sup>and validated 36 σ<sup>B</sup>-positively regulated genes <it>in vivo </it>using a reporter gene fusion system.</p> <p>Conclusion</p> <p>Genes comprising the σ<sup>B </sup>regulon encode solute transporters, novel cell-wall proteins, universal stress proteins, transcriptional regulators and include those involved in osmoregulation, carbon metabolism, ribosome- and envelope-function, as well as virulence and niche-specific survival genes such as those involved in bile resistance and exclusion. Ten of the σ<sup>B</sup>-positively regulated genes of <it>L. monocytogenes </it>are absent in <it>L. innocua</it>. A total of 75 σ<sup>B</sup>-positively regulated listerial genes had homologs in <it>B. subtilis</it>, but only 33 have been previously described as being σ<sup>B</sup>-regulated in <it>B. subtilis </it>even though both species share a highly conserved σ<sup>B</sup>-dependent consensus sequence. A low overlap of genes may reflects adaptation of these bacteria to their respective environmental conditions.</p
A database accelerator for energy-efficient query processing and optimization
Data processing on a continuously growing amount of information and the increasing power restrictions have become an ubiquitous challenge in our world today. Besides parallel computing, a promising approach to improve the energy efficiency of current systems is to integrate specialized hardware. This paper presents a Tensilica RISC processor extended with an instruction set to accelerate basic database operators frequently used in modern database systems. The core was taped out in a 28 nm SLP CMOS technology and allows energy-efficient query processing as well as query optimization by applying selectivity estimation techniques. Our chip measurements show an 1000x energy improvement on selected database operators compared to state-of-the-art systems
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