361 research outputs found
Electron-Phonon Coupling in Boron-Doped Diamond Superconductor
The electronic structure, lattice dynamics, and electron-phonon coupling of
the boron-doped diamond are investigated using the density functional supercell
method. Our results indicate the boron-doped diamond is a phonon mediated
superconductor, con rming previous theoretical conclusions deduced from the
calculations employing the virtual crystal approximation. We show that the
optical phonon modes involving B vibrations play an important role in the
electron-phonon coupling. Di erent from previous theoretical results, our
calculated electron-phonon coupling constant is 0.39 and the estimated
superconducting transition temperature Tc is 4.4 K for the boron doped diamond
with 2.78% boron content using the Coulomb pseudopotential \mu*= 0.10, in
excellent agreement with the experimental result.Comment: 11 pages, 4 figures, Accepted by PR
AZI23'UTR Is a New SLC6A3 Downregulator Associated with an Epistatic Protection Against Substance Use Disorders
Regulated activity of SLC6A3, which encodes the human dopamine transporter (DAT), contributes to diseases such as substance abuse disorders (SUDs); however, the exact transcription mechanism remains poorly understood. Here, we used a common genetic variant of the gene, intron 1 DNP1B sequence, as bait to screen and clone a new transcriptional activity, AZI23'UTR, for SLC6A3. AZI23'UTR is a 3' untranslated region (3'UTR) of the human 5-Azacytidine Induced 2 gene (AZI2) but appeared to be transcribed independently of AZI2. Found to be present in both human cell nuclei and dopamine neurons, this RNA was shown to downregulate promoter activity through a variant-dependent mechanism in vitro. Both reduced RNA density ratio of AZI23'UTR/AZI2 and increased DAT mRNA levels were found in ethanol-naive alcohol-preferring rats. Secondary analysis of dbGaP GWAS datasets (Genome-Wide Association Studies based on the database of Genotypes and Phenotypes) revealed significant interactions between regions upstream of AZI23'UTR and SLC6A3 in SUDs. Jointly, our data suggest that AZI23'UTR confers variant-dependent transcriptional regulation of SLC6A3, a potential risk factor for SUDs
CO2 dissociation activated through electron attachment on reduced rutile TiO2(110)-1x1 surface
Converting CO to useful compounds through the solar photocatalytic
reduction has been one of the most promising strategies for artificial carbon
recycling. The highly relevant photocatalytic substrate for CO conversion
has been the popular TiO surfaces. However, the lack of accurate
fundamental parameters that determine the CO reduction on TiO has
limited our ability to control these complicated photocatalysis processes. We
have systematically studied the reduction of CO2 at specific sites of the
rutile TiO(110)-1x1 surface using scanning tunneling microscopy at 80 K.
The dissociation of CO2 molecules is found to be activated by one electron
attachment process and its energy threshold, corresponding to the
CO/CO redox potential, is unambiguously determined to be 2.3 eV
higher than the onset of the TiO conduction band. The dissociation rate as
a function of electron injection energy is also provided. Such information can
be used as practical guidelines for the design of effective catalysts for
CO photoreduction
Nucleon-Gold Collisions at 200 AGeV Using Tagged d+Au Interactions in PHOBOS
Forward calorimetry in the PHOBOS detector has been used to study charged
hadron production in d+Au, p+Au and n+Au collisions at sqrt(s_nn) = 200 GeV.
The forward proton calorimeter detectors are described and a procedure for
determining collision centrality with these detectors is detailed. The
deposition of energy by deuteron spectator nucleons in the forward calorimeters
is used to identify p+Au and n+Au collisions in the data. A weighted
combination of the yield of p+Au and n+Au is constructed to build a reference
for Au+Au collisions that better matches the isospin composition of the gold
nucleus. The p_T and centrality dependence of the yield of this improved
reference system is found to match that of d+Au. The shape of the charged
particle transverse momentum distribution is observed to extrapolate smoothly
from pbar+p to central d+Au as a function of the charged particle
pseudorapidity density. The asymmetry of positively- and negatively-charged
hadron production in p+Au is compared to that of n+Au. No significant asymmetry
is observed at mid-rapidity. These studies augment recent results from
experiments at the LHC and RHIC facilities to give a more complete description
of particle production in p+A and d+A collisions, essential for the
understanding the medium produced in high energy nucleus-nucleus collisions.Comment: 17 pages, 18 figure
The outer-membrane export signal of Porphyromonas gingivalis type IX secretion system (T9SS) is a conserved C-terminal \beta-sandwich domain
In the recently characterized Type IX Secretion System (T9SS), the conserved C-terminal domain (CTD) in secreted proteins functions as an outer membrane translocation signal for export of virulence factors to the cell surface in the Gram-negative Bacteroidetes phylum. In the periodontal pathogen Porphyromonas gingivalis, the CTD is cleaved off by PorU sortase in a sequence-independent manner, and anionic lipopolysaccharide (A-LPS) is attached to many translocated proteins, thus anchoring them to the bacterial surface. Here, we solved the atomic structure of the CTD of gingipain B (RgpB) from P. gingivalis, alone and together with a preceding immunoglobulin-superfamily domain (IgSF). The CTD was found to possess a typical Ig-like fold encompassing seven antiparallel β-strands organized in two β-sheets, packed into a β-sandwich structure that can spontaneously dimerise through C-terminal strand swapping. Small angle X-ray scattering (SAXS) revealed no fixed orientation of the CTD with respect to the IgSF. By introducing insertion or substitution of residues within the inter-domain linker in the native protein, we were able to show that despite the region being unstructured, it nevertheless is resistant to general proteolysis. These data suggest structural motifs located in the two adjacent Ig-like domains dictate the processing of CTDs by the T9SS secretion pathway
How Graphene Is Cut upon Oxidation?
Our first principles calculations reveal that oxidative cut of graphene is
realized by forming epoxy and then carbonyl pairs. Direct forming carbonyl pair
to tear graphene up from an edge position is not favorable in energy. This
atomic picture is valuable for developing effective graphene manipulation
means. The proposed epoxy pairs may be related to some long puzzling
experimental observations on graphene oxide
Report of the 2021 U.S. Community Study on the Future of Particle Physics (Snowmass 2021) Summary Chapter
The 2021-22 High-Energy Physics Community Planning Exercise (a.k.a.
``Snowmass 2021'') was organized by the Division of Particles and Fields of the
American Physical Society. Snowmass 2021 was a scientific study that provided
an opportunity for the entire U.S. particle physics community, along with its
international partners, to identify the most important scientific questions in
High Energy Physics for the following decade, with an eye to the decade after
that, and the experiments, facilities, infrastructure, and R&D needed to pursue
them. This Snowmass summary report synthesizes the lessons learned and the main
conclusions of the Community Planning Exercise as a whole and presents a
community-informed synopsis of U.S. particle physics at the beginning of 2023.
This document, along with the Snowmass reports from the various subfields, will
provide input to the 2023 Particle Physics Project Prioritization Panel (P5)
subpanel of the U.S. High-Energy Physics Advisory Panel (HEPAP), and will help
to guide and inform the activity of the U.S. particle physics community during
the next decade and beyond.Comment: 75 pages, 3 figures, 2 tables. This is the first chapter and summary
of the full report of the Snowmass 2021 Workshop. This version fixes an
important omission from Table 2, adds two references that were not available
at the time of the original version, fixes a minor few typos, and adds a
small amount of material to section 1.1.
Covariation in Plant Functional Traits and Soil Fertility within Two Species-Rich Forests
The distribution of plant species along environmental gradients is expected to be predictable based on organismal function. Plant functional trait research has shown that trait values generally vary predictably along broad-scale climatic and soil gradients. This work has also demonstrated that at any one point along these gradients there is a large amount of interspecific trait variation. The present research proposes that this variation may be explained by the local-scale sorting of traits along soil fertility and acidity axes. Specifically, we predicted that trait values associated with high resource acquisition and growth rates would be found on soils that are more fertile and less acidic. We tested the expected relationships at the species-level and quadrat-level (20×20 m) using two large forest plots in Panama and China that contain over 450 species combined. Predicted relationships between leaf area and wood density and soil fertility were supported in some instances, but the majority of the predicted relationships were rejected. Alternative resource axes, such as light gradients, therefore likely play a larger role in determining the interspecific variability in plant functional traits in the two forests studied
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