10,915 research outputs found
Influence of Grazing on Soil Microbial Communities on a Mixed Grass Prairie Ecosystem
The grazing of ungulates is the predominant use for much of the world\u27s semiarid rangelands. Grazing these lands can result in significant changes not only in the vegetation community but also in the soil physical, chemical and biological properties. Changes in soil physical and chemical properties and the plant community can potentially lead to changes in soil microbial communities which may have long-term ramifications for nutrient cycling and carbon (C) sequestration. The objective of this research was to ascertain the influence of three long-term grazing treatments on soil microbial communities
Observation of Magnetic Edge State and Dangling Bond State on Nanographene in Activated Carbon Fibers
The electronic structure of nanographene in pristine and fluorinated
activated carbon fibers (ACFs) have been investigated with near-edge x-ray
absorption fine structure (NEXAFS) and compared with magnetic properties we
reported on previously. In pristine ACFs in which magnetic properties are
governed by non-bonding edge states of the \pi-electron, a pre-peak assigned to
the edge state was observed below the conduction electron {\pi}* peak close to
the Fermi level in NEXAFS. Via the fluorination of the ACFs, an extra peak,
which was assigned to the \sigma-dangling bond state, was observed between the
pre-peak of the edge state and the {\pi}* peak in the NEXAFS profile. The
intensities of the extra peak correlate closely with the spin concentration
created upon fluorination. The combination of the NEXAFS and magnetic
measurement results confirms the coexistence of the magnetic edge states of
\pi-electrons and dangling bond states of \sigma-electrons on fluorinated
nanographene sheets.Comment: 4 figures, to appear in Phys. Rev.
Detection of Very Low-Frequency Quasi-Periodic Oscillations in the 2015 Outburst of V404 Cygni
In June 2015, the black hole X-ray binary (BHXRB) V404 Cygni went into
outburst for the first time since 1989. Here, we present a comprehensive search
for quasi-periodic oscillations (QPOs) of V404 Cygni during its recent
outburst, utilizing data from six instruments on board five different X-ray
missions: Swift/XRT, Fermi/GBM, Chandra/ACIS, INTEGRAL's IBIS/ISGRI and JEM-X,
and NuSTAR. We report the detection of a QPO at 18 mHz simultaneously with both
Fermi/GBM and Swift/XRT, another example of a rare but slowly growing new class
of mHz-QPOs in BHXRBs linked to sources with a high orbital inclination.
Additionally, we find a duo of QPOs in a Chandra/ACIS observation at 73 mHz and
1.03 Hz, as well as a QPO at 136 mHz in a single Swift/XRT observation that can
be interpreted as standard Type-C QPOs. Aside from the detected QPOs, there is
significant structure in the broadband power, with a strong feature observable
in the Chandra observations between 0.1 and 1 Hz. We discuss our results in the
context of current models for QPO formation.Comment: 17 pages, 9 figures, published in Ap
Dynamic Analysis of Executables to Detect and Characterize Malware
It is needed to ensure the integrity of systems that process sensitive
information and control many aspects of everyday life. We examine the use of
machine learning algorithms to detect malware using the system calls generated
by executables-alleviating attempts at obfuscation as the behavior is monitored
rather than the bytes of an executable. We examine several machine learning
techniques for detecting malware including random forests, deep learning
techniques, and liquid state machines. The experiments examine the effects of
concept drift on each algorithm to understand how well the algorithms
generalize to novel malware samples by testing them on data that was collected
after the training data. The results suggest that each of the examined machine
learning algorithms is a viable solution to detect malware-achieving between
90% and 95% class-averaged accuracy (CAA). In real-world scenarios, the
performance evaluation on an operational network may not match the performance
achieved in training. Namely, the CAA may be about the same, but the values for
precision and recall over the malware can change significantly. We structure
experiments to highlight these caveats and offer insights into expected
performance in operational environments. In addition, we use the induced models
to gain a better understanding about what differentiates the malware samples
from the goodware, which can further be used as a forensics tool to understand
what the malware (or goodware) was doing to provide directions for
investigation and remediation.Comment: 9 pages, 6 Tables, 4 Figure
Household Tenure and Its Associations with Multiple Long-Term Conditions amongst Working-Age Adults in East London: A Cross-Sectional Analysis Using Linked Primary Care and Local Government Records
Multiple long-term conditions (MLTCs) are influenced in extent and nature by social determinants of health. Few studies have explored associations between household tenure and different definitions of MLTCs. This study aimed to examine associations between household tenure and MLTCs amongst working-age adults (16 to 64 years old, inclusive). This cross-sectional study used the 2019–2020 wave of an innovative dataset that links administrative data across health and local government for residents of a deprived borough in East London. Three definitions of MLTCs were operationalised based on a list of 38 conditions. Multilevel logistic regression models were built for each outcome and adjusted for a range of health and sociodemographic factors. Compared to working-age owner-occupiers, odds of basic MLTCs were 36% higher for social housing tenants and 19% lower for private renters (OR 1.36; 95% CI 1.30–1.42; p < 0.001 and OR 0.81, 95% CI 0.77–0.84, p < 0.001, respectively). Results were consistent across different definitions of MLTCs, although associations were stronger for social housing tenants with physical-mental MLTCs. This study finds strong evidence that household tenure is associated with MLTCs, emphasising the importance of understanding household-level determinants of health. Resources to prevent and tackle MLTCs among working-age adults could be differentially targeted by tenure type
Matrix controlled channel diffusion of sodium in amorphous silica
To find the origin of the diffusion channels observed in sodium-silicate
glasses, we have performed classical molecular dynamics simulations of
NaO--4SiO during which the mass of the Si and O atoms has been
multiplied by a tuning coefficient. We observe that the channels disappear and
that the diffusive motion of the sodium atoms vanishes if this coefficient is
larger than a threshold value. Above this threshold the vibrational states of
the matrix are not compatible with those of the sodium ions. We interpret hence
the decrease of the diffusion by the absence of resonance conditions.Comment: 5 pages, 4 figure
A NICER Discovery of a Low-Frequency Quasi-Periodic Oscillation in the Soft-Intermediate State of MAXI J1535-571
We present the discovery of a low-frequency Hz quasi-periodic
oscillation (QPO) feature in observations of the black hole X-ray binary MAXI
J1535-571 in its soft-intermediate state, obtained in September-October 2017 by
the Neutron Star Interior Composition Explorer (NICER). The feature is
relatively broad (compared to other low-frequency QPOs; quality factor
) and weak (1.9% rms in 3-10 keV), and is accompanied by a weak
harmonic and low-amplitude broadband noise. These characteristics identify it
as a weak Type A/B QPO, similar to ones previously identified in the
soft-intermediate state of the transient black hole X-ray binary XTE J1550-564.
The lag-energy spectrum of the QPO shows increasing soft lags towards lower
energies, approaching 50 ms at 1 keV (with respect to a 3-10 keV continuum).
This large phase shift has similar amplitude but opposite sign to that seen in
Rossi X-ray Timing Explorer data for a Type B QPO from the transient black hole
X-ray binary GX 339-4. Previous phase-resolved spectroscopy analysis of the
Type B QPO in GX 339-4 pointed towards a precessing jet-like corona
illuminating the accretion disk as the origin of the QPO signal. We suggest
that this QPO in MAXI J1535-571 may have the same origin, with the different
lag sign depending on the scale height of the emitting region and the observer
inclination angle.Comment: Accepted for publication in ApJ Letter
Orally active antischistosomal early leads identified from the open access malaria box.
BACKGROUND: Worldwide hundreds of millions of schistosomiasis patients rely on treatment with a single drug, praziquantel. Therapeutic limitations and the threat of praziquantel resistance underline the need to discover and develop next generation drugs. METHODOLOGY: We studied the antischistosomal properties of the Medicines for Malaria Venture (MMV) malaria box containing 200 diverse drug-like and 200 probe-like compounds with confirmed in vitro activity against Plasmodium falciparum. Compounds were tested against schistosomula and adult Schistosoma mansoni in vitro. Based on in vitro performance, available pharmacokinetic profiles and toxicity data, selected compounds were investigated in vivo. PRINCIPAL FINDINGS: Promising antischistosomal activity (IC50: 1.4-9.5 µM) was observed for 34 compounds against schistosomula. Three compounds presented IC50 values between 0.8 and 1.3 µM against adult S. mansoni. Two promising early leads were identified, namely a N,N'-diarylurea and a 2,3-dianilinoquinoxaline. Treatment of S. mansoni infected mice with a single oral 400 mg/kg dose of these drugs resulted in significant worm burden reductions of 52.5% and 40.8%, respectively. CONCLUSIONS/SIGNIFICANCE: The two candidates identified by investigating the MMV malaria box are characterized by good pharmacokinetic profiles, low cytotoxic potential and easy chemistry and therefore offer an excellent starting point for antischistosomal drug discovery and development
Phase-resolved spectroscopy of a quasi-periodic oscillation in the black hole X-ray binary GRS 1915+105 with <i>NICER</i> and <i>NuSTAR</i>
Quasi-periodic oscillations (QPOs) are often present in the X-ray flux from
accreting stellar-mass black holes (BHs). If they are due to relativistic
(Lense-Thirring) precession of an inner accretion flow which is misaligned with
the disc, the iron emission line caused by irradiation of the disc by the inner
flow will rock systematically between red and blue shifted during each QPO
cycle. Here we conduct phase-resolved spectroscopy of a Hz type-C QPO
from the BH X-ray binary GRS 1915+105, observed simultaneously with NICER and
NuSTAR. We apply a tomographic model in order to constrain the QPO
phase-dependent illumination profile of the disc. We detect the predicted QPO
phase-dependent shifts of the iron line centroid energy, with our best fit
featuring an asymmetric illumination profile ( confidence). The
observed line energy shifts can alternatively be explained by the spiral
density waves of the accretion-ejection instability model. However we
additionally measure a significant () modulation in reflection
fraction, strongly favouring a geometric QPO origin. We infer that the disc is
misaligned with previously observed jet ejections, which is consistent with the
model of a truncated disc with an inner precessing hot flow. However our
inferred disc inner radius is small (). For this
disc inner radius, Lense-Thirring precession cannot reproduce the observed QPO
frequency. In fact, this disc inner radius is incompatible with the predictions
of all well-studied QPO models in the literature.Comment: 26 pages, 16 figures, accepted to MNRA
Electronic structure and light-induced conductivity in a transparent refractory oxide
Combined first-principles and experimental investigations reveal the
underlying mechanism responsible for a drastic change of the conductivity (by
10 orders of magnitude) following hydrogen annealing and UV-irradiation in a
transparent oxide, 12CaO.7Al2O3, found by Hayashi et al. The charge transport
associated with photo-excitation of an electron from H, occurs by electron
hopping. We identify the atoms participating in the hops, determine the exact
paths for the carrier migration, estimate the temperature behavior of the
hopping transport and predict a way to enhance the conductivity by specific
doping.Comment: 4 pages including 4 figure
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