262 research outputs found
Optical-Model Description of Time-Reversal Violation
A time-reversal-violating spin-correlation coefficient in the total cross
section for polarized neutrons incident on a tensor rank-2 polarized target is
calculated by assuming a time-reversal-noninvariant, parity-conserving
``five-fold" interaction in the neutron-nucleus optical potential. Results are
presented for the system for neutron incident energies
covering the range 1--20 MeV. From existing experimental bounds, a strength of
keV is deduced for the real and imaginary parts of the five-fold
term, which implies an upper bound of order on the relative -odd
strength when compared to the central real optical potential.Comment: 11 pages (Revtex
The angular distribution of the reaction
The reaction is very important for low-energy
( MeV) antineutrino experiments. In this paper we calculate
the positron angular distribution, which at low energies is slightly backward.
We show that weak magnetism and recoil corrections have a large effect on the
angular distribution, making it isotropic at about 15 MeV and slightly forward
at higher energies. We also show that the behavior of the cross section and the
angular distribution can be well-understood analytically for MeV by calculating to , where is the nucleon mass. The
correct angular distribution is useful for separating events from other reactions and detector backgrounds, as well as for
possible localization of the source (e.g., a supernova) direction. We comment
on how similar corrections appear for the lepton angular distributions in the
deuteron breakup reactions and . Finally, in the reaction , the
angular distribution of the outgoing neutrons is strongly forward-peaked,
leading to a measurable separation in positron and neutron detection points,
also potentially useful for rejecting backgrounds or locating the source
direction.Comment: 10 pages, including 5 figure
Can sacrificial feeding areas protect aquatic plants from herbivore grazing? Using behavioural ecology to inform wildlife management
Effective wildlife management is needed for conservation, economic and human well-being objectives. However, traditional population control methods are frequently ineffective, unpopular with stakeholders, may affect non-target species, and can be both expensive and impractical to implement. New methods which address these issues and offer effective wildlife management are required. We used an individual-based model to predict the efficacy of a sacrificial feeding area in preventing grazing damage by mute swans (Cygnus olor) to adjacent river vegetation of high conservation and economic value. The accuracy of model predictions was assessed by a comparison with observed field data, whilst prediction robustness was evaluated using a sensitivity analysis. We used repeated simulations to evaluate how the efficacy of the sacrificial feeding area was regulated by (i) food quantity, (ii) food quality, and (iii) the functional response of the forager. Our model gave accurate predictions of aquatic plant biomass, carrying capacity, swan mortality, swan foraging effort, and river use. Our model predicted that increased sacrificial feeding area food quantity and quality would prevent the depletion of aquatic plant biomass by swans. When the functional response for vegetation in the sacrificial feeding area was increased, the food quantity and quality in the sacrificial feeding area required to protect adjacent aquatic plants were reduced. Our study demonstrates how the insights of behavioural ecology can be used to inform wildlife management. The principles that underpin our model predictions are likely to be valid across a range of different resource-consumer interactions, emphasising the generality of our approach to the evaluation of strategies for resolving wildlife management problems
Effect of P to A Mutation of the N-Terminal Residue Adjacent to the Rgd Motif on Rhodostomin: Importance of Dynamics in Integrin Recognition
Rhodostomin (Rho) is an RGD protein that specifically inhibits integrins. We found that Rho mutants with the P48A mutation 4.4–11.5 times more actively inhibited integrin α5β1. Structural analysis showed that they have a similar 3D conformation for the RGD loop. Docking analysis also showed no difference between their interactions with integrin α5β1. However, the backbone dynamics of RGD residues were different. The values of the R2 relaxation parameter for Rho residues R49 and D51 were 39% and 54% higher than those of the P48A mutant, which caused differences in S2, Rex, and τe. The S2 values of the P48A mutant residues R49, G50, and D51 were 29%, 14%, and 28% lower than those of Rho. The Rex values of Rho residues R49 and D51 were 0.91 s−1 and 1.42 s−1; however, no Rex was found for those of the P48A mutant. The τe values of Rho residues R49 and D51 were 9.5 and 5.1 times lower than those of P48A mutant. Mutational study showed that integrin α5β1 prefers its ligands to contain (G/A)RGD but not PRGD sequences for binding. These results demonstrate that the N-terminal proline residue adjacent to the RGD motif affect its function and dynamics, which suggests that the dynamic properties of the RGD motif may be important in Rho's interaction with integrin α5β1
Long-term multiwavelength monitoring and reverberation mapping of NGC 2617 during a changing-look event
We present the results of photometric and spectroscopic monitoring campaigns
of the changing look AGN NGC~2617 carried out from 2016 until 2022 and covering
the wavelength range from the X-ray to the near-IR. The facilities included the
telescopes of the SAI MSU, MASTER Global Robotic Net, the 2.3-m WIRO telescope,
Swift, and others. We found significant variability at all wavelengths and,
specifically, in the intensities and profiles of the broad Balmer lines. We
measured time delays of ~ 6 days (~ 8 days) in the responses of the H-beta
(H-alpha) line to continuum variations. We found the X-ray variations to
correlate well with the UV and optical (with a small time delay of a few days
for longer wavelengths). The K-band lagged the B band by 14 +- 4 days during
the last 3 seasons, which is significantly shorter than the delays reported
previously by the 2016 and 2017--2019 campaigns. Near-IR variability arises
from two different emission regions: the outer part of the accretion disc and a
more distant dust component. The HK-band variability is governed primarily by
dust. The Balmer decrement of the broad-line components is inversely correlated
with the UV flux. The change of the object's type, from Sy1 to Sy1.8, was
recorded over a period of ~ 8 years. We interpret these changes as a
combination of two factors: changes in the accretion rate and dust recovery
along the line of sight.Comment: 14 pages, 15 figures, accepted by the MNRA
Barriers to the acceptance of electronic medical records by physicians from systematic review to taxonomy and interventions
<p>Abstract</p> <p>Background</p> <p>The main objective of this research is to identify, categorize, and analyze barriers perceived by physicians to the adoption of Electronic Medical Records (EMRs) in order to provide implementers with beneficial intervention options.</p> <p>Methods</p> <p>A systematic literature review, based on research papers from 1998 to 2009, concerning barriers to the acceptance of EMRs by physicians was conducted. Four databases, "Science", "EBSCO", "PubMed" and "The Cochrane Library", were used in the literature search. Studies were included in the analysis if they reported on physicians' perceived barriers to implementing and using electronic medical records. Electronic medical records are defined as computerized medical information systems that collect, store and display patient information.</p> <p>Results</p> <p>The study includes twenty-two articles that have considered barriers to EMR as perceived by physicians. Eight main categories of barriers, including a total of 31 sub-categories, were identified. These eight categories are: A) Financial, B) Technical, C) Time, D) Psychological, E) Social, F) Legal, G) Organizational, and H) Change Process. All these categories are interrelated with each other. In particular, Categories G (Organizational) and H (Change Process) seem to be mediating factors on other barriers. By adopting a change management perspective, we develop some barrier-related interventions that could overcome the identified barriers.</p> <p>Conclusions</p> <p>Despite the positive effects of EMR usage in medical practices, the adoption rate of such systems is still low and meets resistance from physicians. This systematic review reveals that physicians may face a range of barriers when they approach EMR implementation. We conclude that the process of EMR implementation should be treated as a change project, and led by implementers or change managers, in medical practices. The quality of change management plays an important role in the success of EMR implementation. The barriers and suggested interventions highlighted in this study are intended to act as a reference for implementers of Electronic Medical Records. A careful diagnosis of the specific situation is required before relevant interventions can be determined.</p
Broad-line region in NGC 4151 monitored by two decades of reverberation mapping campaigns. I. Evolution of structure and kinematics
We report the results of long-term reverberation mapping (RM) campaigns of
the nearby active galactic nuclei (AGN) NGC 4151, spanning from 1994 to 2022,
based on archived observations of the FAST Spectrograph Publicly Archived
Programs and our new observations with the 2.3m telescope at the Wyoming
Infrared Observatory. We reduce and calibrate all the spectra in a consistent
way, and derive light curves of the broad H line and 5100\,{\AA}
continuum. Continuum light curves are also constructed using public archival
photometric data to increase sampling cadences. We subtract the host galaxy
contamination using {\it HST} imaging to correct fluxes of the calibrated light
curves. Utilizing the long-term archival photometric data, we complete the
absolute flux-calibration of the AGN continuum. We find that the H time
delays are correlated with the 5100\,{\AA} luminosities as . This is remarkably consistent with
Bentz et al. (2013)'s global size-luminosity relationship of AGNs. Moreover,
the data sets for five of the seasons allow us to obtain the velocity-resolved
delays of the H line, showing diverse structures (outflows, inflows and
disks). Combining our results with previous independent measurements, we find
the measured dynamics of the H broad-line region (BLR) are possibly
related to the long-term trend of the luminosity. There is also a possible
additional 1.86 years time lag between the variation in BLR radius and
luminosity. These results suggest that dynamical changes in the BLR may be
driven by the effects of radiation pressure.Comment: Accepted for publication in MNRAS; comments welcome
Deficiency of the Mitochondrial Electron Transport Chain in Muscle Does Not Cause Insulin Resistance
It has been proposed that muscle insulin resistance in type 2 diabetes is due to a selective decrease in the components of the mitochondrial electron transport chain and results from accumulation of toxic products of incomplete fat oxidation. The purpose of the present study was to test this hypothesis.Rats were made severely iron deficient, by means of an iron-deficient diet. Iron deficiency results in decreases of the iron containing mitochondrial respiratory chain proteins without affecting the enzymes of the fatty acid oxidation pathway. Insulin resistance was induced by feeding iron-deficient and control rats a high fat diet. Skeletal muscle insulin resistance was evaluated by measuring glucose transport activity in soleus muscle strips. Mitochondrial proteins were measured by Western blot. Iron deficiency resulted in a decrease in expression of iron containing proteins of the mitochondrial respiratory chain in muscle. Citrate synthase, a non-iron containing citrate cycle enzyme, and long chain acyl-CoA dehydrogenase (LCAD), used as a marker for the fatty acid oxidation pathway, were unaffected by the iron deficiency. Oleate oxidation by muscle homogenates was increased by high fat feeding and decreased by iron deficiency despite high fat feeding. The high fat diet caused severe insulin resistance of muscle glucose transport. Iron deficiency completely protected against the high fat diet-induced muscle insulin resistance.The results of the study argue against the hypothesis that a deficiency of the electron transport chain (ETC), and imbalance between the ETC and β-oxidation pathways, causes muscle insulin resistance
The Long-Term Consequences of the Global 1918 Influenza Pandemic: A Systematic Analysis of 117 IPUMS International Census Data Sets
Escalating morphine dosing in HIV-1 Tat transgenic mice with sustained Tat exposure reveals an allostatic shift in neuroinflammatory regulation accompanied by increased neuroprotective non-endocannabinoid lipid signaling molecules and amino acids
BACKGROUND: Human immunodeficiency virus type-1 (HIV-1) and opiates cause long-term inflammatory insult to the central nervous system (CNS) and worsen disease progression and HIV-1-related neuropathology. The combination of these proinflammatory factors reflects a devastating problem as opioids have high abuse liability and continue to be prescribed for certain patients experiencing HIV-1-related pain. METHODS: Here, we examined the impact of chronic (3-month) HIV-1 transactivator of transcription (Tat) exposure to short-term (8-day), escalating morphine in HIV-1 Tat transgenic mice that express the HIV-1 Tat protein in a GFAP promoter-regulated, doxycycline (DOX)-inducible manner. In addition to assessing morphine-induced tolerance in nociceptive responses organized at spinal (i.e., tail-flick) and supraspinal (i.e., hot-plate) levels, we evaluated neuroinflammation via positron emission tomography (PET) imaging using the [¹⁸F]-PBR111 ligand, immunohistochemistry, and cytokine analyses. Further, we examined endocannabinoid (eCB) levels, related non-eCB lipids, and amino acids via mass spectrometry. RESULTS: Tat-expressing [Tat(+)] transgenic mice displayed antinociceptive tolerance in the tail withdrawal and hot-plate assays compared to control mice lacking Tat [Tat(-)]. This tolerance was accompanied by morphine-dependent increases in Iba-1 +/- 3-nitrotryosine immunoreactive microglia, and alterations in pro- and anti-inflammatory cytokines, and chemokines in the spinal cord and striatum, while increases in neuroinflammation were absent by PET imaging of [¹⁸F]-PBR111 uptake. Tat and morphine exposure differentially affected eCB levels, non-eCB lipids, and specific amino acids in a region-dependent manner. In the striatum, non-eCB lipids were significantly increased by short-term, escalating morphine exposure, including peroxisome proliferator activator receptor alpha (PPAR-alpha) ligands N-oleoyl ethanolamide (OEA) and N-palmitoyl ethanolamide (PEA), as well as the amino acids phenylalanine and proline. In the spinal cord, Tat exposure increased amino acids leucine and valine, while morphine decreased levels of tyrosine and valine but did not affect eCBs or non-eCB lipids. CONCLUSION: Overall results demonstrate that 3 months of Tat exposure increased morphine tolerance and potentially innate immune tolerance evidenced by reductions in specific cytokines (e.g., IL-1alpha, IL-12p40) and microglial reactivity. In contrast, short-term, escalating morphine exposure acted as a secondary stressor revealing an allostatic shift in CNS baseline inflammatory responsiveness from sustained Tat exposure
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