3,970 research outputs found
Distribution of the second virial coefficients of globular proteins
George and Wilson [Acta. Cryst. D 50, 361 (1994)] looked at the distribution
of values of the second virial coefficient of globular proteins, under the
conditions at which they crystallise. They found the values to lie within a
fairly narrow range. We have defined a simple model of a generic globular
protein. We then generate a set of proteins by picking values for the
parameters of the model from a probability distribution. At fixed solubility,
this set of proteins is found to have values of the second virial coefficient
that fall within a fairly narrow range. The shape of the probability
distribution of the second virial coefficient is Gaussian because the second
virial coefficient is a sum of contributions from different patches on the
protein surface.Comment: 5 pages, including 3 figure
Automated quantification and evaluation of motion artifact on coronary CT angiography images
Abstract Purpose
This study developed and validated a Motion Artifact Quantification algorithm to automatically quantify the severity of motion artifacts on coronary computed tomography angiography (CCTA) images. The algorithm was then used to develop a Motion IQ Decision method to automatically identify whether a CCTA dataset is of sufficient diagnostic image quality or requires further correction. Method
The developed Motion Artifact Quantification algorithm includes steps to identify the right coronary artery (RCA) regions of interest (ROIs), segment vessel and shading artifacts, and to calculate the motion artifact score (MAS) metric. The segmentation algorithms were verified against groundâtruth manual segmentations. The segmentation algorithms were also verified by comparing and analyzing the MAS calculated from groundâtruth segmentations and the algorithmâgenerated segmentations. The Motion IQ Decision algorithm first identifies slices with unsatisfactory image quality using a MAS threshold. The algorithm then uses an artifactâlength threshold to determine whether the degraded vessel segment is large enough to cause the dataset to be nondiagnostic. An observer study on 30 clinical CCTA datasets was performed to obtain the groundâtruth decisions of whether the datasets were of sufficient image quality. A fiveâfold crossâvalidation was used to identify the thresholds and to evaluate the Motion IQ Decision algorithm. Results
The automated segmentation algorithms in the Motion Artifact Quantification algorithm resulted in Dice coefficients of 0.84 for the segmented vessel regions and 0.75 for the segmented shading artifact regions. The MAS calculated using the automated algorithm was within 10% of the values obtained using groundâtruth segmentations. The MAS threshold and artifactâlength thresholds were determined by the ROC analysis to be 0.6 and 6.25 mm by all folds. The Motion IQ Decision algorithm demonstrated 100% sensitivity, 66.7% ± 27.9% specificity, and a total accuracy of 86.7% ± 12.5% for identifying datasets in which the RCA required correction. The Motion IQ Decision algorithm demonstrated 91.3% sensitivity, 71.4% specificity, and a total accuracy of 86.7% for identifying CCTA datasets that need correction for any of the three main vessels. Conclusion
The Motion Artifact Quantification algorithm calculated accurate
Fenofibrate-Loaded Biodegradable Nanoparticles for the Treatment of Neovascular Age-Related Macular Degeneration
Fenofibrate-Loaded Biodegradable Nanoparticles for the Treatment of Neovascular Age-Related Macular Degeneration
Russell Simmers, Depts. of Physics and Chemistry, with Dr. Qingguo Xu, VCU School of Pharmacy
Background: Neovascular age-related macular degeneration (AMD) is a leading cause of visual impairment in the elderly population in the industrialized world. The current treatment for neovascular AMD is anti-vascular endothelial growth factor (anti-VEGF) therapy; however, nearly 40-50% of patients do not fully respond to anti-VEGF therapy. Therefore, non-VEGF therapeutics are required for neovascular AMD treatment. Fenofibrate is a peroxisome proliferator-activated receptor alpha (PPARα) agonist and has demonstrated robust therapeutic effects on neovascular AMD in animal models; however, it must be delivered frequently via intravitreal injection due to quick clearance of the drug from the eye, and may induce injection associated side effects such as retinal detachment, ocular hemorrhage and endophthalmitis. Purpose: To develop and optimize fenofibrate-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles (Feno-NP) with high-drug loading and long-lasting drug release profile to effectively treat neovascular AMD for 6-months with one single intravitreal injection. Methods: Feno-NPs were prepared by emulsification method and were fully characterized in terms of particle size, surface charge, morphology and in vitro drug release profiles and the ocular pharmacokinetics studies were performed in rats following intravitreal injection. Efficacy on neovascular-AMD was determined by measuring vascular leakage, vascular permeability, and the numbers of subretinal neovascular (SRNV) and intraretinal neovascular (IRNV) lesions after intravitreal injection of Feno-NPs in a laser-induced choroid neovascularization (CNV) rat model.https://scholarscompass.vcu.edu/uresposters/1387/thumbnail.jp
Cold Fermi-gas with long range interaction in a harmonic trap
We study equilibrium density and spin density profiles for a model of cold
one-dimensional spin 1/2 fermions interacting via inverse square interaction
and exchange in an external harmonic trap. This model is the well-known
spin-Calogero model (sCM) and its fully nonlinear collective field theory
description is known. We extend the field theory description to the presence of
an external harmonic trap and obtain analytic results for statics and dynamics
of the system. For instance, we find how the equilibrium density profile
changes upon tuning the interaction strength. The results we obtain for
equilibrium configurations are very similar to the ones obtained recently by Ma
and Yang [1] for a model of fermions with short ranged interactions. Our main
approximation is the neglect of the terms of higher order in spatial
derivatives in equations of motion - gradientless approximation [2]. Within
this approximation the hydrodynamic equations of motion can be written as a set
of decoupled forced Riemann-Hopf equations for the dressed Fermi momenta of the
model. This enables us to write analytical solutions for the dynamics of spin
and charge. We describe the time evolution of the charge density when an
initial non-equilibrium profile is created by cooling the gas with an
additional potential in place and then suddenly removing the potential. We
present our results as a simple "single-particle" evolution in the phase-space
reminiscing a similar description of the dynamics of non-interacting
one-dimensional fermions.Comment: 11 pages, 5 figures (figure typo corrected and references added
Simplified three-dimensional tissue clearing and incorporation of colorimetric phenotyping.
Tissue clearing methods promise to provide exquisite three-dimensional imaging information; however, there is a need for simplified methods for lower resource settings and for non-fluorescence based phenotyping to enable light microscopic imaging modalities. Here we describe the simplified CLARITY method (SCM) for tissue clearing that preserves epitopes of interest. We imaged the resulting tissues using light sheet microscopy to generate rapid 3D reconstructions of entire tissues and organs. In addition, to enable clearing and 3D tissue imaging with light microscopy methods, we developed a colorimetric, non-fluorescent method for specifically labeling cleared tissues based on horseradish peroxidase conversion of diaminobenzidine to a colored insoluble product. The methods we describe here are portable and can be accomplished at low cost, and can allow light microscopic imaging of cleared tissues, thus enabling tissue clearing and imaging in a wide variety of settings
Phase transitions in neutron star and magnetars and their connection with high energetic bursts in astrophysics
The phase transition from normal hadronic matter to quark matter in neutron
stars (NS) could give rise to several interesting phenomena. Compact stars can
have such exotic states up to their surface (called strange stars (SS)) or they
can have quark core surrounded by hadronic matter, known as hybrid stars (HS).
As the state of matter of the resultant SS/HS is different from the initial
hadronic matter, their masses also differ. Therefore, such conversion leads to
huge energy release, sometimes of the order of ergs. In the present
work we study the qualitative energy released by such conversion. Recent
observations reveal huge surface magnetic field in certain stars, termed
magnetars. Such huge magnetic fields can modify the equations of state (EOS) of
the matter describing the star. Therefore, the mass of magnetars are different
from normal NS. The energy released during the conversion process from neutron
magnetar (NM) to strange magnetar/hybrid magnetar (SS/HS) is different from
normal NS to SS/HS conversion. In this work we calculate the energy release
during the phase transition in magnetars. The energy released during NS to
SS/HS conversion exceeds the energy released during NM to SM/HM conversion. The
energy released during the conversion of NS to SS is always of the order of
ergs. The amount of energy released during such conversion can only
be compared to the energy observed during the gamma ray bursts (GRB). The
energy liberated during NM to HM conversion is few times lesser, and is not
likely to power GRB at cosmological distances. However, the magnetars are more
likely to lose their energy from the magnetic poles and can produce giant
flares, which are usually associated with magnetars.Comment: 14 pages, 4 figures, 4 table
Quark Stars as inner engines for Gamma Ray Bursts?
A model for Gamma ray bursts inner engine based on quark stars (speculated to
exist in nature) is presented. We describe how and why these objects might
constitute new candidates for GRB inner engines. At the heart of the model is
the onset of exotic phases of quark matter at the surface of such stars, in
particular the 2-flavor color superconductivity. A novel feature of such a
phase is the generation of particles which are unstable to photon decay
providing a natural mechanism for a fireball generation; an approach which is
fundamentally different from models where the fireball is generated during
collapse or conversion of neutron star to quark star processes. The model is
capable of reproducing crucial features of Gamma ray bursts, such as the
episodic activity of the engine (multiple and random shell emission) and the
two distinct categories of the bursts (two regimes are isolated in the model
with \sim 2 s and \sim 81 s burst total duration).Comment: 8 pages, 3 figures, new and more appropriate title. Major changes in
the text (aspects of the models discussed in more details), better quality
Figure 1 and Figure 2 and added Figure 3, version to appear in
Astronomy&Astrophysic
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Continuing mortality of vultures in India associated with illegal veterinary use of diclofenac and a potential threat from nimesulide
AbstractThe collapse of South Asia's Gyps vulture populations is attributable to the veterinary use of the non-steroidal anti-inflammatory drug (NSAID) diclofenac. Vultures died after feeding on carcasses of recently-medicated animals. The governments of India, Nepal and Pakistan banned the veterinary use of diclofenac in 2006. We analysed results of 62 necropsies and 48 NSAID assays of liver and/or kidney for vultures of five species found dead in India between 2000 and 2012. Visceral gout and diclofenac were detected in vultures from nine states and three species: Gyps bengalensis, Gyps indicus and Gyps himalayensis. Visceral gout was found in every vulture carcass in which a measurable level of diclofenac was detected. Meloxicam, an NSAID of low toxicity to vultures, was found in two vultures and nimesulide in five vultures. Nimesulide at elevated tissue concentrations was associated with visceral gout in four of these cases, always without diclofenac, suggesting that nimesulide may have similar toxic effects to those of diclofenac. Residues of meloxicam on its own were never associated with visceral gout. The proportion of Gyps vultures found dead in the wild in India with measurable levels of diclofenac in their tissues showed a modest and non-significant decline since the ban on the veterinary use of diclofenac. The prevalence of visceral gout declined less, probably because some cases of visceral gout from 2008 onwards were associated with nimesulide rather than diclofenac. Veterinary use of nimesulide is a potential threat to the recovery of vulture populations.Financial support and assistance for the project from the Director, Indian Veterinary Research Institute (IVRI), the UK Governmentâs Darwin Initiative and the Royal Society for the Protection of Birds is gratefully acknowledged.This is the accepted manuscript. The final version is available from Cambridge University Press via http://dx.doi.org/10.1017/S003060531500037
Examination of Antibody Responses as a Measure of Exposure to Malaria in the Indigenous Batwa and Their Non-Indigenous Neighbors in Southwestern Uganda
Understanding variations in malaria transmission and exposure is critical to identify populations at risk and enable better targeting of interventions. The indigenous Batwa of southwestern Uganda have a disproportionate burden of malaria infection compared with their non-indigenous neighbors. To better understand the individual- and community-level determinants of malaria exposure, a seroepidemiological study was conducted in 10 local council cells in Kanungu District, Uganda, in April 2014. The Batwa had twice the odds of being seropositive to two Plasmodium falciparumâspecific antigens, apical membrane antigen-1 and merozoite surface protein-119, compared with the non-indigenous Bakiga (odds ratio = 2.08, 95% confidence interval = 1.51â2.88). This trend was found irrespective of altitude level and after controlling for cell location. Seroconversion rates in the Batwa were more than twice those observed in the Bakiga. For the Batwa, multiple factors may be associated with higher exposure to malaria and antibody levels relative to their non-indigenous neighbors
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