1,046 research outputs found
Blood-Brain Barrier Breakdown in a Single Post-stroke Rodent Brain
Stroke is a major cause of global morbidity and mortality. Middle cerebral artery
occlusion (MCAO) has historically been the most common animal model of simulating
ischemic stroke. The extent of neurological injury after MCAO is typically measured by
cerebral edema, infarct zone, and blood-brain barrier (BBB) permeability. A significant
limitation of these methods is that separate sets of brains must be used for each
measurement. Here we examine an alternative method of measuring cerebral edema,
infarct zone and BBB permeability following MCAO in the same set of brain samples.
Ninety-six rats were randomly divided into three experimental groups. Group 1 (n = 27)
was used for the evaluation of infarct zone and brain edema in rats post-MCAO (n = 17)
vs. sham-operated controls (n = 10). Group 2 (n = 27) was used for the evaluation of
BBB breakdown in rats post-MCAO (n = 15) vs. sham-operated controls (n = 10). In
Group 3 (n = 42), all three parameters were measured in the same set of brain slices in
rats post-MCAO (n = 26) vs. sham-operated controls (n = 16). The effect of Evans blue
on the accuracy of measuring infarct zone by 2,3,5-triphenyltetrazolium chloride (TTC)
staining was determined by measuring infarct zone with and without an applied blue
filter. The effects of various concentrations of TTC (0, 0.05, 0.35, 0.5, 1, and 2%) on the
accuracy of measuring BBB permeability was also assessed. There was an increase in
infarct volume (p < 0.01), brain edema (p < 0.01) and BBB breakdown (p < 0.01) in rats
following MCAO compared to sham-operated controls, whether measured separately
or together in the same set of brain samples. Evans blue had an effect on measuring
infarct volume that was minimized by the application of a blue filter on scanned brain slices. There was no difference in the Evans blue extravasation index for the brain
tissue samples without TTC compared to brain tissue samples incubated in TTC. Our
results demonstrate that measuring cerebral edema, infarct zone and BBB permeability
following MCAO can accurately be measured in the same set of brain samples
Non-Equilibrium Statistical Physics of Currents in Queuing Networks
We consider a stable open queuing network as a steady non-equilibrium system
of interacting particles. The network is completely specified by its underlying
graphical structure, type of interaction at each node, and the Markovian
transition rates between nodes. For such systems, we ask the question ``What is
the most likely way for large currents to accumulate over time in a network
?'', where time is large compared to the system correlation time scale. We
identify two interesting regimes. In the first regime, in which the
accumulation of currents over time exceeds the expected value by a small to
moderate amount (moderate large deviation), we find that the large-deviation
distribution of currents is universal (independent of the interaction details),
and there is no long-time and averaged over time accumulation of particles
(condensation) at any nodes. In the second regime, in which the accumulation of
currents over time exceeds the expected value by a large amount (severe large
deviation), we find that the large-deviation current distribution is sensitive
to interaction details, and there is a long-time accumulation of particles
(condensation) at some nodes. The transition between the two regimes can be
described as a dynamical second order phase transition. We illustrate these
ideas using the simple, yet non-trivial, example of a single node with
feedback.Comment: 26 pages, 5 figure
Vitamin D and subsequent all-age and premature mortality: a systematic review
<br>Background:
All-cause mortality in the population < 65 years is 30% higher in Glasgow than in equally deprived Liverpool and Manchester. We investigated a hypothesis that low vitamin D in this population may be associated with premature mortality via a systematic review and meta-analysis.</br>
<br>Methods:
Medline, EMBASE, Web of Science, the Cochrane Library and grey literature sources were searched until February 2012 for relevant studies. Summary statistics were combined in an age-stratified meta-analysis.</br>
<br>Results:
Nine studies were included in the meta-analysis, representing 24,297 participants, 5,324 of whom died during follow-up. The pooled hazard ratio for low compared to high vitamin D demonstrated a significant inverse association (HR 1.19, 95% CI 1.12-1.27) between vitamin D levels and all-cause mortality after adjustment for available confounders. In an age-stratified meta-analysis, the hazard ratio for older participants was 1.25 (95% CI 1.14-1.36) and for younger participants 1.12 (95% CI 1.01-1.24).</br>
<br>Conclusions:
Low vitamin D status is inversely associated with all-cause mortality but the risk is higher amongst older individuals and the relationship is prone to residual confounding. Further studies investigating the association between vitamin D deficiency and all-cause mortality in younger adults with adjustment for all important confounders (or using randomised trials of supplementation) are required to clarify this relationship.</br>
Plasmonically Enhanced Reflectance of Heat Radiation from Low-Bandgap Semiconductor Microinclusions
Increased reflectance from the inclusion of highly scattering particles at
low volume fractions in an insulating dielectric offers a promising way to
reduce radiative thermal losses at high temperatures. Here, we investigate
plasmonic resonance driven enhanced scattering from microinclusions of
low-bandgap semiconductors (InP, Si, Ge, PbS, InAs and Te) in an insulating
composite to tailor its infrared reflectance for minimizing thermal losses from
radiative transfer. To this end, we compute the spectral properties of the
microcomposites using Monte Carlo modeling and compare them with results from
Fresnel equations. The role of particle size-dependent Mie scattering and
absorption efficiencies, and, scattering anisotropy are studied to identify the
optimal microinclusion size and material parameters for maximizing the
reflectance of the thermal radiation. For composites with Si and Ge
microinclusions we obtain reflectance efficiencies of 57 - 65% for the incident
blackbody radiation from sources at temperatures in the range 400 - 1600
{\deg}C. Furthermore, we observe a broadbanding of the reflectance spectra from
the plasmonic resonances due to charge carriers generated from defect states
within the semiconductor bandgap. Our results thus open up the possibility of
developing efficient high-temperature thermal insulators through use of the
low-bandgap semiconductor microinclusions in insulating dielectrics.Comment: Main article (8 Figures and 2 Tables) + Supporting Information (8
Figures
Synthesis and characterization of high-affinity 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene-labeled fluorescent ligands for human β-adrenoceptors
The growing practice of exploiting noninvasive fluorescence-based techniques to study G protein-coupled receptor pharmacology at the single cell and single molecule level demands the availability of high-quality fluorescent ligands. To this end, this study evaluated a new series of red-emitting ligands for the human β-adrenoceptor family. Upon the basis of the orthosteric ligands propranolol, alprenolol, and pindolol, the synthesized linker-modified congeners were coupled to the commercially available fluorophore BODIPY 630/650-X. This yielded high-affinity β-adrenoceptor fluorescent ligands for both the propranolol and alprenolol derivatives; however, the pindolol-based products displayed lower affinity. A fluorescent diethylene glycol linked propranolol derivative (18a) had the highest affinity (log KD of -9.53 and -8.46 as an antagonist of functional β2- and β1-mediated responses, respectively). Imaging studies with this compound further confirmed that it can be employed to selectively label the human β2-adrenoceptor in single living cells, with receptor-associated binding prevented by preincubation with the nonfluorescent β2-selective antagonist 3-(isopropylamino)-1-[(7-methyl-4-indanyl)oxy]-butan-2-ol (ICI 118551) (J. Cardiovasc. Pharmacol. 1983, 5, 430-437.
Being, Becoming and the Undivided Universe: A Dialogue between Relational Blockworld and the Implicate Order Concerning the Unification of Relativity and Quantum Theory
In this paper two different approaches to unification will be compared,
Relational Blockworld (RBW) and Hiley's implicate order. Both approaches are
monistic in that they attempt to derive matter and spacetime geometry 'at once'
in an interdependent and background independent fashion from something
underneath both quantum theory and relativity. Hiley's monism resides in the
implicate order via Clifford algebras and is based on process as fundamental
while RBW's monism resides in spacetimematter via path integrals over graphs
whereby space, time and matter are co-constructed per a global constraint
equation. RBW's monism therefore resides in being (relational blockworld) while
that of Hiley's resides in becoming (elementary processes). Regarding the
derivation of quantum theory and relativity, the promises and pitfalls of both
approaches will be elaborated. Finally, special attention will be paid as to
how Hiley's process account might avoid the blockworld implications of
relativity and the frozen time problem of canonical quantum gravity.Comment: 33 pages, 7 figures. Revised to include modified Regge calculus
results. Accepted for publication in Foundations of Physics. arXiv admin
note: substantial text overlap with arXiv:1106.333
The power of pictures: Vertical picture angles in power pictures
Abstract:
Conventional wisdom suggests that variations in vertical picture angle cause the subject to appear more powerful when depicted from below and less powerful when depicted from above. However, do the media actually use such associations to represent individual differences in power? We argue that the diverse perspectives of evolutionary, social learning, and embodiment theories all suggest that the association between verticality and power is relatively automatic and should, therefore, be visible in the portrayal of powerful and powerless individuals in the media. Four archival studies (with six samples) provide empirical evidence for this hypothesis and indicate that a salience power context reinforces this effect. In addition, two experimental studies confirm these effects for individuals producing media content. We discuss potential implications of this effect
Expected Performance of the ATLAS Experiment - Detector, Trigger and Physics
A detailed study is presented of the expected performance of the ATLAS
detector. The reconstruction of tracks, leptons, photons, missing energy and
jets is investigated, together with the performance of b-tagging and the
trigger. The physics potential for a variety of interesting physics processes,
within the Standard Model and beyond, is examined. The study comprises a series
of notes based on simulations of the detector and physics processes, with
particular emphasis given to the data expected from the first years of
operation of the LHC at CERN
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