1,198 research outputs found
Efficient computation of the Shapley value for game-theoretic network centrality
The Shapley value—probably the most important normative payoff division scheme in coalitional games—has recently been advocated as a useful measure of centrality in networks. However, although this approach has a variety of real-world applications (including social and organisational networks, biological networks and communication networks), its computational properties have not been widely studied. To date, the only practicable approach to compute Shapley value-based centrality has been via Monte Carlo simulations which are computationally expensive and not guaranteed to give an exact answer. Against this background, this paper presents the first study of the computational aspects of the Shapley value for network centralities. Specifically, we develop exact analytical formulae for Shapley value-based centrality in both weighted and unweighted networks and develop efficient (polynomial time) and exact algorithms based on them. We empirically evaluate these algorithms on two real-life examples (an infrastructure network representing the topology of the Western States Power Grid and a collaboration network from the field of astrophysics) and demonstrate that they deliver significant speedups over the Monte Carlo approach. Fo
Retinal Changes in Transgenic Mouse Models of Alzheimer's Disease.
Alzheimer's disease (AD) is a neurodegenerative disorder, the most common form of dementia. AD is characterised by amyloid-β (Aβ) plaques and neurofibrillary tangles (NFT) in the brain, in association with neuronal loss and synaptic failure, causing cognitive deficits. Accurate and early diagnosis is currently unavailable in lifespan, hampering early intervention of potential new treatments. Visual deficits have been well documented in AD patients, and the pathological changes identified in the brain are also believed to be found in the retina, an integral part of the central nervous system. Retinal changes can be detected by real-time non-invasive imaging, due to the transparent nature of the ocular media, potentially allowing an earlier diagnosis as well as monitoring disease progression and treatment outcome. Animal models are essential for AD research, and this review has a focus on retinal changes in various transgenic AD mouse models with retinal imaging and immunohistochemical analysis as well as therapeutic effects in those models. We also discuss the limitations of transgenic AD models in clinical translations
Cognitive Structure and Processing During Cognitive Behavioral Therapy vs. Pharmacotherapy for Depression
Background: Evidence has converged to suggest that cognitive processing and content covary with depression severity, whereas indices of cognitive structure exhibit greater stability and promise as markers of vulnerability for depression. The objective of the current study was to investigate the temporal dynamics and causal role of cognitive structure and processing in treatment for depression. Method: A total of 104 patients with major depressive disorder were randomized to receive cognitive behavioral therapy (CBT; n = 54) or pharmacotherapy (n = 50). Patients completed the Hamilton Depression Rating Scale (HAM-D), Beck Depression Inventory-II (BDI-II), Psychological Distance Scaling Task (PDST), Redundancy Card-Sorting Task (RCST), and Self-Referent Encoding Task (SRET) before, during, and after treatment. Results: Most cognitive indices exhibited change over treatment to a similar degree across both treatments. Evidence for the mediating role of cognition was limited, and not specific to CBT. Discussion: Results suggest that both cognitive structure and processing may be amenable to change, by both CBT and pharmacotherapy. The role of cognitive structure in the course of depression may require qualification
Analytical Formulation of the Local Density of States around a Vortex Core in Unconventional Superconductors
On the basis of the quasiclassical theory of superconductivity, we obtain a
formula for the local density of states (LDOS) around a vortex core of
superconductors with anisotropic pair-potential and Fermi surface in arbitrary
directions of magnetic fields. Earlier results on the LDOS of d-wave
superconductors and NbSe are naturally interpreted within our theory
geometrically; the region with high intensity of the LDOS observed in numerical
calculations turns out to the enveloping curve of the trajectory of Andreev
bound states. We discuss experimental results on YNiBC within the
quasiclassical theory of superconductivity.Comment: 13 pages, 16 figure
Electronic structure and optical properties of ZnX (X=O, S, Se, Te)
Electronic band structure and optical properties of zinc monochalcogenides
with zinc-blende- and wurtzite-type structures were studied using the ab initio
density functional method within the LDA, GGA, and LDA+U approaches.
Calculations of the optical spectra have been performed for the energy range
0-20 eV, with and without including spin-orbit coupling. Reflectivity,
absorption and extinction coefficients, and refractive index have been computed
from the imaginary part of the dielectric function using the Kramers--Kronig
transformations. A rigid shift of the calculated optical spectra is found to
provide a good first approximation to reproduce experimental observations for
almost all the zinc monochalcogenide phases considered. By inspection of the
calculated and experimentally determined band-gap values for the zinc
monochalcogenide series, the band gap of ZnO with zinc-blende structure has
been estimated.Comment: 17 pages, 10 figure
Tumor Necrosis Factor - Related Apoptosis-Inducing Ligand (TRAIL) promotes angiogenesis and ischemia- induced neovascularization via NADPH Oxidase 4 (NOX4) and Nitric Oxide - dependent mechanisms
Background — Tumor necrosis factor–related apoptosis-inducing ligand (TRAIL) has the ability to inhibit angiogenesis by inducing endothelial cell death, as well as being able to promote pro- angiogenic activity in vitro. These seemingly opposite effects make its role in ischemic disease unclear. Using Trail_/_ and wildtype mice, we sought to determine the role of TRAIL in angiogenesis and neovascularization following hindlimb ischemia.
Methods and Results — Reduced vascularization assessed by real-time 3-dimensional Vevo ultrasound imaging and CD31 staining was evident in Trail_/_ mice after ischemia, and associated with reduced capillary formation and increased apoptosis. Notably, adenoviral TRAIL administration significantly improved limb perfusion, capillary density, and vascular smooth-muscle cell content in both Trail_/_ and wildtype mice. Fibroblast growth factor-2, a potent angiogenic factor, increased TRAIL expression in human microvascular endothelial cell-1, with fibroblast growth factor-2-mediated proliferation, migration, and tubule formation inhibited with TRAIL siRNA. Both fibroblast growth factor-2 and TRAIL significantly increased NADPH oxidase 4 (NOX4) expression. TRAIL-inducible angiogenic activity in vitro was inhibited with siRNAs targeting NOX4, and consistent with this, NOX4 mRNA was reduced in 3-day ischemic hindlimbs of Trail_/_ mice. Furthermore, TRAIL-induced proliferation, migration, and tubule formation was blocked by scavenging H2O2, or by inhibiting nitric oxide synthase activity. Importantly, TRAIL-inducible endothelial nitric oxide synthase phosphorylation at Ser-1177 and intracellular human microvascular endothelial cell-1 cell nitric oxide levels were NOX4 dependent.
Conclusions — This is the first report demonstrating that TRAIL can promote angiogenesis following hindlimb ischemia in vivo. The angiogenic effect of TRAIL on human microvascular endothelial cell-1 cells is downstream of fibroblast growth factor-2, involving NOX4 and nitric oxide signaling. These data have significant therapeutic implications, such that TRAIL may improve the angiogenic response to ischemia and increase perfusion recovery in patients with cardiovascular disease and diabetes
Modeling Basal Ganglia for understanding Parkinsonian Reaching Movements
We present a computational model that highlights the role of basal ganglia
(BG) in generating simple reaching movements. The model is cast within the
reinforcement learning (RL) framework with the correspondence between RL
components and neuroanatomy as follows: dopamine signal of substantia nigra
pars compacta as the Temporal Difference error, striatum as the substrate for
the Critic, and the motor cortex as the Actor. A key feature of this
neurobiological interpretation is our hypothesis that the indirect pathway is
the Explorer. Chaotic activity, originating from the indirect pathway part of
the model, drives the wandering, exploratory movements of the arm. Thus the
direct pathway subserves exploitation while the indirect pathway subserves
exploration. The motor cortex becomes more and more independent of the
corrective influence of BG, as training progresses. Reaching trajectories show
diminishing variability with training. Reaching movements associated with
Parkinson's disease (PD) are simulated by (a) reducing dopamine and (b)
degrading the complexity of indirect pathway dynamics by switching it from
chaotic to periodic behavior. Under the simulated PD conditions, the arm
exhibits PD motor symptoms like tremor, bradykinesia and undershoot. The model
echoes the notion that PD is a dynamical disease.Comment: Neural Computation, In Pres
PDF and scale uncertainties of various DY distributions in ADD and RS models at hadron colliders
In the extra dimension models of ADD and RS we study the dependence of the
various parton distribution functions on observable of Drell-Yan process to NLO
in QCD at LHC and Tevatron energies. Uncertainties at LHC due to factorisation
scales in going from leading to next-to-leading order in QCD for the various
distributions get reduced by about 2.75 times for a range . Further uncertainties arising from the error on experimental
data are estimated using the MRST parton distribution functions.Comment: 27 pages, 11 figures, the version to appear in European Physical
Journal
Topical curcumin nanocarriers are neuroprotective in eye disease
Curcumin (1,7-bis-(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5dione) is a polyphenol extracted from turmeric that has long been advocated for the treatment of a variety of conditions including neurodegenerative and inflammatory disorders. Despite this promise, the clinical use of curcumin has been limited by the poor solubility and low bioavailability of this molecule. In this article, we describe a novel nanocarrier formulation comprising Pluronic-F127 stabilised D-α-Tocopherol polyethene glycol 1000 succinate nanoparticles, which were used to successfully solubilize high concentrations (4.3 mg/mL) of curcumin. Characterisation with x-ray diffraction and in vitro release assays localise curcumin to the nanocarrier interior, with each particle measuring <20 nm diameter. Curcumin-loaded nanocarriers (CN) were found to significantly protect against cobalt chloride induced hypoxia and glutamate induced toxicity in vitro, with CN treatment significantly increasing R28 cell viability. Using established glaucoma-related in vivo models of ocular hypertension (OHT) and partial optic nerve transection (pONT), topical application of CN twice-daily for three weeks significantly reduced retinal ganglion cell loss compared to controls. Collectively, these results suggest that our novel topical CN formulation has potential as an effective neuroprotective therapy in glaucoma and other eye diseases with neuronal pathology
Origin of magnetoelectric behavior in BiFeO
The magnetoelectric behavior of BiFeO has been explored on the basis of
accurate density functional calculations. The structural, electronic, magnetic,
and ferroelectric properties of BiFeO are predicted correctly without
including strong correlation effect in the calculation. Moreover, the
experimentally-observed elongation of cubic perovskite-like lattice along the
[111] direction is correctly reproduced. At high pressure we predicted a
pressure-induced structural transition and the total energy calculations at
expanded lattice show two lower energy ferroelectric phases, closer in energy
to the ground state phase. Band-structure calculations show that BiFeO will
be an insulator in A- and G-type antiferromagnetic phases and a metal in other
magnetic configurations. Chemical bonding in BiFeO has been analyzed using
various tools and electron localization function analysis shows that
stereochemically active lone-pair electrons at the Bi sites are responsible for
displacements of the Bi atoms from the centro-symmetric to the
noncentrosymmetric structure and hence the ferroelectricity. A large
ferroelectric polarization (88.7 C/cm) is predicted in accordance
with recent experimental findings. The net polarization is found to mainly (
98%) originate from Bi atoms. Moreover the large scatter in experimentally
reported polarization values is due to the large anisotropy in the spontaneous
polarization.Comment: 19 pages, 12 figures, 4 table
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