3,328 research outputs found
Critical regime of two dimensional Ando model: relation between critical conductance and fractal dimension of electronic eigenstates
The critical two-terminal conductance and the spatial fluctuations of
critical eigenstates are investigated for a disordered two dimensional model of
non-interacting electrons subject to spin-orbit scattering (Ando model). For
square samples, we verify numerically the relation between critical conductivity and
the fractal information dimension of the electron wave function, . Through a detailed numerical scaling analysis of the two-terminal
conductance we also estimate the critical exponent that
governs the quantum phase transition.Comment: IOP Latex, 7 figure
Magnetic Field-Induced Lattice Effects in a Quasi-2D Organic Conductor Close to the Mott Metal-Insulator Transition
We present ultra-high-resolution dilatometric studies in magnetic fields on a
quasi-two-dimensional organic conductor
-(D8-BEDT-TTF)Cu[N(CN)]Br, which is located close to the
Mott metal-insulator (MI) transition. The obtained thermal expansion
coefficient, , reveals two remarkable features: (i) the Mott MI
transition temperature = (13.6 0.6)\,K is insensitive to fields
up to 10\,T, the highest applied field; (ii) for fields along the interlayer
\emph{b}-axis, a magnetic-field-induced (FI) phase transition at =
(9.5 0.5)\,K is observed above a threshold field 1 T,
indicative of a spin reorientation with strong magneto-elastic coupling.Comment: 5 pages, 4 figure
Targeting hepatic glycerolipid synthesis and turnover to treat fatty liver disease
Nonalcoholic fatty liver disease (NAFLD) encompasses a spectrum of metabolic abnormalities ranging from simple hepatic steatosis (accumulation of neutral lipid) to development of steatotic lesions, steatohepatitis, and cirrhosis. NAFLD is extremely prevalent in obese individuals and with the epidemic of obesity; nonalcoholic steatohepatitis (NASH) has become the most common cause of liver disease in the developed world. NASH is rapidly emerging as a prominent cause of liver failure and transplantation. Moreover, hepatic steatosis is tightly linked to risk of developing insulin resistance, diabetes, and cardiovascular disease. Abnormalities in hepatic lipid metabolism are part and parcel of the development of NAFLD and human genetic studies and work conducted in experimentally tractable systems have identified a number of enzymes involved in fat synthesis and degradation that are linked to NAFLD susceptibility as well as progression to NASH. The goal of this review is to summarize the current state of our knowledge on these pathways and focus on how they contribute to etiology of NAFLD and related metabolic diseases
Preferential uptake of the non steroid anti-inflammatory drug diclofenac into inflamed tissues after a single oral dose in rats
BACKGROUND: Diclofenac is a nonsteroidal anti-inflammatory drug which is available as prescription (RX) and over-the-counter (OTC) medication for the systemic and topical treatment of painful and inflammatory conditions such as arthritis and back pain. This study was undertaken to investigate the distribution and retention of diclofenac and/or its metabolites in inflamed tissues, using the carrageenan-induced inflammation model and quantitative whole body autoradiography in rats. METHODS: [14C]diclofenac sodium was administrated as a single 2 mg/kg oral dose 1 h after injection of carrageenan into one front and one hind footpads and subcutaneously into the dorsum of the neck of rats. A control animal received saline injections. Three carrageenan-treated rats and one control rat were sacrificed at 1, 4, 8, and 24 h after [14C]diclofenac sodium administration (total of 4 rats/time point). The carcasses were immediately snap-frozen and prepared for cryosectioning. Lengthwise whole-body sections (40 microm thick), including all major tissues, were obtained from different levels across the body. The tissue concentrations of total radiolabeled components were determined using quantitative autoradioluminography. RESULTS: The radioactivity patterns demonstrated that diclofenac and/or its metabolites preferentially distributed into the inflamed tissues. In unharmed tissues the distribution was similar in control and treated animals. The exposure, based on the areas under the tissue concentration versus time (AUC(0-tlast)), was 26 and 53 fold higher in the inflamed neck and inflamed footpads of treated animals than in control rats; the exposures in unharmed tissues were similar in the treated and control rats, and the AUC(0-tlast) was 17 fold higher in the inflamed paws than in the non inflamed footpads of the carrageenan-treated rats. The higher exposure in the inflamed tissues may be explained partly to the fact that the elimination of total radiolabeled components from inflamed tissues (t(1/2) = 6 h) appeared lower than from the corresponding unharmed tissues (t(1/2) = 2 h). CONCLUSION: This animal study demonstrated that diclofenac and/or its metabolites were rapidly and preferentially taken up and retained in inflamed tissues. Although there were theoretical considerations that mildly acidic NSAID may show some preferential distribution in inflamed tissues there was no clear experimental proof for diclofenac until the present study
Self-propelled particles with fluctuating speed and direction of motion
We study general aspects of active motion with fluctuations in the speed and
the direction of motion in two dimensions. We consider the case in which
fluctuations in the speed are not correlated to fluctuations in the direction
of motion, and assume that both processes can be described by independent
characteristic time-scales. We show the occurrence of a complex transient that
can exhibit a series of alternating regimes of motion, for two different
angular dynamics which correspond to persistent and directed random walks. We
also show additive corrections to the diffusion coefficient. The characteristic
time-scales are also exposed in the velocity autocorrelation, which is a sum of
exponential forms.Comment: to appear in Phys. Rev. Let
Critical conductance of two-dimensional chiral systems with random magnetic flux
The zero temperature transport properties of two-dimensional lattice systems
with static random magnetic flux per plaquette and zero mean are investigated
numerically. We study the two-terminal conductance and its dependence on
energy, sample size, and magnetic flux strength. The influence of boundary
conditions and of the oddness of the number of sites in the transverse
direction is also studied. We confirm the existence of a critical chiral state
in the middle of the energy band and calculate the critical exponent nu=0.35
+/- 0.03 for the divergence of the localization length. The sample averaged
scale independent critical conductance _c turns out to be a function of the
amplitude of the flux fluctuations whereas the variance of the respective
conductance distributions appears to be universal. All electronic states
outside of the band center are found to be localized.Comment: to appear in Phys. Rev.
A k-shell decomposition method for weighted networks
We present a generalized method for calculating the k-shell structure of
weighted networks. The method takes into account both the weight and the degree
of a network, in such a way that in the absence of weights we resume the shell
structure obtained by the classic k-shell decomposition. In the presence of
weights, we show that the method is able to partition the network in a more
refined way, without the need of any arbitrary threshold on the weight values.
Furthermore, by simulating spreading processes using the
susceptible-infectious-recovered model in four different weighted real-world
networks, we show that the weighted k-shell decomposition method ranks the
nodes more accurately, by placing nodes with higher spreading potential into
shells closer to the core. In addition, we demonstrate our new method on a real
economic network and show that the core calculated using the weighted k-shell
method is more meaningful from an economic perspective when compared with the
unweighted one.Comment: 17 pages, 6 figure
Multifractal properties of critical eigenstates in two-dimensional systems with symplectic symmetry
The multifractal properties of electronic eigenstates at the metal-insulator
transition of a two-dimensional disordered tight-binding model with spin-orbit
interaction are investigated numerically. The correlation dimensions of the
spectral measure and of the fractal eigenstate are
calculated and shown to be related by . The exponent
describing the energy correlations of the critical
eigenstates is found to satisfy the relation .Comment: 6 pages RevTeX; 3 uuencoded, gzipped ps-figures to appear in J. Phys.
Condensed Matte
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