599 research outputs found
Composition dependent magnetic properties of iron oxide - polyaniline nanoclusters
Gamma - Iron Oxide prepared by sol -gel process was used to produce
nanocomposites with polyaniline of varying aniline concentrations. TEM shows
the presence of chain like structure for lower polyaniline concentration. The
room temperature hysteresis curves show finite coercivity of 160 Oe for all the
composites while the saturation magnetization was found to decrease with
increasing polymer content. ZFC - FC magnetisation measurements indicate high
blocking temperatures. It is believed that this indicates a strongly
interacting system, which is also shown by our TEM results. Monte Carlo
simulations performed on a random anisotropy model with dipolar and exchange
inteactions match well with experimental results.Comment: 9 (nine) pages, 6 figures (jpeg and eps
Effects of the Nearest-Neighbour Coulomb Interactions on the Ground State of the Periodic Anderson Model
The magnetic and non-magnetic ground states of the periodic Anderson model
with Coulomb interaction between -electrons on the nearest-neighbour(NN)
sites are investigated using a variational method, which gives exact
calculation of the expectation values in the limit of infinite dimensions. It
is shown that for a critical value of NN Coulomb interactions the magnetic
ground state of the periodic Anderson model in the Kondo regime is unstable.
Factors in terms of the physical processes responsible for instability of the
magnetic ground state are also discussed. Our study indicates the importance of
the NN Coulomb interactions for correlated two band models.Comment: RevTeX, 6 pages, 5 figures, to appear in Phys. Rev.
Cooperating Agents for 3D Scientific Data Interpretation
Many organizations collect vast quantities of three-dimensional (3-D) scientific data in volumetric form for a range of purposes, including resource exploration, market forecasting, and process modelling. Traditionally, these data have been interpreted by human experts with only minimal software assistance. However, such manual interpretation is a painstakingly slow and tedious process. Moreover, since interpretation involves subjective judgements and each interpreter has different scientific knowledge and experience, formulation of an effective interpretation often requires the cooperation of numerous such experts. Hence, there is a pressing need for a software system in which individual interpretations can be generated automatically and then refined through the use of cooperative reasoning and information sharing. To this end, a prototype system, SurfaceMapper, has been developed in which a community of cooperating software agents automatically locate and display interpretations in a volume of 3-D scientific data. The challenges and experiences in designing and building such a system are discussed. Particular emphasis is given to the agents' interactions and an empirical evaluation of the effectiveness of different cooperation strategies is presented
Magnetic properties of polypyrrole - coated iron oxide nanoparticles
Iron oxide nanoparticles were prepared by sol -gel process. Insitu
polymerization of pyrrole monomer in the presence of oxygen in iron oxide
ethanol suspension resulted in a iron oxide - polypyrrole nanocomposite. The
structure and magnetic properties were investigated for varying pyrrole
concentrations. The presence of the gamma - iron oxide phase and polypyrrole
were confirmed by XRD and FTIR respectively. Agglomeration was found to be
comparatively much reduced for the coated samples, as shown by TEM. AC
susceptibility measurements confirmed the superparamagnetic behaviour.
Numerical simulations performed for an interacting model system are performed
to estimate the anisotropy and compare favourably with experimental results.Comment: 11 pages,8 figure
Almost sure stability of the Euler-Maruyama method with random variable stepsize for stochastic differential equations
In this paper, the Euler–Maruyama (EM) method with random variable stepsize is studied to reproduce the almost sure stability of the true solutions of stochastic differential equations. Since the choice of the time step is based on the current state of the solution, the time variable is proved to be a stopping time. Then the semimartingale convergence theory is employed to obtain the almost sure stability of the random variable stepsize EM solution. To our best knowledge, this is the first paper to apply the random variable stepsize (with clear proof of the stopping time) to the analysis of the almost sure stability of the EM method
A novel AhR ligand, 2AI, protects the retina from environmental stress.
Various retinal degenerative diseases including dry and neovascular age-related macular degeneration (AMD), retinitis pigmentosa, and diabetic retinopathy are associated with the degeneration of the retinal pigmented epithelial (RPE) layer of the retina. This consequently results in the death of rod and cone photoreceptors that they support, structurally and functionally leading to legal or complete blindness. Therefore, developing therapeutic strategies to preserve cellular homeostasis in the RPE would be a favorable asset in the clinic. The aryl hydrocarbon receptor (AhR) is a conserved, environmental ligand-dependent, per ARNT-sim (PAS) domain containing bHLH transcription factor that mediates adaptive response to stress via its downstream transcriptional targets. Using in silico, in vitro and in vivo assays, we identified 2,2'-aminophenyl indole (2AI) as a potent synthetic ligand of AhR that protects RPE cells in vitro from lipid peroxidation cytotoxicity mediated by 4-hydroxynonenal (4HNE) as well as the retina in vivo from light-damage. Additionally, metabolic characterization of this molecule by LC-MS suggests that 2AI alters the lipid metabolism of RPE cells, enhancing the intracellular levels of palmitoleic acid. Finally, we show that, as a downstream effector of 2AI-mediated AhR activation, palmitoleic acid protects RPE cells from 4HNE-mediated stress, and light mediated retinal degeneration in mice
EXTRACORPOREAL MEMBRANE OXYGENATION FOR STATUS ASTHMATICUS: A CASE REPORT ECMO FOR STATUS ASTHMATICUS
Technological advances in extracorporeal membrane oxygenation and emerging evidence that it improves survival in adults with reversible respiratory failure compared to conventional ventilation has lead to increased utilization of extracorporeal membrane oxygenation in adults, usually in the context of acute respiratory distress syndrome. Refractory status asthmaticus is an uncommon indication for extracorporeal membrane oxygenation. We present a case of near fatal respiratory failure and hypercapnia in a 48-year-old male in status asthmaticus not responsive to optimal ventilatory treatment. The use of veno-venous extracorporeal membrane oxygenation resulted in full recovery with return of normal respiratory function within nine days.
Self-organized stable pacemakers near the onset of birhythmicity
General amplitude equations for reaction-diffusion systems near to the soft
onset of birhythmicity described by a supercritical pitchfork-Hopf bifurcation
are derived. Using these equations and applying singular perturbation theory,
we show that stable autonomous pacemakers represent a generic kind of
spatiotemporal patterns in such systems. This is verified by numerical
simulations, which also show the existence of breathing and swinging pacemaker
solutions. The drift of self-organized pacemakers in media with spatial
parameter gradients is analytically and numerically investigated.Comment: 4 pages, 4 figure
On the Experimental Evidence for Possible Superconductivity in LK99
The desire to create an energy efficient world is bound to be incomplete
without the discovery of a room temperature superconductor at ambient pressure.
A recent report on the room-temperature ambient-pressure superconductor has
inspired scientists to study the Cu doped Lead apatite named as LK-99. Here, we
have synthesized Cu doped LK-99 and Ni-doped LK-99 compounds and studied their
temperature dependent transport and magnetization behavior. In spite of the
presence of impurity phase CuS, the temperature dependent resistance shows
an insulating nature of the sample. The radio frequency penetration depth
measurement unveils the absence of diamagnetic flux expulsion in this sample.
The temperature dependent ac susceptibility measurements reveal the
paramagnetic nature of the Ni doped LK-99
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