Low-Lying Electronic Excitations and Nonlinear Optic Properties of Polymers via Symmetrized Density Matrix Renormalization Group Method

A symmetrized Density Matrix Renormalization Group procedure together with the correction vector approach is shown to be highly accurate for obtaining dynamic linear and third order polarizabilities of one-dimensional Hubbard and $U-V$ models. The $U-V$ model is seen to show characteristically different third harmonic generation response in the CDW and SDW phases. This can be rationalized from the excitation spectrum of the systems.Comment: 4 pages Latex; 3 eps figures available upon request; Proceedings of ICSM '96, to appear in Synth. Metals, 199

TiO2- and BaTiO3-Assisted Photocatalytic Degradation of Selected Chloroorganic Compounds in Aqueous Medium: Correlation of Reactivity/Orientation Effects of Substituent Groups of the Pollutant Molecule on the Degradation Rate

Investigation of the photocatalytic activity of BaTiO3, a perovskite wideband gap semiconductor has been done in comparison with a widely used photocatalyst TiO2 for the degradation of 4-chlorophenol (4-CP), 4-chloroaniline (4-CA), 3,4-dichloronitrobenzene (3,4-DCNB), and 2,4,5-trichlorophenol (2,4,5-TCP). BaTiO3/TiO2 nanoparticles were prepared by gel-to-crystalline conversion method. BaTiO3 has exhibited better catalytic efficiency and process efficiency compared with TiO2 in most of the cases. The present research focuses mainly on two aspects: first the photocatalytic activity of BaTiO3, as there are very few reports in the literature, and second the reactivity/orientation effects of substituent groups of the pollutant molecules on the degradation rate. The above chloroorganic compounds have at least one chlorine substituent in common, along with other functional groups such as −OH, −NH2, and −NO2. Furthermore, the effect of electron acceptors and pH on the rate of degradation is presented. The reactions follow first-order kinetics. The degradation reaction was followed by UV−vis, IR, and GC-MS spectroscopic techniques. On the basis of the identification of the intermediates, a probable degradation reaction mechanism has been proposed for each compoun

Antipsychotic discontinuation syndrome following risperidone withdrawal: a case report from rural India

Risperidone is an atypical antipsychotic agent used primarily to treat schizophrenia. It is a dopamine antagonist with antiserotonergic, antihistaminergic and antiadrenergic properties. Antipsychotic discontinuation symptoms have been described in the literature following abrupt or rapid reduction in the dose. This unusual case demonstrates that sudden withdrawal of even a modest dose of risperidone may cause significant discontinuation symptoms in susceptible individuals. Hence, there is a need for caution while taking a patient off antipsychotic medications in view of the vulnerable subgroup

Nonlinear physics of the ionosphere and LOIS/LOFAR

The ionosphere is the only large-scale plasma laboratory without walls that we have direct access to. From results obtained in systematic, repeatable experiments in this natural laboratory, where we can vary the stimulus and observe its response in a controlled, repeatable manner, we can draw conclusions on similar physical processes occurring naturally in the Earth's plasma environment as well as in parts of the plasma universe that are not easily accessible to direct probing. Of particular interest is electromagnetic turbulence excited in the ionosphere by beams of particles (photons, electrons) and its manifestation in terms of secondary radiation (electrostatic and electromagnetic waves), structure formation (solitons, cavitons, alfveons, striations), and the associated exchange of energy, linear momentum, and angular momentum. We present a new diagnostic technique, based on vector radio allowing the utilization of EM angular momentum (vorticity), to study plasma turbulence remotely.Comment: Six pages, two figures. To appear in Plasma Physics and Controlled Fusio

On the structure of a distinguished-limit quasi-isothermal deflagration for the generalized reaction-rate model

The structure of the quasi-isothermal deflagration is examined by means of an asymptotic analysis of the physical-plane boundary-value problem, with Lewis–Semenov number unity, in the limit of the activation-temperature ratio, β=Ta/Tb, greater than order unity, for the generalized reaction-rate-model case of: (1) the heat-addition-temperature ratio, α=(Tb−Tu)/Tu, of order β−1/2, less than order unity [where Ta, Tb, and Tu are the activation, adiabatic-flame (and/or burned-gas), and unburned-gas temperatures, respectively]; and (2) the exponent, a, which characterizes the pre-exponential thermal dependence of the reaction-rate term, unity. The examination indicates that, as in the order-unity heat-addition case, this deflagration has a four-region structure: the upstream diffusion-convection and downstream diffusion-reaction regions, and the far-upstream (or cold-boundary) and the far-downstream (or hot-boundary) regions

Asymptotic analysis of the structure of a steady planar detonation: Review and extension

The structure of a steady planar Chapman–Jouguet detonation, which is supported by a direct first-order one-step irreversible exothermic unimolecular reaction, subject to Arrhenius kinetics, is examined. Solutions are studied, by means of a limit-process-expansion analysis, valid for Λ, proportional to the ratio of the reaction rate to the flow rate, going to zero, and for β, proportional to the ratio of the activation temperature to the maximum flow temperature, going to infinity, with the product Λβ1/2 going to zero. The results, essentially in agreement with the Zeldovich–von Neumann–Doring model, show that the detonation consists of (1) a three-region upstream shock-like zone, wherein convection and diffusion dominate; (2) an exponentially thicker five-region downstream deflagration-like zone, wherein convection and reaction dominate; and (3) a transition zone, intermediate to the upstream and downstream zones, wherein convection, diffusion, and reaction are of the same order of magnitude. It is in this transition zone that the ideal Neumann state is most closely approached

CYTOTOXIC ACTIVITY OF ENDOPHYTIC FUNGI HHPCYL03 ISOLATED FROM CYMBOPOGON FLEXUOSUS NEES EX STEUD

Objective: Cymbopogon grass is one of common aromatic grass species used for extraction of essential oil. The endophytic fungus HHPCYL03isolated from the Cymbopogon flexuosus, a medicinal grass species collected from Kemmannugundi regions of Karnataka. Methods: Secondary metabolites were extracted from fungi using organic solvent Ethyl Acetate and screened for anticancer assay against breast cancer cell (MDA-MB-231), lung cancer cell (Calu-6) and colorectal cancer cell (HCT116) lines. Results: The extract showed the positive result against HCT116 cells. Conclusion: The fungal endophytes certainly become a repository of good economically, socially benefitted bioactive compounds

Spin lifetimes of electrons injected into GaAs and GaN

The spin relaxation time of electrons in GaAs and GaN are determined with a model that includes momentum scattering by phonons and ionized impurities, and spin scattering by the Elliot-Yafet, D'yakonov-Perel, and Bir-Aronov-Pikus mechanisms. Accurate bands generated using a long-range tight-binding Hamiltonian obtained from empirical pseudopotentials are used. The inferred temperature-dependence of the spin relaxation lifetime agrees well with measured values in GaAs. We further show that the spin lifetimes decrease rapidly with injected electrons energy and reach a local maximum at the longitudinal optical phonon energy. Our calculation predicts that electron spin lifetime in pure GaN is about 3 orders of magnitude longer than in GaAs at all temperatures, primarily as a result of the lower spin-orbit interaction and higher conduction band density of states.Comment: 8 pages and 3 figure

Coarsening and Slow-Dynamics in Granular Compaction

We address the problem of the microscopic reorganization of a granular medium under a compaction process in the framework of Tetris-like models. We point out the existence of regions of spatial organization which we call domains, and study their time evolution. It turns out that after an initial transient, most of the activity of the system is concentrated on the boundaries between domains. One can then describe the compaction phenomenon as a coarsening process for the domains, and a progressive reduction of domain boundaries. We discuss the link between the coarsening process and the slow dynamics in the framework of a model of active walkers on active substrates.Comment: Revtex 4 pages, 4 figures, in press in PRL. More info http://axtnt3.phys.uniroma1.it/Tetri

Hantavirus infection among children hospitalized for febrile illness suspected to be dengue in Barbados

SummaryEmerging picture of hantavirus infection in the South America is characterized by greater proportion of childhood infection and wider spectrum of disease from mild asymptomatic to lethal cardiopulmonary disease. Barbados is endemic for dengue and leptospirosis, both of which share clinical features with hantavirus infection and in many cases neither of these diagnosis could be confirmed. We investigate whether some of the children hospitalized with suspected dengue could indeed have been hantavirus infections. In this prospective study children hospitalized with suspected dengue were tested for hantavirus infection using ELISA for the IgM antibodies. Thirty-eight children tested positive for hantavirus infection. They presented with fever, headache and mild respiratory and gastrointestinal symptoms and signs. None of them had features suggestive of hantavirus cardiopulmonary syndrome. Blood count values ranged from low to normal to high for their age. There were no deaths. Hantavirus infection is prevalent in this Caribbean country. It predominantly presents with milder disease and is responsible for some of the nonspecific febrile illnesses in children