Photoinduced magnetism in the ferromagnetic semiconductors

We study the enhancement of the magnetic transition temperature $T_c$ due to incident light in ferromagnetic semiconductors such as EuS. The photoexcited carriers mediate an extra ferromagnetic interaction due to the coupling with the localized magnetic moments. The Hamiltonian consists of a Heisenberg model for the localized moments and an interaction term between the photoexcited carriers and the localized moments. The model predicts a small enhancement of the transition temperature in semi-quantitative agreement with the experiments.Comment: 5 pages, 5 figure

Effect of magnetic fluctuations on the normal state properties of Sr_2RuO_4

We investigate the normal state transport properties of Sr$_2$RuO$_4$ and we show that a consistent explanation of the experimental results can be obtained assuming that the system is near a quantum phase transition. Within the framework of a self-consistent spin fluctuation theory, we calculate the temperature variation of some relevant physical quantities and we discuss a possible microscopic origin of the quantum phase transition.Comment: 5 pages, 4 figures, to appear on Europhysics Letter

Transbilayer phospholipid asymmetry in Plasmodium knowlesi infected host cell membrane

The membranes from normal and Plasmodium knowlesi-infected rhesus monkey erythrocytes (90 to 95 percent infected with early ring stage) were analyzed for transbilayer distribution of phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylserine (PS), by means of chemical and enzymatic probes. The external monolayer of the normal red cell membrane contained at least 68 to 72 percent of the total phosphatidylcholine and 15 to 20 percent of the total phosphatidylethanolamine. In the infected cell, the transmembrane phosphatidylcholine distribution appeared to be reversed, with only 20 to 30 percent of it being externally localized, whereas roughly equal amounts of phosphatidylethanolamine were present in the outer and inner surfaces. However, total phosphatidylethanolamine were present in the outer and inner surfaces. However, total phosphatidylserine in both the infected and normal red cells was exclusively internal. Unlike that in the normal intact cell, external phosphatidylethanolamine in the parasitized cell was readily accessible to phospholipase A2. These results indicate that significant changes in molecular architecture of the host cell membrane are the result of parasitization

Fabrication of Nano-Gapped Single-Electron Transistors for Transport Studies of Individual Single-Molecule Magnets

Three terminal single-electron transistor devices utilizing Al/Al2O3 gate electrodes were developed for the study of electron transport through individual single-molecule magnets. The devices were patterned via multiple layers of optical and electron beam lithography. Electromigration induced breaking of the nanowires reliably produces 1-3 nm gaps between which the SMM can be situated. Conductance through a single Mn12(3-thiophenecarboxylate) displays the coulomb blockade effect with several excitations within +/- 40 meV.Comment: 10 pages, 5 figure

Fluctuation Induced Non-Fermi Liquid Behavior near a Quantum Phase Transition in Itinerant Electron Systems

The signature for a non-Fermi liquid behavior near a quantum phase transition has been observed in thermal and transport properties of many metallic systems at low temperatures. In the present work we consider specific examples of itinerant ferromagnet as well as antiferromagnet in the limit of vanishing transition temperature. The temperature variation of spin susceptibility, electrical resistivity, specific heat, and NMR relaxation rates at low temperatures is calculated in the limit of infinite exchange enhancement within the frame work of a self consistent spin fluctuation theory. The resulting non-Fermi liquid behavior is due to the presence of the low lying critically damped spin fluctuations in these systems. The theory presented here gives the leading low temperature behavior, as it turns out that the fluctuation correlation term is always smaller than the mean fluctuation field term in three as well as in two space dimensions. A comparison with illustrative experimental results of these properties in some typical systems has been done. Finally we make some remarks on the effect of disorder in these systems.Comment: File RevTex, 7 Figures available on request, Abstract and text modified, To appear in Phys. Rev.

Vector meson masses in hot nuclear matter : the effect of quantum corrections

The medium modification of vector meson masses is studied taking into account the quantum correction effects for the hot and dense hadronic matter. In the framework of Quantum Hadrodynamics, the quantum corrections from the baryon and scalar meson sectors were earlier computed using a nonperturbative variational approach through a realignment of the ground state with baryon-antibaryon and sigma meson condensates. The effect of such corrections was seen to lead to a softer equation of state giving rise to a lower value for the compressibility and, an increase in the in-medium baryonic masses than would be reached when such quantum effects are not taken into account. These quantum corrections arising from the scalar meson sector result in an increase in the masses of the vector mesons in the hot and dense matter, as compared to the situation when only the vacuum polarisation effects from the baryonic sector are taken into account.Comment: 13 pages revtex file, 6 figure

Pair Correlation Functions and a Free-Energy Functional for the Nematic Phase

In this paper we have presented the calculation of pair correlation functions in a nematic phase for a model of spherical particles with the long-range anisotropic interaction from the mean spherical approximation(MSA) and the Percus-Yevick (PY) integral equation theories. The results found from the MSA theory have been compared with those found analytically by Holovko and Sokolovska (J. Mol. Liq. $\bf 82$, 161(1999)). A free energy functional which involves both the symmetry conserving and symmetry broken parts of the direct pair correlation function has been used to study the properties of the nematic phase. We have also examined the possibility of constructing a free energy functional with the direct pair correlation function which includes only the principal order parameter of the ordered phase and found that the resulting functional gives results that are in good agreement with the original functional. The isotropic-nematic transition has been located using the grand thermodynamic potential. The PY theory has been found to give nematic phase with pair correlation function harmonic coefficients having all the desired features. In a nematic phase the harmonic coefficient of the total pair correlation function $h({\bf x_1},{\bf x_2})$ connected with the correlations of the director transverse fluctuations should develop a long-range tail. This feature has been found in both the MSA and PY theories.Comment: 27 pages, 11 figures, Accepted in J. Chem. Phy

APPLICATION OF BOX-JENKINS METHOD AND ARTIFICIAL NEURAL NETWORK PROCEDURE FOR TIME SERIES FORECASTING OF PRICES

Forecasting of prices of commodities, especially those of agricultural commodities, is very difficult because they are not only governed by demand and supply but also by so many other factors which are beyond control, such as weather vagaries, storage capacity, transportation, etc. In this paper time series models namely ARIMA (Autoregressive Integrated Moving Average) methodology given by Box and Jenkins has been used for forecasting prices of Groundnut oil in Mumbai. This approach has been compared with ANN (Artificial Neural Network) methodology. The results showed that ANN performed better than the ARIMA models in forecasting the prices

Force induced stretched state: Effects of temperature

A model of self avoiding walks with suitable constraint has been developed to study the effect of temperature on a single stranded DNA (ssDNA) in the constant force ensemble. Our exact calculations for small chains show that the extension (reaction co-ordinate) may increase or decrease with the temperature depending upon the applied force. The simple model developed here which incorporates semi-microscopic details of base direction provide an explanation of the force induced transitions in ssDNA as observed in experiments.Comment: 5 pages, 8 figures, RevTex