Antiferromagnetism and phase separation in the t-J model at low doping: a variational study

Using Gutzwiller-projected wave functions, I estimate the ground-state energy of the t-J model for several variational states relevant for high-temperature cuprate superconductors. The results indicate antiferromagnetism and phase separation at low doping both in the superconducting state and in the staggered-flux normal state proposed for the vortex cores. While phase separation in the underdoped superconducting state may be relevant for the stripe formation mechanism, the results for the normal state suggest that similar charge inhomogeneities may also appear in vortex cores up to relatively high doping values.Comment: 4 pages, 3 figures, reference adde

Storm-time changes of geomagnetic field at MAGSAT altitudes (325-550 Km) and their comparison with changes at ground locations

The values of H, X, Y, Z at MAGSAT altitudes were first expressed as residuals delta H, delta X, delta Y, delta Z after subtracting the model HMD, XMD, YMD, ZMC. The storm-time variations of H showed that delta H (Dusk) was larger (negative) than delta H (Dawn) and occurred earlier, indicating a sort of hysteresis effect. Effects at MAGSAT altitudes were roughly the same (10% accuracy) as at ground, indicating that these effects were mostly of magnetospheric origin. The delta Y component also showed large storm-time changes. The latitudinal distribution of storm-time delta H showed north-south asymmetries varying in nature as the storm progressed. It seems that the central plane of the storm-time magnetospheric ring current undergoes latitudinal meanderings during the course of the storm

Axions as Quintessence in String Theory

We construct a model of quintessence in string theory based on the idea of axion monodromy as discussed by McAllister, Silverstein and Westphal arXiv:0808.0706. In the model, the quintessence field is an axion whose shift symmetry is broken by the presence of 5-branes which are placed in highly warped throats. This gives rise to a potential for the axion field which is slowly varying, even after incorporating the effects of moduli stabilization and supersymmetry breaking. We find that the resulting time dependence in the equation of state of Dark Energy is potentially detectable, depending on the initial conditions. The model has many very light extra particles which live in the highly warped throats, but these are hard to detect. A signal in the rotation of the CMB polarization can also possibly arise.Comment: 41 pages, 1 figure, v2: references adde

SIMPLE, EFFICIENT AND ECONOMIC METHOD FORISOLATION AND ANALYSIS OF KARANJIN AND PONGAMOL FROM KARANJA SEED OIL AND SCREENING OF ANTIMICROBIAL POTENTIAL

Objective: Study was undertaken with the objective, to develop simple, high yielding and economic method for the isolation as well as analysis of Karanjin and Pongamol from Karanja oil.Methods: Karanja oil was subjected to extraction with methanol. Methanol extract was washed with little quantity of pet ether for removal of residual oil. Resultant extract was dissolved in a sufficient quantity of methanol and kept aside for 6 hours,a white precipitate formed which was subjected to repeated crystallization to get karanjin (1K). Residue obtains after precipitate removal was concentrated into half and extracted with dilute acetic acid and kept aside for 48 hours. A pale yellow crystals were formed on the side wall,collected it and chromatographed over the column with hexane and ethyl acetate (95:5) to obtain pure Pongamol (2P). Karanjin and Pongamol was analyzed by high performance liquid chromatography (HPLC).Results: Yield of Karanjin was 35.5 g (0.89 %) and pongamol was 27.3 g (0.68 %) from 4 l of Karanja oil. HPLC method developed for the analysis of karanjin and pongamol produce results which comply with USP standards. Both compounds fail to produce a significant antibacterial effect on gram positive and negative bacteria as well as on pathogenic fungi and yeast.Conclusion: This method for isolation is simple, economic and gives good yields of karanjin & pongamol from Karanja oil and HPLC method for the analysis of karanjin and pongamol is suitable for simultaneous estimation and reliable.Â

Results of an aqueous source term model for a radiological risk assessment of the Drigg LLW Site, U.K.

A radionuclide source term model has been developed which simulates the biogeochemical evolution of the Drigg low level waste (LLW) disposal site. The DRINK (DRIgg Near field Kinetic) model provides data regarding radionuclide concentrations in groundwater over a period of 100,000 years, which are used as input to assessment calculations for a groundwater pathway. The DRINK model also provides input to human intrusion and gaseous assessment calculations through simulation of the solid radionuclide inventory. These calculations are being used to support the Drigg post closure safety case. The DRINK model considers the coupled interaction of the effects of fluid flow, microbiology, corrosion, chemical reaction, sorption and radioactive decay. It represents the first direct use of a mechanistic reaction-transport model in risk assessment calculations

Orientational and dielectric behaviour of N, N-dimethylformamide in different non-polar solvents

Dielectric behaviour of concentrated solutions of different mole fractions of N, N-dimethylformamide in various non-polar solvents has been studied using precision LCR meter with four terminal liquid dielectric test fixture over a frequency range 20 Hz to 2 MHz at 303.15 K temperature. The dielectric parameters namely dielectric constant (ε′), dielectric loss (ε″) and static dielectric constant (ε0) have been determined by capacitive measurement method. The limiting dielectric constant (ε∞) has been determined by Abbe’s refractometer for the same solutions at 303.15 K temperature. Kirkwood correlation factor geff has also been calculated using determined values of ε0 and ε∞,to gain information about the orientational behaviour of N, N-dimethylformamide in different non-polar solvent environments