Physics

To quantify the magnitude and pattern of spatial variation in local population density within a single species, we analyzed large numbers of samples, representing a large geographic area or a wide range of ecological conditions. Our analyses focused on, but were not ...

Prolonged antiretroviral therapy (ART) with effective HIV suppression and reconstitution of CD4 T cells, fails to restore CD8 T cell lytic effector function that is needed to eradicate the viral reservoir. Better understanding of the phenotype and function of circulating CD8 cells in HIV patients will contribute to new targeted therapies directed at increasing CD8 T cell lytic effector function and destruction of the viral reservoir. We show that CD8 T cells from ART treated patients had sharply reduced expression of CD56 (neural cell adhesion molecule-1), a marker associated with cytolytic function whereas elite patients who control HIV in the absence of ART had CD56+ CD8 T cell levels similar to uninfected controls. The CD56+ CD8 T cells had higher perforin upregulation as well as degranulation following stimulation with HIV gag peptides compared with CD56 negative CD8 T cells. Elite patients had the highest frequencies of perforin producing CD56+ CD8 T cells among all HIV+ groups...

ABSTRACT In this paper the energy, intensity and angular distributions of multiple scattering of 662 keV gamma photons, emerging from targets of aluminium, copper, iron and glass samples are studied as a function of target thickness. An intense collimated beam obtained from a 137Cs source of 5.8 mCi is allowed to impinge on samples of varying thickness. The scattered photons are detected by a properly shielded 76 mm × 76 mm NaI (Tl) scintillation detector. In Compton scattering experiments, it is observed that the number of multiple backscattered photons increase with an increase in target thickness and become almost constant for particular target thickness called saturation thickness. The saturation thickness decreases with increasing atomic number. The multiple scattering, an interfering background noise in Compton profile, has been successfully used to assign effective atomic number (Zeff ) to composite materials. The experimental results are compared with the Monte Carlo calculations using Monte Carlo nuclear particle code.

Results of electronic band structure calculations, electrical resistance, thermoelectric power (TEP), and x-ray diffraction measurements, under pressure carried out on AuGa(2) to investigate its anomalous behaviour are reported. The first principles electronic band structure calculations confirm that a flat band close to the Fermi level along the Γ-X direction of the Brillouin zone is responsible for the unusual behaviour of AuGa(2). In synchrotron-based high-pressure x-ray diffraction measurements, it is observed to undergo a structural phase transition above 7 GPa. The TEP variation with pressure and the P-V data up to 7 GPa transformed to the universal equation of state (UEOS) indicate the existence of an electronic topological transition (ETT) near 3.2 GPa. Consistent with this, in electronic structure calculations carried out at reduced sample volume corresponding to 4 GPa, it is seen that the flat band crosses the Fermi level. The structure above 7 GPa is a distortion of the CaF(2) phase. This structure continuously evolves with increasing pressure. The continuous variation of electrical resistance across the transition is consistent with this.