San Francisco State University

About: San Francisco State University is a education organization based out in San Francisco, California, United States. It is known for research contribution in the topics: Population & Planet. The organization has 5669 authors who have published 11433 publications receiving 408075 citations. The organization is also known as: San Francisco State & San Francisco State Normal School.

Inhibition of HIV-1 infectivity by zinc-ejecting aromatic C -nitroso compounds

Abstract: RETROVIRAL nucleocapsid and gag-precursor proteins from all known strains of retroviruses contain one or two copies of an invariant sequence, Cys-X2-Cys-X4-His-X4-Cys1,2, that is populated with zinc in mature particles3. Modification of cysteine or histidine residues results in defective packaging of genomic viral RNA and formation of non-infectious particles4–8, making these structures potentially attractive targets for antiviral therapy3,8. We recently reported that aromatic C-nitroso ligands of poly(ADP–ribose) polymerase preferentially destabilize one of the two (Cys-X2-Cys-X28-His-X2-Cys) zinc-fingers with concomitant loss of enzymatic activity9,10, coincidental with selective cytocidal action of the C-nitroso substituted ligands on cancer cells11. Based on the occurrence of (3Cys, 1 His) zinc-binding sites in both retroviral nucleocapsid and gag proteins and in poly(ADP-ribose) polymerase12, we reasoned that the C-nitroso compounds may also have antiretroviral effects. We show here that two such compounds, 3-nitrosobenzamide and 6-nitroso-l,2-benzopyrone, inhibit infection of human immunodeficiency virus HIV-1 in human lymphocytes and also eject zinc from isolated HIV-1 nucleocapsid zinc fingers and from intact HIV-1 virions. Thus the design of zinc-ejecting agents that target retroviral zinc fingers represents a new approach to the chemotherapy of AIDS.

The gas-grain interaction in the interstellar medium - Thermal accommodation and trapping

Abstract: The paper develops a numerical model for calculating thermal accommodation coefficients alpha sub T and trapping functions f sub t for gases incident on solid surfaces. The method is especially designed for astrophysical applications in that it treats economically and with moderate accuracy (+ or - 20%) the dependences of alpha sub T and f sub t on finite and different surface and gas temperatures for a large number of gas-surface combinations. In particular, the method is applied to the astrophysical combinations of hydrogen and helium gases incident on graphite, silicon, and ice surfaces. Graphs are presented of the dependence of alpha sub T and f sub t on interstellar gas temperatures in the range of 10 to 10,000 K and grain temperatures in the range 10 to 1000 K, assuming the current estimates of the gas-surface physical parameters such as the composition and the Debye temperature of the grain material, the repulsive range of the surface potential, and the gas-grain adsorption energy.

New Debris Disks around Nearby Main-Sequence Stars: Impact on the Direct Detection of Planets

Abstract: Using the MIPS instrument on Spitzer, we have searched for infrared excesses around a sample of 82 stars, mostly F, G, and K main-sequence field stars, along with a small number of nearby M stars. These stars were selected for their suitability for future observations by a variety of planet-finding techniques. These observations provide information on the asteroidal and cometary material orbiting these stars, data that can be correlated with any planets that may eventually be found. We have found significant excess 70 μm emission toward 12 stars. Combined with an earlier study, we find an overall 70 μm excess detection rate of 13% ± 3% for mature cool stars. Unlike the trend for planets to be found preferentially toward stars with high metallicity, the incidence of debris disks is uncorrelated with metallicity. By newly identifying four of these stars as having weak 24 μm excesses (fluxes ~10% above the stellar photosphere), we confirm a trend found in earlier studies wherein a weak 24 μm excess is associated with a strong 70 μm excess. Interestingly, we find no evidence for debris disks around 23 stars cooler than K1, a result that is bolstered by a lack of excess around any of the 38 K1-M6 stars in two companion surveys. One motivation for this study is the fact that strong zodiacal emission can make it hard or impossible to detect planets directly with future observatories such as the Terrestrial Planet Finder (TPF). The observations reported here exclude a few stars with very high levels of emission, >1000 times the emission of our zodiacal cloud, from direct planet searches. For the remainder of the sample, we set relatively high limits on dust emission from asteroid belt counterparts.

Observation of optical Shockley-like surface states in photonic superlattices.

Abstract: We provide what we believe to be the first experimental demonstration of linear Shockley-like surface states in an optically induced semi-infinite photonic superlattice. Such surface states appear only when the induced superlattice consisting of alternating strong and weak bonds is terminated properly at the surface. Our experimental results are in good agreement with our theoretical analysis.