Radiation Driven Implosion and Triggered Star Formation

We present simulations of initially stable isothermal clouds exposed to ionizing radiation from a discrete external source, and identify the conditions that lead to radiatively driven implosion and star formation. We use the Smoothed Particle Hydrodynamics code SEREN (Hubber et al. 2010) and the HEALPix-based photoionization algorithm described in Bisbas et al. (2009). We find that the incident ionizing flux is the critical parameter determining the evolution: high fluxes simply disperse the cloud, whereas low fluxes trigger star formation. We find a clear connection between the intensity of the incident flux and the parameters of star formation.Comment: 4 pages, 2 figures, conference proceedings, IAU Symposium 270 (eds. Alves, Elmegreen, Girart, Trimble

Interstellar Extinction Law toward the Galactic Center II: V, J, H, and Ks Bands

We have determined the ratios of total to selective extinction directly from observations in the optical V band and near-infrared J band toward the Galactic center. The OGLE (Optical Gravitational Lensing Experiment) Galactic bulge fields have been observed with the SIRIUS camera on the IRSF telescope, and we obtain A(V)/E(V-J)=1.251+-0.014 and A(J)/E(V-J)=0.225+-0.007. From these ratios, we have derived A(J)/A(V) = 0.188+-0.005; if we combine A(J)/A(V) with the near-infrared extinction ratios obtained by Nishiyama et al. for more reddened fields near the Galactic center, we get A(V) : A(J) : A(H) : A(Ks) = 1 : 0.188 : 0.108 : 0.062, which implies steeply declining extinction toward the longer wavelengths. In particular, it is striking that the Ks band extinction is \approx 1/16 of the visual extinction A(V) much smaller than one tenth of A(V) so far employed.Comment: 8 pages, 7 figures, Accepted for publication in Ap

Theoretical and computational analysis of the membrane potential generated by cytochrome c oxidase upon single electron injection into the enzyme

AbstractWe have developed theory and the computational scheme for the analysis of the kinetics of the membrane potential generated by cytochrome c oxidase upon single electron injection into the enzyme. The theory allows one to connect the charge motions inside the enzyme to the membrane potential observed in the experiments by using data from the “dielectric topography” map of the enzyme that we have created. The developed theory is applied for the analysis of the potentiometric data recently reported by the Wikström group [I. Belevich, D.A. Bloch, N. Belevich, M. Wikström and M.I. Verkhovsky, Exploring the proton pump mechanism of cytochrome c oxidase in real time, Proc. Natl. Acad. Sci. U. S. A. 104 (2007) 2685–2690] on the O to E transition in Paracoccus denitrificans oxidase. Our analysis suggests, that the electron transfer to the binuclear center is coupled to a proton transfer (proton loading) to a group just “above” the binuclear center of the enzyme, from which the pumped proton is subsequently expelled by the chemical proton arriving to the binuclear center. The identity of the pump site could not be determined with certainty, but could be localized to the group of residues His326 (His291 in bovine), propionates of heme a3, Arg 473/474, and Trp164. The analysis also suggests that the dielectric distance from the P-side to Fe a is 0.4 or larger. The difficulties and pitfalls of quantitative interpretation of potentiometric data are discussed

Anisotropic magnetic properties of CeAg2_2Ge2_2 single crystal

In order to investigate the anisotropic magnetic properties of CeAg$_2$Ge$_2$, we have successfully grown the single crystals, for the first time, by high temperature solution growth (flux) method. We have performed a detailed study of the grown single crystals by measuring their electrical resistivity, magnetic susceptibility, magnetization, specific heat and magnetoresistance. A clear anisotropy and an antiferromagnetic transition at $T_{\rm N}$ = 4.6 K have been observed in the magnetic properties. The magnetic entropy reaches $R$ ln 4 at 20 K indicating that the ground state and the first excited state are very closely spaced (a quasi-quartet state). From the specific heat measurements and crystalline electric field (CEF) analysis of the magnetic susceptibility, we have found the level splitting energies as 5 K and 130 K. The magnetization measurements reveal that the a-axis is the easy axis of magnetization and the saturation moment is $\mu_{\rm s}$ = 1.6 $\mu_{\rm B}$/Ce, corroborating the previous neutron diffraction measurements on a polycrystalline sample.Comment: Submitted to Phys. Rev.

The effect of small bowel transplantation on the morphology and physiology of intestinal muscle: A comparison of autografts versus allografts in dogs

The effects of acute (AR) and chronic rejection (CR) on intestinal smooth muscle that are responsible for the dysmotility following small bowel transplantation (SBTX) are incompletely understood. Jejunal and ileal specimens from normal control dogs (n=7), and autotransplanted dogs were examined at 7 days (n=6) and 1 (n=7), 3 (n=6), 6 (n=6), and 12 months (n=6). Allotransplanted dogs that developed AR (n=8) and CR (n=5) were examined for gross and microscopic morphology (muscle thickness, the number and size of myocytes, and inflammatory infiltrate), and for contractile and intracellular electrical function in vitro. Auto-SBTX did not alter morphology at any period, but contractile function was impaired at 7 days (73.6%) compared with normal intestine. Acute rejection did not influence myocyte number or size, but was associated with a prominent infiltrate of neutrophils and lymphocytes, and severely impaired contractile function (20.6%) compared with auto-SBTX controls. Acute rejection also significantly inhibited the amplitude of slow waves and of inhibitory junction potentials. Chronic rejection caused thickening of muscularis propria by both hyperplasia (175.5%) and hypertrophy (202.6%) accompanied by moderate inflammatory cell infiltrate compared with auto-SBTX controls. We conclude that the marked inflammatory infiltrate into the muscularis propria indicates that the graft muscle is injured by both acute and chronic rejection; impaired function of intestinal smooth muscle following SBTX results from both rejection and the injury associated with transplantation, and chronic rejection following SBTX is associated with both hyperplasia and hypertrophy of the muscularis propria

Diversification in the Archean Biosphere: Insight from NanoSIMS of Microstructures in the Farrel Quartzite of Australia

The nature of early life on Earth is difficult to assess because potential Early Archean biosignatures are commonly poorly preserved. Interpretations of such materials have been contested, and abiotic or epigenetic derivations have been proposed (summarized in [1]). Yet, an understanding of Archean life is of astrobiological importance, as knowledge of early evolutionary processes on Earth could provide insight to development of life on other planets. A recently-discovered assemblage of organic microstructures in approx.3 Ga charts of the Farrel Quartzite (FQ) of Australia [2-4] includes unusual spindle-like forms and a variety of spheroids. If biogenicity and syngeneity of these forms could be substantiated, the FQ assemblage would provide a new view of Archean life. Our work uses NanoSIMS to further assess the biogenicity and syngeneity of FQ microstructures. In prior NanoSIMS studies [5-6], we gained an understanding of nano-scale elemental distributions in undisputed microfossils from the Neoproterozoic Bitter Springs Formation of Australia. Those results provide a new tool with which to evaluate poorly preserved materials that we might find in Archean sediments and possibly in extraterrestrial materials. We have applied this tool to the FQ forms