Donor states in modulation-doped Si/SiGe heterostructures

We present a unified approach for calculating the properties of shallow donors inside or outside heterostructure quantum wells. The method allows us to obtain not only the binding energies of all localized states of any symmetry, but also the energy width of the resonant states which may appear when a localized state becomes degenerate with the continuous quantum well subbands. The approach is non-variational, and we are therefore also able to evaluate the wave functions. This is used to calculate the optical absorption spectrum, which is strongly non-isotropic due to the selection rules. The results obtained from calculations for Si/Si$_{1-x}$Ge$_x$ quantum wells allow us to present the general behavior of the impurity states, as the donor position is varied from the center of the well to deep inside the barrier. The influence on the donor ground state from both the central-cell effect and the strain arising from the lattice mismatch is carefully considered.Comment: 17 pages, 10 figure

Measurement of the Bottom-Strange Meson Mixing Phase in the Full CDF Data Set

We report a measurement of the bottom-strange meson mixing phase \beta_s using the time evolution of B0_s -> J/\psi (->\mu+\mu-) \phi (-> K+ K-) decays in which the quark-flavor content of the bottom-strange meson is identified at production. This measurement uses the full data set of proton-antiproton collisions at sqrt(s)= 1.96 TeV collected by the Collider Detector experiment at the Fermilab Tevatron, corresponding to 9.6 fb-1 of integrated luminosity. We report confidence regions in the two-dimensional space of \beta_s and the B0_s decay-width difference \Delta\Gamma_s, and measure \beta_s in [-\pi/2, -1.51] U [-0.06, 0.30] U [1.26, \pi/2] at the 68% confidence level, in agreement with the standard model expectation. Assuming the standard model value of \beta_s, we also determine \Delta\Gamma_s = 0.068 +- 0.026 (stat) +- 0.009 (syst) ps-1 and the mean B0_s lifetime, \tau_s = 1.528 +- 0.019 (stat) +- 0.009 (syst) ps, which are consistent and competitive with determinations by other experiments.Comment: 8 pages, 2 figures, Phys. Rev. Lett 109, 171802 (2012

Glucose, Insulin and Renin activity after sodium loading and depletion in Vipera aspis.

Sodium, potassium, chloride, glucose, insulin and renin activity were investigated in fasted Vipera aspis subjected for 3 days to administration of 3% NaCl 5 ml, or injection of a diuretic and water loading to produce sodium depletion. After sodium loading, plasma sodium and glucose were significantly elevated if compared with those of controls, while plasma renin-like activity and plasma insulin were depressed. The insulin and somatostatin producing cells (B- and D-cells) showed only a weak immunoreactivity, while in the glucagon producing cells (A-cells) the immunoreactivity was stronger if compared with the handled controls. After sodium depletion, plasma sodium and glucose were significantly depressed and plasma renin-like activity and plasma insulin were significantly elevated. A strong immunoreactivity was present in B- and D-cells and only a weak immunoreactivity was detectable in the A-cells. These data suggest that the secretory activity of the endocrine pancreas and kidney may be affected, in vipers, by sodium and/or volume status

Angiotensin II binding sites in the rat pancreas and their modulation after sodium loading and depletion

Specific 125I angiotensin II binding sites were identified in the rat pancreas by radioreceptor assay, autoradiography and immunohistochemistry. Scatchard analysis of the binding in normal rats yielded a Kd of 0.51 ± 0.23 nM with a Bmax of 15 ± 3.5 fmol/mg protein (means ± SD, n = 6). Changed plasma sodium concentration resulted in modifications in the binding affinity and capacity. Sodium loading depressed both Kd (0.36 ± 0.1 nM) and Bmax (6.4 ± 0.1 fmol/mg protein), while sodium depletion elevated both Kd (2.03 ± 0.3 nM) and Bmax (45 ± 3.5 fmol/mg protein) (means ± SD, n = 6). Autoradiography using 125I Ang II and immunohistochemistry of the binding sites saturated with unlabeled Ang II and incubated with Ab-Ile5 Ang II, revealed localization of the binding sites on the islet cell membranes and in the exocrine pancreas

Effects of a Simulated Microgravity Model on Cell Structure and Function in Mouse Testis

Decreased testicular blood flow shift occurring under microgravity conditions causes impaired spermatogenesis in males. The tail suspended model has been used mainly in studies of muscle atrophy/osteoporosis and of body fluid shift in few studies aimed at spermatogenesis. We examined serum testosterone levels, testis morphology and apoptotic phenomena in tail suspended mice, a model used to reproduce some of the effects of the absence of gravity. Male C57BL mice (6months old) were divided into two groups: tail suspended (TS) and controls (C). After 14 days of treatment testosterone levels were determined. On fixed sections histological stain (HE) was performed; DNA fragmentation was visualized using TUNEL technique. On the frozen samples immunoblotting for BAX, Bcl2, Caspase 39 and p53 was carried out. Testosterone levels were 0.18±0.09 and 3.74±2.2 ng/ml (mean±DS) in suspended and control animals, respectively. HE staining showed disturbed cell arrangement and a markedly decreased number of spermatozoa in the testes, TUNEL revealed an increased apoptotic index and immunoblotting provided evidence of apoptotic markers in TS animals. These data support results previously obtained by other groups showing a significant influence of short duration microgravity conditions on testicular function