Absorption in quantum electrodynamics cavities in terms of a quantum jump operator

We describe the absorption by the walls of a quantum electrodynamics cavity as a process during which the elementary excitations (photons) of an internal mode of the cavity exit by tunneling through the cavity walls. We estimate by classical methods the survival time of a photon inside the cavity and the quality factor of its mirrors

Silicide formation with bilayers of Pd-Pt, Pd-Ni, and Pt-Ni

Evaporated two-layered thin films of Pd-Ni, Pt-Ni, and Pt-Pd on single-crystal Si have been vacuum annealed in the temperature range 200–900°C. The sequence of films as well as substrate orientation have been varied. The silicide formation has been studied by MeV He + backscattering spectrometry and glancing angle x-ray diffraction. The silicide layers are highly inhomogeneous in the elemental depth distribution for annealing below 600°C. Above 700°C, the distributions become homogeneous. The silicide-substrate interface shows varying sharpness depending upon substrate orientation and evaporation sequence. We suggest the existence of ternary monosilicides of the type Pt1–xPdxSi, Pt1–xNixSi, and Pd1–xNixSi. The Pt1–xPdxSi ternary silicide is stable up to 900°C; the others are not

Defects Annealing of Si^+ Implanted GaAs at RT and 100°C

Annealing behavior of point defects near room temperature is studied by measuring the strain relaxation of Si+ implanted GaAs. Polished semi-insulating GaAs wafers were implanted with 300keV Si^+ at liquid nitrogen (LN_2) and room temperature (RT). The strain profile was obtained by the X-ray Double Crystal Diffraction (DCD) technique and kinematical fitting. The maximum strain of the samples stored at RT and elevated temperature 100°C in air, decreases with time, which indicates the reduction of point defects. Relaxation is exponential in time. At least two time constants of 0.24hrs and 24hrs are needed to fit the data, suggesting that two different processes are responsible for annealing defects. Time constants are obtained for different doses at RT and LN_2 implantation temperature, and found to be insensitive to both these quantities. The activation energy for defect migration is estimated using simple diffusion model

Elastic and thermal properties of mesotaxial CoSi2 layers on Si

Single crystalline 110 nm thick CoSi2 layers formed on both (100)- and (111)-oriented Si wafers by high dose 59Co implantation and thermal annealing were analyzed by x-ray double crystal diffractometry. The lateral mismatch of both (100)- and (111)-oriented samples are similar (~–0.7%) at room temperature, meaning that the average spacing between misfit dislocations is roughly the same (~30 nm). But the perpendicular mismatch differs for the two substrate orientations, reflecting the elastic anisotropy of the single-crystalline CoSi2 layers. The three elastic constants of cubic CoSi2 (C11 = 277, C12C12= 222, C44 = 100 GPa) were extracted from these lattice mismatches and the sample curvature measurements. X-ray rocking curves were also recorded up to ~500 °C. The average spacing between the misfit dislocations remains unchanged, meaning that the misfit dislocations do not shear up to 500 °C. The linear thermal expansion coefficient of CoSi2 (9.5 × 10^–6/°C) was obtained under the assumption that the elastic constants do not change with temperature

Bacterial genomics reveal the complex epidemiology of an emerging pathogen in Arctic and boreal ungulates

Northern ecosystems are currently experiencing unprecedented ecological change, largely driven by a rapidly changing climate. Pathogen range expansion, and emergence and altered patterns of infectious disease, are increasingly reported in wildlife at high latitudes. Understanding the causes and consequences of shifting pathogen diversity and host-pathogen interactions in these ecosystems is important for wildlife conservation, and for indigenous populations that depend on wildlife. Among the key questions are whether disease events are associated with endemic or recently introduced pathogens, and whether emerging strains are spreading throughout the region. In this study, we used a phylogenomic approach to address these questions of pathogen endemicity and spread for Erysipelothrix rhusiopathiae, an opportunistic multi-host bacterial pathogen associated with recent mortalities in arctic and boreal ungulate populations in North America. We isolated E. rhusiopathiae from carcasses associated with large-scale die-offs of muskoxen in the Canadian Arctic Archipelago, and from contemporaneous mortality events and/or population declines among muskoxen in northwestern Alaska and caribou and moose in western Canada. Bacterial genomic diversity differed markedly among these locations; minimal divergence was present among isolates from muskoxen in the Canadian Arctic, while in caribou and moose populations, strains from highly divergent clades were isolated from the same location, or even from within a single carcass. These results indicate that mortalities among northern ungulates are not associated with a single emerging strain of E. rhusiopathiae, and that alternate hypotheses need to be explored. Our study illustrates the value and limitations of bacterial genomic data for discriminating between ecological hypotheses of disease emergence, and highlights the importance of studying emerging pathogens within the broader context of environmental and host factors

Evidence for a companion to BM Gem, a silicate carbon star

Balmer and Paschen continuum emission as well as Balmer series lines of P Cygni-type profile from H_gamma through H_23 are revealed in the violet spectra of BM Gem, a carbon star associated with an oxygen-rich circumstellar shell (`silicate carbon star') observed with the high dispersion spectrograph (HDS) on the Subaru telescope. The blue-shifted absorption in the Balmer lines indicates the presence of an outflow, the line of sight velocity of which is at least 400 km s^-1, which is the highest outflow velocity observed to date in a carbon star. We argue that the observed unusual features in BM Gem are strong evidence for the presence of a companion, which should form an accretion disk that gives rise to both an ionized gas region and a high velocity, variable outflow. The estimated luminosity of ~0.2 (0.03-0.6) L_sun for the ionized gas can be maintained by a mass accretion rate to a dwarf companion of ~10^-8 M_sun yr^-1, while ~10^-10 M_sun yr^-1 is sufficient for accretion to a white dwarf companion. These accretion rates are feasible for some detached binary configurations on the basis of the Bond-Hoyle type accretion process. We concluded that the carbon star BM Gem is in a detached binary system with a companion of low mass and low luminosity. However, we are unable to determine whether this companion object is a dwarf or a white dwarf. The upper limits for binary separation are 210 AU and 930 AU for a dwarf and a white dwarf, respectively. We also note that the observed features of BM Gem mimic those of Mira (omi Cet), which may suggest actual similarities in their binary configurations and circumstellar structures.Comment: 11 pages, 2 figures, 1 table, accepted for publication in Ap