In-situ surface technique analyses and ex-situ characterization of Si1-xGex epilayers grown on Si(001)-2 ×1 by molecular beam epitaxy

Si1-xGex epilayers grown by Molecular Beam Epitaxy on Si(001) at 400 ○C have been analyzed in-situ by surface techniques such as X-ray and Ultraviolet Photoelectron Spectroscopies (XPS and UPS), Low Energy Electron Diffraction (LEED) and photoelectron diffraction (XPD). The Ge surface concentrations (x) obtained from the ratios of Ge and Si core level intensities are systematically higher than those obtained by the respective evaporation fluxes. This indicates a Ge enrichment in the first overlayers confirmed by Ge-like UPS valence band spectra. The structured crystallographic character of the epilayers is ascertained by LEED and XPD polar scans in the (100) plane since the Ge Auger LMM and the Si 2p XPD intensity patterns from the Si1-xGex epilayers are identical to those of the Si substrate. The residual stress in the epilayer is determined by ex-situ X-ray diffraction (XRD) which also allows, as Rutherford Back Scattering (RBS), Ge concentration determinations

Wavelet domain Bayesian denoising of string signal in the cosmic microwave background

An algorithm is proposed for denoising the signal induced by cosmic strings in the cosmic microwave background (CMB). A Bayesian approach is taken, based on modeling the string signal in the wavelet domain with generalized Gaussian distributions. Good performance of the algorithm is demonstrated by simulated experiments at arcminute resolution under noise conditions including primary and secondary CMB anisotropies, as well as instrumental noise.Comment: 16 pages, 11 figures. Version 2 matches version accepted for publication in MNRAS. Changes include substantial clarifications on our approach and a significant reduction of manuscript lengt

CMBPol Mission Concept Study: Prospects for polarized foreground removal

In this report we discuss the impact of polarized foregrounds on a future CMBPol satellite mission. We review our current knowledge of Galactic polarized emission at microwave frequencies, including synchrotron and thermal dust emission. We use existing data and our understanding of the physical behavior of the sources of foreground emission to generate sky templates, and start to assess how well primordial gravitational wave signals can be separated from foreground contaminants for a CMBPol mission. At the estimated foreground minimum of ~100 GHz, the polarized foregrounds are expected to be lower than a primordial polarization signal with tensor-to-scalar ratio r=0.01, in a small patch (~1%) of the sky known to have low Galactic emission. Over 75% of the sky we expect the foreground amplitude to exceed the primordial signal by about a factor of eight at the foreground minimum and on scales of two degrees. Only on the largest scales does the polarized foreground amplitude exceed the primordial signal by a larger factor of about 20. The prospects for detecting an r=0.01 signal including degree-scale measurements appear promising, with 5 sigma_r ~0.003 forecast from multiple methods. A mission that observes a range of scales offers better prospects from the foregrounds perspective than one targeting only the lowest few multipoles. We begin to explore how optimizing the composition of frequency channels in the focal plane can maximize our ability to perform component separation, with a range of typically 40 < nu < 300 GHz preferred for ten channels. Foreground cleaning methods are already in place to tackle a CMBPol mission data set, and further investigation of the optimization and detectability of the primordial signal will be useful for mission design.Comment: 42 pages, 14 figures, Foreground Removal Working Group contribution to the CMBPol Mission Concept Study, v2, matches AIP versio

D-term inflation in non-minimal supergravity

D-term inflation is one of the most interesting and versatile models of inflation. It is possible to implement naturally D-term inflation within high energy physics, as for example SUSY GUTs, SUGRA, or string theories. D-term inflation avoids the $\eta$-problem, while in its standard form it always ends with the formation of cosmic strings. Given the recent three-year WMAP data on the cosmic microwave background temperature anisotropies, we examine whether D-term inflation can be successfully implemented in non-minimal supergravity theories. We show that for all our choices of K\"ahler potential, there exists a parameter space for which the predictions of D-term inflation are in agreement with the measurements. The cosmic string contribution on the measured temperature anisotropies is always dominant, unless the superpotential coupling constant is fine tuned; a result already obtained for D-term inflation within minimal supergravity. In conclusion, cosmic strings and their r\^ole in the angular power spectrum cannot be easily hidden by just considering a non-flat K\"ahler geometry.Comment: 29 pages, 9 figures; minor changes to match publihed versio

Probing Cosmic Strings with Satellite CMB measurements

We study the problem of searching for cosmic string signal patterns in the present high resolution and high sensitivity observations of the Cosmic Microwave Background (CMB). This article discusses a technique capable of recognizing Kaiser-Stebbins effect signatures in total intensity anisotropy maps, and shows that the biggest factor that produces confusion is represented by the acoustic oscillation features of the scale comparable to the size of horizon at recombination. Simulations show that the distribution of null signals for pure Gaussian maps converges to a $\chi^2$ distribution, with detectability threshold corresponding to a string induced step signal with an amplitude of about 100 \muK which corresponds to a limit of roughly $G\mu < 1.5\times 10^{-6}$. We study the statistics of spurious detections caused by extra-Galactic and Galactic foregrounds. For diffuse Galactic foregrounds, which represents the dominant source of contamination, we derive sky masks outlining the available region of the sky where the Galactic confusion is sub-dominant, specializing our analysis to the case represented by the frequency coverage and nominal sensitivity and resolution of the Planck experiment.Comment: 14 pages, 3 figures, to be published in JCA

Demonstration of the metaphylactic use of gamithromycin against bacterial pathogens associated with bovine respiratory disease in a multicentre farm trial

On five commercial cattle rearing sites across Europe, a total of 802 young cattle at high risk of developing bovine respiratory disease (BRD) associated with the bacterial pathogens Mannheimia haemolytica or Pasteurella multocida and/or Mycoplasma bovis were enrolled into a multicentre, controlled field trial. Half were treated with a single dose of gamithromycin at 6 mg/kg bodyweight by subcutaneous injection and half received an injection of a saline placebo as the control. All animals were observed daily for 14 days for signs of BRD as defined by set criteria. The proportion of metaphylactic preventive treatment successes, defined as animals surviving to day 14 without signs of BRD, in the gamithromycin-treated group (86 per cent) was significantly (P=0.0012) higher than in the saline-treated controls (61 per cent). Morbidity among the treated animals was reduced by 64 per cent compared with the controls

The 21 cm Signature of Shock Heated and Diffuse Cosmic String Wakes

The analysis of the 21 cm signature of cosmic string wakes is extended in several ways. First we consider the constraints on $G\mu$ from the absorption signal of shock heated wakes laid down much later than matter radiation equality. Secondly we analyze the signal of diffuse wake, that is those wakes in which there is a baryon overdensity but which have not shock heated. Finally we compare the size of these signals compared to the expected thermal noise per pixel which dominates over the background cosmic gas brightness temperature and find that the cosmic string signal will exceed the thermal noise of an individual pixel in the Square Kilometre Array for string tensions $G\mu > 2.5 \times 10^{-8}$.Comment: 10 pages, 4 figures, Appendix added, version published in JCA

Evidence for Spatial Separation of Galactic Dust Components

We present an implementation of a Bayesian mixture model using Hamiltonian Monte Carlo (HMC) techniques to search for spatial separation of Galactic dust components. Utilizing intensity measurements from \Planck High Frequency Instrument (HFI), we apply this model to high-latitude Galactic dust emission. Our analysis reveals a strong preference for a spatially-varying two-population dust model in intensity, with each population being well characterized by a single-component dust spectral-energy distribution (SED). While no spatial information is built into the likelihood, our investigation unveils spatially coherent structures with high significance, pointing to a physical origin for the observed spatial separation. These results are robust to our choice of likelihood and of input data. Furthermore, they are favored over a single-component dust model by Bayesian evidence calculations. Incorporating \IRAS 100\,$\mu m$ to constrain the Wein-side of the blackbody function, we find the dust populations differ at the $2.5\sigma$ level on the spectral index ($\beta_d$) vs. temperature $(T_d)$ plane. The presence of a multi-population dust has implications for component separation techniques frequently employed in the recovery of the Cosmic Microwave Background.Comment: 16 pages, 8 figures. Submitted to Ap