Theory and design of quantum cascade lasers in (111) n-type Si/SiGe

Although most work towards the realization of group IV quantum cascade lasers (QCLs) has focused on valence band transitions, there are many desirable properties associated with the conduction band. We show that the commonly cited shortcomings of n-type Si/SiGe heterostructures can be overcome by moving to the (111) growth direction. Specifically, a large band offset and low effective mass are achievable and subband degeneracy is preserved. We predict net gain up to lattice temperatures of 90 K in a bound-to-continuum QCL with a double-metal waveguide, and show that a Ge interdiffusion length of at least 8 Å across interfaces is tolerable

Intersubband carrier scattering in n- and p-Si/SiGe quantum wells with diffuse interfaces

Scattering rate calculations in two-dimensional Si/Si1−xGex systems have typically been restricted to rectangular Ge profiles at interfaces between layers. Real interfaces however, may exhibit diffuse Ge profiles either by design or as a limitation of the growth process. It is shown here that alloy disorder scattering dramatically increases with Ge interdiffusion in (100) and (111) n-type quantum wells, but remains almost constant in (100) p-type heterostructures. It is also shown that smoothing of the confining potential leads to large changes in subband energies and scattering rates and a method is presented for calculating growth process tolerances

Structural and magnetic properties of an InGaAs/Fe3_3Si superlattice in cylindrical geometry

The structure and the magnetic properties of an InGaAs/Fe3Si superlattice in a cylindrical geometry are investigated by electron microscopy techniques, x-ray diffraction and magnetometry. To form a radial superlattice, a pseudomorphic InGaAs/Fe3As bilayer has been released from its substrate self-forming into a rolled-up microtube. Oxide-free interfaces as well as areas of crystalline bonding are observed and an overall lattice mismatch between succeeding layers is determined. The cylindrical symmetry of the final radial superlattice shows a significant effect on the magnetization behavior of the rolled-up layers

Submillimeter wavelength survey of the galactic plane from l = -5 deg to l = +62 deg: Structure and energetics of the inner disk

Results from a large scale survey of the first quadrant of the Milky Way galactic plane at wavelengths of 150, 250, and 300 microns with a 10x10 arcmin beam are presented. The emission detected in the survey arises from compact sources, most of which are identified with known peaks of 5 GHz and/or CO emission, and from an underlying diffuse background with a typical angular width of approximately 0.9 deg (FWHM) which accounts for most of the emission. A total of 80 prominent discrete sources were identified and characterized, of which about half were not previously reported at far infrared wavelengths. The total infrared luminosity within the solar circle is approximately 1 to 2x10 to the 10th power L sub 0, and is probably emitted by dust that resides in molecular clouds

Psychological health of Australian veterans of the 1991 Gulf War: an assessment using the SF-12, GHQ-12 and PCL-S

Background. Elevated rates of psychological morbidity and symptomatology have been widely reported in 1991 Gulf War veterans. The present study used brief self-report instruments to compare the psychological health of Australian Gulf War veterans with that of a randomly sampled military comparison group. Method. The 12-item Short Form Health Survey (SF-12), 12-item General Health Questionnaire (GHQ-12), Posttraumatic Stress Disorder Checklist – Specific (PCL-S) and Military Service Experience (MSE) questionnaire were administered to 1424 male Australian Gulf War veterans and 1548 male Australian Defence Force members who were operational at the time of the Gulf War conflict, but were not deployed there. Results. The Gulf War veterans exhibited poorer psychological health, as measured by the above three instruments, than the comparison group members. For Gulf War veterans, the number of stressful experiences, as measured by the MSE questionnaire, was correlated with scores on the three instruments. SF-12 mental health component summary scores and PCL-S caseness, but not GHQ-12 caseness, differed significantly between Gulf War veterans and comparison group members who had been on at least one active deployment. Conclusions. More than a decade after the 1991 Gulf War, Australian Gulf War veterans are exhibiting higher levels of current (past month) psychological ill-health, as measured using the GHQ-12 and PCL-S, as well as lower mental health status, as measured by the SF-12, than the comparison group. Although not a replacement for formal psychiatric diagnosis, instruments such as those above may aid in the assessment of veterans' psychological health.D. P. McKenzie, J. F. Ikin, A. C. McFarlane, M. Creamer, A. B. Forbes, H. L. Kelsall, D. C. Glass, P. Ittak and M. R. Si

The COBE Diffuse Infrared Background Experiment Search for the Cosmic Infrared Background: I. Limits and Detections

The DIRBE on the COBE spacecraft was designed primarily to conduct systematic search for an isotropic CIB in ten photometric bands from 1.25 to 240 microns. The results of that search are presented here. Conservative limits on the CIB are obtained from the minimum observed brightness in all-sky maps at each wavelength, with the faintest limits in the DIRBE spectral range being at 3.5 microns (\nu I_\nu < 64 nW/m^2/sr, 95% CL) and at 240 microns (\nu I_\nu < 28 nW/m^2/sr, 95% CL). The bright foregrounds from interplanetary dust scattering and emission, stars, and interstellar dust emission are the principal impediments to the DIRBE measurements of the CIB. These foregrounds have been modeled and removed from the sky maps. Assessment of the random and systematic uncertainties in the residuals and tests for isotropy show that only the 140 and 240 microns data provide candidate detections of the CIB. The residuals and their uncertainties provide CIB upper limits more restrictive than the dark sky limits at wavelengths from 1.25 to 100 microns. No plausible solar system or Galactic source of the observed 140 and 240 microns residuals can be identified, leading to the conclusion that the CIB has been detected at levels of \nu I_\nu = 25+-7 and 14+-3 nW/m^2/sr at 140 and 240 microns respectively. The integrated energy from 140 to 240 microns, 10.3 nW/m^2/sr, is about twice the integrated optical light from the galaxies in the Hubble Deep Field, suggesting that star formation might have been heavily enshrouded by dust at high redshift. The detections and upper limits reported here provide new constraints on models of the history of energy-releasing processes and dust production since the decoupling of the cosmic microwave background from matter.Comment: 26 pages and 5 figures, accepted for publication in the Astrophyical Journa

Impact of infectious diseases consultation on the management of Staphylococcus aureus bacteraemia in children.

OBJECTIVES: Infectious diseases consultation (IDC) in adults with Staphylococcus aureus bacteraemia (SAB) has been shown to improve management and outcome. The aim of this study was to evaluate the impact of IDC on the management of SAB in children. STUDY DESIGN: Observational cohort study of children with SAB. SETTING: Cambridge University Hospitals National Health Service (NHS) Foundation Trust, a large acute NHS Trust in the UK. PARTICIPANTS: All children with SAB admitted to the Cambridge University Hospitals NHS Foundation Trust between 16 July 2006 and 31 December 2012. METHODS: Children with SAB between 2006 and 31 October 2009 were managed by routine clinical care (pre-IDC group) and data were collected retrospectively by case notes review. An IDC service for SAB was introduced in November 2009. All children with SAB were reviewed regularly and data were collected prospectively (IDC group) until 31 December 2012. Baseline characteristics, quality metrics and outcome were compared between the pre-IDC group and IDC group. RESULTS: There were 66 episodes of SAB in 63 children-28 patients (30 episodes) in the pre-IDC group, and 35 patients (36 episodes) in the IDC group. The median age was 3.4 years (IQR 0.2-10.7 years). Patients in the IDC group were more likely to have echocardiography performed, a removable focus of infection identified and to receive a longer course of intravenous antimicrobial therapy. There were no differences in total duration of antibiotic therapy, duration of hospital admission or outcome at 30 or 90 days following onset of SAB. CONCLUSIONS: IDC resulted in improvements in the investigation and management of SAB in children.This work was supported by grants from the UK Clinical Research Collaboration (UKCRC) Translational Infection Research Initiative (TIRI); the Medical Research Council (G1000803), with contributions from the Biotechnology and Biological Sciences Research Council, the National Institute for Health Research (NIHR) on behalf of the UK Department of Health, and the Chief Scientist of the Scottish Government Health Directorate; the Public Health England; and the NIHR Cambridge Biomedical Research Centre

The COBE Diffuse Infrared Background Experiment Search for the Cosmic Infrared Background: IV. Cosmological Implications

In this paper we examine the cosmological constraints of the recent DIRBE and FIRAS detection of the extragalactic background light between 125-5000 microns on the metal and star formation histories of the universe.Comment: 38 pages and 9 figures. Accepted for publications in The Astrophysical Journa

Roles of the TRAF6 and Pellino E3 ligases in MyD88 and RANKL signaling

It is widely accepted that the essential role of TRAF6 in vivo is to generate the Lys63-linked ubiquitin (K63-Ub) chains needed to activate the "master" protein kinase TAK1. Here, we report that TRAF6 E3 ligase activity contributes to but is not essential for the IL-1-dependent formation of K63-Ub chains, TAK1 activation, or IL-8 production in human cells, because Pellino1 and Pellino2 generate the K63-Ub chains required for signaling in cells expressing E3 ligase-inactive TRAF6 mutants. The IL-1-induced formation of K63-Ub chains and ubiquitylation of IRAK1, IRAK4, and MyD88 was abolished in TRAF6/Pellino1/Pellino2 triple-knockout (KO) cells, but not in TRAF6 KO or Pellino1/2 double-KO cells. The reexpression of E3 ligase-inactive TRAF6 mutants partially restored IL-1 signaling in TRAF6 KO cells, but not in TRAF6/Pellino1/Pellino2 triple-KO cells. Pellino1-generated K63-Ub chains activated the TAK1 complex in vitro with similar efficiently to TRAF6-generated K63-Ub chains. The early phase of TLR signaling and the TLR-dependent secretion of IL-10 (controlled by IRAKs 1 and 2) was only reduced modestly in primary macrophages from knockin mice expressing the E3 ligase-inactive TRAF6[L74H] mutant, but the late-phase production of IL-6, IL-12, and TNFα (controlled only by the pseudokinase IRAK2) was abolished. RANKL-induced signaling in macrophages and the differentiation of bone marrow to osteoclasts was similar in TRAF6[L74H] and wild-type cells, explaining why the bone structure and teeth of the TRAF6[L74H] mice was normal, unlike TRAF6 KO mice. We identify two essential roles of TRAF6 that are independent of its E3 ligase activity

Si/SiGe quantum cascade superlattice designs for terahertz emission

Quantum cascade lasers are compact sources that have demonstrated high output powers at THz frequencies. To date all THz quantum cascade lasers have been realized in III-V materials. Results are presented from Si1−xGex quantum cascade superlattice designs emitting at around 3 THz which have been grown in two different chemical vapor deposition systems. The key to achieving successful electroluminescence at THz frequencies in a p-type system has been to strain the light-hole states to energies well above the radiative subband states. To accurately model the emission wavelengths, a 6-band k.p tool which includes the effects of non-abrupt heterointerfaces has been used to predict the characteristics of the emitters. X-ray diffraction and transmission electron microscopy have been used along with Fourier transform infrared spectroscopy to fully characterise the samples. A number of methods to improve the gain from the designs are suggested