RHEED digital image analysis system for in-situ growth rate and alloy composition measurements of GaAs-based nanostructures

Monitoring the intensity of the reflected spot in a RHEED image is the most important method used to control the growth of semiconductors in MBE. The accurate control of both layer thickness and alloy composition is particularly important for the growth of high quality heterostructures. Indeed, under such conditions, extremely uniform and high quality epitaxial devices become possible. RHEED intensity oscillation can be used as accurate, quick and direct measure of the growth rates and alloy compositions as well. Although analog signal could be obtained by using an optical fiber associated to a photo-detector PM tube and a plotter, this method is troublesome and limited. In some application, the availability of the intensity signal as a digital voltage is useful to realize further advanced analysis, and achieve feedback between growth dynamic and the external parameters, such as the cells temperatures and the synchronization of the shutters. In this paper we describe the advantages gained with the upgrade of our analog system into a digital package using CCD camera, frame grabber and a home made software. Its main purpose is to track RHEED intensity changes and measures the rate of oscillation. A state-of-the-art RHEED digital image analysis system gives us the necessary tools to gain insight into the thin film growth process and optimize material quality

Environmental sensing and response genes in cnidaria : the chemical defensome in the sea anemone Nematostella vectensis

Author Posting. © The Author(s), 2008. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Cell Biology and Toxicology 24 (2008): 483-502, doi:10.1007/s10565-008-9107-5.The starlet sea anemone Nematostella vectensis has been recently established as a new model system for the study of the evolution of developmental processes, as cnidaria occupy a key evolutionary position at the base of the bilateria. Cnidaria play important roles in estuarine and reef communities, but are exposed to many environmental stressors. Here I describe the genetic components of a ‘chemical defensome’ in the genome of N. vectensis, and review cnidarian molecular toxicology. Gene families that defend against chemical stressors and the transcription factors that regulate these genes have been termed a ‘chemical defensome,’ and include the cytochromes P450 and other oxidases, various conjugating enyzymes, the ATP-dependent efflux transporters, oxidative detoxification proteins, as well as various transcription factors. These genes account for about 1% (266/27200) of the predicted genes in the sea anemone genome, similar to the proportion observed in tunicates and humans, but lower than that observed in sea urchins. While there are comparable numbers of stress-response genes, the stress sensor genes appear to be reduced in N. vectensis relative to many model protostomes and deuterostomes. Cnidarian toxicology is understudied, especially given the important ecological roles of many cnidarian species. New genomic resources should stimulate the study of chemical stress sensing and response mechanisms in cnidaria, and allow us to further illuminate the evolution of chemical defense gene networks.WHOI Ocean Life Institute and NIH R01-ES01591

Effects of hospital facilities on patient outcomes after cancer surgery: an international, prospective, observational study

Background Early death after cancer surgery is higher in low-income and middle-income countries (LMICs) compared with in high-income countries, yet the impact of facility characteristics on early postoperative outcomes is unknown. The aim of this study was to examine the association between hospital infrastructure, resource availability, and processes on early outcomes after cancer surgery worldwide.Methods A multimethods analysis was performed as part of the GlobalSurg 3 study-a multicentre, international, prospective cohort study of patients who had surgery for breast, colorectal, or gastric cancer. The primary outcomes were 30-day mortality and 30-day major complication rates. Potentially beneficial hospital facilities were identified by variable selection to select those associated with 30-day mortality. Adjusted outcomes were determined using generalised estimating equations to account for patient characteristics and country-income group, with population stratification by hospital.Findings Between April 1, 2018, and April 23, 2019, facility-level data were collected for 9685 patients across 238 hospitals in 66 countries (91 hospitals in 20 high-income countries; 57 hospitals in 19 upper-middle-income countries; and 90 hospitals in 27 low-income to lower-middle-income countries). The availability of five hospital facilities was inversely associated with mortality: ultrasound, CT scanner, critical care unit, opioid analgesia, and oncologist. After adjustment for case-mix and country income group, hospitals with three or fewer of these facilities (62 hospitals, 1294 patients) had higher mortality compared with those with four or five (adjusted odds ratio [OR] 3.85 [95% CI 2.58-5.75]; p<0.0001), with excess mortality predominantly explained by a limited capacity to rescue following the development of major complications (63.0% vs 82.7%; OR 0.35 [0.23-0.53]; p<0.0001). Across LMICs, improvements in hospital facilities would prevent one to three deaths for every 100 patients undergoing surgery for cancer.Interpretation Hospitals with higher levels of infrastructure and resources have better outcomes after cancer surgery, independent of country income. Without urgent strengthening of hospital infrastructure and resources, the reductions in cancer-associated mortality associated with improved access will not be realised

A novel Al₀.₃₃Ga₀.₆₇As/In₀.₁₅Ga₀.₈₅As/GaAs quantum well Hall device grown on (111) GaAs

In this study, we look at the advantages of (111) GaAs substrate over (001) one, when used to grow Hall devices by MBE. In top of that, we explore the consequence of a modified design of modulation doping pseudomorphic AlGaAs/InGaAs/GaAs, and we suggest a new quantum well structure for a Hall device grown on (111) GaAs substrate, with the objective of improving its performances. From self-consistent calculations, we find that the electron concentration ns in the interface region is enhanced. This implies that one can have a wider spacer layer and still have the same ns with the result that the mobility is improved. This result should be valuable for many types of devices. We specifically consider Hall sensors, where it is desirable to have a low electron concentration and high mobility

Thermal transfer and interaction mechanisms of localized excitons in families of InAs quantum dashes grown on InP(001) vicinal substrate emitting near 1.55 µm wavelength

International audienceno abstrac

Spacer layer thickness effects on the photoluminescence properties of InAs/GaAs quantum dot superlattices

International audienc

Optimizing the spacer layer thickness of vertically stacked InAs/GaAs quantum dots

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