High single-mode power conversion efficiency vertical-cavity top-surface-emitting lasers

Includes bibliographical references.We report advances in the power conversion (wall-plug) efficiency of vertical-cavity top-surface-emitting lasers. The devices were fabricated from molecular beam epitaxial layers using deep proton implants to define gain-guided lasers. The epitaxial structure included low resistance, piecewise linearly graded n-type and p-type mirrors, a triple In0.2Ga0.8As quantum-well active region, and a delta-doped contact layer. Power conversion efficiencies as high as 12.7% for continuous-wave single-mode operation were measured after several hours of device operation.This work was supported by the U.S. Department of Energy under Contract DE-AC04-76DP00789

High-frequency modulation of oxide-confined vertical cavity surface emitting lasers

Includes bibliographical references (page 458).High-speed studies of packaged, submilliampere threshold, oxide-confined vertical cavity surface emitting lasers show modulation bandwidths > 16GHz. Very high modulation current efficiency factors occur at low bias but decrease as the modulation bandwidth and frequency of the relative intensity noise peak saturate at higher currents

Environmental Profile of a Community’s Health (EPOCH): An Ecometric Assessment of Measures of the Community Environment Based on Individual Perception

Background Public health research has turned towards examining upstream, community-level determinants of cardiovascular disease risk factors. Objective measures of the environment, such as those derived from direct observation, and perception-based measures by residents have both been associated with health behaviours. However, current methods are generally limited to objective measures, often derived from administrative data, and few instruments have been evaluated for use in rural areas or in low-income countries. We evaluate the reliability of a quantitative tool designed to capture perceptions of community tobacco, nutrition, and social environments obtained from interviews with residents in communities in 5 countries. Methodology/ Principal Findings Thirteen measures of the community environment were developed from responses to questionnaire items from 2,360 individuals residing in 84 urban and rural communities in 5 countries (China, India, Brazil, Colombia, and Canada) in the Environmental Profile of a Community’s Health (EPOCH) study. Reliability and other properties of the community-level measures were assessed using multilevel models. High reliability (>0.80) was demonstrated for all community-level measures at the mean number of survey respondents per community (n = 28 respondents). Questionnaire items included in each scale were found to represent a common latent factor at the community level in multilevel factor analysis models. Conclusions/ Significance Reliable measures which represent aspects of communities potentially related to cardiovascular disease (CVD)/risk factors can be obtained using feasible sample sizes. The EPOCH instrument is suitable for use in different settings to explore upstream determinants of CVD/risk factors

Adsorption and reaction of CO on (Pd–)Al2O3 and (Pd–)ZrO2: vibrational spectroscopy of carbonate formation

γ-Alumina is widely used as an oxide support in catalysis, and palladium nanoparticles supported by alumina represent one of the most frequently used dispersed metals. The surface sites of the catalysts are often probed via FTIR spectroscopy upon CO adsorption, which may result in the formation of surface carbonate species. We have examined this process in detail utilizing FTIR to monitor carbonate formation on γ-alumina and zirconia upon exposure to isotopically labelled and unlabelled CO and CO2. The same was carried out for well-defined Pd nanoparticles supported on Al2O3 or ZrO2. A water gas shift reaction of CO with surface hydroxyls was detected, which requires surface defect sites and adjacent OH groups. Furthermore, we have studied the effect of Cl synthesis residues, leading to strongly reduced carbonate formation and changes in the OH region (isolated OH groups were partly replaced or were even absent). To corroborate this finding, samples were deliberately poisoned with Cl to an extent comparable to that of synthesis residues, as confirmed by Auger electron spectroscopy. For catalysts prepared from Cl-containing precursors a new CO band at 2164 cm−1 was observed in the carbonyl region, which was ascribed to Pd interacting with Cl. Finally, the FTIR measurements were complemented by quantification of the amount of carbonates formed via chemisorption, which provides a tool to determine the concentration of reactive defect sites on the alumina surface

An argument for the use of Aristotelian method in bioethics

The main claim of this paper is that the method outlined and used in Aristotle's Ethics is an appropriate and credible one to use in bioethics. Here “appropriate” means that the method is capable of establishing claims and developing concepts in bioethics and “credible” that the method has some plausibility, it is not open to obvious and immediate objection. It begins by suggesting why this claim matters and then gives a brief outline of Aristotle's method. The main argument is made in three stages. First, it is argued that Aristotelian method is credible because it compares favourably with alternatives. In this section it is shown that Aristotelian method is not vulnerable to criticisms that are made both of methods that give a primary place to moral theory (such as utilitarianism) and those that eschew moral theory (such as casuistry and social science approaches). As such, it compares favourably with these other approaches that are vulnerable to at least some of these criticisms. Second, the appropriateness of Aristotelian method is indicated through outlining how it would deal with a particular case. Finally, it is argued that the success of Aristotle's philosophy is suggestive of both the credibility and appropriateness of his method.</p

Copper reduces the virulence of bacterial communities at environmentally relevant concentrations

This is the final version. Available on open access from Elsevier via the DOI in this recordData availability: All data and R code used in the analysis is available on GitHub (https://github.com/LukeLear/Lear_et_al_2023_Environment_International.git).Increasing environmental concentrations of metals as a result of anthropogenic pollution are significantly changing many microbial communities. While there is evidence metal pollution can result in increased antibiotic resistance, the effects of metal pollution on the virulence of bacterial communities remains largely undetermined. Here, we experimentally test whether metal stress alters the virulence of bacterial communities. We do this by incubating three wastewater influent communities under different environmentally relevant copper concentrations for three days. We then quantify the virulence of the community phenotypically using the Galleria mellonella infection model, and test if differences are due to changes in the rate of biomass accumulation (productivity), copper resistance, or community composition (quantified using 16S amplicon sequencing). The virulence of the communities was found to be reduced by the highest copper concentration, but not to be affected by the lower concentration. As well as reduced virulence, communities exposed to the highest copper concentration were less diverse and had lower productivity. This work highlights that metal pollution may decrease virulence in bacterial communities, but at a cost to diversity and productivity.Natural Environment Research Council (NERC)UKR

Reconfigurable binary optical routing switches with fan-out based on the integration of GaAs/AlGaAs surface-emitting lasers and heterojunction phototransistors

Includes bibliographical references.The design, fabrication, and experimental demonstration of dynamically reconfigurable binary optical switches based on the integration of GaAs/AlGaAs vertical-cavity surface-emitting lasers and heterojunction phototransistors are reported. These new monolithic optical switches can perform spatial routing and optical amplification functions on input optical data with a fan-out of two, and can be programmed using simple voltage control. The 1 × 2 and 2 × 2 devices provide the basis for a high performance, two-dimensional optical switching fabric with electrical interfaces for optical switching and interconnection networks.The work at UNM was supported by Rome Laboratories (Griffiss AFB), the Advanced Research Projects Agency-MTO, and the Air Force Office of Scientific Research (Bolling AFB). The work performed at Sandia was supported by DOE Contract No. DE-AC04-76DP00789

HT2008-56147 PARAMETRIC CONTROL OF A TWO-PHASE THERMAL MANAGEMENT SYSTEM FOR SPACE APPLICATIONS

ABSTRACT As spacecraft increase in complexity, greater power is required to drive their onboard systems. The resulting generation of waste heat demands efficient thermal control, especially for electrical components emitting heat at high flux densities. Weislogel proposed a passive two-phase heat transport system for space application, driven by constant volume boilers, called the pulse thermal loop (PTL). This paper describes four methods of operating a PTL using real-time pressure data as the control parameter. Preliminary results are presented from an experimental loop using R-134a as the working fluid. Control is exercised through algorithm-based schemes implemented in LabVIEW. Results suggest that stable operation of the loop is best achieved by actuating flow control valves in response to a preset pressure difference between the boilers. Control schemes based on absolute pressure, set pulse frequency, and a combination of absolute and differential pressures are also described. Performance data are presented, and some of the challenges faced during PTL operation are discussed, including start-up and asymmetrical pressurization of the boilers

Binary optical switch and programmable optical logic gate based on the integration of GaAs/AlGaAs surface-emitting lasers and heterojunction phototransistors

Includes bibliographical references.Optical switches based on GaAs/AlGaAs vertical-cavity surface-emitting lasers and heterojunction phototransistors are combined monolithically into new switching configurations that perform optical logic and spatial routing in a dynamically programmable manner. Using simple voltage control, many different logic and routing configurations, including AND and OR gates with variable fan-out, can be implemented using the same hardware.The work at UNM was supported by AFOSR (Bolling AFB), ARPA, and Rome Labs (Griffiss AFB). The Sandia effort was supported by DOE Contract No. DE-AC04-94AL85000