Possibilities for LWIR detectors using MBE-grown Si(/Si(1-x)Ge(x) structures

Traditionally, long wavelength infrared (LWIR) detection in Si-based structures has involved either extrinsic Si or Si/metal Schottky barrier devices. Molecular beam epitaxially (MBE) grown Si and Si/Si(1-x)Ge(x) heterostructures offer new possibilities for LWIR detection, including sensors based on intersubband transitions as well as improved conventional devices. The improvement in doping profile control of MBE in comparison with conventional chemical vapor deposited (CVD) Si films has resulted in the successful growth of extrinsic Si:Ga, blocked impurity-band conduction detectors. These structures exhibit a highly abrupt step change in dopant profile between detecting and blocking layers which is extremely difficult or impossible to achieve through conventional epitaxial growth techniques. Through alloying Si with Ge, Schottky barrier infrared detectors are possible, with barrier height values between those involving pure Si or Ge semiconducting materials alone. For both n-type and p-type structures, strain effects can split the band edges, thereby splitting the Schottky threshold and altering the spectral response. Measurements of photoresponse of n-type Au/Si(1-x)Ge(x) Schottky barriers demonstrate this effect. For intersubband multiquntum well (MQW) LWIR detection, Si(1-x)Ge(x)/Si detectors grown on Si substrates promise comparable absorption coefficients to that of the Ga(Al)As system while in addition offering the fundamental advantage of response to normally incident light as well as the practical advantage of Si-compatibility. Researchers grew Si(1-x)Ge(x)/Si MQW structures aimed at sensitivity to IR in the 8 to 12 micron region and longer, guided by recent theoretical work. Preliminary measurements of n- and p-type Si(1-x)Ge(x)/Si MQW structures are given

Understanding Perceptions of Problematic Facebook Use: When People Experience Negative Life Impact and a Lack of Control

While many people use social network sites to connect with friends and family, some feel that their use is problematic, seriously affecting their sleep, work, or life. Pairing a survey of 20,000 Facebook users measuring perceptions of problematic use with behavioral and demographic data, we examined Facebook activities associated with problematic use as well as the kinds of people most likely to experience it. People who feel their use is problematic are more likely to be younger, male, and going through a major life event such as a breakup. They spend more time on the platform, particularly at night, and spend proportionally more time looking at profiles and less time browsing their News Feeds. They also message their friends more frequently. While they are more likely to respond to notifications, they are also more likely to deactivate their accounts, perhaps in an effort to better manage their time. Further, they are more likely to have seen content about social media or phone addiction. Notably, people reporting problematic use rate the site as more valuable to them, highlighting the complex relationship between technology use and well-being. A better understanding of problematic Facebook use can inform the design of context-appropriate and supportive tools to help people become more in control.Comment: CHI 201

Protein Engineering of a Spectroscopic Probe into Malate Dehydrogenase (MDH)

Malate dehydrogenase (MDH) is an enzyme that has a key role in biological processes, like the Krebs cycle. Specifically, it reversibly catalyzes the interconversion of (S)-malate with NAD+ to oxaloacetate and NADH. Once oxaloacetate is synthesized, MDH dispatches it to citrate synthase, but it is not clear how this happens. One theory is that MDH channels it to citrate synthase by forming a metabolon, a mechanism for direct channeling, preventing diffusion of reaction intermediates into a bulk matrix. There is a lack of research in this area due to the absence of a spectroscopic probe necessary to visualize MDH’s conformational changes. Therefore, a method was tested to incorporate a fluorescent landmark into MDH’s structure and thus be used in future research to reveal the interactions between MDH and citrate synthase. Specific amino acids of MDH were mutated to tryptophan, an amino acid known to fluoresce (V189, I319, A120, I136, P119, G218). The coding sequence for the wildtype MDH and mutant MDHs were incorporated into plasmids and bacterially transformed into Escherichia coli. Both wildtype and mutant proteins were over-expressed, then purified by nickel affinity chromatography using a hexahistidine tag on the N-terminus of MDH. Data will demonstrate that I139W, V189W, and A120W had significantly lower activity than wildtype MDH, and the same is predicted for I136W. I139W and V189W emitted fluorescence at 290 nm, but I136W did not. The mutations P119W and G218W could not be overexpressed or purified. Next steps in design of a fluorescent, active MDH will be discussed

Nasal Congestion on the International Space Station

No abstract availabl

Structured Engagement for a Multi-Institutional Collaborative to Tackle Challenges and Share Best Practices

A National Consortium for Synergistic Undergraduate Mathematics via Multi-institutional Interdisciplinary Teaching Partnerships (SUMMIT-P), funded by the National Science Foundation, is a multi-institutional consortium with members from twelve institutions. The consortium adapted two protocols developed by the School Reform Initiative to: 1. provide advice on challenges or dilemmas a consortium member is facing and 2. share project successes with consortium members. The two protocols—a Modified Descriptive Consultancy protocol and a Modified Success Analysis with Reflective Questions protocol—provide a structured format for these discussions. This paper provides an in-depth description of the two protocols and how they have been used for this project. Examples demonstrating the impact of the protocols are provided by the co-authors

DECOUPLED PAYMENTS IN A CHANGING POLICY SETTING

The studies in this report analyze the effects of decoupled payments in the Federal Agriculture Improvement and Reform (FAIR) Act on recipient households, and assess land, labor, risk management, and capital market conditions that can lead to links between decoupled payments and production choices. Each study contributes a different perspective to understanding the response of U.S. farm households and production to decoupled income transfers. Some use new microdata on farm households collected through USDA's Agricultural Resource Management Survey (ARMS), initiated in 1996, and its predecessor survey. These data are used to compare household and producer behavior and outcomes before and after the FAIR Act. Other studies use applied or conceptual models to characterize the impact of introducing decoupled payments. Collectively, the chapters represent an early stage in the empirical analysis of decoupled payments. The studies address many aspects of the payments' household impacts but remaining issues call for additional analysis. As the analytical paradigm changes with the evolution of farm programs, the development of appropriate data and models will improve our understanding of farm program impacts on the behavior and well-being of U.S. farm households, and the agricultural sector.Agricultural and Food Policy,

Positive affect and its association with viral control among women with HIV infection.

We assessed the relationship between positive affect and viral suppression among women with HIV infection

Redesigning Primary Care Processes to Improve the Offering of Mammography. The use of Clinic Protocols by Nonphysicians.

OBJECTIVE: To develop, within the framework of continuous quality improvement, new processes for offering mammography and determine whether protocols executed completely by nonphysicians would increase mammography utilization. DESIGN: A prospective follow-up study with patients from an intervention clinic and two control clinics. SETTING: Three general internal medicine clinics in a large, urban teaching hospital in Detroit, Michigan. PATIENTS/PARTICIPANTS: A total of 5,934 women, aged 40 through 75 years, making 16,546 visits to one of the clinics during the study period (September 1, 1992, through November 31, 1993). INTERVENTION: Medical assistants and licensed practical nurses in the intervention clinic were trained to identify women due for screening mammography, and to directly offer and order a mammogram if patients agreed. MEASUREMENTS AND MAIN RESULTS: Patients were considered up-to-date with screening if they had a mammogram within 1 year (if age 50-75) or 2 years (if age 40-49) prior to the visit or a mammogram within 60 days after the visit. The proportion of visits each month in which a woman was up-to-date with mammography was calculated using computerized billing records. Prior to the intervention, the proportion of visits in which women were up-to-date was 68% (95% confidence interval [CI] 63%, 73%) in the intervention clinic and 66% (95% CI 61%, 71%) in each of the control clinics. At the end of the evaluation, there was an absolute increase of 9% (95% CI 2%, 16%) in the intervention clinic, and a difference of 1% (95% CI -5%, 7%) in one of the control clinics and -2% (95% CI -3%, 5%) in the other. In the intervention clinic, the proportion of visits in which women were up-to-date with mammography increased over time and was consistent with a linear trend (p = .004). CONCLUSIONS: Redesigning clinic processes to make offering of mammography by medical assistants and licensed practical nurses a routine part of the clinic encounter can lead to mammography rates that are superior to those seen in physicians\u27 usual practice, even when screening levels are already fairly high. Physicians need not be considered the sole, or even the primary, member of the health care team who can effectively deliver some preventive health measures