Laser-assisted local metal-organic vapor phase epitaxy.

Selective area epitaxial growth is an important technique, both for monolithic device integration as well as for defect reduction in heteroepitaxy of crystalline materials on foreign substrates. While surface engineering with masking materials or by surface structuring is an effective means for controlling the location of material growth, as well as for improving crystalline properties of epitaxial layers, the commonly involved integral substrate heating presents a limitation, e.g., due to constraints ofr the thermal budget applicable to existing device structures. As a solution, an epitaxial growth approach using a laser source only locally heating the selected growth area, in combination with metal-organic precursors to feed a pyrolithic chemical reaction (also known as metal-organic vapor phase epitaxy, MOVPE), is presented. Without masking or surface structuring, local epitaxial growth of III-V compound semiconductor layers on a 50-1500 µm length-scale, with high structural and optical quality, is demonstrated. We discuss general design rules for reactor chamber, laser heating, temperature measurement, sample manipulation, gas mixing, and distinguish laser-assisted local MOVPE from conventional planar growth for the important compound semiconductor GaAs. Surface de-oxidation prior to growth is mandatory to realize smooth island surfaces. Linear growth rates in the range 0.5-9 µm/h are demonstrated. With increasing island diameter, the probability for plastic deformation within the island increases, depending on reactor pressure. A step-flow mode on the island surface can be achieved by establishing a sufficiently small temperature gradient across the island.

Direct Imaging of the Carrier Capture into Individual InP Quantum Dots of a Semiconductor Disk Laser Membrane.

We report on nanoscopic exploration of the luminescence from individual InP quantum dots (QDs) by means of highly spatially resolved cathodoluminescence (CL) spectroscopy directly performed in a scanning transmission electron microscope (STEM). A 7-fold layer stack with high-density InP quantum dots is embedded as an active medium membrane in an external-cavity surface-emitting laser. We characterize the vertical transfer of carriers within the periodic separate confinement heterostructure and determine the capture efficiency of carriers from the cladding layer into the quantum dot layers. Benefiting from the nanoscale resolution of our STEM-CL, we perform single-dot spectroscopy on single isolated QDs in the STEM lamella resolving the details of the excitonic structure of individual quantum dots. Executing highly spatially resolved spectrum line scans within the QD layers, we directly visualize the lateral transport, i.e., the efficient lateral capture of carriers into an individual QD. We observe a characteristic change of the spectral fingerprint during this line scan, while the electron beam is approaching and subsequently receding from the quantum dot position. This directly correlates to the increase and decrease of the numbers of excess carriers reaching the dot, i.e., altering the quantum dot population. The characteristic shift of emission energies visualize the renormalization of the ground-state energy of the single dot, and the intensity ratio of the excitonic recombinations verifies this change of the occupation and the state-filling.

General Self-Efficacy and Body Weight: The Role of Race and Gender.

Overweight and obesity have become a prominent concern for policymakers, the Surgeon General, scholars, and for work organizations. The estimated annual cost of obesity in terms of lost productivity is in the tens of billions of dollars, and the estimated annual medical cost of obesity is in the hundreds of millions of dollars. Psychologists have become increasingly interested in issues related to body weight, such as ways to help people reduce body weight. The aims of our study are twofold. First, based on social cognitive theory, we offer the first study of the relationship between general self-efficacy (GSE) and body weight based on a large, representative sample. Second, we also offer an understanding of the role of race and gender as potential boundary conditions of this relationship. Findings indicate that race moderates the relationship between GSE and body weight (both BMI and perceived weight) such that this relationship is positive for Blacks but negative for Whites. Gender did not moderate the relationship between GSE and body weight. These results suggest that body weight is unrelated to general self-efficacy in the population writ large and that body weight is differentially related to self-efficacy based on race but not gender.

Predictors of Attrition Among Accelerated and Traditional Physician Assistant Students.

PURPOSE: Students can be admitted to a physician assistant program via an accelerated bachelor of science/master of science (BS/MS) track or by a postbaccalaureate track. The purpose of this study was to identify predictors of student attrition based on differences in modes of admission. METHODS: Student admissions and retention data were collected for 277 students in the physician assistant program at the New York Institute of Technology from the graduation years 2016 to 2020. A t-test was used to analyze differences among admissions methods for the following variables: age, cumulative grade point average (GPA), science GPA, and patient contact hours. RESULTS: A total of 10.4% (n = 29) of students from the total enrollment left the program for academic reasons. These students had a significantly lower cumulative GPA (3.54 vs. 3.71) and science GPA (3.45 vs. 3.68), and fewer patient contact hours (951 vs. 1720) at admission (p < .05). Furthermore, 44 students entered via the BS/MS track, and 41% (n = 18) were dismissed for academic reasons. This group of 18 BS/MS students comprised 62% of all students dismissed for academic reasons over the past 5 years. When considering only BS/MS students, those who left for academic reasons had a significantly lower science GPA (3.37 vs. 3.62, p < .05) than those who successfully completed the program. CONCLUSIONS: Having dual tracks of entry resulted in varying degrees of academic preparation and, for our institution, a disproportionate number of students from the accelerated track being dismissed despite meeting published admissions criteria.

Managing the health of the eSport athlete: an integrated health management model.

OBJECTIVES: eSport is a form of electronic gaming, also known as professional or competitive video gaming, and is growing at a rapid pace worldwide. Over 50 US colleges have established varsity gaming teams over the past three years; some colleges offer eSport scholarships as they do for traditional sports. There is little objective research on the health habits of these players who are often placed under the direction of the athletics department on college campuses, and there is currently no health management model on how to treat these new athletes. METHODS: Anonymous electronic surveys were sent to 65 collegiate eSport players from nine universities across the USA and Canada inquiring about gaming and lifestyle habits, and musculoskeletal complaints due to eSport competition. RESULTS: Players practiced between 3 and 10 hours per day. The most frequently reported complaint was eye fatigue (56%), followed by neck and back pain (42%). eSport athletes reported wrist pain (36%) and hand pain (32%). Forty per cent of participants do not participate in any form of physical exercise. Among the players surveyed, only 2% had sought medical attention. CONCLUSION: eSport players, just like athletes in traditional sports, are susceptible to overuse injuries. The most common complaint was eye fatigue, followed by neck and back pain. This study shows eSport athletes are also prone to wrist and hand pain. This paper proposes a health management model that offers a comprehensive medical team approach to prevent and treat eSport athletes.

Direct imaging of Indium-rich triangular nanoprisms self-organized formed at the edges of InGaN/GaN core-shell nanorods.

Higher indium incorporation in self-organized triangular nanoprisms at the edges of InGaN/GaN core-shell nanorods is directly evidenced by spectral cathodoluminescence microscopy in a scanning transmission electron microscope. The nanoprisms are terminated by three 46 nm wide a-plane nanofacets with sharp interfaces forming a well-defined equilateral triangular base in the basal plane. Redshifted InGaN luminescence and brighter Z-contrast are resolved for these structures compared to the InGaN layers on the nanorod sidewalls, which is attributed to at least 4 % higher indium content. Detailed analysis of the inner optical and structural properties reveals luminescence contributions from 417 nm up to 500 nm peak wavelength proving the increasing indium concentration inside the nanoprism towards the nanorod surface.

Validation of the RT3 accelerometer for measuring physical activity of children in simulated free-living conditions.

This is a validation study of the RT3 accelerometer for measuring physical activities of children in simulated free-living conditions. Twenty-five children age 12-14 years completed indoor testing, and 18 of them completed outdoor testing. Activity counts from the RT3 accelerometer estimated activity energy expenditure (AEE) and the Cosmed K4b2 analyzer measured oxygen uptake. Correlations were found between activity counts and metabolic cost (r = .95, p < .001), metabolic cost and RT3 estimated AEE (r = .96, p < .001) in the indoor test, activity counts and RT3 estimated AEE (r = .97, p < .001) in the outdoor test, and activity counts and metabolic cost when all activities were combined (r = .77, p < .001). Results indicate that the RT3 accelerometer might be used to provide acceptable estimates of free-living physical activity in children.