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Academic medical centers (AMCs) face challenges in conducting research among traditionally marginalized communities due to long-standing community mistrust. Evidence suggests that some AMC faculty and staff lack an understanding of the history of distrust and social determinants of health (SDH) affecting their communities. Wake Forest Clinical and Translational Science Institute Program in Community Engagement (PCE) aims to build bridges between communities and Wake Forest Baptist Health by equipping faculty, clinicians, administrators, and staff (FCAS) with a better understanding of SDH. The PCE collaborated with community partners to develop and implement community tours to improve cross-community AMC understanding and communication, enhance knowledge of SDH, and build awareness of community needs, priorities, and assets. Nine day-long tours have been conducted with 92 FCAS. Tours included routes through under-resourced neighborhoods and visits to community assets. Participant evaluations assessed program quality; 89% reported enhanced understanding of access-to-care barriers and how SDH affect health; 86% acknowledged the experience would improve future interactions with participants and patients; and 96% agreed they would recommend the tour to colleagues. This work supports the use of community tours as a strategy to improve cross-community AMC communication, build trust, and raise awareness of community needs, priorities, and assets.
Giant electromagnetic pulses (EMP) generated during the interaction of high-power lasers with solid targets can seriously degrade electrical measurements and equipment. EMP emission is caused by the acceleration of hot electrons inside the target, which produce radiation across a wide band from DC to terahertz frequencies. Improved understanding and control of EMP is vital as we enter a new era of high repetition rate, high intensity lasers (e.g. the Extreme Light Infrastructure). We present recent data from the VULCAN laser facility that demonstrates how EMP can be readily and effectively reduced. Characterization of the EMP was achieved using B-dot and D-dot probes that took measurements for a range of different target and laser parameters. We demonstrate that target stalk geometry, material composition, geodesic path length and foil surface area can all play a significant role in the reduction of EMP. A combination of electromagnetic wave and 3D particle-in-cell simulations is used to inform our conclusions about the effects of stalk geometry on EMP, providing an opportunity for comparison with existing charge separation models.
Placodontia were a group of marine reptiles that lived in shallow nearshore environments during the Triassic. Based on tooth morphology it has been inferred that they were durophagous, but tooth morphology differs among species: placodontoid placodonts have teeth described as hemispherical, and the teeth of more highly nested taxa within the cyamodontoid placodonts have been described as flat. In contrast, the sister taxon to the placodonts, Palatodonta bleekeri, like many other marine reptiles, has tall pointed teeth for eating soft-bodied prey. The goals of this paper are to quantify these different tooth morphologies and compare tooth shape among taxa and with a functionally “optimal” tooth. To quantify tooth morphology we measured the radius of curvature (RoC) of the occlusal surface by fitting spheres to 3D surface scans or computed microtomographic scans. Large RoCs correspond to flatter teeth, while teeth with smaller RoCs are pointier; positive RoCs have convex occlusal surfaces, and a negative RoC indicates that the occlusal surface of the tooth is concave. We found the placodontoid taxa have teeth with smaller RoCs than more highly nested taxa, and palatine teeth tend to be flatter and closer to the optimal morphology than maxillary teeth. Within one well-nested clade, the placochelyids, the rearmost palatine teeth have a more complex morphology than the predicted optimal tooth, with an overall concave occlusal surface with a small, medial cusp. These findings are in keeping with the hypothesis that placodonts were specialized durophagous predators with teeth modified to break hard prey items while resisting tooth failure.
The current study examined the influence of phonological structure and language experience on the nonword repetition performance of bilingual children. Twenty-six Spanish-dominant and 26 English-dominant Spanish–English bilingual five-year-old children were matched on current exposure to the dominant language and year of first exposure to English. Participants repeated non-wordlike nonwords in English and Spanish. The Spanish-dominant group performed better than the English-dominant group for both Spanish and English nonwords. In addition, there was a main effect for test language, where Spanish nonwords were produced more accurately than English nonwords overall. The Spanish-dominant group advantage for nonwords is interpreted as emerging from the extra practice the dominant Spanish speakers had producing multisyllabic words.
The purpose of this study was to determine if different language measures resulted in the same classifications of language dominance and proficiency for a group of bilingual pre-kindergarteners and kindergarteners. Data were analyzed for 1029 Spanish–English bilingual pre-kindergarteners who spanned the full range of bilingual language proficiency. Parent questionnaires were used to quantify age of first exposure and current language use. Scores from a short test of semantic and morphosyntactic development in Spanish and English were used to quantify children's performance. Some children who were in the functionally monolingual range based on interview data demonstrated minimal knowledge of their other languages when tested. Current use accounted for more of the variance in language dominance than did age of first exposure. Results indicate that at different levels of language exposure children differed in their performance on semantic and morphosyntax tasks. These patterns suggest that it may be difficult to compare the results of studies that employ different measures of language dominance and proficiency. Current use is likely to be a useful metric of bilingual development that can be used to build a comprehensive picture of child bilingualism.
This paper reports our effort to develop amorphous hydrogenated silicon carbide (a-SiC:H ) films specifically designed for MEMS applications using a semiconductor-grade organosilane known as trimethylsilane (3MS) as the precursor. In our work, the a-SiC:H films were deposited in a commercial PECVD system at a fixed temperature of 350˚C using 3MS diluted in helium (He). Films with thicknesses from ~ 100 nm to ~ 2μm, a typical range for MEMS applications, were deposited. Deposition parameters such RF power, deposition pressure, and 3MS-to-He ratio were explored to obtain films with low residual compressive stresses. Low temperature, post-deposition annealing at 450˚C was used to convert the as-deposited compressive residual stresses to moderate tensile stresses, which are desired for micromachined bridges, membranes and other anchored structures. Compositional analysis indicated that films with a Si-to-C ratio of 1 could be deposited under certain conditions. Mechanical properties such as Young's modulus and fracture strength were derived from the load-deflection behavior of micromachined freestanding membranes. Nanoindentation was used to verify the Young's modulus and determine the hardness. As expected, the films exhibit insulating properties with a relative dielectric constant at 3.90 for as-deposited films and 2.69 after annealing at 1100˚C, as determined from C-V measurements. Chemical inertness was tested in aqueous, corrosive solutions such as KOH and HNA. Prototype structures were fabricated using both surface micromachining and bulk micromachining techniques to demonstrate the potential of the a-SiC:H films for MEMS applications.
The Keck Interferometer Nuller (KIN) is one of the major scientific and technical precursors to the Terrestrial Planet Finder Interferometer (TPF-I) mission. KIN's primary objective is to measure the level of exo-zodiacal mid-infrared emission around nearby main sequence stars, which requires deep broad-band nulling of astronomical sources of a few Janskys at 10 microns. A number of new capabilitites are needed in order to reach that goal with the Keck telescopes: mid-infrared coherent recombination, interferometric operation in “split pupil” mode, N-band optical path stabilization using K-band fringe tracking and internal metrology, and eventually, active atmospheric dispersion correction. We report here on the progress made implementing these new functionalities, and discuss the initial levels of extinction achieved on the sky.
The incorporation of Mn into GaMnN epilayers by MOCVD growth was investigated. Samples with high Mn concentrations lead to room temperature ferromagnetism. In addition an absorption band around 1.5 eV was observed. Intensity and linewidth of this band scaled with the Mn concentration and with the room temperature (RT) saturation magnetization. This band is assigned to the internal Mn3+ transition between the 5E and the partially filled 5T2 levels of the 5D state. The broadening of the absorption band is introduced by the high Mn concentration. Recharging of the Mn3+ to Mn2+ was found to effectively suppress these transitions resulting also in a significant reduction of the RT magnetization. The pronounced sensitivity of the relative position of the Fermi level and 1.5 eV absorption band can be used to predict the magnetization behavior of the Ga1−xMnxN epilayers. The absence of doping-induced strain was observed by Raman spectroscopy. The structural quality, the presence of Mn2+ ions were confirmed by EPR spectroscopy, meanwhile no Mn-Mn interactions were observed.
This paper reports the impact of the Mn incorporation on the structural and magnetic properties of Ga1−xMnxN on the metal-organic vapor phase deposition (MOCVD). Crystalline quality and phase purity were determined by high-resolution X-ray diffraction and indicated that no macroscopic second phases are formed during growth. Atomic force microscopy revealed a 2-dimensional MOCVD step-flow growth pattern in the Mn-incorporated samples. Various annealing steps were applied to some of the samples to reduce compensating defects and to investigate the effects of post processing on the growth. SQUID measurements showed an apparent ferromagnetic hysteresis behavior. However, none of the requirements for room temperature ferromagnetism in the prevailing mean field DMS theories were found. Therefore, different origins of the ferromagnetic signal are discussed.
The phase stability of C-22 alloy (UNS N06022) gas tungsten arc welds was studied by aging samples at 593, 649, 704, and 760°C for times up to 6,000 hours. The tensile properties and the Charpy impact toughness of these samples were measured in the as-welded condition as well as after aging. The corrosion resistance was measured using standard immersion tests in acidic ferric sulfate (ASTM G 28 A) and 2.5% hydrochloric acid solutions at the boiling point. The microstructures of weld samples were examined using scanning electron microscopy (SEM). Precipitate volume fraction measurements were made using optical microscopy.
Degradation of the mechanical and corrosion properties of C-22 welds due to aging at all temperatures investigated was seen to occur sooner than was seen in C-22 base metal. An evaluation of the kinetics of nucleation and growth of the precipitates forming at these temperatures, however, indicated that no significant changes in TCP phase morphology would occur at temperatures below approximately 300°C.a
A significant improvement (40–60%) was reported in the low voltage (100–1000V) cathodoluminescence efficiency of ZnS phosphors coated with SiO2 by the sol-gel technique. The properties of the coatings were found to be critically dependent upon the precursor concentration, pH value and the temperature of the solution with optimum performance being obtained for a SiO2 concentration of 1.0 wt%, pH values between 7–9, and a solution temperature of 83 °C. The efficiency curves exhibited a characteristic voltage dependence which was analyzed by a one-dimensional numerical model. Enhanced low voltage efficiency was attributed to a reduction of surface recombination and the actual shape of the efficiency curve was determined by the interplay between the reduction of surface recombination and energy losses in the SiO2 coating.
Changes in the microstructure, mechanical properties and corrosion resistance of C-22 alloy were studied systematically as a function of aging temperature and aging time. Aging was performed in the temperature range 260°C to 800°C for times between 0.5 h and 40,000 h. For aging temperatures of 600°C and higher, precipitation of tetrahedral close packed (TCP) phases in C-22 alloy induce a decrease in its mechanical properties and corrosion resistance in aggressive acidic solutions. At the lower aging temperatures, long range ordering (LRO) was observed, which did not produce changes in the chemical resistance of the alloy. Arrhenius extrapolations of the high temperature data predict that C-22 alloy will be thermally stable when exposed to temperatures in the order of 300°C for times higher than 10,000 years.
The phase stability of C-22 alloy (UNS #N06022) was studied by aging samples at 593, 649, 704 and 760°C for 2000 h (2.7 mo) and 16,000 h (1.8 yr). The tensile properties and the Charpy impact toughness of these samples were measured in the mill annealed condition as well as after aging. The microstructures of samples aged 16,000 hours were examined using scanning and transmission electron microscopy (SEM and TEM). Preliminary TEM results suggest that μse forms at all temperatures investigated. Discrete carbide particles in addition to a film with very uniform thickness which appears to be μ phase formed on grain boundaries in the sample aged at 593°C. The ordered Ni2(Cr, Mo) phase was also seen in this sample. At the higher aging temperatures, mainly μ phase forms covering all the grain boundaries and also distributed throughout the bulk. Although strength increased somewhat with aging. the ductility decreased due to the formation of these grain boundary precipitates and brittle intermetallics.
Sea urchin embryos have served as a model system for the investigation
of many concepts in developmental biology. Their gastrulation consists of
two stages; primary invagination, where part of the epithelium invaginates
into the blastocoel, and secondary invagination, where the archenteron
elongates to completely traverse the blastocoel. Primary invagination
involves proliferation of cells within the vegetal plate during primary
invagination, but until recently, it was assumed that the larval
gastrointestinal (GI) tract developed without further involution of
epithelial cells. To investigate rigorously the contribution of epithelial
cell involution during archenteron and GI tract development in the sea
urchin, Lytechinus variegatus, we developed a new method for cell
tracking based on two-photon excited photorelease of caged fluorophores.
Single-cell embryos were injected with caged dye and two-photon excitation
uncaging was employed to mark small groups of cells throughout
gastrulation. Two-photon excitation allowed for noninvasive,
three-dimensionally resolved uncaging inside living cells with minimal
biological damage. Cellular involution into the archenteron was observed
throughout primary and secondary invagination, and the larval intestine
was formed by further involution of cells following secondary
invagination, which is inconsistent with the traditional model of sea
urchin gastrulation. Further, as two-photon excitation microscopy becomes
accessible to many researchers, the novel techniques described here will
be broadly applicable to development of other invertebrate and vertebrate
Quantum dot composite films, consisting of II-VI nanocrystals imbedded in a ZnS matrix, are candidate phosphor materials for electroluminescent flat panel displays. The optical properties of such composites can be tailored across the visible spectral region by selecting the composition and size of the nanocrystals. We present combined solution chemistry and electrospray organometallic chemical vapor deposition (ES-OMCVD) methods for realizing such composites. Size selected, CdSe quantum dots with an overlayer of ZnS are synthesized in solution. This surface derivatization produces a large enhancement of the photoluminescence efficiency. The quantum dot composites are subsequently formed by introducing the quantum dot solution by electrospray into an OMCVD ZnS thin film process. Photoluminescence and cathodoluminescence properties of the quantum dot composites are reported.
A novel technique is presented to simultaneously measure temperature and crystallinity insitu during the rapid thermal annealing of thin Si / SiGe films on transparent substrates for active matrix liquid crystal display applications. The technique uses acoustic waves to monitor temperature, by measuring changes in velocity with temperature. The technique enables accurate tracking of crystalline phase transitions along with temperature, since it is independent of emissivity. This provides a methodology for closed-loop control and end-point detection. The experiments on thin amorphous Si on Quartz demonstrate temperature repeatability of 2%. Also, the technique proved sensitive enough to detect the onset of nucleation, as evidenced by TEM.