Graphene formation on SiC substrates

Graphene layers were created on both C and Si faces of semi-insulating, on-axis, 4H- and 6H-SiC substrates. The process was performed under high vacuum (<10-4 mbar) in a commercial chemical vapor deposition SiC reactor. A method for H2 etching the on-axis sub-strates was developed to produce surface steps with heights of 0.5 nm on the Si-face and 1.0 to 1.5 nm on the C-face for each polytype. A process was developed to form graphene on the substrates immediately after H2 etching and Raman spectroscopy of these samples confirmed the formation of graphene. The morphology of the graphene is described. For both faces, the underlying substrate morphology was significantly modified during graphene formation; sur-face steps were up to 15 nm high and the uniform step morphology was sometimes lost. Mo-bilities and sheet carrier concentrations derived from Hall Effect measurements on large area (16 mm square) and small area (2 and 10 um square) samples are presented and shown to compare favorably to recent reports.Comment: European Conference on Silicon Carbide and Related Materials 2008 (ECSCRM '08), 4 pages, 4 figure

Relationship between Yeast Polyribosomes and Upf Proteins Required for Nonsense mRNA Decay

In yeast, the accelerated rate of decay of nonsense mutant mRNAs, called nonsense-mediated mRNA decay, requires three proteins, Upf1p, Upf2p, and Upf3p. Single, double, and triple disruptions of the UPF genes had nearly identical effects on nonsense mRNA accumulation, suggesting that the encoded proteins function in a common pathway. We examined the distribution of epitope-tagged versions of Upf proteins by sucrose density gradient fractionation of soluble lysates and found that all three proteins co-distributed with 80 S ribosomal particles and polyribosomes. Treatment of ly-sates with RNase A caused a coincident collapse of polyribosomes and each Upf protein into frac-tions containing 80 S ribosomal particles, as expected for proteins that are associated with polyribosomes. Mutations in the cysteine-rich (zinc finger) and RNA helicase domains of Upf1p caused loss of function, but the mutant proteins remained polyribosome-associated. Density gradi-ent profiles for Upf1p were unchanged in the absence of Upf3p, and although similar, were modestly shifted to fractions lighter than those containing polyribosomes in the absence of Upf2p. Upf2p shifted toward heavier polyribosome fractions in the absence of Upf1p and into fractions containing 80 S particles and lighter fractions in the absence of Upf3p. Our results suggest that the association of Upf2p with polyribosomes typically found in a wild-type strain depends on the presence and opposing effects of Upf1p and Upf3p

Relationship between Yeast Polyribosomes and Upf Proteins Required for Nonsense mRNA Decay

In yeast, the accelerated rate of decay of nonsense mutant mRNAs, called nonsense-mediated mRNA decay, requires three proteins, Upf1p, Upf2p, and Upf3p. Single, double, and triple disruptions of the UPF genes had nearly identical effects on nonsense mRNA accumulation, suggesting that the encoded proteins function in a common pathway. We examined the distribution of epitope-tagged versions of Upf proteins by sucrose density gradient fractionation of soluble lysates and found that all three proteins co-distributed with 80 S ribosomal particles and polyribosomes. Treatment of ly-sates with RNase A caused a coincident collapse of polyribosomes and each Upf protein into frac-tions containing 80 S ribosomal particles, as expected for proteins that are associated with polyribosomes. Mutations in the cysteine-rich (zinc finger) and RNA helicase domains of Upf1p caused loss of function, but the mutant proteins remained polyribosome-associated. Density gradi-ent profiles for Upf1p were unchanged in the absence of Upf3p, and although similar, were modestly shifted to fractions lighter than those containing polyribosomes in the absence of Upf2p. Upf2p shifted toward heavier polyribosome fractions in the absence of Upf1p and into fractions containing 80 S particles and lighter fractions in the absence of Upf3p. Our results suggest that the association of Upf2p with polyribosomes typically found in a wild-type strain depends on the presence and opposing effects of Upf1p and Upf3p

Micro-Organ Device

A method for fabricating a micro-organ device comprises providing a microscale support having one or more microfluidic channels and one or more micro-chambers for housing a micro-organ and printing a micro-organ on the microscale support using a cell suspension in a syringe controlled by a computer-aided tissue engineering system, wherein the cell suspension comprises cells suspended in a solution containing a material that functions as a three-dimensional scaffold. The printing is performed with the computer-aided tissue engineering system according to a particular pattern. The micro-organ device comprises at least one micro-chamber each housing a micro-organ; and at least one microfluidic channel connected to the micro-chamber, wherein the micro-organ comprises cells arranged in a configuration that includes microscale spacing between portions of the cells to facilitate diffusion exchange between the cells and a medium supplied from the at least one microfluidic channel

The Majority of Yeast UPF1 Co-localizes with Polyribosomes in the Cytoplasm

In Saccharomyces cerevisiae the UPF1 protein is required for nonsense-mediated mRNA decay, the accelerated turnover of mRNAs containing a nonsense mutation. Several lines of evidence suggest that translation plays an important role in the mechanism of nonsense mRNA decay, including a previous report that nonsense mRNAs assemble in polyribosomes. In this study we show that UPF1 and ribosomal protein Li co-localize in the cytoplasm and that UPF1 co-sediments with polyribosomes. To detect UPF1, three copies of the influenza hemagglutinin epitope were placed at the C-terminus. The tagged protein, UPF1-3EP, retains 86% (± 5%) of function. Using immunological detection, we found that UPF1-3EP is primarily cytoplasmic and was not detected either in the nucleus or in the mitochondrion. UPF1-3EP and Li co-distributed with polyribosomes fractionated in a 7-47% sucrose gradient. The sucrose sedimentation profiles for UPF1-3EP and Li exhibited similar changes using three different sets of conditions that altered the polyribosome profile. When polyribosomes were disaggregated, UPF1-3EP and Li accumulated in fractions coincident with 80S ribosomal particles. These results suggest that UPF1-3EP associates with polyribosomes. L3 and S3 mRNAs, which code for ribosomal proteins of the 60S and 40S ribosomal subunits, respectively, were on average about 100-fold more abundant than UPF1 mRNA. Assuming that translation rates for L3, S3, and UPF1 mRNA are similar, this result suggests that there are far fewer UPF1 molecules than ribosomes per cell. Constraints imposed by the low UPF1 abundance on the functional relationships between UPF1, polyribosomes, and nonsense mRNA turnover are discussed

Improvement of Morphology and Free Carrier Mobility through Argon-Assisted Growth of Epitaxial Graphene on Silicon Carbide

Graphene was epitaxially grown on both the C- and Si-faces of 4H- and 6H-SiC(0001) under an argon atmosphere and under high vacuum conditions. Following growth, samples were imaged with Nomarski interference contrast and atomic force microscopies and it was found that growth under argon led to improved morphologies on the C-face films but the Si-face films were not significantly affected. Free carrier transport studies were conducted through Hall effect measurements, and carrier mobilities were found to increase and sheet carrier densities were found to decrease for those films grown under argon as compared to high vacuum conditions. The improved mobilities and concurrent decreases in sheet carrier densities suggest a decrease in scattering in the films grown under argon.Comment: 215th Meeting of the Electrochemical Society (ECS 215), 14 pages, 6 figure

Hall Effect Mobility of Epitaxial Graphene Grown on Silicon Carbide

Epitaxial graphene films were grown in vacuo by silicon sublimation from the (0001) and (000-1) faces of 4H- and 6H-SiC. Hall effect mobilities and sheet carrier densities of the films were measured at 300 K and 77 K and the data depended on the growth face. About 40% of the samples exhibited holes as the dominant carrier, independent of face. Generally, mobilities increased with decreasing carrier density, independent of carrier type and substrate polytype. The contributions of scattering mechanisms to the conductivities of the films are discussed. The results suggest that for near-intrinsic carrier densities at 300 K epitaxial graphene mobilities will be ~150,000 cm2V-1s-1 on the (000-1) face and ~5,800 cm2V-1s-1 on the (0001) face.Comment: Accepted for publication in Applied Physics Letters, 10 pages, 2 figure

Exercise is medicine in rural health centers and federally qualified health centers

The American College of Sports Medicine in collaboration with the American Medical Association developed the the Exercise is Medicine (EIM) initiative to promote physical activity as a vital sign among health care providers. The purpose of the study is to inform initiative advocacy efforts among Rural Health Centers and Federally Qualified Health Centers. An interview guide was developed through literature review and expert feedback. Provider responses will be recorded via field notes which are coded to extract common themes. The qualitative data collected from these interviews will be used to examine healthcare provider knowledge and awareness of the initiative current behaviors related to patient physical activity, assessment, counseling, prescription, referral and follow-up and the likelihood of these providers using existing Exercise is Medicine (EIM)materials and resources in the future. Our findings and recommendations will be communicated back to the American College of Sports Medicine through the Exercise is Medicine (EIM) Community Health Committee