171 research outputs found
Recent Decisions
Comments on recent decisions by Robert E. Sullivan, James H. Graham, John E. Savord, Edward A. Mahoney, Jr., and Ronald P. Rejent
Combined Spatially Resolved Optical Emission Imaging and Modeling Studies of Microwave-Activated H<sub>2</sub>/Ar and H<sub>2</sub>/Kr Plasmas Operating at Powers and Pressures Relevant for Diamond Chemical Vapor Deposition
Microwave
(MW) activated H2/Ar (and H2/Kr)
plasmas operating under powers and pressures relevant to diamond chemical
vapor deposition have been investigated experimentally and by 2-D
modeling. The experiments return spatially and wavelength resolved
optical emission spectra of electronically excited H2 molecules
and H and ArÂ(/Kr) atoms for a range of H2/noble gas mixing
ratios. The self-consistent 2-DÂ(r, z) modeling of different H2/Ar gas mixtures includes calculations
of the MW electromagnetic fields, the plasma chemistry and electron
kinetics, heat and species transfer and gas–surface interactions.
Comparison with the trends revealed by the spatially resolved optical
emission measurements and their variations with changes in process
conditions help guide identification and refinement of the dominant
plasma (and plasma emission) generation mechanisms and the more important
Ar–H, Ar–H2, and H–H2 coupling
reactions. Noble gas addition is shown to encourage radial expansion
of the plasma, and thus to improve the uniformity of the H atom concentration
and the gas temperature just above the substrate. Noble gas addition
in the current experiments is also found to enhance (unwanted) sputtering
of the copper base plate of the reactor; the experimentally observed
increase in gas phase Cu* emission is shown to correlate with the
near substrate ArH+ (and KrH+) ion concentrations
returned by the modeling, rather than with the relatively more abundant
H3+ (and H3O+) ions
Optical Emission Imaging and Modelling Investigations of Microwave Activated SiH<sub>4</sub>/H<sub>2</sub> and SiH<sub>4</sub>/CH<sub>4</sub>/H<sub>2 </sub>Plasmas
Oxygen cost of dynamic or isometric exercise relative to recruited muscle mass
BACKGROUND: Oxygen cost of different muscle actions may be influenced by different recruitment and rate coding strategies. The purpose of this study was to account for these strategies by comparing the oxygen cost of dynamic and isometric muscle actions relative to the muscle mass recruited via surface electrical stimulation of the knee extensors. METHODS: Comparisons of whole body pulmonary Δ [Formula: see text] O(2 )were made in seven young healthy adults (1 female) during 3 minutes of dynamic or isometric knee extensions, both induced by surface electrical stimulation. Recruited mass was quantified in T(2 )weighted spin echo magnetic resonance images. RESULTS: The Δ [Formula: see text] O(2 )for dynamic muscle actions, 242 ± 128 ml • min(-1 )(mean ± SD) was greater (p = 0.003) than that for isometric actions, 143 ± 99 ml • min(-1). Recruited muscle mass was also greater (p = 0.004) for dynamic exercise, 0.716 ± 282 versus 0.483 ± 0.139 kg. The rate of oxygen consumption per unit of recruited muscle ([Formula: see text]) was similar in dynamic and isometric exercise (346 ± 162 versus 307 ± 198 ml • kg(-1 )• min(-1); p = 0.352), but the [Formula: see text] calculated relative to initial knee extensor torque was significantly greater during dynamic exercise 5.1 ± 1.5 versus 3.6 ± 1.6 ml • kg(-1 )• Nm(-1 )• min(-1 )(p = 0.019). CONCLUSION: These results are consistent with the view that oxygen cost of dynamic and isometric actions is determined by different circumstances of mechanical interaction between actin and myosin in the sarcomere, and that muscle recruitment has only a minor role
Optical Emission from C<sub>2</sub><sup>–</sup> Anions in Microwave-Activated CH<sub>4</sub>/H<sub>2</sub> Plasmas for Chemical Vapor Deposition of Diamond
What [plasma used for growing] diamond can shine like flame?
The gas-phase chemistry underpinning the chemical vapour deposition of diamond from microwave-activated methane/hydrogen plasmas is surveyed.</p
Observations of convective and dynamical instabilities in tropopause folds and their contribution to stratosphere-troposphere exchange
With aircraft-mounted in situ and remote sensing instruments for dynamical, thermal, and chemical measurements we studied two cases of tropopause folding. In both folds we found Kelvin-Helmholtz billows with horizontal wavelength of ∼900 m and thickness of ∼120 m. In one case the instability was effectively mixing the bottomside of the fold, leading to the transfer of stratospheric air into the troposphere. Also, we discovered in both cases small-scale secondary ozone maxima shortly after the aircraft ascended past the topside of the fold that corresponded to regions of convective instability. We interpreted this phenomenon as convectively breaking gravity waves. Therefore we posit that convectively breaking gravity waves acting on tropopause folds must be added to the list of important irreversible mixing mechanisms leading to stratosphere-troposphere exchange.United States. National Aeronautics and Space Administration (Grant NAG2-1105)United States. National Aeronautics and Space Administration (Grant NAGl-1758)United States. National Aeronautics and Space Administration (Grant NAGl-1901
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Mutations in the Satellite Cell Gene MEGF10 Cause a Recessive Congenital Myopathy with Minicores
We ascertained a nuclear family in which three of four siblings were affected with an unclassified autosomal recessive myopathy characterized by severe weakness, respiratory impairment, scoliosis, joint contractures, and an unusual combination of dystrophic and myopathic features on muscle biopsy. Whole genome sequence from one affected subject was filtered using linkage data and variant databases. A single gene, MEGF10, contained nonsynonymous mutations that co-segregated with the phenotype. Affected subjects were compound heterozygous for missense mutations c.976T > C (p.C326R) and c.2320T > C (p.C774R). Screening the MEGF10 open reading frame in 190 patients with genetically unexplained myopathies revealed a heterozygous mutation, c.211C > T (p.R71W), in one additional subject with a similar clinical and histological presentation as the discovery family. All three mutations were absent from at least 645 genotyped unaffected control subjects. MEGF10 contains 17 atypical epidermal growth factor-like domains, each of which contains eight cysteine residues that likely form disulfide bonds. Both the p.C326R and p.C774R mutations alter one of these residues, which are completely conserved in vertebrates. Previous work showed that murine Megf10 is required for preserving the undifferentiated, proliferative potential of satellite cells, myogenic precursors that regenerate skeletal muscle in response to injury or disease. Here, knockdown of megf10 in zebrafish by four different morpholinos resulted in abnormal phenotypes including unhatched eggs, curved tails, impaired motility, and disorganized muscle tissue, corroborating the pathogenicity of the human mutations. Our data establish the importance of MEGF10 in human skeletal muscle and suggest satellite cell dysfunction as a novel myopathic mechanism
Antenatal screening and its possible meaning from unborn baby's perspective
In recent decades antenatal screening has become one of the most routine procedure of pregnancy-follow up and the subject of hot debate in bioethics circles. In this paper the rationale behind doing antenatal screening and the actual and potential problems that it may cause will be discussed. The paper will examine the issue from the point of wiew of parents, health care professionals and, most importantly, the child-to-be. It will show how unthoughtfully antenatal screening is performed and how pregnancy is treated almost as a disease just since the emergence of antenatal screening. Genetic screening and ethical problems caused by the procedure will also be addressed and I will suggest that screening is more to do with the interests of others rather than those of the child-to be
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