664 research outputs found

    Advanced thin film thermocouples

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    The fabrication, materials characterization, and performance of thin film platinum rhodium thermocouples on gas turbine alloys was investigated. The materials chosen for the study were the turbine blade alloy systems MAR M200+Hf with NiCoCrAlY and FeCrAlY coatings, and vane alloy systems MAR M509 with FeCrAlY. Research was focussed on making improvements in the problem areas of coating substrate stability, adhesion, and insulation reliability and durability. Diffusion profiles between the substrate and coating with and without barrier coatings of Al2O3 are reported. The relationships between fabrication parameters of thermal oxidation and sputtering of the insulator and its characterization and performance are described. The best thin film thermocouples were fabricated with the NiCoCrAlY coatings which were thermally oxidized and sputter coated with Al2O3

    Particles of Moisture or other Substance Suspended in Air and Visible as Clouds: Complexity in Site-Related Creative Practices

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    Outlining a history, theory and practice of site-related creative practices across poetry, art and architecture, this book chapter works to contextualise the practice-based research of the creative collaborative pair Kreider + O’Leary. Alongside this written component, Kreider + O’Leary engage with an expanded drawing technique to delineate the specific narrative of one of their site-related projects

    Charge storage on emulsion and photoresist irradiated by an electron beam

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    Surface potentials have been measured on photosensitive materials after irradiation by an electron beam. The resulting potentials were measured with a Kelvin Probe device featuring synchronous detection, phase adjustment and continuous data output

    Finite Difference Time Marching in the Frequency Domain: A Parabolic Formulation for the Convective Wave Equation

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    An explicit finite difference iteration scheme is developed to study harmonic sound propagation in ducts. To reduce storage requirements for large 3D problems, the time dependent potential form of the acoustic wave equation is used. To insure that the finite difference scheme is both explicit and stable, time is introduced into the Fourier transformed (steady-state) acoustic potential field as a parameter. Under a suitable transformation, the time dependent governing equation in frequency space is simplified to yield a parabolic partial differential equation, which is then marched through time to attain the steady-state solution. The input to the system is the amplitude of an incident harmonic sound source entering a quiescent duct at the input boundary, with standard impedance boundary conditions on the duct walls and duct exit. The introduction of the time parameter eliminates the large matrix storage requirements normally associated with frequency domain solutions, and time marching attains the steady-state quickly enough to make the method favorable when compared to frequency domain methods. For validation, this transient-frequency domain method is applied to sound propagation in a 2D hard wall duct with plug flow

    Biochemical characterizations of Escherichia coli DnaK and DnaK mutant proteins purified from ndk deficient cells

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    Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Biology, 1999.Includes bibliographical references.by Thomas K. Barthel.Ph.D

    Modeling and Simulation of Coating Growth on Nanofibers

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    This work presents modeling and simulation results of a procedure to coat nanofibers and core-clad nanostructures with thin film materials using plasma enhanced physical vapor deposition. In the experimental effort that motivates the modeling, electrospun polymer nanofibers are coated with metallic materials under different operating conditions to observe changes in the coating morphology. The modeling effort focuses on linking simple models at the reactor, nanofiber, and atomic levels to form a comprehensive model. Numerical simulations that link the concentration field with the evolution of the coating free surface predict that as the Damkohler number is increased the coating morphology changes from a wavy to a nodular to a dendritic needle-type form as observed experimentally

    Muscle fiber and performance adaptations to resistance exercise with MyoVive, colostrum or casein and whey supplementationa

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    This is the publisher's version, also found at http://ehis.ebscohost.com/ehost/detail?sid=ba69ee0d-97cf-4a2c-a1a2-2c26fb60d65c%40sessionmgr13&vid=1&hid=2&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=s3h&AN=10725638To determine the effects of 12 weeks of resistance exercise with MyoVive and/or colostrum supplementation, 19 male and female recreationally weighttrained subjects (X ± SE; age = 28.3 ± 6.9 yrs; hgt = 68.2 ± 3.8 cm) were divided into MyoVive + colostrum (n = 4), MyoVive + casein & whey (n = 4), colostrum + casein & whey (n = 6), and casein & whey (n = 5) groups. All groups similarly increased (p < .05) 1 repetition maximum (RM) leg press (kg; pre = 158.6 ± 12.8, post = 189.3 ± 11.3), body mass (kg; pre = 79.0 ± 3.2, post = 80.7 ± 3.8), and lean body mass (kg; pre = 60.1 ± 3.1, post = 62.2 ± 2.8). Increases were observed for peak force (N; all loads), peak velocity (m.s-1; 70% & 40% 1 RM), and peak power (W; 70% & 40% 1 RM) for all groups for the leg press exercise, with no differences between groups. When performance data were adjusted for body mass, lean body mass, lower body lean mass as determined by DEXA, or % change, no group differences were observed. Relative (%) fiber type content, cross-sectional areas (mm2), % fiber type areas, or % myosin heavy chain expression did not change for any group. These data suggest that MyoVive and colostrum supplementation have no greater effect on cellular and performance adaptations when compared to casein and whey protein

    Effects of Calcium Pyruvate Supplementation During Training On Body Composition, Exercise Capacity, and Metabolic Responses To Exercise

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    Objective: We evaluated the effects of calcium pyruvate supplementation during training on body composition and metabolic responses to exercise. Method: Twenty-three untrained females were matched and assigned to ingest in a double blind and randomized manner either 5 g of calcium pyruvate (PYR) or a placebo (PL) twice daily for 30 d while participating in a supervised exercise program. Prior to and following supplementation, subjects had body composition determined via hydrodensiometry; performed a maximal cardiopulmonary exercise test; and performed a 45-min walk test at 70% of pre-training VO2 max in which fasting pre- and post exercise blood samples determined. Results: No significant differences were observed between groups in energy intake or training volume. Univariate repeated measures ANOVA revealed that subjects in the PYR group gained less weight (PL 1.2 ± 0.3, PYR 0.3 ± 0.3 kg, P = 0.04), lost more fat (PL 1.1 ± 0.5; PYR −0.4 ± 0.5 kg, P = 0.03), and tended to lose a greater percentage of body fat (PL 1.0 ± 0.7; PYR −0.65 ± 0.6%, P = 0.07), with no differences observed in fat-free mass (PL 0.1 ± 0.5; PYR 0.7 ± 0.3 kg, P = 0.29). However, these changes were not significant when body composition data were analyzed by MANOVA (P = 0.16). There was some evidence that PYR may negate some of the beneficial effects of exercise on HDL values. No significant differences were observed between groups in maximal exercise responses or metabolic responses to submaximal walking. Conclusions: Results indicate that PYR supplementation during training does not significantly affect body composition or exercise performance and may negatively affect some blood lipid levels

    Analysis of the efficacy, safety, and regulatory status of novel forms of creatine

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    Creatine has become one of the most popular dietary supplements in the sports nutrition market. The form of creatine that has been most extensively studied and commonly used in dietary supplements is creatine monohydrate (CM). Studies have consistently indicated that CM supplementation increases muscle creatine and phosphocreatine concentrations by approximately 15–40%, enhances anaerobic exercise capacity, and increases training volume leading to greater gains in strength, power, and muscle mass. A number of potential therapeutic benefits have also been suggested in various clinical populations. Studies have indicated that CM is not degraded during normal digestion and that nearly 99% of orally ingested CM is either taken up by muscle or excreted in urine. Further, no medically significant side effects have been reported in literature. Nevertheless, supplement manufacturers have continually introduced newer forms of creatine into the marketplace. These newer forms have been purported to have better physical and chemical properties, bioavailability, efficacy, and/or safety profiles than CM. However, there is little to no evidence that any of the newer forms of creatine are more effective and/or safer than CM whether ingested alone and/or in combination with other nutrients. In addition, whereas the safety, efficacy, and regulatory status of CM is clearly defined in almost all global markets; the safety, efficacy, and regulatory status of other forms of creatine present in today’s marketplace as a dietary or food supplement is less clear

    Modeling, Simulation, and Experiments of Coating Growth on Nanofibers

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    This work is a comparison of modeling and simulation results with experiments for an integrated experimental/modeling investigation of a procedure to coat nanofibers and core-clad nanostructures with thin film materials using plasma enhanced physical vapor deposition. In the experimental effort, electrospun polymer nanofibers are coated with metallic materials under different operating conditions to observe changes in the coating morphology. The modeling effort focuses on linking simple models at the reactor level, nanofiber level and atomic level to form a comprehensive model. The comprehensive model leads to the definition of an evolution equation for the coating free surface around an isolated nanofiber. This evolution equation was previously derived and solved under conditions of a nearly circular coating, with a concentration field that was only radially dependent and that was independent of the location of the coating free surface. These assumptions permitted the development of analytical expressions for the concentration field. The present work does not impose the above-mentioned conditions and considers numerical simulations of the concentration field that couple with level set simulations of the evolution equation for the coating free surface. Further, the cases of coating an isolated fiber as well as a multiple fiber mat are considered. Simulation results are compared with experimental results as the reactor pressure and power, as well as the nanofiber mat porosity, are varied. (C) 2008 American Institute of Physics
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