1,445 research outputs found

    Development of Heterogeneous Photosensitized Transition Metal Oxide Water-Splitting Catalysts on Silica Support

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    The research presented in this manuscript describes the development of photosensitized inexpensive catalysts based on readily available materials. The investigation covers synthesis and characterization of photosensitizers based on porphyrins, mechanical and thermal coating of solid support with semiconducting transition metal oxides, photosensitization of the semiconducting layer, and characterization of the photoelectrochemical properties displayed by the new materials. The process of water oxidation is of primary interest here, with little emphasis put on reduction of protons to gaseous hydrogen. Photoelectrochemically produced protons serve as a probe of effectiveness of the catalysts. Several systems are described, and two catalysts are identified as the most efficient

    Native American Weight Loss Movement: Pilot Test of a Culturally Tailored Weight Loss Program for American Indians

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    American Indians (AIs) have higher rates of obesity than other racial/ethnic groups, placing them at heightened risk for cardiovascular diseases, diabetes, and certain cancers. Culturally appropriate weight loss interventions may be the key to reducing risk. The most successful program used in AI communities has been the Diabetes Prevention Program (DPP), which limits enrollment to individuals with a clinical diagnosis of pre-diabetes. The purpose of this pilot project was to modify and culturally tailor a weight loss intervention to AI communities in Kansas to improve weight loss related behaviors among those who do not qualify for the DPP. The Native American Weight Loss Movement (NAWLM) was developed from 2012-2014 using an iterative process with 4 sequential modifications to the program. Group 1 received a slightly modified version of the DPP that was originally tailored to African Americans. Each group received an improved program based on modifications from the previous group. Our analysis shows 36.1% (95% CI: 25.7, 47.5) of all participants (n=72) lost weight; a majority (63.9%, 95% CI: 52.8-75.0) maintained weight, gained weight, or dropped out. Among individuals who completed the program (n=34), 76.5% lost weight (95% CI: 61.4, 91.5). These individuals lost an average of 2.98% body weight (95% CI: 1.58, 4.37), with 6 participants losing \u3e7% body weight. While most participants who completed the program lost weight, more research is needed to determine factors that discourage drop-out and promote behavioral changes. NAWLM shows promise as a weight loss program for AIs who do not qualify for the DPP

    Longtime behavior of nonlocal Cahn-Hilliard equations

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    Here we consider the nonlocal Cahn-Hilliard equation with constant mobility in a bounded domain. We prove that the associated dynamical system has an exponential attractor, provided that the potential is regular. In order to do that a crucial step is showing the eventual boundedness of the order parameter uniformly with respect to the initial datum. This is obtained through an Alikakos-Moser type argument. We establish a similar result for the viscous nonlocal Cahn-Hilliard equation with singular (e.g., logarithmic) potential. In this case the validity of the so-called separation property is crucial. We also discuss the convergence of a solution to a single stationary state. The separation property in the nonviscous case is known to hold when the mobility degenerates at the pure phases in a proper way and the potential is of logarithmic type. Thus, the existence of an exponential attractor can be proven in this case as well

    Composition and dynamics of high power impulse magnetron discharge at W-Mo-C target in argon atmosphere

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    Metal-doped diamond-like carbon (Me-DLC) is a typical industrial solution for wear resistant coating due to their tribological properties. DLC doping with metal is used to reduce internal stress of the DLC coating, improve its thermal stability, hardness, coating-substrate adhesion, and wear resistance. Furthermore, application of the High Power Impulse Magnetron Sputtering (HiPIMS) for Me-DLC deposition allows improvement of coating adhesion and densification of the coating. To improve the properties of the DLC coatings doping with tungsten and molybdenum from a mixed W-Mo-C target can be used. This study concerns the plasma chemistry and composition for a W-Mo-C target operated with HIPIMS in argon atmosphere. For a HIPIMS discharge with a fixed pulse length of 150 μs a linear dependence of the average power and current are observed. The optical emission spectroscopy experiments reveal a temporal dependence of the plasma composition as the current pulse develops. First plasma is dominated by argon neutrals and ions followed by molybdenum and tungsten. Significant separation between the two metal species is observed in terms of the times of onset and peak of the emission. As a consequence of the change of the neutral gas to metal ratio the estimated effective electron temperature, Te, changes from ~2 eV as estimated from Ar I emission to ~0.3-0.6 eV as indicated by W I emission. A change of Te is also observed with the change of HIPIMS frequency: the Te estimated from metal excitations increases most probably as a result of the processes taking place in the afterglow phase between HIPIMS pulses. The transition from argon plasma at the beginning of the pulse to metal-rich plasma in the second phase of the pulse is discussed in comparison with the ion current measurements performed with a planar probe

    Application of Leg, Vertical, and Joint Stiffness in Running Performance: A Literature Overview

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    Stiffness, the resistance to deformation due to force, has been used to model the way in which the lower body responds to landing during cyclic motions such as running and jumping. Vertical, leg, and joint stiffness provide a useful model for investigating the store and release of potential elastic energy via the musculotendinous unit in the stretch-shortening cycle and may provide insight into sport performance. This review is aimed at assessing the effect of vertical, leg, and joint stiffness on running performance as such an investigation may provide greater insight into performance during this common form of locomotion. PubMed and SPORTDiscus databases were searched resulting in 92 publications on vertical, leg, and joint stiffness and running performance. Vertical stiffness increases with running velocity and stride frequency. Higher vertical stiffness differentiated elite runners from lower-performing athletes and was also associated with a lower oxygen cost. In contrast, leg stiffness remains relatively constant with increasing velocity and is not strongly related to the aerobic demand and fatigue. Hip and knee joint stiffness are reported to increase with velocity, and a lower ankle and higher knee joint stiffness are linked to a lower oxygen cost of running; however, no relationship with performance has yet been investigated. Theoretically, there is a desired “leg-spring” stiffness value at which potential elastic energy return is maximised and this is specific to the individual. It appears that higher “leg-spring” stiffness is desirable for running performance; however, more research is needed to investigate the relationship of all three lower limb joint springs as the hip joint is often neglected. There is still no clear answer how training could affect mechanical stiffness during running. Studies including muscle activation and separate analyses of local tissues (tendons) are needed to investigate mechanical stiffness as a global variable associated with sports performance

    31P-NMR and muSR Studies of Filled Skutterudite Compound SmFe4P12: Evidence for Heavy Fermion Behavior with Ferromagnetic Ground State

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    The 31P-NMR (nuclear magnetic resonance) and muSR (muon spin relaxation) measurements on the filled skutterudite system SmFe4P12 have been carried out. The temperature T dependence of the 31P-NMR spectra indicates the existence of the crystalline electric field effect splitting of the Sm3+$ (J = 5/2) multiplet into a ground state and an excited state of about 70 K. The spin-lattice relaxation rate 1/T1 shows the typical behavior of the Kondo system, i.e., 1/T1 is nearly T independent above 30 K, and varies in proportion to T (the Korringa behavior, 1/T1 \propto T) between 7.5 K and 30 K. The T dependence deviated from the Korringa behavior below 7 K, which is independent of T in the applied magnetic field of 1 kOe, and suppressed strongly in higher fields. The behavior is explained as 1/T1is determined by ferromagnetic fluctuations of the uncovered Sm3+ magnetic moments by conduction electrons. The muSR measurements in zero field show the appearance of a static internal field associated with the ferromagnetic order below 1.6 K.Comment: 6 pages, 9 figures, to be published in J. Phys. Soc. Jpn. 75 (2006

    Nonlinear Magneto-Optical Response of ss- and dd-Wave Superconductors

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    The nonlinear magneto-optical response of ss- and dd-wave superconductors is discussed. We carry out the symmetry analysis of the nonlinear magneto-optical susceptibility in the superconducting state. Due to the surface sensitivity of the nonlinear optical response for systems with bulk inversion symmetry, we perform a group theoretical classification of the superconducting order parameter close to a surface. For the first time, the mixing of singlet and triplet pairing states induced by spin-orbit coupling is systematically taken into account. We show that the interference of singlet and triplet pairing states leads to an observable contribution of the nonlinear magneto-optical Kerr effect. This effect is not only sensitive to the anisotropy of the gap function but also to the symmetry itself. In view of the current discussion of the order parameter symmetry of High-Tc_c superconductors, results for a tetragonal system with bulk singlet pairing for various pairing symmetries are discussed.Comment: 21 pages (REVTeX) with 8 figures (Postscript

    Poisson-Nernst-Planck Systems for Narrow Tubular-like Membrane Channels

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    We study global dynamics of the Poisson-Nernst-Planck (PNP) system for flows of two types of ions through a narrow tubular-like membrane channel. As the radius of the cross-section of the three-dimensional tubular-like membrane channel approaches zero, a one-dimensional limiting PNP system is derived. This one-dimensional limiting system differs from previous studied one-dimensional PNP systems in that it encodes the defining geometry of the three-dimensional membrane channel. To justify this limiting process, we show that the global attractors of the three-dimensional PNP systems are upper semi-continuous to that of the limiting PNP system. We then examine the dynamics of the one-dimensional limiting PNP system. For large Debye number, the steady-state of the one-dimensional limiting PNP system is completed analyzed using the geometric singular perturbation theory. For a special case, an entropy-type Lyapunov functional is constructed to show the global, asymptotic stability of the steady-state

    Plasma Dynamics

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    Contains reports on three research projects.United States Atomic Energy Commission (Contract AT(30-1)-1842)United States Air Force, Air Force Cambridge Research Center (Contract AF19(604)-5992)United States Air Force, Air Force Cambridge Research Center (Contract AF19(604)-4551)National Science Foundation (Grant G-9930)Office of Naval Research through Project SQUID, Phase III, under contract with Massachusetts Institute of Technolog
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