On the gas dynamics of HVOF thermal sprays

An experimental study of the gas-dynamic aspects of the high-velocity oxyfuel (HVOF) thermal spray process has been performed using commercially available HVOF equipment (Hobart-Tafa JP-5000, Ho-bart-Tafa Technologies, Inc., Concord, NH). Optical diagnostic techniques, including microsecond-expo-sure schlieren and shadowgraph imaging, were applied to visualize the hot supersonic jet produced by this equipment without particle injection. Rapid turbulent mixing of the jet with the surrounding atmos-phere was observed, which is an issue of concern in coating quality due to the possibility of oxidation of sprayed particles. This mixing appears to be a function of the ratio of densities of the hot jet and the cold atmosphere as well as a function of the velocity of the jet, rather than one of combustion-chamber pres-sure or barrel length. The supersonic core of the HVOF jet dissipates rapidly due to the mixing, so that the jet is no longer supersonic when it impinges on the target surface being sprayed. Secondary issues also observed in this study include strong jet-noise radiation from the HVOF plume and the entrainment and induced bulk motion of the surrounding air.     

Uterine activity patterns in uterine rupture: a case-control study

The effects of methylprednisolone therapy on the susceptibility of dystrophin-deficient myofibers to contraction-induced injury were evaluated in the mdx mouse diaphragm model of Duchenne dystrophy. Mdx myofibers were abnormally vulnerable to injury induced by high-stress eccentric contractions. However, methylprednisolone therapy did not significantly alter the degree of contraction-induced injury. These data suggest that beneficial effects of corticosteroid therapy in Duchenne dystrophy are unlikely to be related to a change in the threshold for contraction-induced myofiber damage.     

Averaging of products of Lorentzian line shapes over thermal velocities

The algebraic identity(ab)^{-1} = (b pm a)^{-1}(a^{-1} pm b^{-1})is used to reduce the average over thermal velocities of a product of Lorentzian line shapes to a product of Lorentzian line shapes which do not depend on velocity and a sum of plasma dispersion Z-functions. Scaling is used to cancel the velocity-dependent terms in(b pm a).(abc... )^{-1}may be reduced by systematic application of the above identity and tedious integrations can be replaced by algebraic procedures.     

Independent control of HVOF particle velocity and temperature

Independent control of high velocity oxygen fuel (HVOF) spray particle velocity and temperature has not been possible in the past, confusing the effect of either parameter on coating properties. This study describes a method by which velocity and temperature may be varied independently. Commercial HVOF equipment that was fitted with a special conical supersonic nozzle having four distinct particle injection locations was used. The present results, which were predicted in simulations and demonstrated in experiments, revealed several pertinent facts. First, particle velocity is principally related to combustion chamber pressure and is relatively unaffected by other design or operating conditions. Second, particle temperature is related to particle residence time within the nozzle, which can be controlled by the choice of particle injection location. In these experiments, the impact velocity and temperature of stainless steel particles were controlled within the ranges 340 to 660 m/s and 1630 to 2160 K, respectively. This range of parameters produced significant variations in splat morphology, coating microstructure, and coating oxide content. Such particle control allows the effects of velocity and temperature on coating properties to be assessed and controlled independently. These results also have commercial application, potentially enabling the user to tailor particle impact velocity and temperature to achieve specific coating properties.     

Marital distress and the metabolic syndrome: Linking social functioning with physical health.

Mechanisms by which poor relationship functioning contributes to poor health are not fully understood. We conducted a study to evaluate the association between marital distress and the metabolic syndrome (MetS), which refers to a clustering of characteristics that have individually been shown to be associated with elevated risk of cardiovascular disease and diabetes and which collectively have been shown to increase risk for cardiovascular disease, diabetes, stroke, and mortality. A population-based English sample of couples (N = 671 couples) in which both partners were between the ages of 52 and 79 years old completed a self-report measure of marital distress and a nurse visit that included collection of blood pressure, blood samples, and anthropometric measures. Results indicated that for women, after controlling for demographic variables, greater marital distress was significantly associated with increasing likelihood of meeting criteria for the MetS and with the individual MetS criteria of elevated blood pressure and elevated fasting glucose. The association between marital distress and the MetS remained significant for women when additionally controlling for depressive symptoms and health habits (smoking status, physical activity). Marital distress was not significantly associated with the MetS or any of the individual MetS criteria for men. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Surface pressure measurements in shock wave/boundary-layer interactions

An experimental research program establishing a database of the surface pressure in swept shock wave/boundary-layer interactions is described. An equilibrium turbulent boundary-layer on a flat plate is subjected to impingement by swept planar shock waves genterated by a sharp fin. Various fin angles at 4 different freestream Mach numbers produce a variety of interaction strengths from weak to very strong. For each of different interaction cases, the surface flow patterns are obtained by a kerosene-lampblack-adhesive transparent tape technique. Surface pressures within the interactions are also measured from several streamwise row of taps connected to a computer-controlled Scanivalve system. An extensive error analysis is carried out for the experiments yielding an uncertainty of about ±3%. From these measurements, high spatial resolution surface pressure distributions for different interaction cases are obtained.     

Old and new pathways of protein export in chloroplasts and bacteria

Targeting of chloroplast proteins to the thylakoid membrane is analogous to bacterial secretion, and much of what we know has been learned from secretory mechanisms in Escherichia coli. However, chloroplasts also use a delta pH-dependent pathway to target thylakoid proteins, at least some of which are folded before transport. Previously, this pathway seemed to have no cognate in bacteria, but recent results have shown that the HCF106 gene in maize encodes a component of this pathway and has bacterial homologues. This delta pH-dependent pathway might be an ancient conserved mechanism for protein translocation that evolved before the endosymbiotic origin of plastids and mitochondria.     

Laboratory-scale techniques for the measurement of a material response to an explosive blast

Laboratory-scale experiments were performed to measure the deformation of thin plates in response to varying explosive impulse. Experiments were conducted with a known explosive mass suspended in air at a known distance from an aluminum witness plate clamped in a “shock-hole” fixture. Through the use of well-characterized PETN and TATP explosive charges, the explosive impulse applied to each witness plate was determined a priori. The witness-plate response was measured using high-speed digital cameras to determine time-resolved, three-dimensional surface motion and maximum plate deformation. The results show that the maximum dynamic plate deformation is a straightforward function of applied explosive impulse, as determined from the explosive characterization. The experimental trend is the same despite the two different explosives used, highlighting that explosive impulse, determined through a blast characterization, is the controlling parameter in material blast response. A new experimental technique is used here to measure the dynamic blast response and the experimental errors are documented. Ultimately, applications of laboratory-scale explosive testing to computational code validation, material response scaling, and high-speed material property definition are discussed.