Dynamic response of deformable structures subjected to shock load and cavitation reload

The dynamic response of deformable structures subjected to shock load and cavitation reload has been simulated using a multiphase model, which consists of an interface capturing method and a one-fluid cavitation model. Fluid–structure interaction (FSI) is captured via a modified ghost fluid method (Liu et al. in J Comput Phys 190: 651–681, 2003), where the structure is assumed to be a hydro-elasto-plastic material if subjected to a strong shock load. Bulk cavitation near the structural surface is captured using an isentropic model (Liu et al. in J Comput Phys 201:80–108, 2004). The integrated multiphase model is validated by comparing numerical predictions with 1D analytical solutions, and with numerical solutions calculated using the cavitation acoustic finite element (CAFé) method (Sprague and Geers in Shocks vib 7:105–122, 2001). To assess the ability of the multiphase model for multi- dimensions, underwater explosions (UNDEX) near structures are computed. The importance of cavitation reloading and FSI is investigated. Comparisons of the predicted pressure time histories with different explosion center are shown, and the effect on the structure is discussed.     

Auto-charge pump for half-bridge inverters

The auto-charge pump is a self-starting and self-sustaining circuit used to generate a floating voltage supply for the high side circuitry of half-bridge inverters. The switching output of the half-bridge replaces the dedicated pump oscillator thus simplifying the circuit. A model is derived which is then verified experimentally     

Numerical Simulation of Fluid-Structure Interaction Using Modified Ghost Fluid Method and Naviers Equations

In this work, we deal with the 1D compressible fluid coupled with elastic solid in an Eulerian-Lagrangian system. To facilitate the analysis, the Naviers equation for elastic solid is cast into a 2×2 system similar to the Euler equation but in Lagrangian coordinate. The modified Ghost Fluid Method is employed to treat the fluid-elastic solid coupling, where an Eulerian-Lagrangian Riemann problem is defined and a nonlinear characteristic from the fluid and a Riemann invariant from the solid are used to predict and define the ghost fluid states. Theoretical analysis shows that the present approach is accurate in the sense of approximating the solution of the Riemann problem at the interface. Numerical validation of this approach is also accomplished by extensive comparison to 1D problems (both water-solid and gas-solid) with their respective analytical solutions. T.G. Liu’s current address: Department of Mathematics, Beijing University of Aeronautics and Astronautics, Beijing 100083. email: liutg@buaa.edu.cn.     

Human brain metabolic response to caffeine and the effects of tolerance

OBJECTIVE: Since there is limited information concerning caffeine's metabolic effects on the human brain, the authors applied a rapid proton echo-planar spectroscopic imaging technique to dynamically measure regional brain metabolic responses to caffeine ingestion. They specifically measured changes in brain lactate due to the combined effects of caffeine's stimulation of glycolysis and reduction of cerebral blood flow. METHOD: Nine heavy caffeine users and nine caffeine-intolerant individuals, who had previously discontinued or substantially curtailed use of caffeinated products because of associated anxiety and discomforting physiological arousal, were studied at baseline and then during 1 hour following ingestion of caffeine citrate (10 mg/kg). To assess state-trait contributions and the effects of caffeine tolerance, five of the caffeine users were restudied after a 1- to 2-month caffeine holiday. RESULTS: The caffeine-intolerant individuals, but not the regular caffeine users, experienced substantial psychological and physiological distress in response to caffeine ingestion. Significant increases in global and regionally specific brain lactate were observed only among the caffeine-intolerant subjects. Reexposure of the regular caffeine users to caffeine after a caffeine holiday resulted in little or no adverse clinical reaction but significant rises in brain lactate which were of a magnitude similar to that observed for the caffeine-intolerant group. CONCLUSIONS: These results provide direct evidence for the loss of caffeine tolerance in the human brain subsequent to caffeine discontinuation and suggest mechanisms for the phenomenon of caffeine intolerance other than its metabolic effects on elevating brain lactate.     

Upper tibial hyperextension fractures in infants: another occult toddler''s fracture

Our study describes a newly designed stapedotomy prosthesis which consists of two components: (1) a platinum ribbon, and (2) a Teflon shaft. The first innovation is a flattened 'tab' on the posterior aspect of the platinum ribbon. The second innovation concerns the dual diameter cylinder-like shaft. Our prosthesis was implanted into 25 individuals, who underwent stapedotomy for stapes fixation, and the results are shown and discussed. Our innovations offer a proper and safe insertion of the prosthesis into the oval window associated with excellent manipulation and handling. At the same time, maximum visualization of the surgical field is achieved, while the stepped-down design of the shaft prevents the prosthesis protruding into the vestibule.     

Combination antiretroviral therapy and recent declines in AIDS incidence and mortality

The reasons for recent declines in AIDS incidence and mortality may include advances in treatment, but these may be confounded by earlier declines in the incidence of human immunodeficiency virus (HIV) infection. To determine whether the declines in AIDS and mortality may, in part, stem from wider use of combination antiretroviral therapy, 622 HIV-positive men with well-characterized dates of seroconversion were followed. In this group, combination therapy came into widespread use in only 1996. In a Cox proportional hazards model, the 1996 calendar period was significantly associated with slower progression to AIDS (relative hazard [RH]=0. 19, 95% confidence interval [CI], 0.05-0.69, P=.01) and death (RH=0. 45, 95% CI, 0.21-0.95, P=.04). Declines in incidence of HIV infection, changes in HIV virulence, and end-point underreporting cannot fully explain the decline in AIDS and death in 1996. The introduction of combination antiretroviral therapy as the standard of care may already have had measurable effects.     

The use of ceramic onlays for restoring the occlusal surface of the teeth

Computer-aided milling of ceramic insertions helped more effectively repair the masticatory surface of teeth, minimize the incidence of errors, rule out the laboratory stage of making the insertions and the technological errors made at this stage, retain physical and mechanical characteristics of ceramics, optimize marginal adherence of the insertion to the tooth, retain the height of the lower part of the face, and thus prevent the maxillodental dysfunction.     

Assessing program effects in the presence of treatment—baseline interactions: A latent curve approach.

Methods for assessing treatment effects of longitudinal randomized intervention are considered. The focus is on modeling the nonlinear relationship between treatment effects and baseline often observed in prevention programs designed for at-risk populations. Piecewise linear growth modeling was used to study treatment effects during the different periods of development. A multistep multiple-group analysis procedure is proposed for assessing treatment effects in the presence of nonlinear treatment-baseline interactions. Standard errors of the estimates from this multistep procedure were obtained using a bootstrap approach. The methods are illustrated using data from the Johns Hopkins Prevention Research Center involving an intervention aimed at improving classroom behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)