We present a detailed and quantitative examination of the thermodynamics and phase change mechanisms (including amorphization) that occur upon shock wave loading and unloading of silica. We apply DebyeGrüneisen theory to calculate both the Hugoniot of quartz and isentropic release paths. Quartz converts to stishovite between 15 and 46 GPa without undergoing pressure-induced amorphization and pe...

It has been shown that nitric oxide is synthesized in the central nervous system as well as in vascular endothelial cells. Recently, it was reported that nitric oxide was involved in central cardiovascular regulation, baroreflex modulation, and involved in a reciprocal release with excitatory amino acids in the nucleus tractus solitarii of rats. The purpose of the present study was to investiga...

The attenuation of high pressure shock waves has been investigated. High purity copper, 6061-T6 aluminum, 6A1-4V and a phase titanium, an uranium alloy and two alloys of beryllium were examined experimentally at pressures as high as 3 megabars. Low pressure experiments were instrumented with a velocity laser interferometer. Intermediate pressures (to several hundred kilobars) were instrumented ...

The consequences of an extrasystole (ES) on cardiac muscle's energetics and Ca2+ homeostasis were investigated in the beating heart. The fraction of heat release related to pressure development (pressure dependent) and pressure-independent heat release were measured during isovolumic contractions in arterially perfused rat ventricle. The heat release by a contraction showed two pressure-indepen...

a sustained-release tablet formulation should ideally have a proper release profile insensitive to moderate changes in tablet hardness that is usually encountered in manufacturing. in this study, matrix aspirin (acetylsalicylic acid) tablets with ethylcellulose (ec), eudragit rs100 (rs), and eudragit s100 (s) were prepared by direct compression. the release behaviors were then studied in two co...

in the present investigation an attempt has been made to increase therapeutic efficacy, to reduce frequency of administration and to improve patient compliance by developing a sustained release matrix tablets of isosorbide-5-mononitrate. sustained release matrix tablets of isosorbide-5-mononitrate were developed by using different drug: polymer ratios, such in f1 (1:0.75), f2 (1:1), f3 (1:1.5),...

Recent reports suggest that centrally induced increases in sympathetic outflow to the kidney have the potential to enhance the sensitivity of pressure-dependent renin release. In the present study, the possibility was investigated that spontaneously hypertensive rats (SHR), which are thought to have increased tonic sympathetic outflow to the kidney, exhibit enhanced renin release in response to...

Previous results indicate that arterial pulse pressure modulates release of arginine vasopressin (AVP) in humans. The hypothesis was therefore tested that an increase in arterial pulse pressure is the stimulus for suppression of AVP release during central blood volume expansion by water immersion. A two-step immersion model (n = 8) to the xiphoid process and neck, respectively, was used to atta...

Obstructive sleep apnea (OSA) is characterized by noradrenergic activation. Nasal continuous positive airway pressure (CPAP) is the treatment of choice and has been shown to effectively reduce elevated norepinephrine (NE) levels. This study examined whether the reduction in NE after CPAP is due to an increase in NE clearance and/or a decrease of NE release rate. Fifty CPAP-naive OSA patients wi...