Renin, aldosterone and arterial pressure responses to acute beta-adrenergic receptor blockage in hypertensive patients

The effect of acute (intravenous) beta-adrenergic blockade with propranolol or pindolol on arterial pressure (BP), plasma renin activity (PRA), and plasma concentration of aldosterone (PA) was evaluated in 20 essential hypertensive men. BP, PRA and PA were determined during continuous recumbency over-night (8 p.m. to 6 a.m.) every 30 min. Two groups of patients were observed. Patients of group 1 exhibited a characteristic day-night rhythm of PRA with low values before midnight and large increases early in the morning. Conversely, no rhythm and very low PRA values were observed in patients of group II. BP was higher in group II than in group I. In group I following intravenous propranolol or pindolol, BP fell within minutes and levels as well as rhythms of PRA were converted to those of group II without treatment. In group II day-night profiles of PRA and BP remained unchanged. Rhythm and concentration of PA in the two groups were not influenced by either drug. In 4 patients of group I infusion of angiotensin II inhibitor did not lower BP. The observations suggest that in the two groups dissimilarities in rhythms of PRA as well as in BP responses to beta-blockade may reflect differences in neuro-adrenergic tone.     

Heat rate responses in patients with sinus node disease compared to controls: physiological implications and diagnostic possibilities

The autonomic regulation of heart rate was examined in 30 patients with symptoms of sinus node disease (SND) and 18 control subjects. Heart rate, expressed as sinus cycle length, was determined after injection of isoprenaline (0.1 microgram/kg), propranolol (0.1 mg/kg), and atropine (0.02 mg/kg); heart rate was also determined at maximal exercise and during carotid sinus stimulation. In addition, heart rate responses, expressed as the absolute change in sinus cycle length, were calculated. Mean heart rates after the applied maneuvers were all significantly different in the patient group, but so was the mean spontaneous heart rate. None of the induced changes differed significantly between the groups. Thus, although all these patients had impaired sinus node automaticity no uniform decrease in responsiveness to adrenergic or cholinergic stimulation or to inhibition of autonomic influences could be detected. The response patterns were heterogeneous, indicating diversity of the underlying mechanisms. No single heart rate reaction provided a satisfying diagnostic capacity for SND. However, the combined sensitivity of the three tests--isoprenaline stimulation, carotid sinus pressure, and autonomic inhibition--was 97% with a specificity of 50%. Clinically, normal findings in all these three tests, i.e., with resulting heart rates greater than 100, 55, and 70 beats/min, respectively, strongly suggest absence of SND.     

PAN基预氧化纤维不织布增强酚醛树脂制作炭/炭复合材料

以预氧化纤维不织布经不同热处理后,采用液态含浸法浸酚醛树脂后经热压成型,制成炭／炭复合材料前驱体,随之将这些前驱体经２３０℃稳定化,６００℃及１０００℃炭化处理,讨论了不同纤维不织布的结构变异,以及各种炭／炭复合材料其微细结构及物性之变化,在物性分析方面,主要是以挠曲强度的测试为骨架,并以扫瞄式电子显微镜（ＳＥＭ）观察破断表面,探讨各种复合材料经不同温度处理后之破坏行为,研究结果显示,以预氧化纤维及经６００℃处理后之纤维所制复合材料经三个不同温度（２３０℃,６００℃,１０００℃）处理后,其破坏行为均呈现剧烈的脆性破坏,且具有平滑之破断表面,而以经１０００℃处理后之纤维所制复合材料经６００℃及１０００℃炭化后则呈现拟塑性破坏模式,并伴随显著的纤维拖出现象。     

新型前处理工艺

为了克服传统磷化、钝化工艺存在的环境污染重、效率低、能耗大等缺陷,开发了新的环保型UniPrep 磷化工艺和Interlox钝化工艺.对新工艺与传统工艺所得涂膜的结合力、抗冲击强度、卷曲测试和盐雾试验进行了对比.结果表明,新工艺所得涂层均能达到甚至优于传统的磷化、钝化工艺的效果.新型金属表面处理工艺-UniPrep(R)和Interlox完全可以取代传统的磷化、钝化工艺.     

The Interaction between Otto Fuel II and Aqueous Hydroxylammonium Perchlorate (HAP), Part I: Initial Observations and Time‐to‐Event Measurements

Investigations have shown that a violent event (normally auto‐ignition) occurs after a relatively short period of time when the two immiscible liquids Otto Fuel II and 82% aqueous hydroxylammonium perchlorate (HAP) come into contact at temperatures between 30 °C and 50 °C. Under quiescent conditions the time from initial contact to an event (time‐to‐event) depends on the relative volumes of the liquids as well as the temperature but there is no significant difference between the time‐to‐event recorded in an open container and that recorded in a sealed container at the same temperature. It is concluded that key reactions in the build up to an event are taking place in both the Otto Fuel II and in the HAP solution.     

Surface characteristics of HA coated Ti-Hf binary alloys after nanotube formation

Ti-Hf binary alloys contained 10%, 20%, 30% and 40% (mass fraction)Hf were manufactured in the vacuum furnace system. And then, specimens were homogenized for 24 h at 1 000 °C in argon atmosphere. The formation of oxide nanotubes was conducted by anodic oxidation on the Ti-Hf alloy in 1 mol/L H₃PO₄ electrolytes containing small amounts of NaF at room temperature. The hydroxyapatite (HA) coating made of tooth ash prepared by electron-beam physical vapor deposition (EB-PVD) method. The corrosion behaviors of the specimens were examined through potentiodynamic test in 0.9% NaCl solution by potentiostat. The microstructures of the alloys were examined by field emission scanning electron microscopy (FE-SEM) and x-ray diffractometer (XRD). It was observed that the lamellar structure translated to needle-like structure with Hf contents. Nanotube formed and HA coated Ti-xHf alloys had a good corrosion resistance.     

Determining fracture toughness from cutting tests on polymers

A cutting test method has been developed for polymers and analysis schemes derived for the determination of the fracture toughness, G_c from the cutting data. The experimental scheme requires the measurement of forces for a cut of width b, in both the cutting direction, F_c/b and the transverse direction, F_t/b. Depths of cut were varied from 0.025 mm to 0.25 mm and the tool rake angle was varied from ?20° to 30°. Cutting was performed at a speed of 10 mm s^?1 on three polymers (HIPS, PA 4/6 and LLDPE). In addition, values of fracture toughness and yield strength were determined for the polymers using standard tests for comparison with the values obtained from cutting. Three analysis methods were derived to analyse the cutting data with the most favoured scheme based on an energy balance and using Merchant’s force minimisation criterion to determine the shear plane angle. This avoids the need to measure the cut chip thickness. Results for HIPS and PA 4/6 gave values of G_c in good agreement with the values determined via LEFM. However, the cutting method is intended for materials such as LLDPE which has a low yield stress and moderately high toughness, i.e. materials which cannot be tested using standard LEFM fracture mechanics tests. The cutting analysis appeared to give valid values of G_c for LLDPE in that they were independent of rake angle. There were some complications when analysing this polymer due to visco-elastic recovery effects in the chip and these have been considered. Finally, the cutting analyses always determined high values of yield stress which would appear to indicate work hardening.