Time of flight of carriers in simple aromatic hydro-carbon layers I: Theory

It has been found that the drift velocity of carriers in polycrystalline layers of simple aromatic hydrocarbons increases proportionally to the electric field and saturates at a field of 2×10⁶Vm^?>1. In addition it has been inferred that the predominant conduction mechanism in polycrystalline simple aromatic hydro-carbon layers is a hopping process between localized states within the “impurity” band at the Fermi level. A simple model to explain the phenomenon was put forward earlier. In this paper the problem is discussed more exactly, using the assumption that so-called “difficult” jumps of carriers play a significant role in the transport of carriers in polycrystalline simple aromatic hydrocarbon layers.     

Time of flight of carriers in simple aromatic hydro-carbon layers II: Comparison with experimental results

The change in the average distance between the localized states at the Fermi level, which form hopping paths, was calculated as a function of the electric field. The results of the calculations were used to obtain the dependence of the carrier drift velocity on the electric field. A comparison with experimental results was also made.     

含磷低聚醚的合成及聚氨酯阻燃发泡材料的制备

以甲基亚磷酸二甲脂合成了羟基封端的含磷低聚醚,并用邻苯二甲酸酐吡啶法测定了羟值,磷钼蓝法测定了磷含量,凝胶色谱法对其分子最进行了测定,采用红外对其结构进行了表征。并以此制备了阻燃聚氨酯发泡材料,研究了发泡材料的阻燃性能。结果表明,这种含磷的低聚醚能够有效提高聚氯酯泡沫的阻燃性能,且具有较好的水解稳定性。     

负温泵送混凝土性能研究

在大量实验的基础上，结合工程应用实例，从混凝土宏观性能出发，论述实现负温混凝土泵送施工的正确途径，提出使用防冻剂是负温泵送混凝土的关键。     

一种新的直齿轮双样条修形齿面设计

提出一种针对直齿轮的双样条修形方法,分别采用样条曲线来设计修形后齿面的齿廓线及齿向线,齿面由齿廓样条曲线沿齿向样条曲线扫掠得到.相对于传统复合修形,双样条修形方法的控制参数更多,使得齿面几何改变更灵活,并能实现全齿面点的更高阶次连续.通过有限元分析(FEA),对比分析了双样条修形的优越性,结果表明,双样条修形与传统复合...     

Beneficial effects of S-adenosyl-L-methionine on blood-brain barrier breakdown and neuronal survival after transient cerebral ischemia in gerbils

In the present study, the effect of bradykinin on basal and precontracted mouse-isolated trachea was investigated. In basal conditions mouse-isolated tracheal rings do not respond to bradykinin. However, when the tracheal rings were precontracted with carbachol (10(-7) M) a relaxation with bradykinin (3 x 10(-9)-3 x 10(-7)) was found. The maximal response amounted 69.7+/-4.1% (n=15) with a pD2 value of 7.2+/-0.21. The selective bradykinin B2 receptor antagonist HOE 140 (10(-10)-10(-8) M) antagonized the bradykinin-induced relaxation, while the bradykinin B1 receptor antagonist des-Arg9-Leu8-bradykinin (10(-6) M) had no influence. The selective bradykinin B1 receptor agonist des-Arg9-bradykinin (10(-6) M) caused a small relaxation (8.4+/-2.5%, n=6), which could be antagonized completely by the selective bradykinin B1 receptor antagonist des-Arg9-Leu8-bradykinin (10(-6) M) while addition of the selective bradykinin B2 receptor antagonist HOE 140 (10(-8) M) was without effect. In the presence of indomethacin (10(-6) M) the relaxation of bradykinin was completely abolished. Pretreatment of the tracheal rings with capsaicin, or the presence of the selective NK1 receptor antagonist RP 67851 (10(-6) M) or the presence of the nitric oxide synthase inhibitor L-NAME (3 x 10(-4) M) had no effect on the bradykinin-induced relaxation. In conclusion, these results demonstrate that the mouse-isolated tracheal is a preparation in which bradykinin exerts a relaxant response via stimulation of bradykinin B2 receptors. This response is probably mediated by prostaglandins.     

Immunogenic potential of glanders and melioidosis agents

Unlike the glanders agent, the superficial structures of the melioidosis agent were demonstrated to be responsible for marked was immunosuppressive activity. Some antigenic fractions suppressing the blast transformation of lymphocytes, reducing the count of T helpers and profoundly potentiating the infection in vivo were isolated from P. pseudomallei cells. The immunogenic and immunosuppressive activities of both agents' superficial structures were studied by high performance chromatography. Antigenic complexes that were able to protect immunized laboratory animals against fatal infections and to prevent bacterial carriage due to the activation of T cells and to the bacterial activity of macrophages were identified. A composition comprising several immunogens was found to provide an additive protective action against both causative agents. Therefore, the composition may be considered to be a prototype of a molecular antipseudomonadic vaccine.     

冷轧基料孔洞形成原因分析

对河北敬业集团1250车间冷轧基料的孔洞缺陷试样进行了分析,研究了缺陷位置处的宏观及微观特征。对冷轧基料和后续冷硬板缺陷进行扫描电镜和能谱分析后,确定了孔洞、重皮的原因,主要发生在炼钢的冶炼和连铸工序。通过提高钢水的纯净度、减少卷渣的产生、连铸坯的质量明显好转,冷轧基料的孔洞缺陷得到了控制。     

A histopathologic study of direct pulp-capping with adhesive resins

The concentration of heat-shock proteins of 70 kD (HSP70) in heart tissue has been shown to increase during transient myocardial ischaemia and to persist during several hours of reperfusion. In this study the relationship between the local myocardial HSP70 concentration and blood flow was addressed for control physiological conditions and acute myocardial ischaemia. A specific aim of this study was to address the question of whether low flow areas under control physiological conditions have undergone a transient ischaemia during the preceding hours and thus may be in a state of hibernation or stunning. In 12 anaesthetized, open-chest beagle dogs (6 control and 6 with 60-min coronary artery stenosis) heart rate, mean aortic pressure, mean arterial partial pressure of O2 and partial pressure of CO2 averaged 85+/-16 beats/min, 94+/-14 mmHg, 102+/-17 mmHg and 39+/-6 mmHg, respectively. Regional HSP70 and myocardial blood flow (RMBF) were measured using an HSP70-enzyme-linked immunosorbent assay and the tracer microsphere technique, respectively, in samples of 250 mg wet mass. In the control group the mean RMBF was 1.06+/-0.59 ml.min-1.g-1 and the local HSP70 concentration was 7.08+/-1.03 microg/mg cytosolic protein. Myocardial HSP70 showed a blood flow-independent regional biological heterogeneity, equivalent to a coefficient of variation of 0.31. Local HSP70 concentrations did not differ (P>0.05) between control low and high flow samples, 6.16+/-1.0 vs 6.08+/-0.75 microg/mg cytosolic protein, respectively. However, after 60 min of coronary artery occlusion the local HSP70 concentration increased from 7.08 +/-1.03 to 13.43+/-3.19 microg/mg cytosolic protein (P<0. 001). There was a significant inverse relationship between the percent reduction of local blood flow and HSP70 (r=-0.56, P<0.001). From these results it is concluded that: (1) low flow samples under control physiological conditions are unlikely to be in a state of hibernation or stunning since their HSP70 concentration is normal and (2) the increase in the local HSP70 concentration during myocardial ischaemia reflects the degree of impairment of O2 delivery.     

Comparative study between corpus cavernosum-electromyography findings and electron microscopy of cavernosal muscle biopsies in erectile dysfunction patients

BACKGROUND/AIMS: The colonic response to obstruction is poorly understood. Thickening of the proximal bowel following colonic stricture may be due to increased protein synthesis. We have investigated the colonic morphology and collagen concentration during the development of left-sided colonic obstruction in an animal model. METHODS: Twelve male Wistar rats received either a silk ligature obstruction of the colon 2.5 cm above the peritoneal reflection (n = 6) or manipulation of the left colon (controls, n = 6). Twenty-four hours later, three colonic specimens from the ligature zone and from 1 cm proximal and distal to this site, or from equivalent regions in controls, were assayed for hydroxyproline concentration. RESULTS: In controls there was no difference in hydroxyproline concentration between colonic sites. In obstructed rats, the hydroxyproline concentration was greater both at the ligature and distally, when compared with the proximal region. The hydroxyproline concentration was higher (p < 0.05) than corresponding control values at the ligature site (14.95 +/- 2.76 vs. 10.97 +/- 1.95 microgram/mg of dry tissue mean +/- s.d.) but not on either side. CONCLUSION: The colonic collagen concentration is equivalent or raised near an obstruction, demonstrating that obstructed colon may possess an enhanced capacity to hold sutures.