外保护环短路不能减小光电二极管暗电流

通过理论和实验证明了外保护环短路的光电二极管不仅不能减小暗电流,相反会增加暗电流。因此想用外保护环短路,以求减小光电二极管暗电流的方法是不可行的。其结果与预期的正好相反。

光探测与器件

TN364.2 2000053512外保护环短路不能减小光电二极管暗电流=Impossibilityof decrease in dark carrent of guard ringshort circuited photodiodes[刊,中]/何民生,黄启俊(武汉大学光电技术系.湖北,武汉(430027))//半导体光电.—1999,20(6).

Effects of pH management during deep hypothermic bypass on cerebral oxygenation： alpha-stat versus pH-stat

Objective: There is a remarkable lack of scientific evidence to support the option to use alpha-stat or pH-stat management, as to which is more beneficial to brain protection during deep hypothermic CPB. This study examined cortical blood flow (CBF), cerebral oxygenation, and brain oxygen consumption in relation to deep hypothermic CPB with alpha-stat or pH-stat management. Methods: Twenty-two pigs were cooled with alpha-stat or pH-stat during CPB to 15℃ esophageal temperature. CBF and cerebral oxygenation were measured continuously with a laser flowmeter and near-infrared spec-troscopy, respectively. Brain oxygen consumption was measured with standard laboratory techniques. Results: During CPB cooling, CBF was significantly decreased, about 52,2%±6.3% (P<0.01 vs 92.6%±6.5% of pH-stat) at 15℃ in alpha-stat, whereas there were no significant changes in CBF in pH-stat. While cooling down, brain oxygen extraction (OER) progressively decreased, about 9.5%±0.9% and 10.9%±1.5% at 15℃ in alpha-stat and pH-stat, respectively. At 31℃ the decreased value in pH-stat was lower than in alpha-stat (29.9%±2.7% vs 22.5%±1.9%; P<0.05). The ratio of CBF/OER were 2.0±0.3 in alpha-stat and pH-stat, respectively; it was kept in constant level in alpha-stat, and significantly increased by 19 ℃ to 15℃ in pH-stat (4.9±0.9 vs 2.3±0.4; P<0.01). In mild hypothermia, cerebral oxyhemoglobin and oxygen saturation in alpha-stat were greater than that in pH-stat (102.5%±1.4% vs 99.1%±0.7%; P<0.05). In deep hypothermia, brain oxygen saturation in pH-stat was greater than that in alpha-stat (99.2%±1.0% vs 93.8%±1.0%; P<0.01), and deoxyhemoglobin in pH-stat decreased more greatly than that in alpha-stat (28.7%±6.8% vs 54.1%±4.7%; P<0.05). Conclusions: In mild hypothermic CPB, brain tissue oxygen saturation was greater in alpha-stat than in pH-stat. However, cerebral oxygenation and brain tissue oxygen saturation were better in pH-stat than in alpha-stat during profound hypothermia. PH-stat strategy provided much more oxygen to brain tissue before deep hypothermic circulatory arrest.

Vegetation actualities and feasibility of restoration for the periphery of oasis in extreme arid region: taking Qira County of Xinjiang as an example

The periphery of oasis plays an important role in mutual transformation between desert and oasis. Vegetation is an important part in the ecosystem and it is an important index indicating certain landscape, Based on several times field investigation, this paper attaches importance to the feasible measures for vegetation restoration according to the current condition of study area - Qira County of Xinjiang Uygur Autonomous Region, In order to improve die local ecological environment, people lived in Qira County should work bard to protect their homehind and reduce the degree of sandstorm, More protection forest should be established along with other ecological techniques. Results derived from this study contribute largely to the ecological environmental protection of oasis.

The impact of foreign trade and FDI on environmental pollution

Over the past 30 years China＇s economy has made tremendous development and going on the road of opening-up is an important aspect of the successful experience, which should be unswervingly adhered to in the further. However, rationally looking at how different the impact of foreign economic activities on China＇s economy and society is economic workers＇ main task. From 1982 to 2006, based on six categories of China＇s environmental indicators, the paper improves the entropy method to calculate the environmental pollution index which can represent China＇s overall environmental situation, uses the VAR model of the impulse response function and variance decomposition method to study the impact of foreign trade, FDI on China＇s environmental pollution in the long-term. The results show that, FDI and import trade is conducive to the improvement of the quality of our environment and export trade is the deterioration of our environment, ＂pollution haven＂ hypothesis is proved in China. Export trade is an important variable that aggravates environmental pollution.

Quality-Oriented Facade Systems： Technical Data Referred to Maintenance Phase and Residual Value

Nowadays, clients require solutions that are efficient during the service life as a whole. In this view, maintenance has functional value and greatly contributes to increasing quality in environments. With reference to maintenance phase and residual value of building products upon dismantling, the present manuscript investigates a set of technological packages of quality and technical value referred to two alternative facade systems available for recovery actions on Italian council buildings--the ETICS （external thermal insulation composite system） and the external cladding system--complying with one thermal-insulation strategy, but different in terms of service life duration. Preservation of technical value and value increases are strictly related to maintenance quality and efficiency. Volume of investments in maintenance is not the only parameter to be considered to assess facade-system-management quality. Time-accurate economic assessment requires the entity to be related to periodical checks on performance quality in the building system and in its parts. Effective technical data to draw up consistent estimates and appraisals are rarely available in literature. With all that stated above, the present manuscript aims at introducing technical data related to drawing up reliable cost estimates and effective appraisals in terms of economics, quality and environmental sustainability. Conclusions will be drawn from the end of the manuscript.

Environmental Effects of Foreign Trade and Its Spatial Variations in Mid-eastern Provinces and Cities of China

The studies on environmental effects of foreign trade and its spatial variations are helpful to design and implement environmental protection countermeasures.In order to eliminate the adverse effects of insufficient observation values on the accuracy of regression results and dynamic information quantity of fitting equation during empirical study,panel data of the mid-eastern provinces and cities of China from 1985 to 2007 were selected based on the adjustment of classical regression model in this paper.Panel unit root test and panel cointegration analysis method were applied to investigating the environmental effects of foreign trade and its spatial variations in the mid-eastern provinces and cities of China and its three groups divided by foreign trade dependence.The results show that all scale effects are positive,while all technical effects are negative and unable to counteract positive scale effects.Foreign trade development is regarded as an important cause for outstanding eco-environmental problems in the mid-eastern provinces and cities of China.Total effects and structural effects are significantly different among different groups because of spatial variations in environmental policies,export destinations,source of FDI,etc.Following the principle of′coordinating generality and considering differences comprehensively′,it is essential to issue a series of policies and countermeasures corresponding to differences in regional environmental effect of foreign trade,in order to coordinate the relationship between foreign trade development and eco-environment in each region.

Study on the Foreign Eco-tourism Environment Protection Act and Its Enlightenment

China, as a power in ecotourism resources, is luxuriant in eco-tourism resources. With the continuous expansion of the ecological tourism market, however, the ecological tourism environment protection problems are becoming acute. Then, the ecological tourism will be in a fatal blow in China if the ecological tourism environment is not being protected. Therefore, improving China＇ s ecological tourism environmental protection legal system is of important practical significance to the sustainable development of tourism on the basis of introducing the experience of developed countries in ecotourism environmental protection act.

Research on the Prevention Methodologies and Environmental Protection Countermeasures for Oil Pollution based on Latest Techniques from China and Abroad

In this paper, we conduct research on the prevention methodologies and environmental protection countermeasures for oil pollution based on latest techniques from China and abroad. Petroleum and petrochemical industry will also be able to have serious water pollution. Against oil pollution increasingly serious phenomenon, about how to control oil pollution has also carried on the thorough research and accumulated in the process of specific management experiences and lessons. We conduct theoretical analysis between the state-of-the-art methods of environmental protection countermeasures with examples, We firmly believe that more advances will occur in the future.

Myocardial protection with pinacidil induced hyperpolarized arrest during cardiopulmonary bypass

Objective To investigate the myocardial protective effects of pinacidil induced hyperpolarized arrest and compare with those afforded by conventional depolarized hyperkalemic arrestMethods Eighteen dogs were equally divided into three groups: normothermic hyperpolarized group (Group A), hypothermic hyperpolarized group (Group B), and hyperkalemic group (Group C) Pinacidil (50μmol/L) containing 37℃ St Thomas solution (K+5mmol/L, 10ml/kg), pinacidil (50μmol/L, Sigma, USA) containing 4℃ St Thomas solution (K+ 5mmol/L, 10ml/kg) and 4℃ standard St Thomas solution (K+ 16mmol/L, 10ml/kg) were infused respectively through the aortic root after aorticclamping Heart arrest and its recovery, ultrastructure of the myocardium, the level of serum myocardial enzymes, and lipid peroxide and adenine cleotide of the myocardium were measuredHemodynamics during ischemia and after reperfusion were observedResults The percentages of normal mitochondria and glycogen did not change much during ischemia (except at 60 min) and after reperfusion in B Group, but declined markedly in Group C 30 min and 60 min after ischemia and 20 min after reperfusion (P<0.01) In Group A,they were lower than those of Group B before ischemia, but higher than those of Group C The recoveries of CO, SV, CI, LVSW, RVSW and MAP in Group B were significantly better than those in other two groups 15 min and 30 min after reperfusion (P<0.05and0.01, respectively) However, they were still better in Group A than those in Group C(P<0.05 and 0.01, respectively)The onset of heart arrest was faster in Groups C and B than that in Group A Highly elevated serum myocardial enzymes were observed 60 min after ischemia and 20 min after reperfusion in Group C, while they were only mild in the hyperpolarized groups, especially in Group B, and their recoveries were rapid Adenine nucleotides of the myocardium were better preserved in Group B than in other two groups 30 min, 60 min after ischemia, and 20 min after reperfusion (P<0.05 and 0.01, respectively)They were also much better in Group A than in GroupC(P<0.05and0.01,respectively)Lipid peroxide of the myocardium were significantly lower in Group B than in other groups 20 min after reperfusion (P<0.01),and they were lower in Group A than in Group C(P<0.05) Conclusions Myocardial protection for global ischemia during cardiopulmonary bypass (CPB) could be achieved with hyperpolarized heart arrest induced by pinacidil, an ATP sensitive potassium channel opener,especially in the hypothermic state The protection is weaker in normothermia but is still superior to that with traditional depolarized hyperkalemic arrest

半导体二极管

Y99-61799-613 0007497在倍频器应用性能研究中的双势垒谐振隧道二极管=Double barrier resonant tunneling diodes in frequencymultiplier applications performance study[会,英]/Necu-loiu,D.& Dobrescu,D.//Proceedings of 1998 Interna-tional Semiconductor Conference.Vol.2.—613～616(UG)