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51.
Cell death associated with mitochondrial dysfunction is common in acute neurological disorders and in neurodegenerative diseases. Neuronal apoptosis is regulated by multiple proteins, including neuroglobin, a small heme protein of ancient origin. Neuroglobin is found in high concentration in some neurons, and its high expression has been shown to promote survival of neurons in vitro and to protect brain from damage by both stroke and Alzheimer’s disease in vivo. Early studies suggested this protective role might arise from the protein’s capacity to bind oxygen or react with nitric oxide. Recent data, however, suggests that neither of these functions is likely to be of physiological significance. Other studies have shown that neuroglobin reacts very rapidly with cytochrome c released from mitochondria during cell death, thus interfering with the intrinsic pathway of apoptosis. Systems level computational modelling suggests that the physiological role of neuroglobin is to reset the trigger level for the post-mitochondrial execution of apoptosis. An understanding of the mechanism of action of neuroglobin might thus provide a rational basis for the design of new drug targets for inhibiting excessive neuronal cell death.  相似文献   
52.
The author chronicles the way in which the Proceedings of the IRE documented and influenced the changes in electronic devices and systems that took place during the years from 1938 through 1962. The first years of this period were dominated by World War II and the development of radar systems and related devices such as the high-power cavity magnetron and the klystron. The first decade after the war brought the rapid development of television, digital computers, and the transistor. An important structural change that affected the Proceedings took place in 1948, when the IRE (Institute of Radio Engineers) established the professional group system. The period from 1956 through 1962 brought the advent of the space age, the integrated electronic circuit, and the laser. The Proceedings recorded another major institutional change in 1962, when the membership of the IRE voted to approve a merger with the American Institute of Electrical Engineers (AIEE) to form the IEEE  相似文献   
53.
. The feasibility of capturing As as calcium arsenate in reverberatory and Mitsubishi converter slags used in copper pyrometallurgy was studied by torsion-effusion, thermogravimetric, and mass spectrometric methods. In the temperature range from 1376 to 1489 K pure Ca3 (AsO4)2 decomposed to yield very low equilibrium pressures of AsO and O2. Mixtures of Ca3 (AsO4)2 with slag exhibited rapid mass losses between 973 and 1173 K. The vapor phase species evolved under these conditions were As2 and As4, indicating that the arsenate had been reduced by the slag to volatile elemental arsenic.  相似文献   
54.
The rate of E/Z isomerization for the propagating end in group transfer polymerization (GTP) of methyl methacrylate (MMA) is comparable to the rate of propagation for bifluoride catalysis, in contrast to bibenzoate catalysis where propagation is faster. Methyl 2,2,4-trimethyl-5-methoxy-5-(trimethylsiloxy)pent-4-enoate, 4 (the product of the initiation step in the GTP of MMA), was used as the model of the GTP living end. The rate of monomer addition to 4 was independent of the starting E/Z isomer ratio. The observation of random tacticity in the polymers prepared via anionically catalyzed GTP can be adequately explained by comparable rates of E/Z isomerization and propagation or in the case of bibenzoate catalysis, by the assumption that E and Z propagating ends react with similar stereochemistry. Silyl ketene acetal 2 (a model of the polyacrylate propagating end) underwent HgI2 catalyzed E/Z isomerization at a rate comparable to the polymerization of ethyl acrylate.  相似文献   
55.
The relaxation behavior of several epoxy resin systems, which have systematic structural differences, has been studied by the thermally stimulated discharge (TSD) technique. Two TSD peaks centered at about 115°K (β peak) and 185°K (β peak) were found for epoxy resins cured with a diamine. Structural change, either in the epoxy resin molecule or the amine molecule, did not seem to affect those two peaks. The TSD thermogram of the DGEBA (diglycidyl ether of disphenol A) epoxy resin part only showed a small new peak at 160°K instead of the ft peak at 185°K. This result, together with the fact that postcuring increased β peak height, leads to the conclusion that the ft peak is most likely due to the newly-created molecular segment during the curing reaction. The peak at 160°K was assigned to the epoxy group. This assignment was based on the fact that the 160°K peak of an epoxy homopolymer, which has fewer epoxy groups, was smaller than that of the parent DGEBA. The β and γ peaks were found to be of distributed characteristics, and the distribution of activation energy was studied by the partial heating method.  相似文献   
56.
The purpose of this test was to evaluate the effects of calcium magnesium acetate (CMA) and sodium chloride (NaCl)??two common substances used to de-ice roadways??on the corrosion and fatigue behavior of annealed AISI 4140 steel. When CMA-corroded, NaCl-corroded, and as-machined samples were tested using R?=?0.1, and f?=?20?Hz, it was found that, within the scope of this study, samples corroded in both 3.5% CMA solution and 3.5% NaCl solution exhibited a lower fatigue strength than samples tested in the as-machined, uncorroded condition. For the short lives tested in this study, the difference in the effects of CMA and NaCl is minimal. However, at longer lives it is suspected, based on the trends, that the CMA solution would be less detrimental to the fatigue life.  相似文献   
57.
This paper presents results of testing models for the radioactive contamination of river water and bottom sediments by 90Sr, 137Cs and 239,240Pu. The scenario for the model testing was based on data from the Techa River (Southern Urals, Russia), which was contaminated as a result of discharges of liquid radioactive waste into the river. The endpoints of the scenario were model predictions of the activity concentrations of 90Sr, 137Cs and 239,240Pu in water and bottom sediments along the Techa River in 1996. Calculations for the Techa scenario were performed by six participant teams from France (model CASTEAUR), Italy (model MARTE), Russia (models TRANSFER-2, CASSANDRA, GIDRO-W) and Ukraine (model RIVTOX), all using different models. As a whole, the radionuclide predictions for 90Sr in water for all considered models, 137Cs for MARTE and TRANSFER-2, and 239,240Pu for TRANSFER-2 and CASSANDRA can be considered sufficiently reliable, whereas the prediction for sediments should be considered cautiously. At the same time the CASTEAUR and RIVTOX models estimate the activity concentrations of 137Cs and 239,240Pu in water more reliably than in bottom sediments. The models MARTE (239,240Pu) and CASSANDRA (137Cs) evaluated the activity concentrations of radionuclides in sediments with about the same agreement with observations as for water. For 90Sr and 137Cs the agreement between empirical data and model predictions was good, but not for all the observations of 239,240Pu in the river water-bottom sediment system. The modelling of 239,240Pu distribution proved difficult because, in contrast to 137Cs and 90Sr, most of models have not been previously tested or validated for plutonium.  相似文献   
58.
In 1958, the American Institute of Electrical Engineers (AIEE) selected Charles F. Kettering as the recipient of the Edison Medal. He was cited "for invention, research, and development in the broad fields of industry, engineering, transportation, medicine, education, energy, and power resulting in service to all mankind. "He was elected a Fellow of the AIEE in 1914. Remembered especially for his early work on electric self-starters for automobiles, he received 185 patents for inventions in several fields and also became known for his philanthropy later in life.  相似文献   
59.
Hot stage was used to investigate dislocation loop formation and growth at climb sources in Al rich alloys of β-NiAl. The loops grew by absorbing vacancies retained during cooling of the samples. The growth rate was dependent on the speed of cooling and anomalously high growth of loops occurred near the foil surfaces. The loop shapes were nearly square as a result of loop growth by a jog mechanism. Estimates of the vacancy concentration contained in the loops after growth demonstrated that nearly all thermal vacancies can be retained in NiAl.  相似文献   
60.
Productivity in the information age is widely perceived to be a major organizational problem. One strategy for enhancing organizational productivity has been the use of task teams. Assignment to task teams is usually based on individual technical expertise, individual availability, and/or positional politics rather than on the effectiveness of the team members in the specific organizational situation. This paper investigations characteristics of team members and then examines the effect of these characteristics and the requirements of the organizational task on team effectiveness.The findings indicate that the perceptual types of team members and the task structure impacts team effectiveness. It lends evidence that heterogeneity of perceptual types is best for solving unstructured tasks whereas heterogeneity can be counter-productive when solving structured tasks. It also suggests that one team might not be appropriate for all stages of a project. As the structure of the tasks change, the optimum team composition might also change.  相似文献   
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