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71.
The composition of nitrous bases of phage FI-1 DNA was studied. As is evidenced from the values of buoyant density in CsCl (p=1,7093 g/cm(3)), melting temperature (T degrees m=86,05 degrees), spectral parameters and direct chromatographic determination, the DNA analysed contains 41,5 mole% pairs of guanine-cystosine. 5-hydroxymethylcytosine and other anomalous bases were not found. Chemical identification and jaxtposition of data of buoyant density in CsCl and Cs2SO4 (p=1,4466 g/cm(3)) and T degrees m. showed the presence of the extra-sugar component in DNA, most likely in the form of hentibiose. Spectral character of thermal denaturation of DNA in different solvents is indicative of the double helixity of its structure. DNA is characterized by enthalpies of conformational transitions "helix coil" (deltaH=12,3 kcal/g) and (deltaH=10 kcal/g) for the solvents, 1 x SSC, and 0,1 x SSC, correspondingly. The presence of extra-sugar in DNA with standard set of nitrous bases is discussed.  相似文献   
72.
Since 2009, the Spallation Neutron Source (SNS) has been producing neutrons with ion beam powers near 1 MW, which requires the extraction of ~50 mA H(-) ions from the ion source with a ~5% duty factor. The 50 mA are achieved after an initial dose of ~3 mg of Cs and heating the Cs collar to ~170 °C. The 50 mA normally persist for the entire 4-week source service cycles. Fundamental processes are reviewed to elucidate the persistence of the SNS H(-) beams without a steady feed of Cs and why the Cs collar temperature may have to be kept near 170 °C.  相似文献   
73.
The influence of surgical stress on resistance to i.v. challenge with Walker 256 tumour cells was investigated in rats, with respect to the functional state of the reticuloendothelial system (RES). Phagocytic activity of the RES was evaluated by colloid (gelatinized [131I] "RE test lipid emulsion") clearance, and opsonin levels were determined by bioassay. Reticuloendothelial clearance capacity was significantly (P less than 0-05) depressed 60 min following surgery (coeliotomy plus jejunal enterotomy) as quantified by both humoral and cellular parameters of RE function. Phagocytic depression was primarily due to impaired hepatic Kupffer cell function and related to a deficiency in the phagocytic supporting capacity of plasma, also referred to as opsonic or recognition factor (RF) capacity. During the postoperative period of RES colloid clearance depression, pulmonary localization of the blood-borne test particulate matter increased. Rats challenged with 51Cr-labelled viable tumour cells at a dose of 1-0 X 106 i.v., either prior to or during the postoperative period of RE depression, manifested a significant (P less than 0-05) increment in pulmonary localization of the viable tumour cells, and a decrease (P less than 0-05) in hepatic clearance. Evaluation of survival patterns demonstrated a significant (P less than 0-01) decrease in host resistance to i.v. tumour cell challenge (2 X 103 cells) during the postoperative period of RE depression and hypo-opsonaemia. Sham-anaesthetized control animals survived 17-9 +/- 0-8 days, while animals challenged during the period of RE depression survived 7-9 +/- 0-4 days. An increased incidence of respiratory distress and nasal discharge was observed in the animals with impaired survival. Thus, surgical manipulation may transiently compromise RES systemic host defence and may be reflected in an increment in the pulmonary localization of blood-borne tumour cells. The relationship of this altered pattern of tumour cell distribution to the impaired survival remains to be determined, and warrants investigations.  相似文献   
74.
The activity of glutamate dehydrogenase (EC 1.41.1.3) is studied in homogenates and subcellular fractions of five limbic structures: regio superior, regio inferior of hippocampus, fascia dentata, septum and corpora mamillaria. The lowest activity of the enzyme is found in regio superior of hippocampus. 80% of the total enzyme activity of primary fractions is found in "crude" mitochondria. After centrifugation of the latter within the linear sucrose density gradient the distribution of the enzume activity is similar for different structures and the highest activity is found in the region of sucrose molarity from 1.44 up to 1.50 M which corresponds to the mitochondria distribution region. 50% of the total found activity is in the fraction enriched by mitochondria, 30% is in the fraction enriched by nerve endings with the high activity of glutamate decarboxylase. It was found for different fractions that 1 mM of ADF with 0.2 mM NAD-H+ produces about 10-fold increase in the enzyme activity. Pyridoxal-5'-phosphate inhibits the enzyme from inactivation. The results are discussed in connection with the possible role of pyridoxal-5'-phosphate in regulation of the glutamate dehydrogenase activity in vivo.  相似文献   
75.
We present a systematic microscopic approach to diffusion and diffusion-limited processes in Ni3Al. These processes have been identified as controlling the deformation of the material under specific circumstances. The embedded atom method calculations are done using kinetic Monte Carlo combined with the Dimer method of finding saddlepoints. We compute the tracer diffusivities as functions of composition and temperature. The comparison with available experiments is good. We find that at temperatures below about 1000 K, the diffusivity is a sharp function of composition, showing a pronounced dip on the Ni-rich side at 76 at.% Ni. This agrees well with experiment, except that the experiments show this structure setting in a temperatures below about 1300 K. We show that the structure arises from the composition dependence of both the vacancy formation energy and pre-exponential of the diffusivity. We also compute the mobility of an anti-phase boundary perpendicular to its plane, and conclude that vacancy-assistance is very plausible. We conclude that the kMC + Dimer method works well for these problems above 700 K but less effectively below, owing to the presence of short-range, low-energy hops that tend to localize the vacancy and lower the efficiency of the calculation.  相似文献   
76.
Column-based dynamic power supply has been integrated into a high-frequency 70-Mb SRAM design that is fabricated on a high-performance 65-nm CMOS technology. The fully synchronized design achieves a 3-GHz operating frequency at 1.1-V power supply. The power supply at SRAM cell array is dynamically switched between two different voltage levels during READ and WRITE operations. Silicon measurement has proven this method to be effective in achieving both good cell READ and WRITE margins, while lowering the overall SRAM leakage power consumption.  相似文献   
77.
Students (N = 120) guilty of a mock crime, innocent and informed, or innocent and uninformed of crime details were examined by polygraph with an altered form of Control Question Test (CQT). Ambiguous, lie-engendering control questions were altered to form clear direct questions answered truthfully. When these control questions were positioned before crime-relevant questions, most guilty and innocent participants were correctly classified. Most participants were classed as guilty when crime-relevant questions were positioned before control questions. Lying to crime-relevant questions in the second position resulted in skin resistance, F(2,108) = 8.2, and blood volume, F(2, 108) = 6.1, responses larger than Orienting Responses to initial control questions. Accurate detection depends on the position of control questions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
78.
In this note we consider the following problem. Suppose a set of sensors is jointly trying to estimate a process. One sensor takes a measurement at every time step and the measurements are then exchanged among all the sensors. What is the sensor schedule that results in the minimum error covariance? We describe a stochastic sensor selection strategy that is easy to implement and is computationally tractable. The problem described above comes up in many domains out of which we discuss two. In the sensor selection problem, there are multiple sensors that cannot operate simultaneously (e.g., sonars in the same frequency band). Thus measurements need to be scheduled. In the sensor coverage problem, a geographical area needs to be covered by mobile sensors each with limited range. Thus from every position, the sensors obtain a different view-point of the area and the sensors need to optimize their trajectories. The algorithm is applied to these problems and illustrated through simple examples.  相似文献   
79.
This article reviews Computer Mediated Communications (CMC), encompassing the technology and its evaluation, with emphasis on factors crucial to the introduction of this technology in developing countries. The discussion of some promising application areas for developing countries includes education, networks of specialists, international committees and trade groups, and crisis detection and management. Also included is a summary of factors important to fostering and evolving the utilization of CMC technology.  相似文献   
80.
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