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991.
The present paper deals with the inhibition of the specific activity of the acid and alkaline phosphatases in the kidney tissue of mudskipper Boleophthalmus dentatus, exposed to different sublethal concentrations of mercuric chloride. There was a more or less linear inhibition of the specific activity of both the enzymes with increasing concentration of mercuric chloride as well as exposure time. The inhibition of acid phosphatase could be due to the rupture of lysosomal membrane in the presence of mercury compound, which acts as a labilizing agent. The inhibition of alkaline phosphatase probably caused a breakdown of the membrane transport system. 相似文献
992.
H. Tissoux H. Valladas P. Voinchet J.L. Reyss N. Mercier C. Falguères J.-J. Bahain L. Zöller P. Antoine 《Quaternary Geochronology》2010,5(2-3):131-136
As part of a chronological study of the famous Upper Pleistocene Nussloch (Germany) loess sequence, three samples were collected to check the applicability of palaeodosimetric dating methods (OSL and ESR) to quartz grains. The ESR-multicentre method showed a partial bleaching of the ESR centers in aeolian sands. This partial bleaching was also observed by OSL. Laminated loess seemed to be sufficiently bleached but showed a large scatter of the doses, which we ascribed to heterogeneous responses of the luminescent grains to the SAR protocol. Ages could nevertheless be calculated for the three samples and were found to be somewhat older than the IRSL and 14C ages obtained for the same layers of the laminated loess. 相似文献
993.
Abstract. A hydrologic test system has been designed to measure the intrinsic permeabilities of individual fractures in crystalline rock. This report contains the design schematics and specifications necessary to build and/or modify this test system for other similar field applications. This system is used to conduct constant pressure/declining flow rate and pressure pulse hydraulic tests. The system is composed of four distinct units: (1) The Packer System, (2) Injection System, (3) Collection System, and (4) Electronic Data Acquisition System. The apparatus is built in modules so it can be easily transported and reassembled. It is also designed to operate over a wide range of pressures (0–300 psig) and flow rates (0.2–1.0 gal/min). This system has proved extremely effective and versatile in its use at the Climax Facility, Nevada Test Site. 相似文献
994.
New solutions of the equations of the bimetric scalar-tensor theory of gravitation for neutron stars are found. In these solutions the scalar field is constant, φ = φφ, while the metric space-time tensor is determined by the equations of the general theory of relativity. The problem was to find a background metric corresponding to φφ. Solutions with a variable φ were studied earlier [M. R. Avakian, L. Sh. Grigorian, and A. A. Saharian, Astrofizika, 35, 121 (1991)] and are determined by the dimensionless parameter ζ of the theory. Differences between solutions with constant and variable ? are considerable for ¦ζ¦ ≤ 1. 相似文献
995.
B. P. GLASS D. W. MUENOW B. F. BOHOR G. P. MEEKER 《Meteoritics & planetary science》1997,32(3):333-341
Abstract— An examination of data collected over the last 30 years indicates that the percent of glass fragments vs. whole splash forms in the Cenozoic microtektite strewn fields increases towards the source crater (or source region). We propose that this is due to thermal stress produced when tektites and larger microtektites fall into water near the source crater while still relatively hot (>1150 °C). We also find evidence (low major oxide totals, frothing when melted) for hydration of most of the North American tektite fragments and microtektites found in marine sediments. High-temperature mass spectrometry indicates that these tektite fragments and microtektites contain up to 3.8 wt% H2O. The H2O-release behavior during the high-temperature mass-spectrometric analysis, plus high CI abundances (0.05 wt%), indicate that the North American tektite fragments and microtektites were hydrated in the marine environment (i.e., the H2O was not trapped solely on quenching from a melt). The younger Ivory Coast and Australasian microtektites do not exhibit much evidence of hydration (at least not in excess of 0.5 wt% H2O); this suggests that the degree of hydration increases with age. In addition, we find that some glass spherules (with <65 wt% SiO2) from the upper Eocene clinopyroxene-bearing spherule layer in the Indian Ocean have palagonitized rims. These spherules appear to have been altered in a similar fashion to the splash form K/T boundary spherules. Thus, our data indicate that tektites and microtektites that generally contain >65 wt% SiO2 can undergo simple hydration in the marine environment, while impact glasses (with <65 wt% SiO2) can also undergo palagonitization. 相似文献
996.
997.
998.
This paper describes an alternative approach for generating pointing models for telescopes equipped with serial kinematics, esp. equatorial or alt-az mounts. Our model construction does not exploit any assumption for the underlying physical constraints of the mount, however, one can assign various effects to the respective components of the equations. In order to recover the pointing model parameters, classical linear least squares fitting procedures can be applied. This parameterization also lacks any kind of parametric singularity. We demonstrate the efficiency of this type of model on real measurements with meter-class telescopes where the results provide a root mean square accuracy of 1.5?2 arcseconds. 相似文献
999.
1000.