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991.
992.
S. V. Kalenskii S. Kurtz V. I. Slysh P. Hofner C. M. Walmsley L. E. B. Johansson P. Bergman 《Astronomy Reports》2010,54(10):932-939
We present the results of VLA observations of a maser candidate in the low-mass star formation region L1157 in the 70-61 A + transition at 44 GHz. The line is emitted by a compact, undoubtedly maser source associated with clump B0a, which is seen in maps of L1157 in thermal lines of methanol and other molecules. A much weaker compact source is associated with clump B1a, which is brighter than B0a in thermal methanol lines. The newly detected masers may form in thin layers of turbulent post-shock gas. In this case, the maser emission may be beamed, so that only an observer located in or near the planes of the layers can observe strong masers. On the other hand, the maser lines are double with a “red” asymmetry, indicating that the masers may form in collapsing clumps. A detailed analysis of collapsing-cloud maser models and their applicability to the masers in L1157 will be developed in subsequent papers. 相似文献
993.
M. Villalobos D. G. García-Payne J. L. López-Zepeda A. E. Ceniceros-Gómez M. E. Gutiérrez-Ruiz 《Aquatic Geochemistry》2010,16(2):225-250
Arsenic from natural and anthropogenic sources is a worldwide contaminant of aqueous environments, such as groundwater and soils. The present investigation was performed on Mexican soils contaminated with residues from metallurgical processes that have shown a natural As attenuation. Experimental aqueous arsenic extractions in these were successfully simulated for almost half of the soil samples using a database updated for all known metal arsenate formation constants, revealing the predominance of solubility-controlled As mobility via Pb, mixed Pb–Cu, and Ca arsenate solid formation. The relatively low total Fe/As ratios (2–13 w/w) present in the soils studied, together with the high and equivalent contents of As, Pb, and Cu in these, favor the precipitation process over As(V) adsorption to Fe oxides, despite a 2% average Fe content in the soils studied. Under these conditions bicarbonate was found to be a highly unsuitable extractant due to its indirect As release from the solid arsenates, via heavy metal carbonate precipitation processes. 相似文献
994.
Lü Songhui Chao Aimin Liang Qianyan Cen Jingyi Wang Jianyan Jiang Tao Li Si 《中国海洋湖沼学报》2022,40(6):2146-2163
Journal of Oceanology and Limnology - The naked dinoflagellate Takayama acrotrocha was identified as responsible for a bloom in Shenzhen Bay, Guangdong, China, in early spring 2021. The... 相似文献
995.
Journal of Oceanology and Limnology - Salt stress is an abiotic stress to plants in especially saline lakes. Dunaliella, a halophilic microalga distributed throughout salt lakes and seas, can... 相似文献
996.
997.
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
998.
This list is based on 20 stars in the solar neighborhood for which there are 52 spectra. Twelve of them are known as UV Ceti flare stars. The others behave like flare stars, but are not known to be such. Among the 20 there are many binary and triple flare stars. They all belong to the disk population of the Galaxy. Red dwarfs comprise one of the numerous populations of the system. Flare stars either continue to flare or have ceased flare activity. Three diagrams are given that show satisfactory agreement with the expected ones. A cluster analysis is carried out, which is in agreement with the original proposition and confirms the foregoing. 相似文献
999.
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
1000.