共查询到19条相似文献,搜索用时 15 毫秒
1.
2.
3.
4.
5.
6.
7.
Is there a decline in marine phytoplankton? 总被引:1,自引:0,他引:1
McQuatters-Gollop A Reid PC Edwards M Burkill PH Castellani C Batten S Gieskes W Beare D Bidigare RR Head E Johnson R Kahru M Koslow JA Pena A 《Nature》2011,472(7342):E6-7; discussion E8-9
8.
9.
10.
11.
MOMMAERTS WF 《Nature》1954,174(4441):1083-1084
12.
13.
14.
Extensional structures developed extensively in Himalaya with their strikes perpendicular to that of the orogenic belt. The
studies of such structures in Qusum, Burang, Lhozhag, Nyalam and Yadong show that they represent an orogen-parallel extension.
The basins produced by the extension experienced orogen-perpendicular compression during their formation. The ages of the
extension rang from 16 to 13 Ma and coincide with the intensive compressive stage in Southeastern Asia. Therefore, the extension
is syn-shortening and the dominate tectonic movement in Himalaya was compression and uplift during the extension. The extension
was the partition of compressive deformation rather than the indicator for the collapse and falling of the Tibetan Plateau. 相似文献
15.
Xiang-Kun Dong Vadim Baru Feng-Kun Guo Christoph Hanhart Alexey Nefediev Bing-Song Zou 《科学通报(英文版)》2021,(24):2462-2470
In a recent measurement LHCb reported pronounced structures in the J/ψJ/ψ spectrum.One of the var-ious possible explanations of those is that they emerge from n... 相似文献
16.
The diffuse interstellar bands (DIBs), ubiquitous absorption features in astronomical spectra, have been known since early this century and now number more than a hundred. Ranging from 4,400 angstroms to the near infrared, they differ markedly in depth, width and shape, making the concept of a single carrier unlikely. Whether they are due to gas or grains is not settled, but recent results suggest that the DIB carriers are quite separate from the grains that cause visual extinction. Among molecular candidates the polycyclic aromatic hydrocarbons (PAHs) have been proposed as the possible carriers of some of the DIBs, and we present here laboratory measurements of the optical spectrum of the pyrene cation C16H10+ in neon and argon matrices. The strongest absorption feature falls at 4,435 +/- 5 angstroms in the argon matrix and 4,395 +/- 5 angstroms in the neon matrix, both close to the strong 4,430-angstroms DIB. If this or a related pyrene-like species is responsible for this particular band, it must account for 0.2% of all cosmic carbon. The ion also shows an intense but puzzling broad continuum, extending from the ultraviolet to the visible, similar to what is seen in the naphthalene cation and perhaps therefore a common feature of all PAH cations. This may provide an explanation of how PAHs convert a large fraction of interstellar radiation from ultraviolet and visible wavelengths down to the infrared. 相似文献
17.
Solid-state reaction of a CaO?V2O5 mixture: A fundamental study for the vanadium extraction process 下载免费PDF全文
The aim of this study was to investigate the phase transformation and kinetics of the solid-state reaction of CaO?V2O5, which is the predominant binary mixture involved in the vanadium recovery process. Thermal analysis, X-ray diffraction spectroscopy, scanning electron microscopy, and energy dispersive spectrometry were used to characterize the solid-state reaction of the samples. The extent of the solid reac-tion was derived using the preliminary quantitative phase analysis of the X-ray patterns. The results indicate that the solid reaction of the CaO?V2O5 mixture is strongly influenced by the reaction temperature and CaO/V2O5 mole ratio. The transformation of calcium vanadate in-volves a step-by-step reaction of CaO?V2O5, CaO?CaV2O6, and CaO?Ca2V2O7 depending on the CaO/V2O5 mole ratio. The kinetic data of the solid reaction of the CaO?V2O5 (1:1) mixture followed a second-order reaction model. The activation energy (Ea) and preexponential factor (A) were determined to be 145.38 kJ/mol, and 3.67 × 108 min?1, respectively. 相似文献
18.
Xiufan Shi Jingfei Huang Chongrong Liang Shuqun Liu Jun Xie Ciquan Liu 《科学通报(英文版)》2001,46(12):1015-1019
Synonymous codon bias has been examined in 78 human genes (19967 codons) and measured by relative synonymous codon usage (RSCU). Relative frequencies of all kinds of dinucleotides in 2,3 or 3,4 codon positions have been calculated, and codon-anticodon binding strength has been estimated by the stacking energies of codon-anticodon bases in Watson-Crick pairs. The data show common features in synonymous codon bias for all codon families in human genes: all C-ending codons, which possess the strongest codon-anticodon binding energies, are the most favored codons in almost all codon families, and those codons with medium codon-anticodon binding energies are avoided. Data analysis suggests that besides isochore and genome signature , codon-anticodon binding strength may be closely related to synonymous codon choice in human genes. The join-effect of these factors on human genes results in the common features in codon bias. 相似文献