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排序方式: 共有264条查询结果,搜索用时 15 毫秒
1.
In order to obtain a continuous source of mitotic metaphases, gill tissue of Aphaius fasciatus (Pisces, Cyprinodontiformes) has been successfully employed. Results gathered after exposure of fish to R2SnClpenG, R3SnClpenGNa, to the parents R2SnCl2, R3SnCl and to penGNa (penGNa = penicillinGNa; R = methyl, butyl and phenyl) suggest that both the parent organotin (IV) chloride and organotin (IV) chloropenG derivatives are toxic while penGNa exerts no significant toxic activity. Essentially, all of the chromosome abnormalities are classifiable as irregularly staining of chromosomes, breakages, side-arm bridges or pseudochiasmata. 相似文献
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3.
研究非保守力和非完整约束对Hamilton系统的Lie对称性和守恒量的影响.分别研究了Hamilt on系统受到非保守力和非完整约束作用时,系统的Lie对称性保持不变的条件,同时给出了 系统的结构方程和守恒量保持不变的条件.以著名的Emden方程和Appell-Hamel模型为例进行 了分析讨论.
关键词:
分析力学
Hamilton系统
非保守力
非完整约束
对称性
守恒量 相似文献
4.
In proportion to the environmental pollution problems caused by organotin compounds, the genotoxicities of tin compounds in the environments have become of interest so as to estimate their safety in recent years. In this work, isolated λ-DNA (double-strand DNA) was incubated with inorganic tin(II) and tin(IV) and five organotin compounds [n-butyltin trichloride, di(n-butyltin) dichloride, methyltin trichloride, dimethyltin dichloride and trimethyltin chloride] in reaction systems both with and without hydrogen peroxide (H2O2) content. The tin compounds tested in this study did not induce DNA breakage in the absence of hydrogen peroxide. Divalent inorganic tin (SnCl2) and tetravalent inorganic tin (SnCl4) caused DNA breakage in the presence of hydrogen peroxide (10 mM), and the DNA damage activity of inorganic tin was much more potent in divalent inorganic tin (SnCl2) than in tetravalent inorganic tin (SnCl4). Divalent inorganic tin (SnCl2) induced DNA breakage in a concentration-dependent fashion at concentrations greater than 0.1 mM of SnCl2 in the presence of hydrogen peroxide (10 mM). DNA breakage was not caused by n-butyltin compounds and methyltin compounds either in the presence or in the absence of hydrogen peroxide. 相似文献
5.
An Improvement of IAP OGCM for the Pacific Ocean Circulation and Its Simulated Results 总被引:2,自引:0,他引:2
Based on the oceanic CCM with standard stratification subtraction but without the rigid-lid approximation designed in Institute of Atmospheric Physics (IAP OGCM) and its numerical modelings for the large-scale ocean circulation, a numerical model for the Pacific Ocean is developed with higher resolution (2.5°×2° in the longitude and latitude, 8 layers in the vertical),the realistic coastline geometry,the smoothed bottom topography and the Richardson number dependent vertical mixing parameterization.The splitting time integration scheme of the barotropic and baroclinic modes is adopted in the model. The numerical simulation under the annual mean atmospheric forcing shows that the model performance is improved substantially compared with the previous low resolution version.This free surface model,in particular, successfully simulates the well-known ridge-trough structure in the sea level, i.e. the equatorial trough, the equatorial ridge near 3°N, the north countercurrent trough between 8°N and 10°N, 相似文献
6.
When food containing fat is treated by ionizing radiation, a group of 2-alkylcyclobutanones is formed. These components contain the same number of carbon atoms as their precursor fatty acids and the alkyl group is located in ring position 2. Thus, from palmitic acid 2-dodecylcyclobutanone is derived. To date, there is no evidence that the cyclobutanones occur in unirradiated food. Therefore, these components cannot be considered inherent to food, and for questions pertaining to risk assessment of irradiated food it would be advisable to determine the genotoxic and toxic potentials of cyclobutanones. Measurements of DNA damage in cells exposed to 2-dodecylcyclobutanone, employing the single cell microgel electrophoresis technique, have been carried out. In vitro experiments using rat and human colon cells indicate that 2-docylcyclobutanone in the concentration range of about 0.30 – 1.25 mg/ml induces DNA strand breaks in the cells. Simultaneously, a concentration related cytotoxic effect is observed as was determined by trypan blue exclusion. To which extent these in vitro findings are of relevancy for the in vivo human exposure situation needs to be investigated in further studies. In vivo tests in rats are in progress. 相似文献
7.
J. Kaloustian 《Journal of Thermal Analysis and Calorimetry》1992,38(6):1377-1389
Nineteen different polymers having no melting endotherm (foam urea-formol, PVC, vinyl polyacetate, vinyl polybutyral, polymethacrylates, polystyrene and its copolymers) are studied by DTA. The identification is realized due to endothermic decomposition peak and exothermic peaks, according to the general method which has been described previously.
Zusammenfassung Mittels DTA wurden neunzehn verschiedene Polymere ohne endothermen Peak beim Schmelzen untersucht (Schaum Carbamid-Formol, PVC, Vinylpolyacetat, Vinylpolybutyral, Polymethacrylate, Polystyrol und seine Kopolymere). Die Identifizierung erfolgte in Übereinstimmung mit der unlängst beschriebenen allgemeinen Methode anhand der endothermen Zersetzung speaks und der exothermen Peaks.相似文献
8.
A. E. Legzdins B. E. McCarry C. H. Marvin D. W. Bryant 《International journal of environmental analytical chemistry》2013,93(2-4):79-94
Abstract A normal phase HPLC methodology using a semi-preparative polyaminocyano column in conjunction with a selection of short-term genotoxicity assays has been developed for bioassay-directed fractionation studies of complex environmental mixtures. To illustrate the effectiveness of this methodology, an organic extract prepared from respirable air particulate samples collected in Hamilton, Canada was separated into a non-polar aromatic fraction and a polar aromatic fraction using a combination of alumina and Sephadex LH20 chromatography. These fractions were evaluated for their genotoxic potential using the Salmonella/microsome (Ames) assay with six different strains of Salmonella. The non-polar aromatic fraction was analyzed by normal phase HPLC and the eluent was collected in one-minute subfractions; these subtractions were bioassayed in three different Salmonella strains (YG1021 -S9, YG1024 -S9 and YG1029 +S9) to afford three different mutation profiles of this sample. Some subfractions which exhibited high mutagenic responses were subjected to further chemical analyses using GC/MS in order to identify those compounds responsible for the genotoxic responses. The nitroarene compounds 2-nitrofluoranthene, 1-nitropyrene and 2-nitropyrene and higher molecular weight polycyclic aromatic hydrocarbons such as benzo[a]pyrene and indeno[l,2,3-cd]pyrene were identified and quantified in some of the biologically active subfractions. The normal phase gradient conditions afforded very reproducible retention times for a series of polycyclic aromatic standards with a broad range of compound polarities. In addition, polycyclic aromatic hydrocarbons (PAH) were observed to elute from the normal phase HPLC column in a series of peaks; successive peaks contained PAH of increasing molecular weight while any individual peak was shown to contain PAH of the same molecular weight. 相似文献
9.
Kamila Rybczyska-Tkaczyk Teresa Korniowicz-Kowalska Konrad A. Szychowski 《Molecules (Basel, Switzerland)》2021,26(2)
The aim of this study was to evaluate the bioremoval mechanism of anthracycline antibiotics by the white-rot fungus B. adusta CCBAS 930. The activity of oxidoreductases and levels of phenolic compounds and free radicals were determined during the biotransformation of anthraquinone antibiotics: daunomycin (DNR) and doxorubicin (DOX) by B. adusta strain CCBAS 930. Moreover, phytotoxicity (Lepidium sativum L.), ecotoxicity (Vibrio fischeri), genotoxicity and cytotoxicity of anthraquinone dyes were evaluated before and after biological treatment. More than 80% and 90% of DNR and DOX were removed by biodegradation (decolorization). Initial solutions of DNR and DOX were characterized by eco-, phyto-, geno- and cytotoxicity. Despite efficient decolorization, secondary metabolites, toxic to bacteria, formed during biotransformation of anthracycline antibiotics in B. adusta CCBAS 930 cultures. DNR and DOX metabolites did not increase reactive oxygen species (ROS) production in human fibroblasts and resazurin reduction. DNR metabolites did not change caspase-3 activity. 相似文献
10.
Hongmei Yang Zong‐Jun Li Debin Wan Wenhui Lian Shuying Liu 《Journal of mass spectrometry : JMS》2013,48(5):539-543
In this work, laser‐enhanced in‐source decay (LEISD) technique of matrix‐assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI‐FT‐ICR‐MS) was used to distinguish reducing and nonreducing carbohydrates. Interestingly, easier cleavage of (1 → 2)‐linked glycosidic bonds for nonreducing carbohydrates containing D‐fructofuranosyl units was observed in MALDI‐FT‐ICR‐MS, which was in agreement with the result of theoretical calculation by the software package Gaussian 09. Importantly, no cross‐ring cleavage of fructofuranosyl residues was detected in the LEISD spectra of nonreducing carbohydrates. LEISD method therefore offers an attractive alternative for fast and efficient differentiation of reducing and nonreducing carbohydrates, and the positions of nonreducing monosaccharide residues in a carbohydrate chain could be easily speculated. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献