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1.
人类活动影响下新疆生态环境的一些变化 总被引:4,自引:0,他引:4
人类活动引起的新疆生态环境变化主要有以下几方面:1.河流流程缩短,河水矿化度和泥沙含量增加;2.湖泊水位下降,湖面缩小或变干,湖水矿化度升高;3.森林破坏,面积缩小;4.草场的产草量降低,牧草质量下降; 5.土壤次生盐渍化、沼泽化和肥力下降;6.土地沙漠化不断扩大。 相似文献
2.
H M Rajh J H Uitzetter L W Westerhuis C L van den Dries G I Tesser 《International journal of peptide and protein research》1979,14(1):68-79
In order to investigate the special function of tryptophan in peptide hormones, six tryptophan analogues have been synthesized, in which structural resemblance has been grossly retained and potentially essential properties have only partially been varied. The L-enantiomers have been isolated after enzymatic digestion of racemic dipeptide derivatives, and charge-transfer properties of the compounds have been studied. 相似文献
3.
The aliphatic 1H-NMR spectrum of the kringle 4 domain of human plasminogen has been studied via two-dimensional chemical shift correlated (COSY) and nuclear Overhauser correlated (NOESY) experiments at 300 MHz and 620 MHz. A number of aliphatic proton spin systems have been identified and several definite assignments have been made. This was mainly achieved by comparison of the human kringle 4 spectrum with spectra of the porcine, bovine and chicken homologs and also with that of the kringle 1 from human plasminogen on which we have reported previously. The three valyl and two leucyl residues of human kringle 4 have been assigned. The eleven threonyl spin systems have been identified via a RELAYED-COSY experiment and Thr17 has been assigned. The three alanyl spin systems have been identified and assigned. Six seryl spin systems have been identified and the signals from the seven glycyl residues of human kringle 4 have been located with Gly45 assigned. Furthermore, 24 AMX spin systems have been mapped in the COSY spectrum of human kringle 4 and H alpha-H beta,beta' spin systems of Tyr2, Tyr41, Tyr50, Tyr74, Trp25 and Trp62 have been assigned. From the spectrum of a deglycosylated chicken homolog, the epsilon-methyl singlets of Met28 and Met48 have been assigned. Finally, ligand effects on selected aliphatic resonances were observed which could be analyzed in terms of residues likely to neighbor the kringle lysine-binding site. 相似文献
4.
H Koprowski Z Steplewski K Mitchell M Herlyn D Herlyn P Fuhrer 《Somatic cell genetics》1979,5(6):957-971
Hybridoma cells which secrete colorectal carcinoma-specific antibodies have been produced and used to study the antigenic structure of these tumor cells. Nineteen antibodies have been studied in detail, and 15 of these are colorectal carcinoma specific. Only two antibodies reactive with carcinoembryonic antigen (CEA) have been discovered and five other antibodies that react with distinct epitopes on the cell surface have been defined. Several antigens with distinct molecular characteristics have been shown to exist by use of hybridoma antibodies. Six hybridoma antibodies have been shown to mediate antibody-dependent cell-mediated cytotoxicity (ADCC). 相似文献
5.
Marie-Thérèse Chauvet Jacqueline Chauvet Roger Acher 《Biochemical and biophysical research communications》1981,103(2):595-603
Two rat neurophysins have been purified by salt precipitation, molecular sieving and ion-exchange chromatography. The proteins, performic-acid oxidized or reduced-alkylated, have been split either by trypsin or by staphylococcal proteinase and fragments have been separated by peptide mapping. Amino acid sequences of tryptic peptides have been determined either directly or after cleaving the large fragments by subtilisin, chymotrypsin, elastase or staphylococcal proteinase and characterizing the subfragments. Tryptic peptides have been ordered through the fragments given by staphylococcal proteinase. The N-terminal sequences of both proteins have also been established by automated degradation.The two usual types of mammalian neurophysins have been identified. One neurophysin belongs to the MSEL-neurophysin family and shows 11 substitutions and a 2-residue C-terminal truncation when compared with bovine MSEL-neurophysin. The other belongs to the VLDV-neurophysin family and shows 8 substitutions when compared with bovine VLDV-neurophysin. There are 23 differences between the MSEL- and VLDV-neurophysins of the rat. 相似文献
6.
The measurement of 13 items in the face and nose of 220 young adults (110 males and 110 females) of the Han nationality between the ages of 18 and 21 years has been done in the Henan Province of China. The means and standard deviations have been obtained, and the significant differences in many items between males and females have been proved. Some items influencing outer nasal shape have been analyzed. The correlations between nose height, nose length, and morphologic facial height and physiognomic facial height have been discussed. The ratio and amount of nasal breadth to facial breadth and nasal breadth to interocular breadth have been compared and analyzed, and the differences among the different races and between the sexes have been explained. 相似文献
7.
Humoral and cellular mechanisms of defense have been described for cephalopods, a relatively advanced group of mollusks. Typical of other mollusks, cephalopod agglutinins are the most documented component of humoral immunity. Lectins, which have agglutinating properties, have been described and characterized from octopuses. Agglutinins from cephalopod hemolymph have also been shown to agglutinate a variety of vertebrate red blood cells, as well as potential bacterial pathogens. Hemocytes are the primary component of cellular immunity. Although the hemocyte role in phagocytosis has been extensively studied in other mollusks, the mechanisms of phagocytosis have not been described extensively for cephalopods. Cephalopod hemocytes have phagocytic capabilities and may function in encapsulation and neutralization of foreign substances; however, the effects of environmental factors and the full extent of phagocytic capabilities of cephalopod hemocytes have not been reported. Hemocytes from cephalopods have a role in wound healing and inflammation which have been reported in detail by several investigators. 相似文献
8.
The different invasive and noninvasive diagnostic tests for Helicobacter pylori have been applied mainly in emerging countries. Molecular methods have been developed, especially a test for detection of H. pylori and its clarithromycin resistance directly from stools. The long-term effects of eradication on histologic lesions have been studied in a meta-analysis and the prognostic value of post-treatment in gastric mucosa-associated lymphoid tissue lymphoma has been assessed. An operating link for gastritis assessment (the OLGA staging) has also been published. Attempts to simplify the urea breath test protocol have been made, and new stool antigen tests have been proposed and compared to those previously available. 相似文献
9.
J B Ifft 《Biophysical chemistry》1976,5(1-2):137-157
The technique of sedimentation equilibrium in density gradients in the analytical ultracentrifuge has been applied to the study of proteins. A variety of effects and procedures including the use of density marker beads, the effects of pressure on buoyant density and pH, and the calculation of compositional density gradient proportionality constants and density--refractive index relations have been developed. The buoyant densities of twenty-four proteins have been measured and hydration values computed. The buoyant titrations of six proteins have been measured. These data have been interpreted in terms of the buoyant titrations which have been obtained for six ionizable homopolypeptides, five copolypeptides, two non-ionizable homopolypeptides and three chemically modified proteins. Spectropolarimetry and potentiometric titrations were employed to further interpret these data. Approximate values for dissociation constants, numbers of ionizable residues, and the nature of ions bound or dissociated upon ionization have been obtained. The relation between potentiometric and buoyant titrations and the use of density gradient centrifugation as a probe for protein structure have been explored. 相似文献
10.
V A Roginski? 《Molekuliarnaia biologiia》1990,24(6):1582-1589
The structure, thermodynamic, and kinetic features of polyunsaturated fatty acids derivatives as the main substratum of lipid peroxidation (POL) have been considered. The heats of key POL reactions have been estimated. Kinetic consequences of these estimations have been analyzed. The dependence of POL rate on O2 concentration have been considered in detail both in the absence and in the presence of antioxidants. The essential features of POL processes in lipid bilayers resulting from the specific structure and molecular dynamics have been discussed. 相似文献
11.
Phosphorylase has been fractionated during development and germination of seeds of smooth and wrinkled-seeded peas. The total phosphorylase levels have been compared. In addition, a number of other pea tissues and other legumes have been examined. Some kinetic properties of the two enzymes present have been measured. Both enzymes have been further purified by affinity chromatography on Sepharose 4B-starch columns and by sequential gel filtration in the absence and presence of amylopectin. The MW and sub-unit structures of the two enzymes have been examined and their possible roles discussed. 相似文献
12.
Kinetic expressions for the fermentative production of relatively high concentrations [12% (w/v)] of ethanol have been examined. Several expressions which account for both substrate and product inhibition have been formulated, and have been applied to suspended cell and immobilized cell reactors. Experimental data have been used to validate the kinetic expressions used, and the impact of combined inhibition on optimal reactor configuration has been assessed. The process implications of combined substrate and product inhibition for suspended and immobilized cell systems have been discussed. 相似文献
13.
I A Shabarov S N Rumiantsev V F Pospelov 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1985,(6):3-6
As the result of the study of tetanolysin-producing Clostridium tetani strains, their populations have been found to be markedly heterogeneous with respect to the hemolytic activity of clone cultures. On the basis of normal and dialyzed cultures of selected variants with maximum activity the preparations of tetanolysin have been obtained, and their hemolytic activity and antigenic properties have been studied. Antihemolytic rabbit sera have also been obtained and characterized. Partially purified preparations of tetanolysin with high hemolytic activity have been obtained by the fractionation of C. tetani dialyzed cultures with ammonium sulfate. 相似文献
14.
In this, a preliminary report, the advantages and disadvantages of upper lobe lobectomy and concomitant thoracoplasty in tuberculosis have been summarized. There has been no undue increase in the operative hazard, there have been no complications, and the immediate results have been entirely satisfactory.Twenty-six patients were subjected to a combined operation (17 upper lobectomy-thoracoplasty and nine pneumonectomy-thoracoplasty) with one postoperative death. Indications for primary lobectomy have been discussed. The technique of resection and concomitant thoracoplasty has been briefly described. 相似文献
15.
Chlorinated nitroaromatic compounds (CNAs) are persistent environmental pollutants that have been introduced into the environment
due to the anthropogenic activities. Bacteria that utilize CNAs as the sole sources of carbon and energy have been isolated
from different contaminated and non-contaminated sites. Microbial metabolism of CNAs has been studied, and several metabolic
pathways for degradation of CNAs have been proposed. Detoxification and biotransformation of CNAs have also been studied in
various fungi, actinomycetes and bacteria. Several physicochemical methods have been used for treatment of wastewater containing
CNAs; however, these methods are not suitable for in situ bioremediation. This review describes the current scenario of the
degradation of CNAs. 相似文献
16.
Studies with Composite Membranes: I. Preparation and Measurement of Impedances 总被引:1,自引:1,他引:0
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Simple and composite membranes have been prepared from 2% collodion solutions containing different amounts of polystyrenesulfonic acid (PSSA). Various membrane parameters such as water content, electrolyte uptake, exchange capacity, and permselectivity of these membranes have been determined. The resistance and capacitance of simple membranes have been measured as functions of both external electrolyte concentration and internal fixed charge density. The impedance characteristics of composite membranes also have been determined and discussed in terms of the resistance and capacitance characteristics of simple membranes from which the composite structures have been formed. 相似文献
17.
Crescenzi V Francescangeli A Taglienti A Capitani D Mannina L 《Biomacromolecules》2003,4(4):1045-1054
Hydrophilic networks based on functionalized hyaluronic acid and on partially acetylated chitosan, respectively, have been obtained. In the case of hyaluronic acid (HA), primary amino functionalities have been introduced along the polysaccharide chains. The ensuing derivatives, i.e., HA-lysine (HA-K), HA-diamino pentane (HA-DAP), and HA-glycine-lysine (HA-GK), have been characterized by high field NMR spectroscopy. NMR 2D-DOSY experiments have allowed us to optimize the purification procedure. Chitosan was made soluble in water by partial acetylation. Cross-linking reactions have been performed using glutaraldehyde. The obtained networks have been qualitatively characterized by means of (13)C CP-MAS NMR technique. The hydrogels have been characterized also in terms of water uptake. 相似文献
18.
In this, a preliminary report, the advantages and disadvantages of upper lobe lobectomy and concomitant thoracoplasty in tuberculosis have been summarized. There has been no undue increase in the operative hazard, there have been no complications, and the immediate results have been entirely satisfactory.Twenty-six patients were subjected to a combined operation (17 upper lobectomy-thoracoplasty and nine pneumonectomy-thoracoplasty) with one postoperative death.Indications for primary lobectomy have been discussed.The technique of resection and concomitant thoracoplasty has been briefly described. 相似文献
19.
20.
H Kaczorek E Bocian T Mazurczak 《Polski tygodnik lekarski (Warsaw, Poland : 1960)》1991,46(17-18):329-331
The results of cytogenetic examination carried out in 255 couples with a history of infertility have been analysed. Chromosomal aberrations have been detected in 15 examinations (6.7%) with predominance of translocations (mutual - 3.6%; Robertson' - 1.3%). Identified aberrations have been noted in 9 women and 6 men. The obtained results have been analysed in relation to the number of abortions, dead and live newborn babies with inherited abnormalities. It was found that the incidence of chromosomal aberrations increases with the number of the spontaneous abortions in anamnesis. Such aberrations have also been more frequent in the families in which spontaneous abortions have been accompanied by other fertility disorders. 相似文献