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排序方式: 共有553条查询结果,搜索用时 15 毫秒
1.
Rupert Cecil Gillian B. Robinson 《Biochimica et Biophysica Acta (BBA)/General Subjects》1975,404(1):164-168
It is known that insulin is adsorbed onto glass but it has been assumed that it is not adsorbed onto plastic. We find that tritium-labelled insulin is adsorbed onto all materials tried. The adsorption is reduced in the presence of other proteins and can be prevented altogether by coating the vessels with cetyl alcohol. 相似文献
2.
In-depth interviews were conducted among 50 subjects residing in the industrial town of Newcastle, Australia. Half of these subjects were from the general population and half were currently seeking counselling for personal/family problems. None of the subjects were receiving any medical care at the time of interview, though seven had done so during the episode of distress they were discussing. The study shows that while the subjects psychologized their problems, members of both groups tended to somatize at a rate proportional to the level of distress. Subjects were unaware of any relationship between the distress they were experiencing and their physical complaints. The results of this study support previous research which argues that those experiencing distress and those who tend to introspect are also those who are likely to amplify somatic symptoms. At the same time these results depart from findings in the United States which suggest that in the West, people learn to express social and personal distress in psychological terms,, thereby reducing the level of somatization. Though not representative of the population as a whole, the findings raised questions warranting further study. 相似文献
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4.
John Wakeley 《Journal of genetics》1996,75(1):81-89
A number of different migration and isolation models of population subdivision have been studied. In this paper I analyse a general model of two populations derived from a common ancestral population at some time in the past. The two populations may exchange migrants, but they may also be completely isolated from each other. I derive the expectation and variance of the number of differences between two sequences sampled from the two populations. These are then compared to the corresponding results from two other much-used models: equilibrium migration and complete isolation. 相似文献
5.
Wakeley J 《Trends in ecology & evolution》1996,11(4):158-162
Estimates of transition bias provide insight into the process of nucleotide substitution, and are required in some commonly used phylogenetic methods. Transitions are favored over transversions among spontaneous mutations, and the direction and strength of selection on proteins and RNA appears to depend on mutation type. As the complexity of the nucleotide-substitution process has become apparent, problems with classical methods of estimating transition bias have been recognized. These problems arise because there Is a fundamental difference between ratios of numbers of differences among sequences and ratios of rates, and because classical methods are not easily generalized. Several new methods are now available. 相似文献
6.
Eileen Maura Jutras Cecil M. Smart Richard Rupert Ian L. Pepper Raina M. Miller 《Biodegradation》1997,8(1):31-42
Approximately 15000 L of unleaded gasoline werereleased into the surrounding vadose zone from aleaking underground storage tank. Initialremediation was by soil vapor extraction andcombustion which soon became cost prohibitive, asadded propane was required to reach the combustionlimit of the extracted vapors. As a cost effectivealternative, a field-scale compost based biofilterwas used in conjunction with soil vapor extractionto remediate the vadose zone. The biofilter wasconstructed on site using 4:1 diatomaceousearth:composted horse manure. Results of a fivemonth study showed that the biofilter removedapproximately 90% of total petroleum hydrocarbons(TPH) and >90% of the BTEX compounds (benzene,toluene, ethylbenzene, xylene), achieving thestringent permit requirements set at either 90% TPHreduction or less than 1.36 kg per day of volatileorganic compounds (VOC's) released to theatmosphere. The biofilter showed the capacity toreadily adapt to changing environmental conditionssuch as increased contaminant loading, andvariations in temperature and moisture. Thebacterial population in the biofilter was uniformlydiverse throughout the biofilter, suggesting that aconsortium of bacteria was needed for efficientbiodegradation. The cost of biofilter set up andoperation saved 90% in the first year alone of theoperating expenses incurred by soil vapor extractionand combustion. 相似文献
7.
Methanogenic Activity and Structural Characteristics of the Microbial Biofilm On a Needle-Punched Polyester Support 总被引:2,自引:0,他引:2
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Martin Harvey Cecil W. Forsberg Terry J. Beveridge Jack Pos John R. Ogilvie 《Applied microbiology》1984,48(3):633-638
In a downflow stationary fixed-film anaerobic reactor receiving a swine waste influent, few bacteria were observed to be tightly adherent to the surfaces of the needle-punched polyester support material. However, there was a morphologically complex, dense population of bacteria trapped within the matrix. Frequently large microcolonies of a uniform morphological type of bacteria were observed. These were particularly evident for methanosarcina-like bacteria which grew forming large aggregates of unseparated cells. Leafy deposits of electron-dense, calcium- and phosphorus-enriched material coated the polyester matrix and some cells. As the biofilm matured there was more extensive mineral deposition which completely entrapped cells. The entrapped cells appeared to autolyze, and many were partially degraded. Further impregnation of the matrix with minerals and apparent cell death may eventually have a deleterious effect on the methanogenic activity of the biofilm. 相似文献
8.
The antibiotic ristocetin is a glycoproteoid isolated from the culture media of Nocardia lurida N.R.R.L. 2430 whose structural features have yet to be resolved (1–3). The antibiotic has been studied both for its antibiotic properties (4–6) and, more recently, for its inducement of platelet aggregation in humans, both in vivo and in vitro (7–9). This latter phenomena resulted in the discontinued use of ristocetin in antibiotic therapy (10), but has provided a useful tool for studying the bleeding disorder, von Willebrand's disease. The disease is genetic in origin and is characterized by the lack of a functional plasma protein believed to be required for the adhesion of platelets to vascular epithelia during primary thrombotic events (11). This plasma protein, termed von Willebrand's factor, is also necessary to support ristocetin-induced platelet aggregation of human platelets (12). Thus, ristocetin has found increasing use not only in facilitating the diagnosis of von Willebrand's disease but also in characterizing the plasma protein (13). 相似文献
9.
PGE2 can vasoconstrict or vasolidate the isolated Krebs-perfused rat kidney depending on the tone of the renal vasculature. Thus, it is weakly constrictor (threshold 5–10 ng bolus dose) in the perfused kidney whose perfusion pressure is 47 ± 2 SD mmHg (n = 6), but becomes a vasodilator (threshold ~ 10 pg) in the kidney whose perfusion pressure has been raised to 73 ± 6 SD mmHg (n = 6) or 121 ± 8 SD mmHg (n = 6) through constant infusion of Vasopressin (0.1 and 0.25 mU/ml respectively). PGE1 was equally effective as PGE2 while other PGs, I2, I1, and 6-keto E1, were less effective in opposing vasoconstriction. PGF2α was inactive up to a dose of 10 ng. 相似文献
10.
Freeze-fracture electron microscopy was used to study water content related freezing resistance in Grand Rapids lettuce seeds. Consistent and recognizable conformational changes occurred in lipid-water phases of lettuce seeds at different moisture contents. In air-dry lettuce seed cotyledons, the lipids lying in spherical lipid bodies near the cell wall appeared amorphous, while the structure was crystalline above 20% water content. The lipid bodies interassociated into membrane bilayers in seeds containing 20 to 25% water. Such lyotropic phase transitions in membrane lipids during lettuce seed hydration are believed to contribute to the biphasic freezing behavior observed in lettuce seeds at different moisture contents and to provide a natural freezing tolerance mechanism for highly desiccated plant tissues such as seeds. 相似文献