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201.
The chlorination and condensation of acetylene at low temperatures is demonstrated using copper chlorides as chlorinated agents coated to model borosilicate surfaces. Experiments with and without both a chlorine source and borosilicate surfaces indicate the absence of gas-phase and gas-surface reactions. Chlorination and condensation occur only in the presence of the copper catalyst. C2 through C8 organic products were observed in the effluent; PCDD/F were only observed from extraction of the borosilicate surfaces. A global reaction model is proposed that is consistent with the observed product distributions. Similar experiments with dichloroacetylene indicate greater reactivity in the absence of the copper catalyst. Reaction is observed in the gas-phase and in the presence of borosilicate surfaces at low temperatures. The formation of hexachlorobenzene is only observed in the presence of a copper catalyst. PCDD/F were only observed from extraction of the borosilicate surfaces. A global reaction model is proposed for the formation of hexachlorobenzene from dichloroacetylene. 相似文献
202.
N2 fixation (C2H2 reduction) associated with the leaves of the sea grass Thalassia testudinum was investigated at 5 sites in South Florida (Biscayne Bay) and one site in the Bahamas (Bimini Harbor). Significant activities were correlated with the occurrence of a heterocystous blue-green alga (Calothrix sp.) on the leaves. C2H2 reduction was not stimulated by organic compounds, either aerobically or anaerobically in the light or dark. Therefore, other physiological types of microbes were not important in N2 fixation. Diurnal and seasonal variations in N2 fixation occurred, with maximal rates during the daytime and in the late spring and early summer. N2 fixation was negligible at four stations in Biscayne Bay. At the fifth station, near Fowey Rock, about 5 kg N ha-1 year-1 was fixed. In the summer, the N2 fixed per day (4–5 mg N m-2) could provide 4 to 23% of the foliar productivity demands of T. testudinum at this site and the station in Bimini Harbor. N2 fixation at the periphery of a sea-grass patch, near Fowey Rock, could provide 8 to 38% of the daily nitrogen requirement for leaf production, and thereby might compensate for a less effective trapping and recycling of nitrogen from dead leaves in such regions. 相似文献
203.
Weapon size versus body size as a predictor of winning in fights between shore crabs, Carcinus maenas (L.) 总被引:4,自引:0,他引:4
Lynne U. Sneddon Felicity A. Huntingford Alan C. Taylor 《Behavioral ecology and sociobiology》1997,41(4):237-242
Relative body size (carapace width) and weapon size (chela length) were used as indicators of resource holding potential (RHP)
in the agonistic behaviour of male shore crabs, Carcinus maenas (L.). Weapon size was found to be a more reliable predictor of the outcome of pairwise fights than body size. Crabs with
longer chelae than their opponents were more likely to win fights than crabs with relatively larger bodies. Body size had
less influence on the outcome of fights. Relative body and weapon size did not influence initiation of contests but did affect
the likelihood of winning; however, this was significant only for weapon size. Winning crabs had heavier claws with greater
surface area than losing crabs. There was no relationship between relative size and fight duration. The frequency of cheliped
display increased with chela length and win- ners performed significantly more displays than losers.
Received: 5 February 1997 / Accepted after revision: 20 May 1997 相似文献
204.
205.
The Norwegian lobsterNephrops norvegicus (L.) collected from Firth of Clyde, Scotland between December 1987 and March 1988, was unable to survive longer than 18 h experimental emersion at 10°C. During this time the partial pressure of oxygen (P
O2) in the venous blood decreased rapidly and the lobster supplemented cellular energy requirements by anaerobic metabolism. This was indicated by the rapid accumulation ofL-lactate in the blood. Although the survival rate increased (to ca 36 to 48 h) if lobsters were kept on ice, the accumulation ofL-lactate in the blood was not significantly different from lobsters at 10°C, despite the temperature difference. There was no indication thatN. norvegicus was able to further metabolize circulatingL-lactate during emersion. On emersion there was also a marked hyperglycemia in the blood due to the stress of handling and asphyxiation. There was fairly good agreement between results obtained during laboratory studies and simulated fishing activity in the Firth of Clyde. Both sets of results are discussed in the context of adaptation to air breathing within the Crustacea and an assesment of post-harvest treatment of lobsters. 相似文献
206.
The marine sponge Spirastrella cuspidifera Lamarck shows a remarkable capacity to concentrate cobalt-60 from its environment, the specific activity of the radionuclide being two orders of magnitude higher than that in the ambient water. This suggests a very slow equilibrium with stable cobalt. The chemical form of the deposited cobalt-60 has been investigated in S. cuspidifera collected from coastal waters in the vicinity of a nuclear power station. The majority of the cobalt-60, 75 to 85%, is readily extractable into distilled water. Chromatographic analysis of this soluble fraction shows that about 85% of the cobalt is present as a small-molecular weight complex of low stability. No binding to any specific protein could be identified. The possible mechanism for the preferential uptake of cobalt-60 by this species of sponge is discussed. 相似文献
207.
The report includes quantitative and qualitative data on the phytoplankton from the First Canadian Transpacific Oceanographic Cruise from March to May 1969. Nanoplanktonic species (<20 m) were numerically dominant and, together with nertic diatoms, made up the larger portion of the biomass at all stations outside the Western Subarctic and Alaskan Gyres, where Denticulopsis seminae predominated. The nanoplankton consisted mainly of haptophycean, dinophycean and cryptophycean flagellates. Tropical oceanic dinoflagellates and diatoms were abundant in the net samples from Station 17 in the warm Kuroshio current but absent from Stations 24–27 in the Western Subarctic Gyre, Stations 2, 37–39 in the Alaskan Gyre, in which cold water oceanic species predominated, and Stations 31 and 33, south of the Aleutians. Subsurface maxima were common on the outward bound (westerly) leg in March. 相似文献
208.
Service M. Durrant A. E. Mills J. A. Taylor J. E. Faughey D 《Journal of Coastal Conservation》1996,2(1):159-168
Studies were conducted on nutrient cycling in two coastal embayments; Strangford Lough and Belfast Lough, in order to classify
these coastal waters in compliance with the European Union Urban Waste Water Treatment and Nitrates Directives. Analysis of
the data suggests that Strangford Lough is nitrogen-limited throughout much of the growing season with chlorophyll-a levels
comparable to the open Irish Sea. In contrast, much of Belfast Lough is never nitrogen-limited and, with chlorophyll-a levels
at time exceeding 50 μg/l, is exhibiting symptoms of eutrophication. 相似文献
209.
The tibial hemimelia syndrome is a rare autosomal dominant condition associated with limb deficiencies. We recently diagnosed this condition in a pregnancy at 16·5 weeks' gestation by ultrasound and a positive family history. To our knowledge, this represents the first case to be detected prenatally. 相似文献
210.
Paul G. Kratzer Mitchell S. Golbus David E. Finkelstein Robert N. Taylor M.D. Ph.D. 《黑龙江环境通报》1991,11(1):1-6
Sera from women carrying either chromosomally normal or aneuploid fetuses in the first half of pregnancy were assayed for human chorionic gonadotropin (hCG) bioactivity in order to determine whether differences might provide the basis for a useful antenatal screen for aneuploidy. A mouse uterine weight assay was used to assess hCG bioactivity in sera from 35 patients undergoing chorionic villus sampling (12 normal pregnancies and 23 trisomic pregnancies) and in sera from 18 patients undergoing elective second-trimester abortion (12 presumed normal pregnancies, 3 trisomic pregnancies, and 3 pregnancies with neural tube defects). The hCG bioactivity to immunoactivity (B:I) ratio of normal pregnancies progressively decreased from 7.7±1.3 at 4–5 menstrual weeks, to 4.7±0.4 at 9–12 menstrual weeks, to 3.3±0.5 at 16–20 menstrual weeks. There were no significant differences in the B:I ratios between normal and aneuploid pregnancies in either the first-trimester (4.7±0.4 versus 5.2±0.3) or the second-trimester samples (3.3±0.5 versus 2.6±0.3), despite significantly greater hCG concentrations in the trisomic pregnancies. We conclude that while aneuploid pregnancies display dysfunctional regulation of hCG expression, the bioactivity of their hCG is normal and does not appear to form the basis for a useful screen for aneuploidy. 相似文献