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81.
82.
Technology innovation is an increasingly globalized exercise with dramatic consequences for scientific and diplomatic goals alike, and requires enhanced participation and integration of scientists and science-minded diplomats within diplomatic missions to advance shared policy goals. This more general problem is addressed in the present article by focusing on recent collaborations between U.S. and German scientists, including several of the coauthors.  相似文献   
83.
The benthic macrofauna and physical features of 10 sandy beaches along the coast of Oman were surveyed quantitatively. This is a mesotidal regime mostly subject to low to moderate wave energy but more exposed in the south. Five northern beaches are tide-dominated, with low wave energy, and their profiles consist of a berm, a steep, swash-dominated upper shore and a broad tide-dominated terrace from mid-shore downwards. They are composed of moderately sorted fine to medium sands. Southern beaches experience greater wave energy, particularly during the summer southwest monsoon, and exhibit smoother, concave profiles with fine, fairly well sorted carbonate sand. 58 species and species groups were recorded, with crustanceans, polychaetes and molluscs dominant. In general species richness was high, at least 19–25 species per beach, but dry biomass moderate to low at 26–90g/m shoreline, with one high value of 450g/m. Total abundance was moderate at 3–73×103 organisms/m of beach. Some zonation was evident with ocypodid crabs andTylos in the supralittoral, cirolanid isopods on the upper shore and a variety of species on the lower shore. The coast of Oman appears to constitute a single zoogeographic region, but with some regional differentiation between north and south due to varying physical conditions. Thus, OmanÕs beaches are characterized by tide-dominated morphodynamics and exceptionally high species richness.  相似文献   
84.
Five species of bivalves and two species of vestimentiferan tubeworms were collected from hydrocarbon seeps in the Gulf of Mexico, and the composition of their free amino acid and related compounds analysed. Like other marine molluscs, taurine, glycine, glutamic acid, and alanine were abundant in the seep bivalves, but, unlike other molluscs, hypotaurine and thiotaurine were also abundant in the seep species. The relative levels of the most abundant amino compounds indicate that glycine is likely to be an important osmoregulatory compound in the bivalves, but not in the vestimentiferans. A consistent pattern of decreasing taurine:glycine ratio with increasing depth was evident in both vent and seep bivalves, and attributed to differences in the relative availability of taurine and glycine in their diet. Additionally, the generally high glutamate levels and higher levels in the symbiont-containing gills are interpreted as consistent with the proposed role of glutamate as a nutritive transfer molecule in these symbioses. The distribution of hypotaurine and thiotaurine in the seep species is discussed in relation to previously proposed hypotheses on the function of these compounds: hypotaurine as an antioxidant, and thiotaurine as a binding and transport molecule for reduced-sulphur species. Received: 22 October 1998 / Accepted: 4 November 1999  相似文献   
85.
Riftia pachyptila, the giant vestimentiferan tubeworm from the East Pacific Rise, harbors abundant chemolithoautotrophic, sulfide-oxidizing bacteria in an internal organ, the trophosome. Several facts, such as the lack of a digestive system in the host, stable carbon isotope values and net carbon dioxide uptake all suggest that the tubeworms obtain the bulk of their nutrition from their symbionts. Using tissue autoradiography, we investigated the mode of nutritional transfer between symbionts and host, and the site of early incorporation of symbiont fixed-carbon in the host. Fast labeling in the trophosome clearly demonstrates that the symbionts are the primary site of carbon fixation. Appearance of label in some symbiont-free host tissues in as little as 15 min indicates that the symbionts release a significant amount of organic carbon immediately after fixation. The organic carbon is largely incorporated into specific, metabolically active host tissues such as fast-growing body regions in the trunk and plume, and into tube-secreting glands. In addition to immediate release of fixed carbon by the symbionts, there is evidence of a second possible nutritional mode, digestion of the symbionts, which is consistent with previous suggestions based on trophosome ultrastructure. Results suggest that symbiont-containing host cells migrate in a predictable pattern within trophosome lobules and that symbiont division occurs predominately in the center of a lobule, followed eventually by autolysis/digestion at the periphery of the lobule. Received: 1 July 1999 / Accepted: 30 December 1999  相似文献   
86.
A simple, easy to use and selective spectrofluorimetric method for the determination of trace levels of aluminium has been developed. A new Schiff base, N-o-vanillidine-2-amino-p-cresol (OVAC), has been synthesized and its fluorescence activity with aluminium investigated. Based on this chelation reaction, a spectrofluorimetric method has been developed for the determination of aluminium in samples buffered at pH 4.0 using acetic acid-sodium acetate. The chelation reaction between Al(iii) and N-o-vanillidine-2-amino-p-cresol was very fast, requiring only 20 min at room temperature to complex completely. The excitation and emission wavelengths were 423.0 and 553.0 nm, respectively, at which the OVAC-Al complex gave the maximum fluorescence intensity at pH 4.0 in a 50% ethanol-50% water medium. The interference from fluoride ions was minimized by the addition of Be(2+). Other ions were found not to interfere at the concentrations likely to be found in natural waters. Under these conditions, the calibration plot was linear up to 1000 microg L(-1) (r = 0.999). The limit of detection (3sigma) for the determination of Al(iii) was 0.19 microg L(-1) and the precision for multiple determinations of 3 ng mL(-1) Al(iii) prepared in ultra-pure water was found to be 0.29% (n = 16). The Schiff base ligand could be used to determine ultra-trace aluminium from natural waters. Analysis of environmental certified reference materials showed good agreement with the certified values. The procedure was found to be equally applicable to both fresh water and saline solutions (including sea water) using either normal external calibration or the standard additions method.  相似文献   
87.
88.
The association between gestational infection with human parvovirus (B19) and fetal loss has increased interest in this virus and demand for diagnostic testing. However, serological assays for B19 are not yet widely available. Maternal serum alpha-fetoprotein (MSAFP) testing is commonly used during the second trimester to screen for various fetal defects. We attempted to determine whether an elevated level of MSAFP would be an appropriate indication for B19-specific tests. Over a 26-month period, MSAFP tests were performed at Michigan State University for 21 392 women. Sera remaining after that testing were stored frozen. Of these, 22 case samples—from women with MSAFP levels greater than 3·0 multiples of the median (MOM) and pregnancies that ended in fetal loss—and 44 matched control samples—from women with MSAFP levels greater than 0·4 and less than 2·2 MOM and live births at term—were tested for B19 antibodies. None of the 66 samples was IgM positive, while 33 (50 per cent) were IgG positive. The presence of IgG was not significantly associated with case or control status (matched odds ratio=0·77, 95 per cent confidence interval 0·28–2·11). These findings are consistent with other studies indicating prior infection in approximately half of adults and suggest that elevated screening MSAFP levels, in the absence of other evidence of B19 infection, should not prompt B19-specific testing.  相似文献   
89.
We report three cases of amniocentesis in which mosaicism for trisomy 12 was detected in two or more independent cultures. The parents elected to terminate the pregnancy in all three cases. Follow-up studies in two of the cases confirmed the mosaicism in fetal tissues (in subcutaneous tissue in one case; in fetal lung in the other), but not in blood. No fetal anomalies were evident by ultrasound or at autopsy. These results along with other reported cases demonstrate the difficulty in counselling for mosaic trisomy 12.  相似文献   
90.
The dispersion of pollutants from the huge Buncefield oil depot fire that occurred on 11 December 2005 is simulated using a regional Eulerian chemistry-transport model. We analyse the transport and mixing of the fire plume. We show that the hot plume never reached the ground. Instead, it pierced the thin wintertime boundary layer and was injected into the free troposphere at higher altitudes. This is in agreement with data from many air quality stations. This high injection was fortunate because the fine aerosol particles (PM10) mass column generated by the fire smoke exceeded that of ordinary pollution by an order of magnitude. Our regional chemistry-transport modelling is able to predict the early development of the plume dispersion, as shown by a qualitative comparison between simulated PM10 columns and a satellite image obtained by the EOS-TERRA-MODIS sensor.If the accident had occurred in summer when boundary layers are much deeper and convective, a severe degradation in air quality due to PM10 could have occurred, as shown by a sensitivity simulation assuming a similar fire during one of the hottest days of August 2003. The modelled impact of the fire on regional and European air quality levels strongly depends on the altitude reached by the buoyant plume, as shown by a set of sensitivity simulations with variable injection heights. However, in all cases we found that the fire only affected surface aerosol concentrations without increasing photochemical pollution.  相似文献   
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