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981.
D. G. Taimazov 《Seismic Instruments》2009,45(1):115-118
A vertical gravimetric gradient meter is described that is presented by the author and uses large hydrostatic forces with metacenters dispersed along the vertical coordinate and a weak-loaded string converter for actuating on test object in opposite directions. The calculating accuracy of the gradiometer is about ±0.10 E. The possibility of using the gradient meter for precision gravimetric experiments is shown. 相似文献
982.
Abstract. The emergence of the Isthmus of Panama subdivided the amphi-American biota. In the present study, Pacific and Atlantic populations of four cognate pairs of crabs were used to discern whether exposure to different thermal regimes in habitats, in the putative absence of gene flow, has resulted in physiological divergence. Populations that potentially form a common genetic pool were also used; these were populations of the Atlantic Panama cognate that occur in Belize and Florida. Decreases in water temperature occur periodically in Pacific Panama and Florida, but not in Atlantic Panama or Belize. In this study, physiological divergence in oxygen uptake was assessed in response to repeated exposure to either control and decreased temperature or control and increased temperature. Results indicate that, in only some of the genera tested, exposure to decreases in habitat temperature has resulted in divergence. Partial support is found for the corollary that adaptation to an environment with periods of decreased temperature results in reduced compensation during exposure to elevated temperature. 相似文献
983.
A. E. Filonov ;I. E. Tereshchenko 《海洋湖沼学报（英文）》1999,17(4):308-314
Instrumental measurements of the circulation and thermic regimen of tropical Chapala Lake revealed the surface temperature variations in its eastern part. In all of the cross-sections, spatial variations of 3°C were ordinarily registered over a distance of just 100–300 m. The movements of the internal thermal front in the water body with 2°C fluctuation were registered at a buoy station. The front’s forepart was accompanied by intensive internal waves in the form of internal KdeV solitons. The front near the buoy station was formed by the movement of the warm water body coming from the eastern shallow part of the lake and stimulated by the morning breeze. 相似文献
984.
Jennifer L. Mercer Meixun Zhao Steven M. Colman 《Estuarine, Coastal and Shelf Science》2005,63(4):675-682
Alkenone unsaturation indices (UK37 and UK′37) have long been used as proxies for surface water temperature in the open ocean. Recent studies have suggested that in other marine environments, variables other than temperature may affect both the production of alkenones and the values of the indices. Here, we present the results of a reconnaissance field study in which alkenones were extracted from particulate matter filtered from the water column in Chesapeake Bay during 2000 and 2001. A multivariate analysis shows a strong positive correlation between UK37 (and UK′37) values and temperature, and a significant negative correlation between UK37 (and UK′37) values and nitrate concentrations. However, temperature and nitrate concentrations also co-vary significantly. The temperature vs. UK37 relationships (UK37=0.018 (T)−0.162, R2=0.84, UK′37=0.013 (T)−0.04, R2=0.80) have lower slopes than the open-ocean equations of Prahl et al. [1988. Further evaluation of long-chain alkenones as indicators of paleoceanographic conditions. Geochimica et Cosmochimica Acta 52, 2303–2310] and Müller et al. [1998. Calibration of the alkenone paleotemperature index UK′37 based on core-tops from the eastern South Atlantic and the global ocean (60°N–60°S). Geochimica et Cosmochimica Acta 62, 1757–1772], but are similar to the relationships found in controlled studies with elevated nutrient levels and higher nitrate:phosphate (N:P) ratios. This implies that high nutrient levels in Chesapeake Bay have either lowered the UK37 vs. temperature slope, or nutrient levels are the main controller of the UK37 index. In addition, particularly high abundances (>5% of total C37 alkenones) of the tetra-unsaturated ketone, C37:4, were found when water temperatures reached 25 °C or higher, thus posing further questions about the controls on alkenone production as well as the biochemical roles of alkenones. 相似文献
985.
Chen Muyan ;Zhang Xiumei ;Gao Tianxiang ;Chen Chao 《海洋湖沼学报（英文）》2006,24(3):300-306
The protease activity in digestive tract of young turbotScophthalmus maximum was studied, and the optimal pH, temperature and NaCl concentration were determined for different portions of the fish's internal organs. The optimal activity in the fish's stomach was at pH of 2.2, while that in the intestinal extracts was within the alkaline range from 9.5 to 10.0. In hepatopancreas, the optimal pH was in low alkalinity at 8.5. The optimal reaction temperature was above 40°C in stomach, intestine and hepatopancreas. With increasing temperature, the pH value increased in stomach, while in the intestine, an opposite tendency was observed due to combined effect of pH and temperature. NaCl concentration showed inhibitory impact on protein digestion in hepatopancreas. The main protease for protein digestion in turbot seemed to be pepsin. Moreover, the maximum protease activity in different segments of intestine existed in the hindgut. 相似文献
986.
Hirokazu Ozaki Hajime Obata Mikio Naganobu Toshitaka Gamo 《Journal of Oceanography》2009,65(2):235-244
We measured potential temperature, salinity, and dissolved oxygen profiles from the surface to the bottom at two locations in the north Ross Sea (65.2°S, 174.2°E and 67.2°S, 172.7°W) in December 2004. Comparison of our data with previous results from the same region reveals an increase in potential temperature and decreases in salinity and dissolved oxygen concentration in the bottom layer (deeper than 3000 m) over the past four decades. The changes were significantly different from the analytical precisions. Detailed investigation of the temperature, salinity, dissolved oxygen and σ 3 value distributions and the bottom water flow in the north Ross Sea suggests a long-term change in water mass mixing balance. That is to say, it is speculated that the influence of cool, saline, high-oxygen bottom water (high-salinity Ross Sea Bottom Water) formed in the southwestern Ross Sea has possibly been decreased, while the influences of relatively warmer and fresher bottom water (low-salinity Ross Sea Bottom Water) and the Adélie Land Bottom Water coming from the Australia-Antarctic Basin have increased. The possible impact of global warming on ocean circulation needs much more investigation. 相似文献
987.
988.
The tropopause has a complex structure and some interference information may exist in high-resolution global positioning system （GPS）/low earth-orbiting （LEO） radio occultation （RO） data. The position of the tropopause cannot be accurately determined using traditional cold point tropopause （CPT） and lapse rate tropopause （LRT） algorithms. In this paper, an integrative algorithm is developed to determinate tropopause parameters. The algorithm is applied to GPS/COSMIC RO data to obtain a global distribution of the height and temperature of the tropopause. This algorithm improves the utilization rate of GPS/LEO RO data by 30% compared with that from the traditional CPT method. The rationality and reliability of GPS/LEO RO data in probing the Earth＇s atmosphere are verified by our study of the tropopause using COSMIC data. 相似文献
989.
Seong-JoongKim Hye-Sun Choi Baek-Min Kim Sang-Jong Park Taehyoun Shim Joo-Hong Kim 《极地研究(英文版)》2013,(4):326-338
This study investigates recent climate change over the Arctic and its link to the mid-latitudes using the ERA-Interim global atmospheric reanalysis data from the European Center for Medium-Range Weather Forecast （ECMWF）. Since 1979, sub- stantial surface warming, associated with the increase in anthropogenic greenhouse gases, has occurred over the Arctic. The great- est warming in winter has taken place offshore in the Kara-Barents Sea, and is associated with the increase in turbulent heat fluxes from the marginal ice zone. In contrast to the marked warming over the Arctic Ocean in winter, substantial cooling appears over Siberia and eastern Asia, linked to the reduction of Arctic sea ice during the freezing season （September-March）. However, in summer, very little change is observed in surface air temperature over the Arctic because increased radiative heat melts the sea ice and the amount of turbulent heat gain from the ocean is relatively small. The heat stored in the upper ocean mixed layer in summer with the opening of the Arctic Ocean is released back to the atmosphere as turbulent heat fluxes during the autumn and through to the following spring. This warming of the Arctic and the reduced sea ice amplifies surface cooling over Siberia and eastern Asia in winter. 相似文献
990.