The Experts below are selected from a list of 222 Experts worldwide ranked by ideXlab platform
Steven E Campana - One of the best experts on this subject based on the ideXlab platform.
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regulation of calcium and Strontium deposition on the otoliths of juvenile tilapia oreochromis niloticus
Comparative Biochemistry and Physiology Part A: Physiology, 1996Co-Authors: Jacqueline Farrell, Steven E CampanaAbstract:Abstract Radioisotopes of calcium and Strontium were used to test for a relationship between the environmental concentrations of each element and their respective deposition rates on the otolith. On the basis of 45 Ca and 89 Sr assays, the rate of Strontium deposition on the otolith was influenced by Strontium concentrations in the water, while the rate of calcium deposition was affected neither by food nor water calcium concentrations. Thus, the deposition rate of Strontium on the otolith at least partially reflects environmental availability, while that of calcium does not. Sources in the water contributed 75% of calcium and 88% of Strontium to the sagittae of Nile tilapia, Oreochromis niloticus , with the remainder being provided by the diet.
Jacqueline Farrell - One of the best experts on this subject based on the ideXlab platform.
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regulation of calcium and Strontium deposition on the otoliths of juvenile tilapia oreochromis niloticus
Comparative Biochemistry and Physiology Part A: Physiology, 1996Co-Authors: Jacqueline Farrell, Steven E CampanaAbstract:Abstract Radioisotopes of calcium and Strontium were used to test for a relationship between the environmental concentrations of each element and their respective deposition rates on the otolith. On the basis of 45 Ca and 89 Sr assays, the rate of Strontium deposition on the otolith was influenced by Strontium concentrations in the water, while the rate of calcium deposition was affected neither by food nor water calcium concentrations. Thus, the deposition rate of Strontium on the otolith at least partially reflects environmental availability, while that of calcium does not. Sources in the water contributed 75% of calcium and 88% of Strontium to the sagittae of Nile tilapia, Oreochromis niloticus , with the remainder being provided by the diet.
M. Nansteel - One of the best experts on this subject based on the ideXlab platform.
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Excessively bright hydrogen-Strontium discharge light source due to energy resonance of Strontium with hydrogen
Journal of Plasma Physics, 2003Co-Authors: R.l. Mills, M. NansteelAbstract:A plasma formed with a low field (1 V cm $^{-1}$ ) at low temperatures (e.g. $\approx{10}^3$ K) from atomic hydrogen generated at a tungsten filament and Strontium which was vaporized by heating the metal. Strong extreme ultraviolet emission was observed, but not when sodium, magnesium or barium replaced Strontium or with hydrogen or Strontium alone. Characteristic emission was observed which supported a resonant energy-transfer mechanism. Significant Balmer $\alpha$ line broadening corresponding to an average hydrogen atom temperature of 23–45 eV was observed for glow discharges of Strontium–hydrogen, helium–hydrogen, argon–hydrogen, Strontium–helium–hydrogen and Strontium–argon–hydrogen compared with $\approx$ 3 eV for pure hydrogen, krypton–hydrogen, xenon–hydrogen and magnesium–hydrogen. To achieve the same optically measured light output power, hydrogen–sodium, hydrogen–magnesium and hydrogen–barium mixtures required 4000, 7000 and 6500 times the power of the hydrogen–Strontium mixture, respectively. A glow discharge plasma formed for hydrogen–Strontium mixtures at an extremely low voltage of about 2 V compared with 250 V for hydrogen alone and sodium–hydrogen mixtures, and 140–150 V for hydrogen–magnesium and hydrogen–barium mixtures.
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Argon-hydrogen-Strontium discharge light source
IEEE Transactions on Plasma Science, 2002Co-Authors: R.l. Mills, M. NansteelAbstract:We report the observation of vacuum ultraviolet (VUV) emission in the region 40-560 nm from incandescently heated atomic hydrogen and atomized Strontium that increased with argon. The observed plasma formed at low temperatures (e.g., /spl ap/10/sup 3/ K) from atomic hydrogen generated at a tungsten filament that heated a titanium dissociator and atomic Strontium which was vaporized from the metal by heating. The emission intensity of the plasma generated by atomic Strontium increased significantly with the introduction of argon gas only when Ar/sup +/ emission was observed. No emission was observed with hydrogen when sodium, magnesium, or barium replaced Strontium or with hydrogen, hydrogen-argon mixtures, or Strontium alone. The width of the 656.3-nm Balmer /spl alpha/ line emitted from gas discharge plasmas of hydrogen and mixtures of hydrogen with magnesium, Strontium, and noble gases was measured. Significant line broadening corresponding to an average hydrogen atom temperature of 23-45 eV was observed for Strontium-hydrogen, helium-hydrogen, argon-hydrogen, Strontium-helium-hydrogen, and Strontium-argon-hydrogen plasmas; whereas, pure hydrogen, krypton-hydrogen, xenon-hydrogen and magnesium-hydrogen showed no excessive broadening corresponding to an average hydrogen atom temperature of /spl ap/4 eV. The power balance of a gas cell having vaporized Strontium and atomized hydrogen from pure hydrogen or argon-hydrogen mixture (77/23%) was measured by integrating the total light output corrected for spectrometer system response and energy over the visible range. Hydrogen control cell experiments were identical except that sodium, magnesium, or barium replaced Strontium. In the case of hydrogen-sodium, hydrogen-magnesium, and hydrogen-barium mixtures, 4000, 7000, and 6500 times the power of the hydrogen-Strontium mixture was required, respectively, in order to achieve that same optically measured light output power. With the addition of argon to the hydrogen-Strontium plasma, the power required to achieve that same optically measured light output power was reduced by a factor of about two. The power required to maintain a plasma of equivalent optical brightness with Strontium atoms present was 8600 and 6300 times less than that required for argon-hydrogen and argon control, respectively. A plasma formed at a cell voltage of about 250 V for hydrogen alone and sodium-hydrogen mixtures, 140-150 V for hydrogen-magnesium and hydrogen-barium mixtures, 224 V for an argon-hydrogen mixture, and 190 V for argon alone; whereas, a plasma formed for hydrogen-Strontium mixtures and argon-hydrogen-Strontium mixtures at extremely low voltages of about 2 and 6.6 V, respectively.
Huang Si - One of the best experts on this subject based on the ideXlab platform.
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PROGRESS IN Strontium ISOTOPE STRATIGRAPHY
Advance in Earth Sciences, 2020Co-Authors: Huang SiAbstract:Strontium isotope stratigraphy relies on the fundamental principle that the marine Strontium is isotopically homogenous world wide at any time and the 87 Sr/ 86 Sr ratio of Strontium in seawater of geological history has varied through time. By means of the 87 Sr/ 86 Sr ratio of marine carbonate (also phosphate and sulphate) which should record the original composition of sea water, we can date the marine sediments, research global events, such as history of basin subside, sea level change,orogenic events and palaeoclimate variation. The applied expectation of Strontium isotope stratigraphy would be very extensive on stratigraphy, sedimentology, petroleum geology and economic geology, which has attained considerable development internationally. However Strontium isotope stratigraphy is still in its infancy in China. The focus of Strontium isotope stratigraphy is the influence of diagenesis and technology of measurement of 87 Sr / 86 Sr ratio. Meantime, Strontium isotope stratigraphy also needs the support of stratigraphy. The ability of anti alteration of diagenesis of the original component of sample for Strontium isotope stratigraphy is very important. The development of Strontium isotope stratigraphy needs a great effort from stratigraphers, sedimentologists and geochemists, together.
John M. Edmond - One of the best experts on this subject based on the ideXlab platform.
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controls over the Strontium isotope composition of river water
Geochimica et Cosmochimica Acta, 1992Co-Authors: Martin R Palmer, John M. EdmondAbstract:Abstract Strontium concentrations and isotope ratios have been measured in river and ground waters from the Ganges, Orinoco, and Amazon river basins. When compared with major element concentrations, the data set has allowed a detailed examination of the controls over the Strontium isotope systematics of riverine input to the oceans in the following environments: 1. (1) “typical” drainage basins containing limestones, evaporites, shales, and alumino-silicate metamorphic and igneous rocks; 2. (2) shield terrains containing no chemical or biogenic sediments; and 3. (3) the floodplains that constitute the largest areas of many large rivers. The Strontium concentration and isotope composition of river waters are largely defined by mixing of Strontium derived from limestones and evaporites with Strontium derived from silicate rocks. The Strontium isotope composition of the limestone endmember generally lies within the Phanerozoic seawater range, which buffers the 87 Sr 86 Sr ratios of major rivers. A major exception is provided by the rivers draining the Himalayas, where widescale regional metamorphism appears to have led to an enrichment in limestones of radiogenic Strontium derived from coexisting silicate rocks. The Strontium isotope systematics of rivers draining shield areas are controlled by the intense, transportlimited, nature of the weathering reactions, and thereby limits variations in the Strontium flux from these terrains. Floodplains are only a minor source of dissolved Strontium to river waters, and precipitation of soil salts in some floodplains can reduce the riverine flux of dissolved Strontium to the oceans. The most effective mechanisms for altering the isotope ratio and flux of riverine Strontium to the oceans are increased glaciation and large-scale regional metamorphism of the type produced during continental collision. Both mechanisms provide a means for increasing the 87 Sr 86 Sr ratio of the global riverine flux.
