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Search Results: 1 - 10 of 2084 matches for " Division of Isotopes "
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The Spatial Redistribution of Chemical Elements and Their Isotopes in Layered Intrusions Provided by the Gradients of a Temperature, of a Pressure and of a Deformation, Using Lukkulaisvaara Intrusion (North Karelia) as an Example  [PDF]
Alexander Kh. Zilbershtein, Alexander A. Chaihorsky, Vladimir S. Semenov
Open Access Library Journal (OALib Journal) , 2019, DOI: 10.4236/oalib.1105909
Abstract: The spatial local anomalies of the concentration ratios for isotopes 143Nd/144Nd (or εNd) and 87Sr/86S in Lukkulaisvaara intrusion (North Karelia) were discovered. The physical mechanisms and the descriptions of the effect of an arising of those anomalies were developed and presented. The base of the proposed mechanisms is the phenomena of the migration (diffusion) of components, due to the (T, P (or D)) gradients. The description of the processes of an arising of the gradients of a temperature (T), of a pressure (P) and of a deformation (D) in the layered inhomogeneous intrusion during its formation and evolution, were obtained. It was shown that the gradients can induce the spatial redistribution of the chemical elements and their isotopes in the intrusion. The redistribution, in turn, can lead to the observed spatial concentration anomalies for these components. It was first obtained the expressions for the diffusion additions to the isotope’s parameter ε (εNd, in part).
Hydrochemical and Isotopic Characterisation of Groundwaters in the Eastern Region of Ghana  [PDF]
Samuel Y. Ganyaglo, Bruce Banoeng-Yakubo, Shiloh Osae, Samuel B. Dampare, Joseph R. Fianko, Mohammad A. H. Bhuiyan
Journal of Water Resource and Protection (JWARP) , 2010, DOI: 10.4236/jwarp.2010.23022
Abstract: Major ions and stable isotopes of groundwater in the Cape Coast granitoid complex (G1) and Lower Birimian (LB) formations in the Eastern Region of Ghana were evaluated to establish the source of recharge to the groundwater system. Five major hydrochemical facies were identified in the various rocks in the study area. They are calcium-magnesium-bicarbonate, sodium bicarbonate, sodium chloride and calcium chloride waters and mixed or non dominant water type. Sodium chloride and calcium chloride waters dominate aqui-fers of the Cape Coast granitoid complex whereas calcium-magnesium-bicarbonate is the dominant hydro-chemical facies in the Lower Birimian aquifers. The most probable geochemical process responsible for the evolution of these hydrochemical facies is dissolution of minerals in the various rock types. Stable isotope composition of the groundwaters established that the recharge to the groundwater system is derived from rainfall.
Time for cotton to uptake water of a known isotopic signature as measured in leaf petioles  [PDF]
Timothy S. Goebel, Robert J. Lascano
Agricultural Sciences (AS) , 2014, DOI: 10.4236/as.2014.52021
Abstract:

While stable isotopes of water have been used to study water movement through the environment, they generally have not been used to examine shorter, more transient events, e.g., rainfall of <25 mm. With the development of robust methods that use isotope ratio infrared spectrometry, evaluating samples has become faster and simpler, allowing more soil and plant samples to be collected and analyzed. Using larger sampling rates can therefore increase the resolution of changes in stable isotopes within an ecosystem, and allows for a better understanding of how quickly rainwater that enters the soil by infiltration is transpired by a plant via root-water uptake. Quantifying rainwater uptake by plants is essential to increase crop production in rainfed agriculture. Thus the objective of this study was to measure the time required by a plant to transpire water from a source of water with a different isotopic signature than the water that the plant was irrigated. To this end, cotton (Gossypium hirsutum (L.)) plants were grown in a greenhouse and the time required for the enriched water added the soil to show up in the meristematic petioles of cotton leaves was measured. The initial divergence from the irrigation water signature occurred as quickly as 4 hours. The water from the sampled petioles then reached equilibrium with the new source water within 12 hours.

Hydrodynamics and Recharge of the Aioune Sandstone Aquifer in the Taoudenni Transboundary Basin in Mauritania  [PDF]
Bacar Sidi Haiba Teiss, Serigne Faye
Journal of Water Resource and Protection (JWARP) , 2018, DOI: 10.4236/jwarp.2018.107039
Abstract: In Mauritanian, 4/5 of the territory is subject to an arid climate, where groundwater resources are the main sources of drinking water for populations and livestock. The study area is located in south-eastern Mauritania and in the western part of the Taoudenni Transboundary Basin. A better knowledge of the hydrogeological system to ensure a sustainable and rational management is necessary for this vulnerable water resource. This pioneering study, based on the compilation of hydrogeological, geochemical and isotopic data, aims to characterize the hydrodynamics and recharge of this one layer aquifer system, composed of Aioune infracambrian sandstone. The piezometric surface exhibits relatively the same morphology of the soil topography, and computed effective velocity is 94 m/yr (Northeast area), and the direction of flow is generally from cliff to plains area. The chemical data show water types evolving between two poles namely the HCO3-Ca/Mg pole (low mineralized), and the Cl-Ca/Na pole; these waters are characterized by a high vulnerability to pollution, especially at shallow depth area (Douerare, Aioune). The dissolution of bicarbonate and evaporate minerals is likely the main source of mineralization. The isotopic tool used to support comprehension of the system functioning, evidences a local indirect recharge water localized at the cliff or Wadi zones. The age of the waters ranges from the present to 1060 year. The recharge rate calculated by 14C and the chloride masse balance is respectively 0.4 to 5 mm/year. This recharge compared to the water pumping rate is lower and hence this imbalance is likely the cause of water shortages particularly during summer season period.
Helium and Argon Isotopic Studies of Fossil Material and the Theoretical Evolution of He and Ar in Earth’s Atmosphere through Time  [PDF]
Yuko Arakawa, Jun-Ichi Matsuda
International Journal of Geosciences (IJG) , 2012, DOI: 10.4236/ijg.2012.325091
Abstract: We analyzed the elemental concentrations and the isotopic compositions of helium and argon in Cambrian to Jurrassic aged Gastropod, Ammonite and Trilobite fossils in order to examine variation in these gases through time. Fossil samples yielded He and Ar isotopic ratios close to the present day atmospheric values, but also indicated some addition of a radiogenic component. We compared the results to theoretical values calculated from a mathematical model of Earth’s atmosphere assuming mantle degassing. Results from our mathmatical models showed that the 40Ar/36Ar ratio of Earth’s atmosphere increased rapidly after the formation of the Earth, but has been almost identical to the present day value for the last 1 Ga. For atmospheric helium, model results were consistent with present day atmospheric values, assuming complete helium degassing from the continental crust into the atmosphere. The model suggests that the atmospheric 3He/4He ratio has remained relatively constant for the last 0.1 Ga. Given the similarity between present day and ancient He and Ar isotopic ratios, we conclude that the corresponding ratios measured in ancient fossil material may partially reflect composition of the ancient atmosphere and are not necessarily due to contamination by the present day atmosphere.
Hydrochemical and Isotopic Study of Groundwater in the North Djeffara Aquifer, Gulf of Gabès, Southern Tunisia  [PDF]
Mohamed Fethi Ben Hamouda, Ahmed Mamou, Jelloul Bejaoui, Klaus Froehlich
International Journal of Geosciences (IJG) , 2013, DOI: 10.4236/ijg.2013.48A001
Abstract:

The northern Djeffara aquifer system is located in the southeast ofTunisiaand extends over an area of400 km2. This multilayer system of aquifers is essentially recharged by infiltration of rain and by groundwater of the Continental Inter-calaire aquifer, and occurs mainly at two levels between 0 and180 mdepth that belong to the Mio-Pliocene to form the aquifers. A combined hydrogeologic and isotopic investigation using several chemical and isotopic tracers’, i.e., major ions, δ18O, δ2H and tritium, was carried out in order to determine the sources of water recharge to the aquifer and the origin of salinity. The results of geochemical and isotopic studies show that the groundwater in the south of the study area represents a mixture of the Djeffara aquifer groundwater and locally infiltrates modern recharge. In the northern part, the groundwater which resembles that of the Sekhira aquifer originates from locally infiltrated rain and runoff. The salinity of the groundwater is caused by dissolution of evaporate rocks (gypsum and halite minerals) in the aquifer system. The stable isotopes data do not support the hypothesis of mixing with seawater.

Pb Isotopes Study in Recent Sediments from Paraty Bay (Rio de Janeiro, Brazil): Antropogenic Versus Oceanic Signatures  [PDF]
M. C. Geraldes, S. D. Pereira, H. H. Villena, F. W. e Herms
International Journal of Geosciences (IJG) , 2015, DOI: 10.4236/ijg.2015.67052
Abstract: We carried out Pb isotopes studies in sediments fromParatyBaylocated in the SE area of theRio de JaneiroStateto discriminate the signature of metal contamination from domestic sewage, industries, shipyards and geogenic sources. The studied samples have been chosen in two sectors of the Bay, including the Paraty area andJuatingaBay. Sample preparation procedures included: 1) drying and granulometric separations (200 mesh); 2) weighting; 3) complete dissolution and 4) Pb isotope analysis obtained by MC-ICP-MS (ratios 208Pb/204Pb,207Pb/204Pb, 206Pb/204Pb). Preliminary results when plotted in the 207Pb/204Pbversus 208Pb/204Pb and 207Pb/
A resolu??o oral de tarefas de divis?o por crian?as
Correa, Jane;
Estudos de Psicologia (Natal) , 2004, DOI: 10.1590/S1413-294X2004000100016
Abstract: the present study examines mental computational solutions to elementary partitive and quotitive problems given by children aged 6-9 with different levels of arithmetical knowledge. there were four sizes of dividend (4, 8, 12 and 24) and two different divisors (2 and 4). children's performance improved both with age and schooling since these variables are confounded. their performance was overall affected by both the size of the dividend and the divisor. procedures based on double counting and multiplicative facts were more used in quotitive tasks. on the other hand, procedures related to repeated addition and partition of quantities were more frequently used to solve partitive tasks. a small percentage of procedures based on repeated subtraction was observed, suggesting that repeated subtraction cannot be considered as an intuitive procedure associated with division.
Contribui??o ao estudo do magmatismo Paleo e Mesoproterozóico do SW do Craton Amaz?nico através da aplica??o de isótopos estáveis de O, H e S
Geraldes, Mauro Cesar;Teixeira, Wilson;Valladares, Claudia Say?o;
Acta Amazonica , 2008, DOI: 10.1590/S0044-59672008000200012
Abstract: stable isotopes of o, h and s were used to investigate the origin of magmatic rocks of the jauru and the pontes e lacerda terrains, sw portion of the amazonian craton, mato grosso state, brazil. granitic rocks of the alto jauru greenstone belt and cachoeirinha suite, jauru terrain, present δ18o values between +9.0? and +6.3?, indicative of derivation from juvenile magmas. the rio branco intrusive suite basic and felsic rocks' δ18o values fall, respectively, within +5.4? to +5.8? and +8.7? to +9.0? ranges; the intermediate rocks present δ18o between +7.3? and +8.3?. the lower values of δ18o, obtained from basic rocks, are compatible with a mantle source, however the felsic rocks present δ18o values indicative of crustal source. the stable isotopes of hydrogen yielded δd values between - 83? and - 92?, different from the δd signatures of metamorphic rocks and rain water. sulphur isotopes in sulfides from basic and intermediate rocks of the rio branco suite presented δ34s values coherent with a mantle source (between + 0.7? and +3.8?), whereas δ34s values between + 5.2? and + 6.1?, obtained from the felsic rocks, suggest crustal participation in their genesis. for the santa helena suite (pontes e lacerda terrain) the δ18o values fall between +4.4? and +8.9?. the present study confirms the advantages of using stable isotopes to understand magmatic processes and crustal evolution.
Electromagnetic Nature of Nuclear Energy: Application to H and He Isotopes  [PDF]
B. Schaeffer
World Journal of Nuclear Science and Technology (WJNST) , 2013, DOI: 10.4236/wjnst.2013.32A001
Abstract:

The one million times ratio between nuclear and chemical energies is generally attributed to a mysterious strong force, still unknown after one century of nuclear physics. It is now time to reconsider from the beginning the assumptions used, mainly the uncharged neutron and the orbital motion of the nucleons. Except for the long range Coulomb repulsion, the electric and magnetic Coulombs forces between adjoining nucleons are generally assumed to be negligible in the atomic nucleus by the nuclear specialists. The Schrodinger equation with a centrifugal force as in the Bohr model of the atom is unable to predict the binding energy of a nucleus. In contrast, the attractive electric and repulsive magnetic Coulomb forces alone explain quantitatively the binding energies of hydrogen and helium isotopes. For the first time, with analytical formulas, the precision varies between 1 and 30 percent without fitting, adjustment, correction or estimation, proving the electromagnetic nature of the nuclear energy.

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