1,922 research outputs found

    Energy and Momentum Distributions of Kantowski and Sachs Space-time

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    We use the Einstein, Bergmann-Thomson, Landau-Lifshitz and Papapetrou energy-momentum complexes to calculate the energy and momentum distributions of Kantowski and Sachs space-time. We show that the Einstein and Bergmann-Thomson definitions furnish a consistent result for the energy distribution, but the definition of Landau-Lifshitz do not agree with them. We show that a signature switch should affect about everything including energy distribution in the case of Einstein and Papapetrou prescriptions but not in Bergmann-Thomson and Landau-Lifshitz prescriptions.Comment: 12 page

    Use of remote sensing and GIS in mapping the environmental sensitivity areas for desertification of Egyptian territory

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    International audienceDesertification is defined in the first art of the convention to combat desertification as "land degradation in arid, semiarid and dry sub-humid areas resulting from climatic variations and human activities". Its consequence include a set of important processes which are active in arid and semi arid environment, where water is the main limiting factor of land use performance in such ecosystem . Desertification indicators or the groups of associated indicators should be focused on a single process. They should be based on available reliable information sources, including remotely sensed images, topographic data (maps or DEM'S), climate, soils and geological data. The current work aims to map the Environmental Sensitivity Areas (ESA's) to desertification in whole territory of Egypt at a scale of 1:1 000 000. ETM satellite images, geologic and soil maps were used as main sources for calculating the index of Environmental Sensitivity Areas (ESAI) for desertification. The algorism is adopted from MEDALLUS methodology as follows; ESAI = (SQI * CQI * VQI)1/3 Where SQI is the soil quality index, CQI is the climate quality index and VQI is the vegetation quality index. The SQI is based on rating the parent material, slope, soil texture, and soil depth. The VQI is computed on bases of rating three categories (i.e. erosion protection, drought resistance and plant cover). The CQI is based on the aridity index, derived from values of annual rainfall and potential evapotranspiration. Arc-GIS 9 software was used for the computation and sensitivity maps production. The results show that the soil of the Nile Valley are characterized by a moderate SQI, however the those in the interference zone are low soil quality indexed. The dense vegetation of the valley has raised its VQI to be good, however coastal areas are average and interference zones are low. The maps of ESA's for desertification show that 86.1% of Egyptian territory is classified as very sensitive areas, while 4.3% as Moderately sensitive, and 9.6% as sensitive. It can be concluded that implementing the maps of sensitivity to desertification is rather useful in the arid and semi arid areas as they give more likely quantitative trend for frequency of sensitive areas. The integration of different factors contributing to desertification sensitivity may lead to plan a successful combating. The usage of space data and GIS proved to be suitable tools to rely estimation and to fulfill the needed large computational requirements. They are also useful in visualizing the sensitivity situation of different desertification parameters

    Evidence for Induced Magnetization in Superconductor-Ferromagnet Hetero-structures: a Scanning Tunnelling Spectroscopy Study

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    We performed scanning tunneling spectroscopy of c-axis oriented YBCO films on top of which ferromagnetic SRO islands were grown epitaxially in-situ. When measured on the ferromagnetic islands, the density of states exhibits small gap-like features consistent with the expected short range penetration of the order parameter into the ferromagnet. However, anomalous split-gap structures are measured on the superconductor in the vicinity of ferromagnetic islands. This observation may provide evidence for the recently predicted induced magnetization in the superconductor side of a superconductor/ ferromagnet junction. The length scale of the effect inside the superconductor was found to be an order of magnitude larger than the superconducting coherence length. This is inconsistent with the theoretical prediction of a penetration depth of only a few superconducting coherence lengths. We discuss a possible origin for this discrepancy

    MRI Parameters Of Alzheimer's Disease in an Arab Population of Wadi Ara, Israel

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    Magnetic resonance imaging (MRI) findings are reported from 15 individuals in an Arab–Israeli community who were diagnosed with Alzheimer's disease (AD). The quantitative parameters that were used for MRI analyses included gradings (0–3) and linear measurements of different brain structures. Generalized tissue loss was assessed by combined measurements of the ventricles (ventricular score, VS) and sulcal grading and width (SG, SW, respectively). Loss of brain tissue in specific regions of interest, eg, temporal lobes, basal ganglia, and midbrain, was evaluated by precise measurements. We observed abnormal tissue characteristics, expressed as high intensity foci in white matter on T2W sequences, as well as tissue loss, both generalized and focal. Most notable were changes involving the head of the caudate nuclei, the midbrain, and to a lesser degree, medial temporal structures.National Institute of Aging (UO1-AG17173); National Institute on Alcohol Abuse and Alcoholism (R37-AA07112, K05-AA00219); US Department of Veterans Affair

    Absolute Measurements for Uranium Verification Content in Radiographic Containers

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    Depleted Uranium (DU) is used for its very high density in civilian uses include radiation shielding in medical radiation therapy, industrial radiography equipment, containers used to transport radioactive materials. Absolute measurements have been performed for verification of uranium mass content in gamma radiography by using detector’s model developed with MCNP in nuclear safeguard inspection for these samples. Both the experimental results obtained as well as MCNP results are used to estimate the 238U mass content. The determined and the declared 238U masses values are found in an agreement with accuracy from -1.74 % to 1.80 %

    On Construction of Tri-Concept Lattices

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    The main point is to define the structure of a Tri-Concept lattice to deal with data given by different sources and represent it by less complex structures without loosing knowledge. We suggest the algorithm TRI-NEST to form the nested diagrams corresponding to the Tri-Concept lattices. Adding the ICE-T algorithm enables us to generate all frequently closed concepts, which leads to simplifying the Tri-Concept lattices and using the Iceberg Concept lattices as a reduction method to the big data while preserving all information

    Self-consistent treatment of the self-energy in nuclear matter

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    The influence of hole-hole propagation in addition to the conventional particle-particle propagation, on the energy per nucleon and the momentum distribution is investigated. The results are compared to the Brueckner-Hartree-Fock (BHF) calculations with a continuous choice and conventional choice for the single-particle spectrum. The Bethe-Goldstone equation has been solved using realistic NNNN interactions. Also, the structure of nucleon self-energy in nuclear matter is evaluated. All the self-energies are calculated self-consistently. Starting from the BHF approximation without the usual angle-average approximation, the effects of hole-hole contributions and a self-consistent treatment within the framework of the Green function approach are investigated. Using the self-consistent self-energy, the hole and particle self-consistent spectral functions including the particle-particle and hole-hole ladder contributions in nuclear matter are calculated using realistic NNNN interactions. We found that, the difference in binding energy between both results, i.e. BHF and self-consistent Green function, is not large. This explains why is the BHF ignored the 2h1p contribution.Comment: Preprint 20 pages including 15 figures and one tabl

    Synthesis, Characterization and Application of Nano-adsorbent Materials in the Sorption of Pb(II), Ni(II), Co(II), Mn(II), Li(I) from Aqueous Solution

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    In this study, nano-adsorbent materials were synthesized from two different precursors by thermal activation technique. The first was the synthesizing of nano-zinc silicate from chemical reagents of zinc oxide and commercial silica gel. The second was the preparation of nano-pore size activated carbon from different biomass. The synthesized nano-adsorbent materials were characterized by different techniques; Surface Area, FTIR, XRD and SEM. The prepared nano-adsorbent materials were applied in the sorption and separation of some heavy metals from aqueous solution. These metals includes; Pb (II), Ni(II), Co(II), Mn(II) and Li(I). Some factors affecting on the sorption process (e.g. contact time and pH) were investigated. It was found that: the nano-zinc silicate (of ratio 1:1 thermally treated at 700 0C) and nano-pores activated carbon (prepared from saw dust impregnated with 70% H3PO4 overnight, then heated to 500 0C in presence of steam for 80 min.) were the best samples for sorption and separation of concerned heavy metals

    Energy and Momentum densities of cosmological models, with equation of state ρ=μ\rho=\mu, in general relativity and teleparallel gravity

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    We calculated the energy and momentum densities of stiff fluid solutions, using Einstein, Bergmann-Thomson and Landau-Lifshitz energy-momentum complexes, in both general relativity and teleparallel gravity. In our analysis we get different results comparing the aforementioned complexes with each other when calculated in the same gravitational theory, either this is in general relativity and teleparallel gravity. However, interestingly enough, each complex's value is the same either in general relativity or teleparallel gravity. Our results sustain that (i) general relativity or teleparallel gravity are equivalent theories (ii) different energy-momentum complexes do not provide the same energy and momentum densities neither in general relativity nor in teleparallel gravity. In the context of the theory of teleparallel gravity, the vector and axial-vector parts of the torsion are obtained. We show that the axial-vector torsion vanishes for the space-time under study.Comment: 15 pages, no figures, Minor typos corrected; version to appear in International Journal of Theoretical Physic
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