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  • Author or Editor: S. Mohamed x
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Many countries are using GPS for monitoring large engineering structures such as dams. Monitoring deformation pattern is often one of the most effective ways to be informed the safety status of such structures. Thus, the safety control of dams lies on the analysis of its structural behaviour, based on monitoring a large set of variables, which contains information about earthquakes, crustal movement, temperature variations etc. and about corresponding stresses. For the purpose of monitoring the deformations of the High and old Aswan dams, a number of methods have been developed. For monitoring the height changes along the High Dam body, eight levelling lines were established at different levels during its construction. The levelling measurements were carried out each month since 1970 and continue till present. Mohamed et al. (2003) have presented and analysed the levelling measurements from 1970 to 2000.  The results reveal different trends for different levels of the High Dam body. The rates of setting of the High Dam body tend to be stable.  During the last five years the rates of the subsidence range 1-2 mm/a at most benchmarks of the levelling lines along the High Dam body.  During the last decade no significant correlation has been found between the rates of setting and the water level changes at the up- and down-stream sides. For monitoring crustal deformations at the High and old Aswan dams region, a local GPS network consisting of 9 geodetic points was established. Three campaigns from December 2001 to April 2003 were performed. The study results indicate a definite correlation between the amount of water in the lake and the deformation in the area. The reservoir pushes the land towards the north where the two dams are. The paper throws light upon the present state of the crustal deformations in the study area.

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Abstract  

Non-isothermal dehydration of copper chloride dihydrate and nickel chloride hexahydrate were studied by using TG, DTG, DTA and DSC measurements. The copper chloride salt loses its two water molecules in one step while nickel chloride salt dehydrates in three consecutive steps. The first two steps involve the loss of 4 water molecules in two overlapped steps while the third step involves the dehydration of the dihydrate salt to give the anhydrous NiCl2. Activation energies (ΔE) and the frequency factor (A) were calculated from DTG and DTA results. We have also calculated the different thermodynamic parameters, e.g. enthalpy change (ΔH), heat capacity (C p) and the entropy change (ΔS) from DSC measurements for both reactants. The isothermal rehydration of the completely dehydrated salts was studied in air and under saturated vapour pressure of water. Anhydrous nickel chloride was found to rehydrate in three consecutive steps while the copper salt rehydrated in one step.

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Field experiments were conducted at the Agricultural College and Research Institute (Killikulam), Tamil Nadu Agricultural University from September 1992 to June 1995 to optimize the herbicide dose and application techniques for cotton-based intercropping systems.283

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Glasses with compositions 60B2O3–40PbO, 60B2O3–40Bi2O3, and 60B2O3–30Bi2O3–10PbO have been prepared and studied by differential thermal analysis. The crystallization kinetics of the glasses was investigated under non-isothermal conditions. From dependence of the glass transition temperature (T g) on the heating rate, the activation energy for the glass transition was derived. Similarly the activation energy of the crystallization process was determined. Thermal stability of these glasses were achieved in terms of the characteristic temperatures, such as the glass transition temperature, T g, the onset temperature of crystallization, T in , the temperature corresponding to the maximum crystallization rate, T p, beside the kinetic parameters, K(T g) and K(T p). The results revealed that the 60B2O3–40PbO is more stable than the others. The crystallization mechanism is characterized for glasses. The phases at which the glass crystallizes after the thermal process have been identified by X-ray diffraction.

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Instrumental neutron activation analysis, INAA, was utilized for the determination of Al, Au, Br, Ca, Cl, Co, Cr, Cu, Fe, I, K, Mg, Mn, Na, Rb, Sc, V and W in 12 Tilapia Nilotica samples collected from the Aswan High Dam Lake following the destructive techniques.

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The concentration of 18 elements in different cane sugar products, i.e., cane sugar plants, crude and syrup juices, molasses, and the end products of the consumer sugar, were analyzed and processed. The samples were collected from five citics, i.e., Kom Ombo, Edfu, Armant, Deshna and Naga Hammady in Upper Egypt where the main Egyptian sugar industry factories are located. INAA was applied for the determination of Al, Ca, Cl, Co, Cr, Fe, Mg, Mn, Na and Sc, while Cu, Li, P, Sn, V and Zn were determined by ICP-AES and Pb and As were determined by AAS. These three analytical methods were applied to optimize the sensitivity and the accuracy of the measurements in order to provide a sound basis for the obtention of reliable clustering results.

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The non-isothermal decomposition of cobalt acetate tetrahydrate was studied up to 500°C by means of TG, DTG, DTA and DSC techniques in different atmospheres of N2, H2 and in air. The complete course of the decomposition is described on the basis of six thermal events. Two intermediate compounds (i.e. acetyl cobalt acetate and cobalt acetate hydroxide) were found to participate in the decomposition reaction. IR spectroscopy, mass spectrometry and X-ray diffraction analysis were used to identify the solid products of calcination at different temperatures and in different atmospheres. CoO was identified as the final solid product in N2, and Co3O4 was produced in air. A hydrogen atmosphere, on the other hand, produces cobalt metal. Scanning electron microscopy was used to investigate the solid decomposition products at different stages of the reaction. Identification of the volatile gaseous products (in nitrogen and in oxygen) was performed using gas chromatography. The main products were: acetone, acetic acid, CO2 and acetaldehyde. The proportions of these products varied with the decomposition temperature and the prevailing atmosphere. Kinetic parameters (e.g.E and lnA) together with thermodynamic functions (e.g. °H, C p and °S) were calculated for the different decomposition steps.

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The non-isothermal decompositions of silver maleate dihydrate (C4H2O4Ag22H2O) and anhydrous silver fumarate (C4H2O4Ag2) were studied up to 500°C, in a dynamic atmosphere of air, by means of TG and DTA measurements. Both compounds showed some sublimation (at 120°C for silver maleate and at 180°C for silver fumarate) prior to the onset of decomposition (at 170°C for silver maleate and at 280°C for silver fumarate). The gaseous decomposition products of both compounds were found, using IR spectroscopy, to be dominated by maleic anhydride and CO2. Minor proportions of ethylene, ethyl alcohol, acetone, methane and isobutene were also identified. Metallic silver was the final solid product, as identified by X-ray diffractometry. NMR analysis was used to monitor the isomerization of the maleate radical into the more stable fumarate above 230°C. Kinetic parameters (E a and lnA) were calculated from the effect of heating rate, (2, 5, 10, and 20 deg min−1) on the DTA measurements. A mechanism is suggested for the decomposition pathways of these compounds, on basis of the results obtained and, also, on similarities with analogous systems.

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A simple, selective, precise, and stability-indicating thin-layer chromatographic method has been developed and validated for analysis of some angiotensin II receptor antagonists (AIIRAs), namely, Losartan potassium (Los-K), Irbesartan (Irb), and Candesartan cilexetil (Cand) in the bulk drug and in pharmaceutical formulations (tablets). The method was based on using TLC plates pre-coated with silica gel G 60 on aluminum sheets as stationary phase and the development system was performed using chloroform:methanol (9:1) giving well separated and compact spots for all the studied drugs (R F values 0.41–0.53). The separated spots were characterized by viewing under the UV lamp, then visualized as orange spots by spraying with Dragendorff's reagent and measured by densitometry. Under the optimum chromatographic conditions, linear relationships were obtained between response and concentrations of each studied drug with high correlation coefficients (0.9985–0.9994). Good accuracy and precision were successfully obtained for the analysis of tablets containing each drug alone or combined with diuretic drug hydrochlorothiazide (HCTZ). No interferences could be observed from the co-formulated HCTZ, commonly encountered excipients present in tablets as well as the degradation products. The results were compared successfully with reported methods and can be used as a stability-indicating assay.

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Abstract  

The k 0-method of INAA standardization has been implemented using the irradiation facilities of the fast pneumatic rabbit and some selected manually loaded irradiation positions, which designated for short and long irradiation, respectively, at Egypt second research reactor. The neutron flux parameters (f and α) in each site have been determined using Zr–Au sets as neutron flux monitors. The reference materials coal NIST 1632c and IAEA-Soil 7 were analyzed for data validation and good agreement between the experimental values and the certified values was obtained.

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