[en] Pure vacuum-annealed niobium was irradiated at room temperature with 5-MeV protons to a total fluence of 6.8 x 10¹⁶ protons/cm². The sample thickness was much larger than the range of the protons. The local magnetic induction as a function of distance from the surface was determined in the superconducting mixed state using a previously described ac technique. The measurements show a dramatic increase in pinning to a depth of about 100 μm, which corresponds to the approximate range of the protons. The field profiles were obtained at several applied-field values between H/sub c l/ and H/sub c/₂ and the magnetic field dependence of the volume pinning force F/sub v/ shows a strong ''peak effect'' near H/sub c/₂. The results are discussed in terms of several disclocation-loop--flux-line-lattice--pinning models using calculations of irradiation damage based on Rutherford scattering and the simple Kinchin-Pease model of atomic displacements. The results are found to be consistent with previous measurements by Agrawal, Kramer, and Loomis on neutron-irradiated niobium and suggest that a quadratic summation rule first proposed by Labusch should be used to obtain the effective volume pinning force F/sub v/

[en] Very pure annealed Nb samples having a resistivity ratio, GAMMAequivalentrho₂₉₆/rho/sub 4.2/, in the range 1300--1700 were irradiated with 3--8-MeV protons to fluences of 6.8 x 10¹⁶ and 3.4 x 10¹⁶ protons/cm². Local magnetic induction profiles, when the samples were in the superconducting mixed state, were obtained using the ac technique of Rollins, Kuepfer, and Gey. Electron micrographs of the irradiated samples show that the damage caused by proton irradiation was inthe form of dislocation loops. The volume pinning force F/sub v/, calculated for the dislocation loops using flux pinning models and theories for b=0.7 and T=4.2 K, is compared with the experimentally obtained F/sub v/. The F/sub v/ calculated from direct summation law is an order of magnitude higher than the experimental result and the F/sub v/ calculated from models, which use Labusch quadratic summation law, is two to three orders of magnitude smaller than the experimental value. Our experimental pinning force per dislocation loop is in agreement with a master curve obtained by Kramer as an empirical solution to the summation problem. Experimentally obtained F/sub v/, for temperatures lying betweeen 2 and 7 K obey a scaling law. If the temperature dependence is written as F/sub v/proportionalH/sup n//sub c/, then we found n to be slightly dependent on depth x from the sample surface. At x=20 μm, n=3.2 [- 0.2; while at x=84 μm, n=2.7 +- 0.2. The experimental scaling law is compared with the scaling laws obtained from the Labusch model for point pinning centers and Kramer's model for line pinning centers. Irradiated samples were observed to have a region at the surface with no apparent pinning. This observation is discussed in terms of two different effects: (i) reversible motion of flux lines and (ii) a threshold for flux pinning

[en] Transient flux flow voltage are observed when constant current is switched on in a type II superconductor at low magnetic fields. The nature of the transients is related to the method of formation of the flux line lattice. The transients are attributed to changes which occur in the flux line lattice as inhomogeneities created at the time of formation of the lattice move out of the sample as a result of flux flow. A model is developed to describe this process which includes the requirement that when dissimilar regions of flux move across the sample, the rate of flow must be the same for these regions, so that an equipotential exists across the sample width. For currents below the equilibrium critical current, excellent fits to this model are obtained for our data

[en] It is observed that vanadium(V) extracts into nitrobenzene as a mixed complex of oxine and perchlorate or chlorate or nitrate. The optimum pH range for this mixed complex formation and extraction is established for each system. Synergism is noticed in the presence of oxine and anion, and this is attributed to the mixed complex formation. The formaation (extraction) constants are determined. The effectiveness of the anion as synergist is found to be related to its ionic size and to the extraction constant of the mixed complex. (author)

[en] The red coloured, ternary complex formed by molybdenum(VI) with hydroxylamine hydrchloride and 4-(2-pyridylazo) resorcinol (PAR), on heating for 20 minutes in a hot water bath at pH 6-8, can be extracted with a mixture of n-butanol and benzene (4:1). This complex exhibits absorption maximum at 530nm with a molar absorptivity of 2.8x10⁴ lit. mol^-1cm^-1 and obeys Beer's law upto 4.5μg/ml of Mo(VI). The composition of the complex is found to be 1:1:1, for Mo(VI): hydroxylamine hydrochloride: PAR. Large amounts of tartaric acid and 2, 2-diamino-cyclohexane tetra acetic acid (CyDTA) can be tolerated in this method. The extraction becomes highly selective in presence of CyDTA (3ml of 5x10^-2M) and interference of ions like Fe(III)(5mg), Pb(II)(4mg), Zn(II)(2mg), Cu(II)(4mg), Mn(II)(3mg), Ni(II)(4mg), Sn(II)(3mg), Cr(VI)(2mg) and Bi(III)(0.5mg) can be effectively supressed in the determination of 10-45μg of molybdenum. The method can be successfully applied for the determination of molybdenum in steels and nickel base high temperature alloys. (author). 2 tabs., 8 refs

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[en] This paper illustrate the impact of industrialization on water quality in and around Nakkavagu Watershed, due to unplanted industrial development. The study area falls between 78 deg. 05' - 78 deg. 25'E. longitude and 17 deg. 25'-17 deg. 45'N latitude, the catchment area extends 734 sq. km in Medak district, Andhra Predesh, India. The study area lies in the Godavari Basin. Remote sensing and GIS techniques are used to map the spatial and temporal distribution of water quality with respect to land use / land cover (Lu /Lc) changes for a period of three decades. Spatial database consisting of drainage network and geomorphology and land use / land cover change detection maps (1970-2004) have been generated for the entire watershed using remote sensing satellite data. Attribute database consisting of (water quality analysis is carried out and corresponding water quality index is calculated on a five point scale: 0- 25 Excellent, 26 -50 Good, 51 -75 Poor, 76 -100 Very poor, and> 100 Unfit for Drinking. Integrated study to establish the impact of Lu / Lc on water quality is carried out using GIS Analysis. Maps showing Lu / Lc changes and corresponding spatial distribution of water quality index were generated for the years 1979, 1989,2004. The results indicate that the water quality index in the entire Nakkavagu watershed during 1979 is excellent and good and by 2004, the entire watershed is rated in to poor, very poor and unfit for drinking. Best environmental management plans were suggested for restoration of the Nakkavagu watershed. (author)

[en] A potentiometric method for the determination of vanadium(V) and chromium(VI) individually with oxalate using the photochemical reduction of iron(III) is described. The titrations can be best carried out in 0.5 to 3.0N acidity with respect to sulphuric acid with a minimum exposure time of 12-13 minutes. The concentration of iron(III) is found not critical as long as certain minimum is present. The molar stoichiometric ratio for the quantitative reduction of vanadium(V) and chromium(VI) with oxalate are found to be 1:1 and 1:3 respectively. (author)

No abstract available