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  • Author or Editor: N. Naqvi x
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The objective of current study was to look at the variable expression of antioxidant enzymes in wheat genotypes exposed to various water stress regimes. Further the malondialdehyde (MDA) content were measured as an indicative of membrane integrity. Tolerance indices were calculated which reinforce in distinguishing tolerant and susceptible genotypes. The experimental material consisted of thirteen genotypes obtained from different sources. Stress was imposed by withholding irrigation at three different growth stages of plant, i.e. tillering, anthesis and grain filling. Four resistance indices include stress susceptibility index (SSI), yield stability index (YSI), mean productivity (MP) and tolerance index (TOL) was calculated on the basis of grain yield. Water stress treatments had no significant effect on CAT activity. CIM-47, CIM-49 and NR-234 showed minimum MDA content with increased POX activity under three different irrigation conditions and are therefore considered as tolerant genotypes. Higher levels of MDA with decline activity of POX was found in CIM-51, DD-4 and NR-230 led to suggest them as susceptible genotypes. The variable response of genotypes in tolerance could be related to differences in antioxidant enzyme levels. Significant positive correlation was found between SSI and TOL values whereas negative and significant association was noted between SSI and YSI. Significant and negative correlation was observed between YSI and TOL values. These traits are recognized as beneficial water stress tolerance indicators for selecting a stress tolerant variety. The most outstanding tolerance capacity in terms of susceptibility indices was detected in CIM-47 and CIM-50 under all water stresses. They indicated lowest SSI, TOL and MP with high YSI values. It may, therefore, be concluded that these genotypes have the potential of stress tolerance.

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Solid amorphous zirconium phosphate /ZPa/ and hafnium phosphate /HPa/ are mixed with an excess of solid oxalic acid dihydrate and are digested in molten oxalic acid. Then oxalic acid is removed by extraction or by heating. The residue is washed with dilute HCl /0.01M/ and redistilled water. By this method -ZP and -HP is formed from amorphous ones.

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Se80−xTe20Znx (x = 2, 4, 6, 8, and 10) glasses have been prepared using conventional melt quenching technique. The kinetics of phase transformations (glass transition and crystallization) have been studied using differential scanning calorimetry (DSC) under non-isothermal condition at five different heating rates in these glasses. The activation energy of glass transition (E t), activation energy of crystallization (E c), Avrami exponent (n), dimensionality of growth (m), and frequency factor (K o) have been investigated for the better understanding of growth mechanism using different theoretical models. The activation energy is found to be highly dependent on Zn concentration. The rate of crystallization is found to be lowest for Se70Te20Zn10 glassy alloy. The thermal stability of these glasses has been investigated using various stability parameters. The values of these parameters were obtained using characteristic temperatures, such as glass transition temperature T g, onset crystallization temperature T c, and peak crystallization temperature T p. In addition to this, enthalpy-released during crystallization has also been determined. The values of stability parameters show that the thermal stability increases with the increase in Zn concentration in the investigated glassy samples.

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Mixed crystalline zirconium-titanium arsenates ZrxTi(1–x) (HAsO4)2·H2O and harnium-titanium arsenates HfxTi(1–x) (HAsO4)2 H2O (where x=0–1) of various compositions with different Zr/Ti or Hf/Ti ratios have been prepared. The compounds have been characterized by X-ray, thermal analysis, chemical analysis, and pH-titrations. For powder X-rays, the compounds appear to be homogeneous crystalline materials with structures similar to -ZrP, -TiP or -ZrTiP. The thermograms show a loss of approximately two moles of H2O, followed by a small loss of O2 with probable formation of ZrO2, As2O3, HfO2, As2O3, ZrO2, As2O5, HfO2, As2O5 from which As2O3 and As2O5 are practically sublimed in two steps. The exchange capacities at r.t. are generally similar to -ZrP and -TiP but are found to be much lower in value.

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The sandwiched pellet technique using Makrofol-E plastic track detectors has been employed to determine trace quantities of uranium in nine brands of flavored chewing tobaccos consumed by the Indian population. In this technique the nuclear reaction,235U(n,f), is used for the quantitative estimation of uranium. The maximum value of uranium (1.88 ppm) has been found in raw tobacco leaves (Surti), while the minimum (0.13 ppm) in Tulsi (Double Zero brand). Other seven brands showed intermediate values of U-contents which are also reported in this paper. These values are compared with the U-contents reported in the literature for other forms of tobaccos.

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Mixed crystalline alpha zirconium — titanium phosphates with variable zirconium to titanium ratios have been prepared both by the well known gel reflux method and a modified HF method. Chemical analysis, X-ray, i.r. and thermal analysis were used to characterize the materials. Exchange capacities for these ion-exchangers have been evaluated by pH-titration combined with radioisotope tract technique for Na+, K+, Rb+ and Cs+.

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