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  • Author or Editor: R. Tiwari x
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Abstract  

The space charge trapping/detrapping in thermally charged polyimide (PI) samples have been studied by means of “Final Thermally Stimulated Discharge Current” (FTSDC). We investigate the effects associated with space charge behavior in PI near glass transition region. The FTSDC spectra consist of space charge peak attributed trapping of charges at different trapping levels. The peak positions are found to be very sensitive with poling time, discharging time, and heating rate. The apparent activation energy distributed in the range from 0.51 to 1.12 eV, and the charge released has been found to be varying with poling temperature (T p) and poling time (t c)/discharging time (t d). The decay of space charge (Q) resembled an agreement with interfacial polarization.

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4,4′-bismaleimidophenyl methane (BM) and 3,3′-bismaleimidophenyl sulfone (BS) were blended in solution using weight ratios 3∶1 (MS31), 2∶1 (MS21), 1∶1 (MS11), 1∶2 (MS12) and 1∶3 (MS13). Chain extended bismaleimide resins were also prepared by treating BS/BM with 4,4′-diaminodiphenyl ether in molar ratios of 1∶0.3 (BM-E and BS-E resins). These resins were also blended with bismaleimides and the curing characteristics were evaluated by differential scanning calorimetry. Increase in BM content in BM∶BS blends or increase in chain extended bismaleimide content in BM-E∶BS or BS-E ∶ BM blends resulted in a reduction of melting and curing temperatures. Indication about the extent of cross-linking was obtained from solubility measurements (in DMF) of isothermally cured resins (180 °C, lh and 220 °C, lh in an air oven). Thermogravimetric analysis of samples isothermally cured at 180 °C and 220 °C (lh each) was carried out in nitrogen atmosphere. Improvement in thermal stability of chain extended bismaleimides was observed on blending.

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Leaf rust resistance genes Lr9 and Lr10 were detected in wheat (Triticum aestivum) genotypes by PCR based STS markers. Out of sixty-two elite wheat genotypes, screened for the presence of leaf rust resistance gene Lr10, nineteen genotypes revealed the presence through PCR analysis with the primers specific to Lr10 gene. Validation of  the marker for Lr9 gene in the parental lines followed by successful detection of the gene in F4 lines out of cross HP1633 (Lr9) X HP1776, was also done. Usefulness of molecular markers for the detection of rust resistance genes in different genotypes is discussed.

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Summary

The objective of the present investigation was to develop and validate a stability indicating liquid chromatography (LC) method which should possess potential to separate flucloxacillin as well as all the degradation products. Simultaneously, our aim was also to identify, separate, and characterize the major degradation product (DPs) of flucloxacillin, generated under various stress conditions. To achieve this objective, flucloxacillin was subjected to hydrolytic, oxidative, photolytic, and thermal stress as per International Conference on Harmonization (ICH) guidelines Q1A(R2). The drug was found to degrade in acidic, alkaline, neutral, and oxidative stress conditions and showed stable behavior in photolytic and thermal stress conditions. In total, seven degradation products were formed, which were separated on a C-18 column employing a gradient high-performance liquid chromatographic (HPLC) method. A complete mass fragmentation pathway of the drug was established with the help of multi-stage (MSn) and mass spectrometry/time of flight (MS/TOF) accurate mass studies. Then the stress samples were subjected to LC-MS/TOF studies, which provided the fragmentation pattern along with the accurate masses for a major degradation product. The entire mass spectral studies helped to identify the degradation product so as to propose its best possible structure. Finally the total information was used to establish the degradation pathway of the drug.

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Terminal heat referred to as increase in temperature during grain filling, is one of the important stress factors for wheat production and is responsible for decline in wheat production in many environments worldwide. In order to meet the challenges of high temperature ahead of global warming, concerted efforts are needed to evaluate wheat genotypes for heat tolerance and develop genotypes suitable for such stressed environments. Twenty-seven advanced wheat genotypes developed for stress and normal environments by different research centres were evaluated during 2009–10 and 2010–11 under timely sown (normal) and late sown (heat stress) environments. Analysis of variance revealed that the genotypes differed significantly in grain filling duration (GFD), grain growth rate (GGR) and thousand-grain weight (TGW). Out of 27 genotypes, 16 were found to be tolerant for thousand-grain weight under late planting (heat stress) during 2009-10 but only 12 were tolerant during 2010–11. Many of the genotypes registered more reduction in thousand-grain weight during 2010–11 as compared to 2009–10; the temperatures during 2009–10 were higher. The differences in grain filling duration under two conditions during both seasons as well as difference in temperatures during first half of grain filling explain the reduction pattern in the genotypes. GFD had significant negative correlation with temperatures during post heading period and the difference in GFD under two environments had positive correlation with these temperatures. The reduction in GFD had regression of 33.3% on reduction in GGR and reduction in GGR had regression of 41.6% on reduction in TGW genotypes AKW 1071, DBW 17, HS 277, K 7903, K 9107, NW 1014 and RAJ 3765 had less sensitivity to stress environments during both years.

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The aim of this study was to develop a PCR based assay for an efficient selection of Yr10 resistance gene in breeding material. The two primer pairs designed from the Yr10 gene sequence amplified specific DNA fragments in the genotypes carrying Yr10 and did not give a signal with near isogenic line and other lines containing different Yr genes. The genetic linkage of these molecular markers to Yr10 gene was tested on a segregating F 2 population derived from cross between the stripe rust resistant genotype carrying Yr10 (FLW10) and the susceptible line WH542. The data demonstrated that the markers derived from Yr10 gene sequence are completely linked to Yr10 , which will enable to combine this gene with other stripe rust resistance genes in wheat breeding programmes.

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Summary  

The present paper reports the Differential Scanning Calorimetric (DSC) study of some Ag doped Se-Te chalcogenide glasses. DSC runs were taken at different heating rates. Well-defined endothermic and exothermic peaks were obtained at glass transition and crystallization temperatures. The variation of glass transition temperature T gwith Ag concentration has been studied. It has been found that T gdecreases with increase in Ag concentration. The heating rate dependence of T gis used to evaluate the activation energy of glass transition (DE t). The value ofDE thas been found to increase with increase in Ag concentration followed by nearly constant value at higher concentrations of Ag.

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Grain yield and quality under terminal heat stress (post anthesis) are the most complex traits that are influenced by environmental factors and are characterized by low heritability and large genotype × environment interactions. The present study was undertaken to determine effectiveness of selection for genotypes tolerant to heat stress using differences in 1000-grain weight (dTGW) under the optimum and late sown field condition. A Recombinant Inbred Line (RIL) mapping population derived from the heat sensitive genotype Raj 4014 and heat tolerant genotype WH730 was evaluated for the heat stress over 2 years in a replicated trial under optimum and late sown field conditions. The parental lines were screened with approximately 300 SSR (μsatellite) markers out of which about 20% showed polymorphism. These polymorphic markers were utilized for genotyping a subset that had clear contrasting variation for dTGW. The difference in TGW between the timely and late sown conditions was used as a phenotypic trait for association with markers. Analysis of the two years data under timely and late sown condition revealed parents and their RILs clearly showing variation with respect to the dTGW. Regression analysis revealed significant association of dTGW of RILs with two markers viz., Xpsp3094, and Xgwm282 with coefficients of determination (R2) values of 0.14 and 0.11, respectively.

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The aim of this work was to simultaneously separate, identify, and characterize all the degradation products (DPs) of atorvastatin (AT) and olmesartan (OM) formed under different stress conditions as per International Conference on Harmonization (ICH) Q1A(R2) guideline. AT showed labile behavior in acidic, basic, neutral, and oxidative stress and led to the formation of two DPs, while OM degraded under acidic, basic, and neutral and resulted in the formation of four DPs. All the stressed samples of AT and OM were resolved on a C-18 column in single run on a gradient liquid chromatographic (LC) mode. A complete mass fragmentation pathway of both the drugs was established with the help of tandem mass spectrometry (MS/MS) studies. The fragmentation was further supported by MSn studies, and for AT, it was carried out up to MS6, while for OM, it was up to MS5. Then, the stressed samples were analyzed by LC–MS/MS to get the fragmentation patterns of DPs. LC–MS/MS data helped to propose chemical structure of all the DPs. Based on this entire information, degradation pathway of both the drugs was established. The developed method has shown excellent linearity over the range of 10 to 150 μg/mL of OM and AT. The correlation coefficient (r 2) for OM and AT is 0.999 and 0.998, respectively. The main recovery value of OM and AT ranged from 99.97% to 100.54%, while the limit of detection (LOD) for OM and AT was 0.018 and 0.021 μg/mL, and limit of quantitation (LOQ) was found to be 0.051 and 0.063 μg/mL. Finally, the in-silico carcinogenicity, mutagenicity, and hepatotoxicity predictions of AT, OM, and all the DPs were performed by using toxicity prediction softwares, viz., TOPKAT, LAZAR, and Discovery Studio ADMET, respectively.

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Inorganic particulates in removal of toxic heavy metal ions

Part X: Removal behavior of aluminum hydroxide for Hg(II): A radiotracer study

Journal of Radioanalytical and Nuclear Chemistry
Authors: S. Mishra, D. Tiwari, S. Prasad, R. Dubey and Manisha Mishra

Abstract  

The removal behavior of amorphous aluminum hydroxide for Hg(II) ions from aqueous solutions was investigated by employing a radiotracer technique at micro down to trace level concentrations. The batch type experiments were performed to obtain various physico-chemical parameters, viz., effect of sorptive concentration, temperature and pH. It was observed that the increase in sorptive concentration (from 1·10−8 to 1·10−2 mol·dm−3), temperature (from 303 to 333K) and pH (from 3.4 to 10.3) apparently favored the uptake of Hg(II) by this solid. Similarly, the presence of anions (six fold) viz., oxalate, phosphate, glycine and EDTA also enhanced the uptake behavior of aluminum hydroxide for Hg(II). Whereas, the added cations viz., Na+, K+, Ba2+, Sr2+, Mg2+, Cd2+ and Fe3+ more or less suppressed the removal behavior of the adsorbent. Further, the adsorption process followed the classical Freundlich adsorption isotherm and deductions of various thermodynamic data revealed that the uptake of Hg(II) on aluminum hydroxide followed the ion-exchange type mechanism and thermodynamically it was found to be endothermic in nature.

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