Sudha Agrawal

Bio: Sudha Agrawal is an academic researcher from Harcourt Butler Technological Institute. The author has contributed to research in topics: Styrene & Acrylic acid. The author has an hindex of 6, co-authored 7 publications receiving 121 citations.

Individual and interactive effects of elevated carbon dioxide and ozone on tropical wheat (Triticum aestivum L.) cultivars with special emphasis on ROS generation and activation of antioxidant defence system.

Abstract: The effects of elevated CO2 and O3, singly and in combination were investigated on various physiological, biochemical and yield parameters of two locally grown wheat (Triticum aestivum L.) cultivars (HUW-37 and K-9107) in open top chambers (OTCs). Elevated CO2 stimulated photosynthetic rate (Ps) and Fv/Fm ratio and reduced the stomatal conductance (gs). Reactive oxygen species, lipid peroxidation, anti-oxidative enzymes, ascorbic acid and total phenolics were higher, whereas Ps, gs, Fv/Fm, protein and photosynthetic pigments were reduced in elevated O3 exposure, as compared to their controls. Under elevated CO2 + O3, elevated levels of CO2 modified the plant performance against O3 in both the cultivars. Elevated CO2 caused significant increase in economic yield. Exposure to elevated O3 caused significant reduction in yield and the effect was cultivar-specific. The study concluded that elevated CO2 ameliorated the negative impact of elevated O3 and cultivar HUW-37 was more sensitive to elevated O3 than K-9107.

Effect of diluents on the curing behavior of vinyl ester resin

Abstract: An acidic vinyl ester resin (∼6 mg KOH per gram of solid) was prepared by reacting a bisphenol-A-based epoxy resin with acrylic acid in the presence of tributyl amine. The acrylated epoxy resin thus obtained was characterized by Fourier transform infrared spectroscopy. Five samples of vinyl ester resin containing styrene and methyl methacrylate (MMA) in the weight ratios 40:0, 30:10, 20:20, 10:30, and 0:40 were prepared at 30°C, and their curing behavior was studied by differential scanning calorimetry in the presence of benzoyl peroxide (2 phr). Curing behavior was dependent on the ratio of the two monomers used as reactive diluents. The kinetic parameters were determined by Ozawa's method. The energy of activation and frequency factor varied from 17 to 23 kcal mol−1 and 8.47 × 109 to 5.21 × 1012 min−1, respectively and were lowest for the samples containing 30:10 and 10:30 styrene/MMA weight ratios. The curing reactions followed first-order kinetics and obeyed the Arrhenius rate expression. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1948–1951, 2003

Kinetics and mechanism of esterification of monoepoxies

Abstract: The esterification of monoepoxy diluents (phenyl, cresyl, and butyl glycidyl ethers) and acrylic acid in presence of triphenylphosphine as catalyst was performed at 70 ○, 75 ○, 80 ○, 85 ○, and 90 ○C, and it followed first-order kinetics. The reactivity of aromatic monoepoxies was found to be higher than aliphatic, due to the inductive effect of phenyl and butyl groups. The activation energy of the esterification of the monoepoxy increases as Pv < Cv < Bv and varies from 67 to 82 KJ/mole. The specific rate constants were found to obey the Arrhenius expression. The kinetic and thermodynamic parameters viz., activation energy, frequency factor, entropy, enthalpy, and free energy revealed that the reaction was spontaneous and irreversible, resulting in a highly ordered, activated complex. A suitable mechanism is proposed and discussed.

Curing and rheological behavior of vinyl ester resins prepared in the presence of tertiary amines

Abstract: Vinyl ester resins V1, V2 & V3 of acid value (∼6 mg KOH g−1 solid) were synthesized using bisphenol-A epoxy and acrylic acid in the presence of triethyl-, tripropyl- and tributyl-, amines in 210, 270 and 340 minutes, respectively. The synthesized resins were characterized by FTIR spectroscopy and a new peak at 2360 cm−1 was observed which is due to attachment of amines to resin structure by hydrogen bond. The curing behavior of synthesized resin containing 40% styrene (w/w) and 2% benzoyl peroxide was studied using DSC technique and found to be affected by presence of amines. Activation energy and frequency factor for the curing reaction increases from 14 Kcal mol−1 to 23 Kcal mol−1. Rheological behavior of resins containing 40% styrene was studied using a Haake Rotovisco RV20 viscometer, and viscosity was found to increase with shear rate up to 200 sec−1. The average values of activation energy at constant shear stress (6-15 Pa) were 12.94, 13.20, 13.70 Kcal mol−1 for V1, V2 and V3, respectively. The act...

Effect of diluents on the decomposition behavior of vinyl ester resin

Abstract: An acidic vinyl ester resin (∼6 mg KOH per gram of solid) was prepared by reacting a bisphenol-A-based epoxy resin with acrylic acid in the presence of tributylamine. The acrylated epoxy resin thus obtained was characterized by Fourier transform infrared spectroscopy. Five samples of vinyl ester resin containing styrene and methyl methacrylate (MMA) in the weight ratios 40:0, 30:10, 20:20, 10:30, and 0:40 were prepared at 30°C. These samples were cured, using 2 phr benzoyl peroxide, at 90 ± 2 °C for 1 h. The decomposition behavior of all the samples was studied by thermogravimetric analysis (TGA) at 10°C min−1. The TG and dynamic thermogravimetry (DTG) thermograms showed single-step degradation in the individual cases of styrene and MMA, whereas a two-step degradation process was observed when styrene was mixed with MMA in any proportion. For all the samples, the order of the reaction was one for the first step. This value was calculated with the Coats and Redfern equation in accordance with the best-fit analysis and further confirmed by linear regression analysis. From this value of reaction order (n), the activation energy (E) and pre-exponential factor (Z) were calculated, and the validity of the data was checked by statistical analysis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1952–1956, 2003

Antioxidant responses of wheat plants under stress

Abstract: Currently, food security depends on the increased production of cereals such as wheat (Triticum aestivum L.), which is an important source of calories and protein for humans. However, cells of the crop have suffered from the accumulation of reactive oxygen species (ROS), which can cause severe oxidative damage to the plants, due to environmental stresses. ROS are toxic molecules found in various subcellular compartments. The equilibrium between the production and detoxification of ROS is sustained by enzymatic and nonenzymatic antioxidants. In the present review, we offer a brief summary of antioxidant defense and hydrogen peroxide (H2O2) signaling in wheat plants. Wheat plants increase antioxidant defense mechanisms under abiotic stresses, such as drought, cold, heat, salinity and UV-B radiation, to alleviate oxidative damage. Moreover, H2O2 signaling is an important factor contributing to stress tolerance in cereals.

Design and construction

Abstract: This chapter discusses a current comparator. The design of the various components of a comparator may be affected by these factors. To detect short circuit and insulation faults arising during construction and to confirm the effectiveness of the shielding as it is installed, the probe test should be carried out at frequent intervals during the construction.