Gyanendra Singh

Evaluation of oxidative stress before and after control of glycemia and after vitamin E supplementation in diabetic patients.

The present study evaluates the presence of oxidative stress in the uncontrolled diabetic state. Glycemic control reduced the oxidative stress, but total normalization of the parameters of oxidative stress was not achieved, indicating continued oxidant injury despite optimal control of the diabetes. Vitamin E supplementation for 4 weeks in these patients further reduced the oxidative stress, suggesting that vitamin E supplementation might be helpful in reducing free-radical-induced oxidant injury.

Lipid peroxidation and vitamin E levels in preeclampsia

Twenty preeclamptic, 25 normotensive pregnant and 25 healthy nonpregnant women were analyzed with regard to serum malonaldehyde (MDA), vitamin E and lipid profile. In preeclampsia, MDA was significantly higher than control. MDA also showed high correlation to the level of blood pressure. Serum cholesterol and triglycerides were increased in normotensive women and still higher in preeclamptic women. A highly significant fall in vitamin E levels in preeclamptic women was noted as compared to control groups. Our study supports the view that an increased lipid peroxidation may be involved in vasoconstriction in preeclampsia.

Effect of smoking on lipid profile, lipid peroxidation and antioxidant status in normal subjects and in patients during and after acute myocardial infarction.

We studied changes in lipid peroxidation, vitamin E status and lipid profile due to smoking in healthy subjects, patients with acute myocardial infarction (MI), and in stabilized patients surviving MI. A significant increase in malondialdehyde (MDA) concentrations was observed in MI patients, more than in smokers (P<0.05), as compared to control. The plasma vitamin E as well as the ratio of vitamin E/lipids were significantly lower in MI patients as compared to stable ischemic heart disease (IHD) patients and controls. Our data show that smoking is associated with lowered antioxidant status in MI.

Effect of Glycemic Control and Vitamin E Supplementation on Total Glutathione Content in Non-Insulin-Dependent Diabetes mellitus

Thirty patients with non-insulin-dependent diabetes mellitus were selected for the study. 15 age-matched healthy volunteers served as controls. Serum malonaldehyde, total glutathione, and vitamin E levels were estimated before and after glycemic control and after 4 weeks of vitamin E supplementation. Both total glutathione and vitamin E levels increased after glycemic control and showed an increase after vitamin E supplementation. Malonaldehyde levels lowered after glycemic control, but remained higher than controls. Since vitamin E supplementation significantly decreased oxidative stress in the present study, it may play a role in reducing free-radical-induced oxidant injury in diabetes mellitus.

Superoxide Anion Formation and Glutathione Levels in Patients with Preeclampsia

Increased free radical activity has been implicated in the pathogenesis of preeclampsia. This article investigates the glutathione status in preeclampsia and whether superoxide generation is enhanced in preeclampsia. Venous blood samples were obtained from 30 preeclamptic women and 30 normotensive pregnant women (controls). Superoxide generation and glutathione content were measured. There was a significant increase in superoxide generation and a marked reduction in glutathione content in preeclamptic women as compared to controls (p < 0.001). These results indicate that enhanced superoxide generation and impaired glutathione metabolism may be involved in the pathogenesis of preeclampsia.

Effect of gold nano-particles on switch-on voltage and relaxation frequency of nematic liquid crystal cell

We report the observation of large changes in the electro-optical properties of nematic liquid crystal (NLC) due to inclusion of small concentration of 10 nm diameter gold nanoparticles (GNPs). It is observed that GNPs lower switch-on voltage and also lower the relaxation frequency with applied voltage (AC field) to NLC cell. These studies of GNP doped NLC cell have been done using optical interferometry and capacity measurement by impedance analyzer. The change in threshold voltage and relaxation frequency by doping GNPs in NLC is explained theoretically.

Photoluminescence studies of organic phosphor coated diffusing surface using blue inorganic light-emitting diode as excitation source

We report the studies on photoluminescence (PL) of organic phosphor coated on a diffusing surface using a blue inorganic light-emitting diode (LED) array as an excitation source. The organic phosphor composite coated diffuser was used to scatter the directional blue light from the LED array. Some of the blue light is absorbed by the organic phosphor composite and the phosphor molecules are excited and re-emit light at longer wavelengths due to the PL process. The output light consists of scattered blue light plus phosphor generated broadband yellow light, thus making white light. The diffuser was made up of a plastic substrate coated with an organic composite of small molecule fluorescent material zinc(II)bis(8-hydroxyquinoline) (Znq2) doped with different percentages of electro-phosphorescent metal complex iridium(III)bis(2-methyldibenzo-[f, h] quinoxaline) (acetylacetonate) ([Ir(MDQ)2(acac)]). By means of changing the concentration and the thickness of the phosphor composite material the colour coordinates of white light were achieved. The CIE coordinates and correlated colour temperature were calculated for various thicknesses and phosphor composite concentrations and the results are reported.

Generation of Optical Vortex Arrays Using Single-Element Reversed-Wavefront Folding Interferometer

Optical vortex arrays have been generated using simple, novel, and stable reversed-wavefront folding interferometer. Two new interferometric configurations were used for generating a variety of optical vortex lattices. In the first interferometric configuration one cube beam splitter (CBS) was used in one arm of Mach-Zehnder interferometer for splitting and combining the collimated beam, and one mirror of another arm is replaced by second CBS. At the output of interferometer, three-beam interference gives rise to optical vortex arrays. In second interferometric configuration, a divergent wavefront was made incident on a single CBS which splits and combines wavefronts leading to the generation of vortex arrays due to four-beam interference. It was found that the orientation and structure of the optical vortices can be stably controlled by means of changing the rotation angle of CBS.

Measurement of change in refractive index in polymeric flexible substrates using wide field interferometry and digital fringe analysis

Indium tin oxide coated polyethylene terephthalate (PET) polymeric films are widely used as substrates for future optoelectronic devices, such as organic LEDs, organic thin film transistors, and organic solar cells. These PET substrates are thin, flexible, and rugged. But residual stresses are trapped in polymeric substrates due to their manufacturing process, and this leads to the birefringence in flexible displays. In this paper we report the measurement of the change in refractive index of PET substrates using Mach-Zehnder interferometry and the Fourier transform fringe analysis technique. Change in refractive index was observed by means of bending the PET substrate. This change in birefringence varies the optical path difference between the two arms of the interferometer, leading to the fringe shift. From the fringe shift the phase change was extracted as a function of bending, and the change in the refractive index was determined experimentally for two wavelengths, i.e., red and green color lasers. We found that the value of change in the refractive index of these substrates increases on bending of the substrates.

Polarization interferometric digital holographic microscope for quantitative phase imaging and coherent noise reduction

In digital holographic interferometry (DHI), coherent noise degrades accuracy of phase information. We present multi-beam polarization DHI in which two cross polarized interferograms are recorded. Fourier analysis of interferograms reduces coherent noise and increases accuracy.