Nanoindentation studies on waveguides inscribed in chalcogenide glasses using ultrafast laser

Optical straight waveguides are inscribed in GeGaS and GeGaSSb glasses using a high repetition-rate sub-picosecond laser. The mechanical properties of the glasses in the inscribed regions, which have undergone photo induced changes, have been evaluated by using the nanoindentation technique. Results show that the hardness and elastic modulus of the photo-modified glasses are significantly lower as compared to the other locations in the waveguide, which tend to be similar to those of the unexposed areas. The observed mechanical effects are found to correlate well with the optical properties of the waveguides. Further, based on the results, the minimum threshold values of hardness and elastic modulus for the particular propagation mode of the waveguide (single or multi), has been established

Thalidomide attenuates nitric oxide mediated angiogenesis by blocking migration of endothelial cells

BACKGROUND: Thalidomide is an immunomodulatory agent, which arrests angiogenesis. The mechanism of anti-angiogenic activity of thalidomide is not fully understood. As nitric oxide is involved in angiogenesis, we speculate a cross-talk between thalidomide and nitric oxide signaling pathway to define angiogenesis. The aim of present study is to understand the mechanistic aspects of thalidomide-mediated attenuation of angiogenesis induced by nitric oxide at the cellular level. METHODS: To study the cellular mechanism of thalidomide-mediated blocking of angiogenesis triggered by nitric oxide, we used two endothelial cell based models: 1) wound healing and 2) tube formation using ECV 304, an endothelial cell line. These cell-based models reflect pro-angiogenic events in vivo. We also studied the effects of thalidomide on nitric oxide mediated egg yolk angiogenesis. Thalidomide could block the formation of blood vessels both in absence and presence of nitric oxide. Thalidomide effects on migration of, and actin polymerization in, ECV 304 cells were studied at the single cell level using live cell imaging techniques and probes to detect nitric oxide. RESULTS: Results demonstrate that thalidomide blocks nitric oxide-mediated angiogenesis in egg yolk model and also reduces the number of tubes formed in endothelial cell monolayers. We also observed that thalidomide arrests wound healing in presence and absence of nitric oxide in a dose-dependent fashion. Additionally, thalidomide promotes actin polymerization and antagonizes the formation of membrane extensions triggered by nitric oxide in endothelial cells. Experiments targeting single tube structure with thalidomide, followed by nitric oxide treatment, show that the tube structures are insensitive to thalidomide and nitric oxide. These observations suggest that thalidomide interferes with nitric oxide-induced migration of endothelial cells at the initial phase of angiogenesis before cells co-ordinate themselves to form organized tubes in endothelial cells and thereby inhibits angiogenesis. CONCLUSION: Thalidomide exerts inhibitory effects on nitric oxide-mediated angiogenesis by altering sub-cellular actin polymerization pattern, which leads to inhibition of endothelial cell migration

Climate of early Martian surface and loss of water – A review

Mars is one of the interesting planets for geoscientists to explore the presence of water on the surface of terrestrial planets. The age, geology and geomorphic processes of Mars are almost similar to Earth surface processes. However, earth as tremendous influence of tectonism. The Martian surface once it was flourishing with water flow and formations of fluvial channels, lakes, deltas and oceans. The planet Mars evolved through ages with different climatic conditions from warm wetter period to cold drier period. In the present paper, different climatic condition and the reasons for escape of water from surface of Mars are discussed with help of review work

Effect of sodium chloride stress on the pigment and biochemical variation of pigeon pea (Cajanus cajan (L.) Millsp.)

                In the present study, a pot culture experiment was conducted to estimate the effect on NaCl stressed Pigeon pea (Cajanus cajan (L.) Millsp.) the plant belongs to family Fabaceae, is a sub tropical crop, grown world wide particularly in south Asia for edible and fodder purposes, while little is known about its salinity tolerance. The seed were sown in plastic pots from 30 days after sowing (DAS), the plants were treated with 25mM, 50mM, 75mM and 100mM sodium chloride on 20th, 30th and 40th DAS. The plants samples were collected from 30th, 40th and 50th DAS. The leaf were collected for estimating pigment and biochemical content. The sodium chloride treatment decreased the chlorophyll-a, b, total chlorophyll and protein content. Similarly the amino acid and proline content were increased with increasing concentration of NaCl to a larger extent when compared to control in all the treatment day

Modeling of experimental data for the adsorption of methyl orange from aqueous solution using a low cost activated carbon prepared from Prosopis juliflora

This paper presents the feasibility for the removal of methyl orange (MO) dye from aqueous solution using an activated carbon prepared from Prosopis juliflora bark. Batch adsorption experiments were carried out as a function of pH, contact time, adsorbate concentration, adsorbent dosage and temperature. The commonly applicable isotherms namely Freundlich and Langmuir equations are used for the prediction of isotherm parameters. A comparison of linear least-square method and a trial-and-error non-linear method are examined in Freundlich and Langmuir (Four forms) isotherms. The nature of adsorption isotherm feasibility was evaluated with dimensionless separation factors (RL). The dynamics of adsorption process was analyzed with Lagergren’s Pseudo-first order and Pseudo-second order kinetic equations. Thermodynamic parameters like the change in enthalpy (ΔHo), change in entropy (ΔSo) and change in Gibbs free energy (ΔGo) were evaluated and ΔGo shows a negative value whereas ΔHo shows the positive value indicating that the adsorption process was spontaneous and endothermic in nature. The functional group characterization of the adsorbent was done using Fourier transform infrared spectroscopy (FTIR). The thermal stability of activated carbon was analyzed using Thermo gravimetric analysis (TGA) and Differential thermal analysis (DTA)

Optimization of medium components and operating conditions for the production of solvent-tolerant lipase by Bacillus sphaericus MTCC 7542

The production of lipase by Bacillus sphaericus MTCC 7542 growing on basal media with various carbon, nitrogen sources and environmental conditions was studied. Studies were undertaken to improve lipase production. Olive oil, Tween 80, rice bran oil, sunflower oil, soybean oil, palm oil and groundnut oil were tested as different lipid sources in this medium, with olive oil at 1% giving a lipolytic activity of 0.19 U/ml after 48 h, which was the highest yield obtained in this study. The effect of carbon source was studied by adding glucose, fructose, sucrose, lactose, starch and cellulose to a medium containing potassium nitrate and other minerals maintained as constant. The best yield of 0.20 U/ml after 48 h was obtained with the medium supplemented with 0.2% of glucose. The effect of nitrogen source was studied by adding peptone, yeast extract, tryptone, gelatin, casein, ammonium chloride, urea, ammonium sulphate, ammonium nitrate and ammonium acetate. The maximum yield of 0.21 U/ml after 48 h was obtained with the medium supplemented with yeast extract and ammonium chloride. Enzyme production was best at 7.5 pH, within a range tested from 6.5 to 8. The maximum enzyme was obtained at 35°C within a range tested from 25 to 40°C. These results are promising because this strain produces lipase in an inexpensive medium and we succeeded in increasing the lipolytic activity 3-fold over the initial values obtained with the non-optimized medium

A study on leakage current and electrical properties of oleic acid-coated cobalt-doped Mn-Zn ferrite nanocrystalline powders

Abstract Background Mn-Zn ferrites have drawn a continuously an increasing interest because of their potential applications as multifunctional devices. These materials simultaneously exhibit ferroelectricity and ferromagnetism. The dielectric and leakage current properties of Cobalt substituted Mn-Zn ferrites coated with oleic acid were not reported. Methods This paper presents the synthesis, electrical, and leakage properties of nanoparticles of cobalt-doped Mn-Zn ferrite [CoxMnyZnyFe2O4 (x = 0.1, 0.5, and 0.9 and y = 0.45, 0.25, and 0.05)] coated with oleic acid and prepared by chemical co-precipitation method. The crystal structure was determined by X-ray diffraction (XRD), the effect of strain on the electronic structure was analyzed using Williamson-Hall plot. Complex impedance spectroscopic analysis was carried out, and the impedance plots show the resistive and reactive parts of the impedance. Frequency dependence on AC conductivity was investigated for all the compositions, and leakage current properties were also studied. Results The nanoparticles were found to have an average size of 13.62 nm. The average crystallite size (DaveXR) of the precipitated particles found to decrease from 15.22 to 12.65 nm with increasing cobalt substitution. The presence of two semicircular arcs at the lower and higher frequency regions indicates the grain boundary conduction and grain conduction at room temperature. Leakage current density of the order of 10-4 A/cm2 (at field strength of 0.02 kV/cm) was observed for all compositions. Conclusion The variation of the strain values from negative to positive indicates that the strain changes from compression to tensile. The dielectric permittivity was found to decrease from 104to 103 with increase in frequency. The semicircle in the higher frequency region is attributed to the grain conduction of the materials, and the semicircle in the lower frequency region is due to the grain boundary conduction. Both the grain and grain boundary are found to be active at room temperature. AC conductivity is found to be compositional dependent

Salt effect on the enthalpy of mixing of 2-propanol + acetic acid at 303.15 K

This paper presents the effect of two dissolved inorganic salts (zinc chloride, ZnCl2 and ammonium chloride, NH4Cl) on the enthalpy of mixing (HE) of 2-propanol + acetic acid binary system measured at 303.15 K using an isothermal displacement calorimeter with vapour space. A decreasing trend in the excess enthalpy of mixing values in the presence of ZnCl2 and NH4Cl indicate the endothermic behavior of this system. The Redlich-Kister equation has been used to fit the experimental HE data. The deviations from the ideal value and binary parameters were calculated and reported