Enhanced growth rates and reduced parasitic deposition by the substitution of Cl2 for HCl in GaN HVPE

The main limitation in the application of hydride vapor phase epitaxy for the large scale production of thick free-standing GaN substrates is the so-called parasitic deposition, which limits the growth time and wafer thickness by blocking the gallium precursor inlet. By utilizing Cl₂ instead of the usual HCl gas for the production of the gallium chlorine precursor, we found a rapid increase in growth rate from ∼80 to ∼400 μm/h for an equally large flow of 25 sccm. This allowed us to grow, without any additional optimization, 1.2 mm thick high quality GaN wafers, which spontaneously lifted off from their 0.3° mis-oriented GaN on sapphire HCl-based HVPE templates. These layers exhibited clear transparencies, indicating a high purity, dislocation densities in the order of 10⁶ cm⁻², and narrow rocking curve XRD FWHMs of 54 and 166 arcsec in for the 0002 and 101−5 directions, respectively.     

Optimization of Adventitious Root Culture for Production of Biomass and Secondary Metabolites in Prunella vulgaris L.

Adventitious root cultures of Prunella vulgaris L. were established in shaking flask system for the production of biomass and secondary metabolites. Adventitious root cultures were induced from callus cultures obtained from leaf explants on solid Murashige and Skoog (MS) medium containing combination of 6-benzyladenine (BA; 1.0 mg l^?1) and naphthalene acetic acid (NAA; 1.5 mg l^?1). Thereafter, 0.49 g inoculum was transferred to liquid MS medium supplemented with different concentrations of NAA (0.5–2.0 mg l^?1). Growth kinetics of adventitious roots was recorded with an interval of 7 days for 49 days period. Highest biomass accumulation (2.13 g/l) was observed in liquid medium containing 1.0 mg l^?1 NAA after 21 days of inoculation. However, other concentrations of NAA also showed similar accumulation pattern but the biomass gradually decreases after 49 days of inoculation. Adventitious roots were collected and dried for investigation of total phenolics (TP), total flavonoids (TF), and antioxidant activities. Higher TPC (0.995 GAE mg/g-DRB) and TFC (6.615 RE mg/g-DRB) were observed in 0.5 mg l^?1 NAA treated cultures. In contrast, higher antioxidant activity (83.53 %) was observed 1.5 mg l^?1 NAA treated cultures. These results are helpful in up scaling of root cultures into bioreactor for secondary metabolites production.     

O-Alkylation of Menthone Oxime: Synthesis and 13C NMR Studies of a Series of Novel Oxime Ethers

A series of novel menthone oxime ethers were synthesized in three steps starting from (–)-menthol. Analysis of the ¹³C NMR chemical shift differences between α carbons of oxime derivatives (O-alkyl oximes) provides a convenient and reliable means of assigning oxime stereochemistry. It has been found that carbons syn to the oxime are shifted more upfield than carbons anti to the oxime moiety. Significant E products were obtained.     

The explicit series solution of SIR and SIS epidemic models

In this paper the SIR and SIS epidemic models in biology are solved by means of an analytic technique for nonlinear problems, namely the homotopy analysis method (HAM). Both of the SIR and SIS models are described by coupled nonlinear differential equations. A one-parameter family of explicit series solutions are obtained for both models. This parameter has no physical meaning but provides us with a simple way to ensure convergent series solutions to the epidemic models. Our analytic results agree well with the numerical ones. This analytic approach is general and can be applied to get convergent series solutions of some other coupled nonlinear differential equations in biology.     

Engineering of mesoporous silica nanoparticles for release of ginsenoside CK and Rh2 to enhance their anticancer and anti-inflammatory efficacy: in vitro studies

The current study highlights the fabrication of drug delivery system by utilizing 200 nm mesoporous silica nanoparticles (MSNPs) with 4-nm pore size, as a carrier system for delivery ginsenoside compound K (CK) and Rh2 to enhance their efficacy. The two pharmacologically imperative ginsenosides, CK and Rh2, were loaded to the MSNPs to prepare MSNPs-CK and MSNPs-Rh2, respectively. A fluorescein isothiocyanate (FITC) fluorescent dye was combined in the MSNPs carrier system, in order to trace the cellular uptake of ginsenoside-loaded nanoparticles for in vitro studies. Following purification, the so-prepared MSNPs-CK-FITC and MSNPs-Rh2-FITC were characterized by several analytical techniques, which includes, high-pressure liquid chromatography (HPLC), ¹H NMR, field emission transmission electron microscopy (FE-TEM), Fourier transform infrared spectroscopy (FT-IR), x-ray diffraction (XRD), thermogravimetric analysis (TGA), and dynamic light scattering (DLS). In vitro cytotoxicity assay in HaCaT skin cells, A549 lung cancer cells, HepG2 liver carcinoma cells, and HT-29 colon cancer cell lines were tested for MSNPs-CK-FITC and MSNPs-Rh2-FITC. The results demonstrate the excellent biocompatibility of nanoparticles in normal cell lines (HaCaT skin cells) and anticancer efficacy in all the tested cancer cell lines at 10-μM concentration. Additionally, the in vitro anti-inflammatory behavior of MSNPs-CK-FITC and MSNPs-Rh2-FITC were checked in RAW264.7 (murine macrophage) cell lines. The outcomes showed higher anti-inflammatory efficacy of MSNPs-CK-FITC and MSNPs-Rh2-FITC as compared to standard ginsenosides CK and Rh2 in RAW264.7 cell lines. Thus, with 200 nm MSNPs carrier system for the delivery ginsenosides CK and Rh2, a high amount of loading and increasing in vitro pharmacological efficacies of ginsenosides were realized. This study may provide useful insights for designing and improving the applicability of MSNPs for ginsenoside delivery.     

Effect of wall properties on the magnetohydrodynamic peristaltic flow of a Maxwell fluid with heat transfer and porous medium

The elastic effect of the flexible walls is analyzed on the peristaltic motion of Maxwell fluid in a channel with heat transfer. An incompressible and magnetohydrodynamic (MHD) fluid fills the porous space. The series solution of the modeled problem is derived by considering small wave number. The influence of pertinent parameters is shown and discussed with the help of graphs. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2010     

Synthesis and characterization of magnetic poly(acrylic acid) hydrogel fabricated with cobalt nanoparticles for adsorption and catalytic applications

The present study aimed to synthesize poly(acrylic acid) hydrogel embedded with magnetic cobalt (Co) nanoparticles and to investigate their potential in adsorption and catalysis. The hydrogel was prepared by facile free radical polymerization reaction and Co nanoparticles were fabricated within hydrogel by reducing Co (II) ions using NaBH₄ as reducing agent. Co nanoparticles within hydrogel system imparted magnetic properties to the resulting composite gel and also increased the adsorption capacity. The swelling study of hydrogel was carried out by gravimetric analysis. Different functional groups were identified by Fourier Transform Infrared Spectroscopy and Transmission Electron Microscopy analysis was done to investigate dispersion of Co nanoparticles in hydrogel. The bare hydrogel along with Co nanoparticles loaded gel were tested as adsorbent systems for the removal of a cationic dye (methylene blue) from aqueous solution. 95% removal of methylene blue was achieved with a highest adsorption capacity of 836.5 mg/g of adsorbent. The famous adsorption isotherms were used to evaluate adsorption data. Results showed that Freundlich isotherm model was followed with R² value of 0.95. The hydrogel was also used for catalytic reduction in a toxic pollutant, i.e., 4-nitrophenol. Experimental data for 4-nitrophenol reduction followed pseudo first order kinetics model. Activation energy and apparent rate constant were calculated as 9.24 kJ/mol and 0.24 min⁻¹, respectively. Recycling of the magnetic poly(acrylic acid) hydrogel fabricated with Cobalt nanoparticles was carried out for four consecutive cycles and no significant loss in catalytic activity was observed.

     

Mechanical,Biodegradation and Morphological Properties of Sisal Fiber Reinforced Poly(Lactic Acid) Biocomposites

Sisal fiber-reinforced poly(lactic acid) (SF/PLA) biocomposites were prepared by melt mixing and subsequent compression molding. The effect of fiber content and sodium hydroxide (NaOH) concentration, used for the fiber mercerization, on the properties of the biocomposites was investigated. It was found that the SFs had a large potential for improving the mechanical properties of the biocomposites. The tensile strength and impact strength increased linearly up to a fiber content of 20%, and then decreased due to the fiber agglomeration. The water absorption was enhanced with increasing the SF content owing to the SFs containing an abundance of hydroxyl groups. The biodegradability of the SF/PLA biocomposites increased similarly. Furthermore, the mercerization led to an increase of the mechanical properties of the biocomposites, which normally depended on the fiber-matrix adhesion. The mercerization had competing effects on the water absorption and biodegradability, including not only the positive function of the improved hydrophilicity of the mercerized-SF but also the negative role of the increase of fiber-matrix interfacial adhesion. Overall, the optimum SF load for mechanical properties was 20?wt% due to a good balance between the reinforcement and distribution of the SFs, whereas the 6% NaOH concentration was optimal owing to the resulting fibers yielding the highest mechanical properties and acceptable water resistance and biodegradability.     

Kinetics study of a-Se80Te20−xPbx using non-isothermal crystallization

The kinetics of crystallization in Se₈₀Te_20−xPb_x (x=0, 2, 6 and 10) glasses is studied by non-isothermal method using differential scanning calorimetry (DSC). DSC is performed at different heating rates of 5, 10, 15 and 20 K/min. The values of glass transition and crystallization temperatures are found to be composition and heating-rate dependent. From the heating-rate dependence of the glass transition and crystallization temperatures, the activation energy of crystallization (ΔE_c) and order parameter (n) are calculated.