Ion-acoustic dressed solitons in electron-positron-ion plasmas

Expanding the Sagdeev potential to include fourth-order nonlinearities of electric potential and integrating the resulting energy equation, an exact soliton solution is determined for ion-acoustic waves in an electron-positron-ion (e-p-i) plasma system. This exact solution reduces to the dressed soliton solution obtained for the system using renormalization procedure in the reductive perturbation method (RPM), when Mach number (M) is expanded in terms of soliton velocity (λ) and terms up to order of λ² are retained in the analysis. Variation of shape, velocity, width and product (P) of amplitude (A) and square of width (W²) for the KdV soliton, core structure, dressed soliton, and exact soliton are graphically represented for different values of fractional positron concentration (p). It is found that for a given value of the fractional positron concentration (p) and amplitude of soliton, the velocity of the dressed soliton is faster and width is narrower than the KdV or exact soliton, and agrees qualitatively with the experimental observations of Ikezi et al. for small amplitude solitons in the plasma free from positron component. Among all these structures, the product P(AW²) is found to be lowest for the dressed soliton and it decreases as Mach number of soliton or fractional positron concentration in the plasma increases.     

Preparation and characterization of cross-linked guar gum microspheres: optimization using factorial design

In the present work cross-linked guar gum microspheres were prepared for colon specific delivery of ornidazole. Development and optimization of guar gum microspheres for colonic drug delivery was carried out using a 2(4) factorial design based on four independent variables. Microspheres were prepared by emulsification method using glutaraldehyde as cross-linking agent. Morphology and surface characteristics of the formulations were determined by scanning electron microscopy. Particle size of the guar gum microspheres was determined by particle size analyzer. In vitro drug-release studies were performed in conditions simulating stomach-to-colon transit in the presence and absence of rat cecal contents. Only a small fraction of drug was released at acidic pH; however, the release of drug was found to be higher in the presence of rat cecal contents, indicating the susceptibility of guar gum matrix to colonic enzymes released from rat cecal contents. The significance of differences was evaluated by analysis of variance (ANOVA). Differences were considered statistically significant at p<0.05.     

On the curious structural phases in Al-deficient (Al62Cu23Cr15) and Al-rich (Al68Cu17Cr15) quasicrystalline alloys

In the present work investigations on the effect of stoichiometric variations on the Occurrence and stabilization of quasicrystalline (qc) and related phases have been carried out. Based on the explorations of several Al-deficient and Al-rich versions of the ideal nominal composition i.e. Al₆₅Cu₂₀Cr₁₅, it has been found that the alloy compositions corresponding to Al₆₂Cu₂₃Cr₁₅ (Al-deficient) and Al₆₈Cu₁₇Cr₁₅ (Al-rich) exhibit several structural subtleties. The Al-deficient alloy, has been found to exhibit crystalline bcc and fcc phases with a = 8.90 Å and a = 17.98 Å respectively. In addition to these phases, a new crystalline bcc variant (a = 15.42 Å) originating from the bcc (a = 8.90 Å) phase has been found. Also a curious superstructure of the fcc (a = 17.98 Å) has been observed. The Al-rich alloy typified by Al₆₈Cu₁₇Cr₁₅, on the other hand, does not exhibit any structural variants, instead it shows nearly pure i-phase.     

Method for determination of radium in seawater using MnO<Subscript>2</Subscript> co-precipitation technique

Radium is considered to be a useful tracer for studying various physical processes of seawater. There are several methods for analysis of radium; however, analysis of radium in seawater by those analytical techniques is a tedious job. Thus a new methodology was optimized for analysis of radium in sea water using MnO₂ co-precipitation followed by gamma spectrometry. The method produced good yield which ranged from 85–98%. The method is simple and requires less amounts of chemicals and no use of acids. Seawater from different western Indian coastal environments viz. Tarapur, Mumbai and Goa were collected and analysed for ²²⁶Ra and ²²⁸Ra using this method.     

Effects of biquadratic exchange interaction on dynamic susceptibility in Heisenberg ferromagnet

The Green function technique has been employed to study the dynamic susceptibility of a spin-1 system above the Curie temperature. Bilinear and biquadratic terms have been added in writing the Hamiltonian of the system. Higher order Green functions have been decoupled by RPA and Callen type decouplings. The dependence of spin wave energy, intensity and susceptibility on wavevector and biquadratic parameter have been studied.     

Kinetics and mechanism of the oxidation of glycine by N-bromosuccinimide

A systematic kinetic study on the oxidation of glycine by N-bromosuccinimide (NBS) in presence of mercuric acetate in acetic acid—water media has been made. Near first order dependence inNBS and glycine and near inverse first order dependence in hydrogen ion concentrations have been observed. A negligible ionic strength effect and a positive dielectric effect have been observed. Various rate parameters have been computed and hydrocyanic acid identified as the end product. On the basis of the kinetic data, a mechanism of the reaction has been proposed.With 3 Figures     

Carboranyl thymidine analogues for neutron capture therapy

Neutron capture therapy (NCT) is a binary radio-chemotherapeutic modality for the treatment of cancer. A major focus of NCT-related research is the development of novel tumor-selective agents that serve as the chemical component in NCT. Thymidine analogues substituted with a boron-containing carborane cluster at the N3 position, designated 3CTAs (3-carboranyl thymidine analogues), constitute one class of these new improved NCT agents. Their chemical, structural and biological properties are discussed in this Feature Article.     

Workflow based framework for life science informatics

Workflow technology is a generic mechanism to integrate diverse types of available resources (databases, servers, software applications and different services) which facilitate knowledge exchange within traditionally divergent fields such as molecular biology, clinical research, computational science, physics, chemistry and statistics. Researchers can easily incorporate and access diverse, distributed tools and data to develop their own research protocols for scientific analysis. Application of workflow technology has been reported in areas like drug discovery, genomics, large-scale gene expression analysis, proteomics, and system biology. In this article, we have discussed the existing workflow systems and the trends in applications of workflow based systems.     

Simultaneous quantification of diterpenoids in Premna integrifolia using a validated HPTLC method

A sensitive, selective and robust densitometric high‐performance thin layer chromatographic method was developed and validated for the determination of diterpenoids in the root bark of Premna integrifolia. Diterpenoids 1β,3α,8β‐trihydroxy‐pimara‐15‐ene ( A ), 6α,11,12,16‐tetrahydroxy‐7‐oxo‐abieta‐8,11,13‐triene ( B ) and 2α,19‐dihydroxy‐pimara‐7,15‐diene ( C ) were used as chemical markers for the standardization of P. integrifolia plant extracts. The separation was performed on silica gel 60F₂₅₄ high‐performance thin layer chromatography plates using hexane/acetone/ethylacetate (60:20:20 v/v) as mobile phase. The quantitation of diterpenoids was carried out using densitometric reflection/absorption mode at 475 nm after post‐chromatographic derivatization using vanillin–sulfuric acid reagent. A precise and accurate quantification can be performed for compounds A , B and C in the linear working concentration range of 1–10 μg/spot with good correlations (r²=0.9985, 0.9996 and 0.9992, respectively). The method was validated for peak purity, precision, robustness, limit of detection (LOD) and quantitation (LOQ) etc., as per the International Conference on Harmonization (ICH) guidelines. Specificity of quantitation was confirmed using retention factor (R_f) and spectra correlation of markers in standard and sample tracks. The method reported here is simple and reproducible which may be applied for quantitative analysis of above diterpenoids in the root bark of P. integrifolia.     

Substrate promiscuity of N-acetylhexosamine 1-kinases

N-Acetylhexosamine 1-kinase (NahK) catalyzes the direct addition of a phosphate from adenosine 5'-triphosphate (ATP) to the anomeric position of N-acetylhexosamine and shows similar activity towards N-acetylglucosamine (GlcNAc) and N-acetylgalactosamine (GalNAc). Herein we report the cloning, characterization, and substrate specificity studies of two NahKs from Bifidobacterium infantis ATCC15697 and Bifidobacterium longum ATCC55813, respectively. A new capillary electrophoresis assay method has been developed for enzyme activity assays. Both enzymes have a good expression level in E. coli (180-185 mg/L culture) and can tolerate diverse modifications at C2 of GlcNAc and GalNAc. Various GlcNAc derivatives with C6, both C2 and C6, as well as both C2 and C3 modifications are tolerable substrates for the newly cloned NahKs. Quite interestingly, despite of their low activities toward glucose and galactose, the activities of both NahKs are much higher for mannose and some of its C2, C4, and C6 derivatives. These NahKs are excellent catalysts for enzymatic and chemoenzymatic synthesis of carbohydrates.