Rotational bands in79Kr

The level scheme of⁷⁹Kr has been studied through the⁷⁹Br(p,n)⁷⁹Kr reaction at proton energies from 1·7 to 5·0 MeV.γ-ray and internal conversion electron measurements were made using Ge(Li) detectors and a six gap “Orange” electron spectrometer. The level scheme was established by determining the thresholds of variousγ-rays and byγ-γ and n-γ coincidence measurements. New levels at 402, 450, 660, 676, 695, 720, 810, 836, 907 and 1038 keV not observed in earlier radioactivity studies have been established. DefiniteJ ^π assignments have been made to most of the levels below 800 keV. Many of the low-lying levels are identified as rotational levels based on the (301 ↓) 1/2^?, (301 ↑) 3/2^? and (431 ↓) 1/2⁺ Nilsson states.     

Heterogeneous effects on the thermal and photoreactivities of tris(1,2-diaminoethane)chromium(III) cation and hexathiocyanatochromate(III) anion in aqueous media

The ground- and excited-state reactivities of the [Cr- (en)3]3+ (en=1,2-diaminoethane) and [Cr(NCS)6]3− ions in a polyacrylamide (PAA) environment are reported. The aquation kinetics of these complexes has been studied to identify the effect of added PAA with varying molecular weight. Aquation of the complexes in aqueous acid containing PAA yielded the respective substituted products. The macromolecule in solution was found to decrease significantly the rate of ligand replacement. Similarly, photolysis of the cationic and anionic complexes in water–PAA mixtures revealed a decrease in aquation quantum yield. Possible explanations for the decrease in reaction rates and quantum yields are discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Dendrimers based on a three-dimensionally disposed AB4 monomer

[reaction: see text] Design and synthesis of a novel class of dendrons based on an AB(4) monomer are described. These dendrons have been evaluated by using dendritic encapsulation of a redox active core. The electrochemical properties of symmetric ferrocene-cored dendrimers show that significant alterations in redox potential and heterogeneous electron-transfer rate constants could be achieved even at lower generations.     

HPTLC Method for Determination of 20-Hydroxyecdysone in Sida rhombifolia L. and Dietary Supplements

Naturally occurring 20-hydroxyecdysone is an important anabolic ecdysteroid. A simple thin-layer chromatography method to quantitate 20-hydroxyecdysone in methanolic extract of the whole plant material of Sida rhombifolia L. was developed. This method was successfully applied for quantitative evaluation of dietary supplements. The separation was achieved on glass TLC plates coated with silica gel 60F254, using chloroform: methanol (8:2 v/v) as developing solvent. Densitometric evaluation of 20-hydroxyecdysone was performed at 250 nm in reflectance/absorbance mode. The calibration was in the range of 200–1,000 ng spot^?1 and correlation coefficient for the calibration curve was >0.999. In addition, for six different Sida species unique fingerprints were obtained on the HPTLC plate.     

Direct Electrical Wiring of Oxidoreductase Enzymes to Silicate Based Electrodes

Three types of reagentless glucose biosensor based on composite graphite-ormosil materials are described: (1) a redox modified silicate-graphite electrode doped with glucose oxidase, (2) a methyl silicate-graphite material doped with redox modified glucose oxidase, and (3) a methyl silicate and redox modified graphite composite material doped with glucose oxidase.     

Toward globular macromolecules with functionalized interiors: design and synthesis of dendrons with an interesting twist

[see reaction]. Design and synthesis of a novel class of monodendrons, in which the functional units can potentially be directed toward the concave interiors of dendrimers, are described. The key feature of the design is the placement of the amphiphilic and the AB2 functional groups in orthogonal planes.     

Rapid analysis of lignans from leaves of Podophyllum peltatum L. samples using UPLC‐UV‐MS

A new rapid UPLC‐UV‐MS method has been developed that permits the analysis of four lignans (4′‐O‐demethylpodophyllotoxin, podophyllotoxin, α‐peltatin and β‐peltatin) in P. peltatum L. Podophyllotoxin is a natural lignan that is being used as a precursor for the semi‐synthetic anti‐cancer drugs etoposide, teniposide and etopophos. The chromatographic separation was achieved using a reversed‐phase C₁₈ column with a mobile phase of water and acetonitrile, both containing 0.05% formic acid. Analyses of P. peltatum leaves collected from different colonies within a single site indicated a significant variation in 4′‐O‐demethylpodophyllotoxin, α‐peltatin, podophyllotoxin and β‐peltatin content. Within 3.0 min four main lignans could be separated with detection limits of 0.1, 0.3, 0.3 and 0.2 μg/mL, respectively. 4′‐O‐demethylpodophyllotoxin and α‐peltatin appeared most prominently among the lignans obtained. The podophyllotoxin content was found in the range of 0.004–0.77% from 16 samples collected from 6 colonies within the same site. The content of podophyllotoxin is directly proportional to the content of 4′‐O‐demethylpodophyllotoxin and inversely proportional to α‐peltatin and β‐peltatin content. LC‐mass spectrometry coupled with electrospray ionization (ESI) interface method is described for the identification of four lignans in various populations of plant samples. By applying principal component analysis and hierarchical cluster analysis, Podophyllum samples collected from various colonies within a location were distinguished. Copyright © 2011 John Wiley & Sons, Ltd.     

Critical properties of superconducting Ba1−xKxFe2As2

Magnetisation and magneto-resistance measurements have been carried out on superconducting Ba_1?xK_xFe₂As₂ samples with x = 0.40 and 0.50. From high field magnetization hysteresis measurements carried out in fields up to 16 T at 4.2 K and 20 K, the critical current density has been evaluated using the Bean critical state model. The J_C determined from the high field data is >10⁴ A/cm² at 4.2 K and 5 T. The superconducting transitions were also measured resistively in increasing applied magnetic fields up to 12 T. From the variation of the T_C onset with applied field, dH_C2/dT at T_C was obtained to be ?7.708 T/K and ?5.57 T/K in the samples with x = 0.40 and 0.50.     

Determination of Shikimic Acid in Fruits of Illicium Species and Various Other Plant Samples by LC–UV and LC–ESI–MS

A simple and specific analytical method for the quantitative determination of shikimic acid from the methanol extract of the fruits of Illicium species and from various plant samples was developed. The LC–UV separation was achieved by reversed-phase chromatography on a C18 column with potassium dihydrogen phosphate and methanol as the mobile phase. In the LC–MS method, the separation was achieved by a C12 column using water and acetonitrile, both containing 0.1% acetic acid as the mobile phase. The methods were successfully used to study the percentage compositions of shikimic acid present in nine species of Illicium and various other plant samples. The detector response was linear with concentrations of shikimic acid in the range from 1.0–500.0 μg mL^?1 by LC–UV and 100–1000 ng mL^?1 by LC–MS. Mass spectrometry coupled with electrospray ionization interface is described for the identification of shikimic acid in various plant samples. This method involved the use of the [M-H]^? ions of shikimic acid at m/z 173.0455 (calculated mass) in the negative ion mode with extractive ion monitoring.