Caesaldecan, a cassane diterpenoid from the leaves of Caesalpinia decapetala

A new cassane diterpenoid, caesaldecan, was isolated from Caesalpinia decapetala with eight known compounds, spathulenol, 4,5-epoxy-8(14)-caryophyllene, squalene, lupeol, trans-resveratrol, quercetin, astragalin, and stigmasterol. The (1)H- and (13)C-NMR spectra of the new compound were completely assigned by using a combination of 2D NMR techniques, namely, (1)H-(1)H COSY, HMQC, HMBC, and ROESY.     

Determination of trace amounts of scandium by atomic absorption spectroscopy

Optimum instrumental conditions were investigated for the determination of trace quantities of scandium by atomic-absorption spectroscopy. Enhancement effects by organic solvents and by complex extractions were also studied. (46)Sc was used to establish the optimum extraction conditions. A sensitivity of 0.06 ppm of Sc was observed when using extraction into oxine-butanol and atomic absorption was measured with an acetylene-nitrous oxide flame.     

Geometries and molecular properties of phosphaethyne cations

Franck-Condon analyses were carried out on vibrational intensity distributions of the first two photoelectron bands of phosphaethyne (HCP). The CH and CP bond lengths of HCP⁺ were found to be respectively 1.073 Å and 1.600 A in the X²π state and 1.077 Å and 1.572 Å in the A²Σ⁺ state. The calculated structural parameters were compared with those from experimental work and molecular orbital calculations. In addition, force constants for the first two lowest energy ionic states were determined from observed vibrational frequencies. Bonding properties of the ions are discussed in the light of the molecular parameters obtained.     

The role of macromolecular crowding in single-entity electrochemistry: Friend or foe?

The recent development of nanoscale probes has enabled the study of single molecules and single cells with unprecedented resolution and the expansion of the field of single-entity electrochemistry. There is a growing evidence suggesting that highly crowded intracellular environment facilitate nanoelectrochemical measurements in cells by improving the signal-to-noise ratio. In this opinion piece, we discuss the concept of macromolecular crowding and its implications in single-entity electrochemistry.     

Synthetic Studies on Vitamin D3 Analogues: The Synthesis of 8-P-(Hydroxymethyl)-Phenyl-Des-A,B-Cholest-8( 9) +8( 14)-ENE

The Grignard reagent derived from p-bromobenzyltetrahydropyranyl ether on reaction with the des-A, B-cholestan-8-one yielded 8-p-(terahydropyran-2′-yloxymethyl)-phenyl-des-A, B-cholestan-8-ol which on treatment with H²SO⁴ to give 8-p-(hydroxymethyl)-phenyl-des-A, B-cholest-8(9)+8(14)-ene.     

Modulated DSC as a tool for polyethylene structure characterization

The Modulated Differential Scanning Calorimeter (MDSC) technique, using TA Q1000 instrument, has been applied as a tool to study the reversible and non-reversible heat flow characteristics of a wide range of polyethylenes. It was found that the heat flow characteristic is dependent upon the heating rates and modulation period used in the test. By using a set of standard test conditions, MDSC was found to be useful in studying the effect of previous thermal processing conditions, additive effects, and also the density, MI, type of comonomer, and molecular architecture.     

226Ra, 228Ra and 210Pb Isotopes in Some Water Samples of Mines

A method for the determination of ²²⁶Ra, ²²⁸Ra and ²¹⁰Pb in water samples of mining regions by measuring the and intensities with the help of a liquid scintillation counter is presented. The high-energy part of the -particle spectrum emitted by ²¹⁰Bi is used for the determination of ²¹⁰Pb content in the samples. An attempt is also given to explain the radioactive disequilibrium between ²²⁶Ra and ²¹⁰Pb in the samples investigated.     

Interfacial glass transition profiles in ultrathin, spin cast polymer films

Interfacial glass transition temperature (T(g)) profiles in spin cast, ultrathin films of polystyrene and derivatives were investigated using shear-modulated scanning force microscopy. The transitions were measured as a function of film thickness (delta), molecular weight, and crosslinking density. The T(g)(delta) profiles were nonmonotonic and exhibited two regimes: (a) a sublayer extending about 10 nm from the substrate, with T(g) values lowered up to approximately 10 degrees C below the bulk value, and (b) an intermediate regime extending over 200 nm beyond the sublayer, with T(g) values exceeding the bulk value by up to 10 degrees C. Increasing the molecular weight was found to shift the T(g)(delta) profiles further from the substrate interface, on the order of 10 nm/kDa. Crosslinking the precast films elevated the absolute T(g) values, but had no effect on the spatial length scale of the T(g)(delta) profiles. These results are explained in the context of film preparation history and its influence on molecular mobility. Specifically, the observed rheological anisotropy is interpreted based on the combined effects of shear-induced structuring and thermally activated interdiffusion.