Precision of a dual energy X-ray absorptiometry device

The standard method to diagnose and follow-up osteoporosis is the measurement of bone mineral density (BMD) using dual X-ray absorptiometry (DEXA). Manufacturers' manuals of DEXA devices state the intrascanner coefficient of variance is less than 0.01 g/cm². The aim of this study was to evaluate the in vivo coefficient of variance of a Lunar DPX scanner in male and female healthy adult subjects. Average BMD for females and males were 1.170±0.091 g/cm² and 1.272±0.115 g/cm², respectively. Monthly phantom measurements provided and controlled by the manufacturer were 1.243±0.008 g/cm² (range 1.222 to 1.257) and the coefficient of variance was 0.006. It is concluded that the in vivo coefficient of variance of DEXA devices can slightly be higher than that proposed by the manufacturer. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis and structure of cyclopropano-annelated homosesquinorbornene derivatives containing pyramidalized double bonds: evidence for the sterical effect of a cyclopropyl group on the degree of C=C double-bond pyramidalization

[reaction: see text] endo- and exo-2,3,4,7-tetrahydro-1H-1,4-methanobenzocycloheptene-7-carboxylic acid ethyl esters have been synthesized, and their Diels-Alder cycloaddition reactions with maleic anhydride, dimethyl acetylenedicarboxylate and singlet oxygen have been investigated. The X-ray analysis of four adducts indicated the pyramidalization of the central double bond. Density functional theory calculations on the isolated products and model compounds showed excellent agreement between the experimental and theoretical determined butterfly angles. Furthermore, it has been shown that a cyclopropyl group fused to [2.2.2] system decreases significantly the degree of the pyramidalization which is attributed to the steric interactions between the cyclopropyl group and ethano bridge of the norbornene systems. Due to the instability of the bicyclic endoperoxides, their X-ray analysis could not be carried out. DFT calculations on model compounds showed increased bending in the case of the product obtained by the addition of singlet oxygen to endo-2,3,4,7-tetrahydro-1H-1,4-methanobenzocycloheptene-7-carboxylic acid ethyl ester.     

Sodium p‐nitro­benzoxasulfamate monohydrate

The title compound, alternatively named sodium 6‐nitro‐3H‐1,2,3‐benzoxa­thia­zole 2,2‐dioxide monohydrate, Na⁺·C₆H₃­N₂O₅S^?·H₂O, consists of chains of NaO₇ units, with the seven donor‐O atoms coming from two water mol­ecules and five p‐­nitro­benzoxasulfamate anions. The seven‐coordinate geometry around the Na⁺ ion is described as monocapped trigonal prismatic, but with a large distortion from ideal geometry. Each triangular face is defined by one O atom each from a water mol­ecule, a nitro group and a sulfonyl group. An O atom from a sulfonyl group caps one of the square faces of the trigonal prism in an unsymmetrical fashion. The water mol­ecules and one sulfonyl O atom are involved in bridging adjacent units, as is the nitro group of the anion. The sulfamate ions adopt an antiparallel alignment between the NaO₇ units and are connected to each other by C—H?O and π–π interactions. The three‐dimensional crystal structure is stabilized by a network of strong O—H?N hydrogen bonds.     

Sulphate analysis in uranium leach iron(III) chloride solutions by inductively coupled Argon Plasma Spectrometry

Inductively coupled Argon Plasma Spectrometry is used for the indirect determination of sulphate in iron(III) chloride leach solution of Elliot Lake uranium ores via addition of a known amount of barium ions and analyzing for excess of barium. The ore contains approximately 7 wt% pyrite, FeS(2) as the major mineral which oxidizes to generate sulphate during leaching with fe(III). The effects of pH, the concentrations of Fe(III) and chloride ions and for presence of ethanol in the test samples on the accuracy of analysis are studied. It is found that unlike the Rhodizonate method, removal of iron(III) from or addition of ethanol to the test sample prior to analysis are not required. Linear calibration curves are obtained.     

Poly(Methyl Methacrylate) as a matrix for immobilization of lipase

Poly(methyl methacrylate) (PMMA) was found to be suitable for the immobilization of lipase fromCandida rugosa. The best result based on hydrolytic activity was obtained by adsorption of the purified unbuffered enzyme solution onto PMMA beads without any modification of the beads. Prolonged exposure of the protein to the beads increased its adsorption but the expressed activity decreased after 1 h of exposure. The magnitude of the immobilized activity also varied with the size of the beads. Immobilization of the lipase shifted its optimal reaction temperature from 37 to 45°C. The immobilized enzyme is also more stable than the free enzyme in solution. The operational half-life of the immobilized lipase packed in a column and assayed in a closed system is 40 d.     

Synthesis and characterization of a bifunctional amido-thiophene monomer and its copolymer with thiophene and electrochemical properties

A bifunctional amido-thiophene namely hexamethylene (bis-3-thiophene acetamide) (HMTA) was synthesized by the reaction of 3-thiophene acetic acid with hexamethylene diamine. Copolymerization in the presence of thiophene was achieved electrochemically in tetrabutylammonium tetrafluoroborate/acetonitrile (TBAFB/AN). Spectroelectrochemical analysis of the resulting copolymer [P(HMTA-co-Th)] reflected electronic transitions at 505 nm, 740 nm and ∼1000 nm, revealing π to π* transition, polaron and bipolaron band formation respectively. Switching ability was evaluated by a kinetic study via measuring the transmittance (%T) at the maximum contrast. Dual type polymer electrochromic devices (ECDs) based on P(HMTA-co-Th) and poly(ethylene dioxythiophene) (PEDOT) have been constructed. Spectroelectrochemistry, switching ability and stability of the devices were investigated by UV-vis spectroscopy and cyclic voltammetry. These devices exhibit low switching voltages (between 0.0 V and +1.6 V), short switching times with reasonable switching stability under atmospheric conditions.     

Synthesis of chiral building blocks for cephalostatin analogues

The present paper describes the synthesis of 5‐azido‐6‐ketones (14) and 6‐hydroxy‐5‐ketone (20) from Hajos Wiechert ketone as chiral building blocks for cephalostatin analogues. The synthesis of symmetric cephalostatin analogue from 6‐hydroxy‐5‐ketone has also been reported. The characterization of the each synthesized compounds was carried out by IR, ¹H‐NMR, ¹³C‐NMR and High resolution Mass Spectrometry.