Improved detector response characterization method in ISOCS and LabSOCS

The In-Situ Object Calibration Software (ISOCS) and the Laboratory Sourceless Calibration Software (LabSOCS) developed and patented by Canberra Industries have found widespread use in the gamma-spectrometry community. Using the ISOCS methodology, one can determine the full energy peak efficiencies of a germanium detector in the 45 keV-7 MeV energy range, for practically any source matrix and geometry. The underlying mathematical techniques used in ISOCS (and LabSOCS) have undergone significant improvements and enhancements since their first release in 1996. One of these improvements is  a spatial response characterization technique that is capable of handling the large variations in efficiency that occurs within a small region. The technique has been in use in ISOCS and LabSOCS releases since 1999, and has significantly improved the overall quality of the close-in and off-axis response characterization for HPGe detectors, especially for Canberra’s Broad Energy Germanium (BEGe) detectors. In this method, the detector response is characterized by creating a set of fine spatial efficiency grids at 15 energies in the 45 keV-7 MeV range. The spatial grids are created in (r,⊝) space about the detector, with the radius r varying from 0 to 500 meters, and the angle ⊝ varying from 0 to π. The reference efficiencies for creating the spatial grids are determined from MCNP calculations using a validated detector model. Once the efficiency grids are created, the detector response can be determined at any arbitrary point within a sphere of 500-meter radius, and at any arbitrary energy within the specified range. Results are presented highlighting the improved performance achieved using the gridding methodology.     

Hydrocarbon chain conformation in an intercalated surfactant monolayer and bilayer

Cetyl trimethyl ammonium (CTA) ions have been confined within galleries of layered CdPS₃ at two different grafting densities. Low grafting densities are obtained on direct intercalation of CTA ions into CdPS₃ to give Cd_0.93PS₃(CTA)_0.14. Intercalation occurs with a lattice expansion of 4.8 ? with the interlamellar surfactant ion lying flat forming a monolayer. Intercalation at higher grafting densities was effected by a two-step ion-exchange process to give Cd_0.83PS₃(CTA)_0.34, with a lattice expansion of 26.5 ?. At higher grafting densities the interlamellar surfactant ions adopt a tilted bilayer structure.¹³C NMR and orientation-dependent IR vibrational spectroscopy on single crystals have been used to probe the conformation and orientation of the methylene ‘tail’ of the intercalated surfactant in the two phases. In the monolayer phase, the confined methylene chain adopts an essentially all-trans conformation with most of the trans chain aligned parallel to the gallery walls. On lowering the temperature, molecular plane aligns parallel, so that the methylene chain lies flat, rigid and aligned to the confining surface. In the bilayer phase, most bonds in the methylene chain are in trans conformation. It is possible to identify specific conformational sequences containing a gauche bond, in the interior and termini of the intercalated methylene. These high energy conformers disappear on cooling leaving all fifteen methylene units of the intercalated cetyl trimethyl ammonium ion in trans conformational registry at 40 K.     

Strategies for controlling the active layer morphologies in OPVs

This review focuses on the recent developments in our understanding of active layer morphologies for organic photovoltaic cells and approaches to obtain active layer morphologies for high power conversion efficiencies. The evolution of active layer morphologies, as studied by high resolution electron microscopy, X-ray and neutron scattering, and dynamic secondary ion mass spectrometry, is covered, along with strategies including the use of small molecule additives, polymer nanowires and polymer nanoparticles to realize active layer morphologies. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Electron transport in a multichannel one-dimensional conductor: molybdenum selenide nanowires

We have measured electron transport in small bundles of identical conducting molybdenum selenide nanowires where the number of weakly interacting one-dimensional chains ranges from 1 to 300. The linear conductance and current in these nanowires exhibit a power-law dependence on temperature and bias voltage, respectively. The exponents governing these power laws decrease as the number of conducting channels increase. These exponents can be related to the electron-electron interaction parameter for transport in multichannel 1D systems with a few defects.     

Synthesis of Tetraalkenylmethane: Building Blocks for Three-Dimensional Hydrocarbon Networks

In this paper, we show a common strategy to synthesize tetraalkenylmethanes, a cross-linker series for building three-dimensional hydrocarbon networks. To demonstrate the feasibility of this method, we have synthesized tetrapentenylmethane. Attempts to synthesize this cross-linker from pentaerythrityl tetrabromide using substitution reactions resulted in the formation of a spiro compound due to intramolecular cyclization. We also show that the difficulty in reactions at the neopentyl carbon site is due to the neopentyl carbanion stability, not the sterics.     

A study of the analytical behaviour of selected synthetic and naturally occurring coumarins using liquid chromatography, ion trap mass spectrometry, gas chromatography and polarography and the construction of an appropriate database for coumarin characterisation

The aim of this paper is to provide analytical chemical information on a range of naturally occurring and synthetic coumarins. This analytical chemical information on liquid chromatography-electrospray ionisation-mass spectrometry (HPLC-ESI-MS), ion trap mass spectrometry (ESI-MSⁿ), gas chromatography-flame ionisation detection (GLC-FID) and polarographic behaviour is then incorporated into a database which is of use in identifying unknown coumarins isolated from natural sources. This paper is also concerned with understanding the effect of functional groups in coumarins on their analytical chemical behaviour using the above techniques.     

Copper-catalyzed synthesis of 1,3-enynes

[reaction: see text] We report a copper(I)-catalyzed procedure for the synthesis of 1,3-enynes. This method affords a variety of enynes in good to excellent yields. This method can tolerate a variety of functional groups, does not require the use of expensive additives, and is palladium-free.     

Preparation,characterization, and thermal studies of γ-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> and CuO dispersed polycarbonate nanocomposites

Polycarbonate with γ-Fe₂O₃ and CuO dispersions were carried out by solvent casting method to make polycarbonate-γ-Fe₂O₃ and polycarbonate-CuO composite films. These films were characterized for the molecular structure through FTIR spectroscopy and crystallinity by X-ray diffraction (XRD) measurements. The morphology of polycarbonate-γ-Fe₂O₃ was found to be different from that of polycarbonate-CuO composite films based on the scanning electron micrograph (SEM) images. The thermal traces of composites are different from that of pure polycarbonate which indicating the catalytic decomposition when compared with virgin polymer which is oxidative decomposition. An understanding of the structure, morphology, and thermal behaviour of the composite films are envisaged in the present study.     

Analgesic and anti-inflammatory properties of Thespesia populnea leaf extracts

Analgesic and anti-inflammatory activities of the aqueous and ethanol extracts of Thespesia populnea Soland. ex. Correa (Malvaceae) leaves were evaluated in animal models. Orally-administered aqueous and ethanol extracts (100, 200 and 400?mg?kg?1 bw) showed significant analgesic activity in chemical-, mechanical- and thermally-induced pain test models in mice. The extracts also reduced paw oedema induced by carrageenan in rats. The results obtained in this study suggest that Thespesia populnea extracts have analgesic and anti-inflammatory properties.