Chemistry, Physics and Earth Sciences - Collected Works
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ItemLow-Temperature Processed TiOx/Zn1−xCdxS Nanocomposite for Efficient MAPbIxCl1−x Perovskite and PCDTBT:PC70BM Polymer Solar Cells(MDPI, 2019-06-03)The majority of high-performance perovskite and polymer solar cells consist of a TiO2 electron transport layer (ETL) processed at a high temperature (>450 °C). Here, we demonstrate that low-temperature (80 °C) ETL thin film of TiOx:Zn1−xCdxS can be used as an effective ETL and its band energy can be tuned by varying the TiOx:Zn1−xCdxS ratio. At the optimal ratio of 50:50 (vol%), the MAPbIxCl1−x perovskite and PCBTBT:PC70BM polymer solar cells achieved 9.79% and 4.95%, respectively. Morphological and optoelectronic analyses showed that tailoring band edges and homogeneous distribution of the local surface charges could improve the solar cells efficiency by more than 2%. We proposed a plausible mechanism to rationalize the variation in morphology and band energy of the ETL.
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ItemA Review of the Classification of Opal with Reference to Recent New Localities(MDPI, 2019-05-15)Our examination of over 230 worldwide opal samples shows that X-ray diffraction (XRD) remains the best primary method for delineation and classification of opal-A, opal-CT and opal-C, though we found that mid-range infra-red spectroscopy provides an acceptable alternative. Raman, infra-red and nuclear magnetic resonance spectroscopy may also provide additional information to assist in classification and provenance. The corpus of results indicated that the opal-CT group covers a range of structural states and will benefit from further multi-technique analysis. At the one end are the opal-CTs that provide a simple XRD pattern (“simple” opal-CT) that includes Ethiopian play-of-colour samples, which are not opal-A. At the other end of the range are those opal-CTs that give a complex XRD pattern (“complex” opal-CT). The majority of opal-CT samples fall at this end of the range, though some show play-of-colour. Raman spectra provide some correlation. Specimens from new opal finds were examined. Those from Ethiopia, Kazakhstan, Madagascar, Peru, Tanzania and Turkey all proved to be opal-CT. Of the three specimens examined from Indonesian localities, one proved to be opal-A, while a second sample and the play-of-colour opal from West Java was a “simple” Opal-CT. Evidence for two transitional types having characteristics of opal-A and opal-CT, and “simple” opal-CT and opal-C are presented.
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ItemSynthesis and evaluation of aminobenzothiazoles as blockers of N- and T-type calcium channels(Elsevier, 2018-03-19)Both N- and T-type calcium ion channels have been implicated in pain transmission and the N-type channel is a well-validated target for the treatment of neuropathic pain. An SAR investigation of a series of substituted aminobenzothiazoles identified a subset of five compounds with comparable activity to the positive control Z160 in a FLIPR-based intracellular calcium response assay measuring potency at both CaV2.2 and CaV3.2 channels. These compounds may form the basis for the development of drug leads and tool compounds for assessing in vivo effects of variable modulation of CaV2.2 and CaV3.2 channels.
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ItemCalculated meteoroid production of hydroxyl in the atmosphere of Jupiter(Elsevier, 2019-03-12)The atmosphere of Jupiter is mainly hydrogen and methane, with a large number of hydrocarbons calculated to be produced by photodissociation and subsequent reactions. It is assumed that oxygen is added by meteoroids. Recent studies have found that photochemistry does not explain the measured ratios of water to carbon monoxide, if it is assumed that water is the major constituent of meteoroids and vapourises. A possible explanation is that processes that occur during or soon after the meteoroid's passage change the proportions of the oxygen-bearing constituents. In this paper, the processes considered are dissociation, ionization of the original molecules and ionization of dissociated products. The difference between applying these processes in the bulk atmosphere and in the meteor trail itself is investigated, as is the possibility of methane being dissociated in a shock wave produced by the meteoroid. In all cases, there was no significant change to the predicted density of water at the height of a measurement. However, the density of hydroxyl relative to water differed depending on the assumed process, thus presenting the possibility that measurements of electron-driven emissions from hydroxyl could be used for remote sensing of the actual processes occurring.
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ItemOrigins of N-formylmethamphetamine and N-acetylmethamphetamine in methamphetamine produced by the hydriodic acid and red phosphorus reduction of pseudoephedrine(Elsevier, 2019-03-20)N-Formylmethamphetamine (FMA) and N-acetylmethamphetamine (AMA) are suspected to be trace by-products in methamphetamine (MA) produced from pseudoephedrine using the Nagai reaction. However, these amides are not rational by-products of the Nagai reaction. FMA is an intermediate in the synthesis of MA using the Leuckart reaction. However, as there is the possibility that FMA is a by-product of the Nagai reaction, the significance of FMA as an indicator of the Leuckart reaction has been debated. It is therefore important to establish whether AMA and especially FMA are by-products of the Nagai reaction and thus establish their significance as synthetic route markers. From the work presented here, FMA is a by-product of the Nagai reaction but the mechanism by which FMA arises could be not determined. AMA was also shown to be a by-product of the Nagai reaction, most likely due to reaction between MA and phenyl-2-propanone (P-2-P), itself a by-product of the Nagai reaction. Furthermore, during GC analysis of Nagai reaction products, MA has been shown to react with P-2-P or ethyl acetate in the injector to form AMA. Caution is recommended if the relative abundance of AMA and/or FMA are used as a basis for determining whether MA samples have a common source or not. Furthermore, it is clear that FMA cannot be considered to be a route-specific by-product for the Leuckart reaction – it is the abundance of FMA in a reaction mixture or profile, not simply its presence, that points to the involvement of the Leuckart reaction.
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ItemOn the Dynamics of Canyon–Flow Interactions(MDPI, 2018-11-06)This paper explores the dynamical origin and physical characteristics of flow disturbances induced by ocean currents in interaction with shelf-incised submarine canyons. To this end, a process-oriented hydrodynamic model is applied in a series of case studies. The focus of studies is the canyon-upwelling process in which seawater is moved from the upper continental slope onto the shelf within a shelf-break canyon. Results reveal that the generation of canyon upwelling, to zero-order approximation, is a barotropic and friction-independent quasi-geostrophic process. Hence, the principle of conservation of potential vorticity for such flows is sufficient to explain the fundamental physical properties of the canyon-upwelling process. For instance, this principle explains the direction-dependence of the canyon-upwelling process. This principle also explains the formation of stationary topographic Rossby waves downstream from the canyon that can lead to far-field effects. Density effects, being of secondary influence to the canyon-upwelling process, result in the intensification of canyon-upwelling flows via the formation of narrow near-bottom density fronts and associated baroclinic geostrophic frontal flows. Findings of this work reveal that the apparently complex canyon-upwelling process is much more basic than previously thought. View Full-Text