Chemistry, Physics and Earth Sciences - Collected Works

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    Low-Temperature Processed TiOx/Zn1−xCdxS Nanocomposite for Efficient MAPbIxCl1−x Perovskite and PCDTBT:PC70BM Polymer Solar Cells
    (MDPI, 2019-06-03) Duong, Binh; Lohawet, Khathawut; Muangnapoh, Tanyakorn; Nakajima, Hideki; Chanlek, Narong; Sharma, Anirudh; Lewis, David Andrew; Kumnorkaew, Pisist
    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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    A Review of the Classification of Opal with Reference to Recent New Localities
    (MDPI, 2019-05-15) Curtis, Neville J; Gascooke, Jason; Johnson, Martin R; Pring, Allan
    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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    Synthesis and evaluation of aminobenzothiazoles as blockers of N- and T-type calcium channels
    (Elsevier, 2018-03-19) Sairaman, Anjali; Cardoso, Fernanda Caldas; Bispat, Anjie; Lewis, Richard J; Duggan, Peter; Tuck, Kellie L
    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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    Calculated meteoroid production of hydroxyl in the atmosphere of Jupiter
    (Elsevier, 2019-03-12) Campbell, Laurence; Brunger, Michael James
    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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    Origins of N-formylmethamphetamine and N-acetylmethamphetamine in methamphetamine produced by the hydriodic acid and red phosphorus reduction of pseudoephedrine
    (Elsevier, 2019-03-20) Barnes, Christopher; Madaras, Simone; Pigou, Paul; Johnston, Martin Ross; Kirkbride, Kenneth Paul
    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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    On the Dynamics of Canyon–Flow Interactions
    (MDPI, 2018-11-06) Kampf, Jochen
    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
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    Characterizing the shape patterns of dimorphic yeast pseudohyphae
    (The Royal Society Publishing, 2018-10-17) Gontar, Amelia; Bottema, Murk Jan; Binder, Benjamin J; Tronnolone, Hayden
    Pseudohyphal growth of the dimorphic yeast Saccharomyces cerevisiae is analysed using two-dimensional top-down binary images. The colony morphology is characterized using clustered shape primitives (CSPs), which are learned automatically from the data and thus do not require a list of predefined features or a priori knowledge of the shape. The power of CSPs is demonstrated through the classification of pseudohyphal yeast colonies known to produce different morphologies. The classifier categorizes the yeast colonies considered with an accuracy of 0.969 and standard deviation 0.041, demonstrating that CSPs capture differences in morphology, while CSPs are found to provide greater discriminatory power than spatial indices previously used to quantify pseudohyphal growth. The analysis demonstrates that CSPs provide a promising avenue for analysing morphology in high-throughput assays.
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    Polyelectrolyte-Coated Gold Nanoparticles: The Effect of Salt and Polyelectrolyte Concentration on Colloidal Stability
    (MDPI, 2018-12-03) Fuller, Melanie; Koper, Ingo
    Gold nanoparticles are widely used in biomedical applications. Their ease of surface modification, biocompatibility and the presence of surface plasmons makes them ideal tools for a variety of investigations. Polyelectrolyte-coated gold nanoparticles are employed in areas such as imaging, drug delivery and gene therapy; however, it is not well understood how different factors such as the polyelectrolyte and salt concentration affect the coating on the nanoparticles and hence their performance. Here, these parameters were systematically varied and their effect on the stability of the colloidal nanoparticle suspension was monitored. An increase in the polyelectrolyte concentration from 0 to 30 mg/mL led to a red shift of the surface plasmon peak and an increase in the zeta potential. Concentrations between 5 mg/mL and 30 mg/mL resulted in the most stable systems, with 1 mg/mL being the most unstable. Stable nanoparticle suspensions were formed in salt concentrations below 50 mM, while higher concentrations caused colloidal instability and irreversible aggregation.
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    Conducting Copper(I/II)-Metallopolymer for the Electrocatalytic Oxygen Reduction Reaction (ORR) with High Kinetic Current Density
    (MDPI, 2018-09-07) Elmas, Sait; Beelders, Wesley; Pan, Xun; Nann, Thomas
    The oxygen reduction reaction (ORR) is still the most research-intensive aspect of a fuel cell. The sluggish kinetics of the electrocatalysts toward the ORR requires large amounts of platinum to be used as cathode material, which calls for alternatives to replace or minimize the amount of the noble metals used. This study describes the synthesis and complete characterization of a copper metallopolymer (Cu MP) based on a conducting polymer (CP) and single-site catalytic centers for the electrocatalytic ORR. The copper (II) catalyst, embedded in a redox-active and conducting polymeric environment, was pursued as a potential candidate to replace noble metals in fuel cell applications. Performance studies at a rotating disk electrode (RDE) showed that the metallopolymer exhibited a direct four-electron reduction at potentials between −150 and −350 mV vs. the reversible hydrogen electrode (RHE) and high kinetic current densities of over 22.62 mA/cm2. The kinetic current densities obtained at the Cu MP electrode outperformed most of the reported state-of-the art electrocatalysts toward the ORR. Further analysis of the Cu/CP hybrid revealed the copper being largely reduced to the oxidation state +I.
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    Effect of surface density silver nanoplate films toward surface-enhanced Raman scattering enhancement for bisphenol A detection
    (IOP Publishing, 2018) Bakar, Norhayati Abu; Salleh, Muhamad Mat; Umar, Akrajas Ali; Shapter, Joseph George
    This paper reports a study on surface-enhanced Raman scattering (SERS) phenomenon of triangular silver nanoplate (NP) films towards bisphenol A (BPA) detection. The NP films were prepared using self-assembly technique with four different immersion times; 1 hour, 2 hours, 5 hours, and 8 hours. The SERS measurement was studied by observing the changes in Raman spectra of BPA after BPA absorbed on the NP films. It was found that the Raman intensity of BPA peaks was enhanced by using the prepared SERS substrates. This is clearly indicated that these SERS silver substrates are suitable to sense industrial chemical and potentially used as SERS detector. However, the rate of SERS enhancement is depended on the distribution of NP on the substrate surface.
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    Evaluation of the sub-surface morphology and composition of gunshot residue using focussed ion beam analysis
    (Elsevier, 2019-02-11) Lucas, Nick; Seyfang, Kelsey E; Plummer, Andrew Mark; Cook, Michael; Kirkbride, Kenneth Paul; Kobus, Hilton John
    Recent work in the forensic analysis of Gunshot residues (GSR) has suggested that the sub-surface or internal composition and morphology of these residues be explored. A particular area of interest is in heavy metal free, or non-toxic ammunition, which are becoming more frequently encountered in the marketplace. As the formulation of the primer compound changes the conditions of the firearm discharge, there is the possibility that different primer formulations may result in the formation of different GSR particles with distinct internal morphologies and compositions. To that end, the internal morphology and composition of GSR particles may provide additional information that could be useful in the investigation of firearms crime. This research investigated the internal morphology of GSR originating from a variety of different ammunition products. Both traditional three-component primed ammunition, and a selection of heavy metal free and non-toxic alternatives were considered. Particles were identified using SEM–EDS, before being cross-sectioned using a focussed ion beam (FIB) instrument. The FIB-sectioned particles were then re-acquired and mapped using SEM–EDS, to assess both internal morphology and composition. Particles observed in this study presented distinct morphological and compositional features at the sub-particle level that may provide an indication of the primer formulation from which they originated. That said, further investigation of a variety of samples should be undertaken to verify the consistency of these features, or any deviations that may be observed based on primer type. However, these results indicate that there may be promise in obtaining additional detail from sub-particle morphology and composition.
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    Detailed investigations into the Akabori–Momotani reaction for the synthesis of amphetamine type stimulants: Part 2
    (Elsevier, 2018-02-06) Doughty, David; Kent, Emma; Painter, Ben; Pigou, Paul; Johnston, Martin Ross
    The Akabori–Momotani reaction can be used to synthesise pseudoephedrine in 50% yield from N-methylalanine and benzaldehyde. This paper investigates electronic effects of substituted benzaldehydes on the reaction to synthesise amphetamine type stimulants and identifies several new Akabori–Momotani by-products, 1-[(4-methoxybenzyl)(methyl)amino]ethanol (11c), 2-(4-methoxyphenyl)-3,4-dimethyl-1,3-oxazolidine (12c), 1,2,3,4-tetramethyl-5,6-di-(4-methoxyphenyl)piperazine (13c) and 1,2,4,5-tetramethyl-3,6-di-(4-methoxyphenyl)piperazine (14c). This paper also investigates pseudoephedrine and methamphetamine isomeric distribution from the Akabori–Momotani reaction with the aid of molecular modelling to understand why more pseudoephedrine than ephedrine is produced.
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    Toxicogenetic study of omeprazole and the modulatory effects of retinol palmitate and ascorbic acid on Allium cepa
    (Elsevier, 2018-04-05) Braga, Antonio Lima; de Meneses, Ag-Anne Pereira Melo; Santos, Jose Victor de Oliveir; dos Reis, Antonielly Campinho; de Lima, Rosalia Maria Torres; da Mata, Ana Maria Oliveira Ferreira; Paz, Marcia Fernanda Correia Jardim; dos Santos Alves, Leane Brunelle; Shaw, Subrata; Uddin, Shaikh Jamal; Rouf, Razina; Das, Asish Kumar; Dev, Shrabanti; Shill, Manik Chandra; Shilpi, Jamil A; Khan, Ishaq N; Islam, Muhammad Torequl; Ali, Eunus S; Mubarak, Mohammad S; Mishra, Siddhartha Kumar; de Castro e Souza, Joao Marcelo; Melo-Cavalcante, Ana Amelia de Carvalho
    Omeprazole (OME) is a proton pump inhibitor used for the treatment of various gastric and intestinal disease; however, studies on its effects on the genetic materials are still restricted. The present study aimed to evaluate possible toxicogenic effects of OME in Allium cepa meristems with the application of cytogenetic biomarkers for DNA damage, mutagenic, toxic and cytotoxic effects. Additionally, retinol palmitate (RP) and ascorbic acid (AA) were also co-treated with OME to evaluate possible modulatory effects of OME-induced cytogenetic damages. OME was tested at 10, 20 and 40 μg/mL, while RP and AA at 55 μg/mL and 352.2 μg/mL, respectively. Copper sulphate (0.6 μg/mL) and dechlorinated water were used as positive control and negative control, respectively. The results suggest that OME induced genotoxicity and mutagenicity in A. cepa at all tested concentrations. It was noted that cotreatment of OME with the antioxidant vitamins RP and/or AA significantly (p < 0.05) inhibited and/or modulated all toxicogenic damages induced by OME. These observations demonstrate their antigenotoxic, antimutagenic, antitoxic and anticitotoxic effects in A. cepa. This study indicates that application of antioxidants may be useful tools to overcome OME-induced toxic effects.
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    Mechanism and kinetics of hydrothermal replacement of magnetite by hematite
    (Elsevier, 2018-06-28) Zhao, Jing; Brugger, Joel; Pring, Allan
    The replacement of magnetite by hematite was studied through a series of experiments under mild hydrothermal conditions (140–220 °C, vapour saturated pressures) to quantify the kinetics of the transformation and the relative effects of redox and non-redox processes on the transformation. The results indicate that oxygen is not an essential factor in the replacement reaction of magnetite by hematite, but the addition of excess oxidant does trigger the oxidation reaction, and increases the kinetics of the transformation. However, even under high O2(aq) environments, some of the replacement still occurred via Fe2+ leaching from magnetite. The kinetics of the replacement reaction depends upon temperature and solution parameters such as pH and the concentrations of ligands, all of which are factors that control the solubility of magnetite and affect the transport of Fe2+ (and the oxidant) to and from the reaction front. Reaction rates are fast at ∼200 °C, and in nature transport properties of Fe and, in the case of the redox-controlled replacement, the oxidant will be the rate-limiting control on the reaction progress. Using an Avrami treatment of the kinetic data and the Arrhenius equation, the activation energy for the transformation under non-redox conditions was calculated to be 26 ± 6 kJ mol−1. This value is in agreement with the reported activation energy for the dissolution of magnetite, which is the rate-limiting process for the transformation under non-redox conditions.
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    Continuous flow synthesis of phosphate binding h-BN@magnetite hybrid material
    (The Royal Society of Chemistry, 2018-12-05) Al-Antaki, Ahmed H M; Luo, Xuan; Duan, Alex; Lamb, Robert N; Eroglu, Ela; Hutchison, Wayne D; Zou, Yi-chao; Zou, Jin; Raston, Colin L
    Hexagonal boron nitride (h-BN) is rendered magnetically responsive in aqueous media by binding superparamagnetic magnetite nanoparticles 8.5–18.5 nm in diameter on the surface. The composite material was generated under continuous flow in water in a dynamic thin film in a vortex fluidic device (VFD) with the source of iron generated by laser ablation of a pure iron metal target in the air above the liquid using a Nd:YAG pulsed laser operating at 1064 nm and 360 mJ. Optimum operating parameters of the VFD were a rotational speed of 7.5k rpm for the 20 mm OD (17.5 mm ID) borosilicate glass tube inclined at 45 degrees, with a h-BN concentration at 0.1 mg mL−1, delivered at 1.0 mL min−1 using a magnetically stirred syringe to keep the h-BN uniformly dispersed in water prior to injection into the base of the rapidly rotating tube. The resulting composite material, containing 5.75% weight of iron, exhibited high phosphate ion adsorption capacity, up to 171.2 mg PO43− per gram Fe, which was preserved on recycling the material five times.
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    Spatio-temporal geomorphological and ecological evolution of a transgressive dunefield system, Northern California, USA
    (Elsevier, 2018-09-25) Pickart, Andrea J; Hesp, Patrick A
    A series of historic aerial photographs in addition to the U.S. Coast Survey 1870 map were used to document evolution of the coastal barrier and transgressive dunefield system at the Lanphere-Ma-le'l Dunes on Humboldt Bay, California, USA, between 1870 and 2016. Geomorphic units (shorelines, foredunes, nebkha, blowouts, parabolic dunes, deflation basins, and dunefields) as well as vegetation alliance were mapped in ArcGIS at approximately decadal intervals and compared among three subareas delineated based on large scale geomorphic differences that coincided with contrasting biological invasion and management histories. Sand inundation events in the 1930s and 1940s led to deterioration of the foredune and burial of deflation basins in the south, with the transgressive dunefield directly abutting the backshore in places. The transgressive dunefield in the north differentiated into parabolic dunes that decoupled from the foredune complex earlier than in the southern subareas, which have retained undifferentiated transgressive dunefields. Shoreline progradation increased dramatically following the historic 1964 flood, but exhibited a north-south gradient consistent with the Mad River to the north acting as the primary source of sediment, and effective north-south littoral drift. Biological invasions of Lupinus arboreus in the north and Ammophila arenaria in the south contributed to stabilization post-1965, but concomitant increases of native vegetation in other areas suggest these biotic processes were subordinate to other forcing factors. A notable switch from an erosional to a depositional system occurred coincident with the Pacific Decadal Oscillation (PDO) shift from a cool to a warm phase in the late 1970s, suggesting climate forcing as a major driver of dune evolution. Changes in the rate of vegetation stabilization per time interval post 1948 are correlated with change in mean monthly PDO index for the same intervals. Alongshore gradients of sediment availability and tectonic subsidence are likely superimposed on climatic controls. Stability of the dune system reached its maximum extent in 2000, despite erosional effects of the 1998–2000 La Niña event and invasive plant removal projects in the 1990s. Increased storminess (2015–2016 El Niño) resulted in decreased shoreline stability in the most recent interval, coincident with sharply declining rates of progradation and a reduction in mean monthly PDO index. This study provides insights into how transgressive dune phases can be formed, sustained and decoupled, as well as how they change their geomorphology over time. The absence of relict foredunes in the study area and elsewhere on the North Spit barrier suggests that the foredune-blowout-parabolic dune complex may build to quite large proportions for some time, and then be destroyed or destabilized to such a degree that the sediments comprising the complex are released to form a new dunefield phase. Ruptures along the Cascadia subduction zone are a likely mechanism for transgressive dunefield initiation, both in the past, and likely in the future.
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    Morphological evolution of the sandspit at Tortugueros Beach, Mexico
    (Elsevier, 2018-10-14) Escudero, Mireille; Silva, Rodolfo; Hesp, Patrick A; Mendoza, Edgar
    Sand spits occur around the world with different shapes, dimensions and dynamics. While usually considered non-developable coastal features, development has taken place in several locations around the world, and because spits are often very dynamic, a better understanding of their behaviour and evolution is useful. Understanding their stability and morphological cycles can be used as a measure of the health of nearby beaches. The inter-annual and decadal morphological evolution of the beach spit at Tortugueros, on the Yucatan peninsula, Mexico, a re-entrant bay on the Isla del Carmen barrier system, is examined. Digitized information from satellite images and aerial photographs, covering a 31 year period, was used to compare the shoreline evolution with numerical results. The method used consists of the estimation of the wave breaking conditions and the evaluation of the cross and longshore energy flux. The time-averaged wave energy flux allows the estimation of the evolution of those morphological features. The shoreline changes are very dramatic, with rates of accretion up to 160 m yr-1 and erosion up to 196 m yr-1. The results of the comparative analysis show that Tortugueros beach is a resilient system in dynamic equilibrium, governed by the combination of the short period local marine climate of the area and large-scale weather cycles related to the El Niño and La Niña phenomena. The analysis presented in this paper is valid to describe the functioning and resilience of dynamic beach systems elsewhere, where the wave climate is known, based on the wave energy flux of the breaking waves.
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    A forensic investigation on the persistence of organic gunshot residues
    (Elsevier, 2018-09-01) Maitre, Matthieu; Horder, Mark; Kirkbride, Kenneth Paul; Gassner, Anne-Laure; Weyermann, Celine; Roux, Claude; Beavis, Alison
    Gunshot residues (GSR) are a potential form of forensic traces in firearm-related events. In most forensic laboratories, GSR analyses focus on the detection and characterisation of the inorganic components (IGSR), which are mainly particles containing mixtures of lead, barium and antimony originating from the primer. The increasing prevalence of heavy metal-free ammunition challenges the current protocols used for IGSR analysis. To provide complementary information to IGSR particles, the current study concentrated on the organic components (OGSR) arising from the combustion of the propellant. The study focused on four compounds well-known as being part of OGSR: ethylcentralite (EC), methylcentralite (MC), diphenylamine (DPA), N-nitrosodiphenylamine (N-nDPA). This study assessed the retention of these OGSR traces on a shooter’s hands. The overall project aim was to provide appropriate information regarding OGSR persistence, which can be suitable to be integrated into the interpretation framework of OGSR as recommended by the recent ENFSI Guideline for Evaluative Reporting in Forensic Science. The persistence was studied through several intervals ranging from immediately after discharge to four hours and two ammunition calibres were chosen: .40 S&W calibre, used by the NSW Police Force; and .357 Magnum, which is frequently encountered in Australian casework. This study successfully detected the compounds of interest up to four hours after discharge. The trends displayed a large decrease in the amount detected during the first hour. A large variability was also observed due to numerous factors involved in the production, deposition and collection of OGSR.
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    Controlled slicing of single walled carbon nanotubes under continuous flow
    (Elsevier, 2018-08-31) Alharbi, Thaar M D; Vimalanathan, Kasturi; Lawrance, Warren Donald; Raston, Colin L
    Single walled carbon nanotubes (SWCNTs) are sliced with control over their length distribution within a laser irradiated dynamic thin film in a vortex fluidic device (VFD) operating under continuous flow conditions. Length control depends on the laser pulse energy, the flow rate of the liquid entering the device, the speed of the rapidly rotating tube and its tilt angle, choice of solvent and concentration of the as received SWCNTs. The induced mechanoenergy in the thin film while being simultaneously irradiated with a Nd:YAG pulsed laser operating at 1064 nm wavelength results in the slicing, with laser pulse energies of 250, 400 and 600 mJ affording 700, 300 and 80 nm length distributions of SWCNTs respectively. The processing avoids the need for using any other reagents, is scalable under continuous flow conditions, and does not introduce defects into the side walls of the SWCNTs.
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    Tethered membrane architectures - design and applications
    (Frontiers Media, 2018-09-07) Andersson, Jakob; Koper, Ingo; Knoll, Wolfgang
    Membrane proteins perform a large number of essential biological tasks, but the understanding of these proteins has progressed much more slowly than that of globular proteins. The study of membrane proteins is hindered by the inherent complexity of the cellular membrane. Membrane proteins cannot be studied outside their native environment because their natural structure and function is compromised when the protein does not reside in the cellmembrane.Modelmembranes have been developed to provide a controlled, membrane-like environment in which these proteins can be studied in their native form and function without interference from other membrane components. Traditionally used model membranes such as bimolecular or black lipid membranes and floating lipid membranes suffer from several disadvantages including complex assembly protocols and limited stability. Furthermore, these membranes can only be studied with a narrow range of methodologies, severely restricting their use. To increase membrane stability, simplify the assembly process and increase the number of analytical tools that can be used to study the membranes, several strategies of covalently tethering the bilayer to its solid support have been developed. This review provides an overview of the methods used to assemble various membrane architectures, the properties of the resulting membranes and the tools used to study them.