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Effect of carbon nanotube functionalization on the structure and properties of poly(3-hydroxybutyrate)/MWCNTs biocomposites
No full textMulti walled carbon nanotubes (MWCNTs) covalently functionalized with an alkyl chain exhibited a better dispersion in poly(3-hydroxybutyrate) (PHB) solutions and cast films as compared with acid-treated MWCNTs (MWCNT-COOH) due to the much improved solubility in chloroform. The alkylated MWCNTs more effectively strengthened PHB composites than non-alkylated MWCNTs due to their uniform dispersion as well as stronger interaction of alkylated MWCNTs with the PHB matrix. Both acid-treated and alkylated MWCNTs added to PHB matrix facilitated crystallization kinetics. However the crystallization kinetics were found to be slower for the alkylated MWCNTs/PHB composites than acid-treated MWCNTs composites. The results may be ascribed to the inhibitory effect on PHB crystallization caused by the steric hindrance of the long alkyl chains attached to MWCNTs. © The Polymer Society of Korea and Springer Sciene+Business Media Dordrecht 2014
Structural and magnetic studies of perovskite YCr0.5Mn0.5O3
No full textThe structure of YCr0.5Mn0.5O6, established from Rietveld refinement of powder neutron diffraction data, contains Cr and Mn that are disordered on the octahedral sites. The structure is best described in the orthorhombic space group Pbnm. Low temperature neutron diffraction data reveal a G-type antiferromagnetic type arrangement, with a ferromagnetic component along the b-axis, indicating that the Cr and Mn couple ferro (or possibly ferri) magnetically to each other.© 2014, The Royal Society of Chemistry
Neutron Reflectometry Studies Define Prion Protein N-terminal Peptide Membrane Binding
Get PDFThe prion protein (PrP), widely recognized to misfold into the causative agent of the transmissible spongiform encephalopathies, has previously been shown to bind to lipid membranes with binding influenced by both membrane composition and pH. Aside from the misfolding events associated with prion pathogenesis, PrP can undergo various posttranslational modifications, including internal cleavage events. Alpha- and beta-cleavage of PrP produces two N-terminal fragments, N1 and N2, respectively, which interact specifically with negatively charged phospholipids at low pH. Our previous work probing N1 and N2 interactions with supported bilayers raised the possibility that the peptides could insert deeply with minimal disruption. In the current study we aimed to refine the binding parameters of these peptides with lipid bilayers. To this end, we used neutron reflectometry to define the structural details of this interaction in combination with quartz crystal microbalance interrogation. Neutron reflectometry confirmed that peptides equivalent to N1 and N2 insert into the interstitial space between the phospholipid headgroups but do not penetrate into the acyl tail region. In accord with our previous studies, interaction was stronger for the N1 fragment than for the N2, with more peptide bound per lipid. Neutron reflectometry analysis also detected lengthening of the lipid acyl tails, with a concurrent decrease in lipid area. This was most evident for the N1 peptide and suggests an induction of increased lipid order in the absence of phase transition. These observations stand in clear contrast to the findings of analogous studies of Ab and α-synuclein and thereby support the possibility of a functional role for such N-terminal fragment-membrane interactions. © 2014,Biophysical Society
Ferromagnetic ordering in Mn-doped ZnO nanoparticles
Get PDFZn1 - xMn x O nanoparticles have been synthesized by hydrothermal technique. The doping concentration of Mn can reach up to 9 at% without precipitation or secondary phase, confirmed by electron spin resonance (ESR) and synchrotron X-ray diffraction (XRD). Room-temperature ferromagnetism is observed in the as-prepared nanoparticles. However, the room-temperature ferromagnetism disappears after post-annealing in either argon or air atmosphere, indicating the importance of post-treatment for nanostructured magnetic semiconductors.© 2014 Luo et al.; licensee Springer
Local structural changes in LiMn1.5Ni0.5O4 spinel cathode material for lithium-ion batteries
No full textLocal structural changes in LiMn1.5Ni0.5O4 cathode material were investigated by X-ray absorption spectroscopy in-operando using a specially designed electrochemical cell. The average structure of the starting material determined by neutron powder diffraction confirmed partial ordering of Mn and Ni cations on the octahedral sites in the spinel structure. It is observed that the electrochemical activity of the material between 3.5 V and 5.0 V is largely attributed to a two-step Ni2+/Ni4+ redox reaction. However, a small fraction of Mn3+ present in the pristine material also participates in electrochemical processes via a Mn3+/Mn4+ redox reaction. The excess lithium inserted into the material during deep discharge of the cell down to 2.0 V causes a further reduction of Mn4+ to Mn3+, while Ni remains electrochemically inactive. An increased proportion of Mn3+ in the material increases the distortion of MnO6 octahedra by the Jahn-Teller effect, which locally reduces the crystal symmetry from cubic to tetragonal, giving rise to the formation of domains of a Li2Mn2O4-type tetragonal phase. The fraction of this tetragonal phase was found to be directly related to the excess lithium inserted into the material. Upon subsequent charging to 2.9 V, the tetragonal phase tends to revert back to the original cubic spinel phase. The observed decline in the electrochemical performance of the material when cycled between 2.0 V and 5.0 V may be attributed to repetitive structural changes associated with the cubic ↔ tetragonal phase transition. © 2014, Elsevier B.V
Recent history of sediment metal contamination in Lake Macquarie, Australia, and an assessment of ash handling procedure effectiveness in mitigating metal contamination from coal-fired power stations
No full textThis study assessed historical changes in metal concentrations in sediments of southern Lake Macquarie resulting from the activities of coal-fired power stations, using a multi-proxy approach which combines 210Pb, 137Cs and metal concentrations in sediment cores. Metal concentrations in the lake were on average, Zn: 67 mg/kg, Cu: 15 mg/kg, As: 8 mg/kg, Se: 2 mg/kg, Cd: 1.5 mg/kg, Pb: 8 mg/kg with a maximum of Zn: 280 mg/kg, Cu: 80 mg/kg, As: 21 mg/kg, Se: 5 mg/kg, Cd: 4 mg/kg, Pb: 48 mg/kg. The ratios of measured concentrations in sediment cores to their sediment guidelines were Cd 1.8, As 1.0, Cu 0.5, Pb 0.2 and Zn 0.2, with the highest concern being for cadmium. Of special interest was assessment of the effects of changes in ash handling procedures by the Vales Point power station on the metal concentrations in the sediments. Comparing sediment layers before and after ash handling procedures were implemented, zinc concentrations have decreased 10%, arsenic 37%, selenium 20%, cadmium 38% and lead 14%. An analysis of contaminant depth profiles showed that, after implementation of new ash handling procedures in 1995, selenium and cadmium, the main contaminants in Australian black coal had decreased significantly in this estuary. © 2014, Elsevier B.V
Long term PM2.5 trends in the Australian industrial city of Newcastle: a 15-year study from 1998 to 2013
No full textA long-term, large dataset approach combining standard accelerator-based ion beam analysis (IBA) techniques with positive matrix factorisation (PMF) analysis to determine the sources and trends of fine particle pollution in the Newcastle NSW, Australia is discussed. Over 1500 samples of particle matter with aerodynamic diameter less than 2.5 µm (PM2.5) were collected between February 1998 and December 2013 and analysed using IBA techniques to obtain the concentration of 22 different elements from hydrogen to lead. The PM2.5 15-year average mass at the sampling site was 8.11 µg m–3. Statistical PMF analysis was applied to this large dataset to quantitatively determine nine source fingerprints; soil, secondary sulfate, sea, smoke, industrial processes (specifically related to calcium, manganese and iron) and two different automobile sources. Significant step-like reductions of 98, 79 and 69 %, over and above regular seasonal variations, were clearly observed in the industrial-Mn, industrial-Fe and automobile sources during this time period. These trends showed excellent correlation with the cessation of large industrial operations in the local area and clearly demonstrate the advantage of long-term aerosol analysis for monitoring and managing fine particle air pollution sources on a local scale. © 2014, CSIRO
Theoretical and experimental Raman spectroscopic studies of synthetic thorutite (ThTi2O6)
No full textRaman spectra of synthetic non-substituted and U/Np/Pu- substituted thorutite (ThTi2O6) samples were collected. Factor group analysis was used to analyse the possible vibration modes. Theoretical simulations based on density functional theory (DFT) were performed on both CeTi2O6 and ThTi2O6. All possible vibrational modes for thorutite have been identified and assigned to the measured spectra. The presence and the effect of higher valence of U in thorutite has been discussed and the U–O bond lengths have been calculated by using the measured wavenumbers of ν1 (UO2)2+ symmetric stretching vibrations. The presence of U6+ in uranyl form can be inferred from the wavenumbers of U–O vibrations. Corresponding Np–O and Pu–O vibrations were not observed in the Raman spectra. Thus the presence of Np6+ and Pu6+ in the studied samples was not established. © 2016 Elsevier B.V
Simulation of tropospheric chemistry and aerosols with the climate model EC-Earth
Get PDFWe have integrated the atmospheric chemistry and transport model TM5 into the global climate model EC-Earth version 2.4. We present an overview of the TM5 model and the two-way data exchange between TM5 and the IFS model from the European Centre for Medium-Range Weather Forecasts (ECMWF), the atmospheric general circulation model of EC-Earth. In this paper we evaluate the simulation of tropospheric chemistry and aerosols in a one-way coupled configuration. We have carried out a decadal simulation for present-day conditions and calculated chemical budgets and climatologies of tracer concentrations and aerosol optical depth. For comparison we have also performed offline simulations driven by meteorological fields from ECMWF's ERA-Interim reanalysis and output from the EC-Earth model itself. Compared to the offline simulations, the online-coupled system produces more efficient vertical mixing in the troposphere, which reflects an improvement of the treatment of cumulus convection. The chemistry in the EC-Earth simulations is affected by the fact that the current version of EC-Earth produces a cold bias with too dry air in large parts of the troposphere. Compared to the ERA-Interim driven simulation, the oxidizing capacity in EC-Earth is lower in the tropics and higher in the extratropics. The atmospheric lifetime of methane in EC-Earth is 9.4 years, which is 7% longer than the lifetime obtained with ERA-Interim but remains well within the range reported in the literature. We further evaluate the model by comparing the simulated climatologies of surface radon-222 and carbon monoxide, tropospheric and surface ozone, and aerosol optical depth against observational data. The work presented in this study is the first step in the development of EC-Earth into an Earth system model with fully interactive atmospheric chemistry and aerosols.© 2014, Author(s)
Li+ and Ca2+ Derivatives of the Isonicotinate-N-oxide Ion Including Single Crystal-to-Single Crystal Transformations
No full textCrystals of [Li(inox)(H2O)] (where inox– = the isonicotinate-N-oxide ion) are obtained from aqueous solution. The Li+ cations and the carboxylate anions form a two-dimensional (2D) sheet containing four-membered (−Li–O–Li–O−) rings and 16-membered (−Li–O–C–O−)4 rings; the sheets are linked to adjacent parallel sheets through hydrogen bonds. Crystals of solvent-free [Li(inox)], obtained from t-butanol, consist of a three-dimensional network which can also be prepared in microcrystalline form by dehydration of [Li(inox)(H2O)] at 200 °C. Crystals of [Ca(inox)2(H2O)2] contain 2D sheets with 4,4 topology in which Ca2+ ions, bound by trans water molecules, provide the 4-connecting nodes. The Ca(H2O)22+ units are linked by carboxylate groups to generate 16-membered (−Ca–O–C–O−)4 rings. Sheets are bound together by hydrogen bonds between the pyridine-N-oxide units and coordinated water molecules. [Ca(inox)2(H2O)2] can be dehydrated at 190 °C in a single crystal-to-single crystal transformation to give [Ca(inox)2] whose structure is related to that of the hydrated precursor. A proposed solid-state mechanism for this single crystal-to-single crystal transformation, in which the N-oxide takes up the site on calcium vacated by water is proposed © 2014 American Chemical Society