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Particulate pollution in the Sydney Region: source diagnostics and synoptic controls
Get PDFAirborne particulate matter (PM2.5) was sampled at Richmond and Liverpool, located in the Sydney Basin, Australia,
and ion beam analysis was used to obtain the elemental composition. Using self-organising maps to classify synoptic
weather systems, it was found that high PM2.5 concentrations were associated with high pressure systems located to the
east of the sampling sites. The highest median sulfur was associated with weak synoptic conditions and high soil dust days
were more often associated with frontal systems.
To investigate the effect of local flows in the Sydney Basin, the Weather Research and Forecasting model (WRF) was
used to generate meteorological data of 12 km resolution. A comparison was made between back trajectories generated
using the higher-resolution WRF data, the 0.5° by 0.5° Climate Forecast System data and the 1° by 1° Global Data
Assimilation System data. It was found that for high soil dust days, there were small differences between the different back
trajectories. However, under weak synoptic conditions (high sulfur days), the back trajectories generated from higher
resolution data showed larger variations over a 24 hr period. This was attributed to the meandering of local winds and seabreezes.
Lower altitude back trajectories, generated from low resolution data, passed more often over the power stations located
on the western side of the Great Dividing Range (while the sampling sites are on the east). This demonstrates the need for
higher resolution meteorological data for generating low altitude back trajectories when the source and receptor are
separated by hilly terrain.
In estimating the number of high sulfur days for which a power station was crossed, there was up to 20% difference at
Liverpool and up to 10% difference at Richmond, between back trajectories starting at different altitudes and generated
from meteorological data of three different resolutions
Speculation on the origin of sub-baseline excursions of CH4 at Cape Grim
Get PDFThe Advanced Global Atmospheric Gases Experiment (AGAGE) program has historically measured in situ
methane (CH4
) at Cape Grim via gas chromatography with flame ionization detection (GC-FID) in 40 minutely
grab samples. By adding continuous, high precision in situ measurements of CH4
(Picarro cavity ring-down
spectroscopy [CRDS]) at both Cape Grim, Tasmania, and Casey, Antarctica, a new feature has become apparent
in the Cape Grim CH4
record. During the austral summer (December to February), the Cape Grim CH4
record
periodically drops below baseline. For example, in Figure 1, a number of sustained episodes of depressed CH4
concentration can be seen below the baseline selected data shown in red. Notably, these episodes are also seen
in the GC-FID record.
In this presentation, we examine these sub-baseline excursions of CH4
. In conjunction with meteorology and a
variety of other chemical species measured at Cape Grim, including radon, ozone, hydrogen and ethane, we speculate on a number of possible mechanisms that might be responsible for these dips in CH4 mixing ratio
Determination of Fullerene Scattering Length Density: A critical Parameter for understanding the Fullerene distribution in Bulk Heterojunction Organic Photovoltaic devices
No full textFullerene derivatives are commonly used as electron acceptors in combination with (macro)molecular electron donors in bulk heterojunction (BHJ) organic photovoltaic (OPV) devices. Understanding the BHJ structure at different electron donor/acceptor ratios is critical to the continued improvement and development of OPVs. The high neutron scattering length densities (SLDs) of the fullerenes provide effective contrast for probing the distribution of the fullerene within the blend in a nondestructive way. However, recent neutron scattering studies on BHJ films have reported a wide range of SLDs ((3.6–4.4) × 10–6 Å–2) for the fullerenes 60-PCBM and 70-PCBM, leading to differing interpretations of their distribution in thin films. In this article, we describe an approach for determining more precisely the scattering length densities of the fullerenes within a polymer matrix in order to accurately quantify their distribution within the active layers of OPV devices by neutron scattering techniques.© 2014, American Chemical Society
Determination of martensite structures of the Au7Cu5Al4 and Au7Cu5.7Al3.3 shape-memory alloys
No full textThe β-phase of Au7Cu5Al4 undergoes a reversible shape-memory phase transformation for which several conflicting martensite phases have been reported. Here we show the significance of the cooling temperature used to obtain the martensite. If Au7Cu5Al4 is cooled from the parent phase condition to cryogenic temperatures, e.g. below 200 K, the martensitic phase is orthorhombic (space group Pcmn, a = 4.4841 Å, b = 5.8996 Å, c = 17.8130 Å); however, when this composition is cooled to only ∼260 K it will in general consist of a mixture of orthorhombic and monoclinic phase (the latter has space group P21/m, a = 4.4742 Å, b = 5.9265 Å, c = 13.3370 Å, β = 91.425°). In contrast, a sample with decreased Al content (Au7Cu5.7Al3.3) transforms fully to monoclinic phase if cooled to ∼260 K. © 2014 Acta Materialia Inc
Magnetic transitions in LaFe13−x−yCoySix compounds
No full textThe magnetic properties of a set of LaFe13−x−yCoySix compounds (x = 1.6 − 2.6; y = 0, y = 1.0) have been investigated using magnetic measurements, thermal expansion, 57Fe Mössbauer spectroscopy and high resolution neutron powder diffraction methods over the temperature range 10–300 K. The natures of the magnetic transitions in these LaFe13−x−yCoySix compounds have been determined. The Curie temperatures of LaFe13−xSix were found to increase with Si content from TC = 219(5) K for Si content x = 1.6 to TC = 250(5) K for x = 2.6. Substitution of Co for Fe in LaFe10.4Si2.6 resulted in a further enhancement of the magnetic ordering temperature to TC = 281(5) K for the LaFe9.4CoSi2.6 compound. The nature of the magnetic transition at the Curie temperature changes from first order for LaFe11.4Si1.6 to second order for LaFe10.4Si2.6 and LaFe9.4CoSi2.6. The temperature dependences of the mean magnetic hyperfine field values lead to TC values in good agreement with analyses of the magnetic measurements. The magnetic entropy change, −ΔSM, has been determined from the magnetization curves as functions of temperature and magnetic field (ΔB = 0 − 5 T) by applying the standard Maxwell relation. In the case of LaFe12.4Si1.6 for example, the magnetic entropy change around TC is determined to be -ΔSM ∼ 14.5 J kg−1 K−1 for a magnetic field change Δ B = 0 − 5 T. © 2013, Springer Science+Business Media Dordrecht
CLIC proteins, ezrin, radixin, moesin and the coupling of membranes to the actin cytoskeleton: A smoking gun?
No full textThe CLIC proteins are a highly conserved family of metazoan proteins with the unusual ability to adopt both soluble and integral membrane forms. The physiological functions of CLIC proteins may include enzymatic activity in the soluble form and anion channel activity in the integral membrane form. CLIC proteins are associated with the ERM proteins: ezrin, radixin and moesin. ERM proteins act as cross-linkers between membranes and the cortical actin cytoskeleton. Both CLIC and ERM proteins are controlled by Rho family small GTPases. CLIC proteins, ERM and Rho GTPases act in a concerted manner to control active membrane processes including the maintenance of microvillar structures, phagocytosis and vesicle trafficking. All of these processes involve the interaction of membranes with the underlying cortical actin cytoskeleton. The relationships between Rho GTPases, CLIC proteins, ERM proteins and the membrane:actin cytoskeleton interface are reviewed. Speculative models are proposed involving the formation of localised multi-protein complexes on the membrane surface that assemble via multiple weak interactions. This article is part of a Special Issue entitled: Reciprocal influences between cell cytoskeleton and membrane channels, receptors and transporters. © 2013, Elsevier B.V
Sediment accumulation, stratigraphic order, and the extent of time-averaging in lagoonal sediments: a comparison of 210Pb and 14C/amino acid racemization chronologies
No full textCarbon-14 calibrated amino acid racemization (14C/AAR) data and lead-210 (210Pb) data are used to examine sediment accumulation rates, stratigraphic order, and the extent of time-averaging in sediments collected from the One Tree Reef lagoon (southern Great Barrier Reef, Australia). The top meter of lagoonal sediment preserves a stratigraphically ordered deposit spanning the last 600 yrs. Despite different assumptions, the 210Pb and 14C/AAR chronologies are remarkably similar indicating consistency in sedimentary processes across sediment grain sizes spanning more than three orders of magnitude (0.1–10 mm). Estimates of long-term sediment accumulation rates range from 2.2 to 1.2 mm yr−1. Molluscan time-averaging in the taphonomically active zone is 19 yrs, whereas below the depth of final burial (~15 cm), it is ~110 yrs/5 cm layer. While not a high-resolution paleontological record, this reef lagoon sediment is suitable for paleoecological studies spanning the period of Western colonization and development. This sedimentary deposit, and others like it, should be useful, albeit not ideal, for quantifying anthropogenic impacts on coral reef systems.© 2014, The Author(s)
The role of plasticity theory on the predicted residual stress field of weld structures
No full textConstitutive plasticity theory is commonly applied to the numerical analysis of welds in one of three ways: using an isotropic hardening model, a kinematic hardening model, or a mixed isotropic-kinematic hardening model. The choice of model is not entirely dependent on its numerical accuracy, however, as a lack of empirical data will often necessitate the use of a specific approach. The present paper seeks to identify the accuracy of each formalism through direct comparison of the predicted and actual post-weld residual stress field developed in a three-pass 316LN stainless steel slot weldment. From these comparisons, it is clear that while the isotropic hardening model tends to noticeably over-predict and the kinematic hardening model slightly under-predict the residual post-weld stress field, the results using a mixed hardening model are quantitatively accurate. Even though the kinematic hardening model generally provides more accurate results when compared to an isotropic hardening formalism, the latter might be a more appealing choice to engineers requiring a conservative design regarding weld residual stress. © 2014, Trans Tech Publications
Nonlinear analysis of axially loaded circular concrete-filled stainless steel tubular short columns
No full textExperiments show that the ultimate compressive strength of stainless steel is much higher than its tensile strength. The full-range two-stage constitutive model for stainless steels assumes that stainless steels follow the same stress–strain behavior in compression and tension, which may underestimate the compressive strength of stainless steel tubes. This paper presents a fiber element model incorporating the recently developed full-range three-stage stress–strain relationships based on experimentally observed behavior for stainless steels for the nonlinear analysis of circular concrete-filled stainless steel tubular (CFSST) short columns under axial compression. The fiber element model accounts for the concrete confinement effects provided by the stainless steel tube. Comparisons of computer solutions with experimental results published in the literature are made to examine the accuracy of the fiber element model and material constitutive models for stainless steels. Parametric studies are conducted to study the effects of various parameters on the behavior of circular CFSST short columns. A design model based on Liang and Fragomeni's design formula is proposed for circular CFSST short columns and validated against results obtained by experiments, fiber element analyses, ACI-318 codes and Eurocode 4. The fiber element model incorporating the three-stage stress–strain relationships for stainless steels is shown to simulate well the axial load–strain behavior of circular CFSST short columns. The proposed design model gives good predictions of the experimental and numerical ultimate axial loads of CFSST columns. It appears that ACI-318 codes and Eurocode 4 significantly underestimate the ultimate axial strengths of CFSST short columns
Magnetism and magnetocaloric effect of Mn0.98Fe0.02CoGe
No full textThe crystallographic and magnetic properties of Mn0.98Fe0.02CoGe have been investigated by X-ray diffraction, dc magnetization and neutron diffraction over the temperature range 20–450 K. The temperature dependence of the phase fractions of the orthorhombic and hexagonal phases is described well by a Gaussian distribution. The Mn0.98Fe0.02CoGe sample exhibits a first-order magneto-structural transition centred at TMS ∼ 297 K of FWHM ∼37 K with a magnetic entropy change of −ΔSM = 24(1) J kg−1 K−1 for ΔB = 0–5 T. Neutron diffraction indicates a ferromagnetic orthorhombic structure below TMS with only the Mn carrying magnetic moment (3.98(6) µB) at 20 K. The sample is paramagnetic in the hexagonal phase above TMS.© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim