507 research outputs found
An implicit method for radiative transfer with the diffusion approximation in SPH
An implicit method for radiative transfer in SPH is described. The diffusion
approximation is used, and the hydrodynamic calculations are performed by a
fully three--dimensional SPH code. Instead of the energy equation of state for
an ideal gas, various energy states and the dissociation of hydrogen molecules
are considered in the energy calculation for a more realistic temperature and
pressure determination. In order to test the implicit code, we have performed
non--isothermal collapse simulations of a centrally condensed cloud, and have
compared our results with those of finite difference calculations performed by
MB93. The results produced by the two completely different numerical methods
agree well with each other.Comment: 25 pages, 9 figure
Impact behavior of injected PP/nanoclay parts
This work attempts to contribute to bridge the gap between scientific challenges and industrial stakes regarding
PP/nanoclay composites. Pieces of nanocomposites were obtained by direct injection of commercial PP mixed with a
commercial MB of PP with 50% of organoclay, with a double-gated hot runner mould, which produced mouldings with
a weld line. The moulding microstructure was assessed by POM and XRD, while the distribution and exfoliation grade
of clay was evaluated by TEM and XRD. The typical skin-core structure was found, with a skin thickness wider in bulk
than in weld line zones. Regarding clay platelets mostly intercalated structures were seen. The impact properties at
room temperature were assessed by means of tensile and biaxial tests. Properties were monitored at different sites of the
mouldings. At the weld line zone less energy was consumed under tensile conditions and exhibited higher apparent
impact toughness under biaxial conditions than the bulk zone. Visual inspection of biaxially impacted samples showed
that the orientation of polymer molecules and clay platelets induced by melt flow prevailed, and the weld line was not
the determinant of the toughness of the mouldings. An optimum in impact performance was found for moulding with
3% of clay, since at larger clay contents platelets agglomerated and acted as stress raisers
Uni- and biaxial impact behavior of double-gated nanoclay-reinforced polypropylene injection moldings
Polypopylene/nanoclay three-dimensional parts were
produced without intermediate steps by direct injection
molding to explore the influence of flow features and
nanoclay incorporation in their impact performance.
The nanocomposite was obtained by direct compounding
of commercial PP with nanoclay masterbatch. The
as-molded morphology was analyzed by X-ray and
TEM analyses in terms of skin-core structure and
nanoclay particle dispersion. The nanoclay particles
induced the reduction of b-form spherulites, a known
toughener. The impact behavior was assessed in tensile
and biaxial modes. The PP nanocomposite molding
toughness was practically unaffected by the processing
melt temperature and flow rate. Conversely the
nanoclay presence is influent in the impact performance.
Under biaxial stress impact, the regions close to
weld lines are tougher than the bulk and the fracture
develops with main crack paths along the flow direction
and the weld line. Cracking along the weld line
results from less macromolecular interpenetration and
chain entanglement, and unfavorable nanoparticle orientation.
It seems that a failure mechanism which
involves nanoclay delamination and multiple matrix
crazing explains the toughening of PP in the directions
where the nanoparticle orientation with respect to
loading is adequate.Contract grant sponsors: CONICET, ANPCyT from Argentina, MINCyT (Argentina) - FCT (Portugal), Universities Nacional de Mar del Plata and Minho
Characterization of cadmium proteinuria in man and rat.
In workers chronically exposed to cadmium and without signs of renal insufficiency, plasma proteins with molecular weight ranging from 11,800 to 450,000 are excreted in greater amount in urine. Increased urinary excretion of low and high molecular weight proteins can occur independently. Because of its greater stability in urine and provided a sensitive immunological technique is used, the determination of retinol-binding protein is a more practical and reliable test of proximal tubular function than beta 2-microglobulin. The evaluation of renal function of workers removed from cadmium exposure indicates that cadmium-induced renal lesions, albeit of slow progression, are not reversible when exposures ceases. In workers chronically exposed to cadmium or removed from cadmium exposure, metallothionein in urine is directly correlated with cadmium in urine but not with cadmium in blood or years of cadmium exposure. The association between cadmium in urine and metallothionein in urine is independent of the status of renal function and the intensity of current exposure to cadmium. Whereas the repeated IP injection of high doses of cadmium to rat gives rise to a mixed or tubular type proteinuria, the prolonged oral administration of cadmium results mainly in the development of a glomerular type proteinuria. The former is usually reversible after cessation of treatment whereas the latter is not. Circulating antiglomerular basement membrane antibodies have been found in man and in rat chronically exposed to cadmium. The pathogenic significance of this finding deserves further investigation
A faster algorithm for smoothed particle hydrodynamics with radiative transfer in the flux-limited diffusion approximation
We describe a new, faster implicit algorithm for solving the radiation
hydrodynamics equations in the flux-limited diffusion approximation for
smoothed particle hydrodynamics. This improves on the method elucidated in
Whitehouse & Bate by using a Gauss-Seidel iterative method rather than
iterating over the exchange of energy between pairs of particles. The new
algorithm is typically many thousands of times faster than the old one, which
will enable more complex problems to be solved. The new algorithm is tested
using the same tests performed by Turner & Stone for ZEUS-2D, and repeated by
Whitehouse & Bate.Comment: 12 pages, 7 figures. Accepted for publication in MNRA
Evolution of Linear Absorption and Nonlinear Optical Properties in V-Shaped Ruthenium(II)-Based Chromophores
In this article, we describe a series of complexes with electron-rich cis-{Ru^(II)(NH_3)_4}^(2+) centers coordinated to two pyridyl ligands bearing N-methyl/arylpyridinium electron-acceptor groups. These V-shaped dipolar species are new, extended members of a class of chromophores first reported by us (Coe, B. J. et al. J. Am. Chem. Soc. 2005, 127, 4845−4859). They have been isolated as their PF_6− salts and characterized by using various techniques including ^1H NMR and electronic absorption spectroscopies and cyclic voltammetry. Reversible Ru^(III/II) waves show that the new complexes are potentially redox-switchable chromophores. Single crystal X-ray structures have been obtained for four complex salts; three of these crystallize noncentrosymmetrically, but with the individual molecular dipoles aligned largely antiparallel. Very large molecular first hyperpolarizabilities β have been determined by using hyper-Rayleigh scattering (HRS) with an 800 nm laser and also via Stark (electroabsorption) spectroscopic studies on the intense, visible d → π^* metal-to-ligand charge-transfer (MLCT) and π → π^* intraligand charge-transfer (ILCT) bands. The latter measurements afford total nonresonant β_0 responses as high as ca. 600 × 10^(−30) esu. These pseudo-C_(2v) chromophores show two substantial components of the β tensor, β_(zzz) and β_(zyy), although the relative significance of these varies with the physical method applied. According to HRS, β_(zzz) dominates in all cases, whereas the Stark analyses indicate that β_(zyy) is dominant in the shorter chromophores, but β_(zzz) and β_(zyy) are similar for the extended species. In contrast, finite field calculations predict that β_(zyy) is always the major component. Time-dependent density functional theory calculations predict increasing ILCT character for the nominally MLCT transitions and accompanying blue-shifts of the visible absorptions, as the ligand π-systems are extended. Such unusual behavior has also been observed with related 1D complexes (Coe, B. J. et al. J. Am. Chem. Soc. 2004, 126, 3880−3891)
Toward Rare-Earth-Free Permanent Magnets: A Combinatorial Approach Exploiting the Possibilities of Modeling, Shape Anisotropy in Elongated Nanoparticles, and Combinatorial Thin-Film Approach
The objective of the rare-earth free permanent magnets (REFREEPM) project is to develop a new generation of high-performance permanent magnets (PMs) without rare earths. Our approach is based on modeling using a combinatorial approach together with micromagnetic modeling and the realization of the modeled systems (I) by using a novel production of high-aspect-ratio (>5) nanostructrures (nanowires, nanorods, and nanoflakes) by exploiting the magnetic shape anisotropy of the constituents that can be produced via chemical nanosynthesis polyol process or electrodeposition, which can be consolidated with novel processes for a new generation of rare-earth free PMs with energy product in the range of 60 kJ/m3 < (BH)max < 160 kJ/m3 at room temperature, and (II) by using a high-throughput thin-film synthesis and high-throughput characterization approach to identify promising candidate materials that can be stabilized in a tetragonal or hexagonal structure by epitaxial growth on selected substrates, under various conditions of pressure, stoichiometry, and temperature. In this article, we report the progress so far in selected phases.This work is supported by European Commission (REFREEPERMAG project) grant number GA-NMP3-SL-2012-280670
Including Pathogen Risk in Life Cycle Assessment of Wastewater Management. 1. Estimating the Burden of Disease Associated with Pathogens
The environmental performance of wastewater and sewage sludge management is commonly assessed using life cycle assessment (LCA), whereas pathogen risk is evaluated with quantitative microbial risk assessment (QMRA). This study explored the application of QMRA methodology with intent to include pathogen risk in LCA and facilitate a comparison with other potential impacts on human health considered in LCA. Pathogen risk was estimated for a model wastewater treatment system (WWTS) located in an industrialized country and consisting of primary, secondary, and tertiary wastewater treatment, anaerobic sludge digestion, and land application of sewage sludge. The estimation was based on eight previous QMRA studies as well as parameter values taken from the literature. A total pathogen risk (expressed as burden of disease) on the order of 0.2–9 disability-adjusted life years (DALY) per year of operation was estimated for the model WWTS serving 28 600 persons and for the pathogens and exposure pathways included in this study. The comparison of pathogen risk with other potential impacts on human health considered in LCA is detailed in part 2 of this article series
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