744 research outputs found
Improvement of leak tightness for swellable elastomeric seals through the shape optimization
Swellable packers have been widely employed in various oil & gas applications. Downhole conditions are difficult to reproduce using physical testing environments, but can be simulated in a virtual environment using CAE software. A better understanding of packersâ mechanical behaviour in downhole conditions would provide a higher confidence and improvement in existing engineering design practices for the manufacturing of packers. The numerical simulation can be incorporated into optimisation procedures searching for an optimal shape of packers aiming to minimise the time to seal the borehole and maximise the contact pressure between the seal and borehole. Such an optimisation would facilitate the development of a packer with various designs optimised for different downhole conditions. The objective of this work is to develop a design tool integrated into Abaqus/CAE to implement parametric numerical studies using implicit and explicit FE-simulations. However, development of such a CAE plugin is associated with a number of technical challenges specific to this class of multiphysics problems, which are addressed in this research and discussed in the paper
Experience with CommunityâBased Amphotericin B Infusion Therapy
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90368/1/phco.25.5.690.63591.pd
Polyanionic Ligand Platforms for Methyl- and Dimethylaluminum Arrays
Trimethylaluminum
finds widespread applications in chemical and materials synthesis,
most prominently in its partially hydrolyzed form of methylalumoxane
(MAO), which is used as a cocatalyst in the polymerization of olefins.
This work investigates the sequential reactions of trimethylaluminum
with hexaprotic phosphazenes (RNH)6P3N3 (=XH6) equipped with substituents R of varied
steric bulk including tert-butyl (1H6), cyclohexyl (2H6), isopropyl (3H6), isobutyl (4H6), ethyl
(5H6), propyl (6H6), methyl (7H6), and benzyl (8H6). Similar to MAO, the resulting complexes of polyanionic
phosphazenates [XHn]nâ6 accommodate multinuclear arrays
of [AlMe2]+ and [AlMe]2+. Reactions
were monitored by 31P NMR spectroscopy, and structures
were determined by single-crystal X-ray diffraction. They included 1H4(AlMe2)2, 1H3(AlMe2)3, 2H3(AlMe2)3, 3(AlMe2)4AlMe, 4HÂ(AlMe2)5, 4(AlMe2)6, {5HÂ(AlMe2)4}2AlMe, 5(AlMe2)6, 6(AlMe2)6, {7(AlMe2)4AlMe}2, and 8(AlMe2)6. The study shows that subtle
variations of the steric properties of the R groups influence the
reaction pathways, levels of aggregation, and fluxional behavior.
While [AlMe2]+ is the primary product of the
metalation, [AlMe]2+ is utilized to alleviate overcrowding
or to aid aggregation. At the later stages of metalation, [AlMe2]+ groups start to scramble around congested sites.
The ligands proved to be very robust and extremely flexible, offering
a unique platform to study complex multinuclear metal arrangements
Bioavailability and kidney responses to Diclofenac in the fathead minnow (Pimephales promelas)
This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Diclofenac is one of the most widely prescribed nonsteroidal anti-inflammatory drugs worldwide. It is frequently detected in surface waters; however, whether this pharmaceutical poses a risk to aquatic organisms is debated. Here we quantified the uptake of diclofenac by the fathead minnow (Pimephales promelas) following aqueous exposure (0.2-25.0 ÎŒg L(-1)) for 21 days, and evaluated the tissue and biomolecular responses in the kidney. Diclofenac accumulated in a concentration- and time-dependent manner in the plasma of exposed fish. The highest plasma concentration observed (for fish exposed to 25 ÎŒg L(-1) diclofenac) was within the therapeutic range for humans. There was a strong positive correlation between exposure concentration and the number of developing nephrons observed in the posterior kidney. Diclofenac was not found to modulate the expression of genes in the kidney associated with its primary mode of action in mammals (prostaglandin-endoperoxide synthases) but modulated genes associated with kidney repair and regeneration. There were no significant adverse effects following 21 days exposure to concentrations typical of surface waters. The combination of diclofenac's uptake potential, effects on kidney nephrons and relatively small safety margin for some surface waters may warrant a longer term chronic health effects analysis for diclofenac in fish.This work was funded by Knowledge Transfer Partnership (KTP): Use of âomicâ technologies in the environmental risk assessment of pharmaceuticals (KTP007650) and AstraZenecaâs Safety, Health and Environment (SHE) Research Programme. We thank Lina Gunnarsson, Matt Winter and James Cresswell (Exeter University), and former members of the Brixham Environmental Laboratory for their advice and assistance. Authors declare no competing financial interest
MRI channel flows and their parasites
Local simulations of the magnetorotational instability (MRI) in accretion
disks can exhibit recurrent coherent structures called channel flows. The
formation and destruction of these structures may play a role in the
development and saturation of MRI-induced turbulence, and consequently help us
understand the time-dependent accretion behaviour of certain astrophysical
objects. Previous investigations have revealed that channel solutions are
attacked by various parasitic modes, foremost of which is an analogue of the
Kelvin-Helmholtz instability. We revisit these instabilities and show how they
relate to the classical instabilities of plasma physics, the kink and pinch
modes. However, we argue that in most cases channels emerge from developed
turbulence and are eventually destroyed by turbulent mixing, not by the
parasites. The exceptions are the clean isolated channels which appear in
systems near criticality or which emerge from low amplitude initial conditions.
These structures inevitably achieve large amplitudes and are only then
destroyed, giving rise to eruptive behaviour.Comment: 17 pages, 17 figures, accepted by MNRA
Transverse Spin at PHENIX: Results and Prospects
The Relativistic Heavy Ion Collider (RHIC), as the world's first and only
polarized proton collider, offers a unique environment in which to study the
spin structure of the proton. In order to study the proton's transverse spin
structure, the PHENIX experiment at RHIC took data with transversely polarized
beams in 2001-02 and 2005, and it has plans for further running with transverse
polarization in 2006 and beyond. Results from early running as well as
prospective measurements for the future will be discussed.Comment: 6 pages, 2 figures, presented at Transversity 2005, Como, Ital
Collision geometry scaling of Au+Au pseudorapidity density from sqrt(s_NN) = 19.6 to 200 GeV
The centrality dependence of the midrapidity charged particle multiplicity in
Au+Au collisions at sqrt(s_NN) = 19.6 and 200 GeV is presented. Within a simple
model, the fraction of hard (scaling with number of binary collisions) to soft
(scaling with number of participant pairs) interactions is consistent with a
value of x = 0.13 +/- 0.01(stat) +/- 0.05(syst) at both energies. The
experimental results at both energies, scaled by inelastic p(pbar)+p collision
data, agree within systematic errors. The ratio of the data was found not to
depend on centrality over the studied range and yields a simple linear scale
factor of R_(200/19.6) = 2.03 +/- 0.02(stat) +/- 0.05(syst).Comment: 5 pages, 4 figures, submitted to PRC-R
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