1,739 research outputs found
Electrical conductivity and tortuosity of solid foam: Effect of pore connections
International audienceNumerical and analytical methods at both micro-and mesoscales are used to study how the electrical resistivity and the high frequency tortuosity of solid foam are modied by the presence of membranes that partially or totally close the cell windows connecting neighbor pores. Finite element method (FEM) simulations are performed on two pores connected by a single-holed membrane and on well-ordered Kelvin foam. For two pores connected by a single-holed membrane, we show that the equation for pore access resistance obtained by Sahu and Zwolak (Phys. Rev. E 98, 012404, 2018) can predict, after a few modications, the electrical resistivity at the membrane scale for a large range of membrane apertures. In the second part, considering these analytical results, we build a pore-network model by using two kinds of conductances at the pore scale-inter-pore conductance and intra-pore conductance. Local inter-pore resistances govern foam electrical conductivity at small membrane aperture size, but when the membrane aperture has the same order of magnitude as the pore size, the intra-pore resistances are no longer negligible. An important success of this pore-network model is that it can be used to study the eects of percolation on the foam electrical conductivity by using pore-network simulations on larger samples containing a few thousands of pores and having dierent proportions of closed membrane randomly distributed over the sample. The tortuosity is found to be drastically larger than one in foam containing membranes with small apertures or a signicant fraction of closed membranes
Du tĂątonnement ethnographique au discernement de sens : enquĂȘtes participatives en boucherie et dans la zone d'attente des mineurs isolĂ©s Ă©trangers
Partant dâunivers de recherche a priori Ă©loignĂ©s â la boucherie et la zone dâattente des mineurs isolĂ©s Ă©trangers â cet article repose sur une affirmation commune : pour rendre compte des catĂ©gories mobilisĂ©es par les enquĂȘtĂ©s, il faut se mettre en situation de les percevoir. En ce quâelle rend observable et descriptible le recours Ă des catĂ©gories in situ, lâethnographie est apparue comme un moyen dâaccĂ©der Ă ce qui est constitutif des expĂ©riences de travail. LâenrĂŽlement dans les actions en cours sâest rĂ©alisĂ© selon des conditions dâentrĂ©e et des modalitĂ©s distinctes : stagiaire volontaire et experte involontaire. En examinant les configurations dâenquĂȘte, lâarticle montre comment la modulation de la prĂ©sence participative peut induire le dĂ©placement de la problĂ©matique de recherche
Effect of polydispersity on the transport and sound absorbing properties of three-dimensional random fibrous structures
Sophisticated numerical approaches can predict the properties of composite
nonwovens. However, for polydisperse random fibrous media, we need to identify
microstructural descriptors for accurate predictions. We manufactured
polydisperse composite felts with different fibrous structures and
characterized them using scanning electron microscope images. The images showed
a wide distribution of fiber diameters and a decreasing standard deviation of
the azimuthal angle of fibers with increasing compression rate. Current models
could not capture the evolution of their transport properties with compression
rate. Therefore, we developed a fiber network model for the transport processes
of transversely isotropic random fibrous media. The model relates the main
visco-thermal dissipation mechanisms to the largest channels within the fluid
phase, while the smallest channels lead the inertial behaviors. We estimated
the viscous and thermal permeabilities from a representative elementary volume
(REV) with a volume weighted average diameter, and the viscous and thermal
characteristic lengths from a REV with inverse volume weighted average
diameter. A unified empirical model was proposed. The model predictions agree
with the experimental results.Comment: 29 pages, 19 figure
Effectiveness and Overall Safety of NutropinAq (R) for Growth Hormone Deficiency and Other Paediatric Growth Hormone Disorders: Completion of the International Cooperative Growth Study, NutropinAq (R) European Registry (iNCGS)
Objective: The International Cooperative Growth Study, NutropinAqÂź European Registry (iNCGS) (NCT00455728) monitored long-term safety and effectiveness of recombinant human growth hormone (rhGH; NutropinAqÂź [somatropin]) in paediatric growth disorders.
Methods: Open-label, non-interventional, post-marketing surveillance study recruiting children with growth disorders. Endpoints included gain in height standard deviation score (SDS), adult height, and occurrence of adverse events (AEs).
Results: 2792 patients were enrolled. 2082 patients (74.6%) had growth hormone deficiency (GHD), which was isolated idiopathic in 1825 patients (87.7%). Non-GHD diagnoses included Turner syndrome (TS) (n=199), chronic renal insufficiency (CRI) (n=10), other non-GHD (n=498), and missing data for three participants. Improvements from baseline height SDS occurred at all time points to Month 132, and in all subgroups by disease aetiology. At Month 12, mean (95% CI) change in height SDS by aetiology was: idiopathic GHD 0.63 (0.61;0.66), organic GHD 0.71 (0.62;0.80), TS 0.59 (0.53; 0.65), CRI 0.54 (-0.49;1.56), and other non-GHD 0.64 (0.59;0.69). Mean height ( ± SD) at the last visit among the 235 patients with adult or near-adult height recorded was 154.0 cm ( ± 8.0) for girls and 166.7 cm ( ± 8.0) for boys. The most frequent biological and clinical non-serious drug-related AEs were increased insulin-like growth factor concentrations (314 events) and injection site haematoma (99 events). Serious AEs related to rhGH according to investigators were reported (n=30); the most frequent were scoliosis (4 events), epiphysiolysis (3 events), and strabismus (2 events).
Conclusions: There was an improvement in mean height SDS in all aetiology subgroups after rhGH treatment. No new safety concerns were identified
The 2-D electron gas at arbitrary spin polarizations and arbitrary coupling strengths: Exchange-correlation energies, distribution functions and spin-polarized phases
We use a recent approach [Phys. Rev. Letters, {\bf 84}, 959 (2000)] for
including Coulomb interactions in quantum systems via a classical mapping of
the pair-distribution functions (PDFs) for a study of the 2-D electron gas. As
in the 3-D case, the ``quantum temperature'' T_q of a classical 2-D Coulomb
fluid which has the same correlation energy as the quantum fluid is determined
as a function of the density parameter r_s. Spin-dependent exchange-correlation
energies are reported. Comparisons of the spin-dependent pair-distributions and
other calculated properties with any available 2-D quantum Monte Carlo (QMC)
results show excellent agreement, strongly favouring more recent QMC data. The
interesting novel physics brought to light by this study are: (a) the
independently determined quantum-temperatures for 3-D and 2-D are found to be
approximately the same, (i.e, universal) function of the classical coupling
constant Gamma. (b) the coupling constant Gamma increases rapidly with r_s in
2-D, making it comparatively more coupled than in 3-D; the stronger coupling in
2-D requires bridge corrections to the hyper- netted-chain method which is
adequate in 3-D; (c) the Helmholtz free energy of spin-polarized and
unpolarized phases have been calculated. The existence of a spin-polarized 2-D
liquid near r_s = 30, is found to be a marginal possibility. These results
pertain to clean uniform 2-D electron systems.Comment: This paper replaces the cond-mat/0109228 submision; the new version
include s more accurate numerical evaluation of the Helmholtz energies of the
para- and ferromagentic 2D fluides at finite temperatures. (Paper accepted
for publication in Phys. Rev. Lett.
Auxin-Binding Protein 1 is a negative regulator of the SCF(TIR1/AFB) pathway
International audienceAuxin is a major plant hormone that controls most aspects of plant growth and development. Auxin is perceived by two distinct classes of receptors: transport inhibitor response 1 (TIR1, or auxin-related F-box (AFB)) and auxin/indole-3-acetic acid (AUX/IAA) coreceptors, that control transcriptional responses to auxin, and the auxin-binding protein 1 (ABP1), that controls a wide variety of growth and developmental processes. To date, the mode of action of ABP1 is still poorly understood and its functional interaction with TIR1/AFB-AUX/IAA coreceptors remains elusive. Here we combine genetic and biochemical approaches to gain insight into the integration of these two pathways. We find that ABP1 is genetically upstream of TIR1/AFBs; ABP1 knockdown leads to an enhanced degradation of AUX/IAA repressors, independently of its effects on endocytosis, through the SCF TIR1/AFB E3 ubiquitin ligase pathway. Combining positive and negative regulation of SCF ubiquitin-dependent pathways might be a common mechanism conferring tight control of hormone-mediated responses
Open Clusters IC 4665 and Cr 359 and a Probable Birthplace of the Pulsar PSR B1929+10
Based on the epicyclic approximation, we have simulated the motion of the
young open star clusters IC 4665 and Collinder 359. The separation between the
cluster centers is shown to have been minimal 7 Myr ago, 36 pc. We have
established a close evolutionary connection between IC 4665 and the
Scorpius-Centaurus association -- the separation between the centers of these
structures was pc 15 Myr ago. In addition, the center of IC 4665
at this time was near two well-known regions of coronal gas: the Local Bubble
and the North Polar Spur. The star HIP 86768 is shown to be one of the
candidates for a binary (in the past) with the pulsar PSR B1929+10. At the
model radial velocity of the pulsar km s, a close
encounter of this pair occurs in the vicinity of IC 4665 at a time of -1.1 Myr.
At the same time, using currently available data for the pulsar B1929+10 at its
model radial velocity km s, we show that the hypothesis
of Hoogerwerf et al. (2001) about the breakup of the Oph--B1929+10
binary in the vicinity of Upper Scorpius (US) about 0.9 Myr ago is more
plausible.Comment: 19 pages, 8 figure
Measurement of double beta decay of Âčâ°â°Mo to excited states in the NEMO 3 experiment
The double beta decay of Âčâ°â°Mo to the 0_{1}^{+} and 2_{1}^{+} excited states of Âčâ°â°Ru is studied using the NEMO 3 data. After the analysis of 8024 h of data the half-life for the two-neutrino double beta decay of Âčâ°â°Mo to the excited 0_{1}^{+} state is measured to be T_{1/2}^{2v} = [5.7_{-0.9}^{+1.3} (stat.) ± 0.8 (syst.)] x 10ÂČâ° y. The signal-to-background ratio is equal to 3. Information about energy and angular distributions of emitted electrons is also obtained. No evidence for neutrinoless double beta decay to the excited 0_{1}^{+} state has been found. The corresponding half-life limit is T_{1/2}^{0v} (0âșâ0_{1}^{+}) > 8.9 x 10ÂČÂČ y (at 90% C.L.). The search for the double beta decay to the 2_{1}^{+} excited state has allowed the determination of limits on the half-life for the two neutrino mode T_{1/2}^{0v} (0âșâ2_{1}^{+}) > 1.1 x 10ÂČÂč y (at 90% C.L.) and for the neutrinoless mode T_{1/2}^{0v} (0âșâ2_{1}^{+}) > 1.6 x 10ÂČÂł y (at 90% C.L.)
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