Prediction of service life of polymeric sealant compositions for fuel tanks in aerospace structures from measurements of viscoelastic properties Annual report

Prediction of service life of polymeric sealers for fuel tanks from viscoelastic measurement

Pain services and prescription of opioid drugs in Ghana

No Abstrac

Ocean Planet or Thick Atmosphere: On the Mass-Radius Relationship for Solid Exoplanets with Massive Atmospheres

The bulk composition of an exoplanet is commonly inferred from its average density. For small planets, however, the average density is not unique within the range of compositions. Variations of a number of important planetary parameters--which are difficult or impossible to constrain from measurements alone--produce planets with the same average densities but widely varying bulk compositions. We find that adding a gas envelope equivalent to 0.1%-10% of the mass of a solid planet causes the radius to increase 5-60% above its gas-free value. A planet with a given mass and radius might have substantial water ice content (a so-called ocean planet) or alternatively a large rocky-iron core and some H and/or He. For example, a wide variety of compositions can explain the observed radius of GJ 436b, although all models require some H/He. We conclude that the identification of water worlds based on the mass-radius relationship alone is impossible unless a significant gas layer can be ruled out by other means.Comment: 5 pages, 3 figures, accepted to Ap

Mass accretion rates of clusters of galaxies: CIRS and HeCS

We use a new spherical accretion recipe tested on N-body simulations to measure the observed mass accretion rate (MAR) of 129 clusters in the Cluster Infall Regions in the Sloan Digital Sky Survey (CIRS) and in the Hectospec Cluster Survey (HeCS). The observed clusters cover the redshift range of $0.01<z<0.30$ and the mass range of $\sim 10^{14}-10^{15} {h^{-1}~\rm{M_\odot}}$. Based on three-dimensional mass profiles of simulated clusters reaching beyond the virial radius, our recipe returns MARs that agree with MARs based on merger trees. We adopt this recipe to estimate the MAR of real clusters based on measurements of the mass profile out to $\sim 3R_{200}$. We use the caustic method to measure the mass profiles to these large radii. We demonstrate the validity of our estimates by applying the same approach to a set of mock redshift surveys of a sample of 2000 simulated clusters with a median mass of $M_{200}= 10^{14} {h^{-1}~\rm{M_{\odot}}}$ as well as a sample of 50 simulated clusters with a median mass of $M_{200}= 10^{15} {h^{-1}~\rm{M_{\odot}}}$: the median MARs based on the caustic mass profiles of the simulated clusters are unbiased and agree within $19\%$ with the median MARs based on the real mass profile of the clusters. The MAR of the CIRS and HeCS clusters increases with the mass and the redshift of the accreting cluster, which is in excellent agreement with the growth of clusters in the $\Lambda$CDM model.Comment: 25 pages, 19 figures, 7 table

Spin Transfer Torques in MnSi at Ultra-low Current Densities

Spin manipulation using electric currents is one of the most promising directions in the field of spintronics. We used neutron scattering to observe the influence of an electric current on the magnetic structure in a bulk material. In the skyrmion lattice of MnSi, where the spins form a lattice of magnetic vortices similar to the vortex lattice in type II superconductors, we observe the rotation of the diffraction pattern in response to currents which are over five orders of magnitude smaller than those typically applied in experimental studies on current-driven magnetization dynamics in nanostructures. We attribute our observations to an extremely efficient coupling of inhomogeneous spin currents to topologically stable knots in spin structures

Un cas d’hematome extradural cervical non traumatique

L’hématome extradural cervical spontané est une pathologie rare mais une sévère cause de compression médullaire. Il requiert un diagnostic et une prise en charge urgents. Nous en rapportons un cas chez une patiente de 20 ans sans antécédent pathologique, révélé par un syndrome de compression médullaire cervical sévère (grade A de Frankel). Une décompression neurochirurgicale est intervenue avec un délai de48H avec comme corollaire de lourdes séquelles. Les auteurs insistent sur l’intérêt d’un diagnostic et d’une prise en charge précoces pour en minimiser les séquelles neurologiques

Extinction time for some nonlinear heat equations

This paper concerns the study of the extinction time of the solution of the following initial-boundary value problem [left{% begin{array}{ll} hbox{$u_t=varepsilon Lu(x,t)-f(u)quad mbox{in}quad Omegatimesmathbb{R}_{+}$,} \ hbox{$u(x,t)=0quad mbox{on}quadpartialOmegatimesmathbb{R}_{+}$,} \ hbox{$u(x,0)=u_{0}(x)>0quad mbox{in}quad Omega$,} \ end{array}%right. ] where $Omega$ is a bounded domain in $mathbb{R}^{N}$ with smooth boundary $partialOmega$, $varepsilon$ is a positive parameter, $f(s)$ is a positive, increasing, concave function for positive values of s, $f(0)=0$, $int_{0}frac{ds}{f(s)}<+infty$, $L$ is an elliptic operator. We show that the solution of the above problem extincts in a finite time and its extinction time goes to that of the solution $alpha(t)$ of the following differential equation [alpha^{\u27}(t)=-f(alpha(t)),quad t>0,quad alpha(0)=M,] as $varepsilon$ goes to zero, where $M=sup_{xin Omega}u_{0}(x)$. We also extend the above result to other classes of nonlinear parabolic equations. Finally, we give some numerical results to illustrate our analysis

Analysis of caesarean rate and indications of university hospitals in sub-Saharan African developing countries using Robson classification system: the case of Cocody’s hospital center, Abidjan-Cote d’Ivoire

Background: According to the World Health Organization (WHO), it has become imperative to monitor caesarean rates in hospitals since these rates continue to increase; WHO recommends this monitoring by the Robson’s system. The study objective was  to describe caesarean rates in a level 3 maternity of developing country using this system, to identify the groups likely increase overall rate of caesarean.Methods: A retrospective and comparative study made in Cocody University Hospital Center (Abidjan-Cote d’Ivoire) over a period of twelve years.  A total of 21,067 women who delivered during this period by caesarean were included.Results: The overall rate of caesarean during the study period was 38.7% with a significant increase from Period I to Period II (34.8 vs. 41.7%; p ˂0.000). The subgroup 2 (nulliparas, single cephalic term pregnancy, caesarean before labor) made the greatest contribution to the overall CS rate with an increase of +5% (10.1 vs. 15.1%; p˂0,000). Women with previous CS (groups 5, 7, 8, 9, 10) increased the caesarean rate of +3.4% (7 vs. 10.4%; p˂0.000). The group 6 increased it of +2.9% (4.7 vs 7.6%; p˂0.000). Caesarean indications were dominated by fetal acute distress (24.5 vs. 22.6%; p˂0,000), then followed by fetal-pelvic disproportion (21.8 vs. 10.7%), severe preeclampsia/eclampsia (13.5 vs. 17.5%; p˂0.000), scarred uterus and breech presentation.Conclusions: Robson classification has identified the groups led to a significant increase in caesarean rates in our service and therefore has good focus our preventive actions.