Oxidative photopolymerization of thiol-terminated polysulfide resins. Application in antibacterial coatings

A UV photoinduced cross-linking of non-modified commercial poly(disulfide) resins (Thioplast) is reported via the air oxidative photocoupling of terminal thiol functions. Catalyzed by a photogenerated guanidine base (TBD), this step-growth photopolymerization is useful to maximize disulfide functions content. The mechanism proceeds through thiol deprotonation into thiolate anions, further oxidized into thiyl radicals, eventually dimerizing into disulfide cross-links. Starting with a detailed structural characterization of the thiol-terminated resin, photooxidative kinetics are studied under exposure to a polychromatic medium-pressure Hg arc using Raman and infrared spectroscopy. The effects of irradiance, film thickness, photobase concentration, resin molar mass, and content of an additional polythiol monomer (reactive diluent) have been investigated. In an effort of upscaling, irradiation under a 365 nm LED panel has enabled the fast preparation of 1.5 μm thick cross-linked poly(disulfide) coatings in a matter of minutes. Capitalizing on the ability of residual thiol groups to react with silver cations, a post-functionalization has been successfully performed, leading to films exhibiting at their surface stable thiolate-silver bonds as proved by X-ray photoelectron spectroscopy. Despite the well-established biocide action of silver ions, no antibacterial action has been evidenced by confocal fluorescence microscopy because of insufficient release

Reduced Atherosclerotic Lesion Size in P-Selectin Deficient Apolipoprotein E-Knockout Mice Fed a Chow but Not a Fat Diet

Endothelial cells lining atherosclerotic, but not healthy sites, on human arteries express P-selectin. We investigated the role of P-selectin on the development of vascular lesions in an ApoE(−/−) male mice. Double-knockout (ApoE(−/−), P-selectin(−/−); DKO) were compared to single-knockout (ApoE(−/−); SKO) mice. They were fed a chow or fat diet for 3, 6, 15, and 20 weeks, without any differences in cholesterol levels. DKO mice fed a chow diet exhibited a ratio of lesion area over media lower than SKO mice, for 3 (P < .03), 6 (P < .001), and 15 (P < .02) weeks. DKO mice fed a fat diet showed a lower ratio only at 3 weeks. P-selectin deficiency in ApoE(−/−) mice has a protective effect in atherosclerotic lesions development. Reduction of lesion size depends on diet type and duration. A fat diet could neutralize the beneficial effects of P-selectin deficiency, inducing atherosclerotic lesions via probably other adhesion molecules

New Insights into the Molecular Structures, Compositions, and Cation Distributions in Synthetic and Natural Montmorillonite Clays

International audienceWe present a detailed investigation of the molecular structure of montmorillonite, an aluminosilicate clay with important applications in materials sciences, such as for catalysis, drug delivery, or as a waste barrier. Solid-state 29Si, 27Al, 25Mg, and 1H nuclear magnetic resonance (NMR) measurements combined with density functional theory (DFT) calculations provide a comprehensive picture of the local structure and composition of a synthetic clay and its naturally-occurring analogue. A revised composition is proposed based on NMR results that allow the identification and quantification of the signatures of otherwise undetectable non-crystalline impurities, thus largely complementing the traditional elemental analyses. Solid-state 1H NMR at fast magic-angle spinning (MAS) and high magnetic field provide quantitative information on intra- and inter-layer local environments that are crucial for the determination of the amount of Mg/Al substitution within the octahedral layer. In combination with DFT calculations of energies, it suggests that pairs of adjacent Mg atoms are unfavorable, leading to a non-random cationic distribution within the layers

Contrasting crystal packing arrangements in triiodide salts of radical cations of chiral bis(pyrrolo[3,4-d])tetrathiafulvalenes

Crystal structures of six 1 : 1 triiodide salts of a series of enantiopure bis(pyrrolo[3,4-d])TTF derivatives, the first structures of radical cation salts reported for this bis(pyrrolo) donor system, show three different arrangements of triiodide ions, organised either in head-to-tail pairs, in infinite lines, or in a castellated arrangement. The complex crystal structures, obtained by electrocrystallisation, are influenced by the presence of solvent, for example changing an ABCABC packing arrangement to ABAB with inclusion of THF, as well as by the size of the chiral side chain

Acute complications of preeclampsia: prognosis and management at Pikine National Hospital in Dakar (Senegal)

ABSTRACTBackground: The objective of this study was to evaluate the prevalence of acute complications of preeclampsia in order to describe the epidemiological profile of the disease, to assess its prognosis and management.Methods: This was a retrospective study of patients admitted to the Pikine National Hospital from 1 January 2010 to 31 December 2013 (48 months) with severe complicated pre-eclampsia. Included in this study were patients admitted or diagnosed with severe complicated pre-eclampsia and having given birth in the structure or not.Results: The incidence of severe preeclampsia in childbirth varied from 9.7% to 11.5% during the four years of our study. Patients were largely paucigest (55.7% of cases) and paucipares (58.5% of cases). The mean age was 28.14 years with extremes of 14 and 47 years. More than half of the patients (57.7%) were between 21 and 34 years of age. They were mostly married (90.7%). Three-quarters of the patients (76.8%) had proteinuria with ≥ 3 cross-bands. Thrombocytopenia was found in 9.7% of patients, hepatic cytolysis in 12.1%, and elevation of serum creatinine in 13.8%. The level of transaminases was found to be greater than 2 in the normal range in 12.1%. Complicated forms were the most represented in our study. These were acute complications, with 715 cases, or 57.3% of the patients. They were either isolated (52.8%) or associated (4.5%). These included eclampsia (24.9%), followed by retroplacental hematoma (24.6%), fetal death in utero (23.7%), HELLP syndrome (3.4%). , Acute edema of the lungs (1.5%), and acute renal failure (1.4%). The lethality was 2.4%. The causes of maternal death were dominated by eclampsia (14 cases), DIC (3 cases) and OAP (2 cases). We counted 77.7% of live births and a stillbirth of 254.5 ‰.Conclusions: Pre-eclampsia is a serious complication of pregnancy. Its frequency is still high in sub-Saharan Africa. In the presence of signs of severity, maternal (vital and functional) and neonatal prognosis are inevitably involved. If management is based on fetal extraction, resuscitation measures are a guarantee of maternal survival

Low-lying states and structure of the exotic 8^8He via direct reactions on the proton

International audienceThe structure of the light exotic nucleus 8He was investigated using direct reactions of the 8He SPIRAL beam on a proton-rich target. The (p,p') scattering to the Click to view the MathML source state, the (p,d)7He and (p,t)6He transfer reactions, were measured at the energy Elab=15.7 A.MeV. The light charged particles (p,d,t) were detected in the MUST Si-strip telescope array. The excitation spectrum of 8He was extracted from the (p,p') reaction. Above the known Click to view the MathML source excited state at 3.6 MeV, a second resonance was found around 5.4 MeV. The cross sections were analyzed within the coupled-reaction channels framework, using microscopic potentials. It is inferred that the 8He ground state has a more complex neutron-skin structure than suggested by previous α+4n models assuming a pure (1p3/2)4 configuration

Experimental evidence for subshell closure in 8^{8}He and indication of a resonant state in 7^{7}He below 1 MeV

NESTERThe spectroscopy of the unstable $^{8}$He and unbound $^{7}$He nuclei is investigated via the p($^{8}$He, d) transfer reaction with a 15.7A MeV $^{8}$He beam from the SPIRAL facility. The emitted deuterons were detected by the telescope array MUST. The results are analyzed within the coupled-channels Born approximation framework, and a spectroscopic factor $C^2$S=4.4±1.3 for neutron pickup to the $^{7}$He_g.s.$is deduced. This value is consistent with a full p3/2 subshell for$^{8}$He. Tentative evidence for the first excited state of$^{7}$He is found at$E^*$=0.9±0.5 MeV (width$\Gamma$=1.0±0.9 MeV). The second one is observed at a position compatible with previous measurements,$E^*$=2.9±0.1 MeV. Both are in agreement with previous separate measurements. The reproduction of the first excited state below 1 MeV would be a challenge for the most sophisticated nuclear theories

Structure of exotic nuclei from direct reactions

Expérience GANILInternational audienc

Chapitre 8. Dynamique de stockage du carbone dans les sols du Sénégal

Introduction Au Sénégal, la dynamique de stockage du carbone dans les sols est souvent estimée par des approches de modélisation (Tschakert et al., 2004 ; Parton et al., 2004 ; Woomer et al., 2004 ; Lufafa et al., 2008 ; Stoorvogel et al., 2009 ; Dièye et al., 2012 ; Touré et al., 2013 ; Loum et al., 2014). Quelques études expérimentales ont également été réalisées (Elberling et al., 2003 ; Manlay et al., 2002 ; Masse et al., 2004). La teneur des sols en carbone est généralement faible, de mo..