Chemical Durability of Lanthanum-Enriched Borosilicate Glass

The role of lanthanum in the alteration kinetics at different degrees of reaction progress was investigated at 90°C and pH 7 by complementary chemical (SIMS), morphological (SAXS), and structural (NMR, Raman, and EXAFS spectroscopy) approaches. In the first step of alteration, the forward dissolution rate diminishes with the addition of lanthanum, resembling to the behavior previously observed for zirconium. Over longer alteration time, the glasses with the highest lanthanum concentrations reach silicon saturation more slowly, but unlike zirconium, do not result in larger quantities of altered glass. Lanthanum is entirely retained in the alteration layer and is uniformly distributed; it undergoes hydrolysis and recondensation mechanisms, and its coordination number increases from 6 to 9 during leaching. Reconstruction of the alteration layer occurred more slowly at higher REE concentrations, with a slowdown in repolymerization of the silicate network and structuring of its porosity.     

Depth-minimized, large period half-wave corrugation for linear to radial and azimuthal polarization transformation by grating-mode phase management

The transformation of the polarization distribution of a laser beam from linear to radial and azimuthal by means of a subwavelength binary corrugation etched in a high-index substrate faces fabrication difficulties and an inherent contradiction preventing the achievement of both conditions of 100% transmission and of π phase difference between polarization components. The contradiction is solved by resorting to an easily fabricable high-index corrugation on a low-index substrate where a larger period gives rise to grating-mode reflection/transmission phases that permit the fulfillment of both conditions with a depth-minimized corrugation. From the principle of the solution, a targeted numerical search gives the complete set of the corresponding shallow structures, achieving polarization rotation in a fitting analytical form versus normalized variables.     

Viscoelastic properties,morphology, and thermal stability of rigid and plasticized poly(vinyl chloride)/poly(methyl methacrylate) blends

Viscoelastic properties, morphology, and thermal stability of rigid and plasticized poly(vinyl chloride)/poly (methyl methacrylate) (PVC/PMMA) blends were studied. For that purpose, blends of variable composition from 0 to 100 wt% were prepared in the presence (15, 30, and 50 wt%) and in the absence of di(2‐ethylhexyl) phthalate as plasticizer. Their miscibility was investigated by using dynamic mechanical thermal analysis (DMTA) and scanning electron microscopy (SEM). The DMTA and SEM results showed that the two polymers are miscible. Thermogravimetric studies on these blends were carried out in a flowing atmosphere of air from ambient temperature to 550°C. The results showed that the thermal degradation of rigid and plasticized PVC/PMMA in this broad range of temperature is a three‐step process and that PMMA exerted a stabilizing effect on the thermal degradation of PVC during the first step by reducing the rate of dehydrochlorination. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers     

Memory properties and charge effect study in Si nanocrystals by scanning capacitance microscopy and spectroscopy

In this letter, isolated Si nanocrystal has been formed by dewetting process with a thin silicon dioxide layer on top. Scanning capacitance microscopy and spectroscopy were used to study the memory properties and charge effect in the Si nanocrystal in ambient temperature. The retention time of trapped charges injected by different direct current (DC) bias were evaluated and compared. By ramp process, strong hysteresis window was observed. The DC spectra curve shift direction and distance was observed differently for quantitative measurements. Holes or electrons can be separately injected into these Si-ncs and the capacitance changes caused by these trapped charges can be easily detected by scanning capacitance microscopy/spectroscopy at the nanometer scale. This study is very useful for nanocrystal charge trap memory application.     

A new concept of gentamicin loaded HAP/TCP bone substitute for prophylactic action: in vivo pharmacokinetic study

Despite systemic prophylaxis, infection rates after orthopedic surgery can reach more than 1%. A new HAP/TCP bone substitute loaded with 125 mg of gentamicin was designed for prophylactic use. Its aim was to enhance the efficacy of systemic prophylactic treatments by increasing the local antibiotic concentration. The release rate of gentamicin from the bone substitute was investigated after implantation in the femoral condyle of five sheep. In order to investigate the local and systemic gentamicin concentrations, synovial fluids and blood samples were assessed over a 5-day period. The mean gentamicin concentration peak in blood was 4.2 μg/ml and the mean local concentration in synovial fluids during the first 8 h was 305 μg/ml. After 48 h, the concentrations in blood and synovial fluids were less than 0.5 μg/ml. No remaining gentamicin was detected in bone substitutes explanted after 8 days of implantation. The gentamicin release rate from the bone substitutes assessed corresponds to the recommendations for the prophylactic use of antibiotics: high local concentration but limited in time (less than 48 h) not to select antibiotic-resistant bacterial strains. Our results indicated that this implant should be an effective prophylactic tool in orthopedic surgery in combination with systemic prophylaxis.     

Direct estimation of generalized stress intensity factors using a three‐scale concurrent multigrid X‐FEM

A concurrent multigrid method is devised for the direct estimation of stress intensity factors and higher‐order coefficients of the elastic crack tip asymptotic field. The proposed method bridges three characteristic length scales that can be present in fracture mechanics: the structure, the crack and the singularity at the crack tip. For each of them, a relevant model is proposed. First, a truncated analytical reduced‐order model based on Williams' expansion is used to describe the singularity at the tip. Then, it is coupled with a standard extended finite element (FE) method model which is known to be suitable for the scale of the crack. A multigrid solver finally bridges the scale of the crack to that of the structure for which a standard FE model is often accurate enough. Dedicated coupling algorithms are presented and the effects of their parameters are discussed. The efficiency and accuracy of this new approach are exemplified using three benchmarks. Copyright © 2010 John Wiley & Sons, Ltd.     

Mapping scientific institutions

We have developed a set of routines that allows to draw easily different maps of the research carried out in a scientific institution. Our toolkit uses OpenSource elements to analyze bibliometric data gathered from the Web Of Science. We take the example of our institution, ENS de Lyon, to show how different maps, using co-occurrence (of authors, keywords, institutions…) and bibliographic coupling can be built. These maps may become a valuable tool for discussing institutions’ policies, as they offer different views on the institution at a global scale.     

Synthesis and characterization of hybrid films from hyperbranched polyester using a sol–gel process

Hybrid organic/inorganic materials were prepared by an in situ sol–gel process using tetraethoxysilane (TEOS) in the presence of hyperbranched polyester. The influences of hyperbranched polyester molar mass as well as the amount of TEOS were examined. The condensation degree was characterized by solid state ²⁹Si NMR. The combination of solubility tests, calcination tests, SAXS and dynamic mechanical analysis allowed us to investigate the hybrid material nanostructure. The results show high compatibility between the inorganic silica phase and the organic polymer phase, due to the spherical shape of the hyperbranched polymer and its numerous hydroxyl groups. As a consequence, a continuous inorganic phase was formed even with a low silica precursor content without any macroscopic phase separation. These hybrid materials have a high T_g and high storage modulus even at an elevated temperature combined with improved thermal stability. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39830.