Alkylation of Phenols and Naphthols on Silica-Immobilized Triflate Derivatives

Immobilized triflate derivatives (La(OTf)₃, AgOTf, tert-butyldimethylsilyltrifluoro-methanesulfonate), and triflic acid were found to be effective in the alkylation of phenol and naphthols with tert-butanol. The acidic strength and type of acidity (Lewis or Brønsted) are key factors controlling the conversion and product distribution.     

The influence of POSS substituent on synthesis and properties of hybrid materials based on urethane dimethacrylate (UDMA) and various polyhedral oligomeric silsesquioxane (POSS)

DSC was used to follow the degree of conversion (DC) for the methacrylic groups in the case of some hybrid systems based on urethane dimethacrylate (UDMA) monomer and various polyhedral oligomeric silsesquioxane (POSS) structures (HISO‐POSS, CPENTYL‐POSS, and MA‐POSS). The chemical structure of the POSS compound directly influences the DC value. The conversion of the methacrylic groups from the hybrid composites after thermal curing was determined by measuring the residual heat of reaction. Both SEM and AFM techniques were additionally used to performed an advanced morphological characterization for the obtained POSS‐nanocomposites. The DSC data have been corroborated with those resulted from the NIR spectroscopy. The introduction of POSS compound within the UDMA matrix leads to a decrease of the hybrid material transparency due to the formation of agglomerates also pointed out by SEM analysis. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and in vitro,bulk, and surface investigation of chitosan/graphene oxide composite films

Chitosan/graphene oxide (GO) composite films were prepared by solution blending method. Intensive characterization of films, surface, and bulk, was performed by Fourier transmission infrared spectrometry, X‐ray diffraction, scanning and transmission electron microscopy, thermal gravimetric analysis, and mechanical test. The biocompatibility of chitosan/GO films was tested in vitro on the murine osteoblastic cell line MC3T3‐E1. By incorporating 6 wt% GO into chitosan, Young's modulus and tensile strength values exceed those of nacre by about 60 and 20%, respectively. Biocompatibility assays indicated a high cell proliferation rate for the composite films with high GO content. POLYM. COMPOS., 34:2116–2124, 2013. © 2013 Society of Plastics Engineers     

Study of the conversion of aromatic hydrocarbons on EMT-type zeolite: Influence of the partial substitution of Al by Ga

(Al,Ga)EMT-type zeolites (Al:Ga = 1:0, 0.75:0.25 and 0.5:0.5) were prepared and tested as catalysts in the gas-phase toluene–methanol alkylation and toluene–trimethylbenzene transalkylation. Various techniques including XRD, N₂ sorption, MAS NMR and SEM were used to monitor the physico-chemical properties of these solids. The results revealed a high purity and crystallinity of the materials, and that the Ga atoms are entirely incorporated into the framework. The ammonia TPD measurements indicated that the isomorphous substitution of aluminium by gallium leads to a decrease of both acidic strength and acid sites concentration. The catalytic performances of the EMT-type solids in the conversion of methylaromatic hydrocarbons were correlated with their acid properties. Thus, the less acidic (Al,Ga)EMT samples exhibited a lower activity, but a higher selectivity towards the xylenes formation by comparison with (Al)EMT.     

Modification of titanium surface with collagen and doxycycline as a new approach in dental implants

In this work, we investigate for the first time several issues involved in bio-adhesion process for a new type of chemically modified titanium surfaces (in their initial form and after collagen deposition), in order to assess their potential in dental implant surface modification. For this purpose, we studied the following: collagen adhesion, cytotoxicity, osteoblast cytomorphology, cell adhesion and proliferation, doxycycline embedding and modifications in the collagen film deposed on the metal surfaces, drug release from the collagen films. The improvement of adhesion between collagen film and titanium substrate, when hydroxyl and amino functional groups are assisting the surfaces was presented, all materials showing no cytotoxic effects as revealed by lactate dehydrogenase-based assay. The drug release from titanium–coll–doxy systems offers a dual mechanism of the delivery profile (burst release followed by moderate discharge of the antibiotic), with perspectives in soft tissue recovery postoperative stage.     

Surface modifications of the titanium mesh for cranioplasty using selenium nanoparticles coating

The aim of this study was to made and characterized a nanostructured surface on titanium mesh for cranioplasty, by adhesion of selenium nanoparticles (SeNPs) in situ, in a hydrothermal reaction. The structural characterization of selenium nanoparticles was performed using DLS and TEM, revealing that the size and morphology of nanoparticles depends on the nature of saccharide reducing agent. In situ hydrothermal reaction revealed that selenium nanoparticles adherence on titanium mesh surface had the best result in the case of starch-derived SeNPs, as demonstrated by SEM/EDX analysis. In vitro hemolysis and RBC osmotic fragility tests suggest that nanostructured surface created upon SeNPs adhesion doesn’t induce damage to RBC membrane; the hemolysis values indicated a good biocompatibility especially in the case of titanium specimens modified with starch-derived SeNPs. Moreover, the nanostructured surface clearly offers the desired biological response of human fibroblasts cells. The proposed improvement of the surfaces in the case of titanium mesh for cranioplasty may offer important benefits in terms of osteointegration, without using additional screws for fixation and closure procedure.     

Decreased Interactions between Calmodulin and a Mutant Huntingtin Model Might Reduce the Cytotoxic Level of Intracellular Ca2+: A Molecular Dynamics Study

Mutant huntingtin (m-HTT) proteins and calmodulin (CaM) co-localize in the cerebral cortex with significant effects on the intracellular calcium levels by altering the specific calcium-mediated signals. Furthermore, the mutant huntingtin proteins show great affinity for CaM that can lead to a further stabilization of the mutant huntingtin aggregates. In this context, the present study focuses on describing the interactions between CaM and two huntingtin mutants from a biophysical point of view, by using classical Molecular Dynamics techniques. The huntingtin models consist of a wild-type structure, one mutant with 45 glutamine residues and the second mutant with nine additional key-point mutations from glutamine residues into proline residues (9P(EM) model). Our docking scores and binding free energy calculations show higher binding affinities of all HTT models for the C-lobe end of the CaM protein. In terms of dynamic evolution, the 9P(EM) model triggered great structural changes into the CaM protein’s structure and shows the highest fluctuation rates due to its structural transitions at the helical level from α-helices to turns and random coils. Moreover, our proposed 9P(EM) model suggests much lower interaction energies when compared to the 45Qs-HTT mutant model, this finding being in good agreement with the 9P(EM)’s antagonistic effect hypothesis on highly toxic protein–protein interactions.     

Combining Airborne Photographs and Spaceborne SAR Data to Monitor Temperate Glaciers: Potentials and Limits

Monitoring temperate glacier activity has become more and more necessary for economical and security reasons and as an indicator of the local effects of global climate change. Remote sensing data provide useful information on such complex geophysical objects, but they require specific processing techniques to cope with the difficult context of moving and changing features in high-relief areas. This paper presents the first results of a project involving four laboratories developing and combining specific methods to extract information from optical and synthetic aperture radar (SAR) data. Two different information sources are processed, namely: 1) airborne photography and 2) spaceborne C-band SAR interferometry. The difficulties and limitations of their processing in the context of Alpine glaciers are discussed and illustrated on two glaciers located in the Mont-Blanc area. The results obtained by aerial triangulation techniques provide digital terrain models with an accuracy that is better than 30 cm, which is compatible with the computation of volume balance and useful for precise georeferencing and slope measurement updating. The results obtained by SAR differential interferometry using European Remote Sensing Satellite images show that it is possible to measure temperate glacier surface velocity fields from October to April in one-day interferograms with approximately 20-m ground sampling. This allows to derive ice surface strain rate fields required to model the glacier flow. These different measurements are complementary to results obtained during the summer from satellite optical data and ground measurements that are available only in few accessible points