Highly organized crystalline monolayer of a semi-fluorinated alkane on a solid substrate obtained by spin-coating

We have obtained a 40 nm parameter crystalline monolayer of a semifluorinated alkane on a silicon wafer using the spin-coating technique. Its structure, analyzed by atomic force microscopy (AFM), is identical to that recently observed at the air-water interface, showing the existence of hexagonal nanodomains, organized on a long range order hexagonal lattice of a few tens of nanometers lateral parameter. Considering AFM images published on films transferred by the usual Langmuir-Blodgett method, one can note that the monolayers form locally ordered rounded domains. With our procedure, the original highly organized large crystalline structure is recovered.     

Relationship between bioceramics sintering and micro-particles-induced cellular damages

We performed experimental studies to confirm the hypothesis that cellular damages occurring around implanted biphasic bioceramics could be related to a micro-particles release because of an insufficient sintering. First, an in vitro cytotoxicity study was performed on four biphasic ceramic (BCP) samples. Without treatment of the extraction medium, a cytotoxicity was observed, although after centrifugation this cytotoxicity disappeared in all samples. Second, micro-particles of hydroxyapatite (HA), beta-tricalcium phosphate (beta-TCP) and 40% beta-TCP/60%HA mixture were used for a cell inhibition study. A decrease of cell viability was observed with the increase in particles concentration. At 10000 particles per cell, the viability and proliferation were completely inhibited. Third, HA, beta-TCP and BCP ceramic granules were implanted in rabbit femoral cavities for 12 weeks. No degradation of HA granules was observed. The degradation was higher for beta-TCP (40%) than for BCP (5%). On the other hand, new bone formation was significantly higher for beta-TCP (21%) and HA (18%) than for BCP (12%). More micro-particles were formed around BCP granules than around beta-TCP, and phagocytised by macrophages. The release of ceramic micro-particles could be related to the sintering process. BCP ceramic have to be sintered at only 1160 degrees C. Consequently, HA micro-particles of BCP ceramic are incompletely sintered and easily released after immersion or implantation. The microparticles could be at the origin of local inflammation and cell damage and could perhaps modify osteogenesis. Attention must be paid to this problem especially with BCP ceramics because of the sintering difficulties of this bioceramic.     

Fonction du geste interactif et du regard dans la régulation de la résponse d'écoute chez des conjoints conjugalement satisfaits et insatisfaits.

Notes that previous research has shown that spouse's responsive listening contribute to the perception of support by the partner. Videotaped conjugal support interactions of 10 maritally satisfied couples and 10 maritally dissatisfied couples were used to examine the communication regulation of spouses discussing a personal problem. Two regulators of responsive listening were studied: gaze and interactive gestures. The study objectives were (1) to compare the efficacy of gaze and interactive gestures in the regulation of responsive listening, and (2) to verify whether maritally satisfied spouses, compared with dissatisfied spouses, produced more responsive listening contingent to the regulators. The results show that the concurrent occurrences of gaze and interactive gestures were the most effective regulators of responsive listening, particularly for satisfied spouses. The results of this study underline the importance of studying responsive listening to understand the contribution of social support to marital satisfaction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Critical evaluation and optimization of the thermodynamic properties of liquid tin solutions

Thermodynamic and phase equilibrium data for the following 18 elements in molten Sn were collected and critically evaluated: Al, Ca, Ce, Co, Cr, Cu, Fe, H, Mg, Mo, Na, Ni, O, P, S, Se, Si, and Ti. Binary and ternary data were optimized to give polynomial expressions for the excess Gibbs energies as functions of temperature and composition. For some solutes, the optimized expressions are valid over the entire composition range 0 ≤ X_Sn ≤ 1. In other cases, the expressions apply to Snrich solutions. Solute-solute interaction terms were estimated where data were not available. The optimized Gibbs energy expressions are also presented in the form of interaction parameters, and the equivalence between the polynomial and interaction parameter formalisms is discussed. Through the Kohler equation, or the modified interaction parameter formalism, the thermodynamic properties of the multicomponent solution of 18 elements in Sn can be calculated. The database is suitable for computer storage and manipulation.     

Gel Point Investigation of a Chitosan System Using Fourier Transform Rheometry and Multi‐Frequency Excitation

In this study, the sol‐gel transition temperature of a thermosensitive chitosan system was measured using SAOS, in‐real time FTR and multi‐frequency SAOS excitation. From FT analysis, we found that the intensity of the harmonics stayed constant while the chitosan system remained in the solution state, while it increased passed the gelation point. Multi‐frequency SAOS excitation was also carried out using a summation function of sine waves that allowed performing the measurements in the LVR. This last technique could determine the unique (frequency independent) critical sol‐gel transition temperature, and was found to be less tedious than the application of the traditional Chambon and Winter's method.

     

Morphology and antibacterial properties of plasticized chitosan/metallocene polyethylene blends

In this work, plasticized chitosan-based materials were produced through a molten process. A thermo-mechanical treatment was used to achieve chitosan plasticization in the presence of water, acetic acid, and glycerol. Water and glycerol acted as plasticizers, while acetic acid was used as a solvent and plasticizer for chitosan. The influence of acetic acid total content, chitosan/acetic acid solution ratio, and chitosan/glycerol ratio were examined in this study. The various plasticized compounds were blended with a metallocene polyethylene (mPE) and the morphology, rheological, and antibacterial properties of this novel blend system were examined. It was found that an increase in acetic acid content allowed better chitosan dissolution, while a higher glycerol concentration resulted in improved dispersion of the plasticized chitosan phase in the mPE. Following thermo-mechanical treatment, blends presented good antibacterial properties with a reduction of the number of bacteria (non-pathogenic Escherichia coli) by 2 log(CFU/mL) for the chitosan-containing systems with respect to neat mPE. Mechanical properties of the mPE/plasticized chitosan blends were improved by compatibilization with ethylene vinyl acetate, while antibacterial properties were not affected.     

Effects of molecular weight,stereo configuration of PLA,and processing on the dispersion of multiwalled carbon nanotubes and properties of corresponding nanocomposites

Multiwalled carbon nanotubes (MWCNTs) were dispersed and distributed via a co-rotating twin-screw extruder (TSE) in high (h)- and low (l)-molecular-weight amorphous and semicrystalline polylactides (PLAs) (aPLA and scPLA, respectively). Effects of PLA molecular weight and D-lactic acid equivalents content (D-content), as well as processing parameters, were examined on the MWCNT dispersion quality in PLA. The effectiveness of the MWCNT dispersion in various PLA matrices was investigated using scanning electron microscopy (SEM) and small-amplitude oscillatory and transient shear flow rheometry in the molten state. The results showed a better dispersion of MWCNTs in the low-molecular-weight PLA grades (aPLAl and scPLAl). In addition, better MWCNT dispersion was observed in aPLA grades when processed at a higher temperature of 190°C than at 150°C. At 150°C, while MWCNT bundles in aPLAl could be broken down, a good dispersion could not be achieved in aPLAh due to the lower molecular mobility at such a temperature. The electrical conductivity of the samples was also shown to increase as the MWCNT dispersion was improved. The existence of crystallites in scPLA-based nanocomposites, however, disrupted the connectivity of the MWCNTs and decreased the final electrical conductivity. The lower molecular weight aPLAl prepared at 190°C showed the highest electrical conductivity (~10⁻⁵ S/m) at a low loading of 0.5 wt.% MWCNTs.