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121.
122.
Rémy Catteaux Isabelle Grattepanche-Lebecq Françoise Désanglois Feng Chai Jean-Christophe Hornez Stuart Hampshire Claudine Follet-Houttemane 《Chemical Engineering Research and Design》2013
Different kinds of bioactive materials are used as bone substitutes. In particular, bioglasses containing Si, Ca, Na and P, bind to host tissues with a stable chemical bond. The phenomenon of bioactivity is associated with the formation of a crystallized hydroxycarbonated apatite (HCA) layer on the bioglass surface, when soaked in a simulated physiological fluid. This layer is similar to the mineral phase of bone. 相似文献
123.
Michel F. Champagne Michel A. Huneault Claudine Roux Wilfried Peyrel 《Polymer Engineering and Science》1999,39(6):976-984
The reactive compatibilization of polypropylene/polyethylene terephthalate (PP/PET) blends by addition of glycidyl methacrylate grafted PP (PP-g-GMA) was studied. Two PP-g-GMA copolymers, containing either 0.2 or 1.2 wt% of GMA, were used as interface modifiers. These were incorporated into PP blends (with either 70 or 90 wt% PET), replacing 1/5 of PP in the system. The use of these modifiers changed the blends' tensile mechanical behavior from fragile to ductile. Blend tensile strength was improved by 10% and elongation at break showed 10 to 20-fold increases while stiffness remained constant. Scanning electron micrographs showed the PP average domain size in injection molded specimens to decrease to the micron/sub-micron size upon addition of the GMA modified resins, while the unmodified blends exhibited heterogeneous morphology comprising large lamellae 10–20 μm wide. The low-GMA graft content PP seemed slightly more efficient than the high GMA content PP in emulsifiying PP/PET blends. The GMA grafting level on PP had very limited effects on the blends' mechanical behavior in the range of GMA graft density provided by the two modified resins investigated. 相似文献
124.
Adelheid Ehmke Martine Rahier Jacques M. Pasteels Claudine Theuring Thomas Hartmann 《Journal of chemical ecology》1999,25(10):2385-2395
Oreina cacaliae and O. speciosissima are leaf beetles that, as larvae and adults, sequester pyrrolizidine alkaloid N-oxides (PAs) as defensive compounds from their host plants Adenostyles alliariae and Senecio nemorensis. As in most Oreina species, O. speciosissima is also defended by autogenously produced cardenolides (mixed defensive strategy), whereas O. cacaliae does not synthesize cardenolides and is exclusively dependent on host-plant-acquired PAs (host-derived defense). Adults of the two Oreina species were found to have the same PA storage capacity. The larvae, however, differ; larvae of O. speciosissima possess a significantly lower capability to store PAs than O. cacaliae. The ability of Oreina larvae to sequester PAs was studied by using tracer techniques with 14C-labeled senecionine N-oxide. Larvae of the two species efficiently take up [14C]senecionine N-oxide from their food plants and store the alkaloid as N-oxide. In O. cacaliae, there is a slow but continuous loss of labeled senecionine N-oxide. This effect may reflect the equilibrium between continuous PA uptake and excretion, resulting in a time-dependent tracer dilution. No noticeable loss of labeled alkaloid is associated with molting. Senecionine N-oxide is detectable in all tissues. The hemolymph is, with ca. 50–60% of total PAs, the major storage compartment, followed by the integument, with ca 30%. The alkaloid concentration in the hemolymph is approximately sixfold higher than in the solid tissues. The selectivity of PA sequestration in larvae is comparable to PA sequestration in the bodies of adult beetles. 相似文献
125.
Semmer Virginie Batamack Patrice Dorémieux-Morin Claudine Fraissard Jacques 《Topics in Catalysis》1998,6(1-4):119-125
1H broad-line NMR at 4 K has been used to study the acid strength of Brønsted solid and liquid acids and superacids in the presence of water as base. From the simulation of the spectra, the number of hydronium ions per acid site is deduced and is used to rank the compounds. 相似文献
126.
Dalton Cormac T. Ryan Kenneth M. Wall Valerie M. Bousquet Claudine Gilheany Declan G. 《Topics in Catalysis》1998,5(1-4):75-91
The history of the development of useful catalyst systems for the asymmetric epoxidation of alkenes is described. An overview is presented of the present state of understanding of the mechanism of the most successful catalysts to date, metal–salen complexes. Recent results from the chromium–salen series are presented and their implications for the mechanism are discussed. This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
127.
Ahmed Bachar Cyrille Mercier Arnaud Tricoteaux Jean‐Christophe Hornez Anne Leriche Claudine Follet Bertrand Revel Mark R. Towler 《Journal of the American Ceramic Society》2015,98(3):748-757
Glasses in the Na2O–CaO–SrO–ZnO–SiO2 system have previously been investigated for suitability as a reagent in Al‐free glass polyalkenoate cements (GPCs). These materials have many properties that offer potential in orthopedics. However, their applicability has been limited, to date, because of their poor strength. This study was undertaken with the aim of increasing the mechanical properties of a series of these Zn‐based GPC glasses by doping with nitrogen to give overall compositions of: 10Na2O–10CaO–20SrO–20ZnO–(40?3x)SiO2–xSi3N4 (x is the no. of moles of Si3N4). The density, glass‐transition temperature, hardness, and elastic modulus of each glass were found to increase fairly linearly with nitrogen content. Indentation fracture resistance also increases with nitrogen content according to a power law relationship. These increases are consistent with the incorporation of N into the glass structure in threefold coordination with silicon resulting in extra cross‐linking of the glass network. This was confirmed using 29Si MAS‐NMR which showed that an increasing number of Q2 units and some Q3 units with extra bridging anions are formed as nitrogen content increases at the expense of Q1 units. A small proportion of Zn ions are found to be in tetrahedral coordination in the base oxide glass and the proportion of these increases with the presence of nitrogen. 相似文献
128.
Khansa Mahjoub Mohammed Merghani Benoit Sagot Evelyne Gehin Guillaume Da Charles Motzkus 《Indoor air》2021,31(1):7-25
In the last two decades, multidisciplinary research teams worked on developing a comprehensive understanding of the transmission mechanisms of airborne diseases. This article reviews the experimental studies on the characterization of the exhaled airflow and the droplets, comparing the measured parameters, the advantages, and the limitations of each technique. To characterize the airflow field, the global flow-field techniques—high-speed photography, schlieren photography, and PIV—are applied to visualize the shape and propagation of the exhaled airflow and its interaction with the ambient air, while the pointwise measurements provide quantitative measurements of the velocity, flow rate, humidity and temperature at a single point in the flow field. For the exhaled droplets, intrusive techniques are used to characterize the size distribution and concentration of the droplets' dry residues while non-intrusive techniques can measure the droplet size and velocity at different locations in the flow field. The evolution of droplets' size and velocity away from the source has not yet been thoroughly experimentally investigated. Besides, there is a lack of information about the temperature and humidity fields composed by the interaction of the exhaled airflow and the ambient air. 相似文献