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101.
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
102.
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
103.
The performance of thermoplastic composites is known to depend on the intrinsic properties of the two composite components, the quality of the fiber–matrix interface, and the crystalline properties of their matrix. The objective of this work is to characterize the effect of the addition of modified polypropylene (PP) and silane coupling agent on the mechanical and interfacial properties of short fiber reinforced PP composites. Differential scanning calorimetry (DSC), single fiber composite fragmentation tests (SFC), and mechanical testing are used to understand the different parameters regulating the interfacial properties of composites. No influence of the modified PP on the level of crystallinity is observed. Some differences in the size of the spherulites are observed for acrylic acid grafted PP (PP‐g‐AA). Those samples also show lower mechanical properties in spite of good interfacial interactions. Maleic anhydride grafted PP (PP‐g‐MAh) leads to better mechanical performances than PP‐g‐AA. A high MAh content PP‐g‐MAh grade with low viscosity is the best polymeric additive used in the present work. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2047–2060, 2000 相似文献
104.
Andrea Olmos-Ortiz Mayra Hernndez-Prez Pilar Flores-Espinosa Gabriela Sedano Addy Cecilia Helguera-Repetto
scar Villavicencio-Carrisoza María Yolotzin Valdespino-Vazquez Arturo Flores-Pliego Claudine Irles Bruno Rivas-Santiago Elsa Romelia Moreno-Verduzco Lorenza Díaz Vernica Zaga-Clavellina 《International journal of molecular sciences》2022,23(6)
An infectious process into the uterine cavity represents a major endangered condition that compromises the immune privilege of the maternal–fetal unit and increases the risk for preterm birth (PTB) and premature rupture of membranes (PROM). Fetal membranes are active secretors of antimicrobial peptides (AMP), which limit bacterial growth, such as Escherichia coli. Nevertheless, the antibacterial responses displayed by chorioamniotic membranes against a choriodecidual E. coli infection have been briefly studied. The objective of this research was to characterize the profile of synthesis, activity, and spatial distribution of a broad panel of AMPs produced by fetal membranes in response to E. coli choriodecidual infection. Term human chorioamniotic membranes were mounted in a two independent compartment model in which the choriodecidual region was infected with live E. coli (1 × 105 CFU/mL). Amnion and choriodecidual AMP tissue levels and TNF-α and IL-1β secretion were measured by the enzyme-linked immunosorbent assay. The passage of bacterium through fetal membranes and their effect on structural continuity was followed for 24 h. Our results showed that E. coli infection caused a progressive mechanical disruption of the chorioamniotic membranes and an activated inflammatory environment. After the challenge, the amnion quickly (2–4 h) induced production of human beta defensins (HBD)-1, HBD-2, and LL-37. Afterwards (8–24 h), the amnion significantly produced HBD-1, HBD-2, HNP-1-3, S100A7, sPLA2, and elafin, whereas the choriodecidua induced LL-37 synthesis. Therefore, we noticed a temporal- and tissue-specific pattern regulation of the synthesis of AMPs by infected fetal membranes. However, fetal membranes were not able to contain the collagen degradation or the bacterial growth and migration despite the battery of produced AMPs, which deeply increases the risk for PTB and PROM. The mixture of recombinant HBDs at low concentrations resulted in increased bactericidal activity compared to each HBD alone in vitro, encouraging further research to study AMP combinations that may offer synergy to control drug-resistant infections in the perinatal period. 相似文献
105.
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
106.
In honeybees, the cuticular hydrocarbon profiles are partly genetically based and differ between subfamilies, which suggests that they might be used by the workers as labels for subfamily recognition. This ability could potentially form the basis for nepotistic conflicts between subfamilies that would be detrimental to the inclusive fitness of the colony. Here we have compared the subfamily hydrocarbon profiles of 5-day-old workers maintained in isolation with those kept in their parental colony. We demonstrate that the cuticular hydrocarbon profiles tend to be less distant between most subfamilies within the hive compared with those held in isolation. The main consequence of this partial homogenization of the majority of subfamily signatures may result in a reduction of the number of recognizable subfamilies in the colony. Nevertheless, a few subfamilies retain very distinct cuticular hydrocarbon profiles. 相似文献
107.
Interaction between farming systems, riparian zones, and landscape patterns: a case study in western France 总被引:2,自引:0,他引:2
We analyze the factors driving land use within and outside riparian zones in four small (about 800 ha) watersheds in Brittany. The results show a difference between riparian and non-riparian zones (less used for grassland), but other factors are also important, such as field size or farm management type. In large farms, small fields are easily abandoned. A multivariate analysis with farm and field characteristics explains 30% of land use variation. Our results suggest that farm type deflects land use from the regional mode, so it is important, in the implementation of environmental zoning, to assess constraints at the farm level. 相似文献
108.
Tested hypotheses that (a) the relationship between daily activity variation (AV) of Ss and their end-of-day moods (M) is moderated by extraversion-introversion (E-I), the relationship being positive for extraverts and negative for introverts; and (b) the relationships of AV, M, and E-I are stronger on a nonwork (leisure) than a work day (WL). A possible influence of neuroticism-stability (N-S) on the above relationships was also explored. 98 adults were given the Eysenck Personality Inventory and, based on their scores, were placed into 1 of 4 groups (formed by combinations of extraversion or introversion and neuroticism or stability). Ss also completed a time diary for 1 work and 1 nonwork day, indicating their activities, moods, and other information. A 2 * 4 analysis of variance of M scores for the dichotimized classifications of WL, E-I, N-S, and AV supported both hypotheses. Neurotics showed inverted responses from those of stables, such that the positive relationship between AV and M for stable extraverts became negative, and the negative relationship for stable introverts became positive, when Ss were neurotic. A post-hoc formulation to account for results is presented, and there is a discussion of forms of varied experience that leisure days offer. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
109.
110.
Denis Thiery Jean Manuel Bluet Minh -Ha Pham-Delègue Patrick Etiévant Claudine Masson 《Journal of chemical ecology》1990,16(3):701-711
Combined electrophysiological recordings (EAG) and gas chromatographic separation were performed in order to investigate which volatile chemical components of a sunflower extract could be detected by honeybee workers and thus are likely to trigger the foraging behavior. A direct coupling device allowed for the stimulation of the antennal receptors with individual constituents of a polar fraction of the flower aroma shown to be attractive to bees. More than 100 compounds were separated from the extract. Twenty-four compounds elicited clear EAG responses. These compounds were identified by mass spectrometry (electronic impact and chemical ionisation). Both short- and long-chain aliphatic alcohols, one short-chain aliphatic aldehyde, one acid, two esters, and terpenic compounds were found to stimulate the antennal receptors. Six compounds identified in previous behavioral experiments were found to exhibit EAG activity. The chemicals screened by this method may be used for recognition of the plant odor and the selective behavior of honeybees. 相似文献