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41.
Kantesh Balani Flavia C. Brito Lidia Kos Arvind Agarwal 《Journal of the Royal Society Interface》2009,6(40):1097-1102
Pigmentation of murine cardiac tricuspid valve leaflet is associated with melanocyte concentration, which affects its stiffness. Owing to its biological and viscoelastic nature, estimation of the in situ stiffness measurement becomes a challenging task. Therefore, quasi-static and nanodynamic mechanical analysis of the leaflets of the mouse tricuspid valve is performed in the current work. The mechanical properties along the leaflet vary with the degree of pigmentation. Pigmented regions of the valve leaflet that contain melanocytes displayed higher storage modulus (7–10 GPa) than non-pigmented areas (2.5–4 GPa). These results suggest that the presence of melanocytes affects the viscoelastic properties of the mouse atrioventricular valves and are important for their proper functioning in the organism. 相似文献
42.
The tweens are a transitional age group undergoing deep physical and psychological transformations. Based on a thirteen-focus group research design involving 103 students, and applying a tweens-centered approach, the characteristics of SMS, IM, Internet, digital photos, electronic games, and email were analyzed. Categories such as moral issues, psychological and social consequences, problems/drawbacks, general benefits, and technical attributes synthesized the main characteristics attached to each form of digital technology. Their relative relevance was not gender dependent. Furthermore, tweens exhibited both metacognitive knowledge and personal epistemological observations associated with most of the digital technologies. 相似文献
43.
The practice of predictive maintenance depends significantly on the diagnosis of in-service performance and on the decision criteria for the selection of maintenance tasks. The definition of these criteria is limited because several actors are involved, each with their own perspectives of performance and maintenance needs. This paper discusses a set of 17 criteria to help the maintenance choice for building fa?ades, from three viewpoints: physical performance, risk, and costs. A group of experts was surveyed and 30 answers were received. Therefore, each criterion will be discussed according to the answers collected. The relative importance (using quantitative weights) and subclasses for each criterion are proposed. 相似文献
44.
Rogério Fernandes Brito Solidônio Rodrigues de Carvalho Sandro Metrevelle Marcondes de Lima e Silva João Roberto Ferreira 《International Communications in Heat and Mass Transfer》2009
This work studies the heat influence in cutting tools considering the variation of the coating thickness and the heat flux. K10 and diamond tools substrate with TiN and Al2O3 coatings were used. The numerical methodology utilizes the ANSYS® CFX software. Boundary conditions and constant thermo physical properties of the solids involved in the numerical analysis are known. To validate the proposed methodology an experiment is used. The TiN and Al2O3 coatings did not show satisfying results during a continuous cutting process. It showed a slight reduction in the heat flux for the 10 (µm) TiN and Al2O3 coatings. 相似文献
45.
Classical tone-shock conditioning induces zenk expression in the pigeon (Columba livia) hippocampus.
The hippocampus is involved in fear conditioning, although the molecular events underlying this function are still under investigation. The authors analyzed the expression of the Zenk proto-oncogene product within the pigeon (Columba livia) hippocampus after training with a classical aversive conditioning protocol using tone-shock associations. Control groups were trained with shock or tone alone or were only exposed to the experimental chamber and manipulated. Experimental pigeons showed significant increases of Zenk expression in the ventromedial region of the hippocampus, whereas both the experimental and shock groups had increased Zenk expression in the dorsal region. The expression of Zenk in specific neuronal populations within the pigeon hippocampus may be indicative of plasticity-associated aversive classical conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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48.
Due to their outstanding mechanical, thermal, and durability properties, polymer matrix nanocomposites (PMCs) are currently a prominent area of research. The opportunity of applying PMCs in structural reinforcement and rehabilitation of damaged infrastructures, as well as working as a new structural material, justifies the increasing number of recent studies. In this review article, the effect of adding different reinforcements at nano-scale, such as carbon nanotubes, nanoclay, graphene, or nanosilica to polymer matrices, is discussed and the improvement in mechanical properties of PMCs is evaluated. Some concluding remarks and new perspectives on the use of PMCs in structures are given. 相似文献
49.
J.C. Sá R.A. de Brito N.B. Silva C.Alves Júnior 《Surface & coatings technology》2009,203(13):1765-1770
Several studies in vitro and in vivo accomplished in dental implants have demonstrated that the chemical and physical properties of biomaterials are able to regulate the initial tecidual response around the implant. This tecidual response depends directly on the hydrophily, roughness, texture and chemical composition of the surface. Plasma treatment can be used to improve the surface properties of commercial pure Ti, in order to create different surface topographies, changes in roughness, and modifications in the surface wettability. In this study a surface modification in titanium Cp degree II was carried out, through the plasma treatment and using argon-ion bombardment. A comparison of surface properties and their influence on the cells behavior was also accomplished, besides the quantification of surface roughness, wettability and cellular proliferation. The results showed that the argon-ion bombardment influences the surface energy value, surface roughness and the surface topography of Ti materials. These parameters influence the cellular proliferation process. 相似文献
50.
Ellen Y. Sun Paul F. Becher Kevin P. Plucknett Chun-Hway Hsueh Kathleen B. Alexander Shirley B. Waters Kiyoshi Hirao Manuel E. Brito 《Journal of the American Ceramic Society》1998,81(11):2831-2840
Significant improvements in the fracture resistance of self-reinforced silicon nitride ceramics have been obtained by tailoring the chemistry of the intergranular amorphous phase. First, the overall microstructure of the material was controlled by incorporation of a fixed amount of elongated ß-Si3 N4 seeds into the starting powder to regulate the size and fraction of the large reinforcing grains. With controlled microstructures, the interfacial debond strength between the reinforcement and the intergranular glass was optimized by varying the yttria-to-alumina ratio in the sintering additives. It was found that the steady-state fracture toughness value of these silicon nitrides increased with the Y:Al ratio of the oxide additives. The increased toughness was accompanied by a steeply rising R -curve and extensive interfacial debonding between the elongated ß-Si3 N4 grains and the intergranular glassy phase. Microstructural analyses indicate that the different fracture behavior is related to the Al (and O) content in the ß´-SiAlON growth layer formed on the elongated ß-Si3 N4 grains during densification. The results imply that the interfacial bond strength is a function of the extent of Al and Si bonding with N and O in the adjoining phases with an abrupt structural/chemical interface achieved by reducing the Al concentration in both the intergranular phase and the ß´-SiAlON growth layer. Analytical modeling revealed that the residual thermal expansion mismatch stress is not a dominant influence on the interfacial fracture behavior when a distinct ß´-SiAlON growth layer forms. It is concluded that the fracture resistance of self-reinforced silicon nitrides can be improved by optimizing the sintering additives employed. 相似文献