Differentially expressed proteins in ER+ MCF7 and ER- MDA- MB-231 human breast cancer cells by RhoGDI-α silencing and overexpression

Background: The consequence of Rho GDP dissociation inhibitor alpha (RhoGDIα) activity on migration and invasion of estrogen receptor positive (ER+) and negative (ER-) breast cancer cells has not been studied using the proteomic approach. Changes in expression of RhoGDIα and other proteins interacting directly or indirectly with RhoGDIα in MCF7 and MDA-MB-231, with different metastatic potentials is of particular interest. Materials and Methods: ER+ MCF7 and ER- MDA-MB-231 cell lines were subjected to two-dimensional electrophoresis (2-DE) and spots of interest were identified by matrix-assisted laser desorption/ionization time of- flight/timeof- flight (MALDI-TOF/TOF) mass spectrometry (MS) analysis after downregulation of RhoGDIα using short interfering RNA (siRNA) and upregulated using GFP-tagged ORF clone of RhoGDIα. Results: The results showed a total of 35 proteins that were either up- or down-regulated in these cells. Here we identifed 9 and 15 proteins differentially expressed with silencing of RhoGDIα in MCF-7 and the MDA-MB-231 cells, respectively. In addition, 10 proteins were differentially expressed in the upregulation of RhoGDIα in MCF7, while only one protein was identified in the upregulation of RhoGDIα in MDA-MB-231. Based on the biological functions of these proteins, the results revealed that proteins involved in cell migration are more strongly altered with RhoGDI-α activity. Although several of these proteins have been previously indicated in tumorigenesis and invasiveness of breast cancer cells, some ohave not been previously reported to be involved in breast cancer migration. Hence, these proteins may serve as useful candidate biomarkers for tumorigenesis and invasiveness of breast cancer cells. Conclusions: Future studies are needed to determine the mechanisms by which these proteins regulate cell migration. The combination of RhoGDIα with other potential biomarkers may be a more promising approach in the inhibition of breast cancer cell migration

Downregulation of RhoGDIα increased migration and invasion of ER+ MCF7 and ER− MDA-MB-231 breast cancer cells.

Rho GDp dissociation inhibitors (RhoGDIs) can inhibit cell motility, invasion, and metastasis in cancer by inactivating the RhoGTpases. A member of RhoGDI family has been consistently shown to interact with estrogen receptor (eR), and change its transcriptional activity. eR is a receptor known to be inversely correlated with cell motility and invasion in breast cancer. The consequence of RhoGDIα activity on migration and invasion of eR+ and eR− breast cancers is not clear. The aim of our study was to investigate the possible opposing effect of RhoGDIα on the migration and invasion of eR+ MCF7 and eR− MDA-MB-231 breast cancer cells. RhoGDIα was downregulated using short interfering RNA (siRNA) and upregulated using GFp-tagged ORF clone of RhoGDIα, and their ability for migration and invasion was assayed using transwell chambers. It was found that the silencing of RhoGDIα in MCF7 and MDA-MB-231 cells significantly increased migration and invasion of these cells into the lower surface of porous membrane of the chambers. Overexpression of RhoGDIα in MCF7 cells suppressed their migration and invasion, but no significant effect was found on MDA-MB-231 cells. Our results indicate that the downregulation of RhoGDIα similarly affects the in vitro migration and invasion of eR+ MCF7 and eR− MDA-MB-231 cells. however, our assays are differently affected by the upregulation of RhoGDIα in these two cell lines and this may be due to the differences in eR expression, primary invasive ability and/or other molecules between these two cell line models which warrant further investigation

Medication Errors and its Contributing Factors among Midwives

Introduction: Medication errors are among the most serious health errors threatening patient safety in all countries, with major impacts on public health. Midwives as members of healthcare systems are prone to such errors. Therefore, in this study, we aimed to determine medication errors and the contributing factors among midwives working in maternity units of Mashhad University of Medical Sciences, Mashhad, Iran in 2015. Methods: This descriptive, cross-sectional study was performed on 104 employed midwives at four hospitals (Imam Reza, Ghaem, Omolbanin, and Hashemi Nezhad hospitals), affiliated to Mashhad University of Medical Sciences. The validity and reliability of the data collection tools were confirmed through content validity and internal consistency (Cronbach's alpha), respectively. For data analysis, descriptive and analytical tests, multiple linear regression, and negative binomial regression analysis were performed, using SPSS version 20 and STATA version 11. Results: The average incidence of medication errors for each midwife was 21.24±2.89 in the past six months. Among reasons against reporting medication errors, fear of confrontation with authorities (3.79±1.5) and attributing the medication error to individual factors by officials (3.88±1.34) had the highest average scores. The most common causes of medication errors were overcrowding of the ward (4.32±1.01), excessive workload and overexertion (4.19±1.08), and presence of critically ill patients in the ward (4.03±1.18). Conclusion: Overcrowding of the ward, fear of authorities, and attributing the medication error to individual factors were the main reasons against reporting medication errors, respectively. Therefore, more attention should be paid to error reporting systems, and workshops in this area are highly recommended

Tuning Chemical and Optical Properties of Nanomaterials: From Extended Surfaces to Finite Nanoclusters

Modifying the electronic and optical properties of surfaces and nanostructures are in the forefront of surface science. This dissertation\u27s focus is on this problem. The first part is on the adsorption of functionalized naphthalene molecules on Cu(111) surface. The results show that changing the functional group results in modification of charge redistribution at the interface of molecule and surface and the electronic structure of Cu changes. The second part discusses the new Moire structure of h-BN on Rh(111) induced by intrinsic carbon impurities of Rh single crystals. We found that these impurities intercalate between h-BN and Rh(111) with new local properties such as charge transfer from Rh and C atoms to h-BN such as appearance of new states in the BN. The third part is about the study of CO super lattice structure at 1/2ML when adsorbed on Pd(111). By considering all the possible overlayer structures and using several different functionals, we found that two structures can be made by CO adsorbents and all the other structures convert to one of these two. The fourth part is on the electronic and optical properties of ligated Ag44 nanoclusters. Using DFT and TDDFT calculations we show that when the pH level of a solvent is changed, the protecting ligands deprotonate and their interaction with each other as well as the metal core varies and the new peaks in absorption spectrum arise from electron rich deprotonated ligands. The final part is on the adsorption of planar molecules on MoS2. We found that the isomers of di-iodobenzene adsorb with same strength on MoS2 and it is the symmetry of frontier orbitals that identifies their different behavior. Also the adsorption and dissociation of benzenethiol on MoS2 was studied and the results show that benzenethiol dissociates only in the presence of defects and heals the structure

Génération assistée par ordinateur, impression 3D et étude expérimentale de matériaux poreux et composites

The present study deals with computer-aided design, 3D-printing, large strain numerical simulation, and experimental testing of random geometries with focus on porous materials. In particular, we attempt to assess the effect of random porous features on the mechanical response at large strain by comparing the response of well-chosen random and periodic porous geometries. We first investigate the computer-aided design process of a variety of porous geometries including random polydisperse porous materials with spherical and ellipsoidal voids, standard eroded Voronoi geometries, hexagonal honeycombs, and TPMS structures. In addition, we propose a novel computer-aided design strategy to obtain a new type of random Voronoi-type porous materials called M-Voronoi (from mechanically grown) with smooth void shapes and variable intervoid ligament sizes that can reach very low relative densities. This is achieved via a numerical, large strain, nonlinear elastic, void growth mechanical process. The proposed M-Voronoi method is general and can be applied to create both two and three-dimensional random geometries and allows the formation of isotropic or anisotropic materials. The void growth process is a consequence of mass conservation and the incompressibility of the surrounding nonlinear elastic matrix phase and the final achieved relative density may be analytically estimated in terms of the determinant of the applied deformation gradient. The extremely low densities in the M-Voronoi geometries are achieved through an intermediate remesh step in the virtual fabrication process. For this purpose, we developed a versatile and general remeshing algorithm based on the geometry reconstruction of an orphan mesh that can handle arbitrarily complex meshes, including those that contain voids or multiple phases. Moreover, the studied random geometries are general to model seamlessly a wide range of composites involving particles, multi-phase, and even polycrystals with finite interfaces under mechanical or coupled loads (e.g. magneto-electro mechanical, etc.).In the next part of the study, we fabricate the designed porous materials with a polymer 3D-printer via PolyJet technology and a UV-curable resin called TangoBlack which is a highly viscous soft polymer with brittle fracture. Meanwhile, the viscous behavior of TangoBlack is studied under uniaxial tensile, loading-unloading, and relaxation tests on a new proposed specimen geometry and is subsequently characterized by a nonlinear rubber viscoelastic model for incompressible isotropic elastomers. We then use this material to 3D-print the designed two-dimensional porous materials with square representative geometries and isotropic/anisotropic features in terms of void size and realization. The mechanical response of the fabricated porous materials is experimentally investigated by testing them under uniaxial large strain compression and low strain rates. We show that the randomness of the proposed M-Voronoi geometries and their non-uniform intervoid ligament size leads to enhanced mechanical properties at large compressive strains with no apparent peak-stress and strong hardening well before densification, while they become very close to random eroded Voronoi geometries at low densities.In the last part of this study, we investigate numerically the mechanical properties of the three-dimensional random porous geometries consisting of M-Voronoi, polydisperse porous materials with spherical voids, and classical TPMS-like geometries. The simulations are performed at large strains under compression loading while considering the matrix an elastic-perfectly plastic material without hardening. We observe enhanced plastic flow stress in the geometries with random topologies as opposed to the TPMS periodic structures. This behavior is explained by noting that deformation localizes in geometries with a periodic pattern, contrary to the random geometries which exhibit a rather diffused localization.Cette étude porte sur la conception assistée par ordinateur, l'impression 3D, la simulation numérique à grandes transformations et la caractérisation expérimentale de géométries aléatoires, en mettant l'accent sur les matériaux poreux. En particulier, nous cherchons à quantifier l’effet des architectures aléatoires sur la réponse mécanique en grandes transformations de géométries poreuses aléatoires et périodiques bien choisies. Dans un premier temps, nous nous intéressons à la conception assistée par ordinateur d'une variété de géométries poreuses, y compris les matériaux contentant des distributions aléatoires de pores sphériques et ellipsoïdaux, des structures Voronoï, à d'abeilles et TPMS. Par ailleurs, nous proposons une nouvelle famille de matériaux poreux de type Voronoï appelés M-Voronoï (de mécaniquement cultivé) contenant de pores de taille hétérogène et de ligaments d’épaisseur variable. Ces matériaux peuvent atteindre des densités relatives très faibles, et sont obtenus à l’aide de simulations numériques par un processus de croissance de pores dans une matrice élastique non linéaire et à grandes transformations. La méthode M-Voronoï proposée est versatile et peut être appliquée pour créer des géométries aléatoires bidimensionnelles et tridimensionnelles avec (an-)isotropie contrôlée. Cette méthode de génération découle de la conservation de la masse et de l'incompressibilité de la matrice. Les densités extrêmement faibles des géométries M-Voronoï sont obtenues par une étape intermédiaire de remaillage dans le processus de fabrication virtuelle. Pour ce faire, un nouveau algorithme de remaillage a été proposé. Ceci repose sur la reconstruction de la géométrie d'un maillage orphelin qui peut traiter des maillages arbitrairement complexes, contenant des phases multiples. De ce fait, les géométries M-Voronoi peuvent être utilisés pour modéliser de nombreux matériaux composites (y compris ceux à renfort de particules), ainsi que les polycristaux sous des charges mécaniques ou couplées (par exemple magnéto-électro-mécanique, etc.).Dans un deuxième temps, nous nous sommes intéressés à la caractérisation expérimentale des matériaux poreux ainsi obtenus. Ceux-ci ont été fabriqués par impression 3D polymère via la technologie PolyJet en utilisant une résine, appelée TangoBlack moue hautement visqueuse, dont la loi de comportement a été quantifiée à l’aide des essais mécaniques et caractérisé par un modèle viscoélastique non linéaire formulé pour les élastomères isotropes incompressibles. Par la suite, des essais de compression uni-axiales ont été menés pour étudier la réponse mécanique de structures poreuses 3D-imprimées en Tangoblack. Ceux-ci ont montrés que, dans le régime de grandes transformations les géométries M-Voronoï ont des propriétés mécaniques améliorées du fait de leur architecture poreuse. Notamment, leur réponse sous compression durcie bien avant la densification et devient similaire à celle de géométries Voronoï aléatoires érodées à de faibles densités.Dans la dernière partie de cette étude, nous avons étudié à l’aide de simulations numériques les propriétés mécaniques des géométries poreuses aléatoires tridimensionnelles constituées de M-Voronoï, de matériaux poreux polydispersés avec des vides sphériques, et des géométries classiques de type TPMS. Les simulations ont été menées à grandes transformations sous une charge de compression tout en considérant la matrice comme un matériau élastique-parfaitement plastique sans durcissement. Ces résultats ont montré que l’écoulement plastique accrue dans les géométries à topologies aléatoires par rapport aux structures périodiques TPMS. Ce comportement est expliqué en observant que la déformation se localise dans les géométries avec motif périodique, contrairement aux géométries aléatoires qui présentent une localisation plutôt diffusée

Génération assistée par ordinateur, impression 3D et étude expérimentale de matériaux poreux et composites

Cette étude porte sur la conception assistée par ordinateur, l'impression 3D, la simulation numérique à grandes transformations et la caractérisation expérimentale de géométries aléatoires, en mettant l'accent sur les matériaux poreux. En particulier, nous cherchons à quantifier l’effet des architectures aléatoires sur la réponse mécanique en grandes transformations de géométries poreuses aléatoires et périodiques bien choisies. Dans un premier temps, nous nous intéressons à la conception assistée par ordinateur d'une variété de géométries poreuses, y compris les matériaux contentant des distributions aléatoires de pores sphériques et ellipsoïdaux, des structures Voronoï, à d'abeilles et TPMS. Par ailleurs, nous proposons une nouvelle famille de matériaux poreux de type Voronoï appelés M-Voronoï (de mécaniquement cultivé) contenant de pores de taille hétérogène et de ligaments d’épaisseur variable. Ces matériaux peuvent atteindre des densités relatives très faibles, et sont obtenus à l’aide de simulations numériques par un processus de croissance de pores dans une matrice élastique non linéaire et à grandes transformations. La méthode M-Voronoï proposée est versatile et peut être appliquée pour créer des géométries aléatoires bidimensionnelles et tridimensionnelles avec (an-)isotropie contrôlée. Cette méthode de génération découle de la conservation de la masse et de l'incompressibilité de la matrice. Les densités extrêmement faibles des géométries M-Voronoï sont obtenues par une étape intermédiaire de remaillage dans le processus de fabrication virtuelle. Pour ce faire, un nouveau algorithme de remaillage a été proposé. Ceci repose sur la reconstruction de la géométrie d'un maillage orphelin qui peut traiter des maillages arbitrairement complexes, contenant des phases multiples. De ce fait, les géométries M-Voronoi peuvent être utilisés pour modéliser de nombreux matériaux composites (y compris ceux à renfort de particules), ainsi que les polycristaux sous des charges mécaniques ou couplées (par exemple magnéto-électro-mécanique, etc.).Dans un deuxième temps, nous nous sommes intéressés à la caractérisation expérimentale des matériaux poreux ainsi obtenus. Ceux-ci ont été fabriqués par impression 3D polymère via la technologie PolyJet en utilisant une résine, appelée TangoBlack moue hautement visqueuse, dont la loi de comportement a été quantifiée à l’aide des essais mécaniques et caractérisé par un modèle viscoélastique non linéaire formulé pour les élastomères isotropes incompressibles. Par la suite, des essais de compression uni-axiales ont été menés pour étudier la réponse mécanique de structures poreuses 3D-imprimées en Tangoblack. Ceux-ci ont montrés que, dans le régime de grandes transformations les géométries M-Voronoï ont des propriétés mécaniques améliorées du fait de leur architecture poreuse. Notamment, leur réponse sous compression durcie bien avant la densification et devient similaire à celle de géométries Voronoï aléatoires érodées à de faibles densités.Dans la dernière partie de cette étude, nous avons étudié à l’aide de simulations numériques les propriétés mécaniques des géométries poreuses aléatoires tridimensionnelles constituées de M-Voronoï, de matériaux poreux polydispersés avec des vides sphériques, et des géométries classiques de type TPMS. Les simulations ont été menées à grandes transformations sous une charge de compression tout en considérant la matrice comme un matériau élastique-parfaitement plastique sans durcissement. Ces résultats ont montré que l’écoulement plastique accrue dans les géométries à topologies aléatoires par rapport aux structures périodiques TPMS. Ce comportement est expliqué en observant que la déformation se localise dans les géométries avec motif périodique, contrairement aux géométries aléatoires qui présentent une localisation plutôt diffusée.The present study deals with computer-aided design, 3D-printing, large strain numerical simulation, and experimental testing of random geometries with focus on porous materials. In particular, we attempt to assess the effect of random porous features on the mechanical response at large strain by comparing the response of well-chosen random and periodic porous geometries. We first investigate the computer-aided design process of a variety of porous geometries including random polydisperse porous materials with spherical and ellipsoidal voids, standard eroded Voronoi geometries, hexagonal honeycombs, and TPMS structures. In addition, we propose a novel computer-aided design strategy to obtain a new type of random Voronoi-type porous materials called M-Voronoi (from mechanically grown) with smooth void shapes and variable intervoid ligament sizes that can reach very low relative densities. This is achieved via a numerical, large strain, nonlinear elastic, void growth mechanical process. The proposed M-Voronoi method is general and can be applied to create both two and three-dimensional random geometries and allows the formation of isotropic or anisotropic materials. The void growth process is a consequence of mass conservation and the incompressibility of the surrounding nonlinear elastic matrix phase and the final achieved relative density may be analytically estimated in terms of the determinant of the applied deformation gradient. The extremely low densities in the M-Voronoi geometries are achieved through an intermediate remesh step in the virtual fabrication process. For this purpose, we developed a versatile and general remeshing algorithm based on the geometry reconstruction of an orphan mesh that can handle arbitrarily complex meshes, including those that contain voids or multiple phases. Moreover, the studied random geometries are general to model seamlessly a wide range of composites involving particles, multi-phase, and even polycrystals with finite interfaces under mechanical or coupled loads (e.g. magneto-electro mechanical, etc.).In the next part of the study, we fabricate the designed porous materials with a polymer 3D-printer via PolyJet technology and a UV-curable resin called TangoBlack which is a highly viscous soft polymer with brittle fracture. Meanwhile, the viscous behavior of TangoBlack is studied under uniaxial tensile, loading-unloading, and relaxation tests on a new proposed specimen geometry and is subsequently characterized by a nonlinear rubber viscoelastic model for incompressible isotropic elastomers. We then use this material to 3D-print the designed two-dimensional porous materials with square representative geometries and isotropic/anisotropic features in terms of void size and realization. The mechanical response of the fabricated porous materials is experimentally investigated by testing them under uniaxial large strain compression and low strain rates. We show that the randomness of the proposed M-Voronoi geometries and their non-uniform intervoid ligament size leads to enhanced mechanical properties at large compressive strains with no apparent peak-stress and strong hardening well before densification, while they become very close to random eroded Voronoi geometries at low densities.In the last part of this study, we investigate numerically the mechanical properties of the three-dimensional random porous geometries consisting of M-Voronoi, polydisperse porous materials with spherical voids, and classical TPMS-like geometries. The simulations are performed at large strains under compression loading while considering the matrix an elastic-perfectly plastic material without hardening. We observe enhanced plastic flow stress in the geometries with random topologies as opposed to the TPMS periodic structures. This behavior is explained by noting that deformation localizes in geometries with a periodic pattern, contrary to the random geometries which exhibit a rather diffused localization

Génération assistée par ordinateur, impression 3D et étude expérimentale de matériaux poreux et composites

The present study deals with computer-aided design, 3D-printing, large strain numerical simulation, and experimental testing of random geometries with focus on porous materials. In particular, we attempt to assess the effect of random porous features on the mechanical response at large strain by comparing the response of well-chosen random and periodic porous geometries. We first investigate the computer-aided design process of a variety of porous geometries including random polydisperse porous materials with spherical and ellipsoidal voids, standard eroded Voronoi geometries, hexagonal honeycombs, and TPMS structures. In addition, we propose a novel computer-aided design strategy to obtain a new type of random Voronoi-type porous materials called M-Voronoi (from mechanically grown) with smooth void shapes and variable intervoid ligament sizes that can reach very low relative densities. This is achieved via a numerical, large strain, nonlinear elastic, void growth mechanical process. The proposed M-Voronoi method is general and can be applied to create both two and three-dimensional random geometries and allows the formation of isotropic or anisotropic materials. The void growth process is a consequence of mass conservation and the incompressibility of the surrounding nonlinear elastic matrix phase and the final achieved relative density may be analytically estimated in terms of the determinant of the applied deformation gradient. The extremely low densities in the M-Voronoi geometries are achieved through an intermediate remesh step in the virtual fabrication process. For this purpose, we developed a versatile and general remeshing algorithm based on the geometry reconstruction of an orphan mesh that can handle arbitrarily complex meshes, including those that contain voids or multiple phases. Moreover, the studied random geometries are general to model seamlessly a wide range of composites involving particles, multi-phase, and even polycrystals with finite interfaces under mechanical or coupled loads (e.g. magneto-electro mechanical, etc.).In the next part of the study, we fabricate the designed porous materials with a polymer 3D-printer via PolyJet technology and a UV-curable resin called TangoBlack which is a highly viscous soft polymer with brittle fracture. Meanwhile, the viscous behavior of TangoBlack is studied under uniaxial tensile, loading-unloading, and relaxation tests on a new proposed specimen geometry and is subsequently characterized by a nonlinear rubber viscoelastic model for incompressible isotropic elastomers. We then use this material to 3D-print the designed two-dimensional porous materials with square representative geometries and isotropic/anisotropic features in terms of void size and realization. The mechanical response of the fabricated porous materials is experimentally investigated by testing them under uniaxial large strain compression and low strain rates. We show that the randomness of the proposed M-Voronoi geometries and their non-uniform intervoid ligament size leads to enhanced mechanical properties at large compressive strains with no apparent peak-stress and strong hardening well before densification, while they become very close to random eroded Voronoi geometries at low densities.In the last part of this study, we investigate numerically the mechanical properties of the three-dimensional random porous geometries consisting of M-Voronoi, polydisperse porous materials with spherical voids, and classical TPMS-like geometries. The simulations are performed at large strains under compression loading while considering the matrix an elastic-perfectly plastic material without hardening. We observe enhanced plastic flow stress in the geometries with random topologies as opposed to the TPMS periodic structures. This behavior is explained by noting that deformation localizes in geometries with a periodic pattern, contrary to the random geometries which exhibit a rather diffused localization.Cette étude porte sur la conception assistée par ordinateur, l'impression 3D, la simulation numérique à grandes transformations et la caractérisation expérimentale de géométries aléatoires, en mettant l'accent sur les matériaux poreux. En particulier, nous cherchons à quantifier l’effet des architectures aléatoires sur la réponse mécanique en grandes transformations de géométries poreuses aléatoires et périodiques bien choisies. Dans un premier temps, nous nous intéressons à la conception assistée par ordinateur d'une variété de géométries poreuses, y compris les matériaux contentant des distributions aléatoires de pores sphériques et ellipsoïdaux, des structures Voronoï, à d'abeilles et TPMS. Par ailleurs, nous proposons une nouvelle famille de matériaux poreux de type Voronoï appelés M-Voronoï (de mécaniquement cultivé) contenant de pores de taille hétérogène et de ligaments d’épaisseur variable. Ces matériaux peuvent atteindre des densités relatives très faibles, et sont obtenus à l’aide de simulations numériques par un processus de croissance de pores dans une matrice élastique non linéaire et à grandes transformations. La méthode M-Voronoï proposée est versatile et peut être appliquée pour créer des géométries aléatoires bidimensionnelles et tridimensionnelles avec (an-)isotropie contrôlée. Cette méthode de génération découle de la conservation de la masse et de l'incompressibilité de la matrice. Les densités extrêmement faibles des géométries M-Voronoï sont obtenues par une étape intermédiaire de remaillage dans le processus de fabrication virtuelle. Pour ce faire, un nouveau algorithme de remaillage a été proposé. Ceci repose sur la reconstruction de la géométrie d'un maillage orphelin qui peut traiter des maillages arbitrairement complexes, contenant des phases multiples. De ce fait, les géométries M-Voronoi peuvent être utilisés pour modéliser de nombreux matériaux composites (y compris ceux à renfort de particules), ainsi que les polycristaux sous des charges mécaniques ou couplées (par exemple magnéto-électro-mécanique, etc.).Dans un deuxième temps, nous nous sommes intéressés à la caractérisation expérimentale des matériaux poreux ainsi obtenus. Ceux-ci ont été fabriqués par impression 3D polymère via la technologie PolyJet en utilisant une résine, appelée TangoBlack moue hautement visqueuse, dont la loi de comportement a été quantifiée à l’aide des essais mécaniques et caractérisé par un modèle viscoélastique non linéaire formulé pour les élastomères isotropes incompressibles. Par la suite, des essais de compression uni-axiales ont été menés pour étudier la réponse mécanique de structures poreuses 3D-imprimées en Tangoblack. Ceux-ci ont montrés que, dans le régime de grandes transformations les géométries M-Voronoï ont des propriétés mécaniques améliorées du fait de leur architecture poreuse. Notamment, leur réponse sous compression durcie bien avant la densification et devient similaire à celle de géométries Voronoï aléatoires érodées à de faibles densités.Dans la dernière partie de cette étude, nous avons étudié à l’aide de simulations numériques les propriétés mécaniques des géométries poreuses aléatoires tridimensionnelles constituées de M-Voronoï, de matériaux poreux polydispersés avec des vides sphériques, et des géométries classiques de type TPMS. Les simulations ont été menées à grandes transformations sous une charge de compression tout en considérant la matrice comme un matériau élastique-parfaitement plastique sans durcissement. Ces résultats ont montré que l’écoulement plastique accrue dans les géométries à topologies aléatoires par rapport aux structures périodiques TPMS. Ce comportement est expliqué en observant que la déformation se localise dans les géométries avec motif périodique, contrairement aux géométries aléatoires qui présentent une localisation plutôt diffusée

The importance of frontier orbital symmetry in the adsorption of diiodobenzene on MoS\u3csub\u3e2\u3c/sub\u3e(0001)

Evidence of a role of frontier orbital symmetry, in the adsorption process of diiodobenzene on MoS2(0001), appears in the huge differences in the rate of adsorption between 1,3-diiodobenzene, 1,2-diiodobenzene and 1,4-diiodobenzene isomers on MoS2. Experiments indicate that the rate of adsorption of 1,3-diiodobenzene on MoS2(0001) is much greater than that of the 1,2-diodobenzene and 1,4-diiodbenzene isomers. As the differences in calculated diiodobenzene isomer-MoS2 system adsorption energies and electron affinities are negligible, frontier orbital symmetry appears to play a significant role in diiodobenzene adsorption on MoS2(0001). The experimental and theory results, in combination, suggest that a rehybridization requirement, forced by frontier orbital symmetry, comes at a cost of a reduced sticking coefficient. With the introduction of defects, which lower the adsorption site symmetry at the MoS2(0001) surface, the rate of 1,3-diiodobenzene adsorption on MoS2(0001) decreases, while the rates of 1,2-diodobenzene adsorption significantly increases

Co Adsorption On Pd(111) At 0.5Ml: A First Principles Study

It is well-known experimentally that at ½ monolayer (ML) coverage CO forms a c(4×2) phase on Pd(111). There is, however, a debate about whether this adsorption is at the bridge or at the hollow (FCC and HCP) sites, or at a combination of these two types of sites. Using density functional theory based calculations to evaluate the structural and vibrational properties of the c(4×2) overlayer of CO on Pd(111), with all possible highly symmetric adsorption sites, we conclude that the CO molecules prefer to adsorb either only on the hollow (FCC or HCP) sites or only at sites which are located in-between the bridge and the FCC sites and that there is no stable overlayer structure in which the molecule binds only at the bridge sites or combination of bridge and hollow sites

The Relationship between Organizational Citizenship Behavior, Job Satisfaction, and Occupational Stress among Midwives Working in Healthcare Centers of Mashhad, Iran, 2014

Background & aim: Organizational citizenship behavior (OCB) is a voluntary, organizationally desirable action that is not part of the employee’s formal job requirements. Job satisfaction and stress can affect mental health of midwives, and investigating the relationship between these variables can improve the quality of healthcare services. This study, therefore, was conducted to identify the relationship between OCB, occupational stress, and job satisfaction in Iranian midwives. Methods:This descriptive-correlational study was performed on 122 midwives working at healthcare centers of Mashhad, Iran, in 2014. The participants were chosen using a census approach. The tools for data collection included a demographic questionnaire, Podsakoff’s OCB Questionnaire, Minnesota Satisfaction Scale, and Karasek’s Job Content Questionnaire. Data analysis was carried out using Spearman and Pearson’s correlation, one-way ANOVA, and student t test were by SPSS version 20. Results: The mean age of the midwives was 38.46±7.22 years. OCB had a significant direct correlation with job satisfaction (r=0.223) and a significant negative correlation with job stress (r=-0.270)(