Placenta praevia in Najran University hospital: incidence and risk factors

Background: Placenta praevia is a source of drastic pregnancy, fetal and neonatal complications. There was variable incidence in the literature in different parts of the world and within the same country regions. We carried out this study to find the impact in our area and the possible risk factors for this serious obstetric problem.Methods: This study is a cross-sectional descriptive, one-year retrospective one-year prospective study, carried out from April 2014 to April 2016. All pregnant women attended the antenatal care clinic in Najran University Hospital during the study period, were included.Results: The incidence of placenta praevia was found to be 2.7%. AMONG the study group, the most affected age group was between 20-29 years. Previous placenta praevia and previous caesarean  section were the significant risk factors P=0.00 and 0,017 repectively.Conclusions: The incidence of placenta praevia in Najran KSA in this study was high, compared to other regions in Saudi Arabia and the majority of the international figures. Caesarean section and previous placenta praevia were the significant risk factors for placenta praevia in this study

IN SILICO PHARMACOKINETICS AND MOLECULAR DOCKING OF THREE LEADS ISOLATED FROM TARCONANTHUS CAMPHORATUS L.

Objective: To investigate the pharmacokinetic and toxicity profiles and spectrum of biological activities of three phytochemicals isolated from Tarconanthus camphoratus L. Methods: Several integrated web based in silico pharmacokinetic tools were used to estimate the druggability of Hispidulin, Nepetin and Parthenolide. Afterward, the structural based virtual screening for the three compounds' potential targets was performed using PharmMapper online server. The molecular docking was conducted using Auto-Dock 4.0 software to study the binding interactions of these compounds with the targets predicted by PharmMapper server. Results: The permeability properties for all compounds were found within the limit range stated for Lipinski׳s rule of five. Only Parthenolide proved to be able to penetrate through blood brain barrier. Isopentenyl-diphosphate delta-isomerase (IPPI), uridine-cytidine kinase-2 (UCK-2) and the mitogen-activated protein kinase kinase-1 (MEK-1) were proposed as potential targets for Hispidulin, Nepetin and Parthenolide, respectively. Nepetin and Parthenolide were predicted to have anticancer activities. The activity of Nepetin appeared to be mediated through UCK-2 inhibition. On the other hand, inhibition of MEK-1 and enhancement of TP53 expression were predicted as the anticancer mechanisms of Parthenolide. The three compounds showed interesting interactions and satisfactory binding energies when docked into their relevant targets. Conclusion: The ADMET profiles and biological activity spectra of Hispidulin, Nepetin and Parthenolide have been addressed. These compounds are proposed to have activities against a variety of human aliments such as tumors, muscular dystrophy, and diabetic cataracts.Keywords: Tarconanthus camphoratus L., Hispidulin, Nepetin, Parthenolide, In silico pharmacokinetic, Molecular docking, PharmMapper server, and Auto-Dock 4.0 softwareÂ

Stratégies thermo-mécaniques et multi-échelles pour la modélisation du contact rugueux : application aux systèmes de freinage

Les phénomènes de contact (rugosité, frottement, usure, etc.) sont importants dans le fonctionnement des freins à friction. Ils peuvent influencer leurs performances en modifiant l'état de surface et des matériaux. Afin de cerner ce problème, les industriels se basent sur des méthodes de type essai/erreur qui sont coûteuses et peu efficaces face aux exigences actuelles.L'objectif de cette thèse est de proposer une alternative consistant à modéliser numériquement les systèmes, tels qu'un frein à friction, avec des hypothèses réalistes au niveau du contact contrairement aux approches classiques considérant le contact parfait. Ce challenge a été surmonté en développant une stratégie numérique associant un modèle macroscopique du système et plusieurs modèles micro traitant les phénomènes de contact. La modélisation microscopique du contact est faite grâce à des modèles thermique et mécanique considérant la rugosité. Le problème est résolu avec des techniques d'optimisation. Le cas d'un matériau à gradient de propriétés normal à la surface et l'usure sont aussi considérés. A partir de ces calculs, les paramètres de contact (pression, température, etc.) sont analysés en fonction des propriétés de surface et du matériau. Ensuite, le modèle macroscopique est enrichi avec ces paramètres tout en conservant la planéité des surfaces en contact. Avec cette technique, le temps de calcul est réduit en comparaison à des calculs Éléments Finis complets. Cette stratégie multi-échelle a été adoptée pour l'analyse dynamique et thermo-mécanique des freins. Les résultats des simulations numériques montrent l'impact de l'interface et de son évolution sur les performances du frein et vice-versa.Contact phenomena (roughness, friction, wear, etc.) are central to friction brake functioning as they lead to the modification of surface and material properties which may affect the braking performances. To address these issues, the manufacturers use an experimental approach based on feedback tests which is expensive and inefficient against the current requirements.The objective of this work is to propose an alternative based on numerical modeling of applications like brakes with realistic assumptions at the contact interface level, unlike the classical approaches that assume a perfect contact. This challenge has been overcome by building a numerical methodology associating a large scale model of the system and several micro scale models of contact phenomena. The micro scale contact modeling has been performed with thermal and mechanical models considering roughness. The problem is solved by means of constrained quadratic programming. A normal gradient of material properties and wear have also been considered. From this analysis, surface parameters (pressure, temperature,etc.) are analyzed depending on roughness and material properties. Thereafter, a Finite Element large scale model is embedded with these parameters while the surface is flat at this scale. With this technique, the CPU time is considerably reduced and the precision is maintained in comparison to classical Finite Element calculations. This multi-scale methodology has been used for dynamic and thermo-mechanical analyses of braking systems. The results of numerical simulations highlight the impact of the contact interface and its evolution on the system behavior, and vice versa

Multiscale thermomechanical modeling of frictional contact problems considering wear – Application to a pin-on-disc system

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A Multiscale strategy for braking system modeling : from contact surface to the system

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A multiscale method for frictionless contact mechanics of rough surfaces

International audienceAn efficient methodology is proposed for the analysis of frictionless contact between rough surfaces. The surface is described by parabolic asperities which deform according to Hertz Theory. The problem is solved considering interactions between elliptic contact zones. Such analysis provides interface laws that are incorporated into a macroscopic numerical model where contact surfaces are flat. This operation is done by means of Love solution for elastic half spaces and the penalty method.A numerical example of this multiscale method is presented to show its robustness. In comparison with a purely numerical model where roughness is explicitly described, the proposed strategy provides good results and saves a considerable amount of time

A MULTI-SCALE MODEL FOR CONTACT MECHANICS OF ROUGH SURFACES

International audienceAn efficient methodology is proposed for the analysis of contact between rough surfaces. First, a micro-contact model is defined depending on surface topography and material properties. Second, the parameters issued from the model are integrated into a macro-scale numerical model following a specific method. An example of this method is presented to show its robustness. Comparing to a numerical model where surface topography is explicitly meshed, this strategy provides good results and saves considerably computation time

Heat partition and surface temperature in sliding contact systems of rough surfaces

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