Prediction of the elastic modulus of the trabecular bone based on X-ray computed tomography

International audienceThis work aims to estimate the apparent Young's modulus of real human trabecular bones using a numerical micro-macro approach. Cylindrical specimens of trabecular bone were extracted from human femur heads, cleaned and scanned using a SkyScan-1072 micro-computed tomography system. 3D volumetric tetrahedral grids were generated from the exploitation of the reconstructed images using original meshing techniques. Numerical compressive tests were simulated, assuming isotropic tissue Young's modulus for all elements. The large size of the volumes implies grids with a high number of nodes, which required the use of a large number of parallel processors in order to perform the finite element calculations. Numerical Young's moduli varied between 1300 MPa and 1600 MPa, with a good agreement with experiments

Decoherence in the quantum walk on the line

We investigate the quantum walk on the line when decoherences are introduced either through simultaneous measurements of the chirality and particle position, or as a result of broken links. Both mechanisms drive the system to a classical diffusive behavior. In the case of measurements, we show that the diffusion coefficient is proportional to the variance of the initially localized quantum random walker just before the first measurement. When links between neighboring sites are randomly broken with probability $p$ per unit time, the evolution becomes decoherent after a characteristic time that scales as $1/p$. The fact that the quadratic increase of the variance is eventually lost even for very small frequencies of disrupting events, suggests that the implementation of a quantum walk on a real physical system may be severely limited by thermal noise and lattice imperfections.Comment: Elsevier style, 18 pages. New enhanced version with more material: new title, a new section was added and the discussion was updated; references added; submitted to Physica

Structural Evolution and Its Implication for the Emplacement of Gold Deposit in the Central Part of Burkina Faso, West Africa

In order to constrain the structural evolution in the central part of Burkina Faso and its implication for the emplacement of gold deposits, we undertook a structural mapping by coupling Landsat and aeromagnetic images interpretation to outcrop and core mapping followed by laboratory work. This approach reveals that the structural architecture in this locality mainly results from dextral transcurrent progressive deformation due to a NW-SE trending major stress. This architecture is similar to the Riedel-Tchalenko model. Initially, the dominant normal stress created an E-W constriction resulting in the development of N-S shear corridors. Subsequently, the tangential stress that took over this generated the progressive development of simple dextral shear zones with a NE-SW orientation that are locally taken up by ENE-WSW dextral shear bands associated with the Riedel's R structures. As a result of the cooling of the crust, we are witnessing the formation of sinistral NW-SE and dextral NNE-SSW strike-slip faults respectively corresponding to Riedel's R' structures and Tchalenko's P structures. The development of NW-SE pre-Eburnean shear zones and particularly the N-S shear corridors, are synchronous with the circulation of gold-bearing fluids through the zone. However, the intersections of these directional corridors create zones suitable for gold concentration. Within these zones, ductile-brittle deformation following the emplacement of the shear bands has facilitated the remobilization and concentration of gold-bearing fluids within rocks with the appropriate rheological conditions. This is the case for Toega gold deposit

Etude de l’effet antidépresseur de la décoction des rhizomes de Cyperus Articulatus (Cyperaceae) sur les souris blanches Mus musculus Swiss (Muridae)

La présente étude porte sur l’évaluation des effets pharmacologiques de la décoction des rhizomes de Cyperus Articulatus sur le système nerveux central. Cyperus Articulatus est une plante utilisée en médecine traditionnelle par certaines populations d’Asie et d’Afrique pour le traitement de plusieurs maladies telles que l’épilepsie, l’insomnie, les céphalées. Différentes doses (524 ; 262 ; 131 et 52,4 mg/kg) de la décoction des rhizomes C. Articulatus ont été administrées aux souris par voie orale et ces propriétés antidépressives ont été évaluées selon trois méthodes psychopharmacologiques à savoir : le test de la nage forcée ; le test de suspension caudale et le test de l’arène ouverte. L’administration de la décoction de C. Articulatus a entrainé une diminution significative de la durée d’immobilité dans le test de la nage forcée et le test de suspension caudale. Cette durée est passée respectivement de 232,40 ± 43,96 et 262,60 ± 84,00 secondes chez les souris du lot contrôle négatif à 150,00 ± 50,08 et 106,60 ± 56,86 secondes chez les souris traitées par la dose 524 mg/kg de la décoction. Dans le test de l’arène ouverte, nous n’avons pas noté une augmentation significative du nombre de rearing qui est de 16,60 ± 6,42 chez les souris du lot contrôle négatif et 21 ± 20 et 24,60 ± 9,23 secondes pour les doses 524 mg/kg de C. Articulatus et d’imipramine (20 mg/kg). Tous ces effets indiqueraient la présence dans cette décoction des rhizomes de C. Articulatus des composés qui posséderaient des propriétés antidépressives justifiant son utilisation en médecine traditionnelle. The present study reports the pharmacological effects of the decoction of Cyperus Articulatus rhizomes on the central nervous system. Cyperus Articulatus is a plant used in traditional medicine by some populations of Asia and Africa for the treatment of several diseases such as epilepsy, insomnia, and headache. The decoction of C. Articulatus were orally administered to mice at various doses (524; 262; 131 and 52.4 mg/kg) and its anti-depressive properties evaluated according to different psycho-pharmacological methods (forced swimming test, tail suspension test, and open field test). The administration of the decoction of C. Articulatus to the mice led to a significant reduction in the duration of immobility in the forced swimming test and the tail suspension test. This duration reduced respectively from 232.40 ± 43.96 and 262.60 ± 84.00 seconds in the mice of the negative controls batch to 150.00 ± 50.08 and 106.60 ± 56.86 seconds in the mice treated with the dose of 524 mg/kg of the decoction. In the open field test, we did not notice a significant increase in the number of rearing positions; these values were 16.60 ± 6.42 seconds in the negative control batch mice and only 24.60 ± 9.23 and 21 ± 20 seconds for the positive control batch and the dose of 524 mg/kg of C. Articulatus respectively. All these effects indicate the presence of bioactive molecules in this decoction of the rhizomes of C Articulatus which would have anti-depressive properties justifying its use in traditional medicine

Exact results on spin dynamics and multiple quantum dynamics in alternating spin-1/2 chains with XY-Hamiltonian at high temperatures

We extend the picture of a transfer of nuclear spin-1/2 polarization along a homogeneous one-dimensional chain with the XY-Hamiltonian to the inhomogeneous chain with alternating nearest neighbour couplings and alternating Larmor frequencies. To this end, we calculate exactly the spectrum of the spin-1/2 XY-Hamiltonian of the alternating chain with an odd number of sites. The exact spectrum of the XY-Hamiltonian is also applied to study the multiple quantum (MQ) NMR dynamics of the alternating spin-1/2 chain. MQ NMR spectra are shown to have the MQ coherences of zero and $\pm$ second orders just as in the case of a homogeneous chain. The intensities of the MQ coherences are calculated.Comment: 10 pages, 4 figure

Status of thiocyanate levels in the serum and saliva of non-smokers, ex-smokers and smokers

Background: Use of tobacco is often implicated in the development of oral diseases. Questionable accuracy of the traditional questionnaires to assess cigarette exposure necessitates the use of biomarkers like thiocyanate which provide a definitive quantitative measure.Objective: To assess the rise in the level of thiocyanate for measurement of smoking behaviour in adults.Materials and methods: Serum and salivary thiocyanate levels were estimated in 20 non-smokers, 20 ex-smokers and 40 smokers. Smokers were divided into two groups based on the presence or absence of oral mucosal lesions.Results: The mean serum and salivary thiocyanate levels were increased significantly in smokers when compared to non-smokers and ex-smokers. The levels were not significantly different between ex-smokers and non-smokers and between smokers with tobacco related oral mucosal lesions and those without. Statistically significant correlation was seen between the serum and salivary levels of thiocyanate.Conclusion: This study highlights the high level of thiocyanate in the serum and saliva of smokers when compared to non-smokers and ex-smokers. Significant increase in thiocyanate level was also seen in saliva. Hence it can be stated that saliva can be used as a reliable, non-invasive tool to assess smoking behaviour in the population and its changes over time.Keywords: Thiocyanate, tobacco, smoking, cancer, pre-cancer

(Design Criteria for Silicone Rubber Insulators (Composite Insulator

Insulators are used to perform both the electrical and mechanical functions. As such the design of such materials should be made such that the insulators can perform the functions optimally without failing or break. Insulators are used to provide mechanical support as well as prevent the flow of electricity that is not required for the transmission of high voltage electricity. This research paper aims to discuss the design criteria for silicone rubber insulators. The method used in the study involved includes the review of literature from various sources regarding design standards for silicone rubber insulators. The results indicate the electrical and mechanical integrity are some of the most important aspects of insulators.  The composite insulators can thus be affected by elements such as chemicals, temperature, sunlight and humidity. The results of the study can be used to design successfully, construct and install reliable composite insulators to be used in high voltage electricity transmission lines.&nbsp

An algorithm for network-based gene prioritization that encodes knowledge both in nodes and in links

Background: Candidate gene prioritization aims to identify promising new genes associated with a disease or a biological process from a larger set of candidate genes. In recent years, network-based methods - which utilize a knowledge network derived from biological knowledge - have been utilized for gene prioritization. Biological knowledge can be encoded either through the network's links or nodes. Current network-based methods can only encode knowledge through links. This paper describes a new network-based method that can encode knowledge in links as well as in nodes. Results: We developed a new network inference algorithm called the Knowledge Network Gene Prioritization (KNGP) algorithm which can incorporate both link and node knowledge. The performance of the KNGP algorithm was evaluated on both synthetic networks and on networks incorporating biological knowledge. The results showed that the combination of link knowledge and node knowledge provided a significant benefit across 19 experimental diseases over using link knowledge alone or node knowledge alone. Conclusions: The KNGP algorithm provides an advance over current network-based algorithms, because the algorithm can encode both link and node knowledge. We hope the algorithm will aid researchers with gene prioritization. © 2013 Kimmel, Visweswaran