Rates of Heat and Mass Transfers for a Non Darcy Porous Medium Subject to Double Dispersion and Saturated by a Nanofluid

This work aims to quantify the rates of heat and mass transfers occurred between a vertical and nonisothermal plate immersed into a non-Darcy porous medium and saturated with a weak nanofluid. Double dispersion is assumed and natural convection is the exchange mode. The similarity transformations are involved and the governing system of nonlinear partial differential equations is converted into a set of nonlinear ordinary differential equations via similarities. Results are displayed graphically to illustrate the influence of delta and xi on the velocity, the temperature and concentration of the species profiles. For a weak nanofluid, the rate of mass transfer is affected strongly by the double dispersion while the rate of heat transfer coefficient is less sensitive to it

Zero-point quantum swing of magnetic couples

Quantum fluctuations are ubiquitous in physics. Ranging from conventional examples like the harmonic oscillator to intricate theories on the origin of the universe, they alter virtually all aspects of matter -- including superconductivity, phase transitions and nanoscale processes. As a rule of thumb, the smaller the object, the larger their impact. This poses a serious challenge to modern nanotechnology, which aims total control via atom-by-atom engineered devices. In magnetic nanostructures, high stability of the magnetic signal is crucial when targeting realistic applications in information technology, e.g. miniaturized bits. Here, we demonstrate that zero-point spin-fluctuations are paramount in determining the fundamental magnetic exchange interactions that dictate the nature and stability of the magnetic state. Hinging on the fluctuation-dissipation theorem, we establish that quantum fluctuations correctly account for the large overestimation of the interactions as obtained from conventional static first-principles frameworks, filling in a crucial gap between theory and experiment [1,2]. Our analysis further reveals that zero-point spin-fluctuations tend to promote the non-collinearity and stability of chiral magnetic textures such as skyrmions -- a counter-intuitive quantum effect that inspires practical guidelines for designing disruptive nanodevices

Perpendicular Reading of Single Confined Magnetic Skyrmions

Thin-film sub-5 nm magnetic skyrmions constitute an ultimate scaling alternative for future digital data storage. Skyrmions are robust non-collinear spin-textures that can be moved and manipulated by small electrical currents. We show here an innovative technique to detect isolated nanoskyrmions with a current-perpendicular-to-plane geometry, which has immediate implications for device concepts. We explore the physics behind such a mechanism by studying the atomistic electronic structure of the magnetic quasiparticles. We investigate how the isolated skyrmion local-density-of-states which tunnels into the vacuum, when compared to the ferromagnetic background, is modified by the site-dependent spin-mixing of electronic states with different relative canting angles. Local transport properties are sensitive to this effect, as we report an atomistic conductance anisotropy of over 20% for magnetic skyrmions in Pd/Fe/Ir(111) thin-films. In single skyrmions, engineering this spin-mixing magnetoresistance possibly could be incorporated in future magnetic storage technologies

Toward a new interpretation of the mechanical behaviour of As-quenched low alloyed martensitic steels

International audienceThough as-quenched martensite exhibits a low uniform elongation in tension, it is highlighted that this phase has a very high strain-hardening which increases with carbon content and a large Bauschinger effect. Because usual dislocation storage can not explain reasonably this particular behaviour, an approach based on a continuum composite view of martensite (CCA) is developed suitable to capture all the experimental features

Resultat du traitement d’un craniopharyngiome kystique par de la bleomycine

Introduction Le craniopharyngiome est une tumeur bénigne qui provient de nids épithéliaux ou de zones de métaplasies squameuses liées à l’embryogenèse hypophysaire. Touchant surtout l’enfant, peut être potentiellement agressive et caractérisée par un taux élevé de récidive après traitement chirurgical. La bléomycine représente une des molécules de chimiothérapie utilisée souvent dans le traitement insitu dans le craniopharyngiome kystique. L’objectif de notre étude est d’évaluer les résultats clinique et radiologique du traitement d’un craniopharyngiome par la bléomycine et comparer notre expérience à celle de la littérature. Observation Nous avons analysé le dossier de la patiente B. Rania âgée de 11 ans. Elle présente un craniopharyngiome kystique intra et supra sellaire à extension frontale, traité par chimiothérapie intra tumorale (bléomycine), durant la période allant de 2003 à 2004 et suivi jusqu’à présent au service de neurochirurgie du CHU de Annaba- Algérie. Résultat La patiente présentait à son admission une hypertension intracrânienne et une somnolence depuis 24 heures d’où sa ponction en urgence à travers le réservoir d’Ommaya déjà placé auparavant dans un autre service de neurochirurgie. Quatre mois plus tard, la patiente a bénéficié d’un cycle de chimiothérapie étalé sur une période de 20 jours, la dose totale de bléomycine était de 51,5mg soit 2 à 3 mg par dose avec un espacement de 48 à 72 heures ; le volume de la tumeur avant la chimiothérapie était de 46 mm dans son grand axe, à la fin du traitement par la bléomycine, nous constatons une calcification total du kyste après un contrôle scannographique en 2007. Conclusion Le traitement du craniopharyngiome par la bléomycine insitu a donné des résultats satisfaisants. Notre expérience est la première à l’échelle nationale. En espérant que cette expérience se généralise en Algérie afin de mieux nous éclairés à l’avenir.Mots clés : Craniopharyngiome, réservoir d’Ommaya, bléomycine, calcification

Thin film solar cells based on the ternary compound Cu2SnS3

Alongside with Cu2ZnSnS4 and SnS, the p-type semiconductor Cu2SnS3 also consists of only Earth abundant and low-cost elements and shows comparable opto-electronic properties, with respect to Cu2ZnSnS4 and SnS, making it a promising candidate for photovoltaic applications of the future. In this work, the ternary compound has been produced via the annealing of an electrodeposited precursor in a sulfur and tin sulfide environment. The obtained absorber layer has been structurally investigated by X-ray diffraction and results indicate the crystal structure to be monoclinic. Its optical properties have been measured via photoluminescence, where an asymmetric peak at 0.95 eV has been found. The evaluation of the photoluminescence spectrum indicates a band gap of 0.93 eV which agrees well with the results from the external quantum efficiency. Furthermore, this semiconductor layer has been processed into a photovoltaic device with a power conversion efficiency of 0.54%, a short circuit current of 17.1 mA/cm2, an open circuit voltage of 104 mV hampered by a small shunt resistance, a fill factor of 30.4%, and a maximal external quantum efficiency of just less than 60%. In addition, the potential of this Cu2SnS3 absorber layer for photovoltaic applications is discussed

Dynamical amplification of magnetoresistances and Hall currents up to the THz regime

Spin-orbit-related effects offer a highly promising route for reading and writing information in magnetic units of future devices. These phenomena rely not only on the static magnetization orientation but also on its dynamics to achieve fast switchings that can reach the THz range. In this work, we consider Co/Pt and Fe/W bilayers to show that accounting for the phase difference between different processes is crucial to the correct description of the dynamical currents. By tuning each system towards its ferromagnetic resonance, we reveal that dynamical spin Hall angles can non-trivially change sign and be boosted by over 500%, reaching giant values. We demonstrate that charge and spin pumping mechanisms can greatly magnify or dwindle the currents flowing through the system, influencing all kinds of magnetoresistive and Hall effects, thus impacting also dc and second harmonic experimental measurements.Comment: 19 pages, 4 figures, Supplementary Informatio

Modelling the effect of carbon on deformation behaviour of twinning induced plasticity steels

In this article, a physical model describing the deformation behaviour of Twinning Induced Plasticity(TWIP) steels has been extended to include the effect of carbon content. The experimental validation and the analysis show that carbon mainly controls the maximum number of dislocations piled up at the twin boundary, resulting in the increase of back-stresses (i.e. kinematic hardening) and therefore the work hardening rate. This explanation seems to be in agreement with recent TEM observations. © The Author(s) 2011. This article is published with open access at Springerlink.com. © Springer Science+Business Media, LLC 2011.published_or_final_versionSpringer Open Choice, 21 Feb 201

Le xanthoastrocytome pleomorphe anaplasique - A propos d’un cas

We report a case of anaplastic pleomorphic xanthoastrocytoma occurred in a male of 13 years, who presented a syndrom of intracranial hypertension for a year and a half. CT-scan and MRI revealed a cystic and solid tumor in the left parietal lobe. The surgical resection was total. Histopathological examination demonstrated a pleomorphic xanthoastrocytoma with malignant transformation. Seven months later, the patient has a  deterioration of his general condition, the CT revealed a tumor recurrence, which was reoperated. The patient died a few days after surgery. This rare case of anaplastic pleomorphic xanthoastrocytoma is presented, discussed and illustrated in this paper.Nous rapportons un cas de xanthoastrocytome pléomorphe anaplasique chez un garçon de 13 ans. Il présentait un syndrome d’hypertension intracrânienne depuis un an et demi. L’imagerie a visualisé une lésion à double composante kystique et charnue de localisation pariétale gauche. L’exérèse chirurgicale a été totale. L’examen histologique a revélé un xanthoastrocytome pléomorphe anaplasique. Sept mois plus tard, le patient a présenté une altération de l’état général, et le scanner  encéphalique a montré une récidive tumorale qui a été réopérée. Le patient est décédé quelques jours après l’intervention