Effect of multiaxial forging on microstructure and mechanical properties of Mg-0.8Ca alloy

It was shown that multiaxial forging with continuous decrease of temperature from 450°C to 250°C turns coarse structure of the Mg-0.8Ca alloy in homogenized state with grain size of several hundreeds μm into fine structure with average grain size of about 2.1 μm. Refinement of structure is accompanied by drastic increase of mechanical properties: tensile yield strength increases from 50 MPa to 193 MPa, ultimate tensile strength increases from 78 to 308 MPa and elongation to fracture increases from 3.0% to 7.2%. The microstructural evolution during multiaxial forging is studied using optical microscopy, scanning electron microscopy and EBSD analysis. The mechanisms responsible for refinement of microstructure are discusse

Escape orbits and Ergodicity in Infinite Step Billiards

In a previous paper we defined a class of non-compact polygonal billiards, the infinite step billiards: to a given decreasing sequence of non-negative numbers $\{p_{n}$, there corresponds a table \Bi := \bigcup_{n\in\N} [n,n+1] \times [0,p_{n}]. In this article, first we generalize the main result of the previous paper to a wider class of examples. That is, a.s. there is a unique escape orbit which belongs to the alpha and omega-limit of every other trajectory. Then, following a recent work of Troubetzkoy, we prove that generically these systems are ergodic for almost all initial velocities, and the entropy with respect to a wide class of ergodic measures is zero.Comment: 27 pages, 8 figure

Scattering in flatland: Efficient representations via wave atoms

This paper presents a numerical compression strategy for the boundary integral equation of acoustic scattering in two dimensions. These equations have oscillatory kernels that we represent in a basis of wave atoms, and compress by thresholding the small coefficients to zero. This phenomenon was perhaps first observed in 1993 by Bradie, Coifman, and Grossman, in the context of local Fourier bases \cite{BCG}. Their results have since then been extended in various ways. The purpose of this paper is to bridge a theoretical gap and prove that a well-chosen fixed expansion, the nonstandard wave atom form, provides a compression of the acoustic single and double layer potentials with wave number $k$ as $O(k)$-by-$O(k)$ matrices with $O(k^{1+1/\infty})$ nonnegligible entries, with a constant that depends on the relative $\ell_2$ accuracy \eps in an acceptable way. The argument assumes smooth, separated, and not necessarily convex scatterers in two dimensions. The essential features of wave atoms that enable to write this result as a theorem is a sharp time-frequency localization that wavelet packets do not obey, and a parabolic scaling wavelength $\sim$ (essential diameter)${}^2$. Numerical experiments support the estimate and show that this wave atom representation may be of interest for applications where the same scattering problem needs to be solved for many boundary conditions, for example, the computation of radar cross sections.Comment: 39 page

Complexity Analysis of a Fast Directional Matrix-Vector Multiplication

We consider a fast, data-sparse directional method to realize matrix-vector products related to point evaluations of the Helmholtz kernel. The method is based on a hierarchical partitioning of the point sets and the matrix. The considered directional multi-level approximation of the Helmholtz kernel can be applied even on high-frequency levels efficiently. We provide a detailed analysis of the almost linear asymptotic complexity of the presented method. Our numerical experiments are in good agreement with the provided theory.Comment: 20 pages, 2 figures, 1 tabl

Computational Physics on Graphics Processing Units

The use of graphics processing units for scientific computations is an emerging strategy that can significantly speed up various different algorithms. In this review, we discuss advances made in the field of computational physics, focusing on classical molecular dynamics, and on quantum simulations for electronic structure calculations using the density functional theory, wave function techniques, and quantum field theory.Comment: Proceedings of the 11th International Conference, PARA 2012, Helsinki, Finland, June 10-13, 201

Automatic simultaneous measurement of phase velocity and thickness in composite plates using iterative deconvolution

A new method for the automatic and simultaneous measurement of phase velocity and thickness for thin composite plates was developed based on Ping He's method, without any need of a priori knowledge of the material parameters. Two composites were analyzed: a block of clean epoxy and a thin specimen of glass-fiber reinforced plastic produced by resin transfer molding. The proposed method combines cross-correlation functions and iterative deconvolution for accurate measurement of times of flight and gating. The new method has demonstrated to be more accurate than conventional Ping He's method, and can be implemented automatically thus saving processing time and increasing accuracy.This research was funded by a Project IN-SMART, Grant no. VP1-3.1SMM-10-V-02-012 and by the Spanish Ministerio de Ciencia e Innovacion (TEC2011-23403).Rodriguez Martinez, A.; Svilainis, L.; Dumbrava, V.; Chaziachmetovas, A.; Salazar Afanador, A. (2014). Automatic simultaneous measurement of phase velocity and thickness in composite plates using iterative deconvolution. NDT and E International. 66:117-127. https://doi.org/10.1016/j.ndteint.2014.06.001S1171276

Bcl-2 protein family: Implications in vascular apoptosis and atherosclerosis

Apoptosis has been recognized as a central component in the pathogenesis of atherosclerosis, in addition to the other human pathologies such as cancer and diabetes. The pathophysiology of atherosclerosis is complex, involving both apoptosis and proliferation at different phases of its progression. Oxidative modification of lipids and inflammation differentially regulate the apoptotic and proliferative responses of vascular cells during progression of the atherosclerotic lesion. Bcl-2 proteins act as the major regulators of extrinsic and intrinsic apoptosis signalling pathways and more recently it has become evident that they mediate the apoptotic response of vascular cells in response to oxidation and inflammation either in a provocative or an inhibitory mode of action. Here we address Bcl-2 proteins as major therapeutic targets for the treatment of atherosclerosis and underscore the need for the novel preventive and therapeutic interventions against atherosclerosis, which should be designed in the light of molecular mechanisms regulating apoptosis of vascular cells in atherosclerotic lesions

Mathematical model of a telomerase transcriptional regulatory network developed by cell-based screening: analysis of inhibitor effects and telomerase expression mechanisms

Cancer cells depend on transcription of telomerase reverse transcriptase (TERT). Many transcription factors affect TERT, though regulation occurs in context of a broader network. Network effects on telomerase regulation have not been investigated, though deeper understanding of TERT transcription requires a systems view. However, control over individual interactions in complex networks is not easily achievable. Mathematical modelling provides an attractive approach for analysis of complex systems and some models may prove useful in systems pharmacology approaches to drug discovery. In this report, we used transfection screening to test interactions among 14 TERT regulatory transcription factors and their respective promoters in ovarian cancer cells. The results were used to generate a network model of TERT transcription and to implement a dynamic Boolean model whose steady states were analysed. Modelled effects of signal transduction inhibitors successfully predicted TERT repression by Src-family inhibitor SU6656 and lack of repression by ERK inhibitor FR180204, results confirmed by RT-QPCR analysis of endogenous TERT expression in treated cells. Modelled effects of GSK3 inhibitor 6-bromoindirubin-3′-oxime (BIO) predicted unstable TERT repression dependent on noise and expression of JUN, corresponding with observations from a previous study. MYC expression is critical in TERT activation in the model, consistent with its well known function in endogenous TERT regulation. Loss of MYC caused complete TERT suppression in our model, substantially rescued only by co-suppression of AR. Interestingly expression was easily rescued under modelled Ets-factor gain of function, as occurs in TERT promoter mutation. RNAi targeting AR, JUN, MXD1, SP3, or TP53, showed that AR suppression does rescue endogenous TERT expression following MYC knockdown in these cells and SP3 or TP53 siRNA also cause partial recovery. The model therefore successfully predicted several aspects of TERT regulation including previously unknown mechanisms. An extrapolation suggests that a dominant stimulatory system may programme TERT for transcriptional stability

Extrafocal transcutaneous transpedicular fixation as the stage of surgical treatment of inflammatory diseases of the spine

Trachelokyphosis and hematogenous osteomielitis of the spine are common and crippling diseases, in most cases leading to disability. Surgical treatment of inflammatory diseases of the spine is a rather complicated problem due to the fact that often in the postoperative period, an increase in spinal deformity, fracture and resorption of the transplants, festering in the area of plastics. The basis of modern surgical treatment of tuberculosis spondylitis (Pott's disease) is a radical reconstruction of the spine, including the complete removal of the damaged vertebral body abscesses, anterior decompression of the spinal cord and anterior spinal fusion The goal was to analyze the short - and long-term results of open and minimally invasive transpedicular fixation of thoracic and lumbar spine in inflammatory diseases of the spine.The material of this work based on 65 cases with tuberculosis spondylitis (Pott's disease) and nonspecific spondylitis of thoracic and lumbar segments of spine, operated in 2008-2010. In to the main group 35 patients were involved with single and double lower thoracic spine and lumbar spine lesions at the age of 25 to 70 years after surgery with minimally invasive transcutaneous transpedicular fixation (TTF). The control group included 30 patients with tuberculosis spondylitis (Pott's disease) of the thoracic and lumbar segments of spine with conventional open transpedicular internal fixation (TIF). Conclusion. Minimally invasive technology can reduce the period of preparation for surgery in patients with concomitant somatic pathology, reduce operational manuals and traumatic blood loss, trauma of a large array of soft tissue, to provide early mobilization patients despite the severity of degradation of the spine and to ensure good quality of life for a period of prolonged antibiotic and / or anti-tuberculosis therapy.Туберкулезный спондилит и гематогенный остеомиелитпозвоночника до настоящего времени остаются распространенными и калечащими заболеваниями, в большинстве случаев ведущими к инвалидности. Хирургическое лечение воспалительных заболеваний позвоночника до настоящего времени представляет достаточно сложную проблему в связи с тем, что нередко в послеоперационном периоде наблюдается увеличение деформации позвоночника, резорбция и перелом трансплантатов, нагноение в зоне пластики. Основу современного хирургического лечения туберкулезного спондилита составляет радикальная реконструкция позвоночника, включающая полное удаление разрушенных тел позвонков, абсцессов, переднюю декомпрессию спинного мозга и передний спондилодез.Цель исследования: анализ ближайших и отдаленных результатов применения открытой и малоинвазивной транспедикулярной фиксации грудного и поясничного отделов позвоночника при воспалительных заболеваниях позвоночника. Материалом для настоящей работы послужили исследования историй болезней 65 пациентов с туберкулезным и неспецифическим спондилитом грудных и поясничных сегментов, оперированных в период с 2008 по 2010 годы. В основную группу включены 35 больных с одно- и двухсегментарным поражением нижнегрудного и поясничного отделов позвоночника в возрасте от 25 до 70 лет, оперированных с применением минимально-инвазивной транскутанной транспедикулярной фиксации (ТТФ). В группу контроля включены 30 пациентов с туберкулезным спондилитом грудных и поясничных сегментов с применением традиционной открытой внутренней транспедикулярной фиксацией (ОТФ).Заключение. Минимально-инвазивная технология позволяет сократить период подготовки к операции у пациентов с сопутствующей соматической патологией, снизить травматичность оперативного пособия и кровопотерю.травматизацию большого массива мягких тканей, обеспечить раннюю активизацию пациента несмотря на выраженность деструкции позвоночника и обеспечить приемлемое качество жизни на период длительной антибактериальной и/или противотуберкулёзной терапии