Finite element model for vibration and buckling of functionally graded sandwich beams based on a refined shear deformation theory

Finite element model for vibration and buckling of functionally graded sandwich beams based on a refined shear deformation theory is presented. The core of sandwich beam is fully metal or ceramic and skins are composed of a functionally graded material across the depth. Governing equations of motion and boundary conditions are derived from the Hamilton’s principle. Effects of power-law index, span-to-height ratio, core thickness and boundary conditions on the natural frequencies, critical buckling loads and load–frequency curves of sandwich beams are discussed. Numerical results show that the above-mentioned effects play very important role on the vibration and buckling analysis of functionally graded sandwich beams

Concomitant homozygosity for the prothrombin gene variant with mild deficiency of antithrombin III in a patient with multiple hepatic infarctions: a case report

<p>Abstract</p> <p>Introduction</p> <p>Hereditary causes of visceral thrombosis or thrombosis should be sought among young patients. We present a case of a young man presenting with multiple hepatic infarctions resulting in portal hypertension due to homozygosity of the prothrombin gene mutation not previously described in literature.</p> <p>Case presentation</p> <p>A 42-year-old Caucasian man with a previous history of idiopathic deep vein thrombosis 11 years earlier presented with vague abdominal pains and mildly abnormal liver function tests. An ultrasound and computed tomography scan showed evidence of hepatic infarction and portal hypertension (splenic varices). A thrombophilia screen confirmed a homozygous mutation for the prothrombin gene mutation, with mildly reduced levels of anti-thrombin III (AT III). Subsequent testing of his father and brother revealed heterozygosity for the same gene mutation.</p> <p>Conclusion</p> <p>Hepatic infarction is unusual due to the rich dual arterial and venous blood supply to the liver. In the absence of an arterial or haemodynamic insult causing hepatic infarction, a thrombophilia should be considered. To our knowledge, this is the first reported case of a hepatic infarction due to homozygosity of the prothrombin gene mutation. It is unclear whether homozygotes have a higher risk of thrombosis than heterozygotes. In someone presenting with a first thrombosis with this mutation, the case for life-long anticoagulation is unclear, but it may be necessary to prevent a second and more severe second thrombotic event, as occurred in this case.</p

Калибровочные коэффициенты для определения концентрации вакансионно-кислородных комплексов и кислородного димера в кремнии методом ИК-поглощения

Vacancy-oxygen complexes VnOm (n, m ≥ 1) in crystalline silicon are nucleation centers for oxygen precipitates, which are widely used as internal getters in modern technologies of production of silicon-based electronic devices and integrated circuits. For the controllable formation of oxygen precipitates in Si crystals in the technology processes the methods of determination of concentrations of the VnOm complexes are required. The aim of the present work was to find values of the calibration coefficients for determination of concentrations of the VnOm defects in Si from intensities of infrared (IR) absorption bands associated with the local vibrational modes (LVM) of these complexes. A combined electrical (Hall effect) and optical (IR absorption) study of vacancy-oxygen defects in identical silicon crystals irradiated with 6 MeV electrons was carried out. Based on the analysis of the data obtained, the values of the calibration coefficient for the determination of concentration of the vacancy-oxygen (VO) complex in silicon by the infrared absorption method were established: for measurements at room temperature (RT) – NVO = 8.5 · 1016 · αVO-RT cm–3, in the case of low-temperature (LT, Т ≡ 10 K) measurements – NVO = 3.5 · 1016 · αVO-LT cm–3, where αVO-RT(LT) are absorption coefficients in maxima of the LVM bands due to the VO complex in the spectra measured at corresponding temperatures. Calibration coefficients for the determination of concentrations of other VnOm (VO2, VO3, VO4, V2O and V3O) complexes and the oxygen dimer (O2) from an analysis of infrared absorption spectra measured at room temperature have been also determined.Вакансионно-кислородные комплексы VnOm (n, m ≥ 1) в кристаллах кремния являются центрами зарождения кислородных преципитатов, которые широко используются в качестве внутренних геттеров нежелательных примесей в современных технологиях изготовления кремниевых электронных приборов и интегральных ми кросхем. Для контролируемого формирования кислородных преципитатов в кристаллах Si в технологических процессах необходимы методы измерения концентрации комплексов VnOm. Целью настоящей работы было нахождение калибровочных коэффициентов для определения концентрации вакансионно-кислородных дефектов в кремнии из интенсивностей полос инфракрасного (ИК) поглощения, связанных с локальными колебательными модами (ЛКМ) этих комплексов. С использованием электрических (эффект Холла) и оптических (ИК поглощение) измерений проведено комплексное исследование вакансионно-кислородных центров в кристаллах кремния, облученных электронами с энергией 6 МэВ. На основе анализа полученных данных установлены значения калибровочных коэффициентов для определения концентрации комплекса вакансия-кислород (VO) в кремнии методом инфракрасного поглощения: для измерений при комнатной температуре (RT) – NVO = 8,5 · 1016 · αVO-RT см–3, в случае низкотемпературных (LT, Т ≡ 10 К) измерений – N VO = 3,5 · 1016 · αVO-LT см–3, где αVO-RT(LT) – коэффициенты поглощения в максимумах полос ЛКМ комплекса VO в спектрах, измеренных при соответствующей температуре. Установлены также калибровочные коэффициенты для определения концентраций других вакансионно-кислородных комплексов VnOm (VO2, VO3, VO4, V2O и V3O) и кислородного димера (O2) из анализа спектров поглощения измеренных при комнатной температуре