70 research outputs found

    Excess-entropy scaling in supercooled binary mixtures

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    Supercooled liquids near the glass transition show remarkable non-Arrhenius transport phenomena, whose origin is yet to be clarified. Here, the authors use GPU molecular dynamics simulations for various binary mixtures in the supercooled regime to show the validity of a quasiuniversal excess-entropy scaling relation for viscosity and diffusion

    Review of Coronal Oscillations - An Observer's View

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    Recent observations show a variety of oscillation modes in the corona. Early non-imaging observations in radio wavelengths showed a number of fast-period oscillations in the order of seconds, which have been interpreted as fast sausage mode oscillations. TRACE observations from 1998 have for the first time revealed the lateral displacements of fast kink mode oscillations, with periods of ~3-5 minutes, apparently triggered by nearby flares and destabilizing filaments. Recently, SUMER discovered with Doppler shift measurements loop oscillations with longer periods (10-30 minutes) and relatively short damping times in hot (7 MK) loops, which seem to correspond to longitudinal slow magnetoacoustic waves. In addition, propagating longitudinal waves have also been detected with EIT and TRACE in the lowest density scale height of loops near sunspots. All these new observations seem to confirm the theoretically predicted oscillation modes and can now be used as a powerful tool for ``coronal seismology'' diagnostic.Comment: 5 Figure

    Molecular dynamics simulations of non-equilibrium systems

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    Влияние фосфатных связующих на физико-механические свойства периклазохромитовых огнеупоров

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    У данній статті наведено та порівняно фізико-механічні властивості периклазо-хромітових матеріалів в залежності від різних типів фосфатних зв’язуючих та введення різних домішок. Визначено, що найбільш раціональним є введення триполіфосфату натрію.In given clause are resulted and the physycal-mechanical properties periclase-cgromite of materials are compared depending on different of types phosphate binding and introduction of the various additives. Is determined, that most rational is the introduction treepolyphosphate sodume

    Macrophage signaling in HIV-1 infection

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    The human immunodeficiency virus-1 (HIV-1) is a member of the lentivirus genus. The virus does not rely exclusively on the host cell machinery, but also on viral proteins that act as molecular switches during the viral life cycle which play significant functions in viral pathogenesis, notably by modulating cell signaling. The role of HIV-1 proteins (Nef, Tat, Vpr, and gp120) in modulating macrophage signaling has been recently unveiled. Accessory, regulatory, and structural HIV-1 proteins interact with signaling pathways in infected macrophages. In addition, exogenous Nef, Tat, Vpr, and gp120 proteins have been detected in the serum of HIV-1 infected patients. Possibly, these proteins are released by infected/apoptotic cells. Exogenous accessory regulatory HIV-1 proteins are able to enter macrophages and modulate cellular machineries including those that affect viral transcription. Furthermore HIV-1 proteins, e.g., gp120, may exert their effects by interacting with cell surface membrane receptors, especially chemokine co-receptors. By activating the signaling pathways such as NF-kappaB, MAP kinase (MAPK) and JAK/STAT, HIV-1 proteins promote viral replication by stimulating transcription from the long terminal repeat (LTR) in infected macrophages; they are also involved in macrophage-mediated bystander T cell apoptosis. The role of HIV-1 proteins in the modulation of macrophage signaling will be discussed in regard to the formation of viral reservoirs and macrophage-mediated T cell apoptosis during HIV-1 infection

    Effect of the actuation phase on the SIF in delaminated composites with embedded piezoelectric layers

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    The effect of the phase of harmonic actuation on the stress intensity factor(SIF) for delaminated composites with embedded piezoelectric (PZT) layers is studied. A plane-stress finite-element model using a four-node quadrilateral element having one active degree of freedom per node is developed. A fracture mechanics-based approach, which uses a general purpose computational scheme to obtain the strain energy release rate and the SIF due to delamination in orthotropic laminated composite, is employed. The performance of the finite-element result is first validated using the results reported in published literature. A composite double cantilever beam specimen with three embedded PZT layers around the tip of the delamination is considered for actuation. Numerical simulations on the effects of actuation voltage and phase on mode-II SIF are carried out. The results show that for a specified voltage amplitude to the embedded actuators, the actuation phase can have a significant influence on delamination growth

    An iterative system equivalent reduction expansion process for extraction of high frequency response from reduced order finite element model

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    An iterative system equivalent reduction expansion process (SEREP) is proposed for extraction of high frequency response from a reduced-order model (ROM) under frequency band-limited excitation. Various model order reduction methods are discussed. To alleviate the present drawback of the SEREP, which requires computation of full system modal matrix, an iterative method based on Sturm sequence check is proposed. The method uses eigenvalue separation properties on the excitation frequency band to identify the optimal number of the eigenpairs required to capture the accurate response. The basic steps for numerical implementation are given. Numerical results are presented to validate the predicted response. Comparison is also made to explain the reasons for the instability of the ROM based on dynamic condensation to capture the high frequency dynamics. Case studies are carried out to demonstrate the effect of the chosen frequency band for response extraction. Also, it is shown that accurate results are obtained while using the proposed method when the chosen frequency band encompass the excitation frequency band
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