40,248 research outputs found

    Splash jet generated by collision of two liquid wedges

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    A complete nonlinear self-similar solution that characterizes the impact of two liquid wedges symmetric about the velocity direction is obtained assuming the liquid to be ideal and incompressible, with negligible surface tension and gravity effects. Employing the integral hodograph method, analytical expressions for the complex potential and for its derivatives are derived. The boundary value problem is reduced to two integro-differential equations in terms of the velocity modulus and angle to the free surface. Numerical results are presented in a wide range of wedge angles for the free surface shapes, streamline patterns, and pressure distributions. It is found that the splash jet may cause secondary impacts. The regions with and without secondary impacts in the plane of the wedge angles are determined

    Level-Based Analysis of the Population-Based Incremental Learning Algorithm

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    The Population-Based Incremental Learning (PBIL) algorithm uses a convex combination of the current model and the empirical model to construct the next model, which is then sampled to generate offspring. The Univariate Marginal Distribution Algorithm (UMDA) is a special case of the PBIL, where the current model is ignored. Dang and Lehre (GECCO 2015) showed that UMDA can optimise LeadingOnes efficiently. The question still remained open if the PBIL performs equally well. Here, by applying the level-based theorem in addition to Dvoretzky--Kiefer--Wolfowitz inequality, we show that the PBIL optimises function LeadingOnes in expected time O(nλlogλ+n2)\mathcal{O}(n\lambda \log \lambda + n^2) for a population size λ=Ω(logn)\lambda = \Omega(\log n), which matches the bound of the UMDA. Finally, we show that the result carries over to BinVal, giving the fist runtime result for the PBIL on the BinVal problem.Comment: To appea

    Parton Distributions for Event Generators

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    In this paper, conventional Global QCD analysis is generalized to produce parton distributions optimized for use with event generators at the LHC. This optimization is accomplished by combining the constraints due to existing hard-scattering experimental data with those from anticipated cross sections for key representative SM processes at LHC (by the best available theory) as joint input to the global analyses. The PDFs obtained in these new type of global analyses using matrix elements calculated in any given order will be best suited to work with event generators of that order, for predictions at the LHC. This is most useful for LO event generators at present. Results obtained from a few candidate PDF sets (labeled as CT09MCS, CT09MC1 and CT09MC2) for LO event generators produced in this way are compared with those from other approaches.Comment: 35 pages, 19 figures, and 4 table

    Line-symmetric motion generators

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    When a rigid body is axially reflected through a moving line, its image undergoes a so-called line-symmetricmotion. The space comprising all possible line-symmetric motions that share a common initial line is a four-dimensional submanifold, denoted M4, in the special Euclidean group SE(3). Recently, we showed that M4 may be used to characterize motions of a line-symmetric body that are free of self-spin and sliding, thus lending itself to applications such as remote center of motion devices for minimal invasive surgery and haptic interfaces. Aiming at designing robot mechanisms for these applications, we present in this paper a systematic enumeration of line-symmetric motion generators (LSMGs), i.e., robot mechanisms that generate the line-symmetric motion manifold M4, following a procedure based on symmetric space theory. LSMGs present a ubiquitous line symmetry of their joint axes, thus offering a new understanding of the line-symmetric motions

    Norcantharidin (NCTD) induces mitochondria mediated apoptosis in human HepG2 cells

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    Norcantharidin (NCTD), a demethylated form of cantharidin, is now in used as a routine anticancer drug. However, the detailed mechanisms underlying this process are generally unclear. The aims of this study were to evaluate the apoptotic effects and molecular mechanisms of NCTD. MTT assay was used to determine the cell growth inhibitory rate. Flow cytometry were used to detect the apoptosis and the loss of mitochondrial membrane potential (Δψm) induced by NCTD. Caspase detection kit were used to detect the activity of caspase-3 -9. Western-blot was used to detect the expression of Bcl-2, Bax and cytochrome C (cyt C). Our results indicated that, treatment of NCTD resulted in significant decrease in cell viability in a dose-and time-dependent manner. A dose-dependent apoptosis was also observed by flow cytometery analysis. Molecular mechanistic studies of apoptosis revealed that, NCTD treatment resulted in a significant loss of Δψm, release of cyt C, enhanced expression of pro-apoptotic protein Bax and suppression of anti-apoptotic protein Bcl-2. These were followed by activation of caspases-9 and -3, subsequently leading to cell apoptosis. These results indicate that, NCTD induced cytotoxicity in HepG2 cells by apoptosis, which is mediated through mitochondrial pathway.Key words: Norcantharidin, apoptosis, caspase, Bax/Bcl-2, cyto C, HepG2 cells

    Generalized Hamacher aggregation operators for intuitionistic uncertain linguistic sets: Multiple attribute group decision making methods

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    © 2019 by the authors. In this paper, we consider multiple attribute group decision making (MAGDM) problems in which the attribute values take the form of intuitionistic uncertain linguistic variables. Based on Hamacher operations, we developed several Hamacher aggregation operators, which generalize the arithmetic aggregation operators and geometric aggregation operators, and extend the algebraic aggregation operators and Einstein aggregation operators. A number of special cases for the two operators with respect to the parameters are discussed in detail. Also, we developed an intuitionistic uncertain linguistic generalized Hamacher hybrid weighted average operator to reflect the importance degrees of both the given intuitionistic uncertain linguistic variables and their ordered positions. Based on the generalized Hamacher aggregation operator, we propose a method for MAGDM for intuitionistic uncertain linguistic sets. Finally, a numerical example and comparative analysis with related decision making methods are provided to illustrate the practicality and feasibility of the proposed method

    Age-related enhancement of the slow outward calcium-activated potassium current in hippocampal CA1 pyramidal neurons in vitro

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    Aging is associated with learning deficits and a decrease in neuronal excitability, reflected by an enhanced post-burst afterhyperpolarization (AHP), in CA1 hippocampal pyramidal neurons. To identify the current(s) underlying the AHP altered in aging neurons, whole-cell voltage-clamp recording experiments were performed in hippocampal slices from young and aging rabbits. Similar to previous reports, aging neurons were found to rest at more hyperpolarized potentials and have larger AHPs than young neurons. Given that compounds that reduce the slow outward calcium-activated potassium current (sI(AHP)), a major constituent of the AHP, also facilitate learning in aging animals, the sI(AHP) was pharmacologically isolated and characterized. Aging neurons were found to have an enhanced sI(AHP), the amplitude of which was significantly correlated to the amplitude of the AHP (r = 0.63; p < 0.001). Thus, an enhanced sI(AHP) contributes to the enhanced AHP in aging. No differences were found in the membrane resistance, capacitance, or kinetic and voltage-dependent properties of the sI(AHP). Because enhanced AHP in aging neurons has been hypothesized to be secondary to an enhanced Ca2+ influx via the voltage-gated L-type Ca2+ channels, we further examined the sI(AHP) in the presence of an L-type Ca2+ channel blocker, nimodipine (10 μM). Nimodipine caused quantitatively greater reductions in the sIAHP in aging neurons than in young neurons; however, the residual sIAHP was still significantly larger in aging neurons than in young neurons. Our data, in conjunction with previous studies showing a correlation between the AHP and learning, suggest that the enhancement of the sIAHP in aging is a mechanism that contributes to age-related learning deficits
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