4,379 research outputs found

    On the order reduction

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    In this work we present an extension of the technique of the order reduction to higher perturbative approximations in an iterative fashion. The intention is also to analyze more carefully the conditions for the validity of the order reduction technique. With this in mind, a few simple situations in which the iterative order reduction converges analytically to the exact solutions are presented as examples. It is discovered that the order reduction as a perturbative iterative technique does not converge in the weak coupling limit as most of the known perturbative schemes, at least when applied to these examples. Also, considering these specific examples, the convergence of the order reduction occurs in strong coupling regimes. As a more realistic case, the order reduction is applied to Starobinsky's inflationary model is presented. It is verified that the method converges to the inflationary solution in the slow-roll regime

    Route Planning in Transportation Networks

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    We survey recent advances in algorithms for route planning in transportation networks. For road networks, we show that one can compute driving directions in milliseconds or less even at continental scale. A variety of techniques provide different trade-offs between preprocessing effort, space requirements, and query time. Some algorithms can answer queries in a fraction of a microsecond, while others can deal efficiently with real-time traffic. Journey planning on public transportation systems, although conceptually similar, is a significantly harder problem due to its inherent time-dependent and multicriteria nature. Although exact algorithms are fast enough for interactive queries on metropolitan transit systems, dealing with continent-sized instances requires simplifications or heavy preprocessing. The multimodal route planning problem, which seeks journeys combining schedule-based transportation (buses, trains) with unrestricted modes (walking, driving), is even harder, relying on approximate solutions even for metropolitan inputs.Comment: This is an updated version of the technical report MSR-TR-2014-4, previously published by Microsoft Research. This work was mostly done while the authors Daniel Delling, Andrew Goldberg, and Renato F. Werneck were at Microsoft Research Silicon Valle

    Abrupt Rise of the Longitudinal Recoil Ion Momentum Distribution for Ionizing Collisions

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    We report on the experimental observation of an abrupt rise in the longitudinal momentum distribution of recoil ions created in proton helium collision. The details of this structure can be related to electrons traveling with the velocity of the projectile [electron capture to the continuum (ECC)]. The longitudinal as well as the transverse distribution of the recoil ions can be explained as a continuation of the momentum distribution from ions resulting from electron capture illustrating the smooth transition from the capture to bound states of the projectile to the ECC.Fil: Weber, Th.. Institut für Kernphysik; AlemaniaFil: Khayyat, Kh.. Institut für Kernphysik; AlemaniaFil: Dörner, R.. Universität Freiburg; AlemaniaFil: Rodríguez Chariarse, Vladimir Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Mergel, V.. Institut für Kernphysik; AlemaniaFil: Jagutzk, O.. Institut für Kernphysik; AlemaniaFil: Schmidt, L.. Institut für Kernphysik,; AlemaniaFil: Müller, K. A.. Institut für Kernphysik; AlemaniaFil: Afaneh, F.. Institut für Kernphysik; AlemaniaFil: Gonzalez, A.. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Schmidt-Böcking, H.. Institut für Kernphysik; Alemani

    "WissensWert - Wert des Wissens": Kooperativer Bericht von der ODOK 2012 - 14. Österreichisches Online-Informationstreffen und 15. Österreichischer Dokumentartag in Wels (12.-14. September 2012)

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    cooperative report of the Austrian library conference ODOK "worth knowing - the worth of knowledge", September 201

    The contractile vacuole in Ca(2+)-regulation in Dictyostelium: its essential function for cAMP-induced Ca(2+)-influx

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    BACKGROUND: cAMP-induced Ca(2+)-influx in Dictyostelium is controlled by at least two non-mitochondrial Ca(2+)-stores: acidic stores and the endoplasmic reticulum (ER). The acidic stores may comprise the contractile vacuole network (CV), the endosomal compartment and acidocalcisomes. Here the role of CV in respect to function as a potential Ca(2+)-store was investigated. RESULTS: Dajumin-GFP labeled contractile vacuoles were purified 7-fold by anti-GFP-antibodies in a magnetic field. The purified CV were shown for the first time to accumulate and release Ca(2+). Release of Ca(2+ )was elicited by arachidonic acid or the calmodulin antagonist W7, the latter due to inhibition of the pump. The characteristics of Ca(2+)-transport and Ca(2+)-release of CV were compared to similarly purified vesicles of the ER labeled by calnexin-GFP. Since the CV proved to be a highly efficient Ca(2+)-compartment we wanted to know whether or not it takes part in cAMP-induced Ca(2+)-influx. We made use of the LvsA(-)-mutant expected to display reduced Ca(2+)-transport due to loss of calmodulin. We found a severe reduction of cAMP-induced Ca(2+)-influx into whole cells. CONCLUSION: The contractile vacuoles in Dictyostelium represent a highly efficient acidic Ca(2+)-store that is required for cAMP-induced Ca(2+)-influx

    Lack of uniqueness for weak solutions of the incompressible porous media equation

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    In this work we consider weak solutions of the incompressible 2-D porous media equation. By using the approach of De Lellis-Sz\'ekelyhidi we prove non-uniqueness for solutions in LL^\infty in space and time.Comment: 23 pages, 2 fugure

    Quasiparticles governing the zero-temperature dynamics of the 1D spin-1/2 Heisenberg antiferromagnet in a magnetic field

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    The T=0 dynamical properties of the one-dimensional (1D) s=1/2s=1/2 Heisenberg antiferromagnet in a uniform magnetic field are studied via Bethe ansatz for cyclic chains of NN sites. The ground state at magnetization 0<Mz<N/20<M_z<N/2, which can be interpreted as a state with 2Mz2M_z spinons or as a state of MzM_z magnons, is reconfigured here as the vacuum for a different species of quasiparticles, the {\em psinons} and {\em antipsinons}. We investigate three kinds of quantum fluctuations, namely the spin fluctuations parallel and perpendicular to the direction of the applied magnetic field and the dimer fluctuations. The dynamically dominant excitation spectra are found to be sets of collective excitations composed of two quasiparticles excited from the psinon vacuum in different configurations. The Bethe ansatz provides a framework for (i) the characterization of the new quasiparticles in relation to the more familiar spinons and magnons, (ii) the calculation of spectral boundaries and densities of states for each continuum, (iii) the calculation of transition rates between the ground state and the dynamically dominant collective excitations, (iv) the prediction of lineshapes for dynamic structure factors relevant for experiments performed on a variety of quasi-1D antiferromagnetic compounds, including KCuF3_3, Cu(C4_4H4_4N2)(NO3)2_2)(NO_3)_2, and CuGeO3_3.Comment: 13 pages, 12 figure

    MAGNETIC RESONANCE (MR) MEASUREMENTS OF THE MASS FLUX IN GAS-SOLID FLUIDIZED BEDS

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    Magnetic Resonance (MR) Imaging was used to measure the time-averaged voidage and particle velocity in a 3D gas-solid fluidized bed. Two different distributors were used. The mass-flux through a horizontal plane was calculated by combining the local voidage and particle velocity measurements. Based on the conservation of mass it was possible to give an error in the combined voidage and particle velocity measurements. It was found that the error in the mass flux was usually small (\u3c 5%), albeit increasing with increasing fluidization velocities

    A Rapid Review of Randomized Trials Assessing the Effects of High-Intensity Interval Training on Depressive Symptoms in People with Mental Illness

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    [EN] Objective: to systematically search for randomized controlled trials comparing the effects of high-intensity interval training (HIIT) protocols vs. control without exercise or other exercise protocols, in patients with mental disorders experiencing depressive symptoms, and to provide some guidance based on the current HIIT literature to improve further interventions. Methods: we searched for relevant studies, published by 18 August 2022 on PubMed, Embase, PsycINFO and SPORTDiscus databases, that used a HIIT protocol, involving adults (≥18 years) with a diagnosis of a mental disorder, participating in a HIIT or a control condition, and assessed for depressive symptoms. Results: Four studies accounting for 108 participants (n HIIT = 55; n comparison groups = 53) met the inclusion criteria. Three out of the four studies included found significant improvements of depressive symptoms after 12 days to 8 weeks of intervention. However, there were no differences to other forms of low-to-moderate continuous exercise in 2/3 studies. Conclusions: The limited evidence suggests the effectiveness of HIIT interventions for improving depressive symptoms in people with mental illness. However, HIIT was not superior to other exercise treatments, although a trend for its superiority may be recognized. A number of methodological issues should be considered in further interventions to better characterize and identify the most efficient HIIT modalities for the treatment of depressive symptoms in these patients

    Increase of the mean inner Coulomb potential in Au clusters induced by surface tension and its implication for electron scattering

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    Electron holography in a transmission electron microscope was applied to measure the phase shift induced by Au clusters as a function of the cluster size. Large phase shifts Df observed for small Au clusters cannot be described by the well-known equation Df=C_E V_0 t (C_E: interaction constant, V_0: mean inner Coulomb potential (MIP) of bulk gold, t: cluster thickness). The rapid increase of the Au MIP with decreasing cluster size derived from Df, can be explained by the compressive strain of surface atoms in the cluster
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