1,378 research outputs found

    Vers une théorie antivitale, antihoméostatique et antiadaptative de la vie chez Freud: Le travail du concept de pulsion

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    Indexación: Scopus.Situado en el examen del concepto de pulsión [Trieb], piedra angular de la arquitectura teórica del psicoanálisis, el presente artículo pretende destacar dos grandes líneas de análisis: en primer lugar, mostrar el conjunto de los aspectos filosóficos y ontológicos que el concepto moviliza en su reflexión sobre los dinamismos y los sentidos de la vida humana; y, en segundo lugar, evidenciar la subversión que el concepto establece en el seno de los postulados mayores del pensamiento científico, filosófico y médico del siglo XIX, al introducir una concepción general de la vida como un acontecer esencialmente antivital, antihomeostático y antiadaptativo, en el cual las tendencias a la muerte, a la degradación y a la inercia forman parte de su patrimonio más arcaico e inmanente.Placé dans l’examen du concept de pulsion [Trieb], soubassement angulaire de l’architecture théorique de la psychanalyse, cet article prétend souligner deux grandes lignes d’analyse: premièrement, montrer l’ensemble des aspects philosophiques et ontologiques que le concept mobilise dans sa réflexion sur les dynamismes et les sens de la vie humaine ; et, deuxièmement, avérer la subversion que le concept établit au sein des postulats majeures de la pensée scientifique, philosophique et médicale du XIXe siècle, de la sorte d’y introduire une conception générale sur la vie en tant que avènement essentiellement antivital, antihoméostatique et antiadaptatif, dans lequel les tendances envers la mort, la dégradation et l’inertie font partie de son patrimoine le plus archaïque e immanentfile:///C:/Users/paula.pardo/Downloads/246-642-1-PB.pd

    Explicit exactly energy-conserving methods for Hamiltonian systems

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    For Hamiltonian systems, simulation algorithms that exactly conserve numerical energy or pseudo-energy have seen extensive investigation. Most available methods either require the iterative solution of nonlinear algebraic equations at each time step, or are explicit, but where the exact conservation property depends on the exact evaluation of an integral in continuous time. Under further restrictions, namely that the potential energy contribution to the Hamiltonian is non-negative, newer techniques based on invariant energy quadratisation allow for exact numerical energy conservation and yield linearly implicit updates, requiring only the solution of a linear system at each time step. In this article, it is shown that, for a general class of Hamiltonian systems, and under the non-negativity condition on potential energy, it is possible to arrive at a fully explicit method that exactly conserves numerical energy. Furthermore, such methods are unconditionally stable, and are of comparable computational cost to the very simplest integration methods (such as Störmer-Verlet). A variant of this scheme leading to a conditionally-stable method is also presented, and follows from a splitting of the potential energy. Various numerical results are presented, in the case of the classic test problem of Fermi, Pasta and Ulam and for nonlinear systems of partial differential equations, including those describing high amplitude vibration of strings and plates

    The Formation of Alluvial Platinum-Group Minerals: Present Knowledge and the Way Ahead

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    The weathering of platinum-group element (PGE) deposits presents unusual problems, especially in the very active environment of lateritic weathering under tropical conditions. There is clear evidence of the destruction of platinum-group minerals (PGM) to form PGE oxides, or fine intergrowths between relict PGM and iron oxides or hydroxides, as an intermediate stage during weathering. The PGE released by weathering are transported in solution with the more soluble Pd species remaining in solution and travelling further than the less soluble Pt species. The presence of PGM in the laterite differing in mineralogy, mineral assemblage and size from those in the primary rock is difficult to explain, especially when they show secondary textures. Differing interpretations have created controversy. Are alluvial PGM derived unaltered from the primary rock where they are rare and, therefore, not encountered by standard petrographic examination? Is it possible that they could have developed in the laterite by some process that we do not yet fully understand? Some favourable genetic conditions have been outlined and debated. For more than 100 years authors have reported secondary ore textures and recently proposed a biogenic origin. Frank Reith and his co-workers provided evidence of a process involving metallophillic bacteria which, for the first time, demonstrates PGM growth in the laboratory under supergene conditions. Their work shows that a mechanism for supergene growth ('neoformation') can occur, which offers a new field of study of the appropriate Eh, pH, f(O2) conditions and organic and bacterial reactions that could permit supergene growth.Funding from Golden Prospect Mining Company in the UK, and the assistance of the late Prof. H.M. Prichard and Dr M.T. Jackson of Cardiff University. SSB received generous funding from the Department of Education, Universities and Research of the Basque Government (Refs. BFI-2011-254, IT762-13)

    Dimethoxymethane oxidation in a flow reactor

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    The simultaneous reduction of NOx and soot emissions from diesel engines is a major research subject and a challenge in today’s world. One prospective solution involves diesel fuel reformulation by addition of oxygenated compounds, such as dimethoxymethane (DMM). In this context, different DMM oxidation experiments have been carried out in an atmospheric pressure gas-phase installation, in the 573–1373 K temperature range, from pyrolysis to fuel-lean conditions. The results obtained have been interpreted by means of a detailed gas-phase chemical kinetic mechanism. Results indicate that the initial oxygen concentration slightly influences the consumption of DMM. However, certain effects can be observed in the profiles of the main products (CH4, CH3OH, CH3OCHO, CO, CO2, C2H2, C2H4, and C2H6). Acetylene, an important soot precursor, is only formed under pyrolysis and reducing conditions. In general, a good agreement between experimental and modeling data was observed

    Polycyclic aromatic hydrocarbons (PAHs) and soot formation in the pyrolysis of the butanol isomers

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    The formation of polycyclic aromatic hydrocarbons (PAHs) and soot from the pyrolysis of the four butanol isomers: 1-butanol, 2-butanol, iso-butanol and tert-butanol, at three reaction temperatures (1275, 1375 and 1475 K) has been studied. The identification and quantification of the sixteen PAHs, classified by the Environmental Protection Agency (EPA) as priority pollutants, were done using the gas chromatography–mass spectrometry (GC–MS) technique. The soot formed was collected at the reactor outlet. Light gases formed were also quantified. The harmful potential of the PAHs through the benzoa]pyrene equivalent, Ba]P-eq amount, has been evaluated. The main results show that the highest formation of light gases was obtained from the pyrolysis of iso-butanol at 1275 K. The formation of H2 increases significantly as the temperature increases, following the Hydrogen abstraction carbon addition (HACA) route that leads to form PAHs which subsequently form soot. The tendency to soot formation, under the experimental conditions of the present study, is ranked as follows: tert-butanol, 2-butanol, 1-butanol and iso-butanol. The highest PAHs amount and the highest toxic potential, expressed as Ba]P-eq amount, were found in the pyrolysis of all butanol isomers at 1275 K

    Recommendations for reporting ion mobility Mass Spectrometry measurements

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    Here we present a guide to ion mobility mass spectrometry experiments, which covers both linear and nonlinear methods: what is measured, how the measurements are done, and how to report the results, including the uncertainties of mobility and collision cross section values. The guide aims to clarify some possibly confusing concepts, and the reporting recommendations should help researchers, authors and reviewers to contribute comprehensive reports, so that the ion mobility data can be reused more confidently. Starting from the concept of the definition of the measurand, we emphasize that (i) mobility values (K0) depend intrinsically on ion structure, the nature of the bath gas, temperature, and E/N; (ii) ion mobility does not measure molecular surfaces directly, but collision cross section (CCS) values are derived from mobility values using a physical model; (iii) methods relying on calibration are empirical (and thus may provide method‐dependent results) only if the gas nature, temperature or E/N cannot match those of the primary method. Our analysis highlights the urgency of a community effort toward establishing primary standards and reference materials for ion mobility, and provides recommendations to do so. © 2019 The Authors. Mass Spectrometry Reviews Published by Wiley Periodicals, Inc

    Velocity shear instability and plasma billows at the Earth\u27s magnetic boundary

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    The Kelvin-Helmoltz instability (KH) with formation of vortices appears in a wide variety of terrestrial, interplanetary, and astrophysical contexts. We study a series of iterated rolled-up coherent plasma structures (15) that flow in the equatorial Earth\u27s boundary layer (BL), observed on October 24, 2001. The data were recorded during a 1.5 hour-long Wind crossing of the BL at the dawn magnetospheric flank, tailward of the terminator (X≈−13 RE). The interplanetary magnetic field (IMF) was radially directed, almost antiparallel to the magnetosheath (MS) flow. This configuration is expected to be adverse to the KH instability because of the collinearity of field and flow, and the high compressibility of the MS. We analyze the BL stability with compressible MHD theory using continuous profiles for the physical quantities. Upstream, at near Earth sites, we input parameters derived from an exact MHD solution for collinear flows. Further downtail at Wind position we input measured parameters. The BL is found KH unstable in spite of unfavorable features of the external flow. On the experimental side, the passage of vortices is inferred from the presence of low density - hot plasma being accelerated to speeds higher than that of the contiguous MS. It is further supported by the peculiar correlation of relative motions (in the bulk velocity frame): cold-dense plasma drifts sunward, while hot-tenuous plasma moves tailward. This event differs from many other studies that reported BL vortices under strongly northward IMF orientations. This is a case of KH vortices observed under an almost radial IMF, with implicit significance for the more common Parker\u27s spiral fields, and the problem of plasma entry in the magnetosphere

    Decreased infarct size after focal cerebral ischemia in mice chronically infected with Toxoplasma gondii

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    To determine whether Toxoplasma gondii infection could modify biological phenomena associated with brain ischemia, we investigated the effect of permanent middle cerebral artery occlusion (MCAO) on neuronal survival, inflammation and redox state in chronically infected mice. Infected animals showed a 40% to 50% decrease of infarct size compared with non-infected littermates 1, 4 and 14 days after MCAO. The resistance of infected mice may be associated with increased basal levels of anti-inflammatory cytokines and/or a marked reduction of the MCAO-related brain induction of two pro-inflammatory cytokines, tumor necrosis factor-alpha and interferon-gamma (IFNγ). In addition, potential anti-inflammatory/neuroprotective factors such as nerve growth factor, suppressor of cytokine signaling-3, superoxide dismutase activity, uncoupling protein-2 and glutathione (GSH) were upregulated in the brain of infected mice. Consistent with a role of GSH in central cytokine regulation, GSH depletion by diethyl maleate inhibited Toxoplasma gondii lesion resistance by increasing the proinflammatory cytokine IFNγ brain levels. Overall, these findings indicate that chronic toxoplasmosis decisively influences both the inflammatory molecular events and outcome of cerebral ischemia
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