23 resultados para Helimski, Eugene

em Consorci de Serveis Universitaris de Catalunya (CSUC), Spain


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The fundamental debt of E. O'Neill's Mourning Becomes Electra to Aeschylus, and to a lesser degree to Sophocles and Euripides, has been always recognised but, according to the author's hypothesis, O'Neill might have taken advantage of the Platonic image of the cave in order to magnify his both Greek and American drama. It is certainly a risky hypothesis that stricto sensu cannot be proved, but it is also reader's right to evaluate the plausibility and the possible dramatic benefit derived from such a reading. Besides indicating to what degree some of the essential themes of Platonic philosophy concerning darkness, light or the flight from the prison of the material world are not extraneous to O'Neill's work, the author proves he was aware of the Platonic image of the cave thanks to its capital importance in the work of some of his intellectual mentors such as F. Nietzsche or Oscar Wilde. Nevertheless, the most significant aim of the author's article is to emphasize both the dramatic benefits and the logical reflections derived, as said before, from reading little by little O'Neill's drama bearing in mind the above mentioned Platonic parameter.

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The fundamental debt of E. O'Neill's Mourning Becomes Electra to Aeschylus, and to a lesser degree to Sophocles and Euripides, has been always recognised but, according to the author's hypothesis, O'Neill might have taken advantage of the Platonic image of the cave in order to magnify his both Greek and American drama. It is certainly a risky hypothesis that stricto sensu cannot be proved, but it is also reader's right to evaluate the plausibility and the possible dramatic benefit derived from such a reading. Besides indicating to what degree some of the essential themes of Platonic philosophy concerning darkness, light or the flight from the prison of the material world are not extraneous to O'Neill's work, the author proves he was aware of the Platonic image of the cave thanks to its capital importance in the work of some of his intellectual mentors such as F. Nietzsche or Oscar Wilde. Nevertheless, the most significant aim of the author's article is to emphasize both the dramatic benefits and the logical reflections derived, as said before, from reading little by little O'Neill's drama bearing in mind the above mentioned Platonic parameter.

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The fundamental debt of E. O’Neill’s Mourning Becomes Electra to Aeschylus, and to a lesser degree to Sophocles and Euripides, has been always recognised but, according to the author’s hypothesis, O’Neill might have taken advantage of the Platonic image of the cave in order to magnify his both Greek and American drama. It is certainly a risky hypothesis that stricto sensu cannot be proved, but it is also reader’s right to evaluate the plausibility and the possible dramatic benefit derived from such a reading. Besides indicating to what degree some of the essential themes of Platonic philosophy concerning darkness, light or the flight from the prison of the material world are not extraneous to O’Neill’s work, the author proves he was aware of the Platonic image of the cave thanks to its capital importance in the work of some of his intellectual mentors such as F. Nietzsche or Oscar Wilde. Nevertheless, the most significant aim of the author’s article is to emphasize both the dramatic benefits and the logical reflections derived, as said before, from reading little by little O’Neill’s drama bearing in mind the above mentioned Platonic parameter.

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The work presented evaluates the statistical characteristics of regional bias and expected error in reconstructions of real positron emission tomography (PET) data of human brain fluoro-deoxiglucose (FDG) studies carried out by the maximum likelihood estimator (MLE) method with a robust stopping rule, and compares them with the results of filtered backprojection (FBP) reconstructions and with the method of sieves. The task of evaluating radioisotope uptake in regions-of-interest (ROIs) is investigated. An assessment of bias and variance in uptake measurements is carried out with simulated data. Then, by using three different transition matrices with different degrees of accuracy and a components of variance model for statistical analysis, it is shown that the characteristics obtained from real human FDG brain data are consistent with the results of the simulation studies.

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It is found that crystals of molecular nanomagnets exhibit enhanced magnetic relaxation when placed inside a resonant cavity. A strong dependence of the magnetization curve on the geometry of the cavity has been observed, providing indirect evidence of the coherent microwave radiation by the crystals. A similar dependence has been found for a crystal placed between the Fabry-Perot superconducting mirrors.

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We report experimental studies of crystals of Mn12 molecular magnetic clusters in pulsed magnetic fields with sweep rates up to 410^3 T/s . The steps in the magnetization curve are observed at fields that are shifted with respect to the resonant field values. The shift systematically increases as the rate of the field sweep goes up. These data are consistent with the theory of the collective dipolar relaxation in molecular magnets.

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A Reply to the Comment by M. Hanson, C. Johansson, and S. Mørup.

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Recent experiments on liquid water show collective dipole orientation fluctuations dramatically slower than expected (with relaxation time >tation, the self-dipole randomization time tr, which is an upper limit on ta; we find that tr5ta. Third, to check if there are correlated domains of dipoles in water which have large relaxation times compared to the individual dipoles, we calculate the randomization time tbox of the site-dipole field, the net dipole moment formed by a set of molecules belonging to a box of edge Lbox. We find that the site-dipole randomization time tbox2.5ta for Lbox3 , i.e., it is shorter than the same quantity calculated for the self-dipole. Finally, we find that the orientational correlation length is short even at low T.

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We study a model for water with a tunable intramolecular interaction Js, using mean-field theory and off-lattice Monte Carlo simulations. For all Js>~0, the model displays a temperature of maximum density. For a finite intramolecular interaction Js>0, our calculations support the presence of a liquid-liquid phase transition with a possible liquid-liquid critical point for water, likely preempted by inevitable freezing. For J=0, the liquid-liquid critical point disappears at T=0.

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We investigate the phase behavior of a single-component system in three dimensions with spherically-symmetric, pairwise-additive, soft-core interactions with an attractive well at a long distance, a repulsive soft-core shoulder at an intermediate distance, and a hard-core repulsion at a short distance, similar to potentials used to describe liquid systems such as colloids, protein solutions, or liquid metals. We showed [Nature (London) 409, 692 (2001)] that, even with no evidence of the density anomaly, the phase diagram has two first-order fluid-fluid phase transitions, one ending in a gas¿low-density-liquid (LDL) critical point, and the other in a gas¿high-density-liquid (HDL) critical point, with a LDL-HDL phase transition at low temperatures. Here we use integral equation calculations to explore the three-parameter space of the soft-core potential and perform molecular dynamics simulations in the interesting region of parameters. For the equilibrium phase diagram, we analyze the structure of the crystal phase and find that, within the considered range of densities, the structure is independent of the density. Then, we analyze in detail the fluid metastable phases and, by explicit thermodynamic calculation in the supercooled phase, we show the absence of the density anomaly. We suggest that this absence is related to the presence of only one stable crystal structure.

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Using event-driven molecular dynamics simulations, we study a three-dimensional one-component system of spherical particles interacting via a discontinuous potential combining a repulsive square soft core and an attractive square well. In the case of a narrow attractive well, it has been shown that this potential has two metastable gas-liquid critical points. Here we systematically investigate how the changes of the parameters of this potential affect the phase diagram of the system. We find a broad range of potential parameters for which the system has both a gas-liquid critical point C1 and a liquid-liquid critical point C2. For the liquid-gas critical point we find that the derivatives of the critical temperature and pressure, with respect to the parameters of the potential, have the same signs: they are positive for increasing width of the attractive well and negative for increasing width and repulsive energy of the soft core. This result resembles the behavior of the liquid-gas critical point for standard liquids. In contrast, for the liquid-liquid critical point the critical pressure decreases as the critical temperature increases. As a consequence, the liquid-liquid critical point exists at positive pressures only in a finite range of parameters. We present a modified van der Waals equation which qualitatively reproduces the behavior of both critical points within some range of parameters, and gives us insight on the mechanisms ruling the dependence of the two critical points on the potential¿s parameters. The soft-core potential studied here resembles model potentials used for colloids, proteins, and potentials that have been related to liquid metals, raising an interesting possibility that a liquid-liquid phase transition may be present in some systems where it has not yet been observed.