3,687 research outputs found
Generalized thermodynamic and transport properties. II. Molecular liquids
No full textIn the present paper, we extend the method described in paper I [D. Bertolini and A. Tani, preceding paper, Phys. Rev. E 83, 031201 (2011)] to molecular liquids, which allows us to solve the exact kinetic equation proposed by de Schepper et al. [Phys. Rev. A 38, 271 (1988)] without approximations. In particular, generalized thermodynamic properties (enthalpy, specific heat, and thermal expansion coefficient) and transport properties (longitudinal viscosity, thermal conductivity) have been calculated for three liquids of increasing complexity, namely dimethyl sulfoxide, hydrogen fluoride, and SPC/E water. All results have been obtained by the molecular formalism as well as the atomic one, corrected for intramolecular correlations that are due to the models adopted. As done for simple liquids, the coupling between the viscous stress tensor and the energy flux vector has been calculated exactly. We also show that the Markov assumption for the dynamics related to thermal conductivity can only be adopted with caution
STRESS TENSOR AND VISCOSITY OF WATER - MOLECULAR-DYNAMICS AND GENERALIZED HYDRODYNAMICS RESULTS
No full textThe time correlation functions (CF's) of diagonal and off-diagonal components of the stress tenser of water have been calculated at 245 and 298 K in a molecular dynamics (MD) study on 343 molecules in the microcanonical ensemble. We present results obtained at wave number k = 0 and at a few finite. values of k, in the atomic and molecular formalism. In all cases; more than 98% of these functions are due to the potential term of the stress tenser. At k = 0, their main features are a fast oscillatory initial decay, followed by a long-time tail more apparent in the supercooled region. Bulk and shear viscosities, calculated via Green-Kubo integration of the relevant CF at k = 0, are underestimated with respect to experimental data, mainly at low temperature, but their ratio (approximate to 2)is correctly reproduced. Both shear and bulk viscosity decrease as a function of k, the latter more rapidly, so that they become almost equal at approximate to 1 Angstrom(-1) Also, both viscosities drop rapidly from their maximum at omega = 0. This behavior has been related to the large narrowing observed in the acoustic band, mainly in the supercooled region. The infinite frequency bulk and shear rigidity moduli have been shown to be in fair agreement with the experimental data, provided the MD value used for comparison is that corresponding to the frequency range relevant to ultrasonic measurements. The MD results of stress-stress CF's compare well with those predicted by Bertolini and Tani [Phys. Rev. E 51, 1091 (1995)] at k = 0, by an application of generalized hydrodynamics [de Schepper et al., Phys. Rev. A 38, 271 1988)] in the molecular formalism, to the same model of water (TIP4P) [Jorgensen et al., J. Chem. Phys. 79, 926 (1983)]. These CF's are essentially equal in the: atomic and molecular formalism, the only minor difference being restricted to the high frequency librational region of the shear function. By a comparison of atomic and molecular results, we show here that neglecting libration has no effect on the density-density and longitudinal current CF's and very little effect on transverse properties. On the other hand, this study points out the importance of including the oscillation in the nearest-neighbor cage in the memory function of the longitudinal and transverse current CF. The oscillatory local motion turns out to play an important role in all CF's and hence contributes significantly to the value of viscosity and of rigidity moduli
L'iconografia di Aristotele cavalcato nei luoghi di potere
No full text«Senza il comico non è possibile imparare cose serie» (Platone). "I Quaderni di Fillide" è una nuova collana di Edizioni alphabeta Verlag, nata dalla collaborazione con la rivista online "Fillide" e dedicata alla comicità e all'umorismo, nonché a tutti i relativi sottogeneri: grottesco, caricatura, parodia, derisione, satira, beffa. Vi troveranno spazio autori e autrici classici e contemporanei, abbinati a studiosi di estrazione multidisciplinare, che hanno approfondito da un punto di vista narrativo e saggistico tale ambito espressivo, antico quanto l'uomo. In questo primo numero viene illustrata la leggenda di Fillide, bellissima fanciulla indiana amata da Alessandro Magno, e di Aristotele "cavalcato", richiamo misogino contro l'astuzia delle donne, ma anche esaltazione della potenza dell'amore e, insieme, satira del sapiente. Un gioco allegro e irridente, metafora del comico e dell'umorismo inteso come "sublime rovesciato". Il volume racconta la straordinaria fortuna e le svariate interpretazioni di tale leggenda nella poesia, nella letteratura e nell'iconografia medievali. La rivista online "Fillide" (www.fillide.it) è dal 2010 un laboratorio di narrazione e riflessione intorno ai nodi interpretativi connessi al tema dell'umorismo e della comicità. Con la direzione di Luisa Bertolini e un comitato scientifico che si avvale della collaborazione di scrittori e docenti, le linee di ricerca prendono spunto dalle varie teorie del comico spaziando tra filosofia, letteratura e arte, con un'attenzione particolare al rapporto parola-immagine
A imagem de Alessandro Baricco no Brasil
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Comunicação e Expressão, Programa de Pós-Graduação em Estudos da Tradução, Florianópolis, 2013.Com a intenção de delinear o modo pelo qual o escritor italiano Alessandro Baricco se inseriu no sistema literário brasileiro e os caminhos percorridos pelos seus livros traduzidos, esta dissertação dá voz às experiências tradutórias de seus tradutores. A inserção de Bariccono Brasil tem seu início em 1997, através de uma proposição da Profa. Dra. Roberta Barni à editora Iluminuras da tradução de Oceano Mare. A partir daí, outras sete obras foram publicadas no Brasil, sendo três delas traduzidas por Roberta Barni e as outras quatro por quatro tradutores diferentes. De um lado, considera-se o tradutor como figura principal namediação entre culturas, e, de outro, se analisa a realidade desta figuradentro do sistema literário, sua invisibilidade, seus limites e o exercíciode sua profissão. A pesquisa conta, ainda, com críticas e resenhas referentes ao autor italiano publicadas em jornais consagrados no Brasil, considerando estas como parte constituinte da imagem de Baricco refletida em território nacional. Abstract : Intending to delineate the way the Italian writer Alessandro Baricco has been inserted in the Brazilian literary system and the paths his translated books have followed, this thesis gives voice to the translating experiences of his translators. Baricco's insertion in Brazil began in 1997, through a personal project of Dr. Roberta Barni, with her translation of Oceano Mare. Since then, seven other of his works have been published in Brazil, three of which were translated by Roberta Barni and the other four by four different translators. On the one hand,the translator is considered as the main figure in mediation betweencultures and, on the other, this figure's reality is analyzed within theliterary system: its invisibility, its limits and its professional practice. Criticisms and reviews of this Italian author published in well established Brazilian newspapers are also considered, with the understanding that they are part of Baricco's image reflected here
LIBRATIONAL DYNAMICS OF WATER IN TERMS OF ANGULAR VELOCITY CORRELATION-FUNCTIONS AND ORIENTATIONAL STRUCTURE
No full textThe high frequency (librational) dynamics of water is studied by molecular dynamics simulation on the TIP4P model at 245 K. The single-molecule part of the hydrogen current is described by a combination of autocorrelation functions of components of the angular velocity along the principal axes of inertia of the molecules. The distinct part of the hydrogen current is represented by a sum of cross correlation functions of the same components. The spectrum of the self current is almost quantitatively reproduced by the sum of the spectra of two of these contributions. The first is that relative to the component along the axis normal to the molecular plane and the second along the axis normal to the dipole vector, in the molecular plane, both multiplied by a geometrical parameter of the molecule. In the case of the distinct part, the interparticle correlation function of the projection of the angular velocity over the same two axes is weighted by the dot product of the dipole moments of each pair of molecules. The agreement between the results obtained this way and according to the usual definition is qualitatively satisfactory. The axis normal to the dipole in the plane of the molecule turns out to be a favourite channel for the propagation of rotational correlations in the liquid. The analysis of hydrogen current in terms of rotational correlations allows to show that the transition from single-molecule to collective dynamics is essentially complete when clusters of two or three shells of neighbors are considered. A simple model of the distinct hydrogen current as a time-propagated self function is able to qualitatively account for all features of the spectra of both longitudinal and transverse current. The ratio of the transverse to longitudinal delay time is shown to be equal to the square root of the amplitude of the librational band of the dielectric spectrum
Imaging diagnosis: Absence of the left external and both internal jugular veins in a cat
No full textTHE FREQUENCY AND WAVELENGTH DEPENDENT DIELECTRIC PERMITTIVITY OF WATER
No full textThe static and dynamic dielectric behaviour of a model of liquid water is studied in the supercooled region, as a function of wavelength. The data used for this analysis were obtained in a previous molecular dynamics simulation of a sample of 343 water molecules, modelled by the TIP4P potential, at 245 K. A substantial wavelength dependence of the static dielectric permittivity is observed, while the value found for epsilon(0) seems to indicate that the TIP4P model is able to account qualitatively for the increase of dielectric constant upon temperature decrease, as found in real water. The time correlation function of the longitudinal and transverse components of the dipole density as well as that of the individual and total dipole moment is also calculated, to relate collective dielectric properties to the single molecule relaxation. The collective and single molecule dielectric relaxation times are obtained and their ratio seems to be close to a static property, namely the short-range orientational correlation factor, g(s)(k). The frequency dependence of the dielectric constant is compared with previous simulation and experimental values. Furthermore, the longitudinal and transverse components of the hydrogen current are discussed. The molecular symmetry relates the latter properties to the corresponding component of the dipole density in the frequency range 80-200 THz, typical of the librational motions of water. From these results, a simple and unifying picture of the dynamics underlying the three dielectric bands of water in the frequency range 1-200 THz emerges
Thermal conductivity of water: Molecular dynamics and generalized hydrodynamics results
No full textEquilibrium molecular dynamics simulations have been carried out in the microcanonical ensemble at 300 and 255 K on the extended simple point charge (SPC/E) model of water [Berendsen et al., J. Phys. Chem. 91, 6269 (1987)]. In addition to a number of static and dynamic properties, thermal conductivity lambda has been calculated via Green-Kubo integration of the heat current time correlation functions (CF's) in the atomic and molecular formalism, at wave number k=0. The calculated values (0.67 +/- 0.04 W/mK at 300 K and 0.52 +/- 0.03 W/mK at 255 K) are in good agreement with the experimental data (0.61 W/mK at 300 K and 0.49 W/mK at 255 K). A negative long-time tail of the heat current CF, more apparent at 255 K, is responsible for the anomalous decrease of lambda with temperature. An analysis of the dynamical modes contributing to lambda has shown that its value is due to two low-frequency exponential-like modes, a faster collisional mode, with positive contribution, and a slower one, which determines the negative long-time tail. A comparison of the molecular and atomic spectra of the heat current CF has suggested that higher-frequency modes should not contribute to lambda in this temperature range. Generalized thermal diffusivity D-T(k) decreases as a function of k, after an initial minor increase at k = k(min). The k dependence of the generalized thermodynamic properties has been calculated in the atomic and molecular formalisms. The observed differences have been traced back to intramolecular or intermolecular rotational effects and related to the partial structure functions. Finally, from the results we calculated it appears that the SPC/E model gives results in better agreement with experimental data than the transferable intermolecular potential with four points TIP4P water model [Jorgensen et al., J. Chem. Phys. 79, 926 (1983)], with a larger improvement for, e.g., diffusion, viscosities, and dielectric properties and a smaller one for thermal conductivity. The SPC/E model shares, to a smaller extent, the insufficient slowing down of dynamics at low temperature already found for the TIP4P water model
GENERALIZED HYDRODYNAMICS AND THE ACOUSTIC MODES OF WATER - THEORY AND SIMULATION RESULTS
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