655 research outputs found

    Vibrational origin of the fast relaxation processes in molecular glass-formers

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    We study the interaction of the relaxation processes with the density fluctuations by molecular dynamics simulation of a flexible molecule model for o-terphenyl (oTP) in the liquid and supercooled phases. We find evidence, besides the structural relaxation, of a secondary vibrational relaxation whose characteristic time, few ps, is slightly temperature dependent. This i) confirms the result by Monaco et al. [Phys. Rev, E 62, 7595 (2000)] of the vibrational nature of the fast relaxation observed in Brillouin Light Scattering (BLS) experiments in oTP; and ii) poses a caveat on the interpretation of the BLS spectra of molecular systems in terms of a purely center of mass dynamics.Comment: RevTeX, 5 pages, 4 eps figure

    Statistical-mechanical theory of ultrasonic absorption in molecular liquids

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    We present results of theoretical description of ultrasonic phenomena in molecular liquids. In particular, we are interested in the development of microscopical, i.e., statistical-mechanical framework capable to explain the long living puzzle of the excess ultrasonic absorption in liquids. Typically, ultrasonic wave in a liquid can be generated by applying the periodically alternating external pressure with the angular frequency that corresponds to the ultrasound. If the perturbation introduced by such process is weak - its statistical-mechanical treatment can be done with the use of the linear response theory. We treat the liquid as a system of interacting sites, so that all the response/aftereffect functions as well as the energy dissipation and generalized (wave-vector and frequency dependent) ultrasonic absorption coefficient are obtained in terms of familiar site-site static and time correlation functions such as static structure factors or intermediate scattering functions. To express the site-site intermediate scattering functions we refer to the site-site memory equations in the mode-coupling approximation for the first-order memory kernels, while equilibrium properties such as site-site static structure factors, direct and total correlation functions are deduced from the integral equation theory of molecular liquids known as RISM or one of its generalizations. All the formalism is phrased in a general manner, hence the obtained results are expected to work for arbitrary type of molecular liquid including simple, ionic, polar, and non-polar liquids.Comment: 14 pages, 1 eps-figure, RevTeX4-forma

    Metallic Xenon, Molecular Condensates, and Superconductivity

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    A possibility of explaining the light absorption observed to occur under pressure-induced xenon metallization as due to the transition to the superconducting state is analyzed. The mechanism of the van der Waals bonding is discussed.Comment: LaTeX 2.09 (RevTeX), 4 pages, 4 PostScript figures included in tex

    Murder in Jerba : honour, shame and hospitality among Maltese in Ottoman Tunisia

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    Little is known about the sizeable Maltese communities developing along the southern and eastern shores of the Mediterranean in the mid-nineteenth century and the extent to which the migrants reproduced Maltese cultural traditions and practices overseas. This article considers this question through a microhistorical analysis of events culminating in the murder of a Maltese woman in the Ottoman Regency of Tunis in 1866. A close reading of transcripts from the interrogation of witnesses and the accused, all members of a Maltese community in Jerba reveals their shared cultural practices and beliefs surrounding the provision of hospitality, honour and shame. Viewed from this perspective, the curious responses of the witnesses to the murder of their compatriot become meaningful, and the crime is reframed as an honour killing.peer-reviewe

    Coastal Ocean Forecasting: science foundation and user benefits

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    The advancement of Coastal Ocean Forecasting Systems (COFS) requires the support of continuous scientific progress addressing: (a) the primary mechanisms driving coastal circulation; (b) methods to achieve fully integrated coastal systems (observations and models), that are dynamically embedded in larger scale systems; and (c) methods to adequately represent air-sea and biophysical interactions. Issues of downscaling, data assimilation, atmosphere-wave-ocean couplings and ecosystem dynamics in the coastal ocean are discussed. These science topics are fundamental for successful COFS, which are connected to evolving downstream applications, dictated by the socioeconomic needs of rapidly increasing coastal populations

    Quasi Harmonic Lattice Dynamics and Molecular Dynamics calculations for the Lennard-Jones solids

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    We present Molecular Dynamics (MD), Quasi Harmonic Lattice Dynamics (QHLD) and Energy Minimization (EM) calculations for the crystal structure of Ne, Ar, Kr and Xe as a function of pressure and temperature. New Lennard-Jones (LJ) parameters are obtained for Ne, Kr and Xe to reproduce the experimental pressure dependence of the density. We employ a simple method which combines results of QHLD and MD calculations to achieve densities in good agreement with experiment from 0 K to melting. Melting is discussed in connection with intrinsic instability of the solid as given by the QHLD approximation. (See http://www.fci.unibo.it/~valle for related papers)Comment: 7 pages, 5 figures, REVte

    Iphigenia’s sacrifice: generational historicity as a structure of feeling in times of austerity

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    Iphi, an unemployed actor in austerity-ridden Greece, imagines a theatre adaptation of a classic tragedy, Iphigenia at Aulis, in which the heroine is sacrificed on the altar of austerity by politicians. While writing her play-script, Iphi has a dream: she is taken to the sacrificial altar, not by politicians, but by her own parents, the generation who lived through the affluent years before austerity. Iphi’s generational-analogical thinking introduces a politically inspiring historicity, which offers insights into the accountability of austerity. It also allows us to reassess the notion of generations as a local category and an anthropological analytical construct. The article indicates the emergence of an as yet not fully articulated generational awareness—a new structure of feeling—about austerity, which is outlined here as it develops in an incipient form. I argue that the emerging generational historicity communicates a critical message, but also hides from view less visible inequalities

    Brownian motion: a paradigm of soft matter and biological physics

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    This is a pedagogical introduction to Brownian motion on the occasion of the 100th anniversary of Einstein's 1905 paper on the subject. After briefly reviewing Einstein's work in its contemporary context, we pursue some lines of further developments and applications in soft condensed matter and biology. Over the last century Brownian motion became promoted from an odd curiosity of marginal scientific interest to a guiding theme pervading all of the modern (live) sciences.Comment: 30 pages, revie
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