1,721,204 research outputs found
K. N. Kudin, R. Car, and R. Resta, "Longitudinal polarizability of long polymeric chains: Quasi-one-dimensional electrostatics as the origin of slow convergence
No full textFirst-principles Free-energy Calculations on Condensed Matter Systems: Lattice Vacancy in Silicon
No full textIntermolecular dynamical charge fluctuations in water: a signature of the H-bond network
No full textWe report a simulation of deuterated water using a Car-Parrinello approach based on maximally localized Wannier functions. This provides local information on the dynamics of the hydrogen-bond network and on the origin of the low-frequency infrared activity. The oscillator strength of the translational modes, peaked around ∼200 cm-1, is anisotropic and originates from intermolecular—not intramolecular—charge fluctuations. These fluctuations are a signature of a tetrahedral hydrogen-bonding environment
Dipolar correlations and the dielectric permittivity of water
No full textThe static dielectric properties of liquid and solid water are investigated within linear response theory in the context of ab initio molecular dynamics. Using maximally localized Wannier functions to treat the macroscopic polarization we formulate a first-principles, parameter-free, generalization of Kirkwood’s phenomenological theory. Our calculated static permittivity is in good agreement with experiment. Two effects of the hydrogen bonds, i.e., a significant increase of the average local moment and a local alignment of the molecular dipoles, contribute in almost equal measure to the unusually large dielectric constant of water
La sinistra italiana e il conflitto arabo-israelo-palestinese. Dalla nascita dello Stato di Israele alla guerra del Kippur
Full text linkLa tesi ricostruisce l'atteggiamento delle varie anime della sinistra italiana di fronte al conflitto arabo-israelo-palestinese, nel corso degli anni che vanno dalla fondazione di Israele alla guerra del Kippur. Al fine di fornire un quadro, il più completo possibile, si è partiti da una concezione di “sinistra” come categoria politica composita, eterogenea e non confinabile nella sola componente marxista e classista, che consentisse di includere nell’analisi oltre al Partito comunista italiano e il frammentato universo socialista, anche il Partito repubblicano italiano, la sinistra extraparlamentare e la sinistra democristiana. Attraverso cinque capitoli, che riflettono una suddivisione prettamente cronologica del periodo analizzato, si è cercato di ripercorrere le evoluzioni degli orientamenti delle singole forze politiche della sinistra italiana, contestualizzandole nelle dinamiche degli scenari nazionale, mediorientale e internazionale che caratterizzavano le diverse fasi. Questo tipo di approccio, peraltro, ha consentito di cogliere come il dibattito – spesso iperpoliticizzato – sulle complesse implicazioni del conflitto arabo-israelo-palestinese sia diventato talvolta anche un’occasione per soffermarsi e confrontarsi su problematiche di carattere più generale, per ribadire o precisare linee politiche e convinzioni ideologiche, ma anche per definire la propria collocazione nel panorama politico italiano e rispetto al confronto bipolare
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
beta-phase of Pb on Ge(111): the competing roles of electronic bonding and thermal fluctuations
No full textWe have studied the low temperature phases of Pb/Ge(111) at Pb coverages THETA = 1/3, 1, and 4/3 using ab initio molecular dynamics. Stable phases are found to occur at THETA = 1/3 and 4/3. For the low-coverage phase, we confirm the model of Pb atoms adsorbed at T4 sites of the Ge(111) substrate. For the high THETA phase and very low temperature, we determine a structure characterized by the presence of covalently bonded Pb chains parallel to [110BAR] substrate directions. At room temperature, fluctuations are found to disrupt long-range Pb chains and restore the threefold symmetry of the ideal Ge(111). Our results agree well with x-ray diffraction and STM data
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