Multiscale model of global inner-core anisotropy induced by hcp-alloy plasticity

$\bullet$ Multiscale model of inner-core anisotropy produced by hcp alloy deformation$\bullet$ 5 to 20% single-crystal elastic anisotropy and plastic deformation by pyramidal slip $\bullet$ Low-degree inner-core formation model with faster crystallization at the equatorThe Earth's solid inner-core exhibits a global seismic anisotropy of several percents. It results from a coherent alignment of anisotropic Fe-alloy crystals through the inner-core history that can be sampled by present-day seismic observations. By combining self-consistent polycrystal plasticity, inner-core formation models, Monte-Carlo search for elastic moduli, and simulations of seismic measurements, we introduce a multiscale model that can reproduce a global seismic anisotropy of several percents aligned with the Earth's rotation axis. Conditions for a successful model are an hexagonal-close-packed structure for the inner-core Fe-alloy, plastic deformation by pyramidal \textless{}c+a\textgreater{} slip, and large-scale flow induced by a low-degree inner-core formation model. For global anisotropies ranging between 1 and 3%, the elastic anisotropy in the single crystal ranges from 5 to 20% with larger velocities along the c-axis

Is inner core seismic anisotropy a marker for plastic flow of cubic iron?

International audienceThis paper investigates whether observations of seismic anisotropy are compatible with a cubic structure of the inner core Fe alloy.We assume that anisotropy is the result of plastic deformation within a large scale flow induced by preferred growth at the inner core equator. Based on elastic moduli from the literature, bcc- or fcc-Fe produce seismic anisotropy well below seismic observations ($<0.4\%$). A Monte-Carlo approach allows us to generalize this result to any form of elastic anisotropy in a cubic system. Within our model, inner core global anisotropy is not compatible with a cubic structure of Fe alloy.Hence, if the inner core material is indeed cubic, large scale coherent anisotropic structures, incompatible with plastic deformation induced by large scale flow, must be present

Shu-mei Shih, Visuality and Identity. Sinophone Articulation across the Pacific, Berkeley, University Press of California, 2007, 244 p.

Professeur de littérature comparée à l’université de Californie de Los Angeles (UCLA), spécialiste des « gender studies », Shu-mei Shih aborde d’une manière originale, dans ce nouvel ouvrage, la question de l’identité dans le monde sinophone actuel. Long de 244 pages, Visuality and Identity. Sinophone Articulations across the Pacific, est composé d’une introduction et de six parties : la première porte sur la globalisation et ses effets sur les minorités, la deuxième sur le cas, plus précis, ..

Wu Hung, Making History: Wu Hung on Contemporary Art andWu Hung on Contemporary Chinese Artists

Wu Hung, Making History: Wu Hung on Contemporary Art, Hong Kong, Time Zone 8, 2008. Wu Hung on Contemporary Chinese Artists, Hong Kong, Time Zone 8, 2009. University of Chicago art history professor Wu Hung has written two important works published by Time Zone 8, a publisher specialising in Chinese contemporary art under the direction of Beijing-based Robert Bernell. Making History is reminiscent of L’écriture de l’histoire (The Writing of History)by Michel de Certeau, but focuses on an enti..

Contemporary Chinese Art Under Deng Xiaoping

Studying contemporary art in China is not an exclusively aesthetic choice. In the context of an emerging market, art is as much a matter of cultural economy as of socio-politics. Thus art is not the product of an independent condition. In its imagination, as well as in its own diversity and its transformations, it encompasses and summarises the changes of a culture which is appropriating the schemes, images and notions inherited both from an age-old tradition and from the West (a West which i..

Seismic response and anisotropy of a model hcp iron inner core

International audienceWe present a framework for simulating the measurement of seismic anisotropy in a model inner core by computing travel time residuals of synthetic seismic rays propagated through the model. The method is first tested on simple inner core structural models consisting of layers with distinct anisotropy, as often proposed in the literature. Those models are not consistent with geodynamics. Hence, we extend the method to a numerically grown inner core composed of ε-Fe with flow generated from an excess of crystallization in the equatorial belt, inducing polycrystalline textures. The global inner core anisotropy is 7 times smaller than that of the single crystal. Compositional stratification amplifies the global anisotropy by 15% while the addition of solidification textures reduces it by a factor of 2. As such, and within the tested geodynamical models, no published elastic model of ε-Fe at inner core conditions allows for reproducing the 3% cylindrical anisotropy reported in seismology publications. In addition, our models demonstrate that additional information such as the depth dependence and the spread of the observed anisotropy is a key for revealing the dynamics and history of the inner core

Anny Lazarus et Laurent Septier, Art contemporain. Pékin en 11 parcours

Très utile, cet ouvrage concis est un bréviaire de l’art contemporain chinois. Il comporte deux parties : l’une, consacrée à tout ce qui fonde l’art contemporain chinois sur le plan historique et culturel ; l’autre dévolue à Pékin qui reste la ville où cette scène est la plus active et la plus diversifiée. Il s’agit à ce jour du seul guide pratique en langue française proposant une sélection inédite de lieux et de parcours. En dépit de la difficulté de son maniement (le format autant que la r..

Shu-mei Shih, Visuality and Identity. Sinophone Articulations across the Pacific

A Professor of comparative literature at the University of California , Los Angeles (UCLA), and a specialist in gender studies, Shu-mei Shih, in this new book, adopts an original approach to the question of identity in today’s Sinophone world. At 244 pages in length, Visuality and Identity. Sinophone Articulations across the Pacific comprises an introduction and six parts: the first deals with globalisation and its effects on minorities, and the second with the more specific case of transnati..

Thomas J. Berghuis, Performance Art in China, Hong Kong, Timezone 8 Limited, 2006, 310 pp.

Performance Art in China is a major work published by Robert Bernell, founder of Timezone 8 publishers and owner of a bookshop at Dashanzi in Beijing. Written by Thomas J. Berghuis, a young researcher who worked with the guidance of Australian Sinologist John Clark, this is the first book on a largely unknown subject, and consists of an introduction and eight chapters replete with often rare illustrations, an extensive chronology, an index highly useful for looking up artists’ names both in P..