886 resultados para Explosion de Coulomb
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At head of title: Engineering and design.
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The Breslau arts scene during the Weimar period was one of the most vibrant in all of Germany, yet it has disappeared from memory and historiography. Breslau was a key center for innovative artistic production during the Weimar Republic; recovery of its history will shed new light on German cultural dynamics in the 1920s. Such a study has art historical significance because of the incredible extent of innovation that occurred in almost every intellectual field, advances that formed the basis for aesthetic modernism internationally and continue to affect the course of visual art and architecture today. Architecture education, just one example in many, is still largely based on a combination of the Bauhaus model from the 1920s and the model developed at the Breslau Academy of Fine and Applied Art. The exploratory attitude encouraged in Weimar era arts endeavors, as opposed to the conformism of academic art, is still a core value promoted in contemporary art and architecture circles. Given the long-lasting influence of Weimar culture on modernism one would expect to find a spate of studies examining every aspect of its cultural production, but this is not the case. Recent scholarship is almost exclusively focused on Berlin and the Dessau Bauhaus. Although both interests are understandable, the creative explosion was not confined to these cities but was part of a larger cultural ethos that extended into many of the smaller regional centers. The Expressionist associations the Blaue Reiter in Munich and Brücke in Dresden are two well-known examples. Equally, innovation was not confined to a few monumental projects like the Stuttgart Weissenhofsiedlung but part of a broader national cultural ethos. The dispersion of modernism occurred partly because of the political history of Germany as a loosely joined confederation of small city states and principalities that had strong individual cultural identities before unification in 1871 but also because of the German propensity to value and take intense pride in the Heimat, understood both as the hometown and the region. Heimatliebe translated into generous support for cultural institutions in outlying cities. Host to a roster of internationally acclaimed artists and architects, major collectors, arts organizations, museums, presses, galleries, and one of the premier German arts academies of the day, Breslau boasted a thriving modern arts scene until 1933 when the Nazis began their assault on so-called "degenerate" art. This book charts the cultural production of Breslau-based artists, architects, art collectors, urban designers, and arts educators, who were especially interesting because they operated in the space between the margins of Weimar-era cultural debates. Rather than accepting the radical position of the German avant-garde or the reactionary position of German conservatives, many Breslauers sought a middle ground. It is the first book in English to address this history and presents the history in a manner unique to any studies currently on the market. 'Beyond the Bauhaus' explores the polyvalent and contradictory nature of cultural production in Breslau in order to expand the cultural and geographic scope of Weimar history; the book asserts a reciprocal dimension to the relationship between regional culture and national culture, between centers like Breslau and the capital Berlin. With major international figures like the painters Otto Mueller and Oskar Moll, architects Hans Scharoun and Adolf Rading, urban planners Max Berg and Ernst May, collectors Ismar Littmann and Max Silberberg, and an art academy that by 1929 was considered the best in Germany, Breslau clearly had significance to narratives of Weimar cultural production. 'Beyond the Bauhaus' contributes the history of German culture during the Weimar Republic. It belongs alongside histories of art, architecture, urban design, exhibition, collecting, and culture; histories of the Bauhaus; histories of arts education more broadly; and German history. The readership would include those interested in German history; German art, architecture, urban design, planning, collecting, and exhibition history; in the avant-garde; the development of arts academies and arts pedagogy; and the history of Breslau and Silesia.
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The dynamical properties of an extended Hubbard model, which is relevant to quarter-filled layered organic molecular crystals, are analyzed. We have computed the dynamical charge correlation function, spectral density, and optical conductivity using Lanczos diagonalization and large-N techniques. As the ratio of the nearest-neighbor Coulomb repulsion, V, to the hopping integral, t, increases there is a transition from a metallic phase to a charge-ordered phase. Dynamical properties close to the ordering transition are found to differ from the ones expected in a conventional metal. Large-N calculations display an enhancement of spectral weight at low frequencies as the system is driven closer to the charge-ordering transition in agreement with Lanczos calculations. As V is increased the charge correlation function displays a collective mode which, for wave vectors close to (pi,pi), increases in amplitude and softens as the charge-ordering transition is approached. We propose that inelastic x-ray scattering be used to detect this mode. Large-N calculations predict superconductivity with d(xy) symmetry close to the ordering transition. We find that this is consistent with Lanczos diagonalization calculations, on lattices of 20 sites, which find that the binding energy of two holes becomes negative close to the charge-ordering transition.
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We present a new model for the continuous measurement of a coupled quantum dot charge qubit. We model the effects of a realistic measurement, namely adding noise to, and filtering, the current through the detector. This is achieved by embedding the detector in an equivalent circuit for measurement. Our aim is to describe the evolution of the qubit state conditioned on the macroscopic output of the external circuit. We achieve this by generalizing a recently developed quantum trajectory theory for realistic photodetectors [P. Warszawski, H. M. Wiseman, and H. Mabuchi, Phys. Rev. A 65, 023802 (2002)] to treat solid-state detectors. This yields stochastic equations whose (numerical) solutions are the realistic quantum trajectories of the conditioned qubit state. We derive our general theory in the context of a low transparency quantum point contact. Areas of application for our theory and its relation to previous work are discussed.
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Carbon nanotubes (CNT) are well-ordered, high aspect ratio allotropes of carbon. The two main variants, single-walled carbon nanotubes (SWCNT) and multi-walled carbon nanotubes (MWCNT) both possess a high tensile strength, are ultra-light weight, and have excellent chemical and thermal stability. They also possess semi- and metallic-conductive properties. This startling array of features has led to many proposed applications in the biomedical field, including biosensors, drug and vaccine delivery and the preparation of unique biomaterials such as reinforced and/or conductive polymer nanocomposites. Despite an explosion of research into potential devices and applications, it is only recently that information on toxicity and biocompatibility has become available. This review presents a summary of the performance of existing carbon biomaterials and gives an outline of the emerging field of nanotoxicology, before reviewing the available and often conflicting investigations into the cytotoxicity and biocompatibility of CNT. Finally, future areas of investigation and possible solutions to current problems are proposed. (c) 2005 Elsevier Ltd. All rights reserved.
Dual-symmetric Lagrangians in quantum electrodynamics: I. Conservation laws and multi-polar coupling
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By using a complex field with a symmetric combination of electric and magnetic fields, a first-order covariant Lagrangian for Maxwell's equations is obtained, similar to the Lagrangian for the Dirac equation. This leads to a dual-symmetric quantum electrodynamic theory with an infinite set of local conservation laws. The dual symmetry is shown to correspond to a helical phase, conjugate to the conserved helicity. There is also a scaling symmetry, conjugate to the conserved entanglement. The results include a novel form of the photonic wavefunction, with a well-defined helicity number operator conjugate to the chiral phase, related to the fundamental dual symmetry. Interactions with charged particles can also be included. Transformations from minimal coupling to multi-polar or more general forms of coupling are particularly straightforward using this technique. The dual-symmetric version of quantum electrodynamics derived here has potential applications to nonlinear quantum optics and cavity quantum electrodynamics.
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We study the electrical transport of a harmonically bound, single-molecule C-60 shuttle operating in the Coulomb blockade regime, i.e. single electron shuttling. In particular, we examine the dependance of the tunnel current on an ultra-small stationary force exerted on the shuttle. As an example, we consider the force exerted on an endohedral N@C-60 by the magnetic field gradient generated by a nearby nanomagnet. We derive a Hamiltonian for the full shuttle system which includes the metallic contacts, the spatially dependent tunnel couplings to the shuttle, the electronic and motional degrees of freedom of the shuttle itself and a coupling of the shuttle's motion to a phonon bath. We analyse the resulting quantum master equation and find that, due to the exponential dependence of the tunnel probability on the shuttle-contact separation, the current is highly sensitive to very small forces. In particular, we predict that the spin state of the endohedral electrons of N@C-60 in a large magnetic gradient field can be distinguished from the resulting current signals within a few tens of nanoseconds. This effect could prove useful for the detection of the endohedral spin-state of individual paramagnetic molecules such as N@C-60 and P@C-60, or the detection of very small static forces acting on a C-60 shuttle.
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From the break up of the New Left into single issue groups at the end of the 1960s came a variety of groups representing the peace movement, environmental movement, student movement, women’s movement, and gay liberation movement. This explosion of new social movement activism has been heralded as the age of new radical politics. Many theorists and activists understand new social movements, as replacing the working class as an agent for progressive social change. Scholars and activists now alike debate the possibilities for revolutionary change in this era of multinational capitalism and new nationalisms. This paper examines some of the above claims in the context of the contemporary Serbian civil society. It explores the relationship between the civil society, activism, and narratives in Serbia. In particular, it examines the anti-Milosevic’ movement Otpor! (Resistance), and its discourse, practice and politics in public spaces, through an analysis of narratives of a set of roughly 20 interviews with Otpor! activists, aged 18-35. In the following discussion, then, I will focus on some of the particular dilemmas of contemporary Serbian popular movements - they are dilemmas to do with the growing complexity of media life in the Serbian spaces. I ground my debate on particular uses of the notion of civil society in the narratives of Otpor! activists, while I focus on the question of how do Otpor! activists relate to Leftist/radical politics and the idea of civil society.
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The optimum bandwidth for shallow, high-resolution seismic reflection differs from that required for conventional petroleum reflection. An understanding of this issue is essential for correct choice of acquisition instrumentation. Numerical modelling of simple Bowen Basin coal structures illustrates that, for high-resolution imaging, it is important to accurately record all frequencies up to the limit imposed by earth scattering. On the contrary, the seismic image is much less dependent on frequencies at the lower end of the spectrum. These quantitative observations support the use of specialised high-frequency geophones for high-resolution seismic imaging. Synthetic seismic inversion trials demonstrate that, irrespective of the bandwidth of the seismic data, additional low-frequency impedance control is essential for accurate inversion. Inversion provides no compelling argument for the use of conventional petroleum geophones in the high-resolution arena.
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Esta tese analisa o papel dos líderes da Igreja católica institucionalizada antes e durante o movimento e guerra do Contestado de 1912 a 1916. Movimento classificado como messiânico-milenarista ocorrido no sul do Brasil numa área litigiosa pleiteada pelos Estados do Paraná e Santa Catarina. Aponta o contexto sócio-econômico-político e religioso que criou condições para que o movimento pudesse emergir. Analisa a formação do catolicismo rústico popular brasileiro e suas expressões na região do Contestado, destacando-se o papel dos monges. Aprofunda a compreensão do catolicismo oficial em processo de romanização e do papel dos frades franciscanos, de suas concepções e práticas na tentativa de enquadrar a religião cabocla dentro dos princípios da reforma. Analisa a reação cabocla diante das mudanças implantadas na região e a explosão da irmandade, denominada Terra Santa , que buscava efetivar uma nova ordem . Aprofunda especialmente o papel dos frades representantes da Igreja católica, tendo em vista dispersar e pacificar o caboclo rebelde e a aliança, que estabeleceram com as forças repressoras, para implantar a ordem e a paz na região contestada, com a conseqüente eliminação radical da irmandade cabocla e de seus redutos .(AU)