6,561 research outputs found

    A HIERARCHY OF GAUGED GRASSMANIAN MODELS IN 4p4p DIMENSIONS WITH SELF-DUAL INSTANTONS

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    We present a hierarchy of gauged Grassmanian models in 4p4p dimensions, where the gauge field takes its values in the 22p1×22p12^{2p- 1}\times 2^{2p-1} chiral representation of SO(4p). The actions of all these models are absolutely minimised by a hierarchy of self-duality equations, all of which reduce to a single pair of coupled ordinary differential equations when subjected to 4p4p dimensional spherical symmetry.Comment: latex file, 13 page

    Digital Library Education: Some International Course Structure Comparisons

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    Digital Library Education (DLE) is assuming increasing importance and it is clear there is a pressing need from social trends and technology for educational developments in this new and fast moving area [1, 3]. Our latest review of progress in DLE and other recent studies [1, 2] pointed out that the number of library schools offering DL education is still growing. By the end of 2006 (based on modules titles shown on-line), 28% (5/18) of all universities with accredited programmes by CILIP (the Chartered Institute of Library and Information Professionals) in the UK and over 60% (34/56) of all library schools by ALA (American Library Association) in the USA and Canada are offering specific DL education. Around 40% of DLE is now either specialized independent or certificate programmes and courses, mainly in North America. However, there is currently no widely accepted formal curriculum framework for digital librarianship [2]. A major difficulty for academics in library and information science (LIS) is how to incorporate all of the DL technologies to their DLE, and no formal widely accepted framework of DLE has yet been established [1, 2, 3, 4]. It is difficult to compare full-scale independent programmes with other programmes that are more traditionally-based but which have modules on DLs [3, 4]. This and others recent studies [1, 2, 5] show there is a pressing need for educators to explore the specific question of what should be the standard framework for DLE in LIS to ensure that students and their employers – can be assured of having an adequate skill set to work confidently and productively in this area. DLE taught in a Computer Science environment benefits from an outline framework from CC2001 but no such framework has yet been promulgated from LIS based programmes [1, 2]

    Dissecting early regulatory relationships in the lamprey neural crest gene network

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    The neural crest, a multipotent embryonic cell type, originates at the border between neural and nonneural ectoderm. After neural tube closure, these cells undergo an epithelial–mesenchymal transition, migrate to precise, often distant locations, and differentiate into diverse derivatives. Analyses of expression and function of signaling and transcription factors in higher vertebrates has led to the proposal that a neural crest gene regulatory network (NC-GRN) orchestrates neural crest formation. Here, we interrogate the NC-GRN in the lamprey, taking advantage of its slow development and basal phylogenetic position to resolve early inductive events, 1 regulatory step at the time. To establish regulatory relationships at the neural plate border, we assess relative expression of 6 neural crest network genes and effects of individually perturbing each on the remaining 5. The results refine an upstream portion of the NC-GRN and reveal unexpected order and linkages therein; e.g., lamprey AP-2 appears to function early as a neural plate border rather than a neural crest specifier and in a pathway linked to MsxA but independent of ZicA. These findings provide an ancestral framework for performing comparative tests in higher vertebrates in which network linkages may be more difficult to resolve because of their rapid development

    Localisation of Fermions to brane: Codimension d2d \geq 2

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    We investigate 4+d4+d dimensional fermionic models in which the system in codimension-dd supports a topologically stable solution, and in which the fermion may be localised to the brane, with power law in 'instanton' backgrounds and exponentially in 'soliton' backgrounds. When the fermions are isoscalars, the mechanism fails, while for isospinor fermions it is successful. As backgrounds we consider instantons of Yang--Mills and sigma models in even codimensions, solitons of sigma models in odd codimensions, as well as solitons of Higgs and Goldstone models in all codimensions.Comment: 20 pages latex; expande

    Experimental realisation of Shor's quantum factoring algorithm using qubit recycling

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    Quantum computational algorithms exploit quantum mechanics to solve problems exponentially faster than the best classical algorithms. Shor's quantum algorithm for fast number factoring is a key example and the prime motivator in the international effort to realise a quantum computer. However, due to the substantial resource requirement, to date, there have been only four small-scale demonstrations. Here we address this resource demand and demonstrate a scalable version of Shor's algorithm in which the n qubit control register is replaced by a single qubit that is recycled n times: the total number of qubits is one third of that required in the standard protocol. Encoding the work register in higher-dimensional states, we implement a two-photon compiled algorithm to factor N=21. The algorithmic output is distinguishable from noise, in contrast to previous demonstrations. These results point to larger-scale implementations of Shor's algorithm by harnessing scalable resource reductions applicable to all physical architectures.Comment: 7 pages, 3 figure

    Novel type of phase transition in a system of self-driven particles

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    A simple model with a novel type of dynamics is introduced in order to investigate the emergence of self-ordered motion in systems of particles with biologically motivated interaction. In our model particles are driven with a constant absolute velocity and at each time step assume the average direction of motion of the particles in their neighborhood with some random perturbation (η\eta) added. We present numerical evidence that this model results in a kinetic phase transition from no transport (zero average velocity, va=0| {\bf v}_a | =0) to finite net transport through spontaneous symmetry breaking of the rotational symmetry. The transition is continuous since va| {\bf v}_a | is found to scale as (ηcη)β(\eta_c-\eta)^\beta with β0.45\beta\simeq 0.45

    Adding control to arbitrary unknown quantum operations

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    While quantum computers promise significant advantages, the complexity of quantum algorithms remains a major technological obstacle. We have developed and demonstrated an architecture-independent technique that simplifies adding control qubits to arbitrary quantum operations-a requirement in many quantum algorithms, simulations and metrology. The technique is independent of how the operation is done, does not require knowledge of what the operation is, and largely separates the problems of how to implement a quantum operation in the laboratory and how to add a control. We demonstrate an entanglement-based version in a photonic system, realizing a range of different two-qubit gates with high fidelity.Comment: 9 pages, 8 figure

    Immunotherapy of lung cancer: An update

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    In Germany lung cancer is the leading cause of cancer-associated death in men. Surgery, chemotherapy and radiation may enhance survival of patients suffering from lung cancer but the enhancement is typically transient and mostly absent with advanced disease; eventually more than 90% of lung cancer patients will die of disease. New approaches to the treatment of lung cancer are urgently needed. Immunotherapy may represent one new approach with low toxicity and high specificity but implementation has been a challenge because of the poor antigenic characterization of these tumors and their ability to escape immune responses. Several different immunotherapeutic treatment strategies have been developed. This review examines the current state of development and recent advances with respect to non-specific immune stimulation, cellular immunotherapy ( specific and non-specific), therapeutic cancer vaccines and gene therapy for lung cancer. The focus is primarily placed on immunotherapeutic cancer treatments that are already in clinical trial or well progressed in preclinical studies. Although there seems to be a promising future for immunotherapy in lung cancer, presently there is not standard immunotherapy available for clinical routine

    Photonic quantum technologies

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    The first quantum technology, which harnesses uniquely quantum mechanical effects for its core operation, has arrived in the form of commercially available quantum key distribution systems that achieve enhanced security by encoding information in photons such that information gained by an eavesdropper can be detected. Anticipated future quantum technologies include large-scale secure networks, enhanced measurement and lithography, and quantum information processors, promising exponentially greater computation power for particular tasks. Photonics is destined for a central role in such technologies owing to the need for high-speed transmission and the outstanding low-noise properties of photons. These technologies may use single photons or quantum states of bright laser beams, or both, and will undoubtably apply and drive state-of-the-art developments in photonics
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