291 research outputs found

    The Lagrangian method for chiral symmetry

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    We describe the non linear realizations of chiral symmetry group and study some of its implications in elementary particle phycics. In Chapter 1, the basic concepts of non linear realization techniques are introduced the way of reviewing the special case of the chiral SU(2)::SU(2) group. In Chapter 2, the general formalism for chiral SU(η)xSU(η) is developed. This part is wholly dependent on the work by Coleman, Wess and Zumino. In Chapter 3 the method is generalized for local chiral invariance to describe the non-linear gauge fields. The Chapter 4 illustrates the use of non linear realization techniques in conjunction with the phenomenological lagrangian. This chapter is introductory to the final Chapter, 5, in which we have attempted to use the i) phenomenological lagrangian with non linear realization of chiral SU(3)xSU(3) to calculate some low energy hadronic reactions. As an important addition, a description of broken chiral SU(3)xSU(3)' is given. This follows the general scheme put forward by Gell-Kann, Cakes and Renner

    Computational role of sleep in memory reorganization

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    Sleep is considered to play an essential role in memory reorganization. Despite its importance, classical theoretical models did not focus on some sleep characteristics. Here, we review recent theoretical approaches investigating their roles in learning and discuss the possibility that non-rapid eye movement (NREM) sleep selectively consolidates memory, and rapid eye movement (REM) sleep reorganizes the representations of memories. We first review the possibility that slow waves during NREM sleep contribute to memory selection by using sequential firing patterns and the existence of up and down states. Second, we discuss the role of dreaming during REM sleep in developing neuronal representations. We finally discuss how to develop these points further, emphasizing the connections to experimental neuroscience and machine learning.Comment: Accepted for publication in Current Opinion in Neurobiolog

    Exact renormalization group equation in presence of rescaling anomaly II - The local potential approximation

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    Exact renormalization group techniques are applied to mass deformed N=4 supersymmetric Yang-Mills theory, viewed as a regularised N=2 model. The solution of the flow equation, in the local potential approximation, reproduces the one-loop (perturbatively exact) expression for the effective action of N=2 supersymmetric Yang-Mills theory, when the regularising mass, M, reaches the value of the dynamical cutoff. One speculates about the way in which further non-perturbative contributions (instanton effects) may be accounted for.Comment: 13 pages, no figures, uses JHEP3.cl

    Dexterous Humanoid Whole-Body Manipulation by Pivoting

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    ANTIBACTERIAL ACTIVITY OF BIFIDOBACTERIA ISOLATED FROM INFANT FAECES

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    Antibacterial activity of bifidobacteria isolated from Mongolian infant faeces was elucidated on pathogenic intestinal bacteria for the development of a new antibacterial bifidobacteria, the permission for which was granted by the Mongolian Medical Ethics Committee Approval (MMECA). A total of forty-nine single colonies were obtained from 3 samples by using a BL medium enrichment. Among them, 29 isolates had Gram−positive, catalase−negative properties, and maul−like or Y−shaped morphology, and then, 20 Bifidobacterium breve and 9 Bifidobacterium longum strains were detected by the B. breve and B. longum specific primers. Organic acids produced by the isolated bifidobacteria in their cell-free supernatants were quantitatively analyzed by a spectrophotometric absorbance at 340 nm, suggesting that D−lactic, L−lactic, and acetic acids were produced, and the pH of the supernatants was at 3.86−4.55. The isolated bifidobacteria showed antibacterial activity toward Escherichia coli and Salmonella typhimurium as high as that of a standard bifidobacteria, however, lower activity against Staphylococcus aureus. The antibacterial activity was probably due to the production of organic acids
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