5,430 research outputs found
Specific heat amplitude ratios for anisotropic Lifshitz critical behaviors
We determine the specific heat amplitude ratio near a -axial Lifshitz
point and show its universal character. Using a recent renormalization group
picture along with new field-theoretical -expansion techniques,
we established this amplitude ratio at one-loop order. We estimate the
numerical value of this amplitude ratio for and . The result is in
very good agreement with its experimental measurement on the magnetic material
. It is shown that in the limit it trivially reduces to the
Ising-like amplitude ratio.Comment: 8 pages, RevTex, accepted as a Brief Report in Physical Review
Topological Dilatonic Supergravity Theories
We present a central extension of the super-Poincar\'e algebra in two
dimensions. Besides the usual Poincar\'e generators and the
supersymmetry generators we have Grassmann generators, a bosonic
internal symmetry generator and a central charge. We then build up the
topological gauge theory associated to this algebra. We can solve the classical
field equations for the fields which do not belong to the supergravity
multiplet and to a Lagrange multiplier multiplet. The resulting topological
supergravity theory turns out to be non-local in the fermionic sector.Comment: 11 pages, plain TeX, IFUSP-P/112
A new picture of the Lifshitz critical behavior
New field theoretic renormalization group methods are developed to describe
in a unified fashion the critical exponents of an m-fold Lifshitz point at the
two-loop order in the anisotropic (m not equal to d) and isotropic (m=d close
to 8) situations. The general theory is illustrated for the N-vector phi^4
model describing a d-dimensional system. A new regularization and
renormalization procedure is presented for both types of Lifshitz behavior. The
anisotropic cases are formulated with two independent renormalization group
transformations. The description of the isotropic behavior requires only one
type of renormalization group transformation. We point out the conceptual
advantages implicit in this picture and show how this framework is related to
other previous renormalization group treatments for the Lifshitz problem. The
Feynman diagrams of arbitrary loop-order can be performed analytically provided
these integrals are considered to be homogeneous functions of the external
momenta scales. The anisotropic universality class (N,d,m) reduces easily to
the Ising-like (N,d) when m=0. We show that the isotropic universality class
(N,m) when m is close to 8 cannot be obtained from the anisotropic one in the
limit d --> m near 8. The exponents for the uniaxial case d=3, N=m=1 are in
good agreement with recent Monte Carlo simulations for the ANNNI model.Comment: 48 pages, no figures, two typos fixe
Brucelose bovina no Pantanal Sul-Matogrossense: dados preliminares.
Com o objetivo de levantar a freqüência preliminar de bovinos de corte não vacinados do Pantanal, foram visitados, no período de 1994 a 1996, 16 rebanhos e 309 animais, sorteados dentre as fazendas cadastradas na Embrapa Pantanal. A freqüência foi estimada com base no número de animais que apresentavam resultados positivos em ambos os testes (AAT e soroaglutinação lenta/2 mercaptoetanol (2ME)) Os resultados do testes diagnósticos confirmatórios foram positivos, negativos ou inconclusivos e classificou-se como positiva a propriedade que apresentou pelo menos um animal positivo no teste confirmatório (2ME); negativa, quando todas os animais apresentaram-se negativos nos testes sorológicos e inconclusiva, quando existiram resultados sorológicos negativos e inconclusivo em pelo menos um dos animais.bitstream/CPAC/28669/1/COT58.pd
Nuclear alpha-synuclein is present in the human brain and is modified in dementia with Lewy bodies
Dementia with Lewy bodies (DLB) is pathologically defined by the cytoplasmic accumulation of alpha-synuclein (aSyn) within neurons in the brain. Predominately pre-synaptic, aSyn has been reported in various subcellular compartments in experimental models. Indeed, nuclear alpha-synuclein (aSynNuc) is evident in many models, the dysregulation of which is associated with altered DNA integrity, transcription and nuclear homeostasis. However, the presence of aSynNuc in human brain cells remains controversial, yet the determination of human brain aSynNuc and its pathological modification is essential for understanding synucleinopathies. Here, using a multi-disciplinary approach employing immunohistochemistry, immunoblot, and mass-spectrometry (MS), we confirm aSynNuc in post-mortem brain tissue obtained from DLB and control cases. Highly dependent on antigen retrieval methods, in optimal conditions, intra-nuclear pan and phospho-S129 positive aSyn puncta were observed in cortical neurons and non-neuronal cells in fixed brain sections and in isolated nuclear preparations in all cases examined. Furthermore, an increase in nuclear phospho-S129 positive aSyn immunoreactivity was apparent in DLB cases compared to controls, in both neuronal and non-neuronal cell types. Our initial histological investigations identified that aSynNuc is affected by epitope unmasking methods but present under optimal conditions, and this presence was confirmed by isolation of nuclei and a combined approach of immunoblotting and mass spectrometry, where aSynNuc was approximately tenfold less abundant in the nucleus than cytoplasm. Notably, direct comparison of DLB cases to aged controls identified increased pS129 and higher molecular weight species in the nuclei of DLB cases, suggesting putative pathogenic modifications to aSynNuc in DLB. In summary, using multiple approaches we provide several lines of evidence supporting the presence of aSynNuc in autoptic human brain tissue and, notably, that it is subject to putative pathogenic modifications in DLB that may contribute to the disease phenotype
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