Unbiased sampling of globular lattice proteins in three dimensions

We present a Monte Carlo method that allows efficient and unbiased sampling of Hamiltonian walks on a cubic lattice. Such walks are self-avoiding and visit each lattice site exactly once. They are often used as simple models of globular proteins, upon adding suitable local interactions. Our algorithm can easily be equipped with such interactions, but we study here mainly the flexible homopolymer case where each conformation is generated with uniform probability. We argue that the algorithm is ergodic and has dynamical exponent z=0. We then use it to study polymers of size up to 64^3 = 262144 monomers. Results are presented for the effective interaction between end points, and the interaction with the boundaries of the system

The antiferromagnetic transition for the square-lattice Potts model

We solve the antiferromagnetic transition for the Q-state Potts model (defined geometrically for Q generic) on the square lattice. The solution is based on a detailed analysis of the Bethe ansatz equations (which involve staggered source terms) and on extensive numerical diagonalization of transfer matrices. It involves subtle distinctions between the loop/cluster version of the model, and the associated RSOS and (twisted) vertex models. The latter's continuum limit involves two bosons, one which is compact and twisted, and the other which is not, with a total central charge c=2-6/t, for sqrt(Q)=2cos(pi/t). The non-compact boson contributes a continuum component to the spectrum of critical exponents. For Q generic, these properties are shared by the Potts model. For Q a Beraha number [Q = 4 cos^2(pi/n) with n integer] the two-boson theory is truncated and becomes essentially Z\_{n-2} parafermions. Moreover, the vertex model, and, for Q generic, the Potts model, exhibit a first-order critical point on the transition line, i.e., the critical point is also the locus of level crossings where the derivatives of the free energy are discontinuous. In that sense, the thermal exponent of the Potts model is generically nu=1/2. Things are profoundly different for Q a Beraha number, where the transition is second order, with nu=(t-2)/2 determined by the psi\_1 parafermion. As one enters the adjacant Berker-Kadanoff phase, the model flows, for t odd, to a minimal model of CFT with c=1-6/t(t-1), while for t even it becomes massive. This provides a physical realization of a flow conjectured by Fateev and Zamolodchikov in the context of Z\_N integrable perturbations. Finally, we argue that the antiferromagnetic transition occurs as well on other two-dimensional lattices

Dynamic Steerable Blocks in Deep Residual Networks

Filters in convolutional networks are typically parameterized in a pixel basis, that does not take prior knowledge about the visual world into account. We investigate the generalized notion of frames designed with image properties in mind, as alternatives to this parametrization. We show that frame-based ResNets and Densenets can improve performance on Cifar-10+ consistently, while having additional pleasant properties like steerability. By exploiting these transformation properties explicitly, we arrive at dynamic steerable blocks. They are an extension of residual blocks, that are able to seamlessly transform filters under pre-defined transformations, conditioned on the input at training and inference time. Dynamic steerable blocks learn the degree of invariance from data and locally adapt filters, allowing them to apply a different geometrical variant of the same filter to each location of the feature map. When evaluated on the Berkeley Segmentation contour detection dataset, our approach outperforms all competing approaches that do not utilize pre-training. Our results highlight the benefits of image-based regularization to deep networks

Exact enumeration of Hamiltonian circuits, walks, and chains in two and three dimensions

We present an algorithm for enumerating exactly the number of Hamiltonian chains on regular lattices in low dimensions. By definition, these are sets of k disjoint paths whose union visits each lattice vertex exactly once. The well-known Hamiltonian circuits and walks appear as the special cases k=0 and k=1 respectively. In two dimensions, we enumerate chains on L x L square lattices up to L=12, walks up to L=17, and circuits up to L=20. Some results for three dimensions are also given. Using our data we extract several quantities of physical interest

Measurement of absorption with a p-u sound intensity probe in an impedance tube

An alternative method of measuring the normal-incidence sound absorption of a sample of material in an impedance tube is examined. The method is based on measurement of the sound pressure and the normal component of the particle velocity using a "p-u" sound intensity probe. This technique is compared with the traditional, well-established "transfer function method" based on two pressure microphones. The results suggest that the new method can be as accurate as the established method, but whereas the influence of transducer mismatch on the transfer function method can be eliminated using a simple "sensor-switching technique," the method based on a p-u intensity probe relies on accurate calibration of the probe

AÇÕES DE CONTROLE INTERNO DA UNIVERSIDADE FEDERAL DE SANTA CATARINA NA PERSPECTIVA DO GERENCIAMENTO DE RISCOS

A história do Sistema Universitário no Brasil e suas estruturas de gestão sujeitaram-se a vários riscos e incertezas, quanto à sua validade, finalidade e ideais na Instituição Universidade para a permanência até os dias de hoje. Nesse contexto, o objetivo do artigo é analisar os resultados da avaliação do sistema de controle interno de uma Universidade Federal, quanto à avaliação de riscos. Trata-se de uma pesquisa qualitativa, descritiva e de um estudo de caso. A coleta de dados foi realizada a partir de pesquisa documental e bibliográfica. A investigação da avaliação do Sistema de Controle Interno da universidade foi suportada em dados extraídos dos Relatórios de Gestão da Instituição no período compreendido entre 2012 e 2014, seguindo as orientações de avaliação dos controles internos oriundas das Portarias no 150/12, 175/13 e 90/14 do Tribunal de Contas da União (TCU). Portanto, quanto à avaliação de riscos na Universidade investigada, o resultado aponta que o conteúdo é parcialmente observado nos exercícios pesquisados e quanto aos procedimentos de controle não há como se avaliar o cumprimento das exigências para o período

Dense loops, supersymmetry, and Goldstone phases in two dimensions

Loop models in two dimensions can be related to O(N) models. The low-temperature dense-loops phase of such a model, or of its reformulation using a supergroup as symmetry, can have a Goldstone broken-symmetry phase for N<2. We argue that this phase is generic for -2< N <2 when crossings of loops are allowed, and distinct from the model of non-crossing dense loops first studied by Nienhuis [Phys. Rev. Lett. 49, 1062 (1982)]. Our arguments are supported by our numerical results, and by a lattice model solved exactly by Martins et al. [Phys. Rev. Lett. 81, 504 (1998)].Comment: RevTeX, 5 pages, 3 postscript figure

A TERCEIRIZAÇÃO DA SEGURANÇA NAS INSTITUIÇÕES FEDERAIS DE ENSINO SUPERIOR: UM ESTUDO NA UFSC

O presente artigo tem como objetivo analisar efeitos da terceirização no setor de segurança das Instituições Federais de Ensino Superior (IFES) brasileiras, com ênfase na Universidade Federal de Santa Catarina (UFSC). Para alcançá-lo, foram utilizadas a pesquisa descritiva de caráter qualitativo, a pesquisa bibliográfica e documental e o estudo de caso. A coleta de dados ocorreu por meio de entrevista semiestruturada aplicada junto ao gestor do Departamento de Segurança Física e Patrimonial (DESEG) da UFSC, em agosto de 2015. A pesquisa teórica discute os problemas referentes à terceirização da segurança nas Instituições Federais de Ensino Superior (IFES), principalmente após a edição da Lei 9.632 de 07 de maio de 1998 (BRASIL, 1998), que extinguiu o cargo de vigilante nas IFES. Discute as causas do aumento generalizado da violência e os problemas da segurança pública na atualidade. Os resultados da pesquisa demonstram que a reestruturação do capital combinada com a adoção de políticas neoliberais trouxe conseqüências para a classe trabalhadora e para a universidade pública brasileira. A terceirização no setor público, que visa à redução do quadro de servidores, revelou o poder de intervenção do projeto neoliberal e sua ideologia de Estado mínimo e representa, na segurança das IFES, um meio de precarização das relações de trabalho. Sobre o caso da UFSC, a gestão da terceirização no DESEG encontra desafios a serem vencidos, especialmente relativos à necessidade em lidar concomitantemente com 2 categorias de colaboradores (efetivos e terceirizados) na atividade de vigilância e com efeitos da terceirização como salários inferiores e rotatividade de tais profissionais

Ground state magnetic structure of Mn3_3Ge

We have used spherical neutron polarimetry to investigate the magnetic structure of the Mn spins in the hexagonal semimetal Mn$_3$Ge, which exhibits a large intrinsic anomalous Hall effect. Our analysis of the polarimetric data finds a strong preference for a spin structure with $E_{1g}$ symmetry relative to the $D_{6h}$ point group. We show that weak ferromagnetism is an inevitable consequence of the symmetry of the observed magnetic structure, and that sixth order anisotropy is needed to select a unique ground state