The exponential map for the unitary group SU(2,2)

In this article we extend our previous results for the orthogonal group, $SO(2,4)$, to its homomorphic group $SU(2,2)$. Here we present a closed, finite formula for the exponential of a $4\times 4$ traceless matrix, which can be viewed as the generator (Lie algebra elements) of the $SL(4,C)$ group. We apply this result to the $SU(2,2)$ group, which Lie algebra can be represented by the Dirac matrices, and discuss how the exponential map for $SU(2,2)$ can be written by means of the Dirac matrices.Comment: 10 page

Caracterização por microscopia óptica e eletrônica de varredura de amostras da madeira de pínus submetidas à compressão axial.

EVINCI. Resumo 048

Brillouin optical time-domain analysis for geotechnical monitoring

AbstractIn this paper, we show some recent experimental applications of Brillouin optical time-domain analysis (BOTDA) based sensors for geotechnical monitoring. In particular, how these sensors can be applied to detecting early movements of soil slopes by the direct embedding of suitable fiber cables in the ground is presented. Furthermore, the same technology can be used to realize innovative inclinometers, as well as smart foundation anchors

Compact atomic descriptors enable accurate predictions via linear models

We probe the accuracy of linear ridge regression employing a three-body local density representation derived from the atomic cluster expansion. We benchmark the accuracy of this framework in the prediction of formation energies and atomic forces in molecules and solids. We find that such a simple regression framework performs on par with state-of-the-art machine learning methods which are, in most cases, more complex and more computationally demanding. Subsequently, we look for ways to sparsify the descriptor and further improve the computational efficiency of the method. To this aim, we use both principal component analysis and least absolute shrinkage operator regression for energy fitting on six single-element datasets. Both methods highlight the possibility of constructing a descriptor that is four times smaller than the original with a similar or even improved accuracy. Furthermore, we find that the reduced descriptors share a sizable fraction of their features across the six independent datasets, hinting at the possibility of designing material-agnostic, optimally compressed, and accurate descriptors

Expedient Iodocyclization Approach Toward Polysubstituted 3H-Benzo[e]indoles

A facile and expedient iodocyclization of 4-(2-prop-1-ynylphenyl)-1H-pyrroles towards the synthesis of polysubstituted 3H-benzo[e]indoles is reported. The transformation was optimized and the best results were obtained by using iodine (1.2 equiv,) in dichloromethane, and potassium carbonate as base. The starting 1,2,3,4-tetrasubstituted pyrroles were efficiently obtained by means of a nickel(II) chloride-promoted four-component (nitromethane, amine, 2-alkynylbenzaldehyde and ethyl acetoacetate) reaction. Further functionalization of the resulting 5-iodoheterocycles was also explored.Fil: Martins, Guilherme M.. Universidade Federal de Santa Maria. Departamento de Qu ímica; BrasilFil: Zeni, Gilson. Universidade Federal de Santa Maria. Departamento de Qu ímica; BrasilFil: Back, David F.. Universidade Federal de Santa Maria. Departamento de Qu ímica; BrasilFil: Kaufman, Teodoro Saul. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Química Rosario; ArgentinaFil: Silveira, Claudio C.. Universidade Federal de Santa Maria. Departamento de Qu ímica; Brasi

Caracterização anatômica dos anéis de crescimento de espécies arbóreas de Florestas Ombrófila das Terras Baixas e Ombrófila Mista, no Estado do Paraná.

Organizado por Patricia Póvoa de Mattos, Celso Garcia Auer, Rejane Stumpf Sberze, Katia Regina Pichelli e Paulo César Botosso

Lightlike infinity in GCA models of Spacetime

This paper discusses a 7 dimensional conformal geometric algebra model for spacetime based on the notion that spacelike and timelike infinities are distinct. I show how naturally of the dimensions represents the lightlike infinity and appears redundant in computations, yet usefull in interpretationComment: 12 page

Resistência natural das espécies Eucalyptus cloeziana, Eucalyptus mycrocoris, Eucalyptus umbra, Corymbia citriodora e Corymbia maculata à degradação provocada pelo fungo Agrocybe perfecta, causador da podridão branca na madeira, in vitro.

Estudos práticos para a avaliação da resistência natural da madeira de eucalipto, têm recebido considerável atenção dos pesquisadores, em virtude das orientações que fornecem sobre o uso final do produto, evitando perdas econômicas. O apodrecimento da madeira pode ser causado por fungos decompositores. Alguns apresentam alta capacidade de degradação da lignina, cuja degradação é denominada podridão-branca. O objetivo deste trabalho foi analisar, em laboratório, a resistência natural da madeira de cinco espécies de eucalipto, a degradação provocada pelo fungo Agrocybe perfecta na madeira em diferentes posições ao longo do fuste.EBRAMEM