Non-Collinear Ferromagnetic Luttinger Liquids

The presence of electron-electron interactions in one dimension profoundly changes the properties of a system. The separation of charge and spin degrees of freedom is just one example. We consider what happens when a system consisting of a ferromagnetic region of non-collinearity, i.e. a domain wall, is coupled to interacting electrons in one-dimension (more specifically a Luttinger liquid). The ferromagnetism breaks spin charge separation and the presence of the domain wall introduces a spin dependent scatterer into the problem. The absence of spin charge separation and the effects of the electron correlations results in very different behaviour for the excitations in the system and for spin-transfer-torque effects in this model.Comment: 6 pages, submitted to Journal of Physics: Conference Series for JEMS 201

All-sky Relative Opacity Mapping Using Night Time Panoramic Images

An all-sky cloud monitoring system that generates relative opacity maps over many of the world's premier astronomical observatories is described. Photometric measurements of numerous background stars are combined with simultaneous sky brightness measurements to differentiate thin clouds from sky glow sources such as air glow and zodiacal light. The system takes a continuous pipeline of all-sky images, and compares them to canonical images taken on other nights at the same sidereal time. Data interpolation then yields transmission maps covering almost the entire sky. An implementation of this system is currently operating through the Night Sky Live network of CONCAM3s located at Cerro Pachon (Chile), Mauna Kea (Hawaii), Haleakala (Hawaii), SALT (South Africa) and the Canary Islands (Northwestern Africa).Comment: Accepted for publication in PAS

Chiral spin-orbital liquids with nodal lines

Strongly correlated materials with strong spin-orbit coupling hold promise for realizing topological phases with fractionalized excitations. Here we propose a chiral spin-orbital liquid as a stable phase of a realistic model for heavy-element double perovskites. This spin liquid state has Majorana fermion excitations with a gapless spectrum characterized by nodal lines along the edges of the Brillouin zone. We show that the nodal lines are topological defects of a non-Abelian Berry connection and that the system exhibits dispersing surface states. We discuss some experimental signatures of this state and compare them with properties of the spin liquid candidate Ba_2YMoO_6.Comment: 5 pages + supplementary materia

Dirac and Klein-Gordon particles in one-dimensional periodic potentials

We evaluate the dispersion relation for massless fermions, described by the Dirac equation, and for zero-spin bosons, described by the Klein-Gordon equation, moving in two dimensions and in the presence of a one-dimensional periodic potential. For massless fermions the dispersion relation shows a zero gap for carriers with zero momentum in the direction parallel to the barriers in agreement with the well-known "Klein paradox". Numerical results for the energy spectrum and the density of states are presented. Those for fermions are appropriate to graphene in which carriers behave relativistically with the "light speed" replaced by the Fermi velocity. In addition, we evaluate the transmission through a finite number of barriers for fermions and zero-spin bosons and relate it with that through a superlattice.Comment: 9 pages, 12 figure

Segregation in sheared granular media–effects of intrinsic particle properties such as size, density and shape

When granular media which have different size, density, shape or even frictional properties flow they will tend to segregate. This is of fundamental scientific interest but also has significance in a variety of industries including mining, pharmaceuticals, food processing as well as for natural phenomena such as landslides. Here we consider segregation that occurs when a granular mixture is sheared, such as when it flows down along an inclined slope. A partially filled cylindrical drum is being slowly rotated about its axis (which is perpendicular to gravity) is a popular test-bed to examine sheared granular segregation. Here we consider simulation (Discrete Element Method, DEM), experiment and continuum theories in order to understand the segregation that occurs. Using DEM simulations we can clearly determine the underlying causes of segregation which intimately depend on intrinsic particle properties such as their size, density and shape. We compare these DEM simulations with both experiments and continuum theories, for a number of these properties, and find very good agreement. It will be shown that segregation arising from differences in particle size is the strongest, with stable asymptotic states being reached after only one or two cylinder rotations. Density segregation is the next strongest followed by segregation due to particle shape. The underlying physical mechanism leading to segregation is different in each of these properties. We compare and contrast these mechanisms in detail

Suplementacao alimentar de bovinos com misturas multiplas em pastagens de brachiaria brizantha cv. Marandu na seca.

Este trabalho foi realizado pela Embrapa Cerrados em uma fazenda particular, objetivando desenvolver estrategias de suplementacao alimentar de bovinos com Misturas Multiplas. Utilizou-se a ureia como substituto da proteina natural e o milho, como fonte de energia, em B. brizantha cv. Marandu, estabelecida em um Latossolo Vermelho-Escuro, textura argilosa. O experimento foi conduzido durante a seca de 1997 e durou 84 dias. Empregou-se 160 novilho Nelore, com peso medio de 175 kg arranjados em sistemas de pastejo continuo em quatro pastos, em delineamento experimental completamente casualizado, com quatro tratamentos: 1- Sal mineralizado com 38% de superfosfato triplo (Testemunha); 2- Milho triturado 30%, farelo de soja 15%, ureia 10%, sal mineralizado 35%, sal comum 10%; 3- Milho triturado 36,4%, farelo de soja 7,5%, ureia 11,1%, sal mineralizado 35%, sal comum 10%; 4- Milho triturado 42,7%, ureia 12,3%, sal mineralizado 35%, sal comum 10%. A disponibilidade de forragem, nos pastos durante o experimento, permaneceu acima 4500 kg de MS/ha. A pressao de pastejo variou de 7% a 8%, e a taxa de lotacao media foi de 1.0 UA/ha. O conteudo de proteina bruta baixou para menos de 6% em agosto, mas elevou-se acima desse valor nos demais meses. A menor digestibilidade (DIVMS) ocorreu em agosto, e a fibra em detergente neutro variou de 60% em junho e 72% em agosto. Os animais, suplementados com a mistura multipla da Embrapa Cerrados, ganharam peso semelhante aos que consumiram as outras misturas e superior aquelas que receberam apenas sal mineralizado. A suplementacao com Mistura Multipla da Embrapa Cerrados aumentou o lucro liquido por animal em 46%, com retorno de US$ 3.59 por dolar aplicado.bitstream/CPAC-2010/23742/1/bolpd-10.pd

Photo and electroluminescence behavior of Tb(ACAC)3phen complex used as emissive layer on organic light emitting diodes

This work shows the luminescence properties of a rare-earth organic complex, the Tb(ACAC)3phen. The results show the 5D4 -> 7F3,4,5,6 transitions with no influence of any ligand emission. The photoluminescence excitation spectrum is tentatively interpreted by the ligands absorption. An OLED was made by thermal evaporation (total thickness of 1200 Å) using TPD and Alq3 as hole and electron transport layers, respectively. The light emission reproduces the photoluminescence spectrum of the terbium complex at room temperature, with CIE (x,y) color coordinates of (0.28, 0.55). No presence of any bands from the ligands was observed. The potential use of this compound in efficient devices is discussed

Influência do uso nas características físico químicas de um latossolo amarelo, textura muito argilosa, Manaus, AM.

O objetivo deste estudo foi: verificar alterações em algumas propriedades físico-químicas do solos provocadas pelo uso; a que profundidade ocorre e verificar o efeito da cobertura do solo com kudzu. As áreas em que foram feitas as amostragens se localizam no Campo Experimental da EMBRAPA-CPAA, Km 29 da AM-010, no município de Manaus, AM