Theory of Andreev reflection in a two-orbital model of iron-pnictide superconductors

A recently developed theory for the problem of Andreev reflection between a normal metal (N) and a multiband superconductor (MBS) assumes that the incident wave from the normal metal is coherently transmitted through several bands inside the superconductor. Such splitting of the probability amplitude into several channels is the analogue of a quantum waveguide. Thus, the appropriate matching conditions for the wave function at the N/MBS interface are derived from an extension of quantum waveguide theory. Interference effects between the transmitted waves inside the superconductor manifest themselves in the conductance. We provide results for a FeAs superconductor, in the framework of a recently proposed effective two-band model and two recently proposed gap symmetries: in the sign-reversed s-wave ($\Delta\cos(k_x)\cos(k_y)$) scenario resonant transmission through surface Andreev bound states (ABS) at nonzero energy is found as well as destructive interference effects that produce zeros in the conductance; in the extended s-wave ($\Delta[\cos(k_x)+\cos(k_y)]$) scenario no ABS at finite energy are found.Comment: 4 pages, 5 figure

Random Sequential Adsorption: From Continuum to Lattice and Pre-Patterned Substrates

The random sequential adsorption (RSA) model has served as a paradigm for diverse phenomena in physical chemistry, as well as in other areas such as biology, ecology, and sociology. In the present work, we survey aspects of the RSA model with emphasis on the approach to and properties of jammed states obtained for large times in continuum deposition versus that on lattice substrates, and on pre-patterned surfaces. The latter model has been of recent interest in the context of efforts to use pre-patterning as a tool to improve selfassembly in micro- and nanoscale surface structure engineering

Two Kerr black holes with axisymmetric spins: An improved Newtonian model for the head-on collision and gravitational radiation

We present a semi-analytical approach to the interaction of two (originally) Kerr black holes through a head-on collision process. An expression for the rate of emission of gravitational radiation is derived from an exact solution to the Einstein's field equations. The total amount of gravitational radiation emitted in the process is calculated and compared to current numerical investigations. We find that the spin-spin interaction increases the emission of gravitational wave energy up to 0.2% of the total rest mass. We discuss also the possibility of spin-exchange between the holes.Comment: 8 pages, RevTeX, 2 figures, psbox macro include

Manifestation of finite temperature size effects in nanogranular magnetic graphite

In addition to the double phase transition (with the Curie temperatures T_C=300K and T_{Ct}=144K), a low-temperature anomaly in the dependence of the magnetization is observed in the bulk magnetic graphite (with an average granular size of L=10nm), which is attributed to manifestation of the size effects below the quantum temperature. The best fits of the high-temperature data (using the mean-field Curie-Weiss and Bloch expressions) produced reasonable estimates for the model parameters, such as defects mediated effective spin exchange energy J=12meV (which defines the intragranular Curie temperature T_C) and proximity mediated interactions between neighboring grains (through potential barriers created by thin layers of non-magnetic graphite) with energy J_t=exp(-d/s)J=5.8meV (which defines the intergranular Curie temperature T_{Ct}) with d=1.5nm and s=2nm being the intergranular distance and characteristic length, respectively

Temperature oscillations of magnetization observed in nanofluid ferromagnetic graphite

We report on unusual magnetic properties observed in the nanofluid room-temperature ferromagnetic graphite (with an average particle size of l=10nm). More precisely, the measured magnetization exhibits a low-temperature anomaly (attributed to manifestation of finite size effects below the quantum temperature) as well as pronounced temperature oscillations above T=50K (attributed to manifestation of the hard-sphere type pair correlations between ferromagnetic particles in the nanofluid)

New Phase Transition in the Pr1−xCaxMnO3Pr_{1-x}Ca_{x}MnO_{3} System: Evidence for Electrical Polarization in Charge Ordered Manganites

In this Letter a detailed study of the electric field gradient (EFG) across the Pr1-xCaxMnO3 phase diagram and its temperature dependence is given. Clearly, distinct EFG behavior for samples outside or inside the charge order (CO) region are observed. The EFG temperature dependence evidences a new phase transition occurring over the broad CO region of the phase diagram. This transition is discontinuous and occurs at temperatures between the charge ordering and the Néel temperatures. The prominent features observed in the EFG are associated with polar atomic vibrations which eventually lead to a spontaneous local electric polarization below CO transition

Avaliação do pH, temperatura, sal e condutividade no líquido ruminal de ovinos recebendo dietas a base de palma forrageira e feno de atriplex.

Este trabalho teve por objetivo avaliar os efeitos da substituição da palma forrageira (Opuntia ficus indica,Mill) por feno de atriplex (Atriplex nummularia Lind.) sobre o pH, temperatura, concentração de sal e condutividade do líquido ruminal de ovinos. Os níveis de substituição da palma pelo feno foram de 0; 12,5; 25; 37,5 e 50 %. Foram utilizados cinco carneiros adultos, com fístula permanente no rúmen, com peso vivo médio de 60 kg. Os animais foram alojados em baias individuais, distribuídos no delineamento quadrado latino 5 x 5 (cinco animais x cinco dietas e cinco períodos experimentais), cada período foi constituído de 17 dias, sendo os quatros últimos reservados para as coletas de líquido ruminal. As amostras foram tomadas as 0 e 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, e 11 horas após alimentação dos animais. A concentração de amônia ruminal (N-NH3) apresentou efeito significativo (P<0,05) com aumento do feno de atriplex nas dietas, com valores de 10,26 e 39,29 mg/100mL para os respectivos níveis de feno 0 e 50 %. Quanto aos valores de pH, temperatura, concentração de sal e condutividade não tiveram efeito significativo com o aumento dos níveis de feno de atriplex. A substituição da palma por feno de atriplex promoveu efeito sobre a concentração ruminal de amôni

Avaliação e identificação de Pseudomonas sp. e Bacillus sp. dois isolados de rizobactérias antagônicas a Radopholus similis.

As rizobactérias PGPR (plant growth-promoting rhizobacteria) são microrganismos que podem promover o desenvolvimento e crescimento de plantas e atuar no controle biológico de doenças. Bactérias dos gêneros Pseudomonas e Bacillus são amplamente conhecidas pela capacidade de atuarem no biocontrole de fitopatógenos, dentre esses, nematóides. Isso se deve, principalmente, pela produção direta de compostos tóxicos, alteração dos exsudatos radiculares ou da indução de resistência na planta hospedeira. Assim, o uso desses microrganismos como agentes de biocotnrole do Radopholus similis, causador de necroses radiculares, em bananeira, é um alternativa a ser estudada. Visando a identificação de isolados com potencial uso no controle de fitopatógenos, o emprego de técnicas moleculares torna-se uma ferramenta indispensável. Nesse sentido, a técnica de PCR (reação em cadeia da polimerase) é uma forma rápida e eficiente de caracterizar isolados promissores. Dessa forma, este estudo teve como objetivo avaliar o potencial de biocontrole in vitro das rizobactérias ao R. Similis, e identificar por meio de PCR, a prevalência dos gêneros Pseudomonas e Bacillus entre isolados pré-selecionados.PDF. 071

On the gravitational field of static and stationary axial symmetric bodies with multi-polar structure

We give a physical interpretation to the multi-polar Erez-Rozen-Quevedo solution of the Einstein Equations in terms of bars. We find that each multi-pole correspond to the Newtonian potential of a bar with linear density proportional to a Legendre Polynomial. We use this fact to find an integral representation of the $\gamma$ function. These integral representations are used in the context of the inverse scattering method to find solutions associated to one or more rotating bodies each one with their own multi-polar structure.Comment: To be published in Classical and Quantum Gravit

Influência do substrato e da salinidade na germinação de sementes de algaroba [Prosopis juliflora (SW.) DC.].

O objetivo do estudo foi de avaliar o efeito de água com diferentes níveis de salinidade e do substrato na germinação de sementes de algaroba [Prosopis juliflora (SW.) DC.],