Phase Transition and Monopoles Densities in a Nearest Neighbors Two-Dimensional Spin Ice Model

In this work, we show that, due to the alternating orientation of the spins in the ground state of the artificial square spin ice, the influence of a set of spins at a certain distance of a reference spin decreases faster than the expected result for the long range dipolar interaction, justifying the use of the nearest neighbor two dimensional square spin ice model as an effective model. Using an extension of the model presented in ref. [Scientific Reports 5, 15875 (2015)], considering the influence of the eight nearest neighbors of each spin on the lattice, we analyze the thermodynamics of the model and study the monopoles and string densities dependence as a function of the temperature.Comment: 11 pages, 8 figure

Low-field microwave absorption and magnetoresistance in iron nanostructures grown by electrodeposition on n-type lightly-doped silicon substrates

In this study we investigate magnetic properties, surface morphology and crystal structure in iron nanoclusters electrodeposited on lightly-doped (100) n-type silicon substrates. Our goal is to investigate the spin injection and detection in the Fe/Si lateral structures. The samples obtained under electric percolation were characterized by magnetoresistive and magnetic resonance measurements with cycling the sweeping applied field in order to understand the spin dynamics in the as-produced samples. The observed hysteresis in the magnetic resonance spectra, plus the presence of a broad peak in the non-saturated regime confirming the low field microwave absorption (LFMA), were correlated to the peaks and slopes found in the magnetoresistance curves. The results suggest long range spin injection and detection in low resistive silicon and the magnetic resonance technique is herein introduced as a promising tool for analysis of electric contactless magnetoresistive samples.Comment: 12 pages, 5 figure

de Broglie-Proca and Bopp-Podolsky massive photon gases in cosmology

We investigate the influence of massive photons on the evolution of the expanding universe. Two particular models for generalized electrodynamics are considered, namely de Broglie-Proca and Bopp-Podolsky electrodynamics. We obtain the equation of state (EOS) $P=P(\varepsilon)$ for each case using dispersion relations derived from both theories. The EOS are inputted into the Friedmann equations of a homogeneous and isotropic space-time to determine the cosmic scale factor $a(t)$. It is shown that the photon non-null mass does not significantly alter the result $a\propto t^{1/2}$ valid for a massless photon gas; this is true either in de Broglie-Proca's case (where the photon mass $m$ is extremely small) or in Bopp-Podolsky theory (for which $m$ is extremely large).Comment: 8 pages, 2 figures; v2 matches the published versio

Variabilidade genética para caracteres de rendimento e seus componentes em feijão caupi.

O feijão-caupi (Vigna unguiculata (L.) Walp.) é uma leguminosa de grande importância alimentar, econômica e social, tradicionalmente cultivada por agricultores familiares do Nordeste do Brasil, cujo cultivo tem se expandido para as regiões Centro-Oeste e Sudeste do País, devido ao melhoramento genético da espécie. O presente trabalho teve como objetivo estudar a variabilidade genética para caracteres de rendimento da produção em feijão-caupi. Para isso, um experimento foi conduzido com oito genótipos (BRS Marataoã, BRS Paraguaçu, BRS Pajeú, BRS Xiquexique, BRS Guariba, BRS Potengi, BRS Cauamé e BRS Itaim) e quatro repetições, no delineamento estatístico de blocos ao acaso. Foram avaliados os caracteres número de vagens por planta (NVP), número de sementes por vagem (NSV), peso de cem sementes (PCS) e produtividade (PROD). Os genótipos apresentaram variabilidade genética para os caracteres estudados e a possibilidade de seleção e ganhos adicionais no melhoramento genético da espécie

Cultivo do milho: zoneamento agrícola.

bitstream/CNPMS/15593/1/Com_37.pd

Época de plantio de sorgo.

bitstream/CNPMS/16159/1/Com_80.pd

Produção de sementes genéticas de arroz irrigado na Embrapa Arroz e Feijão, na safra 2010/2011.

O objetivo deste trabalho é descrever e apresentar os resultados do processo atual de produção de sementes genéticas de arroz na Embrapa Arroz e Feijão na safra 2010/2011