NMR Determination of an Incommensurate Helical Antiferromagnetic Structure in EuCo2As2

We report $^{153}$Eu, $^{75}$As and $^{59}$Co nuclear magnetic resonance (NMR) results on EuCo$_2$As$_2$ single crystal. Observations of $^{153}$Eu and $^{75}$As NMR spectra in zero magnetic field at 4.3 K below an antiferromagnetic (AFM) ordering temperature $T_{\rm N}$ = 45 K and its external magnetic field dependence clearly evidence an incommensurate helical AFM structure in EuCo$_2$As$_2$. Furthermore, based on $^{59}$Co NMR data in both the paramagnetic and the incommensurate AFM states, we have determined the model-independent value of the AFM propagation vector ${\bf k}$ = (0, 0, 0.73 $\pm$ 0.07)2$\pi$/$c$ where $c$ is the $c$ lattice parameter. Thus the incommensurate helical AFM state was characterized by only NMR data with model-independent analyses, showing NMR to be a unique tool for determination of the spin structure in incommensurate helical AFMs.Comment: 6 pages, 4 figures, accepted for publication in Phys.Rev.

The structure of the space of affine Kaehler curvature tensors as a complex module

We use results of Matzeu and Nikcevic to decompose the space of affine Kaehler curvature tensors as a direct sum of irreducible modules in the complex settin

Características da madeira de algumas espécies de eucalipto plantadas no Brasil.

bitstream/item/94756/1/doc38.pd

Propriedades da madeira de Taxodium distichum (L.) Rich.

bitstream/CNPF-2009-09/43373/1/Com_tec108.pd

The rate of convergence of Euler approximations for solutions of stochastic differential equations driven by fractional Brownian motion

The paper focuses on discrete-type approximations of solutions to non-homogeneous stochastic differential equations (SDEs) involving fractional Brownian motion (fBm). We prove that the rate of convergence for Euler approximations of solutions of pathwise SDEs driven by fBm with Hurst index $H>1/2$ can be estimated by $O(\delta^{2H-1})$ ($\delta$ is the diameter of partition). For discrete-time approximations of Skorohod-type quasilinear equation driven by fBm we prove that the rate of convergence is $O(\delta^H)$.Comment: 21 pages, (incorrect) weak convergence result removed, to appear in Stochastic

NMR studies of the incommensurate helical antiferromagnet EuCo2P2 : determination of the antiferromagnetic propagation vector

Recently Ding et al. [Phys. Rev. B 95, 184404 (2017)] reported that their nuclear magnetic resonance (NMR) study on EuCo$_2$As$_2$ successfully characterized the antiferromagnetic (AFM) propagation vector of the incommensurate helix AFM state, showing that NMR is a unique tool for determination of the spin structures in incommensurate helical AFMs. Motivated by this work, we have carried out $^{153}$Eu, $^{31}$P and $^{59}$Co NMR measurements on the helical antiferromagnet EuCo$_2$P$_2$ with an AFM ordering temperature $T_{\rm N}$ = 66.5 K. An incommensurate helical AFM structure was clearly confirmed by $^{153}$Eu and $^{31}$P NMR spectra on single crystalline EuCo$_2$P$_2$ in zero magnetic field at 1.6 K and its external magnetic field dependence. Furthermore, based on $^{59}$Co NMR data in both the paramagnetic and the incommensurate AFM states, we have determined the model-independent value of the AFM propagation vector k = (0, 0, 0.73 $\pm$ 0.09)2$\pi$/$c$ where $c$ is the $c$-axis lattice parameter. The temperature dependence of k is also discussed.Comment: 8 pages, 10 figures, accepted for publication in Phys. Rev. B. arXiv admin note: substantial text overlap with arXiv:1704.0629

INVESTIGATION ON VOLUME VARIATION FOR ALPHA STIRLING ENGINES ON ISOTHERMAL MODEL

The usage of renewable energies is approximately 11% of the matrix energy worldwide. In countries known for its renewable sources, such as Brazil, the percentage is close to 38%. The importance to study Stirling engines and propose a prototype is that they are a feasible alternative for generation of power and electricity when considering low quality sources such as solar and waste energy. This paper will compare two different approaches of the volume variation, sinusoidal and kinematic, using an isothermal model that represents the Stirling engines. The comparison is made for an a type engine. Such approaches are capable of representing an estimative of work and power output for Stirling engines since the difference of results for these approaches are 8.07% for power output. As both approaches are a valid choice for analyzing the Stirling engine cycle, the availability of the data determines which approach is the most suitable for characterizing the engine performance

Comparação entre métodos de avaliação da estabilidade fenotípica e adaptabilidade aplicados a dados de Eucalyptus cloeziana (F. MUELL).

Foram avaliadas a estabilidade fenotipica e adaptabilidade de 62 progenies pertencentes a 4 procedencias de Eucalyptus cloeziana, estabelecidas em seis locais do Brasil. Foram aplicados e comparados os metodos biometricos de Yates & Cochran, Plaisted & Peterson, Wricke, Finlay & Wilkinson e Eberhart & Russel. Para adaptabilidade, os resultados revelaram uma concordancia entre os metodos de Eberhart & Russel e Finlay & Wilkinson, exceto que o de Finlay & Wilkinson tendeu a apresentar melhores ajustes das similares pela metodologias de Eberhart & Russel, Wricke e Plaisted & Peterson, os quais discordaram dos obtidos pelo metodo de Yates & Cochran. Nao foram detectadas correlacoes entre estabilidade e adaptablidade com produtividade media, tendo sido identificadas progenies de alta produtividade, alta estabilidade e adaptabilidade geral

Ampliação da rede experimental do programa de melhoramento de eucalipto no CNPF/Embrapa.

Edição dos Anais do Congresso Florestal Brasileiro, 6., 1990, Campos do Jordão