Manual de métodos de análise de solo.

Analises fisicas; Preparo da amostra; Terra fina, cascalho e calhaus;Umidade atual; Umidade residual e fator "f"; Umidade obtida no aparelho extrator de Richards; Umidade obtida com a mesa de tensao; Densidade aparente; Porosidade total; Microporosidade (Metodo Mesa de Tensao); Macroporosidade; Analise granulometrica (Dispersao Total); Argila dispersa em agua; Grau de floculacao; Relacao silte/argila; Condutividade hidraulica; Percentagem de saturacao; Percentagem de agregados; Limite de liquidez; Limite e indice de plasticidade; Limite de pegajosidade; Limite de contracao (LC) (Metodo do Mercurio Metalico); Grau de contracao (GC); Superficie especifica (Metodo Simplificado); Separacao de argila e silte para analises de raios X; Coeficiente de extensibilidadelinear (COLE); Expressao dos resultados; Parte II - Analises quimicas; pH (agua, KCl, CaCl2); Carbono organico; Nitrogenio total; Capacidadede troca de cations (CTC) e bases trocaveis; Acidez do solo; Hidrogenio extraivel; Valor T - CTC (Capacidade de Troca de Cations); Valor V (Percentagem de Saturacao de Bases); Percentagem de saturacao com aluminio; Percentagem de saturacao com sodio; Troca compulsiva (CTC e CTA)Ponto de carga zero (PCZ); Ataque sulfurico; Silica; Ferro no extrato sulfurico; Aluminio no extrato sulfurico; Titanio no extrato sulfuricoManganes no extrato sulfurico; Fosforo no extrato sulfurico; Relacoes moleculares Ki e Kr; Relacao molecular Al2O3/ Fe2O3; Ferro, aluminio,manganes e silica extraiveis; Sais soluveis; Equivalente de carbono ...bitstream/item/169149/1/Manual-de-metodos-de-analise-de-solo-2-ed-1997.pdf2. ed. rev. e atual.Autores: Marie Elisabeth Christine Claessen (Organização), Washington de Oliveira Barreto (Coordenação técnica), José Lopes de Paula, Mariza Nascimento Duarte

Simplificação do método de Kjeldahl para a determinação de N-total de solos tropicais.

Solos minerais cultivados apresentam em geral teores de N-total variando de 0,06 a 0,5% nos horizontes superficiais, enquanto que nos horizontes inferiores esses teores decrescem a níveis abaixo de 0,02%. No caso dos solos orgânicos, o N aumenta com a elevação do teor de matéria orgânica, podendo chegar a 2,5%. O N-total determinado pelo método clássico de Kjeldahl inclui formas orgânicas combinadas decorrentes da variada composição da matéria orgânica presente no solo. Os teores de N sob forma de NO2 e NO3 ocorrem em quantidades insignificantes em solos cauliníticos, predominantes nas regiões tropicais, devido aos intensos processos de transformações biológicas e grande lixiviação, não sendo incorporados aos valores de N-total durante a digestão. Pode-se afirmar que nestes casos o N-orgânico é praticamente o N-total. Vermiculitas e ilitas fixam teores significativos de N sob forma de NH4 +, tornando-se importantes na disponibilidade de N em solos de baixo grau de intemperismo. Por serem pouco frequentes nas amostras de solos altamente intemperizados, quase nada contribuem na composição do N-total destes solos

Simplificação do método de Kjeldahl para determinação de N-total de solos tropicais.

Estudou-se a possibilidade de simplificar a metodologia proposta por Kjeldahl para determinação do nitrogênio. Para isso foram selecionadas 20 amostras de horizontes superficiais representativos de algumas das principais classes de solos ocorrentes no pais. Após aplicação de 25, 50, 75 e 100 mg de Se, como catalisador, e aquecimento de 30, 60 e 120 minutos, verificou-se que a determinação do nitrogênio do solo pode ser acelerada reduzindo-se o tempo de aquecimento necessário a mineralização da amostra para 30 minutos empregando-se 25 mg do catalisador salvo pra solos ricos em matéria orgânica onde o tempo sugerido e de 60 minutos

Your Proof Fails? Testing Helps to Find the Reason

Applying deductive verification to formally prove that a program respects its formal specification is a very complex and time-consuming task due in particular to the lack of feedback in case of proof failures. Along with a non-compliance between the code and its specification (due to an error in at least one of them), possible reasons of a proof failure include a missing or too weak specification for a called function or a loop, and lack of time or simply incapacity of the prover to finish a particular proof. This work proposes a new methodology where test generation helps to identify the reason of a proof failure and to exhibit a counter-example clearly illustrating the issue. We describe how to transform an annotated C program into C code suitable for testing and illustrate the benefits of the method on comprehensive examples. The method has been implemented in STADY, a plugin of the software analysis platform FRAMA-C. Initial experiments show that detecting non-compliances and contract weaknesses allows to precisely diagnose most proof failures.Comment: 11 pages, 10 figure

Symmetry-Breaking Phase Transition without Peierls Mechanism in Conducting Monoatomic Chains

The one-dimensional (1D) model system Au/Ge(001), consisting of linear chains of single atoms on a surface, is scrutinized for lattice instabilities predicted in the Peierls paradigm. By scanning tunneling microscopy and electron diffraction we reveal a second-order phase transition at 585 K. It leads to charge ordering with transversal and vertical displacements and complex interchain correlations. However, the structural phase transition is not accompanied by the electronic signatures of a charge density wave, thus precluding a Peierls instability as origin. Instead, this symmetry-breaking transition exhibits three-dimensional critical behavior. This reflects a dichotomy between the decoupled 1D electron system and the structural elements that interact via the substrate. Such substrate-mediated coupling between the wires thus appears to have been underestimated also in related chain systems.Comment: 5 pages, 4 figures, accepted at Physical Review Letters 09/201

Spin gap formation in the quantum spin systems TiOX, X=Cl and Br

In the layered quantum spin systems TiOCl and TiOBr the magnetic susceptibility shows a very weak temperature dependence at high temperatures and transition-induced phenomena at low temperatures. There is a clear connection of the observed transition temperatures to the distortion of the octahedra and the layer separation. Band structure calculations point to a relation of the local coordinations and the dimensionality of the magnetic properties. While from magnetic Raman scattering only a small decrease of the magnetic exchange by -5-10% is derived comparing TiOCl with TiOBr, the temperature dependence of the magnetic susceptibility favors a much bigger change.Comment: 5 figures, 15 pages, further information see http://www.peter-lemmens.d

Electronic structure of the quasi-one-dimensional organic conductor TTF-TCNQ

We study the electronic structure of the quasi-one-dimensional organic conductor TTF-TCNQ by means of density-functional band theory, Hubbard model calculations, and angle-resolved photoelectron spectroscopy (ARPES). The experimental spectra reveal significant quantitative and qualitative discrepancies to band theory. We demonstrate that the dispersive behavior as well as the temperature-dependence of the spectra can be consistently explained by the finite-energy physics of the one-dimensional Hubbard model at metallic doping. The model description can even be made quantitative, if one accounts for an enhanced hopping integral at the surface, most likely caused by a relaxation of the topmost molecular layer. Within this interpretation the ARPES data provide spectroscopic evidence for the existence of spin-charge separation on an energy scale of the conduction band width. The failure of the one-dimensional Hubbard model for the {\it low-energy} spectral behavior is attributed to interchain coupling and the additional effect of electron-phonon interaction.Comment: 18 pages, 9 figure

Cluster Dynamical Mean-field calculations for TiOCl

Based on a combination of cluster dynamical mean field theory (DMFT) and density functional calculations, we calculated the angle-integrated spectral density in the layered $s=1/2$ quantum magnet TiOCl. The agreement with recent photoemission and oxygen K-edge X-ray absorption spectroscopy experiments is found to be good. Th e improvement achieved with this calculation with respect to previous single-site DMFT calculations is an indication of the correlated nature and low-dimensionality of TiOCl.Comment: 9 pages, 3 figures, improved version as publishe

Unoccupied Band Structure of NbSe2 by Very-Low-Energy Electron Diffraction: Experiment and Theory

A combined experimental and theoretical study of very-low-energy electron diffraction at the (0001) surface of 2H-NbSe2 is presented. Electron transmission spectra have been measured for energies up to 50 eV above the Fermi level with k|| varying along the GammaK line of the Brillouin zone. Ab initio calculations of the spectra have been performed with the extended linear augmented plane wave k-p method. The experimental spectra are interpreted in terms of three-dimensional one-electron band structure. Special attention is paid to the quasi-particle lifetimes: by comparing the broadening of the spectral structures in the experimental and calculated spectra the energy dependence of the optical potential Vi is determined. A sharp increase of Vi at 20 eV is detected, which is associated with a plasmon peak in the Im(-1/epsilon) function. Furthermore, the electron energy loss spectrum and the reflectivity of NbSe2 are calculated ab initio and compared with optical experiments. The obtained information on the dispersions and lifetimes of the unoccupied states is important for photoemission studies of the 3D band structure of the valence band.Comment: 17 pages, 11 Postscript figures, submitted to Phys. Rev.