Combinations of Nitrogen and Sulphur for Signal Grass Yield

Signal grass (Brachiaria decumbens) is grown in Brazilian pastures, and the increase in forage yield of such pastures is achieved by fertilization. Nitrogen (N) is the nutrient mostly demanded for increasing grass productivity, and its utilization creates a demand for other nutrients, such as sulphur (S). These two nutrients are well related in plant metabolism, but the S nutrition of signal grass must be better understood. The use of a fractional factorial makes possible the study of several rates of these two nutrients, that combined with the response surface methodology allows anyone to find out the responses to these rates combinations. The objective of this research was to obtain the responses in dry matter yield of plant tops and roots of signal grass grown under N and S combinations

Dynamics of a Generalized Cosmological Scalar-Tensor Theory

A generalized scalar-tensor theory is investigated whose cosmological term depends on both a scalar field and its time derivative. A correspondence with solutions of five-dimensional Space-Time-Matter theory is noted. Analytic solutions are found for the scale factor, scalar field and cosmological term. Models with free parameters of order unity are consistent with recent observational data and could be relevant to both the dark-matter and cosmological-"constant" problems.Comment: 13 page

Utilização de crotalária no controle de nematóides da raiz do feijoeiro.

Este trabalho teve como objetivo avaliar o efeito da palhada de C. spectabilis no controle de nematóides da raiz do feijoeiro.bitstream/CNPAF/22189/1/comt_74.pd

Adubação nitrogenada no feijoeiro cultivado sob palhadas de diferentes culturas.

O objetivo deste trabalho é avaliar a resposta do feijoeiro irrigado, cultivado sob plantio direto em sucessão a diferentes culturas, à adubação nitrogenada em cobertura.bitstream/CNPAF-2009-09/27950/1/comt_159.pd

Processo de Seleção Escape para Obtenção de Plantas de Pessegueiro e Ameixeira com Alta Sanidade.

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Radiolysis of ammonia-containing ices by energetic, heavy and highly charged ions inside dense astrophysical environments

Deeply inside dense molecular clouds and protostellar disks, the interstellar ices are protected from stellar energetic UV photons. However, X-rays and energetic cosmic rays can penetrate inside these regions triggering chemical reactions, molecular dissociation and evaporation processes. We present experimental studies on the interaction of heavy, highly charged and energetic ions (46 MeV Ni^13+) with ammonia-containing ices in an attempt to simulate the physical chemistry induced by heavy ion cosmic rays inside dense astrophysical environments. The measurements were performed inside a high vacuum chamber coupled to the heavy ion accelerator GANIL (Grand Accelerateur National d'Ions Lourds) in Caen, France.\textit{In-situ} analysis is performed by a Fourier transform infrared spectrometer (FTIR) at different fluences. The averaged values for the dissociation cross section of water, ammonia and carbon monoxide due to heavy cosmic ray ion analogs are ~2x10^{-13}, 1.4x10^{-13} and 1.9x10^{-13} cm$^2$, respectively. In the presence of a typical heavy cosmic ray field, the estimated half life for the studied species is 2-3x10^6 years. The ice compaction (micropore collapse) due to heavy cosmic rays seems to be at least 3 orders of magnitude higher than the one promoted by (0.8 MeV) protons . In the case of the irradiated H2O:NH3:CO ice, the infrared spectrum at room temperature reveals five bands that were tentatively assigned to vibration modes of the zwitterionic glycine (+NH3CH2COO-).Comment: Accepted to be published in Astronomy and Astrophysics; Number of pages: 12; Number of Figures: 7; Number of Tables:

A multi-agent system model to integrate Virtual Learning Environments and Intelligent Tutoring Systems

Virtual learning environments (VLEs) are used in distance learning and classroom teaching as teachers and students support tools in the teaching–learning process, where teachers can provide material, activities and assessments for students. However, this process is done in the same way for all the students, regardless of their differences in performance and behavior in the environment. The purpose of this work is to develop an agent-based intelligent learning environment model inspired by intelligent tutoring to provide adaptability to distributed VLEs, using Moodle as a case study and taking into account student's performance on tasks and activities proposed by the teacher, as well as monitoring his/her study material access

Anisotropic elastic theory of preloaded granular media

A macroscopic elastic description of stresses in static, preloaded granular media is derived systematically from the microscopic elasticity of individual inter-grain contacts. The assumed preloaded state and friction at contacts ensure that the network of inter-grain contacts is not altered by small perturbations. The texture of this network, set by the preparation of the system, is encoded in second and fourth order fabric tensors. A small perturbation generates both normal and tangential inter-grain forces, the latter causing grains to reorient. This reorientation response and the incremental stress are expressed in terms of the macroscopic strain.Comment: 7 pages, 2 figures. Accepted version. [email protected] [email protected]