Negative-Energy Perturbations in Circularly Cylindrical Equilibria within the Framework of Maxwell-Drift Kinetic Theory

The conditions for the existence of negative-energy perturbations (which could be nonlinearly unstable and cause anomalous transport) are investigated in the framework of linearized collisionless Maxwell-drift kinetic theory for the case of equilibria of magnetically confined, circularly cylindrical plasmas and vanishing initial field perturbations. For wave vectors with a non-vanishing component parallel to the magnetic field, the plane equilibrium conditions (derived by Throumoulopoulos and Pfirsch [Phys Rev. E {\bf 49}, 3290 (1994)]) are shown to remain valid, while the condition for perpendicular perturbations (which are found to be the most important modes) is modified. Consequently, besides the tokamak equilibrium regime in which the existence of negative-energy perturbations is related to the threshold value of 2/3 of the quantity $\eta_\nu = \frac {\partial \ln T_\nu} {\partial \ln N_\nu}$, a new regime appears, not present in plane equilibria, in which negative-energy perturbations exist for {\em any} value of $\eta_\nu$. For various analytic cold-ion tokamak equilibria a substantial fraction of thermal electrons are associated with negative-energy perturbations (active particles). In particular, for linearly stable equilibria of a paramagnetic plasma with flat electron temperature profile ($\eta_e=0$), the entire velocity space is occupied by active electrons. The part of the velocity space occupied by active particles increases from the center to the plasma edge and is larger in a paramagnetic plasma than in a diamagnetic plasma with the same pressure profile. It is also shown that, unlike in plane equilibria, negative-energy perturbations exist in force-free reversed-field pinch equilibria with a substantial fraction of active particles.Comment: 31 pages, late

Negative-energy perturbations in cylindrical equilibria with a radial electric field

The impact of an equilibrium radial electric field $E$ on negative-energy perturbations (NEPs) (which are potentially dangerous because they can lead to either linear or nonlinear explosive instabilities) in cylindrical equilibria of magnetically confined plasmas is investigated within the framework of Maxwell-drift kinetic theory. It turns out that for wave vectors with a non-vanishing component parallel to the magnetic field the conditions for the existence of NEPs in equilibria with E=0 [G. N. Throumoulopoulos and D. Pfirsch, Phys. Rev. E 53, 2767 (1996)] remain valid, while the condition for the existence of perpendicular NEPs, which are found to be the most important perturbations, is modified. For $|e_i\phi|\approx T_i$ ($\phi$ is the electrostatic potential) and $T_i/T_e > \beta_c\approx P/(B^2/8\pi)$ ($P$ is the total plasma pressure), a case which is of operational interest in magnetic confinement systems, the existence of perpendicular NEPs depends on $e_\nu E$, where $e_\nu$ is the charge of the particle species $\nu$. In this case the electric field can reduce the NEPs activity in the edge region of tokamaklike and stellaratorlike equilibria with identical parabolic pressure profiles, the reduction of electron NEPs being more pronounced than that of ion NEPs.Comment: 30 pages, late

Manejo e utilização de plantas forrageiras dos genêros Panicum brachiaria e Cynodon.

bitstream/item/37976/1/Documentos34-0.pdf2. ed. rev

Avaliação da contaminação de aquífero furnas por pesticidas.

Resumo

Conservação de propágulos de cajueiro anão precoce para enxertia por borbulhia.

No presente trabalho, foram testados varios tipos de materiais com o objetivo de se determinar as condicoes mais adequadas para o acondicionamento de propagulos, fornecedores de borbulhas de cajueiro anao precoce, mantendo sua viabilidade, mesmo quando se necessitar de mais de tres dias para se proceder a enxertia.bitstream/CNPAT-2010/5352/1/Ct-020.pd

Produção de propágulos em jardim clonal de cajueiro anão precoce irrigado e adensado.

bitstream/CNPAT-2010/5596/1/Pa-025.pd

Produção de propágulos de acerola (Malphighia glabra L.) em jardim clonal irrigado e com alta densidade de plantio.

bitstream/CNPAT-2010/5597/1/Pa-026.pd

Evaluation of Physical Properties of Coffee during Roasting

Rosana G. Moreira, Editor-in-Chief; Texas A&M UniversityThis is a Technical Paper from International Commission of Agricultural Engineering (CIGR, Commission Internationale du Genie Rural) E-Journal Volume 5 (2003): M. Rodrigues, M. Borges, A. Franca, L. Oliveira, and P. Correa. Evaluation of Physical Properties of Coffee during Roasting. Vol. V. December 2003

Recuperação de pomares jovens de cajueiro anão precoce pela substituição de copa.

A substituicao de copaem plantas jovens de cajueiro anao-precoce e uma alternativa eficaz para dar iniformidade e aumentar a producao dos pomares formados com mudas propagadas por semente; (...) A substituicao de copa permite, a partir do quarto ano de frutificacao ...bitstream/CNPAT-2010/5354/1/Ct-023.pd

Efeito do número de brotações enxertadas na produção do cajueiro anão precoce com copa substituída (Anacardium occidentale L.).

Trabalho ... demostra a viabilidade da substituicao de copa, como alternativa de recuperar pomares de cajueiro constituidos de mudas de pe franco.bitstream/CNPAT-2010/5353/1/Ct-024.pd