5,067 research outputs found
Long-wavelength limit of gyrokinetics in a turbulent tokamak and its intrinsic ambipolarity
Recently, the electrostatic gyrokinetic Hamiltonian and change of coordinates
have been computed to order in general magnetic geometry. Here
is the gyrokinetic expansion parameter, the gyroradius over the
macroscopic scale length. Starting from these results, the long-wavelength
limit of the gyrokinetic Fokker-Planck and quasineutrality equations is taken
for tokamak geometry. Employing the set of equations derived in the present
article, it is possible to calculate the long-wavelength components of the
distribution functions and of the poloidal electric field to order
. These higher-order pieces contain both neoclassical and turbulent
contributions, and constitute one of the necessary ingredients (the other is
given by the short-wavelength components up to second order) that will
eventually enter a complete model for the radial transport of toroidal angular
momentum in a tokamak in the low flow ordering. Finally, we provide an explicit
and detailed proof that the system consisting of second-order gyrokinetic
Fokker-Planck and quasineutrality equations leaves the long-wavelength radial
electric field undetermined; that is, the turbulent tokamak is intrinsically
ambipolar.Comment: 70 pages. Typos in equations (63), (90), (91), (92) and (129)
correcte
COLA. III. Radio Detection of Active Galactic Nucleus in Compact Moderate Luminosity Infrared Galaxies
We present results from 4.8 GHz Very Large Array (VLA) and global very long baseline interferometry (VLBI) observations of the northern half of the moderate FIR luminosity (median L_(IR) = 10^(11.01) L_☉) COLA sample of star-forming galaxies. VLBI sources are detected in a high fraction (20/90) of the galaxies observed. The radio luminosities of these cores (~10^(21) W Hz^(–1)) are too large to be explained by radio supernovae or supernova remnants and we argue that they are instead powered by active galactic nuclei (AGNs). These sub-parsec scale radio cores are preferentially detected toward galaxies whose VLA maps show bright 100-500 parsec scale nuclear radio components. Since these latter structures tightly follow the FIR to radio-continuum correlation for star formation, we conclude that the AGN-powered VLBI sources are associated with compact nuclear starburst environments. The implications for possible starburst-AGN connections are discussed. The detected VLBI sources have a relatively narrow range of radio luminosity consistent with models in which intense compact Eddington-limited starbursts regulate the gas supply onto a central supermassive black hole. The high incidence of AGN radio cores in compact starbursts suggests little or no delay between the starburst phase and the onset of AGN activity
PWM digital configurable para simples proyectos
This paper presents the software implementation of an adjustable PWM (Pulse Width Modulator) prototype, developed in Verilog code, which functions as a training tool at the undergraduate level, or for the development of small projects. At the schematic level, the prototype presents the main module called PWM which integrates three modules (frequency, useful cycle, and display), as a complement to carry out results under the conditions specified in the functional profile. The base module integrates combinational and sequential circuits, i.e. counters, comparators, flip flops, function generators, etc. The final results obtained by simulation show the expected behavior in terms of frequency setting, duty cycle, and display.Este artículo presenta la implementación, en cuanto a software, de un prototipo de PWM (Modulador por Ancho de Pulso) ajustable, desarrollado en código Verilog, que funcione como herramienta de formación en el ámbito de pregrado, o el desarrollo de pequeños proyectos. En cuanto a esquema, el prototipo presenta un módulo principal llamado PWM el cual integra tres módulos (frecuencia, ciclo útil y display), como complemento para llevar a cabo resultados bajo las condiciones especificadas en el perfil funcional. La base de los módulos integra circuitos combinacionales y secuenciales, es decir contadores, comparadores, Flip Flops, generadores de funciones, etc. Los resultados finales obtenidos por simulación muestran el comportamiento esperado en cuanto a ajuste de frecuencia, ciclo útil y visualización
Atividade diurna de adultos de Diabrótica speciosa na cultura do milho e de cerotoma arcuatus na cultura da soja.
Neste documento são apresentadas importantes informações sobre o ritmo de atividade diurna de adultos de D. speciosa, na cultura do milho, e de C. arcuatus na cultura da soja. Assim, as informações contidas neste trabalho são de grande valia, pois podem auxiliar na definição de táticas para o manejo dessas pragas.bitstream/item/38187/1/DOC200464.pd
Evaluación del efecto del uso y manejo del suelo sobre algunas propiedades de un Hapludol típico en Argentina
Perpendicular momentum injection by lower hybrid wave in a tokamak
The injection of lower hybrid waves for current drive into a tokamak affects
the profile of intrinsic rotation. In this article, the momentum deposition by
the lower hybrid wave on the electrons is studied. Due to the increase in the
poloidal momentum of the wave as it propagates into the tokamak, the parallel
momentum of the wave increases considerably. The change of the perpendicular
momentum of the wave is such that the toroidal angular momentum of the wave is
conserved. If the perpendicular momentum transfer via electron Landau damping
is ignored, the transfer of the toroidal angular momentum to the plasma will be
larger than the injected toroidal angular momentum. A proper quasilinear
treatment proves that both perpendicular and parallel momentum are transferred
to the electrons. The toroidal angular momentum of the electrons is then
transferred to the ions via different mechanisms for the parallel and
perpendicular momentum. The perpendicular momentum is transferred to ions
through an outward radial electron pinch, while the parallel momentum is
transferred through collisions.Comment: 22 pages, 4 figure
Rearing the southern green stink bug using an artificial dry diet and an artificial plant.
Laboratory and greenhouse studies were conducted with an artificial dry diet to rear nymphs, and with an artificial plant as substrate for egg laying by the southern green stink bug, Nezara viridula (L.). The artificial diet was composed of: soybean protein (15 g); potato starch (7.5 g); dextrose (7.5 g); sucrose (2.5 g); cellulose (12.5 g); vitamin mixture (niacinamide 1 g, calcium pantothenate 1 g, thiamine 0.25 g, riboflavin 0.5 g, pyridoxine 0.25 g, folic acid 0.25 g, biotin 0.02 mL, vitamin B12 1 g ? added to 1,000 mL of distilled water) (5.0 mL); soybean oil (20 mL); wheat germ (17.9 g); and water (30 mL). Nymphs showed normal feeding behavior when fed on the artificial diet. Nymphal development time was longer than or similar to that of nymphs fed on soybean pods. Total nymphal mortality was low (ca. 30%), both for nymphs reared on the artificial diet, and for nymphs fed on soybean pods. At adult emergence, fresh body weights were significantly (P<0.01) less on the artificial diet than on soybean pods. Despite the lower adult survivorship and fecundity on artificial plants than on soybean plants, it was demonstrated for the first time that a model simulating a natural plant, can be used as a substrate for egg mass laying, in conjunction with the artificial diet
Host plant effects on the development, survival, and reproduction of dysmicoccus brevipes (Hemiptera: Pseudococcidae) on grapevines.
Dysmicoccus brevipes (Cockerell, 1893) (Hemiptera: Pseudococcidae) is one of the most frequent and abundant mealybugs in Brazilian vineyards, where it causes direct and indirect damage to the vines. In this study, we investigated the effect of plant structures, cultivars, and vine rootstocks on the development, survival, and reproduction of D. brevipes under laboratory conditions. Leaves of the tablegrape cultivar ÔIta´liaÕ (Vitis vinifera) and ÔNia´gara RosadaÕ (Vitis labrusca) and the vine roots of the rootstocks Paulsen 1103 (Vitis berlandieriV. rupestris) and IAC 572 (Vitis caribaea101-14 Mgt) were used as host plants. D. brevipes developed on different vegetative structures, cultivars, and vine rootstocks. D. brevipes showed the shortest developmental period and highest survival and fecundity rates on leaves of cultivar Ita´lia. Survival on leaves was signiÞcantly higher than on roots. Roots of IAC 572 were unsuitable for D. brevipes development, resulting in nonreproductive females.ThemealybugsÕ longevityonleaves and vine roots was similar. Higher intrinsic and Þnite rates of increase and net reproductive rate were observed whenmealybugs developed on Ita´lia leaves.Weconcluded that the host plant affects the development and survival of D. brevipes and that the choice of the most appropriate cultivar or vine rootstock can help to reduce pest infestation, and is therefore an additional component to be included in the integrated pest management of grapes
Positivity and conservation of superenergy tensors
Two essential properties of energy-momentum tensors T_{\mu\nu} are their
positivity and conservation. This is mathematically formalized by,
respectively, an energy condition, as the dominant energy condition, and the
vanishing of their divergence \nabla^\mu T_{\mu\nu}=0. The classical Bel and
Bel-Robinson superenergy tensors, generated from the Riemann and Weyl tensors,
respectively, are rank-4 tensors. But they share these two properties with
energy momentum tensors: the Dominant Property (DP) and the divergence-free
property in the absence of sources (vacuum). Senovilla defined a universal
algebraic construction which generates a basic superenergy tensor T{A} from any
arbitrary tensor A. In this construction the seed tensor A is structured as an
r-fold multivector, which can always be done. The most important feature of the
basic superenergy tensors is that they satisfy automatically the DP,
independently of the generating tensor A. In a previous paper we presented a
more compact definition of T{A} using the r-fold Clifford algebra. This form
for the superenergy tensors allowed to obtain an easy proof of the DP valid for
any dimension. In this paper we include this proof. We explain which new
elements appear when we consider the tensor T{A} generated by a
non-degree-defined r-fold multivector A and how orthogonal Lorentz
transformations and bilinear observables of spinor fields are included as
particular cases of superenergy tensors. We find some sufficient conditions for
the seed tensor A, which guarantee that the generated tensor T{A} is
divergence-free. These sufficient conditions are satisfied by some physical
fields, which are presented as examples.Comment: 19 pages, no figures. Language and minor changes. Published versio
Evaluación del impacto del cambio de uso y manejo de la tierra mediante indicadores de calidad del suelo: Córdoba, Argentina
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