5,833 research outputs found
Considering Fluctuation Energy as a Measure of Gyrokinetic Turbulence
In gyrokinetic theory there are two quadratic measures of fluctuation energy,
left invariant under nonlinear interactions, that constrain the turbulence. The
recent work of Plunk and Tatsuno [Phys. Rev. Lett. 106, 165003 (2011)] reported
on the novel consequences that this constraint has on the direction and
locality of spectral energy transfer. This paper builds on that work. We
provide detailed analysis in support of the results of Plunk and Tatsuno but
also significantly broaden the scope and use additional methods to address the
problem of energy transfer. The perspective taken here is that the fluctuation
energies are not merely formal invariants of an idealized model
(two-dimensional gyrokinetics) but are general measures of gyrokinetic
turbulence, i.e. quantities that can be used to predict the behavior of the
turbulence. Though many open questions remain, this paper collects evidence in
favor of this perspective by demonstrating in several contexts that constrained
spectral energy transfer governs the dynamics.Comment: Final version as published. Some cosmetic changes and update of
reference
The Ecological Basis for Biogeographic Classification: an Example in Orchid Bees (Apidae: Euglossini)
Biogeography has been difficult to apply as a methodological approach because organismic biology is incomplete at levels where the process of formulating comparisons and analogies is complex. The study of insect biogeography became necessary because insects possess numerous evolutionary traits and play an important role as pollinators. Among insects, the euglossine bees, or orchid bees, attract interest because the study of their biology allows us to explain important steps in the evolution of social behavior and many other adaptive tradeoffs. We analyzed the distribution of morphological characteristics in Colombian orchid bees from an ecological perspective. The aim of this study was to observe the distribution of these attributes on a regional basis. Data corresponding to Colombian euglossine species were ordered with a correspondence analysis and with subsequent hierarchical clustering. Later, and based on community proprieties, we compared the resulting hierarchical model with the collection localities to seek to identify a biogeographic classification pattern. From this analysis, we derived a model that classifies the territory of Colombia into 11 biogeographic units or natural clusters. Ecological assumptions in concordance with the derived classification levels suggest that species characteristics associated with flight performance, nectar uptake, and social behavior are the factors that served to produce the current geographical structure.Universidad Nacional de Colombia, Facultad de Ciencias, Departments of Biology and StatisticsUniversidad Nacional de Colombia, Facultad de Ciencias, Departments of Biology and Statistics"Convocatoria Nacional Fortalecimiento de la Visibilidad de Produccion Academica mediante el Apoyo para Traduccion y Correccion de Estilo de Articulos de Investigacion" centerConvocatoria Nacional Fortalecimiento de la Visibilidad de Produccion Academica mediante el Apoyo para Traduccion y Correccion de Estilo de Articulos de Investigacion cente
Scaling of spontaneous rotation with temperature and plasma current in tokamaks
Using theoretical arguments, a simple scaling law for the size of the
intrinsic rotation observed in tokamaks in the absence of momentum injection is
found: the velocity generated in the core of a tokamak must be proportional to
the ion temperature difference in the core divided by the plasma current,
independent of the size of the device. The constant of proportionality is of
the order of . When the
intrinsic rotation profile is hollow, i.e. it is counter-current in the core of
the tokamak and co-current in the edge, the scaling law presented in this
Letter fits the data remarkably well for several tokamaks of vastly different
size and heated by different mechanisms.Comment: 5 pages, 3 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
Respuesta supraóptima a los inhibidores de PCSK-9: ¿es obligatorio darlos cada 2 semanas? A propósito de un caso
Los inhibidores del PCSK-9 se presentan como una excelente alternativa de tratamiento en aquellos casos de hipercolesterolemia que no alcanzan las metas con tratamiento usual con estatinas de alta potencia y ezetimiba, adicionalmente en los pacientes con intolerancia a estatinas que necesiten tener metas de colesterol LDL. En este caso exponemos la posibilidad de titular el tiempo de aplicación de PCSK-9i de acuerdo con las metas de los niveles de LDL
On Duality in the Born-Infeld Theory
The duality symmetric action for the Born-Infeld theory in terms of
two potentials, coupled with non-trivial backgroud fields in four dimensions is
established. This construction is carried out in detail by analysing the
hamiltonian structure of the Born-Infeld theory. The equivalence with the usual
Born-Infeld theory is shown.Comment: revtex, 4 page
Evaluación del impacto del cambio de uso y manejo de la tierra mediante indicadores de calidad del suelo: Córdoba, Argentina
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