The genus Sipha Passerini (Hemiptera: Aphididae) in North America

Five species of the aphid genus Sipha Passerini (Hemiptera: Aphididae) are reported in North America and are reviewed herein. Of these species, three are adventive species and include: Sipha elegans del Guercio, Sipha glyceriae (Kaltenbach), and Sipha maydis Passerini. Sipha maydis was discovered in California in 2007 and now has been found in Georgia. The genus also includes two native species: Sipha agropyronensis (Gillette) and Sipha flava (Forbes). Sipha maydis can be distinguished easily from all the other species in the genus that occur in North America because it is black. All the species except S. agropyronensis have been implicated in damage to crop plants. A key to the apterae and alatae of Sipha found in North America is included

ESTADO E GOVERNO NO PENSAMENTO DE MARSÍLIO DE PÁDUA: RAÍZES MEDIEVAIS DE UMA TEORIA MODERNA

This study brings light to the concepts of State and Government in the thought of Marsilio de Padua pointing out to profoundly modern institutions present in the reflection of this medieval philosopher. We attempt to show that Marsilio de Padua reflects based on Aristotle´s categories, but proposes a State and Government conception different from that common place of medieval politics as he insists on the need of the popular consent as a criterion of political legitimacy. O estudo explicita os conceitos de Estado e de Governo no pensamento de Marsílio de Pádua apontando as intuições profundamente modernas presentes na reflexão desse filósofo medieval. Procuramos mostrar que Marsílio reflete com categorias aristotélicas, mas propõe uma concepção de Estado e de Governo que se distancia do lugar comum da reflexão política medieval ao insistir na necessidade do consentimento dos súditos como critério de legitimidade política

Symmetric periscope for concentric beam configuration in an ultra-high precision laser interferometric beam launcher

An optical component especially suited for common path heterodyne interferometry comprises a symmetric dual-periscope configuration. Each periscope is substantially identical to the other with regard to certain design aspects. The resulting design is an optical component that is highly stable with variations in temperature and angular deviations

A CENSORED SYSTEM ESTIMATION OF HISPANIC HOUSEHOLD FOOD CONSUMPTION PATTERNS

A system of nine censored Engel curve equations was estimated for Hispanic households in the U.S.: grains, vegetables, fruits, milk, meat, legumes, fats, sugar, and beverages. Income and household size elasticities, with their respective confidence intervals, are reported and the results compared with other ethnic groups in the U.S.Food Consumption/Nutrition/Food Safety,

COMPARISONS OF HISPANIC HOUSEHOLDS' DEMAND FOR MEATS WITH OTHER ETHNIC GROUPS

The objective of this research was to analyze the demand patterns of Hispanic households for meats in comparison with other ethnic groups using data from the 1998 Consumer Expenditure Survey. A system of demand equations of the LinQuad form were estimated for ten meat products using an incomplete system of censored equations. Hispanic households showed a clear preference for beef. Price, income, and household-size elasticities were estimated for each meat product by ethnic group. The demand for ground beef was the most income-inelastic product regardless of ethnicity. Household size had a positive effect on the probability of consuming a particular meat product but a negative effect on actual item expenditures.Consumer/Household Economics, Demand and Price Analysis,

The myth ofa population explosion in yamerican society

Desde hace unos años, el público norteamericano está sometido a un verdadero bombardeo propagandista de argumentos antinatalistas, llamamientos emocionales y «slogans» publicitarios sobre el llamado «problema» de,1 crecimiento demográfico en Estados Unidos. Al mismo tiempo, numerosos «expertos» y muchas organizaciones sociales intentan buscar «soluciones» a es'e «problema», para evitar una catástrofe demográfica en el futuro. Estas «soluciones» muchas veces son radicales y carecen de realismo, desde los contraceptivos para los menores de edad hasta el aborto generalizado para todos. En este artículo los autores demuestran, científicamente, la falacia de los planteamientos apocalípticos y antinatalistas en cuanto al caso de Estados Unidos. Lo más importante en la historia demográfica de este países el hecho de que las tasas de fertilidad han ido bajando de forma drástica desde 1800; en la actualidad, la tasa de natalidad está a nivel de reemplazo, y los pronósticos de cara al futuro inmediato indican que eI proceso de declive va a continuar. Este fenómeno se debe a una combinación de factores -un mayor número de mujeres solteras, incorporadas en el trabajo profesional; un incremento de matrimonios tardíos; el cambio de mentalidad con respecto a las familias numerosas- que hacen suponer que la sociedad norteamericana no camina hacia el desastre demográfico, sino hacia un vacío demográfíco. Además, e·1 argumento malthusiano no corresponde a la realidad, y no encuentra apoyo estadísticamente. El impacto del descenso continuo de la fertilidad se sentirá en el futuro no lejano de forma muy negativa, especialmente en las categorías de edad dependientes (menos de 15 y más de 65 años de edad), y llevará consigo problemas socioeconómicos y demográficos graves. Por otra parte, los argumentos sobre la e'scasez de alimentos, las altas densidades de población, la contaminación del medio ambiente, etc., carecen de validez científica y de realismo. Por lo tanto, en Estados Unidos, los abogados de la «explosión demográfica» actúan no sólo en un vacío factual, sino también en un vacío intelectual. Sus argumentos, aunque estén cargados de ruido y de emoción, carecen de sentido común y por tanto defienden una posición mítica

Effects of a Conducting Sphere Moving Through a Gradient Magnetic Field

We examine several conducting spheres moving through a magnetic field gradient. An analytical approximation is derived and an experiment is conducted to verify the analytical solution. The experiment is simulated as well to produce a numerical result. Both the low and high magnetic Reynolds number regimes are studied. Deformation of the sphere is noted in the high Reynolds number case. It is suggested that this deformation effect could be useful for designing or enhancing present protection systems against space debris.Comment: Presented at the AIAA Aerospace Sciences Meeting, Orlando, Florida, Jan 4-7, 201

Beam masking to reduce cyclic error in beam launcher of interferometer

Embodiments of the present invention are directed to reducing cyclic error in the beam launcher of an interferometer. In one embodiment, an interferometry apparatus comprises a reference beam directed along a reference path, and a measurement beam spatially separated from the reference beam and being directed along a measurement path contacting a measurement object. The reference beam and the measurement beam have a single frequency. At least a portion of the reference beam and at least a portion of the measurement beam overlapping along a common path. One or more masks are disposed in the common path or in the reference path and the measurement path to spatially isolate the reference beam and the measurement beam from one another

The profile of an emission line from relativistic outflows around a black hole

Recent observations show strong evidence for the presence of Doppler-shifted emission lines in the spectrum of both black hole candidates and active galactic nuclei. These lines are likely to originate from relativistic outflows (or jets) in the vicinity of the central black hole. Consequently, the profile of such a line should be distorted by strong gravitational effects near the black hole, as well as special relativistic effects. In this paper, we present results from a detailed study on how each process affects the observed line profile. We found that the profile is sensitive to the intrinsic properties of the jets (Lorentz factor, velocity profile, and emissivity law), as well as to the spin of the black hole and the viewing angle (with respect to the axis of the jets). More specifically, in the case of approaching jets, an intrisically narrow line (blue-shifted) is seen as simply broadened at small viewing angles, but it shows a doubly peaked profile at large viewing angles for extreme Kerr black holes (due to the combination of gravitational focusing and Doppler effects); the profile is always singly peaked for Schwarzschild black holes. For receding jets, however, the line profile becomes quite complicated owing to complicated photon trajectories. To facilitate comparison with observations, we searched a large parameter space to derive representative line profiles. We show the results and discuss how to use emission lines as a potential tool for probing the inner region of a black hole jet system.Comment: 16 pages in emulateapj style, 11 figure

Solving the time-dependent Schr\"odinger equation with absorbing boundary conditions and source terms in Mathematica 6.0

In recent decades a lot of research has been done on the numerical solution of the time-dependent Schr\"odinger equation. On the one hand, some of the proposed numerical methods do not need any kind of matrix inversion, but source terms cannot be easily implemented into this schemes; on the other, some methods involving matrix inversion can implement source terms in a natural way, but are not easy to implement into some computational software programs widely used by non-experts in programming (e.g. Mathematica). We present a simple method to solve the time-dependent Schr\"odinger equation by using a standard Crank-Nicholson method together with a Cayley's form for the finite-difference representation of evolution operator. Here, such standard numerical scheme has been simplified by inverting analytically the matrix of the evolution operator in position representation. The analytical inversion of the N x N matrix let us easily and fully implement the numerical method, with or without source terms, into Mathematica or even into any numerical computing language or computational software used for scientific computing.Comment: 15 pages, 7 figure