Resonant Interactions Between Protons and Oblique Alfv\'en/Ion-Cyclotron Waves

Resonant interactions between ions and Alfv\'en/ion-cyclotron (A/IC) waves may play an important role in the heating and acceleration of the fast solar wind. Although such interactions have been studied extensively for "parallel" waves, whose wave vectors ${\bf k}$ are aligned with the background magnetic field ${\bf B}_0$, much less is known about interactions between ions and oblique A/IC waves, for which the angle $\theta$ between ${\bf k}$ and ${\bf B}_0$ is nonzero. In this paper, we present new numerical results on resonant cyclotron interactions between protons and oblique A/IC waves in collisionless low-beta plasmas such as the solar corona. We find that if some mechanism generates oblique high-frequency A/IC waves, then these waves initially modify the proton distribution function in such a way that it becomes unstable to parallel waves. Parallel waves are then amplified to the point that they dominate the wave energy at the large parallel wave numbers at which the waves resonate with the particles. Pitch-angle scattering by these waves then causes the plasma to evolve towards a state in which the proton distribution is constant along a particular set of nested "scattering surfaces" in velocity space, whose shapes have been calculated previously. As the distribution function approaches this state, the imaginary part of the frequency of parallel A/IC waves drops continuously towards zero, but oblique waves continue to undergo cyclotron damping while simultaneously causing protons to diffuse across these kinetic shells to higher energies. We conclude that oblique A/IC waves can be more effective at heating protons than parallel A/IC waves, because for oblique waves the plasma does not relax towards a state in which proton damping of oblique A/IC waves ceases

Molecular gas associated with IRAS 10361-5830

We analyze the distribution of the molecular gas and the dust in the molecular clump linked to IRAS 10361-5830, located in the environs of the bubble-shaped HII region Gum 31 in the Carina region, with the aim of determining the main parameters of the associated material and investigating the evolutionary state of the young stellar objects identified there. Using the APEX telescope, we mapped the molecular emission in the J=3-2 transition of three CO isotopologues, 12CO, 13CO and C18O, over a 1.5' x 1.5' region around the IRAS position. We also observed the high density tracers CS and HCO+ toward the source. The cold dust distribution was analyzed using submillimeter continuum data at 870 \mu\ obtained with the APEX telescope. Complementary IR and radio data at different wavelengths were used to complete the study of the ISM. The molecular gas distribution reveals a cavity and a shell-like structure of ~ 0.32 pc in radius centered at the position of the IRAS source, with some young stellar objects (YSOs) projected onto the cavity. The total molecular mass in the shell and the mean H$_2$ volume density are ~ 40 solar masses and ~(1-2) x 10$^3$ cm$^{-3}$, respectively. The cold dust counterpart of the molecular shell has been detected in the far-IR at 870 \mu\ and in Herschel data at 350 \mu. Weak extended emission at 24 \mu\ from warm dust is projected onto the cavity, as well as weak radio continuum emission. A comparison of the distribution of cold and warm dust, and molecular and ionized gas allows us to conclude that a compact HII region has developed in the molecular clump, indicating that this is an area of recent massive star formation. Probable exciting sources capable of creating the compact HII region are investigated. The 2MASS source 10380461-5846233 (MSX G286.3773-00.2563) seems to be responsible for the formation of the HII region.Comment: Accepted in A&A. 11 pages, 10 Postscript figure

Source amplitudes for active exterior cloaking

The active cloak comprises a discrete set of multipole sources that destructively interfere with an incident time harmonic scalar wave to produce zero total field over a finite spatial region. For a given number of sources and their positions in two dimensions it is shown that the multipole amplitudes can be expressed as infinite sums of the coefficients of the incident wave decomposed into regular Bessel functions. The field generated by the active sources vanishes in the infinite region exterior to a set of circles defined by the relative positions of the sources. The results provide a direct solution to the inverse problem of determining the source amplitudes. They also define a broad class of non-radiating discrete sources.Comment: 21 pages, 17 figure

Effects of lattice distortion and Jahn–Teller coupling on the magnetoresistance of La0.7Ca0.3MnO3 and La0.5Ca0.5CoO3 epitaxial films

Studies of La0.7Ca0.3MnO3 epitaxial films on substrates with a range of lattice constants reveal two dominant contributions to the occurrence of colossal negative magnetoresistance (CMR) in these manganites: at high temperatures (T → TC, TC being the Curie temperature), the magnetotransport properties are predominantly determined by the conduction of lattice polarons, while at low temperatures (T ≪ TC/, the residual negative magnetoresistance is correlated with the substrate-induced lattice distortion which incurs excess magnetic domain wall scattering. The importance of lattice polaron conduction associated with the presence of Jahn–Teller coupling in the manganites is further verified by comparing the manganites with epitaxial films of another ferromagnetic perovskite, La0.5Ca0.5CoO3. Regardless of the differences in the substrate-induced lattice distortion, the cobaltite films exhibit much smaller negative magnetoresistance, which may be attributed to the absence of Jahn–Teller coupling and the high electron mobility that prevents the formation of lattice polarons. We therefore suggest that lattice polaron conduction associated with the Jahn–Teller coupling is essential for the occurrence of CMR, and that lattice distortion further enhances the CMR effects in the manganites

Effective gravity from a quantum gauge theory in Euclidean space-time

We consider a $SO(d)$ gauge theory in an Euclidean $d$-dimensional space-time, which is known to be renormalizable to all orders in perturbation theory for $2\le{d}\le4$. Then, with the help of a space-time representation of the gauge group, the gauge theory is mapped into a curved space-time with linear connection. Further, in that mapping the gauge field plays the role of the linear connection of the curved space-time and an effective metric tensor arises naturally from the mapping. The obtained action, being quadratic in the Riemann-Christoffel tensor, at a first sight, spoils a gravity interpretation of the model. Thus, we provide a sketch of a mechanism that breaks the $SO(d)$ color invariance and generates the Einstein-Hilbert term, as well as a cosmological constant term, allowing an interpretation of the model as a modified gravity in the Palatini formalism. In that sense, gravity can be visualized as an effective classical theory, originated from a well defined quantum gauge theory. We also show that, in the four dimensional case, two possibilities for particular solutions of the field equations are the de Sitter and Anti de Sitter space-times.Comment: 20 pages; Final version accepted for publication in Class.Quant.Gra

Dissipative Dynamics of Collisionless Nonlinear Alfven Wave Trains

The nonlinear dynamics of collisionless Alfven trains, including resonant particle effects is studied using the kinetic nonlinear Schroedinger (KNLS) equation model. Numerical solutions of the KNLS reveal the dynamics of Alfven waves to be sensitive to the sense of polarization as well as the angle of propagation with respect to the ambient magnetic field. The combined effects of both wave nonlinearity and Landau damping result in the evolutionary formation of stationaryOA S- and arc-polarized directional and rotational discontinuities. These waveforms are freqently observed in the interplanetary plasma.Comment: REVTeX, 6 pages (including 5 figures). This and other papers may be found at http://sdphpd.ucsd.edu/~medvedev/papers.htm

Convective Fingering of an Autocatalytic Reaction Front

We report experimental observations of the convection-driven fingering instability of an iodate-arsenous acid chemical reaction front. The front propagated upward in a vertical slab; the thickness of the slab was varied to control the degree of instability. We observed the onset and subsequent nonlinear evolution of the fingers, which were made visible by a {\it p}H indicator. We measured the spacing of the fingers during their initial stages and compared this to the wavelength of the fastest growing linear mode predicted by the stability analysis of Huang {\it et. al.} [{\it Phys. Rev. E}, {\bf 48}, 4378 (1993), and unpublished]. We find agreement with the thickness dependence predicted by the theory.Comment: 11 pages, RevTex with 3 eps figures. To be published in Phys Rev E, [email protected], [email protected], [email protected]

Floristic Composition and Diversity of a Transect in a Locality of the Lowland Evergreen Forest of the Amazon of Cuyabeno City

The present research determined the high diversity and structure of the lowland evergreen forest of the Amazon in a locality (Rey de los Andes) of Cuyabeno city, since there is no updated information on this important biome. The linear transect methodology of 0.1 hectares was applied along the river and separated 2 m from the edge, all trees and shrubs with a diameter at breast height greater than 10 cm were measured, fertile botanical samples were collected and were processed and identified in the CHEP Herbarium. A total of 86 individuals were obtained between trees and shrubs distributed in 20 families, 39 genera, and 41 species, and a basal area of 10.95 m2 was obtained. The dominant family was Fabaceae with seven genera and the most frequent species were Astrocaryum urostachys, Celtis sp., and Leonia crassa. The highest importance value index was 15.56% for Astrocaryum urostachys and 10.33% for Otoba glycycarpa and the Simpson Diversity Index was 0.96. The diameters obtained were classified into 3 diameter classes, where Class I was made up of 68 individuals, which represents 79.07% of the total. It is concluded that the forest of the Rey de los Andes community has a high diversity of tree and shrub species. Likewise, considering the type of vegetation found, list of species, site, and diameters obtained, it can be stated that it is a well-preserved forest. Keywords: Floristic composition, Lowland evergreen forest, Cuyabeno. Resumen La presente investigación determinó la alta diversidad y estructura del bosque siempreverde de tierras bajas de la amazonía de una localidad (Rey de los Andes) del Cantón Cuyabeno; ya que no se cuenta con información actualizada de este importante bioma. Se aplicó la metodología de transecto lineal de 0,1 hectáreas a lo largo del río y separado a dos metros del borde, se midió todos los árboles y arbustos con diámetro a la altura del pecho mayor a 10 centímetros, se recolectó muestras botánicas fértiles y fueron procesadas e identificadas en el Herbario CHEP. Se obtuvo un total de 86 individuos entre árboles y arbustos distribuidos en 20 familias, 39 géneros y 41 especies y se obtuvo un área basal de 10,95 m2; la familia dominante fue Fabaceae con siete géneros y las especies más frecuentes fueron Astrocaryum urostachys, Celtis sp. y Leonia crassa. El Índice de Valor de Importancia más alto fue de 15,56% para Astrocaryum urostachys y de 10,33% para Otoba glycycarpa y el Índice de Diversidad de Simpson fue de 0,96. Los diámetros obtenidos fueron clasificados en 3 clases diamétricas, donde la Clase I estuvo conformada por 68 individuos lo que representa al 79,07% del total. Se concluye que el bosque de la comunidad Rey de los Andes posee una alta diversidad de especies de árboles y arbustos; así mismo tomando en cuenta el tipo de vegetación encontrada, listado de especies, sitio y diámetros obtenidos, se puede manifestar que se trata de un bosque bien conservado. Palabras Clave: Composición florística, Bosque siempreverde, Cuyaben

Periodic Integral Equation Formulation for the Numerical Analysis of Glide Structures

In this paper, we propose a technique based on integral equations, the periodic Green's function, and the method of moments discretization to analyze the dispersion diagram of non-canonical glide-symmetry unit cells. The technique is combined with a root finder approach to automatically identify the values of the wavevector that make the unit cell resonant. The proposed technique is tested on a glide fully metallic implementation of a Luneburg lens

El proyecto “Cartagena Puerto de Culturas”: un modelo de gestión urbana sostenible basado en la recuperación del patrimonio cultural

El bien cultural constituye un modo de identidad social y juega un importante papel en el desarrollo de la economía española. La reflexión sobre la necesidad de intervención en este patrimonio, además de establecer qué y cómo se debe hacer, plantea la necesidad de definir el porqué y para qué como decisions imprescindibles para determinar si es sostenible económicamente su mantenimiento. Nos enfrentamos ante una discusión sobre los modos de integración del patrimonio cultural en el proyecto urbano de ciudad, como elemento regenerador del modelo adoptado de manera que se garantice la sostenibilidad del conjunto. Su anàlisis puede tener dos perspectivas diferentes de acuerdo a su escala.Peer Reviewe