ELECTRONIC STATES IN GRADED-GAP JUNCTIONS WITH BAND INVERSION

We theoretically study electronic states in graded-gap junctions of IV-VI compounds with band inversion. Using a two-band model within the ${\bf k}\cdot{\bf p}$ approximation and assuming that the gap and the gap centre present linear profiles, we demonstrate the existence of a set of localized states along the growth direction with a discrete energy spectrum. The envelope functions are found to be combination of harmonic oscillator eigenfunctions, and the corresponding energy levels are proportional to the square root of the quantum number. The level spacing can be directly controlled by varying the structure thickness.Comment: REVTEX 3.0, 7 pages, no figures, to appear in Phys. Lett.

Universality of quantum Brownian motion

Are Markovian master equations for quantum Brownian motion independent of model assumptions used in the derivation and, thus, universal? With the aim of answering this question, we use a random band-matrix model for the system-bath interaction to derive Markovian master equations for the time evolution of one-dimensional quantum systems weakly coupled to a heat bath. We study in detail two simple systems, the harmonic oscillator and the two-level system. Our results are in complete agreement with those of earlier models, like the Caldeira-Legget model and, in the large-band limit, with the Agarwal equations (both with and without rotating-wave approximation). This proves the universality of these master equations.Comment: 24 page

Historias de viajeros y trashumantes: el Presbítero J. Holartes

Este documento rescata un manuscrito de origen incierto, en el cuál se describe un tramo de la vida de un religioso muy cercano, tanto en su espíritu cómo a través de sus escritos, al vasto mundo de la Ictiología Neotropical. La calificación de “origen incierto” a este documento, se basa en que, en nuestros archivos, no hemos encontrado ninguna referencia sobre el autor; sí sobre P. J. Holartes (ver López et al., 1981), así como la existencia de objetos artesanales que testimonian la presencia de este domínico en el centro y NO de nuestro país. Sólo podemos especular que su paso por el Valle de Traslasierra no sería casual, ya que seguramente, entre sus objetivos estaba el reunirse con el hoy beato J. G. Brochero. Nosotros pensamos, quizás sin demasiados fundamentos, que Clementino Agassi es un pseudónimo utilizado para plasmar este relato intemporal, ya que como dijo Henri Bergson “El tiempo es invención o no es nada en absoluto

Role of non-collective excitations in heavy-ion fusion reactions and quasi-elastic scattering around the Coulomb barrier

Despite the supposed simplicity of double-closed shell nuclei, conventional coupled-channels calculations, that include all of the known collective states of the target and projectile, give a poor fit to the fusion cross section for the $^{16}$O + $^{208}$Pb system. The discrepancies are highlighted through the experimental barrier distribution and logarithmic derivative, that are both well defined by the precise experimental fusion data available. In order to broaden our search for possible causes for this anomaly, we revisit this system and include in our calculations a large number of non-collective states of the target, whose spin, parity, excitation energy and deformation paramter are known from high-precision proton inelastic-scattering measurements. Although the new coupled-channels calculations modify the barrier distribution, the disagreemnt with experiment remains both for fusion and for quasi-elastic (QE) scattering. We find that the Q-value distributions for large-angle QE scattering become rapidly more important as the incident energy increases, reflecting the trend of the experimental data. The mass-number dependence of the non-collective excitations is discussed.Comment: 8 pages, 7 figure

A novel technique for extracting clouds base height using ground based imaging

The height of a cloud in the atmospheric column is a key parameter in its characterization. Several remote sensing techniques (passive and active, either ground-based or on space-borne platforms) and in-situ measurements are routinely used in order to estimate top and base heights of clouds. In this article we present a novel method that combines thermal imaging from the ground and sounded wind profile in order to derive the cloud base height. This method is independent of cloud types, making it efficient for both low boundary layer and high clouds. In addition, using thermal imaging ensures extraction of clouds' features during daytime as well as at nighttime. The proposed technique was validated by comparison to active sounding by ceilometers (which is a standard ground based method), to lifted condensation level (LCL) calculations, and to MODIS products obtained from space. As all passive remote sensing techniques, the proposed method extracts only the height of the lowest cloud layer, thus upper cloud layers are not detected. Nevertheless, the information derived from this method can be complementary to space-borne cloud top measurements when deep-convective clouds are present. Unlike techniques such as LCL, this method is not limited to boundary layer clouds, and can extract the cloud base height at any level, as long as sufficient thermal contrast exists between the radiative temperatures of the cloud and its surrounding air parcel. Another advantage of the proposed method is its simplicity and modest power needs, making it particularly suitable for field measurements and deployment at remote locations. Our method can be further simplified for use with visible CCD or CMOS camera (although nighttime clouds will not be observed)

Penentuan Konsep Perancangan Alat Pengering Simplisia Jahe Menggunakan Sumber Panas Sinar Matahari Dengan Backup Panas Kompor Biomassa

The ginger drying process used by Biofarmaka farmers of Karanganyar to produce simplisia, used heat source from solar energy of the sunlight. Sunlight is a free source of energy that can be obtained in the universe but can not be controlled. Production of simplisia can be stopped or obstructed if there is no sunlight that gives solar energy for the drying process (cloudy or rainy). This obstacle of production process of simplisia becomes an important matter considering the low durability of fresh ingredients (ginger). This requires the presence of an additional source of heat energy which is cheap and can be controlled to produce simplisia if the heat source from solar energy of the sunlight can not be used. This study aims to construct concept of design solar dryer with a biomass stove for heat backup to produce ginger simplisia. The step of design are identification of user requirements, construction of product specifications, product concept development, and product concept selection. This study resulted in 36 product concept of the ginger solar dryer

Multiphonon and ``hot''-phonon Isovector Electric-Dipole Excitations

We argue that a substantial increase in the cross section for Coulomb excitation in the region of the Double Giant Dipole Resonance should be expected from Coulomb excitation of excited states involved in the spreading of the one-phonon resonance, in a manifestation of the Brink-Axel phenomenon. This generates an additional fluctuating amplitude and a corresponding new term to be added incoherently to the usual cross-section. The appropriate extension of an applicable reaction calculation is considered in order to estimate this effect.Comment: 6 pages, Latex, 1 figure available on reques