4,666 research outputs found
A Routh-like algorithm in system identification and adaptive control
This paper introduces algorithms to be used for finding the Cauchy index of a transfer function and for solving the Diophantine equation. The algorithms are similar to the Routh-Hurwitz array in structure and are simple to implement. The first algorithm also provides a simple check for the presence of almost common factors between two polynomials, and so is useful as a computationally inexpensive alternative to the sylvester determinant. It also finds the almost common factor, and so is potentially useful as an alternative to [8] in implementing self-tuning regulators for nonminimum-phase systems [6]
An effective mass theorem for the bidimensional electron gas in a strong magnetic field
We study the limiting behavior of a singularly perturbed
Schr\"odinger-Poisson system describing a 3-dimensional electron gas strongly
confined in the vicinity of a plane and subject to a strong uniform
magnetic field in the plane of the gas. The coupled effects of the confinement
and of the magnetic field induce fast oscillations in time that need to be
averaged out. We obtain at the limit a system of 2-dimensional Schr\"odinger
equations in the plane , coupled through an effective selfconsistent
electrical potential. In the direction perpendicular to the magnetic field, the
electron mass is modified by the field, as the result of an averaging of the
cyclotron motion. The main tools of the analysis are the adaptation of the
second order long-time averaging theory of ODEs to our PDEs context, and the
use of a Sobolev scale adapted to the confinement operator
CaracterizaciĂłn del ĂĄrea de puesta de especies de tĂșnidos en las costas del norte de TĂșnez
Early life stages of tuna species were investigated along the northern coasts of Tunisia in the summer of 2010, from 7 to 14 July. A total of 74 stations, distributed on a regular grid, were sampled. Larvae of five tuna species were identified: the Atlantic bluefin tuna, the bullet tuna, the Atlantic black skipjack, the Atlantic bonito and the albacore tuna. Larval distribution patterns show that Atlantic bluefin tuna and albacore tuna usually spawn in offshore oligotrophic waters and Atlantic black skipjack larvae on the continental shelf. The widespread distribution of bullet tuna larvae, suggests that it spawns on the entire continental shelf and over the shelf break. The results from the quotient analysis carried out to characterize the spawning habitat of each species, show that the input of recent surface Atlantic water (AW) masses play a key role in the spawning strategy of tuna species, particularly in the case of the Atlantic bluefin tuna, whose larvae were mainly caught in the mixed waters resulting from the interaction between recent AW and resident AW, as demonstrated by their preference for salinity values between 36.9 and 37.4.Se investigaron las fases larvarias tempranas de especies de tĂșnidos a lo largo de las costas del norte de TĂșnez, durante el verano de 2010, del 7 al 14 de julio. Se muestrearon un total de 74 estaciones, distribuidas en una malla regular. Se identificaron larvas de cinco especies: el atĂșn rojo, la melva, la bacoreta, el bonito y el atĂșn blanco. Los patrones de distri-buciĂłn de larvas muestran que el atĂșn rojo y el atĂșn blanco desovan generalmente en aguas oligotrĂłficas alejadas de la costa. Por contra, la localizaciĂłn relativamente mĂĄs costera de las larvas de bacoreta indica que esta especie se reproduce sobre la plataforma continental, mientras que la amplia distribuciĂłn de las larvas de melva sugiere que esta especie desova a lo largo de toda la plataforma y el margen continental. Los resultados del anĂĄlisis de proporcionalidad, llevado a cabo para caracteri-zar el hĂĄbitat de puesta de cada especie, muestran que la entrada de masas de agua superficial atlĂĄntica (AW) reciente juegan un papel clave en la estrategia de desove de las especies de tĂșnidos, sobre todo en el caso del atĂșn rojo, cuyas larvas fueron capturadas principalmente en las aguas de mezcla, resultantes de la interacciĂłn entre el AW reciente y la residente, como lo demuestra su preferencia por los valores de salinidad entre 36.9 y 37.4.VersiĂłn del editor1,006
Effect of annealing temperature on structural, morphology and dielectric properties of La0.75Ba0.25FeO3 perovskite
The effect of annealing temperature on the structure, morphology and dielectric properties of La0.75Ba0.25FeO3 compound prepared by the sol-gel method was investigated. The increase of the annealing temperature from 900 to 1100âŻÂ°C, promotes an increase of the average grain size value. Two dielectric relaxations are detected using the dielectric modulus formalism, attributed to grain and grain boundary relaxations. This behavior was confirmed by both Nyquist and Argand's plots of dielectric impedance and Modulus results at different measuring temperatures. The ac conductivity could be described by Jonscher's power law revealing the presence of both overlapping large polaron tunneling and non-overlapping small polaron tunneling mechanisms.publishe
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The Functionality of the three-sited Ferroxidase center of E. coli Bacterial Ferritin (EcFtnA)
At least three ferritins are found in the bacterium Escherichia coli, the heme-containing bacterioferritin
(EcBFR) and two non-heme bacterial ferritins (EcFtnA and EcFtnB). In addition to the conserved A- and
B-sites of the diiron ferroxidase center, EcFtnA has a third iron-binding site (the C-site) of unknown
function that is nearby the diiron site. In the present work, the complex chemistry of iron oxidation and
deposition in EcFtnA has been further defined through a combination of oximetry, pH stat, stopped-flow
and conventional kinetics, UV-visible, fluorescence and EPR spectroscopic measurements on the wildtype
protein and site-directed variants of the A-, B- and C-sites. The data reveal that, while H2O2 is a
product of dioxygen reduction in EcFtnA and oxidation occurs with a stoichiometry of Fe(II)/O2 ~ 3:1,
most of the H2O2 produced is consumed in subsequent reactions with a 2:1 Fe(II)/H2O2 stoichiometry,
thus suppressing hydroxyl radical formation. While the A- and B-sites are essential for rapid iron
oxidation, the C-site slows oxidation and suppresses iron turnover at the ferroxidase center. A tyrosyl
radical, assigned to Tyr24 near the ferroxidase center, is formed during iron oxidation and its possible
significance to the function of the protein is discussed. Taken as a whole, the data indicate that there are
multiple iron-oxidation pathways in EcFtnA with O2 and H2O2 as oxidants. Furthermore, the data are
inconsistent with the C-site being a transit site, providing iron to the A- and B-sites, and does not support a
universal mechanism for iron oxidation in all ferritins as recently proposed
Second order averaging for the nonlinear Schroedinger equation with strongly anisotropic potential
International audienceWe consider the three dimensional Gross-Pitaevskii equation (GPE) describing a Bose-Einstein Condensate (BEC) which is highly confi ned in vertical z direction. The highly confi ned potential induces high oscillations in time. If the confi nement in the z direction is a harmonic trap (which is widely used in physical experiments), the very special structure of the spectrum of the confi nement operator will imply that the oscillations are periodic in time. Based on this observation, it can be proved that the GPE can be averaged out with an error of order of epsilon, which is the typical period of the oscillations. In this article, we construct a more accurate averaged model, which approximates the GPE up to errors of order epsilon squared. Then, expansions of this model over the eigenfunctions (modes) of the vertical Hamiltonian Hz are given in convenience of numerical application. Effi cient numerical methods are constructed for solving the GPE with cylindrical symmetry in 3D and the approximation model with radial symmetry in 2D, and numerical results are presented for various kinds of initial data
RECAST: Extending the Impact of Existing Analyses
Searches for new physics by experimental collaborations represent a
significant investment in time and resources. Often these searches are
sensitive to a broader class of models than they were originally designed to
test. We aim to extend the impact of existing searches through a technique we
call 'recasting'. After considering several examples, which illustrate the
issues and subtleties involved, we present RECAST, a framework designed to
facilitate the usage of this technique.Comment: 13 pages, 4 figure
Information dynamics: patterns of expectation and surprise in the perception of music
This is a postprint of an article submitted for consideration in Connection Science © 2009 [copyright Taylor & Francis]; Connection Science is available online at:http://www.tandfonline.com/openurl?genre=article&issn=0954-0091&volume=21&issue=2-3&spage=8
The African hind's (Cephalopholis taeniops, serranidae) use of artificial reefs off Sal Island (Cape Verde): a preliminary study based on acoustic telemetry
The African hind Cephalopholis taeniops (Valenciennes, 1828) is one of the most important commercial demersal species caught in the Cape Verde archipelago. The species is closely associated with hard substrate and is one of the main attractions for SCUBA divers. In January 2006 a former Soviet fishing vessel - the Kwarcit - was sunk off Santa Maria Bay (Sal Island). Young C. taeniops are commonly observed in this artificial reef (AR). In order to investigate the species' use of the AR, 4 specimens were captured and surgically implanted underwater with Vemco brand acoustic transmitters. The fish were monitored daily with an active telemetry receiver for one week after release. Simultaneously, an array of 3 passive VR2 / VR2W receivers was set for 63 days, registering data that allowed an analysis of spatial, daily and short term temporal activity patterns. The results showed site fidelity to the AR, with no migrations to the nearby natural reef. The method used allowed to register a consistent higher activity during daytime and a preference for the area opposite the dominant current
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