8,794 research outputs found
Porto Oscillation Code (POSC)
The Porto Oscillation Code (POSC) has been developed in 1995 and improved
over the years, with the main goal of calculating linear adiabatic oscillations
for models of solar-type stars. It has also been used to estimate the
frequencies and eigenfunctions of stars from the pre-main sequence up to the
sub-giant phase, having a mass between 0.8 and 4 solar masses.
The code solves the linearised perturbation equations of adiabatic pulsations
for an equilibrium model using a second order numerical integration method. The
possibility of using Richardson extrapolation is implemented. Several options
for the surface boundary condition can be used. In this work we briefly review
the key ingredients of the calculations, namely the equations, the numerical
scheme and the output.Comment: Accepted for publication in Astrophysics and Space Science
Aerosol-assisted metallo-organic chemical vapour deposition of Bi2Se3 films using single-molecule precursors: the crystal structure of bismuth(m) dibutyldiselenocarbamate
The complexes [Bi{Se2CN(C2H5)2}3], [Bi{Se2CN(C4H9)2}3], [Bi{Se2CN(CH3)(C4H9)}3] and
[Bi{Se2CN(CH3)(C6H13)}3] have been synthesized and characterized structurally using IR, 1H and 13C NMR. In
addition, the crystal structure of [Bi{Se2CN(C4H9)2}3] was determined by single-crystal X-ray diffraction,
showing the bismuth centre coordinated to three dialkyldiselenocarbamate ligands through the selenium donor
atoms. The Bi(III) compounds were used as precursors for the deposition of Bi2Se3 films on glass substrates
through aerosol-assisted metallo-organic chemical vapour deposition (AA-MOCVD)
Representation of Nelson Algebras by Rough Sets Determined by Quasiorders
In this paper, we show that every quasiorder induces a Nelson algebra
such that the underlying rough set lattice is algebraic. We
note that is a three-valued {\L}ukasiewicz algebra if and only if
is an equivalence. Our main result says that if is a Nelson
algebra defined on an algebraic lattice, then there exists a set and a
quasiorder on such that .Comment: 16 page
Deutsche Fachsprachen : alte und neue Erfahrungen mit dem Begriff 'Kultur' in den Geisteswissenschaften und im Bereich Deutsch als Fremdsprache
In the last few years, the areas of study of German as Foreign Language and German for Specific Purposes have evidently made an inflationary, and sometimes even inadequate use of concepts related to the adjectives 'cultural' and 'intercultural'. The concepts have often been used so as to serve only to instigate the increase, permanency and dissemination of stereotypes and pre-conceptions. In the Winter 2006/07 Semester, a course called "Fachsprachen und Kultur" was offered on the way the concepts of culture are approached in different fields of study. This paper presents the conclusions of some of the participants on the use of the concept in their primary or secondary areas. The results show that it is urgent and necessary to examine the concepts of culture used in our field of study so that stereotypes do not become the basis for a didactics of German as a Foreign Language.Nas áreas de estudos Alemão como Língua Estrangeira e Alemão para Fins Específicos é evidente, nos últimos anos, o uso inflacionário e até, às vezes, impróprio, de conceitos relacionados aos adjetivos cultural e intercultural. Freqüentemente, os conceitos são usados de tal forma que apenas servem para fomentar o crescimento, a fixação e a difusão de estereótipos e preconceitos. No semestre de inverno 2006/07 foi oferecido um curso denominado "Fachsprachen und Kultur" (Magisterstudiengang Deutsch als Fremdsprache), no qual deveriam ser estudados os conceitos de cultura usados nas diferentes disciplinas. Aqui são apresentadas as conclusões de alguns participantes sobre o uso do conceito nas suas áreas principais ou secundárias. Os resultados mostram que se faz urgente e necessário ocupar-se com os conceitos de cultura que vigoram em nossa disciplina, para que estereótipos não se tornem a base de uma didática do Alemão como Língua Estrangeira
Cavity cooling a single charged nanoparticle
The development of laser cooling coupled with the ability to trap atoms and
ions in electromagnetic fields, has revolutionised atomic and optical physics,
leading to the development of atomic clocks, high-resolution spectroscopy and
applications in quantum simulation and processing. However, complex systems,
such as large molecules and nanoparticles, lack the simple internal resonances
required for laser cooling. Here we report on a hybrid scheme that uses the
external resonance of an optical cavity, combined with radio frequency (RF)
fields, to trap and cool a single charged nanoparticle. An RF Paul trap allows
confinement in vacuum, avoiding instabilities that arise from optical fields
alone, and crucially actively participates in the cooling process. This system
offers great promise for cooling and trapping a wide range of complex charged
particles with applications in precision force sensing, mass spectrometry,
exploration of quantum mechanics at large mass scales and the possibility of
creating large quantum superpositions.Comment: 8 pages, 5 figures Updated version includes additional references,
new title, and supplementary information include
Fractional -scaling for quantum kicked rotors without cantori
Previous studies of quantum delta-kicked rotors have found momentum
probability distributions with a typical width (localization length )
characterized by fractional -scaling, ie in regimes
and phase-space regions close to `golden-ratio' cantori. In contrast, in
typical chaotic regimes, the scaling is integer, . Here we
consider a generic variant of the kicked rotor, the random-pair-kicked particle
(RP-KP), obtained by randomizing the phases every second kick; it has no KAM
mixed phase-space structures, like golden-ratio cantori, at all. Our unexpected
finding is that, over comparable phase-space regions, it also has fractional
scaling, but . A semiclassical analysis indicates that the
scaling here is of quantum origin and is not a signature of
classical cantori.Comment: 5 pages, 4 figures, Revtex, typos removed, further analysis added,
authors adjuste
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