6,416 research outputs found
A Combined Component-Based Approach for the Design of Distributed Software Systems
Component-based software development enables the construction of software artefacts by assembling binary units of production, distribution and deployment, the so-called components. Several approaches to component-based development have been proposed recently. Most of these approaches are based on the Unified Modeling Language (UML). UML has been increasingly used in component-based development, despite some shortcomings of this language. This paper presents a methodology for the design of component-based applications that combines a model-based approach with a UML-based approach. This combined approach tackles some of the limitations of UML, allowing a better control of the design proces
Diagnostics and control of wavenumber stability and purity of tunable diode lasers relevant to their use as local oscillators in heterodyne systems
Initial operation of the tunable diode lasers (TDL) showed that it was not possible to adjust the wavenumber to one selected a priori in the TDL tuning range. During operation, the operating point would change by 0.1/cm over the longer term with even larger changes occurring during some thermal cycles. Most changes during thermal cycling required using lower temperatures and higher currents to reach the former wavenumber (when it could be reached). In many cases, an operating point could be selected by changing TDL current and temperature to give both the desired wavenumber and most of the power in a single mode. The selection procedure had to be used after each thermal cycling. Wavenumber nonlinearities of about 10% over a 0.5 cm tuning range were observed. Diagnostics of the single mode selected by a grating monochromator showed wavenumber fine structure under certain operating conditions. The characteristics due to the TDL environment included short term wavenumber stability, the instrument lineshape function, and intermediate term wavenumber stability
Universality of weakly bound dimers and Efimov trimers close to Li-Cs Feshbach resonances
We study the interspecies scattering properties of ultracold Li-Cs mixtures
in their two energetically lowest spin channels in the magnetic field range
between 800 G and 1000 G. Close to two broad Feshbach resonances we create
weakly bound LiCs dimers by radio-frequency association and measure the
dependence of the binding energy on the external magnetic field strength. Based
on the binding energies and complementary atom loss spectroscopy of three other
Li-Cs s-wave Feshbach resonances we construct precise molecular singlet and
triplet electronic ground state potentials using a coupled-channels
calculation. We extract the Li-Cs interspecies scattering length as a function
of the external field and obtain almost a ten-fold improvement in the precision
of the values for the pole positions and widths of the s-wave Li-Cs Feshbach
resonances as compared to our previous work [Pires \textit{et al.}, Phys. Rev.
Lett. \textbf{112}, 250404 (2014)]. We discuss implications on the Efimov
scenario and the universal geometric scaling for LiCsCs trimers
Universal three-body recombination and Efimov resonances in an ultracold Li-Cs mixture
We study Efimov resonances via three-body loss in an ultracold two-component
gas of fermionic Li and bosonic Cs atoms close to a Feshbach
resonance at 843~G, extending results reported previously [Pires \textit{et
al.}, Phys. Rev. Lett. 112, 250404 (2014)] to temperatures around 120~nK. The
experimental scheme for reaching lower temperatures is based upon compensating
the gravity-induced spatial separation of the mass-imbalanced gases with
bichromatic optical dipole traps. We observe the first and second excited
Li-Cs-Cs Efimov resonance in the magnetic field dependence of the three-body
event rate constant, in good agreement with the universal zero-range theory at
finite temperature [Petrov and Werner, Phys. Rev. A 92, 022704 (2015)].
Deviations are found for the Efimov ground state, and the inelasticity
parameter is found to be significantly larger than those for
single-species systems
Avaliação da viabilidade de uso do B-apo-8`-carotenal como padrão interno na análise de carotenóides em milho por CLAE.
XMM-Newton observations of the low-luminosity cataclysmic variable V405 Pegasi
V405 Peg is a low-luminosity cataclysmic variable (CV) that was identified as
the optical counterpart of the bright, high-latitude ROSAT all-sky survey
source RBS1955. The system was suspected to belong to a largely undiscovered
population of hibernating CVs. Despite intensive optical follow-up its subclass
however remained undetermined.
We want to further classify V405 Peg and understand its role in the CV zoo
via its long-term behaviour, spectral properties, energy distribution and
accretion luminosity.
We perform a spectral and timing analysis of \textit{XMM-Newton} X-ray and
ultra-violet data. Archival WISE, HST, and Swift observations are used to
determine the spectral energy distribution and characterize the long-term
variability.
The X-ray spectrum is characterized by emission from a multi-temperature
plasma. No evidence for a luminous soft X-ray component was found. Orbital
phase-dependent X-ray photometric variability by occurred without
significant spectral changes. No further periodicity was significant in our
X-ray data. The average X-ray luminosity during the XMM-Newton observations was
L_X, bol simeq 5e30 erg/s but, based on the Swift observations, the
corresponding luminosity varied between 5e29 erg/s and 2e31 erg/son timescales
of years.
The CV subclass of this object remains elusive. The spectral and timing
properties show commonalities with both classes of magnetic and non-magnetic
CVs. The accretion luminosity is far below than that expected for a standard
accreting CV at the given orbital period. Objects like V405 Peg might represent
the tip of an iceberg and thus may be important contributors to the Galactic
Ridge X-ray Emission. If so they will be uncovered by future X-ray surveys,
e.g. with eROSITA.Comment: A&A, in pres
Metodologia para determinação de carotenóides de importância biológica em grãos de milho por CLAE.
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