1,634 research outputs found
Reference map technique for finite-strain elasticity and fluid-solid interaction
The reference map, defined as the inverse motion function, is utilized in an Eulerian-frame representation of continuum solid mechanics, leading to a simple, explicit finite-difference method for solids undergoing finite deformations. We investigate the accuracy and applicability of the technique for a range of finite-strain elasticity laws under various geometries and loadings. Capacity to model dynamic, static, and quasi-static conditions is shown. Specifications of the approach are demonstrated for handling irregularly shaped and/or moving boundaries, as well as shock solutions. The technique is also integrated within a fluid–solid framework using a level-set to discern phases and using a standard explicit fluid solver for the fluid phases. We employ a sharp-interface method to institute the interfacial conditions, and the resulting scheme is shown to efficiently capture fluid–solid interaction solutions in several examples.United States. Dept. of Energy. Office of Science (Computational and Technology Research, contract number DE-AC02-05CH11231)National Science Foundation (U.S.) (Grant DMS-0813648)National Science Foundation (U.S.) (Mathematical Sciences Postdoctoral Research Fellowship)Natural Sciences and Engineering Research Council of Canada (NSERC Discovery Program)
A Correction Function Method for Poisson problems with interface jump conditions
In this paper we present a method to treat interface jump conditions for constant coefficients Poisson problems that allows the use of standard “black box” solvers, without compromising accuracy. The basic idea of the new approach is similar to the Ghost Fluid Method (GFM). The GFM relies on corrections applied on nodes located across the interface for discretization stencils that straddle the interface. If the corrections are solution-independent, they can be moved to the right-hand-side (RHS) of the equations, producing a problem with the same linear system as if there were no jumps, only with a different RHS. However, achieving high accuracy is very hard (if not impossible) with the “standard” approaches used to compute the GFM correction terms.
In this paper we generalize the GFM correction terms to a correction function, defined on a band around the interface. This function is then shown to be characterized as the solution to a PDE, with appropriate boundary conditions. This PDE can, in principle, be solved to any desired order of accuracy. As an example, we apply this new method to devise a 4th order accurate scheme for the constant coefficients Poisson equation with discontinuities in 2D. This scheme is based on (i) the standard 9-point stencil discretization of the Poisson equation, (ii) a representation of the correction function in terms of bicubics, and (iii) a solution of the correction function PDE by a least squares minimization. Several applications of the method are presented to illustrate its robustness dealing with a variety of interface geometries, its capability to capture sharp discontinuities, and its high convergence rate.National Science Foundation (U.S.) (Grant DMS-0813648)Brazil. Coordenacao de Aperfeicoamento de Pessoal de Nivel SuperiorFulbright Program (Grant BEX 2784/06-8
Electronic structure of strongly correlated d-wave superconductors
We study the electronic structure of a strongly correlated d-wave
superconducting state. Combining a renormalized mean field theory with direct
calculation of matrix elements, we obtain explicit analytical results for the
nodal Fermi velocity, v_F, the Fermi wave vector, k_F, and the momentum
distribution, n_k, as a function of hole doping in a Gutzwiller projected
d-wave superconductor. We calculate the energy dispersion, E_k, and spectral
weight of the Gutzwiller-Bogoliubov quasiparticles, and find that the spectral
weight associated with the quasiparticle excitation at the antinodal point
shows a non monotonic behavior as a function of doping. Results are compared to
angle resolved photoemission spectroscopy (ARPES) of the high temperature
superconductors.Comment: final version, comparison to experiments added, 4+ pages, 4 figure
Fe I Oscillator Strengths for the Gaia-ESO Survey
The Gaia-ESO Public Spectroscopic Survey (GES) is conducting a large-scale
study of multi-element chemical abundances of some 100 000 stars in the Milky
Way with the ultimate aim of quantifying the formation history and evolution of
young, mature and ancient Galactic populations. However, in preparing for the
analysis of GES spectra, it has been noted that atomic oscillator strengths of
important Fe I lines required to correctly model stellar line intensities are
missing from the atomic database. Here, we present new experimental oscillator
strengths derived from branching fractions and level lifetimes, for 142
transitions of Fe I between 3526 {\AA} and 10864 {\AA}, of which at least 38
are urgently needed by GES. We also assess the impact of these new data on
solar spectral synthesis and demonstrate that for 36 lines that appear
unblended in the Sun, Fe abundance measurements yield a small line-by-line
scatter (0.08 dex) with a mean abundance of 7.44 dex in good agreement with
recent publications.Comment: Accepted for publication in Mon. Not. R. Astron. So
Oncology patients' experience at the interface between hospital and community care: a mixed method investigation
Diffusivity and configurational entropy maxima in short range attractive colloids
We study tagged particle diffusion at large packing fractions, for a model of
particles interacting with a generalized Lennard-Jones 2n-n potential, with
large n. The resulting short-range potential mimics interactions in colloidal
systems. In agreement with previous calculations for short-range potential, we
observe a diffusivity maximum as a function of temperature. By studying the
temperature dependence of the configurational entropy -- which we evaluate with
two different methods -- we show that a configurational entropy maximum is
observed at a temperature close to that of the diffusivity maximum. Our
findings suggest a relationbetween dynamics and number of distinct states for
short-range potentials.Comment: 4 pages, 3 figures, submited to Physical Review Lette
LepidĂłpteros tortricĂdeos em pomares de pomĂłideas e de prunĂłideas da Beira Interior
Comunicação apresentada no 6.Âş Encontro Nacional de Protecção Integrada que decorreu em Castelo Branco, na Escola Superior Agrária do Instituto PoliĂ©cnico de Castelo Branco, de 14 a 16 de Maio de 2003, no âmbito do painel sobre PrunĂłideas.Neste trabalho sĂŁo apresentados resultados de uma prospecção relativa Ă s espĂ©cies de tortricĂdeos fitĂłfagos de
pomares de pomĂłideas e de prunĂłideas, na Beira Interior.
O trabalho reporta-se a dados obtidos no ano de 2002, tendo sido utilizadas armadilhas sexuais para as
capturas de adultos e observação visual para a detecção de larvas.
As espécies monitorizadas foram: Adoxophyes orana, Cacoecimorpha pronubana, Pandemis heparana, Pandemis
ribeana (=cerasana) e Cydia molesta. Das cinco espécies monitorizadas apenas houve capturas de Cacoecimorpha
pronubana e de Pandemis heparana. Relativamente a estas duas espécies são apresentadas curvas de voo.
Embora tenham sido detectados frutos com a sintomatologia caracterĂstica do ataque destas espĂ©cies, nĂŁo
foram encontradas larvas, sugerindo populações economicamente insignificantes no ano de 2002
A High-Resolution Atlas of Uranium-Neon in the H Band
We present a high-resolution (R ~ 50 000) atlas of a uranium-neon (U/Ne)
hollow-cathode spectrum in the H-band (1454 nm to 1638 nm) for the calibration
of near-infrared spectrographs. We obtained this U/Ne spectrum simultaneously
with a laser-frequency comb spectrum, which we used to provide a first-order
calibration to the U/Ne spectrum. We then calibrated the U/Ne spectrum using
the recently-published uranium line list of Redman et al. (2011), which is
derived from high-resolution Fourier transform spectrometer measurements. These
two independent calibrations allowed us to easily identify emission lines in
the hollow cathode lamp that do not correspond to known (classified) lines of
either uranium or neon, and to compare the achievable precision of each source.
Our frequency comb precision was limited by modal noise and detector effects,
while the U/Ne precision was limited primarily by the signal-to-noise ratio
(S/N) of the observed emission lines and our ability to model blended lines.
The standard deviation in the dispersion solution residuals from the
S/N-limited U/Ne hollow cathode lamp were 50% larger than the standard
deviation of the dispersion solution residuals from the modal-noise-limited
laser frequency comb. We advocate the use of U/Ne lamps for precision
calibration of near-infrared spectrographs, and this H-band atlas makes these
lamps significantly easier to use for wavelength calibration.Comment: 23 pages, 7 figures, submitted and accepted in ApJSS. Online-only
material to be published online by ApJS
In vitro metabolism of beclomethasone dipropionate, budesonide, ciclesonide, and fluticasone propionate in human lung precision-cut tissue slices
<p>Abstract</p> <p>Background</p> <p>The therapeutic effect of inhaled corticosteroids (ICS) may be affected by the metabolism of the drug in the target organ. We investigated the <it>in vitro </it>metabolism of beclomethasone dipropionate (BDP), budesonide (BUD), ciclesonide (CIC), and fluticasone propionate (FP) in human lung precision-cut tissue slices. CIC, a new generation ICS, is hydrolyzed by esterases in the upper and lower airways to its pharmacologically active metabolite desisobutyryl-ciclesonide (des-CIC).</p> <p>Methods</p> <p>Lung tissue slices were incubated with BDP, BUD, CIC, and FP (initial target concentration of 25 ÎĽM) for 2, 6, and 24 h. Cellular viability was assessed using adenosine 5'-triphosphate content and protein synthesis in lung slices. Metabolites and remaining parent compounds in the tissue samples were analyzed by HPLC with UV detection.</p> <p>Results</p> <p>BDP was hydrolyzed to the pharmacologically active metabolite beclomethasone-17-monopropionate (BMP) and, predominantly, to inactive beclomethasone (BOH). CIC was hydrolyzed initially to des-CIC with a slower rate compared to BDP. A distinctly smaller amount (approximately 10-fold less) of fatty acid esters were formed by BMP (and/or BOH) than by BUD or des-CIC. The highest relative amounts of fatty acid esters were detected for BUD. For FP, no metabolites were detected at any time point. The amount of drug-related material in lung tissue (based on initial concentrations) at 24 h was highest for CIC, followed by BUD and FP; the smallest amount was detected for BDP.</p> <p>Conclusion</p> <p>The <it>in vitro </it>metabolic pathways of the tested ICS in human lung tissue were differing. While FP was metabolically stable, the majority of BDP was converted to inactive polar metabolites. The formation of fatty acid conjugates was confirmed for BMP (and/or BOH), BUD, and des-CIC.</p
Aspectos fitossanitários em olival na Beira Interior Norte e na Beira Interior Sul
Comunicação oral apresentada no 6.º Encontro Nacional de Protecção Integrada que decorreu em Castelo Branco, na Escola Superior Agrária do Instituto Politécnico de Castelo Branco, no âmbito do painel sobre o OlivalPara uma análise dos problemas fitossanitários do olival na Beira Interior foram realizados observações e
estimativas do risco, em 2002, em quatro olivais na Beira Interior Norte e outros quatro na Beira Interior Sul.
Os olivais da Beira Interior Norte ficam localizados nos concelhos de Seia, Pinhel, Guarda e Figueira de
Castelo Rodrigo e os da Beira Interior Sul nos concelhos de Penamacor, Fundão, Proença-a-Nova e Vila Velha
de RĂłdĂŁo. Os inimigos mais importantes e para que foram feitas estimativas do risco foram: gafa, olho de
pavão, mosca-da-azeitona, traça-da-oliveira e cochonilha-negra.
Em todos os olivais foram encontrados todos os inimigos avaliados, mas com pouca expressĂŁo para o olho de
pavĂŁo nos olivais da cultivar Galega. Os dados da estimativa do risco sĂŁo apresentados, assim como o nĂşmero
das intervenções quĂmicas que foram necessárias realizar. SĂŁo discutidas e comparadas as intervenções
realizadas
- …