1,289 research outputs found
Rayleigh-Brillouin light scattering spectroscopy of nitrous oxide (NO)
High signal-to-noise and high-resolution light scattering spectra are
measured for nitrous oxide (NO) gas at an incident wavelength of 403.00 nm,
at 90 scattering, at room temperature and at gas pressures in the range
bar. The resulting Rayleigh-Brillouin light scattering spectra are
compared to a number of models describing in an approximate manner the
collisional dynamics and energy transfer in this gaseous medium of this
polyatomic molecular species. The Tenti-S6 model, based on macroscopic gas
transport coefficients, reproduces the scattering profiles in the entire
pressure range at less than 2\% deviation at a similar level as does the
alternative kinetic Grad's 6-moment model, which is based on the internal
collisional relaxation as a decisive parameter. A hydrodynamic model fails to
reproduce experimental spectra for the low pressures of 0.5-1 bar, but yields
very good agreement (\%) in the pressure range bar. While these
three models have a different physical basis the internal molecular relaxation
derived can for all three be described in terms of a bulk viscosity of Pas. A 'rough-sphere' model, previously
shown to be effective to describe light scattering in SF gas, is not found
to be suitable, likely in view of the non-sphericity and asymmetry of the N-N-O
structured linear polyatomic molecule
Dynamic light scattering in shear flows
We describe a new dynamic light scattering technique for measuring diffusion in sheared suspensions. It involves a scattering geometry with two crossing laser beams. A detailed analysis of the correlation function of scattered light is given. The viability of our method is demonstrated in an experiment where the effect of Taylor diffusion on the scattered light correlation function is measured
Turbulence of a free surface
We study the free surface of a turbulent channel flow, in particular, the relation between the statistical properties of the wrinkled surface and those of the velocity field beneath it. For an irregular flow shed off a vertical cylinder, surface indentations are strongly correlated with vortices in the subsurface flow. For fully developed turbulence this correlation is dramatically reduced. This is because the large eddies excite random capillary-gravity waves that travel in all directions across the surface. Both their predominant wavelength and their anisotropy are determined by the subsurface turbulence
Effect of the depth on the pattern formation of Faraday waves
The symmetry of standing wave patterns on the surface of a vertically oscillated fluid layer depends on the depth of the layer. In a large experiment we trace out the stability diagram. The dependency can be understood on the basis of the oscillatory character of the waves and the dispersion relation. A simple amplitude equation can be constructed with the variation with depth of the dispersion relation and a general quadratic nonlinearity as its only ingredients. The predictions of this model agree well with the experiment
Molecular tagging velocimetry in turbulence using biacetyl
We evaluate various molecular tagging velocimetry (MTV) techniques for application in turbulent flows of gases where the smallest length scales must be resolved. We argue that tracer diffusion dictates the use of large complex molecules and discuss a few candidate molecules. The accuracy of MTV is determined by the profile of written lines which widen due to molecular dynamics, including both diffusion and chemical reaction. We evaluate these profiles for tagging with phosphorescing biacetyl molecules, which is a commonly used probe in MTV. For relatively large laser power, these profiles are determined not by molecular diffusion, but by the triplet-triplet annihilation reaction of excited biacetyl molecules. We identify a new reaction pathway, and present a model for the observed line shapes. The rapid widening of tagged lines of biacetyl molecules due to chemical reaction restricts this MTV technique to large-scale turbulent motion in gases of comparable molecular weight
Management of elderly patients with breast cancer : towards evidence based medicine
Breast cancer is the most common malignancy diagnosed in women1. The incidence of breast cancer increases with age; currently, in developed countries more than 40% of breast cancer patients is 65 years or older at diagnosis1. In the Netherlands in 2011, 5,441 women aged 65 years or older were diagnosed with breast cancer2. The remaining life expectancy of persons aged 65 is still increasing, from almost 19 years in 1980, up to more than 21 years in 2010. Moreover, in last decades the birth rate has decreased, resulting in a higher proportion of older persons in the general population3. Both an increasing life expectancy and the increasing number of elderly in the population will further enhance the number of elderly women confronted with breast cancerGSK; Roche; ChipsoftUBL - phd migration 201
The Kaon B-parameter in Mixed Action Chiral Perturbation Theory
We calculate the kaon B-parameter, B_K, in chiral perturbation theory for a
partially quenched, mixed action theory with Ginsparg-Wilson valence quarks and
staggered sea quarks. We find that the resulting expression is similar to that
in the continuum, and in fact has only two additional unknown parameters. At
one-loop order, taste-symmetry violations in the staggered sea sector only
contribute to flavor-disconnected diagrams by generating an O(a^2) shift to the
masses of taste-singlet sea-sea mesons. Lattice discretization errors also give
rise to an analytic term which shifts the tree-level value of B_K by an amount
of O(a^2). This term, however, is not strictly due to taste-breaking, and is
therefore also present in the expression for B_K for pure G-W lattice fermions.
We also present a numerical study of the mixed B_K expression in order to
demonstrate that both discretization errors and finite volume effects are small
and under control on the MILC improved staggered lattices.Comment: 29 pages, 4 figures; Expanded spurion discussion, other discussions
clarified, version to appear in PR
Temporal discounting for self and friends in adolescence:A fMRI study
Adolescence is characterized by impulsivity but also by increased importance of friendships. This study took the novel perspective of testing temporal discounting in a fMRI task where choices could affect outcomes for 96 adolescents (aged 10–20-years) themselves and their best friend. Decisions either benefitted themselves (i.e., the Self Immediate – Self Delay’ condition) or their friend (i.e., ‘Friend Immediate – Friend Delay’ condition); or juxtaposed rewards for themselves and their friends (i.e., the ‘Self Immediate – Friend Delay’ or ‘Friend Immediate – Self Delay’ conditions). We observed that younger adolescents were more impulsive; and all participants were more impulsive when this was associated with an immediate benefit for friends. Individual differences analyses revealed increased activity in the subgenual anterior cingulate cortex extending in the ventral striatum for immediate relative to delayed reward choices for self. Temporal choices were associated with activity in the prefrontal cortex, parietal cortex, insula, and ventral striatum, but only activity in the right inferior parietal lobe was associated with age. Finally, temporal delay choices for friends relative to self were associated with increased activity in the temporo-parietal junction and precuneus. Overall, this study shows a unique role of the social context in adolescents’ temporal decision making.</p
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