2,897 research outputs found
Vapour-liquid equilibrium of propanoic acid+water at 423.2, 453.2 and 483.2K from 1.87 to 19.38bar. Experimental and modelling with PR, CPA, PC-SAFT and PCP-SAFT
Vapour–liquid equilibrium data were measured for the propanoic acid + water system at 423.2, 453.2 and 483.2 K from 1.87 to 19.38 bar over the entire range of concentrations. An experimental apparatus based on the static–analytical method with sampling of both phases was used with quantitative analysis by GC. The system is highly non-ideal showing azeotropic behaviour. The Peng–Robinson (PR), the cubic plus association (CPA), the perturbed chain statistical associating fluid theory (PC-SAFT) and the PC-polar-SAFT (PCP-SAFT) equations of state modelled the data. Two association sites were assumed for both compounds. A single–binary interaction parameter (kij ) was used in all models, and predictive (kij=0) and correlative (View the MathML source) capabilities were assessed. Available data at 313.1, 343.2 and 373.1 K from the open literature were included in the analysis. PCP-SAFT presented higher predictive and correlative capabilities over the entire temperature range. PC-SAFT in predictive mode was not able to represent the azeotropic behaviour but resulted in the second best correlations. CPA presented a satisfactory balance between the two modes. PR predictions were rather poor but correlations were better than those of CPA, at the expense of a larger kij
In-vivo, cardiac-cycle related intimal displacement of coronary plaques assessed by 3-D ECG-gated intravascular ultrasound: Exploring its correlate with tissue deformability identified by palpography
Background: ECG-gated image acquisition of intravascular ultrasound (IVUS) has been shown to provide more accurate measurements at different phases of the cardiac cycle. Objective: We sought to explore the ability dynamic assessment of ECG-gated 3-D IVUS to identify deformable regions of coronary plaques, by testing the hypothesis that at a given pressure and region, a faster displacement of the intima would correspond to high strain (soft tissue) regions assessed by palpography. Methods: ECG-gated 3-D IVUS and palpograms were acquired using 30 and 20 MHz IVUS imaging catheters respectively. Frames with high and/or low strain spots identified by palpography were randomly selected and the spots were assigned to a respective quadrant within the cross section. A color-blinded side-by-side view was performed to enable the co-localization of the same region. Subsequently, the pressure driven displacement of the intima was established for each quadrant and a binary score (significant displacement or no displacement) was decided. Results: One hundred and twenty-four quadrants were studied and the prevalence of highly deformable quadrants was low (n=7, 5.6% of the total). The sensitivity, specificity, positive predictive value and negative predictive value of 3-D ECG-gated IVUS to detect deformable quadrants as assessed by palpography were 42.9, 87.2, 16.7, and 96.2% respectively. Conclusion: In this pilot in vivo study, the intimal displacement velocity in the radial direction assessed by gray-scale 3-D ECG-gated IVUS failed to correlate with highly deformable regions. However, these preliminary findings suggest that the absence of significant displacement of the intima might be accurate to predict the absence of deformable tissue
Effect of electronic angular momentum exchange on photoelectron anisotropy following the two-colour ionization of krypton atoms
We present photoelectron energy and angular distributions for resonant two-photon ionization via several low-lying Rydberg states of atomic Kr. The experiments were performed by using synchrotron radiation to pump the Rydberg states and a continuous wave laser to probe them. Photoelectron images, recorded with both linear and circular polarized pump and probe light, were obtained in coincidence with mass-analyzed Kr ions. The photoelectron angular distributions and branching ratios for direct ionization into the Kr+ 2P3/2 and 2P1/2 spin-orbit continua show considerable dependence on the intermediate level, as well as on the polarizations of the pump and probe light. Photoelectron angular distributions were also recorded with several polarization combinations following two-colour excitation of the (2P1/2)5f[5/2]2 autoionizing resonance. These results are compared with the results of recent work on the corresponding autoionizing resonance in atomic Xe
Gromov-Hausdorff-like distance function defined in the aspect of Riemannian submanifold theory
In this paper, we discuss how a Gromov-Hausdorff-like distance function over
the space of all isometric classes of compact -Riemannian manifolds should
be defined in the aspect of the Riemannan submanifold theory, where .
The most important fact in this discussion is as follows. The Hausdorff
distance function between two spheres of mutually distinct radii isometrically
embedded into the hypebolic space of curvature converges to zero as
. The key in the construction of the Gromov-Hausdorff-like
distance function given in this paper is to define the distance of two
-isometric embeddings of distinct compact -Riemannian manifolds
into a higher dimensional Riemannian manifold by using the Hausdorff distance
function in the tangent bundle of order equipped with the Sasaki metric.
Furthermore, we show that the convergence of a sequence of compact Riemannian
manifolds with respect to this distance function coincides with the convergence
in the sense of R. S. Hamilton.Comment: 14 page
Proton-neutron quadrupole interactions: an effective contribution to the pairing field
We point out that the proton-neutron energy contribution, for low multipoles
(in particular for the quadrupole component), effectively renormalizes the
strength of the pairing interaction acting amongst identical nucleons filling
up a single-j or a set of degenerate many-j shells. We carry out the
calculation in lowest-order perturbation theory. We perform a study of this
correction in various mass regions. These results may have implications for the
use of pairing theory in medium-heavy nuclei and for the study of pairing
energy corrections to the liquid drop model when studying nuclear masses.Comment: 19 pages, TeX, 3 tables, 2 figures. Accepted in PR
Stellar archaeology with Gaia: the Galactic white dwarf population
Gaia will identify several 1e5 white dwarfs, most of which will be in the
solar neighborhood at distances of a few hundred parsecs. Ground-based optical
follow-up spectroscopy of this sample of stellar remnants is essential to
unlock the enormous scientific potential it holds for our understanding of
stellar evolution, and the Galactic formation history of both stars and
planets.Comment: Summary of a talk at the 'Multi-Object Spectroscopy in the Next
Decade' conference in La Palma, March 2015, to be published in ASP Conference
Series (editors Ian Skillen & Scott Trager
Solitons in nonlocal nonlinear media: exact results
We investigate the propagation of one-dimensional bright and dark spatial
solitons in a nonlocal Kerr-like media, in which the nonlocality is of general
form. We find an exact analytical solution to the nonlinear propagation
equation in the case of weak nonlocality. We study the properties of these
solitons and show their stability.Comment: 9 figures, submitted to Phys. Rev.
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