568 research outputs found
Nodal degenerations of plane curves and Galois covers
Globally irreducible nodes (i.e. nodes whose branches belong to the same
irreducible component) have mild effects on the most common topological
invariants of an algebraic curve. In other words, adding a globally irreducible
node (simple nodal degeneration) to a curve should not change them a lot. In
this paper we study the effect of nodal degeneration of curves on fundamental
groups and show examples where simple nodal degenerations produce
non-isomorphic fundamental groups and this can be detected in an algebraic way
by means of Galois coverings.Comment: 16 pages, 3 figure
Intraocular scattering compensation in retinal imaging
Intraocular scattering affects fundus imaging in a similar way that affects vision; it causes a decrease in contrast which depends on both the intrinsic scattering of the eye but also on the dynamic range of the image. Consequently, in cases where the absolute intensity in the fundus image is important, scattering can lead to a wrong estimation. In this paper, a setup capable of acquiring fundus images and estimating objectively intraocular scattering was built, and the acquired images were then used for scattering compensation in fundus imaging. The method consists of two parts: first, reconstruct the individual’s wide-angle Point Spread Function (PSF) at a specific wavelength to be used within an enhancement algorithm on an acquired fundus image to compensate for scattering. As a proof of concept, a single pass measurement with a scatter filter was carried out first and the complete algorithm of the PSF reconstruction and the scattering compensation was applied. The advantage of the single pass test is that one can compare the reconstructed image with the original one and see the validity, thus testing the efficiency of the method. Following the test, the algorithm was applied in actual fundus images in human eyes and the effect on the contrast of the image before and after the compensation was compared. The comparison showed that depending on the wavelength, contrast can be reduced by 8.6% under certain conditions
Evaluation of Eggplant Accessions for Resistance to Bacterial Wilt Caused by Ralstonia solanacearum (E.F. Smith) Yabuuchi et Al.
Forty-one eggplant accessions were screened in a sick plot for bacterial wilt resistance at Indian Institute of Horticultural Research, Hessaraghatta, Bengaluru. Nine accessions, viz., IIHR-322, AVT-IIRES-1, AVT-IIRES-2, AVT-IIRES-4, AVT-IIRES-5, IIHR500-A, BPLH-1, IIHR-3 and IIHR-5 showed highly resistant reaction, with no wilting of plants; five accessions, viz., RES-2, RES-5, RES-6, 37-36-4-4 and 36-37-13, showed resistance reaction per cent wilt 3.33 -10.0. Two accessions, viz., 36-37-3 and 37-4-20, showed moderately resistant reaction, with 11.0 and 12.0 per cent wilt incidence, respectively; while, 22 accessions were 'moderately susceptible to highly susceptible', with wilt incidence ranging from 25.45 to 100.0%
Effect of intraocular scattering in macular pigment optical density measurements
Fundus reflectometry is a common in-vivo, noninvasive method to estimate the macular pigment optical density (MPOD). The measured density, however, can be affected by the individual’s intraocular scattering. Scattering causes a reduction in the contrast of the fundus image, which in turn leads to an underestimation of the measured density. Intraocular scattering was measured optically in a group of seven young, healthy subjects using the method of optical integration and was subsequently used to correctly estimate the MPOD from fundus images. It was shown that when scattering is not considered, the measured optical density using fundus reflectometry can be underestimated by as high as 16% for our group of subjects
Torsion divisors of plane curves and Zariski pairs
In this paper we study the embedded topology of reducible plane curves having
a smooth irreducible component. In previous studies, the relation between the
topology and certain torsion classes in the Picard group of degree zero of the
smooth component was implicitly considered. We formulate this relation clearly
and give a criterion for distinguishing the embedded topology in terms of
torsion classes. Furthermore, we give a method of systematically constructing
examples of curves where our criterion is applicable, and give new examples of
Zariski tuples.Comment: 19 page
Objective method for measuring the macular pigment optical density in the eye
Macular pigment is a yellowish pigment of purely dietary origin, which is thought to have a protective role in the retina. Recently, it was linked to age-related macular degeneration and improved visual function. In this work, we present a method and a corresponding optical instrument for the rapid measurement of its optical density. The method is based on fundus reflectometry and features a photodetector for the measurement of reflectance at different wavelengths and retinal locations. The method has been tested against a commercially available instrument on a group of healthy volunteers and has shown good correlation. The proposed instrument can serve as a rapid, non-midriatic, low-cost tool for the measurement of macular pigment optical density
The Lack of Structural and Dynamical Evolution of Elliptical Galaxies since z ~ 1.5: Clues from Self-Consistent Hydrodynamical Simulations
We present results of a study on the evolution of the parameters
characterizing the structure and dynamics of the relaxed elliptical-like
objects (ELOs) identified at z=0, z=1 and z=1.5 in a set of hydrodynamical,
self-consistent simulations operating in the context of a concordance
cosmological model. The values of the stellar mass, the stellar half-mass
radius and the stellar mean-square velocity have been measured in each ELO and
found to populate, at any z, a flattened ellipsoid close to a plane (the
dynamical plane, DP). Our simulations indicate that, at the intermediate zs
considered, individual ELOs evolve, increasing the values of these parameters
as a consequence of on-going mass assembly, but, nevertheless, their DP is
roughly preserved within its scatter, in agreement with observations of the
Fundamental Plane of ellipticals at different zs. We briefly discuss how this
lack of significant dynamical and structural evolution in ELO samples arises,
in terms of the two different phases operating in the mass aggregation history
of their dark matter halos. According with our simulations, most dissipation
involved in ELO formation takes place at the early violent phase, causing the
stellar mass, the stellar half-mass radius and the stellar mean-square velocity
parameters to settle down to the DP, and, moreover, the transformation of most
of the available gas into stars. In the subsequent slow phase, ELO stellar mass
growth preferentially occurs through non-dissipative processes, so that the DP
is preserved and the ELO star formation rate considerably decreases. These
results hint, for the first time, to a possible way of explaining, in the
context of cosmological simulations, different apparently paradoxical
observational results on ellipticals.Comment: 12 pages, 1 figure. Minor changes to match the published versio
Thermophysical study of 2-acetylthiophene: experimental and modelled results
Several thermophysical properties have been studied for 2-acetylthiophene: (i) vapour pressure was determined at temperatures within 336.16–445.02 K; (ii) density, speed of sound, static permittivity, refractive index, surface tension, and kinematic viscosity were measured at p = 0.1 MPa and at temperatures from 278.15 K (or 283.15 K for the refractive index) to 338.15 K; (iii) volumetric properties were also determined at temperatures in the (283.15–338.15) K range and at pressures up to 65.0 MPa. From these experimental values, different derivative properties have been calculated such as enthalpy of vaporization, isobaric expansibility, isothermal and isentropic compressibility, dipole moment, entropy and enthalpy of surface formation, and dynamic viscosity. All experimental properties were correlated and the results were explained through the intermolecular interactions. Moreover PC-SAFT EoS was used to model the thermodynamic behaviour of the compound. Finally, this EoS combined with the Density Gradient Theory allowed obtaining the influence parameter for the surface tension of 2-acetylthiophene
Clues on Regularity in the Structure and Kinematics of Elliptical Galaxies from Self-consistent Hydrodynamical Simulations: the Dynamical Fundamental Plane
[Abridged] We have analysed the parameters characterising the mass, size and
velocity dispersion both at the baryonic scale and at the halo scales of two
samples of relaxed elliptical-like-objects (ELOs) identified, at z=0, in a set
of self-consistent hydrodynamical simulations operating in the context of a
concordance cosmological model. At the halo scale they have been found to
satisfy virial relations; at the scale of the baryonic object the (logarithms
of the) ELO stellar masses, projected stellar half-mass radii, and stellar
central l.o.s. velocity dispersions define a flattened ellipsoid close to a
plane (the intrinsic dynamical plane, IDP), tilted relative to the virial one,
whose observational manifestation is the observed FP. The ELO samples have been
found to show systematic trends with the mass scale in both, the relative
content and the relative distributions of the baryonic and the dark mass ELO
components, so that homology is broken in the spatial mass distribution
(resulting in the IDP tilt), but ELOs are still a two-parameter family where
the two parameters are correlated. The physical origin of these trends
presumably lies in the systematic decrease, with increasing ELO mass, of the
relative amount of dissipation experienced by the baryonic mass component along
ELO stellar mass assembly. ELOs also show kinematical segregation, but it does
not appreciably change with the mass scale.
The non-homogeneous population of IDPs explains the role played by the virial
mass to determine the correlations among intrinsic parameters. In this paper we
also show that the central stellar line-of-sight velocity dispersion of ELOs,
is a fair empirical estimator of the virial mass, and this explains the central
role played by this quantity at determining the observational correlations.Comment: 20 pages, 17 Figures. Only changed to a more readable styl
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