1,459 research outputs found
Preliminary study on electrophysiological changes after cellular autograft in age-related macular degeneration
Background: Evolving atrophic macular degeneration represents at least 80% of all macular degenerations and is currently without a standardized care. Autologous fat transplantation (AFT) efficacy was demonstrated by several studies, since these cells are able to produce growth factors. The aim of the work was to demonstrate possible therapeutic effect of the joined suprachoroidal graft of adipocytes, adipose derived stem-cells (ADSCs) in tissue adipose’s stromal vascular fractions (SVF), and platelet rich plasma (PRP).
Methods: Twelve eyes in 12 dry age macular degeneration (AMD) patients, aged 71.25 (SD ± 6.8) between 62 and 80 years, were analyzed. A complete ocular evaluation was performed using: best corrected visual acuity (BCVA), retinographic analysis, spectral-domain optical coherence tomography, microperimetry, computerized visual field, and standard electroretinogram (ERG). Each eye received a cell in graft between choroid and sclera by means of the variant second Limoli, grafting of mature fat cells and ADSCs in SVF enriched with PRP (LRRT). In order to test if the differences pre- and post-treatment were significant the Wilcoxon signed rank test has been performed.
Results: Adverse effects were not reported in the patients. After surgery with LRRT the most significant increase in the ERG values was recorded by scotopic rod-ERG (answer coming from the rods), from 41.26 to 60.83 μVolts (µV) with an average increase of 47.44% highly significant (p<0.05). Moderately significant was the one recorded by scotopic maximal ERG (answer coming from the rods and cones), from 112.22 to 129.68 μV with an average increase of 15.56% (p<0.1).
Conclusions: Cell-mediated therapy based on growth factors used appears interesting because it can improve the retinal functionality responses in the short term. The ERG could, therefore, be used to monitor the effect of cell-mediated regenerative therapies
Chiral exponents of the square-lattice frustrated XY model: A Monte Carlo transfer-matrix calculation
Thermal and chiral critical exponents of the fully frustrated XY model on a square lattice are obtained from a finite-size scaling analysis of the free energy of chiral domain walls. Data were obtained by extensive Monte Carlo transfer-matrix computations for infinite strips of widths up to 14 lattice spacings. Two transfer matrices were implemented, one for each of two principal lattice directions. The results of both are consistent, but the critical exponents differ significantly from the pure Ising values. This is in agreement with other recent Monte Carlo simulations. Our results also support the identification of the critical behavior of this model with that along the line of transitions of simultaneous ordering or becoming critical of Ising and planar rotor degrees of freedom in the XY-Ising model studied recently
Detection of Surface Brightness Fluctuations in Elliptical Galaxies imaged with the Advanced Camera for Surveys. B- and I-band measurements
Taking advantage of the exceptional capabilities of ACS on board of HST, we
derive Surface Brightness Fluctuation (SBF) measurements in the B and I bands
from images of six elliptical galaxies with . Given the
low S/N ratio of the SBF signal in the blue band images, the reliability of the
measurements is verified both with numerical simulations and experimental data
tests.
This paper presents the first published B- and I-band SBF measurements for
distant ( 20 Mpc) galaxies, essential for the comparisons of the models
to observations of normal ellipticals. By comparing I-band data with our new
Simple Stellar Population (SSP) models we find an excellent agreement and we
confirm that I-band SBF magnitudes are mainly sensitive to the metallicity of
the dominant stellar component in the galaxy, and are not strongly affected by
the contribution of possible secondary stellar components. As a consequence
I-band fluctuations magnitudes are ideal for distance studies. On the other
hand, we show that standard SSP models do not reproduce the B-band SBF
magnitudes of red ((B-I)_0 \gsim 2.1) galaxies in our sample. We explore the
capability of two non--canonical models in properly reproducing the high
sensitivity of B SBF to the presence of even small fractions of bright, hot
stars (metal poor stars, hot evolved stars, etc.). The disagreement is solved
both by taking into account hot (Post--AGB) stars in SSP models and/or by
adopting Composite Stellar Population models. Finally, we suggest a limit value
of the S/N for the B-band SBF signal required to carry out a detailed study of
stellar population properties based on this technique.Comment: ApJ accepte
Spectral libraries and their uncertainties
Libraries of stellar spectra are fundamental tools in the study of stellar
populations and in automatic determination of atmospheric parameters for large
samples of observed stars. In the context of the present volume, here I give an
overview of the current status of stellar spectral libraries from the
perspective of stellar population modeling: what we have currently available,
how good they are, and where we need further improvement
Approximate analytical description of the nonaffine response of amorphous solids
An approximation scheme for model disordered solids is proposed that leads to
the fully analytical evaluation of the elastic constants under explicit account
of the inhomogeneity (nonaffinity) of the atomic displacements. The theory is
in quantitative agreement with simulations for central-force systems and
predicts the vanishing of the shear modulus at the isostatic point with the
linear law {\mu} ~ (z - 2d), where z is the coordination number. The vanishing
of rigidity at the isostatic point is shown to be a consequence of the
canceling out of positive affine and negative nonaffine terms
Random walk in a random environment and 1f noise
A simple model showing a behavior is proposed. It is argued, on the basis of a scaling argument, that is has corrections. Numerical simulations confirm this picture
The distance to NGC1316 (Fornax A): yet another curious case
The distance of NGC1316, the brightest galaxy in Fornax, is an interesting
test for the cosmological distance scale. First, because Fornax is the 2nd
largest cluster of galaxies at <~25 Mpc after Virgo and, in contrast to Virgo,
has a small line-of-sight depth; and second, because NGC1316 is the galaxy with
the largest number of detected SNeIa, giving the opportunity to test the
consistency of SNeIa distances internally and against other indicators.
We measure SBF mags in NGC1316 from ground and space-based imaging data,
providing a homogeneous set of measurements over a wide wavelength interval.
The SBF, coupled with empirical and theoretical calibrations, are used to
estimate the distance to the galaxy. We present the first B-band SBF
measurements of NGC1316 and use them together with the optical and near-IR SBF
data to analyze the properties of field stars.
Our distance modulus m-M=31.59 +-0.05(stat) +-0.14(sys), when placed in a
consistent Cepheid distance scale, agrees with the results from other
indicators. However, our result is ~17% larger than the most recent estimate
based on SNeIa. Possible explanations for this disagreement are the
uncertainties on internal extinction, or calibration issues. Concerning the
stellar population analysis, we confirm earlier results from other indicators:
the field stars in NGC1316 are dominated by a solar metallicity, intermediate
age component. A substantial mismatch exists between B-band SBF models and
data, a behavior that can be accounted for by an enhanced percentage of hot
horizontal branch stars.
Our study of the SBF distance to NGC1316, and the comparison with distances
from other indicators, raises some concern about the homogeneity between the
calibrations of different indicators. If not properly placed in the same
reference scale, significant differences can occur, with dramatic impact on the
cosmological distance ladder.Comment: 21 pages, 13 figures; A&A accepte
The End of Amnesia: Measuring the Metallicities of Type Ia SN Progenitors with Manganese Lines in Supernova Remnants
The Mn to Cr mass ratio in supernova ejecta has recently been proposed as a
tracer of Type Ia SN progenitor metallicity. We review the advantages and
problems of this observable quantity, and discuss them in the framework of the
Tycho Supernova Remnant. The fluxes of the Mn and Cr Kalpha lines in the X-ray
spectra of Tycho observed by the Suzaku satellite suggests a progenitor of
supersolar metallicity.Comment: 4 pages, 1 figure, Proceedings of 'Probing Stellar Populations out to
the Distant Universe'. September 15-19 2008, Cefalu, Sicily, Ital
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