383 research outputs found
Tissue iron quantification in chronic liver diseases using MRI shows a relationship between iron accumulation in liver, spleen, and bone marrow
Aim: To investigate iron loading within the liver, pancreas, spleen, and bone marrow using magnetic resonance imaging (MRI) transverse relaxation rate (R2*), in patients with diffuse liver diseases; to evaluate the relationships between iron accumulation in these tissue compartments; and to assess the association between tissue iron overload and the pattern of hepatic cellular iron distribution (hepatocytes versus Kupffer cells).
Material and methods: Fifty-six patients with diffuse liver diseases had MRI-derived R2* values, using a multi-echo chemical-shift encoded MRI sequence, of the liver, pancreas, spleen, and vertebral bone marrow. All patients had liver biopsy samples scored for hepatic iron grading (0â4) and iron cellular distribution (within hepatocytes only or within both hepatocytes and Kupffer cells).
Results: Liver R2* increased with histological iron grade (RS=0.58, p<0.001) and correlated with spleen (RS=0.71, p<0.001) and bone marrow R2* (RS=0.66, p<0.001), but not with pancreatic R2* (RS=0.22, p=0.096). Splenic and bone marrow R2* values were also correlated (RS=0.72, p<0.001). Patients with iron inside Kupffer cells had the highest R2* in liver, spleen and bone marrow.
Conclusions: Patients with chronic diffuse liver diseases have concomitant hepatic, splenic, and bone marrow iron loading. The highest hepatic iron scores and iron inside Kupffer cells were associated with the highest splenic and bone marrow deposits, suggesting systemic iron accumulation in the mononuclear phagocytic system.The present study was supported by the Teaching and Research Department of Centro Hospitalar do Porto with a research grant number DEFI:309/12(213-DEFI/251-CES). The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. L.M.B. and A.A.B. are co-founders of QUIBIM SME
Fluctuations of company yearly profits versus scaled revenue: Fat tail distribution of Levy type
We analyze annual revenues and earnings data for the 500 largest-revenue U.S.
companies during the period 1954-2007. We find that mean year profits are
proportional to mean year revenues, exception made for few anomalous years,
from which we postulate a linear relation between company expected mean profit
and revenue. Mean annual revenues are used to scale both company profits and
revenues. Annual profit fluctuations are obtained as difference between actual
annual profit and its expected mean value, scaled by a power of the revenue to
get a stationary behavior as a function of revenue. We find that profit
fluctuations are broadly distributed having approximate power-law tails with a
Levy-type exponent , from which we derive the associated
break-even probability distribution. The predictions are compared with
empirical data.Comment: 6 pages, 6 figure
Accurate simultaneous quantification of liver steatosis and iron overload in diffuse liver diseases with MRI
Purpose: To evaluate the diagnostic performances of 3 Tesla multi-echo chemical shift-encoded gradient echo magnetic resonance (MECSE-MR) imaging to simultaneously quantify liver steatosis and iron overload in a wide spectrum of diffuse liver diseases having biopsy as reference standard.
Methods: MECSE-MR-acquired images were used to calculate fat fraction and iron content in a single breath-hold in 109 adult patients. Proton density fat fraction (PDFF) was prospectively estimated using complex-based data reconstruction with multipeak fat modeling. Water R2* was used to estimate iron content. Biopsy was obtained in all cases, grading liver steatosis, siderosis, inflammation, and fibrosis. Differences in PDFF and R2* values across histopathological grades were analyzed, and ROC curves analyses evaluated the MR diagnostic performance.
Results: Calculated fat fraction measurements showed significant differences (p < 0.001) among steatosis grades, being unaffected by the presence of inflammation or fibrosis (p â„ 0.05). A strong correlation was found between fat fraction and steatosis grade (R S = 0.718, p < 0.001). Iron deposits did not affect fat fraction quantitation (p â„ 0.05), except in cases with severe iron overload (grade 4). A strong positive correlation was also observed between R2* measurements and iron grades (R S = 0.704, p < 0.001). Calculated R2* values were not different across grades of steatosis, inflammation, and fibrosis (p â„ 0.05).
Conclusion: A MECSE-MR sequence simultaneously quantifies liver steatosis and siderosis, regardless coexisting liver inflammation or fibrosis, with high accuracy in a wide spectrum of diffuse liver disorders. This sequence can be acquired within a single breath-hold and can be implemented in the routine MR evaluation of the liver.This work was partially funded by a research grant from the Teaching and Research Department of Centro Hospitalar do Porto (DEFI:309/12(213-DEFI/251-CES)) and from a Spanish Ministry of Health and Carlos III Health Institute funding grant (PI12/01262). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
Magnetic field and wind of Kappa Ceti: toward the planetary habitability of the young sun when life arose on earth
We report magnetic field measurements for Îș1 Cet, a proxy of the young Sun when life arose on Earth. We carry out an analysis of the magnetic properties determined from spectropolarimetric observations and reconstruct the
large-scale surface magnetic field to derive the magnetic environment, stellar winds, and particle flux permeating
the interplanetary medium around k1 Cet. Our results show a closer magnetosphere and mass-loss rate of M = 9.7 Ì 10-13 M yr-1, i.e., a factor of 50 times larger than the current solar wind mass-loss rate, resulting in a larger interaction via space weather disturbances between the stellar wind and a hypothetical young-Earth analogue, potentially affecting the planetâs habitability. Interaction of the wind from the young Sun with the planetary ancient magnetic field may have affected the young Earth and its life conditions
Accurate masses and radii of normal stars: modern results and applications
This paper presents and discusses a critical compilation of accurate,
fundamental determinations of stellar masses and radii. We have identified 95
detached binary systems containing 190 stars (94 eclipsing systems, and alpha
Centauri) that satisfy our criterion that the mass and radius of both stars be
known to 3% or better. To these we add interstellar reddening, effective
temperature, metal abundance, rotational velocity and apsidal motion
determinations when available, and we compute a number of other physical
parameters, notably luminosity and distance. We discuss the use of this
information for testing models of stellar evolution. The amount and quality of
the data also allow us to analyse the tidal evolution of the systems in
considerable depth, testing prescriptions of rotational synchronisation and
orbital circularisation in greater detail than possible before. The new data
also enable us to derive empirical calibrations of M and R for single (post-)
main-sequence stars above 0.6 M(Sun). Simple, polynomial functions of T(eff),
log g and [Fe/H] yield M and R with errors of 6% and 3%, respectively.
Excellent agreement is found with independent determinations for host stars of
transiting extrasolar planets, and good agreement with determinations of M and
R from stellar models as constrained by trigonometric parallaxes and
spectroscopic values of T(eff) and [Fe/H]. Finally, we list a set of 23
interferometric binaries with masses known to better than 3%, but without
fundamental radius determinations (except alpha Aur). We discuss the prospects
for improving these and other stellar parameters in the near future.Comment: 56 pages including figures and tables. To appear in The Astronomy and
Astrophysics Review. Ascii versions of the tables will appear in the online
version of the articl
Cytogenetic markers as diagnoses in the identification of the hybrid between Piauçu (Leporinus macrocephalus) and Piapara (Leporinus elongatus)
Critical behavior at superconductor-insulator phase transitions near one dimension
I argue that the system of interacting bosons at zero temperature and in
random external potential possesses a simple critical point which describes the
proliferation of disorder-induced topological defects in the superfluid ground
state, and which is located at weak disorder close to and above one dimension.
This makes it possible to address the critical behavior at the superfluid-Bose
glass transition in dirty boson systems by expanding around the lower critical
dimension d=1. Within the formulated renormalization procedure near d=1 the
dynamical critical exponent is obtained exactly and the correlation length
exponent is calculated as a Laurent series in the parameter \sqrt{\epsilon},
with \epsilon=d-1: z=d, \nu=1/\sqrt{3\epsilon} for the short range, and z=1,
\nu=\sqrt{2/3\epsilon}, for the long-range Coulomb interaction between bosons.
The identified critical point should be stable against the residual
perturbations in the effective action for the superfluid, at least in
dimensions 1\leq d \leq 2, for both short-range and Coulomb interactions. For
the superfluid-Mott insulator transition in the system in a periodic potential
and at a commensurate density of bosons I find \nu=(1/2\sqrt{\epsilon})+
1/4+O(\sqrt{\epsilon}), which yields a result reasonably close to the known XY
critical exponent in d=2+1. The critical behavior of the superfluid density,
phonon velocity and the compressibility in the system with the short-range
interactions is discussed.Comment: 23 pages, 1 Postscript figure, LaTe
Astrobiologically Interesting Stars within 10 parsecs of the Sun
The existence of life based on carbon chemistry and water oceans relies upon
planetary properties, chiefly climate stability, and stellar properties, such
as mass, age, metallicity and Galactic orbits. The latter can be well
constrained with present knowledge. We present a detailed, up-to-date
compilation of the atmospheric parameters, chemical composition, multiplicity
and degree of chromospheric activity for the astrobiologically interesting
solar-type stars within 10 parsecs of the Sun. We determine their state of
evolution, masses, ages and space velocities, and produce an optimized list of
candidates that merit serious scientific consideration by the future
space-based interferometry probes aimed at directly detecting Earth-sized
extrasolar planets and seeking spectroscopic infrared biomarkers as evidence of
photosynthetic life. The initially selected stars number 33 solar-type within
the population of 182 stars (excluding late M-dwarfs) closer than 10 pc. A
comprehensive and detailed data compilation for these objects is still
essentially lacking: a considerable amount of recent data has so far gone
unexplored in this context. We present 13 objects as the nearest "biostars",
after eliminating multiple stars, young, chromospherically active, hard X-ray
emitting stars, and low metallicity objects. Three of these "biostars", HD
1581, 109358 and 115617, closely reproduce most of the solar properties and are
considered as premier targets. We show that approximately 7% of the nearby
stars are optimally interesting targets for exobiology.Comment: 36 pages, recommended for publication in Astrobiolog
Cytogenetical studies in five Atlantic Anguilliformes fishes
The order Anguilliformes comprises 15 families, 141 genera and 791 fish species. Eight families had at least one karyotyped species, with a prevalence of 2n = 38 chromosomes and high fundamental numbers (FN). The only exception to this pattern is the family Muraenidae, in which the eight species analyzed presented 2n = 42 chromosomes. Despite of the large number of Anguilliformes species, karyotypic reports are available for only a few representatives. In the present work, a species of Ophichthidae, Myrichthys ocellatus (2n = 38; 8m+14sm+10st+6a; FN = 70) and four species of Muraenidae, Enchelycore nigricans (2n = 42; 6m+8sm+12st+16a; FN = 68), Gymnothorax miliaris (2n = 42; 14m+18sm+10st; FN = 84), G. vicinus (2n = 42; 8m+6sm+28a; FN = 56) and Muraena pavonina (2n = 42; 6m+4sm+32a; FN = 52), collected along the Northeastern coast of Brazil and around the St Peter and St Paul Archipelago were analyzed. Typical large metacentric chromosomes were observed in all species. Conspicuous polymorphic heterochromatic regions were observed at the centromeres of most chromosomes and at single ribosomal sites. The data obtained for Ophichthidae corroborate the hypothesis of a karyotypic diversification mainly due to pericentric inversions and Robertsonian rearrangements, while the identification of constant chromosome numbers in Muraenidae (2n = 42) suggests a karyotype diversification through pericentric inversions and heterochromatin processes
Effects of endurance racing on horse plasma extracellular particle miRNA
Background: Physical exercise is an essential factor in preventing and treating metabolic diseases by promoting systemic benefits throughout the body. The molecular factors involved in this process are poorly understood. Micro RNAs (miRNAs) are small non-coding RNAs that inhibit mRNA transcription. MiRNAs, which can participate in the benefits of exercise to health, circulate in plasma in extracellular particles (EP). Horses that undergo endurance racing are an excellent model to study the impact of long-duration/low intensity exercise in plasma EP miRNAs. Objectives: To evaluate the effects of 160 km endurance racing on horse plasma extracellular particles and their miRNA population. Study design: Cohort study. Methods: We collected plasma from five Arabian horses during five time-points of an endurance ride. Extracellular particles were purified from plasma and characterised by electron microscopy, resistive pulse sensing (qNano) and western blotting. Small RNAs were purified from horse plasma EP, and sequencing was performed. Results: Endurance racing increased EP concentration and average diameter compared to before the race. Western blotting showed a high concentration of extracellular vesicles proteins 2 hours after the race, which returned to baseline 15 hours after the race. MicroRNA differential expression analysis revealed increasing levels of eca-miR-486-5p during and after the race, and decreasing levels of eca-miR-9083 after the end. Conclusions: This study adds new data about the variation in plasma EP concentrations after long-distance exercise and brings new insights about the roles of exercise-derived EP miRNAs during low-intensity endurance exercise
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