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Search Results: 1 - 10 of 87722 matches for " I. Ligi "
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Developmental Origins of Chronic Renal Disease: An Integrative Hypothesis
F. Boubred,M. Saint-Faust,C. Buffat,I. Ligi,I. Grandvuillemin,U. Simeoni
International Journal of Nephrology , 2013, DOI: 10.1155/2013/346067
Abstract: Cardiovascular diseases are one of the leading causes of mortality. Hypertension (HT) is one of the principal risk factors associated with death. Chronic kidney disease (CKD), which is probably underestimated, increases the risk and the severity of adverse cardiovascular events. It is now recognized that low birth weight is a risk factor for these diseases, and this relationship is amplified by a rapid catch-up growth or overfeeding during infancy or childhood. The pathophysiological and molecular mechanisms involved in the “early programming” of CKD are multiple and partially understood. It has been proposed that the developmental programming of arterial hypertension and chronic kidney disease is related to a reduced nephron endowment. However, this mechanism is still discussed. This review discusses the complex relationship between birth weight and nephron endowment and how early growth and nutrition influence long term HT and CKD. We hypothesize that fetal environment reduces moderately the nephron number which appears insufficient by itself to induce long term diseases. Reduced nephron number constitutes a “factor of vulnerability” when additional factors, in particular a rapid postnatal growth or overfeeding, promote the early onset of diseases through a complex combination of various pathophysiological pathways. 1. Introduction Cardiovascular diseases ((CVD) hypertension, coronary disease and stroke, and heart failure) are one of the leading causes of mortality in industrialized countries, and the prevalence is increasing in emerging societies. All cardiovascular diseases account for 4.3 million deaths per year in the European Union, and the prevalence of chronic heart failure in the United States of America is approximately 6 million [1, 2]. In industrialized countries, hypertension (HT) affects 25% to 35% of the global population and reaches 60% to 70% of the population aged 60 or more. Hypertension is the principal risk factor of death worldwide [3]. It increases the severity of ischemic vascular diseases and, with obesity and type 2 diabetes, is one of the important risk factors for chronic kidney disease (CKD). Chronic kidney disease is defined as reduced glomerular filtration rate (GFR) up to end-stage renal disease (ESRD), proteinuria, or both. Prevalence of ESRD, estimated to be 0.5–2.5‰ worldwide, is increasing in several countries [4]. In turn, impaired renal factor favors the development of and amplifies the severity of CVD [5–7]. During the last two decades, it has been raised the concept of developmental programming of adult chronic
Cutaneous Metastasis In Visceral Malignancy
Mathew Ligi,Kuruvila Maria,Dinesh M
Indian Journal of Dermatology , 2002,
Abstract: Cutaneous metastasis from visceral malignancy is uncommon. We report a 54 year old female operated for adenocarcinoma caecum who developed multiple cutaneous metastatic nodules while on chemotherapy.
A new interferometric study of four exoplanet host stars : θ Cygni, 14 Andromedae, {\upsilon} Andromedae and 42 Draconis
R. Ligi,D. Mourard,A. M. Lagrange,K. Perraut,T. Boyajian,Ph. Bério,N. Nardetto,I. Tallon-Bosc,H. McAlister,T. ten Brummelaar,S. Ridgway,J. Sturmann,L. Sturmann,N. Turner,C. Farrington,P. J. Goldfinger
Physics , 2012, DOI: 10.1051/0004-6361/201219467
Abstract: Studying exoplanet host stars is of the utmost importance to establish the link between the presence of exoplanets around various types of stars and to understand the respective evolution of stars and exoplanets. Using the limb-darkened diameter (LDD) obtained from interferometric data, we determine the fundamental parameters of four exoplanet host stars. We are particularly interested in the F4 main-sequence star, {\theta} Cyg, for which Kepler has recently revealed solar-like oscillations that are unexpected for this type of star. Furthermore, recent photometric and spectroscopic measurements with SOPHIE and ELODIE (OHP) show evidence of a quasi-periodic radial velocity of \sim150 days. Models of this periodic change in radial velocity predict either a complex planetary system orbiting the star, or a new and unidentified stellar pulsation mode. We performed interferometric observations of {\theta} Cyg, 14 Andromedae, {\upsilon} Andromedae and 42 Draconis for two years with VEGA/CHARA (Mount Wilson, California) in several three-telescope configurations. We measured accurate limb darkened diameters and derived their radius, mass and temperature using empirical laws. We obtain new accurate fundamental parameters for stars 14 And, {\upsilon} And and 42 Dra. We also obtained limb darkened diameters with a minimum precision of \sim 1.3%, leading to minimum planet masses of Msini=5.33\pm 0.57, 0.62 \pm 0.09 and 3.79\pm0.29 MJup for 14 And b, {\upsilon} And b and 42 Dra b, respectively. The interferometric measurements of {\theta} Cyg show a significant diameter variability that remains unexplained up to now. We propose that the presence of these discrepancies in the interferometric data is caused by either an intrinsic variation of the star or an unknown close companion orbiting around it.
Tectonics and seismicity of the ApulianRidge south of Salento peninsula(Southern Italy)
A. Argnani,F. Frugoni,R. Cosi,M. Ligi
Annals of Geophysics , 2001, DOI: 10.4401/ag-3573
Abstract: Multichannel reflection seismic data were acquired south of the Salento peninsula, in an area where crustal seismicity has been recorded. Seismic profiles show the presence of small grabens bounded by extensional faults with NW-SE direction. These grabens are filled with Plio-Quaternary sediments and represent the prolongation of the grabens located onshore in the Salento peninsula. Outer arc extension due to flexuring of the Adriatic-Apulian lithosphere under the double load of the Hellenides and Apennines-Calabrian arc is thought to have originated these grabens. The Adriatic-Apulian continental lithosphere presents a very small radius of curvature and a decoupling between upper crust and mantle lithosphere is expected. Inner arc compression within the upper crust may be responsible for the seismicity recorded in the area.
The operation of VEGA/CHARA : from the scientific idea to the final products
Roxanne Ligi,Denis Mourard,Nicolas Nardetto,Jean-Michel Clausse
Physics , 2014, DOI: 10.1142/S2251171713400035
Abstract: We describe the data flow in the operation of the VEGA/CHARA instrument. After a brief summary of the main characteristics and scientific objectives of the VEGA instrument, we explain the standard procedure from the scientific idea up to the execution of the observation. Then, we describe the different steps done after the observation, from the raw data to the archives and the final products. Many tools are used and we show how the Virtual Observatory principles have been implemented for the interoperability of these software and databases.
Chromosphere of K giant stars Geometrical extent and spatial structure detection
P. Berio,T. Merle,F. Thevenin,D. Bonneau,D. Mourard,O. Chesneau,O. Delaa,R. Ligi,N. Nardetto,K. Perraut,B. Pichon,P. Stee,I. Tallon-Bosc,J. M. Clausse,A. Spang,H. McAlister,T. ten Brummelaar,J. Sturmann,L. Sturmann,N. Turner,C. Farrington,P. J. Goldfinger
Physics , 2011, DOI: 10.1051/0004-6361/201117479
Abstract: We aim to constrain the geometrical extent of the chromosphere of non-binary K giant stars and detect any spatial structures in the chromosphere. We performed observations with the CHARA interferometer and the VEGA beam combiner at optical wavelengths. We observed seven non-binary K giant stars. We measured the ratio of the radii of the photosphere to the chromosphere using the interferometric measurements in the Halpha and the Ca II infrared triplet line cores. For beta Ceti, spectro-interferometric observations are compared to an non-local thermal equilibrium (NLTE) semi-empirical model atmosphere including a chromosphere. The NLTE computations provide line intensities and contribution functions that indicate the relative locations where the line cores are formed and can constrain the size of the limb-darkened disk of the stars with chromospheres. We measured the angular diameter of seven K giant stars and deduced their fundamental parameters: effective temperatures, radii, luminosities, and masses. We determined the geometrical extent of the chromosphere for four giant stars. The chromosphere extents obtained range between 16% to 47% of the stellar radius. The NLTE computations confirm that the Ca II/849 nm line core is deeper in the chromosphere of ? Cet than either of the Ca II/854 nm and Ca II/866 nm line cores. We present a modified version of a semi-empirical model atmosphere derived by fitting the Ca II triplet line cores of this star. In four of our targets, we also detect the signature of a differential signal showing the presence of asymmetries in the chromospheres. Conclusions. It is the first time that geometrical extents and structure in the chromospheres of non-binary K giant stars are determined by interferometry. These observations provide strong constrains on stellar atmosphere models.
Detection of high energy cosmic rays with the resonant gravitational wave detector NAUTILUS and EXPLORER
P. Astone,D. Babusci,M. Bassan,P. Bonifazi,G. Cavallari,E. Coccia,S. D'Antonio,V. Fafone,G. Giordano,C. Ligi,A. Marini,G. Mazzitelli,Y. Minenkov,I. Modena,G. Modestino,A. Moleti,G. V. Pallottino,G. Pizzella,L. Quintieri,A. Rocchi,F. Ronga,R. Terenzi,M. Visco
Physics , 2008, DOI: 10.1016/j.astropartphys.2008.09.002
Abstract: The cryogenic resonant gravitational wave detectors NAUTILUS and EXPLORER, made of an aluminum alloy bar, can detect cosmic ray showers. At temperatures above 1 K, when the material is in the normal conducting state, the measured signals are in good agreement with the values expected based on the cosmic rays data and on the thermo-acoustic model. When NAUTILUS was operated at the temperature of 0.14 K, in superconductive state, large signals produced by cosmic ray interactions, more energetic than expected, were recorded. The NAUTILUS data in this case are in agreement with the measurements done by a dedicated experiment on a particle beam. The biggest recorded event was in EXPLORER and excited the first longitudinal mode to a vibrational energy of about 670 K, corresponding to about 360 TeV absorbed in the bar. Cosmic rays can be an important background in future acoustic detectors of improved sensitivity. At present, they represent a useful tool to verify the gravitational wave antenna performance.
Spectral and spatial imaging of the Be+sdO binary phi Persei
D. Mourard,J. D. Monnier,A. Meilland,D. Gies,F. Millour,M. Benisty,X. Che,E. D. Grundstrom,R. Ligi,G. Schaefer,F. Baron,S. Kraus,M. Zhao,E. Pedretti,P. Berio,J. M. Clausse,N. Nardetto,K. Perraut,A. Spang,P. Stee,I. Tallon-Bosc,H. McAlister,T. ten Brummelaar,S. T. Ridgway,J. Sturmann,L. Sturmann,N. Turner,C. Farrington
Physics , 2015, DOI: 10.1051/0004-6361/201425141
Abstract: The rapidly rotating Be star phi Persei was spun up by mass and angular momentum transfer from a now stripped-down, hot subdwarf companion. Here we present the first high angular resolution images of phi Persei made possible by new capabilities in longbaseline interferometry at near-IR and visible wavelengths. We observed phi Persei with the MIRC and VEGA instruments of the CHARA Array. Additional MIRC-only observations were performed to track the orbital motion of the companion, and these were fit together with new and existing radial velocity measurements of both stars to derive the complete orbital elements and distance. The hot subdwarf companion is clearly detected in the near-IR data at each epoch of observation with a flux contribution of 1.5% in the H band, and restricted fits indicate that its flux contribution rises to 3.3% in the visible. A new binary orbital solution is determined by combining the astrometric and radial velocity measurements. The derived stellar masses are 9.6+-0.3Msol and 1.2+-0.2Msol for the Be primary and subdwarf secondary, respectively. The inferred distance (186 +- 3 pc), kinematical properties, and evolutionary state are consistent with membership of phi Persei in the alpha Per cluster. From the cluster age we deduce significant constraints on the initial masses and evolutionary mass transfer processes that transformed the phi Persei binary system. The interferometric data place strong constraints on the Be disk elongation, orientation, and kinematics, and the disk angular momentum vector is coaligned with and has the same sense of rotation as the orbital angular momentum vector. The VEGA visible continuum data indicate an elongated shape for the Be star itself, due to the combined effects of rapid rotation, partial obscuration of the photosphere by the circumstellar disk, and flux from the bright inner disk.
Improving the surface brightness-color relation for early-type stars using optical interferometry
M. Challouf,N. Nardetto,D. Mourard,D. Graczyk,H. Aroui,O. Chesneau,O. Delaa,G. Pietrzyński,W. Gieren,R. Ligi,A. Meilland,K. Perraut,I. Tallon-Bosc,H. McAlister,T. ten Brummelaar,J. Sturmann,L. Sturmann,N. Turner,C. Farrington,N. Vargas,N. Scott
Physics , 2014, DOI: 10.1051/0004-6361/201423772
Abstract: The aim of this work is to improve the SBC relation for early-type stars in the $-1 \leq V-K \leq 0$ color domain, using optical interferometry. Observations of eight B- and A-type stars were secured with the VEGA/CHARA instrument in the visible. The derived uniform disk angular diameters were converted into limb darkened angular diameters and included in a larger sample of 24 stars, already observed by interferometry, in order to derive a revised empirical relation for O, B, A spectral type stars with a V-K color index ranging from -1 to 0. We also took the opportunity to check the consistency of the SBC relation up to $V-K \simeq 4$ using 100 additional measurements. We determined the uniform disk angular diameter for the eight following stars: $\gamma$ Ori, $\zeta$ Per, $8$ Cyg, $\iota$ Her, $\lambda$ Aql, $\zeta$ Peg, $\gamma$ Lyr, and $\delta$ Cyg with V-K color ranging from -0.70 to 0.02 and typical precision of about $1.5\%$. Using our total sample of 132 stars with $V-K$ colors index ranging from about $-1$ to $4$, we provide a revised SBC relation. For late-type stars ($0 \leq V-K \leq 4$), the results are consistent with previous studies. For early-type stars ($-1 \leq V-K \leq 0$), our new VEGA/CHARA measurements combined with a careful selection of the stars (rejecting stars with environment or stars with a strong variability), allows us to reach an unprecedented precision of about 0.16 magnitude or $\simeq 7\%$ in terms of angular diameter.
The diameter of the CoRoT target HD 49933. Combining the 3D limb darkening, asteroseismology, and interferometry
L. Bigot,D. Mourard,P. Berio,F. Thévenin,R. Ligi,I. Tallon-Bosc,O. Chesneau,O. Delaa,N. Nardetto,K. Perraut,Ph. Stee,T. Boyajian,P. Morel,B. Pichon,P. Kervella,F. X. Schmider,H. McAlister,T. Ten Brummelaar,S. T. Ridgway,J. Sturmann,L. Sturmann,N. Turner,C. Farrington,P. J. Goldfinger
Physics , 2011, DOI: 10.1051/0004-6361/201117349
Abstract: Context. The interpretation of stellar pulsations in terms of internal structure depends on the knowledge of the fundamental stellar parameters. Long-base interferometers permit us to determine very accurate stellar radii, which are independent constraints for stellar models that help us to locate the star in the HR diagram. Aims: Using a direct interferometric determination of the angular diameter and advanced three-dimensional (3D) modeling, we derive the radius of the CoRoT target HD 49933 and reduce the global stellar parameter space compatible with seismic data. Methods: The VEGA/CHARA spectro-interferometer is used to measure the angular diameter of the star. A 3D radiative hydrodynamical simulation of the surface is performed to compute the limb darkening and derive a reliable diameter from visibility curves. The other fundamental stellar parameters (mass, age, and Teff) are found by fitting the large and small p-mode frequency separations using a stellar evolution model that includes microscopic diffusion. Results: We obtain a limb-darkened angular diameter of {\theta}LD = 0.445 \pm 0.012 mas. With the Hipparcos parallax, we obtain a radius of R = 1.42 \pm 0.04 Rsun. The corresponding stellar evolution model that fits both large and small frequency separations has a mass of 1.20 \pm 0.08 Msun and an age of 2.7 Gy. The atmospheric parameters are Teff = 6640 \pm 100 K, log g = 4.21 \pm 0.14, and [Fe/H] = -0.38.
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