Aims. We investigate the capability of multistranded loop models subject to nanoflare heating to reproduce the properties recently observed in coronal loops at extreme ultraviolet (EUV) wavelengths. ...Methods. One-dimensional hydrodynamic simulations of magnetic loop strands were performed with an impulsive, footpoint-localised heating, with a moderate asymmetry between the two loop halves that was produced either by a sequence of identical nanoflares with a given cadence time tC or by a single energy pulse. The temporal evolution of the emission of a multistranded loop was modelled by simply combining the results of independent single-strand simulations, neglecting any spatial interaction among the strands, and was compared with TRACE and SDO/AIA light curves. The density excess with respect to hydrostatic equilibrium (the ψ factor) was evaluated with the filter-ratio technique. Results. Both loop models exhibit a density excess compared with hydrostatic equilibrium models, which agrees well with the observed values (1 ≲ ψ ≲ 12). However, in the single-pulse model the light curve and density excess maxima do not match. On the other hand, the models with a sequence of nanoflares predict strong emission at lower temperatures that cannot be reconciled with the available observations.
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Aims. We report the discovery of two Li-rich giants, with A(Li) ~ 1.50, in an analysis of a sample of 40 giants of the open cluster Trumpler 20 (with turnoff mass ~1.8 M⊙). The cluster was observed ...in the context of the Gaia-ESO Survey. Methods. The atmospheric parameters and Li abundances were derived using high-resolution UVES spectra. The Li abundances were corrected for nonlocal thermodynamical equilibrium (non-LTE) effects. Results. Only upper limits of the Li abundance could be determined for the majority of the sample. Two giants with detected Li turned out to be Li rich: star MG 340 has A(Li)non−LTE = 1.54 ± 0.21 dex and star MG 591 has A(Li)non−LTE = 1.60 ± 0.21 dex. Star MG 340 is on average ~0.30 dex more rich in Li than stars of similar temperature, while for star MG 591 this difference is on average ~0.80 dex. Carbon and nitrogen abundances indicate that all stars in the sample have completed the first dredge-up. Conclusions. The Li abundances in this unique sample of 40 giants in one open cluster clearly show that extra mixing is the norm in this mass range. Giants with Li abundances in agreement with the predictions of standard models are the exception. To explain the two Li-rich giants, we suggest that all events of extra mixing have been inhibited. This includes rotation-induced mixing during the main sequence and the extra mixing at the red giant branch luminosity bump. Such inhibition has been suggested in the literature to occur because of fossil magnetic fields in red giants that are descendants of main-sequence Ap-type stars.
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Aims.We present the results of a contemporaneous photometric and spectroscopic monitoring of two RS CVn binaries, namely λ And and II Peg. The aim of this work is to investigate the behavior of ...surface inhomogeneities in the atmospheres of the active components of these systems that have nearly the same temperatures but different gravities. Methods.The light curves and the modulation of the surface temperature, as recovered from line-depth ratios (LDRs), were used to map the photospheric spots, while the Hα emission was used as an indicator of chromospheric inhomogeneities. The spot temperatures and sizes were derived from a spot model applied to the contemporaneous light and temperature curves. Results.We find larger and cooler spots on II Peg ($T_{\rm sp} \simeq 3600$ K) than on λ And ($T_{\rm sp} \simeq 3900$ K); this could be the result of both the difference in gravity and the higher activity level of the former. Moreover, we find a clear anti-correlation between the Hα emission and the photospheric diagnostics (temperature and light curves). We have detected a modulation in the intensity of the $\ion{He}{i}$ D3 line with the star rotation, suggesting surface features also in the upper chromosphere of these stars. A rough reconstruction of the 3D structure of their atmospheres was also performed by applying a spot/plage model to the light and temperature curves and to the Hα flux modulation. In addition, a strong flare affecting the Hα, the $\ion{He}{i}$ D3, and the cores of $\ion{Na}{i}$ D$_{1,2}$ lines has been observed on II Peg. Conclusions.The spot/plage configuration has been reconstructed in the visible component of λ And and II Peg, which have nearly the same temperature but very different gravities and rotation periods. A close spatial association of photospheric and chromospheric active regions, at the time of our observations, was found in both stars. Larger and cooler spots were found on II Peg, the system with the active component of higher gravity and a higher activity level. The area ratio of plages to spots seems to decrease when the spots get bigger. Moreover, with both this and literature data, a correlation between the temperature difference $\Delta T = T_{\rm ph}-T_{\rm sp}$ and the surface gravity is also suggested.
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Several studies have shown increased serum levels of proinflammatory cytokines (IL-1α, IL-6, and TNF-α) in patients with cholelithiasis. The local expression of the proteins involved in pathogenesis ...of the disease is poorly recognised.
The authors examined immunohistochemically (IHC) the expression status of IL-1α, IL-6, and TNF-α in gallbladder mucosa of the patients with cholelithiasis as related to acute (ACC) and chronic (CCC) types of cholecystitis. Proinflammatory cytokines were quantitatively evaluated in gallbladder mucosa (epithelium and lamina propria) in ACC (n = 16) and CCC (n = 55) groups using modern spatial visualisation technique.
Quantitative analysis of IHC signals showed no significant differences in IL-1α and IL-6, and immunoexpression in patients with ACC and CCC. A significantly greater IHC expression of TNF-α was detected in CCC as compared with ACC group. In either of the patient groups immunoexpression of IL-1α and of TNF-α was significantly higher than that of IL-6. Immunoexpression of TNF-α was significantly higher than that of IL-1α only in CCC group. A positive correlation was disclosed between IHC expression of IL-1α and body mass index in CCC group. IHC expression of TNF-α correlated positively with expression of CD68 molecule (histiocytic marker), number of leukocytes in blood and higher grading of gallbladder wall in ACC group.
A more pronounced IHC expression of TNF-α and IL-1α than IL-6 in both types of cholecystitis may suggest the role of these cytokines in pathogenesis of cholelithiasis. IHC expression of TNF- α shows better correlation with clinical/laboratory data in acute cholecystitis, and its quantitative prevalence over the remaining cytokines points to the role of the TNF-α in maintenance of inflammation in the course of cholelithiasis.
Context. Stellar evolution models predict that internal mixing should cause some sodium overabundance at the surface of red giants more massive than ~1.5–2.0 M⊙. The surface aluminium abundance ...should not be affected. Nevertheless, observational results disagree about the presence and/or the degree of Na and Al overabundances. In addition, Galactic chemical evolution models adopting different stellar yields lead to very different predictions for the behavior of Na/Fe and Al/Fe versus Fe/H. Overall, the observed trends of these abundances with metallicity are not well reproduced. Aims. We readdress both issues, using new Na and Al abundances determined within the Gaia-ESO Survey. Our aim is to obtain better observational constraints on the behavior of these elements using two samples: i) more than 600 dwarfs of the solar neighborhood and of open clusters and ii) low- and intermediate-mass clump giants in six open clusters. Methods. Abundances were determined using high-resolution UVES spectra. The individual Na abundances were corrected for nonlocal thermodynamic equilibrium effects. For the Al abundances, the order of magnitude of the corrections was estimated for a few representative cases. For giants, the abundance trends with stellar mass are compared to stellar evolution models. For dwarfs, the abundance trends with metallicity and age are compared to detailed chemical evolution models. Results. Abundances of Na in stars with mass below ~2.0 M⊙, and of Al in stars below ~3.0 M⊙, seem to be unaffected by internal mixing processes. For more massive stars, the Na overabundance increases with stellar mass. This trend agrees well with predictions of stellar evolutionary models. For Al, our only cluster with giants more massive than 3.0 M⊙, NGC 6705, is Al enriched. However, this might be related to the environment where the cluster was formed. Chemical evolution models that well fit the observed Na/Fe vs. Fe/H trend in solar neighborhood dwarfs cannot simultaneously explain the run of Al/Fe with Fe/H, and vice versa. The comparison with stellar ages is hampered by severe uncertainties. Indeed, reliable age estimates are available for only a half of the stars of the sample. We conclude that Al is underproduced by the models, except for stellar ages younger than about 7 Gyr. In addition, some significant source of late Na production seems to be missing in the models. Either current Na and Al yields are affected by large uncertainties, and/or some important Galactic source(s) of these elements has as yet not been taken into account.
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This study investigated the reciprocal cross-interactions between two distinct allosteric sites on the M 4 muscarinic acetylcholine receptor (mAChR) in the absence or presence of different ...orthosteric ligands. Initial studies revealed
that two novel benzimidazole allosteric modulators, 17-β-hydroxy-17-α-ethy nyl-delta(4)-androstano3,2- b pyrimido1,2- a benzimidazole (WIN 62,577) and 17-β-hydroxy-17-α-ethynyl-5-α-androstano3,2- b pyrimido1,2- a benzimidazole (WIN 51,708), exhibited different degrees of positive, negative, or close-to-neutral cooperativity with the
orthosteric site on M 1 or M 4 mAChRs, depending on the chemical nature of the orthosteric radioligand that was used 3 H N -methylscopolamine ( 3 HNMS) versus 3 Hquinuclidinylbenzilate ( 3 HQNB). The largest window for observing an effect (negative cooperativity) was noted for the combination of WIN 62,577 and
3 HQNB at the M 4 mAChR. Experiments involving the combination of these two ligands with unlabeled agonists acetylcholine, 4-( m -chlorophenylcarbamoyloxy)-2-butynyltrimethylammonium (McN-A-343), or xanomeline revealed low degrees of negative cooperativity
between WIN 62,577 and each agonist, whereas stronger negative cooperativity was observed against atropine. It is interesting
that when these experiments were repeated using the prototypical modulators heptane-1,7-bis-(dimethyl-3â²-phthalimidopropyl)-ammonium
bromide (C 7 /3-phth), alcuronium, or brucine (which act at a separate allosteric site), WIN 62,577 exhibited negative cooperativity with
each modulator when the orthosteric site was unoccupied, but this switched to neutral cooperativity when the receptor was
occupied by 3 HQNB. Dissociation kinetic experiments using 3 HNMS and combination of C 7 /3-phth with WIN 62,577 also provided evidence for neutral cooperativity between the two allosteric sites when the orthosteric
site is occupied. Together, these results provide insight into the nature of the interaction between two distinct allosteric
sites on the M 4 mAChR and how this interaction is perturbed upon occupancy of the orthosteric site.
Aims. We study how diffuse interstellar bands (DIBs) measured toward distance-distributed target stars can be used to locate dense interstellar (IS) clouds in the Galaxy and probe a line-of-sight ...(LOS) kinematical structure, a potentially useful tool when gaseous absorption lines are saturated or not available in the spectral range. Cool target stars are numerous enough for this purpose. Methods. We devised automated DIB-fitting methods appropriate for cool star spectra and multiple IS components. The data were fitted with a combination of a synthetic stellar spectrum, a synthetic telluric transmission, and empirical DIB profiles. The initial number of DIB components and their radial velocity were guided by HI 21 cm emission spectra, or, when available in the spectral range, IS neutral sodium absorption lines. For NaI, radial velocities of NaI lines and DIBs were maintained linked during a global simultaneous fit. In parallel, stellar distances and extinctions were estimated self-consistently by means of a 2D Bayesian method from spectroscopically-derived stellar parameters and photometric data. Results. We have analyzed Gaia-ESO Survey (GES) spectra of 225 stars that probe between ~2 and 10 kpc long LOS in five different regions of the Milky Way. The targets are the two CoRoT fields, two open clusters (NGC 4815 and γ Vel), and the Galactic bulge. Two OGLE fields toward the bulge observed before the GES are also included (205 target stars). Depending on the observed spectral intervals, we extracted one or more of the following DIBs: λλ 6283.8, 6613.6, and 8620.4. For each field, we compared the DIB strengths with the Bayesian distances and extinctions, and the DIB Doppler velocities with the HI emission spectra. Conclusions. For all fields, the DIB strength and the target extinction are well correlated. For targets that are widely distributed in distance, marked steps in DIBs and extinction radial distance profiles match each other and broadly correspond to the expected locations of spiral arms. For all fields, the DIB velocity structure agrees with HI emission spectra, and all detected DIBs correspond to strong NaI lines. This illustrates how DIBs can be used to locate the Galactic interstellar gas and to study its kinematics at the kpc scale, as illustrated by Local and Perseus Arm DIBs that differ by ≳30 km s-1, in agreement with HI emission spectra. On the other hand, if most targets are located beyond the main absorber, DIBs can trace the differential reddening within the field.
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Context. HD 61005 is a nearby young solar type star that shows a large infrared excess due to a debris disk. The disk has been recently imaged from ground and space, with indications of several ...components. Some characteristics of the disk suggest the presence of planetary companions around the star, that remain undetected in deep adaptive optics imaging. Aims. For a better understanding of the system we aim to refine the determination of the stellar parameters, with emphasis on the stellar age and system orientation. Methods. We used ASAS and Hipparcos photometry and FEROS spectra to determine the rotation period, radial and rotational velocity, chromospheric emission, effective temperature, and chemical composition. Results. We find no indication of any misalignment between the star rotation axis and the disk. The standard age calibrations applied to several indicators yield an age close to that of the Pleiades (120 Myr); however the kinematic properties strongly support its membership in the younger (40 Myr) Argus association, which also includes the IC 2391 open cluster. Detailed comparison of the properties of HD 61005 and IC 2391 members shows that the characteristics of HD 61005 are compatible with membership to the Argus association, once its rather slow rotation is taken into account, because lithium and other age indicators are somewhat correlated with stellar rotation at a fixed age. We also identify systematic differences between the field and cluster population of the Argus association, which are probably selection effects, so we suggest that additional members with slower rotation and lower activity level are waiting to be identified.
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A Doppler image of the zero-age main-sequence (ZAMS) late-type rapidly rotating star LO Pegasi, based on spectra acquired between 2003 September 12 and 15 is presented. The least-squares ...deconvolution technique is applied to enhance the signal-to-noise ratio of the mean rotational broadened line profiles extracted from the observed spectra. In the present application, an unbroadened spectrum is used as a reference, instead of a simple line list, to improve the deconvolution technique applied to extract the mean profiles. The reconstructed image is similar to those previously obtained from observations taken in 1993 and 1998, and shows that LO Peg photospheric activity is dominated by high-latitude spots with a non-uniform polar cap. The latter seems to be a persistent feature as it has been observed since 1993 with little modifications. Small spots, observed between ∼10° and ∼60° of latitude, appears to be different with respect to those present in the 1993 and 1998 maps.
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