4,665 research outputs found
Changes in the secretory profile of NSCLC-associated fibroblasts after ablative radiotherapy: potential impact on angiogenesis and tumor growth
In the context of radiotherapy, collateral effects of ablative ionizing radiation (AIR) on stromal components of tumors remains understudied. In this work, cancer-associated fibroblasts (CAFs) isolated from freshly resected human lung tumors were exposed to AIR (1x18Gy) and analyzed for their release of paracrine factors. Inflammatory mediators and regulators of angiogenesis and tumor growth were analyzed by multiplex protein assays in conditioned medium (CM) from irradiated and non-irradiated CAFs. Additionally, the profile of secreted proteins was examined by proteomics. In functional assays, effects of CAF-CM on proliferative and migratory capacity of lung tumor cells (H-520/H-522) and endothelial cells (HUVECs), and on the tube-forming capacity of endothelial cells was assessed. Our data show that exposure of CAFs to ablative doses of ionizing radiation results in a) down-regulated release of angiogenic factors SDF-1, angiopoietin and thrombospondin-2; b) up-regulated release of growth factor bFGF from most donors, and c) unaffected expression-levels of HGF and inflammatory mediators IL-6, IL-8, IL-1ƒÒ and TNF-£. Conditioned medium from irradiated and control CAFs did not affect differently the proliferative or migratory capacity of tumor cells (H-520/H-522), whereas migratory capacity of endothelial HUVEC cells was partially reduced in the presence of irradiated CAF conditioned medium. Overall we conclude that AIR mediates a transformation on the secretory profile of CAFs that could influence the behavior of other cells in the tumor tissue and hence guide to some extent therapeutic outcomes. The downstream consequences of the changes observed in this study merits further investigations
The Patterns of High-Level Magnetic Activity Occurring on the Surface of V1285 Aql: The OPEA Model of Flares and DFT Models of Stellar Spots
Statistically analyzing Johnson UBVR observations of V1285 Aql during the
three observing seasons, both activity level and behavior of the star are
discussed in respect to obtained results. We also discuss the out-of-flare
variation due to rotational modulation. Eighty-three flares were detected in
the U-band observations of season 2006 . First, depending on statistical
analyses using the independent samples t-test, the flares were divided into two
classes as the fast and the slow flares. According to the results of the test,
there is a difference of about 73 s between the flare-equivalent durations of
slow and fast flares. The difference should be the difference mentioned in the
theoretical models. Second, using the one-phase exponential association
function, the distribution of the flare-equivalent durations versus the flare
total durations was modeled. Analyzing the model, some parameters such as
plateau, half-life values, mean average of the flare-equivalent durations,
maximum flare rise, and total duration times are derived. The plateau value,
which is an indicator of the saturation level of white-light flares, was
derived as 2.421{\pm}0.058 s in this model, while half-life is computed as 201
s. Analyses showed that observed maximum value of flare total duration is 4641
s, while observed maximum flare rise time is 1817 s. According to these
results, although computed energies of the flares occurring on the surface of
V1285 Aql are generally lower than those of other stars, the length of its
flaring loop can be higher than those of more active stars.Comment: 44 pages, 10 figures, 5 tables, 2011PASP..123..659
Melting in multilayer adsorbed films
We present both an improved model and new experimental data concerning the problem of melting in multilayer adsorbed films. The model treats in a mutually consistent manner all interfaces in a stratified film. This results in the prediction of substrate freezing, a phenomenon thermodynamically analogous to surface melting. We also compare the free energies of stratified films to those of homogeneous films. This leads to an orderly classification of multilayer phase diagrams in the vicinity of the bulk triple point. The results of the model are compared with the experimentally known systems. Of these, only methane/graphite exhibits melting from homogeneous solid to homogeneous liquid in multilayer films. The systems Ne/graphite and Ar/graphite, studied by Zhu and Dash, exhibit surface melting and substrate freezing instead. We observe experimentally, by means of pulsed nuclear magnetic resonance, that melting in methane adsorbed on graphite extends below the film thickness at which the latent heat of melting is known to vanish. The multilayer melting curve in this system is a first-order prewetting transition, extending from triple-point dewetting at bulk coexistence down to a critical point where the latent heat vanishes at about four layers, and apparently extending to thinner films as a higher-order, two-dimensional phase transition. It would therefore seem that methane/graphite is an ideal system in which to study the evolution of melting from two dimensions to three dimensions
Analysis and modeling of high temporal resolution spectroscopic observations of flares on AD Leo
We report the results of a high temporal resolution spectroscopic monitoring
of the flare star AD Leo. During 4 nights, more than 600 spectra were taken in
the optical range using the Isaac Newton Telescope (INT) and the Intermediate
Dispersion Spectrograph (IDS). We have observed a large number of short and
weak flares occurring very frequently (flare activity > 0.71 hours-1). This is
in favour of the very important role that flares can play in stellar coronal
heating. The detected flares are non white-light flares and, though most of
solar flares belong to this kind, very few such events had been previously
observed on stars. The behaviour of different chromospheric lines (Balmer
series from H_alpha to H_11, Ca II H & K, Na I D_1 & D_2, He I 4026 AA and He I
D_3) has been studied in detail for a total of 14 flares. We have also
estimated the physical parameters of the flaring plasma by using a procedure
which assumes a simplified slab model of flares. All the obtained physical
parameters are consistent with previously derived values for stellar flares,
and the areas - less than 2.3% of the stellar surface - are comparable with the
size inferred for other solar and stellar flares. Finally, we have studied the
relationships between the physical parameters and the area, duration, maximum
flux and energy released during the detected flares.Comment: Latex file with 17 pages, 11 figures. Available at
http://www.ucm.es/info/Astrof/invest/actividad/actividad_pub.html Accepted
for publication in: Astronomy & Astrophysics (A&A
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