23 research outputs found
Evidence for enhanced chromospheric Ca II H & K emission in stars with close-in extrasolar planets
The planet-star interaction is manifested in many ways. It was found out that
a close-in exoplanet causes small but measurable variability in the cores of a
few lines in the spectra of several stars which corresponds to the orbital
period of the exoplanet. Stars with and without exoplanets may have different
properties. The main goal of our study is to search for influence which
exoplanets might have on atmospheres of their host stars. Unlike the previous
studies, we do not study changes in the spectrum of a host star or differences
between stars with and without exoplanets. We aim to study a large number of
stars with exoplanets, current level of their chromospheric activity and look
for a possible correlation with the exoplanetary properties. To analyse the
chromospheric activity of stars we exploit our own (2.2m ESO/MPG telescope) and
publicly available archival spectra (Keck Observatory Archive), measure the
equivalent widths of the cores of Ca II H and K lines and use them as a tracer
of their activity. Subsequently, we search for their dependence on the orbital
parameters and mass of the exoplanet. We found a statistically significant
evidence that the equivalent width of the Ca II K line emission and log R'_{HK}
activity parameter of the host star varies with the semi-major axis and mass of
the exoplanet. Stars with T_eff <= 5500 K having exoplanets with semi-major
axis a <= 0.15 AU (P_orb <= 20 days) have a broad range of Ca II K emissions
and much stronger emission in general than stars at similar temperatures but
with higher values of semi-major axes. Ca II K emission of cold stars (T_eff <=
5500 K) with close-in exoplanets (a <= 0.15 AU) is also more pronounced for
more massive exoplanets. The overall level of the chromospheric activity of
stars may be affected by their close-in exoplanets. Stars with massive close-in
exoplanets may be more active.Comment: 9 pages, 8 figures, 1 tabl
Extrasolar Planet Transits Observed at Kitt Peak National Observatory
We obtained J-, H- and JH-band photometry of known extrasolar planet
transiting systems at the 2.1-m Kitt Peak National Observatory Telescope using
the FLAMINGOS infrared camera between October 2008 and October 2011. From the
derived lightcurves we have extracted the mid-transit times, transit depths and
transit durations for these events. The precise mid-transit times obtained help
improve the orbital periods and also constrain transit-time variations of the
systems. For most cases the published system parameters successfully accounted
for our observed lightcurves, but in some instances we derive improved
planetary radii and orbital periods. We complemented our 2.1-m infrared
observations using CCD z'-band and B-band photometry (plus two Hydrogen Alpha
filter observations) obtained with the Kitt Peak Visitor's Center telescope,
and with four H-band transits observed in October 2007 with the NSO's 1.6-m
McMath-Pierce Solar Telescope. The principal highlights of our results are: 1)
our ensemble of J-band planetary radii agree with optical radii, with the
best-fit relation being: (Rp/R*)J = 0.0017 + 0.979 (Rp/R*)optical, 2) We
observe star spot crossings during the transit of WASP-11/HAT-P-10, 3) we
detect star spot crossings by HAT-P-11b (Kepler-3b), thus confirming that the
magnetic evolution of the stellar active regions can be monitored even after
the Kepler mission has ended, and 4) we confirm a grazing transit for
HAT-P-27/WASP-40. In total we present 57 individual transits of 32 known
exoplanet systems.Comment: 33 pages, 6 figures, accepted in Publications of the Astronomical
Society of the Pacifi
Signatures of Star-planet interactions
Planets interact with their host stars through gravity, radiation and
magnetic fields, and for those giant planets that orbit their stars within
10 stellar radii (0.1 AU for a sun-like star), star-planet
interactions (SPI) are observable with a wide variety of photometric,
spectroscopic and spectropolarimetric studies. At such close distances, the
planet orbits within the sub-alfv\'enic radius of the star in which the
transfer of energy and angular momentum between the two bodies is particularly
efficient. The magnetic interactions appear as enhanced stellar activity
modulated by the planet as it orbits the star rather than only by stellar
rotation. These SPI effects are informative for the study of the internal
dynamics and atmospheric evolution of exoplanets. The nature of magnetic SPI is
modeled to be strongly affected by both the stellar and planetary magnetic
fields, possibly influencing the magnetic activity of both, as well as
affecting the irradiation and even the migration of the planet and rotational
evolution of the star. As phase-resolved observational techniques are applied
to a large statistical sample of hot Jupiter systems, extensions to other
tightly orbiting stellar systems, such as smaller planets close to M dwarfs
become possible. In these systems, star-planet separations of tens of stellar
radii begin to coincide with the radiative habitable zone where planetary
magnetic fields are likely a necessary condition for surface habitability.Comment: Accepted for publication in the handbook of exoplanet
Innate immunity based cancer immunotherapy: B16-F10 murine melanoma model
Abstract
Background
Using killed microorganisms or their parts to stimulate immunity for cancer treatment dates back to the end of 19th century. Since then, it undergone considerable development. Our novel approach binds ligands to the tumor cell surface, which stimulates tumor phagocytosis. The therapeutic effect is further amplified by simultaneous application of agonists of Toll-like receptors. We searched for ligands that induce both a strong therapeutic effect and are safe for humans.
Methods
B16-F10 murine melanoma model was used. For the stimulation of phagocytosis, mannan or N-formyl-methionyl-leucyl-phenylalanine, was covalently bound to tumor cells or attached using hydrophobic anchor. The following agonists of Toll-like receptors were studied: monophosphoryl lipid A (MPLA), imiquimod (R-837), resiquimod (R-848), poly(I:C), and heat killed Listeria monocytogenes.
Results
R-848 proved to be the most suitable Toll-like receptor agonist for our novel immunotherapeutic approach. In combination with covalently bound mannan, R-848 significantly reduced tumor growth. Adding poly(I:C) and L. monocytogenes resulted in complete recovery in 83% of mice and in their protection from the re-transplantation of melanoma cells.
Conclusion
An efficient cancer treatment results from the combination of Toll-like receptor agonists and phagocytosis stimulating ligands bound to the tumor cells.http://deepblue.lib.umich.edu/bitstream/2027.42/134739/1/12885_2016_Article_2982.pd
Biomechanics of pelvic ring fixation techniques
This work is supported by the European Regional Development Fund-Project Application of Modern Technologies in Medicine and Industry (No. CZ.02.1.01/0.0/0.0/17 048/0007280) and by the project LO1506 of the Czech Ministry of Education, Youth and Sports under the program NPU I.The study focuses on development of computational tools for prediction and analysis of osteosynthesis of pelvic ring injuries. Fractures of pelvic bones may occur after high-energy impact events such as car accidents or sports injuries. For surgical treatment of unstable fractures either internal or external fixators can be applied in order to support the healing bone structures. In the following, a special attention is paid to minimally invasive internal fixation techniques for management of sacral bone injuries