304 research outputs found
Classical nonintegrability of a quantum chaotic SU(3) Hamiltonian system
We prove nonintegrability of a model Hamiltonian system defined on the Lie
algebra suitable for investigation of connections between
classical and quantum characteristics of chaos.Comment: 17 page
Analysis of new high-precision transit light curves of WASP-10 b: starspot occultations, small planetary radius, and high metallicity
The WASP-10 planetary system is intriguing because different values of radius
have been reported for its transiting exoplanet. The host star exhibits
activity in terms of photometric variability, which is caused by the rotational
modulation of the spots. Moreover, a periodic modulation has been discovered in
transit timing of WASP-10 b, which could be a sign of an additional body
perturbing the orbital motion of the transiting planet. We attempt to refine
the physical parameters of the system, in particular the planetary radius,
which is crucial for studying the internal structure of the transiting planet.
We also determine new mid-transit times to confirm or refute observed anomalies
in transit timing. We acquired high-precision light curves for four transits of
WASP-10 b in 2010. Assuming various limb-darkening laws, we generated best-fit
models and redetermined parameters of the system. The prayer-bead method and
Monte Carlo simulations were used to derive error estimates. Three transit
light curves exhibit signatures of the occultations of dark spots by the planet
during its passage across the stellar disk. The influence of stellar activity
on transit depth is taken into account while determining system parameters. The
radius of WASP-10 b is found to be no greater than 1.03 Jupiter radii, a value
significantly smaller than most previous studies indicate. We calculate
interior structure models of the planet, assuming a two-layer structure with
one homogeneous envelope atop a rock core. The high value of the WASP-10 b's
mean density allows one to consider the planet's internal structure including
270 to 450 Earth masses of heavy elements. Our new mid-transit times confirm
that transit timing cannot be explained by a constant period if all literature
data points are considered. They are consistent with the ephemeris assuming a
periodic variation of transit timing...Comment: Accepted for publication in A&
Phantom cosmology as a scattering process
We study the general chaotic features of dynamics of the phantom field
modelled in terms of a single scalar field conformally coupled to gravity. We
demonstrate that the dynamics of the FRW model with dark energy in the form of
phantom field can be regarded as a scattering process of two types: multiple
chaotic and classical non-chaotic. It depends whether the spontaneously
symmetry breaking takes place. In the first class of models with the
spontaneously symmetry breaking the dynamics is similar to the Yang-Mills
theory. We find the evidence of a fractal structure in the phase space of
initial conditions. We observe similarities to the phenomenon of a multiple
scattering process around the origin. In turn the class of models without the
spontaneously symmetry breaking can be described as the classical non-chaotic
scattering process and the methods of symbolic dynamic are also used in this
case. We show that the phantom cosmology can be treated as a simple model with
scattering of trajectories which character depends crucially on a sign of a
square of mass. We demonstrate that there is a possibility of chaotic behavior
in the flat Universe with a conformally coupled phantom field in the system
considered on non-zero energy level. We obtain that the acceleration is a
generic feature in the considered model without the spontaneously symmetry
breaking. We observe that the effective EOS coefficient oscillates and then
approach to .Comment: RevTeX4, 19 pages, 17 figures; v2 - added a comment on the Yang-Mills
cosmological models and bibliography; v3 - added a section on acceleration, 2
figures, some references
Recommended from our members
Remote measurements of volcanic gases : applications of open-path Fourier transform infra-red spectroscopy (OP-FTIR) and Correlation spectroscopy (COSPEC)
The composition of volcanic gas plumes depends largely on the chemistry of the degassing magma, the depth of volatile exsolution, and the level of volcanic activity. The ratios between the most common volcanic gases: CO2, H2O, SO2, HCl and HF, as measured at the surface, can be used to provide information on the evolution of the magma body. My research on volcanic gases has centred on the use of open-path Fourier transform IR spectroscopy (Op_FTIR) and correlation spectroscopy (COSPEC). I have also used data collected using other direct and remote-sensing techniques.
Remote-sensing techniques rely on the characteristic IR or UV absorbances of natural and/or artificial radiation by different gases. The longer range of these techniques enables the analysis of gases in inaccessible plumes; thus reducing the need for operators to enter hazardous areas. As the instruments do not interact with the analysed gases there is no contamination, condensation or secondary reactions. However, the instruments tend to be heavy, expensive, and complex. Environmental factors can complicate analyses; clouds can dissolve and remove analyte rapidly, and variations in wind speed can result in gas fluxes having high errors. It is also much more difficult to analyse specific gas sources remotely as mixing of gases from different sources can occur.
Direct-sampling techniques rely on gases being trapped, dissolved or adsorbed before being analysed by traditional methods, e. g. wet-chemistry, colourimetry, and gas chromatography. The capture of gases is best achieved as close to the source as possible, thus increasing the risk to the operator, and may only be possible during periods of low activity. The physical interaction of gases with instrument and collection vessels can lead to contamination and initiation of secondary reactions. Direct-sampling techniques are labour intensive and thus are capable of only generating a relatively small amount of data compared to the more automated remote-sensing techniques. The suitability of an individual technique therefore depends greatly on: the type of gas to be measured; the location of vent or fumamle; the level of volcanic activity; and the environment in which data are collected.
I used OP-FTIR on La Fossa di Vulcano to measure the SO2: HCL mass ratios of gases emitted from the rim and central crater fumaroles, -4.3 - 6.1 and 0.9 - 2.6 respectively. I attributed the higher crater rim gas ratios to the interaction of the gases with shallow hydrothermal reservoirs, causing scrubbing of the more soluble HCl- At Mt. Etna, my OP-FTIR analysis of gases emitted from the central craters showed that, in 1994, SO2: HCl mass ratios were ~4.9 - 5.8. These values lie between those reported for eruptive degassing, >10, and background degassing, 2 fluxes for the 1991 - 1993 Etna eruption showed that variations were generally synchronous; small scale differences relating to the drainage of degassed magma from beneath the summit craters into the eruptive fissure. I also conducted OP-FTIR and COSPEC analyses on Montserrat in June 1996 to show the gas plume to be relatively SO2 poor, with SO2: HCl mass ratios of 4 in volcanic plumes to be made. I have also used HF-SiF4 ratios to estimate gas equilibrium temperatures at La Fossa and Mt. Etna to be ~200°C and ~250 - 290°C respectively.
I have also investigated the structural evolution of the Masaya Volcanic Complex. The visible complex has formed over ~1000 years; with average rates of effusion of -0.2 x 106 m3/y, much lower than those required to provide the estimated volume of caldera infill, -2 x 106 m3/y. Historic activity has centred on the twin massifs of Volcán Masaya and Volcán Santiago and is dominated by pit-crater collapses. I propose that the degassing episodes, which occur with no increase in eruptive activity, are related to the convective overturn of magma beneath the craters
Towards the Rosetta Stone of planet formation
Transiting exoplanets (TEPs) observed just about 10 Myrs after formation of
their host systems may serve as the Rosetta Stone for planet formation
theories. They would give strong constraints on several aspects of planet
formation, e.g. time-scales (planet formation would then be possible within 10
Myrs), the radius of the planet could indicate whether planets form by
gravitational collapse (being larger when young) or accretion growth (being
smaller when young). We present a survey, the main goal of which is to find and
then characterise TEPs in very young open clusters.Comment: Poster contribution to Detection and Dynamics of Transiting
Exoplanets (Haute Provence Observatory Colloquium, 23-27 August 2010
False-positive radioiodine whole-body scan due to a renal cyst
Patients affected by differentiated thyroid cancer are treated surgically and by ablative radioiodine therapy. A post-therapy whole-body scan allows detection of thyroid remnants or local and distant metastases, although false-positive findings may be observed. We report a case of a 75-year-old woman with follicular thyroid cancer, who underwent ablative radioiodine treatment. On post-therapy wholebody scan, abnormal uptake in the left upper abdomen was found, although stimulated thyroglobulin level was not suggestive for distant metastases of differentiated thyroid carcinoma. Additional SPECT/CT acquisition revealed focal 131I uptake located at the posterolateral wall of the left kidney corresponding to a round lesion 47 mm in maximal diameter. In order to verify this finding abdominal ultrasound and abdominal contrast-enhanced CT were performed, confirming multiple renal cysts in the left kidney; the largest one was the site of abnormal radioiodine accumulation. Despite the high incidence of renal cysts, especially in the elderly, radioiodine uptake in renal cystsis extremely rare. Different hypotheses on the mechanism of radioiodine uptake in the cyst were proposed, among them active secretion by sodium-iodide symporter or other transporting proteins. We conclude that abnormal radioiodine uptake in renal cysts can be an exceptional finding mimicking a metastasis
A Possible Detection of Occultation by a Proto-planetary Clump in GM Cephei
GM Cep in the young (~4 Myr) open cluster Trumpler 37 has been known to be an
abrupt variable and to have a circumstellar disk with very active accretion.
Our monitoring observations in 2009-2011 revealed the star to show sporadic
flare events, each with brightening of < 0.5 mag lasting for days. These
brightening events, associated with a color change toward the blue, should
originate from an increased accretion activity. Moreover, the star also
underwent a brightness drop of ~1 mag lasting for about a month, during which
the star became bluer when fainter. Such brightness drops seem to have a
recurrence time scale of a year, as evidenced in our data and the photometric
behavior of GM Cep over a century. Between consecutive drops, the star
brightened gradually by about 1 mag and became blue at peak luminosity. We
propose that the drop is caused by obscuration of the central star by an
orbiting dust concentration. The UX Orionis type of activity in GM Cep
therefore exemplifies the disk inhomogeneity process in transition between
grain coagulation and planetesimal formation in a young circumstellar disk.Comment: In submission to the Astrophysical Journal, 4 figure
Does the type of a centre in which the resection of extensive tumours of the limbs and truck is performed, affect the patients’ survival?
Nowoczesna chirurgia rekonstrukcyjna opiera się na odpowiednim wykorzystaniu dostępnych metod rekonstrukcyjnych, w tym mikronaczyniowych. Zaplanowanie odpowiedniej operacji rekonstrukcyjnej daje możliwość wykonania maksymalnie szerokiej resekcji, co dodatkowo zwiększa radykalność zabiegu.
Ostatnimi czasy zaznacza się tendencja do wykonywania rozległych resekcji nowotworów w ośrodkach nie dysponujących bogatym doświadczeniem w tego rodzaju procedurach. Istnieje obawa, że, z uwagi na brak możliwości wykonania jednoczasowej rekonstrukcji, zakres resekcji może być niewystarczający do uzyskania pełnej radykalności zabiegu.
W oparciu o wyniki badań 71 chorych leczonych w Klinice Chirurgii Onkologicznej i Rekonstrukcyjnej w latach 2006 – 2017 z powodu rozległych zmian nowotworowych tułowia i kończyn wykazano, że chorzy leczeni pierwotnie (zabieg resekcyjny) poza Instytutem charakteryzowali się znacząco krótszym czasem przeżycia do wznowy.
Powyższe wyniki stanowią głos potwierdzający zasadność przeprowadzania rozległych zabiegów resekcyjno – rekonstrukcyjnych w przypadku zaawansowanych zmian nowotworowych, w ośrodkach o bogatym doświadczeniu w tym zakresie
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