912 research outputs found
Utilisation du grand épiploon dans la chirurgie reconstructrice du cancer du sein localement avancé ou récidivant.
Problématique : En Suisse, près de 5300 nouveaux cas de cancer du sein chez la femme et 30 à 40 chez l'homme sont diagnostiqués chaque année. Une femme sur huit sera touchée par la maladie au cours de sa vie (1-2). Malgré l'avancée de la médecine dans le traitement de cette maladie, il arrive encore que des situations dramatiques se présentent suite à une tumeur localement avancée ou récidivante. Une plaie chronique douloureuse et nécrotique parfois surinfectée ne répondant pas aux traitements de chimio- et de radiothérapie nécessite alors d'effectuer une résection large de la zone atteinte afin d'améliorer la qualité de vie de ces patients. Cette opération entraîne un vaste défect de la paroi thoracique antérieure qui demande une chirurgie de couverture complexe. Le lambeau épiploïque proposé par Kiricuta en 1963 est encore utilisé de nos jours pour ce genre d'intervention (3). L'évolution des techniques chirurgicales fait que nous disposons actuellement d'autres lambeaux myocutanés performants pour de telles situations oncologiques. Ce travail s'intéresse à l'évaluation de l'épiplooplastie proposée il y a maintenant près de 50 ans, afin de s'interroger sur la place qu'elle occupe aujourd'hui parmi ces autres techniques.
Objectifs : Comprendre la technique du lambeau de Kiricuta et évaluer sa place parmi les techniques de reconstruction dans la chirurgie du cancer du sein localement avancé ou récidivant.
Méthodes : Une revue de la littérature des articles s'intéressant au lambeau de Kiricuta depuis 1963 a permis d'évaluer ses qualités et ses inconvénients. Cette technique a été illustrée par l'analyse rétrospective des dossiers de 4 patients ayant bénéficié d'une reconstruction à partir du grand épiploon au CHUV suite à un cancer du sein récidivant ou localement avancé. La présentation des autres techniques de reconstructions de la paroi thoracique antérieure s'est également basée sur la récolte d'articles d'études comparant ces différentes opérations.
Résultats: Le grand épiploon est un organe doté de capacités étonnantes, immunologiques et angiogéniques. Sa taille souvent généreuse convient à de grands défects de la paroi thoracique, particulièrement lors d'atteinte bilatérale ou de la région axillaire. Son utilisation ne convient toutefois pas lors d'exérèse de plus de 3 côtes par manque de stabilité de la cage thoracique. Apprécié en milieu infecté et/ou radique, il convient aux situations où les lambeaux myocutanés sont inadéquats. En effet, comme sa taille n'est pas prédictible et que l'opération demande souvent une laparotomie, cette technique est envisagée en seconde intention ou suivant des situations particulières.
Conclusion : L'amélioration des symptômes locaux lors de cancer du sein localement avancé ou récidivant a pu être obtenue en excisant la lésion et en la recouvrant par le lambeau de Kiricuta. Le bénéfice sur la qualité de vie ainsi apporté à ces patients fait de l'épiplooplastie un choix à considérer dans le traitement chirurgical du cancer du sein
Temporal relation between quiet-Sun transverse fields and the strong flows detected by IMaX/SUNRISE
Localized strongly Doppler-shifted Stokes V signals were detected by
IMaX/SUNRISE. These signals are related to newly emerged magnetic loops that
are observed as linear polarization features. We aim to set constraints on the
physical nature and causes of these highly Doppler-shifted signals. In
particular, the temporal relation between the appearance of transverse fields
and the strong Doppler shifts is analyzed in some detail. We calculated the
time difference between the appearance of the strong flows and the linear
polarization. We also obtained the distances from the center of various
features to the nearest neutral lines and whether they overlap or not. These
distances were compared with those obtained from randomly distributed points on
observed magnetograms. Various cases of strong flows are described in some
detail. The linear polarization signals precede the appearance of the strong
flows by on average 84+-11 seconds. The strongly Doppler-shifted signals are
closer (0.19") to magnetic neutral lines than randomly distributed points
(0.5"). Eighty percent of the strongly Doppler-shifted signals are close to a
neutral line that is located between the emerging field and pre-existing
fields. That the remaining 20% do not show a close-by pre-existing field could
be explained by a lack of sensitivity or an unfavorable geometry of the
pre-existing field, for instance, a canopy-like structure. Transverse fields
occurred before the observation of the strong Doppler shifts. The process is
most naturally explained as the emergence of a granular-scale loop that first
gives rise to the linear polarization signals, interacts with pre-existing
fields (generating new neutral line configurations), and produces the observed
strong flows. This explanation is indicative of frequent small-scale
reconnection events in the quiet Sun.Comment: 11 pages, 8 figure
A note on the Landauer principle in quantum statistical mechanics
The Landauer principle asserts that the energy cost of erasure of one bit of
information by the action of a thermal reservoir in equilibrium at temperature
T is never less than . We discuss Landauer's principle for quantum
statistical models describing a finite level quantum system S coupled to an
infinitely extended thermal reservoir R. Using Araki's perturbation theory of
KMS states and the Avron-Elgart adiabatic theorem we prove, under a natural
ergodicity assumption on the joint system S+R, that Landauer's bound saturates
for adiabatically switched interactions. The recent work of Reeb and Wolf on
the subject is discussed and compared
Properties of sunspots in cycle 23: I. Dependence of brightness on sunspot size and cycle phase
In this paper we investigate the dependence of umbral core brightness, as
well as the mean umbral and penumbral brightness on the phase of the solar
cycle and on the size of the sunspot. Albregtsen & Maltby (1978) reported an
increase in umbral core brightness from the early to the late phase of solar
cycle from the analysis of 13 sunspots which cover solar cycles 20 and 21. Here
we revisit this topic by analysing continuum images of more than 160 sunspots
observed by the MDI instrument on board the SOHO spacecraft for the period
between 1998 March to 2004 March, i.e. a sizable part of solar cycle 23. The
advantage of this data set is its homogeneity, with no seeing fluctuations. A
careful stray light correction, which is validated using the Mercury transit of
7th May, 2003, is carried out before the umbral and penumbral intensities are
determined. The influence of the Zeeman splitting of the nearby NiI spectral
line on the measured 'continuum' intensity is also taken into account. We did
not observe any significant variation in umbral core, mean umbral and mean
penumbral intensities with solar cycle, which is in contrast to earlier
findings for the umbral core intensity. We do find a strong and clear
dependence of the umbral brightness on sunspot size, however. The penumbral
brightness also displays a weak dependence. The brightness-radius relationship
has numerous implications, some of which, such as those for the energy
transport in umbrae, are pointed out.Comment: 16 pages, 21 postscript figures, accepted for publication in A&
Structure of even-even nuclei using a mapped collective Hamiltonian and the D1S Gogny interaction
A systematic study of low energy nuclear structure at normal deformation is
carried out using the Hartree-Fock-Bogoliubov theory extended by the Generator
Coordinate Method and mapped onto a 5-dimensional collective quadrupole
Hamiltonian. Results obtained with the Gogny D1S interaction are presented from
dripline to dripline for even-even nuclei with proton numbers Z=10 to Z=110 and
neutron numbers N less than 200. The properties calculated for the ground
states are their charge radii, 2-particle separation energies, correlation
energies, and the intrinsic quadrupole shape parameters. For the excited
spectroscopy, the observables calculated are the excitation energies and
quadrupole as well as monopole transition matrix elements. We examine in this
work the yrast levels up to J=6, the lowest excited 0^+ states, and the two
next yrare 2^+ states. The theory is applicable to more than 90% of the nuclei
which have tabulated measurements. The data set of the calculated properties of
1712 even-even nuclei, including spectroscopic properties for 1693 of them, are
provided in CEA website and EPAPS repository with this article \cite{epaps}.Comment: 51 pages with 26 Figures and 4 internal tables; this version is
accepted by Physical Review
Comparison of solar photospheric bright points between SUNRISE observations and MHD simulations
Bright points (BPs) in the solar photosphere are radiative signatures of
magnetic elements described by slender flux tubes located in the darker
intergranular lanes. They contribute to the ultraviolet (UV) flux variations
over the solar cycle and hence may influence the Earth's climate. Here we
combine high-resolution UV and spectro-polarimetric observations of BPs by the
SUNRISE observatory with 3D radiation MHD simulations. Full spectral line
syntheses are performed with the MHD data and a careful degradation is applied
to take into account all relevant instrumental effects of the observations. It
is demonstrated that the MHD simulations reproduce the measured distributions
of intensity at multiple wavelengths, line-of-sight velocity, spectral line
width, and polarization degree rather well. Furthermore, the properties of
observed BPs are compared with synthetic ones. These match also relatively
well, except that the observations display a tail of large and strongly
polarized BPs not found in the simulations. The higher spatial resolution of
the simulations has a significant effect, leading to smaller and more numerous
BPs. The observation that most BPs are weakly polarized is explained mainly by
the spatial degradation, the stray light contamination, and the temperature
sensitivity of the Fe I line at 5250.2 \AA{}. The Stokes asymmetries of the
BPs increase with the distance to their center in both observations and
simulations, consistent with the classical picture of a production of the
asymmetry in the canopy. This is the first time that this has been found also
in the internetwork. Almost vertical kilo-Gauss fields are found for 98 % of
the synthetic BPs. At the continuum formation height, the simulated BPs are on
average 190 K hotter than the mean quiet Sun, their mean BP field strength is
1750 G, supporting the flux-tube paradigm to describe BPs.Comment: Accepted for publication in Astronomy & Astrophysics on May 30 201
Full counting statistics and phase diagram of a dissipative Rydberg gas
Ultra-cold gases excited to strongly interacting Rydberg states are a
promising system for quantum simulations of many-body systems. For off-resonant
excitation of such systems in the dissipative regime, highly correlated
many-body states exhibiting, among other characteristics, intermittency and
multi-modal counting distributions are expected to be created. So far,
experiments with Rydberg atoms have been carried out in the resonant,
non-dissipative regime. Here we realize a dissipative gas of rubidium Rydberg
atoms and measure its full counting statistics for both resonant and
off-resonant excitation. We find strongly bimodal counting distributions in the
off-resonant regime that are compatible with intermittency due to the
coexistence of dynamical phases. Moreover, we measure the phase diagram of the
system and find good agreement with recent theoretical predictions. Our results
pave the way towards detailed studies of many-body effects in Rydberg gases.Comment: 12 pages, 5 figure
Dynamics of multi-cored magnetic structures in the quiet Sun
We report on the dynamical interaction of quiet-Sun magnetic fields and
granular convection in the solar photosphere as seen by \textsc{Sunrise}. We
use high spatial resolution (0\farcs 15--0\farcs 18) and temporal cadence (33
s) spectropolarimetric Imaging Magnetograph eXperiment data, together with
simultaneous CN and Ca\,\textsc{ii}\,H filtergrams from \textsc{Sunrise} Filter
Imager. We apply the SIR inversion code to the polarimetric data in order to
infer the line of sight velocity and vector magnetic field in the photosphere.
The analysis reveals bundles of individual flux tubes evolving as a single
entity during the entire 23 minute data set. The group shares a common canopy
in the upper photospheric layers, while the individual tubes continually
intensify, fragment and merge in the same way that chains of bright points in
photometric observations have been reported to do. The evolution of the tube
cores are driven by the local granular convection flows. They intensify when
they are "compressed" by surrounding granules and split when they are
"squeezed" between two moving granules. The resulting fragments are usually
later regrouped in intergranular lanes by the granular flows. The continual
intensification, fragmentation and coalescence of flux results in magnetic
field oscillations of the global entity. From the observations we conclude that
the magnetic field oscillations first reported by \citet{2011ApJ...730L..37M}
correspond to the forcing by granular motions and not to characteristic
oscillatory modes of thin flux tubes.Comment: 12 pages, 7 figures. Accepted in ApJ. Animation 1 can be downloaded
from: http://spg.iaa.es/download
Convective motions and net circular polarization in sunspot penumbrae
We have employed a penumbral model, that includes the Evershed flow and
convective motions inside penumbral filaments, to reproduce the azimuthal
variation of the net circular polarization (NCP) in sunspot penumbrae at
different heliocentric angles for two different spectral lines. The theoretical
net circular polarization fits the observations as satisfactorily as penumbral
models based on flux-tubes. The reason for this is that the effect of
convective motions on the NCP is very small compared to the effect of the
Evershed flow. In addition, the NCP generated by convective upflows cancels out
the NCP generated by the downflows. We have also found that, in order to fit
the observed NCP, the strength of the magnetic field inside penumbral filaments
must be very close to 1000 G. In particular, field-free or weak-field filaments
fail to reproduce both the correct sign of the net circular polarization, as
well as its dependence on the azimuthal and heliocentric angles.Comment: Accepted for publication in the Astrophysical Journal. 10 pages, 7
figures (3 in color). Uses emulatedap
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