451 research outputs found
Laser-induced electron emission from a tungsten nanotip: identifying above threshold photoemission using energy-resolved laser power dependencies
We present an experiment studying the interaction of a strongly focused 25 fs
laser pulse with a tungsten nanotip, investigating the different regimes of
laser-induced electron emission. We study the dependence of the electron yield
with respect to the static electric field applied to the tip. Photoelectron
spectra are recorded using a retarding field spectrometer and peaks separated
by the photon energy are observed with a 45 % contrast. They are a clear
signature of above threshold photoemission (ATP), and are confirmed by
extensive spectrally resolved studies of the laser power dependence.
Understanding these mechanisms opens the route to control experiment in the
strong-field regime on nanoscale objects.Comment: 9 pages, 6 figure
Experimental Tool of woven Reinforcement Forming
International audienceThis paper concerns the development of an experimental device which is able to form very complex double curved geometry. Objectives are to analyze the evolution of the woven preform during the forming process. This device contains one mechanical module containing the classical tools in forming process, (punch, blank holder, and open-die), and one optical module to measure the 3D-deformed shape and the distribution of local deformations, like shear angles of the woven reinforcement during all the process. Experimental results are obtained with an interlock carbon woven fabric, used in aeronautical applications. Wrinkling and buckling will be analyzed at the global scale of the piece. The evolution of the shear angle will be presented at local scale (on face, or edges of the geometry)
Factorization of Numbers with the temporal Talbot effect: Optical implementation by a sequence of shaped ultrashort pulses
We report on the successful operation of an analogue computer designed to
factor numbers. Our device relies solely on the interference of classical light
and brings together the field of ultrashort laser pulses with number theory.
Indeed, the frequency component of the electric field corresponding to a
sequence of appropriately shaped femtosecond pulses is determined by a Gauss
sum which allows us to find the factors of a number
The Non--Ergodicity Threshold: Time Scale for Magnetic Reversal
We prove the existence of a non-ergodicity threshold for an anisotropic
classical Heisenberg model with all-to-all couplings. Below the threshold, the
energy surface is disconnected in two components with positive and negative
magnetizations respectively. Above, in a fully chaotic regime, magnetization
changes sign in a stochastic way and its behavior can be fully characterized by
an average magnetization reversal time. We show that statistical mechanics
predicts a phase--transition at an energy higher than the non-ergodicity
threshold. We assess the dynamical relevance of the latter for finite systems
through numerical simulations and analytical calculations. In particular, the
time scale for magnetic reversal diverges as a power law at the ergodicity
threshold with a size-dependent exponent, which could be a signature of the
phenomenon.Comment: 4 pages 4 figure
One-step facial feminization surgery: The importance of a custom-made preoperative planning and patient satisfaction assessment
Background: The availability of more accurate techniques used for transgender surgery has resulted in an increased number of patients requesting facial feminization surgery (FFS). The aim of this study was to present the FFS pre-operative planning of the authors’ male-to-female transsexual patients using photo-editing software, computer-aided design (CAD), modeling, and three-dimensional (3D) printing. Material and Methods: Twenty-five patients underwent FFS between November 2015 and May 2018. They were retrospectively included in this study, and their records were analyzed. Patients’ 3D facial models were printed and used for an accurate preoperative planning and shown to the patients. To assess patient satisfaction, the preoperative, six-month, and one-year postoperative scores obtained using Satisfaction With Life Scale (SWLS) and Subjective Happiness Scale (SHS) were compared. The scores following a normal distribution obtained for each patient were compared using a paired t-test. Results: The 3D model preparation mean time was 145±13.2 min. A total of 114 surgical procedures were carried out. The mean operative time was 420±23 min. Patients experienced no postoperative complication. All patients were very satisfied after surgery, with a significant difference between pre- and postoperative scores (p = 0.002; p = 0.03). Conclusion: With use of 3D modeling, surgeons are nearing a custom-made surgery era, especially required for complex procedures such as FFS. We suggest using 3D technology for a more accurate preoperative planning
Unbiasing the density of TTV-characterised sub-Neptunes: Update of the mass-radius relationship of 34 Kepler planets
Transit Timing Variations (TTVs) can provide useful information on compact
multi-planetary systems observed by transits, by putting constraints on the
masses and eccentricities of the observed planets. This is especially helpful
when the host star is not bright enough for radial velocity follow-up. However,
in the past decades, numerous works have shown that TTV-characterised planets
tend to have a lower densities than RV-characterised planets. Re-analysing 34
Kepler planets in the super-Earth to sub-Neptunes range using the RIVERS
approach, we show that at least part of these discrepancies was due to the way
transit timings were extracted from the light curve, which had a tendency to
under-estimate the TTV amplitudes. We recover robust mass estimates (i.e. low
prior dependency) for 23 of the planets. We compare these planets the
RV-characterised population. A large fraction of these previously had a
surprisingly low density now occupy a place of the mass-radius diagram much
closer to the bulk of the known planets, although a slight shift toward lower
densities remains, which could indicate that the compact multi-planetary
systems characterised by TTVs are indeed composed of planets which are
different from the bulk of the RV-characterised population. These results are
especially important for obtaining an unbiased view of the compact
multi-planetary systems detected by Kepler, TESS, and the upcoming PLATO
mission
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