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

Timeflux: an open-source framework for the acquisition and near real-time processing of signal streams

International audienc

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

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

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

Space-time coupling of shaped ultrafast ultraviolet pulses from an acousto-optic programmable dispersive filter

A comprehensive experimental analysis of spatio-temporal coupling effects inherent to the acousto-optic programmable dispersive filter (AOPDF) is presented. Phase and amplitude measurements of the AOPDF transfer function are performed using spatially and spectrally resolved interferometry. Spatio-temporal and spatio-spectral coupling effects are presented for a range of shaped pulses that are commonly used in quantum control experiments. These effects are shown to be attributable to a single mechanism: a group-delay--dependent displacement of the shaped pulse. The physical mechanism is explained and excellent quantitative agreement between the measured and calculated coupling speed is obtained. The implications for quantum control experiments are discussed.Comment: 8 pages, 6 figures; accepted for publication within JOSA

Associahedra via spines

An associahedron is a polytope whose vertices correspond to triangulations of a convex polygon and whose edges correspond to flips between them. Using labeled polygons, C. Hohlweg and C. Lange constructed various realizations of the associahedron with relevant properties related to the symmetric group and the classical permutahedron. We introduce the spine of a triangulation as its dual tree together with a labeling and an orientation. This notion extends the classical understanding of the associahedron via binary trees, introduces a new perspective on C. Hohlweg and C. Lange's construction closer to J.-L. Loday's original approach, and sheds light upon the combinatorial and geometric properties of the resulting realizations of the associahedron. It also leads to noteworthy proofs which shorten and simplify previous approaches.Comment: 27 pages, 11 figures. Version 5: minor correction