353 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
An evaluation of factors affecting show jumping warm-up on subsequent show jumping performance in 1.30m class
Timeflux: an open-source framework for the acquisition and near real-time processing of signal streams
International audienc
The prediction of the operating conditions on the permeate flux and on protein aggregation during membrane processing of monoclonal antibodies
The lack of available material during early stage bioprocess development poses numerous processing challenges such as limiting the number of full-scale experiments. Extended fundamental process understanding could be gained with the use of an ultra scale-down (USD) device using as little as 1.7âŻmL per experimental run. The USD system is used to predict diafiltration and ultrafiltration/diafiltration (UF/DF) performance of a pilot-scale tangential flow filtration (TFF) system, fitted with a flat-sheet cassette, operating at 500-fold larger scale. Both systems were designed by maintaining a volumetric loading of 8.1âŻL of feed per m2. Permeate flux was predicted for monoclonal antibody solutions with the USD system across a range of transmembrane pressure drops, feed concentrations and flow conditions during diafiltration, and desired retentate concentrations during UF/DF operations. The resulting USD data were in good agreement with the pilot-scale TFF when scaled based on similar shear rates over the membrane surface. Little change in soluble aggregates was observed in both systems but there were significantly higher increases in product turbidity in the USD system. A correlation was established to relate turbidity increase based on the volume fraction of high shear stress zone for USD systems and various pilot-scale TFF systems. The correlation was extended to encompass the processing time and concentration for a wide range of membrane processing challenges in both scales
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
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
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
Formation and interactions of cold and ultracold molecules: new challenges for interdisciplinary physics
Progress on researches in the field of molecules at cold and ultracold
temperatures is reported in this review. It covers extensively the experimental
methods to produce, detect and characterize cold and ultracold molecules
including association of ultracold atoms, deceleration by external fields and
kinematic cooling. Confinement of molecules in different kinds of traps is also
discussed. The basic theoretical issues related to the knowledge of the
molecular structure, the atom-molecule and molecule-molecule mutual
interactions, and to their possible manipulation and control with external
fields, are reviewed. A short discussion on the broad area of applications
completes the review.Comment: to appear in Reports on Progress in Physic
BRSMG Curinga: cultivar de arroz de terras altas de ampla adaptação para o Brasil.
O objetivo deste trabalho Ă© a apresentação das caracterĂsticas da BRSMG Curinga, a sĂ©tima cultivar de arroz de terras altas originĂĄria da colaboração da Embrapa com o programa CIAT/CIRAD, lançada em 2005 para cultivo em condiçÔes de terras altas nos Estados de Minas Gerais, GoiĂĄs, Mato Grosso, RondĂŽnia, ParĂĄ, Roraima, MaranhĂŁo, PiauĂ e Tocantins.bitstream/CNPAF/23577/1/comt_114.pd
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