Search results for "25"
showing 10 items of 3263 documents
On List Coloring with Separation of the Complete Graph and Set System Intersections
2022
We consider the following list coloring with separation problem: Given a graph $G$ and integers $a,b$, find the largest integer $c$ such that for any list assignment $L$ of $G$ with $|L(v)|= a$ for any vertex $v$ and $|L(u)\cap L(v)|\le c$ for any edge $uv$ of $G$, there exists an assignment $\varphi$ of sets of integers to the vertices of $G$ such that $\varphi(u)\subset L(u)$ and $|\varphi(v)|=b$ for any vertex $u$ and $\varphi(u)\cap \varphi(v)=\emptyset$ for any edge $uv$. Such a value of $c$ is called the separation number of $(G,a,b)$. Using a special partition of a set of lists for which we obtain an improved version of Poincar\'e's crible, we determine the separation number of the c…
Statistics of transitions for Markov chains with periodic forcing
2013
The influence of a time-periodic forcing on stochastic processes can essentially be emphasized in the large time behaviour of their paths. The statistics of transition in a simple Markov chain model permits to quantify this influence. In particular the first Floquet multiplier of the associated generating function can be explicitly computed and related to the equilibrium probability measure of an associated process in higher dimension. An application to the stochastic resonance is presented.
"Safe" Coulomb excitation of 30Mg.
2004
We report on the first radioactive beam experiment performed at the recently commissioned REX-ISOLDE facility at CERN in conjunction with the highly efficient $\gamma$ -spectrometer MINIBALL. Using $^{30}$Mg ions accelerated to an energy of 2.25MeV/u together with a thin $^{nat}$Ni target, Coulomb excitation of the first excited 2+ states of the projectile and target nuclei well below the Coulomb barrier was observed. From the measured relative de-excitation $\gamma$ -ray yields the B(E2; 0$^{+}_{gs} \rightarrow 2^{+}_{1}$) value of $^{30}$Mg was determined to be 241(31)$e^{2}$fm$^{4}$. Our result is lower than values obtained at projectile fragmenttion facilities using the intermediate-ene…
Prospects for advanced electron cyclotron resonance and electron beam ion source charge breeding methods for EURISOL
2011
International audience; As the most ambitious concept of isotope separation on line (ISOL) facility, EURISOL aims at producing unprecedented intensities of post-accelerated radioactive isotopes. Charge breeding, which transforms the charge state of radioactive beams from 1+ to an n+ charge state prior to postacceleration, is a key technology which has to overcome the following challenges: high charge states for high energies, efficiency, rapidity and purity. On the roadmap to EURISOL, a dedicated R&D is being undertaken to push forward the frontiers of the present state-of-the-art techniques which use either electron cyclotron resonance or electron beam ion sources. We describe here the gui…
High-order Kerr nonlinearity of air calibrated with transient molecular alignment
2009
Talk given by O. Faucher; International audience; Nonlinear electronic Kerr index of the major air constituents has been measured up to high order terms using transient molecular alignment as a reference. Sign reversal associated to negative nonlinearity is observed above a pulse intensity of 26 TW/cm^2.
Near-field observation of subwavelength confinement of photoluminescence by a photonic crystal microcavity
2006
We present a direct, room-temperature near-field optical study of light confinement by a subwavelength defect microcavity in a photonic crystal slab containing quantum-well sources. The observations are compared with three-dimensional finite-difference time-domain calculations, and excellent agreement is found. Moreover, we use a subwavelength cavity to study the influence of a near-field probe on the imaging of localized optical modes. © 2006 Optical Society of America.
Radiation-induced defects in fluorine-doped silica-based optical fibers: Influence of a pre-loading with H2
2009
International audience; We investigated the effects of 10-keV X-ray radiation on the transmission properties of F-doped optical fibers in the 200–850 nm range of wavelengths (1.5–6 eV). We also studied the influence of pre-loading this kind of fibers with hydrogen on its radiation sensitivity. Our results showed that, for our experimental conditions (pre-treatment with H2 several months before irradiation with diffusion of all the H2 out the fiber core and cladding before X-ray exposure), this pre-treatment increases the radiation-induced attenuation in the ultraviolet part (200–300 nm) of the spectrum. A previous H2-loading has no influence at greater wavelengths. The nature of the radiati…
Decay and Fission Hindrance of Two- and Four-Quasiparticle K Isomers in 254Rf
2015
International audience; Two isomers decaying by electromagnetic transitions with half-lives of 4.7(1.1) and 247(73) mu s have been discovered in the heavy (254)Rf nucleus. The observation of the shorter-lived isomer was made possible by a novel application of a digital data acquisition system. The isomers were interpreted as the K-pi = 8(-), nu(2)(7/2(+)[624]; 9/2(-)[734]) two-quasineutron and the K-pi = 16(+), 8(-)nu(2)(7/2(+)[624]; 9/2(-)[734] circle times 8(-)pi(2) (7/2(-)[514]; 9/2(+)[624]) four-quasiparticle configurations, respectively. Surprisingly, the lifetime of the two-quasiparticle isomer is more than 4 orders of magnitude shorter than what has been observed for analogous isomer…
Multifunctionality: refocusing a spreading, loose and fashionable concept for looking at sustainability?
2008
International audience; The notion of agriculture's Multifunctionality (MF) emerged in the 1980s. It then followed two trajectories since the 1990s: a conflicting period linked to its use in the international trade negotiations on the one hand, a spreading in terms of meaning, use and geographically on the other hand. Specific meanings appeared in connection with policy making, at national or international levels, or through the involvement of new disciplines. Yet, very few authors discuss the implication of the chosen meaning on their findings. To explore and take advantage of using this word and to deliver it from its controversial use in international trade negotiations, it is absolutely…
Nodulating symbiotic bacteria and soil quality
2005
Chapitre 9 : Plant microbe interactions and soil quality Partie : 9-2; International audience