2,091 research outputs found
Gas Absorption Detected from the Edge-on Debris Disk Surrounding HD32297
Near-infrared and optical imaging of HD32297 indicate that it has an edge-on
debris disk, similar to beta Pic. I present high resolution optical spectra of
the NaI doublet toward HD32297 and stars in close angular proximity. A
circumstellar absorption component is clearly observed toward HD32297 at the
stellar radial velocity, which is not observed toward any of its neighbors,
including the nearest only 0.9 arcmin away. An interstellar component is
detected in all stars >90 pc, including HD32297, likely due to the interstellar
material at the boundary of the Local Bubble. Radial velocity measurements of
the nearest neighbors, BD+07 777s and BD+07 778, indicate that they are
unlikely to be physically associated with HD32297. The measured circumstellar
column density around HD32997, log N(NaI) ~ 11.4, is the strongest NaI
absorption measured toward any nearby main sequence debris disk, even the
prototypical edge-on debris disk, beta Pic. Assuming that the morphology and
abundances of the gas component around HD32297 are similar to beta Pic, I
estimate an upper limit to the gas mass in the circumstellar disk surrounding
HD32297 of ~0.3 M_Earth.Comment: 13 pages, 2 figures; Accepted for publication in ApJ Letter
Les bifurcations du Sentier
Réaction à l'assassinat de deux jeunes coopérants français, cette note émet quelques hypothèses sur la stratégie actuelle du Sentier lumineux (Résumé d'auteur
The LHC string2 supervision system
This paper describes the implementation of the supervision system for the LHC Prototype Full-Cell also known as String 2. The supervision application is based on a commercial package targeted to industrial controls, but because of the complexity and the specifics of such a system, integration with custom components is necessary in order to merge the industrial requirements with the specificity of the accelerator controls
Cyclic and ruled Lagrangian surfaces in complex Euclidean space
We study those Lagrangian surfaces in complex Euclidean space which are
foliated by circles or by straight lines. The former, which we call cyclic,
come in three types, each one being described by means of, respectively, a
planar curve, a Legendrian curve of the 3-sphere or a Legendrian curve of the
anti de Sitter 3-space. We also describe ruled Lagrangian surfaces. Finally we
characterize those cyclic and ruled Lagrangian surfaces which are solutions to
the self-similar equation of the Mean Curvature Flow. Finally, we give a
partial result in the case of Hamiltonian stationary cyclic surfaces
All-optical control of ferromagnetic thin films and nanostructures
The interplay of light and magnetism has been a topic of interest since the
original observations of Faraday and Kerr where magnetic materials affect the
light polarization. While these effects have historically been exploited to use
light as a probe of magnetic materials there is increasing research on using
polarized light to alter or manipulate magnetism. For instance deterministic
magnetic switching without any applied magnetic fields using laser pulses of
the circular polarized light has been observed for specific ferrimagnetic
materials. Here we demonstrate, for the first time, optical control of
ferromagnetic materials ranging from magnetic thin films to multilayers and
even granular films being explored for ultra-high-density magnetic recording.
Our finding shows that optical control of magnetic materials is a much more
general phenomenon than previously assumed. These results challenge the current
theoretical understanding and will have a major impact on data memory and
storage industries via the integration of optical control of ferromagnetic
bits.Comment: 21 pages, 11 figure
Factorization of the soft gluon divergence from the dipole picture deep inelastic scattering cross sections at next-to-leading order
We use a factorization scheme analogous to one proposed for single inclusive forward hadron production to factorize the soft gluon divergence present in the deep inelastic scattering cross sections in the dipole picture at next-to-leading order (NLO). We show numerically that in this carefully constructed scheme it is possible to obtain meaningful results for the DIS cross sections at NLO, and so we are able to quantitatively study the recently derived NLO corrections to the DIS cross sections. We find that the NLO corrections can be significant and sensitive to the details of the factorization scheme used for the resummation of the large logarithms into the BK evolution equation. In the case of an approximative factorization scheme we observe a problematic behavior of the DIS cross sections similar to what has been seen with analogously factorized single inclusive cross sections.Peer reviewe
Matrix approach for modeling of emission from multilayer spin-polarized light-emitting diodes and lasers
Spin-polarized light sources such as the spin-polarized light-emitting diodes (spin-LEDs) and spin-polarized lasers (spin-lasers) are prospective devices in which the radiative recombination of spin-polarized carriers results in emission of circularly polarized photons. The main goal of this article is to model emitted radiation and its polarization properties from spin-LED and spin-controlled vertical-cavity surface-emitting laser (spin-VCSEL) solid-state structures. A novel approach based on 4 × 4 transfer matrix formalism is derived for modeling of the interaction of light with matter in active media of resonant multilayer anisotropic structure and enables magneto-optical effects. Quantum transitions, which result in photon emission, are described using general Jones source vectors.Web of Science166art. no. 06500
Influence of crosswise non-homogeneity of particulate flow on residence time distribution in a continuous mixer
Symposium on Powder Science and Technology - Powders and Sintered Material, Albi, FRANCE, MAY 23-25, 2007International audienceThe objective of the study is to develop a mathematical model of continuous mixing of granular materials, which takes into account the crosswise non-homogeneity of particulate flow inside a mixer. The target function of modeling is the residence time distribution of a tracer injected into the inflow. The model is built on the basis of the theory of Markov chains. The working space of a mixer is presented as a 2D array of perfectly mixed cells, through which the tracer travels according to the matrix of transition probabilities. The model covers the tendency of the tracer to upward/downward segregation. Finally, for a given flow pattern, the model allows calculating the RTD curves for various throughputs and for various properties of an imperfect tracer
Theoretical Study of Superposition of Macro- and Microscale Mixing and its Influence on Mixing Kinetics and Mixture Quality
4th RELPOWFLO Symposium 2008, Tromso, NORWAY, JUN 10-12, 2008International audienceThe objective of this study was to build a model that describes evolution of the state of a mixture where microscale mixing (penetration of particles into the closest neighborhood of its position during a small period of time) is accompanied by macroscale mixing (periodical exchange of large parts of the mixture inside a mixing volume after a certain period of time). The mixing kinetics for segregation and nonsegregation mixtures, agitated by blades placed in a certain sequence inside the mixing volume, was modeled. The case of exchange by the halves of material was examined as well. Two variants of the exchange were examined: the parallel displacement and the symmetric turn. It is shown that there exist optimal parameters of the macroscale transitions providing the highest rate of mixing. The proposed model helps to achieve better understanding of the process and suggests some ideas to improve the design of the mixers
- …