110 research outputs found
The Darrieus-Landau instability in fast deflagration and laser ablation
The problem of the Darrieus-Landau instability at a discontinuous
deflagration front in a compressible flow is solved. Numerous previous attempts
to solve this problem suffered from the deficit of boundary conditions. Here,
the required additional boundary condition is derived rigorously taking into
account the internal structure of the front. The derived condition implies a
constant mass flux at the front; it reduces to the classical Darrieus-Landau
condition in the limit of an incompressible flow. It is demonstrated that in
general the solution to the problem depends on the type of energy source
present in the system. In the common case of a strongly localized source,
compression effects make the Darrieus-Landau instability considerably weaker.
In particular, the Darrieus-Landau instability growth rate is reduced for laser
ablation in comparison with the classical incompressible case. The instability
disappears completely in the Chapman-Jouguet regime of ultimately fast
deflagration.Comment: 24 pages, 3 figures, version to appear in Physics of Plasma
Potential model of a 2D Bunsen flame
The Michelson Sivashinsky equation, which models the non linear dynamics of
premixed flames, has been recently extended to describe oblique flames. This
approach was extremely successful to describe the behavior on one side of the
flame, but some qualitative effects involving the interaction of both sides of
the front were left unexplained. We use here a potential flow model, first
introduced by Frankel, to study numerically this configuration. Furthermore,
this approach allows us to provide a physical explanation of the phenomena
occuring in this geometry by means of an electrostatic analogy
Non-linear model equation for three-dimensional Bunsen flames
The non linear description of laminar premixed flames has been very successful, because of the existence of model equations describing the dynamics of these flames. The Michelson Sivashinsky equation is the most well known of these equations, and has been used in different geometries, including three-dimensional quasi-planar and spherical flames. Another interesting model, usually known as the Frankel equation,which could in principle take into account large deviations of the flame front, has been used for the moment only for two-dimensional expanding and Bunsen flames. We report here for the first time numerical solutions of this equation for three-dimensional flames
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Maintaining Disorder: Some Technical and Aesthetic Issues Involved in the Performance of Ligetiâs EÂŽ tudes for Piano
This article examines some of the particular questions and associated strategies concerning matters of rhythm, perceived metre, notation, accentuation, line, physical approach to the keyboard, pedalling, and more in the performance of Ligetiâs Ătudes for piano. I relate these issues to those encountered in earlier repertoire, including works of Schumann, Liszt, Stravinsky, Prokofiev, BartĂłk and Blacher, and argue that particular approaches and attitudes to both technical and musical matters in the context of these Ătudes can fundamentally affect the concept of the music. A particular focus is upon issues of continuity and discontinuity, and the âsituationâ of these works within particular pianistic and other traditions by virtue of the approach taken to performance
A Novel Protein LZTFL1 Regulates Ciliary Trafficking of the BBSome and Smoothened
Many signaling proteins including G protein-coupled receptors localize to primary cilia, regulating cellular processes including differentiation, proliferation, organogenesis, and tumorigenesis. Bardet-Biedl Syndrome (BBS) proteins are involved in maintaining ciliary function by mediating protein trafficking to the cilia. However, the mechanisms governing ciliary trafficking by BBS proteins are not well understood. Here, we show that a novel protein, Leucine-zipper transcription factor-like 1 (LZTFL1), interacts with a BBS protein complex known as the BBSome and regulates ciliary trafficking of this complex. We also show that all BBSome subunits and BBS3 (also known as ARL6) are required for BBSome ciliary entry and that reduction of LZTFL1 restores BBSome trafficking to cilia in BBS3 and BBS5 depleted cells. Finally, we found that BBS proteins and LZTFL1 regulate ciliary trafficking of hedgehog signal transducer, Smoothened. Our findings suggest that LZTFL1 is an important regulator of BBSome ciliary trafficking and hedgehog signaling
Lattice gas experiments on a non-exothermic diffusion flame in a vortex field
It is a known shortcoming of lattice gas models for fluid flow that they do not possess Galilean invariancy. In the case of a single component incompressible flow, this problem can be compensated by a suitable rescaling of time, viscosity and pressure. However this procedure cannot be applied to a flow containing more than one species. We describe here an extension of the Frisch Hasslacher Pomeau collision model which restores a pseudo Galilean invariancy. We then present a simulation of a 2-D reactive shear layer in the configuration of a diffusion flame subjected to the Kelvin-Helmholtz instability.Une limitation bien connue du gaz sur réseau provient du fait qu'il n'est pas invariant par transformation galiléenne. On peut remédier à ce problÚme, dans le cas d'un fluide incompressible à une seule espÚce, par une renormalisation du temps, de la pression et de la viscosité. Malheureusement, cette transformation n'est plus possible dans le cas d'un fluide formé de plusieurs espÚces de particules. Nous proposons ici une extension du modÚle collisionnel de Frisch Hasslacher et Pomeau qui permet de restaurer une pseudo invariance galiléenne. Nous présentons ensuite une simulation bi-dimensionnelle d'une couche de cisaillement réactive dans la configuration d'une flamme de diffusion soumise à l'instabilité de Kelvin-Helmholtz
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