Asymptotically self-similar propagation of the spherical ionization waves

It is shown that a new type of the self-similar spherical ionization waves may exist in gases. All spatial scales and the propagation velocity of such waves increase exponentially in time. Conditions for existence of these waves are established, their structure is described and approximate analytical relationships between the principal parameters are obtained. It is notable that spherical ionization waves can serve as the simplest, but structurally complete and physically transparent model of streamer in homogeneous electric field.Comment: Corrected typos, the more precise formulas are obtaine

Electric discharge contour dynamics model: the effects of curvature and finite conductivity

In this paper we present the complete derivation of the effective contour model for electrical discharges which appears as the asymptotic limit of the minimal streamer model for the propagation of electric discharges, when the electron diffusion is small. It consists of two integro-differential equations defined at the boundary of the plasma region: one for the motion and a second equation for the net charge density at the interface. We have computed explicit solutions with cylindrical symmetry and found the dispersion relation for small symmetry-breaking perturbations in the case of finite resistivity. We implement a numerical procedure to solve our model in general situations. As a result we compute the dispersion relation for the cylindrical case and compare it with the analytical predictions. Comparisons with experimental data for a 2-D positive streamers discharge are provided and predictions confirmed.Comment: 23 pages, 3 figure

Boundary critical behaviour at mm-axial Lifshitz points: the special transition for the case of a surface plane parallel to the modulation axes

The critical behaviour of $d$-dimensional semi-infinite systems with $n$-component order parameter $\bm{\phi}$ is studied at an $m$-axial bulk Lifshitz point whose wave-vector instability is isotropic in an $m$-dimensional subspace of $\mathbb{R}^d$. Field-theoretic renormalization group methods are utilised to examine the special surface transition in the case where the $m$ potential modulation axes, with $0\leq m\leq d-1$, are parallel to the surface. The resulting scaling laws for the surface critical indices are given. The surface critical exponent $\eta_\|^{\rm sp}$, the surface crossover exponent $\Phi$ and related ones are determined to first order in \epsilon=4+\case{m}{2}-d. Unlike the bulk critical exponents and the surface critical exponents of the ordinary transition, $\Phi$ is $m$-dependent already at first order in $\epsilon$. The \Or(\epsilon) term of $\eta_\|^{\rm sp}$ is found to vanish, which implies that the difference of $\beta_1^{\rm sp}$ and the bulk exponent $\beta$ is of order $\epsilon^2$.Comment: 21 pages, one figure included as eps file, uses IOP style file

Functional Relationship between Protein Disulfide Isomerase Family Members during the Oxidative Folding of Human Secretory Proteins

We systematically depleted PDI family members and show that whereas ERp72 and P5 contributed minimally to oxidative protein folding, PDI and ERp57 were the predominant catalysts. Depletion of PDI or ERp57 alone modestly delayed folding, but depletion of both led to generalized protein misfolding and degradation

Resonant reflection of two-dimensional acoustic waves from shocks in solids

Le problème d'émission spontanée des ondes sonores generées par chocs dans les solides est exploré. Un modèle auto-consistant du milieu est construit, qui permet le calcul des propriétés thermodynamiques comme l'énergie interne, l'entropie, le paramètre de Gruneisen et, en particulier, le nombre de Mach derrière le choc. Ce dernier est utilisé pour calculer le critère de stabilité, représentant la condition d'occurence d'émission acoustique spontanée derrière le choc. Les adiabatique de choc expérimentales sont reproduites par le modèle. Une forme simple du critère de stabilité est obtenue, s'exprimant au moyen du paramètre de Gruneisen du milieu non-perturbé et de la compression relative maximale. Il est montré que l'émission spontanée peut avoir lieu dans les métaux sous certaines conditions expérimentales disponibles.The problem of spontaneous emission of sound waves from shocks in solids is investigated. A self-consistent model of the medium is constructed that allows the calculations of the various thermodynamic properties such as the internal energy, the entropy, the Gruneisen parameter and in particular the Mach number behind the shock. The latter is employed in calculating the stability criterion that determines whether spontaneous acoustic emission occurs behind the shock. The experimental shock adiabatic curves are reproduced by the model. A simple explicit form of the stability criterion is derived in terms of Gruneisen parameter of the unperturbed medium and the maximum compression ratio. It is shown that spontaneous emission may occur in metals under available experimental conditions