A cut-and-paste method for computing the Seifert volumes

We use methods from gauge theory to compute the Seifert volumes of 3-manifolds. As applications, we are able to find the Seifert volumes of several hyperbolic manifolds obtained by surgery on 2-bridge knots.     

Signature of electron-plasmon quantum kinetics in GaAs

We predict a carrier-density dependent oscillation, which is superimposed on the decay of the coherent control photon echo signal of a semiconductor. It reflects the oscillatory transfer of excitation back and forth between electrons and a mixed plasmon-phonon mode. This signature provides obvious and unique evidence for the finite duration of the interaction process, i.e., evidence for the collective Coulomb quantum kinetics. The theoretical predictions for the model semiconductor GaAs are reproduced in corresponding experiments.     

Classe de compacite d’operateur intervenant dans une classe de problemes elliptiques degeneres

We compute here the class of compacity of those operators onL ² (Ω) the image of which belongs to some families of weighted Sobolev spaces. Such spaces are relevant for the study of some elliptic problems which degenerate at the boundary of Ω.     

Three photon virtual annihilation contributions to positronium hyperfine structure

Three photon virtual annihilation contributions to the positronium hyperfine interval are calculated to order α⁶m(α⁴R_∞). The result is obtained in analytic form and leads to the small value of -0.91 MHz for the contribution to the ground state energy difference from this source.     

A determination of the rate and heat of evaporation by measuring the radius variations of a metal tip

A new material loss technique for the experimental determination of the free evaporation rate of a metal is presented. This technique is based on the study of tip profile changes. The tip radius variation is a consequence of the simultaneous action of free evaporation and surface self-diffusion. The rate of free evaporation is related to the tip radius evolution, so the vapor pressure and heat of evaporation can be determined by measuring in situ the radius changes with time. The method permits an easy control of the cleanliness of the surface by field electron microscopy, and should enable one to study the influence of adsorption on evaporation. The method is tested with molybdenum tips. The variation of the radius of the tips, heated in ultra-high vacuum, is determined by field electron and scanning microscope measurements. Vapor pressures and heat of evaporation values obtained are in agreement with values obtained by other techniques.     

Structural properties of cyanobacterial hemoglobins: the unusual heme-protein cross-link of Synechocystis sp. PCC 6803 Hb and Synechococcus sp. PCC 7002 Hb

The truncated hemoglobins from Synechocystis sp. PCC 6803 and Synechococcus sp. PCC 7002 ligate the heme iron with two axial histidines (HisF8 and HisE10). In addition, these two proteins are able to form a heme-protein cross-link between a vinyl substituent and a histidine at position 16 of the H helix. The product is a protein with improved resistance to thermal and acid denaturation.     

A New Lignan from the Leaves of Styrax annamensis

Chemistry of Natural Compounds - Phytochemical investigation of the ethyl acetate extract of Styrax annamensis leaves has led to the isolation and determination of a new lignan,...     

Explicit formulas for the top Lyapunov exponents of planar linear stochastic differential equations

Our aim in this article is to establish explicit formulas for the top Lyapunov exponents of planar linear stochastic differential equations. We use these formulas to examine the sample-path stability of a linear stochastic differential equations arising in fluid dynamics and of a model of stochastic Hopf bifurcation.     

Spectral conditions for admissibility of evolution equations in Hilbert space

We study properties of solutions of the evolution equation , where B is a closable operator on the space AP(R,H) of almost periodic functions with values in a Hilbert space H such that B commutes with translations. The operator B generates a family of closed operators on H such that (whenever eiλtx∈D(B)). For a closed subset Λ⊂R, we prove that the following properties (i) and (ii) are equivalent: (i) for every function f∈AP(R,H) such that σ(f)⊆Λ, there exists a unique mild solution u∈AP(R,H) of Eq. (∗) such that σ(u)⊆Λ; (ii) is invertible for all λ∈Λ and .