Cluster description of water-in-oil microemulsions near the critical and percolation points

The three-component ionic microemulsion system consisting of AOT/water/decane shows an unusual phase behavior in the vicinity of room temperature. The phase diagram in the temperature-volume fraction (of the dispersed phase) plane exhibits a lower consolute critical point at about 40 degrees centigrades and 10% volume fraction. A percolation line, starting from the vicinity of the critical point, cuts across the plane, extending to high volume fraction side at progressively lower temperatures. In this paper we review the evidence that allows to interpret the phase behavior of our system in terms of interacting spherical droplets. We also investigate the dynamics of droplets, below and approaching the critical point by dynamic light scattering. The first cumulant and time evolution of the droplet density correlation function can be quantitatively calculated by assuming the existence of polydispersed fractal clusters formed by the microemulsion droplets due to attraction. The relaxation phenomena observed in an extensive set of measurements of electrical conductivity and permittivity close to percolation is also reviewed and interpreted through the same cluster-forming mechanism, which reproduces the most relevant features of the frequency-dependent complex dielectric constant of this system. Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994.     

Invariant Tori and Boundedness in Asymmetric Oscillations

In this paper,we are concerned with the boundedness of all the solutions of the equation x″ ax^ -bx- Ф(x)=p(t),where p(t) is a smooth 2π-periodic function,a and b are positive constants,and the perturbation Ф(x) is bounded.     

Semilinear elliptic problems and concentration compactness on non-compact Riemannian manifolds

Existence of solution for semilinear problem with the Laplace-Beltrami operator on non-compact Riemannian manifolds with rich symmetries is proved by concentration compactness based on actions of the manifold's isometry group.     

Search for a transient electric field gradient in the system90Zr→148Nd with the crystal ball spectrometer

The particle- angular correlation of the 2⁺0⁺ transition in¹⁴⁸Nd, Coulomb excited by⁹⁰Zr projectiles, was investigated to search for a transient electric field gradient expected to be present during the stopping of the recoils in²⁰⁸Pb. An upper limit of V_zz <>¹⁹V/cm² was obtained for¹⁴⁸Nd recoiling with initial velocities of 0.05 c.     

Analysis of the results of calibrating meteoritic olivine crystals with238U nuclei at the Bevalac accelerator

The results are presented of calibrating the sensitivity of olivine crystals from meteorites by the²³⁸U nuclei produced at the Bevalac accelerator. The comparative studies of the spectra of the etchable track lengths due to the²³⁸U nuclei and to fossil tracks in these olivines have shown that the group of the 210 m fossil tracks observed in 1980 at the LNR, JINR is due to the galactic cosmic-ray nuclei of the Th-U group. As regards the origin of the 340–360 m group of fossil tracks which were considered in [2] to be candidates for superheavy nuclei in cosmic rays the presence of the track with a length of up to 360 m in the calibrating²³⁸U track length spectra indicates that the above interpretation has to be questioned. The possible ways of the unambiguous identification of the group of the abnormally long fossil tracks are discussed.In conclusion the authors express their deep gratitude to Academician G.N. Flerov for thoughtful guidance and permanent attention to this study. The authors wish to thank Dr. G.M. Ter-Akopian for very useful discussions and advice and also for his help during the calibrations on Bevalac, Dr. R.I. Petrova for her help in preparing olivine crystal mounts and for their subsequent annealing and etching, and Mrs. G.G. Bankova and G.P. Knyazeva for the thorough microscopic measurements of the²³⁸U track spectra.     

Muonic x-ray intensity measurements on a highT c superconductor

Muonic x-ray spectra from the high-T _c superconductor YBa₂Cu₃O_6.95 have been measured in the superconducting and normal states. No significant differences were found between the two spectra when comparing the intensities of 27 lines.Dedicated to Prof. Dr. H. J. Mang on the occasion of his 60th birthday     

The relativistic Hartree-Fock-Approximation for finite temperatures and its semiclassical expansion

A derivation of the relativistic Hartree-Fock-Approximation for finite temperatures is given by utilizing a thermodynamic extremum principle for the construction of an approximate (thermal HF-) hamiltonian of single-particle structure. By use of the Wigner transform one can obtain the so-called quasi-classical expansion of the theory; i.e. the thermal Thomas-Fermi theory plus quantum corrections. The details are illustrated for the Walecka Lagrangian density.Dedicated to Prof. Dr. H.J. Mang on the occasion of his 60th birthday     

The spin-orbit field in superdeformed nuclei: a relativistic investigation

Relativistic Mean Field (RMF) theory is used to investigate the behavior of the spin orbit potential,V _ls, in nuclear states of very large deformation and high angular velocity. As a by-product we present a set of parameters for an approximation of the relativistic scalar- and vector-potentialsS andV in the Dirac equation in terms of Saxon-Woods shapes. These reproduce more or less the same single particle specta as a full selfconsistent relativistic mean field calculation.Dedicated to Prof. Dr. H.J. Mang on the occasion of his 60th birthday     

Jet production rates at LEP and the scale of αs

We discuss the scale dependence of _s in connection with jet multiplicities on theZ pole in the framework of perturbative QCD. Several scale defining procedures are applied to jet fractions and compared to recent measurements at LEP.Dedicated to Prof. Dr. H.J. Mang on the occasion of his 60th birthday