Calcium complex grease as a low-polarity stationary phase

Considerable and unexpected thermal stability has been found with a calcium complex hydrocarbon grease proposed as a non-polar stationary phase. Although the polarity is unsatisfactory, improved stability has been achieved by the addition of an antioxidant. The use of an antioxidant increased significantly the thermal stability of low-polarity hydrogenated Apiezon M, which has been reported as an acceptable non-polar basic stationary phase for use of high temperatures.     

Anisotropy in Tendon Investigated in Vivo by a Portable NMR Scanner, the NMR-MOUSE

Ordered tissue like tendon is known to exhibit the magic-angle phenomenon in magnetic resonance investigations. Due to the anisotropic structure the transverse relaxation time T₂ depends on the orientation of the tendon in the magnetic field. In medical imaging, relaxation measurements of tendon orientation are restricted by the size of the object and the space available in the magnet. For humans, tendon orientation can only be varied within small limits. As a consequence, the magic-angle phenomenon may lead to a misjudgement of tendon condition. It is demonstrated that the NMR-MOUSE (mobile universal surface explorer), a hand-held NMR sensor, can be employed to investigate the anisotropy of T₂ in Achilles tendon in vivo. The NMR-MOUSE provides a convenient tool for analyzing the correlation of T₂ and the physical condition of tendon.     

Quantummechanical solutions of the laser masterequation I

The masterequation for the statistical operatorW of a Laser mode andA active two-level atoms 1 is solved by using the coherent state representation 2 of the lightfield. The ansatz forW represents the most general symmetrical coupling of the light mode to all atoms and therefore contains the full influence of quantum fluctuations of the atomic system on the light mode. The system of equations can be solved practically exactly in the stationary case and leads to a photon number distribution in the laser valid for arbitrary pumping. This distribution agrees with that found by a Fokker-Planck equation 3 for not too high pumping and approaches the Poisson distribution for very high pumping. The smooth transition of the inversion from σ₀ (below threshold) to σ (above threshold) can also be calculated.     

Triangulation a v5 séparés dans le problème des quatre couleurs

Considérant la notion classique minimal planaire 5-chromat ique, les auteurs étudient les triangulations du plan dont tons les sommets sont de degré ? 5 et dont les sommets de degré 5 sont séparés (aucune arete ne retie deux sommets de degré 5); its prouvent qu'un graphe minimal comporte nécessairement une arête 5-5. L'article présente 1 °) une démonstration fondée sur un ensemble minimum de 14 configurations réductibles, 2°) une demonstration fondée sur un algorithme applicable au cas général     

Critical fluctuations in continuous non-equilibrium systems

We treat a continuously extended non-equilibrium system described by a set of space and time dependent variablesq. Theq's are assumed to obey linearized equations of motion with fluctuating forces which areδ-correlated in space and time. We calculate the two-time and two-space-point correlation functions.     

Nonequilibrium phase transitions and bifurcation of limit cycles and multiperiodic flows

In many nonequilibrium physical systems such as lasers, fluids, chemical reactions, semiconductors etc. new structures or patterns occur when external parameters are changed. Furthermore with further changing parameters a whole hierarchy of new pattern formations may occur where the first step starting from a homogeneous state is well understood. The present paper investigates what happens at the next steps where a system performs complicated motions in the form of a limit cycle or, still more generally, in the form of a multiperiodic flow. In this latter case the time dependence is composed of periodic motions of different frequencies. We study the case in which by change of an external parameter the stable motion (trajectory) becomes unstable and is replaced by a set of new trajectories (bifurcation). It is assumed that the bifurcating trajectories remain in the neighbourhood of the former stable trajectory. Our procedure allows for a number of applications to lasers, fluid dynamics, chemical waves etc. as will be shown in subsequent papers.     

Spiral patterns in thermal convection

We report on spiral type convection patterns obtained from a numerical treatment of a generalized Swift-Hohenberg equation.