Effect of Tm concentration on the tunability of the YLF laser in the 1.9 µm region

We describe the continuous-wave (cw) operation of a LiYF₄ laser based on crystals doped with different concentrations of Tm³⁺. We observed the fluorescence spectra from the upper laser level when the crystal is placed inside the laser resonator, in the same optical environment of the coherent emission. We measured the laser intensity as a function of pump power and obtained a 24% slope efficiency by selecting a suitable orientation of the crystal. Using all this information, we were able to demonstrate laser tunability at 1.9 µm in a 50 cm^–1 wide interval.     

Duality in Function Spaces

In this paper we use Bartle’s technique to study duality between a topological space and a function space. Normally such a duality forms an essential part of Functional Analysis. We introduce several new topologies such as the topology of even convergence T_e, the closed-cocompact topology T_{k ′}, the (strong) local proximal convergence. We explore the topological groups of self-homeomorphisms of a topological space and shed light on the earlier work of Arens, Dieudonné, Di Concilio. We also study the concepts such as evenly equidistant, functionally equicontinuous, due to Bouziad-Troallic and topologically equicontinuous due to Royden. In memory of Professor Enrico Meccariello who made a considerable contribution to this work and who suddenly passed away before his time     

Conformational effects on circular dichroism in the photoelectron angular distribution.

The B-spline density-functional method has been applied to the conformers of the (1R, 2R)-1,2-dibromo-1,2-dichloro-1,2-difluoroethane molecule. The cross section, asymmetry, and dichroic parameters relative to core and valence orbitals, which do not change their nature along the conformational curve, have been systematically studied. While the cross section and the asymmetry parameter are weakly affected, the dichroic parameter appears to be rather sensitive to the particular conformer of the molecule, suggesting that this dynamical property could be a useful tool for conformational analysis. The computational method has also been applied to methyl rotation in methyloxirane. Unexpected and dramatic sensitivity of the dichroic-parameter profile to the methyl rotation, both in the core and valence states, has been found. Boltzmann averaging over the conformers reproduces quite closely the profiles previously obtained for the minimum-energy conformation, which is in good agreement with the experimental results.     

Relativistic Navier-Stokes equations in the Meixner-Prigogine scheme

Viscous effects are included in the relativistic Meixner-Prigogine scheme (see: A. Sandoval-Villalbazo, L.S. García-Colín, Physica A 234 (1996) 358). A relativistic generalization of the Navier-Stokes equations is obtained within this framework. The system obtained is analyzed and compared with related work.     

Yunnandaphninines F and G,New C30 Alkaloids from Daphniphyllum yunnanense

Eight C₃₀ Daphniphyllum alkaloids, including two new ones, yunnandaphninines F and G ( 1 and 2 , resp.), were isolated from the leaves and stems of Daphniphyllum yunnanense. Their structures were elucidated on the basis of the spectroscopic data.     

Inclusive sum rules for isotopic spin

Inclusive sum rules for non-abelian symmetry generators and in particular for isospin are studied. A compact formalism is introduced which allows to exaract in a simple way all the consequences of invaraince properties.     

The role of hydration water in isothermal step annealing of neutron irradiated sodium nitroprusside

A kinetic study of isothermal step annealing of neutron-irradiated sodium nitroprusside has been performed. The influence of water and -irradiation on the behaviour of the compound is analyzed and compared with previous results obtained with the analogous compound Na₂/Fe/CN/₅NO/.2H₂O. It is possible to characterize two different fundamental processes that, in spite of occurring at two different temperatures, present the same activation energy than the hydrated system.     

Formamidines and triazenes as precursors for the preparation of rhenium imido-complexes

Summary The rhenium(V) imido-complexes [Re(NR)Cl₃(PPh₃)₂] have been obtained by heating the rhenium(V) derivative [ReOCl₃(PPh₃)₂] with RNHCHNR R = Ph (1a), p-MeC₆H₄ (1b), p-ClC₆H₄ (1c) andp-FC₆H₄ (1d) in THF under reflux. [Re(NR)Cl₃(PPh₃)₂] (R =p-MeQ₆H₄) has also been obtained by heating the rhenium(III)-triazenido complex [ReCl₂(RN N NR)(PPh₃)₂] in CCl₄ under reflux.     

Configurational equilibria and 13C NMR spectra of tetracyclic saturated hydrocarbons

The stereoisomeric equilibrium composition over Pd/C at high temperature of a series of tetracyclic saturated hydrocarbons having general formula C₁₈H₃₀ was determined by gas chromatography and compared with that calculated on the basis of conformational analysis. Several stereoisomers were isolated. Their ¹³C NMR spectra agree very well with those calculated according to standard procedures. This method of structural determination was applied to perhydronaphthacene, perhydrobenzo(a)anthracene, 2- and 5-methylper-hydrobenzo (d,e)anthracene and 2,7-dimethylperhydropyrene.