On the Set of Cycle Lengths in a Hamiltonian Graph with a Given Maximum Degree

Let n and be two integers such that 2n–1. We describe the set of cycle lengths occurring in any hamiltonian graph G of order n and maximum degree . We conclude that for the case this set contains all the integers belonging to the union [3,2–n+2][n–+2,+1], and for it contains every integer between 3 and +1. We also study the set of cycle lengths in a hamiltonian graph with two fixed vertices of large degree sum. Our main results imply that the stability s(P) for the property of being pancyclic satisfies      

Scaling Algebras for Charged Fields and Short-Distance Analysis for Localizable and Topological Charges

The method of scaling algebras, which has been introduced earlier as a means for analyzing the short-distance behavior of quantum field theories in the setting of the model-independent, operator algebraic approach, is extended to the case of fields carrying superselection charges. In doing so, consideration will be given to strictly localizable charges (DHR-type superselection charges) as well as to charges which can only be localized in regions extending to spacelike infinity (BF-type superselection charges). A criterion for the preservance of superselection charges in the short-distance scaling limit is proposed. Consequences of this preservance of superselection charges are studied. The conjugate charge of a preserved charge is also preserved, and for charges of DHR-type, the preservance of all charges of a quantum field theory in the scaling limit leads to equivalence of local and global intertwiners between superselection sectors.Communicated by Klaus Fredenhagensubmitted 21/01/03, accepted 26/02/04     

Self-regulation of E x B flow shear via plasma turbulence

The momentum balance has been applied to the ExB flow in the edge region of a reversed field pinch (RFP) configuration. All terms, including those involving fluctuations, have been measured in stationary condition in the edge region of the Extrap-T2R RFP experiment. It is found that the component of the Reynolds stress driven by electrostatic fluctuations is the term playing the major role in driving the shear of the ExB flow to a value marginal for turbulent suppression, so that the results are in favor of a turbulence self-regulating mechanism underlying the momentum balance at the edge. Balancing the sheared flow driving and damping terms, the plasma viscosity is found anomalous and consistent with the diffusivity due to electrostatic turbulence.     

Systematic evaluation of molecular recognition phenomena. 3. Selective diphosphate binding to isomeric hexaazamacrocyclic ligands containing xylylic spacers

The crystal structure of 3,7,11,18,22,26-hexaazatricyclo[26.2.2.2(13,16)]tetratriaconta-1(31),13(34),14,16(33),28(32),29-hexaene hexahydrobromide salt [(H6P3)Br6] has been determined by means of X-ray diffraction analysis. It crystallizes with an additional molecule of ethanol and half a molecule of water per molecule of the hydrobromide P3 ligand. The protonation constants of P3 and its host-guest interactions with monophospate (Ph) and pyrophosphate (Pp) have been investigated by potentiometric equilibrium methods. Ternary complexes are formed in aqueous solution as a result of hydrogen bond formation and Coulombic interactions between the host and the guest; formation constants for all the species obtained are reported and compared with the isomeric 3,7,11,19,23,27-hexaazatricyclo[27.3.1.1(13,17)]tetratriaconta-1(33),13, 15,17(34),29,31-hexaene (Bn) ligand. For the H6P3Pp(2+) those bonding interactions reach a maximum yielding a log KR6 of 5.87. The selectivity of the P3 ligand with regard to the monophosphate and pyrophosphate substrates (S) is discussed and illustrated with global species distribution diagrams showing a strong preference for the latter over the former as a consequence of the much stronger formation constants with pyrophosphate. An analysis of the isomeric effect is also carried out by comparing the P3-S versus Bn-S systems. In the best case, a selectivity of over 88% is achieved for the diphosphate complexation when using the meta isomer over the para, due solely to the size and shape of the receptors cavity.     

Field emission properties of a-CN<Subscript>x</Subscript> films prepared by pulsed laser deposition

Amorphous carbon nitride (a-CN_x) films were grown on silicon substrates by ArF excimer laser ablation of a graphite target in the presence of nitrogen at various gas pressures. By working at elevated pressures (up to 100 Pa), large amounts of nitrogen can be incorporated into the films (up to 40 at. %, which leads to a strong enhancement of their field emission properties. This behaviour was demonstrated to be mainly related to changes in the surface morphology of the samples, in connection with the development of graphite-like structures. Received: 22 February 2002 / Accepted: 3 March 2002 / Published online: 10 September 2002 RID="*" ID="*"Corresponding author. Fax: +33-(0)/388-106-230, E-mail: fogarassy@phase.c-strasbourg.fr     

The study of atropoisomers of meso-tetrakis[2.2]paracyclophanylporphyrin

Theoretical considerations of atropoisomers of the title compound have revealed the existence of a large number of stable isomeric species. Syntheses, carried out according to two procedures at widely separated temperatures, resulted in the formation of mixtures of atropoisomers in good yield. Two isomeric fractions have been separated and characterized. Some analytical methods have been worked out and have proved useful in separational techniques.     

Determination of concentration-dependent diffusion coefficients in amorphous Ni-P films studied by auger electron depth profiling

Studies of the interdiffusion in ion-plated Ni₁₀₀- _x P _x /Ni₁₀₀- _y /P _y thin films are described. The diffusion coefficients are evaluated from depth profiles obtained by using Auger electron spectroscopy (AES). The well-known Boltzmann-Matano method is applied for extraction of the diffusion coefficients from the depth profile data. The results show a strong composition dependence.     

Arsen

Ohne Zusammenfassung     

On formulation of stress-strain relations for soils at failure

Résumé Une forme générale des relations contrainte-vitesse de déformation est étudiée pour un mouvement non visqueux. Le tenseur contrainte est représenté par une fonction tensorielle isotrope du tenseur vitesse de déformation: le nombre et la forme des fonctions indépendantes décrivant le matériau sont déterminés.Le principe de la vitesse de dissipation maximale est employé pour obtenir des restrictions supplémentaires pour la relation constitutive. De plus, ce principe permet d'expliquer les contradictions provenant de la forme standard de la loi d'écoulement du potentiel plastique appliquée aux sols. Des formes particulières des relations tensorielles linéaires, dans le cas d'incompressibilité et de dissipation constante sont discutés.