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     

Renaissance notions of number and magnitude

In the 16th and 17th centuries the classical Greek notions of (discrete) number and (continuous) magnitude (preserved in medieval Latin translations of Euclid's Elements) underwent a major transformation that turned them into continuous but measurable magnitudes. This article studies the changes introduced in the classical notions of number and magnitude by three influential Renaissance editions of Euclid's Elements. Besides providing evidence of earlier discussions preparing notions and arguments eventually introduced in Simon Stevin's Arithmétique of 1585, these editions document the role abacus algebra and Renaissance views on the history of mathematics played in bridging the gulf between discrete numbers and continuous magnitudes.     

Thermal stability of amorphous carbon films deposited by pulsed laser ablation

Diamond-like carbon (DLC) films have been grown on Si substrates at ambient temperature by the pulsed-laser ablation technique, using pulses of different durations both in the nano- and picosecond ranges and at various energy fluences. The stability of these films was investigated as a function of thermal anneals performed in UHV conditions up to 1273 K. Their physico-chemical properties have been characterized by different techniques including X-ray photo-emission, Auger electron and electron-energy-loss spectroscopies, Raman scattering, spectroscopic ellipsometry and atomic-force microscopy. The thermal stability of the films has been demonstrated to be related to their initial structural (sp³/sp² ratio) and chemical (contaminant) properties. DLC layers prepared under optimized conditions have been found to show a very good thermal stability up to 900 K. Received: 4 Jule 2000 / Accepted: 6 July 2000 / Published online: 6 September 2000     

Dinuclear Cobalt Complexes with a Decadentate Ligand Scaffold: Hydrogen Evolution and Oxygen Reduction Catalysis

A new decadentate dinucleating ligand containing a pyridazine bridging group and pyridylic arms has been synthesized and characterized by analytical and spectroscopic techniques. Four new dinuclear cobalt complexes featuring this ligand have been prepared and thoroughly characterized both in the solid state (X‐ray diffraction) and in solution (1D and 2D NMR spectroscopy, ESI‐MS, and electrochemical techniques). The flexible but stable coordination environment provided by the ligand scaffold when coordinating Co in different oxidation states is shown to play a crucial role in the performance of the set of complexes when tested as catalysts for the photochemical hydrogen evolution reaction (HER) and chemical oxygen reduction reaction (ORR).     

Physical Science in Barcelona

We provide a tour of Barcelona, Catalonia, Spain, following four routes through the city and one elsewhere in the city and beyond, focusing on sites of importance in physics. Route 1 covers the Old Town, its Gothic Quarter, Plaça del Rei, Plaça de Sant Jaume, and Jewish Quarter. Route 2 identifies sites on and close to La Rambla, the main promenade in the city. Route 3 goes from the medieval shipyards to the Board of Commerce to Citadel Park. Route 4 concentrates on the Extension (Eixample) and covers the restored University, the Industrial University, and the new campus of the University of Barcelona. Elsewhere in the city and beyond are the Fabra Observatory; the Plaça de les Glòries with its large steel sculpture depicting the meridian arc from Dunkirk to Barcelona; Montjuïc, the site of the National Art Museum of Catalonia; and the National Museum of Science and Technology in Terrassa.     

Structural Study of O-Specific Polysaccharides of Proteus

Abstract

Proteus bacteria are important human opportunistic pathogens which frequently cause urinary tract infections. According to Bergey's Manual of Systematic Bacteriology,¹ this genus includes three species: P. mirabilis, P. vulgaris, and P. myxofaciens. A novel species of P. penneri has been recently proposed^2,3 for strains formerly called P. vulgaris biogroup I. Proteus is an antigenically heterogeneous group of bacteria, and this is mainly associated with diverse composition and structures of O-specific polysaccharide chains of outer-membrane lipopolysaccharides (O-antigens). The Kauffman-Perch serological classification⁴ of P. mirabilis and P. vulgaris includes 49 O-serogroups. However, a number of S-strains remain unclassified,⁵ including strains of P. penneri.