Lidar measurements of atmospheric transmissivity

Summary The possibility of performing atmospheric-transmissivity measurements by lidar is considered. In the present paper two distinct methods have been successfully applied. The first one is based on the detection of the Raman return from molecular nitrogen. An alternative method is based on the simultaneous detection of the elastic and N₂ Raman returns. Measurements based on both techniques are discussed in detail, the second technique producing more accurate results. Through this technique an estimation of the ?ngstr?m coefficient can also be obtained.     

Decision algorithms for elementary topology I. Topological syllogistics with set and map constructs,connectedness, and cardinality comparison

In this paper we give a decision procedure for a topological syllogistic, denoted ?²,∞, involving, besides the standard Boolean set operators (∩, ∩, ′ (set complementation)) and predicates ( ? (membership), = (equality)), also the Kuratowski closure operator, continuous and closed maps with the notion of direct and inverse images, surjectivity and injectivity, as well as point evaluation, the singleton operator {·}, a predicate for comparing the cardinalities of two given sets, and a predicate expressing that a given set is topologically connected. Several examples are also discussed. © 1994 John Wiley & Sons, Inc.     

Contact metric manifolds whose characteristic vector field is a harmonic vector field

In this paper, contact metric manifolds whose characteristic vector field ξ is a harmonic vector field are called H-contact manifolds. We show that a (2n+1)-dimensional contact metric manifold is an H-contact manifold if and only if ξ is an eigenvector of the Ricci operator (J.C. González-Dávila and L. Vanhecke [J. Geom. 72 (2001) 65–76] proved this result for n=1). Consequently, the class of H-contact manifolds is very large. Moreover, we give some application about the topology of a compact H-contact manifold.     

Cellular Simulation

Cellular simulation, a method of organizing simulation models to improve experimental efficiency, is described and shown to have the further advantages of reconciling the event based approach with the activity approach to simulation modelling and to have implication for modelling large systems.     

A study of high transverse energy interactions of 150 and 300 GeV pions and protons on a hydrogen target using a large acceptance calorimeter

Interactions of 150 GeV pions and 300 GeV pions and protons on hydrogen which result in final states with large transverse energy in the central rapidity region ?0.88 < y < 0.67 were studied with a calorimeter trigger. The dependence of the cross section on the azimuthal acceptance of the trigger, on the beam energy and on the incident particle type and the jet properties of the events were investigated. No dominant two-jet structure was found. Nevertheless, the parton spectrum in the colliding hadrons appears to be relevant for large transverse energy reactions.     

Mass spectrometric characterization of poly(ethylene terephthalate-co-p-oxybenzoate)

Copolyesters containing ethylene terephthalate and p-oxybenzoate units in mole ratios of ca. 80:20, 70:30, 40:60, and 20:80, respectively, were examined by direct pyrolysis–mass spectrometry to obtain information about the thermal stabilities and the sequences distributions of the two types of units as a function of composition. Thermal stability as measured by rate of volatilization increased with increasing oxybenzoate content, as did the amount of char residue formed. The electron impact mass spectrum of the volatile fragments showed the formation of predominantly linear fragments with carboxyl and vinyl end groups. Dimer, trimer, and tetramer fragments containing either or both types of units could be identified and their relative amounts could be estimated from peak intensities. The results were consistent with those expected for random distributions of the two units, i.e., for statistical copolymers.     

The LITE correlative measurements campaign in southern Italy: preliminary results

A,355 and R_A,532); the two data sets appearing to be highly correlated. LITE vs. Potenza LIDAR measurements of R_A,355 and R_A,532 display a correlation coefficient of 0.72 and 0.86, respectively. Stratospheric aerosol dimensional characteristics are determined starting from the measured values of the ?ngstrom coefficient. Received: 24 May 1996/Revised version: 8 October 1996     

Stoichiometric hydrogenation of the heterobimetallic (α-alkynyl) complex [μ(1σ, 23η3H2CC  CCH3)] [(CO)3FeCo(CO)3]

The title compound reacts with molecular hydrogen at 60°C giving rise to the homometallic complexes Fe(CO)₅ and Co₂(CO)₈, and a very rich mixture of gaseous hydrocarbons (e.g. butenes from partial hydrogenation, butane from total hydrogenation and methane and propene from selective hydrogenolysis of the organic chain).The influence of concentration of the title complex, and partial pressure of hydrogen or carbon monoxide on the hydrogenation rate have been investigated. Although an unequivocal mechanism cannot be ascertained from the kinetic data owing to the complexity of the reaction, the pattern of products strongly indicates that the σ-interaction between the iron atom and the organic chain is preserved in the transition state.     

Synthesis of cavity extended cyclotriveratrylenes

Aromatic nucleophilic substitution reaction of cyclotriguaiacylene 1 with fluorobenzene derivatives bearing electron-withdrawing groups X (CHO, COCH(3), CN, NO(2)) in the para position gives a series of cyclotriveratrylene derivatives (3a-d), where the X substituents can be transformed to hydrogen-bond donor groups to afford new CTV-based heteroditopic receptors. The substituents of compounds 3a-d favor the facile demethylation reaction of the CTV derivatives. Attempts to perform alkylation reactions on derivatives (8c,d) evidenced the formation of a stereoisomeric mixture of symmetrical and unsymmetrical compounds.     

Silicon oxycarbide glasses from gels

Silicon-oxycarbide glasses can be synthesized from modified silica gels through a pyrolysis process in inert atmosphere. A critical analysis of the literature suggests a close relationship between oxygen content in the gel precursors and the amount of carbon atoms covalently bonded to silicon atoms in the corresponding silicon-oxycarbide phase. The problem of the formation of a free carbon phase will be discussed and related to the amount of carbon in the starting gel. An example of successful synthesis of an almost pure carbon-rich oxycarbide phase will also be presented.