Determination of the perpendicular magnetic parameters for Cu(II) EPR spectra from angular anomalies

A method is outlined to obtain accurate values of g_? and A_? in EPR spectra of Cu(II) compounds, provided that an extra absorption peak due to an angular anomaly can easily be recognized. This method turns out to be useful especially in the case of low resolution and in the presence of a superhyperfine pattern due to the ligands.     

Micromorphic continua: non-redundant formulations

The kinematics of generalized continua is investigated and key points concerning the definition of overall tangent strain measure are put into evidence. It is shown that classical measures adopted in the literature for micromorphic continua do not obey a constraint qualification requirement, to be fulfilled for well-posedness in optimization theory, and are therefore termed redundant. Redundancy of continua with latent microstructure and of constrained Cosserat continua is also assessed. A simplest, non-redundant, kinematic model of micromorphic continua, is proposed by dropping the microcurvature field. The equilibrium conditions and the related variational linear elastostatic problem are formulated and briefly discussed. The simplest model involves a reduced number of state variables and of elastic constitutive coefficients, when compared with other models of micromorphic continua, being still capable of enriching the Cauchy continuum model in a significant way.     

Parallel solution of three‐dimensional Marangoni flow in liquid bridges

This paper describes the implementation and performances of a parallel solver for the direct numerical simulation of the three‐dimensional and time‐dependent Navier–Stokes equations on distributed‐memory, massively parallel computers. The feasibility of this approach to study Marangoni flow instability in half zone liquid bridges is examined. The results indicate that the incompressible, non‐linear Navier–Stokes problem, governing the Marangoni flows behavior, can effectively be parallelized on a distributed memory parallel machine by remapping the distributed data structure. The numerical code is based on a three‐dimensional Simplified Marker and Cell (SMAC) primitive variable method applied to a staggered finite difference grid. Using this method, the problem is split into two problems, one parabolic and the other elliptic A parallel algorithm, explicit in time, is utilized to solve the parabolic equations. A parallel multisplitting kernel is introduced for the solution of the pseudo pressure elliptic equation, representing the most time‐consuming part of the algorithm. A grid‐partition strategy is used in the parallel implementations of both the parabolic equations and the multisplitting elliptic kernel. A Message Passing Interface (MPI) is coded for the boundary conditions; this protocol is portable to different systems supporting this interface for interprocessor communications. Numerical experiments illustrate good numerical properties and parallel efficiency. In particular, good scalability on a large number of processors can be achieved as long as the granularity of the parallel application is not too small. However, increasing the number of processors, the Speed‐Up is ever smaller than the ideal linear Speed‐Up. The communication timings indicate that complex practical calculations, such as the solutions of the Navier–Stokes equations for the numerical simulation of the instability of Marangoni flows, can be expected to run on a massively parallel machine with good efficiency. Copyright © 1999 John Wiley & Sons, Ltd.     

Efficient and selective oxidation of methyl substituted cycloalkanes by heterogeneous methyltrioxorhenium–hydrogen peroxide systems

Polymer-supported methyltrioxorhenium (MTO) systems are efficient catalysts for the oxidative functionalisation of cyclohexane and cyclopentane derivatives with H₂O₂ as oxygen donor. Using poly(4-vinyl)pyridine and poly(4-vinyl)pyridine-N-oxide as MTO supports, cycloalkanol, cycloalkanediol, cycloalkanone and ω-hydroxy methyl ketone derivatives were obtained in different yields depending on the experimental conditions. Interestingly, cycloalkane dimers were selectively recovered in acceptable to good yields when the oxidation was performed with polystyrene-microencapsulated MTO catalyst. The EPR investigation suggests that the homolytic cleavage of the CH₃–Re bond with formation of CH₃ radicals occurs inside the polystyrene capsule, indicating a possible role of methyl radical in the cycloalkane dimerisation pathway.     

Multiple-attribute decision support system based on fuzzy logic for performance assessment

This paper deals with the problem of assessing the performance of a set of production units, simultaneously considering different kinds of information, yielded by a Data Envelopment Analysis, a qualitative data analysis and an expert assessment. The tool for integrating heterogeneous data is a model that applies fuzzy logic to decision support systems. The results obtained are a holistic performance assessment of each unit of the set and a ranking order of the units.     

A Universal Geochemical Scenario for Formamide Condensation and Prebiotic Chemistry

The condensation of formamide has been shown to be a robust chemical pathway affording molecules necessary for the origin of life. It has been experimentally demonstrated that condensation reactions of formamide are catalyzed by a number of minerals, including silicates, phosphates, sulfides, zirconia, and borates, and by cosmic dusts and meteorites. However, a critical discussion of the catalytic power of the tested minerals, and the geochemical conditions under which the condensation would occur, is still missing. We show here that mineral self-assembled structures forming under alkaline silica-rich solutions are excellent catalysts for the condensation of formamide with respect to other minerals. We also propose that these structures were likely forming as early as 4.4 billion years ago when the whole earth surface was a reactor, a global scale factory, releasing large amounts of organic compounds. Our experimental results suggest that the conditions required for the synthesis of the molecular bricks from which life self-assembles, rather than being local and bizarre, appears to be universal and geologically rather conventional.     

A high-pressure parallel-grid gas scintillation proportional counter for high-energy X-ray astronomy

Summary We present preliminary results on a new detector for X-ray astronomy sensitive in the energy range from 3 to 120 keV. The detector can be implemented either as a narrow-field instrument (∼1 degree field of view) or as wide field camera (30×30 degree field of view). This detector with its large area, good energy resolution and background rejection represents a valid option to the present generation of instruments for high-energy X-ray astronomy. Paper presented at the 2° Convegno Nazionale di Fisica Cosmica, held at L'Aquila, 29 May–2 June 1984.     

FIGARO IV: Large-area balloon-borne telescope to study rapid time variabilities in the gamma-ray sources at energies above 50 MeV

Summary We present a new γ-ray telescope based on the Limited Streamer Tube technology, used as tracking chambers to detect photons above 100 MeV. This technique allows to obtain very large sensitive areas (16 m² in our experiment), together with a good angular resolution for payloads embarcable in high-altitude balloon flights. The capability to collect a large signal in a short exposure time makes the telescope particularly suitable and competitive with respect to satellite-based detectors for studying both periodic and random time variabilities on galactic and extragalactic γ-ray sources. Paper presented at the 6th Cosmic Physics National Conference, Palermo, 3–7 November 1992.     

Identification des composés phénoliques dans les feuilles de Homogyne alpina,Petasites albus,Petasites hybridus et Adenostyles alliariae

Four polyphenolheterosides have been isolated from the leaves of Homogyne alpina, Petasites albus, Petasites hybridus and Adenostyles alliariae by means of thin layer and column chromatography on polyamide. Isoquercitrine (II) has been isolated from Petasites albus, Petasites hybridus and Adenostyles alliariae; Astragaline (III) from Petasites albus and Petasites hybridus; Glucoluteoline (IV) from Adenostyles alliariae and Rutine (I) from Homogyne alpina. Piceine (V) has also been isolated from Homogyne alpina.