Magnetic field behavior of resonant current steps in one dimensional arrays of Josephson tunnel junctions

We study the magnetic field behavior of the resonant current steps appearing in one dimensional arrays of Josephson tunnel junctions. The analysis is carried out in the framework of the Kulik theory of resonances in small Josephson junctions, and the theoretical maximum current amplitude of the Fiske steps is computed as a function of the applied magnetic field. Preliminary measurements of the Fiske step current modulations induced by varying the magnetic field is also reported and discussed.     

A dust plasma

A dust plasma was created using spores in a glass discharge tube. The dust particles become negatively charged, levitate in the positive plasma potential, and behave like massive electrons. A laser beam is used to make the dust visible, revealing plasma structure, such as the wall sheath and the direction of the local electric field     

Efficiency of face-plated underwater acoustic transducers

The possibility of obtaining the efficiency of simple disc transducers, broad-banded by use of face-plates, from input electrical conductance measurements under air-loading is explored. For an air-backed ceramic disc with a Perspex face-plate it was found that the main limitation to the accuracy of efficiency estimates is due to departures from uniformity of the face-plate thickness.     

Prediction of excess enthalpies for ternary aqueous solutions of nonelectrolytes

The excess enthalpiesH _xy ^E of ternary aqueous solutions of nonelectrolytes are used to test the possibility of making predictions for ternary solutions from the properties of the binary solutions only. Two methods are proposed: one is based on the empirical rule (h _xx ·h _yy )^1/2=h _xy . Another leads to the numerical prediction of the overallH _xy ^E . Both are successful for most of the pairs of solutes for whichH _x ^E ,H _y ^E >0.     

The Skyrmion Skyrmion interaction and the meson exchange model for the NN potential

The properties of nucleon-nucleon (NN) potentials derived from the Skyrme model are investigated compared to those of typical One-Boson-Exchange (OBE) models, For that purpose the NN as well as the nucleon-antinucleon (N¯N) potentials are evaluated for the isoscalar central channel, the isovector spin channel, and the isovector tensor channel. A comparison of NN and N¯N interactions allows a separation into terms with positive and negativeG-parity and therefore a detailed comparison with the properties of the OBE model. This analysis is performed using the classical Lagrangian of the Skyrme model and considering an extension of this Lagrangian by a term of sixth order, which has recently been proposed. The results indicate that the extended Lagrangian yields an interaction which is quite consistent with the OBE picture. The extended model, however, is much more sensitive to the values of the parameters and the approximations being used for the evaluation of the field for two baryons.     

1-Azetines

The synthesis, characteristics and chemical behaviour of some 3,3-disubstituted-2-ethoxy- and 2-ethy lthio-1-azetines, the first examples of a new class of heterocyclic compounds, are described.     

Molecular dynamics study of host–guest interactions in cyclodextrins: methodology and data analysis for a comparison with solution data and the solid-state structure

A general method is proposed to model the behavior of cyclodextrins (CDs) and of their inclusion compounds through energy minimizations and molecular dynamics (MD) simulations at a constant temperature. In this way, the formation of a host–guest compound is obtained starting from many trial geometries with the guest outside the CD cavity without any a priori assumption. The MD simulation results are analyzed through two functions: (i) the similarity maps of the root-mean-square distances between instantaneous conformations found in the MD runs to recognize different families of conformers; (ii) the pair distribution function PDF, yielding the probability density of finding appropriate atom pairs as a function of their distance at equilibrium. As an example, the inclusion compound formed by β-CD and (−)-menthol-β-d-glucoside is investigated. The lowest-energy inclusion compound is in good agreement with the results of single-crystal X-ray analysis, while at room temperature the MD runs show a closely similar arrangement with thermal fluctuations. In this case, the PDF between diagnostic hydrogen atoms of β-CD and of the guest molecule are fully consistent with the experimental NOE results obtained from NMR measurements in solution.     

NMR analysis of restricted internal rotation in 2-substituted-2,3-dihydro-3-o-tolyl(chlorophenyl)-4(1H)-quinazolinones

Steric interactions between aryl and heterocyclic moieties in 2-substituted-2,3-dihydro-3-o-tolyl(chlorophenyl)-4(1H)-quinazolinones 1a-j produce sufficient restriction to rotation about the aryl C? N bond that the presence of torsional isomers may be detected at room temperature. Diastereomeric population and free energy of activation for rotation have been calculated by ¹H nmr spectra. Probably due to a preferred axial position of R² substituent no dramatic variation both in A /B ratio and in ΔG≠ value has been observed for 1a-f . The comparison between 1a and 1j ΔG^≠ values allows to formulate a hypothesis on the structure of the transition state.     

Application of a classical least-squares regression method to the assay of 1,4-dihydropyridine antihypertensives and their photoproducts

A multicomponent UV spectrophotometric method using a classical least-squares (CLS) algorithm has been developed for the quantitative determination of 1,4-dihydropyridine (DHP) calcium antagonists and respective photoproducts. The procedure was optimized by defining a fractionation scheme for selecting the more useful wavelength ranges to be used in the calibration model. The method is potentially able to be extended to the other drugs of the same family. The recovery values from synthetic mixtures and commercial formulations were verified to be 99.09 and 97.85% for drug parents and degradation products, respectively. The sensitivity for the photoproducts determination was found to be below 0.8%. The results obtained from laboratory mixtures and commercial formulations were compared with those provided by UV derivative spectrophotometry.     

Effect of solute polarity on the performance of porapak type porous polymers

Summary The breakthrough volume of ådsorbent traps made with porous polymer beads Porapak N, P. Q, R, S was evaluated by analysis of polarity reference substances proposed by Rohrschneider (ethanol, methyl ethyl ketone, nitrometane, benzene, pyridine) by McReynolds (butanol, methyl propyl ketone) and of the first term of some homologous series: alcohols, aldehides, carboxilic acids, nitrocompounds, iodoalkanes and nitriles.Adjusted retention times of the compounds were measured at 200°C and correlated with the physical properties and with polarity class according to Ewell.Trapping efficiency of the various Porapak types was evaluated and the theoretical breakthrough volumes at 25°C was calculated for the used test substances.Dedicated to Prof. Dr. A. Liberti on the occasion of his 70th birthday.