New polyazaheterocycles. 9-Methyl-di-s-triazolo[4,3-a:4,3-c]pyrimidine and 9-methyl-s-triazolo[4,3-c]tetrazolo[1,5-a]pyrimidine

9-Methyl-di-s-triazolo[4,3-a:4,3-c]pyrimidine and 9-methyl-s-triazolo[4,3-c]tetrazolo[1,5-a]pyrimidine have been synthetized from 4-hydrazino-7-methyl-s-triazolo[4,3-c]pyrimidine. Structural assignments based on nmr, ir and chemical manipulations are discussed.     

Exact solution for a trapped Fermi gas with population imbalance and BCS pairing

The problem of a two-component Fermi gas in a harmonic trap, with an imbalanced population and a pairing interaction of zero total momentum, is mapped onto the exactly solvable reduced BCS model. For a one-dimensional trap, the complete ground state diagram is determined with various topological features in ground state energy spectra. In addition to the conventional two-shell density profile of a paired core and polarized outer wings, a three-shell structure as well as a double-peak superfluid distribution are unveiled.     

Ferromagnetic superconducting film in external parallel field

Summary By using the boson transformation method, the electromagnetic properties of a ferromagnetic superconducting film have been studied. The magnetic field, the induction field and the magnetization have been calculated analytically in the London limit. Particularly, we have studied the dependence of the various fields on the phenomenological parameter μ, on the temperature and on the film thickness and the dependence oft _s , a critical temperature below which a spontaneous magnetization appears, on the parameter μ and on the film thickness. Finally, the magnetic properties of the film are analysed in the linear and nonlinear approximation as functions of temperature and thickness.

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Riassunto Utilizzando il metodo della trasformazione bosonica le proprietà elettromagnetiche di un film superconducente ferromagnetico sono state studiate. Il campo magnetico, il camp di induzione magnetica e la magnetizzazione sono stati calcolati analiticamente nel limite di London. In particolare, abbiamo studiato la dipendenza dei vari campi dal parametro fenomenologico μ, dalla temperatura e dallo spessore del film e la dipendenza dit _s , temperatura critica al di sotto della quale appare la magnetizzazione spontanea, dal parametro μ e dallo spessore del film. Infine le proprietà magnetiche del film sono analizzate in approssimazione lineare e non lineare in funzione della temperatura e dello spessore.

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Резюме Исследуются электромагнитные свойства ферромагнитной сверхпро водящей пленки с помощъю метода бозонного нреобразования. В пределе Лондона аналитически вычисляются магнитное поле, индуцированное поле и намагниченность. В частности, рассматривается зависимость вышеуказанных полей от феноменологического параметра μ, от температуры и от толщины пленки, а также зависимостьt _s критической температуры, ниже которой возникает спонтанная намагниченность, от параметра μ и толщины пленки. В заключение, анализируются свойства пленки в зависимости от температуры и толщины в линейном и нелинейном приближениях.

     

Low frequency transport measurements in

Low frequency transport measurements are performed on GdSr₂RuCu₂O₈ pellets. The observed current-voltage curves are qualitatively explained in the framework of a simple phenomenological model accounting for coexistence in the sample of ferromagnetism and superconductivity. A Curie temperature T _cM = 133 K and a superconducting critical temperature T _cS = 18 K, with an onset temperature T _cO = 33 K, are extracted from the analysis of the current-voltage curves. Received 18 September 2002 Published online 4 February 2003 RID="a" ID="a"e-mail: canio@sa.infn.it     

Selective Determination of Organic and Inorganic Thiocyanates in Aqueous Solution by IR Spectrophotometry

Abstract

A new spectrophotometric method for the determination in aqueous solution of both organic and inorganic thiocyanates is described. Organic thiocyanates are determined by measuring at wavenumber of 2150 cm^?1 the absorption of solutions directly extracted with carbon tetrachloride. Inorganic thiocyanates require a previous derivatization reaction with dimethylsulfate, and are determined as methylthiocyanates. The method is quick, accurate and selective. The results obtained suggest its utilization in analysis of aqueous samples.     

A diagram method for the anderson model

Summary A diagram method to treat the Anderson model has been introduced. By applying this technique to the study of chemisorption phenomena, the density of states of adatom electrons has been calculated at finite temperature. Comparison with the results obtained in the symmetric limit atT=0 is given.

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Riassunto Un metodo diagrammatico è stato introdotto per studiare il modello di Anderson. Applicando questa tecnica al problema del chemisorbimento, è stata calcolata la densità degli stati elettronici localizzati a temperatura finita. è inoltre riportato un confronto con risultati ottenuti aT=0 nel limite simmetrico.

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Резуме Вводится диаграммный метод для рассмотрения модели Андерсона. Предложенная техника применяется для исследоваия явлений хемосорбции. При конечных температурах вычисляется плотность состояний электронов адатома. Проводится сравнение с результатами, полученными в симметричном пределе приT=0.

     

Phase diagram and deformed phase separation for a trapped Fermi gas with population imbalance and BCS pairing interaction

We study the phase separated state of an ultracold atomic Fermi gas confined in a three-dimensional quantum harmonic trap with a BCS pairing interaction. Examining various finite-temperature phase diagrams, we investigate the interplay between the filling of the quantum trap energy levels and the pairing energy. We find that a low (high) filling leads to a large (small) critical population imbalance for the superfluid/normal transition, together with a fully (partially) polarized normal part. We also show that the decrease of the density leads to a changeover of the shape of the superfluid core from an equipotential form to a deformed one. Moreover, we clarify the intrinsic mechanisms that lead to the deformation, providing a unified scenario for phase separation and deformation in a trapped Fermi gas, allowing for a possible interpretation of the apparently controversial experimental findings.