An inverse spectral problem

In this article an infinite periodic Jacobi matrix is under consideration. It is shown that the spectrum of the matrix consists of a single finite interval if and only if the period of the matrix is equal to unity.     

Designing risk management support systems

The major movements emerging in the field of risk analysis over the past decades are reviewed with special emphasis placed on their treatment of non-technical issues and their relevance to risk management needs. With this background, the requirements for an effective system to support risk management activities are discussed and a user-oriented design process outlined. The Ispra Risk Management Support (IRIMS) System is briefly described.Invited for presentation at the 12th Symposium on Operations Research, University of Passau, Federal Republic of Germany, September 9–12, 1987.     

Struktur und Energie von Blochlinien in dünnen ferromagnetischen Schichten

For circular Bloch lines (° of Fig. 1) in ferromagnetic thin films the structure (Fig. 2) and the energy (Fig. 5) have been calculated. The radius of the region in which the magnetization is tilted considerably out of the film plane, depends only weakly on the film thickness and has the order of 100 Å for 80/20 nickel-iron films (Fig. 4). This region is surrounded by a circularly magnetized region. The transition to the noncircular configuration of the walls and domains takes place at an essentially higher radius (Fig. 6).     

Die Hyperfeinstruktur des übergangs Ag I, λ=19372 å

The hyperfinestructure of the transition AgI, 4d ⁹ 5s ^{2 2} D _3/2-4d ¹⁰ 5p ² P _1/2,λ=19372 å has been investigated with a photoelectric recording Fabry-Perot interferometer and digital data processing. The isotope shiftδ Ν _IS and the magnetic splittings factorsA have been determined to beδ Ν _IS=35,77 (12) mK,A(¹⁰⁹Ag, 5p ² P _1/2)=?7,00 (45) mK, andA(¹⁰⁹Ag, 4d ⁹ 5s ^{2 2} D _3/2)=?12,18 (23) mK. The influence of shielding effects on the value of the volume effect of the isotope shift and the influence of core polarisation on the splitting factors are discussed.     

A chiral nitronate dianion from (=d)-glyceraldehyde. Enantiospecific syntheses of 2,3-dideoxy-3-nitro furanosides and pyranosides

A new enantiospecific protocol for the synthesis of 2,3-dideoxy-3- nitro and 3-amino sugars is reported. Chiral nitronate dianion 3, derived from (+)-(=d)-glyceraldehyde, is allylated and the resulting adduct 7 is transformed to either the methyl furanoside 9 or the methyl pyranoside 10 depending on the reaction sequence.     

Luminescence of the hydrolysis products of Th(IV)

Raising the pH of an aqueous solution of thorium nitrate results in the precipitation of a hydrated thorium oxide. At room temperature this material does not exhibit any emissive properties, but upon cooling to 77 K a strong green luminescence can be observed. The emission spectrum is fairly broad, and is characterized by an emission lifetime of 125 μs. Calcination of the hydrolysis product produces an anhydrous thorium oxide which is not luminescent at any temperature. Through the production of a series of mixed lanthanide/thorium hydrolysis products, it was established that the luminescent species was a clustered thorium compound. Sensitization of Eu(III) emission by the thorium hydrolysis product was observed.