Fractal dimension,attractors, and the boussinesq approximation in three dimensions

The Boussinesq approximation, where the viscosity depends polynomially on the shear rate, finds more and more frequent use in geological practice. In the paper, this modified Boussinesq approximation is investigated as a dynamical system for which the existence of a global attractor is proved. Finally, a new criterion for estimating the fractal dimension of invariant sets is formulated and its application to the problem under consideration is illustrated.     

A weak approach to finite elasticity

On the ground of four axioms we define thekinematics of perfectly elastic bodies and in particular the notion ofweak deformations of a perfectly elastic body. Weak deformations turn out to agree withweak diffeomorphisms introduced in [10], a class of rectifiable currents which enjoys good closure and compactness properties. Defining thedynamics of perfectly elastic bodies in terms of twoconstitutive conditions on the stored energy function, we can therefore prove existence of stable equilibrium weak deformations for mixed boundary value problems, which moreover satisfy equilibrium and conservation equations.This work has been partially supported by the Ministero dell'Universitá e della Ricerca Scientifica, by C.N.R. contract n. 91.01343.CT01, by the European Research Project GADGET, and by Grant n.11957 of the zech Acad. of Sciences.This article was processed by the author using the LaT_EX style filepljour1 from Springer-Verlag.     

Bell-type inequalities in horizontal sums of Boolean algebras

We give a necessary and sufficient condition for a Bell-type inequality to hold in a horizontal sum of finitely many finite Boolean algebras.     

Difference posets,effects, and quantum measurements

Difference posets as generalizations of quantum logics, orthoalgebras, and effects are studied. Observables and measures generalizing normalized POV-measures and generalized measures on sets of effects are introduced. Characterization of orthomodularity of subsets of a difference poset in terms of triangle closedness and regularity of these subsets enables us to characterize observables with a Boolean range. Boolean powers of difference posets are investigated; they have similar properties to that of tensor products, and their connection with quantum measurements is studied.     

Oxygen incorporation in polyethylene implanted with 150 keV Sb+ ions

Samples of polyethylene (PE) loaded with carbon black up to 8 wt.% and implanted with 150 keV Sb⁺ ions to the doses from 2×10¹³–2×10¹⁵ cm^–2 were studied using standard Rutherford Back Scattering (RBS) technique. On the PE samples implanted to the doses above 2×10¹⁴ cm^–2, a considerable surface carbonization is observed. The measured parameters of the Sb depth profile are compared with theoretical TRIM estimations. The projected range is by 25% lower than the theoretical one and the range straggling is about twice of that predicted. The differences are explained by stepwise polymer degradation during the ion bombardment. Strong oxidation of the ion implanted polymers is also observed. The oxygen depth profiles from the sample surface up to the depth comparable with Sb⁺ ion range evolve from nearly uniform one for low ion doses to highly non-uniform one for doses above 1×10¹⁵ cm^–2. The total oxygen content in the sample surface layer 300 nm thick reaches a maximum for the doses of (1–2)×10¹⁴ cm^–2.On leave from Belorussian State University, 220050 Minsk, Belarus.The authors thank the member of electrostatic accelerator group at INP for help during RBS measurements. The work was partly (V.H. and J.K.) supported by the Internal Grant Agency of the Academy of Sciences of Czech Republic under the grant No. 14805 and by the Internal Grant Agency of the Ministry of Education of Czech Republic under the grant No. 1002 (V.., V.R., V.H. and J.K.). In the final stage, the work was also supported by the Grant Agency of Czech Republic under the grant No. 202/93/0121.     

Iron sites in greigite from the “Cypris series”

Results of the⁵⁷Fe Mössbauer spectroscopy of greigite from the greigite-rich horizon of the middle part of the miocene series (Sokolov Basin, North Bohemia) are reported. From the room-temperature transmission spectra of the powdered samples magnetically separated from claystones, the Mössbauer analyses were performed. Relative abundances of various magnetic and non-magnetic Fe²⁺ and Fe³⁺ species led to the identification of the two magnetic iron sites in greigite in accordance with its spinel structure having mutually near effective magnetic inductions of 32.1 and 31.3 T, respectively. In addition, three pyrrhotite and two magnetite magnetic sites plus probably two pyrite and/or arsenopyrite iron positions were identified, of which some have been reported in the literature as the greigite iron contributions.     

Influence of oxygen concentration on optical properties of semi-insulating polycrystalline silicon films

Optical properties of semi-insulating polycrystalline silicon (SIPOS) films were investigated over the wide region of wavelengths. The vibrational modes of Si-O-Si and Si-Si bonds were studied by IR and Raman spectroscopy. A pronounced effect of oxygen content on the measured spectra was observed. Optical constants of SIPOS films have been compared with those of amorphous silicon and glassy silicon dioxide and their values have been successfully interpreted in terms of the theory of effective medium. The results have shown that the amorphous character prevails in the as-deposited SIPOS films.     

Topologically nontrivial field configurations in noncommutative geometry

In the framework of noncommutative geometry we describe spinor fields with nonvanishing winding number on a truncated (fuzzy) sphere. The corresponding field theory actions conserve all basic symmetries of the standard commutative version (space isometries and global chiral symmetry), but due to the noncommutativity of the space the fields are regularized and they contain only a finite number of modes.Part of the Project P8916-PHY of the Fonds zur Förderung der wissenschaftlichen Forschung in Österreich.     

The axial dependence of the cathode current density in the longitudinal hollow cathode discharge

In the present paper the axial dependence of the cathode current distribution in the longitudinal hollow cathode discharge is investigated. On the basis of experimental results the model of the longitudinal hollow cathode discharge is developed and axial distribution of the cathode current is discussed.This work has been done in the frame of the Association for Education, Research and Application in Plasma-Chemical Processes and has been partially financially supported by Nos. 202/93/0659 and 202/95/1222 grants of Grant Agency of the Czech Republic. The main results have been presented as a poster on 10th Symposium on Elementary Processes and Chemical Reaction in Low Temperature Plasma, Stará Lesná (Slovakia), 1994.     

Resonances in low-energy rare-gas atom scattering

Precise values of energies and widths of low-lying resonances in some rare-gas atom systems (Ar-Ar, Ne-Kr, Ne-Xe) are reported.