Generation of Complex Metal Oxides by Aerosol Processes: Superconducting Ceramic Particles and Films

Complex metal oxides, including ferroelectric, ferrimagnetic and superconducting ceramics, have a variety of technologically useful properties that can be exploited for a number of applications. Fabrication of complex metal oxides ceramics with specific properties reqires high-purity powders with controlled chemical compositions, size distributions, and morphologies. Powders with these characteristics can be produced by aerosol processes in which fine particles are generated in gaseous flow systems. The particles can also be deposited from the gas phase onto surfaces to form films. This paper will discuss the use of aerosol processes for the generation of complex metal oxide powders. A review of aerosol processes will be presented first, followed by a discussion of the methods used for the generation of superconducting ceramic powders. Examples include the production of YBa₂Cu₃O₇, La_1.85Sr_0.15CuO₄, and Tl-Ca-Ba-Cu-O powders and films. Emphasis will be placed on defining the conditions required for the generation of chemically homogeneous particles with controlled morphologies.     

Abschnittspositive Matrizen und Positivitätsfaktoren in der Limitierungstheorie

Let A and B be normal matrices. In :={x=(x_k) ¦ x_k} we define the order relation _A by x_A0:<=> _k=0 ⁿ a_nkx_k0 (n ). Let T be a row-finite matrix. A is called T-section-positive, if _kt_mkx_ke^(k) _A0 (m ) for x_A0 (see [5]). We study the relation between T-sectional positivity and T-sectional boundedness. An (A,B)-summability factor sequence =(_k) is called positive, if (_kx_k)_B0 for each xc_A with x_A0. For B-section-positive matrices A we give a functional analytic characterization of positive (A,B)-summability factor sequences.

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Die Arbeit entstand während eines vom DAAD unterstützten Forschungsaufenthalts an der Fernuniversität-Gesamthochschule Hagen     

Determination of wear metals in lubrication oils: a comparison study of ICP-OES and FAAS.

Certain wear metals (Fe, Cr, Ni, Cu and Zn) of various lubrication oils were determined by means of ICP-OES and FAAS. The kerosene dilution method, which is used widely together with ICP-OES, was applied with both methods here. Calibration standards were made from a commercial organo-metallic standard. Our aim was to clarify the possibility of using the quick kerosene dilution method together with FAAS for a rapid check for certain indicator metals. Metal determinations with FAAS were accurate enough for quantitative work in machine condition diagnostics and waste oil characterization, when compared with those with ICP-OES.     

Sequences of 0’s and 1’s: Special sequence spaces with the separable Hahn property

As pointed out in [4] the paper [2], authored by G. Bennett, J. Boos and T. Leiger, contains a nontrivial gap in the argumentation of the proof of Theorem 5.2 which is one of main results of that paper and has been applied three times. Till now neither the gap is closed nor a counterexample has been stated. That is why the authors have examined in [4] the situation around the ‘gap’ aiming to a better understanding for the gap. The aim of this paper is to prove the mentioned applications of the theorem in doubt by using gliding hump arguments (quite similar to the classical proofs of the Theorems of Schur and Hahn in the first case (cf. [3]) and a very technical and artful construction, being of independent mathematical interest, in the second case). Research of T. Leiger supported by Estonian Science Foundation Grant 5376.     

Isolation and determination of alizarin in cell cultures of Rubia tinctorum and emodin in Dermocybe sanguinea using solid-phase extraction and high-performance liquid chromatography

A high-performance liquid chromatographic method was developed for the determination of the non-glycosidic anthraquinones alizarin (1,2-dihydroxy-9,10-anthracenedione), emodin (1,3,8-trihydroxy-6-methyl-9,10-anthracenedione) and anthraquinone (9,10-anthracenedione). The anthraquinones were separated by isocratic elution on a 125 × 4.6 mm I.D. column containing ODS Hypersil 5 reversed-phase material using methanol-5% acetic acid (pH 3.0) (70:30) as the mobile phase. Free alizarin was determined in plant cell suspension cultures of Rubia tinctorum and free emodin in mushrooms (Dermocybe sanguinea). The effective extraction of anthraquinones from plant cells was achieved with 80% (v/v) ethanol after incubation for 10 h at 80°C. Prepurification and concentration of anthraquinones in the plant cell and mushroom extracts were effected by a solid-phase technique using C₈ cartridges.     

‘Duality’ of the Nikodym property and the Hahn property: Densities defined by sequences of matrices

The authors investigated in Boos and Leiger (2008) [5] the ‘duality’ of the Nikodym property (NP) of the set of all null sets of the density defined by any nonnegative matrix and the Hahn property (HP) of the strong null domain of it. In this paper, the investigation of the intimated duality is continued by considering densities defined by sequences of nonnegative matrices. These considerations are motivated by the known result that the ideal of the null sets of the uniform density has NP. In this context the general notion of S-convergence of double sequences (cf. Drewnowski, 2002 [8]) containing Pringsheim convergence, Hardy convergence and uniform convergence of double sequences is used.     

Sequence Spaces with Oscillating Properties

In this note we consider various types of oscillating properties for a sequence spaceEbeing motivated by an oscillating property introduced by Snyder and by recent papers dealing with theorems of Mazur–Orlicz type and gliding hump properties. Our main tools, two summability theorems, allow us to identify two such oscillating properties for a sequence spaceEone of which provides a sufficient condition forEFto implyEW_Fwhile the other affords a sufficient condition forEFto implyES_F. HereFis anyL-space, a class of spaces which includes the class of separable FK-spaces,S_Fdenotes the elements ofFhaving sectional convergence, andW_Fdenotes the elements ofFhaving weak sectional convergence. This, in turn, is applied to yield improvements on some other theorems of Mazur–Orlicz type and to obtain a general consistency theorem. Furthermore, combining the above observations with the work of Bennett and Kalton we obtain the first oscillating property on a sequence spaceEas a sufficient condition forE^β, the β-dual ofE, to be σ(E^β, E) sequentially complete whereas the second assures both the weak sequential completeness ofE^βand the AK-property forEwith the Mackey topology of the dual pair (E, E^β).