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  • 1
    Electronic Resource
    Electronic Resource
    Performance Rating via the Feast Indices (1999)
    Springer
    Computing 63 (1999), S. 283-297 
    Details
    ISSN: 1436-5057
    Keywords: AMS Subject Classifications:65Y20, 65N22, 65M55, 65M60. ; Key words.Benchmarking, Numerical Linear Algebra, multigrid, finite elements.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract. Based on algorithmic and computational studies, we present the Feast Indices which are new indicators for the realistic performance of many recent processors, as typically used in ‘low cost’ PC's/workstations up to (parallel) supercomputers. Since these tests are very specifically designed for the evaluation of modern numerical simulation techniques, with a special emphasis on `large scale' FEM computations and iterative solvers of Krylov-space/multigrid type, they examine new aspects in comparison to the standard benchmark tests (LINPACK, SPEC FP95, NAS, STREAM) and allow new qualitative and particularly quantitative ratings of the various hardware platforms. We explore the computational efficiency of certain Linear Algebra components, hereby applying the typical sparse approaches and additionally the sparse banded style from Feast which enables us to exploit a significant percentage of the available Peak performance. The tests include ‘simple’ matrix-vector applications as well as complete multigrid solvers with very robust smoothers which are necessary for the efficient treatment of highly adapted meshes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s006070050035
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  • 2
    Electronic Resource
    Electronic Resource
    The formation of HCN during the reduction of NO by isobutane over Fe‐MFI made by solid‐state ion exchange (1999)
    Springer
    Catalysis letters 63 (1999), S. 214-244 
    Details
    ISSN: 1572-879X
    Keywords: hydrogen cyanide ; NO reduction ; isobutane ; Fe‐MFI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract FTIR analysis of the gaseous products of the selective catalytic reduction of NO by isobutane over a Fe‐MFI catalyst made by solid‐state ion exchange shows, for the first time, that HCN can be a substantial product. Under dry conditions the amounts formed can exceed that of N2 for temperatures up to 280°C and NO conversions of 25% with a maximum HCN concentration of∼150 ppm formed at 315°C. However, introduction of 0.7% water causes the subsequent conversion of about one‐half the HCN to N2, probably through hydrolysis to NH3 and the NH3‐SCR reaction which is very rapid on Fe‐MFI. The steps through which HCN forms remain to be established.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019029307571
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  • 3
    Electronic Resource
    Electronic Resource
    Simultaneous catalytic reduction of NO and N2O using Fe-MFI prepared by solid-state ion exchange (1998)
    Springer
    Catalysis letters 51 (1998), S. 23-25 
    Details
    ISSN: 1572-879X
    Keywords: nitrous oxide ; nitric oxide ; reduction ; propane ; Fe-MFI ; platinum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Solid-state ion exchange in the presence of air has been used to prepare Fe-MFI catalysts that exhibit activities comparable to preparations obtained under anaerobic conditions. Preliminary results obtained during the simultaneous catalytic reduction of NO and N2O with propane in the temperature range from 473 to 773 K show that Fe-MFI might be of interest for the treatment of exhaust gases containing NOx and nitrous oxide. Undesirable CO formed in a side-reaction can be oxidized to CO2 by promotion of Fe-MFI with small amounts of Pt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019049420697
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  • 4
    Electronic Resource
    Electronic Resource
    A generalized mean intensity approach for the numerical solution of the radiative transfer equation (1995)
    Springer
    Computing 54 (1995), S. 27-38 
    Details
    ISSN: 1436-5057
    Keywords: Radiative transfer equation ; mean intensity ; nonsymmetric CG-variants ; astrophysics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung In [7] führten wir einen allgemeinen Zugang zur numerischen Lösung der (linearen) Strahlungstransportgleichung ein, der aber zu sehr hoch dimensionierten Gleichungssystemen führte. Indem wir das Konzept der verallgemeinerten mittleren Intensität verwenden, kann die Dimension drastisch verringert werden, ohne dabei Information zu verlieren. Darüberhinaus werden die Systemmatrizen unter geeigneten Bedingungen an die Wahl der diskreten Ordinaten positiv definit, und das klassische konjugierte Gradientenverfahren (CG) führt zu Konvergenz. In Verbindung mit lokalen Vorkonditionierungstechniken können wir robuste und effiziente Methoden von konjugierten Gradiententyp konstruieren, die sich bei gleichem numerischen Aufwand der klassischen approximativen Λ-Iteration als überlegen erweisen. In numerischen Tests, die den astrophysikalisch interessanten Fall von Sternstrahlung in Staubwolken simulieren, vergleichen wir die verschiedenen hergeleiteten Methoden und geben Beispiele für ihre numerische Effizienz.
    Notes: Abstract In [7] we proposed a general numerical approach to the (linear) radiative transfer equation which resulted in a high-dimensional linear system of equations. Using the concept of the generalized mean intensity, the dimension of the system can be drastically diminished, without losing any information. Additionally, the corresponding system matrices are positive definite under appropriate conditions on the choice of the discrete ordinates and, therefore, the classical conjugate gradient-iteration (CG) is converging. In connection with local preconditioners, we develop robust and efficient methods of conjugate gradient type which are superior to the classical approximate Λ-iteration, but with about the same numerical effort. For some numerical tests, which simulate the astrophysically interesting case of radiation of stars in dust clouds, we compare the methods derived and give some examples for their efficiency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02238078
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  • 5
    Electronic Resource
    Electronic Resource
    Preparation and Thermal Decomposition of Copper(II) Complexes with 4-Methylimidazole (1998)
    Springer
    Journal of thermal analysis and calorimetry 54 (1998), S. 133-137 
    Details
    ISSN: 1572-8943
    Keywords: copper(II) compounds ; 4-methylimidazole complexes of copper(II) ; mono(o-hydroxy-benzaldoxime) of Cu(II) ; mono(o-hydroxy-benzoate) of Cu(II) ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Simple and mixed compounds of the formulae Cu(4-Meim)2, CuSal(4-Meim), CuSal(4-Meim)2 and CuSalox(4-Meim)2, where 4-Meim=4-methylimidazole, Sal=(OC6H4COO)2−, Salox=(OC6H4CHNO)2− have been prepared. Thermal decomposition reactions have been established on the basis of thermal and X-ray analyses of these compounds. The pyrolysis proceeds in several (3–4) stages connected with the mass loss and exothermic effects. As a result of the last stage of decomposition CuO is formed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010121003321
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  • 6
    Electronic Resource
    Electronic Resource
    Explosivstoffe (1934)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 99 (1934), S. 377-381 
    Details
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01366407
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  • 7
    Electronic Resource
    Electronic Resource
    Ab-initio theory of the CPP-magnetoconductance (1999)
    Springer
    Czechoslovak journal of physics 49 (1999), S. 1583-1589 
    Details
    ISSN: 1572-9486
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The current-perpendicular-to-plane (CPP) magnetoconductance of a trilayer consisting of a spacer sandwiched between two ideal leads is described on an ab initio level. We employ the transmission matrix formulation of the conductance within the framework of the spin-polarized surface Green function technique as formulated in terms of the tight-binding linear muffin-tin orbital method. The formalism is extended to the case of lateral supercells in each layer with random arrangements of atoms which allows to treat both the ballistic and diffusive transports on equal footing. The application is made to fcc-based Co/Cu/Co(001) trilayers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022871831961
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  • 8
    Electronic Resource
    Electronic Resource
    Stability and magnetism of ultrathin Cr films on a Fe(001) substrate (1999)
    Springer
    Czechoslovak journal of physics 49 (1999), S. 1639-1644 
    Details
    ISSN: 1572-9486
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Itinerant magnetism of ultrathin epitaxial Cr overlayers on a Fe(001) substrate and their energy stability with respect to Cr–Fe interdiffusion were studied by means of ab initio electronic structure calculations. The latter were based on the tight-binding linear muffin-tin orbital method and the coherent potential approximation. The interdiffusion was simulated by two-dimensional substitutionally disordered Cr–Fe alloys formed within two layers at the Cr/Fe interface. For a 1 monolayer Cr film a tendency to surface alloy formation is found in contrast to a 2 monolayer Cr film which seems to be stable with respect to Fe–Cr intermixing. A comparison of the calculated results to recent experimental data is presented and an interplay between the energy stability and magnetism of the films is pointed out.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022888302827
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  • 9
    Electronic Resource
    Electronic Resource
    Etiology of ovarian dysfunction in chronic murine toxoplasmosis (1995)
    Springer
    Parasitology research 81 (1995), S. 114-120 
    Details
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Ovarian dysfunction develops in Nya:NYLAR mice chronically infected withToxoplasma gondii. To differentiate between primary ovarian failure and pituitary gonadotropin insufficiency, we (a) monitored ovarian responsiveness to pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG) and (b) assessed endogenous pituitary gonadotropin capacity by the degree of ovarian compensatory hypertrophy (OCH) developing after unilateral ovariectomy (ULO). PMSG stimulated vigorous folliculogenesis and estrogen synthesis, but not ovulation. HCG given 3 days after PMSG induced “superovulation” within 16 h. These observations indicate the absence of the critical preovulatory surge of endogenous luteinizing hormone (LH) from the pituitary. In addition, ULO did not result in compensatory hypertrophy of the contralateral ovary, an indication of follicle-stimulating hormone (FSH) insufficiency. We hypothesize that cytokines released peripherally in response to the parasite reached the hypothalamus and initiated a sequence of events that inhibited the pulsatile release of gonadotropin-releasing hormone (GnRH), leading to the subsequent impairment of the pituitary-ovarian axis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00931615
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  • 10
    Electronic Resource
    Electronic Resource
    The Occurrence of Metals in Composted Municipal Wastes and Their Removal (1999)
    Springer
    Water, air & soil pollution 111 (1999), S. 159-170 
    Details
    ISSN: 1573-2932
    Keywords: composting ; heavy metals ; municipal solid wastes ; sequential extraction ; speciation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The organic fraction of municipal wastes has been composted on the laboratory scale. In the obtained compost the content of cadmium, cobalt, copper, manganese, nickel, lead and zinc were determined, as well as the speciation i.e, the form of their occurrence, making use of Rudd's method of sequential extraction. The investigations also concerned the way of removing these metals from the compost by means of leaching with solutions of sulphuric and nitric acid, as well as by electrochemically separating the metals from the solution after the compost had been leached with sulphuric acid. It has been found that the application of the electrochemical method with varying pH values of the leaching solution within the range of 6.8–2.8 allows for the separation of 83.5% Cd, 55.0% Co, 65.4% Cu, 59.4% Mn, 70.3% Ni, 90.5% Pb and 56.2% Zn.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005029532602
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