Showing papers by "University of Paderborn published in 1985"

How to Find Long Paths Efficiently

Abstract: We study the complexity of finding long paths in directed or undirected graphs, Given a graph G =(V, E) and a number k our algorithm decides within time O(K! · |V| · |E|) for all u,v ɛ V Whether there exists some path of length k firm u to v. The complexity of this algorithm has to be compared with 0(|V| k−1 · |E|) Which is the worst case behaviour of the algorithms described up to now in the literature, We get similar results for the problems of finding a longest path, a cycle of length k or a longest cycle, respectively. Our approach is based on the idea of representing certain families of sets by subfamilies of small cardiality. We also discuss the border lines of this idea.

Trade Unions as Intermediary Organizations

Abstract: In advanced capitalist societies trade unions are under structural constraints to pursue a policy of intermediation between the opposing interests of labour and capital. The article traces the historical lines of the evolution from 'classical' to 'intermediary' unionism, especially in regard to union structure, interest representation at plant and industry level, institutionalization of class conflict and union involvement in economic policy (section I). A typology of unionism is introduced and three variants of intermediary union policies are described (section II). Finally, the internal processes of intermediary unions are analysed in terms of prerequisites of collective actions, selective processes in interest representation, alternative and complementary agencies to unions (section III).

Theory of indirect hyperfine interactions of oxygen-aluminum defects in ionic crystals.

Abstract: Aluminum hyperfine interactions of the ${\mathrm{Al}}^{3+}$--${\mathrm{O}}^{\mathrm{\ensuremath{-}}}$-trapped-hole center in a number of oxides containing Al ions either as a constituent (${\mathrm{Al}}_{2}$${\mathrm{O}}_{3}$:${\mathrm{Mg}}^{2+}$, Na \ensuremath{\beta}-alumina) or as an impurity (${\mathrm{GeO}}_{2}$, ${\mathrm{SiO}}_{2}$) are analyzed with use of a semiempirical model of the exchange polarization mechanism of transferred hyperfine interactions. The theory quantitatively predicts the observed strong dependence of the negative isotropic hyperfine constant on the ${\mathrm{O}}^{\mathrm{\ensuremath{-}}}$-${\mathrm{Al}}^{3+}$ distance and, from estimates of the electrostatic-crystal-field energy at ${\mathrm{O}}^{\mathrm{\ensuremath{-}}}$, indicates a reasonable outward expansion (\ensuremath{\sim}10%) of the ${\mathrm{Al}}^{3+}$ ions next to the ${\mathrm{O}}^{\mathrm{\ensuremath{-}}}$ hole center. The theory also accounts well for the observation that the anisotropic hyperfine constants in these centers vary only slightly despite the large variation in the corresponding isotropic splittings.

Facile synthesis of 2'-deoxyribofuranosides of allopurinol and 4-amino-1H-pyrazolo[3,4-d]pyrimidine via phase-transfer glycosylation

Abstract: Phase-transfer glycosylation of 4-methoxy-1H-pyrazolo[3,4-d]pyrimidine with the 2-deoxyribofuranosyl chloride 9 formed the N(1)-β-nucleoside 10a as main product (39%). As by-products the α-D-anomer 11a (7%) and the N(2)-isomer 12a (18%) were isolated. Assignment of these isomers was made on the basis of their 1H- and 13C-NMR spectra. Removal of the sugar-protecting groups yielded the 4-methoxy-nucleosides 10b, 11b, and 12b, respectively. Nucleophilic displacement of the 4-MeO-group gave the 2-deoxyribofuranosides 1–4 of allopurinol and 4-amino-1H-pyrazolo[3,4-d]pyrimidine.

Design of an active suspension for a passenger vehicle model using input processes with time delays

Abstract: SUMMARY In vehicles with traditional passive suspension, the spring and damping elements between car body and axles have a fixed characteristic. This means that when the suspension is adjusted, a compromise between comfort and safety has to be arrived at. With active suspension, on the other hand, both these criteria can be enhanced at the same time. Moreover, further improvements in driving behaviour can be made which are not possible with passive suspension. In this case, the time delay between front and rear axle excitation is represented by a fade approximation, which means that linear controller design methods in the state space (Riccati controller, Kalman filter) can be used to implement active vehicle suspension. A spatial model of a medium-range passenger vehicle is augmented by a disturbance model (stochastic dual track excitation of the road surface with excitation delay time, if need be with irregularity sensors), a perception filter (weighting of human sensitivity to vibration) and a filter fo...

Similarity Solutions of the Euler Equation and the Navier-Stokes Equation in Two Space Dimensions

Abstract: With the help of the continuous symmetries of the Euler equations and the Navier-Stokes equations, respectively, we derive similarity solutions of these equations for two space dimensions. We show that all group theoretical reductions lead to linear nonautonomous or linear autonomous ordinary differential equations for incompressible fluids.

Cyclic nucleotide specificity of the activator and catalytic sites of a cGMP‐stimulated cGMP phosphodiesterase from Dictyostelium discoideum

Abstract: The cellular slime mold Dictyostelium discoideum has an intracellular phosphodiesterase which specifically hydrolyzes cGMP. The enzyme is activated by low cGMP concentrations, and is involved in the reduction of chemoattractant-mediated elevations of cGMP levels. The interaction of 20 cGMP derivatives with the activator site and with the catalytic site of the enzyme has been investigated. Binding of cGMP to the activator site is strongly reduced (more than 80-fold) if cGMP is no longer able to form a hydrogen bond at N2H2 or O2'H. Modifications at N7, C8, O3' and O5' induce only a small reduction of binding affinity. A cyclic phosphate structure, as well as a negatively charged oxygen atom at phosphorus, are essential to obtain activation of the enzyme. Substitution of the axial exocyclic oxygen atom by sulphur is tolerated; modification of the equatorial oxygen atom reduces the binding activity of cGMP to the activator site by 90-fold. Binding of cGMP to the catalytic site is strongly reduced if cGMP is modified at N1H, C6O, C8 and O3', while modifications at N2H2, N3, N7, O2'H, and O5' have minor effects. Both exocyclic oxygen atoms are important to obtain binding of cGMP to the catalytic site. The results indicate that activation of the enzyme by cGMP and hydrolysis of cGMP occur at different sites of the enzyme. cGMP is recognized at these sites by different types of molecular interaction between cGMP and the protein. cGMP derivatives at concentrations which saturate the activator site do not induce the same degree of activation of the enzyme (activation 2.3-6.6-fold). The binding affinities of the analogues for the activator site and their maximal activation are not correlated. Our results suggest that the enzyme is activated because cGMP bound to the activator site stabilizes a state of the enzyme which has a higher affinity for cGMP at the catalytic site.

Integrability of dynamical systems and the singular-point analysis

Abstract: Various aspects of the integrability of dynamical systems are discussed with the help of the singular point analysis. In particular the connection with the Painleve property is described. Several examples will serve as illustrations.

Master Symmetries and Similarity Equations of the XYh Model

Abstract: On deduit des symetries principales du modele XYh et on les utilise pour etablir une equation matricielle aux differences de similitude

Direktsynthese von orthometallierten Ketonen des Typs RCO (o‐C6H4)Mn(CO)4−nLn (R = Alkyl‐ und Arylrest, n = 0, 1, 2, L = Ligand)

Abstract: Verbindungen vom Typ RMn(CO)5−nLn und (C6H5)2 Hg setzen sich zu Produkten des Typs RCO(o-C6H4)Mn(CO)4−nLn[n = 0, R = Ch3, C2H5, C3H7, C6H5,CH2; R = C6H5, n = 1, L = E(C6H5)3, E = P, As, Sb; R = C6H5, n = 2, L = P(OR′)3, R′ = C6H5, CH3, C2H5, C3H7] um. Fur die Reaktanden werden Teilschritte fur ihren komplexen Reaktionsablauf vorgeschlagen. Die Charakterisierung der Orthometallierungsprodukte erfolgt durch 1H-NMR-, IR- und UV-spektroskopische Mesergebnisse. Die Resultate der Einkristall-Rontgenstrukturbestimmungen von den beiden Verbindungen RCO(o-C6H4)Mn(CO)3L [R = C2H5, L = CO; R = C6H5, L = As(C6H5)3] zeigen, das sie als zentrales Molekulfragment jeweils einen planaren heterozyklischen Funfring besitzen. Direct Synthesis of Orthometallated Ketones of the Type RCO(o-C6H4)Mn(CO)4−nLn (R = Alkyl and Aryl Groups, n = 0, 1, 2, L = Ligand) The starting materials of the type RMn(CO)5−nLn und (C6H5)2 Hg react to the products of the type RCO(o-C6H4)Mn(CO)4−nLn[n = 0, R = Ch3, C2H5, C3H7, C6H5,CH2; R = C6H5, n = 1, L = E(C6H5)3, E = P, As, Sb; R = C6H5, n = 2, L = P(OR′)3, R′ = C6H5, CH3, C2H5, C3H7]. Steps of their complex reaction pathway are proposed. These orthometallated substances have been characterized by means of 1H-n.m.r., i.r. and u.v. spectroscopic measurements. The determination of the molecular structure of the two compounds RCO(o-C6H4)Mn(CO)3L [R = C2H5, L = CO; R = C6H5, L = As(C6H5)3] show that both contain a planar heterocyclic five-membered ring of the type .

A Nonlinear Derivative Schroedinger-Equation: Its Bi-Hamilton Structures, Their Inverses, Nonlocal Symmetries and Mastersymmetries

Abstract: On etudie la formulation bi-hamiltonienne pour l'equation de schrodinger non lineaire derivee. Les operateurs symplectiques et implectiques peuvent etre inverses explicitement en donnant une hierarchie de Lax de transformations de symetrie locales et non locales et des lois de conservation. On construit une suite infinie de symetries principales pour cette hierarchie

Biotin Deficiency and Biotin Supply

Abstract: The requirement and the supply of biotin for man and animal are fairly uncertain up to now. There are two main reasons for this inadequate knowledge. Firstly, a spontaneous outbreak of biotin deficiency with clinical signs in humans and mammals has never been observed.6 As far as clinical symptoms were visible, whether induced by an egg-white diet or due to therapy with antibiotics or incomplete parenteral nutrition, the symptoms were not very specific. Often these symptoms resembled those resulting from a deficiency of pantothenic acid or of zinc.I6 On the other hand, biotin is the only essential nutrient, except vitamin K (the menaquinones), being assumed that the enteral microflora of mammals supplies the host to a remarkable extent with this nutrient. However, it is still doubtful to what extent the daily requirement is covered by the enteral synthesis. Therefore, it is not surprising that some authors deny the essential character of biotin. In their opinion, the gut microflora are able to meet completely the daily demand of the host organism for biotin. Others deny the significant contribution of enteral synthesis to the host’s requirements. Nevertheless, if the enteral biotin production is insufficient, as for instance in poultry, there will be an enhanced need for the alimentary supply of biotin. There is also a twofold risk for newborn infants being suboptimally supplied with this vitamin:

The Second Economy in the Soviet Union and its Implications for Economic Policy

Abstract: A survey of the activities of the second economy in the Soviet Union and its causes is given. The impact of the second economy for Soviet economic performance is analysed with respect to the supply of consumer goods, the input of labor, the functioning of the planning mechanism, the distribution of income, and the moral and politicalideological implications. The second economy appears to have positive impacts with respect to increasing consumer goods, to improving plan coordination and the flexibility of the official planning mechanism. On the other hand it loosens the planners’ control, leads to an active role of money and weakens socialist ethics. On balance, the second economy has a stabilizing impact on the economy which works to the benefit of the Soviet leadership and which leads to a certain toleration of this phenomenon.

Nonlinear Diffusion Equations, Integrability and the Painlevé Property

Abstract: The Painleve property for nonlinear diffusion equations is investigated. The results are compared with other approaches for testing the integrability of nonlinear field equations.

Relativistic field equations and the Painlevé test

Abstract: The Painleve test for classes of relativistic field equations is performed. The connection with the complete integrability is discussed.

Phosphoramidites of Chiral (Rp)-and (Sp)-Configurated d(T[P-18O]-A): Synthesis, Configurational Assignment, and Use as Dimer Blocks in Oligonucleotide Synthesis

Abstract: The N,N-diisopropylphosphoramidites 10a and 10b of appropriately protected chiral diastereoisomers of d(T[P-18O]-A) (8a and 8b, resp.), chiral by virtue of the isotope 18O at the P-atom, have been synthesized. The 18O-isotope was incorporated by oxidation of the phosphite triester 3 with H2[18O]/I2. Separation of the diastereoisomers was accomplished by flash chromatography of the O-3′-deprotected phosphate triesters 5a/b. The absolute configuration at the chiral P-atom was deduced from the methylation products of the fully deprotected diastereoisomers 8a and 8b. Phosphinylation of 5a and 5b yielded the configurationally pure phosphoramidites 10a and 10b, respectively, which were then employed in solid-phase synthesis to yield the self-complementary oligomers d(G-A-G-T-(Rp)-[P-18O]-A-C-T-C) (13) and d(G-A-G-T-(SP)-[P-18O]-A-C-T-C) (14), respectively.

Microscopic Identification of Anion Antisite Defects in GaAs by Optically Detected Magnetic Resonance

Abstract: Anion antisite defects in GaAs have been identified so far by their electron spin resonance (ESR) spectrum as one specific point defect, which was found in as-grown, plastically deformed and electron and neutron irradiated GaAs. By optical detection of electron nuclear double resonance (ODENDOR), it could be shown that several species of anion antisite defects exist having practically the same ESR spectrum, which cannot any longer be taken as “fingerprint” identification for this defect. Recent results of ODESR and ODENDOR investigations in as-grown, plastically deformed and electron irradiated GaAs are reviewed. It is also pointed out that the spin lattice relaxation time is an important quantity for the microscopic identification and the properties of anion antisite defects.

Mastersymmetries for completely integrable systems in statistical mechanics

Abstract: For dynamical systems,mastersymmetries are a useful tool to construct conservation laws and symmetry groups. They have first been discovered in the case of the Benjamin-Ono equation I and the Kadomtsew Petviashvili equation2.They exist for almost all the popular completely integrable systems 3 and recently they have been studied on a systematic basis 4,5 . We give the relevant definitions in the abstract case of an arbitrary Lie-algebra L , this is suitable for all the situations we have in mind. Let L 1 be a sub-Lie-algebra of L . Recall that a map d : L 1 ~ L is said to be a derivation (on L 1) if.

Transport in hydrogenated amorphous germanium

Abstract: In contrast to the case of a-Si:H the density of dangling bond states in a-Ge:H is higher by at least one order of magnitude and, therefore, less sensitive to the doping level. The density of states distribution for a-Ge:H is derived from Spin densities published by the Marburg group. This distribution in turn is used for the interpretation of the transport data at different doping levels. The high density of charged D + (D − ) centers in p-type (n-type) material gives rise to a significant longranged potential. This manifests itself by a rather high E Q value even for undoped material.