Showing papers by "Johannes Kepler University of Linz published in 1988"
TL;DR: The ryanodine receptor of sarcoplasmic reticulum from fast-twitch skeletal muscle has been purified and found by electron microscopy to be equivalent to the feet structures, and it is concluded that the identity of the Ca2+-release channel of SR is the foot structure, which consists of an oligomer of the high molecular weight polypeptide.
Abstract: The ryanodine receptor of sarcoplasmic reticulum (SR) from fast-twitch skeletal muscle has been purified and found by electron microscopy to be equivalent to the feet structures that are involved in situ in the junctional association of transverse tubules with terminal cisternae of SR. We now find that when the purified receptor is incorporated into vesicle-derived planar bilayers, it forms Ca2+-specific channels, which are dependent on submicromolar Ca2+ for activity. In the presence of 1 mM ATP, the channel shows essentially no activity at 10 nM Ca2+ but becomes highly activated at 50 nM Ca2+. At suboptimal Ca2+ levels (100 nM), the channel is strongly activated by 1 mM ATP and can be blocked by ruthenium red, both effects being prevented by higher Ca2+ levels (1 microM). Mg2+, added from the cis side at millimolar concentrations, blocks Ca2+ flux through the channel from trans to cis (equivalent to flux from luminal to myoplasmic compartment). Ryanodine stabilizes the open state of the channel and blocks the action of ruthenium red to close the channel. Thus, the purified ryanodine receptor incorporated into a bilayer has the Ca2+-channel characteristics consistent with the calcium release observed in isolated terminal cisternae vesicles. Furthermore, ryanodine induced the appearance of a sublevel gating mode characterized by long open conductance states, which were integral multiples of the smallest observed conductance, 3.8 pS in 50 mM Ca2+. The purified receptor consists essentially of a single-sized high molecular weight polypeptide (Mr. approximately equal to 360,000), which on reconstitution forms the square rectangles diagnostic of the feet structures. We conclude that the identity of the Ca2+-release channel of SR is the foot structure, which consists of an oligomer of the high molecular weight polypeptide.
205 citations
159 citations
TL;DR: For continuous and iterative regularization methods for solving linear ill-posed problems, the authors propose an a posteriori parameter choice strategy and stopping rule that always leads to optimal convergence rates and does not require the knowledge of the smoothness of the exact solution.
93 citations
TL;DR: In this paper, the authors derived conditions under which constrained Tikhonov-regularized solutions x α, c of an ill-posed linear operator equation Tx = y converged to the best-approximate solution of the equation in C with rates o(α 1 2 ) and O( α ), respectively.
51 citations
TL;DR: Methods with minimal sample preparation are described for determination of iodide or bromide in serum, milk, salt and water.
44 citations
TL;DR: In this article, the authors summarized some recent developments in this rapidly expanding field and summarized some of the potential applications in different areas of technology and applied it in various areas of science.
Abstract: Chemical processing of materials with lasers is a new and interdisciplinary field with many already realized and potential applications in different areas of technology This overview summarizes some recent developments in this rapidly expanding field
37 citations
TL;DR: In this article, CdTe layers with a thickness of 3-15 μm were grown on (100) oriented GaAs substrates in a hot-wall-epitaxy system.
32 citations
TL;DR: In this article, a method for the synthesis of symmetrically substituted 2,2′-bipyrroles using the oxidation of α-unsubstituted pyrrole derivatives is presented together with four examples.
Abstract: A method for the synthesis of symmetrically substituted 2,2′-bipyrroles using the oxidation of α-unsubstituted pyrrole derivatives—in analogy to the oxidative coupling of phenols—is presented together with four examples. The mechanistic implications are discussed.
29 citations
TL;DR: Convergence rates are established and an a-posteriori parameter choice method is derived that leads to optimal convergence rates withrespect to data errors and with respect to the finite-dimensional subspace, without using any information about the exact solution.
Abstract: In this paper we consider a particular variant of finite-dimensional Tikhonov regularization for ill-posed operator equations. Convergence rates are established and an a-posteriori parameter choice method is derived that leads to optimal convergence rates with respect to data errors and with respect to the finite-dimensional subspace, without using any information about the exact solution. Finally, using linear splines we present several numerical examples that confirm the theoretical results.
21 citations
TL;DR: B-nor-biladienes-ac is a planar system of (4Z,9E,15Z) configuration in the crystal, whereas in solutions there are indications of a more twisted conformation at their exocyclic chromophore single bonds as discussed by the authors.
Abstract: B-Nor-biladienes-ac are prepared by oxidative coupling of dipyrrinones in nearly quantitative yields. Further oxidation of these derivatives yieldsb-nor-bilatrienes-abc. Constitutions, tautomerism, configurations at exocyclic double bonds, and conformations at exocyclic chromophore single bonds are determined for the crystalline state and their states of solution using X-ray structural analysis and spectroscopic methods, respectively.B-nor-biladienes-ac are found to be of (4Z,15Z)5sp,9sc,14sp geometry,b-nor-bilatrienes-abc are planar systems of (4Z,9E,15Z) configuration in the crystal, whereas in solutions there are indications of a more twisted conformation at their exocyclic chromophore single bonds.
20 citations
TL;DR: In the 5 K photoluminescence spectra of Fe+ implanted and subsequently annealed CdTe samples, two emission bands, peaked at 1.03 and 1.13 eV, respectively, appeared.
01 Dec 1988-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this article, a new procedure is presented for extracting the stopping power from the widths of a number of backscattering spectra, which can be applied irrespectively of the magnitude of the kinematic factor.
Abstract: A new procedure is presented for extracting the stopping power from the widths of a number of backscattering spectra. It can be applied irrespectively of the magnitude of the kinematic factor. For this method we introduce a function dependent on four parameters, the shape of which is sufficiently adaptable not to cause a relevant bias. This is demonstrated by fitting this function to the proton stopping power tables of Janni: for all 92 elements we list the fit parameters together with the mean and the maximum deviation. By computer simulation it is shown that the projectile energies in the backscattering measurements have to cover a certain range — depending on the kinematic factor — to give the correct stopping cross section. Finally, we applied this procedure to the measurement of the stopping cross section of Al for He-ions.
02 Jun 1988-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, the stopping cross sections of protons were determined by using transmission and backscattering techniques at equivalent target foils at different energy levels over the whole energy range (30 to 370 keV).
Abstract: The stopping cross sections of protons were determined by using transmission and backscattering techniques at equivalent target foils. Over the whole energy range compared (30 to 370 keV) both methods delivered the same data within ± 1%. The uncertainty in the derived cross sections amounts to ± 2%.
TL;DR: The efficiency of a production planning system (PPS) for solving the 3D cutting problem in a crepe rubber mill has been investigated in this paper, where a heuristic for the same problem is compared with the optimal solution.
TL;DR: In this paper, the laser-induced reduction of YBa2Cu3O7−x was investigated, where the oxygen content of the material was diminished by local heating under cw Kr+ laser irradiation in H2 atmosphere.
Abstract: The first investigations on the laser-induced reduction of YBa2Cu3O7−x are presented. Here, the oxygen content of the material is diminished by local heating under cw Kr+ laser irradiation in H2 atmosphere. The technique permits the superconducting properties of the material to be locally changed or destroyed. Laser-induced surface metallization may be useful for the electroding of such materials.
TL;DR: On decrit les fonctions signe ayant un nombre fini de changements de signe dependant des polynomes orthogonaux as discussed by the authors.
TL;DR: In this article, the number of atoms forming the near surface quasi-gas transition layers has been estimated based on quadrupole-mass spectroscopical (QMS) studies.
Abstract: Quadrupole-mass spectroscopical (QMS) studies on isothermal reevaporation of Cd and Te species from the CdTe (111) surface have been performed in two extreme cases. The first concerns the reevaporation of thick, bulk-like non-crystalline Cd and Te films deposited in high vacuum at room temperature on the (111) surface, whereas in the second case evaporation of the constituent species from the bare single crystalline (111) surface has been investigated. The fluxes of the species desorbing in high vacuum (10−6 Pa) have been monitored with QMS and the desorption temperatures have been measured with a thermocouple mounted as near as possible to the sample surface. The following values Ea(Cd)bulk = 1.13 ± 0.12 eV, Ea(Te)bulk = 1.64 ± 0.18 eV and Ea(Cd)(111) = 1.13 ± 0.06 eV, Ea(Te)(111) = 1.92 ± 0.13 eV of the activation energies for these two cases have been determined from the slopes of the Arrhenius plots.
Using these experimental values, the numbers of atomic bonds NCd and NTe occurring in the atomic aggregates of quasi-gas molecules forming the near surface quasi-gas transition layers have been estimated. For Cd quasi-gas molecules 2 ≤ NCd ≤ 5, whereas for Te molecules 3 ≤ NTe ≤ 10. However, no prediction concerning the number of atoms creating the quasi-gas molecules could be made on the basis of the QMS investigations.
It has also been shown that Cd atoms evaporate from the bare single crystalline CdTe (111) surface with an activation energy that is equal (in the limits of the experimental error) to the activation energy for sublimation of Cd atoms from pure, non-crystalline, bulk Cd pieces. The analogous activation energy measured for Te atoms is about 20% larger than that of the relevant sublimation process. This result confirms the fact that Te atoms are bound much stronger in the CdTe crystal lattice than Cd atoms.
TL;DR: In this paper, the bisher unbekannte Thioaurat K4Au6S5 konnte durch Umsetzung eines entsprechenden Gemenges aus Kaliumsulfid, Gold and Schwefel bei 600 °C and langsames Abkuhlen aus der Schmelze in Form of gelbgrunen Kristallen erhalten werden.
Abstract: Zusammenfassung Das bisher unbekannte Thioaurat K4Au6S5 konnte durch Umsetzung eines entsprechenden Gemenges aus Kaliumsulfid, Gold und Schwefel bei 600 °C und langsames Abkuhlen aus der Schmelze in Form von gelbgrunen Kristallen erhalten werden. Die Kristallstruktur von K4Au6S5 wurde uber Vierkreisdiffraktometerdaten bestimmt und auf einen konventionellen R-Wert von 0,037 fur 342 beobachtete Reflexe verfeinert. Als Raumgruppe ergab sich P62c mit Z = 2. Die Gitterkonstanten sind a = 9,631(3) A und c = 9,856(4) A . Als charakteristisches Strukturmerkmal treten anionische, in Richtung [001] im Muster einer hexagonal dichten Packung angeordnete [Au6S5] Baugruppen auf. In diesen bilden die Schwefelatome trigonale Bipyramiden; die Goldatome sind uber den Pyramidenkanten so angeordnet, dass trigonale Prismen entstehen. Die Schwefelkoordination der Goldatome ist nahezu linear. Die Abstande zwischen den Goldatomen sowohl innerhalb der trigonalen Prismen einer Baugruppe als auch zwischen den Baugruppen lassen schwache Wechselwirkungen zwischen den d10-konfigurierten Atomen erkennen.
TL;DR: In this article, the donor and acceptor properties of tetrahydro-thiophene were evaluated by means of electrochemical and spectroscopic methods, and the potentials of the Ag/0.01 M Ag+-ion electrodes in these two solvents were given.
Abstract: The donor and acceptor properties of tetrahydrofuran and tetrahydro-thiophene were evaluated by means of electrochemical and spectroscopic methods. Polarographic and cyclovoltammetric data for LiClO4, NaClO4, KClO4, RbClO4, CsClO4, Ba(ClO4)2, AgCF3SO3, TlClO4, Zn(CF3SO3)2, Cd(CF3SO3)2, Cu(CF3SO3)2, Pb(CF3SO3)2, Mn(CF3SO3)2, Co(CF3SO3)2, Ni(ClO4)2·2H2O, oxygen, perylene, ferrocene, and bis(biphenyl)chromium tetraphenylborate in tetrahydrofuran and of TlClO4, CuCF3SO3, Pb(CF3SO3)2, Cd(CF3SO3)2, oxygen, ferrocene and bis(biphenyl)chromium tetraphenylborate in tetrahydrothiophene together with the potentials of the Ag/0.01 M Ag+-ion electrodes in these two solvents are given. Molar Gibbs (free) energies for the transfer from acetonitrile into tetrahydrofuran for Na+, K+, Rb+, Ag+, Tl+, Zn2+, Cd2+, and Pb2+, and for the transfer into tetrahydrothiophene for Ag+, Cu+, Tl+, Cd2+, and Pb2+ were calculated from these data. Visible spectra were obtained for the solvatochromic dyes acetylacetonato(N,N,N′,N′,-tetramethylethylenediamine) copper(II) perchlorate and for 2,6-diphenyl-4-(2,4,6-triphenyl-l-pyridinio)phenoxide, which served as secondary standards to obtain donor and acceptor numbers. The changes in half-wave potentials of the cations vs. bis(biphenyl)chromium(I)/(0) and the Gibbs energies of transfer are discussed on basis of hard and soft donor properties of these two solvents.
TL;DR: In this article, the laser-induced oxidation of YBa2Cu3O6 was investigated and the oxygen content of the material was locally increased by laserinduced heating under cw Ar+ or Kr+ laser irradiation in O2 atmosphere.
Abstract: Investigations on the laser-induced oxidation of YBa2Cu3O6 are presented. Here, the oxygen content of the material is locally increased by laser-induced heating under cw Ar+ or Kr+ laser irradiation in O2 atmosphere. The technique permits direct-writing of superconducting patterns into the semiconducting sample surface.
TL;DR: Results indicate that in vivo bromination of tyrosyl residues in thyroglobulin might be of some importance in cases of either iodine deficiency or excessive bromide intake.
TL;DR: In this paper, the ablation of ceramic Bi-Ca-Sr-Cu-O by XeCl-excimer-laser projection has been investigated in both air and vacuum, etching commences at about 2.4 J/cm2 and then increases with fluence within the regime investigated.
Abstract: The ablation of ceramic Bi-Ca-Sr-Cu-O by XeCl-excimer-laser projection has been investigated. In both air and vacuum, etching commences at about 2.4 J/cm2 and then increases with fluence within the regime investigated (Φ <) 20 J/cm2). At 10 J/cm2 the respective etch rates are around 1 μm/pulse and 1.6 μm/pulse.
04 Jul 1988
TL;DR: The algorithm is able to construct the simplest subsidiary conditions with respect to certain predefined criteria, such as lowest degree or dependence on a given set of variables.
Abstract: Grobner bases have been used in various ways for dealing with the problem of geometry theorem proving as posed by Wu. Kutzler and Stifter have proposed a procedure centered around the computation of a basis for the module of syzygies of the geometrical hypotheses. We elaborate this approach and extend it to a complete decision procedure. Also, in geometry theorem proving the problem of constructing subsidiary (or degeneracy) conditions arises. Such subsidiary conditions usually are not uniquely determined and obviously one wants to keep them as simple as possible. This problem, however, has not received enough attention in the geometry theorem proving literature. Our algorithm is able to construct the simplest subsidiary conditions with respect to certain predefined criteria, such as lowest degree or dependence on a given set of variables.
TL;DR: In this article, the authors deal with linear differential-algebraic equations which arise by coupling ordinary differential equations with solution invariants, and a parametrization into transferable equations is shown to present a regularization.
TL;DR: In this article, the authors demonstrate the approximate nature of the Onsager-Casimir relations for the example of the linearized Burnett equations for a dilute gas and show that the usual expressions for the thermodynamic forces require modifications at the Burnett level.
Abstract: We demonstrate the approximate nature of the Onsager-Casimir relations for the example of the linearized Burnett equations for a dilute gas. For any discussion of Onsager relations the choice of a correct set of thermodynamic forces and fluxes is of course crucial. By retracing the Chapman-Enskog procedure, we show that the usual expressions for the thermodynamic forces require modifications at the Burnett level. However, inclusion of these terms does not remedy the violation of Onsager symmetry first noticed by McLennan. A modified version of the Onsager symmetry that involves thermodynamic forces derived from an entropy Lagrangian rather than from the entropy itself does remain valid on the Burnett level. Throughout, we allow for the presence of an external potential; the Burnett equations including potential terms are derived in an appendix for a set of variables particularly suited for our discussion. We stress that in discussing Onsager relations one should use the full thermodynamic fluxes rather than their dissipative parts only, in spite of the fact that only the latter contribute to the entropy production.
TL;DR: In this paper, the electrical activity of substitutional Co in CdTe was investigated and the threshold energies for photoquenching and the excitation of the Co 2+ EPR were determined and a configuration coordinate model was presented.
01 Jan 1988
TL;DR: Three arylazide photo affinity probes are used in Ca2+ channel research, and the benzothiazinones and diphenylbutylpiperidines have been suggested to act at yet another site.
Abstract: Photoaffinity labeling is an important, extremely valuable tool for the characterization of pharmacological receptors. Radioactive photoaffinity probes allow, even in crude preparations with very low receptor densities, identification of the polypeptide(s) which bind the ligand. In general, the photoaffinity protection profile (obtained by adding unlabeled compounds interacting competitively or allosterically with the receptor) should reflect the reversible binding interaction profile. In Ca2+ channel research, three arylazide photo affinity probes are useful, namely ( - )- or (±)[3H]azidopine (1,4-dihydropyridines), [N-methyl-3H]LU49888 (a phenylalkylamine), and an azido derivative of [125I]ω-conotoxin GVIA (CgTx). The first two ligands are well characterized by reversible binding experiments and interact in a stereoselective manner and with high affinity with L-type Ca2+ channels [1-5]. The 125I-iodinated CgTx photoaffinity probe presumably incorporates into the N-type channel components, exclusively found in neuronal tissues [6]. L-type Ca2+ channels have distinct drug-receptor domains for different classes of drugs (e.g., the 1,4-dihydropyridines, phenylalkylamines, and benzothiazepines) linked to each other (and to high- and low-affinity divalent cation binding sites) by reciprocal allosteric coupling mechanisms [7]. Recently, the benzothiazinones [8] and diphenylbutylpiperidines [9, 10] have been suggested to act at yet another site.
TL;DR: In this paper, the nature of interactions between solutes and the solvents ethanediol and 2-mercaptoethanol were studied employing polarography, cyclic voltammetry and visible spectroscopy.
Abstract: The nature of interactions between solutes and the solvents ethanediol and 2-mercaptoethanol were studied employing polarography, cyclic voltammetry and visible spectroscopy. The polarographic and voltammetric behavior of TlClO4, Zn(CF3SO3)2, Cd(CFP3SO3)2, Pb(CF3SO3)2, Cu(CF3SO3)2, Mn(CF3SO3)2, Co(CF3SO3)2, Ni(ClO4)2·2H2O, oxygen and bis(biphenyl)-chromium(I) tetraphenylborate or iodide were measured. Gibbs energies of transfer based on the bis(biphenyl)chromium assumption were calculated for the transfer from acetonitrile into ethanediol for Tl+, Ag+, Cd2+, and Pb2+ as well as for Tl+, Cu+, Cd2+, and Pb2+ into 2-mercaptoethanol. The solvatochromic shift of acetylacetonato (N, N, N′, N′-tetramethyl-ethylenediamine)copper(II) perchlorate was used to evaluate the hard donor properties of ethanediol. The acceptor properties of both solvents were estimated from the low energy visible absorption band of bis(cyano)bis(1,10-phenanthroline)iron(II). The different behavior of ethanediol and 2-mercaptoethanol is discussed on the basis of the changes of half-wave potentials, of Gibbs energies of transfer and of the shifts of the solvatochromic compounds.
TL;DR: In this paper, the lateral growth rates observed during the Kr + laser-induced deposition of W spots from gaseous mixtures of WF 6 and H 2 have been analyzed on the basis of model calculations for pyrolytic laser-CVD.
TL;DR: The redox couple b-nor-biladiene-ac (2)/b-norbilatriene-abc (3) exhibits an oxidative half wave potential of 800 mV in acetonitrile solution as mentioned in this paper.
Abstract: The redox coupleb-nor-biladiene-ac (2)/b-nor-bilatriene-abc (3) exhibits an oxidative half wave potential of 800 mV in acetonitrile solution. It is demonstrated that it can be used as an extremely efficient electron carrier through bulk membranes. Whereas2 is not suitable as a ligand in carrier mediated cation transport,3 is a medium suited carrier for Cu(II) or Zn(II) ions, however, it is the most efficient one found so far for transport of Hg(II) ions. A 1:1 zinc chelate of3 is isolated and characterized. it is deduced to represent a polymer consisting of about 73 monomer units.