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Showing papers by "University of Erlangen-Nuremberg published in 1984"


Journal ArticleDOI
TL;DR: In this article, two approaches are proposed to predict particle trajectories in the fluid phase as a result of forces acting on particles, which are referred to as the Lagrangian approach and the Eulerian approach.

287 citations


Journal ArticleDOI
TL;DR: In this article, two experimental techniques are described for the determination of the change of specific volume of polymers with temperature and aging time, which allow measurements between − 160 °C and + 200 °C.
Abstract: Two experimental techniques are described for the determination of the change of specific volume of polymers with temperature and aging time, which allow measurements between − 160 °C and + 200 °C. Four technical amorphous polymers, PS, PVC, PMMA and PC have been investigated. Volume-temperature curves under constant rate of cooling are presented and interpreted with respect to relaxation processes known from other physical investigations. The rate dependence of dilatometric glass transition temperatures is compared with the time dependence of rheometric glass transition temperatures from shear creep data. Volume relaxation data at constant aging temperature are presented. Aging is found to proceed until very low temperatures in the glassy state for e.g. PMMA.

232 citations


Journal ArticleDOI
TL;DR: Radiolysis of bovine serum albumin under aerobic and anaerobic conditions was studied by SDS-polyacrylamide gel electrophoresis and the radiation-induced broadening of the serumalbumin peak is interpreted as being a result of intramolecular disulfide exchange.
Abstract: Radiolysis of bovine serum albumin under aerobic and anaerobic conditions was studied by SDS-polyacrylamide gel electrophoresis. After Coomassie Blue or Fast Green staining quantitative evaluations give information about the degradation processes of the protein. Under nitrogen the main reaction is the aggregation caused by covalent cross-links, which includes only a small portion of intermolecular S-S bridges. Under air the radiolysis leads to peptide chain scission, which is not a random process, but yields specific protein fragments. A mechanism for this fragmentation reaction is suggested. The radiation-induced broadening of the serum albumin peak is interpreted as being a result of intramolecular disulfide exchange. In contrast to lactate dehydrogenase the degradation of serum albumin is enhanced by oxygen, probably because of its low tryptophan content.

232 citations


Journal ArticleDOI
TL;DR: In this article, a typical control actuator system consisting of a brushless synchronous motor and a transistor chopper inverter is described, and several types of construction are described.
Abstract: High-quality electrical servo drives can only be designed and manufactured by using especially compatible and sophisticated components. A typical control actuator system is described consisting of a brushless synchronous motor and a transistor chopper inverter. Important aspects of the design and rating of a three-phase motor with rare-earth permanent magnets are pointed out. Several types of construction are described. The machine control system used is the familiar method of cascade control. By application of "space vectors" two special methods for fast response current control are developed. In the first case, inverter control signals are derived only from measured quantities. In the second case, the optimum controller output can be calculated if additional information about the controlled system exists. Finally, experimental results prove the excellent performance of this drive system.

229 citations


Journal ArticleDOI
01 Jul 1984-Nature
TL;DR: The isolation of autoreactive T cells from six patients with myasthenia gravis is reported on, finding that AChR-induced proliferation could be inhibited with two monoclonal antibodies against monomorphic DR determinants and also with DR3-specific alloantiserum.
Abstract: Myasthenia gravis is one of the best characterized human autoimmune disorders1–4. Circulating autoantibodies to the nicotinic acetylcholine receptor (AChR) at the neuromuscular junction play a prominent part in the effector phase of the disease5,6, but little is known about the induction phase, that is, the immunoregulation. Indirect evidence, such as thymic abnormalities7 and the association with certain histocompatibility antigens (for example HLA-B8,-DR38,9) suggests a defect of immunoregulation at the level of thymus-dependent (T) lymphocytes. We report here on the isolation of autoreactive T cells from six patients with myasthenia gravis. From one of these patients, who is homozygous for HLA-DR3, we established a long-term T-cell line. The line cells are specific for purified fish and human AChR, display the surface phenotype of inducer/helper T cells and are genetically restricted to HLA-DR3. AChR-induced proliferation could be inhibited with two monoclonal antibodies against monomorphic DR determinants and also with DR3-specific alloantiserum.

219 citations


Journal ArticleDOI
TL;DR: This work presents mathematical proof based on the theory of analytic functions and discusses the restrictions involved for the reconstruction from sampled data of the bispectrum of the autotriple correlation.
Abstract: The bispectrum is the Fourier transform of the triple correlation, sometimes also referred to as triple product integral. We are concerned here with the bispectrum of the autotriple correlation. Bispectrum analysis can be used to solve phase problems in signal processing, since the knowledge of the bispectrum of a signal usually allows one to reconstruct both amplitude and phase of the Fourier transform signal. We present mathematical proof based on the theory of analytic functions and discuss the restrictions involved. A recursive algorithm is outlined for the reconstruction from sampled data. In addition, possibilities for noise reduction by averaging redundant information will be described. Examples are included for 1-D signals.

211 citations


01 Jul 1984
TL;DR: The triple correlation l(3) as discussed by the authors is defined as the triple function integral, applied to the signal l(t) l (3)(t 1, t 2 ) = ∫ l (t)l(t + t 1 )l (t + T 2 ) dt.
Abstract: The (auto)triple correlation l(3)(t 1 , t 2 ) is defined as the triple function integral, applied to the signal l(t) l(3)(t 1 , t 2 ) = ∫ l(t)l(t + t 1 )l(t + t 2 ) dt. The triple correlation l(3)(t 1 , t 2 ) is less popular than the standard (double) correlation l(2)(t 1 ) for several reasons: l(2)is sometimes easier to observe and to process, l(3)is small for many bipolar or complex signals, the mathematics associated with l(2)is better known. On the other hand, the triple correlation l(3)knows more about the signal l than does the ordinary autocorrelation l(2). Also l(3)is in some ways more sensitive, in other ways less sensitive to noise, to bias drifts, etc. Hence, there are situations, where it is quite favorable to evaluate one-dimensional signals or two-dimensional pictures by means of their triple correlations. We will review the underlying mathematical tools and report on our projects where triple correlations were employed for studying laser pulse shapes, sound quality, halftone print statistics, mobility of bacteria, and astronomical speckle interferometry. We will mention also how others have used the triple correlation for ocean waves, engine noises, intensity interferometry, and other optical signal processing tasks.

173 citations


Journal ArticleDOI
30 Jan 1984-Virology
TL;DR: Four classes of monoclonal antibody-producing cell lines have been obtained that detect human cytomegalovirus virion structural proteins and provide useful tools for studying the molecular biology of virus replication, for diagnosing cytomeGalovirus infections, and for studying virus latency and activation.

128 citations


Journal ArticleDOI
TL;DR: Pulse-chase experiments with [2-3H]glycerol and [14C]acetate revealed that in Staphylococcus aureus lipoteichoic acid biosynthesis plays a dominant role in membrane lipid metabolism.
Abstract: Pulse-chase experiments with [2-3H]glycerol and [14C]acetate revealed that in Staphylococcus aureus lipoteichoic acid biosynthesis plays a dominant role in membrane lipid metabolism. In the chase, 90% of the glycerophosphate moiety of phosphatidylglycerol was incorporated into the polymer: 25 phosphatidylglycerol + diglucosyldiacylglycerol leads to (glycerophospho)25-diglucosyldiacylglycerol + 25 diacylglycerol. Glycerophosphodiglucosyldiacylglycerol was shown to be an intermediate, confirming that the hydrophilic chain is polymerized on the final lipid anchor. Total phosphatidylglycerol served as the precursor pool and was estimated to turn over more than twice for lipoteichoic acid synthesis in one bacterial doubling. Of the resulting diacylglycerol approximately 10% was used for the synthesis of glycolipids and the lipid anchor of lipoteichoic acid. The majority of diacylglycerol recycled via phosphatidic acid to phosphatidylglycerol. Synthesis of bisphosphatidylglycerol was negligible and only a minor fraction of phosphatidylglycerol passed through the metabolically labile lysyl derivative. In contrast to normal growth, energy deprivation caused an immediate switch-over from the synthesis of lipoteichoic acid to the synthesis of bisphosphatidylglycerol.

116 citations


Journal ArticleDOI
TL;DR: In this paper, the authors used a first-principles Green's-function formalism of charge-transfer exciton theory to calculate the visible optical spectrum of two typical polydiacetylene (PDA) crystals.
Abstract: The visible optical spectrum of two typical polydiacetylene (PDA) crystals, $\mathrm{poly}[2,4\ensuremath{-}\mathrm{h}\mathrm{e}\mathrm{x}\mathrm{a}\mathrm{d}\mathrm{i}\mathrm{y}\mathrm{n}\mathrm{e}\ensuremath{-}1,6\ensuremath{-}\mathrm{d}\mathrm{i}\mathrm{o}\mathrm{l}\ensuremath{-}\mathrm{b}\mathrm{i}\mathrm{s}\ensuremath{-}(p\ensuremath{-}\mathrm{t}\mathrm{o}\mathrm{l}\mathrm{u}\mathrm{e}\mathrm{n}\mathrm{e}\phantom{\rule{0ex}{0ex}}\mathrm{s}\mathrm{u}\mathrm{l}\mathrm{f}\mathrm{o}\mathrm{n}\mathrm{a}\mathrm{t}\mathrm{e})]$ (PTS) with an acetylene-like structure and poly[5,7-dodecadiyne-1,2-diol-bis-(phenylurethane)] (TCDU) with a butatriene-like structure, is investigated with the use of a first-principles Green's-function formalism of charge-transfer exciton theory The energy-band structures of the ground state are calculated first at the Hartree-Fock level with nonlocal exchange and they are corrected afterward for electron correlation effects using the electron-polaron model of Toyozawa The electron-hole interaction ${\stackrel{^}{H}}_{e,h}$ is treated by first-order perturbation theory in the framework of the Lax-Koster-Slater resolvent method as proposed by Takeuti The influence of screening on ${\stackrel{^}{H}}_{e,h}$ is also investigated with the help of an $\stackrel{\ensuremath{\rightarrow}}{\mathrm{r}}$-dependent static dielectric function The results show that correlation corrections play an important role in the calculation of the optical spectrum since they substantially modify the Green's function of the host crystal as well as ${\stackrel{^}{H}}_{e,h}$ Both the singlet and triplet excitons are found to be delocalized with a radius of 25-30 \AA{} in PDA's: the Frenkel exciton contributes only \ensuremath{\sim}30% of the binding energy The calculations predict the first-singlet absorption maximum for PTS at 21-22 eV and for TCDU at 17-18 eV, with an exciton bandwidth of \ensuremath{\sim}29 and \ensuremath{\sim}35 eV, respectively The exciton binding energy is found to be \ensuremath{\sim}04 eV for both systems Triplet levels are located at 08-09 eV below the singlets at $K=0$ and they form relatively flat bands The theoretical ionization potentials are 57 and 50 eV for PTS and TCDU crystals, respectively

102 citations


Journal ArticleDOI
TL;DR: In this article, the influence of wall proximity on hot-wire readings was eliminated by using a highly insulating wall material and using a single hotwire boundary layer probe to obtain the longitudinal velocity informatemperature-wake sensor for the cross flow flow information.
Abstract: Hot-wire anemometer measurements, using two types of probes, are reported for wall boundary layer flows with particular attention being given to the near-wall region and to measurements at high Reynolds numbers up to Rϕ≈ 15,000. To obtain accurate near-wall measurements, the influence of wall proximity on hot-wire readings was eliminated by using a highly insulating wall material. Measurements were carried out with a single hot-wire boundary layer probe to obtain the longitudinal velocity informatemperature-wake sensor for the cross flow tion and a hot-wire, information.

Journal ArticleDOI
TL;DR: The tissue architecture of synovial membranes obtained from patients with non-inflammatory joint diseases and patients with rheumatoid arthritis was studied, focusing on the localization of the type I, type II and type III synoviocytes that previously had been defined by their cell surface phenotype.
Abstract: Tissue specimens of synovial membranes from patients with rheumatoid arthritis (RA) and non-inflammatory joint diseases were analyzed with a panel of monoclonal antibodies directed towards T-lymphocyte subsets and natural killer (NK) cells. In the RA group, mononuclear cell infiltrations in the synovium presented a distinguished pattern as compared to the non-RA group. Inflammatory synovial membranes displayed an increased level of cells recognized by the monoclonal antibodies OKT4 and OKT8, especially attributable to the broadened layer of synoviocytes and to the fibrous synovial tissue. No significant difference in the RA patients was observed with regard to the percentage of OKT4 and OKT8 positive cells in different investigated compartments of the synovium, e.g., diffuse inflamed synovial tissue, fibrous synovial tissue, and perivascular infiltrations. OKT4 and OKT8 positive staining was additionally observed on spindle-shaped cells present in the fibrous and diffuse inflamed synovium. OKT10 binding cells were located in the deeper layers of synoviocytes, in the inflamed synovial tissue, and in one case in perivascular areas, whereas HNK1 positive cells were scattered in the fibrous synovial and perivascular cells, as well as in lymphocyte clusters of synovium in RA patients.

Journal ArticleDOI
TL;DR: In this paper, a pea stem sections were incubated in 32P-phosphate and shown to be phosphorylated in vivo only after blue light irradiation and that the photosensitive fluence range matches that for phototropism.
Abstract: — We have continued to characterize the blue light-regulated phosphorylation of a 120 kDa pea plasma membrane protein thought to be involved in sensory transduction for phototropism (Short and Briggs, 1990, Plant Physiol.92, 179–185). By incubating pea stem sections in 32P-phosphate, we show that the 120 kDa protein is phosphorylated in vivo only after blue light irradiation and that the photosensitive fluence range matches that for phototropism. Blue light induces phosphorylation of the protein in vitro as well, but the fluences required to elicit the response are at least 30-fold higher. Triton solubilization of the plasma membrane vesicles does not further alter the fluence-response relationship. Very little turnover was detected over 20 min phosphorylation time courses or by pulse-chase experiments on unirradiated, blue light pulse-irradiated, or continuously irradiated membranes. Experiments with a dark period intervening between irradiation and addition of adenosine triphosphate show the light-induced change to persist for several minutes at 30°c. Agents that disrupt the normal photochemistry of flavins preferentially inhibit the light-induced enhancement of phosphorylation, suggesting a flavin chromophore. However, exogenous free flavins do not affect the sensitivity of the response. Staphylococcus aureus V-8 proteolysis of the phosphorylated protein from membranes subjected to a range of fluences before phosphorylation shows that the radiolabel on each of three peptides increases in proportion to the phosphorylation level of the undigested polypeptide. These studies may be valuable for assessing the nature of the photoreceptor and for unravelling the early sensory transduction steps in phototropism.

Journal ArticleDOI
TL;DR: Basic principles for logical operations with theta modulation are outlined and experimental examples are given for different types of information encoding, for binary and ternary logical operations, and for addition in the residue-number system.
Abstract: Theta modulation is used to implement in parallel the nonlinear class of logical operations. This includes binary logic as well as higher-order logic, such as residue-number arithmetic. Theta modulation, which means encoding of pixel information by grating structures of different orientations, involves a preprocessing operation. For this purpose, a hybrid optical–electronic system is used. Basic principles for logical operations with theta modulation are outlined and experimental examples are given for different types of information encoding, for binary and ternary logical operations, and for addition in the residue-number system.

Journal ArticleDOI
15 Apr 1984-Virology
TL;DR: Polyadenylated RNA was isolated from fibroblast cultures infected with human cytomegalovirus strain AD169 during the late phase of viral replication and translated into an abundant 65-kDa polypeptide which had the same size as the major structural phosphoprotein of HCMV.

Journal ArticleDOI
TL;DR: Des images d'echographie B obtenues a partir de different positions angulaires du plan de section transversale sont retenues for la reconstruction d'image en mode de reflexion as discussed by the authors.
Abstract: Des images d'echographie B obtenues a partir de differentes positions angulaires du plan de section transversale sont retenues pour la reconstruction d'image en mode de reflexion

Journal ArticleDOI
TL;DR: A filter combination consisting of a lens and two pure phase filters, situated in the two focal planes, that apparently does not absorb any light and is capable of shaping wave fronts with 100% efficiency independent of the object function is discussed.
Abstract: A filter combination consisting of a lens and two pure phase filters, situated in the two focal planes, is discussed. This element, which we call a tandem component, apparently does not absorb any light; in other words, the tandem component is capable of shaping wave fronts with 100% efficiency independent of the object function. We describe a basic configuration and outline its space-variant system properties. The tandem component can be used for many of the standard applications of computer-generated holograms and possibly for some new types as well in view of its space variance.

Journal Article
01 Jan 1984-Surgery
TL;DR: It can be concluded that the use of fibrin tissue adhesive is a safe and reliable method for repair in the majority of incidental and traumatic splenic injuries.


Journal ArticleDOI
TL;DR: Input of line drawings to computers may be accomplished using digital image processing and pattern recognition methods for automatic digitization and a one-pass algorithm is used for the segmentation of the binary image into primary components.
Abstract: Input of line drawings to computers may be accomplished using digital image processing and pattern recognition methods for automatic digitization. Part of a system for the recognition of electrical schematics is presented. A one-pass algorithm is used for the segmentation of the binary image into primary components. Primary components are simply groups of connected black pixels. The segmentation yields a picture graph representing the binary image. Every node of the graph represents a primary component. Strings of alphanumeric symbols in the drawing are located by computing connected components, i.e., connected subgraphs, and clustering the small connected components. The line elements are computed with two different methods. First, primary components are merged into classified line elements which describe the dominant large lines of the drawing. Second, the details are analyzed within the context of dominant lines using a production system.

Journal ArticleDOI
TL;DR: The entire DNA of Rhizobium meliloti MVII /1 cells was isolated preparatively by gentle lysis and sucrose gradient centrifugation and the length of the megaplasmid could be measured, which allowed an exact determination of the molecular weight.

Journal ArticleDOI
TL;DR: Chronic lead exposure resulting in blood-lead levels of below 70 μg/dl is no occupational risk causing a functionally significant slowing of nerve conduction velocities, and multiple stepwise regression analyses revealed statistically significant correlations between the four NCV and age as well as Pb-B.
Abstract: A cross-sectional study was performed in order to investigate the influence of chronic lead-exposure on the peripheral nervous system. We examined 148 male workers of a storage battery manufacturing plant, who had been exposed to lead metal and inorganic lead compounds for 1 to 28 years (mean 11 years). Fifteen workers with non-occupational risks of peripheral neuropathy (former diseases, alcohol abuse, medication) were excluded from the study. The investigation program comprised: case history, physical examination, analyses of blood- and urine-samples and determination of maximal motor, mixed and sensory conduction velocity (NCV) of the ulnar and median nerve of the right forearm. Objectively no worker showed any signs of health effects related to lead exposure. The “Biological Monitoring” included the determination of (1) Blood-lead level (Pb-B), (2) Free erythrocyte porphyrins (FEP), (3) δ-Aminolevulinic acid dehydratase (ALA-D) and (4) δ-Aminolevulinic acid in urine (ALA-U). Further “time-weighted-average (TWA)”-values of Pb-B were calculated on the basis of several determinations over the period 1975–1981. The following “actual” (“TWA”) median values resulted: Pb-B 53 μg/dl (54 μg/dl), ALA-U 5.6 mg/l (8.4 mg/l), FEP 2.0 mg/l (2.0 mg/l). The “Biologischer Arbeitsstoff Toleranz Wert (BAT)” of 70 μg//dl for Pb-B was exceeded in 15 workers (11%), and of 15 mg/l for ALA-U in 30 cases (23%). In comparison with age-matched controls, the lead workers showed a mild slowing of NCV with mean values between 0.8 and 2.0 m/s. Multiple stepwise regression analyses revealed statistically significant correlations between the four NCV and age as well as Pb-B. There were better correlations by using “TWA” than “actual” data of Pb-B. Consideration of the results of the regression analyses, together with an evaluation of the individual neurophysiological status as a function of internal lead exposure, a “dose-effect-relationship” was found only in the case of Pb-B exceeding 70 μg/dl. From our study it is concluded that chronic lead exposure resulting in blood-lead levels of below 70 μg/dl is no occupational risk causing a functionally significant slowing of nerve conduction velocities.

Journal ArticleDOI
01 Apr 1984
TL;DR: In this paper, the rate constants of self exchange reactions between the half oxidized and the totally oxidized or the reduced forms of some p-phenylenediamine derivatives are investigated at 293 K by ESR line-broadening in various aprotic solvents (dielectric constants ϵ between 4.7 and 49).
Abstract: The rate constants k1, and k2 of the self exchange reactions between the half oxidized and the totally oxidized or the reduced forms of some p-phenylenediamine derivatives are investigated at 293 K by ESR line-broadening in various aprotic solvents (dielectric constants ϵ between 4.7 and 49). The dimerization constants of the radicals at 183 K and the enthalpies of dimerization are measured, too. The results are discussed in terms of Marcus' theory. In k1, is found to depend linearly on γ = 1/n2 - 1/ϵ (n = refractive index), the covered range being 0.27 < γ < 0.53. The distance parameter g is obtained from the slope and compared with values derived from different molecular models. The results are represented satisfactorily by ellipsoidal molecules with half axes obtained from crystallographic data, the distance in the activated complex being approximately the same as in the radical dimers. The inner reorganization energy is calculated by Huckel methods and compared with experimental values obtained from the intercept of the straight line ln k1 (γ). The deviations are considerable. The calculated Marcus activation free enthalpies are smaller then the measured ones. — The slow rate constant k2 of the second step can be computed, if the Coulomb forces between the radical cation and the dication of the quinone diimine are considered. The inner reorganization energy of the transformation between aromatic and quinoidic structures is negligible. The rate constants of different cross reactions with p-phenylene diamines are calculated with Marcus' formula which, however, has to be extended by work terms. The symproportionation rate is nearly diffusion controlled. With some other reactions the conformity of measured and calculated rate constants is excellent.

Book ChapterDOI
TL;DR: This chapter discusses three tRNA modifications: ribosylthymine (T) at position 54; N6-(2-isopentenyl) adenosine (i6A) and its derivatives at position 37; and queuosine (Q), indicating that these modified nucleosides in tRNAs provide cells with a survival advantage under unfavorable environmental conditions, indicating that they probably played an important role in the evolution of organisms.
Abstract: Publisher Summary This chapter discusses three tRNA modifications: ribosylthymine (T) at position 54; N6-(2-isopentenyl) adenosine (i6A) and its derivatives at position 37; and queuosine (Q) and its derivatives at position 34 These modified nucleosides in tRNAs provide cells with a survival advantage under unfavorable environmental conditions, thus, indicating that these tRNA modifications probably played an important role in the evolution of organisms A total lack of any one of these modifications in an organism that usually contains the normal nucleoside in specific tRNAs decreases its ability to survive under unfavorable environmental conditions The modification T in elongator tRNAs of eubacteria and of eukaryotes increases the Vmax of ribosomal A-site interaction of a cognate (EF-Tu)·GTP·(AA-tRNA) complex These changes are probably important to regulate the overall rate of protein synthesis In cell-free systems of homopeptide synthesis, the absence of T in tRNA increases significantly the inisincorporation of an amino acid by an error-prone tRNA The modification of A-37 in specific tRNAs of microorganism also exhibits an all-or-none effect in codon recognition The replacement of i6A by A, or ms2i6A by i6A reverses the suppression of particular codons by specific suppressor tRNAs In eukaryotes, Q modification of tRNA has been suggested to play a role in the processes of differentiation and aging and neoplastic transformation

Journal ArticleDOI
TL;DR: According to an X-ray structural analysis, the 2-azaallenium hexachloroantimonate 23 crystallizes with the topology of an allene (geometry 1a) and not of a 2azaallyl cation (1b).
Abstract: According to an X-ray structural analysis, the 2-azaallenium hexachloroantimonate 23 crystallizes with the topology of an allene (geometry 1a) and not of a 2-azaallyl cation (1b). Ab initio molecular orbital calculations (3–21 G basis set) and semiempirical MNDO calculations for the unsubstituted 2-azaallenium cation and for some mono- and disubstituted derivatives (24) confirm the experimental results: In many cases the allenium geometry 24a is more stable than the 2-azaallylium form 24b. Electron-releasing substituents reduce the energy difference between 24b and 24a. With two amino substituents the allylium geometry 24b is energetically preferred to the allenium form 24a. In general, substituted 2-azaallenium salts are sterically flexible around the central nitrogen atom. Compound 23 was synthesized by a new method. Zum Bau von 2-Azaallenium-Kationen Entsprechend einer Rontgenstrukturanalyse kristallisiert das 2-Azaallenium-hexachloroantimonat 23 in der Topologie eines Allens (Geometrie 1a) und nicht eines 2-Azaallyl-Kations (1b). Ab-initio-Molekulorbital- (3–21 G Basissatz) und semiempirische MNDO-Rechnungen fur das unsubstituierte 2-Azaallenium-Kation und einige mono- und disubstituierte Derivate (24) bestatigen die experimentellen Befunde: In vielen Fallen ist die Allengeometrie 24a stabiler als die 2-Azaallylium-Form 24b. Elektronenspendende Substituenten verringern den Energieunterschied zwischen 24b und 24a. Ein diaminosubstituiertes Allylium-Kation 24b ist energetisch stabiler als die entsprechende Allenium-Form 24a. Ganz allgemein sind substituierte 2-Azaallenium-Kationen um das zentrale Stickstoffatom sterisch flexibel. Verbindung 23 wurde nach einer neuen Synthese hergestellt.

Journal ArticleDOI
TL;DR: In this article, the authors discuss the diffusion mechanism of oxygen in the silicate network, on oxidation kinetics, and on viscosity-related phenomena in two types of glasses (vitreous silica and soda-lime-silica glass) diffusion data with respect to their relevance in explaining diffusion controlled properties.
Abstract: Mass transport processes in glass melts can be differentiated according to the type of diffusing species: gases, network, modifiers, and network formers. The mobilities of these species give rise to a variety of diffusion-controlled processes and properties. The basic concepts of self-diffusion and chemical diffusion are discussed as well as the question of network defects in non-crystalline solids. The treatment of structural defects in the silicate network can be approached differently, i.e. structurally, thermodynamically, and on the basis of chemical bonding. Of particular interest are the diffusivities of the network-forming species (e.g. oxygen and silicon), being the least mobile species, and their influence on diffusion-controlled properties. An understanding of diffusion-controlled processes requires an insight into the underlying mechanisms of mass transport. One of the most important objectives is to clarify the rate-controlling steps and to identify the rate-controlling species. For two types of glasses (vitreous silica and soda-lime-silica glass) diffusion data will be discussed with respect to their relevance in explaining diffusion-controlled properties. Special emphasis is placed on the diffusion mechanism of oxygen in the silicate network, on oxidation kinetics, and on viscosity-related phenomena.

Journal ArticleDOI
TL;DR: In this paper, a three-electrode cell is proposed to shift the appearance of the distortions to considerably higher frequencies by using the shape and relative position of the three electrodes and their electric and electrolytic connections.

Journal ArticleDOI
TL;DR: In this paper, the authors measured the rate of electron transfer between p -benzoquinone Q and its anion radical by means of cyclic voltammetry at a plane Au electrode in nine aprotic solvents of different polarity γ, where γ = 1/n 2 −1/ϵ( n 2 is the optical and ϵ the static dielectric constant).

Book ChapterDOI
TL;DR: The present review will try to give a condensed survey of the more fundamental results and interpretations contained in these chapters, supplemented by papers published afterwards.
Abstract: The present knowledge on the physiology of turgor movements up to 1978 has been reported in several chapters in Vol. 7 of the Encyclopedia of Plant Physiology, viz. “Reception and Transduction of Electrical and Mechanical Stimuli” (BENTRUP), “Endogenous Rhythms in the Movement of Plants”(SWEENEY), “Movements of Stomata” (RASCHKE), and “Leaf Movements and Tendril Curling” (SATTER). The present review will try to give a condensed survey of the more fundamental results and interpretations contained in these chapters, supplemented by papers published afterwards. Only the latter will be referred to individually in the text and in the reference list, whereas for the older literature the reader is referred to the chapters in question by (cf.) with the author of the Encyclopedia chapter.

Journal ArticleDOI
TL;DR: The results show that the metabolism of arachidonic acid in macrophages via the cyclooxygenase or the lipoxygen enzyme pathway is dependent on the stimulus applied, and differences in anti-inflammatory activity claimed for some of the drugs tested can be explained by differential inhibition of either pathway.
Abstract: Leukotriene and prostaglandin production by mouse peritoneal macrophages was investigated. It could be shown that the tumour promoter 12-O-tetradecanoylphorbol-13-acetate initiated the release of prostaglandin E2 but had little effect on the release of leukotriene C4-like immunoreactivity. The divalent cation ionophore A 23187 at concentrations between 10−6 and 10−8 mol/l initiated prostaglandin as well as leukotriene release. This prostaglandin and leukotriene release could be modulated by drugs. Non-steroidal anti-inflammatory drugs including benoxaprofen inhibited prostaglandin release but simultaneously enhanced leukotriene production. The analgesics paracetamol and 4-methylaminoantipyrine had similar effects at high concentrations. The experimental compound BW 755 c inhibited prostaglandin and leukotriene production while the antithrombotic compound nafazatrom inhibited the production of leukotriene C4-like immunoreactivity but enhanced prostaglandin E2 production. Nordihydroguaiaretic acid inhibited prostaglandin and leukotriene production. The results show that the metabolism of arachidonic acid in macrophages via the cyclooxygenase or the lipoxygenase pathway is dependent on the stimulus applied. Both pathways can be inhibited conjointly or selectively by drugs. Our results do not provide evidence that differences in anti-inflammatory activity claimed for some of the drugs tested can be explained by differential inhibition of either pathway. The experimental system described may be used for assessing the potency of drugs to inhibit the lipoxygenase and the cyclooxygenase pathway of arachidonic acid metabolism.