Showing papers by "University of Jena published in 1990"
TL;DR: The main result shows that the class of cographs (P4-free graphs) is WQO by ≤i, and that this is the unique maximal lower ideal with one forbidden subgraph that is W QO.
Abstract: We study classes of finite, simple, undirected graphs that are (1) lower ideals (or hereditary) in the partial order of graphs by the induced subgraph relation ≤i, and (2) well-quasi-ordered (WQO) by this relation. The main result shows that the class of cographs (P4-free graphs) is WQO by ≤i, and that this is the unique maximal lower ideal with one forbidden subgraph that is WQO. This is a consequence of the famous Kruskal theorem. Modifying our idea we can prove that P4-reducible graphs build a WQO class. Other examples of lower ideals WQO by ≤i are also given.
93 citations
TL;DR: Electroencephalograms, heart rate, skin conductance, and respiration rate were recorded before, during and after one series of 3 periods of mental training (MT).
61 citations
TL;DR: The different acinar distribution of cytochromes P-450 and of GSH and GSH-related detoxication pathways points to a greater susceptibility of perivenous hepatocytes to xenobiotic-induced damage.
Abstract: The hepatic glutathione (GSH) system and the influences of xenobiotics have been reviewed. Key steps in the regulation of hepatic GSH are GSH biosynthesis, the GSH-peroxidase/reductase cycle, the cystathionine pathway, and the carrier-mediated export processes. Influences of xenobiotics on these different pathways are discussed. Xenobiotics may lead to liver injury after biotransformation to highly reactive electrophilic metabolites (mainly cytochrome P-450 mediated), which easily conjugate with GSH, thus producing GSH depletion. This GSH depletion and probably an additional loss of protein sulfhydryl groups cause a disturbance of the intracellular calcium homeostasis which leads to an irreversible cell injury. The different acinar distribution of cytochromes P-450 and of GSH and GSH-related detoxication pathways points to a greater susceptibility of perivenous hepatocytes to xenobiotic-induced damage. Also, the intracellular compartmentation of GSH is important for the understanding of hepatocellular injury induced by several xenobiotics.
55 citations
TL;DR: Glass-ceramics of the type Bioverit can be used as implants for hard tissue (bones) and applications are possible in orthopaedics, head and neck surgery and stomatology.
Abstract: Glass-ceramics of the type Bioverit can be used as implants for hard tissue (bones). The structures of four biomaterials of the type Bioverit are discussed: biocompatible machineable glass ceramics with mica crystals; bioactive machineable glass ceramics with mica and apatite crystals; bioactive phosphate glass ceramics with apatite and AlPO4-crystals; and a new composite material. Applications of Bioverit are possible in orthopaedics, head and neck surgery and stomatology.
55 citations
TL;DR: The evaluation of the fluorescence decay of the photoproduct-enriched HpD solution shows an increase in the short-lived components, especially about 2 ns, in comparison with HpPD without photOProducts.
Abstract: Haematoporphyrin derivative (HpD) photoproducts are formed in aqueous solutions during light exposure in the presence of oxygen. The evaluation of the fluorescence decay of the photoproduct-enriched HpD solution shows an increase in the short-lived components, especially about 2 ns, in comparison with HpD without photoproducts. The bleaching of the HpD fluorescence and the photoproduct formation by the fluorescence-exciting radiation has to be taken into account in the evaluation of stationary as well as time-resolved fluorescence measurements.
48 citations
TL;DR: In uterine smooth muscle, G-proteins of the Gi-family (Gi2, Gi3) couple high-affinity bradykinin receptors to their effector enzymes, and in rat myometrial membranes, two 3H-BradykinIn binding sites with KD values of 16 pM and 1.0 nM were identified.
45 citations
TL;DR: In this paper, the Jump-number problem for partially ordered sets and the problem of counting maximum cardinality matchings in hexagonal systems were investigated, motivated by alternating cycle-free matchings.
Abstract: The investigation of alternating cycle-free matchings is motivated by the Jump-number problem for partially ordered sets and the problem of counting maximum cardinality matchings in hexagonal systems.
45 citations
TL;DR: The rotation of cytochrome P-450 LM2 (CYPIIB4) incorporated into large microsomal-like lipid vesicles was investigated by saturation transfer EPR and the distribution and size of protein particles in the bilayer were studied by freeze-fracture electron microscopy, suggesting an oligomeric and membrane-spanning aggregate.
37 citations
TL;DR: In this article, small-and wide-angle X-ray scattering (SAXS and WAXS) was used to examine in situ formation and evolution of SiO2-structures in alcoholic solutions of tetra-alkoxysilanes (TAOS) as a function of chemical conditions.
Abstract: Small- and wide-angle X-ray scattering (SAXS and WAXS, respectively) were used to examine in situ formation and evolution of SiO2-structures in alcoholic solutions of tetra-alkoxysilanes (TAOS) as a function of chemical conditions. In acid-catalyzed reactions with a molar ratio of ⩽rw ⩽ 51 forH 2O against TAOS primary particles with a diameter of ∼ 1 nm were always found. These particles aggregated to form secondary clusters. The resulting aggregated clusters can be described by means of the fractal concept, diffusion-limited or chemical-limited cluster-cluster aggregations being the dominant mechanisms of formation. When using an under-stoichiometric water content (rw = 1) the formation of smaller primary particles with a diameter of ∼ 0.5 nm is observed; these particles preferably aggregated to form linear particle chains. In alkaline-catalyzed reactions the SiO2-particles grew beyond the visual field of the measurement (rmax = 20 nm) and featured nearly smooth surfaces. As a result of WAXS examinations, it was found that the internal structure of the condensates is characterized by a well-defined topology (polyhedrons). The liquid environment exerts a force on the SiO2-particles and the polyhedron size varies with the composition of the solution.
37 citations
20 Jun 1990
TL;DR: In this paper, it was shown that the INDUCED SUBGRAPH ISOMORPHISM problem remains NP-complete when restricted to cographs (P4-free graphs).
Abstract: We prove by a reduction from 3SAT that the INDUCED SUBGRAPH ISOMORPHISM problem remains NP-complete when restricted to cographs (P4-free graphs).
34 citations
TL;DR: In this paper, the problem of spectral filtering of quantized light fields is studied, based on the recently developed quantum-optical theory of the action of passive, lossless optical systems.
Abstract: The problem of spectral filtering of quantized light fields is studied, based on the recently developed quantum-optical theory of the action of passive, lossless optical systems [L. Kn\"oll, W. Vogel, and D.-G. Welsch, Phys. Rev. A 36, 3803 (1987)]. Expressions for the operator of the electric field strength of the light and the normally and time-ordered field-correlation functions are derived for the case of a Fabry-P\'erot interferometer being present. Various kinds of field decomposition that are usually considered in classical optics are studied. The results are compared with the Fourier approach to spectral properties of light. It is shown that, dependent on the experimental scheme used, new quantum effects appear, which may prevent the observation of the Fourier structure of the light as predicted from classical optics. Quantitatively this is demonstrated for the example of spectral squeezing in resonance fluorescence, where significant discrepancies between the measured and the full Fourier spectrum are found.
TL;DR: The CSH is without value for predicting sinus node dysfunction and AV conduction disorder.
Abstract: In order to evaluate the diagnostic value of carotid sinus hypersensitivity (CSH) we have investigated 163 asymptomatic patients (88 male, 75 female, mean age 57.9 +/- 22.7 years) and 210 symptomatic patients (108 males, 102 females, mean age 61.1 +/- 28.1 years) with syncopes or dizziness. Thirty two of the 163 asymptomatic patients (20%) and 87 of the 210 symptomatic patients (41%) showed CSH (asystole greater than or equal to 3 sec during carotid sinus pressure). Male patients had a higher number of CSH than female (28% vs 10% in the asymptomatic group, 48% vs 34% in the symptomatic group). Electrophysiological investigations were performed in all 210 symptomatic patients. Normal electrophysiological results had 94 of the 210 patients. Thirty seven of these 94 patients showed CSH (39%). Prolonged sinus node recovery time (SNRT) and/or prolonged sinoatrial conduction time (SACT) were evaluated in 38 patients. Seventeen of the 38 patients had CSH (45%). Disorders of atrioventricular (AV) conduction were evaluated in 43 patients. Seventeen of the 43 patients showed CSH (40%). Thirty-five patients had both AV conduction disorders and prolonged SNRT or SACT. Sixteen of these 35 patients showed CSH (46%). In conclusion, no significant difference was found between patients with and without pathological electrophysiological results. The CSH is without value for predicting sinus node dysfunction and AV conduction disorder.
TL;DR: In this paper, the optical response of a bent nonlinear directional coupler was studied in the framework of a coupled mode approach. And the effects of waveguide bending on the switching characteristic of the coupler geometry were considered.
TL;DR: Results are consistent with the well-known fact that CA3 neurones show spontaneous burst activity, while CA1 cells do not, and conclude that these differences reflect two types of pyramidal cells within the same subregion.
Abstract: The fast sodium (Na)current of hippocampal neurones was recorded using the intracellular perfusion method. Neurones were isolated from the CA1 and CA3 hippocampal subregions separately, after treatment of the tissue with trypsin. There were no differences between the current-voltage (I-V) characteristics of CA1 and CA3 neurones. In contrast to this, the steady-state inactivation (h∞) of both types of neurones was significantly different. Additionally, there were two subpopulations of CA1 neurones, which showed different courses of h∞. Compared with CA1 neurones, the steady-state activation and inactivation curves of CA3 neurones overlapped much more in the potential range −80 mV to −50 mV. These results are consistent with the well-known fact that CA3 neurones show spontaneous burst activity, while CA1 cells do not. The time constant of activation (τm) depended upon the membrane potential in the same way for all CA3 neurones investigated. However, there were two different subpopulations of CA3 cells, showing different voltage dependence of the time constant of inactivation. We conclude that these differences reflect two types of pyramidal cells within the same subregion.
Journal Article•
TL;DR: In patients with ventricular tachycardia, mechanical stimulation extends the therapeutic possibilities, and the rate of success is higher, the lower the tachycardsia rate, which is the only predictive parameter for therapeutic success.
Abstract: To determine value and limitations of mechanical cardiac stimulation by precordial thumps for termination of ventricular arrhythmias, we systematically treated 47 consecutive cases of ventricular tachycardias (resp. ventricular flutter or fibrillation) by this method. In 20 of 37 cases of ventricular tachycardias the arrhythmia was terminated by manual stimulation. The mean tachycardia rate amounted to 145/min (range from 102 to 222/min) in successfully treated patients. Bursts of rapid precordial thumps were more effective than single precordial thumps. In 17 of the 37 cases of ventricular tachycardia. The mean tachycardia rate was significantly higher (176/min, range from 120 to 250/min) than in successfully treated cases. Altogether, ventricular tachycardias with heart rate less than or equal to 160/min were terminated by mechanical stimulation in 17 of 22 cases, and ventricular tachycardias with heart rate greater than 160/min only in 3 of 15 cases. Ventricular fibrillation (n = 3) or ventricular flutter (n = 7) was not interrupted in any case by precordial thumps. In patients with ventricular tachycardia, mechanical stimulation extends the therapeutic possibilities. The rate of success is higher, the lower the tachycardia rate. The tachycardia rate is the only predictive parameter for therapeutic success.
TL;DR: Periodically curved bilayer structures showing a tetragonal pattern were revealed by freeze-fracture electron microscopy in hyphal cells, stable L-form cells, and liposomes prepared from extracted lipids of Streptomyces hygroscopicus NG 33-354.
TL;DR: In this article, the optical response behavior of dielectric multifilm systems containing an arbitrary number of film components with self-focusing Kerr nonlinearity has been investigated for an oblique s-polarized incident wave.
TL;DR: In this paper, a measure-geometric analogue to Hadwiger's characterization of linear combinations of Minkowski functionals of convex bodies as continuous additive euclidean invariants is given.
Abstract: A differential-geometric and measure-geometric analogue to Hadwiger's characterization of linear combinations of Minkowski functionals of convex bodies as continuous additive euclidean invariants is given. The equivalent of the quermassintegrals are generalised Lipschitz-Killing curvatures and measures. By means of polyhedral approximation with respect to flat seminorms of associated normal cycles the general problem may be reduced to the classical case.
TL;DR: Preparation des polymeres de structure [-CO-Ph-O 2 C-RCO 2 -Ph-CO 2 ] n (R=(CH 2 ) 4, (CH 2 ǫ 6, CH 2 ) 8, CH 2 ] 2 -O-(CH 2 ), 6 -O(CH 2 )) 2, etc as discussed by the authors.
Abstract: Preparation des polymeres de structure [-CO-Ph-O 2 C-R-CO 2 -Ph-CO 2 ] n (R=(CH 2 ) 4 , (CH 2 ) 6 , (CH 2 ) 8 , (CH 2 ) 2 -O-(CH 2 ) 6 -O-(CH 2 ) 2 , etc. Leur Tg varie entre 33 et 53°C et leur masse moleculaire Mn entre 2900 et 12900
Journal Article•
TL;DR: Quite inverse relations between ranks and hepatic excretion have been found: low ranks indicate an ineffective secretion of the respective drug into bile, and with increasing ranks, biliary excretion reaches a maximum and is caused by limited hepatic blood flow and by the capacity of hepatic uptake carriers.
Abstract: Relation between kidney and liver in the excretion of drugs depends on the physicochemical properties of each substance tested. The calculations of this relationship are based on a so-called rank coefficient (0-100) calculated from molecular weight, lipophilicity, degree of dissociation under physiological conditions, and protein binding rate. The results of the correlation between one of these physicochemical values and drug elimination were stochastically. Experiments were performed with 9 test substances which were distinctly different concerning their physicochemical features. Substances with a rank coefficient less than 20 (low molecular weight, low lipophilicity, preferentially ionic at pH 7.4) are eliminated effectively via the kidney. Compounds having an intermediate rank coefficient (40-60) were quantitatively excreted into urine as well. For drugs with high ranks greater than 60 (high values of molecular weight, protein binding, and lipophilicity, almost exclusively nonionic), renal excretion can be neglected. Quite inverse relations between ranks and hepatic excretion have been found: low ranks indicate an ineffective secretion of the respective drug into bile. With increasing ranks (40-60), biliary excretion increases and reaches a maximum (approximately 40% of supply). This maximum is caused by limited hepatic blood flow and by the capacity of hepatic uptake carriers. Blockade of one elimination pathway (bilateral nephrectomy or bile duct ligation) is followed by a sufficient compensation of drug excretion via the alternative elimination route only, if the test substance belongs to the intermediate group (ranks between 40 and 60). For substances with high or low ranks a compensation of drug excretion can be excluded.
TL;DR: In this article, the results of measurements of bulk scattering as well as absorption losses of evaporated ZrO2 single-layer films are presented, where a special layer design was used to eliminate the losses originating from the film interfaces.
Journal Article•
TL;DR: The current practice is discussed considering antibody and enzyme selection, optimization of elution conditions, and washing steps using different media.
Abstract: Immunoaffinity chromatography of enzymes represents an attractive purification technique suitable for one-step and large-scale purification of enzymes to homogeneity. Monoclonal and polyclonal antibodies can be used equally well. The broad use of the technique is restricted by the harsh elution conditions which are often required. The efforts to overcome these limitations and to optimize the method are reviewed, viz. proenzyme purification, purification of enzymes as part of multienzyme complexes carried out by a mild dissociation step, specific elution by substrates and effectors, enzyme stabilization, electrophoretical desorption and negative elution by adsorbing impurities from the crude extract, and hypotonic elution. The current practice is discussed considering antibody and enzyme selection, optimization of elution conditions, and washing steps using different media. Representative examples are given for various approaches.
TL;DR: In this paper, the authors have studied CdS microcrystallites embedded in glass by a sensitive modulation spectroscopy technique at room temperature and observed a two-line spectrum and a quadratic dependence on the applied field.
Abstract: This paper reports on the electric field induced absorption change in the situation of zero-dimensional quantum confinement. We have studied CdS microcrystallites embedded in glass by a sensitive modulation spectroscopy technique at room temperature. We observe a two-line spectrum and a quadratic dependence on the applied field. This absorption change is related to the Stark shift of the lowest electron-hole pair state of the quantum dot.
Auf der Basis modulationsspektroskopischer Transmissionsmessungen an CdS-Mikrokristallitglasern bei Raumtemperatur wird der Einflus eines elektrischen Feldes auf die Absorption eines quasinull-dimensionalen Systems untersucht. Das beobachtete Zweilinienspektrum und die dem Quadrat der Feldstarke proportionale Absorptionsanderung werden der Starkverschiebung des Elektron-Loch. Paar-Grundzustandes zugeordnet.
TL;DR: In this article, the 22Na-tracer diffusion studies applied to the (x = 0.25) sample of the ZrF4 (0.62-0.4x) BaF2(0.30−0.5x) LaF3(0.,08−0.,1.1x) NaF(x) (0 ⩽ x⩽ 0.30) glasses have shown the non-contribution of the Na+ ions as charge carriers to the conductivity of this mixed alkali fluoride glass.
Abstract: The 22Na-tracer diffusion studies applied to the (x = 0.25) sample of the ZrF4(0.62–0.4x)BaF2(0.30–0.5x)LaF3(0.08–0.1x)NaF(x) (0 ⩽ x ⩽ 0.30) glasses have shown the non-contribution of the Na+ ions as charge carriers to the conductivity of this mixed alkali fluoride glass. This result confirms the previously announced hypothesis based on conductivity measurements and 23Na NMR investigations. It is evident that the Na+ ions in these glasses play a role very different from that of the Li+ ions which contribute to the conductivity, in particular for high contents of LiF ( LiF ⪸ 20% ).
TL;DR: The results suggest that in homogeneous cell culture, Müller cells form some kind of epithelium-like specialized intercellular junctions which resembles that of closely related glial cell types which form homogeneous layers in situ as e.g. retinal pigment epithelioid cells expressing tight junctions, and marginal astrocytes being coupled by extensive gap junctions.
Journal Article•
TL;DR: Identical distribution patterns of neuronal elements after immunofluorescence double-staining with anti-GABA antibodies and antibodies against the GABA-synthesizing enzyme glutamic acid decarboxylase demonstrated the high specificity of the anti- GABA serum used in this paper.
TL;DR: In this paper, the formation, the structure and some areas of application of ionotropic gels obtained from natural, biotechnologically produced and chemically modified polysaccharides containing carboxy functions as anionic groups are discussed.
Abstract: Die vorliegende Ubersichtsarbeit behandelt die Bildungsweise, die chemische und morphologische Struktur und die wesentlichen Anwendungsmoglichkeiten von ionotropen Gelen auf Basis naturlicher, biotechnologisch gewonnener und chemisch modifizierter Polysaccharide mit Carboxyfunktionen als anionischen Gruppen. Schwerpunkte sind dabei die Wechselwirkung zwischen den Carboxygruppen und den mehrwertigen Metallkationen und die Selektivitat dieser Wechselwirkung, die Morphologie ionotroper Kapillargele einschlieslich der Modellvorstellungen zu ihrer Bildung sowie die Anwendung solcher Gele zur Zell-Immobilisierung und kontrollierten Wirkstoff-Freisetzung.
This review covers the formation, the structure and some areas of application of ionotropic gels obtained from natural, biotechnologically produced and chemically modified polysaccharides containing carboxy functions as anionic groups. Special points of interest are the interaction between the carboxylic groups and polyvalent metal cations and the selectivity of this interaction, the morphology of ionotropic capillary gels inclusive of model considerations on structure formation, and the application of these gels for cell immobilization and for the controlled release of bioactive compounds.
TL;DR: In this article, the single-particle Hamiltonian of the electron-phonon interaction was investigated considering a GaAs-Ga1−xAlxAs heterostructure.
Abstract: Considering a GaAs-Ga1−xAlxAs heterostructure we investigate the single-particle Hamiltonian of the electron-(long-wave optical) phonon interaction. In detail the dispersion relations of long-wave optical phonons, i.e. of longitudinal optical (LO) phonons and of interface phonons of the polar semiconductor heterostructures are analyzed. The coupling function of the electron-phonon interaction is calculated using a continuum theory. The coupling functions describing the modified Frohlich interaction of a single electron with the continuous field of polarization of the LO and interface phonons are discussed and presented in graphical form.
02 Jan 1990-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, the position and depth distribution of the displaced atoms in a room-temperature nitrogen-implanted GaAs has been investigated and two characteristic positions for displaced atoms were found to fit the experimental data very well over a broad range of ion fluences (2 × 1013 ⩽ Ni ⌽ 1 × 1016cm−2).
Abstract: Weakly damaged GaAs layers are characterized by a slight increase of the yield of backscattered light ions. In such cases, displaced atoms with preferred positions in the lattice are more probable than a random distribution. Information about the position of the displaced atoms can be provided by the temperature dependence of the dechanneling. By this the position and the depth distribution of the defects can be obtained. The investigation of room-temperature nitrogen-implanted GaAs has shown that two characteristic positions for displaced atoms — ra,1 = 0.018 nm and ra,2 = 0.065 nm — fit the experimental data very well over a broad range of ion fluences (2 × 1013 ⩽ Ni ⩽ 1 × 1016cm−2). The observed behaviour may be understood assuming defect complexes containing heavily and slightly displaced atoms, the concentration of which varies with the ion fluence and with the dose rate.
TL;DR: In this paper, a quasi-monochromatic backlighting scheme for the diagnosis of laser-produced plasmas using spherically curved crystals to produce the monochromatically beam is proposed.