Showing papers by "University of Bonn published in 1981"
TL;DR: The method yields polynomial algorithms for vertex packing in perfect graphs, for the matching and matroid intersection problems, for optimum covering of directed cuts of a digraph, and for the minimum value of a submodular set function.
Abstract: L. G. Khachiyan recently published a polynomial algorithm to check feasibility of a system of linear inequalities. The method is an adaptation of an algorithm proposed by Shor for non-linear optimization problems. In this paper we show that the method also yields interesting results in combinatorial optimization. Thus it yields polynomial algorithms for vertex packing in perfect graphs; for the matching and matroid intersection problems; for optimum covering of directed cuts of a digraph; for the minimum value of a submodular set function; and for other important combinatorial problems. On the negative side, it yields a proof that weighted fractional chromatic number is NP-hard.
2,170 citations
805 citations
368 citations
TL;DR: In this paper, an explicit boson-exchange model for the nucleon-nucleon interaction including the δ-isobar is presented, and results for NN-scattering, the deuteron and nuclear matter.
343 citations
295 citations
15 May 1981
TL;DR: In this article, the potential curves for the ground and excited states of the chlorine molecules and its positive and negative ions have been calculated by means of the MRD-CI method, and the results at the corresponding full CI level are estimated for each state via a perturbation correction.
Abstract: Potentials curves for the ground and excited states of the chlorine molecules and its positive and negative ions have been calculated by means of the MRD-CI method. The standard AO basis employed consists of 74 functions including two atomic d and one set of s and p bond species, and the results at the corresponding full CI level are estimated for each state via a perturbation correction. Special emphasis is placed upon the treatment of Rydberg-valence mixing in this system, which phenomenon is found to be essential to the understanding of Cl2 electronic absorption spectrum. All singlet states which correlate with the lowest dissociation limit plus many others which go to ionic Cl++Cl− or Rydberg Cl+Cl asymptotes are given explicit consideration. Among the triplet species of Cl2 which dissociate into the ground state atoms only the 3Πu state is not repulsive. The calculated D0 value for the ground state is 2.455 eV compared to the experimental value of 2.475 eV, while the vertical ionization energy and electron affinity are found to be 11.48 and 2.38 eV respectively, also in very good agreement with the corresponding measured data of 11.50 and 2.51 ± 0.1 eV. In addition to Cl2 laser line is confirmed to result from a 3Πg → 3Πu emission, whereby the calculated downward vertical transition energy of 4.86 eV fits in quite well with the known location of this line at 4.805 eV. The first two dipole-allowed transitions from the ground state of chlorine involve 1Σu+ and 1Πu states which are calculated to be nearly isoenergetic, and these results also match very well with the location of the first absorption band in this spectrum. Finally quite similarly as in O2 it is found that an avoided crossing between Rydberg and valences states produces a relatively steep potential well for an upper state (2 1Σu+), whose location concides with that of a second absorption band recently observed in synchrotron radiation studies.
241 citations
TL;DR: The inhibitory action and binding characteristics of the new anti-fungal antibiotic myxothiazol has been described and a red shift of the ferrocytochrome b spectrum is indicated, independent of and differs from the antimycin red shift.
232 citations
TL;DR: It is shown that the max-cut problem can be solved in polynomial time for weakly bipartite graphs and an algorithm that computes a shortest path of even length is presented.
165 citations
TL;DR: A general method for calculating the dosage scheme for any linear model is presented, if the desired blood level or amount of drug in any other compartment is given.
Abstract: The problem of correctly administering drugs is considered with respect to pharmacokinetics. A general method for calculating the dosage scheme for any linear model is presented, if the desired blood level or amount of drug in any other compartment is given.
159 citations
TL;DR: In this paper, four rocket-borne mass spectrometers, which employed shock-freezing cryo-ion sources, were used to determine the atmospheric composition in the turbopause regime.
129 citations
TL;DR: Diazepam pharmacokinetics was determined from concentrations measured in multiple plasma samples drawn during 7 days after each dose, and Diazepam was extensively bound to plasma protein, with a mean free fraction among male subjects of 1.34%.
Abstract: 27 male volunteers aged 20 to 91 years, and 13 female volunteers aged 21 to 33 years, received single 5 to 10 mg doses of diazepam intravenously. Diazepam pharmacokinetics were determined from concentrations measured in multiple plasma samples drawn during 7 days after each dose. Diazepam elimination half-life among males (mean: 66 h) increased significantly with age (r = 0.53, p less than 0.005). Volume of distribution (mean: 1.39 liters/kg) also increased significantly with age (r = 0.67, p less than 0.001). Clearance of total diazepam in males (mean: 0.42 ml/min/kg) tended to decline with age (r = 0.32), but the association was of borderline significance (p = 0.1). Diazepam was extensively bound to plasma protein, with a mean free fraction among male subjects of 1.34%. Free fraction tended to increase with age (r = 0.14). Correction of volume of distribution and clearance for individual differences in binding did not alter the conclusions. Compared to young males, young females had larger volumes of distribution (1.87 vs. 1.34 liters/kg) and higher total clearance (0.63 vs. 0.49 ml/min/kg). These differences were even greater after correction for sex-related changes in protein binding. Elimination half-life did not differ between sexes. Since both age and sex can influence diazepam disposition, both should be considered as independent variables in studies of diazepam pharmacokinetics.
TL;DR: In this paper, a method for the construction of families of first integrals in involution for Hamiltonian systems which are invariant under the Hamiltonian action of a Lie group G is presented.
Abstract: A method is exposed which allows the construction of families of first integrals in involution for Hamiltonian systems which are invariant under the Hamiltonian action of a Lie group G. This is applied to invariant Hamiltonian systems on the tangent bundles of certain homogeneous spaces M = G/K. It is proved, for example, that every such invariant Hamiltonian system is completely integrable if M is a real or complex Grassmannian manifold or SU(n + 1)/SO(n + 1) or a distance sphere in ℂPn+1. In particular, the geodesic flows of these homogeneous spaces are integrable.
01 Jan 1981
TL;DR: The reason for this specialized treatment of cell morphogenesis is best explained through an examination of tip growth, the locally restricted enlargement of a cell that usually has a tubular shape (Frey-Wyssling 1959).
Abstract: Morphogenesis of a plant cell, as treated in this chapter, is, in general, morphogenesis of the cell wall with an emphasis on growth. The reason for this specialized treatment of cell morphogenesis is best explained through an examination of tip growth, the locally restricted enlargement of a cell that usually has a tubular shape (Frey-Wyssling 1959). Tip growth is associated with polar, local secretion of wall material and represents a conspicuous example of cell polarity. Usually, cells with tip growth show unipolar growth. There are also, however, examples of a bipolar tip growth-phloem (Schoch-Bodmer and Huber 1951) and xylem (Bosshard 1952) fibers. Sometimes there are cells with multipolar growth, i.e., branched systems of coenocytic fungi or algae, stellately armed parenchyma cells, and nonarticulated laticifers. Even the morphogenesis of cells with a complicated shape like the cells of Micrasterias (see p. 147 f.) can be regarded as multipolar growth.
TL;DR: Although absorption was almost complete after oral administration, absolute bioavailability was low, due to extensive hepatic first-pass metabolism, so it can be concluded that verapamil clearance is liver blood flow-dependent.
Abstract: Following i. v. administration, the plasma concentration-time curve of verapamil could best be described by either a mono- or biexponential equation. Total plasma clearance (1.26 l/min) approached liver blood flow (1.5 l/min), so it can be concluded that its clearance is liver blood flow-dependent. Although absorption was almost complete after oral administration, absolute bioavailability (20%) was low, due to extensive hepatic first-pass metabolism. The approach using stable isotope-labelled and unlabelled drug permits simultaneous administration by the intravascular and extravascular routes, thus allowing determination of absolute bioavailability in a single experiment.
TL;DR: A suitable approach is the planning and synthesis of arrangements of various types of molecules, which are all constructed such that they fit into one another and thus by themselves and in an organized way build up to functional systems where the functional groups are held fast in the desired arrangement by the intermolecular forces.
Abstract: Definite complexes between various uncharged molecules are still relatively unexplored 1) although this type of complexation plays a fundamental role in biochemical processes, eg the base-pairing of nucleic acids 2), enzyme/substrate or pharmacon/receptor interactions “The molecular biology is a striking example of the fact that molecules which fit into one another sterically and functionally, lead together to fundamentally new functional possibilities” 1d) A suitable approach in this respect is “the planning and synthesis of arrangements of various types of molecules, which are all constructed such that they fit into one another and thus by themselves and in an organized way build up to functional systems where the functional groups are held fast in the desired arrangement by the intermolecular forces” 1d)
TL;DR: Three new antibiotically active metabolites were isolated from cultures of the fungus Pleurotellus hypnophilus, and the mode of action was compared with the antimicrobial and cytotoxic effects of complicatic acid and other α-methylene ketones and lactones from higher plants.
Abstract: Three new antibiotically active metabolites were isolated from cultures of the fungus Pleurotellus hypnophilus. The structures which are closely related to the coriolins were elucidated by spectroscopic methods. Hypnophilin (1) has a hirsutane sceleton whereas pleurotellol (2) and pleurotellic acid (3) are sesquiterpenoids with novel hirsutane skeletons. The common structural feature of all three metabolites is an α-methylene ketone moiety. The antibiotics inhibited the growth of several bacteria as well as of some fungi. In cells of the ascitic form of Ehrlich carcinoma RNA and DNA syntheses were more affected than protein synthesis. The mode of action was compared with the antimicrobial and cytotoxic effects of complicatic acid (4) and other α-methylene ketones and lactones from higher plants. All the compounds tested reacted rapidly with cysteine to form adducts which were almost devoid of biological activity.
TL;DR: The method was used in a study of six females who received single intravenous doses of midazolam for purposes of anesthetic induction prior to minor gynecologic procedures, and concentrations following single therapeutic doses can be quantitated using electron-capture gas-liquid chromatography.
Abstract: Plasma midazolam concentrations following single therapeutic doses can be quantitated using electron-capture gas-liquid chromatography. After addition of a benzodiazepine analogue as an internal standard, samples are extracted with benzeneisoamyl alcohol (98.5:1.5). The organic extract is evaporated to dryness, reconstituted, and chromatographed on an SP-2250 liquid phase. The automatic sampler allows up to 100 chromatographic analyses per 24-h period. The sensitivity limits are 2-3 ng of midazolam per ml of plasma, and the variation of identical samples is 7 per cent or less. The method was used in a study of six females who received single intravenous doses of midazolam for purposes of anesthetic induction prior to minor gynecologic procedures. Mean (+/- SE) kinetic variables for midazolam were: volume of central compartment, 0.37 (+/ 0.06 l/kg; total volume of distribution, 1.72 (+/- 0.05) l/kg: initial distribution half-life, 7.2 (+/- 1.6) min; elimination half-life, 2.5 (+/- 0.2) h; total clearance, 8.1 (+/- 0.52) ml.min-1.kg-1.
TL;DR: In this article, the exact quantum reaction probabilities for the collinear I + HI (v ⩽ 3) → IH (v' ⩾ 3) +I and I + MuI (v⩽ 2) → IMu (v') +I reactions on three different LEPS potential surfaces are evaluated by S -matrix propagation along Delves' radial coordinate.
24 Aug 1981
TL;DR: Pratorinine is a new phenanthridone alkaloid and anhydrolycorin-7-one was known before only as a synthetic compound and the physiological significance of hippadine is appraised.
TL;DR: Characteristics of the processes by which steroid and thyroid hormones enter tissues, cells and membrane vesicles are reviewed, and several authors suggest that entry is by passive diffusion: the accumulation within cells is attributed to cytoplasmic binding proteins.
TL;DR: Some deviations from additivity in chemical shifts, calculated for oligosaccharides from the data on their constituent sugar residues, furnished information on the conformational changes in crowded glycolipid molecules.
TL;DR: First results from the UA5 detector on charged particle production at √s = 540 GeV in the pseudorapidity range ∣ν∣ were reported in this article.
TL;DR: In this paper, the Holder continuity of bounded weak solutions of quasilinear parabolic systems with main part in diagonal form is proved via a parabolic hole-filling technique.
Abstract: The Holder continuity of bounded weak solutions of quasilinear parabolic systems with main part in diagonal form is proved via a “parabolic hole-filling technique”.
TL;DR: Several classes of facets for the convex hull of incidence vectors of stable sets in a K 1,3 -free graph are given, including facets with ( a, a + 1)-valued coefficients, where a = 1, 2, 3,….
TL;DR: In this paper, the existence of the third integral of motion for the classical Hamiltonian describing a hydrogen atom in a magnetic field is studied by numerical methods, and it is found that the integral is isolating for all initial conditions for which the energy is lower than a critical energy, beyond which the phase orbits are unstable and the Hamilton system can behave stochastically.
Abstract: The problem of the existence of the third integral of motion for the classical Hamiltonian describing a hydrogen atom in a magnetic field is studied by numerical methods. It is found that the third integral is isolating for all initial conditions for which the energy is lower than a critical energy, beyond which the phase orbits are unstable and the Hamilton system can behave stochastically. This critical energy depends upon the strength of the magnetic field and the value of the z component of the angular momentum. The critical energy approaches the (classical) ionisation energy in the weak-field and strong-field limits, while it is lowest in the transition region. The consequences for the quantum mechanical energy spectrum of the hydrogen atom are discussed: the existence of this approximate dynamical symmetry would allow for close anti-crossings of levels, and might facilitate the analytic calculations of the energy levels below the critical energy. In discussion of the correspondence diagram a criticism of an earlier paper is given.
TL;DR: In this article, the decay properties of charmed D mesons produced near the peak of the {psi} (3770) resonance in e{sup +}e{sup -} annihilation were studied.
Abstract: We present a study of the decay properties of charmed D mesons produced near the peak of the {psi}" (3770) resonance in e{sup +}e{sup -} annihilation. Branching fractions for nine Cabibbo-favored and three Cabibbo-suppressed decay modes are presented along with upper limits on one additional Cabibbo-favored and four additional Cabibbo-suppressed decay modes. A study of K{pi}{pi} decay mode Dalitz plots reveals a large quasi-two-body pseudoscalar-vector component for the D{sup 0} decays and an apparent nonuniform population an the Dalitz plot for the D{sup +} decay into K{sup -}{pi}{sup +}{pi}{sup +}. Using tagged events, we measure the charged particle multiplicity and strange particle content of D decays. A measurement of the D{sup +} and D{sup 0} semileptonic decay fractions indicates that the D{sup +} has a significantly longer lifetime than the D{sup 0}.
TL;DR: Evidence is presented that some diseases like insulin-dependent diabetes mellitus, multiple sclerosis, and idiopathic membranous nephropathy, which are primarily associated with HLA-D,DR, are also related to the rare C2, C4, and Factor B alleles.
Abstract: In this review article, recent evidence is presented that some diseases like insulin-dependent diabetes mellitus, multiple sclerosis, and idiopathic membranous nephropathy, which are primarily associated with HLA-D,DR, are also related to the rare C2, C4, and Factor B alleles. Circumstantial evidence is available that at least some of these rare variants may be functionally deficient. Based on the concept of functionally interacting gene clusters, mutant complement genes may lead to impaired effector mechanisms in virus neutralization or lysis of virus-infected cells. Other mechanisms such as alteration of vascular permeability may be involved in the development of proliferative retinopathy and familial hypertension. In lepromatous lepra, an impaired cell-mediated lysis of M. leprae may be related to the hemolytically inactive C4F1 allelic product.
TL;DR: Using this technique the bioavailability of verapamil tablets (Isoptin® 80) relative to a stable labelled solution of verAPamil was found to be 108.1%, with a 95% confidence interval between 89.1 and 127.1%.
Abstract: Although the absorption of verapamil is almost complete after oral administration, its bioavailability is low due to extensive hepatic first-pass metabolism. Besides large interindividual differences in first-pass metabolism, pronounced day-to-day intraindividual variations in first-pass metabolism are observed, leading to erroneous results in relative bioavailability studies. Stable isotope techniques, which permit simultaneous administration of a solution and a tablet, can successfully be used to overcome these difficulties. The method has the advantage that two experiments can be carried out in a single test. Furthermore, the number of subjects required in bioavailability studies can be greatly reduced. Using this technique the bioavailability of verapamil tablets (Isoptin® 80) relative to a stable labelled solution of verapamil was found to be 108.1%, with a 95% confidence interval between 89.1 and 127.1%.
TL;DR: The behavior of statoliths in rhizoids differently oriented with respect to the gravity vector indicates that there are cytoskeleton elements which exert forces on thestatoliths, mostly in the longitudinal directions, and it is inferred that microfilaments are involved in controlling the position of statolithics, and that there is a considerable tension on these microfilmaments.
Abstract: The behavior of statoliths in rhizoids differently oriented with respect to the gravity vector indicates that there are cytoskeleton elements which exert forces on the statoliths, mostly in the longitudinal directions. Compared to the sum of the forces acting on a statolith, the gravitational force is a relatively small component,i.e., less than 1/5 of the cytoskeleton force. The balance is disturbed by displacing the rhizoid from the normal vertical orientation. It is also reversibly disturbed by cytochalasin B such that some statoliths move against the gravity force. Phalloidin stabilizes the position of the statoliths against cytochalasin B. We infer that microfilaments are involved in controlling the position of statoliths, and that there is a considerable tension on these microfilaments. The vibration frequency of the microfilaments corresponding to this tension is in the ultrasonic range.