Showing papers by "University of Antwerp published in 1982"
TL;DR: This article reviews the different methods used for the determination of selenium species in all types of environmental waters and basic difficulties are discussed and the efficiency of the methods is explained in view of the sub-mug/1.
176 citations
TL;DR: It is indicated that the interaction of 5-hydroxytryptamine with S2-receptors of the vascular smooth muscle cells is essential to allow the expression of the monoamine-induced amplification of the response to other vasoconstrictor substances.
120 citations
TL;DR: In this article, all published procedures for multi-element preconcentration of trace elements, prior to x-ray fluorescence analysis of water, are reviewed and evaluated, and most of them apply to the determination of single elements in water.
111 citations
TL;DR: The authors analyse the nature of strategy formation in complex organizations and present some tools for improving this critical activity and are confronted with specific management modes, drawn from literature reporting on German and Japanese business practice.
Abstract: The present article is concerned with strategic management as a specific field of general management. The authors analyse the nature of strategy formation in complex organizations and present some tools for improving this critical activity. Section 2 sets out with a simple terminology and framework for the analysis of strategic management. Next, an open-systems view is presented for analysing the strategic activity and a brief literature survey is added to support the concepts presented (Section 3). After discussing their own model of strategic management in complex organizations, the authors proceed to investigate the task of top managers in this specific field (Section 4).
Finally, the concepts presented are confronted with specific management modes, drawn from literature reporting on German and Japanese business practice (Section 5).
90 citations
TL;DR: This paper considers a possible classification of embedding mechanisms for (node-rewriting) graph grammars, which allows one to fit a number of existing notions of a graph grammar into a common framework and points out new “natural” possibilities for defining the embedding mechanism in a graph Grammar.
89 citations
TL;DR: A unified secondary structure model applicable to all 5S RNA sequences known to-date, which contains the five helices already present in the eukaryotic model, extended by additional segments that were not previously assumed to be universally present.
80 citations
TL;DR: A multiplicative equivalent of the zero utility premium calculation principle is introduced in this paper, where the utility function happens to be a normalized Young function and the new premium calculation is related to Orlicz norms.
Abstract: A multiplicative equivalent of the zero utility premium calculation principle is introduced. If the utility function happens to be a normalized Young function the new premium calculation principle is related to Orlicz norms.
73 citations
TL;DR: A systematic investigation has been made of various methods for decomposition of blood and plasma for determination of selenium, and various sources of error have been identified.
71 citations
TL;DR: The facultative and strictly anaerobic vaginal microbial flora was investigated in 40 women with non-specific vaginitis and in 40 control women seen in private gynaecological practice.
Abstract: The facultative and strictly anaerobic vaginal microbial flora was investigated in 40 women with non-specific vaginitis and in 40 control women seen in private gynaecological practice.Gardnerella vaginalis, anaerobic gram-negative bacilli, anaerobic gram-negative and gram-positive cocci were all associated with non-specific vaginitis (p<0.001), whereas lactobacilli occurred less frequently in non-specific vaginitis than in controls (p<0.01). The most common anaerobes wereVeillonella parvula, Bacteroides bivius, Bacteroides assaccharolyticus, Bacteroides capillosus andPeptococcus asaccharolyticus. Anaerobic gram-negative curved rods were found in 11% of cases of non-specific vaginitis. A characteristic pattern of short chain organic acids was found on gas liquid chromatographic analysis of vaginal secretions in non-specific vaginitis. A succinate/lactate peak ratio of 0.3 or more was found in 75% of women with non-specific vaginitis (p<0.001). Clue cells, a Positive amine test, a pH higher than 5.0, and the absence of lactobacilli on a Gram stained vaginal smear strongly correlated with non-specific vaginitis (p<0.001).
61 citations
TL;DR: In this article, the free energy of an ideal polaron gas in a static magnetic field is calculated using Feynman's pathintegral formalism, which is extended to take into account the anisotropy of the effective electron-phonon interaction.
Abstract: The free energy of an ideal polaron gas in a static magnetic field is calculated using Feynman's path-integral formalism. The trial action, used in Feynman's polaron theory, is extended to take into account the anisotropy of the effective electron-phonon interaction. This results in a free-energy expression with four variational parameters. According to Feynman's conjecture, the resulting free energy is an upper bound to the exact result. The approximate free energy is expected to provide accurate results for arbitrary electron-phonon coupling strength ($\ensuremath{\alpha}$), temperature ($T$), and magnetic field strength ($\mathcal{H}$). The free energy per polaron is evaluated for limiting values of $\ensuremath{\alpha}$, $T$, and $\mathcal{H}$.
56 citations
TL;DR: The ultrastructural study of a skeletal muscle biopsy in a case of familial oculopharyngeal muscular dystrophy confirms the presence of 7–8 nm wide tubular filaments within muscle fiber nuclei.
Abstract: The ultrastructural study of a skeletal muscle biopsy in a case of familial oculopharyngeal muscular dystrophy confirms the presence of 7–8 nm wide tubular filaments within muscle fiber nuclei.
TL;DR: In this paper, it was shown that high resolution electron micrographs viewed along the columns may still show a one-to-one correspondence with the atomic configurations even for crystal thicknesses beyond the thin phase grating limit.
TL;DR: The biosynthesis of 15-hydroxy-5,8,11,13-eicosatetraenoic acid could be confirmed during examination of the monohydroxy acids obtained without addition of fatty acids, thus formed from endogenously released substrate.
TL;DR: Two embedding mechanisms used in graph grammars are discussed and compared: a connection relation mechanism ( introduced in Janssens and Rozenberg) and a stencil mechanism (introduced in Culik and Lindenmayer).
TL;DR: In this paper, the capacity of cultured mesothelial cells to produce prostaglandins from both exogenous and endogenous arachidonic acid has been investigated, which indicated the formation of prostacyclin and prostaglanin E 2.
TL;DR: The modifications by 4-AP of theiK1 and pacemaker currents explain the changes in resting potential, action potential duration and the induction of spontaneous activity.
Abstract: 1.
4-Aminopyridine (4-AP), in a concentration of 1–5mM, prolongs the action potential duration, induces spontaneous activity and depolarizes sheep cardiac Purkinje strands. These effects are different from those obtained with 0.1mM and are reversible.
2.
Voltage clamp experiments demonstrate that the higher drug concentrations affect membrane currents measured in the potential range between-100 and-40mV, in addition to the reduction of the transient outward current already described for small amounts of the drug (0.1–0.5mM).
3.
The analysis of membrane current modifications by 4-AP in the presence of cesium and barium ions indicates that 4-AP, in the higher concentration range, reduces the inward rectifying time independent potassium currentiK1 and modifies the voltage dependence of the time and voltage dependent pacemaker current. The steady-state activation curve of the pacemaker, current is shifted towards less negative potentials and is less steeply voltage dependent. The time constant (τ) curve has an increased maximum, displaced towards less negative potentials.
4.
The modifications by 4-AP of theiK1 and pacemaker currents explain the changes in resting potential, action potential duration and the induction of spontaneous activity. The latter effect is not the result of an indirect effect of 4-AP through increased release of neurotransmitters from sympathetic nerve endings. A possible action of 4-AP at the inside of the membrane, explaining the multiple actions, is discussed.
TL;DR: It is suggested that light-controlled flower bud abscission in Lilium X ‘Enchantment’ is mediated by ethylene, and that an increase in ethylene evolution in darkness is a consequence of the influence of light on ethylene action rather than a direct influence on Ethylene biosynthesis.
Abstract: The ethylene evolution from 3 cm-long flower buds of Lilium X ‘Enchantment’ increased when the plants were placed in darkness. Also shortening the daily light period led to an increase in ethylene evolution from the buds. Dark-enhanced ethylene evolution could only be evoked in flower buds between 2 and 3.5 cm long. Flower bud abscission induced by dakrness could be prevented by injecting silver thiosulphate into the flower buds, or by using plants grown from bulbs previously immersed in a silver thiosulphate solution. It is suggested that light-controlled flower bud abscission in Lilium X ‘Enchantment’ is mediated by ethylene, and that an increase in ethylene evolution in darkness is a consequence of the influence of light on ethylene action rather than a direct influence on ethylene biosynthesis.
TL;DR: The collection of known 5 S rRNA primary structures is enriched with the sequences from three mollusca, the snails Helix pomatia and Arion rufus, and the mussel Mytilus edulis, to be fitted in a five-helix secondary structure model to apply to all 5 S RNAs regardless of their origin.
Abstract: The collection of known 5 S rRNA primary structures is enriched with the sequences from three mollusca, the snails Helix pomatia and Arion rufus, and the mussel Mytilus edulis. The three sequences can be fitted in a five-helix secondary structure model previously shown (De Wachter et al. (1982) Biochimie 64, 311-329) to apply to all 5 S RNAs regardless of their origin. One of the helices in this model can undergo a bulge-internal loop transition. Within the metazoan kingdom, the dimensions of each helix and loop are rigidly conserved, except for one helix which can comprise either 6 or 7 base pairs.
TL;DR: In this paper, the authors show that the product of the topotactic transformation from an individual particle behaves like a single crystal to common reflections and like an agglomerate of hematite crystallite pieces to non-common reflections.
Abstract: X-ray diffraction peaks recorded from hematite derived from goethite by a dehydration reaction and its isostructural system corundum from diaspore exhibit systematic peak broadening for l ≠ 3n, which corresponds to the reflections belonging to either the obverse or reverse variant of hematite. The peak width of l = 3n lines, which are common to both twin components remains as sharp as that of goethite. Estimation of the size of the scatterer from half peak widths shows that the product of the topotactic transformation from an individual particle behaves like a single crystal to common reflections and like an agglomerate of hematite crystallite pieces to non-common reflections. This implies a markedly good coherence at the twin boundaries. A decrease in peak width of non-common reflections with dehydration temperature is observed. It is due to an increase of crystallite size in the grain growth process by surface diffusion and coalescence following transformation. The difference in peak broadening is interpreted in terms of the fact that the structure of the scatterer is the same, i.e. the final reaction product hematite, but the shape factor is different for common and non-common reflections and after dehydration at different temperatures. The different sensitivity of X-rays and electrons to the incoherency at twin boundaries is also considered in relation to their wavelengths.
Die Rontgenbeugungsmaxima, die von Hamatit aufgezeichnet werden, das aus Goethit durch Dehydrationsreaktion abgeleitet wird, und von seinem isostrukturellen System Korund von Diaspor zeigen eine systematische Maximumverbreiterung fur l = 3n, die mit den Reflexen uber-einstimmen, die entweder zu der Vorder- oder Ruckseitenvariante von Hamatit gehoren. Die Maximumbreite von l = 3n-Linien, die beiden Zwillingskomponenten gemeinsam sind, bleiben so scharf wie die von Goethit. Berechnungen der Grose der Streuer aus den Halbwertsbreiten zeigen, das das Produkt der topotaktischen Transformation von einem individuellen Teilchen sich wie ein Einkristall gegenuber gemeinsamen Reflexionen und wie ein Agglomerat von Hamatitkristalliten gegenuber nicht gemeinsamen Reflexionen verhalt. Dies schliest eine bemerkenswerte gute Koharenz an der Zwillingsgrenze ein. Eine Abnahme der Breite der Maxima der nichtgemeinsamen Reflexionen mit der Dehydrationstemperatur wird beobachtet. Sie wird verursacht durch eine Zunahme der Kristallitgrose im Kornwachstumsprozes durch Oberflachendiffusion und Koaleszenz nach dem Ubergang. Der Unterschied der Maximumverbreiterung wird mit der Tatsache erklart, das die Struktur des Streuers dieselbe' ist, z. B. das Endprodukt Hamatit, jedoeh ist der Formfaktor fur gemeinsame und nichtgemeinsame Reflexionen und nach Dehydration bei unterschiedlichen Temperaturen verschieden. Die unterschiedliche Empfindlichkeit von Rontgenstrahlen und Elektronen gegenuber der Inkoharenz an Zwillingsgrenzen wird ebenfalls hinsichtlich ihrer Wellenlangen untersucht.
TL;DR: Addition of nitric and perchloric acids with gradual heating up to 210 degrees seemed to be the best method: at this temperature the labelled selenium was still recovered quantitatively, and the destruction was fast and efficient.
27 Sep 1982
TL;DR: Formal language theory is used to some extent in the investigation of properties of Petri nets and the language of a Petri net consists of the set of all firing sequences (or only of those firing sequences that lead to one of the finite number of final markings).
Abstract: Formal language theory is used to some extent in the investigation of properties of Petri nets (see, e.g. [H], [JV] and [P]). In most applications of language theory for Petri nets one considers completely sequentialized versions of Petri nets only. That is one assumes that a Petri net has one central run place which allows only a single transition to fire at a time; any sequence of such firings is called a firing sequence and the language of a Petri net consists of the set of all firing sequences (or only of those firing sequences that lead to one of the finite number of final markings).
TL;DR: It is concluded that the patient under examination is affected by Mucolipidosis IV and the term ‘sialolipidsosis’ is suggested for this inborn disorder.
Abstract: A female patient of Italian, non-Jewish, descent, 22 years of age, with cloudy corneae, capsular lens opacities and severe and progressive mental and motor deterioration is described.
TL;DR: Dimethylselenide, dimethyldiselenide and diethylselenides are sampled from air by cryogenic trapping and determined by gas chromatography with electrothermal atomic absorption spectrometric detection as mentioned in this paper.
TL;DR: Results support the hypothesis of glycine receptors occurring on dopamine cell bodies and/or dendrites in the substantia nigra of patients with senile dementia.
Abstract: Specific [3H]strychnine binding was used to identify the glycine receptor macromolecular complex in human spinal cord, substantia nigra, inferior olivary nucleus, and cerebral cortex. In material from control patients a high-affinity KD (3--8 nM) was observed in the spinal cord and the substantia nigra, both the pars compacta and the pars reticulata. This is very similar to the values observed in the rat and bovine spinal cord (8 and 3 nM, respectively) and rat substantia nigra (12 nM). In the human brain the distribution of [3H]strychnine binding (at 10 nM) was: spinal cord = substantia nigra, pars compacta greater than substantia nigra, pars reticulata = inferior olivary nucleus greater than cerebral cortex. The binding capacity (Bmax) of the rat brain (substantia nigra or spinal cord) was approximately 10-fold that of the human brain. [3H]Strychnine binding was significantly decreased in the substantia nigra from Parkinson's disease patients, both in the pars compacta (67% of control) and the pars reticulata (50% of control), but not in the inferior olivary nucleus. The results were reproduced in preliminary experiment in rats with unilateral 6-hydroxydopamine lesions of the medial forebrain bundle. In the substantia nigra from patients who died with Huntington's disease, [3H]strychnine binding tended to be high (150% of control, NS) in both the pars compacta and the reticulata. [3H]Strychnine binding was unaltered in the substantia nigra of patients with senile dementia. Together with previous neurophysiological and neuropharmacological findings, those results support the hypothesis of glycine receptors occurring on dopamine cell bodies and/or dendrites in the substantia nigra.
TL;DR: The procedures used and the chemical and instrumental problems associated with them, as well as the most important analytical results, are reviewed.
TL;DR: In this article, the structure of 3-phenyl/benzyl-8-mercaptoxanthines with various alkyl halides under different conditions is studied and confirmed by spectroscopic studies and elemental analyses.
TL;DR: The primary structure of 5.8 S rRNA from the crustacean Artemia salina shows length heterogeneity at the 5'-terminus, but consists of uninterrupted RNA chains, in contrast to some insect 5.2 S - 26 S rRNAs.
Abstract: We report the primary structure of 5.8 S rRNA from the crustacean Artemia salina. The preparation shows length heterogeneity at the 5'-terminus, but consists of uninterrupted RNA chains, in contrast to some insect 5.8 S rRNAs, which consist of two chains of unequal length separated in the gene by a short spacer. The sequence was aligned with those of 11 other 5.8 S rRNAs and a general secondary structure model derived. It has four helical regions in common with the model of Nazar et al. (J. Biol. Chem. 250, 8591-8597 (1975)), but for a fifth helix a different base pairing scheme was found preferable, and the terminal sequences are presumed to bind to 28 S rRNA instead of binding to each other. In the case of yeast, where both the 5.8 S and 26 S rRNA sequences are known, the existence of five helices in 5.8 S rRNA is shown to be compatible with a 5.8 S - 26 S rRNA interaction model.
TL;DR: In this article, a conformai technique is given for the generation of exact solutions for the spherically symmetric vacuum field in the general Bergmann-Wagoner-Nordtvedt scalar-tensory theory with vanishing cosmological constant.
Abstract: A conformai technique is given for the generation of exact solutions for the spherically symmetric vacuum field in the general Bergmann-Wagoner-Nordtvedt scalar-tensory theory with vanishing cosmological constant. We discuss in particular the solution for Schwinger's theory and for models withφ
n coupling or with curvature coupling. It appears that all theories with vanishing cosmological term lead to the presence of naked singularities.