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Showing papers by "Ghent University published in 1989"


Book ChapterDOI
01 Jan 1989
TL;DR: In this paper, the authors used the fibre contraction theorem to prove the differentiability of the centre manifold, which is the basis for the present paper, as well as the idea of using spaces of exponentially growing functions in order to formulate and prove the center manifold theorem.
Abstract: These notes originated from a seminar on dynamical systems held at the University of Louvain-la-Neuve (Belgium) in the spring of 1985. Our guide for that seminar was the book Nonlinear Oscillations, Dynamical Systems and Bifurcations of Vector Fields by Guckenheimer and Holmes [9]. This otherwise excellent book has one disadvantage for mathematicians: it contains very few proofs, and hence one is forced to go searching in the literature if one wants to fill in the details. When I tried to do this for chapter 3 of the book (on centre manifolds, normal form theory, and codimension one bifurcations), I rapidly got frustrated by the rather sketchy way in which most texts deal with the more technical parts of this theory. Around the same time I found in the PhD thesis of S. Van Gils [36] the idea of using spaces of exponentially growing functions in order to formulate and prove the centre manifold theorem. This seemed (at least for me) to be a more natural approach, and later we found out that also others had already used this idea to some extent. Stimulated by a few colleagues I then started on the project of writing some notes which would contain a reasonably complete account of the theory, which would use the new approach as its main guiding principle, and which would be suitable for use in seminars and graduate courses. Of course I had seriously underestimated the efforts needed to finish such a project, and it was only with a considerable delay that I was able to produce a first version during the summer of 1986. Since then this version has circulated among some colleagues and was tried out at a few seminars. The many remarks and suggestions which I received were taken into consideration when I wrote the version presented here; the main difference with the earlier version is the use of the fibre contraction theorem to prove the differentiability of the centre manifold. I leave it to the reader to judge to what extent the text still reflects its original goals.

288 citations


Book
12 Oct 1989
TL;DR: The use of orthonormal functions, tests for composite hypotheses, and tests of categorised data for goodness of fit has been extensively studied in the literature as discussed by the authors, including the use of X2 tests and their components.
Abstract: Summary A comprehensive approach to goodness of fit testing is possible using the smooth tests described in detail in Rayner & Best (1989). Here we give an overview of this area and demonstrate the power and flexibility of the smooth tests. Our emphasis is on the use of orthonormal functions, tests for composite hypotheses, and tests of categorised data. We have developed tests for families of distributions, such as the univariate and multivariate normal, exponential and Poisson. The tests are essentially omnibus tests but the components provide useful and powerful directional tests. The history of the smooth tests of goodness of fit is reviewed from Neyman (1937), through to Lancaster, to Thomas, Kopecky and Pierce, and to Rayner and Best. The formulation of categorised smooth models leads to X2 tests and their components. A generalisation of the smooth categorised model, when allied with Hall's (1985) idea of overlapping, leads to focused tests, and to an alternative to pooling. Examples are taken from D'Agostino & Stephens (1986), who have several different contributors and therefore approaches, none of which is recommended above the others. Our resolution is simple: don't use those other methods-use a smooth test!

231 citations


Journal ArticleDOI
TL;DR: Various heterotrophic nitrifiers have been tested and found to also be aerobic denitrifiers, and one strain, formerly known as “PseudomonasDenitrificans”, was shown to achieve nitrification rates of up to 44 nmol NH3 min−1 mg protein−1 and denitrification rates up to 69 nmol NOinf3sup−1min−1mg protein+1.
Abstract: Various heterotrophic nitrifiers have been tested and found to also be aerobic denitrifiers. The simultaneous use of two electron acceptors (oxygen and nitrate) permits these organisms to grow more rapidly than on either single electron acceptor, but generally results in a lower yield than is obtained on oxygen, alone. One strain, formerly known as “Pseudomonas denitrificans”, was grown in the chemostat and shown to achieve nitrification rates of up to 44 nmol NH3 min−1 mg protein−1 and denitrification rates up to 69 nmol NOinf3sup−1min−1 mg protein−1.

201 citations


Journal ArticleDOI
TL;DR: In this article, the authors tabulated k0-factors and related nuclear data for 112 radionuclides of interest in (n, γ) reactor neutron activation analysis.
Abstract: Abstractk0-Factors and related nuclear data are tabulated for 112 radionuclides of interest in (n, γ) reactor neutron activation analysis. Whenever relevant, critical comments are made with respect to the accuracy of literature data for e. g. isotopic abundances, half-lives, absolute gamma-intensities and 2200 m · s−1 (n, γ) cross-sections. As to the latter, a comparison is made with the values calculated from the experimentally determined k0-factors, by introduction of selected literature data for the input parameters.

175 citations


Journal ArticleDOI
M. De Vos1, Claude Cuvelier1, Herman Mielants1, Eric Veys1, F. Barbier1, A. Elewaut1 
TL;DR: This study identified a group of patients with seronegative spondylarthropathy which, even in the absence of gastrointestinal symptoms, showed evidence of gut inflammation, probably inducing an increased gut permeability with transgression of the oral tolerance and absorption of provocative antigens into the circulation.

148 citations


Journal ArticleDOI
01 Jan 1989-Plasmid
TL;DR: Two plasmids, pLAB1000 and pLAB2000, have been isolated from a grass silage strain of Lactobacillus hilgardii and could stably be maintained in LactOBacillus, Enterococcus, and Bacillus under selective conditions.

147 citations


Journal ArticleDOI
TL;DR: Analysis of genomic endonuclease cleaved DNA from nitrate utilising transformants by DNA hybridisation, showed that most integration events are as a result of homologous recombination.
Abstract: Aspergillus niger transformation frequencies of up to 1,176 transformants per μg DNA were achieved using the plasmid vector pSTA10 containing the A niger nitrate reductase structural gene Analysis of genomic endonuclease cleaved DNA from nitrate utilising transformants by DNA hybridisation, showed that most integration events are as a result of homologous recombination The niaD transformation system was used successfully for the introduction of the unselected Escherichia coli fusion genes lacZ, encoding β-galactosidase, and uidA, for β-glucuronidase, as well as the Neurospora crassa tub-2 gene, for β-tubulin pSTA10 was also capable of transforming niaD mutants of other filamentous fungi such as A nidulans, A oryzae and Penicillium chrysogenum

127 citations


Journal ArticleDOI
TL;DR: The development of an efficient and homologous transformation system for Aspergillus oryzae based on nitrate reductase (niaD) of the nitrate assimilation pathway offers a number of inherent advantages over many other systems and may be of general use for nitrate-utilising filamentous fungi.
Abstract: The development of an efficient and homologous transformation system for Aspergillus oryzae is described. This is based on nitrate reductase (niaD) of the nitrate assimilation pathway. The niaD system offers a number of inherent advantages over many other systems and may be of general use for nitrate-utilising filamentous fungi. Transformation frequencies of up to 800 transformants per microgram DNA are observed with A. oryzae. The preponderance of integration events take place at the resident niaD locus either by gene conversion (41%), single integration (23%) or multiple tandem integration (36%). Heterologous expression of the A. oryzae niaD gene in the filamentous fungi A. nidulans, A. niger and Penicillum chrysogenum is observed. That heterologous putative niaD hybridisation signals are seen with other fungal DNAs affords the oppotunity to isolate the corresponding niaD from various fungi in order to develop homolgous transformation. Co-transformation with the introduction of the non-selected markers pyrG, tub-2, and uidA has been achieved.

124 citations


Journal ArticleDOI
TL;DR: The cyst-based rotifer B. plicatilis test is an important advance in acute toxicity testing since it eliminates stock cultures, is rapid, sensitive, highly repeatable, easy to execute and cost effective.

123 citations


Journal ArticleDOI
TL;DR: The present review focuses on new data related to specific drugs dealing with benzodiazepines, cephalosporins, digitalis glycosides, general anaesthetics, glyceryl trinitrate (nitroglycerin), lignocaine, muscle relaxants, nitroprusside, opiates, papaverine and propranolol.
Abstract: Cardiopulmonary bypass is accompanied by profound changes in the organism that may alter the pharmacokinetics of drugs. Drug distribution can be altered, for example, by changes in blood flow and by haemodilution, with a decrease in protein binding; a decrease in the elimination of some drugs can be caused by impairment of renal or hepatic clearance, due, for example, to lowered perfusion and hypothermia. The subject was reviewed in the Journal in 1982, and the emphasis of the present review is on new data related to specific drugs. The following substances are dealt with: benzodiazepines, cephalosporins, digitalis glycosides, general anaesthetics, glyceryl trinitrate (nitroglycerin), lignocaine (lidocaine), muscle relaxants, nitroprusside, opiates, papaverine and propranolol. For many of these substances an abrupt decrease has been observed in serum concentration upon initiation of bypass, which is explained by haemodilution and an increase in distribution due to decreased protein binding. For nitrates and some opiates, adsorption to the bypass apparatus was shown to be important. The gradual increase in serum concentrations seen during cardiopulmonary bypass with some drugs after the initial fall is usually explained by redistribution of the drug and/or decrease in its elimination. The same phenomena are thought to explain why in the post-bypass period a concentration increase occurs, or at least a slower decrease than expected. However, drug elimination has been directly measured in only a few studies. The short duration of the bypass procedure and the continuous changes during the process hamper a rigorous pharmacokinetic evaluation. Studies allowing more precise understanding of the mechanisms underlying the observed concentration changes are needed, but are difficult to design. Similarly, more data are awaited on the pharmacodynamic and clinical consequences of the concentration changes.

121 citations


Journal ArticleDOI
TL;DR: The study has revealed that the variation in toxicity resulting from changing environmental conditions, is both species- and chemical-specific and (within the limits of this study) ranged from a minimum of a factor 2.5 to a maximum exceeding a factor of 100.

Journal ArticleDOI
TL;DR: In this paper, three native starches, varying in their amylose/amylopectin content were pregelatinized by extrusion, drum-drying and a controlled pre-gelatinization-spraydrying technique to produce cold water-swellable starches.

Journal ArticleDOI
TL;DR: The rotifer Brachionus rubens hatched from cysts is used in a simple protocol that provides for LC50 calculation and yields highly repeatable results, making it a useful new tool for routine assessment of aquatic toxicity of chemicals and effluents.

Journal ArticleDOI
TL;DR: GCP/IL-8 was found to be chemotactic for granulocytes with a specific activity of 10(5) units/mg, whereas none of the beta-thromboglobulin species possessed detectable chemotaxis activity.
Abstract: Stimulated human peripheral blood leukocytes produce a chemotactic factor for granulocytes (granulocyte chemotactic peptide/interleukin-8; GCP/IL-8), which is structurally related to platelet-derived beta-thromboglobulin. Analytically pure CGP/IL-8 and beta-thromboglobulin could be obtained after three purification steps, comprising adsorption to silicic acid, heparin-Sepharose chromatography and ion-exchange chromatography. Although GCP/IL-8 and beta-thromboglobulin had a similar affinity for heparin, they could be separated on a cation-exchange column. Both molecules were heterogeneous in that 6-7-kDa protein doublets were detected upon SDS/PAGE. N-terminal amino acid sequence analysis revealed the presence of six immunologically related but differently truncated polypeptides of beta-thromboglobulin, of which only two corresponded to previously described forms. Similarly, apart from a major polypeptide, five minor species of GCP/IL-8 were detected that also differed by N-terminal truncation. The most processed forms of beta-thromboglobulin and GCP/IL-8 were found to have their N-terminus in that region of the primary structure where a significant similarity between the two molecules starts. GCP/IL-8 was found to be chemotactic for granulocytes with a specific activity of 10(5) units/mg, whereas none of the beta-thromboglobulin species possessed detectable chemotactic activity.

Journal ArticleDOI
TL;DR: A homologous transformation system for Aspergillus oryzae is described in this paper, which is based on an A.oryzae strain deficient in orotidine-5′-phosphate decarboxylase (pyrG) and the vector pA04-2.
Abstract: A homologous transformation system for Aspergillus oryzae is described. The system is based on an A. oryzae strain deficient in orotidine-5′-phosphate decarboxylase (pyrG) and the vector pA04-2, which contains a functional A. oryzae pyrG gene as selection marker. Transformation of the A. oryzae pyrG mutant with circular PA04-2 resulted in the appearance of Pyr+ transformants at a frequency of up to 20 per μg of DNA, whereas with linear pA04-2 up to 200 transformants per μg DNA were obtained. In 75 % of the Pyr+ transformants recombination events had occurred at the pyrG locus, most of which (90%) resulted in insertion of one or two copies of the vector and the others (10%) in a replacement of the mutant allele by the wild-type allele. Vector pA04-2 is also capable of transforming a corresponding mutant of Aspergillus niger. This transformation system was used to introduce into A. oryzae the heterologous and non-selectable bacterial genes lacZ, encoding β-galactosidase, and uidA, encoding β-glucuronidase. Using the Aspergillus nidulans gpdA promoter to drive bacterial gene expression in A. oryzae, relatively high levels of activity, as well as protein per se, as judged by western blot analyses, were obtained.

Journal ArticleDOI
TL;DR: Determination des facteurs k 0 des raies gamma de 112 radioisotopes d'interet analytique. as discussed by the authors presented de la methode experimentale and des tableaux de resultats
Abstract: Determination des facteurs k 0 des raies gamma de 112 radioisotopes d'interet analytique. Presentation de la methode experimentale et des tableaux de resultats

Journal ArticleDOI
TL;DR: Recombinant human tumour necrosis factor (rhTNF) had anti‐tumour activity against 2 of 3 human ovarian cancer xenografts growing intraperitonealy in nude mice, producing a moderate increase in mouse survival time and promoting the adhesion of tumour cells to the peritoneum and their establishment as tumour nodules below the mesothelial surface.
Abstract: Recombinant human tumour necrosis factor (rhTNF) had anti-tumour activity against 2 of 3 human ovarian cancer xenografts growing intraperitonealy (i.p.) in nude mice, producing a moderate (2- to 3-fold) increase in mouse survival time. rhTNF therapy caused a marked influx of polymorphonuclear neutrophils into the peritoneal cavity during the first few days of daily therapy. This was accompanied by a decrease in the number of peritoneal macrophages and lymphocytes. rhTNF also caused an increase in peripheral blood neutrophils. With continuation of daily therapy, the peritoneal neutrophil influx diminished, with restoration of the macrophage and lymphocyte populations. After 2 to 3 weeks there was a small but significant increase in peritoneal Thy 1.2 cells. In the peripheral blood, the neutrophilia was less marked than at the start of therapy. Mild myelosuppression was indicated by significant falls in haemoglobin and platelet counts. Within 24 hr of the start of therapy in the 2 responsive xenografts (HU and LA) tumour clumps in the peritoneum were surrounded by host inflammatory cells, and tumours fixed to the omentum were infiltrated by neutrophils and mononuclear cells. In both instances necrosis was evident by 4 to 7 days. The third xenograft (OS) grew although the rhTNF therapy induced the same inflammatory changes in the peritoneum. In contrast to its positive effect on the survival of tumour-bearing mice, rhTNF promoted the adhesion of tumour cells to the peritoneum and their establishment as tumour nodules below the mesothelial surface. This phenomenon was seen in all 3 xenografts including the OS xenograft which did not respond in any other way to rhTNF therapy.

Journal ArticleDOI
TL;DR: In this paper a morphological study of the retinal vascular patterns in various species of domestic animals is reported and a classification of these patterns into four well-defined groups is described.

Journal ArticleDOI
TL;DR: In this paper, a comprehensive analysis of the carrier-induced FM response of DFB lasers is given, and it is found that the FM response can sometimes vary strongly from chip to chip.
Abstract: A comprehensive analysis of the carrier-induced FM response of DFB lasers is given. Experimentally it is found that the FM response can sometimes vary strongly from chip to chip. In a number of cases anomalies either as a function of frequency or as a function of bias are observed. Theoretically, a dynamic model which includes spectral as well as longitudinal spatial hole burning is presented. The main feature of the model is that local variations of the Bragg wavelength caused by hole burning are rigorously and self-consistently taken into account. By comparing the experimental results with theoretical calculations, it is shown that in DFB lasers, spatial hole burning is an important phenomenon. The model confirms that the dynamic (FM) behavior can vary from DFB chip to DFB chip. The model shows that spatial hole burning is indeed the dominant factor which induces the anomalies that are found experimentally in the FM response. >

Journal ArticleDOI
J. Herman1, J.P. Remon1
TL;DR: In this paper, the authors used thermally modified starches as excipients for sustained release tablets and found that the gel strength of hydrated tablets seemed proportional to the degree of amylose in the formulated starch.

Journal ArticleDOI
TL;DR: The single dose pharmacokinetics of recombinant human erythropoietin (r-HuEPO) were compared in six continuous ambulatory peritoneal dialysis patients after intravenous, subcutaneous, and intraperitoneal administration of 300 U/kg to find results close to those obtained in hemodialysis patients.
Abstract: The single dose pharmacokinetics of recombinant human erythropoietin (r-HuEPO) were compared in six continuous ambulatory peritoneal dialysis (CAPD) patients after intravenous (i.v.), subcutaneous (s.c.), and intraperitoneal (i.p.) administration of 300 U/kg. Intravenous administration gave results close to those obtained in hemodialysis patients, with a half-life of 11.2 h and a volume of distribution of 5.0% of body weight. After subcutaneous administration, the serum concentration rose slowly to plateau between 24 and 36 h, the area under the serum concentration vs. time curve from 6 to 72 h being 18.2% of that after intravenous administration. After intraperitoneal administration, the serum concentration was even lower, the area under the curve from 0 to 24 h was between 2.5 and 3.6% of that after intravenous administration, and 80% of the administered dose was recovered in the first peritoneal effluent after a 4-h dwell time.

Journal ArticleDOI
01 Mar 1989-Planta
TL;DR: Higher canopy darkrespiration rates under elevated CO2 level and low irradiance during the growing period are the primary causes for the increase in dry-matter production being much lower than expected, being much higher than expected merely based on the NCERmax difference.
Abstract: The relationship between leaf photosynthetic capacity (pn, max), net canopy CO2- and H2O-exchange rate (NCER and Et, respectively) and canopy dry-matter production was examined in Lollium perenne L. cv. Vigor in ambient (363±30 μl· l-1) and elevated (631±43 μl·l-1) CO2 concentrations. An open system for continuous and simultaneous regulation of atmospheric CO2 concentration and NCER and Et measurement was designed and used over an entire growth cycle to calculate a carbon and a water balance. While NCERmax of full-grown canopies was 49% higher at elevated CO2 level, stimulation of pn, max was only 46% (in spite of a 50% rise in one-sided stomatal resistance for water-vapour diffusion), clearly indicating the effect of a higher leaf-area index under high CO2 (approx. 10% in one growing period examined). A larger amount of CO2-deficient leaves resulted in higher canopy dark-respiration rates and higher canopy light compensation points. The structural component of the high-CO2 effect was therefore a disadvantage at low irradiance, but a far greater benefit at high irradiance. Higher canopy darkrespiration rates under elevated CO2 level and low irradiance during the growing period are the primary causes for the increase in dry-matter production (19%) being much lower than expected merely based on the NCERmax difference. While total water use was the same under high and low CO2 levels, water-use efficiency increased 25% on the canopy level and 87% on a leaf basis. In the course of canopy development, allocation towards the root system became greater, while stimulation of shoot dry-matter accumulation was inversely affected. Over an entire growing season the root/shoot production ratio was 22% higher under high CO2 concentration.


Journal ArticleDOI
TL;DR: The results suggest that M cells arise exclusively from the midline, prenodal rudiment, from which M cells extend caudally throughout the entire length of the neuroepithelium.
Abstract: The origin of prospective M cells, which are median neuroepithelial cells that become wedge-shaped during bending of the neural plate and eventually form the midline floor of the neural tube, was determined by constructing quail/chick chimeras and using the quail nucleolar marker to identify quail donor cells in chick host blastoderms. Two possible sites of prospective M-cell origin in the epiblast were examined: a single, midline rudiment located just rostral to Hensen's node and paired rudiments flanking the cranial part of the primitive streak. Our results suggest that M cells arise exclusively from the midline, prenodal rudiment. From this rudiment, M cells extend caudally throughout the entire length of the neuroepithelium. This new information on the origin of prospective M cells will aid in the analysis of their role in neurulation.

Journal ArticleDOI
TL;DR: Clinical, cytomorphologic, and cytogenetic investigations were carried out in a series of 76 secondary MDS and ANLL patients, and six other chromosomes seemed to be consistently involved in the pathogenetic mechanisms of secondary leukemia and MDS.

Journal ArticleDOI
15 May 1989-Gene
TL;DR: A homologous transformation for Aspergillus niger was developed based on the nitrate reductase structural gene niaD, and it was demonstrated that while some transformants were as stable as the wild-type (wt), others were markedly less so.

Journal ArticleDOI
TL;DR: In this article, an integral equation method for the calculation of capacitance and inductance matrices is presented, which is suitable for multiconductor transmission lines embedded in a multilayered dielectric medium on top of a ground plane.
Abstract: An integral equation method for the calculation of capacitance and inductance matrices is presented. The method is suitable for multiconductor transmission lines embedded in a multilayered dielectric medium on top of a ground plane. Conductors of arbitrary polygonal cross section can be handled, as well as infinitely thin conductors. The method is new in two respects. The kernel of the integral equation is the space-domain Green's function of the layered medium. The accuracy of the solution is enhanced by using basis functions that exactly model the singular behavior of the charge density in the neighborhood of a conductor edge. Numerical examples show the accuracy of the calculations and the complexity of the configurations that can be treated. >

Journal ArticleDOI
TL;DR: The power of several biochemical and physical markers was evaluated for their ability to discriminate between semen of infected and noninfected infertile men and the total output of citric acid had the strongest discriminating power.
Abstract: Infection of the male accessory sex glands may result in impaired secretory function and alteration of the composition of seminal plasma. Using receiver operating characteristic curves and accuracy tests, the power of several biochemical and physical markers was evaluated for their ability to discriminate between semen of infected and noninfected infertile men. The total output of citric acid had the strongest discriminating power, followed by acid phosphatase and gamma-glutamyltranspeptidase. Measurement of the concentration of fructose was found to be nondiscriminatory.

Journal ArticleDOI
TL;DR: Cytogenetic analysis of a mesenchymal hamartoma of the liver in a 3-year-old child revealed a balanced translocation between chromosomes 15 and 19 as the sole chromosome change.

Journal ArticleDOI
TL;DR: It is discussed to what extent decentralized time-varying feedback control strategies may eliminate fixed modes and structurally fixed modes in a large-scale control system.