Showing papers by "Ghent University published in 1983"
TL;DR: A least squares algorithm for fitting additive trees to proximity data using a penalty function to enforce the four point condition on the estimated path length distances is described.
Abstract: A least squares algorithm for fitting additive trees to proximity data is described. The algorithm uses a penalty function to enforce the four point condition on the estimated path length distances. The algorithm is evaluated in a small Monte Carlo study. Finally, an illustrative application is presented.
514 citations
TL;DR: Evidence is presented that Ia present on HUVE cells and HDF cells can be functionally recognized by human T cells, resulting in a two-way interaction between T cells and mesenchymal cells that may be important in allograft rejection.
Abstract: T-lymphocyte-mediated responses to the cellular components of blood vessels are important in rejection of allografts. The induction of cytolytic T lymphocytes (CTLs) depends on recognition of foreign class II major histocompatibility complex antigens (human HLA-DR, DC/DS, SB and others, collectively referred to as Ia) on the target cells whereas killing by CTLs usually depends on recognition of foreign class I antigens (HLA-A, B), although some alloreactive CTLs recognize foreign Ia instead of HLA-A, B (refs 5-8). The expression of Ia antigens has traditionally been regarded as restricted to immunological cell types, and the presence of class II antigen-bearing 'passenger' leukocytes in rodent organ grafts appears necessary for graft rejection. Recently, Ia antigens have been observed by immunofluorescence microscopy on human renal and dermal capillary endothelium. We have previously shown that human umbilical vein endothelial (HUVE) cells in standard culture conditions do not bear Ia antigens, but may be induced to do so by products of lectin- or alloantigen-activated T lymphocytes. Furthermore, we found that recombinant immune interferon (IFN-gamma), free of other lymphokines, is a potent inducer of Ia expression in HUVE cells. Here we report that IFN-gamma also induces Ia expression on human foreskin capillary endothelial (HFCE) cells, HUVE cells transformed by Simian virus 40 viral DNA (SV-HUVE cells) and human dermal fibroblast (HDF) cells in culture. Further, we present evidence that Ia present on HUVE cells and HDF cells can be functionally recognized by human T cells, resulting in a two-way interaction between T cells and mesenchymal cells that may be important in allograft rejection.
455 citations
TL;DR: The partial purification procedure for K. fragilis inulinase is based upon fixation and elution on DEAE-cellulose, the selective nonprecipitation of inulin enzyme in saturated (NH 0 ) 2 SO 4 , and the reversible precipitation of in insulinase with precooled acetone.
Abstract: Publisher Summary The microbial enzyme, inulinase, hydrolyzes the plant polymer inulin into practically pure fructose. Several methods have been applied to prepare stable crude Kluyveromyces fragilis inulinase preparations: acetone drying of cells, P 2 O 5 , drying, and cell autolysis yielded preparations which were stable at 0°C for at least one month. The partial purification procedure for K. fragilis inulinase is based upon fixation and elution on DEAE-cellulose, the selective nonprecipitation of inulinase in saturated (NH 0 ) 2 SO 4 ,, and the reversible precipitation of inulinase with precooled acetone (–10°C). A semipurified inulinase preparation was obtained with about 55–65% recovery yield. Industrially applicable production schemes to produce Ultra High Fructose Glucose Syrups (UHFGS) from inulin have been proposed, with Jerusalem artichoke as the source of inulin. Recently, interest has been concentrated toward direct alcohol fermentation from inulin sources such as Jerusalem artichoke, using yeasts with inulinase activity. This research fits into the framework of research on new energy sources.
380 citations
TL;DR: In this paper, a description of the method generally used in Belgium to assess the quality of running water is given, which involves the determination of a biotic index with scores between 0 and 10, based on samples of the aquatic macro-invertebrate community collected in situ, using a handnet.
Abstract: A description is given of the method generally used in Belgium to assess the quality of running water. It involves the determination of a biotic index with scores between 0 and 10, based on samples of the aquatic macro-invertebrate community collected in situ, using a handnet.
347 citations
TL;DR: It was demonstrated that relaxation by histamine and acetylcholine of pre-contracted rat aorta segments required the presence of endothelial cells, and histamine acting on H1-receptors seemed to initiate the production of mediator(s) from the endothelium, which leads to relaxation of the vascular smooth muscle cells.
252 citations
TL;DR: It is argued that, in spite of considerable abilities for passive dispersal, vicariance can develop well in this group of rotifers and an explanation for these patterns is found in drifting continents and Pleistocene climatic changes.
Abstract: The biogeography of rotifers is discussed in light of general biogeographical concepts. It is argued that, in spite of considerable abilities for passive dispersal, vicariance can develop well in this group. Examples selected from the Brachionidae illustrate the high levels of endemicity found in Australia and South America, while the Indian subcontinent and Africa have a predominantly cosmopolitan fauna. An explanation for these patterns is found in drifting continents and Pleistocene climatic changes.
205 citations
TL;DR: The hatching quality of Reference Cysts and cysts from Canada and Argentina can be significantly improved by incubation of the cysts at low salinity, and for almost all commercial sources the use of decapsulated cysts results in a significant increase of the hatching output.
154 citations
TL;DR: A known stabilizability criterion and a simple stability theorem for the open-loop system are obtained as special cases of the main result.
140 citations
TL;DR: In this article, the radiation losses in arbitrarily curved integrated-optic waveguides are computed numerically by means of the beam-propagation method, and design rules for bends and S-shaped curves connecting two straight waveguiders are derived.
Abstract: Radiation losses in arbitrarily curved integrated-optic waveguides are computed numerically by means of the beam-propagation method. From the results obtained, design rules for bends and S-shaped curves connecting two straight waveguides are derived.
109 citations
TL;DR: In this paper, an iterative procedure for obtaining maximum likelihood estimates of the model parameters is developed, and the possibility of testing various hypotheses by means of likelihood ratio tests is discussed.
Abstract: After introducing some extensions of a recently proposed probabilistic vector model for representing paired comparisons choice data, an iterative procedure for obtaining maximum likelihood estimates of the model parameters is developed. The possibility of testing various hypotheses by means of likelihood ratio tests is discussed. Finally, the algorithm is applied to some existing data sets for illustrative purposes.
109 citations
TL;DR: Congenital malformations have been investigated in a consecutive series of 445 monozygotic twin pairs coming from two twin surveys numbering 1,424 pairs, finding Concordant malforms in 6 pairs, discordant in 20 pairs.
TL;DR: A phylogeny of the subfamily is proposed, with Megafenestra as the more primitive genus, closely allied to Ceriodaphnia, and within Scapholeberis, S. mucronata as the most apomorphic species.
Abstract: The group of hyponeustonic daphniid cladocera previously known under the generic name Scapholeberis is raised to the rank of a subfamily (Scapholeberinae) and contains two genera, Megafenestra n.gen. (2 species), and Scapholeberis s.s. (7 species and one subspecies). The characters upon which this revision is based are: structure of the rostrum, structure of the first antennae, structure of trunk limbs 1, 2, and 5, presence and nature of headpore(s), structure of the ventral rim of the valves, armature of the distal rim of the valves, structure of the postabdomen and its end-claws. Males were examined in all but two species, and proved to be more primitive than females and much less diagnostic than in the Chydoridae. It also appeared that the shape and armature of the postabdomen are less important taxonomical tools than heretofore supposed. In more than half of the species, it is of generalised shape and hardly usable beyond the species-group level. The same, although less drastically, holds true for the P1 of males. Of greatest diagnostic value at the species level are the shape of the rostrum and the armature of the valve margins. A phylogeny of the subfamily is proposed, with Megafenestra as the more primitive genus, closely allied to Ceriodaphnia, and within Scapholeberis, S. mucronata as the most apomorphic species. In biogeographical respect, no species is cosmopolitan, although their ranges may be of continental dimensions. Species and populations appear to concentrate in the temperate and continental climate belts of the northern hemisphere, but more research in the southern hemisphere is needed. A key for the identification of all species is given.
TL;DR: The rise in hematocrit in CAPD patients is due to an increase in red cell mass and also to a decrease in plasma volume, which represents an improvement in renal anemia in these patients.
TL;DR: Axenic cultures of Rhodopseudomonas capsulata, Rhodospirillum rubrum, and Rhodomicrobium vannielii grown with glutamate as the nitrogen source converted lactate, acetate, and butyrate to H2 and CO2, leading to a slowdown of hydrogen production.
Abstract: Axenic cultures of Rhodopseudomonas capsulata. Rhodospirillum rubrum, and Rhodomicrobium vannielii grown with glutamate as the nitrogen source converted lactate, acetate, and butyrate to H(2) and CO(2). Conversion rates ranged from 100 to 926 mL H(2) L(r) (-1) day(-1) (where L(r) is the reactor contents), and efficiencies varied from 23 to 100% When grown with N(2), conversion rates up to 760 mL H(2) L(r) (-1) day(-1) and efficiencies up to 100%were achieved. Upon aging, cultures appear to rapidly increase in hydrogen uptake activity and furthermore decrease in nitrogenase activity, both factors leading to a slowdown of hydrogen production. This was particularly the case for diazotrophically grown photobacteria.
TL;DR: Several constructions of spreads of the quadratic Q−(5, q) are given and new examples of semi-partial geometries are deduced.
TL;DR: The activating effect of propionate administration upon milk fatty acid production was largest for odd-numbered followed by monomethyl-substituted fatty acids, which agrees with the conception that iso and anteiso fatty acids are synthesized by rumen bacteria.
TL;DR: A peak with the same retention time as the nitropyridine derivative of nifedipine was detected in the plasma of patients who had taken 10 mg nifingipine orally.
TL;DR: In this article, a custom-built, movable on-column injection device is described, in which the injection point is cooled outside the oven during injection, simplifying routine capillary gas chromatographic analysis of high-boiling compounds.
TL;DR: In this article, a small signal model which employs two different magnetizing reactances to incorporate the effect of main flux saturation on induction machine dynamic response is presented, and three different types of experiments which confirm the improved accuracy of the saturated model are discussed.
Abstract: A small signal model which employs two different magnetizing reactances to incorporate the effect of main flux saturation on induction machine dynamic response is presented. Three different types of experiments which confirm the improved accuracy of the saturated model are discussed, and the model is used to examine the effect of saturation on dynamic response in variable frequency applications. The results indicate that whereas saturation has a relatively small effect under normal operating conditions, it does have an important stabilizing effect when the damping is poor. It is also shown that neglecting saturation leads to significant errors in both pole and zero locations when the operating frequency is low.
TL;DR: In this article, the decomposition of nitrite was studied in the presence of different amounts of ferrous iron and an amorphous and a crystalline (haematite) iron product at different pH and Eh conditions.
Abstract: The decomposition of nitrite was studied in the presence of (1) different amounts of ferrous iron and (2) an amorphous and a crystalline (haematite) iron product at different pH and Eh conditions. It was found that ferrous iron positively influenced the nitrite decomposition. Even at pH 6, where self-decomposition is excluded, some nitrite was decomposed. It was shown that at all studied pH values the second order decomposition rate increased as the amount of ferrous iron increased. From the calculation of the activation energy it was found that the dependence of the rate constant on temperature increased when the medium was more acid, or when the amount of Fe2+ increased at the same pH. The nitrite half-life was longest at pH 6, 25°C and 200 mg Fe2+ l−1; it was shortest at pH 4, 30°C and 800 mg Fe2+ l−1. The experiments with Fe2+ derived from solid iron compounds showed that all conditions favouring a high amount of ferrous iron in solution, such as low redox potential, low pH, amorphous or less crystalline material, enhanced nitrite decomposition.
TL;DR: In this article, the influence of a large particle size distribution of reversed-phase silica gel packing materials in high-performance liquid chromatography (HPLC) was studied and the efficiency of columns packed with mixtures of different compositions was measured and the usual chromatographic parameters were deduced.
TL;DR: The feasibility of large-scale bloom induction of nutritionally suited natural phytoplankton species, to feed a semi-industrial nursery of edible shellfish, built on the Belgian coast, was tested and various biological and technological problems encountered during year round operation are commented.
TL;DR: Deoxyribonucleic acid-DNA-DNA hybridization and physiological studies on 15 strains of S. sciuri subsp.
TL;DR: Examples of simple single- step, as well as complex multi-step, enzyme reactions point to the vast potential of immobilized biocatalyst technology in fermentation science, in organic synthesis and in biotechnological processes in general.
TL;DR: The first time that these steroids have been identified in insect hemolymph was reported in this article, where a testosterone concentration of 92 ng/100 ml was found by GC; the concentration of progesterone, calculated on the basis of the radioimmunoassay (RIA) was about two times higher.
TL;DR: In this paper, an efficient synthesis of functionalized trialkyl substituted cyclopentanoids is presented, secured by their formation from norbornane precusors, which is illustrated by the total synthesis of (±)-boschnialactone (13 ), (±-teucriumlactone C ( 14 ) and (±]-loganin ( 2 ).
TL;DR: In anesthetized dogs which were given methyl parathion orParathion intravenously, high hepatic extraction ratios were found, suggesting that the low systemic availability after oral administration can be explained by an important hepatic first-pass extraction.
Abstract: Methyl parathion (20 mg · kg−1 intravenously and orally) and parathion (5 mg · kg−1 intravenously and 10 mg · kg−1 orally) were given to non-anesthetized dogs and the serum concentrations were followed in function of time. For both substances a low bioavailability after oral administration was found. In other dogs radioactivity was followed in urine after oral and after intravenous administration of labeled methyl parathion or parathion. The results suggest a good gastro-intestinal absorption of the substances. In anesthetized dogs which were given methyl parathion or parathion intravenously, high hepatic extraction ratios were found, suggesting that the low systemic availability after oral administration can be explained by an important hepatic first-pass extraction. Binding of methyl parathion and parathion to dog serum, to human serum and to a solution of human albumin was determined with equilibrium dialysis. In both species a high binding (>90%) was found for both substances and there was no concentration-dependency in the concentration range used (0.2–30 μg · ml−1). In man and in dog the serum protein binding of parathion was about 5% higher than that of methyl parathion.
TL;DR: The difficulties in separating the role of psychosocial factors from the classic risk factors strengthen the importance and need for these factors to be considered in the design of further clinical and epidemiologic studies, not only to explore their independent predictive value but also to study their role in adherence to preventive advice and in the reversibility of risk.
TL;DR: There was no decrease in time to first claudication pain or to intolerable pain with either propranolol or metoprolol as compared to placebo in a double-blind, randomized cross-over study of chronic intermittentClaudication.
Abstract: Ten patients with chronic intermittent claudication were included in a double-blind, randomized cross-over study of placebo, propranolol 80 mg b.i.d. and metoprolol 100 mg b.i.d., each given for two months. At the end of each treatment period, the patients were tested on a treadmill and the time to first claudication pain and to intolerable claudication pain was noted. There was no decrease in time to first claudication pain or to intolerable pain with either propranolol or metoprolol as compared to placebo.
01 Jan 1983
TL;DR: In this paper, it is shown that the classical induction-machine model does not correctly take into account the actual saturation effects of the magnetising field in situations different from sinusoidal supply/steady state conditions.
Abstract: It is shown that the classical induction-machine model does not correctly take into account the actual saturation effects of the magnetising field in situations different from sinusoidal supply/steady state conditions. An improved set of stationary equations is derived, making more accurate allowances for the magnetising-field saturation. Owing to saturation, both this modified nonlinear 2-axis model and the modified linearised model (small signal model) derived from it are not symmetrical with respect to the two axes. Indeed, for the calculation of transients or dynamics of a saturated machine, one has to consider two different magnetising inductances for the two axes. This point of view is also confirmed by experiments. The paper is in two parts. Part 1 contains the derivation of the corrected machine model and a concise report on an experimental confirmation of it. In Part 2, some practical applications of the proposed machine model concerning dynamic behaviour are discussed. Such applications constitute further proofs in support of the correctness of the proposed theory.