Showing papers by "Université catholique de Louvain published in 1986"
TL;DR: In this article, the authors describe regional market equilibria, where consumers of each region allocate their purchases of private goods between domestic and non-domestic ones according to the structure of relative prices, taxes, and transportation costs.
354 citations
TL;DR: In this paper, a general framework for the formulation and analysis of rigid no-slip boundary conditions for numerical schemes for the solution of the incompressible Navier-Stokes equations is presented.
Abstract: A general framework is presented for the formulation and analysis of rigid no-slip boundary conditions for numerical schemes for the solution of the incompressible Navier-Stokes equations. It is shown that fractional-step (splitting) methods are prone to introduce a spurious numerical boundary layer that induces substantial time differencing errors. High-order extrapolation methods are analyzed to reduce these errors. Both improved pressure boundary condition and velocity boundary condition methods are developed that allow accurate implementation of rigid no-slip boundary conditions.
318 citations
TL;DR: The method unifies Benders Decomposition and Lagrangean relaxation into a single framework that involves successive solutions to a transportation problem and a simple plant location problem to solve the capacitated facility location problem.
Abstract: We present an implementation of the Cross Decomposition method to solve the capacitated facility location problem. The method unifies Benders Decomposition and Lagrangean relaxation into a single framework that involves successive solutions to a transportation problem and a simple plant location problem. Computational tests on problems with as many as 100 candidate facility locations and 200 customers provide evidence that the approach is superior to several other methods. The specialized Cross Decomposition program is, on a common set of test problems, about ten times faster than several recently developed programs. We also present a simple algorithm to strengthen Benders cuts.
265 citations
TL;DR: In this paper, spectral methods (Fourier Galerkin, Fourier pseudospectral, Chebyshev Tau, Chebyhev collocation, spectral element) and standard finite differences are applied to solve the Burgers equation with small viscosity (v = 1 100 π ).
202 citations
TL;DR: The findings suggest that the present type of cell death can be inhibited by growth stimuli and is therefore a controlled event serving to eliminate an excess of cells, rather than a manifestation of toxic injury to hepatocytes.
Abstract: Hyperplasia of the rat liver can be induced by cyproterone acetate (CPA). The fate of this hyperplasia after cessation of CPA treatment has been studied and the following findings were obtained:
1.
Liver DNA content decreased by about 25% within a few days after CPA withdrawal.
2.
In histological sections some hepatocytes showed degenerative changes. Among these, small membrane bounded bodies (“apoptotic bodies”; ABs) with or without chromatin were most numerous. Their incidence coincided with the phase of DNA elimination. Inflammatory reactions were not observed.
3.
Their small size and occurrence in clusters suggests that many of these ABs are formed by fragmentation of dying hepatocytes.
4.
Liver DNA was prelabelled with3H-thymidine. Autoradiographic evaluation showed that many hepatocytes contained labelled nuclei, but unlabelled ABs. This finding strongly suggests that ABs, after the fragmentation stage, can be phagocytized by intact hepatocytes. About 80% of all ABs were found within hepatocytes.
5.
Extracellular ABs (early stage) contained no or very few active lysosomes. Intracellular ABs were sometimes surrounded by lysosomes, while others were in various stages of digestion. These observations suggest that the lysosomes of the phagocytizing hepatocytes degrade intracellular ABs, whereas intraapoptotic lysosomes seem to be inactive until the late stages of this degradation.
6.
Hepatocytes that did not replicate during CPA-induced liver growth appear to die off preferentially after CPA withdrawal.
7.
Retreatment with CPA greatly reduced the number of ABs within 4 h. Phenobarbital, another stimulus of liver growth, had the same effect.
150 citations
TL;DR: In this paper, the authors analyze the commensurate-in-commensurate transition in uniaxial systems in terms of a gas of interacting domain walls and show that the transition can be modeled as a rounding of facets in the equilibrium shape of crystals.
Abstract: In this paper we study several problems in statistical mechanics involving systems of fluctuating extended objects, such as interacting steps and domain walls. We reconsider the roughening transition and relate it to the free energy of a gas of steps and to the rounding of facets in the equilibrium shape of crystals, defined via the Wulff construction. Using an idealized description due to Fisher and Fisher we analyze the commensurate-incommensurate transition in uniaxial systems in terms of a gas of interacting domain walls. We also study the interactions between a domain wall and a rigid wall and between two interfaces, a problem which is central for the understanding of wetting. Among our results are a quantitative analysis of entropic repulsion between extended objects and a calculation of deviations from mean-field theory in the commensurate-incommensurate transition in dimension 2 ⩽d ⩽ 3.
148 citations
TL;DR: A class of valid inequalities is derived for a typical region appearing in mixed 0–1 programs, namely a single row with variable or simple lower and/or upper bounds on the continuous variables.
139 citations
TL;DR: In this article, the authors examine the optimal product range of a monopolist in an industry producing products which differ in quality, to consumers who vary in their willingness to pay, and explore the precise nature of this switch of policy, which occurs at a certain critical distribution of consumer incomes.
126 citations
TL;DR: In this paper, Lienard considered the problem of finding 2π-periodique solutions to the differentielle version of the equation, and studied the nombre of solutions.
Abstract: On considere l'equation differentielle de Lienard x″+f(x)x'+g(t,x)=s, ou s est un parametre reel, f et g sont des fonctions continues, et g est 2π-periodique en t. On etudie le nombre de solutions 2π-periodiques quand g satisfait lim |x|→+∞ g(t,x)=+∞, uniformement en t
119 citations
TL;DR: Continuous time algorithms for the on-line estimation of microbial specific growth rates of fermentation processes are proposed and the stability and convergence properties of the algorithms are described and their feasibility is illustrated by real life experiments.
116 citations
TL;DR: An algorithm is presented for solving a set of linear equations on the nonnegative orthant which can be made equivalent to the maximization of a simple concave function subject to a similar set oflinear equations and bounds on the variables.
Abstract: An algorithm is presented for solving a set of linear equations on the nonnegative orthant. This problem can be made equivalent to the maximization of a simple concave function subject to a similar set of linear equations and bounds on the variables. A Newton method can then be used which enforces a uniform lower bound which increases geometrically with the number of iterations. The basic steps are a projection operation and a simple line search. It is shown that this procedure either proves in at mostO(n2m2L) operations that there is no solution or, else, computes an exact solution in at mostO(n3m2L) operations.
TL;DR: In this article, a complete study of the local properties which are conserved by a Johnson-Segalman fluid flow is made, and counter examples are given where the evolutionary character is indeed lost.
Abstract: For the Maxwell model, it has been proved that an initially evolutionary flow remains so at any time: the property is transported along the streamlines. This is generally not the case for other differential models. A complete study is made of the local properties which are conserved by a Johnson-Segalman fluid flow. Evolution is not preserved, and counter examples are given where the evolutionary character is indeed lost. Two conservation properties are demonstrated and their relationship with the Second Law is also examined. The evolutionary character of a system is a physical requirement which should be satisfied by all models.
TL;DR: In this paper, the authors investigated the behavior of three crystalline forms of carbamazepine during compression and grinding and tabletting conditions and found that polymorphous transformations may occur during technologic operations such as grinding or compression owing to the increase of internal energy.
Abstract: Carbamazepine is a potent anticonvulsivant, but, irregular plasma levels are noticed. The variability of therapeutic efficiency can be attributed to interindividual sensibility, chronobiologic effect, but also to rates of dissolution which can differ when polymorphs are induced by technologic operations.Several crystalline forms of Carbamazepine have been characterized. As for us, we have studied three crystalline modifications which can be found in commercialized galenic forms: the most usual beta form, the alpha form and the dihydrate.The aim of this work was to investigate:- the behaviour of these three crystalline forms during compression- the possibility of crystalline structural changes under grinding and tabletting conditions. Indeed, polymorphous transformations may occur during technologic operations such as grinding or compression owing to the increase of internal energy.Grinding was performed in a ball mill for 15 and 60 minutes. Compression was carried out using an instrumented single punch ma...
TL;DR: In this article, the main reaction is an exchange reaction identical to that occurring in bisphenol-A polycarbonate-poly(butylene terephthalate) mixtures, probably resulting from the instability of the ethylene carbonates produced by transesterification.
Abstract: This paper is devoted to the study of the reactions taking place in molten bisphenol-A polycarbonate-poly(ethylene terephthalate) mixtures. The analysis of the reaction products by infrared, proton and nuclear magnetic resonance spectroscopy, and by thermogravimetric analysis shows that the main reaction is an exchange reaction identical to that occurring in bisphenol-A polycarbonate-poly(butylene terephthalate) mixtures. However, some other reactions consecutive to this exchange reaction also take place, probably resulting from the instability of the ethylene carbonates produced by transesterification.
TL;DR: Evidence obtained in animal models suggests that tissue-type plasminogen activator, obtained by recombinant DNA technology, may constitute a specific clot-selective thrombolytic agent with higher specific activity and fewer side effects than those currently in use.
Abstract: The fibrinolytic system comprises a proenzyme, plasminogen, which can be activated to the active enzyme plasmin, that will degrade fibrin by different types of plasminogen activators. Inhibition of fibrinolysis may occur at the level of plasmin or at the level of the activators. Fibrinolysis in human blood seems to be regulated by specific molecular interactions between these components. In plasma, normally no systemic plasminogen activation occurs. When fibrin is formed, small amounts of plasminogen activator and plasminogen adsorb to the fibrin, and plasmin is generated in situ. The formed plasmin, which remains transiently complexed to fibrin, is only slowly inactivated by alpha 2-antiplasmin, while plasmin, which is released from digested fibrin, is rapidly and irreversibly neutralized. The fibrinolytic process, thus, seems to be triggered by and confined to fibrin. Thrombus formation may occur as the result of insufficient activation of the fibrinolytic system and (or) the presence of excess inhibitors, while excessive activation and/or deficiency of inhibitors might cause excessive plasmin formation and a bleeding tendency. Evidence obtained in animal models suggests that tissue-type plasminogen activator, obtained by recombinant DNA technology, may constitute a specific clot-selective thrombolytic agent with higher specific activity and fewer side effects than those currently in use.
TL;DR: In this article, a study of the preparation of carbides using hydrous oxide precursors is presented, where two different precurors (WO3 · H2O and hexagonal WO3· xH2O), obtained by homogeneous precipitation from ammonium tungstate solutions, are converted into carbides after preliminary dehydration and reduction steps.
TL;DR: Enteropathogenic strains of Yersinia enterocolitica harbor a virulence plasmid which specifies, at 37 degrees C, a calcium requirement for growth, autoagglutinability, resistance to the bactericidal activity of human serum, and the expression of outer membrane proteins (OMP).
TL;DR: In this article, a new type of rectangular finite element for calculating viscoelastic flows is introduced, where Hermitian shape functions are used for interpolating the velocity field, while the stress shape function is able to represent every derivative of the velocity fields.
Abstract: Numerical calculations of the flow of viscoelastic fluids through an abrupt contraction are prone to important errors in the evaluation of the stress and velocity fields near the re-entrant corner. We introduce a new type of rectangular finite element for calculating viscoelastic flows. Hermitian shape functions are used for interpolating the velocity field, while the stress shape functions are able to represent every derivative of the velocity field. The domain of convergence in Deborah number for the flow of an Oldroyd-B fluid is extended by a factor of four by comparison with earlier calculations. The numerical results show important differences between plane and axisymmetric flows in a four-to-one abrupt contraction.
TL;DR: In this article, the conditions under which nanoparticles should be prepared and lyophilized in order to be sterile and free of bacterial endotoxins were described, and preliminary stability assays, carried out after 6 and 12 months of storage, showed no modification in nanoparticle size, drug content and relative moisture content.
TL;DR: In this paper, the authors investigate how firms in the Vancouver, British Columbia retail gasoline market view their rivals and how consumers in turn view these firms, and reveal systematic patterns in seller behavior and buyer attitudes.
TL;DR: In this paper, the coefficients of the three-term recurrence relation an + 1 Pn + 1(x) = (x − bn) pn(x), − anpn − 1(ex), are shown to be unique "admissible" solution of the equations Fn(a, b) = 0, n = 1, 2, etc.
TL;DR: The main applications of oligonucleotides in biological studies, the protecting group chemistry, the coupling procedures, and the methods for isolating and characterizing products are described, as well as established methods of synthesis and general strategies.
TL;DR: Serial chromosome investigations performed in untreated myelodysplastic syndromes revealed that multiple chromosomaily unrelated cell populations may emerge during the course of the disease and chromosome changes of the clonal type may disappear or become undetectable, and may or may not reappear during further evolution.
Abstract: Summary. Serial chromosome investigations performed in untreated myelodysplastic syndromes (MDS) revealed that: (a) multiple chromosomaily unrelated cell populations may emerge during the course of the disease; (b) chromosome changes of the clonal type may disappear or become undetectable, and may or may not reappear during further evolution. The former of these phenomena was found in four cases and was consistently associated with clinical-haematological progression of the disease to a more malignant form, including acute leukaemia. The second was apparently unrelated to clinical and haematological changes in the evolution pattern.
These observations are in favour of the hypothesis that MDS evolve as a multistep process in which several events, including the acquisition of sometimes unrelated chromsome changes determine the progression of the disease.
TL;DR: The present observations suggest that the alterations induced by gentamicin treatment impair the lysosomes' ability to fuse with incoming endocytic vesicles.
TL;DR: In this paper, a model compound of poly(ethylene terephthalate) (PETP) is used to simulate the behavior of PETP in the presence of an organic acid salt, sodium o-chlorobenzoate (SOCB).
TL;DR: The structure of a lean formaldehyde-oxygen flame burning at 22.5 Torr has been investigated experimentally using molecular beam sampling coupled with mass spectrometric analysis as discussed by the authors.
TL;DR: In this article, les methodes utilisees for the preparation of solides inorganiques homodisperses are examined, and the avantages et les inconvenients des methodes partant de phases liquides ou de gaz are examined.
Abstract: On examine dans cette mise au point, les methodes utilisees pour la preparation de solides inorganiques homodisperses. Les avantages et les inconvenients des methodes partant de phases liquides ou de gaz sont examines. Les procedes en phase liquide peuvent fournir une grande variete de composes de nombreux metaux. Les tailles de particules sont adaptees a de multiples usages; la repartition en taille est etroite. Les procedes en phase gazeuse peuvent fournir des particules ultrafines (inferieures a 10 nm). Les principes a la base des preparations sont resumes, et les raisons de la reussite de certaines methodes de production de poudres homodisperses sont analysees. En particulier, le role de couplages ou decouplages entre reactions elementaires (germination et croissance; diffusion et reaction heterogene) est mentionne. Les perspectives de nouveaux developpements sont evoquees. On fera allusion a certaines applications nouvelles des solides homodisperses