Showing papers by "Université catholique de Louvain published in 1987"
TL;DR: In this paper, a new mixed finite element has been used to calculate flows of Maxwell-B and Oldroyd-B fluids at very high values of the Deborah number, De.
Abstract: A new mixed finite element has allowed us to calculate flows of Maxwell-B and Oldroyd-B fluids at very high values of the Deborah number, De . The element is divided into several bilinear sub-elements for the stresses, while streamline-upwinding is used for discretizing the constitutive equation. The method is applied to the stick-slip problem, the flow through a tapered contraction and the flow through four-to-one abrupt plane and circular contractions. Important corner vortices develop at high values of De in the circular contraction. We have not encountered upper limits for the Deborah number in our calculations with Oldroyd-B fluids.
531 citations
01 Dec 1987
392 citations
TL;DR: Yersinia enterocolitica is now the species of Yersinia most frequently isolated from human and animal infections, and among the human pathogens, those isolated in America are more virulent than those isolated elsewhere, especially in Europe and Japan, and these isolates differ biochemically and serologically.
Abstract: Yersinia enterocolitica is now the species of Yersinia most frequently isolated from human and animal infections. The species includes pathogens and ubiquitous strains. Among the human pathogens, those isolated in America are more virulent than those isolated elsewhere, especially in Europe and Japan, and these isolates differ biochemically and serologically. The relation between Y. enterocolitica and Y. pestis only became obvious in 1980 with the discovery that at 37 degrees C Y. enterocolitica requires Ca++, a phenotype described in the 1960s for Y. pestis. This requirement as well as virulence is dependent on a 70-kilobase plasmid found later in Y. pseudotuberculosis and Y. pestis. Thus, many bacteriologists elected Y. enterocolitica as a model for bacterial invasiveness. However, studies with non-American strains were impeded by the lack of an inexpensive, simple animal test, a difficulty now circumvented by supplying an appropriate siderophore to the bacteria. Ca++ dependence can be viewed as a transition between free growth and protection against the immune system. In the latter phase, Y. enterocolitica synthesizes and releases large amounts of six plasmid-encoded outer membrane proteins. Most of these are under the control of the plasmid region governing Ca++ dependence. Mutants in this region either lose the Ca++ requirement at 37 degrees C or become unable to grow at 37 degrees C irrespective of the Ca++ concentration. The complex events leading to Ca++ dependence is still not understood. Virulence in Y. enterocolitica also depends on chromosomal genes: the endocytosis in intestinal epithelial cells seems not to be encoded by the pYV plasmid. Studies of Y. pseudotuberculosis suggest that this property depends on a single chromosomal locus, the study of which might be particularly important in the understanding of the first step in infection.
324 citations
TL;DR: The stroke volume ratio (SVR) is a new, non invasive method to quantify ventricular volume overload (VVO) and cardiac equilibrium blood pool scintigraphy has an adequate sensitivity and specificity to evaluate patients with VVO.
Abstract: The stroke volume ratio (SVR) is a new, non invasive method to quantify ventricular volume overload (VVO). We have analyzed its value, sensitivity and specificity in routine clinical practice. The results of 238 consecutive patients (pts) were analysed prospectively within a 3 months period. The SVR was expressed as the ratio of left ventricular (LV) stroke counts over the right ventricular (RV) stroke counts measured on the time-activity curves. One region of interest was drawn per ventricle on the phase and amplitude images. Values above 1.6 were considered as LVVO and below 0.9 as RVVO. Fifty-one patients had VVO due to valvular regurgitation or left-to-right shunt; 187 patients had no evidence of VVO. Mean value obtained for 23 normal subjects with adequate positioning was 1.27 +/- 0.14 (MV +/- SD), ranging from 0.9 to 1.47. Among patients with adequate positioning, no difference was observed in subgroups with dilated cardiopathy (DC) or anteroseptal aneurysm (AA) despite a low EF. MV for patients with LV or RV hypertrophy (H) were statistically different. Sensitivity was 82% for the 51 patients with VVO. False negatives were due to biventricular overload or mild VVO. Specificity evaluated in the 187 patients without VVO was 76%. The 45 false positives were due to poor separation of the right cardiac chambers and/or of the 2 ventricles. They were observed in 4 patients with AA, 3 patients with DC, 7 patients with LVH, 4 patients with RVH and 24 patients with inadequate positioning. No explanation was found in 3 patients. We conclude that cardiac equilibrium blood pool scintigraphy has an adequate sensitivity and specificity to evaluate patients with VVO.
300 citations
TL;DR: The solution to optimality of 18 medium-to large-size problems, including production planning problems with setup costs and capacity constraints, multilevel distribution planning problems, drainage and heating system design problems, and electricity generator scheduling problems is reported on.
Abstract: In this paper we describe computational experience in solving mixed 0-1 programming problems using strong valid inequalities as cutting planes. In particular we report on the solution to optimality of 18 medium-to large-size problems, including production planning problems with setup costs and capacity constraints, multilevel distribution planning problems, drainage and heating system design problems, and electricity generator scheduling problems. The solution approach uses the theory of strong valid inequalities that we developed in a series of earlier papers. Here we report specifically on the implementation of an experimental system, MPSARX, which consists of the SCICONIC mathematical programming system and an automatic reformulation executor ARX that use this theory, and on the results obtained with this system.
260 citations
TL;DR: Analysis of the PDR1 deduced amino acid sequence revealed several homologies to four different regulatory proteins involved in the control of gene expression, including a cysteine-rich motif suggested to be a metal-binding domain for DNA recognition.
256 citations
TL;DR: The adhesion of three microorganisms (Saccharomyces cerevisiae, Acetobacter aceti, and Moniliella pollinis) to different materials has been studied using various supports (glass, metals, plastics), some of which were treated by an Fe(III) solution.
Abstract: The adhesion of three microorganisms (Saccharomyces cerevisiae, Acetobacter aceti, and Moniliella pollinis) to different materials has been studied using various supports (glass, metals, plastics), some of which were treated by an Fe(III) solution. The surface properties of the cells were characterized by the zeta potential and an index of hydrophobicity; characterization of the supports involved surface chemical analysis (XPS) and contact angle measurements. Cell suspensions in pure water at a given pH were left to settle on plates; the latter were then rinsed and examined microscopically, Saccharomyces cerevisiae and A. aceti adhere to metals under certain pH conditions but do not adhere to any of the other materials tested unless it is previously treated by ferric ions; adhesion of these hydrophilic cells is essentially controlled by electrostatic interactions. Moniliella pollinis adhere spontaneously to glass and to polymeric materials, but its attachment is also influenced by cell-cell or cell-support electrostatic repulsions; near the cell isoelectric point, cell flocculation is competing with adhesion to a support.
239 citations
TL;DR: Comparison of the results and discussion of the meaning of the parameters involved indicate that the water contact angle is a significant measure of cell hydrophobicity.
226 citations
TL;DR: In this paper, it was shown that the Ising model with a small random magnetic field has two phases at low temperatures, i.e., its lower critical dimension is at most two.
Abstract: We show that the Ising model in three dimensions with a small random magnetic field has two phases at low temperatures, i.e., that its lower critical dimension is at most two. This is shown by our devising an exact renormalization-group flow which takes the theory to the zero-temperature, zero-field fixed point.
217 citations
TL;DR: The uptake of various host plasma proteins by the bloodstream form of Trypanosoma brucei was studied both biochemically, using radiolabeled proteins, and with the electron microscope, using colloidal gold particles as molecular tracers onto which plasma proteins had been adsorbed.
Abstract: The uptake of various host plasma proteins by the bloodstream form of Trypanosoma brucei was studied both biochemically, using radiolabeled proteins, and with the electron microscope, using colloidal gold particles as molecular tracers onto which plasma proteins had been adsorbed. Total plasma proteins and serum albumin were taken up by a mechanism of fluid endocytosis with low clearance (0.1 microliter [mg cell protein]-1 h-1), while low-density lipoprotein (LDL) and transferrin were taken up by a receptor-mediated process with a clearance of two to three orders of magnitude higher than that of serum albumin. Binding prior to uptake of LDL and transferrin was saturable, depended on the presence of Ca2+, and the labeled ligand could be displaced by the homologous but not by heterologous protein. Binding of gold-labeled proteins was seen only to the membrane of the flagellar pocket and not elsewhere on the plasma membrane. After 1 h of incubation at 30 degrees C with gold-labeled LDL and transferrin, labeled cellular structures represented respectively half and one-third of the total volume of all single-membrane bounded endocytotic and electron-dense vacuoles within the cell.
216 citations
TL;DR: The numbers, depths and volumes (but not the plan-areas) of the resorption pits in dentine were significantly reduced by Z-Phe-Ala-CHN2 and E-64, and the volumes and the depths were smaller in these experimental groups compared with control dentine specimens.
TL;DR: In this paper, the authors examined the effects of a uniform ad valorem tariff on the welfare of a small economy and showed that the optimal tariff rate is an increasing function of the size of the economy and the degree of production differentiation.
TL;DR: It is proposed that iron must be reduced to be taken up by the cells in the same way as other divalent cations, and uptake was strongly inhibited by an iron(II)-trapping reagent like ferrozine.
Abstract: Among several parameters affecting the rate and amount of iron uptake by Saccharomyces cerevisiae, the oxidation state of iron appeared to be determinant. Iron presented as Fe(II) was taken up faster than Fe(III) and the kinetic parameters were different. Iron was taken up by the cells from different ferric chelates, at rates that did not depend on their stability constants, and uptake was strongly inhibited by an iron(II)-trapping reagent like ferrozine. Iron was physiologically reduced by a transplasmamembrane redox system, which was induced in iron-deficient conditions. We propose that iron must be reduced to be taken up by the cells in the same way as other divalent cations.
TL;DR: Transcription of the yop genes was very poor in E. coli K12, even in the presence of a fully functional calcium region, and one Cl double mutant severely affected in transcription of yop51 defined a new locus called virF in the calcium region of pYV.
TL;DR: In this paper, the gravimetric factors for an elliptical uniformly rotating Earth are computed according to a new definition with respect to Wahr's results and considering the mantle inelasticity.
TL;DR: In this article, beidellite was synthesized hydrothermally from a non-crystalline gel at 320~ and 130 bar pressure and verified by infrared spectroscopy on the NH4 § exchanged form.
Abstract: Beidellite was synthesized hydrothermally from a noncrystalline gel at 320~ and 130 bar pressure. The beidellitic character of the product was verified by infrared spectroscopy on the NH4 § exchanged form. Intercalation was achieved with hydroxy-aluminum solutions having different OH/A1 molar ratios. The solutions were investigated by several methods, including 27A1 nuclear magnetic res- onance. Essentially, two Al species were detected: monomeric A1 and a polymerized form containing A1 in four-fold coordination. This latter species was found to be selectively fixed in the interlamellar region, which resulted in a stable spacing of 18 ,~ at 110~ and 16.2 ~ at 700~ The pillared beidellites had specific surface areas of > 300 m2/g, mainly due to micropores. Both Br6nsted and Lewis acid sites were evidenced by infrared spectroscopy using pyridine as a probe molecule.
TL;DR: Studies with nifedipine show quantitatively that the therapeutic effect in angina is related to the interaction of this drug with membrane calcium channels in human coronary arteries, giving support to a classification based on studies at the molecular, tissue and organ levels.
Abstract: Drugs of several chemical families have been identified as calcium antagonists. This article examines some pharmacologic properties of these drugs to clarify their terminology and their classification and to provide a rationale for their clinical use. Studies with nifedipine show quantitatively that the therapeutic effect in angina is related to the interaction of this drug with membrane calcium channels in human coronary arteries. This gives support to a classification based on studies at the molecular, tissue and organ levels. Among calcium antagonists, calcium entry blockers are defined as agents able to block calcium inward fluxes evoked by various stimuli. They may be subdivided in 2 groups. Group I is the group of selective calcium entry blockers. Group IA consists of those agents selective for slow calcium channels in myocardium (slow channel blockers); the leading agents are verapamil, nifedipine and diltiazem. Group IB contains agents without action on slow calcium channels in myocardium but with selective action on arteries; the leading agents are cinnarizine and flunarizine. Group II is the group of nonselective calcium entry blockers. Group IIA contains agents acting at similar concentration on calcium and on fast sodium channels. Group IIB consists of agents interacting with calcium channels while having another primary site of action. Other agents modulate calcium movements by an action on sodium-calcium exchange and by an action within the cell. Their identification requires the use of cell biology. The actual clinical uses of these drugs are consistent with this pharmacologic classification.
TL;DR: The intracellular accumulation and subcellular distribution of 14C-labelled roxithromycin and erythromycin has been studied in macrophages and polymorphonuclear neutrophils of both human and animal origin to give a distinct advantage over other antimicrobial agents.
Abstract: The intracellular accumulation and subcellular distribution of 14C-labelled roxithromycin and erythromycin has been studied in macrophages and polymorphonuclear neutrophils of both human and animal origin. Roxithromycin was consistently and significantly more accumulated than erythromycin, reaching intracellular/extracellular concentration ratios between 14 (in polymorphonuclear neutrophils) and 190 (in alveolar macrophages from smokers). Uptake was reversible, insensitive to anaerobiosis and to the presence of an aminoglycoside, but inhibited by acid pH. Upon subcellular fractionation by isopycnic centrifugation in sucrose gradients., half the roxithromycin or erythromycin recovered in cell homogenates was found associated with the lysosomes in macrophages, and about one third with azurophil granules in polymorphonuclear leucocytes. Inasmuch as cellular uptake is a necessary, albeit not sufficient, condition for antimicrobials to kill or inhibit the growth of intracellular bacteria the properties of roxithromycin may give it a distinct advantage over other antimicrobial agents.
TL;DR: A 12-year-old female suffering fromosteogenesis imperfecta was treated with 3-amino-1-hydroxypropylidene-1,1-bisphosphonate orally, 250 mg daily, for periods of 2 months, alternating with periods of2 months of abstinence, and X-rays of the bones showed large, parallel radio-opaque striae corresponding exactly to the periods of therapy.
Abstract: A 12-year-old female suffering from osteogenesis imperfecta (OI) was treated with 3-amino-1-hydroxypropylidene-1,1-bisphosphonate (APD) orally, 250 mg daily, for periods of 2 months, alternating with periods of 2 months of abstinence. Total duration of therapy was 1 year. Radiological and clinical improvement was striking. Furthermore, X-rays of the bones showed large, parallel radio-opaque striae, corresponding exactly to the periods of therapy. These were present in all metaphyses.
TL;DR: In this article, the melting points and the water contents are determined and the crystalline structure is differenciated by powder X Ray diffraction, and four polymorphic forms have been characterized: the a form and the f3 form, which have been obtained in pure state.
Abstract: Mannitol is an exclpient commonly used in pharmaceutical formulation. Several polymorphic forms have been described but there are only few reports in past literature about their crystalline structures and about their differential properties.The aim of this work is to prepare and to study the different polymorphic forms. An investigation of commercialized products is then carried out.The melting points and the water contents are determined and the crystalline structure is differenciated by powder X Ray diffraction.Four polymorphic forms have been characterized: the a form and the f3 form, which have been obtained in pure state, and the 6 form containing the a form as an impurity, and a fourth form which we have not identified at this time.Among the commercial products, we have characterized: the g form, the a form and the unidentified form.The compressibility of these different samples has been studied: the a form is the best. This valuable property has been found again in the commercial α product....
TL;DR: The sequence of the S. pombe mutant pma-1-1 allele reveals that the glycine residue 268, which is perfectly conserved in the transduction domain of all animal and fungal transport ATPases sequenced so far, is modified into an aspartate residue by the mutation.
TL;DR: The influence on the survival of ascitic liver tumor‐bearing mice of combined vitamins C and K3 administered before or after a single i.p. dose of cytotoxic drugs, all commonly used in human cancer therapy, was investigated.
Abstract: The influence on the survival of ascitic liver tumor (TLT)-bearing mice of combined vitamins C and K3 administered before or after a single i.p. dose of 6 different cytotoxic drugs, all commonly used in human cancer therapy, was investigated. Combined i.p. administration of these vitamins produced a distinct chemotherapy-potentiating effect for all drugs examined, especially when injected before chemotherapy. This potentiating treatment did not increase the general and organ toxicity that accompanies cancer chemotherapy. The possible generation of peroxides followed by membrane lipid alteration, DNase activation and DNA destruction by combined vitamin C and K3 in catalase-deficient cancer cells might be involved in the mechanisms of this selective potentiation.
TL;DR: One hundred four patients with a diagnosis of polycythemia vera and a variable period of follow-up had one or more cytogenetic investigations, and Chromosomally two patterns of acute leukemia were observed in patients, suggesting the occurrence of secondary leukemia.
TL;DR: Six liver carboxylesterases previously isolated from rat liver microsomes were compared with genetically defined liver esterases of various reference strains using polyacrylamide gel electrophoresis and isoelectric focusing to identify alloenzymic forms of ES-3, ES4, ES-8/ES-10 and ES-15 according to the genetic nomenclature recommended by van Zutphen.
TL;DR: In this article, the effects of these changes on variations in global temperature and ice volume characteristic of the late Quaternary were studied. And the authors used the novel framework of Boolean delay equations (BDEs) to formulate a conceptual model of the climatic system under study, and analyzed this formal model.
Abstract: A large fraction of climatic varability on the Quaternary time scale can be explained by nonlinear interactions between the radiation balance of the global atmosphere-ocean system and the mass balance of Northern Hemisphere ice sheets. Recent analyses of paleoclimatic proxy data indicate a further important contribution to this variability from changes in deep-water formation occurring in the North Atlantic Subpolar Sea. We study the effects of these changes on variations in global temperature and ice volume characteristic of the late Quaternary. The novel framework of Boolean delay equations (BDEs) is used to formulate a conceptual model of the climatic system under study, and to analyze this formal model. Selfsustained oscillations in the intensity of the Atlantic Ocean's thermohaline circulation result from the interaction of sea-ice formation with the waxing and waning of continental ice sheets. The comparison of model results with paleoclimatic records suggests a considerable slowing down of the abyssal circulation during glacial episodes.
TL;DR: The CES demand function is a special case of a nested logit model whose second-stage is deterministic because the first-stage of the model is a deterministic function.
TL;DR: The results show that beta-lactam antibiotics can be driven into cells by appropriate modification, and further efforts therefore may be warranted in the design of active compounds or prodrugs that may prove useful in the chemotherapy of intracellular infections.
Abstract: beta-Lactam antibiotics do not accumulate in phagocytes, probably because of their acidic character. We therefore synthesized a basic derivative of penicillin G, namely, 14C-labeled N-(3-dimethylamino-propyl)benzylpenicillinamide (ABP), and studied its uptake and subcellular localization in J774 macrophages compared with that of 14C-labeled penicillin G. Whereas the intracellular concentration (Ci) of penicillin G remained lower than its extracellular concentration (Ce), ABP reached a Ci/Ce ratio of 4 to 5. Moreover, approximately 50% of intracellular ABP was found associated with lysosomes after isopycnic centrifugation of cell homogenates in isoosmotic Percoll or hyperosmotic sucrose gradients. The behavior of ABP was thus partly consistent with the model of de Duve et al. (C. de Duve, T. de Barsy, B. Poole, A. Trovet, P. Tulkens, and A. Van Hoof, Biochem. Pharmacol. 23:2495-2531, 1974), in which they described the intralysosomal accumulation of weak organic bases in lysosomes. Although ABP is microbiologically inactive, our results show that beta-lactam antibiotics can be driven into cells by appropriate modification. Further efforts therefore may be warranted in the design of active compounds or prodrugs that may prove useful in the chemotherapy of intracellular infections.
TL;DR: The SOS chromotest, carried out following the recommendations of the commercially available kits, revealed that only 4 Ames test-positive compounds were mutagenic towards E. coli strain PQ 37.
TL;DR: The transfer paradox may occur in a world with only two countries at a dynamically stable intertemporal competitive equilibrium as mentioned in this paper, where a transfer of income may immiserize the recipient while enriching the donor.
Abstract: The transfer paradox may occur in a world with only two countries at a dynamically stable intertemporal competitive equilibrium. In a framework of overlapping generations with production and investment, a transfer of income may immiserize the recipient while enriching the donor. Away from the golden rule, a transfer may result in a Pareto improvement.