Showing papers by "Université catholique de Louvain published in 1984"

Measuring labor-efficiency in post offices

Abstract: Three methods of measuring technical efficiency are defined, and their results compared in an application to Belgian postal data The first one is that of adjusting a Cobb-Douglas production frontier; the second is that of computing the convex hull of the data, a la Farrell; the third one is developed on the basis of the sole assumptions of input and output disposability We conclude with an estimated average labor-efficiency of about 90% (This abstract was borrowed from another version of this item)

Defecography: I. Description of a new procedure and results in normal patients

Abstract: To solve frequently encountered clinical problems in the anorectal area, we have developed a simplified dynamic method of defecography. A radiopaque substance, the consistency of normal stools, is introduced into the rectum and the patient is then seated on a specially designed seat composed of superposed air chambers which, for technical reasons, are filled with water. The movements induced by evacuation of the rectum are recorded using 100-mm ampliphotography. After recording findings in 56 normal patients, we are able to define 5 criteria for “normal”: increase in anorectal angulation, obliteration of the impression of the puborectal muscle, wide opening of the anal canal, total evacuation of the rectal contents, and normal resistance of the pelvic floor. The mean value of the anorectal angle (ARA) was 91.96° (±1.52 SEM) at rest and 136.76° (±1.51 SEM) during straining. The increase of ARA during straining is 44.8°.

Strong Formulations for Multi-Item Capacitated Lot Sizing

Abstract: Multi-item capacitated lot-sizing problems are reformulated using a class of valid inequalities, which are facets for the single-item uncapacitated problem. Computational results using this reformulation are reported, and problems with up to 20 items and 13 periods have been solved to optimality using a commercial mixed integer code. We also show how the valid inequalities can easily be generated as part of a cutting plane algorithm, and suggest a further class of inequalities that is useful for single-item capacitated problems.

Defecography: II. Contribution to the diagnosis of defecation disorders.

Abstract: Our simple method of defecography has proved to be more sensitive than clinical evaluation in the detection and description of defecation disorders. Among the different types of disorders, described on the basis of 144 abnormal defecograms, the most common are rectal intussusception (RI), intraanal rectal intussusception (IRI), external manually (EMRP) or spontaneously (ESRP) reducible prolapses, rectocele, and accentuation of the impression of the puborectalis sling (AIPR). Study of the mean values of the anorectal angle (ARA) (normal mean value=92° at rest) reveals an increase (p<0.05) in the ARA in IRI and ESRP and a decrease (p<0.05 at rest,p<0.001 at strain) in AIPR. The most striking observation is a highly significant increase (p<0.001) in the ARA associated with incontinence.

Enhanced responsiveness of rat isolated aorta to clonidine after removal of the endothelial cells.

Abstract: With the endothelium present, the maximum response of rat isolated aorta to clonidine was much lower than that to noradrenaline. Removal of endothelium enhanced the response to both adrenoceptor agonists and the clonidine-induced maximum contraction became almost equal to that produced by noradrenaline, although it was much more sensitive to inhibition by flunarizine and nifedipine. These results indicate that clonidine and noradrenaline activate receptors present in the endothelial cells and that these receptors are highly sensitive to clonidine.

Uncapacitated lot-sizing: The convex hull of solutions

Abstract: It is well-known that the economic lot-sizing model is well-solved by dynamic programming. On the other hand, the standard mixed integer programming formulation of this problem leads to a very large duality gap. Here the convex hull of the solutions of the economic lot-sizing model is given. In addition, an alternative formulation as a simple plant location problem is examined, and here too the convex hull of solutions is obtained.

Purification, morphometric analysis, and characterization of the glycosomes (microbodies) of the protozoan hemoflagellate Trypanosoma brucei.

Abstract: Trypanosoma brucei glycosomes (microbodies containing nine enzymes involved in glycolysis) have been purified to near homogeneity from bloodstream-form trypomastigotes for the purpose of morphologic and biochemical analysis. Differential centrifugation followed by two isopycnic centrifugations in an isotonic Percoll and in a sucrose gradient, respectively, resulted in 12- to 13-fold purified glycosomes with an overall yield of 31%. These glycosomes appeared to be highly pure and contained less than 1% mitochondrial contamination as judged by morphometric and biochemical analyses. In intact cells, glycosomes displayed a remarkably homogeneous size distribution centered on an average diameter of 0.27 micron with a standard deviation of 0.03 micron. The size distribution of isolated glycosomes differed only slightly from that measured in intact cells. One T. brucei cell contained on average 230 glycosomes, representing 4.3% of the total cell volume. The glycosomes were surrounded by a single membrane and contained as phospholipids only phosphatidyl choline and phosphatidyl ethanolamine in a ratio of 2:1. The purified glycosomal fraction had a very low DNA content of 0.18 microgram/mg protein. No DNA molecules were observed that could not have been derived from contaminating mitochondrial or nuclear debris.

The Mechanism By Which Glucose Increases Fructose 2,6-bisphosphate Concentration in Saccharomyces-cerevisiae - a Cyclic-amp-dependent Activation of Phosphofructokinase-2

Abstract: When glucose was added to a suspension of Saccharomyces cerevisiae in stationary phase, it caused a transient increase in the concentration of cyclic AMP and a more persistent increase in the concentration of hexose 6-phosphate and of fructose 2,6-bisphosphate. These effects of glucose on cyclic AMP and fructose 2,6-bisphosphate but not that on hexose 6-phosphate were greatly decreased in the presence of 0.15 mM acridine orange or when a temperature-sensitive mutant deficient in adenylate cyclase was used at the restrictive temperature. Incubation of the cells in the presence of dinitrophenol and in the absence of glucose increased the concentration of both cyclic AMP and fructose 2,6-bisphosphate, but with a minimal change in that of hexose 6-phosphate. Glucose induced also in less than 3 min a severalfold increase in the activity of 6-phosphofructo-2-kinase and this effect was counteracted by the presence of acridine orange. When a cell-free extract of yeast in the stationary phase was incubated with ATP-Mg and cyclic AMP, there was a 10-fold activation of 6-phosphofructo-2-kinase. Finally, the latter enzyme was purified 150-fold and its activity could then be increased about 10-fold upon incubation with ATP-Mg and the catalytic subunit of cyclic-AMP-dependent protein kinase. This activation resulted from a 4.3-fold increase in V and a 2-fold decrease in Km. Both forms of the enzyme were inhibited by sn-glycerol 3-phosphate. From these results it is concluded that the effect of glucose in increasing the concentration of fructose 2,6-bisphosphate in S. cerevisiae is mediated by the successive activation of adenylate cyclase and of cyclic-AMP-dependent protein kinase and by the phosphorylation of 6-phosphofructo-2-kinase by the latter enzyme. In deep contrast with what is known of the liver enzyme, yeast 6-phosphofructo-2-kinase is activated by phosphorylation instead of being inactivated.

Cadmium in human population

Abstract: Due to man’s activity, trace metals are slowly being redistributed in the environment. During the last decades, concentrated metal deposits that are confined in the earth’s crust and which are usually harmless to living beings, have been exploited at an increasing rate and discharged partly in the environment. Among these metals, cadmium has raised the most concern because of its high toxicity coupled with an exceptional tendency to accumulate in the human organism.

Microanalysis of plant mitochondrial protein synthesis products: : Detection of variant polypeptides associated with cytoplasmic male sterility

Abstract: A mitochondrial fraction obtained from 0.5 g of leaves was purified on a 0.75 ml Percoll gradient and used for an in vitro mitochondrial protein synthesis assay in the presence of [35S] methionine. A set of 15 to 20 labeled polypeptides were revealed by autoradiography after sodium dodecylsulfate polyacrylamide gel electrophoresis. This could be applied at an early growth stage by using a few leaves from individual seedlings. It revealed the presence of variant mitochondrially translated polypeptides in green leaves of cytoplasmic male sterile lines from various cultivated plants of large economic importance: maize, wheat, sugar beet, tobacco and faba bean. This non-destructive microanalysis is thus of general use and opens new possibilities for rapid and large mass screening of mitochondrial parameters such as male sterility.

Numerical-simulation of the Flow of a Viscoelastic Fluid Through An Abrupt Contraction

Abstract: The flow of a Phan Thien-Tanner fluid through an abrupt 4/1 contraction is anaylzed by means of finite elements. It is found that the choice of such a fluid gives rise to an important corner vortex growth and to an increasing Couette correction when the flow-rate increases

Some Properties of Location Problems with Block and Round Norms

Abstract: The point-objective problem and the Weber problem are two well-known formulations for locating a new facility with respect to a set of fixed facilities. When locations are represented as points on a plane, the point-objective problem is a multiple objective formulation of minimizing the distance from a variable point to each of the fixed points. Similarly, the Weber problem is a single objective formulation of minimizing the sum of transportation costs between the variable point and the fixed points, where transportation cost is a function of distance. Generalizing solution properties for these problems from distance measures given by the Euclidean, rectilinear, Ip, and one-infinity norms; this paper develops solution properties under the broad classes of distance measures given by block and round norms. For the point-objective problem, we show that i the efficient set for all round norms is the convex hull of the set of fixed points and ii the efficient set under a block norm tends to the convex hull for a sequence of block norms approaching a round norm. For the Weber problem, we prove that i an optimal location for any block norm may be found in a finite set of intersection points belonging to the convex hull and ii this set tends to the convex hull for a sequence of block norms approaching a round norm. Finally, we use these results to propose a synthesis of some of the main properties in continuous and network location theory.

Localization of CRF immunoreactivity in the central nervous system of three vertebrate and one insect species.

Abstract: By use of a specific antiserum against synthetic ovine corticotropin-releasing factor (CRF) in the peroxidase-antiperoxidase (PAP) immunocytochemical procedure (Vandesande and Dierickx 1976), CRF-like antigenic determinants were demonstrated in the central nervous system of a human fetus, the Wistar rat, the frog Rana ridibunda, and the American cockroach Periplaneta americana. The immunoreactive CRF-producing cells occur mainly in the nucleus paraventricularis of the rat, while in Rana ridibunda these cells occur in the nucleus praeopticus. Immunoreactive CRF-containing fibres were also visualized. Very clear CRF-immunoreactive products were observed in the brain as well as the corpora cardiaca (CC) and corpora allata (CA) of the cockroach Periplaneta americana. ACTH-immunoreactivity was also demonstrated in the brain-CC-CA complex of this insect. Double immunohistochemical staining (Vandesande 1983) also revealed that both the CRFand ACTH-like substances occur in different neurosecretory neurons and nerve fibres. These results suggest that the antigenic determinants of CRF are very similar in vertebrates and insects bespeaking their very long evolutionary history.