Showing papers by "Université catholique de Louvain published in 1981"
TL;DR: The urinary elimination of the metabolites of arsenic has been followed up as a function of time in volunteers who ingested a single oral dose of arsenic either as sodium arsenite (Asi), monomethylarsonate (MMA), or cacodylate (DMA).
Abstract: The urinary elimination of the metabolites of arsenic has been followed up as a function of time in volunteers who ingested a single oral dose of arsenic (500 μg As) either as sodium arsenite (Asi), monomethylarsonate (MMA), or cacodylate (DMA). The excretion rate increased in the order Asi < DMA < MMA. After 4 days, the amount of arsenic excreted in urine represents 46, 78, and 75% of the ingested dose in the case of Asi, MMA and DMA, respectively. With regard to the in vivo biotransformations, it is concluded that DMA is excreted unchanged; MMA is slightly (13%) methylated into DMA while roughly 75% of the arsenic excreted after ingestion of Asi is methylated arsenic (about 1/3 as MMA and about 2/3 as DMA).
519 citations
469 citations
TL;DR: It is shown that when incomes are ranked in descending order the social-evaluation function corresponding to the Gini relative inequality index can be written as a linear function with the weights being the even numbers in increasing order and the weights to be an arbitrary non-decreasing sequence of numbers.
425 citations
TL;DR: In this article, it was shown that Mn(IV) oxide is a very effective oxidant with respect to As(III), despite the thermodynamic favourability, the evidence obtained from colorimetry and X-ray photoelectron spectroscopy shows that a redox reaction between Fe(III) oxide and As(3) does not occur within 72 h, indicating that the kinetics of the redox reactions between As( III) and Fe(3), is relatively slow.
Abstract: The biological availability and the toxicological effects of As depend on its chemical state1,2. It is therefore important to know the speciation and transformations of As in terrestrial and aquatic environments. Arsenite, As(III), is much more toxic than arsenate As(V) (ref. 2). The suspended and bottom sediments can potentially detoxify As(III) that enters aquatic systems by converting it to As(V) through abiotic oxidation3. We hypothesized that the oxides of Mn(IV) and Fe(III) may be the primary electron acceptors in the oxidation of As(III) because Mn and Fe readily participate in many oxidation–reduction reactions in natural environments; however, their role in the oxidation of As(III) to As(V) is yet to be established. We report here that Mn(IV) oxide is a very effective oxidant with respect to As(III); on the other hand, despite the thermodynamic favourability3, the evidence obtained from colorimetry and X-ray photoelectron spectroscopy shows that a redox reaction between Fe(III) oxide and As(III) does not occur within 72 h, indicating that the kinetics of the redox reaction between As(III) and Fe(III) is relatively slow.
309 citations
TL;DR: Determination of in organic arsenic, MMA and DMA in urine appears to be the method of choice for the biological monitoring of workers exposed to inorganic arsenic since these measurements are not influenced by the presence of organoarsenicals from marine origin.
Abstract: Arsenic (125, 250, 500 or 1000 μg as NaAsO2) was administered orally once a day for five consecutive days to 4 volunteers who refrained from eating marine organisms during the experiment. Urine was collected during 24-h periods starting one day before the first administration and up to 14 days later. The following determinations were performed: total arsenic, inorganic arsenic (As;), monomethyl arsenic (MMA) and dimethylarsinic (DMA) acids. In each case, the sum of As;, MMA and DMA approximated very closely the urinary concentration of total arsenic determined after mineralisation of the urine sample. It was concluded that these arsenicals are the only metabolic forms of arsenic following absorption of inorganic arsenic. Since a steady state in the urinary excretion of arsenic is reached within 5 days, our results demonstrated that at equilibrium, the total amount of arsenic excreted in urine per day amounts to 60% of the ingested dose. Speciation of the arsenic metabolites in urine indicated that the arsenic methylation capacity of the human body was not yet saturated, even with an oral daily dose of 1000 μg As for 5 days. However, when the administration of arsenic was stopped, the biological half life of arsenic in urine increased slightly with the dose (from 39 h at 125 μg to 59 h at 1000 μg). Determination of inorganic arsenic, MMA and DMA in urine appears to be the method of choice for the biological monitoring of workers exposed to inorganic arsenic since these measurements are not influenced by the presence of organoarsenicals from marine origin. From the linear relationship found in this study between arsenic administered and that excreted in urine, it was estimated that a time-weighted average exposure of 50 μg As/m3 would lead to an average urinary excretion of 220 μg As (sum of Asi, MMA and DMA) per gram creatinine.
256 citations
01 Jan 1981
TL;DR: In this paper, the authors deal with the general problem of space vehicle dynamics and control and present the various approaches of this problem in a rather unified manner; the classical simplifying assumptions are curefully pointed out.
Abstract: This paper deals with the general problem of space vehicle dynamics and control It presents the various approaches of this problem in a rather unified manner; the classical simplifying assumptions are curefully pointed out
162 citations
TL;DR: The economic implications of a duality theory for integer programming, in particular the necessity of using price functions in place of prices, and the possibility of carrying out sensitivity analysis of optimal solutions are examined.
Abstract: Recently a duality theory for integer programming has been developed. Here we examine some of the economic implications of this theory, in particular the necessity of using price functions in place of prices, and the possibility of carrying out sensitivity analysis of optimal solutions. In addition we consider the form of price functions that are generated by known algorithms for integer programming.
145 citations
TL;DR: A constraint generation algorithm and a branch-and-bound algorithm that uses linear programming relaxations that uses greedy heuristics to produce feasible solutions, which, in turn, are used to generate upper bounds.
Abstract: We consider integer programming formulations of problems that involve the maximization of submodular functions. A location problem and a 0–1 quadratic program are well-known special cases. We give a constraint generation algorithm and a branch-and-bound algorithm that uses linear programming relaxations. These algorithms are familiar ones except for their particular selections of starting constraints, subproblems and partitioning rules. The algorithms use greedy heuristics to produce feasible solutions, which, in turn, are used to generate upper bounds. The novel features of the algorithms are the performance guarantees they provide on the ratio of lower to upper bounds on the optimal value.
142 citations
139 citations
TL;DR: Intracellular iron storage in many different cell types is assured by a specialised protein, ferritin which consists of a hydrolysed polymeric ferric iron core deposited in the interior of a hollow protein shell (apoferritin), which maintains the iron in a soluble, non-toxic and bio-available form, from which iron can be mobilised as and when required by the cell.
118 citations
TL;DR: The development of stable nuclear-cytoplasmic gynodioecy in a mathematical model is new and is possible because of the consideration of the separate relative female fertilities, as well as some theoretical schemes that seem to correspond to observed actual situations.
Abstract: A study is described of the influence of the introduction of a dominant nuclear restorer gene into a cytoplasmic gynodioecious plant population. This study includes the consideration of separate effects on the relative female fertility of nuclear, cytoplasmic and sex (phenotypic) factors. Under these assumptions, the introduction of a dominant nuclear restorer gene into a cytoplasmic gynodioecious population can lead to several different situations: persistence of cytoplasmic gynodioecy, appearance of a nuclear-cytoplasmic gynodioecy, appearance of a nuclear gynodioecy or complete restoration of male fertility. The development of stable nuclear-cytoplasmic gynodioecy in a mathematical model is new and is possible because of the consideration of the separate relative female fertilities. The possibility of a transformation of cytoplasmic gynodioecy into a nuclear one has never been obtained before. It could constitute a route for the appearance of this latter kind of gynodioecy in plant populations. Finally, the possibilities of evolution of gynodioecy from one kind to the other, and towards dioecy, are discussed, as are some theoretical schemes that seem to correspond to observed actual situations.
TL;DR: When measured in the high-speed supernatant obtained from isolated rat hepatocytes, the apparent activity of this enzyme was decreased several fold by treatment of the cells with glucagon, and could be separated from the classical phosphofructokinase (ATP-D-fructose 6-phosphate 1-ph phosphotransferase) which is now called phosphofructureokinase 1.
TL;DR: In this paper, an experimental method for the cross-beam measurement of absolute cross sections is presented, which essentially consists in sweeping one of the beams across the other in a linear'see-saw' motion.
Abstract: A new experimental method is reported for the crossed beam measurement of absolute cross sections. It essentially consists in sweeping one of the beams across the other in a linear 'see-saw' motion. The method is applied to one case of electron-ion collisions. A description is given of an electron gun designed to realise a linear and distortionless motion of a ribbon electron beam. Measurements are reported regarding the electron impact ionisation of He+ in the energy range 55-74 eV.
TL;DR: Treatment with the catalytic subunit of cyclic AMP-dependent protein kinase induced the following modifications in the kinetic properties of purified phosphofructokinase 2: the affinity for Fru-6-P, the Vmax and the stimulatory effect of Pi were decreased; the inhibitory actions of P-enol-pyruvate and citrate were increased; the pH activity curve was modified.
TL;DR: In this article, the authors compared the locations of voting and planning procedures in a general network and showed that a voting location exists and coincides with that minimizing the total distance covered by the users to go to the facility when the transportation network contains no cycles.
TL;DR: This procedure allowed us to prepare fructose 2,6-bisphosphate in millimolar amounts and this ester had all the chemical and biological properties previously described for the natural stimulator of phosphofructokinase extracted from rat liver.
Abstract: The method described by Pontis and Fischer [Pontis, H. G. and Fischer, C. L. (1963) Biochem. J. 89, 452–459] for the conversion of fructose 1-phosphate into fructose 2-phosphate has been applied to fructose 1,6-bisphosphate. This procedure allowed us to prepare fructose 2,6-bisphosphate in millimolar amounts. This ester had all the chemical and biological properties previously described for the natural stimulator of phosphofructokinase extracted from rat liver [Van Schaftingen, E., Hue, L., and Hers, H. G. (1980) Biochem. J. 192, 897–901].
TL;DR: In this paper, the authors show that interstratified kaolinite-smectites have many X-ray, morphological and chemical features in common with tabular halloysite.
Abstract: Interstratified kaolinite-smectite minerals form the major part of a pedon transitional between 'red' kaolinitic and black smectitic soils in a soil toposequence derived from basalt in Burundi, Central Africa. These interstratified kaolinite-smectites have many X-ray, morphological and chemical features in common with 'tabular halloysite'. Modifications to the 001 spacings of these minerals brought about by thermal and chemical treatments, however, show that they are not halloysite but consist of a mixture of ~ 70~o kaolinite and 30~o smectite randomly interstratified. Field evidence indicates that these clays can be considered as a transient stage in the overall reaction smectite--,kaolinite + iron oxides, which takes place in this landscape whenever the slope gradients give rise to better drainage conditions.
TL;DR: In this paper, an astronomical climate index (ACLIN) is introduced which combines the three orbital variables in the time-lag bivariant model designed to predict the major climate changes in the late and middle Pleistocene, and in the near future.
Abstract: A specific orbital configuration—high obliquity combined with the June perihelion—marked the beginning of the past three interglacials. This suggests that the primary cause of the glacial cycle may be astronomical. An astronomical climate index (ACLIN) is introduced which combines the three orbital variables in the time-lag bivariant model designed to predict the major climate changes in the late and middle Pleistocene, and in the near future. ACLIN closely correlates with the major climatic events revealed by independently dated proxy climate indicators of the past 130,000 yr. It successfully differentiates the interglacials, and displays a 100,000-yr periodicity. It predicts an early end of the present inter glacial and the start of a new one in 114,000 yr.
TL;DR: This paper deals exclusively with the HF (/b X//sup 1/ Sigma /sup +/) molecule and proposes a new method for improving the quality of a wave function.
Abstract: Information theory can be used to evaluate the quality of a wave function by considering its ability to give values for some observables as close as possible to the experimental ones. A new method for improving the quality of a wave function is proposed. This paper deals exclusively with the HF (/b X//sup 1/ Sigma /sup +/) molecule.
TL;DR: Two Ca2+-transport systems resembled, respectively, the sarcolemmal and sarcoplasmic reticulum Ca1+ pumps in cardiac and skeletal muscle, in accordance with the subcellular locations established by density gradient centrifugation.
TL;DR: In this article, the closed-loop representation of a jointly stationary vector (y, u)-proccss was studied and conditions were derived on the closed loop models for the joint process model to be stable and minimum phase.
Abstract: Stable constant linear closed-loop systems relating an input vector u to an output vector u and vice versa produce a jointly stationary (y, u)-procoss. On the other hand it is often natural to split up a stationary vector random process z into component vectors yand u, and to examine the closed-loop relations between y and u. This paper presents a number of new results on the spectral factorization and the closed-loop representation of a jointly stationary vector (y, u)-proccss. Conditions are derived on the closed-loop models for the joint process model to bo oE minimal degree, stable and minimum-phase. Relations between different joint process models producing the same spectrum φyu(z)are established.
TL;DR: This paper describes an effort based on state-of-the-art, modular linear programming software (IBM's MPSX/370), which indicates that much improvement is possible through advanced implementations and careful selection of computational strategies.
Abstract: Since the original work of Dantzig and Wolfe in 1960, the idea of decomposition has persisted as an attractive approach to large-scale linear programming However, empirical experience reported in the literature over the years has not been encouraging enough to stimulate practical application Recent experiments indicate that much improvement is possible through advanced implementations and careful selection of computational strategies This paper describes such an effort based on state-of-the-art, modular linear programming software (IBM's MPSX/370)
TL;DR: Fructose 2,6-bisphosphate was identified in Saccharomyces cerevisiae grown on glucose both by its property to be an acid-labile stimulator of 6-phosphofructo 1-kinase and by its ability to be quantitatively converted into fructose 6- phosphate under mild acid conditions.
TL;DR: In this article, the authors present the following elegant proposition due to Arrow: " Proposition : If an insurance company is willing to offer any insurance policy against loss desired by the buyer at a premium which depends only on the policy's actuarial value, then the policy chosen by a risk-averting buyer will take the form of 100 percent coverage above a deductible minimum.
Abstract: Of the numerous results provided over the past 30 years by the theory of decision under uncertainty, none has proved more helpful to me in solving practical problems than the following elegant proposition due to Arrow : " Proposition : If an insurance company is willing to offer any insurance policy against loss desired by the buyer at a premium which depends only on the policy's actuarial value, then the policy chosen by a risk-averting buyer will take the form of 100 percent coverage above a deductible minimum.
TL;DR: In this paper, the presence of glial fibrillary acidic (GFA) protein using the immunoperoxidase technique was found focally in epithelial tumor cells in nine of the 22 choroid plexus papillomas.
Abstract: Choroid plexus papillomas are usually easily distinguishable from papillary ependymomas by their delicate fibrovascular stroma and their cytologic similarity to normal choroid plexus epithelium. Exceptionally, however, examples are met which give rise to diagnostic difficulty. We therefore tested 22 choroid plexus papillomas for the presence of glial fibrillary acidic (GFA) protein using the immunoperoxidase technique. Positivity for the protein was found focally in epithelial tumor cells in nine of the 22 papillomas. All were in adults ranging from 19-66 years of age. Eight of the nine tumors originated in the 4th ventricle or one of its lateral recesses. In six papillomas showing GFA protein in the cells, intracellular fibrils were found in a small number of elongated epithelial cells with the PTAH and/or Masson trichrome stains; in all these six cases, the GFA protein-positive cells were considerably more numerous than cells containing fibrils. Normal choroid plexus epithelium lacks GFA protein, but pathologically altered ependymal cells are often GFA protein-positive. Our findings therefore suggest that focal divergent glial (presumably ependymal) differentiation may be expressed in neoplastic choroid plexus epithelium, consistent with the origin of this epithelium from primitive neuroepithelial (ventricular) cells.
TL;DR: It appears that all the standard algorithms terminate by constructing primal and dual feasible solutions of equal value, i.e., by satisfying generalised optimality conditions.
Abstract: We survey some recent developments in duality theory with the idea of explaining and unifying certain basic duality results in both nonlinear and integer programming. The idea of replacing dual variables (prices) by price functions, suggested by Everett and developed by Gould, is coupled with an appropriate dual problem with the consequence that many of the results resemble those used in linear programming. The dual problem adopted has a (traditional) economic interpretation and dual feasibility then provides a simple alternative to concepts such as conjugate functions or subdifferentials used in the study of optimality. In addition we attempt to make precise the relationship between primal, dual and saddlepoint results in both the traditional Lagrangean and the more general duality theories and to see the implications of passing from prices to price functions. Finally, and perhaps surprisingly, it appears that all the standard algorithms terminate by constructing primal and dual feasible solutions of equal value, i.e., by satisfying generalised optimality conditions.
TL;DR: Speciation of arsenicals in urine might be useful to determine the duration of BAL treatment and the proportion of the three species of urinary arsenic changes markedly with time.
Abstract: The urinary excretion of inorganic arsenic and of its less toxic metabolites [monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA)] has been followed-up in five cases of acute oral intoxicat...
TL;DR: It is shown that one of these 3-linked glucans,callose, is always localized, independently of the fibre age, in the innermost wall layer bordering the cell lumen, from the onset of the secondary thickening up to the end of fibre development.
Abstract: Several recent biochemical studies concerning the hemicellulosic content of the developing cotton fibre wall have pointed to an important increase of 1,3-linked glucans at the onset of the secondary wall formation and their slow decrease until the end of fibre development (Meinert andDelmer 1977,Huwyler
et al. 1978, 1979,Maltby
et al. 1979). These almost insoluble glucans are extra-cellular and possibly associated with the S1 or winding layer, but no other data on their exact localization were given. By means of a specific fluorescence method, using a 0.05% decolourized aniline blue solution, we show that one of these 3-linked glucans,callose, is always localized, independently of the fibre age, in the innermost wall layer bordering the cell lumen, from the onset of the secondary thickening up to the end of fibre development. Some possible roles assumed by these callose deposits are suggested and discussed. They may be involved in the normal mechanism of cellulose biosynthesis, as being effectively consumed by turnover or, more probably, as forming a permanently restored interface or matrix where cellulose microfibrils undergo a sort of maturation and are oriented before their definitive incorporation in the organized cell wall. They are not to be confused with the wound callose deposits which characterize damaged or immature fibres.
TL;DR: In this paper, the NO group with dienes gives 3, 6-dihydrooxazine derivatives which isomerise to epoxyepimines in most cases of β-substituted nitrosoalkenes.
Abstract: Some α- and β-halonitrosoalkenes 1 have been synthesized and characterized. The halogen atoms of the oxime precursors 2 can be substituted by alkoxy groups. Two kinds of cycloaddition reaction of 1 have been observed: (i) reaction of the NO group with dienes gives 3, 6-dihydrooxazine derivatives 6 which isomerise to epoxyepimines 7 in most cases of β-substituted nitrosoalkenes; (ii) if 4, 5-dihydrooxazines 22 are obtained, the cycloaddition of the nitrosoalkenes as 4π-component is presumed.