Showing papers by "Université catholique de Louvain published in 1973"
TL;DR: In this article, the results of a comparison of precurseurs amorphes with pyrolyse a Pair sous forme tres divisee, are presented, with respect to phase, taille des particules, surface specifique.
289 citations
01 Jan 1973
TL;DR: In this article, the concentrations of all stable and unstable species have been measured in the reaction zone of lean and stoichiometric methane-oxygen flames burning at 40 torr, and it is shown conclusively that the great majority of the methyl radicals is removed by Reaction [2], CH3+O→CH2O+H, with k2=1.3×1014 exp (−2000/RT).
Abstract: The concentrations of all stable and unstable species have been measured in the reaction zone of lean and stoichiometric methane-oxygen flames burning at 40 torr. The rate constant of Reaction [1], CH4+OH→CH3+H2O, was found to be k1=3×1013×exp(−6000/RT) mole−1 cm3 sec−1. In stoichiometric flames, half of the fuel is consumed via Reaction [1′], CH4+H→CH3+H2 and at T=1600°K, k1′ is reported to be 3.2×1012. It is shown conclusively that the great majority of the methyl radicals is removed by Reaction [2], CH3+O→CH2O+H, with k2=1.3×1014 exp (−2000/RT). The rate-determining step is a reaction resulting in an increase of the number of particles, Reaction [13]: CH2O+M→CO+H2+M; the value k13=2.1×1016 exp(−35,000/RT) was derived. Another part of the formaldehyde disappears via Reaction [3]: CH2O+OH→CHO+H2O; the rate constant is k3≅2.3×1013 in the range T=1400°–1800°K. Most of the CHO radicals react with O2: CHO+O2→HO2+CO; k4≅3×1013 at T=1600°K. In lean flames, HO2 is removed mainly by reactions involving OH and O: HO2+OH(O)→O2+H2O(OH); and k5≅5×1013 at T=1600°K. Carbon dioxide is formed by Reaction [6]: CO+OH→CO2+H; the rate constant was found to be k6=2.8×1011 at T=1750°K, and the activation energy E6=5.5±2 kcal/mole in the range T=1500°–1900°K. In the burned gas of lean flames, the radical “pool” decays by Reaction [11]: H+O2+M→HO2+M,the rate constant (for M=O2) being k11=2.5×1015 at T=1900°K.
120 citations
TL;DR: Pronase at low concentration produces a reversible increase of glucose-stimulated insulin release in isolated islets of Langerhans and affects the ultrastructure of the beta cells by inducing extensive development of tight junctions and the accumulation of secretory product within the extracellular spaces.
Abstract: Pronase at low concentration (4 micrograms per milliliter) produces a reversible increase of glucose-stimulated insulin release in isolated islets of Langerhans. Pronase also affects the ultrastructure of the beta cells by inducing extensive development of tight junctions as well as the accumulation of secretory product within the extracellular spaces.
97 citations
TL;DR: Kinetic properties, stability characteristics and competitive inhibition experiments are interpreted as an indication of at least three different acid phosphatases in bone cells: phosphoprotein phosphatase, acid β-glycerophosphatase (orthophosphoric monoester phosphohydrolase, EC 3.1.2) and acid inorganic pyrophosphat enzyme, the latter enzyme being apparently responsible for the acid p -nitrophenylphosphate activity of the homogenates.
82 citations
77 citations
TL;DR: In this article, the authors proposed two analogous mechanisms for explaining the variation of the proportions of spontaneously reducible and initiable nickel oxide with NiO content and temperature, and showed that copper restores the nucleation ability of all domains.
70 citations
69 citations
TL;DR: In this paper, a causal and causally invertible innovations representation (IR) whose existence depends only on the positive definite nature of the separable covariance is presented, and it is shown that least squares filtered and smoothed estimates of one process given observations of a related colored process can be expressed as linear combinations of the state vector of the IR of the observed process.
Abstract: The linear stochastic discrete-time realization problem is to find a white-noise driven finite-dimensional linear system whose output generates a specified separable covariance. The solution to this problem is presented in the form of a causal and causally invertible innovations representation (IR) whose existence depends only on the positive definite nature of the separable covariance. It is also shown that least-squares filtered and smoothed estimates of one process given observations of a related colored process can be expressed as linear combinations of the state vector of the IR of the observed process. The analogous continuous-time problems have been studied earlier, and it has been shown that an important role is played by what is known as the relative order of the covariance. Here this is defined as the number of differencing operations required to produce a delta function component in the differenced covariance. It is shown that, unlike the continuous-time case, the relative order of the covariance does not necessarily induce similar (relative order) constraints on the impulse response of all models whose responses to white noise have the given covariance. This fact is at the heart of certain differences between continuous-time and discrete-time results. It is shown, however, that the innovations representations obey a number of constraints equal to the relative order of the covariance.
69 citations
TL;DR: The mechanism by which the administration of fructose to patients with hereditary fructose intolerance makes them unresponsive to the hyperglycaemic action of glucagon was studied and inhibition of phosphorylase in the liver appears to be a likely explanation for the unresponsiveness to glucagon.
Abstract: 1. The mechanism by which the administration of fructose to patients with hereditary fructose intolerance makes them unresponsive to the hyperglycaemic action of glucagon was studied. In four patients, a 10-fold increase in the urinary excretion of cyclic AMP was induced by glucagon, but this effect was drastically decreased by the previous administration of fructose (250mg/kg). Further, the intravenous injection of 6-N,2'-O-dibutyryl cyclic AMP did not cause an increase in the blood glucose during fructose-induced hypoglycaemia. 2. The administration of a large dose of fructose (5g/kg) to mice decreased markedly both the concentration of ATP and the increase in the concentration of cyclic AMP caused by glucagon in the liver. Other ATP-depleting agents had a similar effect and a linear correlation could be drawn between the concentration of ATP and the change in cyclic AMP concentration; a half-maximal effect was obtained for a concentration of ATP close to the K(m) value of adenylate cyclase. 3. The administration of fructose to mice caused the inactivation of phosphorylase in the liver, but this effect was easily reversed by glucagon. 4. At a concentration of 10mm-fructose 1-phosphate and 1.5mm-P(i), purified liver phosphorylase a was inhibited by 70%. This inhibition appears to be a likely explanation for the unresponsiveness to glucagon of patients with hereditary fructose intolerance.
67 citations
TL;DR: In this article, the carbon atoms of dichloromethylenedimethylammonium chloride (DHMCL) are activated by an amino group on the same carbon atom.
Abstract: Dichloromethylenammonium salts, particularly dichloromethylenedimethylammonium chloride, occupy a unique place as stable but reactive building blocks for synthesis. They contain three mobile chlorine atoms activated by an amino group on the same carbon atom. These salts can be regarded as chlorinated Vilsmeier or Mannich reagents and are thus at a higher oxidation level. As in the Mannich or Vilsmeier reaction, the carbon condenses here as an electrophile with formation of CC or Chetero atom bonds in a variety that is still far from being exhausted.
48 citations
TL;DR: The data suggest that the mutation affects a chromosomal DNA product involved in a central process of mitochondrial biogenesis, and the Dio-9-sensitive ATPase purified from mutant submitochondrial particles reacts like the wild type enzyme to anions, cations, inhibitors, and low temperature.
TL;DR: Dichlormethylen-ammoniumsalze as discussed by the authors enthalten drei bewegliche Chloratome, die durch eine Aminogruppe am selben Kohlenstoffatom aktiviert sind.
Abstract: Dichlormethylen-ammoniumsalze, speziell Dichlormethylen-dimethyl-ammoniumchlorid, sind einzig als stabile, aber reaktionsfahige Synthese-Bausteine. Sie enthalten drei bewegliche Chloratome, die durch eine Aminogruppe am selben Kohlenstoffatom aktiviert sind. Diese Salze konnen als chlorierte Vilsmeier- oder Mannich-Reagentien angesehen werden und haben somit einen hoheren Oxidationszustand. Ahnlich wie bei der Mannich- oder Vilsmeier-Reaktion kondensiert dabei der Kohlenstoff als Elektrophil unter Bildung von CC- oder C—Heteroatom-Bindungen in einer Vielfalt, die noch lange nicht ausgeschopft ist.
TL;DR: The ratio of association between viral infections and exacerbations is high; the seroconversion study during exacerbations and at other times revealed a great difference, 58.3 percent to 3.7 percent.
TL;DR: Food preferences and feeding behaviour of abundant species of oribatid mites in a black pine plantation have been studied by soil sectioning technique and it is suggested that Microtritia minima, Rhysotritia duplicata and Phthiracarus sp.
Abstract: Food preferences and feeding behaviour of abundant species of oribatid mites in a black pine plantation have been studied by soil sectioning technique. It is suggested that Microtritia minima, Rhysotritia duplicata and Phthiracarus sp. play an important role in the mechanical breakdown of decaying litter and, by contributing to the humification process, help in the accumulation of plant nutrients. Due to poor mobility their contribution to fungal spore dissemination is insignificant.
TL;DR: It is asserted that the stimulation of RNA synthesis by cycloheximide during metabolic starvation presents several analogies with the release of stringent bacterial control by chloramphenicol.
Abstract: THE respiratory adaptation of anaerobic yeast and aerobic glucose-derepression are usually induced in conditions of limited growth resulting from glucose or nitrogen downshift of the culture medium1. In these conditions, mitochondrial as well as cytoplasmic RNA and protein syntheses are required for the full development of functional mitochondria. Cycloheximide, which specifically blocks the cytoplasmic ribosomes2, is often added to the respiratory adaptation or glucose-derepression media to study the specific products of mitochondrial protein synthesis3. This inhibitor, however, probably disturbs the regulatory relationships that exist not only between mitochondrial and cytoplasmic protein syntheses but also between the latter and nucleic acid synthesis. It has been shown that cycloheximide depresses RNA synthesis in growing yeast4,5 although Fukuhara6 observed that during the respiratory adaptation of Saccharomyces cerevisiae, RNA synthesis is only slightly depressed by cycloheximide. In other circumstances, the occasional stimulation of RNA synthesis by cycloheximide has been reported7. Here we assert that the stimulation of RNA synthesis by cycloheximide during metabolic starvation presents several analogies with the release of stringent bacterial control by chloramphenicol.
TL;DR: In this paper, the minimum of the HF capacitance and the threshold voltage for nonuniformly doped MOS structures are calculated by means of an analytical model containing an adequate definition of the condition of strong surface inversion.
Abstract: The minimum of the HF capacitance and the threshold voltage, for nonuniformly doped MOS structures, are calculated by means of an analytical model containing an adequate definition of the condition of strong surface inversion The results obtained for profiles piling up close to the surface are in excellent agreement with those obtained by a numerical integration of Poisson's equation
TL;DR: Magnesium-containing calcites are concentrated in clay (< 2 μ) and fine silt (2-10 μ) sizes of Cca horizons and their presence in the clay fraction of Ck horizons is an indication that carbonate mineralogy may change at profile depths often considered to be unaffected by pedogenic processes.
TL;DR: The dependence on protein concentration is much smaller than expected from the law of mass action, and this deviation can be explained by the presence of different thermodynamic components.
TL;DR: Rat liver mitochondria may suffer extensive biochemical and morphological alterations during highspeed centrifugation in a sucrose gradient, which led us to investigate directly the effects of pressure on subcellular organelles by hydraulically compressing rat-liver granules under various conditions.
TL;DR: Estrone and estradiol-17β have been measured in non-pregnancy plasma, by radioimmunoassay, after Chromatographie separation on short Sephadex LH 20 columns, and a good correlation was found between the level of unconjugated estrogens in the plasma and thelevel of urinary estriol.
TL;DR: In this article, a comparison between a Mossbauer spectroscopy determination and the classical chemical analysis of the Fe/sup 2+/ content in SiO/sub 2/-Na/sub O/sub 3/ glass systems, for different iron concentrations, and for 16.0 and 24.0 wt% Na/sub 1/O respectively is given.
Abstract: A comparison is given between a Mossbauer spectroscopy determination and the classical chemical analysis of the Fe/sup 2+/ content in SiO/sub 2/-Na/sub 2/O-Fe/sub 2/O/sub 3/ glass systems, for different iron concentrations, and for 16.0 and 24.0 wt% Na/sub 2/O respectively. The agreement between Mossbauer analysis and chemical analysis is good only for large Fe/sub 2/O /sub 3/ contents, while for small Fe/sub 2/O/sub 3/ contents the Mossbauer analysis gives a much larger Fe/sup 2+//(Fe /sup 2+/+Fe/sup 3+/) ratio than the chemical analysis: a physical reason is given for this fact. The Fe/sub 2/O/sub 3/ content below which Fe/sup 2+/ becomes predominant in glass is rather sharply defined, and a qualitative explanation is proposed to account for this rapid transition from Fe/sup 3+/ to Fe/sup 2+/.
TL;DR: In this article, the microwave spectra of D217O and D218O have been measured in the region from 8 to 400 GHz and analyzed according to Watson's centrifugal distortion theory.
TL;DR: Helix pomatia haemocyanin dissociates on the alkaline side of the stability region successively into halves, tenths and twentieths, which still bear twenty copper atoms2.
Abstract: Helix pomatia haemocyanin has a molecular weight of 9 × 106 and a copper content of 0.25%. One oxygen molecule is bound per two copper atoms. This haemocyanin dissociates on the alkaline side of the stability region successively into halves, tenths1 and twentieths, which still bear twenty copper atoms2.
TL;DR: In this article, the formation of 1:1 hydrogen bonded complexes formed by N,N-dimethylacetamide (DMA) and substituted phenols have been studied by infrared spectrometry in nonpolar solvents at 27°C.
TL;DR: These data confirm the extensive recycling of estradiol within the uterine cell and show in the nucleus, the existence of a more slowly exchangeable pool, of limited capacity, which appears to be possibly a final but still reversible step in the hormone distribution within the cell.
TL;DR: Continuous cell lines derived from a number of transplantable immunoglobulin-producing tumors of rat origin are more capable of inducing tumors comparable to the original growths when injected intraperitoneally or subcutaneously into histocompatible animals.
TL;DR: The responsiveness measured in terms of increase in plasma LH concentrations was lowest during the early and mid-follicular phase, generally highest around the spontaneous LH surge and was higher during the late-luteal phase than during the follicular phase.
TL;DR: The enzymatic activity on dl-DOPA-l-14C was optimum in air and inhibited in a N2 atmosphere, and the Michaelis-Menten law, from which it was found that Km = 8·3 × 10−4M for decarboxylation.
Abstract: Properties of diphenol oxidases extracted from salts. Salmine and SP-Sephadex C-25 were used to separate the enzyme system associated with humic materials in the neutral extracts of fresh soils (NAFS Extract). Electrophoresis on polyacrylamide gel shows that this preparation is heterogeneous. The elementary analysis of the soil enzyme is C 43·13%; N 5·09%; H 7·21%; O 44·58%. Chromatographic analyses indicate that the soil enzyme contains 53 per cent amino acids, 36 per cent sugars and amino sugars and 10 per cent ammonium and inorganic materials. The soil enzyme has a maximum absorption at 270–280 nm. The soil enzyme degrades the following substrates at the relative rate mentioned in parentheses : d-catechin (298);p-cresol (251); catechol (156); dl-DOPA (100);p-phenylene diamine (59);p-quinol (20) in terms of rate of oxygen absorption. This enzymatic preparation has the properties of an o- and p-diphenol oxidase. The rate of decarboxylation was measured using a radiorespirometer. The following relative values are dl-DOPA-l-14C (100); dl-tyrosine-l-14C (35) ; dl-tyrptophan-1-14C (7); dl-phenylalanine-l-14C (2). The dl-DOPA-2-14C was partially degraded to 14CO2. The O2 absorbed and CO2 (carboxyl) evolved in case of dl-DOPA was in the ratio of 1·8 at 37°C. The activation energy on dl-DOPA was 3·1 and 7·9 kcal/mole/°C for oxygen absorption and decarboxylation respectively. The enzymatic activity on dl-DOPA-l-14C was optimum in air and inhibited in a N2 atmosphere. Decarboxylation on dl-DOPA-l-14C followed the Michaelis-Menten law, from which we found that Km = 8·3 × 10−4M for decarboxylation. The oxidative decarboxylation was inhibited by H2O2 (74%); KCN (75%); ascorbate (92%); BAL (97%);DIECA(90%).
Melanogenesis of dl-DOPA followed first order kinetics. The maximum absorption at 305 nm during melanogenesis shows the formation of dopachrome.
TL;DR: The results support the concept of an association of phosphoprotein phosphatase, acid inorganic pyrophosphatases, acid β-glycerophosphatase and the other acid phosphatases activities with lysosomes in bone.
TL;DR: Polyphenoloxidase (PPO) activity was detected in autoclaved muskmelon tissues colonized in vitro by Fusarium oxysporum f.
Abstract: Polyphenoloxidase (PPO) activity was detected in autoclaved muskmelon tissues colonized in vitro by Fusarium oxysporum f. sp. melonis and different isoenzymes were separated by polyacrylamide disk electrophoresis. During the colonization of propylene oxide sterilized tissues, new isoenzymes with the same E f values as fungal PPO appeared in addition to the plant PPO isoenzymes. With these methods only four fungal peroxidase (PO) isoenzymes of low activity were detected. In extracts of hypocotyls, stems, petioles and leaves from infected plants, harvested before the appearance of symptoms on the leaves, higher PPO and PO activities were measured as compared to uninoculated plants of the same age, without any relation to the presence of the pathogen in the analyzed tissues. The qualitative and quantitative changes in the PO zymograms observed during this first stage of the disease bear a resemblance to the changes detected in leaves of older uninoculated plants. In the second stage of the disease, characterized by the appearance of the leaf symptoms and correlated with an exponential increase of the colonization density of the plant by the parasite, there was still a more rapid increase of the PPO and PO activities. In the PPO zymograms, isoenzymes with the same E f as the fungal PPO appeared and/or increased while the activity of some PPO isoenzymes characteristics of the healthy plant decreased. This suggests that beside its action on the host metabolism, the parasite also directly contributes to the increase of PPO activity and the alteration of the isoenzyme pattern which are observed in the infected plants.