Showing papers by "Université libre de Bruxelles published in 1969"
TL;DR: In this paper, Goldfeld and Quandt presented a test for heteroskedasticity based on the absolute values of the residuals obtained by ordinary least-squares on some variable(s).
Abstract: The quite general test for heteroskedasticity presented here regresses the absolute values of the residuals obtained by ordinary least-squares on some variable(s). Denoting the O.L.S. residuals by , one obtains, for instance, a regression like where z is a variable, a and b regression coefficients and the residuals of the new regression. We call the acceptance of a non-zero value for both a and b a case of “mixed heteroskedasticity”, which we deem frequent in practice though neglected in handbooks. The paper also summarizes another test due to S. M. Goldfeld and R. E. Quandt and examines the powers of the two by using Monte-Carlo simulations: the new test seems to compare favourably, except perhaps in the case of large samples.
542 citations
TL;DR: In this article, it is shown that at the yield stress, glassy polymers exhibit viscous flow which is in agreement with the generalized theory of Eyring, and they conclude that every secondary transition corresponds to the liberation of one of the degrees of freedom of a segment of the main chain.
Abstract: It is shown that, at the yield stress, glassy polymers exhibit viscous flow which is in agreement with the generalized theory of Eyring. The study of the yield stress over a wide range of temperatures and strain rates provides evidence on the secondary transitions found by other methods. From our measurements we conclude that every secondary transition corresponds to the liberation of one of the degrees of freedom of a segment of the main chain.
266 citations
TL;DR: In this paper, the authors introduce operateurs de projection Π(j) ρ of the fonction de distribution ρ (ou la matrice densite) and show that these projections satisfy des equations separees.
156 citations
TL;DR: Evidence is provided for the existence of Ter, a function which generates linear λ chromosome from structures in which the termini are linked, and specifically between genes R and A—the terminal genes of the mature chromosome.
Abstract: Bacterial strains lysogenic for two prophages in tandem undergo a special kind of prophage excision ("dilysogenic excision") which does not depend on the three known recombination mechanisms. This excision is specifically between genes R and A - the terminal genes of the mature chromosome. This is evidence for the existence of Ter, a function which generates linear λ chromosome from structures in which the termini are linked. © 1969 Nature Publishing Group.
111 citations
TL;DR: In this paper, an auditory warning signal occurring in a high time-uncertainty situation produced an acceleration of the choice reaction to a visual stimulus which followed it by a predictable interval.
111 citations
TL;DR: In this article, the authors define an ensemble of points as a set of points distinct from one another, and define a plan for each of these points, which can be expressed as a triple of points.
Abstract: 1. Nous dirons qu'un espace linOaire [4] est un ensemble L d'dldments appel6s points dans lequel on distingue une famille de sous-ensembles contenant au moins deux points et appel6s droites, de telle mani6re que toute paire de points distincts p, q soit contenue dans une et une seule droite, not6e p+q. Une vari~t~ linOaire de L [1] sera un ensemble de points V tel que p, qE V entraine p + q c V. I1 est clair que toute intersection de vari6t6s lin6aires est une vari6t6 lin4aire; de ce fait, tout ensemble de points X engendre une vari6t6 lin6aire X qui est l 'intersection des vari6t6s lin6aires contenant X. L'ensemble vide, un point, une droite, L sont des exemples de vari6t6s lin6aires. Dans les espaces affins et projectifs les > sont des vari4t6s lin6aires et ce sont les seules sauf dans les espaces affins d 'ordre deux. Dans ces derniers tout ensemble de points est une vari6t6 lin6aire. Un plan de L sera une vari6t6 lin6aire engendr6e par un triple de points >.
101 citations
TL;DR: In this paper, the yield stress behavior of two glassy polymers is studied through the glass transition region over a wide range of strain rates, and it is described as a non-Newtonian flow in agreement with Eyring's theory, excepts a narrow range relating to the slowest strain rates.
Abstract: The yield-stress behavior of two glassy polymers is studied through the glass transition region over a wide range of strain rates. For temperatures below the glass transition temperature, the yield stress behavior could be described as a non-Newtonian flow in agreement with Eyring's theory, if one excepts a narrow range relating to the slowest strain rates. For temperatures above Tg, the yield-stress behavior is still nonlinear but fits the relations based on the concept of free volume.
91 citations
TL;DR: In this article, sound frequency patterns and sound pressure levels of distress calls from pups of several litters of albino mice were analyzed and it was suggested that reduction in the acoustic energy of the calls (intensity × duration) could decrease their effectiveness in eliciting maternal responses and could be the result of reduced cold stress as the pups developed homoiothermy.
91 citations
TL;DR: In this paper, it was shown that the regulatory protein is an arginase which, when its substrate, arginine, and the product of its action, ornithine, are simultaneously present, binds OTC and inhibits its activity.
86 citations
TL;DR: In this article, the authors define an ensemble of points as "a family of sous-ensembles appel6s droites, v6rifiant les conditions suivantes (i) toute paire de points distincts p, q est contenue dans une and une seule droite not6e p + q; (ii) tout droite contient au moins trois points; (iii) si a, b, c, d, e sont des points distinct, tels que a + b =
Abstract: Dans cette note, l'expression > d~signera un ensemble de points, muni d'une famille de sous-ensembles appel6s droites, v6rifiant les conditions suivantes (i) toute paire de points distincts p, q est contenue dans une et une seule droite not6e p + q; (ii) toute droite contient au moins trois points; (iii) si a, b, c, d, e sont des points distincts tels que a + b = a + e e t a + d = a + e, les droites b + e et c + d ont un point commun. Divers concepts tels que vari6t6 lin6aire, dimension, perspectivit6, hyperplan ainsi que leurs propri6t6s, seront utilis6s sans rappels. I1 est bien connu que les espaces projectifs peuvent atre class6s de la mani6re suivante: a) les espaces projectifs triviaux caract6ris6s par le fair qu'ils ont au plus une droite, ou encore, que leur dimension est inf6rieure/~ 2; b) les plans projectifs nonargu6siens; c) les espaces projectifs argu6siens de dimension > 2 qui ne sont autres que les espaces projectifs h coordonn6es homogSnes dans un corps. Les espaces de dimension infinie ne seront pas syst6matiquement 6cart6s de notre 6tude bien que notre d6monstration des principaux r6sultats utilise l'hypoth6se de finitude de la dimension. Notons qu'une vari6t6 lin6aire sera toujours consid6r6e comme un ensemble de points.
78 citations
TL;DR: Strong reduction of ATP output by antimycin, oxamate with anaerobiosis or the combination of oligomycin and oxamate increased the spontaneous release of chymotrypsinogen, suggesting that retention of the enzymes in the cell is also dependent on a minimal energy supply.
TL;DR: In this paper, the authors measured the sound velocity of high-frequency phonons (1-3 GHz) in liquid argon and liquid neon along their vapor pressure equilibrium curves using the Brillouin scattering technique.
Abstract: Recent theoretical work has suggested that at high frequencies, there should be significant departure from classical hydrodynamic behavior in simple fluids. In particular, the frequency dependence of transport coefficients is no longer negligible and may introduce observable effects into the propagation of high-frequency sound. We have measured the sound velocity of high-frequency phonons (1-3 GHz) in liquid argon and liquid neon along their vaporpressure equilibrium curves using the Brillouin scattering technique. The Brillouin spectra were excited with a single-mode argon-ion laser operating at 5145 or 4765 and were analyzed and detected with a Fabry-Perot interferometer and standard photoelectric techniques. Hypersonic (3 GHz) velocities observed in argon decrease linearly from 850 m/sec at 85°K to 742 m/sec at 100°K and uniformly exhibit a small departure from low-frequency (1 MHz) data obtained under the same thermodynamic conditions. This effect is in qualitative agreement with theoretical-model predictions of a negative velocity dispersion at high frequencies. Our measurements of the sound velocity in liquid neon are the first in this material by any technique, and hance cannot be compared with ultrasonic values. The hypersonic velocity in neon decreases not quite linearly from 620 m/sec at 24.9°K to 508 m/sec at 32°K. When compared with results in other noble-gas liquids through corresponding-state arguments, these data suggest the existence of measurable quantum effects in the hypersonic velocity of liquid neon. In addition, an interesting change in slope of the velocity-versus-temperature curve (of 17%) is observed at 28°K. © 1969 The American Physical Society.
TL;DR: Results indicate that the main promotor for transcription of the late functions is located in the Q-R segment, and insertion of phage Mu within prophage λ results in defectiveness of the λ-lysogen.
Abstract: Insertion of phage Mu. 1 within prophage λ results in defectiveness of the λ-lysogen. When Mu is located in the genetic segment involved in the late functions, the expression of all the genes distal to the insertion is severely depressed. The results indicate that the main promotor for transcription of the late functions is located in the Q-R segment.
TL;DR: In this paper, the results of a comparative study of the NMR spectra of phenanthrene to nonahelicene have been reported and the four spin systems present in these hydrocarbons (end rings) have been calculated and the corresponding protons have been assigned on the basis of the coupling constants.
TL;DR: The different types of hybrids obtained with respect to the genes for exonuclease and β protein provide genetic evidence that exonUClease andβ protein are distinct polypeptides rather than polymeric forms of the same peptides.
TL;DR: Dividing haemoflagellates lose their kinetoplast DNA in the presence of ethidium bromide but resting cells are not so affected by the drug.
TL;DR: The data indicate that the vascular pole of the capillary endothelial cells can adsorb labelled insulin and either exchange it with unlabelled insulin or release it under the direct influence of glucose.
Abstract: Normal anaesthetized bull-dogs were perfused with constant amounts of 125I bovine insulin. During the control period, steady state arterio-venous gradients and lymph levels were achieved. Positive arterio-venous differences were observed across the hind limbs and the head. Lower levels of 125I-insulin were found in cervical and leg lymph than in corresponding venous plasma. The rapid intravascular injection of unlabelled insulin resulted in an almost immediate reversal of the arterio-venous gradients of 125I-insulin in the head and the hind limb. The injection of small amounts of glucose into the lower abdominal aorta induced a very rapid diminution of the arterio-venous gradient across the hind quarters; the effect was not mediated by the release of endogenous insulin. In both experiments, the lymph levels of 125I-insulin remained relatively constant.
TL;DR: In this article, a dependence of bond energy on the isomeric structure of the molecules and radicals and on the type of bond broken (primary, secondary, or tertiary) was shown.
Abstract: CCl and CC bond energies in the chloroethanes and CH, CCl, and CC bond energies in the chloroethyl radicals are calculated from known heats of formation of chloroethanes and chloroethylenes and known CH bond energies in chloroethanes.
The results obtained show a dependence of bond energy on the isomeric structure of the molecules and radicals and on the type of bond broken (primary, secondary, or tertiary). Heats of formation and bond energies estimated from group property additivity rules are in close agreement with experimental values.
TL;DR: Cytological alterations of the follicle cells were found, some of which suggested an increased metabolic activity, and emperipolesis was encountered in the autoimmune thyroiditis cases studied with the electron microscope.
Abstract: In an investigation of autoimmune thyroiditis, two cases of chronic asymptomatic thyroiditis, two cases of nodular goitre with focal thyroiditis and two cases of Hashimoto goitre were studied with the electron microscope. The ultrastructural observations were similar in the six cases. Cytological alterations of the follicle cells were found, some of which suggested an increased metabolic activity. Lymphocytes and plasmocytes established close relationships with the thyroid cells: emperipolesis was encountered.
TL;DR: Results seem to provide some further arguments in favour of an endocrine role of the neurosecretory brain cells in the formation of apical tissue of the testes in the tests.
TL;DR: In this article, the probability density of a pair of heavy particles in a fluid of lighter particles is derived from the Liouville equation and proceeds by expansion in the ratio of light to heavy masses, using the technique previously applied successfully to the singlet distribution.
Abstract: The equation of evolution governing the probability density of a pair of heavy particles in a fluid of lighter particles is derived. The derivation starts from the Liouville equation and proceeds by expansion in the ratio of light to heavy masses, using the technique previously applied successfully to the singlet distribution.
TL;DR: The mitochondrial system is very similar to that occurring in bacteria but differs from the latter by its sensitivity to some phenanthrene alkaloids, and the size of the mito- chondrial ribosome remains controversial.
TL;DR: An electron microscope study of one of the BALB/cf cell lines, the C+T5, maintained through more than 200 consecutive grafting generations, particularly from the point of view of virus particles (VP) which have been found associated with the tumor cells.
Abstract: Andervont established the BALB/cf strain of mice as a high mammary tumor strain by foster nursing original young BALB/c on C3H mothers. The occurrence of endemic adenocarcinoma in this strain was first reported from this laboratory in 1958. Since then, a substrain (BALB/cf/Cd) has been developed by inbreeding and selection, with a renal tumor incidence of 60–70%. The spontaneous tumors are transplantable and a number of renal tumor cell lines have been maintained by grafting. The present work is an electron microscope study of one of these cell lines, the C+T5, maintained through more than 200 consecutive grafting generations, particularly from the point of view of virus particles (VP) which have been found associated with the tumor cells. From their morphology, morphogenesis, and distribution in and outside the cell, these VP resemble virus particle types observed in mammary tumors and lymphomas of mice. They can be carried over in cells through the process of mitosis. The BALB/cf inbred substrain, which in our stock has retained the original high mammary tumor incidence, is free of renal tumors, whereas the new BALB/cf/Cd high renal-tumor strain can no longer produce mammary tumors. The VP described in this paper are quite different, in their morphology, localization, and morphogenesis, from the VP previously described in another transplantable renal tumor cell line of the original BALB/c strain.
TL;DR: Purification, enzymatic activity and amino acid composition of the chymotrypsinogen and the trypsinogens of the rat pancreas and the purification of each proenzyme is achieved by a second chromatography on phosphocellulose at pH 5.25.
TL;DR: The homologous relationship between the different chains and fragments of immunoglobulins and ferredoxins has been investigated by a sensitive method and the results lend weight to theories which suggest that all the chains of immunity have evolved from a common ancestor.
Abstract: The homologous relationship between the different chains and fragments of immunoglobulins has been investigated by a sensitive method. The results lend weight to theories which suggest that all the chains of immunoglobulins have evolved from a common ancestor. Moreover, the results suggest that the variable and constant parts of light chains have also a common ancestor. The occurrence of several possible internal regularities has been investigated. The results suggest that immunoglobulins and ferredoxins derive from the repetition of a primordial (pseudo)symmetrical peptide. The significance of the results is discussed.
TL;DR: EB inhibits 3 H-uridine incorporation into kinetoplast and nuclear RNA, but this effect on RNA synthesis is slower than the very quick process which affects DNA replication.