Showing papers by "Université de Montréal published in 1978"
TL;DR: The question of whether there is an automaton with n states which agrees with a finite set D of data is shown to be NP-complete, although identification-in-the-limit of finite automata is possible in polynomial time as a function of the size of D.
Abstract: The question of whether there is an automaton with n states which agrees with a finite set D of data is shown to be NP-complete, although identification-in-the-limit of finite automata is possible in polynomial time as a function of the size of D. Necessary and sufficient conditions are given for D to be realizable by an automaton whose states are reachable from the initial state by a given set T of input strings. Although this question is also NP-complete, these conditions suggest heuristic approaches. Even if a solution to this problem were available, it is shown that finding a minimal set T does not necessarily give the smallest possible T.
819 citations
TL;DR: In this article, the Voronoi diagram is constructed given a configuration of points, and a procedure for constructing the corresponding Voroni diagram is given, exact for molecules in the bulk polyhedra of surface molecules can be either eliminated or included using a periodic boundary condition.
221 citations
IBM1, Princeton University2, University of Illinois at Urbana–Champaign3, Oak Ridge National Laboratory4, Université du Québec5, Max Planck Society6, Grumman Aircraft Corporation7, Université de Montréal8, Yale University9, California Institute of Technology10, University of Pittsburgh11, Sandia National Laboratories12
TL;DR: In this article, a consensus profile of hydrogen ion-implanted into silicon has been produced, which is used as a calibration standard for silicon ion-beam profiling, with capabilities ranging from very high depth resolution to high sensitivity.
188 citations
TL;DR: Reduction in concentration of this most active vitamin-D metabolite correlated with the dose of steroid administered and with reduction in forearm bone mineral content measured by the photon absorption technique, suggesting that reduced serum-1,25-(OH)2D3 concentration may be important in the pathogenesis of steroid-induced osteopenia.
174 citations
TL;DR: Using single nephron preparations, it is demonstrated that the major and probably exclusive site of synthesis of 1,25(OH)2D3 is the proximal tubule.
Abstract: FRASER AND KODICEK1 have reported, and others hae confirmed2–4, that the kidney is the exclusive site of synthesis of 1,25-dihydroxycholecalciferol (1,25(OH)2D3). The 1-α-hydroxylation of 25-hydroxycholecalciferol (25-OH-D3) occurs in mitochondria1,4,5 and is influenced by cytosol6,7, although conflicting data have been reported8. Preparations of whole tubules from the cortex possess 1-α-hydroxylase activity10 but the precise localisation of the enzyme along the nephron is not known. In the dog, no evidence of 1-α-hydroxylase was found in medulla, enzymatic activity being observed only in cortical preparations5. In mice given systemic injections of 3H-vitamin D3 autoradiography shows the tracer to be present in the proximal tubules9. However, whether hydroxylation occurred at this site was not established. Using single nephron preparations, we have now demonstrated that the major and probably exclusive site of synthesis of 1,25(OH)2D3 is the proximal tubule.
172 citations
TL;DR: A trip distribution, modal split and trip assignment model is developed that shows that when two distribution models of this type are linked with route choice models based on Wardrop's “user optimized” principle, the mode choice is given by a logit model.
170 citations
01 Jan 1978
TL;DR: In this paper, the authors investigated the efficiency of the first of the Bland's rules for pivot selection in the simplex method and showed that for problems with 50 nonnegative variables and 50 additional inequalities, Bland's rule requires about 400 iterations on the average; the corresponding figure for the popular "largest coefficient" rule is only about 100.
Abstract: Recently R.G. Bland proposed two new rules for pivot selection in the simplex method. These elegant rules arise from Bland’s work on oriented matroids; their virtue is that they never lead to cycling. We investigate the efficiency of the first of them. On randomly generated problems with 50 nonnegative variables and 50 additional inequalities, Bland’s rule requires about 400 iterations on the average; the corresponding figure for the popular “largest coefficient” rule is only about 100. Comparable behaviour seems to persist even on highly degenerate problems. On the theoretical side, we analyse the performance of Bland’s rule on the classical Klee-Minty examples: for problems with n nonnegative variables and n additional inequalities, the number of iterations is bounded from below by the n-th Fibonacci number.
118 citations
117 citations
TL;DR: In this article, the functional form of the two equations of a cross-sectional inter-city travel demand model and of two time-series urban travel demand models are presented, using current maximum likelihood techniques extended to take multiple-order auto-correlations into account, and it is demonstrated that estimating the functional forms dominates more restricted procedures on grounds both of the statistical significance and of the economic reasonableness of the results.
115 citations
TL;DR: In this paper, the rare earth elements (REE) LaLu are generally considered to be unaffected by weathering and are thus often used to characterise variations in basalt and magma composition.
Abstract: DREDGED oceanic basalts and those sampled by deep-ocean drilling have commonly undergone some weathering with subsequent changes in their chemical composition1–7. The rare-earth elements (REE) La–Lu are generally considered to be unaffected by weathering and are thus often used to characterise variations in basalt and magma composition. When considered relative to chondritic abundances8, the overall REE distribution is a critical diagnostic tool. In particular, the relative depletion of light-REE is used to discriminate between magma types. We present here new findings which show that REE are affected by low-temperature weathering processes. In particular, the light-REE show enrichments which may result in a basalt with a primary light-REE depleted pattern showing a flat or enriched light-REE pattern.
113 citations
TL;DR: A non-commutative analogue of the central limit theorem and the weak law of large numbers has been derived in this paper, with the analogues of integrable functions being non commutative polynomials, without the assumption of positivity higher central limit theorems hold which have no analogy in the classical probabilistic case.
Abstract: A non-commutative analogue of the central limit theorem and the weak law of large numbers has been derived, the analogues of integrable functions being non-commutative polynomials. Without the assumption of positivity higher central limit theorems hold which have no analogy in the classical probabilistic case. The treatment includes this classical case and the convergence to so-called “quasi-free states” in the quantum mechanics of bosons [3, 4].
TL;DR: The MACER sled-mounted suprabenthic sampler as discussed by the authors has been used extensively in the Gulf and Estuary of the St. Lawrence for the purpose of studying micro-stratification above bottom.
Abstract: Enlarged versions of the MACER sled-mounted suprabenthic sampler were tested, improved, calibrated and used extensively (598 tows) at depths of 10—384 m since 1968 in the Gulf and Estuary of the St. Lawrence. Two half-metre zooplankton nets are mounted at 28—64 and 106—142 cm from the sea-bed, on a steel chassis and toboggan plate. Each has a flow-meter and 3 horizontal shutters which open via a lever upon contact with the sea floor. They close automatically, through springs and water pressure, whenever the sled leaves the bottom, ensuring uncontaminated suprabenthic samples. Although heavy (228 kg), the device is sturdy, used like a beam trawl, reliable, and collects very little sediment. It has been used to study micro-stratification above bottom. Data on filtered water volumes, special problems encountered and future improvements are discussed.
TL;DR: The autoradiographic fiber tracing method was used to determine the contribution of climbing fibers to the cerebellar cortex from the olive and other brainstem precerebellar structures and concluded that the large majority and probably all the climbing fibers originate from the inferior olive.
TL;DR: The findings indicate that this approach to modifying type A behavior may reduce coronary risk and therefore warrants further exploration, leaving questions of clinical validity, durability, and generalizability unresolved.
Abstract: This report presents the design and initial findings of an attempt to reduce the risk of coronary heart disease in healthy men by modifying their type A behavior pattern. A group of 27 professional and executive volunteers, aged 39–59, who had been medically assessed as free from coronary heart disease, were randomly assigned to brief psychotherapy and behavior therapy groups. Each treatment group met for 14 sessions over a period of 5 months. Pre- and postmeasures of physiological (serum cholesterol, serum triglycerides, blood pressure) and psychological (anxiety, psychological symptoms, satisfaction) variables were taken. Results indicate that both treatment groups changed in the desired direction on most of the psychological and physiological variables without apparent change in habits of diet, exercise, smoking, or work load. The findings are provocative, but only tentative, leaving questions of clinical validity, durability, and generalizability unresolved. Nevertheless, they indicate that this approach to modifying type A behavior may reduce coronary risk and therefore warrants further exploration.
TL;DR: The encoding of simple features such as lines and angles leads naturally to size and position invariance when these features are analyzed symbolically in terms of structure and connectedness, but no such analysis is possible for a spatial frequency encoding, so an additional transformation of spatial frequency information is demonstrated that automatically derives a size invariant representation of form.
Abstract: The encoding of simple features such as lines and angles leads naturally to size and position invariance when these features are analyzed symbolically in terms of structure and connectedness. No such analysis is possible for a spatial frequency encoding, however, as all a priori indications of pattern unity are lost. An additional transformation of spatial frequency information is therefore demonstrated that automatically derives a size invariant representation of form. The feasibility of the transform scheme in the visual system is outlined with a hypothetical processing sequence. It is found that the organization of cells in the striate cortex shows a marked similarity to an intermediate stage of the proposed sequence.
TL;DR: In this article, the authors use the models of Torbert (1973) and Kohlberg (1969) to examine the scope of influence of popular organization development approaches and conclude that OD theories have probably appealed principally to individuals and organizations functioning at relatively high levels of development.
Abstract: This paper describes our belief that organization development (OD), to be effective, should link with the progressively mature reasoning processes which characterize managers working within increasingly higher stages in the evolution of an organization. The paper uses the models of Torbert (1973) and Kohlberg (1969) to examine the scope of influence of popular OD approaches and concludes that OD theories have probably appealed principally to individuals and organizations functioning at relatively high levels of development. It also points up the need for theories which guide developmental energies at lower levels of orientation and which provide additional understanding of the transitional events individuals and organizations have to experience in order to pass from one stage of development to the next.
TL;DR: It is suggested that microtubules not only participate in cell elongation but also that they are involved, through interkinetic nuclear migration, in the broadening of the basal region of the cells; this widening progressively creates the strain that ensures the invagination of the neuroepithelium.
Abstract: The hypotheses dealing with mechanisms of neurulation are reviewed briefly. The phenomenon of interkinetic nuclear migration is thought to be an important factor to be considered in the invagination of the neuroepithelium in the chick embryo. Evidence is presented that implicates cytoplasmic microtubules in this phenomenon. It is suggested that microtubules not only participate in cell elongation but also that they are involved, through interkinetic nuclear migration, in the broadening of the basal region of the cells; this widening progressively creates the strain that ensures the invagination of the neuroepithelium.
TL;DR: The transfer represented an equilibration of molecules, but no net mass transfer of cholesterol esters could be demonstrated from HDL to LDL, and this transfer was reversible, time-dependent and a function of the concentration of the d greater than 1.25 fraction, but independent of lecithin : cholesterol acyltransferase reaction.
TL;DR: To determine whether the long-term feeding of dietary fats affect platelet functions in man, platelet aggregation and clotting activity of platelet-rich plasma (PRP), Platelet-poor plasma and of washed platelets were studied in a mobile-laboratory in 44 healthy male farmers from two French regions.
Abstract: To determine whether the long-term feeding of dietary fats affect platelet functions in man, platelet aggregation (to thrombin ADP, collagen, epinephrine) and clotting activity of platelet-rich plasma (PRP), platelet-poor plasma and of washed platelets were studied in a mobile-laboratory in 44 healthy male farmers (40--45 years) from two French regions Var and Moselle, in relation to lipemia, glycemia, dietary nutriments, and platelet phospholipid composition. In the Moselle subjects, the platelet clotting activity of PRP and of washed platelets, the platelet aggregation to thrombin and ADP, were highly significantly (p less than 0.001) increased as compared to those of Var, but not the plasma cholesterol, which was identical in the two regions. In Moselle, the intake of total calories, total lipids and saturated fats was higher than in the Var. However, it was only with the saturated fat intake (mostly stearic acid) that the platelet clotting activity (p less than 0.01) and the platelet aggregation (p less than 0.001) were highly significantly correlated. The platelet clotting activity was also significantly (p less than 0.001) correlated with the fatty acid composition of the platelet phospholipid fractions phosphatidyl serine + phosphatidyl inositol.
TL;DR: Aneurysmectomy does not abolish ventricular tachyarrhythmia and probably should be reserved for patients who remain symptomatic despite an adequate medical trial, and the persistence of complex arrhythmias following operation warrants a close follow-up in these patients.
TL;DR: Using the isolated rat mesenteric artery preparation, the pressor effects of norepinephrine, angiotensin II, and potassium chloride were all significantly increased when vasopressin was added to the perfusion buffer, and the potentiation by vasopressingin was almost completely prevented.
Abstract: Arginine vasopressin in physiological concentrations potentiated the vascular effects of various vasoconstrictor agents. By using the isolated rat mesenteric artery preparation, the pressor effects of norepinephrine, angiotensin II, and potassium chloride were all significantly increased when vasopressin was added to the perfusion buffer. Cortisol and lithium both inhibited the potentiating effect of vasopressin but had no effect on the control pressor response to norepinephrine. When the vascular effects of norepinephrine were first blocked with indomethacin and then restored by the addition of prostaglandin E2, the potentiation by vasopressin was almost completely prevented. This suggests that vasopressin may be acting by stimulating prostaglandin biosynthesis. Cortisol and lithium may exert their inhibitory effects by preventing the activation of prostaglandin synthesis by vasopressin. These findings may be of clinical significance because the phenomena occur well within the range of vasopressin levels found in human plasma.
TL;DR: It is shown that parent-offspring correlations as well as sib correlations are of the same order of magnitude as that between spouses for various age groups at death in a French Canadian isolate.
Abstract: Familial correlations for age at time of death have been computed in a French Canadian isolate. We show that parent-offspring correlations as well as sib correlations are of the same order of magnitude as that between spouses for various age groups at death. It is suggested that heritability of survival is nearly zero. Observed variability in survival is interpreted as the effect of environmental differences acting upon age-dependent genes.
TL;DR: D dopamine, norepinephrine and serotonin were able to block acetylcholine-induced excitations and for longer periods of time than GABA in the photically-evoked unitary activity.
Abstract: The predominant effect of dopamine, norepinephrine and serotonin on the photically-evoked urinary activity was a prolonged inhibition of firing. These amines were also able to block acetylcholine-induced excitations and for longer periods of time than GABA.
TL;DR: In this paper, the three-dimensional conformational space available to α-D-(1 → 6)-linked glycans is reported, which can be used to predict properties of (1 − 6)-α-D-homoglycans having either an axial or equatorial hydroxyl group at C-4.
TL;DR: In this article, the authors describe zonal variations in the vertical plane of the placenta by the application of different morphometric parameters, which suggest that the zonal differences may be the result of a physiologic adaptation of the Placenta, which is dependent upon its structural relationships with the maternal tissues.
TL;DR: It is concluded that BHT, given by stomach tube and in doses higher than 100 mg/kg, produces extensive cell proliferation in mouse lung and acts as a promoting agent in adenoma development.
TL;DR: Steroid sulfatase of human placenta has been solubilized by treatment of the microsomal fraction with an amphoteric surface active agent, Miranol H2M and ultrasound and the addition of dithiothreitol was found necessary to maintain the stability of the enzyme indicating the presence of sulfhydryl groups in the molecule.
TL;DR: Some important data structures and computer science techniques, and their applications to operations research problems are discussed, and some of which are novel are novel.
Abstract: We discuss some important data structures and computer science techniques, and their applications to operations research problems. The purpose of our discussion of applications, some of which are novel, is to stimulate further reading, for which adequate references are given. The techniques that we discuss are among the most important, but many valuable ones had to be omitted.