Showing papers by "Université de Sherbrooke published in 1974"

A high-precision digital readout flow densimeter for liquids

Abstract: A precision densimeter for liquids, based on the oscillating-tube principle, has been designed. The apparatus allows relative density measurements to be carried out routinely with ppm precision, on 5–7 cm3 of solution, in a total time ranging between 5 to 10 min. The results of various tests reported here show the densimeter to be useful for investigation in aqueous as well as nonaqueous media; it is particularly well adapted to accurate measurements of small density increments, as required in excess-volume studies. Since the instrument operates in the flow regime, it is also adaptable to on-line monitoring of density in continuous processes.

Membrane associated particles: distribution in frog urinary bladder epithelium at rest and after oxytocin treatment.

Abstract: The fine structure of the plasmic membrane of the frog urinary bladder epithelium has been studied with a freeze-etching technique. The results reveal that the external face of the cytoplasmic leaflet (A face) of the apical membrane of epithelial cells is characterized by: 1) A markedly reduced number of membrane associated particles compared to the value observed on the A face of the lateral membranes of these cells. 2) The existence after oxytocin treatment of numerous spots of clustered particles.

Thermodynamic properties of alkali halides. II. Enthalpies of dilution and heat capacities in water at 25°C

Abstract: The enthalpies of dilution and volumetric specific heats of most alkali halides were measured in water at 25°C with flow microcalorimeters in the concentration range 0.01 to 1m. Apparent molal relative enthalpiesφ L, derived from the enthalpies of dilution, can be represented by a parametric equation in molality. Combiningφ L with osmotic data, excess entropies can be calculated. Excess free energies, enthalpies, and entropies are compared at 0.5m, and the observed trends are consistent with a model of structural interactions in aqueous alkali halide solutions. The apparent molal heat capacitiesφ C were fitted with the equationφ C=φ C ° +AC(d0m)1/2+B C m. Theφ C ° are, in general, additive to better than 1 J-K−1-mole−1 and reflect mostly the structural part of ion-solvent interactions. Takingφ C ° (H+)=0, conventional ionicφ C ° are obtained. The parameterB C for different pairs of ions follows approximately the same trends as the corresponding parameterB V for apparent molal volumes and seems to reflect structural interactions between the ions.

A study of the rheological properties of a non‐Newtonian Fermentation broth

Abstract: Polysaccharide was synthesized by Aureobasidium pullulans (or Pullularia pullulans) 2552 in a sucrose medium. The field apparent viscosity of the culture medium from shake flask experiments rose to 24,500 cP and then dropped toward its initial value as the fermentation progressed. The magnitude of the maximum apparent viscosity depended on the initial pH of the fermentation broth. The inoculum age influenced the cultivation period before which the maximum viscosity was reached. Rheograms of the fermentation broths showed a change in viscosity behavior from Newtonian to pseudoplastic, and then toward Newtonian characteristics during the fermentation. The calculated non-Newtonian index was found to be a sensitive factor for the indication of the non-Newtonian behavior. Such behavior could not be detected from rheograms. Viscosity profiles of polysaccharide isolated from various stages of the fermentation showed a change from Newtonian to pseudoplastic behavior depending on the concentration (0–2%) of polysaccharide.

Powder processing in a plasma jet: A proposed model

Abstract: A theoretical study is reported on the use of d.c. and r.f. plasma jets as chemical reactors for the processing of minerals in the form of a fine powder. The temperature and flow fields of the jet are calculated by solving the integral boundary layer equations. Single particles trajectories are obtained by solving the Basset-Odar equations. A multi-particle model is then developed for a feed of known particle size and injection velocity distributions under low loading conditions. Calculators are made on the thermal decomposition of molybdenum disulphide (5 to 30-micron equivalent diameter). The parameters investigated are the free jet velocity, the mean injection velocity, and the reactor ambient conditions. The results are presented as the probability density distributions of the gas loading, particle temperature, and conversion at different levels downstream of the nozzle. On presente une etude theorique sur l'emploi de jets de plasma produits par courant direct et radio-frequence comme reacteurs chimiques pour le traitement des mineraux sous forme de poudres fines. On calcule les champs de temperature et d'ecoulement du jet en resolvant les equations integrates de la couche-limite. On obtient les trajectoires des particles simples au moyen de la solution des equations de Basset et Odar. On a mis au point un modele pour une alimentation de particules de dimensions connues et des distributrions de la vitesse d'injection lorsqu'on est en presence de peu de matieres solides. On fait les calculs sur la decomposition thermique du sulfure de molybdene (dont le diametre equivalent est de 3 a 30 microns). Les parametres etudies sont: la vitesse du jet libre, la vitesse moyenne d'injections et les conditions ambiantes du reacteur. On presente les resultats sous forme de distributions des densites de probabilite de l'alimentation de gaz, de la temperature des particles et de la transformation a differents niveaux en aval du jet.

Thermodynamic properties of alkali halides. IV. Apparent molal volumes, expansibilities, compressibilities, and heat capacities in urea-water mixtures

Abstract: The apparent molal volume φv, expansibility φE, compressibility φK, and heat capacity φc of NaCl were measured in urea-water mixtures, as a function of salt (<1.5m) and urea (<13m) concentrations at 25°C. At a fixed urea concentration, the transfer functions from H2O to 3m urea are linear functions of the NaCl aquamolality. At a fixed salt aquamolality, (0.1m), the sign of the transfer functions is in the direction of a decrease in the structure-breaking effect, and the absolute values of the transfer functions tend to level off at high urea concentrations (13m). The functions φv, φE, φK, φc, and (∂φv/∂T)p were measured for the sodium halides and alkali, bromides (chlorides in the case of φK) at a fixed salt aquamolality of 0.1m and fixed urea molality of 3m. The corresponding transfer functions from H2O to 3m urea are opposite those from H2O to D2O and similarly are relatively independent of ionic size. This suggests that urea, shows no specific interaction affinity for ions and that the overall number of water molecules influenced by the ions is relatively constant for all alkali halides. The lithium halides are an exception in that Li+ seems to have hardly any structure-breaking effect.

Thermodynamic properties of alkali halides. III. Volumes and heat capacities of transfer from H 2 O to D 2 O at 25°C

Abstract: The volumetric specific heats and densities of alkali fluorides, alkali bromides, and soduum halides were measured in D2O at 25°C in the concentration range 0.05 to 1 aquamolal. The results can be combined with data in H2O to give the corresponding standard and excess transfer functions from H2O to D2O. The volumes and heat capacities of transfer are both negative but, contrary to the hydration functions, show little dependence on ionic size and sign. Also, while heats, entropies, and volumes of transfer are usually small compared with the hydration functions, the heat capacity of transfer is of comparable magnitude. These observations, when interpreted with the Frank and Wen model, suggest that the total number of water molecules in the hydration cosphere is approximately constant for all alkali halides and that heat capacities are more sensitive to structural interactions than volumes and enthalpies. The sign of the excess transfer functions is consistent with the presence of structural ion-ion interactions, but no systematic trend with ionic size can be detected in view of the large experimental uncertainty.

Glucose-6-phosphatase heterogeneity within the hepatic lobule of the phenobarbital-treated rat

Abstract: The action of phenobarbital daily injected has been studied on the rat liver. After 3 injections of 100 mg/kg, the centrolobular hepatocytes exhibit a large proliferation of the smooth endoplasmic reticulum with an important decrease of the glucose-6-phosphatase activity cytochemically detected. The perilobular hepatocytes do not show any modifications of their structure or of their enzymatic activity. These observations demonstrate that in the centrolobular zone, the glucose-6-phosphatase sites became separated from each other by the extension of the new smooth endoplasmic reticulum membranes.

Release of prostaglandins from the rabbit perfused kidney: effects of vasoconstrictors

Abstract: 1 The rat stomach strip was used to assay prostaglandin E2-like material released by a rabbit isolated kidney perfused with Krebs solution. 2 Doses of noradrenaline and angiotensin II producing similar vasoconstrictor effects released equivalent amounts of prostaglandins from the kidney. 3 8-Leu-angiotensin II, a specific inhibitor of the natural octapeptide, blocked the action of angiotensin II on perfusion pressure and the release of prostaglandins, while the action of noradrenaline on both parameters was unaffected. 4 Indomethacin, a specific inhibitor of prostaglandin biosynthesis, blocked the effects of both vasoconstrictors on prostaglandin release while their action on perfusion pressure was significantly enhanced. 5 In the kidney effluent, amounts of prostaglandin E2-like material increased linearly with the rise in perfusion pressure induced by increasing doses of angiotensin II. These results indicate that prostaglandin output from the isolated kidney follows the rise in perfusion pressure.

Neutral evolution and immunoglobulin diversity.

Abstract: THE origin of immunoglobulin diversity and species specificity continues to be a controversial topic. Proponents of the germ line theory have presented a limited gene expansion-contraction model in general terms1–3; the mechanism has not yet been demonstrated to produce sufficiently rapid changes in a multigene system to account for the observed phenomena. Species divergence of immunoglobulin V regions continues to be cited as strong evidence against multiple germ line V genes4,5. We report here computer simulation of random unequal crossing over within a system of multiple related genes and compare the results with the relationships observed between immunoglobulin V region sequences from different species. We conclude that the species-specific features of immunoglobulin V regions can arise as a result of such random processes operating in the multigene set.

Release of renomedullary prostaglandins in normal and hypertensive rats.

Abstract: On a montre que les papilles renales de rats rendus hypertendus par diverses manipulations experimentales ou de rats spontanement hypertendus, ont tendance a produire moins de prostaglandines que les papilles de rats normotendus. Sans permettre d'etablir une relation certaine de cause a effet, les resultats suggerent fortement qu'il y ait une correlation entre la severite de l'hypertension et l'importance de la diminution de la production des prostaglandines renales.

CALCIUM EFFLUX AND SECRETION OF α-AMYLASE FROM RAT PANCREAS

Abstract: 1 The efflux of 45Ca from rat pancreas was investigated in relation to the secretion of α-amylase. 2 The 45Ca space in the pancreas was increased 1.6 times when pancreatic tissue was incubated in media in which the extracellular calcium concentration was reduced from 1.0 to 0.05 mM. 3 Carbachol increased the rate of 45Ca efflux from the tissue and this effect was associated with an increase in the release of α-amylase. Dibutyryl cyclic adenosine monophosphate (AMP) also evoked a secretory response, but did not alter the rate of 45Ca efflux. In combination with carbachol, the dibutyryl analogue of cyclic AMP reduced the carbachol-stimulated increase in 45Ca efflux while enhancing the release of secretory protein. 4 The stimulatory effect of carbachol on 45Ca efflux was observed when pancreatic tissues were incubated in media containing a high concentration of ethyleneglycolbis (β-aminoethyl)-N,N′-tetraacetic acid (EGTA). 5 Atropine blocked the effects of carbachol on both 45Ca efflux and secretion of α-amylase. 6 It was concluded that intracellular calcium can and may sustain stimulus-secretion coupling in the rat exocrine pancreas.

Hydrophobic nitroxide radicals as probes to investigate the hydrophobic interaction

Abstract: The EPR spectrum of 2,2,6,6-tetramethylpiperidine-N-oxide (TEMPO) has been systematically investigated in several solvents and in aqueous solutions of glycerol,t-BuOH, Bu4NBr,n-HexNH3Br,n-OctNH3Br, NaBPh4, and Ph4AsCl. Most of the results have been obtained at 25°C, though the temperature dependence of the linewidths has been examined in water and several organic solvents. Data on the spectrum of ditertiarybutylnitroxide in aqueous solutions of glycerol and Bu4NBr are also presented. The spectrum was simulated to determine WH, the linewidth after allowance for the unresolved proton hyperfine interaction, in each manifold of the triplet due to the nitrogen hyperfine interaction. The linewidth WH is analyzed in terms of the reorientational correlation time Aθ and the angular velocity correlation time AJ. In most solutions Aθ is determined only by the bulk solution viscosity, except in situations where significant clustering of hydrophobic solute molecules occurs. In pure nonaqueous solvents the temperature dependence results are consistent with AJ being determined by the bulk viscosity, while in water or aqueous solutions, a very different behavior is found which is interpreted as a manifestation of clathrate-like hydration of the hydrophobic radical. This interpretation is incorporated in a two-state model developed to account for the WH data of TEMPO in aqueous solutions of various hydrophobic solutes. The equilibrium parameters derived from the model, for the association of TEMPO with several hydrophobic solutes, support the concept of hydrophobic interactions as pictured from thermodynamic excess functions.

Organ culture of adult guinea-pig intestine. II. Biochemical and ultracytochemical findings.

Abstract: Explants of adult guinea-pig intestine have been maintained in organ culture for 6 to 48 hours. The evolution of glucose-6-phosphatase, alkaline phosphatase and dipeptidase activities has been analysed by biochemical means. The activity of glucose-6-phosphatase alkaline phosphatase, acid phosphatase and thiamine pyrophosphatase has been localized at the ultrastructural level. No significant modifications were recorded during the first 24 hours of culture. However a very important drop of all the enzymatic activities was observed between 24 and 48 hours of culture.

Imperfection sensitivity of coincident buckling systems

Abstract: A two-degree of freedom structural system with both buckling loads equal or nearly so is examined, allowing for the presence of small imperfections specified by the values of two general imperfection parameters. A discrete generalized coordinates energy method is used, and the system considered is non-symmetric in the two modes of deflection. Conclusions regarding the types of behaviour possible are obtained by examination of all possible equilibrium path shapes. Comparison is made to behaviour of idealized systems. Change in buckling load value with imperfection size, or imperfection sensitivity, is established and imperfection sensitivity surface forms are sketched.

A table of good lattice points in three dimensions

Abstract: A table of three-dimensional lattice points with moduli ranging from 2120 to 6066, sufficient for high-precision numerical computation of triple integrals is presented; the data are shown to confirm some conjectures concerning good lattice points.

On the Relation Between the Factor of Safety and Reliability

Abstract: An approximate relation between the reliability of a design and the classical deterministic factor of safety, used in the design, is presented. An expression of the reliability as function of the mean value and coefficient of variation of the probability density distribution of the factor of safety, is derived. Further, the relation between the deterministic factor of safety and the statistical values of the probabilistic factor of safety, is discussed. Finally an expression for the reliability as a function of the deterministic factor of safety and the parameters determining the stress and strength distributions, is obtained. This function relationship is expressed in a design nomogram relating all the parameters involved.

Digital converter from pulse code modulation to continuous variable slope delta modulation

Abstract: A digital converter for digitally converting a coded signal being at a PCM rate into another coded signal flowing at a delta rate. First, the code of the PCM signal is converted into an intermediate code, this intermediate code being at a rate corresponding to the PCM rate. Then, the rate of the intermediate coded signal is converted into the rate of the delta signal. And, finally, the code of the intermediate signal is changed into the code of the delta signal.

Digital converter from continuous variable slope delta modulation to pulse code modulation

Abstract: The invention relates to a digital converter and to a method for digitally converting a coded signal being at a delta rate into another coded signal flowing at a PCM rate. First, the code of the delta signal is converted into an intermediate code, this intermediate code being at a rate corresponding to the delta rate. Then, the rate of the intermediate coded signal is converted into the rate of the PCM signal. And, finally, the code of the intermediate signal is changed into the code of the PCM signal.

Action of phenobarbital on the ultastructure and the enzymatic activity of the mouse intestine and the mouse liver.

Abstract: The fine structure and the cytochemical activity of the liver, the duodenum and the jejunum of adult mice have been studied after phenobarbital (P.B.) treatment. A smooth endoplasmic reticulum proliferation has been observed in the centrolobular hepatocytes after 3 injections of P.B. and in the apical cells of the intestinal villi after 1 to 7 injections of P.B. The distribution of glucose-6-phosphatase remained unchanged but the specific activity decreased. Biochemical measurements of alkaline phosphatase activity have shown a differential response in the duodenum and in the jejunum.

Chemical models of the hydrophobic interaction: Apparent molal volumes and heat capacities of three symmetrical bolaform electrolytes and their homologous monomers in aqueous solution at 25°C

Abstract: The densities and volumetric specific heats of aqueous solutions of Bu3NHBr, Pent3NHCl, and three diazonium salts, HN−Oct3−NHBr2, HN−Dec3−NHCl2, and Bu3N−Oct−NBu3Br2, have been measured at 25°C. From these data, the apparent molal volumes φv and apparent molal heat capacities φc have been calculated and are reported here. In the series of compounds chosen, the diazonium (higher homologs) can be regarded as dimers of the alkyl-substituted ammonium ions (lower homologs), and these systems are examined as chemical models for the hydrophobic interaction. With the three homologous pairs studied here, the chemical model predicts that the strong interaction (limitingly, chemical binding) of two hydrocarbon chains in water leads to a major decrease in both φv and φc of the interacting solutes, ca.−22 cm3-mole−1 and −200 J-oK−1-mole−1. These predictions constitute limiting behavior — useful, but not sufficient, to explain the observed concentration dependence of φv and φc in aqueous solutions of the lower homologs Bu3NHBr, Pent3NHCl, and Bu4NBr. An explanation for the concentration dependence of φc is suggested with reference to ultrasonic relaxation data.