Showing papers by "University of Antwerp published in 1973"

Effect of Calcium on Force-Velocity-Length Relations of Heart Muscle of the Cat

Abstract: The influence of calcium concentration in the bathing solution on the force-velocity relations of the isolated, electrically excited cat papillary muscle was examined. Shortening velocity was directly measured at minimum loads by unloading or load clamping the muscle from the preload (at the length, Lmax, where maximum active tensio was developed) to 0 (zero-load clamp), 2, 5, 10, and 15% of the total tension, P0. All measurements were made in the physiological length range between Lmax and 12.5% below Lmax. Increasing the calcium concentration augmented the measured maximum unloaded shortening velocity and shifted the normalized force-velocity relation when force was expressed as a fraction of P0. These observations suggest that the activating calcium has an action more complex than the binding to troponin alone.

An analysis of the mechanical capabilities of heart muscle during hypoxia

Abstract: The influence of oxygen deprivation on mammalian heart muscle has been measured in terms of the mechanical capabilities open to the muscle as described by the interrelationship between force, velocity of shortening, and length using isolated cat papillary muscle preparations. Velocity-length relationships have been directly measured from isometric to near zero force. The three-dimensional surface relating force, velocity, and length was reversibly depressed by hypoxia but asymmetrically, which contrasts with the symmetrical shift with altered buffer calcium. On reoxygenation a transient further decrease in maximum unloaded shortening velocity occurred with prolongation of contraction. Experimental evidence is presented that Vmax is truly decreased by hypoxia and that this may not be caused solely by a decrease in the number of actin-myosin crossbridges activated.

Influence of caffeine and other inotropic interventions on the onset of unloaded shortening velocity in mammalian heart muscle. Time course of activation.

Abstract: The onset of maximum unloaded shortening velocity was measured in cat papillary muscles by analyzing velocity with respect to time and length after zero load clamps imposed at different times. Unloaded shortening velocity rose rapidly to a constant level by 20% of the time to peak force under all conditions studied except with application of 10 mM caffeine, which markedly slowed its onset. Load-clamping experiments showed that the force-velocity-length interrelationship which characterizes shortening remained constant throughout most of shortening except with caffeine, which delayed the onset of steady state. It is suggested that the time course of the force-velocity-length interrelationship usefully describes velocity active state, the onset of which can be measured independently of force generation at zero load. In afterloaded contractions, manifestation of velocity active state may be delayed by the slower time course of force generation which precedes shortening. It is concluded that velocity active s...

Cortisone influences developing collaterals. 1. A morphologic study.

Abstract: Light microscopic and ultrastructural changes in developing coronary collateral vessels were investigated after treatment with hydrocortisone (20 mg/kg/day orally) in the dog. The expected inflammatory reaction in the early stage of development (3 weeks) was absent, signs of injury to the vascular wall were lacking. At 3 and 8 weeks proliferation of rough and smooth endoplasmic reticulum and of the Golgi field was prominent indicating changes in the metabolism of the cells. The amount of extracellular MPS, collagen and new elastic material was decreased. Intimal hyperplasia occurred at the same rate in the treated as in the untreated animals. At 3 months the vascular architecture was restored, cellular hyperactivity had decreased.

Numerical Study of Two-Phonon Sidebands in the Optical Absorption of Free Polarons in the Strong-Coupling Limit

Abstract: Using the theory and the analytical results of Kartheuser, Evrard, and Devreese (KED), we have calculated numerically the two-phonon sideband in the optical absorption coefficient of free polarons. Therefore, integrals of the type $\ensuremath{\int}(\frac{d\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}}{{\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}}^{2}})\ensuremath{\int}(\frac{d{\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}}^{\ensuremath{'}}}{{\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}}^{\ensuremath{'}2}}){\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}}^{\ensuremath{'}2j}{cos}^{2j}{\ensuremath{\theta}}^{\ensuremath{'}}{\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}}^{2i}{cos}^{2i}\ensuremath{\theta}\ensuremath{\delta}({(\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}+{\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}}^{\ensuremath{'}})}^{2}\ensuremath{-}{\ensuremath{\epsilon}}^{2}){e}^{\ensuremath{-}x{\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}}^{2}\ensuremath{-}y{\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}}^{\ensuremath{'}2}}$ as obtained by KED, are treated analytically and reduced to a finite sum of single integrals for integer $i$ and $jg~0$, for all real $x$, $yg0$ and for any real $\ensuremath{\epsilon}$. Our numerical results, combined with the zero-phonon line and the one-phonon sideband obtained by KED, confirm the mechanism for the absorption of light by free polarons proposed by KED.

Effect of internal excitations of polarons on magneto-optical absorption and cyclotron resonance in polar crystals

Abstract: The energy spectrum of Frohlich polarons in a magnetic field is investigated theoretically. The constants of the motion of the system are studied and a “Feynman model” serves as B guide in this study. A crucial difference between the energy spectra of polarons and rigid particles is predicted at rather strong coupling strengthsor large magnetic fields. It is due to the internal structure of the polaron system. When the electron-LO-phonon coupling constant becomes large enough to allow internal excitations, a resonance may appear in the one-phonon continuum. This resonance is split by Zeeman effect at small field values and the components of the multiplet tend asymptotically to the Landau levels with increasing field strengths. The stability of one component at least is enhanced by the magnetic field, so that magnetic fields could be used to reveal internal excitations of polarons, in cyclotron resonance or magneto-optical absorption experiments. Recent experimental results on magneto-absorption by excitons are discussed in the light of the present work. Es wird das Energiespektrum Frohlichscher Polaronen im Magnetfeld theoretisch untersucht. Die Bewegungskonstanten des Systems werden untersucht, wobei ein „Feynman-Modell” als Fuhrer bei dieser Untersuchung dient. Fur starke Kopplungsstarken oder grose magnetische Felder wird eine entscheidende Differenz zwischen den Energiespektren der Polaronen und starren Partikel vorhergesagt. Diese wird durch die innere Struktur des Polaronensystems hervorgerufen. Wenn die Elektronen-LO-Phononen-Kopplungskon-stante gros genug wird, um innere Anregung zu erlauben, kann eine Resonanz im Einphononenkontinuum auftreten. Diese Resonanz wird durch den Zeemaneffekt bei kleinen Feldwerten aufgespalten und die Komponenten des Multiplett gehen mit steigenden Feldstarken asymptotisch in die Landau-Niveaus uber. Die Stabilitat wenigstens einer der Komponenten wird durch das magnetische Feld verstarkt, so das Magnetfelder benutzt werden konnen, um innere Anregung von Polaronen in Zyklotronresonanz- oder magneto-optischen Absorptionsexperimenten zu beobachten. Kurzlich erhaltene experimentelle Ergebnisse der Magneto-Absorption durch Exzitonen werden im Hinblick auf diese Arbeit diskutiert.

Measuring Performance in a Decentralized Firm with Interrelated Divisions: Profit Cost Center Versus Cost Center

Abstract: Two problems arise in the decentralization of a firm with interrelated divisions. First, there is the possibility that the overall objectives of the firm are not optimized when individual divisions try to optimize their own performance. The question of assuring maximum overall profitability for the firm has been studied extensively in the literature on transfer pricing. The objective of this paper is to provide insight in a second problem, less often raised but equally important, namely: Given a transfer pricing mechanism that maximizes overall company profit, should divisional performance be measured on a profit or on a cost basis?

A Discussion and Generalization of Bethe's Second‐Order Approximation

Abstract: Using the Howie and Whelan system a perturbation technique is presented, based on the Lowdin partioning technique, to take into account the effect of weak beams in contrast calculations. This method is a generalization of the well known Bethe second order correction method. The usual Bethe method is found in the limit of very small weak beam interaction. Some explicit situations are discussed which show the limitations of the usual Bethe method for practical calculations. Mit dem Howie- und Whelan-System wird eine Storungsrechnung dargestellt, die auf der Lowdinschen Technik beruht, urn den Einflus des schwachen Strahls bei Kontrast-berechnungen zu berucksichtigen. Diese Methode ergibt eine Verallgemeinerung der wohlbekannten Korrokturmethode zweiter Ordnung von Bethe. Die gewohnliche Bethesche Methode wird im Grenzfall sehr kleiner Wechselwirkung des schwachen Strahls wieder-gefunden. Einige Falle werden diskutiert, die die Grenzen der gewohnlichen Betheschen Methode fur praktische Berechnungen zeigen.

The synthesis of 3-acetyl-5-alkylpyridines

Abstract: The synthesis of 3-acetyl-5-methyl- ; 3-acetyl-5-ethyl- ; 3-acetyl-5-propyl- and 3-acetyl-5-isopropylpyridine was accomplished by the condensation of the corresponding acroleine derivatives and 1-amino-1-buten-3-one.

Towards an adequate formalization of linguistic descriptions

Abstract: We are often expected to consider the notion of formalization in direct relation to linguistic material Although such a relation ought to be established, it will be argued that basically any such approach is incorrect A real discussion of the role of formalization in linguistic description should not be carried out in terms of examples from some natural language, but rather in terms of the notion ‘formal model’ operating on the level of theory construction; that is, a model for linguistic theory which at the same time illustrates a form of mental organization 1 S Ginsburg and B Partee, A Mathematical Model of Transformational Grammars, Systems Development Corporation, Santa Monica, California (1968), and also H Whitaker, “Rules versus strategies as a distinction between competence and performance”, Working Papers in Phonetics, (1969), UCLA

Absence of respiratory activity in bovine thyroid nuclei.

Abstract: Mukherjee & Narayanaswami (1972) report the presence of respiratory activity in pig brain nuclei. They conclude that, in those nuclei, oxidative energy-yielding metabolic pathways exist that serve as sources of nuclear ATP. Two kinds of nuclear fractions were isolated by these authors: a crude nuclear pellet and a more purified nuclear fraction. The purified fraction was obtained by centrifuging the crude nuclear pellet first in 0.44 M sucrose (pH 7.7, 3 mM MgCl2) and subsequently through a two step discontinuous sucrose gradient (0.88-1.0 m). In the final preparation 8 % of the original proteins were recovered. No contamination by other particulate subfractions could be demonstrated by phase contrast microscopy. The final RNA: DNA ratio was 0.56. During the purification procedure removal of extranuclear enzymes occurred. However, the final preparation still contained 14 % of total glutamic dehydrogenase and succinic dehydrogenase and 8 % of monoamine oxidase. In this purified nuclear preparation ...

Preparative separation and isolation of three epimeric 2-methylcycloalkanols by counter current distribution

Abstract: Diastereoisomeric mixtures of 2-methylcyclopentanol (I), 2-methylcyclohexanol (II) and 2-methylcycloheptanol (III) can be separated in very good yields into the cis and trans isomers by counter current distribution. A suitable method for isolation is also given.