Showing papers by "Instituto Superior Técnico published in 1981"
50 citations
TL;DR: A comprehensive survey of low-melting elements and compounds has been carried out, covering 190 substances from neon to carbon tetrachloride, which span T t values from 24.5 to 250.5 K.
46 citations
TL;DR: In this article, a new process to couple amyloglucosidase (AG) to inorganic supports is described, which consists in activating the support with a transition metal salt according to the metal-link method and subsequent amination and linkage of the alkylamine derivative using glutaraldehyde.
Abstract: A new process to couple amyloglucosidase (AG) to inorganic supports is described. The technique consists in activating the support with a transition metal salt according to the metal-link method and subsequent amination and linkage of the alkylamine derivative using glutaraldehyde. The various parameters susceptible of influencing the properties of the immobilized enzyme (IME) preparation are investigated. The best result are obtained when 100 mg of 1000-A controlled porous glass (CPG) are treated with 45 mg of TiCl4 and the activated carrier aminated using a 10-g/L solution of hexamethylenediamine (HMDA) in carbon tetrachloride (10 Ml/100 mg). Preparation obtained according to the process here described show operational stabilities much superior to those of AG immobilized on the same support by the traditional metal-link method or its variations. The mechanism involved in the preparation of the amino derivative of CPG is proposed.
43 citations
TL;DR: This paper presents an algorithm for obtaining a small frontwidth that is of interest when employing the frontal technique for solution of systems of linear equations in the finite element method.
Abstract: This paper presents an algorithm for obtaining a small frontwidth. This feature is of interest when employing the frontal technique for solution of systems of linear equations in the finite element method. The performance of the algorithm is assessed by several examples at the end of the paper.
26 citations
TL;DR: Glucoamylase (EC 3.3) was coupled to controlled pore glass by using titanium(IV) chloride as mentioned in this paper, and the drying conditions used during the activation step were studied, and the highest activity (237 units/g of matrix) of immobilized enzyme was obtained when the support and the titanium-IV chloride solution were dried at 45°C in vacuo for 16 h.
26 citations
TL;DR: In this paper, a set of equations is derived which make possible to study the radiative energy transfer process whereby the photons emitted by the energy donor are absorbed by the acceptor and so increase the efficiency of the overall energy transfer.
19 citations
TL;DR: In this paper, the vicinal H-H coupling constants of succinic acid were obtained as a function of pH and related to its conformation, and the syn-clinal arrangement of the two CO2H groups appeared as more stable than the anti-periplanar conformation at variance with previous work but in agreement with recent data on similar molecules.
18 citations
14 citations
TL;DR: In this paper, the standard enthalpies of formation of the title crystalline complexes at 298.15 K have been determined by reaction-solution calorimetry, and the method of calculation of these values is analysed and earlier relevant thermochemical data are reviewed.
14 citations
TL;DR: In this article, the axially symmetric model for the lanthanide-induced shift (l.i.s.) data is presented for cytidine 5′-monophosphate (cydmp) and L-alanine binding to a series of Ln-edta chelates at high pH (edta = ethylenediaminetetra-acetate).
Abstract: Lanthanide-induced shift (l.i.s.) data are presented for cytidine 5′-monophosphate (cydmp) and L-alanine binding to a series of lanthanide–edta chelates at high pH (edta = ethylenediaminetetra-acetate). Slow exchange of these substrates between their bound and free environments precludes the use of the heavier Ln(edta) chelates at 25 °C. The cydmp proton l.i.s. ratios at 90 °C are independent of the Ln(edta) used, indicative of effective axial symmetry for this substrate. The alanine l.i.s. values contain large contact shift components which once removed yield corrected pseudo-contact shifts which also are adequately described by an effective axial symmetry model. The results indicate that chemically reasonable structures may be determined from l.i.s. data for substrates acting as bidentate chelators of the lanthanide, providing rapid exchange conditions are met and contact shift contributions are extracted from experimental l.i.s. values for nuclei near the co-ordination site(s). Therefore the fact that the substrate acts as a bidentate chelator does not necessarily exclude the possibility that the axially symmetric model for the l.i.s. is a satisfactory model.
11 citations
01 Jan 1981
TL;DR: Although many elasticity problems have been solved by both analytical and numerical techniques, solutions for actual problems involving complex geometries are still relatively scarce as discussed by the authors, and solutions for real-world problems involving real-time elasticity have not yet been solved.
Abstract: Although many elasticity problems have been solved by both analytical and numerical techniques, solutions for actual problems involving complex geometries are still relatively scarce.
01 Apr 1981
TL;DR: This paper discusses a form of non-linear prediction, namely, the prediction of the phase of speech signals, based upon a new treatment of the classical speech production model within a short-time analysis/synthesis framework.
Abstract: Prediction plays a key role in many signal processing applications. Linear Prediction has, in particular, been extremely useful to the development of digital speech processing techniques and applications. There is however a growing need for improved forms of prediction. We discuss, in this paper, a form of non-linear prediction, namely, the prediction of the phase of speech signals. This study is conducted within a short-time analysis/synthesis framework and is based upon a new treatment of the classical speech production model. Experimental data are presented confirming the theoretical results. Finally the use of phase prediction to low-bit rate, high-quality coding applications is discussed.
TL;DR: In this article, phase plane analysis and simulation on a hybrid computer is used to study the dynamics of a continuous biomethanization process, where stable and unstable stationnary states for the anaerobic reactor are found along with conditions on the nutrient feedrate and concentration for converging towards such states.
TL;DR: In this paper, the thermodynamic parameters of the reactions of formation of complexes between uramildiacetic acid (UDA) and several transition metals have been determined by calorimetry.
TL;DR: In this paper, it was shown that uramildiacetic acid is tetradentate and that it coordinates to metal ions through the iminodiacetate group and one of the carboxyl groups in position 4,6 of the molecule.
TL;DR: In this paper, the authors derived the equations to obtain the correction for radiative energy transfer when the observation of the fluorescence emission is made from the same face of the cell where excitation takes place.
01 Jan 1981
TL;DR: A new description for the geometry is presented, whereby the array is given by a set of (possibly random) ordinary differential equations that are either parameterized by a vector of unknown parameters or described as finite dimensional stochastic processes.
Abstract: The design of underwater acoustic ranging systems is considered in three of its basic components: modeling assumptions, algorithmic implementations and performance results. A new description for the geometry is presented, whereby the array is given by a set of (possibly random) ordinary differential equations. The motions are either parameterized by a vector of unknown parameters (including range) or also described as finite dimensional stochastic processes. Hierarchy configurations are disttinguished, leading to different receiver design methodologies and implementations The advantages and pitfalls of each are analysed. Basic points are illustrated in the context of a simple, meaningful example.
TL;DR: In this article, the thermodynamic functions (enthalpy and entropy changes) for the formation of mixed complexes of transition metals with uramildiacetic acid (UDA) and nitrilotriacetic acid(NTA) as primary ligand and glycine as secondary ligand, using the temperature coefficient method.
01 Jan 1981
TL;DR: This chapter discusses the order of magnitude of electroosmotic water flows associated with the proposed geometrical and physical junction model of water transport in epithelial junctions in Diamond and Bossert model.
Abstract: Publisher Summary This chapter discusses the numerical simulation of water transport in epithelial junctions. The epithelia performing solute-linked water transport have been the subject of a vast amount of studies. Different transport routes are proposed with particular emphasis to the ones crossing the cells. On the other hand the extracellular routes have been little explored. In Diamond and Bossert model, a combination of the two types of pathways is required. The chapter discusses the order of magnitude of electroosmotic water flows associated with the proposed geometrical and physical junction model. The geometrical model is based on the morphological data available in the literature for the Necturus gall bladder epithelium. The junctional system is made of two distinct phases: a solid matrix constituting the walls of long and narrow channels filled with a fluid phase of ions and water. An important feature of electroosmotic model is the fact that significant amounts of water can be transported through the junctions in conditions not far from isotonicity.