Showing papers by "Wrocław University of Technology published in 1989"
TL;DR: In this paper, a single cation-exchange bead, loaded with ferroin and bathed in BZ reaction mixture containing no catalyst, develops to form a rotating spiral.
Abstract: THE concentric-circular and spiral patterns exhibited by the Belousov–Zhabotinsky (BZ) reaction in thin films of solution are representative of spatiotemporal behaviour in a two-dimensional, planar excitable medium1–6. Here we report BZ chemical waves propagating on the two-dimensional surface of a sphere. A wave on the surface of a single cation-exchange bead, loaded with ferroin and bathed in BZ reaction mixture containing no catalyst, develops to form a rotating spiral. Unlike spiral waves in thin films of solution, which typically wind out to connect with a twin rotating in the opposite direction, these waves rotate from pole to pole in a single direction. The spiral winds outward from a meandering source at one pole, crosses the equator, and undergoes self-annihilation as it winds into itself at the other pole. This behaviour, which is not possible in a two-dimensional planar configuration, arises from qualitative (negative to positive) and quantitative changes in wavefront curvature as the wave traverses the spherical surface. These observations of a single spiral wave contrast with theoretical predictions7,8 of counter-rotating spirals in this geometry.
125 citations
TL;DR: The most effective inhibitor was [1-amino-2-(N-cyclohexylamino)ethyl]phosphonic acid, which has a Ki value of 0.87 microM toward the microsomal aminopeptidase--a value that can be considered as equipotent with bestatin and with leucinal and hydroxamic acids, the strongest known nonpeptide inhibitors of this enzyme.
Abstract: More than 30 aminophosphonates were synthesized to probe how the structural changes introduced into the phosphonic acid analogue of leucine, a potent inhibitor of cytosolic leucine aminopeptidase (Giannousis & Bartlett, 1987), affect their ability to inhibit cytosolic (EC 3.4.11.1) and microsomal (EC 3.4.11.2) aminopeptidases. Although most of the compounds studied were found to exert only a modest competitive inhibitory effect, nearly every modification of the structure of the phosphonic acid analogue of leucine was reflected in a marked difference in the affinities of these compounds for the two enzymes. [1-Amino-2-(N-alkylamino)ethyl]phosphonic acids are effective inhibitors of the microsomal enzyme, acting in a time-dependent manner. Kinetic data obtained for these inhibitors correspond to the mechanism for a biphasic slow-binding inhibition process: E + I in equilibrium E* in equilibrium E*I, in which the slow initial isomerization of the enzyme is followed by the fast formation of enzyme-inhibitor complex. The most effective inhibitor of this type was [1-amino-2-(N-cyclohexylamino)ethyl]phosphonic acid, which has a Ki value of 0.87 microM toward the microsomal aminopeptidase--a value that can be considered as equipotent with bestatin and with leucinal and hydroxamic acids, the strongest known nonpeptide inhibitors of this enzyme.
124 citations
TL;DR: It is shown that the algorithms converge to the unknown characteristic in a pointwise manner and that the mean integrated square error converges to zero as the number of observations tends to infinity.
Abstract: The non-linearity in a discrete system governed by the Hammerstein functional is identified. The system is driven by a random while input signal and the output is disturbed by a random white noise. No parametric a priori information concerning the non-linearity is available and non-parametric algorithms are proposed. The algorithms are derived from the trigonometric as well as Hermite orthogonal series. It is shown that the algorithms converge to the unknown characteristic in a pointwise manner and that the mean integrated square error converges to zero as the number of observations tends to infinity. The rate of convergence is examined. A numerical example is also given.
84 citations
TL;DR: In this paper, the magnetic relaxation rate Λ was investigated via quasielastic neutron scattering of the Kondo lattice CeCu2Ge2, and it was shown that Λ(T) is characteristic of heavy-fermion systems with a high temperature square root dependence and a limiting low temperature value, yielding a Kondo temperatureTK≈10K.
Abstract: Elastic and inelastic neutron scattering studies of the Kondo lattice CeCu2Ge2 were performed. AtTN=4.1 K an incommensurate magnetic order develops with an ordering wave vectorq0=(0.28, 0.28, 0.54) and an ordered moment µs=0.74 µB. The crystalline electric field splits the 4f1-J-multiplet of the Ce ion into a ground state doublet and a quartet at 191 K. The wave function of the ground state yields an ordered moment of 1.54µB. Thus, due to the onset of the formation of a Kondo singlet the magnetic moment is considerably reduced. The magnetic relaxation rate Λ was investigated via quasielastic neutron scattering. The temperature dependence of Λ(T) is characteristic of heavy-fermion systems with a high temperature square root dependence and a limiting low temperature value, yielding a Kondo temperatureTK≈10K. The quasielastic component of the scattered neutron intensities persists down to the lowest temperatures, well belowTN. This quasielastic line is regarded as a characteristic feature of heavy-fermion systems and corresponds to the enhanced value of the linear term of the specific heat.
71 citations
TL;DR: It is shown that given a class of membership functions of fuzzy goals assigned to objective functions in the problem, wider than primarily proposed by Zimmermann, the use of classical linear programming methods to solve and analyse the problem is also possible.
67 citations
TL;DR: In this article, an ultrafiltration system with a tubular membrane module was used in an experimental study on the efficiency of organic dye removal from aqueous solutions and actual textile effluents.
64 citations
TL;DR: The existence of generalized complex space forms with nonconstant functionh is proved in this article, and the existence of non-convex generalized complex spaces with non-constant functionsh is also proved.
Abstract: The existence of generalized complex space forms with nonconstant functionh is proved.
50 citations
TL;DR: An optimized medium for the production of extracellular lipase by Penicillium citrinum contained 5% peptone as the nitrogen source and 2% starch as the carbon source and the temperature of 22°C and pH 7.2 were most effective for lipolytic productivity.
Abstract: An optimized medium for the production of extracellular lipase byPenicillium citrinum contained 5% peptone as the nitrogen source and 2% starch as the carbon source. The temperature of 22°C and pH 7.2 were most effective for lipolytic productivity. Rapeseed oil was used as an inducer.
50 citations
TL;DR: In this paper, the ultrafiltration process described involved polysulfone membranes prepared on a flat glass support and on a surface of poly(methyl methacrylate) bar Comparable studies including the effect of casting parameters an hydraulic conditions existing in the system on membrane performance were reported Separation characteristics of each membrane module were determined.
47 citations
TL;DR: A new method of global random search in Rn devised from a model of evolution, regarded as a randomization of Eigen's model of macromolecular evolution, which appears especially efficient in crossing gaps between regions of attraction of local optima.
Abstract: A new method of global random search in R n devised from a model of evolution is proposed. The model can be regarded as a randomization of Eigen's model of macromolecular evolution. The novelty of the method is in a random choice of modification basepoints with probabilities depending on results of the last group of trials -- soft selection. In other aspects, the proposed search and the widely used evolutionary search are identical, and the performance of the former can be conveniently assessed against the latter. The method appears especially efficient in crossing gaps between regions of attraction of local optima. This effect, crucial for global optimization, comes from an ability of soft selection to shift distributions of trials toward gaps. Numerical estimates show significant advantages of soft selection which grow with the gap size and the problem dimension.
45 citations
TL;DR: The selected random variable is used for the construction of a random variable probability distribution serving as a random generator of a value of the fuzzy variable with values restricted by the fuzzy set.
TL;DR: In this article, a quantitative analysis concerning the influence of the sky temperature values variations on net radiant heat loss and the heat balance of the low-sloped roofs is presented, and the results of calculated and measured sky temperatures for a horizontal surface in clear night-time sky conditions are compared and discussed.
TL;DR: In this paper, a systematic classification of design and operations parameters, typical of steering systems of mobile earthmoving equipment, in respect of various steering gears and the main elements of a steering unit are compared.
TL;DR: Two new algorithms of a recursive form for estimating the nonlinear characteristic of the Hammerstein system converge at all continuity points of the characteristic, and the integrated absolute error converges to zero.
Abstract: A discrete-time nonlinear Hammerstein system is identified. The dynamical subsystem is recovered using the standard correlation method. The main results concern the estimation of the nonlinear memoryless subsystem. The class of nonlinearities considered in the paper consists of a broad class of functions which cannot be parametrized. Two new algorithms of a recursive form for estimating the nonlinear characteristic are proposed. It is shown that they converge at all continuity points of the characteristic. The integrated absolute error also converges to zero. The algorithms are equivalent with respect to the asymptotical rate of convergence. The efficiency of the algorithms is discussed, and numerical examples are presented.
TL;DR: In this article, the growth of granule size in the coating process is conducted in a conic-cylindrical column and the dependence on granule mass distributions on the time for coating of inert particles in a spouted bed is presented.
TL;DR: In this paper, phase transitions in a ferroelectric crystal tris(trimethylammonium)mnachlorodiantimonate (III) (TMACA) were studied by calorimetric, dielectric and pyroelectric methods.
Abstract: Phase transitions occurring in a ferroelectric crystal tris(trimethylammonium)mnachlorodiantimonate (III) (TMACA) were studied by calorimetric, dielectric and pyroelectric methods. Anomalies of dielectric and thermal properties were found around 200 K and at ca. 364 K. The anoumalies in the low-temperature region exhibit a pronounced relaxational character. A detailed study of the behaviour of TMACA around 364 K clearly indicates that in fact TMACA undergoes two closely lying phase transitions, one of them being probably of the first order and the other of the second order. The temperature of the second order transition was determined to amount to (364.0±0,3)K irrespective of the method employed, wh Nous avons etudie des transitions de phase dans les cristaux de tris (trimethylammonium) nonachlorodiantimonate (III) (TMACA) par microcalorimetrie differentielle (DSC), ainsi que par des mesures des proprietes dielectriques et pyroeletriques. A 364 K, TMACA presente une transition depuis une phase basse temperature ferroelectrique vers une phase haute temperature paraelectrique. Une anomalie a ete aussi observee a environ 200 K, associee probablement a une relaxation. Les resultats obtenus montrent que la transition a 364 K presente en fait deux transitions tres rapprochees, l'une etant probablement du premier ordre et l'autre du second ordre. La transition du deuxieme ordre est observee a la meme temperature (364.0±0,3)K quelle que soit la methode utilisee, alors que celle du premier ordre est decelee par mesure de la constante dielectrique un degre plus bas que par calorimetrie. Celle-ci montre de plus un phenomene inhabituel, qu'on opere en programmation de temperature croissante ou decroissante: dans deux cas, la transition du second ordre precede la transition du premier ordre. L'etude de la reponse pyroelectrique du cristal montre que le passage a l'etat polaire est gouverne par la transition du premier ordre
TL;DR: Chromium coatings from sulphate, chloride and perchlorate electrolytes based on the [Cr(H2O)4(HCOO)]2+ complex ion were investigated in this article.
Abstract: Chromium coatings deposited from sulphate, chloride and perchlorate electrolytes based on the [Cr(H2O)4(HCOO)]2+ complex ion were investigated. The current efficiency reached 30% in the case of chloride electrolyte for various current densities in the range 4–10 A dm-2 depending on pH. Such a large current efficiency is due to the catalytic effect of the chloride ions on the electroreduction of the chromium complex to metallic chromium. Deposition of chromium from sulphate electrolyte took place with a current efficiency of 16% which rose for higher pH and lower current densities. Semi-bright and bright coatings with thickness of approximately 10μm of good adhesion to a copper electrode were deposited from chloride and sulphate electrolytes.
TL;DR: In this article, the initial flux of Co2+ cations through the feed-membrane solutions interface (JFo) was more than six times higher than flux through the stripping-means-interface (JRo), thus the stripping process was much slower than the extraction process.
TL;DR: In this article, a theoretical study of the problem of heat and mass transfer in a falling film apparatus is presented for binary mixtures and the respective differential equations for heat transfer in the liquid film are solved numerically.
Abstract: During molecular distillation in a falling film apparatus, temperature and concentration of the more volatile components undergo a marked decrease in axial and radial directions, due to the distillation in vacuo. The gradients produce changes in the rate of surface evaporation and separation efficiency along the flow path. A theoretical study of this problem is presented for binary mixtures. The respective differential equations for heat and mass transfer in the liquid film are solved numerically. As the results demonstrate, the aspect ratio of an apparatus should be large when a high separation is required and small when a high distillation rate is more important.
TL;DR: In this paper, the dielectric and pyroelectric properties of (CH 3 NH 3 ) 5 Bi 2 Br 11 single crystals were measured in the range 10-315 K revealing the existence of a new ferroelectric phase transition at 77K.
TL;DR: In this paper, a convenient way for the oxidation of organic diselenides to organoseleninic acids was reported, and the selenium-containing heterocyclic compounds were obtained.
TL;DR: In this paper, the authors considered the vibration of a linear structure caused by a random series of pulses and developed an analytical technique to determine the probabilistic characteristics: i.e., the response of the structure as the expected value, the covariance, the cumulants, the characteristic function and the probability density function of the response.
TL;DR: In this paper, polytetrafluoroethylene (PTFE) membranes of different porosity were used for lipase from rhizopus immobilization, which achieved the activity of 1228 U/m2 of the membrane area and the half-life time was calculated to be 7 days.
Abstract: Polytetrafluoroethylene (PTFE) membranes of different porosity were used for lipase from Rhizopus immobilization. The immobilized enzyme applied to sunflower oil hydrolysis achieved the activity of 1228 U/m2 of the membrane area and the half-life time was calculated to be 7 days.
01 Aug 1989
TL;DR: In this article, critical micelle concentrations and changes in enthalpy, entropy, and free energy that accompany micelle formation of selected amphiphilic N,N′ -bisdimethyl-1,2-ethanediamine derivatives were determined by means of titration calorimetry in an aqueous solution at 298.16 K.
Abstract: Critical micelle concentrations and the changes in enthalpy, entropy, and free energy that accompany micelle formation of selected amphiphilic N,N′ -bisdimethyl-1,2-ethanediamine derivatives (of general formula [C n H 2 n +1 OOCCH 2 (CH 3 ) 2 NCH 2 CH 2 N(CH 3 ) 2 CH 2 COOC n H 2 n +1 ] 2+ · 2Cl − where n = 8, 10, 12, 14, 16) were determined by means of titration calorimetry in an aqueous solution at 298.16 K. It was found that the critical micelle concentrations and thermodynamic data of the studied compounds are close to those of betaine chloride alkyl esters (of general formula [(CH 3 ) 3 NCH 2 COOC n H 2 n +1 ] + · Cl − ) with the alkyl chain longer by four CH 2 groups.
TL;DR: Two optimal (Bayes) strategies for performing the classification at each nonterminal node are derived from a multistage classifier based on a decision tree scheme.
01 Nov 1989
TL;DR: Using the Fourier technique, Kalman filter theory and Walsh functions, non-recursive algorithms for online determination of basic waveforms of signals are introduced, investigated and compared as discussed by the authors.
Abstract: Using the Fourier technique, Kalman filter theory and Walsh functions, nonrecursive algorithms for online determination of basic waveforms of signals are introduced, investigated and compared. The Fourier algorithms very efficiently reject the higher harmonics. For non-harmonic random noise of higher frequencies the new non-recursive allgorithms based on the Kalman filter theory have better filter properties than Fourier ones. The Walsh methods are very simple for computer implementation, but their filter properties are not very convenient, especially for the odd harmonics.
TL;DR: In this paper, the authors present the problems related to mathematical modelling of two-phase turbulent flows, including charging of PVC particles being a result of collision with a pipe wall, as well as influence of non-homogeneous field and external forces on aerodynamics of particles.
TL;DR: In this paper, the acceptor levels in Zn3P2 were investigated by optical and electrical methods, and the absorption processes connected with these levels were successfully described by the quantum defect method.
TL;DR: In this paper, the absorption spectra of the dye depended on the ionic form of the membrane and the decay of MB+ upon irradiation in Nafion membrane containing an excess of ferrous and hydrogen ions followed the first-order kinetics and the linearity of the function In C=f(t) was valid for over two half-lives.
TL;DR: In this article, a high-pH water treatment technology with processed dolomite as coagulant is proposed, which is successful when applied to the treatment of surface water, irrespective of the influent concentration of pollutants.