Showing papers by "Linköping University published in 1978"

Convergence analysis of parametric identification methods

Abstract: A certain class of methods to select suitable models of dynamical stochastic systems from measured input-output data is considered. The methods are based on a comparison between the measured outputs and the outputs of a candidate model. Depending on the set of models that is used, such methods are known under a variety of names, like output-error methods, equation-error methods, maximum-likelihood methods, etc. General results are proved concerning the models that are selected asymptotically as the number of observed data tends to infinity. For these results it is not assumed that the true system necessarily can be exactly represented within the chosen set of models. In the particular case when the model set contains the system, general consistency results are obtained and commented upon. Rather than to seek an exact description of the system, it is usually more realistic to be content with a suitable approximation of the true system with reasonable complexity properties. Here, the consequences of such a viewpoint are discussed.

Fast calculation of gain matrices for recursive estimation schemes

Abstract: A sequence of vectors {x(t)} with dimension N is given, such that x(t+1) is obtained from x(t) by introducing p new elements, deleting p old ones, and shifting the others in some fashion. The sequence of vectors $ is sought. This paper presents a method of calculating these vectors with proportional-to-Np operations and memory locations, in contrast to the conventional way which requires proportional-to-N 2 operations and memory locations. A non-symmetric case is also treated.

Application of Fast Kalman Estimation to Adaptive Equalization

Abstract: Very rapid initial convergence of the equalizer tap coefficients is a requirement of many data communication systems which employ adaptive equalizers to minimize intersymbol interference. As shown in recent papers by Godard, and by Gitlin and Magee, a recursive least squares estimation algorithm, which is a special case of the Kalman estimation algorithm, is applicable to the estimation of the optimal (minimum MSE) set of tap coefficients. It was furthermore shown to yield much faster equalizer convergence than that achieved by the simple estimated gradient algorithm, especially for severely distorted channels. We show how certain "fast recursive estimation" techniques, originally introduced by Morf and Ljung, can be adapted to the equalizer adjustment problem, resulting in the same fast convergence as the conventional Kalman implementation, but with far fewer operations per iteration (proportional to the number of equalizer taps, rather than the square of the number of equalizer taps). These fast algorithms, applicable to both linear and decision feedback equalizers, exploit a certain shift-invariance property of successive equalizer contents. The rapid convergence properties of the "fast Kalman" adaptation algorithm are confirmed by simulation.

Calculated bulk properties of the actinide metals

Abstract: Self-consistent relativistic calculations of the electronic properties for seven actinides (Ac-Am) have been performed using the linear muffin-tin orbitals method within the atomic-sphere approximation. Exchange and correlation were included in the local spindensity scheme. The theory explains the variation of the atomic volume and the bulk modulus through the $5f$ series in terms of an increasing $5f$ binding up to plutonium followed by a sudden localization (through complete spin polarization) in americium.

Programming in an Interactive Environment: the ``Lisp'' Experience

Abstract: Lisp systems have been used for highly interactive programming for more t han a decade During tha t time, special properties of the Lisp language (such as program/ data equivalence) have enabled a certain style of interact ive programming to develop, characterized by powerful interact ive support for the programmer, nons tandard program structures, and nons tandard program development methods. The paper summarazes the LISP style of interactive programming for readers outside the LisP community, describes those propertms of LisP systems t ha t were essential for the development of this style, and discusses some current and not yet resolved issues

Pharmacological classification of adrenergic α receptors in the guinea pig

Abstract: THE actions of sympathomimetic amines have attracted considerable attention for some time. Ahlquist1–3 introduced the concept of adrenergic α and β receptors to explain the differences in the effects of some of these amines on various organ systems and then Lands et al.4,5 suggested the existence of two types of β receptors, β1 and β2. It has been claimed that there is a pharmacological difference between α receptors at adrenergic neurones and those in smooth muscle6–9. I have previously shown that the inhibitory α receptor of the cholinergic neurone in guinea pig ileum is pharmacologically different from the excitatory α receptor located in the smooth muscle of the guinea pig ileocaecal sphincter and rabbit aorta10–13. Langer14 suggested that there are two kinds of α receptors, α1 and α2 (see also ref. 15). Adopting this nomenclature, it was proposed that α1 receptors are present when the relative affinity of phenylephrine for the receptors is stronger than that of clonidine, and α2 receptors when the relative affinities are reversed13, α1 Receptors have thus been shown to be present in smooth muscle cells of rabbit aorta and pulmonary artery, and in guinea pig ileocaecal sphincter; and inhibitory α2 receptors in cholinergic neurones of guinea pig ileum and in adrenergic neurones of rabbit pulmonary artery and rat vas deferens. I report here the results of further studies supporting the theory of two types of α receptors.

Ordered oxygen overlayer associated with chemisorption state on Al(111)

Abstract: We present experimental evidence of a unique, ordered chemisorption phase in the initial interaction of oxygen with the Al(111) surface. At high oxygen exposure or high temperature, this phase is shown to transform irreversibly to a bulklike aluminum oxide. The measured temperature dependence, as well as the low-energy electron diffraction, suggests a threefold, centered bonding site. A comparison between calculated and experimental valence-band density of states for the oxygen-covered Al(111) surface is made for the estimated oxygen-atom-substrate-surface distance.

Photoemission study of the bulk and surface electronic structure of single crystals of gold

Abstract: Angle-resolved energy distributions for photoelectrons emitted from the (111), (110), and (100) crystal faces of Au are presented for photon energies in the range 7.0-11.6 eV. The variation of peak-energy positions as a function of photon energy and electron emission angle has been studied. We have found very good qualitative agreement between the experimental results and the predictions of the three-step model applied to a relativistic-augmented-plane-wave band structure. To fit the theoretical peak-energy positions to the experimental data, it is necessary to lower bands Nos. 3, 4, and 5 (numbered from the bottom of the valence-band complex) by on the average 0.2 eV and to raise band No. 6 by 0.2 eV along the $\ensuremath{\Gamma}K$ symmetry line. Considerable emission must also be attributed to nondirect processes such as phonon-assisted nondirect transitions, scattering of electrons excited in direct transitions, and surface photoemission. A shoulder due to nondirect processes is always seen at -2.3 eV, whenever the emission due to direct transitions is low. The dispersion of the surface state in the $L$ gap has been measured. A parabolic fit to the data gives ${E}_{0}=0.45\ifmmode\pm\else\textpm\fi{}0.05$ eV and ${m}^{*}=(0.37\ifmmode\pm\else\textpm\fi{}0.05){m}_{0}$. We also report measurements on the local work function for the three low-index crystal faces.

Differentiation between pre- and postjunctional α-receptors in guinea pig ileum and rabbit aorta

Abstract: Electric stimulation of proximal and terminal guinea pig ileum induced contractions which were mediated by stimulation of cholinergic neurons. After blocking β-receptors, prejunctional α-receptors mediating inhibition could be studied in these neurons. In proximal ileum the order of potencies of the following agonists was: clonidine (8)* clonidine (0.04). On the postjunctional α-receptor in terminal guinea pig ileum phentolamine was 55 fold more effective in blocking the response of norepinephrine than it was on blocking the response on the prejunctional receptor of the same preparation. Phenoxybenzamine (4 times 10-8 M) was ineffective on the prejunctional α-receptor of the cholinergic neuron, while it blocked the postjunctional α-receptor of smooth muscle in guinea pig terminal ileum noncompetitively. It is suggested that the differences in the activities of clonidine and phenylephrine between prejunctional α-receptors located to cholinergic neurons and postjunctional α-receptors located to smooth muscle cells was due to a pharmacological difference between the receptors. The results obtained with the blockers support this suggestion.

Asymptotic normality of prediction error estimators for approximate system models

Abstract: A general class of parameter estimation methods for stochastic dynamical systems is studied. The class contains the least squares method, output-error methods, the maximum likelihood method and several other techniques. It is shown that the class of estimates so obtained are asymptotically normal and expressions for the resulting asymptotic covariance matrices are given. The regularity conditions that are imposed to obtain these results are fairly weak. It is, for example, not assumed that the true system can be described within the chosen model set, and, as a consequence, the results in this paper form a part of the so-called approximate modeling approach to system identification. It is also noteworthy that arbitrary feedback from observed system outputs to observed system inputs is allowed and that stationarity is not required.

Tubal Closing Failure in Retraction Type Cholesteatoma and Adhesive Middle Ear Lesions

Abstract: In cases of retraction type cholesteatoma and related conditions it has been observed that the Eustachian tube may show a reduced ability to withstand respiratory pressure variations. The reduced resistance of the tube may play an important role in the development and course of middle ear disease. In the present study 42 subjects who had middle ear disease of this type and confirmed habitual sniffing behaviour were examined for symptoms and signs that would indicate a patulous tube. Different degrees of malfunction were recognized: in the presence of total closing failure, with an intermittently free transfer of respiratory pressures to the middle ear, the sniffing procedure maintains a negative intratympanic pressure. The condition is identical to the patulous tube state in the classical sense. In relative closing failure there is no free pressure transfer, and no patulous tube symptoms. Sniffing may however cause a repeated evacuation of the middle ear space. The results of this study cast doubt upon th...

Photoemission from surface states and surface resonances on the (100), (110), and (111) crystal faces of aluminum

Abstract: The angular-resolved energy distributions for photoelectrons emitted from the (100), (110), and (111) crystal faces of aluminum are presented for photon energies in the range 7.0-11.6 eV. The emission in this photon energy range is dominated by surface photoemission excited by the normal optical field or the surface-plasmon field. Three structures in the spectra are identified as emission from electronic surface states that have been predicted in theoretical calculations. Two of these surface-state bands, seen in emission from the (100) and (110) crystal faces, are associated with the $\mathrm{sp}$ band gap around the $X$ point in $\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}$ space. We interpret a structure in the emission from the (111) crystal face as due to a surface resonance band also associated with the $\mathrm{sp}$ band gap around the $X$ point. No conclusive evidence for the existence of structures in the spectra due to direct transitions in the bulk has been obtained.

Clinical pharmacokinetics of procainamide.

Abstract: Procainamide is almost completely absorbed after oral administration and peak plasma concentrations are generally reached within 1 to 2 hours. Upon intravenous administration there is a rapid initial distribution phase, which is completed after about 30 minutes. The pharmacokinetics can be described by a 2-compartment open model. The plasma half-life during the beta-phase averages 3 hours. The apparent volume of distribution is about 2L/kg body weight. At therapeutic plasma levels about 15% is bound to plasma proteins. Approximately 50% of administered procainamide is eliminated as unchanged drug via the kidneys. N-Acetylprocainamide is the main metabolite and is the main metabolite and is pharmacologically active, with a recovery in urine of about 15% (range 7 to 34% in healthy subjects). The acetylation of procainamide seems to be under the same monogenic control as that of isoniazid. At least 2 more metabolites have been found but are not yet identified. The renal clearance of procainamide ranges from 179 to 660ml/min. Glomerular filtration and active tubular secretion seem to be the most important mechanisms. In patients with low-output cardiac and/or renal impairment, the absorption, distribution and elimination of the drug may be significantly altered. Determination of plasma levels is of particular value in these cases and will contribute to more safe and effective therapy in the majority of patients. As N-acetylprocainamide seems to have pharmacological effects comparable with those of procainamide, both agents should be monitored simultaneously in order to optimise therapy.

Fast time-invariant implementations of Gaussian signal detectors

Abstract: A new implementation is presented for the optimum likelihood ratio detector for stationary Gaussian signals in white Gaussian noise that uses only two causal time-invariant filters. This solution also has the advantage that fast algorithms based on the Levinson and Chandrasekhar equations can he used for the determination of these time-invariant filters. By using a notion of "closeness to stationarity,' there is a natural extension of the above results for nonstationary signal processes.

On isoparametric elements

Abstract: Optimal order error estimates in H, for the Q1 isoparametric interpolation, were obtained in [2] for a very general class of degenerate convex quadrilateral elements. In this work we show that the same conlusions are valid in W 1,p for 1 ≤ p < 3 and we give a counterexample for the case p ≥ 3, showing that the result can not be generalized for more regular functions. Despite this fact, we show that optimal order error estimates are valid for any p ≥ 1, keeping the interior angles of the element bounded away from 0 and π, independently of the aspect ratio. We also show that the restriction on the maximum angle is sharp for p ≥ 3.

Convergence of an Adaptive Filter Algorithm

Abstract: A state-space representation of a dynamical, stochastic system is given. A corresponding model, parametrized in a particular way, is considered and an algorithm for the estimation of its parameters is analysed. The class of estimation algorithms thus considered contains general output error methods and model reference methods applied to stochastic systems. It also contains adaptive filtering schemes and, e.g. the extended least squares method. It is shown that if a certain transfer function associated with the true system is positive real, then the estimation algorithm converges with probability 1 to a value that gives a correct input-output model.

New Rapid Bioassay of Gentamicin Based on Luciferase Assay of Extracellular ATP in Bacterial Cultures

Abstract: Bacterial ATP levels in Escherichia coli cultures were determined by luciferin/luciferase assay. Rapid effects of gentamicin on ATP levels in the cultures were studied, and a dose-dependent accumulation of extracellular ATP was demonstrated. This phenomenon was used to develop a rapid bioassay of gentamicin in clinical serum specimens. The accuracy of the assay, expressed as coefficient of variation over the range 16 to 1 mug/ml, varied between 1.8 and 6.5%, compared to 2.3 to 4.7% for an agar disk diffusion assay. Serum gentamicin concentrations were determined by both methods in 122 serum specimens from 43 patients receiving gentamicin alone or in combination with other antibiotics, and the results were compared (r = 0.942). Determination of gentamicin based on luciferase assay of extracellular ATP in bacterial cultures requires only 10 mul of serum, allowing for capillary sampling, and results are available within 2 h.

Uptake and retrograde axonal transport of horseradish peroxidase in regenerating facial motor neurons of the mouse.

Abstract: Uptake and retrograde axonal transport of intravenously injected horseradish peroxidase (HRP) was studied during regeneration after a crush injury of the facial nerve of the mouse. The circulation time of HRP was 12 to 24 h. HRP injected immediately after the crush diffused into injured axons in the crushed region and accumulated subsequently in perikarya of facial neurons in the brain stem. After a time interval of 1 h or 5 days between the crush and the injection only a faint HRP accumulation occurred in a few facial neurons. After an interval of 7 days a moderate number of neurons had incorporated the tracer, while after more than 9 days the HRP activity in the regenerating neurons was more pronounced than in the contralateral neurons. Ultrastructurally, muscles of the vibrissae showed denervated subneural apparatuses 6 days after the crush. 8 days after the crush regenerating axon terminals containing small clusters of synaptic vesicles, dense cored vesicles and some HRP-labelled vesicles, were found over some gutters and after 10 to 13 days all examined gutters contained axon terminals with large numbers of synaptic vesicles and some HRP-containing vesicles. More than one axon terminal profile was seen in the same synaptic gutter. 32 and 64 days after the crush the neuromuscular junctions had regained a more mature appearance. The calibre spectra of the crushed facial nerves still showed a shift towards smaller diameters 134 days after the crush, at a time when a slight increase in HRP activity in the facial neurons persisted.

Low-compliance perfusion pump for oesophageal manometry

Abstract: A low-compliance perfusion pump has been constructed to increase the bandwidth of perfused measurement systems in oesophageal manometry. This pump gives a constant flow at a high mechanical impedance by forcing the perfusion fluid through a steel capillary. With this low-compliance perfusion pump a wide bandwidth was obtained for the catheter types and perfusion flows investigated. The pump improves the accuracy of oesophageal manometry.

Comment on the Iterative Refinement of Least-Squares Solutions

Abstract: Three different iterative algorithms for refining a computed least-squares estimate are compared. The first two algorithms are based on the orthogonal decomposition of the matrix X, whereas the third, recently advocated by Fletcher (1975), uses the Cholesky decomposition of XT X. The third algorithm theoretically can give good results even when the condition number κ (X) is very large, but in general, the first two algorithms are superior and far more reliable. A variant of one of these may be advantageous when X is large and sparse. Numerical results confirm the theoretical analysis.

Changes of plasma lipid metabolism in males during estrogen treatment for prostatic carcinoma.

Abstract: Fourteen patients with prostatic carcinoma were treated with 1.0–0.5 mg ethinyl estradiol orally daily and 160–80 mg polyestradiol phosphate im monthly. Lipid concentrations were determined in plasma and the high density lipoprotein fraction, and the plasma lecithin-cholesterol acyl transfer rate was measured before and 1 and 6 months after the start of therapy. During treatment, the concentration of total cholesterol was unchanged while there was a 60% increase of high density lipoprotein-total cholesterol. Triglyceride (TG) concentration increased 40%, indicating an augmented level of very low density lipoprotein concentration. The plasma lecithin-cholesterol acyl transfer rate increased 20–35%, indicating that an increased rate of production and turnover of TG, cholesteryl esters, and very low density lipoproteins probably was a main cause of the elevated TG concentration. The potential effects on the development of atherosclerosis by the plasma lipid changes during estrogen treatment are discussed.

The Dna Content and Nuclear Size in Normal, Dysplastic and Carcinomatous Laryngeal Epithelium: A Spectrophotometric Study

Abstract: The aim of the present study was to obtain a more objective evaluation of nuclear hyperchromasia and polymorphism in laryngeal epithelium. The method is based on a photometric assay of nuclear size and DNA content in Feulgen stained slides. The DNA content of hyperchromatic nuclei should exceed the mean for nuclei of normal epithelium by more than twice the standard deviation. In comparison with lymphocytes (2N) the DNA content in hyperchromatic nuclei corresponds to 3.3 N. The mean DNA contents of normal, dysplastic and carcinomatous laryngeal nuclei were 69, 71 and 118 A.U. The mean nuclear area for normal, dysplastic and carcinomatous epithelial cells were 48, 41 and 73 fim2. The higher the degree of atypia displayed by the cells the greater was the variability of the DNA content and the nuclear size. The investigation shows that the method may provide a more objective basis for evaluating hyperchromasia and polymorphism.