Showing papers by "Linköping University published in 1977"

Analysis of recursive stochastic algorithms

Abstract: Recursive algorithms where random observations enter are studied in a fairly general framework. An important feature is that the observations my depend on previous "outputs" of the algorithm. The considered class of algorithms contains, e.g., stochastic approximation algorithm, recursive identification algorithm, and algorithms for adaptive control of linear systems. It is shown how a deterministic differential equation can be associated with the algorithm. Problems like convergence with probability one, possible convergence points and asymptotic behavior of the algorithm can all be studied in terms of this differential equation. Theorems stating the precise relationships between the differential equation and the algorithm are given as well as examples of applications of the results to problems in identification and adaptive control.

Measurement of water exchange through skin.

Abstract: A new method for the measurement of the water exchange through the human skin has been developed. The method, based on the estimation of the vapour-pressure gradient immediately adjacent to the surface of the skin, permits the surface investigated to be exposed to normal ambient air during the entire period of measurement. A minimal influence on the humidity and the temperature of the microclimate surrounding the skin is thereby achieved. On the basis of the new method an instrument for measuring small amounts of water evaporated from or absorbed by a surface per unit time and area is described and its accuracy discussed. The instrument, which is intended for use in the temperature range 15–40°C and the atmospheric pressure range 98–104 kPa, has proved to offer a high accuracy and an improved sensitivity in comparison with devices previously employed. It has been used primarily for investigations of the rate of evaporation from the skin surface of newborn infants as well as of thyrotoxic and burned patients. The construction of the instrument, however, makes it well suited for the measurement of evaporation rates in many other fields of application.

On positive real transfer functions and the convergence of some recursive schemes

Abstract: The convergence with probability one of a recently suggested recursive identification method by Landau is investigated. The positive realness of a certain transfer function is shown to play a crucial role, both for the proof of convergence and for convergence itself. A completely analogous analysis can be performed also for the extended least squares method and for the self-tuning regulator of Astrom and Wittenmark. Explicit conditions for convergence of all these schemes are given. A more general structure is also discussed, as well as relations to other recursive algorithms.

Algorithms for the regularization of ill-conditioned least squares problems

Abstract: Two regularization methods for ill-conditioned least squares problems are studied from the point of view of numerical efficiency. The regularization methods are formulated as quadratically constrained least squares problems, and it is shown that if they are transformed into a certain standard form, very efficient algorithms can be used for their solution. New algorithms are given, both for the transformation and for the regularization methods in standard form. A comparison to previous algorithms is made and it is shown that the overall efficiency (in terms of the number of arithmetic operations) of the new algorithms is better.

Atopic disease in seven-year-old children. Incidence in relation to family history.

Abstract: The incidence of atopic disease and its relation to the family history was studied by questionnaire in 1325 children, 7 years of age. A higher incidence of bronchial asthma (2.7%) was found than in a previous Swedish study. The total incidence of atopic disease in the children was 15.1% with a higher level when there was a double parental history of such disease (42.6%) as compared with a single such history (19.8%). When both parents had an identical type of atopic disease, i.e. respiratory or skin, the incidence of atopic disease was higher (72.2%) than when non-identical types occurred in the parents (20.8%). The findings support theories of a polygenic transmission of atopic disease as well as a genetic influence on symptom specificity in such disease and may be of value in genetic counselling.

Body fat and adipose tissue cellularity in infants: A longitudinal study☆

Abstract: Body fat, fat cell size, and fat cell number were determined in a longitudinal study on 16 normal-weight infants during the age period 1-18 mo. The methods used included whole-body counting of 40K for determination of body fat and adipose tissue biopsies. A new method of calculation of body fat in infants is presented. No sex differences were found. Body fat expressed as per cent of body weight increased from 16.2% to 28.1%. From 1 to 12 mo of age the expansion of body fat was explained by and increase in fat cell size, while in the age period 12-18 mo it was mainly due to an increase in fat cell number. At 18 mo lthe fat cell size was the same as in 8-yr-old girls and 22-yr-old women (normal-weight females previously studied). The fat cell number at 18 mo, however, was far below the number at 8 yr of age, as well as the still higher number of the 22-yr-old women.

C-peptide in juvenile diabetics beyond the postinitial remission period. Relation to clinical manifestations at onset of diabetes, remission and diabetic control.

Abstract: Ludvigsson, J., Heeling, L. G., Larsson, Y. and Leander, E. (Department of Paediatrics, Linkoping University, Sweden, Novo Research Institute, Copenhagen, Denmark, Department of Mathematics, Linkoping University, Sweden). C-peptide in juvenile diabetics beyond the postinitial remission period.—Relation to clinical manifestations at onset of diabetes, remission and diabetic control. Acta Paediatr Scand, 66:177, 1977.—A group of 58 diabetics, age 6–17 years and with a duration of diabetes of 3–14 years was studied in order to show whether the nature of the clinical manifestations and the treatment at the onset of the disease are related to the subsequent C-peptide production and also whether remaining C-peptide production is related to better diabetic control. The relations between a number of clinical and laboratory variables were analysed including the degree of ketosis and the insulin dose given at onset of diabetes, the incidence of postinitial remission period, the fasting C-peptide level after the remission period, the level of insulin antibodies and the actual diabetic control expressed as the degree of glucosuria in the patients' urine tests at home. Multiple regression analysis was the main method used. Postinitial remission was positively correlated to initial insulin dose and negatively correlated to duration of ketonuria at onset. C-peptide, which was found in 24.1% of the patients was positively correlated to age at onset and initial insulin dose, but negatively correlated to ketonuria at onset. Diabetic control was positively correlated to insulin dose at onset and to C-peptide level, but negatively correlated to insulin antibodies. It could further be shown that patients who had received a more vigorous treatment immediately at onset had both a higher incidence of postinitial remission and a better diabetic control. The results suggest that an early diagnosis followed by rapid normalization of the metabolism at the onset of juvenile diabetes increase the possibility of preservation of some of the endogenous insulin production, which seems to facilitate diabetic control.

Localization of Adrenergic Receptors in Guinea Pig Ileum and Rabbit Jejunum to Cholinergic Neurons and to Smooth Muscle Cells

Abstract: The localization of adrenergic receptors mediating a relaxing action was investigated in innervated and denervated longitudinal muscle strips from guinea pig ileum and rabbit jejunum. Denervated preparations were contracted by drugs that had a direct effect on smooth muscle cells, such as acetylcholine and histamine, but not by stimuli acting on cholinergic neurons, such as electrical field stimulation or nicotine. After blockade of beta-adrenoceptors, norepinephrine relaxed the innervated guinea pig ileum contracted by electrical field stimulation, by stimulating alpha-adrenoceptors. Norepinephrine in low concentrations did not relax denervated preparations contracted by agents acting directly on smooth muscle. In high concentrations, it relaxed denervated preparations by a nonadrenergic mechanism, resistant to alpha- and/or beta-receptor blockade, but which was also activated by 1-(3,4-dihydroxyphenyl) ethanol. Phenylephrine only had a weak agonistic effect on the electrically stimulated innervated preparation and did not relax the denervated one. The denervated rabbit intestine contracted by acetylcholine was relaxed by norepinephrine and phenylephrine by stimulation of alpha-adrenoceptors. In the innervated preparations both drugs were more effective in inhibiting contractions induced by electrical field stimulation or eserine than those induced by exogenous acetylcholine. Both the denervated guinea pig and rabbit intestine were relaxed by stimulation of beta-adrenoceptors. It is suggested that in the guinea pig ileum alpha-adrenoceptors mediating relaxation are located only in cholinergic neurons, whereas in rabbit jejunum they are located both in these neurons and in the smooth muscle cells. Beta-adrenoceptors are located in the smooth muscle cells of both organs.

Socio-psychological factors and metabolic control in juvenile diabetes.

Abstract: The influence of exogenous and environmental factors on metabolic control was studied in 58 insulin treated juvenile diabetics, 6-17 years of age. Duration of diabetes varied between 3-14 years and age at onset of diabetes between 1-13 years. The social situation as well as knowledge about and attitudes towards diabetes among the patients and their parents were estimated by interviews, questionnaires and special tests. The quality of the diet, exercise and insulin treatment was assessed. An index of diabetic control was calculated on the basis of the patients daily urinalysis made at home. Multiple regression analysis and a special statistical "instrumental" variable technique were used in an effort to analyse the correlations between all variables. The social situation of the diabetic children was comparable with that of other Swedish children, but many parents felt the economic burden of the diabetic treatment as a problem. Knowledge tests showed that 25% of the parents and 62% of the patients above 12 years had unsatisfactory knowledge about diabetes. However, 93% of the patients seemed to have predominantly positive attitudes towards the treatment. Severe psychological problems had occurred in 7 cases. Food habits were appropriate among 21% of the patients and 26% had very regular exercise customs. Physical exercise seemed to be the most important of the exogenous factors for the diabetic control (p less than 0.001). Among teenagers knowledge was positively correlated to positive attitudes which in turn were positively correlated to physical exercise. Instrumental variable technique gave further indications of a positive influence of knowledge on control, and the correlation between diabetic control on one hand and knowledge combined with positive attitudes on the other was significantly positive. The results emphasize the importance of assisting young diabetic patients and their families in their socio-psychological adaptation to the strains of diabetic therapy.

HLA-types, C-peptide and insulin antibodies in juvenile diabetes.

Abstract: HLA-types were determined in 102 juvenile diabetics. HLA-B8 was found in 39 patients (RR 2.64; p < 0.01) and HLA-BW15 in 32 patients (RR 1.33; n.s.). HLA-B7 was found in 14 patients (RR 0.40; p < 0.05). There were no correlations between HLA-B8 or BW15 and family history of diabetes, occurrence of infection before onset of diabetes, ketonuria at onset or the age at onset of diabetes. Serum C-peptide, insulin binding capacity of IgG and total serum insulin, IRI, were determined in 94 patients who had had diabetes for more than two years and who were beyond the remission period. Measurable amounts of C-peptide were found in 33 patients (34.7%). There was no evidence of a relationship between any particular HLA-antigen and the B-cell function except for an increased incidence of detectable C-peptide in patients with HLA-B18 and a tendency to a decreased incidence of detectable C-peptide in patients with the combination HLA-B8, W15. Only four patients (4.3%) were lacking insulin antibodies. HLA-BW15 positive patients had higher levels of insulin antibodies than other groups, while HLA-B7 positive patients had lower levels. The results suggest that HLA-B7 and HLA-B 18 might be associated with a different and perhaps milder form of juvenile diabetes.

Adenoid cystic carcinoma of the larynx: a report of four cases and a review of the literature.

Abstract: Adenoid cystic carcinoma (cylindroma) is a well-recognized tumor that is frequently encountered in the major salivary glands, the lacrimal glands and in the minor salivary glands of the oral cavity and upper respiratory tract. Only 60 cases of adenoid cystic carcinoma have been described arising in the larynx. Four new cases are reported and the literature is reviewed. In the larynx, these tumors arise almost exclusively in the subglottic and supraglottic regions--areas having large numbers of seromucinous glands of the minor salivary gland type. These malignant tumors, whether occurring in the larynx or elsewhere, tend to grow quite slowly with prolonged non-specific symptomatology and protracted clinical course. Despite their slow growth, in a majority of cases, they eventually lead to the death of the patient.

Release of 3H-acetylcholine from isolated guinea pig ileum. A radiochemical method for studying the release on the cholinergic neurotransmitter in the intestine.

Abstract: Innervated strips of longitudinal muscle of guinea pig ileum were incubated with 3H-choline in the presence of physostigmine, after which the efflux of tritiated metabolites was studied. Under resting conditions 3H-acetylcholine, 3H-choline and other tritiated metabolites were released into the incubation medium. Analysis of the kinetics of the release of the metabolites indicated that the release occurred from at least 2 different compartments. Under the unstimulated conditions used, between 72 and 78% of the radio-activity remained in a third, non-releasable compartment. The release of 3H-acetylcholine showed spontaneous fluctuations which were positively correlated to spontaneous variations of the isometric tension of the preparation. Electrical field stimulation at low frequency (0.5 Hz) consistently increased the release of 3H-acetylcholine. The release of 3H-choline was increased only slightly or not at all by the electrical stimulation. For studying stimulation-evoked release of 3H-acetylcholine, it is suggested that the measurement of the total quaternary amine release is of similar value to measurement of 3H-acetylcholine itself. This approach considerably simplified the method. During 5 consecutive stimulation periods of 150 pulses each, the increase in the release of total quaternary amines diminished with time. By taking into account the reduction of the stores of radioactivity in the tissue during the experiment, correction for the negative trend could be made. When the preparation was stimulated with between 30 and 3000 pulses a close correlation was found between the increase in the release of total quaternary amines and the number of pulses delivered. The volley output of the quaternary amines was not constant, however, but diminished by increasing stimulation frequency.

Blood Pressure and Heart Rate Regulating Capacity of the Carotid Sinus during Changes in Blood Volume Distribution in Man

Abstract: The influence of changes in blood volume distribution on the carotid baroreflex was studied in 18 subjects. Blood volume distribution was changed by varying the pressure around the lower body above and below ambient, thereby varying the amount of blood pooled in this region and exerting a secondary influence on the central blood volume. The carotid arterial stretch receptors were stimulated by varying the pressure in air-tight box enclosing the neck. To obtain a standardized carotid sinus stimulus (SCS) the pressure in the box was varied sinusoidally between - 10 and - 40 mmHg with a fixed freqency of 0.03 Hz. The effects on heart rate and blood pressure were assessed by harmonic analysis performed off-line on a digital computer. During lower body negative pressure of -40 mmHg (LBNP -40), i.e. during a procedure known to reduce the central blood volume, SCS induced an augmented effect on the blood pressure regulating capacity but not on the heart rate response. Expressing the blood pressure regulating capacity as peak-to-peak changes in systolic arterial pressure, the response during LBNP -40 mmHg was almost twice the control value. The opposite stimulus-lower body postive pressure-influenced the SCS-induced effects only slightly but on the average a minor reduction in both blood pressure and heart rate regulating capacity was found compared with the control condition, though the difference did not reach significant levels. The results support the hypothesis that changes in blood volume distribution modify the function of the carotid baroreflex, possibly via intrathoracic receptors sensitive to changes in central blood volume and/or central venous pressure.

Optimal reception of digital data over the Gaussian channel with unknown delay and phase jitter

Abstract: Asymptotically optimum (in the sense of minimum per-symbol error rate) receiver structures for data communication over the white Gaussian channel with unknown time delay and carrier phase jitter are developed. The receiver structures apply to the following suppressed-carrier modulation systems: double sideband (DSB), quadrature amplitude modulation (QAM) with an arbitrary constellation, vestigial sideband (VSB) and single sideband. The resulting minimum error probability receivers are asymptotically equivalent to maximum-likelihood digital {\em sequence}-estimating receivers. The optimum structures implicitly derive joint maximum-likelihood estimates of the unknown parameters and of the sequence of data symbols. It is shown that the parameter estimates can be obtained from two data-directed stochastic approximation algorithms. Unlike traditional theoretical treatments of this communication situation, which have separated the highly important carrier phase and timing recovery problem from the detection problem, a unified theory is presented from which the complete ideal receiver structure can be deduced.

Vitamin C as a Preventive Medicine against Common Colds in Children

Abstract: During 7 weeks in the spring of 1973 a double-blind pilot study on 172 children in the age group 8-9 was carried out to test the possible effect of 1000 mg vitamin C daily as a prophylactic agent against common colds. During the autumn of 1973, a main study was carried out on 642 children of the same age. The investigations had the same pattern and lasted for 3 months. Both studies have been processed on the same principles. The results were somewhat divergent but, like previously published studies on children, seemed to indicate that the duration and severity of the colds were reduced while, on the other hand, the incidence remained unaltered or indeed increased. The total number of days of upper respiratory tract infection was smaller for the vitamin C group only in the pilot study (not in the main study). No proven biochemical effects were obtained. Preventive treatment of healthy children with vitamin C in large doses thus had no definitely proved effect against colds.

The Effect of Salbutamol and Terbutaline in the Management of Premature Labour

Abstract: A comparative study concerning the effect of salbutamol and terbutaline in the management of premature labour with intact membranes has been performed. Each group included 34 patients between 27–36 weeks gestation. The drugs used were given by intravenous infusion. Salbutamol arrested labour activity in 33 of 34 patients and terbutaline in 32 of 34 patients. Delivery was postponed for more than one week in 74% of the patients receiving salbutamol and in 80% of the patients receiving terbutaline. No significant difference in effect was found between the drugs used. The effect was equally good independent of the gestational age. Dilatation of cervix beyond 2 cm was associated with successful treatment (delay of delivery more than one week) in 27% compared to 91% if cervix was dilated 2 cm or less. In 12 patients with ruptured membranes a temporary arrest of labour activity (1–7 days) was obtained in 7 patients, and in 1 patient the delivery was delayed for 6 weeks. In the dosage used an increase in maternal...

Thresholds for linear frequency ramps of a continuous pure tone.

Abstract: The human auditory sensitivity in detecting linear frequency ramps of a continuous pure tone has been studied. It is shown that for short ramp durations ( 200 msec), discrimination was found to be based on detection of the actual frequency sweep. No significant difference was found between thresholds for upward and downward sweeps. Expressed in Hz, the threshold for frequency change was approximately constant for base frequencies up to 1 kHz, above which it increased, reaching approximately 14 Hz at 4 kHz. There was no significant difference in the threshold for frequency change from 40 to 80 dB HL but at 20 dB HL the threshold was significantly higher than at 40 dB HL. Intra-individual variation in thresholds was found to be smaller than inter-individual variation. The results are discussed in relation to previous frequency discrimination data,...

Efficient change of initial conditions, dual chandrasekhar equations, and some applications

Abstract: We give simple proofs of formulas for converting linear least-squares filtered and smoothed estimates derived for one set of initial conditions to estimates valid for some other set. These are then used to study the possible advantages of first deliberately mischoosing the initial conditions so as to allow computational benefits to be obtained by using certain fast algorithms. In the course of this application we also obtain a new "dual" set of Chandrasekhar equations that provide a fast algorithm for fixed-point smoothing.

Changes in lactate dehydrogenase isoenzyme patterns in patients with tumours of the central nervous system.

Abstract: The total activities of lactate dehydrogenase (LD) and the LD isoenzyme distribution were determined on homogenates from 61 benign and malignant intracranial tumours, and in serum and cerebrospinal fluid from 45 and 28 of the tumour patients respectively.

Xylene Exposure Electronystagmographic and Gaschromatographic Studies in Rabbits

Abstract: Complaints of vertigo from people who are exposed to industrial solvents have focused interest on their toxic effect on the nervous system. In order to evaluate the influence of an organic solvent, xylene, on the mammalian vestibular system, a series of rabbit experiments were performed. To achieve a constant concentration, the xylene was infused as a lipid emulsion. Blood concentrations were estimated by gas chromatography. Elec-tronystagmography in darkness revealed that at blood xylene concentrations of 30 ppm all rabbits had a positional nystagmus. The beat direction was the opposite of positional alcohol nystagmus. Another difference between the alcohol and the xylene reaction was that rotatory nystagmus responses were exaggerated. The relations between the present findings and the reactions and blood concentrations in people exposed to industrial solvents are discussed.

Oxidation of Aluminum Surfaces Studied by Synchrotron Radiation Photoelectron Spectroscopy

Abstract: A review is presented of a series of electron spectroscopic measurements investigating the surface properties of aluminum by its interaction with molecular oxygen. The studies performed at the Stanford Synchrotron Radiation Laboratory have used the unique properties of synchrotron radiation. The tunability of the excitation source in the spectral range 30-700 eV has made it possible to obtain maximum surface sensitivity and measure core-level photoabsorption.