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Showing papers by "Linköping University published in 1993"


Journal ArticleDOI
TL;DR: In this paper, the surface plasmon resonance angle shifts are calculated as a function of the amount of organic material in the interaction matrix and the influence of physical parameters, such as matrix thickness and wavelength of the light, on the expected performance is considered.
Abstract: Surface plasmon resonance is one of the surface-oriented biosensing techniques that can be used to monitor biomolecular interactions. It is utilized in instrumentation for real-time biospecific interaction analysis capable of determining not only the concentrations of biomolecules but also kinetic constants, binding specificity, etc. In this contribution biosensing with surface plasmon resonance is reviewed. Special attention is given to an extended interaction matrix on the sensing surface, which enables the covalent binding of, e.g., antigens or antibodies. The surface plasmon resonance angle shifts are calculated as a function of the amount of organic material in the matrix. The influence of physical parameters, such as matrix thickness and wavelength of the light, on the expected performance is considered. Finally, a few illustrative experimental results obtained with a recently introduced commercial instrument are given.

520 citations


Journal ArticleDOI
TL;DR: Results of this study indicate that under identical conditions, mitochondria from shorter-lived species produce relatively higher amounts of reactive oxygen species than those from the longer- lived species, and, thus, support the free radical hypothesis of aging.

473 citations


Journal ArticleDOI
TL;DR: A theory for the system inherent amplification factor dependence on the distance between individual measurement points and detector is proposed, and correction measures are presented.
Abstract: A laser Doppler perfusion imaging technique based on dynamic light scattering in tissue is reported. When a laser beam sequentially scans the tissue (maximal area approximately 12 cm*12 cm), moving blood cells generate Doppler components in the backscattered light. A fraction of this light is detected by a remote photodiode and converted into an electrical signal. In the signal processor, a signal proportional to the tissue perfusion at each measurement point is calculated and stored. When the scanning procedure is completed, the system generates a color-coded perfusion image on a monitor. A perfusion image is typically built up of data from 4096 measurement sites, recorded during a time period of 4 min. This image has a spatial resolution of about 2 mm. A theory for the system inherent amplification factor dependence on the distance between individual measurement points and detector is proposed and correction measures are presented. Performance results for the laser Doppler perfusion imager obtained with a flow simulator are presented. The advantages of the method are discussed. >

469 citations


Journal ArticleDOI
TL;DR: Simulations with long image sequences of real-world scenes indicate that the approach to estimating the motion of the head and facial expressions in model-based facial image coding not only greatly reduces computational complexity but also substantially improves estimation accuracy.
Abstract: An approach to estimating the motion of the head and facial expressions in model-based facial image coding is presented. An affine nonrigid motion model is set up. The specific knowledge about facial shape and facial expression is formulated in this model in the form of parameters. A direct method of estimating the two-view motion parameters that is based on the affine method is discussed. Based on the reasonable assumption that the 3-D motion of the face is almost smooth in the time domain, several approaches to predicting the motion of the next frame are proposed. Using a 3-D model, the approach is characterized by a feedback loop connecting computer vision and computer graphics. Embedding the synthesis techniques into the analysis phase greatly improves the performance of motion estimation. Simulations with long image sequences of real-world scenes indicate that the method not only greatly reduces computational complexity but also substantially improves estimation accuracy. >

405 citations


Journal ArticleDOI
TL;DR: In this article, the tradeoff between speed and power consumption for low power consumption in CMOS VLSI by using the supply voltage and the threshold voltage as variables was investigated.
Abstract: The trading of speed for low power consumption in CMOS VLSI by using the supply voltage and the threshold voltage as variables was investigated. It is shown that it is desirable to minimize the supply voltage for minimizing the power consumption. The lower bound of the supply voltage and the possible decrease in power consumption without speed loss were investigated under different circuit constraints, and the consequences for circuit performance were calculated. Results show, for example, that power reductions of about 40 times can be obtained without speed loss by using supply voltages down to about 0.48 V. >

276 citations


01 Jan 1993
TL;DR: In this article, it is shown how false operator responses due to missing or uncertain data can be signiflcantly reduced or eliminated using simple combinations of appropriately chosen convolutions, such as Normalized convolution, Difierential convolution and Normalized differential convolution.
Abstract: In this paper it is shown how false operator responses due to missing or uncertain data can be signiflcantly reduced or eliminated. Perhaps the most well-knownofsuchefiectsarethevarious‘edgeefiects’ which invariably occur at the edges of the input data set. Further,itisshownhowoperatorshavingahigher degreeofselectivityandhighertoleranceagainstnoise can be constructed using simple combinations of appropriately chosen convolutions. The theory is based on linear operations and is general in that it allows for both data and operators to be scalars, vectors or tensors of higher order. Threenewmethodsarepresented: Normalized convolution, Difierential convolutionand Normalized Differential convolution. All three methods are examples of the power of the signal/certainty - philosophy, i.e. the separation of both data and operator into a signal part and a certainty part. Missing data is simply handled by setting the certainty to zero. In the case of uncertain data, an estimate of the certainty must accompany the data. Localization or ‘windowing’ of operators is done using an applicability function, the operator equivalent to certainty, not by changing the actual operator coe‐cients. Spatially or temporally limited operators are handled by setting the applicability function to zero outside the window. Consistentwiththephilosophyofthispaperallalgorithms produce a certainty estimate to be used if further processing is needed. Spectrum analysis is discussed and examples of the performance of gradient, divergence and curl operators are given.

238 citations


Journal Article
TL;DR: Glucose metabolic capacity and whole body insulin sensitivity were reduced in patients with diabetes and with impaired glucose tolerance, and the reduction was more pronounced in diabetic patients.
Abstract: Objective To investigate glucose metabolism and insulin secretion on patients with pancreatic cancer compared with healthy control subjects. Design Open study. Setting Linkoping University Hospital, Sweden. Subjects 44 consecutive patients referred for radical operations for pancreatic carcinoma, and eight healthy age and sex matched volunteers. Interventions Hyperglycaemic glucose clamp in 36 of patients and all volunteers. Main outcome measures Glucose tolerance according to WHO criteria, plasma insulin and C-peptide concentrations, and insulin secretion measurements both during hyperglycaemia and after stimulation by glucagon. Results Thirty-three patients (75%) had either impaired glucose tolerance or diabetes. Fasting insulin concentrations were raised in the non-insulin-requiring diabetic patients, but similar in the insulin-requiring group compared with healthy control subjects and patients with normal glucose tolerance. In neither diabetic group was insulin secretion affected during hyperglycaemia. After stimulation with glucagon, insulin secretion increased in non-insulin-requiring diabetic patients but remained unchanged in those who required insulin. Glucose metabolic capacity and whole body insulin sensitivity were reduced in patients with diabetes and with impaired glucose tolerance, and the reduction was more pronounced in diabetic patients. Conclusions There is a high incidence of impaired glucose tolerance and diabetes in patients with pancreatic cancer, which cannot be explained by impaired secretion of insulin. Other factors that reduce insulin sensitivity seem to have a role in the development of diabetes in this group of patients.

215 citations


Journal ArticleDOI
TL;DR: In this article, plan-view transmission electron microscopy revealed an open columnar structure with a relatively constant average grain size of ∼ 65 nm, and the amount of intercolumnar pores or voids gradually decreased.

195 citations


Journal ArticleDOI
TL;DR: Simulations show that the median measuring depth is strongly dependent on the perfusion profile, and favouring the choice of a probe with a small fibre separation when linearity is more important than a large sampling depth.
Abstract: Monte Carlo simulation of photon migration in tissue was used to assess the sampling depth, measuring depth and photon pathlength in laser Doppler flowmetry. The median sampling depth and photon pathlength in skin, liver and brain tissue were calculated for different probe geometries. The shallowest median sampling depth found was 68 μm for a 120 μm diameter single fibre probe applied to a one-layered skin tissue model. By using separate transmitting and receiving fibres, the median sampling depth, which amounted to 146 μm for a 250 μm fibre centre separation, by be successively increased to 233 μm when the fibres' centres are separated by 700 μm. Total photon pathlength and thereby the number of multiple Doppler shifts increase with fibre separation, thus favouring the choice of a probe with a small fibre separation when linearity is more important than a large sampling depth. Owing mainly to differences in the tissue g-value and scattering coefficient, the median sampling depth is shallower for liver and deeper for brain, in comparison with skin tissue. For skin tissue, the influence on the sampling depth of a homogeneously distributed blood volume was found to be limited to about 1 per cent per percentage increase in tissue blood content, and may, therefore, be disregarded in most practical situations. Simulations show that the median measuring depth is strongly dependent on the perfusion profile.

189 citations


Book ChapterDOI
01 Jan 1993
TL;DR: In this paper, the authors argue that algebraic methods can be very useful for both linear and nonlinear systems, and they provide a few examples of applications of algebraic techniques in control systems.
Abstract: The analysis and design of control systems has been greatly influenced by the mathematical tools being used. Maxwell introduced linear differential equations in the 1860’s. Nyquist, Bode and others started the systematic use of tranfer functions, utilizing complex analysis in the 1930’s. Kalman brought forward state space analysis around 1960. For nonlinear systems, differential geometric concepts have been of great value recently. We will argue here that algebraic methods can be very useful for both linear and nonlinear systems. To give some motivation we will begin by looking at a few examples.

178 citations


Journal ArticleDOI
TL;DR: This work suggests variants for 2, 3 and arbitrary dimensions that are separable, suitable for various parallel architectures, and presents a 4-scan algorithm for 3-dimensional images.


Journal ArticleDOI
Ming Zhao1
TL;DR: The maximum likelihood estimation of the change-point is derived and some numerical applications in software reliability modelling are presented.
Abstract: In this paper, we present the change-point problems in software reliability and hardware reliability. Some change-point models motivated by a basic software reliability model are proposed. It is shown that the proposed change-point models are slightly different from the common ones. The maximum likelihood estimation of the change-point is derived and some numerical applications in software reliability modelling are presented.

Journal ArticleDOI
01 Jan 1993
TL;DR: The results are interpreted as indicating generation of hydroxyl radicals within the secondary lysosomal compartment due to the occurrence of reactive ferrous iron, leading to peroxidative alterations of the lYSosomal membrane resulting in loss of lysOSomal membrane integrity with dissipation of the proton gradient and leakage of l Lysosomal contents, including hydrolytic enzymes, into the cell sap.
Abstract: The effects of hydrogen peroxide on cell viability and, in particular, on lysosomal integrity were investigated in a model system of cultured, established, macrophage-like J-774 cells. The cells were found to rapidly degrade added hydrogen peroxide, withstanding concentrations or = 500 microM resulted in a pronounced and rapid decrease in cell viability preceded by the loss of lysosomal integrity, as judged by the relocalization of acridine orange, a lysosomotropic weak base, in pre-labelled cells. Hydrogen peroxide-induced relocalization of acridine orange and cell death were either enhanced or much prevented, according to if the cells were initially allowed to endocytose ferric iron or the specific iron-chelator deferoxamine, respectively. Depletion of ATP, however, was not associated with the loss of lysosomal integrity and viability regardless of iron or deferoxamine pretreatment. Pre-exposure to E-64, an inhibitor of lysosomal thiol proteases, resulted in the reduction of both lysosomal membrane damage and cell death. The results are interpreted as indicating (i) generation of hydroxyl radicals within the secondary lysosomal compartment due to the occurrence of reactive ferrous iron, leading to (ii) peroxidative alterations of the lysosomal membrane resulting in (iii) loss of lysosomal membrane integrity with dissipation of the proton gradient and leakage of lysosomal contents, including hydrolytic enzymes, into the cell sap.

Journal ArticleDOI
TL;DR: The results show that the area of perfusion increase corresponds to the size of the receptive fields of afferent polymodal C fibres and must have been due in part to impulse conduction to, and release of transmitters from, axon endings terminating in skin outside the contact area of the probe.
Abstract: 1. Laser Doppler perfusion imaging was used to map the cutaneous vascular axon response induced by trains of electrical skin stimuli (1 ms, 2 Hz) on the dorsum of the hand, finger and foot in twenty-four healthy subjects. Conduction anaesthesia was applied to nerves supplying the stimulated skin areas. Subtraction of images recorded before and after stimulation was used for data analysis of the intensity and area of the response. 2. The stimulation evoked a localized perfusion increase around the stimulating electrode which lasted approximately 30 min and increased in intensity and area with increasing stimulation strength to a maximum at 20 pulses and 20 mA. The intensity and area of the response was greater on the hand than on the foot. 3. Approximating the response area as a circle, the maximal perfusion increase in the hand extended 9 +/- 3 mm (mean +/- S.D.) outside the perimeter of the stimulating electrode. When stimulating within skin which had been subjected to surface anaesthesia, no response occurred, but when stimulating at the border of surface-anaesthetized skin, the perfusion increase extended 2 +/- 1 mm (mean +/- S.D.) into anaesthetized skin. 4. The results show that the perfusion increase must have been due in part to impulse conduction to, and release of transmitters from, axon endings terminating in skin outside the contact area of the probe. It is concluded that the area of perfusion increase corresponds to the size of the receptive fields of afferent polymodal C fibres.

Journal ArticleDOI
TL;DR: Determinants of papillary thyroid cancer were evaluated in a questionnaire-based case-control study from southeastern Sweden and an increased risk was found for a pregnancy soon after puberty and Multiparity seemed to potentiate the effect from prior radiographic examinations.
Abstract: Determinants of papillary thyroid cancer were evaluated in a questionnaire-based case-control study from southeastern Sweden. A total of 104 cases, diagnosed from 1977 to 1987, and 387 randomly selected controls were included in the analyses. Female subjects with papillary cancer reported a work history as dentists/dental assistants, telephone operators, teachers, and day nursery personnel, and an occupational contact with chemicals and video display terminals more often than did controls. The 11 male cases more often reported working as mechanics and metal workers and having occupational contact with solvents. Other factors associated with increased risk for female papillary cancer were having private well water at the birth address; leisure time exposure to combustion smoke; low intake of cruciferous vegetables and seafood; and a family history of goiter, heart disease, biliary disorder, or female genital cancer. Diagnostic radiographic examinations, especially to the head, neck, or upper back/chest area, or repeated dental examinations, were also found to be associated with this form of cancer. With regard to the possible influence from hormonal factors among women less than age 50 years at time of diagnosis, an increased risk was found for a pregnancy soon after puberty. Tendencies toward a decreasing risk with increasing age at first pregnancy as well as an increasing risk with increasing number of pregnancies were found as well. Multiparity seemed to potentiate the effect from prior radiographic examinations.

Journal ArticleDOI
TL;DR: In this paper, the bending beam method was used to study the volume changes in polypyrole (PPy) by observing the bending behavior of a bipolymer laminate strip, made of a PPy layer and a polyethylene layer, during electrochemical redox of PPy.

Journal ArticleDOI
TL;DR: Transgenic micye containing a rat insulin‐I promoter‐human IAPP fusion gene is created to model islet amyloidogenesis in NIDDM and explore the glucoregulatory role of isletAmyloid polypeptide (IAPP) and other proposed functions of IAPP.

Journal ArticleDOI
TL;DR: In this article, the electronic structure of PPV was studied using photoelectron spectroscopy, UPS and XPS, and it was shown that the Na-doping of a PPV results in the formation of bipolaron bands in the otherwise forbidden energy gap at saturation doping.

Journal ArticleDOI
TL;DR: In this paper, an in vitro model is developed for application in studies of the optical and physical characteristics of flowing blood in rigid and flexible tubes (artificial vessels) The results indicate that both transmission and reflection of light are dependent on blood volume changes and orientation as well as the deformability of the red blood cells.
Abstract: An in vitro model is developed for application in studies of the optical and physical characteristics of flowing blood in rigid and flexible tubes (artificial vessels) The results indicate that both transmission and reflection of light are dependent on blood volume changes and orientation as well as the deformability of the red blood cells Light transmission and reflection in human blood shows a parabolic behavior at hematocrit levels greater than 40%, when plotted against blood flow At both low and high flow rates, the light transmission increases when compared to an intermediate flow where the transmission shows a minimum The optical wavelength used also affects the light transmission and reflection in moving blood The results of studies of blood in flow-through models are important for the understanding of the optical mechanisms behind the signal generation in photometrical measurement techniques

Journal ArticleDOI
TL;DR: In this paper, the ability of soil extracts to catalyze chlorination was investigated and it was found that chlorination of monochlorodimedone (MCD) and anisole followed by gas chomatographic analysis of chlorinated reaction products represented sensitive methods for determination of chloroperoxidase activity.
Abstract: The objectives of the present study were: (i) to evaluate methods for detection of low rates of chloroperoxidase activity in aqueous solutions; (ii) to investigate the ability of soil extracts to catalyze chlorination; (iii) to investigate if the catalyzing ability of soil extracts is due to enzymatic activity. Initially, solutions of a commercially-available chloroperoxidase (EC 1.11.1.10, CPO) were studied, and it was found that chlorination of monochlorodimedone (MCD) and anisole followed by gas chomatographic analysis of chlorinated reaction products represented sensitive assay methods for determination of chloroperoxidase activity. Using these methods, eight out of nine soil extracts, obtained by performing a modified peroxidase extraction procedure, were found to catalyze chlorination. Further experimentation provided the following information: (i) the reaction did not proceed in the absence of hydrogen peroxide; (ii) the catalyst had a molecular weight larger than 10,000; (iii) the incorporation of chlorine was strongly pH-dependent, with an optimum at pH 3.0–3.5; (iv) the reaction was inhibited by orcinol, resorcinol and phloroglucinol. All these properties are similar to those of the commercial chloroperoxidase. It was therefore concluded that a chloroperoxidase-like catalyst was present in the investigated soils.

Journal Article
TL;DR: Acute pancreatitis in rats causes systemic bacterial colonisation, probably as a result of bacterial translocation, which may therefore be a mechanism of pancreatic infection.
Abstract: Objective To see if bile-induced pancreatitis could cause bacterial translocation to mesenteric lymph nodes, and therefore pancreatic necrosis, in rats. Design Controlled experiment. Material 18 Male Wistar rats. Interventions Pancreatitis was induced in the experimental group (n = 12) by infusion of 0.2 ml of a solution containing 4 mumol (20 mumol/ml) sodium taurodeoxycholate into the pancreatic duct over one minute. The controls had sham operations (no infusion). Two days later repeat laparotomy was done on all surviving animals and samples taken for microbiological analysis. All animals were weighed at the beginning and end of the experiment. Results Bacteria were isolated from the mesenteric lymph nodes in all survivors in the experimental group (9/12), and from the pancreas in all but one. Blood and peritoneal fluid were colonised in 5 and 7 rats, respectively. Escherichia coli was the most common organism isolated. Positive anaerobic cultures were obtained from mesenteric lymph nodes in 5, and from the pancreas in one. Rats with pancreatitis developed overgrowth of both aerobic and anaerobic bacteria in the caecum and the ileum, but on light microscopic examination the proximal and distal intestinal mucosa did not differ between control and experimental rats. Bacterial translocation increased as the condition of the animals worsened. Conclusion Acute pancreatitis in rats causes systemic bacterial colonisation, probably as a result of bacterial translocation, which may therefore be a mechanism of pancreatic infection.

Journal ArticleDOI
TL;DR: Additional enzymatic and immunological characterization of mitochondria are reported, suggesting a more generalized abnormality of the synthesis, import, processing, or assembly of a group of proteins containing iron-sulfur clusters.
Abstract: Recently, we described a patient with severe exercise intolerance and episodic myoglobinuria, associated with marked impairment of succinate oxidation and deficient activity of succinate dehydrogenase and aconitase in muscle mitochondria (1). We now report additional enzymatic and immunological characterization of mitochondria. In addition to severe deficiency of complex II, manifested by reduction of succinate dehydrogenase and succinate:coenzyme Q oxidoreductase activities to 12 and 22% of normal, respectively, complex III activity was reduced to 37% and rhodanese to 48% of normal. Furthermore, although complex I activity was not measured, immunoblot analysis of complex I showed deficiency of the 39-, 24-, 13-, and 9-kD peptides with lesser reductions of the 51- and 18-kD peptides. Immunoblots of complex III showed markedly reduced levels of the mature Rieske protein in mitochondria and elevated levels of its precursor in the cytosol, suggesting deficient uptake into mitochondria. Immunoreactive aconitase was also low. These data, together with the previous documentation of low amounts of the 30-kD iron-sulfur protein and the 13.5-kD subunit of complex II, compared to near normal levels of the 70-kD protein suggest a more generalized abnormality of the synthesis, import, processing, or assembly of a group of proteins containing iron-sulfur clusters.

Journal ArticleDOI
01 Feb 1993-Cancer
TL;DR: A study of representative patients with cutaneous malignant melanoma performed to investigate the role of patient selection in the results of surgical treatment of this disease.
Abstract: Background. Results of surgical treatment of cutaneous malignant melanoma (CMM) have been highly variable, probably because of patient selection. Therefore, a study of representative patients with this disease was performed. Methods. In a defined area of Sweden, 581 patients were analyzed. Clinical records and histopathologic findings were reviewed. The minimum follow-up time was 7 years. Prognostic factors were evaluated by the Cox proportional hazards model. Results. Evaluation of sex distribution, age, and anatomic site of the primary tumor showed that the patients were representative of all Swedish patients with CMM of the head and neck. The mean patient age at diagnosis was 64 years for both sexes. Fifty-three percent of the patients were women. Female patients had more tumors of the face than did male patients, whereas male patients were overrepresented among patients with tumors of the auricle-external ear canal and scalp-neck area. Localization to the face was observed in 68%, which is an overrepresentation of three to four times when skin surface is taken into consideration. Twenty-four percent of the patients had lentigo maligna melanoma. Only 33% of the patients had superficial spreading melanoma. In univariate analyses, sex, anatomic site of the primary tumor, histogenetic type, Clark level of invasion, and tumor thickness had prognostic power. In a multivariate analysis, tumor thickness, anatomic site of the primary tumor, and sex of the patient were independent prognostic factors. Conclusions. In representative patients with CMM of the head and neck, tumor thickness, anatomic site of the primary tumor, and sex of the patients were independent prognostic factors.

Journal ArticleDOI
TL;DR: The susceptibility in SJL mice to develop ANoA during mercury treatment was codominantly inherited in a cross with mice carrying the H-2b and H2d haplotypes, and non-H-2 genes dampened A noA expression to a degree which varied between the strains.

Journal ArticleDOI
TL;DR: In this paper, a model for the behaviour of the contact interface is proposed and combined with the conventional equations of linear thermoelasticity for the bulk material of the contacting bodies.

Journal ArticleDOI
TL;DR: 131 patients treated by radical prostatectomy for localized prostatic cancer were studied with regard to quality of life and only distress due to lack of erection persisted, but the overall well-being after 18 months was nevertheless better than before treatment.

Journal ArticleDOI
TL;DR: A transformation matrix is derived that makes it possible to theoretically attain the full-dimension Cramer-Rao bound also in the reduced space and the problem of estimating parameters of sinusoidal signals from noisy data is addressed by a direct application of the results derived herein.

Proceedings ArticleDOI
15 Dec 1993
TL;DR: In this contribution the connections between frequency domain and time domain expressions are discussed and some aspects of using frequency domain data as primary observations are considered.
Abstract: The usefulness of frequency domain interpretations in linear systems is well known. In this contribution the connections between frequency domain and time domain expressions are discussed. In particular, the author considers some aspects of using frequency domain data as primary observations. >

Journal ArticleDOI
TL;DR: In this paper, the bending beam method was used to detect and make use of volume changes in conjugated polymers during electrochemical doping and undoping of polypyrrole (PPy) in aqueous solutions.