Showing papers by "Helsinki University of Technology published in 1991"
TL;DR: The results show that visual information from articulatory movements has an entry into the auditory cortex, which could be explained by activity in the supratemporal auditory cortex.
398 citations
TL;DR: In this paper, the use of phase change materials (PCM) for short-term heat storage in direct-gain passive solar applications is discussed, and approximate formulae are presented for optimum phase change temperature and the thickness of a PCM wall.
314 citations
TL;DR: Mutual friction is calculated within a microscopic quantum-mechanical Green's-function formalism, valid for dynamical processes, and it is predicted that strong dissipation should be observed at a resonant frequency of about 10 kHz, owing to transitions between the bound-state energy levels.
Abstract: The motion of singular quantized vortex lines in superfluid $^{3}\mathrm{He}$ is considered for the A and B phases. Mutual friction is calculated within a microscopic quantum-mechanical Green's-function formalism, valid for dynamical processes. This enables us to include all the different physical phenomena in a unified approach. We consider axisymmetric vortices for temperatures considerably lower than ${\mathit{T}}_{\mathit{c}}$. In this regime, the main contribution to the force exerted on a moving vortex originates from the localized Fermi excitations occupying quantized energy eigenstates in the vortex core. These $^{3}\mathrm{He}$ quasiparticle states are similar to the quantized motion of charge in a magnetic field; thus vortex motion in $^{3}\mathrm{He}$ resembles the Hall phenomenon in metals. The outcome is that the viscous drag cannot simply be expressed through the cross sections for $^{3}\mathrm{He}$ quasiparticles scattering off the vortex, but is rather due to the mutual interactions between the localized quasiparticles and the normal excitations. Our calculations conform with the experimental values for the mutual-friction parameters. We also discuss vortex oscillations, and predict that strong dissipation should be observed at a resonant frequency of about 10 kHz, owing to transitions between the bound-state energy levels. This effect could be used for detecting and measuring the quantization of the bound-state spectrum for superfluid $^{3}\mathrm{He}$ in the vortex-core matter.
273 citations
TL;DR: In this article, an error analysis for the recently introduced mixed-interpolated finite element methods for Reissner-Mindlin plates is given, which are valid uniformly with respect to the thickness of the plate.
Abstract: We give an error analysis for the recently introduced mixed-interpolated finite element methods for Reissner-Mindlin plates. Optimal error estimates, which are valid uniformly with respect to the thickness of the plate, are proven for the deflection, rotation and the shear force. In addition, the earlier families are augmented with a new method with linear approximations for the deflection and the rotation. We also introduce a simple postprocessing method by which an improved approximation for the deflection can be obtained.
216 citations
TL;DR: Results show that attention can modify the activity of two different areas in the supratemporal auditory cortex, including changed activity in neurons underlying N100m to relevant tones and the later effect as a modification of P200m to irrelevant tones.
189 citations
TL;DR: In this article, a new method for cloud attenuation calculation on an earth-satellite link is presented, which uses temperature and humidity profiles as input parameters, and has been applied to radiosonde measurements and to the gridded data of the numerical analyses of ECMWF.
Abstract: A new method for cloud attenuation calculation on an earth–satellite link is presented. The method uses temperature and humidity profiles as input parameters. The method has been applied to radiosonde measurements and to the gridded data of the numerical analyses of ECMWF.
181 citations
TL;DR: Spontaneous magnetoencephalographic activity was recorded over the lateral aspects of the head in 3 healthy adults and the equivalent sources of the rhythm were in the supratemporal auditory cortex, and the activity may represent 'idling' of the auditory cortex.
158 citations
TL;DR: All mismatch fields, i.e., responses elicited by different deviant tones, as well as N100m to the standards and deviants, could be explained by neural activity in the supratemporal auditory cortex.
Abstract: Magnetic responses to frequent and infrequent auditory stimuli, all presented in the same stimulus block in randomized order, were recorded. The standard stimuli, comprising 90% of all the stimuli, were 100-ms, 1000 Hz, 90dB sinusoidal tone bursts. There were three deviant tones, each presented at a probability of 3.3%, which differed from the standard tone on one dimension only: frequency deviant (1500 Hz), intensity deviant (67dB SPL), or duration deviant (50 ms). All mismatch fields, i.e., responses elicited by different deviants, as well as N100m to the standards and deviants, could be explained by neural activity in the supratemporal auditory cortex. The source of N100m to standards and deviants was significantly posterior to the sources for the three different mismatch fields. The mean locations of the equivalent dipoles for the different mismatch fields did not differ significantly from each other, but some differences were found for individual subjects.
147 citations
Abstract: The constitutive relations of general bi-isotropic media, requiring four material parameters, can be written in different ways to describe their electromagnetic behavior. This communication contains a two-way “dictionary” between a proposed formulation of the constitutive relations with three other sets of relations, generalized from relations used for chiral materials.
143 citations
TL;DR: In this paper, the concept of propagation invariance in partially coherent optics is introduced and explicit expressions for the cross-spectral density and the angular correlation function (crossangular spectrum) characterizing a class of fields that are propagation invariant in the sense that their correlation properties in the space-frequency domain are exactly the same in every transverse plane.
Abstract: The concept of propagation invariance in partially coherent optics is introduced. Explicit expressions are given for the cross-spectral density and the angular correlation function (cross-angular spectrum) characterizing a class of fields that are propagation invariant in the sense that their correlation properties in the space-frequency domain are exactly the same in every transverse plane. The so-called diffraction-free beams are shown to be members of this new, wider class of wave fields, which itself is a subset of a generalized class of partially coherent self-imaging fields. The existence of partially coherent propagation-invariant fields with a sharp correlation peak is verified experimentally by considering radiation from a planar J0 Bessel-correlated source.
132 citations
TL;DR: The findings point to the need for a possible reassessment of the dietary requirements of young infants, with respect to minor and trace elements, particularly for the elements Ca, Cr, Cu, F, Fe, Mg, Mn, Mo, P, and Zn.
Abstract: Concentrations of As, Ca, Cd, Cl, Co, Cr, Cu, F, Fe, Hg, I, K, Mg, Mn, Mo, Na, Ni, P, Pb, Sb, Se, Sn, V, and Zn were determined in human whole milk samples from Guatemala, Hungary, Nigeria, Phillippines, Sweden, and Zaire; in most of these countries, three groups of subjects representing different socioeconomic conditions were studied. Analytical quality control was a primary consideration throughout. The analytical techniques used were atomic absorption spectrophotometry, atomic emission spectrometry with an inductively coupled plasma, colorimetry, electrochemistry, using an ionselective electrode and neutron activation analysis. The differences between median concentrations of Ca, Cl, Mg, K, Na, and P (minor elements) were lower than 20% among the six countries. Among trace elements, concentrations observed in Filipino milk for As, Cd, Co, Cr, Cu, F, Fe, Mn, Mo, Ni, Pb, Sb, Se, and V were higher than for milk samples from other countries. The remaining five countries showed a mixed picture of high and low values. In the case of at least some elements, such as, F, I, Hg, Mn, Pb, and Se, the environment appears to play a major role in determining their concentrations in human milk. The nutritional status of the mother, as reflected by her socioeconomic status, does not appear to influence significantly the breast milk concentrations of minor and trace elements. Significant differences exist between the actual daily intakes observed in this study and current dietary recommendations made by, for example, WHO and the US National Academy of Sciences. These differences are particularly large (an order of magnitude or more!) for Cr, F, Fe, Mn, and Mo; for other elements, such as, Ca, Cu, Mg, P, and Zn, they amount to at least a factor 2. In the opinion of the present authors, these findings point to the need for a possible reassessment of the dietary requirements of young infants, with respect to minor and trace elements, particularly for the elements Ca, Cr, Cu, F, Fe, Mg, Mn, Mo, P, and Zn.
TL;DR: This paper examined magnetic cortical responses of 15 healthy humans to 46 different pictures of faces and found at least three areas outside the occipital visual cortex appeared to be involved in processing this input, 105-560 ms after the stimulus onset.
TL;DR: The results indicate that crackling lung sounds in different diseases have distinctive features and that their analysis can be of diagnostic value.
TL;DR: The effects of mechanical ventilation on the sick building syndrome (SBS) were studied in an office building with 2150 employees, where the mechanical ventilation and indoor air quality were commonly blamed for causing symptoms typical of the SBS.
Abstract: The effects of mechanical ventilation on the sick building syndrome (SBS) were studied in an office building with 2150 employees, where the mechanical ventilation and indoor air quality were commonly blamed for causing symptoms typical of the SBS (nasal, eye, and mucous membrane symptoms, lethargy, skin symptoms and headache). The mechanical ventilation rates in the building were high (mean 26 l/s/person). To test the hypothesis that mechanical ventilation causes the SBS, a controlled experimental study was carried out by shutting off the ventilation in one part of the building and reducing the ventilation rate by 75% and 60% in two areas while leaving one part unaltered as a control. The experimental reduction of the ventilation rate did not alleviate the symptoms. On the contrary, the reduction of the ventilation rate caused a slight but statistically significant relative increase in symptoms (p < 0.05). In the cross-sectional analysis of the baseline data the SBS symptoms did not associate significantly with the ventilation rate (range 7–70 l/s/person). In the linear regression model, a positive correlation was found between temperatures above 22°C and the occurrence of symptoms (p < 0.05). Subjects exposed to environmental tobacco smoke had more symptoms than those not exposed (p < 0.01). Women reported more symptoms than men (p < 0.001). In addition, any prior history of allergic diseases (p < 0.001) and a negative attitude towards the social atmosphere at work (p < 0.001) were significant determinants of the SBS.
TL;DR: The localization model and high-resolution magnetocardiographic (HR-MCG) mapping were applied to localize noninvasively the ventricular preexcitation site in ten patients suffering from Wolff-Parkinson-White syndrome.
Abstract: A fast and numerically effective biomagnetic inverse solution using a moving current dipole in a realistic homogeneous torso is described. The localization model and high-resolution magnetocardiographic (HR-MCG) mapping were applied to localize noninvasively the ventricular preexcitation site in ten patients suffering from Wolff-Parkinson-White syndrome. In all cases, the computed localization results were compared to the results obtained by the invasive catheter technique. Using a standard-size torso model in all cases, the average 3-D distance between the computed noninvasive locations and the invasively obtained results was 2.8+or-1.4 cm. When the torso was rescaled to better match the true shape of the subject, the 3-D average was improved to 2.2+or-1.0 cm. This accuracy is very satisfactory, suggesting that the method would be clinically useful. >
TL;DR: The introduction of multichannel superconducting quantum interference device magnetometers with over 20 sensors is now revolutionizing MEG recordings, and data are starting to accumulate about the functions of different sensory systems.
Abstract: Magnetoencephalography (MEG) as a tool to study the brain's responses to external stimuli is briefly reviewed. The introduction of multichannel superconducting quantum interference device magnetometers with over 20 sensors is now revolutionizing MEG recordings, and data are starting to accumulate about the functions of different sensory systems. Magnetic evoked responses also can be used in clinical assessment of the integrity of sensory pathways.
01 Jan 1991
TL;DR: In this discussion, the Self-Organizing Map algorithm is related to the formalisms of stochastic approximation and optimization theory and derived of the optimal recursive formula for the basic Vector Quantization is included.
Abstract: In this discussion, the Self-Organizing Map algorithm is related to the formalisms of stochastic approximation and optimization theory. Derivation of the optimal recursive formula for the basic Vector Quantization is also included.
TL;DR: In this article, thin aluminium oxide thin films were prepared by the ALE process using AICI3 and A1(OR)3 (R = Et,Pr) as aluminium source and H2O, O2 or various aliphatic alcohols as oxygen source.
TL;DR: In this article, the theoretical performance limits of stationary Fourier spectrometers without mechanical scanning are analyzed and compared with the performance of a scanning Fourier Spectrometer employing uncollimated light are most favorable.
Abstract: Theoretical performance limits of stationary Fourier spectrometers without mechanical scanning are analyzed and compared with the performance of a scanning Fourier spectrometer. Spectrometers employing uncollimated light are most favorable. In amplitude-splitting interferometers the reduction in fringe visibility brought about by the extended source can be avoided and leads to high optical throughput in the corresponding spectrometer. In a stationary wave-front-splittirig interferometer, realized without a beam splitter, the fringe contrast depends on the size of the source. The use of a slit source increases the optical throughput of source-size-limited spectrometers.
TL;DR: In this paper, exact image theory is applied to the problem of electromagnetic wave scattering from a small dielectric object above an interface separating two isotropic and homogeneous media.
Abstract: Exact-image theory is applied to the problem of electromagnetic wave scattering from a small dielectric object above an interface separating two isotropic and homogeneous media. The object is assumed to be electrically small and far enough from the interface so that its internal field can be assumed to be uniform. The approach is applicable to any scatter that can be represented by an electric dipole.
TL;DR: In this paper, stability bounds for one-step and multistep discretizations of evolution equations are derived for a linear operator with respect to the resolvent of the generator.
Abstract: As many numerical processes for time discretization of evolution equations can be formulated as analytic mappings of the generator, they can be represented in terms of the resolvent. To obtain stability estimates for time discretizations, one therefore would like to carry known estimates on the resolvent back to the time domain. For different types of bounds of the resolvent of a linear operator, bounds for the norm of the powers of the operator and for their sum are given. Under similar bounds for the resolvent of the generator, some new stability bounds for one-step and multistep discretizations of evolution equations are then obtained.
TL;DR: The results show further that the configuration of {ital V}{sub As}{sup {minus}} is strongly relaxed inwards compared to the structure of{ital V}-type GaAs, which may be isolated or part of a complex.
Abstract: The properties of the native monovacancy defects are systematically investigated by positron-lifetime measurements in n-type GaAs with carrier concentrations of n=${10}^{15--}$${10}^{18}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$. The native defects present two ionization levels at ${\mathit{E}}_{\mathit{C}}$-30 meV and ${\mathit{E}}_{\mathit{C}}$-140 meV. The first corresponds to a charge transition 1-\ensuremath{\rightarrow}0 and the second to 0\ensuremath{\rightarrow}1+. The transitions are attributed to ionizations of As vacancy, which may be isolated or part of a complex. In a simple identification of the defect with ${\mathit{V}}_{\mathrm{As}}$, the ionization level at ${\mathit{E}}_{\mathit{C}}$-30 meV is attributed to the transition ${\mathit{V}}_{\mathrm{As}}^{\mathrm{\ensuremath{-}}}$\ensuremath{\rightarrow}${\mathit{V}}_{\mathrm{As}}^{0}$ and the ionization level at ${\mathit{E}}_{\mathit{C}}$-140 meV to the transition ${\mathit{V}}_{\mathrm{As}}^{0}$\ensuremath{\rightarrow}${\mathit{V}}_{\mathrm{As}}^{+}$. The results show further that the configuration of ${\mathit{V}}_{\mathrm{As}}^{\mathrm{\ensuremath{-}}}$ is strongly relaxed inwards compared to the structure of ${\mathit{V}}_{\mathrm{As}}^{0}$.
TL;DR: The results showed that epithelial cells attached and spread more readily on smooth than on rough, sandblasted titanium surfaces, suggesting that smooth of finely grooved titanium surfaces could be optimal in maintaining the adhesion and specialized phenotype of gingival epithelium cells.
Abstract: The localization of desmoplakins 1 and 2 (DP 1&2), components of desmosomes, vinculin, and actin, was studied in gingival epithelial cells grown on cell culture glass and on titanium plates with various surface topography. The results showed that epithelial cells attached and spread more readily on smooth than on rough, sandblasted titanium surfaces. Moreover, the cells appeared to develop more granular DP 1&2 immunoreactivity at their ventral surfaces when grown on smooth or etched titanium as compared to glass. In cells grown on sandblasted titanium surfaces, DP 1&2-specific immunoreactivity was primarily located at cell-cell contacts. Cells grown on smooth titanium surfaces harbored a fine network of actin filaments with apparent cell-to-cell organization. Vinculin was confined to cell-cell contact areas. No vinculin-containing focal adhesions could be detected, suggesting that the cells adhere either by means of close contacts, extracellular matrix contacts, or by means of hemidesmosomes. The findings suggest that smooth of finely grooved titanium surfaces could be optimal in maintaining the adhesion and specialized phenotype of gingival epithelial cells.
TL;DR: Four commercial strains and two mutants of the yeast speciesYarrowia lipolytica were screened using batch fermentation and strain A-101-1.14 (induced with UV irradiation) was found to be the most suitable for citric acid production from glucose hydrol, a byproduct of glucose production from potato starch.
Abstract: Four commercial strains and two mutants of the yeast species Yarrowia lipolytica were screened using batch fermentation. Strain Y. lipolytica A-101-1.14 (induced with UV irradiation) was found to be the most suitable for citric acid production from glucose hydrol (39.9% glucose and 2.1% other sugars), a byproduct of glucose production from potato starch. The specific rate of total citric and isocitric acid production was 0.138 g/g.h, the yield on consumed glucose 0.93 g/g, and the productivity achieved was as high as 1.25 g/L.h. All of the tested yeast strains were able to utilize only the glucose from the glucose hydrol medium. Thus, some residual higher oligosaccharides remained in the process effluent.
TL;DR: In this article, a small object located close to an interface is analyzed according to the exact image theory formulation, and the scatterer is assumed to be small compared with wavelength, permitting the electric-dipole approximation, and to have a scalar polarizability.
Abstract: Scattering by a small object located close to an interface is analyzed according to the exact-image theory formulation The scatterer is assumed to be small compared with wavelength, permitting the electric-dipole approximation, and to have a scalar polarizability After the derivation of the dipole moment, investigations concentrate on far-field scattering Backscattering enhancement and reversal of linear polarization are confirmed through statistical averaging over scatterer height and system orientation
TL;DR: In this paper, a model was developed for estimating elastic and shrinkage properties of a softwood cell-wall, which was enlarged to simulate the elastic properties of defect-free softwoods.
Abstract: In a previous article of the authors a model was developed for estimating elastic and shrinkage properties of a softwood cell-wall. In the present article this model is enlarged to simulate the elastic properties of defect-free softwoods. The wood model consists of earlywood, latewood and ray cells, each of which have a different cell-wall structure. In the model the ratio of earlywood to latewood is defined by a given wood density. The calculated elastic properties are in good agreement with test results.
TL;DR: High-resolution magnetocardiographic mapping was applied to localize the ventricular preexcitation site in ten patients suffering from Wolff-Parkinson-White syndrome, and the average three-dimensional difference between the invasive localization results and the HR-MCG results was smallest for the source model consisting of the magnetic dipole.
Abstract: High-resolution magnetocardiographic (HR-MCG) mapping was applied to localize the ventricular preexcitation site in ten patients suffering from Wolff-Parkinson-White syndrome. Three different source models were tested, consisting of current and magnetic dipole and the current quadrupole moments in a general multipole expansion. Noninvasive localizations were performed by computations based on measured magnetic maps without a priori assumptions of the source location and without imposing any constraints. In all cases, the computed results were compared with invasive localization results obtained by a catheter mapping technique. Preoperative catherization localizes the atrial end of the accessory pathway, while the authors' method localizes the ventricular preexcitation site. Of the models used the average three-dimensional difference between the invasive localization results and the HR-MCG results was smallest for the source model consisting of the magnetic dipole. >
11 Dec 1991
TL;DR: In this paper, the finite spectrum assignment law of linear systems is extended to single-input single-output (SISO) systems having a time-varying input delay and state prediction via the given system model is applied together with a state estimation procedure to obtain the feedback signal for the controller.
Abstract: The finite spectrum assignment law of linear systems is extended to single-input single-output systems having a time-varying input delay. State prediction via the given system model is applied together with a state estimation procedure to obtain the feedback signal for the controller. Ordinary pole placement design laws are used for determining the feedback, and estimator gains. The stable feedback control and estimator error systems are obtained to guarantee asymptotic tracking of a given reference model having the same time-varying delay as the original system. >