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Showing papers by "Helsinki University of Technology published in 1977"


Journal ArticleDOI
TL;DR: In this paper, the use of N-point Pade approximants to analytically continue the complex frequency Green's function from the Matsubara points to the real frequency axis was studied.
Abstract: We study the use ofN-point Pade approximants to analytically continue the complex frequency Green's function from the Matsubara points to the real frequency axis. The method is applied to solutions of the Eliashberg equations and the approximants are compared with tabulated real frequency results. The overall agreement is good. We further show that the method can serve to make imaginary frequency calculations consistent with real frequency calculations by fixing the pseudopotential μ* to the energy gap Δ o .

458 citations


Journal ArticleDOI
TL;DR: In this article, the annihilation characteristics of a positron trapped in spherical clusters of 1., 50 vacancies in Al and Mo were calculated, and the results were found to depend sensitively on the void size up to a radius of about 5 A, beyond which the size dependence disappears.
Abstract: The annihilation characteristics of a positron trapped in spherical clusters of 1., 50 vacancies in Al and Mo are calculated. The results are found to depend sensitively on the void size up to a radius of about 5 A, beyond which the size dependence disappears. The residual resistivity is shown to be nearly independent of the microvoid size during initial stages of vacancy clustering. The sizes of the microvoids in electron irradiated Mo as a function of annealing temperatures are evaluated from recent experimental positron lifetime results.

143 citations


Journal ArticleDOI
TL;DR: Tracer response functions can be interpreted and used under conditions of variable flow, if they are presented in terms of an integrated flow variable and if the flow patterns are not affected by changes of flow rate.

142 citations


Journal ArticleDOI
TL;DR: The estimation of parameters in several dynamic models, which describe growth and substrate consumption, has been carried out using a modified Gauss–Newton‐type method using Trichoderma viride growing on glucose as the main carbon source.
Abstract: The estimation of parameters in several dynamic models, which describe growth and substrate consumption, has been carried out using a modified Gauss-Newton-type method. The four models considered are Monod, Contois, linear specific growth rate, and an enzyme kinetic model. The initial values of the differential equations are included in the parameter vector which will be estimated. The efficiency of the method and the confidence limits of the parameters were studied using simulated measurement noise. The experimental results describe Trichoderma viride growing on glucose as the main carbon source.

97 citations


Journal ArticleDOI
TL;DR: A model based upon a hypothesis of synaptic modification is constructed, and its behaviour is analysed with the aid of computer simulations to demonstrate the selective recall of a large number of signal patterns from an associative memory network based upon assumptions that are anatomically and physiologically feasible.

80 citations


Journal ArticleDOI
TL;DR: In this paper, the authors considered a Doppler broadened two-level system, where alternative absorption and emission from two oppositely travelling waves is interpreted as a multi-quantum absorption (or emission) process with quanta h kv.

68 citations


Journal ArticleDOI
TL;DR: It is concluded that after even brief periods of halothane or enflurane anesthesia patients should not drive or operate machinery for at least 7 hours, and the magnitudes and durations of the residual effects of both agents on psychomotor performance were less than those previously found after thiopental, methohexital, or diazepam.
Abstract: Recovery from anesthesia was assessed in a controlled manner in 34 healthy student volunteers, using a psychomotor test battery 1 and 5 hours and a driving simulator 2, 4.5, and 7 hours after 3.5 minutes of anesthesia with halothane or enflurane combined with nitrous oxide and oxygen. Psychomotor pe

50 citations


Journal ArticleDOI
TL;DR: In this paper, the Kohn-Sham density functional method is used to calculate selfconsistent electron densities around H, He and Li impurities in jellium host corresponding to Li, Al and Mg metals.

46 citations


Journal ArticleDOI
TL;DR: A computer method for quantification of fetal heart rate (FHR) variability from fetal magnetocardiography during pregnancy and from direct fetal electrocardiography during labor is presented, based on statistical analysis of the QRS interval sequences.

45 citations


Journal ArticleDOI
TL;DR: In this paper, the forward and reverse interactions between the SQUID input and output via the weak link are investigated in detail and presented in the form of an electronic equivalent circuit of the Squid.
Abstract: The forward and reverse interactions between the SQUID input and output via the weak link are investigated in detail and presented in the form of an electronic equivalent circuit of the SQUID. The input and output impedances and the gain of the SQUID are given. The noise properties for all kinds of source impedances are computed and optimal values derived.

39 citations


Journal ArticleDOI
TL;DR: In this paper, the clustering of atoms around slow positrons in helium gases is experimentally studied and the results are interpreted in terms of liquid drop formation, and the critical temperature and pressure of the droplet phase are found to be 6.6 K, 5.4 K, 7.6 atm in $2.4
Abstract: The clustering of atoms around slow positrons in helium gases is experimentally studied and the results are interpreted in terms of liquid drop formation. The critical temperature and pressure of the droplet phase are found to be 6.6 K, 5.4 atm in $^{2}\mathrm{He}$ and 8.4 K, 7.6 atm in $^{4}\mathrm{He}$. The critical densities coincide with those of the helium liquids.

Journal ArticleDOI
TL;DR: In this paper, the numerical solution of the nonlinear initial value problem was studied and sharp bounds for the global error were derived by relating the stability region of the method to the monotonicity properties of a nonlinear operator in real Hilbert space.
Abstract: We study the numerical solution of the nonlinear initial value problem $$\left\{ {\begin{array}{*{20}c} {{{du(t)} \mathord{\left/ {\vphantom {{du(t)} {dt}}} \right. \kern- ulldelimiterspace} {dt}} + Au(t) = f(t),t > 0} \\ {u(0) = c,} \\ \end{array} } \right.$$ whereA is a nonlinear operator in a real Hilbert space. The problem is discretized using linear multistep methods, and we assume that their stability regions have nonempty interiors. We give sharp bounds for the global error by relating the stability region of the method to the monotonicity properties ofA. In particular we study the case whereAu is the gradient of a convex functional φ(u).

Journal ArticleDOI
TL;DR: In this paper, a simple and mild technique to entrap glucose isomerase active A. missouriensis cells within α-cellulose beads has been developed, which is suitable for continuous isomerization of 45% glucose solution.
Abstract: A novel simple and mild technique to entrap glucose isomerase activeA. missouriensis cells within α-cellulose beads has been developed. Regenerated α-cellulose beads were shown by SEM to be highly loaded with microbial cells. Kinetics, high operational stability, reactor performance, and low cost of carrier showed the entrapped cell preparation to be suitable for continuous isomerization of 45% glucose solution. This paper was presented at the 4th Enzyme Engineering Conference, Bad Neuenahr, Germany. Sponsored by the Engineering Foundation, New York, New York.

Journal ArticleDOI
TL;DR: In this article, the K?h hypersatellite spectra of Mg, V, Cr, Mn, and Fe were measured with a plane crystal Bragg spectrometer for the first time in photon excitation.
Abstract: The K?h hypersatellite spectra of Mg, V, Cr, Mn, and Fe are measured with a plane crystal Bragg spectrometer for the first time in photon excitation. The experimental energies of the K?2h lines are obtained and the energies of the K?1,2 and K?1,2h lines are calculated using a multiconfiguration Dirac-Fock program of Desclaux. The K-shell double photoionization cross sections are estimated from the experimental hypersatellite intensities. Results agree qualitatively with existing theoretical calculations based on the shake theory and correlated wave functions.

Journal ArticleDOI
TL;DR: In this paper, the diagram-line energies and intensities of sulphur KLL Auger spectra for the gaseous compounds H2S, SO2 and SF6 are measured.

Journal ArticleDOI
TL;DR: In this article, a generalization of the Josephson-Lekner formalism was used to study the drag force on an ion in low-temperature, with higher order terms in the velocity and coherence factors in the superfluid phase.
Abstract: The drag force on an ion in low-temperature $^{3}\mathrm{He}$ is studied with a generalization of the Josephson-Lekner formalism, keeping higher-order terms in the velocity and coherence factors in the superfluid phase. In the normal state, a diffusive model for inelastic-scattering corrections provides an estimate of the onset velocity for nonlinearity in the drag force. Analytic calculations in $^{3}\mathrm{He}\ensuremath{-}B$ for elastic scattering at low and high velocity ($v\ensuremath{\ll}\frac{\ensuremath{\Delta}}{{p}_{F}}$ and $v\ensuremath{\gg}\frac{\ensuremath{\Delta}}{{p}_{F}}$) agree qualitatively with the experimental observations near ${T}_{c}$.

Journal ArticleDOI
TL;DR: In this paper, the band structures of the transition metal layer compounds ZrS2, TiS2 and TiSe2 in the 1T-phase were determined by means of the symmetrized self-consistent OPW method.
Abstract: The band structures of the transition metal layer compounds ZrS2, TiS2 and TiSe2 in the 1T-phase have been determined by means of the symmetrized self-consistent OPW method No additional constraints are set on the effective crystal potential Energy spectra and valence charge densities are discussed In addition, conclusions on the layer-layer interaction are drawn

Book ChapterDOI
TL;DR: In this article, it was shown that negative ion mobility increases rapidly below Tc in both superfluid 3He and normal 3He phases and that the ratio of negative ion to normal mobility is larger in the B phase than in the A phase.
Abstract: We have found that the mobility of negative ions increases rapidly below Tc in both superfluid 3He phases. The ratio μ/μN of superfluid to normal mobility is larger in the B phase than in the A phase. A critical velocity consistent in magnitude with the Landau limit for pair breaking has also been observed. In the normal fluid we find a temperature independent mobility between 40 mK and Tc for all pressures between 0 and 28 bar. The increase of μN with increasing pressure is in agreement with the bubble model for the negative ion.

Journal ArticleDOI
TL;DR: In this article, the theory of homogeneous filter is developed and results are employed to analyze tests made with SS430 fiber metal or stainless steel wool matrices, which seem to disagree with particle trajectory models quantitatively but show agreement with the creeping flow model qualitatively.
Abstract: Theory of homogeneous filter is developed. Results are employed to analyze tests made with SS430 fiber metal or stainless steel wool matrices. As regards filter efficiency, the experiments seem to disagree with particle trajectory models quantitatively but show agreement with the creeping flow model qualitatively. The method used is extended from laboratory to field experiments.

Journal ArticleDOI
TL;DR: Furoin reacts smoothly with dimethyl acetylenedicarboxylate via a Michael addition, which is followed by a dihydrofuran ring formation as mentioned in this paper.

Journal ArticleDOI
TL;DR: A new mycotoxin was isolated from a strain of Fusarium tricinctum cultivated for four months on a grain mixture and shown to be 4β, 8α-diacetoxy-12,13-epoxytrichotec-9-ene-3α, 15-diol by PMR and MS-analysis.

Journal ArticleDOI
TL;DR: In this paper, the renewal limit theorem for semi-Markov kernels is proved for α-recurrent (resp. α-transient, α-positive recurrent, α null recurrent) and α-negative recurrent (resp., α-null recurrent) models.

Journal ArticleDOI
TL;DR: In this paper, the Pekilo-process is used to produce single-cell protein from the spent sulphite liquor by fermenting a species of microfungi (Paecilomyces varioti), which serves also as a waste treatment unit by reducing the organic content of the spent liquor.

Journal ArticleDOI
TL;DR: In this article, a combination technique consisting of the interval length continuation method and the back-and-forth shooting method is proposed to solve the two-point boundary-value problem, and a numerical example of a problem originating in optimal control is given.
Abstract: We consider the solution of the following two-point boundary-value problem: $$\begin{gathered} \dot x(t) = f(t,x(t),p(t)), \dot p(t) = g(t,x(t),p(t)), t \in [0,T], \hfill \\ h(x(0),p(0)) = 0, p(T) = q. \hfill \\ \end{gathered} $$ We propose a combination technique consisting of the interval length continuation method and the back-and-forth shooting method. Certain alternative ways of employing continuation are discussed, and some of them are well suited for the problem under consideration. As a test for the method, a numerical example of a problem originating in optimal control is given.

Journal ArticleDOI
TL;DR: A new game theoretic worst case design method based on games with periodic open-closed information structure is proposed and applied to the design of a state regulator for a pilot process and the results suggest that this new approach can be successfull.
Abstract: Nash equilibrium strategies of general linear-quadratic two-player difference games with two kinds of periodic information structures are considered. Solution algorithms are developed for problems where the players' information is of periodic open-loop or periodic open-closed type. In the former case the players receive measurements of the state periodically only at the beginning of each interval and in the latter case one of the players has a perfect memory information of the state within each period. The solutions are obtained by recursive algorithms where a series of coupled difference equations of Riccati type are solved repeatedly and where the boundary values of these equations are determined by similar difference equations. A new game theoretic worst case design method based on games with periodic open-closed information structure is then proposed and applied to the design of a state regulator for a pilot process. The results obtained in the example suggest that this new approach can be successfull...

Journal ArticleDOI
TL;DR: In this paper, the authors compared Kelly's many-body-perturbation-theory calculations with absolute rates, obtained from experiments of Gelius et al. and Krause et al., with the mixing between the final 2S channels.

Journal ArticleDOI
TL;DR: In this article, the authors show that ifg is monotone andx(t) is smooth enough at infinity, then the global error tends to a trigonometric polynomial asn h??? with step size h fixed.
Abstract: We consider the numerical solution of the nonlinear initial value problem $$x' + g\left( x \right) = f\left( t \right), t > 0, x\left( 0 \right) = c \in R^n $$ by some linear multistep methods. We show that ifg is monotone andx(t) is smooth enough at infinity, then the global error tends to a trigonometric polynomial asn h ? ? with step sizeh fixed. Often the trigonometric polynomial vanishes identically.

Journal ArticleDOI
TL;DR: In this article, the residual resistivities of simple metals are estimated by using the Kohn-Sham method to calculate a self-consistent scattering potential for free electrons, compared to other calculations and experimental resistivities.


Journal ArticleDOI
TL;DR: In this article, an analogy between the Landau theory of phase transitions and lasers is discussed and it is shown that the AC-response of the output intensity to the modulation of the passive cavity losses gives an appealing correspondence to the specific heat.
Abstract: The well-known analogy between the Landau theory of phase transitions and lasers is discussed. It is shown that the AC-response of the output intensity to the modulation of the passive cavity losses gives an appealing correspondence to the specific heat. Experiments performed with a laser having an intracavity absorber are described to illustrate the first-order analogy.