| 1. |
- Aspholm-Hurtig, Marina, et al.
(författare)
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Functional adaptation of BabA, the H. pylori ABO blood group antigen binding adhesin.
- 2004
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Ingår i: Science (New York, N.Y.). - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 305:5683, s. 519-22
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Tidskriftsartikel (refereegranskat)abstract
- Adherence by Helicobacter pylori increases the risk of gastric disease. Here, we report that more than 95% of strains that bind fucosylated blood group antigen bind A, B, and O antigens (generalists), whereas 60% of adherent South American Amerindian strains bind blood group O antigens best (specialists). This specialization coincides with the unique predominance of blood group O in these Amerindians. Strains differed about 1500-fold in binding affinities, and diversifying selection was evident in babA sequences. We propose that cycles of selection for increased and decreased bacterial adherence contribute to babA diversity and that these cycles have led to gradual replacement of generalist binding by specialist binding in blood group O-dominant human populations.
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| 2. |
- Bengtsson, Göran, et al.
(författare)
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Irregular walks and loops combines in small-scale movement of a soil insect : implications for dispersal biology
- 2004
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Ingår i: Journal of Theoretical Biology. - : Elsevier BV. - 0022-5193 .- 1095-8541. ; 231:2, s. 299-306
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Tidskriftsartikel (refereegranskat)abstract
- Analysis of small-scale movement patterns of animals we may help to understand and predict movement at a larger scale, such as dispersal, which is a key parameter in spatial population dynamics. We have chosen to study the movement of a soil-dwelling Collembola, Protaphorura armata, in an experimental system consisting of a clay surface with or without physical obstacles. A combination of video recordings, descriptive statistics, and walking simulations was used to evaluate the movement pattern. Individuals were found to link periods of irregular walk with those of looping in ahomogeneous environment as well as in one structured to heterogeneity by physical obstacles. The number of loops varied between 0 and 44 per hour from one individual to another and some individuals preferred to make loops by turning right and others by turning left. P. armata spent less time at the boundary of small obstacles compared to large, presumably because of a lower probability to track the steepness of the curvature as the individual walks along a highly curved surface. Food deprived P. armata had amore winding movement and made more circular loops than those that were well fed. The observed looping behaviour is interpreted in the context of systematic search strategies and compared with similar movement patterns found in other species.
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| 3. |
- Blazhev, A., et al.
(författare)
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Observation of a core-excited E4 isomer in Cd-98
- 2004
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 69
-
Tidskriftsartikel (refereegranskat)abstract
- A core-excited I-pi=(12(+)) spin-gap isomer was identified in Cd-98 in an experiment at EUROBALL IV. It was found to feed the known I-pi=(8(+)) seniority isomer by an E4 transition. Half-lives of T-1/2=0.23 ((+4)(-3)) mus and 0.17 ((+6)(-4)) mus were measured for the two states at E-x=6635 keV and 2428 keV, respectively. From the excitation energy of the core-excited isomer a Sn-100 shell gap of 6.46(15) MeV is inferred. The measured E4 and E2 strengths, Sn-100 core excitations and the origin of empirical polarization charges are discussed in the framework of large-scale shell model calculations. An E2 polarization charge for protons of deltae(pi)
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| 4. |
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| 5. |
- Britt, Östlund
(författare)
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Ageing and Technology
- 2004
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Ingår i: Science Studies. - 0786-3012. ; 17:2, s. 3-4
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Tidskriftsartikel (refereegranskat)
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| 6. |
- Britt, Östlund
(författare)
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Social Science Research on technology and the Elderly - does it exist?
- 2004
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Ingår i: Science Studies. - 0786-3012. ; 17:2, s. 44-62
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Despite the fact that old people´s technological needs have been payed much attention to in the last decennium, especially old users of information- and communication technology, technology has not found its natural place in research on ageing in modern societies. Purpose: This article examines to what extent social science research exist in the field of ageing and technology and where we can find the interface between technological and social science expertise. Method: Scientific publications during the period 1983-2002 are analysed in terms of theoretical content, the role of the elderly as being regarded as objects or subjects, and if technology is called into question in any respect. Result: Scientific well-grounded knowledge exist besides less well-substantiated assumptions regarding the effects of technology and a premature body of thoughts on the relationship between technology and the elderly.
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| 7. |
- Burmeister, F., et al.
(författare)
-
A study of the inner-valence ionization region in HCl and DCl
- 2004
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 37:6, s. 1173-1183
-
Tidskriftsartikel (refereegranskat)abstract
- An in-depth photoionization study of the inner-valence electrons in HCl and DCl has been performed using synchrotron radiation. A series of photoelectron spectra of HCl were obtained at a resolution of 23 meV over the binding energy range 25-30.5 eV at various excitation energies and at two different electron collection angles relative to the plane of polarization of the undulator radiation. In addition, photoelectron spectra of DCl were recorded at two different excitation energies. These spectra were compared directly with the threshold photoelectron spectra of HCl and DCl that were recorded previously under similar resolution conditions (similar to30 meV). This comparative study reveals new information on the nature of the numerous band systems observed in this binding energy region. In addition, we present the experimental confirmation of the theoretical prediction given by Andersson et al (2001 Phys. Rev. A 65 012705) that a vibrational progression showing interference structure would appear in the main inner-valence ionization band in the photoelectron spectrum of DCl at a resolution of 10 meV.
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| 8. |
- Busenlehner, L.S., et al.
(författare)
-
Stress sensor triggers conformational response of the integral membrane protein microsomal glutathione transferase 1
- 2004
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 43:35, s. 11145-11152
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Tidskriftsartikel (refereegranskat)abstract
- Microsomal glutathione (GSH) transferase 1 (MGST1) is a trimeric, integral membrane protein involved in cellular response to chemical or oxidative stress. The cytosolic domain of MGST1 harbors the GSH binding site and a cysteine residue (C49) that acts as a sensor of oxidative and chemical stress. Spatially resolved changes in the kinetics of backbone amide H/D exchange reveal that the binding of a single molecule of GSH/trimer induces a cooperative conformational transition involving movements of the transmembrane helices and a reordering of the cytosolic domain. Alkylation of the stress sensor preorganizes the helices and facilitates the cooperative transition resulting in catalytic activation.
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| 9. |
- Douc, R, et al.
(författare)
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Asymptotic properties of the maximum likelihood estimator in autoregressive models with Markov regime
- 2004
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Ingår i: Annals of Statistics. - : Institute of Mathematical Statistics. - 0090-5364 .- 2168-8966. ; 32:5, s. 2254-2304
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Tidskriftsartikel (refereegranskat)abstract
- An autoregressive process with Markov regime is an autoregressive process for which the regression function at each time point is given by a nonobservable Markov chain. In this paper we consider the asymptotic properties of the maximum likelihood estimator in a possibly nonstationary process of this kind for which the hidden state space is compact but not necessarily finite. Consistency and asymptotic normality are shown to follow from uniform exponential forgetting of the initial distribution for the hidden Markov chain conditional on the observations.
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| 10. |
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| 11. |
- Eriksson, Torny, et al.
(författare)
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Heterogeneity of homologously expressed Hypocrea jecorina (Trichoderma reesei) Cel7B catalytic module
- 2004
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Ingår i: European Journal of Biochemistry. - : Wiley. - 0014-2956 .- 1432-1033. ; 271:7, s. 1266-1276
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Tidskriftsartikel (refereegranskat)abstract
- The catalytic module of Hypocrea jecorina (previously Trichoderma reesei) Cel7B was homologously expressed by transformation of strain QM9414. Post-translational modifications in purified Cel7B preparations were analysed by enzymatic digestions, high performance chromatography, mass spectrometry and site-directed mutagenesis. Of the five potential sites found in the wild-type enzyme, only Asn56 and Asn182 were found to be N-glycosylated. GlcNAc(2)Man(5) was identified as the predominant N-glycan, although lesser amounts of GlcNAc(2)Man(7) and glycans carrying a mannophosphodiester bond were also detected. Repartition of neutral and charged glycan structures over the two glycosylation sites mainly accounts for the observed microheterogeneity of the protein. However, partial deamidation of Asn259 and a partially occupied O-glycosylation site give rise to further complexity in enzyme preparations.
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| 12. |
- Feifel, R., et al.
(författare)
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Profile of resonant photoelectron spectra versus the spectral function width and photon frequency detuning
- 2004
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 70:3
-
Tidskriftsartikel (refereegranskat)abstract
- The outermost, singly ionized valence state of N-2, the X (2)Sigma(g)(+) state, is investigated in detail as a function of the photon frequency bandwidth for core excitation to the N 1s-->pi(*) resonance, where the photon frequency is tuned in between the first two vibrational levels of this bound intermediate electronic state. We find a strong, nontrivial dependence of the resulting resonant photoemission spectral profile on the monochromator function width and the frequency of its peak position. For narrow bandwidth excitation we observe a well resolved vibrational fine structure in the final electron spectrum, which for somewhat broader bandwidths gets smeared out into a continuous structure. For even broader monochromator bandwidths, it converts again into a well resolved vibrational progression. In addition, spectral features appearing below the adiabatic transition energy of the ground state of N-2(+) are observed for broadband excitation. A model taking into account the interplay of the partial scattering cross section with the spectral function is presented and applied to the X (2)Sigma(g)(+) final state of N-2(+).
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| 13. |
- Feifel, R., et al.
(författare)
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Role of stray light in the formation of high-resolution resonant photoelectron spectra : an experimental and theoretical study of N-2
- 2004
-
Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 134:1, s. 49-65
-
Tidskriftsartikel (refereegranskat)abstract
- We show that the undular stray light, diffusely scattered by the optical system of a synchrotron beamline, can play an important role in the formation of high-resolution resonant photoelectron (RPE) spectra. The influence of the stray light is mediated through the Stokes doubling effect, with the Lorentzian tail of the spectral function being replaced by a more complicated form. This effect is shown to appear in the high-resolution resonant photoelectron spectrum of the N-2 molecule in which the spectral shape of the non-Raman (NR) bands differs qualitatively for the A(2)Pi(u) and X(2)Sigma(g)(+) final states. A particularly large enhancement of the non-Raman Stokes line is observed for the A-state while the picture is inverted for the X-state where the non-Raman band is suppressed. It is shown that the resonant photoemission profile is affected by two qualitatively different detunings, the detuning of the monochromatized line relative to the photoabsorption line and the detuning of the undulator harmonic relative to the same reference line. The experimental data show that the relative intensity of the non-Raman line strongly depends on the tuning of the undulator harmonic with respect to the selected monochromator bandpass, leading to a strong decrease of the Stokes line intensity for certain undulator detunings. A clear red-shift asymmetry for the decrease in the Stokes line intensity is observed when the monochromator line is detuned towards negative photon frequencies, whereas the picture is reverted for the situation of a positively detuned monochromator line. The results show the necessity to control the stray light and to investigate both the Raman and non-Raman contributions to the spectral profiles in order to avoid misinterpretation and in order to make full use of the information available in resonant photoemission spectra of molecules.
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| 14. |
- Friedlein, Rainer, et al.
(författare)
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Role of electronic localization and charge-vibrational coupling in resonant photoelectron spectra of polymers : Application to poly(para-phenylenevinylene)
- 2004
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 69:12
-
Tidskriftsartikel (refereegranskat)abstract
- A combination of x-ray absorption and resonant photoemission (RPE) spectroscopy has been used to study the electronic structure of the one-dimensional conjugated polymer poly (para-phenylenevinylene) in nonordered (as prepared) thin films. The dispersion of RPE features for the decay to localized and delocalized bands are qualitatively different. A theory for band dispersion of RPE in polymers is given, showing the important roles of electronic state localization and vibrational (phonon) excitations for the character of the dispersion.
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| 15. |
- Hedenmalm, Håkan, et al.
(författare)
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Mean value surfaces with prescribed curvature form
- 2004
-
Ingår i: Journal des Mathématiques Pures et Appliquées. - : Elsevier BV. - 0021-7824 .- 1776-3371. ; 83:9, s. 1075-1107
-
Tidskriftsartikel (refereegranskat)abstract
- The Gaussian curvature of a two-dimensional Riemannian manifold is uniquely determined by the choice of the metric. The formulas for computing the curvature in terms of components of the metric, in isothermal coordinates, involve the Laplacian operator and therefore, the problem of finding a Riemannian metric for a given curvature form may be viewed as a potential theory problem. This problem has, generally speaking, a multitude of solutions. To specify the solution uniquely, we ask that the metric have the mean value property for harmonic functions with respect to some given point. This means that we assume that the surface is simply connected and that it has a smooth boundary. In terms of the so-called metric potential, we are looking for a unique smooth solution to a nonlinear fourth order elliptic partial differential equation with second order Cauchy data given on the boundary. We find a simple condition on the curvature form which ensures that there exists a smooth mean value surface solution. It reads: the curvature form plus half the curvature form for the hyperbolic plane (with the same coordinates) should be less than or equal to 0. The same analysis leads to results on the question of whether the canonical divisors in weighted Bergman spaces over the unit disk have extraneous zeros. Numerical work suggests that the above condition on the curvature form is essentially sharp. Our problem is in spirit analogous to the classical Minkowski problem, where the sphere supplies the chart coordinates via the Gauss map.
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| 16. |
- Helgstrand, Magnus, et al.
(författare)
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QSim, a program for NMR simulations
- 2004
-
Ingår i: Journal of Biomolecular NMR. - 0925-2738 .- 1573-5001. ; 30:1, s. 71-80
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Tidskriftsartikel (refereegranskat)abstract
- We present QSim, a program for simulation of NMR experiments. Pulse sequences are implemented and analyzed in QSim using a mouse driven interface. QSim can handle almost any modern NMR experiment, using multiple channels, shaped pulses, mixing, decoupling, phase-cycling and pulsed field gradients. Any number of spins with any spin quantum number can, in theory, be used in simulations. Relaxation is accounted for during all steps of pulse sequences and relaxation interference effects are supported. Chemical kinetics between any numbers of states can be simulated. Both classical and quantum mechanical calculations can be performed. The result of a simulation can be presented either as magnetization as a function of time or as a processed spectrum.
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| 17. |
- Helsing, Johan, et al.
(författare)
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A Seventh-Order Accurate and Stable Algorithm for the Computation of Stress Inside Cracked Rectangular Domains
- 2004
-
Ingår i: International Journal for Multiscale Computational Engineering. - 1543-1649. ; 2:1, s. 47-68
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Tidskriftsartikel (refereegranskat)abstract
- A seventh-order accurate and extremely stable algorithm for the rapid computation of stress fields inside cracked rectangular domains is presented. The algorithm is seventh-order accurate since it incorporates basis functions, taking the asymptotic shape of the stress fields close to crack tips and corners into account at least up to order six. The algorithm is stable since it is based on a Predholm integral equation of the second kind. The particular form of the integral equation represents the solution as the limit of a function which is analytic inside the domain. This allows for an efficient implementation. In an example, involving 112 discretization points on an elastic square with a center crack, values of normalized stress intensity factors and T-stress with a relative error of 10(-6) are computed in seconds on a workstation. More points reduce the relative error down to 10(-15), where it saturates in double precision arithmetic. A large-scale setup with up to 1024 cracks in an elastic square is also studied, using up to 740,000 discretization points. The algorithm is intended as a basic building block in general-purpose solvers for fracture mechanics. It can also be used as a substitute for benchmark tables.
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| 18. |
- Huang, Ping, et al.
(författare)
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Light-induced multistep oxidation of dinuclear manganese complexes for artificial photosynthesis
- 2004
-
Ingår i: Journal of Inorganic Biochemistry. - : Elsevier BV. - 0162-0134 .- 1873-3344. ; 98:5, s. 733-745
-
Tidskriftsartikel (refereegranskat)abstract
- Two dinuclear manganese complexes, [Mn2BPMP(mu-OAc)(2)] . ClO4 (1, where BPMP is the anion of 2,6-bis {[N,N-di(2-pyridinemethyl)amino]methyl}-4-methylphenol) and [Mn2L(mu-OAc)(2)] . ClO4 (2, where L is the trianion of 2,6-bis{[N-(2-hydroxy-3,5-di-tert-butylbenzyl)-N-(2-pyridinemethyl)amino]methyl}-4-methylphenol), undergo several oxidations by laser flash photolysis, using ruthenium(II)-tris-bipyridine (tris(2,2-bipyridyl)dichloro-ruthenium(II) hexahydrate) as photo-sensitizer and penta-amminechlorocobalt(III) chloride as external electron acceptor. In both complexes stepwise electron transfer was observed. In 1, four Mn-valence states from the initial Mn-2(II,II) to the Mn-2(III,IV) state are available. In 2, three oxidation steps are possible from the initial Mn-2(III,III) state. The last step is accomplished in the Mn-2(IV,IV) state, which results in a phenolate radical. For the first time we provide firm spectral evidence for formation of the first intermediate state, Mn-2(II,III) in 1 during the stepwise light-induced oxidation. Observation of Mn-2(II,III) is dependent on conditions that sustain the mu-acetato bridges in the complex, i.e., by forming Mn-2(II,III) in dry acetonitrile, or by addition of high concentrations of acetate in aqueous solutions. We maintain that the presence of water is necessary for the transition to higher oxidation states, e.g., Mn-2(III,III) and Mn-2(III,IV) in 1, due to a bridging ligand exchange reaction which takes place in the Mn-2(II,III) state in water solution. Water is also found to be necessary for reaching the Mn-2(IV,IV) state in 2, which explains why this state was not reached by electrolysis in our earlier work (Eur. J. Inorg. Chem (2002) 2965). In 2, the extra coordinating oxygen atoms facilitate the stabilization of higher Mn valence states than in 1, resulting in formation of a stable Mn-2(IV,IV) without disintegration of 2. In addition, further oxidation of 2, led to the formation of a phenolate radical (g = 2.0046) due to ligand oxidation. Its spectral width (8 mT) and very fast relaxation at 15 K indicates that this radical is magnetically coupled to the Mn-2(IV,IV) center.
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| 19. |
- Hällqvist, Thomas, et al.
(författare)
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Numerical study of swirling impinging jets with heat transfer
- 2004
-
Ingår i: Proceedings of the ASME Heat Transfer/Fluids Engineering Summer Conference 2004, HT/FED 2004.
-
Konferensbidrag (refereegranskat)abstract
- Thispaper deals with numerical simulations of circular impinging jets withheat transfer, by means of Large Eddy Simulation (LES). TheLES code uses higher order finite-differences on staggered Cartesian non-uniformgrids. The current LES have the potential of dealing withtransition as well as providing data on details of largerscale structures, statistical correlations and turbulent spectral content. The impingingcircular jet has a nozzle-to-plate spacing ranging from 0.5 to2 nozzle diameters and the Reynolds number is 20000. Threedifferent swirl numbers have been considered, ranging from non-swirling tostrongly swirling flow. From the LES results the transition processin the jet is clearly detected. Swirling flow strongly influencesthe development of the jet. The wall heat transfer ratesbecome obstructed, even though the turbulence level increases.
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| 20. |
- Iftime, Orest, et al.
(författare)
-
A Grassmanian Approach to the Hankel Norm Approximation Problem
- 2004
-
Ingår i: Proceedings of the 16th International Symposium on Mathematical Theory of Networks and Systems, Leuven, Belgium.
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Konferensbidrag (refereegranskat)abstract
- This paper concerns the unifying framework to strictly contractive extension problems, which is usually referred to as the band method. The solution to the so-called strictly contractive extension problem in this abstract framework, when applied to a certain concrete case, yields a complete characterization of solutions to the sub-optimal Nehari problem. The sub-optimal Hankel norm approximation problem is a more general problem, which is closely related to the model reduction problem in control theory. It covers the Nehari problem as a special case, but does not fit into the existing abstract framework. This problem is addressed in the present paper. In this paper the Grassmannian version of the band method is suitable enlarged so as to include the sub-optimal Hankel norm approximation problem as a special case as well. Our abstract result is illustrated on two concrete problems, one for time-invariant infinite dimensional systems and the other for time-variant periodic finite dimensional systems.
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| 21. |
- Jackson, A D, et al.
(författare)
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Phase diagram of a rotating Bose-Einstein condensate with anharmonic confinement
- 2004
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 69:5, s. 053619-
-
Tidskriftsartikel (refereegranskat)abstract
- We examine the phase diagram of an effectively repulsive Bose-Einstein condensate of atoms that rotates in a quadratic-plus-quartic potential. With use of a variational method we identify the three possible phases of the system as a function of the rotational frequency of the trap and of the coupling constant. The derived phase diagram is shown to be universal and partly exact in the limit of weak interactions and small anharmonicity. The variational results are found to be consistent with numerical solutions of the Gross-Pitaevskii equation.
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| 22. |
- Jansson, D. S., et al.
(författare)
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Brachyspira hyodysenteriae and other strongly beta-haemolytic and indole-positive spirochaetes isolated from mallards (Anas platyrhynchos)
- 2004
-
Ingår i: Journal of Medical Microbiology. - : Microbiology Society. - 0022-2615 .- 1473-5644. ; 53:4, s. 293-300
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Tidskriftsartikel (refereegranskat)abstract
- The aims of the current study were to collect intestinal spirochaetes (genus Brachyspira) from farmed and wild mallards (Anas platyrhynchos) and to identify and classify those isolates that phenotypically resembled Brachyspira hyodysenteriae, an enteric pathogen of pigs. The isolation rate of Brachyspira spp. was high from both farmed (93%) and wild mallards (78%). In wild mallards, it appeared that Brachyspira spp. were more likely to be found in migratory birds (multivariate analysis: RR = 1(.)8, 95% Cl 1(.)1-3(.)1) than in mallards sampled in a public park. Pure cultures of putative B. hyodysenteriae were obtained from 22 birds. All five isolates from farmed mallards and ten randomly selected isolates with this phenotype were used for further studies. All isolates from farmed mallards and two of the isolates from wild mallards were PCR-positive for the tlyA gene of B. hyodysenteriae. Two isolates from farmed mallards were selected for pulsed field gel electrophoresis (PFGE) and randomly amplified polymorphic DNA (RAPD) analysis. These isolates clustered with the type and reference strains of B. hyodysenteriae. 16S rDNA sequence analysis performed on 11 of the strains showed that they were all closely related to each other and to the B. hyodysenteriae-Brachyspira intermedia cluster. Three of the mallard isolates had 16S rDNA sequences that were identical to those of B. hyodysenteriae strains R1 and NIV-1 previously isolated from common rheas (Rhea americana). To conclude, the isolates from farmed mallards and two isolates from wild mallards were classified as B. hyodysenteriae based on the factthat they could not be differentiated by any of the applied methods from type, reference and field strains of B. hyodysenteriae. The remaining isolates could not be assigned irrefutably to any of the presently recognized Brachyspira species. These results point to a broader host spectrum of B. hyodysenteriae than is generally recognized, and to the presence in mallards of strongly haemolytic and indole-producing spirochaetes that possess many, but not all, of the currently recognized characteristics of B. hyodysenteriae.
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| 23. |
- Johansson, Björn, et al.
(författare)
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Untripped SUV rollover detection and prevention
- 2004
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Ingår i: 2004 43RD IEEE CONFERENCE ON DECISION AND CONTROL (CDC), VOLS 1-5. - 0780386825 ; , s. 5461-5466
-
Konferensbidrag (refereegranskat)abstract
- Untripped Sport Utility Vehicle rollovers are dangerous and possibly lethal accidents. A new kinetic energy based measure, that indicates an imminent wheel lift-off, is introduced. This measure is used by a gain scheduled linear quadratic (LQ) controller to prevent wheel lift-off. The LQ controller outputs the desired changes of the forces acting on the chassis. These force changes acre mapped to braking and traction system commands by a control allocator. A new allocation strategy based on convex optimization is proposed. The controller is capable of preventing wheel lift-off in the simulated test cases.
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| 24. |
- Johansson, Tomas, et al.
(författare)
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Transcriptional responses of Paxillus involutus and Betula pendula during formation of ectomycorrhizal root tissue
- 2004
-
Ingår i: Molecular Plant-Microbe Interactions. - 0894-0282 .- 1943-7706. ; 17:2, s. 202-215
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Tidskriftsartikel (refereegranskat)abstract
- In order to obtain information on genes specifically expressed in the ectomycorrhizal symbiosis, 3,555 expressed sequence tags (ESTs) were analyzed from a cDNA library constructed from ectomycorrhiza formed between the basidiomycete Paxillus involutus and birch (Betula pendula). cDNA libraries from saprophytically growing fungus (3,964 ESTs) and from axenic plants (2,532 ESTs) were analyzed in parallel. By clustering all the EST obtained, a nonredundant set of 2,284 unique transcripts of either fungal or plant origin were identified. The expression pattern of these genes was analyzed using cDNA microarrays. The analyses showed that the plant and fungus responded to the symbiosis by altering the expression levels of a number of enzymes involved in carbon metabolism. Several plant transcripts with sequence similarities to genes encoding enzymes in the tricarboxylic cycle and electron transport chain were down regulated as compared with the levels in free-living roots. In the fungal partner, a number of genes encoding enzymes in the lipid and secondary metabolism were down regulated in mycorrhiza as compared with the saprophytically growing mycelium. A substantial number of the ESTs analyzed displayed significant sequence similarities to proteins involved in biotic stress responses, but only a few of them showed differential expression in the mycorrhizal tissue, including plant and fungal metallothioneins and a plant defensin homologue. Several of the genes that were differentially expressed in the mycorrhizal root tissue displayed sequence similarity to genes that are known to regulate growth and development of plant roots and fungal hyphae, including transcription factors and Rho-like GTPases.
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| 25. |
- Kao, ChungYao, et al.
(författare)
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Simple stability criteria for systems with time-varying delays
- 2004
-
Ingår i: Automatica. - : Elsevier BV. - 0005-1098 .- 1873-2836. ; 40:8, s. 1429-1434
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Tidskriftsartikel (refereegranskat)abstract
- This paper considers the problem of checking stability of linear feedback systems with time-varying but bounded delays. Simple but powerful criteria of stability are presented for both continuous-time and discrete-time systems. Using these criteria, stability can be checked in a closed loop Bode plot. This makes it easy to design the system for robustness.
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| 26. |
- Kao, Chung-Yao, et al.
(författare)
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A MATLAB toolbox for robustness analysis
- 2004
-
Ingår i: Proceedings of the IEEE International Symposium on Computer-Aided Control System Design. ; , s. 297-302, s. 297-302
-
Konferensbidrag (refereegranskat)abstract
- Verification of control systems is often done using extensive simulation. This gives the engineer useful qualitative information about the system performance. However, simulation cannot be used to rigorously prove stability and robustness of the system. Such properties can only be verified using mathematical analysis which for many realistic systems becomes rather involved. This paper presents the MATLAB toolbox IQCβ. It provides a user friendly interface for advanced semi-automatic systems analysis.
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| 27. |
- Karlgren, Daniel, et al.
(författare)
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High-angular-momentum structures in Zn-64
- 2004
-
Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 69, s. 1-034330
-
Tidskriftsartikel (refereegranskat)abstract
- High-angular-momentum states in Zn-64 were populated in the Ca-40(Si-28,4p) reaction at a beam energy of 122 MeV. Evaporated, light, charged particles were identified by the Microball, while gamma rays were detected using the Gammasphere array. The main focus of this paper is on two strongly coupled, collective bands. The yrast band, which was previously known, has been linked to lower-lying states establishing the excitation energies and angular momenta of in-band states for the first time. The newly identified excited band decays to the yrast band but firm angular-momentum assignments could not be made. In order to interpret these structures cranked-Nilsson-Strutinsky calculations have been performed. The calculations have been extended to account for the distribution of nucleons within a configuration. The yrast collective band is interpreted as based on the pi(f(7/2))(-1)(p(3/2)f(5/2))(2)(g(9/2))(1)nu(p(3/2)f(5/2))(4)(g(9/2))(2) configuration. There are several possible interpretations of the second band but it is difficult to distinguish between the different possibilities.
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| 28. |
- Kikas, A., et al.
(författare)
-
Resonant inelastic x-ray scattering at the F 1s photoabsorption edge in LiF : Interplay of excitonic and conduction states, and Stokes' doubling
- 2004
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 70:8
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Tidskriftsartikel (refereegranskat)abstract
- The excitation-decay processes at the F 1s photoabsorption edge in LiF crystal are studied using resonant inelastic x-ray scattering spectroscopy. The Raman-type linear dispersion and the narrowing of the x-ray fluorescence peak are observed at resonant excitation. A theoretical model based on the Kramers-Heisenberg formula describes well the main features in fluorescence spectra and allows one to separate the contributions of the exciton and the conduction states in the scattering spectra. At the same time, the role of the shape of the spectral distribution within the incident radiation is emphasized as being critically sensitive to the number, kind, and onset of the spectral features which finally appear in the scattering spectra at a particular incident photon energy, particularly in the subthreshold excitation region.
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| 29. |
- Kvikliene, Adriana, et al.
(författare)
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Modelling of nonlinear effects and the response of ultrasound contrast micro bubbles : simulation and experiment
- 2004
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Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X .- 1874-9968. ; 42:01-Sep, s. 301-307
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Tidskriftsartikel (refereegranskat)abstract
- The propagation of diagnostic ultrasonic imaging pulses in tissue and their interaction with contrast micro bubbles is a very complex physical process, which we assumed to be separable into three stages: pulse propagation in tissue, the interaction of the pulse with the contrast bubble, and the propagation of the scattered echo. The model driven approach is used to gain better knowledge of the complex processes involved. A simplified way of field simulation is chosen due to the complexity of the task and the necessity to estimate comparative contributions of each component of the process. Simulations are targeted at myocardial perfusion estimation. A modified method for spatial superposition of attenuated waves enables simulations of low intensity pulse pressure fields from weakly focused transducers in a nonlinear, attenuating, and liquid-like biological medium. These assumptions enable the use of quasi-linear calculations of the acoustic field. The simulations of acoustic bubble response are carried out with the Rayleigh-Plesset equation with the addition of radiation damping. Theoretical simulations with synthesised and experimentally sampled pulses show that the interaction of the excitation pulses with the contrast bubbles is the main cause of nonlinear scattering, and a 2-3 dB increase of second harmonic amplitude depends on nonlinear distortions of the incident pulse. (C) 2004 Elsevier B.V. All rights reserved.
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| 30. |
- Lenells, Jonatan, 1981-
(författare)
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A variational approach to the stability of periodic peakons
- 2004
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Ingår i: Journal of Nonlinear Mathematical Physics. - : Springer Science and Business Media LLC. - 1402-9251 .- 1776-0852. ; 11:2, s. 151-163
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Tidskriftsartikel (refereegranskat)abstract
- The peakons are peaked traveling wave solutions of an integrable shallow water equation. We present a variational proof of their stability.
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| 31. |
- Lenells, Jonatan, 1981-
(författare)
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Stability of Periodic Peakons
- 2004
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Ingår i: International mathematics research notices. - 1073-7928 .- 1687-0247. ; :10, s. 485-499
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Tidskriftsartikel (refereegranskat)
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| 32. |
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| 33. |
- Lenells, Jonatan, 1981-
(författare)
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Traveling wave solutions of the Camassa-Holm and Korteweg-de Vries equations
- 2004
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Ingår i: Journal of Nonlinear Mathematical Physics. - : Springer Science and Business Media LLC. - 1402-9251 .- 1776-0852. ; 11:4, s. 508-520
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Tidskriftsartikel (refereegranskat)abstract
- We show that the smooth traveling waves of the Camassa-Holm equation naturally correspond to traveling waves of the Korteweg-de Vries equation.
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| 34. |
- Lindahl, Lars, et al.
(författare)
-
Normative positions within an algebraic approach to normative systems
- 2004
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Ingår i: Journal of Applied Logic. - : Elsevier BV. - 1570-8683 .- 1570-8691. ; 2:1, s. 63-91
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Tidskriftsartikel (refereegranskat)abstract
- The formal analysis of normative systems as initiated by Alchourrón and Bulygin can be complemented by the analysis of normative positions as pursued by Kanger, Lindahl, Sergot and Jones. The paper is a step towards integrating the two approaches within an algebraic theory of so-called Boolean quasi-orderings (Bqo's). In the general Bqo theory presented, a number of theoretical tools are introduced and elucidated by theorems, in particular those of fragment, connection, coupling and pair coupling. Condition implication structures (cis's) are models of the Bqo theory used for the representation of normative systems. A system of normative positions is introduced as a special kind of cis. The final section is devoted to an example exhibiting a legal mini-system where a cis of normative positions (np-cis) is joined to a descriptive cis.
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| 35. |
- Lörstad, Daniel, et al.
(författare)
-
Assessment of volume of fluid and immersed boundary methods for droplet computations
- 2004
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Ingår i: International Journal for Numerical Methods in Fluids. - : Wiley. - 0271-2091 .- 1097-0363. ; 46:2, s. 109-125
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Tidskriftsartikel (refereegranskat)abstract
- The volume of fluid (VOF) and immersed boundary (IB) methods are two popular computational techniques for multi-fluid dynamics. To help shed light on the performance of both techniques, we present accuracy assessment, which includes interfacial geometry, detailed and global fluid flow characteristics, and computational robustness. The investigation includes the simulations of a droplet under static equilibrium as a limiting test case and a droplet rising due to gravity for Re less than or equal to 1000. Surface tension force models are key issues in both VOF and IB and alternative treatments are examined resulting in improved solution accuracy. A refined curvature model for VOF is also presented. With the newly developed interfacial treatments incorporated, both IB and VOF perform comparably well for the droplet dynamics under different flow parameters and fluid properties.
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| 36. |
- Lörstad, Daniel, et al.
(författare)
-
High-order surface tension VOF-model for 3D bubble flows with high density ratio
- 2004
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Ingår i: Journal of Computational Physics. - : Elsevier BV. - 0021-9991 .- 1090-2716. ; 200:1, s. 153-176
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Tidskriftsartikel (refereegranskat)abstract
- An improved Volume of Fluid (VOF) method is presented which is applicable to high density ratio 3D flows for a large range of bubble Reynolds number (Re). The method is based on the Navier-Stokes equations for incompressible multi-phase flows which are discretized on a Cartesian staggered grid. The multi-grid technique together with the pressure-velocity coupling scheme for multi-phase flows have resulted in an efficient solver which nearly exponentially converge with the number of iterations. The convergence speed also shows negligible dependence on density ratio, viscosity ratio and Re. A second-order accurate, non-diffusive, mass conservative phase transport model is presented which does not suffer from unphysical over- or under-shoots of the phase variable. The high accurate normal, curvature and surface tension force model in combination with the high-order defect-correction scheme for multi-phase flows shows second-order global accuracy when applied to the transient bubble rise where the viscosity ratio is equal to one. In contrast, the commonly used viscosity model for VOF introduces a first order error for the same problem. The VOF method has been tested for different types of bubble flows at low Re and for path-oscillating and wobbling air bubbles (in water) with a diameter range of 1.82 < D < 6 mm. The numerical results agree quantitatively with the available experimental data. The investigations show that the proposed high accurate surface tension model can be used successfully for wobbling flows with bubble deformation while maintaining the mass of the phases. The error in mass conservation is directly proportional to the residual in solving the discrete problem.
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| 37. |
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| 38. |
- Mihaescu, Mihai, et al.
(författare)
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Noise computation of a turbo-engine jet exhaust based on LES and lighthill's acoustic analogy
- 2004
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Ingår i: Proceedings of the ASME Turbo Expo 2004. - : ASME. ; 5 B, s. 1723-1731, s. 1723-1731
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Konferensbidrag (refereegranskat)abstract
- Increasing noise regulations at urban airports force jet engine manufactures to develop and build more quiet engines. Over recent years, a significant reduction in fan and mechanical noise has been achieved. However, the jet exhaust is the principal source of noise. The acoustical field that is generated by a turboengine jet exhaust running near the ground level is considered. The full equations of motion for compressible and unsteady flows describe both flow field and sound generation. The flow variables are decomposed into semi-compressible components and inviscid, irrotational acoustical components. The turbulent flow and mixing are computed using Large Eddy Simulation (LES). The radiated acoustical field is computed using the Lighthill's acoustic analogy with acoustic sources provided by instantaneous LES data.
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| 39. |
- Minkov, Ivaylo, et al.
(författare)
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Core-excitations of naphthalene : Vibrational structure versus chemical shifts
- 2004
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 121:12, s. 5733-5739
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Tidskriftsartikel (refereegranskat)abstract
- The initial state chemical shifts and vibrational fine structure of core excitations of naphthalene were analyzed using high-resolution x-ray photoelectron emission (XPS) and near-edge x-ray absorption fine structure (NEXAFS) spectra. The carbon atoms at peripheral sites were found to experience a small chemical shift and exhibit similar charge-vibrational coupling. The C-H stretching modes provide significant contributions to overall shape of spectra in the XPS spectra. The results show that vibrational fine structure dominates by particular C-C stretching modes, and in XPS of C2 and C3 sites also by high-energy C-H stretching modes.
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| 40. |
- Moroianu, Dragos, et al.
(författare)
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LES of the flow and particle ingestion into an air intake of a jet engine running on the ground
- 2004
-
Ingår i: Proc. ASME Turbo Expo. - : ASMEDC. ; 2, s. 209-217
-
Konferensbidrag (refereegranskat)abstract
- The flow field generated by the flow into a jet engine air-intake, with near ground effects, is considered. The axial inflow in the neighborhood of the ground generates a system of unsteady vortices. Some of these vortices extend from the air-intake towards the ground. Some of these vortices are strong enough to dislocate and even lift small objects from the ground up to the air-intake. The dynamics of the vortex system makes it difficult to study the problem by standard numerical and experimental methods. The dynamics of the vortices can be captured by using Large Eddy Simulations (LES), which is used here to enhance the understanding of the dynamics of the flow field. The computed flow field is used also to assess the ingestion of particles into the air-intake. It is shown that particles of several mm sizes can be ingested into the jet engine. This in turn may result in enhanced erosion of the compressor blades. The results of the computations in terms of mean velocity field have been compared to experimental data. These results are in good agreement with the experiments.
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| 41. |
- Olsson, Crister, et al.
(författare)
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DNA based classification of food associated Enterobacteriaceae previously identified by biolog GN microplates
- 2004
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Ingår i: Systematic and Applied Microbiology. - : Elsevier BV. - 0723-2020 .- 1618-0984. ; 27:2, s. 219-228
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Tidskriftsartikel (refereegranskat)abstract
- Enterobacteriaceae are frequently isolated from food products and it is essential to have methods for correct identification for both food hygiene and epidemiology reasons. Phenotypic methods are not always sufficient and have to be supplemented by DNA based methods. In the present study, 70 strains of Enterobacteriaceae derived from milk, fish and meat that had previously been identified by Biolog GN Microplates were genomically classified together with 15 representative type strains of species of Enterobacteriaceae. The field strains were dominated by Hafnia alvei, Serratia liquefaciens and Rahnella aquatilis. All strains were subjected to temporal temperature gel electrophoresis (TTGE) analysis using amplicons encompassing the V3, V4 and V9 variable regions of the 16S rRNA gene. Selected strains were analysed by ribotyping and partial 16S rDNA sequencing. The type strains were differentiated into 10 different TTGE groups. Two of the groups contained two type strains. Enterobacter aerogenes and Klebsiella planticola were not distinguished due to their identical sequences and Yersinia ruckeri and Citrobacter freundii showed the same migration pattern. The 70 food strains could be differentiated into 14 TTGE groups where 33 strains (47.1%) could be assigned to TTGE groups including type or reference strains. Rabnella strains were dispersed into three TTGE groups of which one group corresponded to Rahnella genomospecies 1 and one to genomospecies 3. The grouping of Rabnella strains was supported by ribotyping and phylogenetic analysis. TTGE can be a useful additional tool for identification on the species level of food related Enterobacteriaceae.
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| 42. |
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| 43. |
- Pan, Jingxi, et al.
(författare)
-
Stepwise charge separation from a ruthenium-tyrosine complex to a nanocrystalline TiO2 film
- 2004
-
Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 108:34, s. 12904-12910
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Tidskriftsartikel (refereegranskat)abstract
- A supramolecular complex composed of Ru(II) tris-bipyridine, tyrosine, and dipicolylamine was synthesized and characterized. This complex was attached to TiO2 nanocrystalline films via ester groups at the Ru(II) chromophore, and photoinduced multistep electron transfer was investigated by laser flash photolysis and electron paramagnetic resonance techniques. Following ultrafast electron injection from the metal-ligand charge transfer excited states of Ru(II) to the conduction band of TiO2, fast intramolecular electron transfer from the tyrosine moiety to the photogenerated Ru(III) was observed, characterized by a rate constant of similar to2 x 10(6) s(-1). By comparison of recovery kinetics at the isosbestic point with that of the reference compound lacking the tyrosine, it was found that the intramolecular electron-transfer efficiency is 90%. A hydrogen-bond-promoted electron-transfer mechanism is proposed.
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| 44. |
- Pettersson, Erik, et al.
(författare)
-
Surfactant/nonionic polymer interaction. a NMR diffusometry and NMR electrophoretic investigation
- 2004
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 20:4, s. 1138-1143
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Tidskriftsartikel (refereegranskat)abstract
- The interaction between the nonionic polymer poly(ethylene oxide) (PEO) of molecular weight 20 000 and surfactants of various types [sodium dodecyl sulfate (SDS), dodecyl trimethylammonium bromide, octyl beta-D-glucoside, and potassium laurate] has been investigated in an aqueous solution at 25 degreesC by H-1 NMR pulsed-gradient spin-echo self-diffusion techniques. The SDS/PEO study was further complemented by component-resolved H-1 NMR-based studies of the electrophoretic mobility of PEO and the alkyl part of SDS under the same measurement conditions. Through such combined studies, a much more complete picture of the binding and aggregation processes becomes accessible.
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| 45. |
- Rosendahl, Lars, 1971-, et al.
(författare)
-
Increase in muscle nociceptive substances and anaerobic metabolism in patients with trapezius myalgia : microdialysis in rest and during exercise
- 2004
-
Ingår i: Pain. - : Ovid Technologies (Wolters Kluwer Health). - 0304-3959 .- 1872-6623. ; 112:3, s. 324-334
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Tidskriftsartikel (refereegranskat)abstract
- Local metabolic changes are suggested to be involved in muscle pain development in humans. Nineteen women with chronic work-related trapezius myalgia (TM) and 20 healthy female controls (CON) were studied during baseline rest, 20 min repetitive low-force exercise, and 120 min recovery. Interstitial serotonin (5-HT), glutamate, lactate, pyruvate, and blood flow were determined by microdialysis in the trapezius muscle. Baseline pressure pain threshold (PPT) was lower (143+/-18 (TM) vs. 269+/-17 (CON) kPa) (mean +/- SEM), pain intensity (visual analogue scale, VAS) higher (33+/-5 vs. 2+/-1 mm), muscle 5-HT higher (22.9+/-6.7 vs. 3.8+/-1.3 nmol/l), and glutamate higher (47+/-3 vs. 36+/-4 mumol/l) in TM than in CON (all P<0.05), whereas muscle blood flow was similar in groups. Furthermore, muscle pyruvate was higher (180+/-15 vs. 135+/-12 mumol/l) and lactate higher (4.4+/-0.3 vs. 3.1+/-0.3 mmol/l) in TM than in CON (P<0.001). In response to exercise, VAS and glutamate increased in both TM and CON (all P<0.05). In TM only, lactate and pyruvate increased significantly (P<0.02), whereas blood flow increased to similar levels in both groups. During the initial 20 min recovery period, blood flow remained increased in TM (P<0.005) whereas it decreased to baseline levels in CON. In conclusion, patients with chronic work-related TM have increased levels of muscle 5-HT and glutamate that were correlated to pain intensity (r=0.55, P<0.001) and PPT (r=-0.47, P<0.001), respectively. In addition, TM was associated with increased anaerobic metabolism, whereas a normal rise in blood flow was seen with exercise. These findings indicate that peripheral nociceptive processes are active in work-related TM.
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| 46. |
- Rubel, Marek, et al.
(författare)
-
Overview of tracer techniques in studies of material erosion re-depostion and fuel inventory in tokamaks
- 2004
-
Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 329, s. 795-799
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Tidskriftsartikel (refereegranskat)abstract
- C-13 labeled methane and rhenium-boron coated plates were used at the JET tokamak as tracers for studies of the material transport, its erosion and re-deposition. Experimental procedures are described. The results are discussed in terms of processes underlying the material transport and the change of morphology of targets exposed to the plasma: physical sputtering, chemical erosion, prompt re-deposition. The influence of wall materials on fuel inventory is also addressed. C-14 measurements in the TEXTOR tokamak are presented and possibilities of using C-14 in carbon migration studies are considered.
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| 47. |
- Rydén, Tobias, et al.
(författare)
-
Hidden Markov models
- 2004
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Ingår i: Encyclopedia of Actuarial Science. - : Wiley-Blackwell. ; 2, s. 821-827, s. 821-827
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 48. |
- Sandberg, Henrik, et al.
(författare)
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A Bode sensitivity integral for linear time-periodic systems
- 2004
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Ingår i: Proceedings 43rd IEEE Conference on Decision and Control. - 0191-2216. - 0780386825 ; 3, s. 2644-2649
-
Konferensbidrag (refereegranskat)abstract
- For linear time-invariant systems Bode's sensitivity integral is a well-known formula that quantifies some of thelimitations in feedback control. In this paper we show that a very similar formula holds for linear time-periodicsystems. We use the infinite-dimensional frequency-response operator called the harmonic transfer function to prove the result. It is shown that the harmonic transfer function isan analytic operator and a trace class operator under the assumption that the periodic system has roll-off 2. A periodic system has roll-off 2 if the first time-varying Markov parameter is equal to zero.
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| 49. |
- Sandberg, Henrik, et al.
(författare)
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Balanced truncation of linear time-varying systems
- 2004
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Ingår i: IEEE Transactions on Automatic Control. - 0018-9286 .- 1558-2523. ; 49:2, s. 217-229
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, balanced truncation of linear time-varying systems is studied in discrete and continuous time. Based on relatively basic calculations with time-varying Lyapunov equations/inequalities we are able to derive both upper and lower error bounds for the truncated models. These results generalize well-known time-invariant formulas. The case of time-varying state dimension is considered. Input-output stability of all truncated balanced realizations is also proven. The method is finally successfully applied to a high-order model.
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| 50. |
- Sandberg, Henrik, et al.
(författare)
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Frequency-Domain Analysis of Linear Time-Periodic Systems
- 2004
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Ingår i: Proceedings of the 2004 American Control Conference.. - 0743-1619. - 0780383354 ; 4, s. 3357-3362
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Konferensbidrag (refereegranskat)abstract
- In this paper we study how a system with a time-periodic impulse response may be expanded into a sum of modulated time-invariant systems. This allows us to define a linear frequency-response operator for periodic systems, called the harmonic transfer function (HTF). Similar frequency-response operators have been derived before for sampled-data systems and periodic finite-dimensional state-space systems. The HTF is an infinite-dimensional operator that captures the frequency coupling of a time-periodic system. The paper includes analysis of convergence of truncated HTFs. For this reason the concepts of input/output roll-off are developed and related to time-varying Markov parameters.
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