| 11. |
- Eriksson, Torny, et al.
(author)
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Heterogeneity of homologously expressed Hypocrea jecorina (Trichoderma reesei) Cel7B catalytic module
- 2004
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In: European Journal of Biochemistry. - : Wiley. - 0014-2956 .- 1432-1033. ; 271:7, s. 1266-1276
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Journal article (peer-reviewed)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.
(author)
-
Profile of resonant photoelectron spectra versus the spectral function width and photon frequency detuning
- 2004
-
In: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 70:3
-
Journal article (peer-reviewed)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.
(author)
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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
-
In: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 134:1, s. 49-65
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Journal article (peer-reviewed)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.
(author)
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Role of electronic localization and charge-vibrational coupling in resonant photoelectron spectra of polymers : Application to poly(para-phenylenevinylene)
- 2004
-
In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 69:12
-
Journal article (peer-reviewed)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.
(author)
-
Mean value surfaces with prescribed curvature form
- 2004
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In: Journal des Mathématiques Pures et Appliquées. - : Elsevier BV. - 0021-7824 .- 1776-3371. ; 83:9, s. 1075-1107
-
Journal article (peer-reviewed)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.
(author)
-
QSim, a program for NMR simulations
- 2004
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In: Journal of Biomolecular NMR. - 0925-2738 .- 1573-5001. ; 30:1, s. 71-80
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Journal article (peer-reviewed)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.
(author)
-
A Seventh-Order Accurate and Stable Algorithm for the Computation of Stress Inside Cracked Rectangular Domains
- 2004
-
In: International Journal for Multiscale Computational Engineering. - 1543-1649. ; 2:1, s. 47-68
-
Journal article (peer-reviewed)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.
(author)
-
Light-induced multistep oxidation of dinuclear manganese complexes for artificial photosynthesis
- 2004
-
In: Journal of Inorganic Biochemistry. - : Elsevier BV. - 0162-0134 .- 1873-3344. ; 98:5, s. 733-745
-
Journal article (peer-reviewed)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.
(author)
-
Numerical study of swirling impinging jets with heat transfer
- 2004
-
In: Proceedings of the ASME Heat Transfer/Fluids Engineering Summer Conference 2004, HT/FED 2004.
-
Conference paper (peer-reviewed)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.
(author)
-
A Grassmanian Approach to the Hankel Norm Approximation Problem
- 2004
-
In: Proceedings of the 16th International Symposium on Mathematical Theory of Networks and Systems, Leuven, Belgium.
-
Conference paper (peer-reviewed)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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