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61.
Behrndt Jussi; Malamud Mark M.; Neidhardt Hagen 《Proceedings London Mathematical Society》2008,97(3):568-598
For a scattering system {A, A0} consisting of self-adjoint extensionsA and A0 of a symmetric operator A with finite deficiency indices,the scattering matrix {S()} and a spectral shift function arecalculated in terms of the Weyl function associated with a boundarytriplet for A*, and a simple proof of the Krein–Birmanformula is given. The results are applied to singular Sturm–Liouvilleoperators with scalar and matrix potentials, to Dirac operatorsand to Schrödinger operators with point interactions. 相似文献
62.
Sarah Klingler Benedikt Bagemihl Dr. Alexander K. Mengele Dr. Simon Kaufhold Dr. Pasi Myllyperkiö Dr. Jussi Ahokas Prof. Dr. Mika Pettersson Prof. Dr. Sven Rau Prof. Dr. Boris Mizaikoff 《Angewandte Chemie (International ed. in English)》2023,62(44):e202306287
Currently, most photosensitizers and catalysts used in the field of artificial photosynthesis are still based on rare earth metals and should thus be utilized as efficiently and economically as possible. While repair of an inactivated catalyst is a potential mitigation strategy, this remains a challenge. State-of-the-art methods are crucial for characterizing reaction products during photocatalysis and repair, and are currently based on invasive analysis techniques limiting real-time access to the involved mechanisms. Herein, we use an innovative in situ technique for detecting both initially evolved hydrogen and after active repair via advanced non-invasive rotational Raman spectroscopy. This facilitates unprecedently accurate monitoring of gaseous reaction products and insight into the mechanism of active repair during light-driven catalysis enabling the identification of relevant mechanistic details along with innovative repair strategies. 相似文献
63.
Walter M Häkkinen H Lehtovaara L Puska M Enkovaara J Rostgaard C Mortensen JJ 《The Journal of chemical physics》2008,128(24):244101
We present the implementation of the time-dependent density-functional theory both in linear-response and in time-propagation formalisms using the projector augmented-wave method in real-space grids. The two technically very different methods are compared in the linear-response regime where we found perfect agreement in the calculated photoabsorption spectra. We discuss the strengths and weaknesses of the two methods as well as their convergence properties. We demonstrate different applications of the methods by calculating excitation energies and excited state Born-Oppenheimer potential surfaces for a set of atoms and molecules with the linear-response method and by calculating nonlinear emission spectra using the time-propagation method. 相似文献
64.
Electron spin resonance (ESR) measurements were carried out to study the rotation of methyl radicals (CH3) in a solid argon matrix at 14-35 K temperatures. The radicals were produced by dissociating methane by plasma bursts generated either by a focused 193 nm laser radiation or a radio frequency discharge device during the gas condensation on the substrate. The ESR spectrum exhibits axial symmetry at the lowest temperature and is ascribed to ground state molecules with symmetric total nuclear spin function I=3/2. The hyperfine anisotropy (Aparallel)-Aperpendicular) was found to be -0.01 mT, whereas that of the g value was 2.5x10(-5). The anisotropy is observed for the first time in Ar and is manifested by the splitting of the low-field transition. Elevation of temperature leads reversibly to the appearance of excited state contribution having antisymmetric I=1/2. As a function of the sample temperature, the relative intensities of symmetric and antisymmetric spin states corresponding to ground and excited rotor states, respectively, proton hyperfine and electron g-tensor components, and spin-lattice relaxation rates were determined by a numerical fitting procedure. The experimental observations were interpreted in terms of a free rotation about the C3 axis and a thermal activation of the C2-type rotations above 15 K. The ground and excited rotational state energy levels were found to be separated by 11.2 cm-1 and to exhibit significantly different spin-lattice coupling. A crystal field model has been applied to evaluate the energy levels of the hindered rotor in the matrix, and crystal field parameter varepsilon4=-200 cm-1, corresponding to a 60 cm-1 effective potential barrier for rotation of the C3 axis, was obtained. 相似文献
65.
Jussi Laitila 《Integral Equations and Operator Theory》2007,58(4):487-502
Analytic composition operators
are studied on X-valued versions of BMOA, the space of analytic functions on the unit disk that have bounded mean oscillation on the unit
circle, where X is a complex Banach space. It is shown that if X is reflexive and C
φ is compact on BMOA, then C
φ is weakly compact on the X-valued space BMOA
C
(X) defined in terms of Carleson measures. A related function-theoretic characterization is given of the compact composition
operators on BMOA. 相似文献
66.
Moilanen P Talmant M Bousson V Nicholson PH Cheng S Timonen J Laugier P 《The Journal of the Acoustical Society of America》2007,122(3):1818
Previously it has been demonstrated that cortical bone thickness can be estimated from ultrasonic guided-wave measurements, in an axial transmission configuration, together with an appropriate analytical model. This study considers the impact of bone thickness variation within the measurement region on the ultrasonically determined thickness (UTh). To this end, wave velocities and UTh were determined from experiments and from time-domain finite-difference simulations of wave propagation, both performed on a set of ten human radius specimens (29 measurement sites). A two-dimensional numerical bone model was developed with tunable material properties and individualized geometry based on x-ray computed-tomography reconstructions of human radius. Cortical thickness (CTh) was determined from the latter. UTh data for simulations were indeed in a excellent accordance (root-mean-square error was 0.26 mm; r2=0.94, p<0.001) with average CTh within the measurement region. These results indicate that despite variations in cortical thickness along the propagation path, the measured phase velocity can be satisfactorily modeled by a simple analytical model (the A(0) plate mode in this case). Most of the variability (up to 85% when sites were carefully matched) observed in the in vitro ultrasound data was explained through simulations by variability in the cortical thickness alone. 相似文献
67.
Eigenvalues and eigenspaces of selfadjoint Schrödinger operators on are expressed in terms of Dirichlet-to-Neumann maps corresponding to Schrödinger operators on the upper and lower half space. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
68.
Jussi Behrndt 《Integral Equations and Operator Theory》2013,77(3):299-301
In this note we conjecture that the eigenvalues of singular indefinite Sturm–Liouville operators accumulate to the real axis whenever the eigenvalues of the corresponding definite Sturm–Liouville operator accumulate to the bottom of the essential spectrum from below. 相似文献
69.
Jussi Paatero K. Vesterbacka U. Makkonen K. Kyllönen H. Hellen J. Hatakka P. Anttila 《Journal of Radioanalytical and Nuclear Chemistry》2009,282(2):473-476
Two major wild fire episodes occurred in north-western Russia in April/May and August 2008. The burning biomass and heating
of the surface soil released several hazardous components into the atmosphere. During the spring smoke episode the 137Cs activity concentration in the air in southern Finland increased by a factor of 10 compared to values just before the episode.
Simultaneously there was an increase of a same order of magnitude in the concentrations of PM10, trace metals (e.g. lead), polycyclic aromatic hydrocarbons (e.g. benzo[a]pyrene) and potassium. The 210Po/210Pb activity ratio increased from the usual 3–5% to even as high as 35% because Po is more volatile than Pb. The summer episode
was less severe but still the mercury concentration in the air increased by a factor of two while 137Cs activity concentration rose by a factor of eight. From the radiological point of view the exposure to the increased radionuclide
concentration was insignificant compared to health hazards due to the increased concentration of aerosol particles and their
chemical components. 相似文献
70.
Antti Koponen Axel Ekman Keijo Mattila Ahmad M. Al-Qararah Jussi Timonen 《Transport in Porous Media》2017,117(2):247-259
A Kozeny–Carman-based model of permeability for fibrous networks is proposed: the original model is extended by incorporating information about the local structure of the void space. Furthermore, it is demonstrated how in practice this added structural information can be retrieved from a three-dimensional digital image of a fibrous material. The proposed model is then validated for both foam- and water-deposited laboratory sheets of bleached kraft pulp (Scots pine) and chemi-thermo-mechanical pulp (CTMP, Norway spruce). The validation is carried out by comparing the model predictions against computationally determined permeability values. The related fluid-flow simulations are executed using the lattice-Boltzmann method together with high-resolution X-ray microtomography images. For both pulp materials, the sample sets had nearly equal porosities, but deviated substantially in their permeabilities. The proposed model was shown to improve prediction of permeability for the fibrous materials considered: the deviation between the predicted and computationally determined values was no more than 8%. 相似文献