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71.
Hogben HJ Krzystyniak M Charnock GT Hore PJ Kuprov I 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2011,208(2):179-194
We introduce a software library incorporating our recent research into efficient simulation algorithms for large spin systems. Liouville space simulations (including symmetry, relaxation and chemical kinetics) of most liquid-state NMR experiments on 40+ spin systems can now be performed without effort on a desktop workstation. Much progress has also been made with improving the efficiency of ESR, solid state NMR and Spin Chemistry simulations. Spinach is available for download at http://spindynamics.org. 相似文献
72.
de Fouquieres P Schirmer SG Glaser SJ Kuprov I 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2011,212(2):412-417
We report some improvements to the gradient ascent pulse engineering (GRAPE) algorithm for optimal control of spin ensembles and other quantum systems. These include more accurate gradients, convergence acceleration using the Broyden–Fletcher–Goldfarb–Shanno (BFGS) quasi-Newton algorithm as well as faster control derivative calculation algorithms. In all test systems, the wall clock time and the convergence rates show a considerable improvement over the approximate gradient ascent. 相似文献
73.
Kummerlöwe G Grage SL Thiele CM Kuprov I Ulrich AS Luy B 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2011,209(1):19-30
The successful measurement of anisotropic NMR parameters like residual dipolar couplings (RDCs), residual quadrupolar couplings (RQCs), or residual chemical shift anisotropy (RCSA) involves the partial alignment of solute molecules in an alignment medium. To avoid any influence of the change of environment from the isotropic to the anisotropic sample, the measurement of both datasets with a single sample is highly desirable. Here, we introduce the scaling of alignment for mechanically stretched polymer gels by varying the angle of the director of alignment relative to the static magnetic field, which we call variable angle NMR spectroscopy (VA-NMR). The technique is closely related to variable angle sample spinning NMR spectroscopy (VASS-NMR) of liquid crystalline samples, but due to the mechanical fixation of the director of alignment no sample spinning is necessary. Also, in contrast to VASS-NMR, VA-NMR works for the full range of sample inclinations between 0° and 90°. Isotropic spectra are obtained at the magic angle. As a demonstration of the approach we measure 13C-RCSA values for strychnine in a stretched PDMS/CDCl? gel and show their usefulness for assignment purposes. In this context special care has been taken with respect to the exact calibration of chemical shift data, for which three approaches have been derived and tested. 相似文献
74.
We studied nonlinear effects in plasmonic metal film waveguides and couplers stimulated by third-order optical response due to ponderomotive metal nonlinearities. We analyzed the structure and dispersion of nonlinear plasmonic guided modes and predicted the bifurcations and symmetry breaking of nonlinear modes for the critical powers, depending on the structure dimensions. 相似文献
75.
Lanin AA Voronin AA Sokolov VI Fedotov IV Fedotov AB Akhmanov AS Panchenko VY Zheltikov AM 《Optics letters》2011,36(10):1788-1790
Slow-light effects induced by stimulated Raman scattering in polymer waveguides on a printed circuit board are shown to enable a widely tunable delay of broadband optical signals, suggesting an advantageous platform for optical information processing and ultrafast optical waveform transformation. 相似文献
76.
Voronin AA Fedotov IV Doronina-Amitonova LV Ivashkina OI Zots MA Fedotov AB Anokhin KV Zheltikov AM 《Optics letters》2011,36(4):508-510
Light-assisted ionization accompanying coherent anti-Stokes Raman scattering (CARS) of ultrashort laser pulses in brain tissue is shown to manifest itself in a detectable blueshift of the anti-Stokes signal. This blueshift can serve as an indicator of ionization processes in CARS-based neuroimaging. 相似文献
77.
We consider derivation of the effective potential for a scalar field in curved space-time within the physical regularization scheme, using two sorts of covariant cut-off regularizations. The first one is based on the local momentum representation and Riemann normal coordinates and the second is operatorial regularization, based on the Fock-Schwinger-DeWitt proper-time representation. We show, on the example of a self-interacting scalar field, that these two methods produce equal results for divergences, but the first one gives more detailed information about the finite part. Furthermore, we calculate the contribution from a massive fermion loop and discuss renormalization group equations and their interpretation for the multi-mass theories. 相似文献
78.
Slobodan M. Vuković Zoran Jakšić Ilya V. Shadrivov Yuri S. Kivshar 《Applied Physics A: Materials Science & Processing》2011,103(3):615-617
We study the properties of electromagnetic waves propagating along the waveguides with a periodic core created by alternating
metal and dielectric layers, the so-called quasi-one-dimensional plasmonic crystal waveguides. Such waveguides can be symmetric
or asymmetric, depending on the cladding or substrate material properties, as well as on the termination of the periodic structure.
We analyze the dispersion characteristics as well as the profiles of the guided modes for several types of waveguide structure. 相似文献
79.
Dima Grigoriev Mikhail Muzychuk Ilya Ponomarenko 《Foundations of Computational Mathematics》2014,14(3):457-481
We study the polynomial equations vanishing on tensors of a given rank. By means of polarization we reduce them to elements $A$ of the group algebra ${\mathbb {Q}}[S_n\times S_n]$ and describe explicit linear equations on the coefficients of $A$ to vanish on tensors of a given rank. Further, we reduce the study to the Schur ring over the group $S_n\times S_n$ that arises from the diagonal conjugacy action of $S_n$ . More closely, we consider elements of ${\mathbb {Q}}[S_n\times S_n]$ vanishing on tensors of rank $n-1$ and describe them in terms of triples of Young diagrams, their irreducible characters, and nonvanishing of their Kronecker coefficients. Also, we construct a family of elements in ${\mathbb {Q}}[S_n\times S_n]$ vanishing on tensors of rank $n-1$ and illustrate our approach by a sharp lower bound on the border rank of an explicitly produced tensor. Finally, we apply this construction to prove a lower bound $5n^2/4$ on the border rank of the matrix multiplication tensor (being, of course, weaker than the best known one $(2-\epsilon )\cdot n^2$ , due to Landsberg, Ottaviani). 相似文献
80.
We prove that if A ? {1, ..., N} has no nontrivial solution to the equation x 1 + x 2 + x 3 + x 4 + x 5 = 5y, then \(|A| \ll Ne^{ - c(\log N)^{1/7} } \) , c > 0. In view of the well-known Behrend construction, this estimate is close to best possible. 相似文献