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191.
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194.
First‐order systems in
on
with periodic matrix potentials and vanishing instability intervals
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Sonja Currie Thomas T. Roth Bruce A. Watson 《Mathematical Methods in the Applied Sciences》2015,38(17):4435-4447
First‐order systems in on with absolutely continuous real symmetric π‐periodic matrix potentials are considered. A thorough analysis of the discriminant is given. Interlacing of the eigenvalues of the periodic, antiperiodic and Dirichlet‐type boundary value problems on [0,π] is shown for a suitable indexing of the eigenvalues. The periodic and antiperiodic eigenvalues are characterized in terms of Dirichlet‐type eigenvalues. It is shown that all instability intervals vanish if and only if the potential is the product of an absolutely continuous real scalar valued function with the identity matrix. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
195.
Juliane Khler Sonja Lindenmeier Ingo Fischer Holger Braunschweig Thomas Kupfer Daniela Gamon Ching‐Wen Chiu 《Journal of Raman spectroscopy : JRS》2010,41(6):636-641
We report an investigation of four differently substituted boroles by resonance Raman (RR) spectroscopy with the aim of gaining insight into the structural changes that occur upon electronic π–π* excitation in the five‐membered BC4 ring. Such boroles are prototypes for the theory of antiaromaticity, because the empty pz orbital at the boron interacts with the π system of the carbon backbone to delocalize the four π electrons. The magnitude of this interaction depends on the substituents at the boron atom. In all compounds, an intense band appears around 1600 cm−1, which can be assigned to a CC stretching vibration. The selective amplification of this mode indicates an expansion of the borole ring upon electronic excitation. The resonant enhancement of another mode at around 1300 cm−1, which can be assigned to a vibration between the boron and the substituent, gives evidence that the degree of antiaromaticity in the borole depends strongly on the interaction between the substituent at the boron atom with the empty pz orbital of the boron. When the boron is connected to a ferrocene, this band appears with high intensity, indicating a strong interaction between B and Fe. Furthermore, we studied the dependence of the excitation wavelength on the Raman intensities. In addition, we used DFT calculations to determine the vibrational wavenumbers. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
196.
Sonja Hermann Nils-Peter Harder Rolf Brendel Dirk Herzog Heinz Haferkamp 《Applied Physics A: Materials Science & Processing》2010,99(1):151-158
In this work, we report on laser ablation of thermally grown SiO2 layers from silicon wafer substrates, employing an 8–9 ps laser, at 1064 (IR), 532 (VIS) and 355 nm (UV) wavelengths. High-intensity
short-pulse laser radiation allows direct absorption in materials with bandgaps higher than the photon energy. However, our
experiments show that in the intensity range of our laser pulses (peak intensities of <2×1012 W/cm2) the removal of the SiO2 layer from silicon wafers does not occur by direct absorption in the SiO2 layer. Instead, we find that the layer is removed by a “lift off” mechanism, actuated by the melting and vaporisation of
the absorbing silicon substrate. Furthermore, we find that exceeding the Si melting threshold is not sufficient to remove
the SiO2 layer. A second threshold exists for breaking of the layer caused by sufficient vapour pressure. For SiO2 layer ablation, we determine layer thickness dependent minimum fluences of 0.7–1.2 J/cm2 for IR, 0.1–0.35 J/cm2 for VIS and 0.2–0.4 J/cm2 for UV wavelength. After correcting the fluences by the reflected laser power, we show that, in contrast to the melting threshold,
the threshold for breaking the layer depends on the SiO2 thickness. 相似文献
197.
Gilberto Jerez Gregory Kaufman Michael Prystai Sonja Schenkeveld Kingsley K. Donkor 《Journal of separation science》2009,32(7):1087-1095
Thermodynamic pKa values for benzimidazole and several substituted benzimidazoles were determined by CE. Electrophoretic mobilities of benzimidazoles were determined by CE at different pH levels and ionic strengths. The dependence of electrophoretic mobilities on pH was used to obtain pKa values at different ionic strengths. Extrapolations to zero ionic strength were used to determine the thermodynamic pKa values. Using this method the thermodynamic pKa values of 15 benzimidazoles were determined and found to range from 4.48 to 7.38. Results from the CE measurements were compared with spectrophotometric measurements which were evaluated at wavelengths where the highest absorbance difference for varying pH was recorded. The two analytical techniques were in good agreement. 相似文献
198.
Moran N Bassani DM Desvergne JP Keiper S Lowden PA Vyle JS Tucker JH 《Chemical communications (Cambridge, England)》2006,(48):5003-5005
A novel anthracene-tagged oligonucleotide can discriminate between a fully-matched DNA target sequence and one with a single mismatching base-pair through a remarkable difference in fluorescence emission intensity upon duplex formation. 相似文献
199.
Crystalline samples of rare earth carbodiimides were synthesized by solid-state metathesis reactions of rare earth trichlorides with lithium cyanamide in sealed silica ampules. Two distinct structures were determined by single-crystal X-ray diffraction. The structure determined for Sm2(CN2)3 [C2/m, Z = 2, a = 14.534(2) A, b = 3.8880(8) A, c = 5.2691(9) A, beta = 95.96(2) degrees , R1 = 0.0267, and wR2 = 0.0667] was assigned for RE2(CN2)3 compounds with RE = Y, Pr, Nd, Sm, Gd, Tb, Dy, Ho, and Er, and the structure determined for Lu2(CN2)3 [R32, Z = 3, a = 6.2732(8) A, c = 14.681(2) A, R1 = 0.0208, and wR2 = 0.0526] was assigned for the smallest rare earth ions with RE = Tm, Yb, and Lu by powder X-ray diffraction. Both types of crystal structures are characterized by layers of [NCN](2-) ions whose arrangements can be derived from the motif of a closest packed layer of sticks. These layers alternate with layers of rare earth ions in a one-by-one sequence. Different tilting arrangements of the N-C-N-axes relative to the stacking directions (c) and different arrangements of RE3+ ions within metal atom layers account for the two distinct structures in which Sm3+ and Lu3+ ions adopt the coordination numbers 7 and 6, respectively. 相似文献
200.
Ishikawa A Abe K Adachi I Aihara H Anipko D Asano Y Aushev T Bakich AM Balagura V Barbero M Bitenc U Bizjak I Blyth S Bondar A Bozek A Bracko M Browder TE Chang P Chao Y Chen A Cheon BG Choi Y Choi YK Chuvikov A Dalseno J Danilov M Dash M Drutskoy A Eidelman S Fratina S Gabyshev N Gershon T Gokhroo G Golob B Gorisek A Ha H Haba J Hara T Hayasaka K Hayashii H Hazumi M Hinz L Hokuue T Hoshi Y Hou S Hou WS Hsiung YB Iijima T Ikado K Inami K Ishino H Itoh R Iwasaki M Iwasaki Y Kang JH Kataoka SU 《Physical review letters》2006,96(25):251801
We report the first measurement of the forward-backward asymmetry and the ratios of Wilson coefficients and in A9/A7 and A10/A7 in B --> K*l+l-, where l represents an electron or a muon. We find evidence for the forward-backward asymmetry with a significance of 3.4sigma. The results are obtained from a data sample containing 386 x 10(6) BB pairs that were collected on the Y(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. 相似文献