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Inclusive proton-induced charged pion production was studied on 12C, 89Y and natPb at 201 and 180 MeV. A QQD spectrometer was used for forward angles and a plastic scintillator range spectrometer for backward angles. The angular dependence, variation with the pion energy, and total cross sections are deduced from doubly differential cross section measurements.  相似文献   

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In the Letter [B.A. Nguyen, Phys. Lett. A 350 (2006) 174], a quantum exam protocol was presented. Here we show a cheating protocol, by which any student can get the other students' solution without being detected. Then we propose a possible modified protocol against this attacking strategy.  相似文献   

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The so-called Biphase termination on α-Fe2O3 has been widely accepted to be a structure with a 40 Å unit supercell composed of coexisting islands of Fe1−xO and α-Fe2O3. Based on thermodynamic arguments and experimental evidence, including transmission electron diffraction, imaging, magnetic and spectroscopic information, it is found that the previously proposed structure model is inaccurate. The actual Biphase structure is instead a layered structure related to the reduction of α-Fe2O3 to Fe3O4. A model for the Biphase termination is proposed which does not contain islands of Fe1−xO but instead consists of bulk α-Fe2O3 and a Fe3O4-derived overlayer. The proposed model is consistent with all current and previously reported experimental findings.  相似文献   

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In a recent paper [Opt. Comm. 282 (2009) 1939], a quantum sealed-bid auction protocol was proposed. However, in this comment, it is shown that the protocol does not complete the task of a sealed-bid auction fairly when any bidder colludes with the auctioneer.  相似文献   

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In this paper, we corrected some errors in [J. Geom. Phys. 40 (2002) 370]. In [J. Geom. Phys. 40 (2002) 370], the errors in Eqs. (32) and (44) influenced the conclusion of Theorem 3.1, Corollary 3.1 and Theorem 3.2.  相似文献   

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A partial wave analysis of the 3π-system has been performed for the reaction π+p→ (π+π?π0) Δ++ (1232) at 16 GeV/c. Beside the well-established A20 (1300), the resonant state ω* with isospin I = 0 and spin-parity JP = 3? decaying mainly into (?π) has been found. Its mass and width have been determined to be M = (1.71 ± 0.03) GeV and Γ = (0.22 ± 0.10) GeV. The cross section for the reaction π+p→ ω* (1700) Δ++ (1232) is σ = (12 ± 6) μb.  相似文献   

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Intersubband transitions in quantum well have extremely large oscillator strengths and induce strong nonlinear effects in structures where inversion symmetry is broken, realized by growing AlGaAs quantum wells with asymmetrical A1 gradients. These compositionally asymmetrical multiquantum wells may thus be viewed as giant “quasimolecules” optimized for optimal nonlinearities in the mid infrared. Optical rectification as well as second harmonic generation have been measured in those structures using a continuous CO2 laser. At 10.6 μm the nonlinear coefficients are more than 3 orders of magnitude higher in these samples than for bulk GaAs (i.e. χ0(2) = 5.3 × 10−6m/V, χ2ω(2) = 7.2 × 10−7 m/V) and are in good agreement with theoretical predictions. We present more complex “pseudo-molecules” involving weakly coupled quantum wells. The optical rectification effects in these devices are so large χ0(2) = 1.6 × 10−3 m/V) that application to infrared detection may be envisioned.  相似文献   

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We compare the surface dynamics of the adsorbate systems Mo(1 1 0)–H and Mo(1 1 0)–Li. In both cases electron energy loss spectroscopy measurements revealed strong substrate surface phonon anomalies. Whereas the phonon anomaly of the hydrogen-covered surface was unequivocally assigned to be of the Kohn type, the anomalous behavior of the surface phonons of the lithium-covered surface remained obscure. In this paper we develop an experimental criterion based on the dispersion of adsorbate phonons, which allows to decide whether the observed substrate surface phonon anomaly is of the Kohn type or not. Employing this criterion we now definitely rule out that the anomaly on Mo(1 1 0)–Li is due to the Kohn effect.  相似文献   

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A. Drezet 《Physics letters. A》2006,350(5-6):416-418
In the above Letter, it is claimed that Bohm's mechanics can be challenged by a simple gedanken experiment involving a protecting measurement. Here we show that this gedanken experiment can be justified without problem and without contradicting the axiom attributing a physical meaning to the Bohmian trajectory.  相似文献   

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We performed density functional theory calculations using the full-potential linearized augmented plane wave method and generalized gradient approximation to investigate the interaction of hydrogen with Fe surface layers in the Fe/M(0 0 1) system, where M=Cu, Ag. The adsorption of hydrogen is found to be preferable at bridge sites in both H/Fe(0 0 1) and H/Fe/Ag(0 0 1), whereas the preferred sites are the fourfold site above the surface layer in the H/Fe/Cu(0 0 1) system. The adsorption energies are enhanced due to Cu and Ag substrates as compared to Fe(0 0 1) substrates. The local density of states at the Fermi level and the magnetic moments are reduced due to the presence of H for the different systems.  相似文献   

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