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941.
Juan Arias de Reyna 《Monatshefte für Mathematik》1988,106(2):95-97
We give another proof of Seymour and Zaslavsky's theorem: For every familyf
1,f
2,...,f
n of continous functions defined on [0, 1], there exists a finite setF[0, 1] such that the average sum off
k
overF coincides with the integral off
k
for everyk=1, 2,...,n. 相似文献
942.
Let the following be given: two n × m real matrices, E and F, such that F ? E, three real n-rows, p, a and b, such that b ? a, and three real m-columns, t, c and d, such that d ? c. We give inequalities relating the given matrices and vectors, equivalent to the consistency of the system , , , where X is an n × m unknown real matrix. 相似文献
943.
944.
Stoffels E. Stoffels W.W. Vender D. Kroesen G.M.W. de Hoog F.J. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1994,22(2):116-121
The interaction of particulates formed in an argon RF discharge containing 1-5% CCl2F2 admixture with a pulsed infrared laser (Nd:YAG, intensity ~109 W m-2, pulse duration ~10-4 s) has been studied in situ. The white light emitted during this process has been monitored as a function of time and wavelength using a fast photo diode and an optical multichannel analyser. The spectra have been fitted with blackbody curves with a standard deviation of 5%. A spectral temperature of about 3500 K has been obtained for various plasma conditions and attributed to the decomposition temperature of the particulate material. A model based on laser heating, internal heat conduction and chemical decomposition is compared with the experimental results. This model predicts the time constants for heating and decomposition of the particulates and explains the dependence of the measured emission intensity on the laser intensity 相似文献
945.
946.
A construction of grand unified models of the strong, weak and electromagnetic interactions is described based on the transformation properties of the group generators under a maximal subgroup decomposition without recourse to large representation matrices or to the specific algebraic structures of some classical Lie-groups, such as the Clifford algebra associated with the orthogonal groups or the octonionic structure of the exceptional groups. To illustrate the procedure an explicit construction is given of the SU(5) model useful in the discussion of higher rank groups, of SO(10) under the maximal subalgebras SU(2)L × SU(2)R × SU(4)c and SU(5) × U(1)r and of the exceptional group E6 under SU(3)L × SU(3)R × SU(3)c and SO(10) × U(1)t. The construction procedure can be used as well with any classical Lie-group. 相似文献
947.
A.M Ozorio de Almeida 《Annals of Physics》1983,145(1):100-115
The Wigner representation of a quantum state, corresponding to a classically integrable Hamiltonian, has been shown to be intimately tied to a classical phase space torus of the same energy. The fact that the semiclassical approximation of the Wigner function there derived turns out to be singular on the torus, as well as on the “Wigner caustic” which contains it, is due to well known limitations of the stationary phase method. The uniform approximation, here derived, does indeed ascribe to the Wigner function a high amplitude along the Wigner caustic, but this is modulated by rapid oscillations except at the torus itself. Asymptotic expansion away from the torus leads back to the semiclassical approximation. Close to the torus the Wigner function is described by a simple transitional approximation which can be resolved into a product of Wigner functions corresponding to one dimensional tori. These results permit one to explicitly project the Wigner function onto any (Lagrangian) coordinate plane so as to obtain the corresponding wave intensity. 相似文献
948.
Emmanuelle Canet Didier Revel Rmy Forrat Claire Baldy-Porcher Michel de Lorgeril Laurent Sebbag Jean-Paul Vallee Dominique Didier Michel Amiel 《Magnetic resonance imaging》1993,11(8):1139-1145
Superparamagnetic iron oxide particles (SPIOs) are usually referred to as T2 MR contrast agents, reducing signal intensity (SI) on T2-weighted MR images (negative enhancement). This study reports the original use of SPIOs as T1-enhancing contrast agents, primarily assessed in vitro, and then applied to an in vivo investigation of a myocardial perfusion defect. Using a strongly T1-weighted subsecond MR sequence with SPIOs intravenous (IV) bolus injection, MR imaging of myocardial vascularization after reperfusion was performed, on a dog model of coronary occlusion followed by reperfusion. Immediately after the intravenous bolus injection of 20 μmol/kg of SPIOs, a positive signal intensity enhancement was observed respectively, in the right and left ventricular cavity and in the nonischemic left myocardium. Moreover, compared to normal myocardium, the remaining ischemic myocardial region (anterior wall of the left ventricle) appeared as a lower and delayed SI enhancing area (cold spot). Mean peak SIE in the nonischemic myocardium (posterior wall) was significantly higher than in the ischemic myocardium (anterior wall) (110 ± 23% vs. 74 ± 22%, Mann-Whitney test < 1%, n1 = 6, n2 − n1 = 0, U > 2). In conclusion, the T1 effect of SPIOs at low dose, during their first intravascular distribution, suggests their potential use as positive markers to investigate the regional myocardial blood flow and some perfusion defects such as the “no-reflow phenomenon”. 相似文献
949.
950.
Gidal G Boyer J Butler F Cords D Abrams GS Amidei D Baden AR Barklow T Boyarski AM Burchat P Burke DL Dorfan JM Feldman GJ Gladney L Gold MS Goldhaber G Golding LJ Haggerty J Hanson G Hayes K Herrup D Hollebeek RJ Innes WR Jaros JA Juricic I Kadyk JA Karlen D Klein SR Lankford AJ Larsen RR LeClaire BW Levi ME Lockyer NS Lüth V Matteuzzi C Nelson ME Ong RA Perl ML Richter B Riles K Rowson PC Schaad T Schellman H Schmidke WB Sheldon PD Trilling GH de la Vaissière C Wood DR Yelton JM Zaiser C 《Physical review letters》1987,59(18):2016-2019