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91.
92.
Sara Cruz?y?Cruz Oscar Rosas-Ortiz 《International Journal of Theoretical Physics》2011,50(7):2201-2210
The Schr?dinger equation for position-dependent mass singular oscillators is solved by means of the factorization method and
point transformations. These systems share their spectrum with the conventional singular oscillator. Ladder operators are
constructed to close the su(1,1) Lie algebra and the involved point transformations are shown to preserve the structure of the Barut-Girardello and Perelomov
coherent states. 相似文献
93.
Oscar Perdomo 《Proceedings of the American Mathematical Society》2002,130(11):3379-3384
The stability operator of a compact oriented minimal hypersurface is given by , where is the norm of the second fundamental form. Let be the first eigenvalue of and define . In 1968 Simons proved that for any non-equatorial minimal hypersurface . In this paper we will show that only for Clifford hypersurfaces. For minimal surfaces in , let denote the area of and let denote the genus of . We will prove that . Moreover, if is embedded, then we will prove that . If in addition to the embeddeness condition we have that , then we will prove that .
94.
The influence of previous exposure to ultraviolet-A radiation (UVA) was studied on the susceptibility of Enterobacter cloacae to undergo the growth delay effect. Comparison of growth curves corresponding to irradiated and control cells showed that a previous treatment with UVA almost abolished the growth delay effect. UV absorption spectra of tRNA, and reverse phase HPLC analysis of hydrolysed tRNA, demonstrated a low content of 4-thiouridine in E. cloacae cells grown after UVA exposure at low doses. Since 4-thiouridine is the UVA target responsible for initiation of growth delay, this observation explained the influence of previous exposure to UVA on the susceptibility of this organism to undergo growth delay. A similar but weaker alteration was found when Escherichia coli was assayed. The results suggest that, in addition to cross-linking with cytidine residues, the content of 4-thiouridine in tRNA may be modified by UVA by an unknown mechanism. 相似文献
95.
Oscar Palmas 《Bulletin of the Brazilian Mathematical Society》1999,30(2):139-161
In this paper we classify all complete rotation hypersurfaces withH
k
constant in
n+1 andH
n+1, is the normalizedk-th symmetric function of the principal curvatures. Partial results are also given forH
n+1.Partially supported by DGAPA-UNAM, México, CONACYT, México, under Project 1068P, and CNPp, Brazil. 相似文献
96.
97.
98.
A model for earthquake dynamics consisting of two rough profiles interacting via fragments filling the gap is introduced, the fragments being produced by the local breakage due to the interaction of the local plates. The irregularities of the fault planes can interact with the fragments between them to develop a mechanism for triggering earthquakes. The fragment size distribution function comes from a nonextensive formulation, starting from first principles. An energy distribution function, which gives the Gutenberg-Richter law as a particular case, is analytically deduced. 相似文献
99.
Baker KL Stappaerts EA Gavel D Wilks SC Tucker J Silva DA Olsen J Olivier SS Young PE Kartz MW Flath LM Kruelevitch P Crawford J Azucena O 《Optics letters》2004,29(15):1781-1783
Results of atmospheric propagation for a high-speed, large-actuator-number adaptive optics system are presented. The system uses a microelectromechanical system- (MEMS-) based spatial light modulator correction device with 1024 actuators. Tests over a 1.35-km path achieved correction speeds in excess of 800 Hz and Strehl ratios close to 0.5. The wave-front sensor was based on a quadrature interferometer that directly measures phase. This technique does not require global wave-front reconstruction, making it relatively insensitive to scintillation and phase residues. The results demonstrate the potential of large-actuator-number MEMS-based spatial light modulators to replace conventional deformable mirrors. 相似文献
100.
We deal with the imaging problem of determining the internal structure of a body from backscattered laser light and low-coherence interferometry. Specifically, using the interference fringes that result when the backscattering of low-coherence light is made to interfere with the reference beam, we obtain maps detailing the values of the refractive index within the sample. Our approach accounts fully for the statistical nature of the coherence phenomenon; the numerical experiments that we present, which show image reconstructions of high quality, were obtained under noise floors exceeding those present for various experimental setups reported in the literature. 相似文献