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991.
Estrada H Candelas P Uris A Belmar F García de Abajo FJ Meseguer F 《Physical review letters》2008,101(8):084302
We report extraordinary effects in the transmission of sound through periodically perforated plates, supported by both measurements and theory. In agreement with recent observations in slit arrays, M. H. Lu et al. [Phys. Rev. Lett. 99, 174301 (2007)10.1103/PhysRevLett.99.174301], nearly full transmission is observed at certain resonant frequencies, pointing out similarities of the acoustic phenomena and their optical counterpart. However, acoustic screening well beyond that predicted by the mass law is achieved over a wide range of wavelengths in the vicinity of the period of the array, resulting in fundamentally unique behavior of the sound as compared to light. 相似文献
992.
García J Giruzzi G Artaud JF Basiuk V Decker J Imbeaux F Peysson Y Schneider M 《Physical review letters》2008,100(25):255004
Burning tokamak plasmas with internal transport barriers are investigated by means of integrated modeling simulations. The barrier sustainment in steady state, differently from the barrier formation process, is found to be characterized by a critical behavior, and the critical number of the phase transition is determined. Beyond a power threshold, alignment of self-generated and noninductively driven currents occurs and steady state becomes possible. This concept is applied to simulate a steady-state scenario within the specifications of the International Thermonuclear Experimental Reactor. 相似文献
993.
Washik MC Healy J Herrmann F Hinder I Shoemaker DM Laguna P Matzner RA 《Physical review letters》2008,101(6):061102
The spin of the final black hole in the coalescence of nonspinning black holes is determined by the "residual" orbital angular momentum of the binary. This residual momentum consists of the orbital angular momentum that the binary is not able to shed in the process of merging. We study the angular momentum radiated, the spin of the final black hole, and the gravitational bursts in a sequence of equal mass encounters. The initial orbital configurations range from those producing an almost direct infall to others leading to numerous orbits before infall, with multiple bursts of radiation. Our sequence consists of orbits with fixed impact parameter. What varies is the initial linear momentum of the black holes. For this sequence, the final black hole of mass M_{h} gets a maximum spin parameter a/M_{h} approximately 0.823, with this maximum occurring for initial orbital angular momentum L/M_{h};{2} approximately 1.176. 相似文献
994.
D. Kasprowicz T. Runka A. Speghini D. Falcomer J. García Solé M. Bettinelli 《Journal of luminescence》2008,128(5-6):985-987
Vibrational Raman spectra have been measured for strontium barium niobate (Sr0.5Ba0.5Nb2O6, SBN50) single crystals and nanopowders doped with 1 mol% of the luminescent ions Eu3+ and Er3+. The nanocrystalline materials show slightly broader spectra with respect to the single crystals with the same composition. The presence of the Eu3+ and Er3+ ions at the 1 mol% doping level, and the present particle size (200 nm) do not appear to affect the ferro-to-paraelectric phase transition temperature typical of undoped SBN50 single crystals, as detected from anomalies in the dependence of the position of the Raman peak around 635 cm?1 as a function of the temperature. 相似文献
995.
S. García-Revilla R. Valiente Y.E. Romanyuk M. Pollnau 《Journal of luminescence》2008,128(5-6):934-936
Crystalline Er3+ and Yb3+ singly and doubly doped KY(WO4)2 thin films were grown by low-temperature liquid-phase epitaxy. Absorption, luminescence, excitation and temporal evolution measurements were carried out for both Er3+ and Yb3+ transitions from 10 K to room temperature. Green Er3+ upconversion luminescence was observed after Yb3+ and Er3+ excitation. The mechanisms responsible for the upconversion phenomena detected in each case were identified. 相似文献
996.
997.
Karásek V Cizmár T Brzobohatý O Zemánek P Garcés-Chávez V Dholakia K 《Physical review letters》2008,101(14):143601
We create extended longitudinally optically bound chains of microparticles with the use of counterpropagating "nondiffracting" light fields, the so-called Bessel beams. The beam homogeneity and extended propagation range allow the creation of 200 microm long chains of organized microparticles. We observe short-range multistability within a single chain and long-range multistability between several distinct chains. Our observations are supported by theoretical results of the coupled dipole method. 相似文献
998.
Solar forcing on climate has been reported in several studies although the evidence so far remains inconclusive. Here, we analyze the stream flow of one of the largest rivers in the world, the Paraná in southeastern South America. For the last century, we find a strong correlation with the sunspot number, in multidecadal time scales, and with larger solar activity corresponding to larger stream flow. The correlation coefficient is r=0.78, significant to a 99% level. In shorter time scales we find a strong correlation with El Ni?o. These results are a step toward flood prediction, which might have great social and economic impacts. 相似文献
999.
We report scanning tunneling microscope measurements showing a substantial decrease of the current, almost to zero, on the Si(111)-(7x7) reconstruction in the near-to-contact region under low bias conditions. First principles simulations for the tip-sample interaction and transport calculations show that this effect is driven by the substantial local modification of the atomic and electronic structure of the surface. The chemical reactivity of the adatom dangling bond states that dominate the electronic density of states close to the Fermi level and their spatial localization result in a strong modification of the electronic current. 相似文献
1000.