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921.
Moreno E Fernández-Domínguez AI Cirac JI García-Vidal FJ Martín-Moreno L 《Physical review letters》2005,95(17):170406
Recently, it has been observed that transmission of light through subwavelength apertures, which is usually negligible, can be significantly enhanced when surface plasmons are resonantly excited. Here we introduce the idea that similar effects can be expected for cold atoms in structures supporting surface matter waves. We show that surface matter waves are possible in properly designed structures, and then we theoretically demonstrate 100% transmission of rubidium atoms through an array of slits much narrower than the de Broglie wavelength of the atoms. Our results open up the possibility of using surface matter waves to control the flow of neutral atoms. 相似文献
922.
Ferrando A Zacarés M García-March MA Monsoriu JA de Córdoba PF 《Physical review letters》2005,95(12):123901
Using group theory arguments and numerical simulations, we demonstrate the possibility of changing the vorticity or topological charge of an individual vortex by means of the action of a system possessing a discrete rotational symmetry of finite order. We establish on theoretical grounds a "transmutation pass" determining the conditions for this phenomenon to occur and numerically analyze it in the context of two-dimensional optical lattices. An analogous approach is applicable to the problems of Bose-Einstein condensates in periodic potentials. 相似文献
923.
Puertas AM Fernández-Barbero A de Las Nieves FJ 《The European physical journal. E, Soft matter》2005,18(3):335-341
The structure factor, S(q), of a system composed of a 1:1 mixture of oppositely charged colloids undergoing heteroaggregation
is studied by Browninan dynamics simulations. A peak develops in S(q) at low wave vectors, which can be scaled for different
times to overlap using the scaling of spinodal decomposition, as shown for DLCA. The same master function is obtained for
different interaction ranges. The origin of the peak can be traced back to a depletion layer of clusters surrounding every
aggregate. At those long distances, cluster-cluster interaction is negligible and the aggregation is diffusion limitted, as
deduced from the evolution of peak position, and the S(q) scaling at different interaction ranges. The interaction is, nevertheless,
strong enough to affect the internal cluster structure. 相似文献
924.
925.
Rubio EM García-Moreno MI Balbuena P Mellet CO García Fernández JM 《Organic letters》2005,7(4):729-731
The application of the "rigid spacer-mediated linkage between nonreacting centers" concept to the preparation of nonsymmetrical bis-spiroketal structures is demonstrated by the stereoselective synthesis of the bis-spiro fructodisaccharide 1, a minor component of industrial caramels. An o-xylylene bridge has been used to limit the conformational space during the intramolecular glycosylation-spirocyclization reaction of a difructopyranose precursor, thus controlling both the ring size and the stereochemistry at the spiro centers. [Structure: see text] 相似文献
926.
Elena?FernándezEmail author Yolanda?Hinojosa Justo?Puerto 《Annals of Operations Research》2005,136(1):259-283
In this paper we deal with two stationary loss queuing network location models. We analyze the influence of filtering policies
on the locational aspect of the problems. We assume that requests for service are placed at nodes of a transportation network
and they arrive in time as independent homogeneous Poisson processes with different input rates. The considered policies only
cover a given proportion of requests even if there are idle service units. This proportion is stationary and fixed in advance
and only depends on the node where the request is originated. The objective is to find the location of the facilities together
with the filtering policy to be applied that minimize the expected total cost per unit time with respect to a given cost structure.
Properties and computational results are presented enabling the resolution of these problems efficiently and showing the good
performance of filtering policies in terms of both the overall operating costs, and the demand that is served. 相似文献
927.
928.
Carrera E García T Céspedes A González I Fernández A Asensio LM Hernández PE Martín R 《Journal of AOAC International》2000,83(2):341-346
Raw and smoked samples of Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss) were identified using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) of the p53 gene. DNA from S. salar and 0. mykiss was amplified by using primers flanking exons 5 to 6 of the p53 nuclear gene. PCR products of different length were obtained for each species (532 and 518 base pairs, respectively). Sequences of PCR products obtained from S. salar and O. mykiss were compared in the search for polymorphic restriction sites. The restriction fragments obtained with Eco RV, Hinf I, and Taq I endonucleases showed interspecific polymorphism, making it a useful method for identification of Atlantic salmon and rainbow trout. 相似文献
929.
Mealiness assessment in apples and peaches using MRI techniques 总被引:5,自引:0,他引:5
Barreiro P Ortiz C Ruiz-Altisent M Ruiz-Cabello J Fernández-Valle ME Recasens I Asensio M 《Magnetic resonance imaging》2000,18(9):1175-1181
Mealiness (woolliness in peaches) is a negative attribute of sensory texture that combines the sensation of a desegregated tissue with the sensation of lack of juiciness. In this study, 24 apples cv. Top Red and 8 peaches cv. Maycrest, submitted to 3 and 2 different storage conditions respectively have been tested by mechanical and MRI techniques to assess mealiness. With this study, the results obtained on apples in a previous work have been validated using mathematical features from the histograms of the T2 maps: more skewed and the presence of a tail in mealy apples, similar to internal breakdown. In peaches, MRI techniques can also be used to identify woolly fruits. Not all the changes found in the histograms of woolly peaches are similar from those observed in mealy apples pointing to a different underlying physiological change in both disorders. 相似文献
930.
Silver J Marsh PJ Symons MC Svistunenko DA Frampton CS Fern GR 《Inorganic chemistry》2000,39(13):2874-2881
The crystal structure of the title compound is presented and shown to be one of a class of low-spin iron porphyrin complexes having a ground-state electronic configuration of (dxy)2(dxz)2(dyz)1. If their Fe-N bond lengths (average N-porphyrin plotted against average N-axial) are considered, this class of low-spin iron(III) porphyrins of general formula [Fe(III)Por(L)2]+X- and of 2B ground state is shown to be distinctly different crystallographically from a similar class of compounds with the same general formula but with a 2E or a (dxy)2(dxz,dyz)3 ground state. A third group of compounds with the same general formula have a (dxz,dyz)4(d)1 ground state and again are in a different region of the plot. Compounds showing intermediate properties can be forecast from the simple relationship presented in this work. The electron paramagenetic resonance data are shown to be dependent on the ground state, and those of configuration (dxy)2(dxz,dyz)3 and the 2B ground state obey a correlation previously suggested in the literature. 相似文献