Spatial dispersion in Casimir forces: A brief review

We present the basic principles of non-local optics in connection with the calculation of the Casimir force between half-spaces and thin films. At currently accessible distances $L$, non-local corrections amount to about half a percent, but they increase roughly as 1/L at smaller separations. Self consistent models lead to corrections with the opposite sign as models with abrupt surfaces.Comment: Proceedings of QFEXT05, Barcelona, Sept. 5-9, 200

The Abrikosov vortex structure revealed through near-field radiative heat exchange

One of the signatures of superconductivity is the formation of the Abrikosov vortex lattice in type-II superconductors in the presence of an external magnetic field. Here, we study the near-field radiative heat transfer between a spherical nanoparticle and a nearby planar substrate, both made of optimally-doped YBa$_2$Cu$_3$O$_{7-\delta}$. We show that the heat flux displays a periodic spatial pattern congruent with the material optical response modulated by the Abrikosov lattice. Our results enrich the toolbox of methods available to study non-conventional superconductivity.Comment: 3 figures, Supplementary material availabl

Casimir-like tunneling-induced electronic forces

We study the quantum forces that act between two nearby conductors due to electronic tunneling. We derive an expression for these forces by calculating the flux of momentum arising from the overlap of evanescent electronic fields. Our result is written in terms of the electronic reflection amplitudes of the conductors and it has the same structure as Lifshitz's formula for the electromagnetically mediated Casimir forces. We evaluate the tunneling force between two semiinfinite conductors and between two thin films separated by an insulating gap. We discuss some applications of our results.Comment: 8 pages, 3 figs, submitted to Proc. of QFEXT'05, to be published in J. Phys.

Estudio de algunos haploxerolles de la provincia de Murcia

This paper gives account of the results obtained on the macromorphological, analytical and rninerailogical study of three representative HAPLOXEROLLS from the province of Murcia (Spain). They show an A-B-C profile, with an A horizon reaching 40-50 cm in depth, and enough organic matter content to be a moUic epipedon. Taking into account the variations of the organic mater and equivalen calcium carbonate contents with depth, the fluventic characteristics of the profile are evidents. Calcareous from the surface, these soiis are saturated, being calcium the dominant exchangeáble catión. The heavy mineral fraction from the fine sand is made up by resistant minerals with tourmaline as the main component, making up several associations with other minerals. The clay fraction shows a rather complex mineralogical composition, with illite and caolinite as the main components and vermiculite, chlorite, smectites, quartz and athapulgite in minor amounts.En el presente trabajo se da cuenta del estudio macromorfalógico, analítico y mineralógico de tres perfiles de suelos representativos de HAPLOXEROLLES de la provincia de Murcia. Se trata de suelos con perfil A-B-C, en los que el horizonte A alcanza profundidades de 40 a 50 cm o más, con contenidos en materia orgánica suficientes para ser epipedon móllico, y se ponen en evidencia las características fluvénticas de los perfiles, dadas las variaciones que sufren en profundidad tanto los contenidos en materia orgánica como en carbonato calcico equivalente. Calizos desde la superficie, son suelos totalmente saturados en bases, siendo el calcio el catión dominante en el complejo de cambio. La fracción pesada de Ja arena fina está constituida por minerales resistentes entre los que predomina la turmalina, que forma diversas asociaciones con otros minerales. La fracción arcilla posee una composición mineralógica bastante compleja, con ilita, caolinita, vermicuilita, clorita, smectitas, cuarzo y en ocasiones atapulgita, pero, en general, es bastante similar en los distintos perfiles estudiados

Sources of parthenocarpy for Zucchini breeding: relationship with ethylene production and sensitivity

Parthenocarpy is becoming an essential trait for off-season greenhouse production of Zucchini squash. Given that winter conditions promote a reduction in the number of male flowers and in the activity of pollinators, the application of synthetic auxins is currently the most widespread method to induce fruit set. We have evaluated the parthenocarpic tendency of 48 long-fruited accessions of Cucurbita pepo spp. pepo, from morphotypes Zucchini, Vegetable marrow and Cocozelle, including 45 traditional cultivars and 3 commercial hybrids, with the goal of identifying new sources of parthenocarpy for breeding programs. After the first screening, 20 selected accessions were evaluated for the growth rate of unpollinated fruit. Twelve of the selected accessions identified as either strongly parthenocarpic or non-parthenocarpic, were compared for fruit rate growth, ethylene production and ethylene sensitivity. Apart from the three control hybrids, the fastest parthenocarpic fruit growth was observed in 'CpCAL112', 'CM-37', 'E-27', 'PI261610', and 'V-185'. The source of the parthenocarpy of some of these accessions differs from that of the hybrids as it was not associated with the conversion of female into bisexual flowers or with the so-called "fruits with attached flowers" syndrome, which is an undesirable trait in current parthenocarpic hybrids. The alternative sources of parthenocarpy may be of great importance in current Zucchini breeding programs. We also demonstrate that the parthenocarpy of these accessions is associated with downregulation of ethylene production in unpollinated fruits during the first days post anthesis (DPA). In non-parthenocarpic accessions, unpollinated fruits boosted ethylene production at 3 DPA, concomitantly with fruit abortion and senescence, while in parthenocarpic accessions, fruits produced little ethylene at 3 DPA. Therefore, ethylene production in ovaries/fruits at 3 DPA can be used as a marker to identify and select parthenocarpy in Zucchini squash. However, in the cultivars tested here, ethylene production and sensitivity in vegetative organs and in male flowers earlier than 3 PDA do not appear well associated with parthenocarpy.Martinez, C.; Manzano, S.; Megias, Z.; Garrido, D.; Picó Sirvent, MB.; Jamilena, M. (2014). Sources of parthenocarpy for Zucchini breeding: relationship with ethylene production and sensitivity. Euphytica. 200(3):349-362. doi:10.1007/s10681-014-1155-83493622003Byers R, Baker L, Dilley D, Sell H (1972) Chemical induction of perfect flowers on a gynoecious line of muskmelon, Cucumis melo L. HortSci 9:321–331Carbonell-Bejerano P, Urbez C, Granell A, Carbonell J, Perez-Amador MA (2011) Ethylene is involved in pistil fate by modulating the onset of ovule senescence and the GA-mediated fruit set in Arabidopsis. 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High-multipolar effects on the Casimir force: the non-retarded limit

We calculate exactly the Casimir force or dispersive force, in the non-retarded limit, between a spherical nanoparticle and a substrate beyond the London's or dipolar approximation. We find that the force is a non-monotonic function of the distance between the sphere and the substrate, such that, it is enhanced by several orders of magnitude as the sphere approaches the substrate. Our results do not agree with previous predictions like the Proximity theorem approach.Comment: 7 pages including 2 figures. Submitted to Europjysics Letter

Spectral representation of the Casimir Force Between a Sphere and a Substrate

We calculate the Casimir force in the non-retarded limit between a spherical nanoparticle and a substrate, and we found that high-multipolar contributions are very important when the sphere is very close to the substrate. We show that the highly inhomegenous electromagnetic field induced by the presence of the substrate, can enhance the Casimir force by orders of magnitude, compared with the classical dipolar approximation.Comment: 5 page + 4 figures. Submitted to Phys. Rev. Let