Plasmonic Brownian ratchet

Here we present a Brownian ratchet based on plasmonic interactions. By periodically turning on and off a laser beam that illuminates a periodic array of plasmonic nanostructures with broken spatial symmetry, the random thermal motion of a subwavelength dielectric bead is rectified into one direction. By means of the Molecular Dynamics technique we show a statistical directed drift in particle flow

Theory of strong coupling between quantum emitters and propagating surface plasmons

Under the terms of the Creative Commons Attribution License 3.0 (CC-BY).Here we present the theoretical foundation of the strong coupling phenomenon between quantum emitters and propagating surface plasmons observed in two-dimensional metal surfaces. For that purpose, we develop a quantum framework that accounts for the coherent coupling between emitters and surface plasmons and incorporates the presence of dissipation and dephasing. Our formalism is able to reveal the key physical mechanisms that explain the reported phenomenology and also determine the physical parameters that optimize the strong coupling. A discussion regarding the classical or quantum nature of this phenomenon is also presented. © 2013 American Physical Society.This work was supported by the Spanish MINECO (Contracts No.MAT2011-22997, No.MAT2011-28581-C02, and No. CSD2007-046-NanoLight.es) and CAM (Contract No. S-2009/ESP-1503). A. G.-T. and P. A.-H acknowledge FPU Grants No. AP2008-00101 and No. AP2008-00021, respectively, from the Spanish Ministry of Education. This work has been partially funded by the European Research Council (ERC-2011-AdG Proposal No. 290981).S-2009/ESP-1503/Q&C LIGHTPeer Reviewe

Superradiance mediated by Graphene Surface Plasmons

We demonstrate that the interaction between two emitters can be controlled by means of the efficient excitation of surface plasmon modes in graphene. We consider graphene surface plasmons supported by either two-dimensional graphene sheets or one-dimensional graphene ribbons, showing in both cases that the coupling between the emitters can be strongly enhanced or suppressed. The super- and subradiant regimes are investigated in the reflection and transmission configurations. Importantly, the length scale of the coupling between emitters, which in vacuum is fixed by the free space wavelength, is now determined by the wavelength of the graphene surface plasmons that can be extremely short and be tuned at will via a gate voltage

Separación de las clases de lípidos neutros de polen apícola mediante cromatografía líquida de alta resolución (HPLC)

A fast method for the separation of neutral lipid classes of bee-collected pollen by isocratic HPLC is described using ultraviolet detection at 206 nm and direct injection of the sample into a silica column. The mobile phase was n-hexane-2-propanolacetic acid (100:0.5:0.1). Three fractions of neutral lipids were isolated from 35 samples: Sterol esters and other nonpolar compounds such as carotenoids and waxes; triglycerides; and fatty acids.Se describe un método rápido mediante HPLC para la separación de las diferentes clases de lípidos neutros del polen apícola en condiciones isocráticas, con detección UV a 206 nm e inyección directa de la muestra en columna de sílica. Como fase móvil se usa n-hexano-2-propanol-ácido acético (100:0,5:0,1). Se aislaron 3 fracciones de lípidos neutros en las 35 muestras analizadas: Esteres de esteroles y otros componentes no polares tales como carotenoides y ceras; triglicéridos y ácidos grasos

Transformation Plasmonics

This review article provides the state of the art in the emerging topic of transformation plasmonics, with applications thought in cloaking.International audienceSurface plasmons polaritons (SPPs) at metal/dielectric interfaces have raised lots of expectations in the on-going quest towards scaling down optical devices. SPP optics offers a powerful and flexible platform for real two-dimensional integrated optics, capable of supporting both light and electrons. Yet, a full exploitation of the features of SPPs is conditioned by an accurate control of their flow. Most efforts have so far focused on the extrapolation of concepts borrowed from guided optics. This strategy has already led to many important breakthroughs but a fully deterministic control of SPP modes remains a challenge. Recently, the field of optics was stimulated by a novel paradigm, transformation optics, which offers the capability to control light flow in any desired fashion. While it has already significantly contributed to the design of metamaterials with unprecedented optical properties, its versatility offers new opportunities towards a fully deterministic control of SPPs and the design of a new class of plasmonic functionalities. Here, we review recent progress in the application of transformation optics to SPPs. We first briefly describe the theoretical formalism of transformation plasmonics, focusing on its specificities over its three-dimensional optical counterpart. Numerical simulations are then used to illustrate its capability to tame SPP flows at a metal interface patterned with a dielectric load. Finally, we review recent experimental implementations leading to unique SPP functionalities at optical frequencies

Algunos parámetros físico-químicos de la grasa del polen apícola

Refractive index, acid, saponification, ester, and iodine numbers were determinated in lipids from bee-collected pollen commercially purchased samples. Mean values are 1,4799 (1,4777-1,4825), 62 (48- 83), 142 (102-156), 80 (48-102) and 102 (108-134), respectively.Se determinan los índices de refracción, acidez, saponificación, éster e iodo de la grasa en 35 muestras de polen apícola manufacturadas obteniéndose unos valores promedios de 1,4799 (1,4777-1.4825), 62 (48-83), 142 (102-156), 80 (48-102) y 102 (108-134), respectivamente

Reversible dynamics of single quantum emitters near metal-dielectric interfaces

Under the terms of the Creative Commons Attribution License 3.0 (CC-BY).Here we present a systematic study of the dynamics of a single quantum emitter near a flat metal-dielectric interface. We identify the key elements that determine the onset of reversibility in these systems by using a formalism suited for absorbing media and through an exact integration of the dynamics. Moreover, when the quantum emitter separation from the surface is small, we are able to describe the dynamics within a pseudomode description that yields analytical understanding and allows more powerful calculations.Work supported by the Spanish MINECO (MAT2011-22997, MAT2011-28581-C02, CSD2007-046-NanoLight.es) and CAM (S-2009/ESP-1503). A.G.-T. acknowledges funding by the EU integrated project SIQS. P.A.-H. acknowledges a FPU grant (AP2008-00021) from the Spanish Ministry of Education. This work has been partially funded by the European Research Council (ERC-2011-AdG Proposal No. 290981).Peer Reviewe

Epigenetic repression of ROR2 has a Wnt-mediated, pro-tumourigenic role in colon cancer

Background: Wnt factors control cell differentiation through semi-independent molecular cascades known as the beta-catenin-dependent (canonical) and -independent (non-canonical) Wnt signalling pathways. Genetic and epigenetic alteration of components of the canonical Wnt signalling pathway is one of the primary mechanisms underlying colon cancer. Despite increasing evidence of the role of the non-canonical pathways in tumourigenesis, however, the underlying molecular mechanisms are poorly understood. Results: Here we report that the receptor tyrosine kinase-like orphan receptor 2 (ROR2), a transmembrane receptor for Wnt factors that activates non-canonical pathways, is frequently repressed by aberrant promoter hypermethylation in human colon cancer cell lines and primary tumours. By restoring ROR2 activity in colon cancer cells harbouring ROR2 promoter hypermethylation, we show that the role of ROR2 in colon cancer cells is mediated, at least in part, by canonical Wnt and that its epigenetic-dependent loss can be pro-tumourigenic. Conclusions: Our data show the importance of epigenetic alterations of ROR2 in colon cancer, highlighting the close interconnection between canonical and non-canonical Wnt signalling pathways in this type of tumour