Spontaneous symmetry breaking as a resource for noncritically squeezed light

In the last years we have proposed the use of the mechanism of spontaneous symmetry breaking with the purpose of generating perfect quadrature squeezing. Here we review previous work dealing with spatial (translational and rotational) symmetries, both on optical parametric oscillators and four-wave mixing cavities, as well as present new results. We then extend the phenomenon to the polarization state of the signal field, hence introducing spontaneous polarization symmetry breaking. Finally we propose a Jaynes-Cummings model in which the phenomenon can be investigated at the single-photon-pair level in a non-dissipative case, with the purpose of understanding it from a most fundamental point of view.Comment: Review for the proceedings of SPIE Photonics Europe. 11 pages, 5 figures

Teratoma ovárico en una perra : caso clínico

En este artículo se describe el caso clínico de una perra de tres años en la que se halló de manera casual un quiste dermoide ovárico, tipo especial y poco habitual de los teratomas ováricos. El animal acudió a la consulta por un cuadro de apatía y desinterés por los cachorros una semana después del parto, observándose a la exploración hipertermia, secreción mamaria anormal y descarga vulvar purulenta. El estudio citológico, analítico, radiológico y ecográfico abdominal diagnosticaron una mamitis-metritis post parto. Sin embargo, al realizar la radiografía abdominal, se evidenció una masa de densidad tejido blando situada caudalmente al riñón derecho que ecográficamente se observó como una gran estructura quística. El diagnóstico histopatológico definitivo de un quiste dermoide ovárico se obtuvo tras la realización de la ovariohisterectomía, que en este caso fue curativa ante la ausencia de malignidad. Los tumores ováricos de las células germinales son muy poco frecuentes en la perra por lo que el objetivo del presente artículo no sólo es la descripción de un quiste dermoide sino también la revisión de la escasa bibliografía existente acerca de los tipos, incidencia, síntomas, patogenia, diagnóstico, pronóstico y tratamiento de los tumores ováricos en la especie canina

Optics of Astigmatism and Retinal Image Quality

In the first part of this chapter, the optical condition of astigmatism is defined. The main causes and available classifications of ocular astigmatism are briefly described. The most relevant optical properties of image formation in an astigmatic eye are analysed and compared to that of an emmetropic eye and an eye with spherical ametropia. The spectacle prescription and axis notation for astigmatism are introduced, and the correction of astigmatism by means of lenses is briefly described. The formation of the retinal image for extended objects and the related blurring are also analysed, and the real limits of tolerance of uncorrected astigmatism are provided. Simulations of retinal images in astigmatic eyes, obtained by means of commercial optical design software, are also presented. Finally, the clinical assessment of retinal image quality by means of wavefront aberrometry and double-pass systems in eyes with astigmatism is presented, and current trends in research related to this topic are highlighted.Peer ReviewedPostprint (published version

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Theory of quantum fluctuations of optical dissipative structures and its application to the squeezing properties of bright cavity solitons

We present a method for the study of quantum fluctuations of dissipative structures forming in nonlinear optical cavities, which we illustrate in the case of a degenerate, type I optical parametric oscillator. The method consists in (i) taking into account explicitly, through a collective variable description, the drift of the dissipative structure caused by the quantum noise, and (ii) expanding the remaining -internal- fluctuations in the biorthonormal basis associated to the linear operator governing the evolution of fluctuations in the linearized Langevin equations. We obtain general expressions for the squeezing and intensity fluctuations spectra. Then we theoretically study the squeezing properties of a special dissipative structure, namely, the bright cavity soliton. After reviewing our previous result that in the linear approximation there is a perfectly squeezed mode irrespectively of the values of the system parameters, we consider squeezing at the bifurcation points, and the squeezing detection with a plane--wave local oscillator field, taking also into account the effect of the detector size on the level of detectable squeezing.Comment: 10 figure

Quadrature and polarization squeezing in a dispersive optical bistability model

We theoretically study quadrature and polarization squeezing in dispersive optical bistability through a vectorial Kerr cavity model describing a nonlinear cavity filled with an isotropic chi(3) medium in which self-phase and cross-phase modulation, as well as four--wave mixing, occur. We derive expressions for the quantum fluctuations of the output field quadratures as a function of which we express the spectrum of fluctuations of the output field Stokes parameters. We pay particular attention to study how the bifurcations affecting the non-null linearly polarized output mode squeezes the orthogonally polarized vacuum mode, and show how this produces polarization squeezing.Comment: 10 text pages + 12 figure

Effects of ammonium nitrate, cesium chloride and tetraethylammonium on high-affinity potassium uptake in habanero pepper plantlets (Capsicum chinense Jacq.)

Potassium (K+) is an essential nutrient and the most abundant cation in plant cells. Plants have a wide variety of transport systems for K+ acquisition that catalyze K+ uptake across a wide spectrum of external K+ concentrations and mediate K+ movement within the plant, as well as its release into the environment. The KUP/HAK/KT transporter family plays a key role in K+ homeostasis in plant cells. The present study demonstrates that habanero pepper plantlets have a clear pattern of K+ uptake when resupplemented with K+ after K+ starvation. Habanero pepper plantlets, re-supplemented with a solution containing low concentrations of K+ after 72, 96 or 120 h of K+ starvation were able to decrease the amount of K+ in the solution at different time points. To study the effect of NH4+, we added different concentrations of NH4NO3 to the medium solution and demonstrated that NH4+ inhibited K+ uptake in a dose-dependent manner. When the plantlets were subjected to K+ starvation for 72 h and then resupplemented with 50 or 100 μM K+, exposure to K+ channel blockers (10 mM CsCl and 20 mM TEA) decreased their K+ uptake compared with the control treatment. A model demonstrating the process of K+ uptake through an NH4+-insensitive component was proposed.Key words: Potassium, high affinity transporters, channel blockers, ammonium

Preliminary study of the adaptation of Senegalese sole Solea senegalensis Kaup, 1858 to different salinities

Osmoregulatory and metabolic effects of adaptation to different water salinities (5, 15, 25, 42 and 55) were assessed during a period of 14 days in juveniles of Senegalese sole Solea senegalensis Kaup, 1858. The results showed a good capacity to adapt within the range of water salinities tested. Gill Na+,K+-ATPase activity showed a direct lineal relationship with regard to water salinity, whereas kidney Na+,K+-ATPase activity did not change. Plasma osmolality and ions levels did not present differences among the groups. Plasma cortisol, glucose and lactate were higher in the group maintained in the highest water salinity.El crecimiento del lenguado senegalés Solea senegalensis Kaup, 1858 está influido por diferentes variables, y una de ellas es la salinidad ambiental. En este trabajo, se estudian los efectos osmorreguladores y metabólicos de la aclimatación a distintas salinidades (5, 15, 25, 42 y 55) durante un periodo de 14 días en juveniles de esta especie. La actividad Na+,K+-ATPasa branquial presentó una relación lineal directa respecto a la salinidad ambiental, mientras que la actividad Na+,K+-ATPasa renal no experimentó variación alguna. Ni la osmolalidad ni los niveles de iones plasmáticos analizados mostraron diferencias significativas entre los diferentes grupos. El cortisol y los niveles de glucosa y lactato plasmático aumentaron en los ejemplares adaptados a la mayor salinidad. Los resultados mostraron una buena capacidad de aclimatación en el rango de salinidades ambientales analizado.Instituto Español de Oceanografí