Properties of entangled photon pairs generated in one-dimensional nonlinear photonic-band-gap structures

We have developed a rigorous quantum model of spontaneous parametric down-conversion in a nonlinear 1D photonic-band-gap structure based upon expansion of the field into monochromatic plane waves. The model provides a two-photon amplitude of a created photon pair. The spectra of the signal and idler fields, their intensity profiles in the time domain, as well as the coincidence-count interference pattern in a Hong-Ou-Mandel interferometer are determined both for cw and pulsed pumping regimes in terms of the two-photon amplitude. A broad range of parameters characterizing the emitted down-converted fields can be used. As an example, a structure composed of 49 layers of GaN/AlN is analyzed as a suitable source of photon pairs having high efficiency.Comment: 14 pages, 23 figure

Electro-Thermal Parameters of Graphene Nano-Platelets Films for De-Icing Applications

This paper provides a study of some relevant electro-thermal properties of commercial films made by pressed graphene nano-platelets (GNPs), in view of their use as heating elements in innovative de-icing systems for aerospace applications. The equivalent electrical resistivity and thermal emissivity were studied, by means of models and experimental characterization. Macroscopic strips with a length on the order of tens of centimeters were analyzed, either made by pure GNPs or by composite mixtures of GNPs and a small percentage of polymeric binders. Analytical models are derived and experimentally validated. The thermal response of these graphene films when acting as a heating element is studied and discussed

Squeezed-light generation in a nonlinear planar waveguide with a periodic corrugation

Two-mode nonlinear interaction (second-harmonic and second-subharmonic generation) in a planar waveguide with a small periodic corrugation at the surface is studied. Scattering of the interacting fields on the corrugation leads to constructive interference that enhances the nonlinear process provided that all the interactions are phase matched. Conditions for the overall phase matching are found. Compared with a perfectly quasi-phase-matched waveguide, better values of squeezing as well as higher intensities are reached under these conditions. Procedure for finding optimum values of parameters for squeezed-light generation is described.Comment: 14 pages, 14 figure

Moderate inappropriately high aldosterone/NaCl constellation in mice: cardiovascular effects and the role of cardiovascular epidermal growth factor receptor

Non-physiological activation of the mineralocorticoid receptor (MR), e.g. by aldosterone under conditions of high salt intake, contributes to the pathogenesis of cardiovascular diseases, although beneficial effects of aldosterone also have been described. The epidermal growth factor receptor (EGFR) contributes to cardiovascular alterations and mediates part of the MR effects. Recently, we showed that EGFR is required for physiological homeostasis and function of heart and arteries in adult animals. We hypothesize that moderate high aldosterone/NaCl, at normal blood pressure, affects the cardiovascular system depending on cardiovascular EGFR. Therefore we performed an experimental series in male and female animals each, using a recently established mouse model with EGFR knockout in vascular smooth muscle cells and cardiomyocytes and determined the effects of a mild-high aldosterone-to-NaCl constellation on a.o. marker gene expression, heart size, systolic blood pressure, impulse conduction and heart rate. Our data show that (i) cardiac tissue of male but not of female mice is sensitive to mild aldosterone/NaCl treatment, (ii) EGFR knockout induces stronger cardiac disturbances in male as compared to female animals and (iii) mild aldosterone/NaCl treatment requires the EGFR in order to disturb cardiac tissue homeostasis whereas beneficial effects of aldosterone seem to be independent of EGFR

Optothermal characterization of vanadium dioxide films by Infrared Thermography

The thickness of vanadium dioxide (VO2) films is a crucial parameter for the study of their optical and thermal properties. In this paper we studied the effect of the film thickness on the thermal hysteresis loop during the phase transition of VO2 deposited on a sapphire substrate by pulsed laser deposition (PLD), by the application of the Infrared Thermography technique. We measure the main thermal hysteresis parameters of VO2 samples with different thicknesses in the LWIR range (8–14 μm) showing how the transition temperature during the heating and cooling cycles, and the width of the hysteresis loop, may change with thickness. We analyzed and compared the obtained results with, in situ Grazing Incidence X-Ray Diffraction (GI-XRD). A good agreement between the results obtained with the two techniques was found demonstrating the reliability of the IR Thermography as a quantitative characterization tool. The results show that the structural and IR emissivity properties of the VO2 layer exhibit a dynamic range dependent on the layer thickness due to a correlation with the crystalline grain size. This has important effects in view of a tailored energy management for the use of those materials as smart radiators or smart windows

Wnt signaling and Loxl2 promote aggressive osteosarcoma

Osteosarcoma (OS) is the most frequent primary malignant bone tumor in urgent need of better therapies. Using genetically modified mouse models (GEMMs), we demonstrate that Wnt signaling promotes c-Fos-induced OS formation via the actions of the collagen-modifying enzyme Loxl2. c-Fos/AP-1 directly regulates the expression of the Wnt ligands Wnt7b and Wnt9a in OS cells through promoter binding, and Wnt7b and Wnt9a in turn promote Loxl2 expression in murine and human OS cells through the transcription factors Zeb1 and Zeb2. Concordantly, inhibition of Wnt ligand secretion by inactivating the Wnt-less (Wls) gene in osteoblasts in c-Fos GEMMs either early or in a therapeutic setting reduces Loxl2 expression and progression of OS. Wls-deficient osteosarcomas proliferate less, are less mineralized and are enriched in fibroblastic cells surrounded by collagen fibers. Importantly, Loxl2 inhibition using either the pan-Lox inhibitor BAPN or a specific inducible shRNA reduces OS cell proliferation in vitro and decreases tumor growth and lung colonization in murine and human orthotopic OS transplantation models. Finally, OS development is delayed in c-Fos GEMMs treated with BAPN or with specific Loxl2 blocking antibodies. Congruently, a strong correlation between c-FOS, LOXL2 and WNT7B/WNT9A expression is observed in human OS samples, and c-FOS/LOXL2 coexpression correlates with OS aggressiveness and decreased patient survival. Therefore, therapeutic targeting of Wnt and/or Loxl2 should be considered to potentiate the inadequate current treatments for pediatric, recurrent, and metastatic OS

Agent based modelling helps in understanding the rules by which fibroblasts support keratinocyte colony formation

Background: Autologous keratincoytes are routinely expanded using irradiated mouse fibroblasts and bovine serum for clinical use. With growing concerns about the safety of these xenobiotic materials, it is desirable to culture keratinocytes in media without animal derived products. An improved understanding of epithelial/mesenchymal interactions could assist in this. Methodology/Principal Findings: A keratincyte/fibroblast o-culture model was developed by extending an agent-based keratinocyte colony formation model to include the response of keratinocytes to both fibroblasts and serum. The model was validated by comparison of the in virtuo and in vitro multicellular behaviour of keratinocytes and fibroblasts in single and co-culture in Greens medium. To test the robustness of the model, several properties of the fibroblasts were changed to investigate their influence on the multicellular morphogenesis of keratinocyes and fibroblasts. The model was then used to generate hypotheses to explore the interactions of both proliferative and growth arrested fibroblasts with keratinocytes. The key predictions arising from the model which were confirmed by in vitro experiments were that 1) the ratio of fibroblasts to keratinocytes would critically influence keratinocyte colony expansion, 2) this ratio needed to be optimum at the beginning of the co-culture, 3) proliferative fibroblasts would be more effective than irradiated cells in expanding keratinocytes and 4) in the presence of an adequate number of fibroblasts, keratinocyte expansion would be independent of serum. Conclusions: A closely associated computational and biological approach is a powerful tool for understanding complex biological systems such as the interactions between keratinocytes and fibroblasts. The key outcome of this study is the finding that the early addition of a critical ratio of proliferative fibroblasts can give rapid keratinocyte expansion without the use of irradiated mouse fibroblasts and bovine serum

Chiral light intrinsically couples to extrinsic/pseudo-chiral metasurfaces made of tilted gold nanowires

xtrinsic or pseudo-chiral (meta)surfaces have an achiral structure, yet they can give rise to circular dichroism when the experiment itself becomes chiral. Although these surfaces are known to yield differences in reflected and transmitted circularly polarized light, the exact mechanism of the interaction has never been directly demonstrated. Here we present a comprehensive linear and nonlinear optical investigation of a metasurface composed of tilted gold nanowires. In the linear regime, we directly demonstrate the selective absorption of circularly polarised light depending on the orientation of the metasurface. In the nonlinear regime, we demonstrate for the first time how second harmonic generation circular dichroism in such extrinsic/pseudo-chiral materials can be understood in terms of effective nonlinear susceptibility tensor elements that switch sign depending on the orientation of the metasurface. By providing fundamental understanding of the chiroptical interactions in achiral metasurfaces, our work opens up new perspectives for the optimisation of their properties

ZyFISH: A Simple, Rapid and Reliable Zygosity Assay for Transgenic Mice

Microinjection of DNA constructs into fertilized mouse oocytes typically results in random transgene integration at a single genomic locus. The resulting transgenic founders can be used to establish hemizygous transgenic mouse lines. However, practical and experimental reasons often require that such lines be bred to homozygosity. Transgene zygosity can be determined by progeny testing assays which are expensive and time-consuming, by quantitative Southern blotting which is labor-intensive, or by quantitative PCR (qPCR) which requires transgene-specific design. Here, we describe a zygosity assessment procedure based on fluorescent in situ hybridization (zyFISH). The zyFISH protocol entails the detection of transgenic loci by FISH and the concomitant assignment of homozygosity using a concise and unbiased scoring system. The method requires small volumes of blood, is scalable to at least 40 determinations per assay, and produces results entirely consistent with the progeny testing assay. This combination of reliability, simplicity and cost-effectiveness makes zyFISH a method of choice for transgenic mouse zygosity determinations

A despistagem do VIH/sida: saúde pública e motivações dos utentes do teste rápido no Nordeste de Portugal

The article examines the adherence of citizens to the quick test for HIV in the Counseling and Early Detection of HIV/AIDS Center (CAD), in the city of Bragança (Northeast Portugal). Specifically, it seeks to examine the role of a fast diagnosis in the fight against AIDS within the Portuguese public health system, to understand the circumstances underlying the demand for the service and to interpret the perceptions and practices of CAD users. In terms of methodology, it was a case study based on ethnographic inquiry, linking direct observation, informal conversations and interviews, which was associated with extensive documental and statistic research. The results obtained allow us to state that the quick test gave a very positive contribution to the fight against HIV/AIDS infection, facilitating citizen access to knowledge of their serological status almost instantly and improving their follow-up by health technicians. The so-called “dissipation of uncertainty”, following sexual risk behavior, is the main reason that leads users to perform a quick test.O artigo analisa a adesão dos cidadãos ao teste rápido de despistagem do VIH no Centro de Aconselhamento e Deteção Precoce do VIH/sida (CAD) da cidade de Bragança (Nordeste de Portugal). Em concreto, procura-se examinar o papel do diagnóstico rápido na luta contra a infeção pelo VIH/sida no quadro do sistema público de saúde português, compreender as circunstâncias subjacentes à procura do serviço e interpretar as percepções e práticas dos utentes do CAD objecto desta pesquisa. Em termos metodológicos, tratou-se de um estudo de caso assente em inquirição etnográfica, articulando observação direta, diálogos informais e entrevistas, a que se associou uma extensa pesquisa documental e estatística. Os resultados apurados permitem afirmar que o teste rápido proporcionou um contributo muito positivo para a luta contra a infeção pelo VIH/sida, facilitando o acesso dos cidadãos ao conhecimento praticamente imediato do seu estado serológico e melhorando o seguimento destes por parte dos técnicos de saúde. A chamada “dissipação da incerteza”, na sequência de uma situação de risco, é o principal motivo que leva os utentes a realizar o teste rápido