169 research outputs found

    High refractive index inverse vulcanized polymers for organic photonic crystals

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    Photonic technologies are nowadays dominated by highly performing inorganic structures that are commonly fabricated via lithography or epitaxial growths. Unfortunately, the fabrication of these systems is costly, time consuming, and does not allow for the growth of large photonic structures. All-polymer photonic crystals could overcome this limitation thanks to easy solubility and melt processing. On the other hand, macromolecules often do not offer a dielectric contrast large enough to approach the performances of their inorganic counterparts. In this work, we demonstrate a new approach to achieve high dielectric contrast distributed Bragg reflectors with a photonic band gap that is tunable in a very broad spectral region. A highly transparent medium was developed through a blend of a commercial polymer with a high refractive index inverse vulcanized polymer that is rich in sulfur, where the large polarizability of the S–S bond provides refractive index values that are unconceivable with common non-conjugated polymers. This approach paves the way to the recycling of sulfur byproducts for new high added-value nanostructures

    All-polymer methylammonium lead iodide perovskite microcavities

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    open8Thanks to a high photoluminescence quantum yield, large charge carrier diffusion, and ease of processing from solution, perovskite materials are becoming increasingly interesting for flexible optoelectronic devices. However, their deposition requires wide range solvents that are incompatible with many other flexible and solution-processable materials, including polymers. Here, we show that methylammonium lead iodide (MAPbI3) films can be directly synthesized on all-polymer microcavities via simple addition of a perfluorinated layer which protects the polymer photonic structure from the perovskite processing solvents. The new processing provides microcavities with a quality factor Q = 155, that is in agreement with calculations and the largest value reported so far for fully solution processed perovskite microcavities. Furthermore, the obtained microcavity shows strong spectral and angular redistribution of the the MAPbI3 photoluminescence spectrum, which shows a 3.5 fold enhanced intensity with respect to the detuned reference. The opportunity to control and modify the emission of a MAPbI3 film via a simple spun-cast polymer structure is of great interest in advanced optoelectronic applications requiring high colour purity or emission directionality.openLova, Paola; Giusto, Paolo; Di Stasio, Francesco; Manfredi, Giovanni; Paternò, Giuseppe M; Cortecchia, Daniele; Soci, Cesare; Comoretto, DavideLova, Paola; Giusto, Paolo; DI STASIO, Francesco; Manfredi, Giovanni; Paternò, Giuseppe M; Cortecchia, Daniele; Soci, Cesare; Comoretto, David

    Shine Bright Like a Diamond: New Light on an Old Polymeric Semiconductor

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    Brilliance usually refers to the light reflected by the facets of a gemstone such as diamond due to its high refractive index. Nowadays, high-refractive-index materials find application in many optical and photonic devices and are mostly of inorganic nature. However, these materials are usually obtained by toxic or expensive production processes. Herein, the synthesis of a thin-film organic semiconductor, namely, polymeric carbon nitride, by thermal chemical vapor deposition is presented. Among polymers, this organic material combines the highest intrinsic refractive index reported so far with high transparency in the visible spectrum, even reaching the range of diamond. Eventually, the herein presented deposition of high quality thin films and their optical characteristics open the way for numerous new applications and devices in optics, photonics, and beyond based on organic materials

    Resource dedication problem in a multi-project environment

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    There can be different approaches to the management of resources within the context of multi-project scheduling problems. In general, approaches to multiproject scheduling problems consider the resources as a pool shared by all projects. On the other hand, when projects are distributed geographically or sharing resources between projects is not preferred, then this resource sharing policy may not be feasible. In such cases, the resources must be dedicated to individual projects throughout the project durations. This multi-project problem environment is defined here as the resource dedication problem (RDP). RDP is defined as the optimal dedication of resource capacities to different projects within the overall limits of the resources and with the objective of minimizing a predetermined objective function. The projects involved are multi-mode resource constrained project scheduling problems with finish to start zero time lag and non-preemptive activities and limited renewable and nonrenewable resources. Here, the characterization of RDP, its mathematical formulation and two different solution methodologies are presented. The first solution approach is a genetic algorithm employing a new improvement move called combinatorial auction for RDP, which is based on preferences of projects for resources. Two different methods for calculating the projects’ preferences based on linear and Lagrangian relaxation are proposed. The second solution approach is a Lagrangian relaxation based heuristic employing subgradient optimization. Numerical studies demonstrate that the proposed approaches are powerful methods for solving this problem

    Comparison of the efficiency of the nebulization of salbutamol, epinephrine and normal saline on treatment of bronchiolitis

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    Background: Bronchiolitis is a frequent cause of hospitalization. Despite the frequency of this pathology, there is not a single, widely practiced evidence-driven treatment especially using of nebulization. Present purpose was to compare which is efficient: nebulized salbutamol, epinephrine or normal saline.Methods: We have preceded to a prospective study from January 1st 2011 to March 31st 2012 including children between 29 days old and 2 years old.Results: We have included 90 patients divided in three groups and received nebulized salbutamol, epinephrine or normal saline. There was no real difference in the variables of the groups: clinical score, oxygen saturation, heart rate, temperature and weight but the hospitalization duration was shorter in the group who have been cured by normal salineConclusions: This study shows that salbutamol, epinephrine and normal saline can be used in the same situation but the normal saline has more advantages because of his low coast and the absence of risk of side effects

    Almond witches’-broom phytoplasma (Candidatus Phytoplasma phoenicium): a real threat to almond, peach and nectarine.

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    Within less than a decade, Almond witches’-broom (AlmWB) phytoplasma killed over a hundred thousand almond trees in Lebanon (Abou-Jawdah et al., 2002). AlmWB belongs to the pigeon pea witches’ broom group (16SrIX), and the scientific name (Candidatus Phytoplasma phoenicium) was suggested (Verdin et al., 2003). Grafting experiments revealed that AlmWB may also affect peaches and nectarines (Abou-Jawdah et al, 2003). Later on, a similar disease was reported in Iran (Verdin et al., 2003; Salehi et al., 2006). This disease is still spreading on almond trees to new areas in North Lebanon, but more recently shoot proliferation with succulent small light green leaves were observed on peach and nectarine in South Lebanon, where the disease seemed to be spreading relatively fast. DNA sequencing showed over 99% sequence homology with AlmWB (Abou-Jawdah et al. 2008). This report shows that epidemics of AlmWB may occur also on peach and nectarine under field conditions, and strongly suggests the presence of an efficient vector

    A selective role for phosphatidylinositol 3,4,5-trisphosphate in the Gi-dependent activation of platelet Rap1B.

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    The small GTP-binding protein Rap1B is activated in human platelets upon stimulation of a G(i)-dependent signaling pathway. In this work, we found that inhibition of platelet adenylyl cyclase by dideoxyadenosine or SQ22536 did not cause activation of Rap1B and did not restore Rap1B activation in platelets stimulated by cross-linking of Fcgamma receptor IIA (FcgammaRIIA) in the presence of ADP scavengers. Moreover, elevation of the intracellular cAMP concentration did not impair the G(i)-dependent activation of Rap1B. Two unrelated inhibitors of phosphatidylinositol 3-kinase (PI3K), wortmannin and LY294002, totally prevented Rap1B activation in platelets stimulated by cross-linking of FcgammaRIIA, by stimulation of the P2Y(12) receptor for ADP, or by epinephrine. However, in platelets from PI3Kgamma-deficient mice, both ADP and epinephrine were still able to normally stimulate Rap1B activation through a PI3K-dependent mechanism, suggesting the involvement of a different isoform of the enzyme. Moreover, the lack of PI3Kgamma did not prevent the ability of epinephrine to potentiate platelet aggregation through a G(i)-dependent pathway. The inhibitory effect of wortmannin on Rap1B activation was overcome by addition of phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P(3)), but not PtdIns(3,4)P(2), although both lipids were found to support phosphorylation of Akt. Moreover, PtdIns(3,4,5)P(3) was able to relieve the inhibitory effect of apyrase on FcgammaRIIA-mediated platelet aggregation. We conclude that stimulation of a G(i)-dependent signaling pathway causes activation of the small GTPase Rap1B through the action of the PI3K product PtdIns(3,4,5)P(3), but not PtdIns(3,4)P(2), and that this process may contribute to potentiation of platelet aggregation
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