Photon recycling in Fabry-Perot micro-cavities based on Si3_3N4_4 waveguides

We present a numerical analysis and preliminary experimental results on one-dimensional Fabry-Perot micro-cavities in Si$_3$N$_4$ waveguides. The Fabry-Perot micro-cavities are formed by two distributed Bragg reflectors separated by a straight portion of waveguide. The Bragg reflectors are composed by a few air slits produced within the Si$_3$N$_4$ waveguides. In order to increase the quality factor of the micro-cavities, we have minimized, with a multiparametric optimization tool, the insertion loss of the reflectors by varying the length of their first periods (those facing the cavity). To explain the simulation results the coupling of the fundamental waveguide mode with radiative modes in the Fabry-Perot micro-cavities is needed. This effect is described as a recycling of radiative modes in the waveguide. To support the modelling, preliminary experimental results of micro-cavities in Si$_3$N$_4$ waveguides realized with Focused Ion Beam technique are reported.Comment: 5 pages, 5 figure

A polissemia de "coxinha" no português paulista: uma abordagem segundo a Gramática das Construções Cognitiva

This dissertation describes and explains the polysemy of the word "coxinha" in Paulista Portuguese, in specific, and in Brazilian Portuguese, in general. Within the framework of Cognitive Linguistics, the approach is formulated according to Cognitive Construction Grammar, a model which emphasizes the development of new meanings out of conventional meanings associated to a grammatical construction. What the dissertation uses from the theory is the conception of meaning as encyclopedic, viewpointed, flexible, and usage-based. What it uses from the model is the conception of polysemy as a radial categorization of meanings motivated by metaphoric and metonymic patterns. Therefore, the word "coxinha" is the grammatical construction that this dissertation takes for its object, which does not include the grammatical constructions of which this is part. Therefore, we address (i) the description of the meanings that the construction shows and (ii) the explanation of its polysemy by means of two cognitive processes: metaphor and metonymy. The pursuit of such aims revealed the insufficiency of the cognitive processes to explain the value of judgement in two new meanings, present in Paulista Portuguese: the one related to the police officer and the one related to a voter profile. In order to explain both of them, we have to appeal to the concept of subjectification, developed by Functional Linguistics and absorbed by Cognitive Linguistics, and we conclude that the subjectification contributes to the systematic polysemy of nouns in the diminutive and participates in the designations we take for metonymic. The construction of the meanings is investigated diachronically: (i) the first meaning of the word "coxinha", entrenched in Brazilian Portuguese, is the name of a snack, and such designation is attributed to metaphor; (ii) the second meaning, new and originated in São Paulo, is a nickname for the civil servant, in general, and the military police officer, in particular, of São Paulo state, and such designation is attributed to metonymy associated with subjectification; and (iii) the third meaning, also new and originated in São Paulo, refers to right-wing voters according to a folk theory of politics, is also attributed to metonymy and subjectification. In this dissertation, metaphor and metonymy remain as cognitive processes responsible for conceptualization, a central phenomenon in Cognitive Linguistics, which defines it as dynamic and imagistic, while subjectification is situated in the realm of viewpoint. Since meaning is defined as viewpointed, encyclopedic, flexible and usage-based,it becomes necessary to distinguish between conceptualization based on cognitive processes and subjectification as a manifestation of viewpoint. Following the usage-based path, we chose the newspaper O Estado de São Paulo as a source of data. Although we do not include usage frequency in our aims, the word was found in several editorials, which led us to divide the tokens of the word in three groups for the formation of a corpus: (i) from 1894 to 1999, for the analysis of "coxinha" as a snack name; (ii) from 2000 to 2012, for the analysis of "coxinha" as the nickname of the police officer; and (iii) from 2013 to 2018, for the analysis of "coxinha" as a voter profile. The division does not imply that the meaning relative to the snack does not occur beyond the first period, or that the meaning relative to the police officer does not occur beyond the second. Our thesis is that perspectivization, a species of which subjectification is a specimen, plays a preponderant role in the development of the latest meanings, given that subjectification is both part of the systematic polysemy relative to the word-formation process and associates with metonymy. Thus, this dissertation contributes to the recognition of the role of metaphor and metonymy with a case study where, without perspectivization, cognitive processes are not enough to explain the value of judgement. By doing so, this dissertation articulates the situated and the distributed characters of cognition, as defended by Cognitive Linguistics and Cognitive Sociolinguistics.Esta dissertação tem por objetivos descrever e explicar a polissemia da palavra “coxinha” no português paulista, em particular, e no português brasileiro, em geral. Sob o viés da Linguística Cognitiva, a abordagem se formula segundo a Gramática das Construções Cognitiva, modelo que enfatiza o desenvolvimento de significados novos a partir de significados estabelecidos em relação a uma construção gramatical. O que a dissertação emprega da teoria é a concepção do significado como enciclopédico, perspectivista, flexível e baseado no uso. O que emprega do modelo é a concepção de polissemia como categorização radial de significados motivados por padrões metafóricos e metonímicos. Assim, a palavra “coxinha” é a construção gramatical que esta dissertação toma por objeto, sem adentrar nas construções gramaticais de que faz parte, ou seja, nos dedicamos aqui (i) à descrição dos significados que a construção exibe e (ii) à explicação de sua polissemia por meio de dois processos cognitivos: a metáfora e a metonímia. A busca desses objetivos revelou a insuficiência dos processos cognitivos para explicar o juízo de valor em dois significados novos, presentes no português paulista: o correspondente ao policial e o correspondente a um perfil de eleitor. Para explicá-los, recorremos ao conceito de subjetivização, desenvolvido pela Linguística Funcional e absorvido pela Linguística Cognitiva, e concluímos que essa manifestação do ponto de vista constitui a polissemia sistemática dos substantivos no diminutivo e as nomeações que consideramos metonímicas. A formação dos significados é apresentada de forma diacrônica: (i) o primeiro significado da palavra “coxinha”, considerado como rotinizado no português brasileiro, é o nome de um salgado, e tal nomeação é atribuída à metáfora; (ii) o segundo significado, considerado como novo e de origem paulista, é uma alcunha para o funcionário público, em geral, e o policial militar, em particular, do Estado de São Paulo, e tal nomeação é atribuída à metonímia associada à subjetivização; e (iii) o terceiro significado, também considerado como novo e de origem paulista, remete à posição político-partidária de direita segundo o senso comum e é igualmente atribuído à metonímia e à subjetivização. Na abordagem aqui desenvolvida, a metáfora e a metonímia se mantêm como processos cognitivos responsáveis pela conceptualização, fenômeno central na Linguística Cognitiva, que o define como dinâmico e imagístico, enquanto a subjetivização se situa na esfera do ponto de vista. Sendo o significado definido como perspectivista e enciclopédico, se faz necessária a distinção entre conceptualização, com base em processos cognitivos, e subjetivização, como manifestação do ponto de vista.Em busca de dados da língua em uso, escolhemos como fonte o jornal O Estado de São Paulo. Embora o trabalho não se incline ao estudo da frequência de uso, a palavra foi encontrada em diversos editoriais do periódico, o que levou à divisão das ocorrências da palavra “coxinha” em períodos, que, na formação do corpus, foram divididos em três: (i) de 1894 a 1999, para a análise de “coxinha” como nome de salgado; (ii) de 2000 a 2012, para a análise de “coxinha” como alcunha do policial; e (iii) de 2013 a 2018, para a análise de “coxinha” como um perfil de eleitor. A divisão não implica que o significado relativo ao salgado não ocorra além do primeiro período, tampouco que o significado relativo ao policial não ocorra além do segundo. A hipótese de trabalho é que a perspectivização, espécie da qual a subjetivização é um tipo, tem papel preponderante no desenvolvimento dos significados mais recentes, dado que a subjetivização atua tanto na polissemia sistemática relativa ao processo de formação da palavra “coxinha” quanto associada à metonímia. Assim, o trabalho acrescenta ao reconhecimento do papel da metáfora e da metonímia um caso em que, sem a perspectivização, os processos cognitivos não bastam para explicar o juízo de valor. Com isso, a dissertação articula o caráter situado e o caráter distribuído da cognição, conforme defendido pela Linguística Cognitiva e pela Sociolinguística Cognitiva.Dados abertos - Sucupira - Teses e dissertações (2019

Porous silicon microparticles as efficient carriers for immunologic adjuvants

In this work we report a first-time combination of porous silicon (pSi) particles with the immunologic adjuvant Pam3CSK4, a TLR 1/2 agonist, as a tool for immunotherapy. pSi is a sponge-like biocompatible and biode gradable nanomaterial with high porosity, large surface-to-volume ratio and tunable surface, suitable for drug delivery applications. This study provides, by means of live-cell confocal microscopy, an insight about the time course of the interaction of free Pam3CSK4 vs vectorized by pSi microparticles with human dendritic cells (DCs). We found a delay in the ingestion of the agonist when carried by pSi microparticles. These findings were sup ported by the observation of the morphological changes related to the activation of DCs that occurred with a 5 h difference when treated with the vectorized ligand. These results provide the first demonstration of pSi as a conceivable candidate to deliver Pam3CSK4 to DCs paving the way towards immunotherapy practice

Viscosity, Boson Peak and Elastic Moduli in the Na2O-SiO2 System

The temperature and chemical dependence of the melt viscosity are ubiquitous in the model development of the volcanic dynamics, as well as in the glass production and design. We focussed on the yet-explored relationship between the bulk and shear moduli ratio and boson peak with the melt fragility of their parental glasses. Here, we explored the extension of the observed trend by testing the conventional binary system Na2O-SiO2, thus providing new evidence supporting the link between the flow of melts and supercooled liquids and the vibrational dynamics of their parental glasses. This was accomplished by integrating new low-frequency Raman measurements and integrating data from the literature on Brillouin light scattering and viscometry. This approach allows us to feed the MYEGA equation with reliable input parameters to quantitatively predict the viscosity of the Na2O-SiO2 system from the liquid up to the glass transition

Schwartz - Zippelov teorem i neke njegove primjene

U ovom radu izložen je rezultat poznat pod nazivom Schwartz - Zippelova lema ili Schwartz - Zippelov teorem. Tema rada pripada pretežno algebri, ali ima značajne primjene u drugim matematičkim područjima kao što je na primjer teorija algoritama, te kombinatorika. Rad se sastoji od tri poglavlja. U uvodu je ukratko opisana tema i cilj rada. Prvo poglavlje sadrži kratku povijest nastanka teorema, različite oblike rezultata pojedinih autora, te kratki opis pojmova korištenih u samom radu. Drugo poglavlje sastoji se od iskaza i dokaza Schwartz - Zippelovog teorema, a u trećem poglavlju izložene su neke primjene tog teorema na probleme koji se mogu svesti na testiranje jednakosti polinoma. Takvi su, primjerice, problem postojanja savršenog sparivanja u grafu i ispitivanje svojstva asocijativnosti u grupoidu. Uz svaku primjenu navedeni su i prikladni primjeri.In this diploma thesis we present the result usually called the Schwartz-Zippel lemma or the Schwartz-Zippel theorem. The nature of this theorem is basically algebraic, but it has significant applications in other areas of mathematics, such as the theory of algorithms and combinatorial theory. The thesis consists of three chapters. The main theme and objective are briefly described in the introduction. The first chapter contains a short history of the theorem’s origins, various forms of the main results by different authors and some comments of basic concepts related to this topic. The statement and a proof of the Schwartz-Zippel theorem are given in the second chapter, together with the general outline of its applications. The third and final chapter consists of some applications to problems which can be reduced to polynomial identity testing, including the existence of a perfect matching in a graph and testing of the associativity property in a groupoi

Role of interface region on the optoelectronic properties of silicon nanocrystals embedded in SiO2

Light emitting silicon nanocrystals embedded in SiO2 have been investigated by x-ray absorption measurements in total electron and photoluminescence yields, by energy filtered TEM analysis and by ab-initio total energy calculations. Both experimental and theoretical results show that the interface between the silicon nanocrystals and the surrounding SiO2 is not sharp: an intermediate region of amorphous nature and of variable composition links the crystalline Si with the amorphous stoichiometric SiO2. This region plays an active role in the light emission process

Instalative art as a teaching resource for environmental education in Childhood Education

RESUMEN El niño aprende haciendo, manipulando los objetos y la realidad que se encuentra. Mediante la creación artística se puede abrir la puerta a nuevos aprendizajes, algunos de ellos pueden ser los siguientes: psicomotriz, emocional, cognitivo, artístico, lógico-matemático, lingüístico… Con el trabajo centrado en la instalación artística se le da al niño un espacio físico que le permite pensar mediante la actividad. De este modo, la manipulación de objetos durante el juego, ayuda al niño a descubrir y a experimentar a través del manejo de los materiales de dicha composición artística. La propuesta escogida en este caso ha sido la utilización de materiales presentes en la naturaleza. Con esta elección se intenta acercar la educación medioambiental a los niños a través del arte. Este trabajo, diseñado para aulas de educación infantil (2-6 años), consta de dos partes diferenciadas y relacionadas entre sí. Por un lado, se hace un recorrido teórico por los antecedentes del arte de la instalación enmarcada en el arte contemporáneo, donde se verán algunos de los autores que han contribuido al desarrollo de esta disciplina artística. De igual manera se revisa la importancia de la educación en contenidos de naturaleza y medio ambiente. En una segunda parte del trabajo, se desarrolla una parte más práctica para ilustrar a maestros y maestras acerca de cómo se lleva al espacio físico esta idea de instalación artística. Para ello, se mostrarán tres ejemplos de ellas y se llevará a cabo el análisis de su montaje, desarrollo y documentación de la actividad.ABSTRACT The child learns by doing, manipulating the objects and the reality arround them. Through artistic creation he will be able to access new learnings, such as: psychomotor, emotional, cognitive, artistic, logical-mathematical, linguistic,... Such work focused on the artistic installation, allows children to enjoy a place that gives them the chance to think while they are active. Thereby, object manipulation during the game helps them to learn through the handling of the materials of such artistic trend. The chosen approach in this case has been the usage of the materials which are found in nature. Along with this, we try to bring the environment friendly education close to the clindren through art. This work designed for preschool classrooms (2-6 years), consists of two different parts which are related to each other. The first one, consists in a theoretical journey through the background of the art of the installation framed in contemporary art, where we will talk about some of the authors who have contributed to the development of this artistic style. As well, the importance of education in content of nature and environment is reviewed. In the second part of the work, the development of a more practical part will be done to illustrate teachers about how the idea of artistic installation is taken to the physical space. Three examples of it will be shown and the analysis will be carried out, as well the development and the documentation of the activity.Grado en Magisterio en Educación Infanti

Effect of thermal treatment on the growth, structure and luminescence of nitride-passivated silicon nanoclusters

Silicon nanoclusters (Si-ncs) embedded in silicon nitride films have been studied to determine the effects that deposition and processing parameters have on their growth, luminescent properties, and electronic structure. Luminescence was observed from Si-ncs formed in silicon-rich silicon nitride films with a broad range of compositions and grown using three different types of chemical vapour deposition systems. Photoluminescence (PL) experiments revealed broad, tunable emissions with peaks ranging from the near-infrared across the full visible spectrum. The emission energy was highly dependent on the film composition and changed only slightly with annealing temperature and time, which primarily affected the emission intensity. The PL spectra from films annealed for duration of times ranging from 2 s to 2 h at 600 and 800°C indicated a fast initial formation and growth of nanoclusters in the first few seconds of annealing followed by a slow, but steady growth as annealing time was further increased. X-ray absorption near edge structure at the Si K- and L3,2-edges exhibited composition-dependent phase separation and structural re-ordering of the Si-ncs and silicon nitride host matrix under different post-deposition annealing conditions and generally supported the trends observed in the PL spectra

Si solid-state quantum dot-based materials for tandem solar cells

The concept of third-generation photovoltaics is to significantly increase device efficiencies whilst still using thin-film processes and abundant non-toxic materials. A strong potential approach is to fabricate tandem cells using thin-film deposition that can optimise collection of energy in a series of cells with decreasing band gap stacked on top of each other. Quantum dot materials, in which Si quantum dots (QDs) are embedded in a dielectric matrix, offer the potential to tune the effective band gap, through quantum confinement, and allow fabrication of optimised tandem solar cell devices in one growth run in a thin-film process. Such cells can be fabricated by sputtering of thin layers of silicon rich oxide sandwiched between a stoichiometric oxide that on annealing crystallise to form Si QDs of uniform and controllable size. For approximately 2-nm diameter QDs, these result in an effective band gap of 1.8 eV. Introduction of phosphorous or boron during the growth of the multilayers results in doping and a rectifying junction, which demonstrates photovoltaic behaviour with an open circuit voltage (VOC) of almost 500 mV. However, the doping behaviour of P and B in these QD materials is not well understood. A modified modulation doping model for the doping mechanisms in these materials is discussed which relies on doping of a sub-oxide region around the Si QDs

Experimental measurement of plasmonic nanostructures embedded in silicon waveguide gaps

“© 2016 Optical Society of America. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited"In this work, we report numerical simulations and experiments of the optical response of a gold nanostrip embedded in a silicon strip waveguide gap at telecom wavelengths. We show that the spectral features observed in transmission and reflection when the metallic nanostructure is inserted in the gap are extremely different than those observed in free-space excitation. First, we find that interference between the guided field and the electric dipolar resonance of the metallic nanostructure results in highcontrast (> 10) spectral features showing an asymmetric Fano spectral profile. Secondly, we reveal a crossing in the transmission and reflection responses close to the nanostructure resonance wavelength as a key feature of our system. This approach, which can be realized using standard semiconductor nanofabrication tools, could lead to a full exploitation of the extreme properties of subwavelength metallic nanostructures in an on-chip configuration, with special relevance in fields such as biosensing or optical switching.We acknowledge support from the Spanish Ministry of Economy and Competiveness (MINECO) under grants TEC2014-51902-C2-1-R and TEC2014-61906-EXP, and the Valencian Conselleria d'Educacion, Cultura i Esport under grant PROMETEOII/2014/034.Espinosa-Soria, A.; Griol Barres, A.; Martínez Abietar, AJ. (2016). Experimental measurement of plasmonic nanostructures embedded in silicon waveguide gaps. Optics Express. 24(9):9592-9601. https://doi.org/10.1364/OE.24.009592S9592960124