Strong light-matter coupling in bulk GaN-microcavities with double dielectric mirrors fabricated by two different methods

Two routes for the fabrication of bulk GaN microcavities embedded between two dielectric mirrors are described, and the optical properties of the microcavities thus obtained are compared. In both cases, the GaN active layer is grown by molecular beam epitaxy on (111) Si, allowing use of selective etching to remove the substrate. In the first case, a three period Al0.2Ga0.8N / AlN Bragg mirror followed by a lambda/2 GaN cavity are grown directly on the Si. In the second case, a crack-free 2,mu m thick GaN layer is grown, and progressively thinned to a final thickness of lambda. Both devices work in the strong coupling regime at low temperature, as evidenced by angle-dependent reflectivity or transmission experiments. However, strong light-matter coupling in emission at room temperature is observed only for the second one. This is related to the poor optoelectronic quality of the active layer of the first device, due to its growth only 250 nm above the Si substrate and its related high defect density. The reflectivity spectra of the microcavities are well accounted for by using transfer matrix calculations. (C) 2010 American Institute of Physics. [doi:10.1063/1.3477450

One-Dimensional ZnO/Gold Junction for Simultaneous and Versatile Multisensing Measurements

The sensing capabilities of zinc oxide nano/micro-structures have been widely investigated and these structures are frequently used in the fabrication of cutting-edge sensors. However, to date, little attention has been paid to the multi-sensing abilities of this material. In this work, we present an efficient multisensor based on a single zinc oxide microwire/gold junction. The device is able to detect in real time three different stimuli, UV-VIS light, temperature and pH variations. This is thanks to three properties of zinc oxide its photoconductive response, pyroelectricity and surface functionalization with amino-propyl groups, respectively. The three stimuli can be detected either simultaneously or in a sequence/random order. A specific mathematical tool was also developed, together with a design of experiments (DoE), to predict the performances of the sensor. Our micro-device allows reliable and versatile real-time measurements of UV-VIS light, temperature and pH variations. Therefore, it shows great potential for use in the field of sensing for living cell cultures

the effects of the film thickness and roughness in the anodization process of very thin aluminum films

Introduction The anodization of aluminum foils having micrometer thickness is a common process and results in hexagonally self-ordered alumina membranes. However, anodic aluminum oxide (AAO) membranes fabricated from nanometer-thin films present new challenges to the anodization process, since aluminum films adheres poorly on supporting substrates and the smoothness of the film is highly related to the kind of substrate. In the current work we studied the effect of the aluminum thickness and roughness, using films ranging from 100 to 800 nm in thickness and from 2 to 15 nm in root means square roughness (on a scan area of 100 μm2), on the final alumina morphology. We deposited Al thin films by sputtering method on transparent conductive glass substrates. A strong dependence between the Al film roughness and the final alumina pore organization was observed. It was also determined that by reducing the Al film thickness, smaller Al grains were generated, leading to a homogenous pore formation. It was found that, for thicknesses below 300 nm, the electrolyte used to perform anodization becomes a critical parameter due to the competitive effect of aluminum delamination with respect to the anodization reaction. Phosphoric acid showed less delamination problems than oxalic acid

Facile synthesis of cubic cuprous oxide for electrochemical reduction of carbon dioxide

Abstract: High level of atmospheric carbon dioxide (CO2) concentration is considered one of the main causes of global warming. Electrochemical conversion of CO2 into valuable chemicals and fuels has promising potential to be implemented into practical and sustainable devices. In order to efficiently realize this strategy, one of the biggest efforts has been focused on the design of catalysts which are inexpensive, active and selective and can be produced through green and up-scalable routes. In this work, copper-based materials are simply synthesized via microwave-assisted process and carefully characterized by physical/chemical/electrochemical techniques. Nanoparticle with a cupric oxide (CuO) surface as well as various cuprous oxide (Cu2O) cubes with different sizes is obtained and used for the CO2 reduction reaction. It is observed that the Cu2O-derived electrodes show enhanced activity and carbon monoxide (CO) selectivity compared to the CuO-derived one. Among various Cu2O catalysts, the one with the smallest cubes leads to the best CO selectivity of the electrode, attributed to a higher electrochemically active surface area. Under applied potentials, all Cu2O cubes undergo structural and morphological modification, even though the cubic shape is retained. The nanoclusters formed during the material evolution offer abundant and active reaction sites, leading to the high performance of the Cu2O-derived electrodes

In situ generation of silver nanoparticles in PVDF for the development of resistive switching devices

It is widely accepted that resistive switching devices (RSDs) are extremely appealing as active components in computer memories and logic gates in electronics, directly enabling neuromorphic functionalities. The aim of this study is to investigate the chemical and electrical properties of a nanocomposite polymer, the active component of the device, in order to characterise its composition and behaviour under electric field. This paper presents the morphological and chemical characterization of an in-situ generated silver – Polyvinylidene fluoride-hexafluoropropylene PVDF-HFP nanocomposite (NC) material. A silver salt is added as precursor to the polymer solution and then, after a film casting step, the nanoparticles generation and growth processes are carried out by way of UV irradiation; the growth and the distribution of in-situ generated silver nanoparticles (NPs) in the polymer matrix are described. The devices, built on a planar electrode structure, undergo an I/V test to explore their resistance states at different switching voltages. Furthermore, after electrical analysis a remarkable R off /R on ratio and a relatively low switching voltage (3 V) are achieved, demonstrating the suitability of the developed material for the next generation of soft, wearable, RSDs

Chainlike Mesoporous SnO2 as a Well-Performing Catalyst for Electrochemical CO2 Reduction

In this Article, we present an easy, quick, and scalable route, based on anodic oxidation, for the preparation of mesoporous SnO2 as an efficient electrocatalyst for the CO2 reduction reaction (CO2RR). Crystallographically interconnected SnO2 nanocrystals with abundant grain boundaries, high specific surface area, and easily accessible porosity result to be active and selective for the CO2RR. This electrocatalyst shows faradaic efficiency (FE) of about 95% at-0.97 and-1.06 V versus reversible hydrogen electrode (RHE) toward the formation of predominant HCOOH and minor CO. A peak FE value of 82% for the HCOOH production is obtained at-1.06 V vs RHE. High HCOOH partial current densities of 10.2 and 15.3 mA cm-2 are observed at-0.97 and-1.15 V vs RHE, respectively. Thorough electrochemical characterizations demonstrate that the synthesized SnO2-based gas diffusion electrode allows efficient diffusion of CO2 even at high kinetics because of the highly open porous structure. The good understanding of the catalyst behavior is achieved also after the electrode testing, and it shows that the proposed preparation route results in a stable and durable material. The here reported promising results can be exploited for developing high-performance and sustainable electrocatalysts with a high potentiality to be implemented in real CO2 conversion devices

Facile synthesis of cubic cuprous oxide for electrochemical reduction of carbon dioxide

Abstract High level of atmospheric carbon dioxide (CO2) concentration is considered one of the main causes of global warming. Electrochemical conversion of CO2 into valuable chemicals and fuels has promising potential to be implemented into practical and sustainable devices. In order to efficiently realize this strategy, one of the biggest efforts has been focused on the design of catalysts which are inexpensive, active and selective and can be produced through green and up-scalable routes. In this work, copper-based materials are simply synthesized via microwave-assisted process and carefully characterized by physical/chemical/electrochemical techniques. Nanoparticle with a cupric oxide (CuO) surface as well as various cuprous oxide (Cu2O) cubes with different sizes is obtained and used for the CO2 reduction reaction. It is observed that the Cu2O-derived electrodes show enhanced activity and carbon monoxide (CO) selectivity compared to the CuO-derived one. Among various Cu2O catalysts, the one with the smallest cubes leads to the best CO selectivity of the electrode, attributed to a higher electrochemically active surface area. Under applied potentials, all Cu2O cubes undergo structural and morphological modification, even though the cubic shape is retained. The nanoclusters formed during the material evolution offer abundant and active reaction sites, leading to the high performance of the Cu2O-derived electrodes. Graphic abstrac

Индивидуальная факторная структура биомеханических и психофизиологических показателей, как основа для определения стиля ведения боя квалифицированных боксеров-ветеранов

Purpose: to reveal the fighting style of veteran boxers based on the individual factor structure of psychophysiological and biomechanical indicators. Material and methods. The study involved 42 qualified veteran boxers (aged 45-50). A biomechanical analysis of the indicators of the movement speed of various points and the values of the joint angles while performing a direct blow by boxers has been used as a research method. The psychophysiological method has been used to determine the time of a simple and complex reaction under standard conditions and in various testing modes. Descriptive Statistics and Factor Analysis have been applied as methods of statistical analysis. Results. Two main factors have been identified in the structure of the complexperformance of qualified veteran boxers. Factor 1 (55.063% of the total aggregate variance) is named "Speed". Factor 2 (44.937% of the total aggregate variance) stands for “Speed Endurance”. Individual factor structure, which is characterized by the distinctive factor "Speed and Coordination Endurance" by more than 80% as well as by the marked factor "Speed" by less than 30% is considered to be a particularity of the tempo style boxers. Individual factor structure, which is characterized by the intensity of the factor "Speed" by more than 80%, and by the distinctive factor "Speed and Coordination Endurance" by less than 30% is considered to be typical for the playing style boxers. The individual factor structure, which is characterized by the marked factor "Speed" by more than 50%, and by the intencity of the factor "Speed and Coordination Endurance" by less than 30% is seen to be peculiar to the strength style boxers. Conclusions. It is shown that the psychophysiological features of boxers of different fighting styles are reflected in the features of the direct strike technique. The lack of speed at the beginning of the movement in tempo style boxers is supplemented and compensated by the high speed of movement. Playing style boxers are characterized by a high speed of movement at the very beginning of the strike. Strength style boxers are characterized by the gradual development of movement speed.Мета: виявити стиль ведення поєдинку боксерів ветеранів на основі індивідуальної факторної структури психофізіологічних і біомеханічних показників. Матеріал і методи. У дослідженні взяли участь 42 кваліфікованих боксера-ветерана (вік 45-50 років). В якості методів дослідження використовувався біомеханічний аналіз показників швидкості руху різних точок і значення кутів в суглобах при виконанні прямого удару боксерами. Використовувався психофізіологічний метод визначення часу простої і складної реакції в стандартних умовах і в різних режимах тестування. В якості методів статистичного аналізу застосовувався метод описової статистики (Descriptive Statistics) і метод факторного аналізу. Результати.Вструктурікомплексноїпідготовленостікваліфікованих боксерів-ветераніввиділено 2 основних фактори.Фактор 1 (55,063 % від загального сумарної дисперсії) названий «Швидкість».Фактор 2 (44,937%відзагальноїсумарноїдисперсії) був названий «Швидкісна та координаційна витривалість».Індивідуальна факторна структура, яка характеризується виразністю фактору «Швидкісна та координаційна витривалість» більш ніж на 80%, і виразністю фактору «Швидкість» менш ніж на 30%, характерна для боксерів темпового стилю. Індивідуальна факторна структура, яка характеризується виразністю фактору «Швидкість» більш ніж на 80%, і виразністю фактору «Швидкісна та координаційна витривалість» менш ніж на 30%, характерна для боксерів ігрового стилю. Індивідуальна факторна структура, яка характеризується виразністю фактору «Швидкість» більш ніж на 50%, і виразністю фактору «Швидкісна та координаційна витривалість» менш ніж на 30%, характерна для боксерів силового стилю.Висновки. Показано, що психофізіологічні особливості боксерів різних стилів ведення поєдинку відображаються на особливостях техніки прямого удару. Недолік швидкості на початку руху у боксерів темпового стилю доповнюється і компенсується високою швидкістю переміщень. Боксери ігрового стилю відрізняються високою швидкістю рухів на самому початку виконання удару. Боксери силового стилю відрізняються поступовим розвитком швидкості руху.Цель работы: выявить стиль ведения поединка боксеров-ветеранов на основе индивидуальной факторной структуры психофизиологических и биомеханических показателей. Материал и методы. В исследовании приняли участие 42 квалифицированных боксера-ветерана (возраст 45-50 лет). В качестве методов исследования использовался биомеханический анализ показателей скорости движения различных точек и значения углов в суставах при выполнении прямого удара боксерами. Использовался психофизиологический метод определения времени простой и сложной реакции в стандартных условиях и в различных режимах тестирования. В качестве методов статистического анализа применялся метод описательной статистики (DescriptiveStatistics) и метод факторного анализа Результаты.В структуре комплексной подготовленности квалифицированных боксеров-ветеранов выделено 2 основных фактора. Фактор 1 (55,063% от общего суммарной дисперсии) назван «Скорость». Фактор 2 (44,937% от общего суммарной дисперсии) был назван «Скоростная выносливость». Индивидуальная факторная структура, которая характеризуется выраженностью фактора «Скоростная и координационная выносливость» более чем на 80%, и выраженностью фактора «Скорость» менее, чем на 30%, характерная для боксеров темпового стиля. Индивидуальная факторная структура, которая характеризуется выраженностью фактора «Скорость» более чем на 80%, и выраженностью фактора «Скоростная и координационная выносливость» менее, чем на 30%, характерная для боксеров игрового стиля. Индивидуальная факторная структура, которая характеризуется выраженностью фактора «Скорость» более чем на 50%, и выраженностью фактора «Скоростная и координационная выносливость» менее, чем на 30%, характерная для боксеров силового стиля. Выводы. Показано, что психофизиологические особенности боксеров различных стилей ведения поединка отражаются на особенностях техники прямого удара. Недостаток скорости в начале движения у боксеров-темпового стиля дополняется и компенсируется высокой скоростью перемещений. Боксеры игрового стиля отличаются высокой скоростью движений в самом начале выполнения удара. Боксеры силового стиля отличаются постепенным развитием скорости движения

The influences of moisture content variation, number and width of gaps on the withdrawal resistance of self tapping screws inserted in cross laminated timber

A large experimental campaign comprised of 470 withdrawal tests was carried out, aiming to quantify the withdrawal resistance of self-tapping screws (STS) inserted in the side face of cross laminated timber (CLT) elements. In order to deeply understand the “CLT-STS” composite model, the experimental tests considered two main parameters: (i) simple and cyclic changes on moisture content (MC) and (ii) number and width of gaps. Regarding (i), three individual groups of test specimens were stabilized with 8%, 12% and 18% of moisture content and one group was submitted to a six month RH cycle (between 30% and 90% RH). Concerning (ii), different test configurations with 0 (REF), 1, 2 and 3 gaps, and widths equal to 0mm (GAP0) or 4mm (GAP4), were tested. The influences of MC and number of gaps were modeled by means of least square method. Moreover, a revision of a prediction model developed by Uibel and Blaß (2007) was proposed. The main findings of the experimental campaign were: the decrease of withdrawal resistance for specimens tested with MC=18% in most configurations; the unexpected increase of withdrawal resistance as the number of gaps with 0mm increased; and, the surprising increase of withdrawal resistance for REF specimens submitted to the RH cycle.The development of the present work was possible only thanks to the financial support of the 391 Portuguese Science Foundation (Fundação de Ciência e Tecnologia, FCT), through PhD grant SFRH / BD17392 / 79972 / 2011. Further, the valuable partnerships with the Institute of Timber Engineering and Wood393 Technology, at Graz University of Technology (Austria), and Rusticasa are gratefully acknowledged