Silver oxide particles/silver nanoparticles interconversion: Susceptibility of forward/backward reactions to the chemical environment at room temperature

The thermal stability of the silver oxide particles (Ag 2O)/ metallic silver nanoparticles (AgNPs) system in aqueous and gaseous environments is investigated with UV-Visible spectroscopy, TEM, SEM and DLS as characterisation techniques, and with calculations using electromagnetic theory. Thermal decomposition of aqueous Ag 2O colloids to produce AgNPs is conclusively demonstrated and used as a base reaction to produce clean AgNPs without any external reducing agent. Such a spontaneous character of Ag 2O decomposition in alkaline aqueous/water-enriched environments at room temperature makes the formation of silver oxide films on silver nanoparticles/nanostructures unlikely, keeping the silver surface oxide-free, a crucial feature in determining the silver catalytic and Raman enhancing properties. The synthetic suitability of this reaction to develop new routes to produce AgNPs is explored by analyzing the effect of temperature, complexing agents, and environment polarity on the AgNPs size/shape control. Thermal decomposition of Ag 2O colloids in aqueous/water-enriched environments offers the possibility to produce AgNPs at low cost, with easy, clean, safe and green chemistry procedures.Fil: Douglas Gallardo, Oscar Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Moiraghi, Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Macchione, Micaela Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Godoy, Jorge A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Perez, Manuel Alejo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Coronado, Eduardo A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Macagno, Vicente Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentin

Testing a fault tolerant mixed-signal design under TID and heavy ions

This work presents results of three distinctradiation tests performed upon a fault tolerant data acqui-sition system comprising a design diversity redundancytechnique. The first and second experiments are Total Ion-izing Dose (TID) essays, comprising gamma and X-rayirradiations. The last experiment considers single eventeffects, in which two heavy ion irradiation campaignsare carried out. The case study system comprises threeanalog-to-digital converters and two software-based vot-ers, besides additional software and hardware resourcesused for controlling, monitoring and memory manage-ment. The applied Diversity Triple Modular Redundancy(DTMR) technique, comprises different levels of diversity(temporal and architectural). The circuit was designed ina programmable System-on-Chip (PSoC), fabricated in a130nm CMOS technology process. Results show that thetechnique may increase the lifetime of the system underTID if comparing with a non-redundant implementation.Considering the heavy ions experiments the system wasproved effective to tolerate 100% of the observed errorsoriginated in the converters, while errors in the process-ing unit present a higher criticality. Critical errors occur-ring in one of the voters were also observed. A secondheavy ion campaign was then carried out to investigatethe voters reliability, comparing the the dynamic cross sec-tion of three different software-based voter schemes im-plemented in the considered PSoC

Reliability on ARM Processors Against Soft Errors Through SIHFT Techniques

ARM processors are leaders in embedded systems, delivering high-performance computing, power efficiency, and reduced cost. For this reason, there is a relevant interest for its use in the aerospace industry. However, the use of sub-micron technologies has increased the sensitivity to radiation-induced transient faults. Thus, the mitigation of soft errors has become a major concern. Software-Implemented Hardware Fault Tolerance (SIHFT) techniques are a low-cost way to protect processors against soft errors. On the other hand, they cause high overheads in the execution time and memory, which consequently increase the energy consumption. In this work, we implement a set of software techniques based on different redundancy and checking rules. Furthermore, a low-overhead technique to protect the program execution flow is included. Tests are performed using the ARM Cortex-A9 processor. Simulated fault injection campaigns and radiation test with heavy ions have been performed. Results evaluate the trade-offs among fault detection, execution time, and memory footprint. They show significant improvements of the overheads when compared to previously reported techniques.This work was supported in part by CNPq and CAPES, Brazilian agencies

X-rays detector sensitive to the position.

Um contador a gás, com multifios, sensível à posição, para a detecção de raios X foi construído utilizando linhas de atraso integradas para leitura da posição. Seis linhas de atraso (50ns de atraso cada, frequência de corte de 40MHz) cobrem um comprimento sensível total de 150mm, possuindo uma razão do atraso total pelo tempo de subida dos sinais na linha adequadas para a detecção em posição raios X de 5,9keV do ANTIPOT. 55 Fe com alta resolução. Testes usando a forneceram uma não-linearidade linha de integral máxima menor que 0,1% e não-linearidade diferencial máxima de ±4,0%, com o detector utilizando a mistura 700torr. Testes similares foram feitos usando de Ar-CH IND 4 (90%-10%) a a linha de 8,04keV de um tubo de raios X de Cu. Uma resolução total de 330m, e as mesmas não-linearidades integral e diferencial foram obtidas. Com a finalidade de t.est.ar o comportamento do detector sob condições experimentais reais, duas diferentes amostras foram analisadas na região de espalhamento em baixo ângulo. As amostras analisadas foram o carvão vítreo e o dodecil sulfato de sódio (SLS). O feixe de raios X foi colimado por um conjunto de fendas, com 50,um cada uma delas e separadas de 98mm. A distância entre a amostra e o detector era de 404,5mm, fazendo com que a região sensível do detector cobrisse um ângulo de espalhamento de ±12 °. Foram obtidos um raio de giro de 22 Å para o carvão vítreo e um dos parâmetros da rede cristalina c de 39,1 Å para o SLS. Estes resultados estão de acordo com trabalhos anteriores obtidos com técnicas tradicionais de maior dispêndio de tempo que utilizam detectores de Nal(T1) e chapas fotográficas em uma câmara de Laue.A multiware position sensitive gas counter for X-Ray detection was developed in our laboratory making use or commercial delay-lines for position sensing. Six delay-line chips (50ns delay each 40Mhz cut-off frequency) cover a total sensitive length of 190mm leading to a delay-risetime ratio that allows for a high-resolution position detection. Tests using the 5,9keV X-Ray line from a 55Fe source an integral linearity better than 0,1% and a maximum differential linearity or ±4,0% were obtained operating the detector with an Ar-CH 4 (90%-10%) gas mixture at 700torr. Similar tests were performed using the 8,04keV line from a Cu X-Ray tube. A total resolution or 330m, and the same integral and differential linearities were obtained. In order to check the detector performance under usual experimental conditions two different samples were analyzed in the low scattering-angle region. The samples analyzed were vitreous carbon and sodium dodecyl sulfate (SLS). The X-Rays were collimated by a set or slits each 50m wide separated by 98mm. The distance between the sample and the detector was 404,5mm, so that the detector covered a scattering angle of ±12°. A radius of gyration of 22Å for vitreous carbon and a crystallographic parameter of 39,1Å for SLS were obtained. These values are in good agreement with those obtained with the more time-consuming traditional techniques making use of a rotating NaI(T1) detector and photographic plates with a Laue camera

Time-of-flight mass spectrometer for analysis of macromolecules

Um espectrômetro de massa por tempo de vôo foi projetado e construído. A técnica de Plasma Desorption é empregada para provocar a dessorção e ionização das moléculas da amostra por colisões com os produtos de fissão emitidos de uma fonte radioativa de ANTPOT.252 Cf. O espectrômetro encontra-se instalado no interior de uma câmara de vácuo, que permite a sua operação a pressões da ordem de 10 POT.-7 torr. Uma pré-câmara é utilizada para a manipulação e troca de até três amostras simultaneamente, sem a necessidade da abertura da câmara principal para a atmosfera, reduzindo o tempo de recuperação da pressão do sistema para início das análises. No tubo de vôo, que possui uma extensão de 111 cm, encontra-se instalado um guia eletrostático de partículas, usado para aumentar a transmissão dos íons secundários até o sistema de detecção. Medidas foram feitas utilizando-se amostras-padrão para a caracterização do instrumento. Estudos também foram realizados sobre o comportamento da resolução e da eficiência de transmissão do aparelho em função entre 1600 e 1800 para íons com massas em torno de 900 u.m.a.A time-of-flight mass spectrometer was projected and constructed. The Plasma Desorption technique is employed to desorb and ionize the molecules sample by collisions with fission fragments emitted from ANTPOT.252 Cf source. The spectrometer is placed inside a vacuum chamber, allowing operation at a pressure around of 10 POT.-7 torr. A pre-chamber is used to insert three samples simultaneously into the mass spectrometer, without the need of opening the main chamber to the atmosphere, reducing the recover time of the pressure system for the beginning of analyzes. Inside the flight tube (111 cm length) was installed an electrostatic particle guide, used to increase the secondary ion transmission to the detection system. Measurements using standard samples were done to characterize the apparatus performance. The instrument resolution and transmission efficiency were analyzed with respect to the secondary ion acceleration voltage. The mass resolution of m/m from 1600 to 1800 for rnass ions around 900 u.m.a. was obtained

Time-of-flight mass spectrometer for analysis of macromolecules

Um espectrômetro de massa por tempo de vôo foi projetado e construído. A técnica de Plasma Desorption é empregada para provocar a dessorção e ionização das moléculas da amostra por colisões com os produtos de fissão emitidos de uma fonte radioativa de ANTPOT.252 Cf. O espectrômetro encontra-se instalado no interior de uma câmara de vácuo, que permite a sua operação a pressões da ordem de 10 POT.-7 torr. Uma pré-câmara é utilizada para a manipulação e troca de até três amostras simultaneamente, sem a necessidade da abertura da câmara principal para a atmosfera, reduzindo o tempo de recuperação da pressão do sistema para início das análises. No tubo de vôo, que possui uma extensão de 111 cm, encontra-se instalado um guia eletrostático de partículas, usado para aumentar a transmissão dos íons secundários até o sistema de detecção. Medidas foram feitas utilizando-se amostras-padrão para a caracterização do instrumento. Estudos também foram realizados sobre o comportamento da resolução e da eficiência de transmissão do aparelho em função entre 1600 e 1800 para íons com massas em torno de 900 u.m.a.A time-of-flight mass spectrometer was projected and constructed. The Plasma Desorption technique is employed to desorb and ionize the molecules sample by collisions with fission fragments emitted from ANTPOT.252 Cf source. The spectrometer is placed inside a vacuum chamber, allowing operation at a pressure around of 10 POT.-7 torr. A pre-chamber is used to insert three samples simultaneously into the mass spectrometer, without the need of opening the main chamber to the atmosphere, reducing the recover time of the pressure system for the beginning of analyzes. Inside the flight tube (111 cm length) was installed an electrostatic particle guide, used to increase the secondary ion transmission to the detection system. Measurements using standard samples were done to characterize the apparatus performance. The instrument resolution and transmission efficiency were analyzed with respect to the secondary ion acceleration voltage. The mass resolution of m/m from 1600 to 1800 for rnass ions around 900 u.m.a. was obtained

X-rays detector sensitive to the position.

Um contador a gás, com multifios, sensível à posição, para a detecção de raios X foi construído utilizando linhas de atraso integradas para leitura da posição. Seis linhas de atraso (50ns de atraso cada, frequência de corte de 40MHz) cobrem um comprimento sensível total de 150mm, possuindo uma razão do atraso total pelo tempo de subida dos sinais na linha adequadas para a detecção em posição raios X de 5,9keV do ANTIPOT. 55 Fe com alta resolução. Testes usando a forneceram uma não-linearidade linha de integral máxima menor que 0,1% e não-linearidade diferencial máxima de ±4,0%, com o detector utilizando a mistura 700torr. Testes similares foram feitos usando de Ar-CH IND 4 (90%-10%) a a linha de 8,04keV de um tubo de raios X de Cu. Uma resolução total de 330m, e as mesmas não-linearidades integral e diferencial foram obtidas. Com a finalidade de t.est.ar o comportamento do detector sob condições experimentais reais, duas diferentes amostras foram analisadas na região de espalhamento em baixo ângulo. As amostras analisadas foram o carvão vítreo e o dodecil sulfato de sódio (SLS). O feixe de raios X foi colimado por um conjunto de fendas, com 50,um cada uma delas e separadas de 98mm. A distância entre a amostra e o detector era de 404,5mm, fazendo com que a região sensível do detector cobrisse um ângulo de espalhamento de ±12 °. Foram obtidos um raio de giro de 22 Å para o carvão vítreo e um dos parâmetros da rede cristalina c de 39,1 Å para o SLS. Estes resultados estão de acordo com trabalhos anteriores obtidos com técnicas tradicionais de maior dispêndio de tempo que utilizam detectores de Nal(T1) e chapas fotográficas em uma câmara de Laue.A multiware position sensitive gas counter for X-Ray detection was developed in our laboratory making use or commercial delay-lines for position sensing. Six delay-line chips (50ns delay each 40Mhz cut-off frequency) cover a total sensitive length of 190mm leading to a delay-risetime ratio that allows for a high-resolution position detection. Tests using the 5,9keV X-Ray line from a 55Fe source an integral linearity better than 0,1% and a maximum differential linearity or ±4,0% were obtained operating the detector with an Ar-CH 4 (90%-10%) gas mixture at 700torr. Similar tests were performed using the 8,04keV line from a Cu X-Ray tube. A total resolution or 330m, and the same integral and differential linearities were obtained. In order to check the detector performance under usual experimental conditions two different samples were analyzed in the low scattering-angle region. The samples analyzed were vitreous carbon and sodium dodecyl sulfate (SLS). The X-Rays were collimated by a set or slits each 50m wide separated by 98mm. The distance between the sample and the detector was 404,5mm, so that the detector covered a scattering angle of ±12°. A radius of gyration of 22Å for vitreous carbon and a crystallographic parameter of 39,1Å for SLS were obtained. These values are in good agreement with those obtained with the more time-consuming traditional techniques making use of a rotating NaI(T1) detector and photographic plates with a Laue camera

PERCEPÇÃO DO CONSUMIDOR SOBRE OS ATRIBUTOS DE DIFERENCIAÇÃO NO SEGMENTO RURAL: CAFÉ NO MERCADO INTERNO

Differentiation through added value improvement has been explored by strategy and marketing literature. However, because of the distance between growers, final-consumers and technical features not always easily understood by the consumers, differentiation attributes adopted in agricultural production may not be perceived or valorized by the consumers. The article aims to verify whether the strategies of differentiation of rural coffee growers, through the introduction of products that value the origin or the production process have been noticed by Brazilian consumers. For that purpose, a research was conducted with 300 upper-crust consumers in coffee shops and supermarkets in the capital of the state of São Paulo in March and April 2005. The results demonstrated consumers’ perception, particularly related to the coffees which were produced without the use of pesticides. However, the products differentiated by the attributes of the processing companies brand are perceived as more attractive when compared with those regarding to the region of origin or process of agricultural production

Organocatalytic Control over a Fuel-Driven Transient Esterification Network

Signal transduction in living systems is the conversion of information into a chemical change and the principal process by which cells communicate. This process enables phenomena such as time-keeping and signal amplification. In nature, these functions are encoded in non-equilibrium (bio)chemical reaction networks (CRNs) controlled by enzymes. While these catalytically controlled processes are an integral part of biocatalytic pathways, man-made analogs are rare. Here, we incorporate catalysis in an artificial fuel driven out-of-equilibrium CRN. The study entails the design of an organocatalytically controlled fuel driven esterification CRN, where the forward (ester formation) and backward reaction (ester hydrolysis) are controlled by varying the ratio of two different organocatalysts: pyridine and imidazole. This catalytic regulation enables full control over ester yield and lifetime. The fuel-driven strategy is subsequently used in the design of a responsive polymer system, where transient polymer conformation and aggregation can be controlled through variation of fuel and catalysts levels. Altogether, we show how organocatalysis is an important tool to exert control over a man-made fuel driven system and induce a change in a macromolecular superstructure, as ubiquitously found in natural non-equilibrium systems. </p

Gold decoration of silica by decomposition of aqueous gold(iii) hydroxide at low temperatures

The decomposition of gold hydroxide to give metallic gold is known to take place around 300 °C in dry environments. However, little information about the gold hydroxide stability in wet environments has been recorded. Here, we present experimental evidence which shows that aqueous/water-enriched gold(iii) hydroxide colloids decompose spontaneously to form gold nanoparticles at temperature values above the freezing point of water. Based on this reaction, we developed a method to decorate silica spheres with gold nanoparticles by precipitation and decomposition of gold(iii) hydroxide onto the silica surface in wet media by a simple one-pot/one-step protocol. The silica-gold nanostructures are prepared in high yield and with a low level of by-products.Fil: Macchione, Micaela Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Samaniego, J. E.. Centro de Investigación y Estudios Avanzados del Instituto Politécnico Nacional unidad Querétaro; MéxicoFil: Moiraghi, Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Passarelli, Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Macagno, Vicente Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Coronado, Eduardo A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Yacaman, M. J.. University Of Texas. Departament Of Physics; Estados UnidosFil: Pérez, M. A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentin