In the present paper, the results of combined theoretical and experimental investigation of small non-stoichiometric bromine-doped potassium clusters are reported. Potassium-bromide clusters were ...obtained by the Knudsen cell combined with surface ionization in the temperature range of 1000–1600 K, and selected by a magnetic sector mass spectrometer. Positive ions of KnBr (n = 3–6) and KnBrn-1 (n = 3–5) clusters were detected for the first time in one set measurement. In order to reveal the geometrical structure of each type of detected cluster, the randomized search algorithm was employed to survey the (Born-Oppenheimer) potential energy surface of both the neutral and cationic KnBr(0,1+) (n = 1–6) and KnBrn-1(0,1+) (n=3–5) clusters, followed by Density functional theory geometry optimizations, and many lowest-energy conformational isomers are presented. From the total electronic energies of clusters computed by the ab initio RCCSD(T)/ECP10MDF(K),cc-pVTZ-PP(Br) method at obtained equilibrium nuclear geometries, the following stability parameters of clusters were computed: their relative energies, the adiabatic and vertical ionization energies, binding energies per atom, and dissociation energies. Both experimental and theoretical results have shown that the title clusters belong to the group of “superalkali” clusters.
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•Both experimental and theoretical results have shown that the title clusters belong to the group of “superalkali” clusters.•The presence of a bromine atom leads to decreased ionization energy of potassium clusters.•Binding energy per atom and dissociation energies indicates that this class of heterogeneous clusters is stable.
Connaitre précisément la structure interne des corps célestes est indispensable pour, à la fois, comprendre la physique qui régit leur existence et le processus qui leur a donné naissance. La ...sismologie, d’abord appliquée à la Terre puis au soleil, s’est révélée être un outil très efficace pour sonder leurs intérieurs. Dans les années 70 (Vorontsov et al 1976), des premiers travaux théoriques ont étudié la possibilité d’une sismologie des planètes géantes gazeuses. Les premières tentatives de mesures d’oscillations ont eu lieu à la fin des années 80. La détection des modes d’oscillations de Jupiter s’est avérée une entreprise très délicate en raison de sa rotation rapide. Pour augmenter les chances de détection, un instrument spécifique a été construit au début des années 2000 à l’OCA. Cet instrument, appelé SYMPA, est un spectromètre imageur de type Mach-Zehnder capable de produire une carte de vitesse radiale de Jupiter. Une détection de modes d’oscillations sur Jupiter par cet instrument a été publiée par Gaulme et al en 2011. Une version améliorée de l’instrument (appelé DSI) a été proposée pour la mission spatiale JUICE à destination de Jupiter, et un nouveau prototype a été construit dans ce but. Par la suite, le projet s’est réorienté vers un programme d’observation depuis le sol sous la forme d’un réseau de trois télescopes répartis en longitude (USA, France, Japon) et financé par l’ANR à partir de 2015 (ANR JOVIAL). L’intérêt de la mise en réseau est d’assurer la continuité des données (météo mise à part). L’instrument étant capable de produire des cartes de vitesse radiales, le projet permet également l’étude de la dynamique atmosphérique des planètes géantes. Ce travail de thèse s’inscrit dans le contexte de préparation de JOVIAL, avec pour objectif de caractériser l’instrument en laboratoire et d’identifier les problèmes liés aux conditions réelles d’observation. Les mesures en laboratoires ont montré des performances conformes aux attentes, avec un bruit de mesure propre à l’instrument inférieur au bruit de photon attendu sur Jupiter. Les premières mesures sur le ciel avec un télescope ont mis en évidence une sensibilité de l’instrument au degré de polarisation de la lumière ainsi qu’une dérive de la vitesse mesurée liée aux instabilités de position de la pupille pendant les observations. Le design de l’instrument et de son interface avec le télescope a été revu pour résoudre ces problèmes. Plusieurs campagnes d’observations de Jupiter ont été réalisées, permettant de mettre sur pied une chaine complète de traitement des données, dont la validité a été vérifiée par des simulations réalistes. Les observations de Jupiter ont donné des résultats scientifiques particulièrement intéressants. L’analyse des données de deux campagnes de 2015 et 2016 a fourni des séquences temporelles de cartes de vitesses radiales de Jupiter. Une première étude a consisté à chercher dans ces cartes la signature des vents zonaux et de les comparer aux mesures réalisées par suivi des nuages sur des images résolues (cloud-tracking). Une telle mesure n’avait jamais été faite par effet Doppler. Le résultat, bien qu’affecté par des biais de mesures identifiés, montre des profils de vents stables d’une année sur l’autre et en cohérence avec les valeurs issues du cloud-tracking, sauf au niveau de la partie nord de la bande équatoriale de Jupiter. La mesure Doppler suggère en effet une vitesse de vent bien inférieure à la vitesse apparente dans cette zone, ce qui a potentiellement des implications sur les modèles de dynamique atmosphérique. Ces résultats sont très importants pour mieux comprendre les mesures de la sonde Juno, actuellement en orbite autour de Jupiter. L’analyse fréquentielle des données temporelles a été abordée en fin de thèse. Les analyses préliminaires ne semblent pas pour l’instant reproduire la détection de SYMPA. Une analyse plus poussée est nécessaire avant de conclure à une absence du signal.
To know precisely the internal structure of the celestial bodies is essential to both to understand the physics which governs their existence, and the process which gave them birth. First applied to the Earth and then to the sun, seismology has proven to be a very effective tool to sound their interiors. It has become natural and legitimate to question the possibility of seismology of gaseous giant planets. The first theoretical work was carried out in the 1970s (Vorontsov et al. 1976), and the first attempts to measure oscillations at the end of the 1980s. The detection of Jupiter's oscillating modes turned out to be very difficult (reduced flux, small apparent diameter, fast rotation ...). To increase the chances of detection, a specific instrument was built in the early 2000s at the OCA. This instrument, called SYMPA, is a Mach-Zehnder-type imaging spectrometer enable to produce radial velocity maps of Jupiter. A first detection of acoustic modes on Jupiter with this instrument was published by Gaulme et al in 2011. An improved version of the instrument (called DSI), based on the same principle, was built in the wake, with the primary objective of boarding a spacecraft to Jupiter. The project was finally reoriented towards an observation program from the ground in the form of a network of three telescopes equidistant in longitude (USA, France, Japan) and supported by the ANR fund starting in 2015 (ANR JOVIAL). The interest of the network is to ensure the continuity of data (weather apart). The instrument being able to produce radial velocity maps, the project also aims to study the atmospheric dynamics of giant planets. This thesis work is part of a preparation for JOVIAL, with the aim of characterizing the instrument and identifying the problems related to real observations conditions. Laboratory measurements showed expected performances with an instrumental noise level (related to thermal fluctuations) lower than expected photon noise on Jupiter. The first measurements on the sky with a telescope showed a sensitivity of the instrument to the degree of polarization of the light as well as drifts of the velocity measurements due the motions of the pupil position. Some adjustments of the design of the instrument and its interface with the telescope were necessary to solve these issues. Several Jupiter observation campaigns were carried out during the thesis, allowing the development of full data processing software. The complete procedure was tested against simulated data and validated. Two observations runs in 2015 and 2016 were analyzed to produce time sequences of radial velocity maps of Jupiter, providing very interesting scientific results. First, the maps were analyzed to look for the signature of the zonal winds and to compare them with the measurements made by cloud-tracking. Such measurements by Doppler effect were never made before. The result, albeit affected by measurement biases, showed stable year-to-year wind patterns and coherent results with cloud-tracking measurements, except at the northern part of the Jovian’s equatorial band. The Doppler measurement indeed suggests a wind speed well below the apparent speed in this area, which potentially has implications for the theory of atmospheric dynamics and will be helpful to interpret the Juno (a spacecraft presently orbiting Jupiter) measurements. Frequency analysis of temporal data was undertaken at the end of the thesis. The preliminary results do not seem for the moment to reproduce the SYMPA detection. Further analysis is necessary before concluding if the signal is absent or attenuated.
To realize multi-point real-time measurements of LIBS (Laser-induced Breakdown Spectroscopy), this paper introduces software to control LIBS multi-point measurement based on Qt cross-platform C++ ...application development environment, including the overall structure, functional module and concrete implementation. Multi-threaded technology, database, QWT open source database and communication technology were used in the measurement system. It realizes the cascade of spectrometer and motion controller, and completes the fast planning of different measurement trajectories and real-time acquisition of display spectral data. Experiments indicate that the measurement system software provides a user-friendly interface, stable performance, and can realize the real-time multi-point measurement of LIBS, while it can reduce the measurement errors caused by sample in homogeneity, laser and spectrometer stage differences, etc, and improve the measurement accuracy.
The activity size distribution of the short-lived radon decay products in ambient air was measured continuously over several weeks. Two different measurement techniques were used: A direct ...measurement with a low-pressure on-line alpha cascade impactor (OLACI) and an indirect determination based on measurement with a differential mobility analyser (5–200
nm) and a laser aerosol spectrometer (100–5000
nm). In parallel, the meteorological parameters like temperature, rainfall intensity and wind velocity were registered.
The measured activity size distribution of the radon progeny can be approximated by a sum of three log-normal distributions. The greatest activity fraction was adsorbed on aerosol particles in the accumulation size range (100–1000
nm) with activity median diameters (AMD
a) and geometric standard deviations (
σ
ga) values of 250–450
nm, and 1.5–3.0, respectively. The influence of the weather conditions on the activity of the accumulation particles was not significant.
In contrast to the results of measurements in houses, a small but significant fraction of the radon progeny (average value: 2%) was attached to coarse particles (>1000
nm). This fraction varied between 0 and 10%.
The direct measurements with the OLACI yielded a higher activity fraction (20–40%) in the nucleation size range (<100
nm) compared to the values evaluated from the number size distribution measurement (indirect measurement). This fraction depends on the number concentration of the atmospheric aerosol in this size range. A diurnal variation of the particle number concentration and of the activity fraction for the nucleation particles was found. In the case of lower particle concentrations (diameters <50
nm) in air during the night no nucleation mode was registered using the indirect measurement technique.
Resumo Este estudo apresenta a segunda etapa da avaliação espaço-temporal das tendências a longo prazo nos valores da Coluna Total de Ozônio (CTO) sobre o Nordeste Brasileiro (NEB) durante a atuação ...do modo de variabilidade atmosférica El Niño - Oscilação Sul (ENOS), com foco na fase La Niña (modalidades Canônica e Modoki). O objetivo é analisar a variação anual e os efeitos desse fenômeno na região de estudo no período entre 1997 e 2018. Os dados utilizados são provenientes de sensoriamento remoto, gerados pelos sensores Total Ozone Mapping Spectrometer (TOMS) e Ozone Monitoring Instrument (OMI), disponibilizados pela National Aeronautics and Space Administration (NASA), e analisados através de médias, valores de anomalias e diagramas hovmoller. Foi constatado que eventos La Niña provocam, predominantemente, aumento na concentração de ozônio sobre o NEB. Nos períodos de atuação desse modo de variabilidade a desaceleração da Circulação Brewer-Dobson (CBD) é causada pela intensificação dos ventos alísios gerando acúmulo de ozônio na região tropical. Entre as duas modalidades, fenômenos Modoki apresentam esse efeito mais intensificado. O maior (+6,5) e menor (-3,0) valor médio mensal de anomalia obtidos ocorreram durante sua atuação, registrados na região norte do NEB em julho e setembro, respectivamente.
Abstract This study presents a second stage of the spatio-temporal assessment of long-term trends in ozone concentrations in Northeast Brazil (NEB) under the influence of the El Niño - South Oscillation (ENSO) with emphasis on the La Niña phase (Canonical and Modoki). The objective is to analyze the annual variation and the effects of this phenomenon in the Total Ozone Column (TOC) over the NEB, between 1997 and 2018. The data come from remote sensing, generated by the Total Ozone Mapping Spectrometer (TOMS) and Ozone Monitoring Instrument (OMI) sensors, made available by National Aeronautics and Space Administration (NASA), and analyzed using mean, anomaly values and hovmoller diagrams. It was found that La Niña events cause, predominantly, an increase in the concentration of ozone over the NEB. During periods of action of this mode of variability, the deceleration of Brewer-Dobson circulation (CBD) is caused by the intensification of trade winds, generating ozone accumulation in the tropical region. Between the two modalities, Modoki show this effect more intensified. The highest (+6.5) and lowest (-3.0) average monthly anomaly values obtained occurred during his performance, recorded in the northern region of NEB in July and September, respectively.
Resumo O objetivo deste trabalho é analisar a variação anual e os efeitos do modo de variabilidade atmosférica El Niño (Canônico e Modoki) na Coluna Total de Ozônio (CTO) sobre o Nordeste Brasileiro ...(NEB) entre 1997 e 2018 utilizando dados dos sensores Total Ozone Mapping Spectrometer (TOMS) e Ozone Monitoring Instrument (OMI). Foi constatada uma variação mensal média em toda área estudada com comportamento típico de domínio do ciclo anual na variabilidade sazonal, apresenta valor mínimo no mês de maio e máximo em outubro. Observou-se uma tendência de decaimento na série dos valores médios durante o período analisado. Análises de agrupamento revelaram que diferentes regiões da NEB possuem comportamentos e valores médios de CTO diferenciados. Análise de ondeletas expôs ciclos de doze meses de duração atuando na CTO em toda área estudada, ciclos de seis meses, demonstrando que o ciclo semianual domina a variabilidade sazonal em menores latitudes, e ciclos de dois-três anos, representando a importante atuação da Oscilação Quase Bienal (OQB). As médias das anomalias mostram que eventos El Niño afetam a CTO causando, predominantemente, diminuição de seus valores. Esses eventos em modalidade Modoki tem maior potencial em afetar a CTO que os Canônicos com anomalias negativas de maior intensidade.
Abstract The objective of this work is to analyze the annual variation and the effects of the atmospheric variability mode El Niño (Canonical and Modoki) on the concentration of the Total Ozone Column (TOC) on the NEB between 1997 and 2018 using data generated by the sensors Total Ozone Mapping Spectrometer (TOMS) and Ozone Monitoring Instrument (OMI). An average monthly variation was observed, with typical behavior of the annual cycle domain in the seasonal variability, presenting a minimum value in May and maximum in October. There was a declining trend in the series of average values for the entire area. Cluster analysis revealed that different regions of the study area have slightly different behaviors and mean values of the total ozone column. Wavelet analysis was used, which exposed cycles of twelve months in length throughout the studied area, six-month cycles, demonstrating that the semi-annual cycle dominates seasonal variability in lower latitudes, and also two to three years cycles, representing the important performance of the Quasi-Biennial Oscillation (QBO). Anomaly averages show that El Niño events affect TOC causing predominantly a decrease in their values. These Modoki events have a greater potential to affect TOC variations than canonical events, with negative anomalies of greater intensity.
Esse trabalho descreve, passo a passo, a construção de um espectrômetro, com base em materiais de fácil obtenção e manipulação. A física envolvida, a óptica ondulatória, é contextualiza ...historicamente de forma breve; o princípio de Huygens é apresentado também resumidamente. A seguir, a construção do espectrômetro é detalhada e as imagens de alguns espectros de emissão são apresentadas. Por fim, algumas dentre as muitas explorações possíveis são sugeridas e a conclusão aponta para dois aspectos em especial. No primeiro, a construção do dispositivo pode dar ocasião a uma atividade teórico-prática motivadora. O segundo aspecto destaca o potencial de investigação de espectros, tanto de emissão quanto de absorção que se abre para os estudantes, propiciando assim ambientes de aprendizagem de grande potencial motivador.
O monitoramento de longo prazo dos eventos de Influência do Buraco de Ozônio Antártico sobre o Sul do Brasil foi realizado no período de 35 anos entre 1979 e 2013 e calculada a climatologia e ...anomalias dos campos estratosféricos quando de sua ocorrência. Para isso, foram analisados os dados da coluna total de ozônio (CTO) obtidos através de Espectrofotômetros Brewer, instalados no Observatório Espacial do Sul - OES/CRS/INPE - MCTIC (29,4 °S; 53,8 °O; 488,7 m) e pelos instrumentos de satélite Total Ozone Mapping Spectrometer (TOMS) e Ozone Monitoring Instrument (OMI), além de parâmetros da reanálise II do NCEP/DOE (National Centers for Environmental Prediction/ Departament of Energy) e trajetórias retroativas do modelo HYSPLIT (HYbrid Single-Particle Lagrangian Integrated Trajectory). A metodologia empregada mostrou-se eficaz na identificação de 62 eventos com uma redução média de -9,35 ± 2,93% no conteúdo de ozônio. Além disso, foi realizada a identificação do padrão de circulação estratosférica através de campos médios e anomalias da vorticidade potencial, vento e temperatura para os dias de ocorrência do fenômeno, sendo observado um padrão de deslocamento de onda, embebida dentro de uma ampla região de circulação ciclônica, com ventos predominantemente de sul é advectado em direção ao Sul do Brasil.
ANÁLISE ISOTÓPICA ( C) E LEGALIDADE EM NÉCTARES DE UVA FIGUEIRA, RICARDO; NOGUEIRA, ANDRESSA MILENE PARENTE; DUCATTI, CARLOS ...
Bolim do Centro de Pesquisa e Processamento de Alimentos,
12/2010, Letnik:
28, Številka:
2
Journal Article
Recenzirano
O objetivo deste trabalho foi desenvolver um método de análise isotópica para quantificar o carbono do ciclo fotossintético C 3 em néctares de uva e identificar as bebidas comerciais em ...desacordo com as normas do Ministério da Agricultura, Pecuária e Abastecimento (MAPA). Os néctares foram produzidos em laboratório conforme a legislação brasileira. Também foram produzidas bebidas com quantidade de suco de uva abaixo do estabelecido pelo MAPA. Nas análises isotópicas foi mensurado o enriquecimento isotópico relativo dos néctares de uva e de sua fração açúcar purificado. Com esses resultados estimou-se a quantidade de fonte C3 por meio da equação da diluição isotópica. Para determinar a existência de adulteração nos néctares comerciais foi necessário calcular o limite de legalidade de acordo com a legislação brasileira. Doze marcas de néctares foram analisadas e uma classificada como adulterada. A metodologia desenvolvida mostrou-se eficiente para quantificar o carbono de origem C3 e identificar néctares comerciais de uva adulterados.
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