A novel approach to diamondlike carbon based mid-infrared attenuated total reflectance spectroelectrochemistry

Structural changes of electroactive species during electrochemical reactions cannot be determined from the electroanalytical technique alone. By incorporating spectroscopic techniques with electrochemistry, additional information about analyte structure and composition of the double layer can be obtained during electrochemical processes. Several spectroscopic methodologies have been tailored for this purpose including electronic and vibrational spectroscopies. Mid-infrared ATR spectroscopy is especially interesting as it provides in-situ information about adsorbates at the electrode surface. Mass transport limitations present in mid-infrared (mid-IR) external reflection and transmission spectroelectrochemistry are circumvented with attenuated total reflectance (ATR) spectroelectrochemistry. However, limitations of appropriate electrode materials for internal reflection configurations have hindered widespread adoption of the technique. The work described in this thesis focuses on the development and coupling of electrically conducting DLC films with mid-IR transparent multi-reflection waveguides for ATR spectroelectrochemistry. Conducting diamondlike carbon (DLC) thin films were developed utilizing pulsed laser deposition systems in collaboration with Joanneum Research (Leoben, Austria) and at the University of North Carolina (Chapel Hill). Nitrogen doping and incorporation of noble metal nanoclusters were investigated as approaches aimed at improving the electrical conductivity of DLC. Detailed compositional studies of nitrogen-doped DLC layers showed that sp2-hybridized carbon is responsible for the observed electrochemical activity. Optical transparency of thin (~ 40 nm) DLC layers in the mid-IR regime was confirmed by transmission-absorption measurements upon deposition on zinc selenide ATR waveguides. Additionally, the first spectroelectrochemical application of conducting DLC films was demonstrated via the electropolymerization of polyaniline onto coated ATR elements. Metal-DLC nanocomposite layers were investigated with various analytical techniques obtaining detailed compositional information. Improved electrochemical activity of metal-DLC demonstrated their suitability as electrode materials. Sufficient mid-IR transmissivity of metal-DLC coated germanium waveguides was displayed to enable spectroelectrochemical application. Finally, electropolymerization of poly(4-vinylpyridine) in acetonitrile was pursued to produce highly cross-linked ion-exchange membranes for spectroelectrochemical sensing. The composition of the pre-polymerization mixture and deposition conditions were tailored to obtain uniform semipermeable membranes. Diffusion of cations to electrodes is restricted by performing the electropolymerization as established herein. By employing the described electropolymerization procedure at DLC-coated waveguides, spectroelectrochemical sensing strategies can now be extended into the mid-IR regime.Ph.D.Committee Chair: Mizaikoff, Boris; Committee Member: Bottomley, Lawrence; Committee Member: Hunt, William; Committee Member: Janata, Jiri; Committee Member: Josowicz, Miroslaw

EpiCollect+: linking smartphones to web applications for complex data collection projects.

© 2014 Aanensen DM et al.Previously, we have described the development of the generic mobile phone data gathering tool, EpiCollect, and an associated web application, providing two-way communication between multiple data gatherers and a project database. This software only allows data collection on the phone using a single questionnaire form that is tailored to the needs of the user (including a single GPS point and photo per entry), whereas many applications require a more complex structure, allowing users to link a series of forms in a linear or branching hierarchy, along with the addition of any number of media types accessible from smartphones and/or tablet devices (e.g., GPS, photos, videos, sound clips and barcode scanning). A much enhanced version of EpiCollect has been developed (EpiCollect+). The individual data collection forms in EpiCollect+ provide more design complexity than the single form used in EpiCollect, and the software allows the generation of complex data collection projects through the ability to link many forms together in a linear (or branching) hierarchy. Furthermore, EpiCollect+ allows the collection of multiple media types as well as standard text fields, increased data validation and form logic. The entire process of setting up a complex mobile phone data collection project to the specification of a user (project and form definitions) can be undertaken at the EpiCollect+ website using a simple drag and drop procedure, with visualisation of the data gathered using Google Maps and charts at the project website. EpiCollect+ is suitable for situations where multiple users transmit complex data by mobile phone (or other Android devices) to a single project web database and is already being used for a range of field projects, particularly public health projects in sub-Saharan Africa. However, many uses can be envisaged from education, ecology and epidemiology to citizen science

"Caught between Two Allegiances": The Representation of Racial Passing in Jessie Redmon Fauset's Plum Bun and Brit Bennett's The Vanishing Half

openThe main purpose of this thesis is to analyze and compare two novels, Plum Bun: A Novel Without a Moral (1929) by Jessie Redmon Fauset and The Vanishing Half (2020) by Brit Bennett, to explore the evolution and the employment of the trope of racial passing in African American literature. As both novels take place in a century of radical social change, the events of the 20th century will be outlined to provide a context for the reading of these two works. In particular, this thesis will examine and compare the rationales behind the passers’ choice to cross the color line. Moreover, it will discuss the representation of passing, womanhood and female sexuality as well as the issues of identity and the power dynamics that regulate the relationships between men and women

Search for correlations between solar flares and decay rate of radioactive nuclei

The deacay rate of three different radioactive sources 40K, 137Cs and natTh has been measured with NaI and Ge detectors. Data have been analyzed to search for possible variations in coincidence with the two strongest solar flares of the years 2011 and 2012. No significant deviations from standard expectation have been observed, with a few 10-4 sensitivity. As a consequence, we could not find any effect like that recently reported by Jenkins and Fischbach: a few per mil decrease in the decay rate of 54Mn during solar flares in December 2006.Comment: 5 pages, 3 figure

Precise measurement of the 222Rn half-life: a probe to monitor the stability of radioactivity

We give the results of a study on the 222Rn decay we performed in the Gran Sasso Laboratory (LNGS) by detecting the gamma rays from the radon progeny. The motivation was to monitor the stability of radioactivity measuring several times per year the half-life of a short lifetime (days) source instead of measuring over a long period the activity of a long lifetime (tens or hundreds of years) source. In particular, we give a possible reason of the large periodical fluctuations in the count rate of the gamma rays due to radon inside a closed canister which has been described in literature and which has been attributed to a possible influence of a component in the solar irradiation affecting the nuclear decay rates. We then provide the result of four half-life measurements we performed underground at LNGS in the period from May 2014 to January 2015 with radon diffused into olive oil. Briefly, we did not measure any change of the 222Rn half-life with a 8*10^-5 precision. Finally, we provide the most precise value for the 222Rn half-life: 3.82146(16){stat}(4){syst} days.Comment: Accepted for publication in Physics Letters B, 6 pages, 6 figure

LUNA: Nuclear Astrophysics Deep Underground

Nuclear astrophysics strives for a comprehensive picture of the nuclear reactions responsible for synthesizing the chemical elements and for powering the stellar evolution engine. Deep underground in the Gran Sasso laboratory the cross sections of the key reactions of the proton-proton chain and of the Carbon-Nitrogen-Oxygen (CNO) cycle have been measured right down to the energies of astrophysical interest. The salient features of underground nuclear astrophysics are summarized here. The main results obtained by LUNA in the last twenty years are reviewed, and their influence on the comprehension of the properties of the neutrino, of the Sun and of the Universe itself are discussed. Future directions of underground nuclear astrophysics towards the study of helium and carbon burning and of stellar neutron sources in stars are pointed out.Comment: Invited review, submitted to Annu. Rev. Nucl. Part. Scienc

Search for time modulations in the decay rate of 40K and 232Th

Time modulations at per mil level have been reported to take place in the decay constant of about 15 nuclei with period of one year (most cases) but also of about one month or one day. In this paper we give the results of the activity measurement of a 40K source and a 232Th one. The two experiments have been done at the Gran Sasso Laboratory during a period of about 500 days, above ground (40K) and underground (232Th) with a target sensitivity of a few parts over 10^5. We also give the results of the activity measurement at the time of the X-class solar flares which took place in May 2013. Briefly, our measurements do not show any evidence of unexpected time dependence in the decay rate of 40K and 232Th.Comment: version accepted for publication (Astroparticle Physics

CÁRIE OCULTA E A TÉCNICA DA MATRIZ OCLUSAL INDIVIDUAL COM RESINA ACRÍLICA – RELATO DE CASO

A cárie oculta é descrita como lesões de cárie em dentina sob superfícies de esmalte aparentemente hígidos ou minimamente desmineralizados. Sua progressão é silenciosa, sendo diagnosticada por meio de radiografias interproximais. Com este trabalho visou-se relatar um caso clínico de cárie oculta em que visivelmente o elemento apresentava-se hígido, visto que o achado radiográfico foi primordial para o diagnóstico da lesão, demostrando a importância do diagnóstico precoce com exames radiográficos. Paciente de 12 anos de idade, gênero feminino, com leucodermia, apresentou-se na Clínica de Odontologia da Unoesc para consulta de rotina. Durante a anamnese, não relatou sintomatologia dolorosa e não foi constatada nenhuma alteração sistêmica. Ao exame clínico apresentou uma cárie na oclusal do elemento 26, como exame complementar foram indicadas as radiografias interproximais, a partir das quais se pôde confirmar a existência de lesão de cárie profunda em dentina no elemento 37, caracterizando a cárie oculta, e que visivelmente não apresentava alterações, a não ser aparentemente um selante na oclusal deste. O tratamento restaurador proposto foi utilizar a técnica da matriz oclusal. Após definida a técnica foi realizada a cópia da anatomia oclusal com resina acrílica autopolimerizável, em seguida foi realizada a anestesia no dente 37 e o isolamento absoluto do dente em questão. Removida a lesão cariosa, iniciou-se a restauração com resina composta opaca, e na última camada a resina translúcida, que foi reposicionada com a matriz a qual devolveu a anatomia original. Concluiu-se que para restaurar esse tipo de lesão visando manter a estética e a anatomia do dente, o tratamento pela técnica da matriz oclusal individual com resina acrílica permite uma cópia dessa face antes da intervenção, e assim se obtém ganho de tempo, facilidade na execução, menores ajustes oclusais, conseguindo, também, uma excelente estética.Palavras-chave: Radiografia interproximal. Cárie dentária. Coroa do dente

Special issue “metal nanoparticles as catalysts for green applications”

This Special Issue of Processes on “Metal Nanoparticles as Catalysts for Green Applications” collects recent works of researchers on metal nanoparticles as catalysts for green applications [...

Comportamento da conversão de glicose, galactose e lactose em ácido lático por grãos de kefir

Few studies have been reported on lactic acid production by kefir grains. Kefir has been widely associated with probiotic use due to its cell growth in food matrices such as milks, juices and sugary solutions. However, from industrial scale there are no reports of its use in lactic acid production. In this work, we carried out experiments to test and understand how glucose, galactose and lactose, during lactic-acid fermentation, were converted in lactic acid by kefir grains. Given the microbial complexity in coexistence in kefir grains, it is likely that kinetic studies are not the most appropriate for the positive or negative definition of the kefir use as a starter in the lactic acid fermentative production on an industrial scale. It was concluded that, although with a higher Lag phase, lactose was the substrate that best presented a product and cell conversion rate, although glucose and galactose can also be used as a substrate in the production of this carboxylic acid.Poucos estudos foram relatados sobre a produção de ácido lático pelos grãos de kefir. O kefir tem sido amplamente associado ao uso de probióticos devido ao seu crescimento celular em matrizes alimentares como leites, sucos e soluções açucaradas. Entretanto, em escala industrial não há relatos de sua utilização na produção de ácido lático. Neste trabalho, realizamos experimentos para testar e entender como a glicose, galactose e lactose, durante a fermentação láctica, são convertidas em ácido lático pelos grãos de kefir. Dada a complexidade microbiana em coexistência nos grãos de kefir, é provável que os estudos cinéticos não sejam os mais adequados para a definição positiva ou negativa do uso do kefir como starter na produção fermentativa de ácido lático em escala industrial. Concluiu-se que, embora com maior fase Lag, a lactose foi o substrato que melhor apresentou produto e taxa de conversão celular, embora glicose e galactose também possam ser utilizadas como substrato na produção desse ácido carboxílico