The initial oxidation of transition metal surfaces

Due to their numerous novel technological applications ranging from the example of exhaust catalysts in the automotive industry to the catalytic production of hydro- gen, surface reactions on transition metal substrates have become to be one of the most essential subjects within the surface science community. Although numerous applications exist, there are many details in the different processes that, after many decades of research, remain unknown. There are perhaps as many applications for the corrosion resistant materials such as stainless steels. A thorough knowledge of the details of the simplest reactions occuring on the surfaces, such as oxidation, play a key role in the design of better catalysts, or corrosion resistant materials in the future. This thesis examines the oxidation of metal surfaces from a computational point of view mostly concentrating on copper as a model material. Oxidation is studied from the initial oxidation to the oxygen precovered surface. Important parameters for the initial sticking and dissociation are obtained. The saturation layer is thoroughly studied and the calculated results arecompared with available experimental results. On the saturated surface, some open questions still remain. The present calculations demonstrate, that the saturated part of the surface is excluded from being chemically reactive towards the oxygen molecules. The results suggest, that the reason for the chemical activity of the saturated surface is due to a strain effect occuring between the saturated areas of the surface.

Comportamento da dose glandular versus contraste do objeto em mamografia: determinação de formalismo semi-empírico para diferentes combinações alvo-filtro

OBJETIVO: Verificar o efeito da mudança no contraste do objeto, tempo de exposição e dose de radiação quando diferentes espessuras de filtração de molibdênio (Mo) e ródio (Rh) são empregadas em mamógrafos. MATERIAIS E MÉTODOS: Realizaram-se medidas da exposição na entrada da pele com uma câmara de ionização para diferentes espessuras para os filtros de Mo e Rh. Para determinar a dose glandular média foi utilizado simulador de BR12 (50% tecido adiposo e 50% tecido glandular) de diferentes espessuras (4 cm e 8 cm). Energias na faixa de 24 kVp a 34 kVp foram empregadas e filmes Kodak MinR 2000 foram utilizados. RESULTADOS: Os resultados evidenciaram dados de contraste do objeto, dose glandular e tempo de exposição para diferentes espessuras de filtros adicionais e diferentes tensões. Esses dados indicaram aumento nos valores de contraste do objeto e tempo de exposição, com o aumento da espessura dos filtros. A dose glandular apresentou comportamento com diferentes tendências para cada caso analisado. Equações foram definidas para possibilitar a estimativa do contraste do objeto, dose glandular e tempo de exposição para os casos estudados. CONCLUSÃO: Os resultados possibilitaram a estimativa de equações que auxiliam na verificação do comportamento do contraste do objeto e da dose glandular para simuladores com espessura de 4 cm e 8 cm e para os filtros de Rh e Mo. Dessa forma, torna-se possível estimar a figura de mérito (razão entre o contraste do objeto e a dose glandular), podendo auxiliar na análise da relação risco-benefício dos casos estudados.

Nutritional behaviour and beliefs of ski-mountaineers: a semi-quantitative and qualitative study.

BACKGROUND: Endurance athletes are advised to optimize nutrition prior to races. Little is known about actual athletes' beliefs, knowledge and nutritional behaviour. We monitored nutritional behaviour of amateur ski-mountaineering athletes during 4 days prior to a major competition to compare it with official recommendations and with the athletes' beliefs. METHODS: Participants to the two routes of the 'Patrouille des Glaciers' were recruited (A, 26 km, ascent 1881 m, descent 2341 m, max altitude 3160 m; Z, 53 km, ascent 3994 m, descent 4090 m, max altitude 3650 m). Dietary intake diaries of 40 athletes (21 A, 19 Z) were analysed for energy, carbohydrate, fat, protein and liquid; ten were interviewed about their pre-race nutritional beliefs and behaviour. RESULTS: Despite belief that pre-race carbohydrate, energy and fluid intake should be increased, energy consumption was 2416 ± 696 (mean ± SD) kcal · day(-1), 83 ± 17 % of recommended intake, carbohydrate intake was only 46 ± 13 % of minimal recommended (10 g · kg(-1) · day(-1)) and fluid intake only 2.7 ± 1.0 l · day(-1). CONCLUSIONS: Our sample of endurance athletes did not comply with pre-race nutritional recommendations despite elementary knowledge and belief to be compliant. In these athletes a clear and reflective nutritional strategy was lacking. This suggests a potential for improving knowledge and compliance with recommendations. Alternatively, some recommendations may be unrealistic.

Influência da metodologia de avaliação da camada semi-redutora em radiologia diagnóstica

OBJETIVO: A análise crítica da metodologia de medida da camada semi-redutora em feixes de raios X teve como base o regulamento técnico para proteção radiológica e controle de qualidade em radiodiagnóstico médico e odontológico. MATERIAIS E MÉTODOS: Na medida da camada semi-redutora, a técnica radiográfica, o arranjo experimental, os meios espalhadores, a instrumentação, o tamanho de campo de radiação e a metodologia de análise dos dados foram considerados. RESULTADOS: A camada semi-redutora obtida em condições de boa geometria, para a técnica escolhida, foi de 2,44 ± 0,02 mmAl. Em relação a este valor, observaram-se desvios máximos na camada semi-redutora de 4,1% na variação da geometria, de 98,8% na variação da câmara de ionização e do meio espalhador, e de até 29,5% com outro tipo de detector. CONCLUSÃO: Os resultados mostraram que não ocorre variação significante na camada semi-redutora para diferentes tamanhos de campo de radiação, mas foram evidentes a influência do espalhamento na superestimação da camada semi-redutora e a redução desta na presença de blocos de chumbo como meio espalhador. O procedimento prático adotado mostrou-se bastante confiável e evidenciou a grande discrepância decorrente da adoção de metodologias impróprias, enfatizando a necessidade de estabelecer um procedimento padrão para a medida da camada semi-redutora.

Systematic review with meta-analysis: self-expanding metal stents in patients with cirrhosis and severe or refractory oesophageal variceal bleeding.

BACKGROUND: The prognosis of patients with cirrhosis and acute variceal bleeding is very poor when the standard-of-care fails to control bleeding. New treatment modalities are needed in these patients. AIM: To synthesise the available evidence on the efficacy of self-expanding metal stents (SEMS) in patients with cirrhosis and severe or refractory oesophageal variceal bleeding. METHODS: Meta-analysis of trials evaluating SEMS in patients with cirrhosis and severe or refractory oesophageal variceal bleeding. RESULTS: Thirteen studies were included. The pooled estimate rates were 0.40 (95% confidence interval, CI = 0.31-0.49) for death, 0.41 (95% CI = 0.29-0.53) for liver-related death and 0.36 (95% CI = 0.26-0.47) for death at day 30, with low heterogeneity between studies. The pooled estimate rates were 0.12 (95% CI = 0.07-0.21) for mortality related to variceal bleeding, and 0.18 (95% CI = 0.11-0.29) for failure to control bleeding with SEMS, with no or low heterogeneity between studies. The pooled estimate rate were 0.16 (95% CI = 0.04-0.48) for rebleeding after stent removal and 0.28 (95% CI = 0.17-0.43) for stent migration, with high heterogeneity. A significant proportion of patients had access to liver transplantation or to TIPSS [pooled estimate rate 0.10 (95% CI = 0.04-0.21) and 0.26 (95% CI = 0.18-0.36), respectively]. CONCLUSIONS: Fewer than 40% of patients treated with SEMS were dead at 1 month. SEMS can be used as a bridge to TIPSS or to liver transplantation in a significant proportion of patients. Additional studies are required to identify potential risk factors leading to a poor prognosis in patients with acute variceal bleeding in whom the use of SEMS could be considered.

Anàlisi del bloc de fonaments individuals per demarcació (fid) corresponent a la defensa de l'espai per la posició dels laterals en el futbol: comparació entre categories amateur i semi-professional

L’objectiu d’aquest estudi va ser analitzar un element del component tàctic com a factor determinant en el rendiment del futbol, és a dir, comprovar si hi ha diferències en l’execució del bloc de Fonaments Individuals per Demarcació (FID) corresponent a la defensa de l’espai per la posició dels laterals en el futbol, entre les categories amateur i semi-professional. Es van enregistrar un total de 18 partits, on 9 dels quals feien referència a l’equip de l’Arbúcies Club de Futbol i la resta a l’equip de la Unió Esportiva Llagostera. Les variables estudiades van ser les següents: cobertures al central que defensa al possessor de la pilota, evitar passades interiors que guanyin l’esquena, defensa individual dels jugadors que intenten passar per l’esquena del segon central (entrar-sortir) i eliminar l’espai de desmarcada en profunditat, mantenint la línia amb el central. Per analitzar-les es va utilitzar el programa Longomatch i el Excel on hi vam configurar un instrument d’avaluació. Els principals resultats del treball van ser que l’equip de la Unió Esportiva Llagostera va fer menys errors en l’execució dels FID, tot i que va seguir tenint errors en el compliment d’aquests fonaments.

Suitability of human and mammalian cells of different origin for the assessment of genotoxicity of metal and polymeric engineered nanoparticles.

Nanogenotoxicity is a crucial endpoint in safety testing of nanomaterials as it addresses potential mutagenicity, which has implications for risks of both genetic disease and carcinogenesis. Within the NanoTEST project, we investigated the genotoxic potential of well-characterised nanoparticles (NPs): titanium dioxide (TiO2) NPs of nominal size 20 nm, iron oxide (8 nm) both uncoated (U-Fe3O4) and oleic acid coated (OC-Fe3O4), rhodamine-labelled amorphous silica 25 (Fl-25 SiO2) and 50 nm (Fl-50 SiO) and polylactic glycolic acid polyethylene oxide polymeric NPs - as well as Endorem® as a negative control for detection of strand breaks and oxidised DNA lesions with the alkaline comet assay. Using primary cells and cell lines derived from blood (human lymphocytes and lymphoblastoid TK6 cells), vascular/central nervous system (human endothelial human cerebral endothelial cells), liver (rat hepatocytes and Kupffer cells), kidney (monkey Cos-1 and human HEK293 cells), lung (human bronchial 16HBE14o cells) and placenta (human BeWo b30), we were interested in which in vitro cell model is sufficient to detect positive (genotoxic) and negative (non-genotoxic) responses. All in vitro studies were harmonized, i.e. NPs from the same batch, and identical dispersion protocols (for TiO2 NPs, two dispersions were used), exposure time, concentration range, culture conditions and time-courses were used. The results from the statistical evaluation show that OC-Fe3O4 and TiO2 NPs are genotoxic in the experimental conditions used. When all NPs were included in the analysis, no differences were seen among cell lines - demonstrating the usefulness of the assay in all cells to identify genotoxic and non-genotoxic NPs. The TK6 cells, human lymphocytes, BeWo b30 and kidney cells seem to be the most reliable for detecting a dose-response.

An automated microreactor for semi-continuous biosensor measurements.

Living bacteria or yeast cells are frequently used as bioreporters for the detection of specific chemical analytes or conditions of sample toxicity. In particular, bacteria or yeast equipped with synthetic gene circuitry that allows the production of a reliable non-cognate signal (e.g., fluorescent protein or bioluminescence) in response to a defined target make robust and flexible analytical platforms. We report here how bacterial cells expressing a fluorescence reporter ("bactosensors"), which are mostly used for batch sample analysis, can be deployed for automated semi-continuous target analysis in a single concise biochip. Escherichia coli-based bactosensor cells were continuously grown in a 13 or 50 nanoliter-volume reactor on a two-layered polydimethylsiloxane-on-glass microfluidic chip. Physiologically active cells were directed from the nl-reactor to a dedicated sample exposure area, where they were concentrated and reacted in 40 minutes with the target chemical by localized emission of the fluorescent reporter signal. We demonstrate the functioning of the bactosensor-chip by the automated detection of 50 μgarsenite-As l(-1) in water on consecutive days and after a one-week constant operation. Best induction of the bactosensors of 6-9-fold to 50 μg l(-1) was found at an apparent dilution rate of 0.12 h(-1) in the 50 nl microreactor. The bactosensor chip principle could be widely applicable to construct automated monitoring devices for a variety of targets in different environments.

Sulfitos duplos contendo cobre (I) e um metal de transição M(II) tipo Cu2SO3.M(II)SO3.2H 2O [M(II) = Cu(II), Fe(II), Mn(II) e Cd(II)]: preparação e seletividade na incorporação de M(II)

The metal-catalyzed autooxidation of S(IV) has been studied for more than a century without a consensus being obtained as to reaction rates, rate laws or mechanisms. The main objective in this work was to explore the reaction between Cu(II) and SO2 in the presence of M(II), paying special attention to the formation of double sulfites like Cu2SO3.M(II)SO3.2H 2O. The two principal aspects studied were: i) a new way to prepare double sulfites with high purity degree and the selectivity in the M(II) incorporation during the salt formation.

Stabilization of fluoroindate glasses by magnesium fluoride and other heavy metal fluorides

Their extended transparency in the IR makes them attractive for use as optical fibers for CO laser power delivery and optical amplification. This paper firstly describes the spectacular stabilizing effect of MgF2 on the binary system InF3-BaF2. The investigation of the InF3-BaF2-MgF2 system led to samples up to 5mm in thickness. Further optimization of this system was achieved by incorporation of limited amounts of other fluorides and resulted in increased resistence to devitrification. The second approach of this work was concerned to the investigation of the pseudo-ternary system InF3-GdF3-GaF3 at constant concentrations of ZnF2-SrF2-BaF2-NaF. Several compositions were studied in this system. The samples presented a better thermal stability when compared to other families of fluoride glasses. Therefore, these glasses seem to be very promising for the fabrication of special optical fibers. Thermal data are reported.