Formation of carbonyl compounds in lean premixed atmospheric-pressure Ethylene/O2/N2 flames

Motivated by a better understanding of lean-fuel combustion, the present study has determined experimentally the chemical structure of four lean ethylene-oxygen-nitrogen flames stabilized on the flat-flame burner at atmospheric pressure (φ = 0.47, 0.508, 0.693 and 0.81). Species mole fraction profiles were also computed by the Premix code (Chemkin II version) and three detailed reaction mechanisms .A very good agreement was observed between the main flame properties: reactants consumption, final products (CO2, H2O), main intermediates, and other hydrocarbons in small concentrations, and the modeling. A special care was brought to the examination of the relative importance of carbonyl compounds formation and consumption, mainly (CH2O and CH3CHO). Pathway analyses were performed to identify the formation from the direct consumption of ethylene through the C2H3 and CH2HCO. Sensitivity analyses were also performed in order to delineate the most sensitive reaction on the formation and consumption of these two carbonyl compounds.Keywords: Flame structure, lean flames, ethylene, carbonyl compounds, combustion, mechanisms

Chemical structures and theoretical models of lean premixed atmospheric-pressure propene/O2/N2 flames

To better understand the chemistry involved in the lean-fuel combustion, the chemical structure of lean premixed propene-oxygen-nitrogen flames stabilized on a flat-flame burner at atmospheric pressure was determined experimentally. The species mole fraction profiles were also computed by the Premix code and three detailed reaction mechanisms. A very good agreement was observed for the main properties: reactants consumption, final products (CO2, H2O) and the main intermediates: CO and H2. Only a general agreement is also observed between predicted and measured mole fraction profiles for minor intermediates. Marked differences occurred in the prediction of active intermediate species present in small concentrations. Pathways analyses were performed to identify the origins of these discrepancies. It was shown that the same reactions were involved in the three mechanisms to describe the consumption of propene, but with marked differences in their importance. C2H5, C2H4, and C3H5 are the main species formed in the first step and their consumption increases the differences between the mechanisms either by the use of different kinetics data for common reactions or by differences in the nature of the consumption reactions. KEY WORDS: Flame structure, Lean flame, Propene, Combustion mechanisms Bull. Chem. Soc. Ethiop. 2012, 26(2), 211-226.DOI: http://dx.doi.org/10.4314/bcse.v26i2.

A kinetic formulation for multidimensional scalar conservation laws with boundary conditions and applications

International audienceWe state a kinetic formulation of weak entropy solutions of a general multidimensional scalar conservation law with initial and boundary conditions. We first associate with any weak entropy solution a entropy defect measure; the analysis of this measure at the boundary of the domain relies on the study of weak entropy sub and supersolutions and implies the introduction of the notion of sided boundary defect measures. As a first application, we prove that any weak entropy subsolution of the initial-boundary value problem is bounded above by any weak entropy supersolution (Comparison Theorem). We next study a BGK-like kinetic model that approximates the scalar conservation law. We prove that such a model converges by adapting the proof of the Comparison Theorem

What "best practice" could be in Palliative Care: an analysis of statements on practice and ethics expressed by the main Health Organizations

<p>Abstract</p> <p>Background</p> <p>In palliative care it would be necessary to refer to a model. Nevertheless it seems that there are no official statements which state and describe that model. We carried out an analysis of the statements on practice and ethics of palliative care expressed by the main health organizations to show which dimensions of end-of-life care are taken into consideration.</p> <p>Methods</p> <p>The official documents by the most representative health organisations committed to the definition of policies and guidelines for palliative and end-of-life care had been considered. The documents were analysed through a framework of the components of end-of-life care derived from literature, which was composed of 4 main "areas" and of 12 "sub-areas".</p> <p>Results</p> <p>Overall, 34 organizations were identified, 7 international organisations, and 27 organisations operating on the national level in four different countries (Australia, Canada, UK and United States). Up to 56 documents were selected and analysed. Most of them (38) are position statements. Relevant quotations from the documents were presented by "areas" and "sub-areas". In general, the "sub-areas" of symptoms control as well as those referring to relational and social issues are more widely covered by the documents than the "sub-areas" related to "preparation" and to "existential condition". Indeed, the consistency of end-of-life choices with the patient's wishes, as well as completion and meaningfulness at the end of life is given only a minor relevance.</p> <p>Conclusions</p> <p>An integrated model of the best palliative care practice is generally lacking in the documents. It might be argued that the lack of a fixed and coherent model is due to the relevance of unavoidable context issues in palliative care, such as specific cultural settings, patient-centred variables, and family specificity. The implication is that palliative care staff have continuously to adapt their model of caring to the specific needs and values of each patient, more than applying a fixed, although maybe comprehensive, care model.</p

O caso da destruição das pinturas murais da sede da Fazenda Rialto, Bananal

This article is about the eighteenth century mural paintings at the headquarters of Fazenda Rialto, in Bananal, which were destroyed in 1996. These constituted one of the most important sets of ambient paintings with secular themes produced in the state of São Paulo during the period corresponding to the first cycle of coffee production. Orally attributed to the painter José Maria Villaronga y Panella, all that remains of these paintings are some photographs and dozens of fragments, impossible to reassemble. Studying the fragments of the paintings of Rialto as primary material documents, the main objective of this article is to identify the artistic, technical, and executive characteristics of three sets of murals attributed to a single painter. A methodology which combines laboratory tests and historical research on artistic techniques was adopted for objectively recognizing the artistic and artisan characteristics of the period and discussing the attribution of exclusive authorship to the work. The analytical systems adopted for this purpose were: examination with ultraviolet and infra-red radiation, optical microscopy, Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometry (EDS) to analyze its chemical elements. Issues related to the limitations on official Brazilian preservation activities for this category of artistic work were also discussed, reflecting on the development and changes in notions of historicity related to the preservation of works from the past and their methodological implications for conservation and restoration.Este artigo trata dos murais artísticos oitocentistas da sede da Fazenda Rialto, em Bananal, destruídos em 1996, que constituíam um dos mais importantes conjuntos de pinturas ambientais de temática profana produzidos no Estado de São Paulo no período correspondente ao primeiro ciclo da cultura do café. Atribuídas oralmente ao pintor José Maria Villaronga y Panella, dessas pinturas restaram apenas algumas fotografias e centenas de fragmentos, de impossível reassemblagem. Estudando-se os fragmentos de pintura da Rialto como documento material primário, o trabalho apresentado tem como principal objetivo a identificação das características artísticas e tecnoexecutivas de três conjuntos de murais tributados a um mesmo pintor. Para reconhecimento objetivo dos fazeres artístico-artesanais do período e discussão da atribuição de autoria exclusiva, adotou-se uma metodologia que combina exames laboratoriais e pesquisa histórica das técnicas artísticas. Os sistemas analíticos adotados para esse fim foram: exame com radiação ultravioleta e infravermelha, microscopia óptica, microscopia eletrônica de varredura (MEV) e espectroscopia de energia dispersiva (EDS) para análise química elementar. Discutem-se também questões relativas aos limites da ação preservacionista oficial brasileira sobre essa categoria de obra artística, refletindo sobre o desenvolvimento e as mudanças das noções de historicidade relativas à preservação dos bens do passado e suas implicações metodológicas nos conceitos de conservação e restauro

Razão, religião e revolução: luzes e sombras nas telas de Jacques-Louis David

O artigo analisa a produção pictórica de Jacques-Louis David entre o final da década de 1770 e 1793, destacando o entrelaçamento entre arte, religião e política nas obras do artista francês. Em sua luta contra o Antigo Regime, “filósofos artistas”, como Jacques-Louis David, apossaram-se das armas que eram manipuladas, há séculos, por um de seus principais inimigos: a Igreja. A transmissão do ideário iluminista não poderia ficar restrita à “aridez” dos textos acadêmicos, devendo buscar na religião e nas artes o “encantamento” indispensável à conquista de olhos, ouvidos, cérebros e corações. Depois de recorrer aos heróis das antigas Grécia e Roma, Jacques-Louis David debruçou-se sobre os homens do seu tempo: os deputados de O juramento do jogo de pela e os mártires que sacrificaram suas vidas em prol da revolução. Entrelaçando a arte clássica com a cristã, razão, revolução e religião, Jacques-Louis David forjou estratégias que seriam mobilizadas na propagação de líderes e ideários políticos nos séculos XIX e XX.The article analyzes the pictorial production of Jacques-Louis David between the late 1770s and 1793, highlighting the links between art, religion and politics in the works of the French artist. In their struggle against the Old Regime “philosophers artists,” as Jacques-Louis David, they took possession of the weapons that were manipulated for centuries by one of its main enemies: the Church. The transmission of Enlightenment ideas could not be restricted to “aridity” of academic papers and should seek in religion and the arts the “enchantment” indispensable to the conquest of eyes, ears, brains and hearts. After resorting to the heroes of ancient Greece and Rome, Jacques-Louis David leaned across the men of his time: the deputies of Tennis Court Oath and the martyrs who sacrificed their lives for the sake of revolution. Interweaving classical art with Christian art, reason, revolution and religion, Jacques-Louis David forged strategies that would be mobilized in the spread of political leaders and ideologies in the nineteenth and twentieth centuries

Na mira do olhar: um exercício de análise da fotografia nas revistas ilustradas cariocas, na primeira metade do século XX

This article presents a historical approach for the analysis of photographic images, followed by the application of these theoretical and methodological considerations to a series of photographs issued in two popular magazines, published in the city of Rio de Janeiro between 1900 and 1960. Through the analysis of the photographic message, class behaviour codes are related to their social representations.Este artigo traz considerações sobre a análise histórica de imagens fotográficas, aplicando as propostas teórico-metodológicas apresentadas a uma série fotográfica composta pelas imagens de duas revistas ilustradas, Careta e O Cruzeiro, publicadas na cidade do Rio de Janeiro entre 1900 e 1960. Por meio da análise da mensagem fotográfica relaciona-se a elaboração dos códigos de comportamento de classe às suas representações sociais