1,721,071 research outputs found
Agricultura, ganadería e industrias derivadas : lecciones escritas para los estudiantes del curso de industrias de la sección de E. Secundaria
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Belousov-Zhabotinsky type reactions: the non-linear behavior of chemical systems
Full text linkChemical oscillators are open systems characterized by periodic variations of some reaction species concentration due to complex physico-chemical phenomena that may cause bistability, rise of limit cycle attractors, birth of spiral waves and Turing patterns and finally deterministic chaos. Specifically, the Belousov-Zhabotinsky reaction is a noteworthy example of non-linear behavior of chemical systems occurring in homogenous media. This reaction can take place in several variants and may offer an overview on chemical oscillators, owing to its simplicity of mathematical handling and several more complex deriving phenomena. This work provides an overview of Belousov-Zhabotinsky-type reactions, focusing on modeling under different operating conditions, from the most simple to the most widely applicable models presented during the years. In particular, the stability of simplified models as a function of bifurcation parameters is studied as causes of several complex behaviors. Rise of waves and fronts is mathematically explained as well as birth and evolution issues of the chaotic ODEs system describing the Györgyi-Field model of the Belousov-Zhabotinsky reaction. This review provides not only the general information about oscillatory reactions, but also provides the mathematical solutions in order to be used in future biochemical reactions and reactor designs
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Cryodependent and cryoproducting involvement of organs in type II essential mixed cryoglobulinemia
No full textVariations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Urinary albumin excretion as an index of total cardiovascular stress: Relationship to macro-angiopathic complications in non-insulin-dependent diabetes mellitus
No full textActivity and degradation study of a Fe-N-C catalyst for ORR in Direct Methanol Fuel Cell (DMFC)
No full textTechno-economic-environmental analysis of CO2 fermentation to acetic acid
Full text linkAcetic acid, a key chemical in textiles, pharmaceuticals, and food industries, is largely produced via energyintensive, fossil-based processes, driving greenhouse gas emissions. Gas fermentation using CO2 and H2 provides a sustainable alternative for bio-acetic acid production. The process, simulated on Aspen Plus®, targets the
production of 37 kton.y− 1 of glacial acetic acid (99.9 wt%). It includes an upstream phase to purify reactants, a
fermentation stage, and a downstream step to concentrate the dilute culture broth into glacial acetic acid. H2 is
generated via alkaline water electrolysis, while CO2 is captured using monoethanolamine absorption. The CO2
originates from upgrading biogas into bio-methane, derived from anaerobic digestion of the organic fraction of
municipal solid waste. Fermentation was modeled at 2 and 10 bar headspace pressures. Despite lower singlefermenter productivity, 2 bar operations reduced production costs and minimized formic acid formation,
simplifying purification. The purification of acetic acid occurs with a hybrid process, which combines liquidliquid extraction and azeotropic distillation using methyl tert-butyl ether as solvent, achieving 99.9 wt% purity. Economic analysis revealed an acetic acid production cost of 1.58 €.kg− 1 for 37 kton.y− 1 capacity,
decreasing to 1.17 €.kg− 1 at larger scales. With 2030 hydrogen cost projections, the acetic acid price could drop
to 1.11 €.kg− 1
, though remaining higher than the 2023 market price of 0.6 €.kg− 1
. Environmental assessments
proved that glacial bio-acetic acid production reached 47 % lower climate change impact, 73 % less fossil
resource use, and 61 % reduced water consumption compared to traditional methods, confirming environmental
benefit
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