Search results for "Chemical engineering"
showing 10 items of 5892 documents
Vanadium pentoxide nanoparticles mimic vanadium haloperoxidases and thwart biofilm formation
2012
Marine biofouling—the colonization of small marine microorganisms on surfaces that are directly exposed to seawater, such as ships' hulls—is an expensive problem that is currently without an environmentally compatible solution1. Biofouling leads to increased hydrodynamic drag, which, in turn, causes increased fuel consumption and greenhouse gas emissions. Tributyltin-free antifouling coatings and paints1, 2, 3, 4 based on metal complexes or biocides have been shown to efficiently prevent marine biofouling. However, these materials can damage5 the environment through metal leaching (for example, of copper and zinc)6 and bacteria resistance7. Here, we show that vanadium pentoxide nanowires ac…
Towards controlling PCDD/F production in a multi-fuel fired BFB boiler using two sulfur addition strategies. Part II: Thermodynamic analysis
2014
Abstract A staged equilibrium process model was developed for a bubbling fluidized bed boiler firing SRF, bark and sludge. The model was used to study the influence of sulfur addition strategies (S-pellet additive and peat co-firing) on the behavior of copper, bromine, and alkalis. Aerosol samples collected from the backpass of the boiler were used to validate the chemistry predicted by the model. The model revealed that Cu existed as Cu 2 S (s3) in the reducing zone, and CuCl (g) (for all test cases) and CuO (s) (during peat co-firing) in the oxidation zones. CuBr 3(g) was also present after the introduction of tertiary air. However the model failed to predict the formation of CuSO 4 , an …
Multiple-scan voltammetry and OCP: Archaeometric tools for dating archaeological bronzes
2021
[EN] The application of a multiple-scan strategy to nanosamples taken from 18 cross-sections of Bronze Age arms and armour, as well as two Roman coins using two solid-state electrochemical techniques, the voltammetry of immobilized microparticles (VIMP) and open circuit potential measurements (OCP) is described. The voltammetric responses in contact with aqueous acetate buffer can be attributed to the reduction of cuprite with variable degree of compaction and crystallinity revealing significant differences in the gradient of such properties with depth. Such differences are also revealed by "dry" OCP measurements connecting points in the cross section near and separated from the corrosion l…
A Solar Photothermocatalytic approach for the CO2 conversion: Investigation of different synergisms on CoO-CuO/Brookite TiO2-CeO2 catalysts
2022
Abstract The photoactive features of the least common polymorph of TiO2, i.e. brookite, were combined with the thermocatalytic redox ones of cerium oxide, focusing on the effects of the addition of small amounts of Co-Cu oxides for the solar CO2 conversion. By considering the characterization data, a surface segregation of the hosted metal oxides on the TiO2-CeO2 composite was evidenced, and their presence increased the amount of oxygen vacancies and improved the charge carriers separation. The bimetallic oxides-based sample was the most performing one in the photocatalytic carbon dioxide reduction at room temperature. The formation of carbon monoxide and methane was 5 and 0.5 μmol g−1h−1, …
Controlled radical polymerization of styrene in miniemulsion polymerization using reversible addition fragmentation chain transfer
2003
Abstract Miniemulsion polymerizations of styrene in the presence of two reversible addition–fragmentation chain-transfer (RAFT) agents were studied. The rates were significantly retarded by the presence of a RAFT agents S -(thiobenzoyl)thioglycolic acid, 1 , or dithiobenzoic acid 1-phenylethyl ester, 2 . Control in miniemulsion polymerization is not as good as for bulk polymerizations. The miniemulsions could also be stabilized against Ostwald ripening by a polymer terminated by a dithiobenzoic moiety. In this case, the polymerization was not controlled because of the generation of renucleated particles. To cite this article: I. Uzulina et al., C. R. Chimie 6 (2003).
Techniques to measure sorption and migration between small molecules and packaging. A critical review
2015
The mass transfer parameters diffusion and sorption in food and packaging or between them are the key parameters for assessing a food product's shelf-life in reference to consumer safety. This has become of paramount importance owing to the legislations set by the regulated markets. The technical capabilities that can be exploited for analyzing product–package interactions have been growing rapidly. Different techniques categorized according to the state of the diffusant (gas or liquid) in contact with the packaging material are emphasized in this review. Depending on the diffusant and on the analytical question under review, the different ways to study sorption and/or migration are present…
Erysacleuxins C and D, new isoflavones from the twigs of Erythrina sacleuxii Hua and their cytotoxic activity
2020
Two previously undescribed isoflavones, erysacleuxin C (1) and erysacleuxin D (2), together with seven known compounds (3–9), were isolated and identified from the EtOAc extract of the twigs of Erythrina sacleuxii Hua (Leguminosae). The structures of the isolated compounds were determined on the basis of their spectroscopic and spectrometric data. Evaluation of their cytotoxicity against the human cancer HeLa-S3 cell lines indicated IC50 values of 130.4, 54.9 and 73.9 µM for erysacleuxin C (1), erysacleuxin D (2) and butin (9), respectively. Keywords: Erythrina sacleuxii, Leguminosae, Isoflavone, Erysacleuxin C, Erysacleuxin D, Cytotoxicity
Organizational Virtues, Performance and Job Satisfaction. Differences according individual and organizational factors in Argentinean employees
2017
El presente trabajo se basa en las propuestas de la Psicología Organizacional Positiva (POP) que intenta integrar a la mirada clásica de estudios organizacionales –que se focaliza en analizar condiciones negativas–, una perspectiva que visualice variables positivas que contribuyan a obtener resultados óptimos (Cameron & Spreitzer, 2012). Se planteó como objetivo analizar si existen diferencias en las virtudes nivel organizacional (Apoyo y respeto, Significado e inspiración, Perdón) según variables individuales (e.g. personal a cargo) y organizacionales (e.g. tamaño y tipo de empresa). Asimismo, se buscó establecer si existe relación entre dichas virtudes y medidas resultado (performance org…
Preliminar construction of a multidimensional scale to assess clinical symptoms of anxiety. Evidences of content and face validity
2017
La medición de la ansiedad debería contemplar la multidimensionalidad de este constructo. Los instrumentos de uso local presentan limitaciones relacionadas con su abordaje incompleto, el contenido de sus ítems, la capacidad para discriminar los síntomas ansiosos de los depresivos y la desactualización con respecto a los diagnósticos vigentes. Un instrumento que tome en cuenta la conceptualización multidimensional de ansiedad y los criterios diagnósticos para el trastorno de ansiedad según la última versión del Manual de Diagnóstico y Estadístico de los Trastornos Mentales (DSM-5; American Psychiatric Association, 2013) podría responder a las limitaciones de sus predecesores. L…
High Five Model: The High Factors are Associated with Low-Risk of Medical, Mental and Personality Diseases
2017
El Modelo de los Cinco Altos (MCA; High Five Model, HFM, por sus siglas en inglés)establece cinco rasgos positivos de la personalidad: erudición, paz, jovialidad, honestidad,y tenacidad, llamados factores altos. Un estudio previo había mostrado la validezconvergente, discriminante y estructural del MCA. Este estudio tuvo por objetivocorroborar que el MCA está asociado positivamente a variables relacionadas con la saludfísica y mental de los individuos. Se realizó este estudio con una muestra de participantesde población general no consultante. Específicamente, se estudió la asociación entre losfactores del MCA y el modelo de Salud Mental Positiva, el bajo riesgo de enfermedadmédica, la ause…