Academic literature on the topic 'Especies reactivas'

1933-, Asada Kozi, and Yoshikawa Toshikazu, eds. Frontiers of reactive oxygen species in biology and medicine: Proceedings of the 6th International Conference on Superoxide and Superoxide Dismutase, Kyoto, Japan, October 11-15, 1993. Excerpta Medica, 1994.

Toledo Tello, Sonia, Anna María Garza Caligaris, and Gracia Imberton Deneke, eds. Miradas etnográficas sobre San Cristóbal de Las Casas y localidades alteñas de Chiapas. Siglos XIX-XXI. Universidad Autónoma de Chiapas-Instituto de Estudios Indígenas/Universidad de Ciencias y Artes de Chiapas-Centro de Estudios Superiores de México y Centroamérica, 2020. http://dx.doi.org/10.29043/cesmeca.rep.1024.

Rojas Nieves, Dorkys Coromoto, Yamarú del Valle Chirinos Araque, Yasmira del Carmen Alaña, and María Victoria Agudelo Vargas. "Responsabilidad social de las cooperativas en su comunidad." In Tendencias en la Investigación Universitaria. Una Visión desde Latinoamérica. Volumen V. Fondo Editorial Universitario Servando Garcés de la Universidad Politécnica Territorial de Falcón Alonso Gamero / Alianza de Investigadores Internacionales S.A.S., 2019. http://dx.doi.org/10.47212/tendencias_v_2019_2.

"minutes retention depending on the oil processed. Then, Synthetic silica hydrogels: Described in the immediately the oil is heated to 70°C, (158°F) to assist "breaking" the preceding section. emulsion and the mixture is passed through a primary (first) centrifuge. The general dosage of acid-activated bleaching earths is 0.3-0.6%, depending on the quality of the oil and bleach-In contrast, the short-mix process, developed in Europe, ing earth. Bleaching earths provide catalytic sites for de-is conducted at 90°C (84°F), uses a more highly concen-composition of oxidation products. Peroxide values (mea-trated caustic, and a mixing time and primary centrifuging sure of aldehydes) and p-anisidine values (precursors for time of less than 1 minute [135]. Less heat damage to the oxidative degradation) first rise and then decrease during oil and higher refining yield are claimed by advocates of bleaching. Bleaching processes used include atmospheric the long mix process. batch, vacuum batch, and continuous vacuum. Vacuum 4. Silica Absorption bleaching has the advantage of excluding air, partially by In traditional refining, oil from the primary centrifuge is vaporization of water in the earth, and is recommended. A washed with warm soft water to remove residual soap and typical vacuum bleaching process is 20-30 minimum at passed through a (secondary) centrifuge. The washed oil 100-110°C (212-230°F) and 50 mmHg absolute [135]. then is dried under vacuum. However, disposal of wash The reactions catalyzed during bleaching continue into water is increasingly becoming a problem, and the indus-the filter bed and are known as the "press bleaching ef-try is shifting to a modified caustic "waterless" refining fect." The reactive components of oil remain in the bleach-process. Soaps poison the adsorption sites of clays in later ing bed. Care should be taken to "blow" the filter press as bleaching operations and are removed by silica hydrogels. free of oil as possible and to wet the filter cake (which can The oil may be degummed with use of chelating acids, be very dusty) to prevent spontaneous combustion [137]. caustic neutralized, passed through a primary centrifuge, At this point, the product is RB ("refined, bleached") and may be partially vacuum-dried. Synthetic silica hy-oil. If the intended product is an oil, it can be sent to the de-drogels, effective in removing 7-25 times more phos-odorizer and become RBD. If solids are desired, the solids-phatides and soaps than clay on a solids basis, and for re-temperature profile of the oil may be modified by hydro-moving phosphorus and the major metal ions, is added genation, interesterification, or chill fractionation, alone or and mixed with the oil. By absorbing these contaminants in combination. first, the bleaching clay is spared for adsorbing chloro-6. Hydrogenation phyll and the oxidation-degradation products of oil Hydrogenation is the process of adding hydrogen to satu-[136-138]. rate carbon-to-carbon double bonds. It is used to raise try-5. Bleaching glyceride melting points and to increase stability as by jective of bleaching is to remove various contami-converting linolenic acid to linoleic in soybean oil [141]. A The ob lighter, "brush" hydrogenation is used for the latter pur-nants, pigments, metals, and oxidation products before the pose. oil is sent to the deodorizer. Removal of sulfur is especial-Most of the catalysts that assist hydrogenation are nick-ly important before hydrogenation of canola and rapeseed el-based, but a variety is available for special applications. oils. Flavor of the oil also is improved. As mentioned in the "Selectivity" refers to ability of the catalyst and process to preceding section, silica hydrogels will adsorb many of sequentially saturate fatty acids on the triglycerides in the these contaminants and spare the bleaching earth. Howev-order of most unsaturated to the fully saturated. For row er, earths are still used for these purposes in installations crop oils, perfect selectivity would be: that have not adopted hydrated silicas. Types of bleaching materials available include [136,139,140]: C18:3 C18:2 C18:1 Linolenic acid Linoleic acid Oleic acid Neutral earths: Basically hydrated aluminum silicates, sometimes called "natural clays" or "earths," and C18:0 fuller's earth, which vary in ability to absorb pigments. Stearic acid Acid-activated earths: Bentonites or montmorillonites, Although typical hydrogenation is not selective, it can be treated with hydrochloric or sulfuric acid to improve favored to a limited degree by selection of catalyst and by their absorption of pigments and other undesirable temperature and pressure of the process. Efficient hydro-components, are most commonly used. genation requires the cleanest possible feed stock (without Activated carbon: Expensive, more difficult to use, but of soaps, phosphatides, sulfur compounds, carbon monoxide, special interest for adsorbing polyaromatic hydrocar-nitrogen compounds, or oxygen-containing compounds) bons from coconut and fish oils. and the purest, driest hydrogen gas possible [140]." In Handbook of Cereal Science and Technology, Revised and Expanded. CRC Press, 2000. http://dx.doi.org/10.1201/9781420027228-35.

Díez Marcelo, Rodrigo, José Javier García Criado, and Andrés Díez Herrero. "Patrimonio histórico-minero en El Espinar (Segovia): primera aproximación al catálogo de bienes y elementos." In I Simposio anual de Patrimonio Natural y Cultural ICOMOS España. Editorial Universitat Politècnica de València, 2020. http://dx.doi.org/10.4995/icomos2019.2020.11724.

Puentes Mojica, Javier, Gonzalo Barluenga Badiola, and Cynthia Guardia Martín. "Influencia de las condiciones de curado en las propiedades a edades tempranas de hormigones autocompactantes con filler calizo, microsílice y nanosílice." In HAC2018 - V Congreso Iberoamericano de Hormigón Autocompactable y Hormigones Especiales. Universitat Politècnica València, 2018. http://dx.doi.org/10.4995/hac2018.2018.5339.