732 resultados para CuO microparticles
Resumo:
When a tree is chopped to bits, or a sweater unraveled, its matter still exists. Since antiquity, it has sometimes been inferred that nothing really has been destroyed: what has happened is just that this matter has assumed new form. Contemporary versions hold that apparent destruction of a familiar object is just rearrangement of microparticles or of 'physical simples' or 'world stuff'. But if destruction of a familiar object is genuinely to be reduced to mere alteration of something else, we must identify an alternation proper to the career, the course of existence, of this something else; relatedly, the alteration must be characterizable without asserting the existence of the familiar object. All contemporary views fail one of these requirements.
Resumo:
Concretions of iron and manganese oxides and hydrous oxidesóobjects commonly called manganese nodulesóare widely distributed not only on the deep-sea floor but also in shallow marine environments1. Such concretions were not known to occur north of Cape Mendocino in the shallow water zones bordering the North-East Pacific Ocean until the summer of 1966 when they were recovered by one of us (J. W. M.) in dredge samples from Jervis Inlet, a fjord approximately 50 miles north-west of Vancouver, British Columbia.
Resumo:
Deep-sea deposits, which resemble in nearly every respect the deep-sea oozes have been observed in many islands of the East-Indian Archipelago, notably the islands of Borneo, Rotti and Timor. Manganese nodules are found in equivalents of deeep-sea red clays on Timor and Rotti island. In this paper, those relative to red clay deposits dating from a Cretaceous ocean are analysed in detail in the vicinity of the town of Niki Niki in Western Timor.
Resumo:
A 181 m deep ice core drilled in 1994/95 on the south dome of Berkner Island, Antarctica, was analyzed for stable isotopes, major ions and microparticle concentrations. Samples for ion chromatography were prepared by using a novel technique of filling decontaminated sample from a device for continuous ice-core melting directly into the sample vials. The core was dated through identification of volcanic horizons and interpolative layer counting. The core, together with a similar core from the north dome, reveals a 1000 year history of relatively stable climate. Temporal variations in the two cores deviate from each other owing to changing patterns of regional-scale circulation; the best correspondence between them is found for MSA-. delta18O, accumulation rate and a sea-salt proxy show only negligible correlation, which suggests a complex meteorological setting. Increasing annual accumulation is observed for the last 100 years. A period of increased sea-salt concentrations started around AD 1405, as has also been observed in other cores. Microparticle concentrations are on average 1220 particles (>=1.0 ?m diameter)/mL; they are enhanced from AD 1200 to 1350, possibly because of a higher atmospheric mineral dust load or because local volcanic activity was stronger than previously thought. Microparticles and NH4+show marked but multiple and very irregular sub-annual peaks; long-term stacking of 1 year data intervals yields seasonal maxima in austral spring or mid-summer, respectively. Post-depositional redistribution was observed for MSA, NO3- and F- at volcanic horizons.
Resumo:
A novel laser microparticle detector used in conjunction with continuous sample melting has provided a more than 1500 m long record of particle concentration and size distribution of the NGRIP ice core, covering continuously the period approximately from 9.5-100 kyr before present; measurements were at 1.65 m depth resolution, corresponding to approximately 35-200 yr. Particle concentration increased by a factor of 100 in the Last Glacial Maximum (LGM) compared to the Preboreal, and sharp variations of concentration occurred synchronously with rapid changes in the delta18O temperature proxy. The lognormal mode µ of the volume distribution shows clear systematic variations with smaller modes during warmer climates and coarser modes during colder periods. We find µ ~ 1.7 µm diameter during LGM and µ ~ 1.3 µm during the Preboreal. On timescales below several 100 years µ and the particle concentration exhibit a certain degree of independence present especially during warm periods, when µ generally is more variable. Using highly simplifying considerations for atmospheric transport and deposition of particles we infer that (1) the observed changes of µ in the ice largely reflect changes in the size of airborne particles above the ice sheet and (2) changes of µ are indicative of changes in long range atmospheric transport time. From the observed size changes we estimate shorter transit times by roughly 25% during LGM compared to the Preboreal. The associated particle concentration increase from more efficient long range transport is estimated to less than one order of magnitude.
Resumo:
El trabajo aborda a la vez la historia de una institución local en particular y su devenir en relación con el campo artístico de Mendoza y la genealogía europeizante del museo de arte impuesto como paradigma desde la formación de los estados nacionales europeos. El Museo de Bellas Artes como entidad reproductora del gusto de la burguesía y como factor de distinción social verifica en esta región americana el cumplimiento de un ciclo reforzado por la copia del modelo civilizatorio que asume como propio en la Mendoza de los siglos XIX y XX. Tras la institución del primer Museo Provincial de Bellas Artes y su posterior refundación como Museo Fader; sorprende hallar un programa museológico de cuño modernizador; atento a la realidad latinoamericana sin perder de vista la historia del sector.
Resumo:
La concepción de la notitia intuitiva, tal como la entienden los filósofos del siglo XIV, constituye un modo de acceso a la realidad de cuño agustiniano que subsiste a pesar del progresivo avance de la teoría aristotélica de la abstracción. Tomando como punto de partida la notitia intuitiva, Ockham propone una construcción del conocimiento y de la ciencia que procura una interpretación más delimitada y precisa del pensamiento de Duns Escoto. Esta doctrina ockhamista va a ser puesta a prueba por un desarrollo paradojal vinculado al conocimiento de lo no-existente. La importancia del ejemplo ha sido clave a la hora de la valoración de su gnoseología. En particular, el tema es expuesto, con algunos matices de diferenciación, en tres obras: en la quaestio primera del Prólogo del Commentarium in Sententiis; en las quaestiones 12-13 de la Reportatio II y en las Quaestiones Quodlibetales V y VI, a las que también se suman precisiones puntualizadas en el marco de sus composiciones físicas, en particular, en las Quaestiones Physicorum. Constituye nuestro propósito el análisis de estas fuentes en orden a discernir la importancia que el controvertido paso asume en el marco de la gnoseología ockhamista. El ejemplo ha sido interpretado de modo contrastante: para algunos introduce claramente una concepción escéptica de la doctrina del conocimiento, en el sentido que, una vez admitida la posibilidad de una intuición de cosas que no existen, no tenemos ningún criterio para establecer cuándo nuestro conocimiento es objetivo o subjetivo. Para otros, en cambio, debe ser entendido como una hipótesis que no interfiere sobre el plano natural del conocimiento. El recurso a las fuentes nos permitirá comparar los planos de explicitación del ejemplo aludido y determinar su contexto y alcance en orden a un examen del problema en el doble ámbito de lo natural y de lo sobrenatural, aportando nuestras propias conclusiones al caso.
Resumo:
Este artículo trata sobre las constituciones de nuevo cuño del siglo XXI – Venezuela, Bolivia y Ecuador– indagando en los procesos políticos de los cuales son expresión. Se reflexiona acerca de por qué los movimientos políticos que los conducen avanzaron en la creación de constituciones antes de haberse consolidado en lo estructural o de haber producido cambios sociales de fondo. Se interroga también si se puede hablar de un nuevo constitucionalismo en dichos procesos y en torno a qué sería nuevo. Además, se ofrece información sobre los respectivos textos constitucionales en perspectiva comparada con algunos aspectos de la Constitución de Argentina.
Resumo:
This report studies the principal paramters governing the distribution of iron-manganese concretions on the sea floor of the Indian Ocean, as well as their petrography and mineralogy. The results are mainly based on the recoveries made during voyages 31, 33 and 35 of the "Vityaz"' (1959-1962) and partly during voyages 36 and 41 (1964-1966). During these voyages samples of Mn concretions and Mn crust were collected (by bottom grabs, cores, trawlings, and dredgings) at 39 stations. The following account is devoted to the problems concerning the geochemistry of these concretions.
Resumo:
TEM (transmission electron microscopy) observations and microanalyses on smectite microparticles in the sediments of the CRP-2A core were carried out to determine their origin (authigenic or detrital) and the source rocks. Smectites are dioctahedral and are Fe-rich members of the nontronite-beidellite series. They generally display both flaky and hairy shapes, but no large compositional difference between the two forms was observed. Flaky smectites are detrital while hairy smectites probably formed in situ through the reorganisation of previous flaky particles. The source rocks for smectites are probably represented by the McMurdo Volcanic Group to the south, but also by the Ferrar Dolerites and Kirkpatrick Basalts in the Transantarctic Mountains. CRP-2A smectites are Fe and Mg richer than those of the coeval or not coeval levels of the CIROS-I, DSDP 270 and 274 cores. The average compositions of smectite in CRP-1 and CRP-2A cores show a downcore trend toward more alluminiferous terms, which might reflect the increase of the chemical weathering processes on the continent.
Resumo:
The data collection "Deep Drilling of Glaciers: Soviet-Russian projects in Arctic, 1975-1995" was collected by the following basic considerations: - compilation of deep (>100 m) drilling projects on Arctic glaciers, using data of (a) publications; (b) archives of IGRAN; (c) personal communication of project participants; - documentation of parameters, references. Accuracy of data and techniques applied to determine different parameters are not evaluated. The accuracy of some geochemical parameters (up to 1984 and heavy metalls) is uncertain. Most reconstructions of ice core age and of annual layer thickness are discussed; - digitizing of published diagrams (in case, when original numerical data were lost) and subsequent data conversion to equal range series and adjustment to the common units. Therefore, the equal-range series were calculated from original data or converted from digitized chart values as indicated in the metadata. For the methodological purpose, the equal-range series obtained from original and reconstructed data were compared repeatedly; the systematic difference was less then 5-7%. Special attention should be given to the fact, that the data for individual ice core parameters varies, because some parameters were originally measured or registered. Parameters were converted in equal-range series using 2 m steps; - two or more parameter values were determined, then the mean-weighted (i.e. accounting the sample length) value is assigned to the entire interval; - one parameter value was determined, measured or registered independently from the parameter values in depth intervals which over- and underlie it, then the value is assigned to the entire interval; - one parameter value was determined, measured or registered for two adjoining depth intervals, then the specific value is assigned to the depth interval, which represents >75% of sample length ; if each of adjoining depth intervals represents <75% of sample length, then the correspondent parameter value is assigned to both intervals of depth. This collection of ice core data (version 2000) was made available through the EU funded QUEEN project by S.M. Arkhipov, Moscow.
Resumo:
A felsic volcanic series (605-825 mbsf) overlain by upper Eocene shallow-water sediments (500-605 mbsf) and basalticandesitic sills that intruded into sediments of Holocene to Miocene age (0-500 mbsf) was drilled in the forearc region of the Lau Basin at a water depth of 4810 m. The volcanic sequence at Site 841 includes altered and mineralized calc-alkaline rhyolites and dacites, dacitic tuffs, lapilli tuffs, flow breccias, and welded tuffs. These rocks formed subaerially or in a very shallow-water environment suffering a subsidence of >5000 m since Eocene times. Calculations of gains and losses of the major components during alteration show most pronounced changes in the uppermost 70 m of the volcanic sequence. Here, Al, Fe, Mg, and K are enriched, whereas Si and Na are strongly depleted. Illite, vermiculite, chlorite, and hematite predominate in this part of the hole. Throughout the section, quartz, plagioclase, kaolinite, and calcite are present. Sulfide mineralization (up to 10 vol%) consisting mainly of disseminated pyrite (with minor pyrrhotite inclusions) and marcasite together with minor amounts of chalcopyrite is pervasive throughout. Locally, a few sulfide-bearing quartz-carbonate veins as well as Ti-amphibole replacement by rutile and then by pyrite were observed. Strong variations in the As content of sulfides (from 0 to 0.69 wt%) from the same depth interval and local enrichments of Co, Ni, and Cu in pyrite are interpreted to result from fluctuations in fluid composition. Calculations of oxygen and sulfur fugacities indicate that fO2 and fS2 were high at the top and lower at the bottom of the sequence. Sulfur isotope determinations on separated pyrite grains from two samples give d34S values of +6.4ë and +8.4ë, which are close to those reported from Kuroko and Okinawa Trough massive sulfide deposits and calc-alkaline volcanic rocks of the Japanese Ryukyu Island Arc. Calculated chlorite formation temperatures of 265°-290°C at the top of the sequence are consistent with minimum formation temperatures of fluid inclusions in secondary quartz, revealing a narrow range of 270°-297°C. Chlorite formation temperatures are constant downhole and do not exceed 300°C. The presence of marcasite and 4C-type pyrrhotite indicates a formation temperature of <= 250°C. At a later stage, illite was formed at the top of the volcanic series at temperatures well below 200°C.
Resumo:
Este artículo enfoca eltrabajo docente enlas universidades públicas provincialesdel Paraná/Brasil. Inicialmente se problematiza loactual contexto marcado por la restructuraciónproductiva y por la reforma de Estado y lastransformaciones por lascualesvienepasandolauniversidadbrasileña. A partir de ahíelestudio se vuelve para el cotidiano docente mediante entrevistas realizadas contreinta y seis docentes vinculados latres universidades públicas provinciales. Se analizalas entrevistas hechasconlos docentes y se discute tendencias observadas enlosdatoscolectados. Se postula laconstitución de una nueva métrica deltiempo y una nuevaespacializacióneneltrabajo docente resultante de loscambiospolítico-económicos, cuya tónica es la gradual exencióndelfinanciamiento público y lacomercializacióndelconocimiento a través de laprivatización de cursos y de lainnovación tecnológica subordinada. Se aborda algunasrepercusiones de las condiciones objetivas sobre lasactividades académico-científicas y políticas delcuerpo de profesores como elenvolvimiento de este conprácticasdelcasi mercado educacional, la falta de tiempo para eltrabajo de cuño intelectual y elvaciamiento de la política sindical
Resumo:
En este trabajo reflexionamos acerca de la presencia hispánica en la provincia de Tucumán (Argentina) centrándonos en el teatro como espacio de circulación de la cultura española. Para ello hemos seleccionado un corpus de obras de cuño hispánico puestas en escena en Tucumán a partir del año 2000 en adelante.
Resumo:
La novela de Roberto Arlt, El juguete rabioso (1926), pone en marcha a la narrativa del siglo XX en los estertores del período celebratorio del Centenario y abre una genealogía en la literatura argentina identificada con lo que José Amícola define como una "escritura de la exageración" y con una narrativa de cuño netamente urbano. Las dinámicas que se perciben en la narrativa actual, con toda la savia aportada por los medios masivos de comunicación y la cultura de masas, remiten a otro tipo de imaginarios que incluyen a la técnica como elemento configurador e inseparable de la percepción de los eventos narrados. El Bicentenario se inaugura con una narrativa que sigue siendo vital y no pierde su aptitud novelesca, hereditaria de la tradición de la novela de aventuras, del folletín, pero a su vez atravesada por una estética aun más violenta y paródica. Cómo se inserta en la tradición abierta por Arlt y qué elementos se exacerban en un contexto tan conflictivo como el del principio del milenio, es lo que será analizado en dos novelas recientes, Los topos (2008) de Félix Bruzzone y Letra muerta (2009) de Mariano García.