977 resultados para cal micropulverizada


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Mode of access: Internet.

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Description based on: 1970-1973; title from caption.

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Mode of access: Internet.

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We have made AMS measurements on a series of 10-ring samples from a subfossil Huon pine log found in western Tasmania (42degreesS, 145degreesE). The results show a pronounced rise in Delta(14)C over the first 200 years, and a decrease over the following 160 years. Tree-ring width measurements indicate that this log (catalogue SRT-447) can be cross-dated with another subfossil log (SRT-416) for which a series of high-precision radiometric C-14 measurements have previously been made. When the two tree-ring series are thus aligned, SRT-447 is the older of the two logs, and there is a 139-year overlap. We then have a Huon pine floating chronology spanning 680 years, with C-14 measurements attached. The C-14 data sets agree well within the period of overlap indicated by the tree-rings. The C-14 variations from Huon pine show excellent agreement with those from German oak and pine for the period 10,350-9670 cal BP. Aligning the Huon pine C-14 Series with that from German oak and pine allows us to examine the inter-hemispheric offset in C-14 dates in the early Holocene. (C) 2004 Elsevier B.V. All rights reserved.

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This study examines the forcing mechanisms driving long-term carbonate accumulation and preservation in lacustrine sediments in Lake Iznik (northwestern Turkey) since the last glacial. Currently, carbonates precipitate during summer from the alkaline water column, and the sediments preserve aragonite and calcite. Based on X-ray diffraction data, carbonate accumulation has changed significantly and striking reversals in the abundance of the two carbonate polymorphs have occurred on a decadal time scale, during the last 31 ka cal BP. Different lines of evidence, such as grain size, organic matter and redox sensitive elements, indicate that reversals in carbonate polymorph abundance arise due to physical changes in the lacustrine setting, for example, water column depth and lake mixing. The aragonite concentrations are remarkably sensitive to climate, and exhibit millennial-scale oscillations. Extending observations from modern lakes, the Iznik record shows that the aerobic decomposition of organic matter and sulphate reduction are also substantial factors in carbonate preservation over long time periods. Lower lake levels favour aragonite precipitation from supersaturated waters. Prolonged periods of stratification and consequently enhanced sulphate reduction favour aragonite preservation. In contrast, prolonged or repeated exposure of the sediment-water interface to oxygen results in in situ aerobic organic matter decomposition, eventually leading to carbonate dissolution. Notably, the Iznik sediment profile raises the hypothesis that different states of lacustrine mixing lead to selective preservation of different carbonate polymorphs. Thus, a change in the entire lake water chemistry is not strictly necessary to favour the preservation of one polymorph over another.

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Paleomagnetic data including inclination, declination, MAD values and MDF are given on an event correct composite depth (ECCD) and age for the composite lacustrine record TAN12-2 from Lake Tangra Yumco, Tibetan Plateau.

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Programa de doctorado: La Restauración y la Rehabilitación arquitetónica. Investigación, tendencias e innovaciones. La fecha de publicación es la fecha de lectura

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Caló is a language/variety spoken by the Spanish Calé (i.e. the Roma). The variety belongs to a group oflanguages referred to as “Para-Romani”, characterized by Romani vocabulary, but largely non-Romani morphology, phonology and syntax, in the case of Caló deriving from Spanish. Much research has been carried out regarding the vocabulary and the grammar of this variety.The conclusions drawn in those studies indicate that Caló is on its way to extinction. However, thereis an expressed interest in reintroducing the variety, in a form called “Romanó-Caló”. Language attitudes play a decisive role for the destiny of endangered languages. In order for arevitalization project to be successful, the attitudes towards the variety being reintroduced have to bepositive. The aim of this study is to measure the attitudes that both Calé and non-Calé have towards Calóand Caló speakers, a type of study never carried out in the past. The methods applied are both direct andindirect. In part one, 231 informants listened to different recordings of voices acting as either a “Spanishspeaking person” or a “Caló speaking person”, a technique referred to as ‘matched guise’. Firstly,the informants were asked to write down their first three impressions of the speakers. Secondly, nineshort questions related to the voices were asked, to which the subjects expressed their answers on attitudescales. They were also asked to match the voices with photos of people. Furthermore, theinformants have answered questions regarding what variety is spoken at home, as well as if he or she hasany knowledge of, or contact with, any language/variety, apart from Spanish. 182 informants continuedwith part two of the questionnaire, which consisted of 20 items – positive and negative statementstowards Caló and Caló speakers. The informants have rated their agreement or disagreement to thesestatements on a Likert scale. Another exercise measured the willingness of the informants to use Calówords for naming various objects. In addition, the subjects were tested on their knowledge of some Calówords, as well as asked whether they thought it was “useful” to know how to speak Caló. Variousstatistical methods have been used in order to establish whether or not the results are statisticallysignificant. The results of the analysis indicate that the attitudes differ towards Caló and Calóspeakers, depending on the informant’s (a) ethnicity (b) contact with Caló as well as with Calóspeakers, and (c) gender. It is those who – in their own opinion – belong to the ethnic group Calé, as wellas those who claim that they have some contact with the variety and its speakers, who show positiveattitudes in both parts of the study. The women also show more positive attitudes than the men. It is alsopossible to note positive attitudes towards the variety and its speakers among the subjects with a highlevel of knowledge of Caló words, as well as among those with the highest willingness to use Caló. These observations suggest that a revitalization project of the variety Caló has a clear chance ofbeing successful.

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La presente propuesta educativa, propone y dise?a una cartilla que informa y educa a la comunidad educativa acerca de la problem?tica de extracci?n minera de carb?n presente en el rio Mel?ndez. Con esto se pretende evidenciar la situaci?n, con el fin de que se reconozcan los graves da?os que estas pr?cticas ocasionan no solo a nivel ambiental sino tambi?n social. Este trabajo se enmarca en una metodolog?a cualitativa, presentada en dos fases, que finalizando permitieron la creaci?n de una cartilla educativa que responde a todos los objetivos y planteamientos realizados en el presente trabajo.

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Urban paving is of paramount importance for a city, both socioeconomic and in quality of life. The urban flooring not different so-called road surface are constituted by a set of horizontal layers, overlaid on the ground, which have the main function of supporting the actions induced by the vehicle redistributing the stresses transmitted to the ground. Soils are important materials for the execution of paving, mainly because they are part of the basic structure of the floor and mostly be available in abundance, with a very low cost, however, their properties usually do not meet the requirements necessary to perform the floor. The soil stabilization for the implementation of urban pavement bases and sub-bases is an increasingly important aspect in the current situation, because always there is the concern with the environment, and there is now the clear awareness that every effort should be made to minimize the effects caused by the exploitation of deposits and deposition of material. In this sense this work presents the effects of adding different proportions of lime to stabilize a sedimentary soil sample from the urban area of the city of Curitiba. It selected a sample quantity of soil in the region to study the stabilization insertion of hydrated lime type (CHIII) powder. The two variables in the study are related to the content of lime mixed with the soil at 0% percentages of 3%, 6%, 8% and 16%, and cure times at which these mixtures were subjected to (0, 7, 14, 28 and 56 days). The tested mixtures were prepared from dosages defined by two methods: one checking the chemical behavior of the samples by means of changes in pH values, and the second analyzing the mechanical behavior through the RCS values. It has been found that the chemical stability analyzed by addition of lime, provided an average increase of RCS in most soil samples studied, because of some physical and chemical characteristics thereof. For mixtures with 6%, 8% and 16% of lime after 28 days of curing, the average RCS was 0,57 MPa, 1,06 MPa and 2,37 MPa, respectively, for the normal proctor, and as for intermediate proctor, in the same curing time and on the same percentages RCS results were 0,54 MPa, 1,04 MPa and 2,71 MPa, respectively. In global terms, the soil-lime mixtures studied showed acceptable behavior by law to use as layers of sub-base. However, only the mixture with 16% of lime, at 28 days, is recommended for use on floors bases. Even so, the mixtures studied constitute a good alternative economic and socio-environmental.

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The rapid population growth is the great motivator for the development of the construction industry and the increased demand for drinking water, resulting in a gradual increase in the generation of solid waste. Thus, this work was carried out in order to recycle industrial and municipal wastes incorporating them into materials for civil construction. The composite produced from water treatment sludge and marble polishing mud, applying lime production waste as a binder, was evaluated for its mechanical performance and its morphological structure. The raw materials were characterized for their chemical composition, mineralogy, morphology, particle size and also the moisture content. With the featured materials nine compositions have been developed varying the content of the water treatment sludge between 25 to 50%, marble polishing mud between 35 to 50% and the lime production waste between 10 to 30%. The composites were subjected to mechanical strength tests, water absorption, chemical and mineralogical composition and morphology. The developed materials presented, on the 3rd day of hydration, maximum strength value of 4.65 MPa, the 7th day 6.36 MPa, on the 14th day 6.74 MPa, the 28th day 5.98 MPa, on the 60th day 8.52 MPa at 90th day 11.75 MPa and 180th day 12.06 MPa. The water absorption values after 28 days of hydration ranged from 16.27% to 26.32% and after 90 days, from 13.57% to 23.56%.

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As argamassas mistas de cal e terra devem ter resultado da prática profissional quando as condições económicas foram possibilitando a adição de cais aérea às argamassas vernaculares só de terra. Baixas adições de cal aérea a argamassas de terra têm conduzido a drásticas alterações da cor e das resistências mecânicas das argamassas de terra. No entanto, a substituição parcial de massa de cal por terra em argamassas de cal ao traço volumétrico 1:2 (correspondendo a argamassas com traço em massa de 1:8, com substituições de 10% a 50%) resulta em argamassas mais ecológicas e que tecnicamente indiciam ser adequadas para aplicação em rebocos de edifícios antigos e mesmo em construção nova com características compatíveis. Os resultados obtidos foram particularmente interessantes para uma substituição de 10% mas muito há ainda a fazer para um conhecimento aprofundado deste tipo de argamassas mistas de cal e terra, muito utilizadas no passado, com vista à otimização de formulações que possam vir a ser aplicadas correntemente.