Chemical and Sr isotopic compositions and timing of carbonate mineral precipitation, ODP Leg 115

The strontium isotope ratios of authigenic carbonates from Indian Ocean sea-floor basalts have been used to determine the timing of carbonate mineral precipitation and fluid flow. The samples include calcites from 57.2 Ma crust from Ocean Drilling Project (ODP) Site 715, and calcites, aragonites, and siderites from 63.7 Ma crust from ODP Site 707. At Site 715, calcite precipitation may have begun at any time after the basalts cooled, and it continued until approximately 31 Ma, or 26 m.y. after basalt eruption. At Site 707, aragonite and siderite did not begin to precipitate until about 36 Ma, almost 30 m.y. after basalt eruption, and continued to precipitate until at least 30 and 28 Ma, respectively. Calcite precipitation began at approximately 32 Ma and continued until 22 Ma. These ages suggest that vein mineral deposition and low-temperature fluid circulation in the ocean crust may continue for much longer periods of time than previously observed.

Determinación del contenido de alúmina reactiva de las adiciones puzolánicas naturales y artificiales, por termogravimetría y por el método de Rietveld

Tanto el tema de esta investigación, como sus objetivos, fundamentos, materiales seleccionados y parte experimental para alcanzarlos, han sido promovidos por la situación y el estado de las construcciones de hormigón armado que se comenzaron a realizar en España a partir del año 1975, con hormigones y morteros de cemento que contenían cenizas volantes hasta un 20 %, en principio, y hasta un 35 %, más tarde, de su dosificación de cemento Portland (CP), los cuales y en contra de lo esperado, han demandado y continúan demandando, muy a pesar de sus aparentes bondades de todo tipo que se les atribuían, una necesidad de mejora de sus prestaciones, especialmente, debido a un nivel inesperadamente bajo de la durabilidad de algunas obras construidas con los mismos. Todo era debido, en definitiva, a que las adiciones puzolánicas, naturales y artificiales, tales como las cenizas volantes, referidas antes, se vienen utilizando reglamentariamente para la fabricación de cementos y/o de sus productos derivados, hormigones, morteros y pastas, en la mayor parte de los países industrializados, desde hace ya más de tres décadas aproximadamente, en las mismas condiciones e idénticos usos constructivos que los hormigones y morteros de CP puro, viniendo además, dictada dicha utilización de estos materiales residuales, hoy sub-productos industriales, por cuestiones medioambientales y/o económicas, principalmente, motivo por el cual esta Tesis Doctoral ha pretendido responder también, adecuadamente y de manera esquemática (en forma de diagrama de flujo), a los criterios que deben de tenerse en cuenta a la hora de su selección y caracterización normalizada y reglamentada de estas adiciones minerales activas, sobre todo, antes de su dosificación y uso en forma del denominado cemento Portland con puzolana, o con ceniza volante, o con esquistos calcinados o con puzolanas calcinadas o con humo de sílice, cemento Portland mixto, cemento puzolánico o cemento compuesto, para que dichos problemas no se le produzcan al hormigón armado ni en masa. De aquí el enfoque tan particular y especial de esta investigación, al haberla circunscrito únicamente a las puzolanas naturales y artificiales, por considerarlas todas ellas, independientemente de por su origen, como materiales constituidos por pequeñas fracciones cristalinas distribuidas aleatoriamente en una matriz mayoritariamente vítrea y/o amorfa, la cual es la que le confiere su reactividad con el hidróxido de calcio en forma de cal apagada o de portlandita procedente de la hidratación del CP. A su vez, dichas fracciones vítreas y/o amorfas están constituidas, en su mayor parte, por sílice reactiva, SiO2r-, alúmina reactiva, Al2O3r-, y óxido de hierro reactivo, Fe2O3r-, recibiendo además, en conjunto, el nombre específico de "factores hidráulicos" de la puzolana, los cuales, por lo común, difieren cuantitativamente de sus contenidos totales, determinados por fusión alcalina mediante procedimientos normalizados. De los tres óxidos reactivos mencionados y desde el punto de vista técnico, los más importantes por su mayor presencia en casi todas las puzolanas naturales y artificiales y, también, transcendencia en la durabilidad química que les pueden llegar a conferir al hormigón armado y en masa, mortero o pasta de cemento que las contenga, son la SiO2r- y la Al2O3r-. El primero de los dos, la SiO2r-, reacciona nada más que con la portlandita (y el Ca(OH)2) para formar geles C-S-H, más tarde transformados en tobermoritas o en jennitas, semejantes a los que originan la alita y la belita del CP en su hidratación. Y desde el punto de vista normativo, la presencia de esta fracción silícica reactiva en las puzolanas viene regulada por la norma EN 197-1, de modo general, siendo además referida por la norma EN 450-1:2006, en el contexto de las cenizas volantes en su adición al hormigón, como "un polvo fino de partículas principalmente de forma esférica y cristalina, procedentes de la combustión de carbón pulverizado, que tiene propiedades puzolánicas y que está compuesto fundamentalmente de SiO2 y Al2O3". Además y de acuerdo con la primera de las dos normas, "El contenido de dióxido de silicio reactivo (definido y determinado según la norma EN 196-2 o su equivalente la UNE 80225) no debe ser inferior al 25 % en masa". Por su parte, cuantiosos estudios experimentales realizados por Talero solo y con otros investigadores, han demostrado que si la puzolana no es adecuada en calidad ni en cantidad, la durabilidad del cemento del que forme parte, y, por consiguiente, de los productos derivados que con él se fabriquen, hormigones, morteros, pastas y prefabricados, puede llegar a ser anormalmente baja, porque la alúmina reactiva, Al2O3r-, o alúmina tetra- o penta-coordinada que la constituye, se implica como tal, de una forma muy directa y con resultados totalmente contrapuestos incluso, en los ataques químicos agresivos naturales que se les producen, provenientes de terrenos y aguas selenitosas (sulfatos, que atacan en su caso al propio material hormigón, mortero y pasta que la contiene para formar ettringita de rápida formación, ett-rf, la cual puede llegar incluso a provocar un ataque rápido del yeso), del rocío marino y de las sales de deshielo (cloruros, que atacan, en cambio, a las armaduras de acero del hormigón provocándoles su corrosión electroquímica por "picadura", si bien, en este otro ataque químico, dicha Al2O3r- lo que origina es sal de Friedel de rápida formación, sF-rf, también, cuyo efecto es, en cambio, colmatador y protector, en definitiva, de dicha corrosión electroquímica), del agua de mar (acción agresiva mutua de cloruros y sulfatos), de la carbonatación, de la reactividad árido-álcali, además de intervenir en la liberación del calor de hidratación, así como también, en el comportamiento reológico de sus pastas, etc., acortándoles de este modo su durabilidad prevista y, en ocasiones, muy seriamente incluso. Pero lo más paradójico de todo es, que a pesar de su referido comportamiento totalmente contrapuesto, frente a sulfatos y cloruros, - aún no se dispone de un método de análisis químico para su determinación cuantitativa, que sea además relativamente sencillo en su operatividad, veraz, preciso, de respuesta rápida, desde el punto de vista técnico de la construcción (no más de 28 días), repetible, reproducible, que no implique peligro alguno para la seguridad vital de las personas que lo tengan que manipular y poner en práctica, económico, y que sirva también tanto para investigación -vertiente científica-, como, sobre todo, para control de calidad -vertiente técnica-, - y ni mucho menos tampoco se dispone todavía, de especificación química alguna que precise el contenido máximo de Al2O3r- (%) que tiene que poseer una puzolana natural o artificial, para poder ser añadida al cemento Portland y/o al hormigón que va a estar sometido a un determinado ataque químico agresivo de los mencionados antes, y, en especial, a sulfatos, a cloruros o al agua de mar. Y para mayor justificación de ambas necesidades, se ha de decir también que la vigente Instrucción de Hormigón Estructural EHE-08 no contempla tampoco especificación química alguna sobre los "factores hidráulicos", en general, ni del contenido de Al2O3r-(%) de las cenizas volantes, muy en particular, en su Artículo 30º "Adiciones", ni en ningún otro Artículo, a pesar de que sí contempla, en cambio, - otras especificaciones químicas que carecen del necesario significado en cuanto a la necesidad de llevar explícita o implícitamente, el mensaje de la Durabilidad Química deseado, y - el Artículo 37º, el cual y para mayor abundamiento se titula paradójicamente "Durabilidad del hormigón y de las armaduras". Asimismo, tampoco se contempla en la última versión que acaba de publicarse de la norma EN 197-1 titulada: "Cementos. Parte 1: Composición, especificaciones y criterios de conformidad de los cementos comunes". Ni tampoco, en la norma EN 450-1:2006 titulada "Cenizas volantes para hormigón. Parte 1: Definiciones, especificaciones y criterios de conformidad", ni en la vigente Instrucción española para la Recepción de Cementos, RC-08, ni en la norma ASTM C618-03 tampoco. La única especificación química que ambas normas, la europea y la norteamericana, refieren es aquella que dice que la suma de los contenidos porcentuales de SiO2 total, Al2O3 total y Fe2O3 total, de la puzolana natural o artificial, ha de ser mayor o igual que 70 %, definiendo, además, a las puzolanas de este modo tan genérico: "materiales silíceos o silíceos y aluminosos, que por sí mismos no poseen valor cementante alguno, pero que finamente divididos y en presencia de humedad, reaccionarán químicamente con hidróxido de calcio a temperaturas ordinarias para formar compuestos que poseen propiedades cementantes". Por consiguiente y de acuerdo con todo lo anterior, el objetivo primordial de esta Tesis Doctoral ha sido: Diseñar y poner a punto un nuevo método analítico de utilidad técnica (que la duración máxima del ensayo no sea mayor de 28 días), para determinar el contenido de alúmina reactiva, vítrea o amorfa, Al2O3r-, de las puzolanas naturales y artificiales. Y una vez puesto a punto, validarlo a nivel de su repetibilidad, de acuerdo con parámetros estadísticos apropiados, poniendo especial énfasis en los criterios de aceptación establecidos por la American Association of Official Analytical Chemists (AOAC). Y para conseguirlo, la innovación de esta investigación se ha basado en los siguientes fundamentos generales, a saber: - Toda la alúmina de cualquier puzolana natural o artificial, capaz de ser atacada, disuelta y lixiviada en 28 días, por la portlandita o por el hidróxido de calcio, Ca(OH)2, en medio acuoso, es considerada como alúmina reactiva, Al2O3r-. - Dicha fracción alumínica reactiva de la puzolana natural o artificial se tiene que encontrar, además, en el estado físico-químico de poder reaccionar químicamente también, en presencia de hidróxido de calcio, cloruro de sodio y agua, para originar monocloro¿aluminato de calcio hidratado, C3A·CaCl2·10H2O, o sal de Friedel. Además, dicho estado físico-químico de la puzolana ha de ser acorde con la definición de alúmina reactiva adoptada en esta investigación en razón de las prestaciones reales de durabilidad química que le puede llegar a conferir a los cementos de mezcla y a sus productos derivados, hormigones, morteros y pastas, que se fabriquen con la misma. - La originalidad de este nuevo método analítico, respecto a los demás métodos ya existentes, reside en que la cuantificación de dicha fracción alumínica reactiva de la puzolana natural o artificial, se realiza mediante cálculo estequiométrico, basándose, para ello, en dicha reacción química de formación de sal de Friedel precisamente, tras 28 días de hidratación básica-salina acelerada de la puzolana natural o artificial, habiéndose realizado, además, en esta investigación dicha determinación cuantitativa de la cantidad de sal de Friedel originada por cada puzolana, mediante dos técnicas analíticas instrumentales que fueron las siguientes: el análisis termogravimétrico (variante I ó I-I en su caso) y el método de Rietveld con la difracción de Rayos X en polvo (variante II). - La reacción química de formación de sal de Friedel tras 28 días de hidratación básica-salina acelerada de las puzolanas que se analicen, se optimizó para asegurar que el único compuesto químico de aluminio y cloro formado fuese sal de Friedel nada más (dosificando para ello en cantidad adecuada los reactivos químicos necesarios: Ca(OH)2, NaCl y agua destilada), manteniendo, además y por otra parte, el compromiso apropiado entre el máximo rendimiento de dicha reacción química (ataque, disolución y lixiviación en 28 días, de toda la alúmina reactiva de la puzolana) y el modo y medios más adecuados de acelerarlo para conseguirlo fue a 40°C de temperatura, con agitación constante y cierre hermético del reactor. - La aplicabilidad y selectividad del nuevo método analítico, objeto de esta Tesis Doctoral, fue estudiada con una serie de puzolanas naturales y artificiales españolas, silíceas y/o silíceas y aluminosas en naturaleza, que fueron las siguientes: M0 (metacaolín 0), M1 (M0 con 50 % de cuarzo), C y L (puzolanas naturales de las Islas Canarias), CV10 y CV17 (cenizas volantes), A (puzolana natural de Almagro), O (puzolana natural de Olot) y HS (humo de sílice). - Todas las adiciones minerales anteriores cumplieron con los principales requisitos físicos y químicos que son preceptivos para poder considerarlas, antes de todo, como puzolanas, lo que era indispensable y de obligado cumplimiento, para poderles determinar su contenido total de Al2O3r- (%) mediante el nuevo método analítico. Estos condicionantes fueron los siguientes: grado adecuado de finura de molido o tamaño medio de partícula (según la norma EN 451-2), haber sido analizadas químicamente antes de todo (según la norma EN 196-2 ó la ASTM C311), con el fin de determinarles especialmente, sus contenidos totales de SiO2 (%), Al2O3 (%) y Fe2O3 (%), haberles determinado, además, su contenido de sílice reactiva, SiO2r- (%) (según la norma UNE 80225), y haber cumplido con el ensayo de puzolanicidad o de Frattini (según la norma EN 196-5) a la edad de 28 días al menos. Este último requisito, otrora de obligado cumplimiento hasta el año 1988, para cualquier puzolana natural y artificial que una fábrica de cementos pretendiera introducir en el proceso de fabricación de un nuevo cemento puzolánico o cemento tipo CEM IV, ha logrado así, que se tenga que volver utilizar de nuevo de forma obligada con esta Tesis Doctoral. Y los resultados obtenidos con el nuevo método analítico de los contenidos de Al2O3r-(%) de las puzolanas seleccionadas, fueron los siguientes: - Mediante su variante I: M0 29.9 %, M1 16.9 %, CV10 11.4 %, L 12.3 %, C 12.6 %, A 8.0 %, CV17 9.5 % y O 6.3 % de Al2O3r-, y - Mediante su variante II: M0 30.7 %, M1 15.4 %, CV10 14.7%, L 11.8 %, C 11.1 %, A 8.9 %, CV17 9.6 % y O 6.8 % de Al2O3r-. Finalmente, todos ellos fueron contrastados, además, mediante la calibración y validación del nuevo método analítico, con los valores de referencia obtenidos de esas mismas puzolanas, los cuales se les habían determinado mediante el método de Florentín, consistente en atacar, disolver y lixiviar también toda la fracción alumínica soluble de la puzolana (y además, aquella silícica y férrica que la constituyen a la par), pero, en especial, su contenido total de alúmina reactiva, mediante un ataque básico (con Ca(OH)2 en medio acuoso a temperatura del laboratorio, habiendo sido, además, su duración hasta 1 año), seguido de otro ácido (con HCl, d = 1.12), habiéndose obtenido esta vez los siguientes resultados de sus contenidos de Al2O3r- (%): M0 28.8 %, M1 16.7 %, CV10 9.7 %, L 11.2 %, C 12.2 %, A 13.0 %, CV17 10.6 % y O 9.5 %. Dicha validación realizada ha puesto de manifiesto, en términos generales, que el nuevo método analítico es más fidedigno que el de Florentín, por lo que resulta ser totalmente apropiado para obtener los resultados que se han pretendido, además de proporcionarlos en un espacio de tiempo relativamente corto (28 días a lo sumo) y a un coste económico razonable por no elevado (salvo error u omisión y libre de impuestos directos e indirectos, el coste económico estimado de la variante I estaría en torno a 800.00 - 900.00 €/puzolana -caso más probable-, y aproximadamente una tercera parte nada más, en el caso de que la edad máxima del ensayo acelerado sea 7 días nada más -caso menos probable-), y, por consiguiente, técnicamente aceptable, al cumplir, además, en todo el rango considerado de variabilidad posible de concentraciones o contenidos del analito buscado en la puzolana, con tales parámetros de validación como son: linealidad (los resultados obtenidos son directamente proporcionales a la señal-respuesta instrumental recibida), sensibilidad, precisión excelente, repetibilidad satisfactoria de los valores obtenidos de los contenidos de Al2O3r- de todas y cada una de las adiciones puzolánicas seleccionadas, confirmando, por ello, la universalidad de su uso. Finalmente, las ventajas del nuevo método analítico, respecto a los métodos ya existentes recopilados de la bibliografía (el método de Florentín, el método de López Ruiz -HF 40 % y HNO3 2N-, el método de Murat y Driouche para arcillas -HF 0.5M-, el método de Arjuan, Silbee y Roy para cenizas volantes -HF 1 %- y su modificación por Fernández-Jiménez y cols. -HF 1 %, 27Al NMR MAS y XRD (método de Rietveld)-, y el método de determinación de la relación SiO2r-/Al2O3r- para arcillas y cenizas volantes por Ruiz-Santaquiteria y cols. -HF 1 %, NaOH 8M y ICP-AES-) son, principalmente, estar exento de peligro alguno para la seguridad vital de las personas que lo tengan que manipular y poner en práctica, ser bastante apropiado para control de calidad además de para investigación, su considerable menor coste económico, su relativamente corto espacio de tiempo que se necesita para obtener la respuesta-resultado pretendida (28 días a lo sumo), así como su universalidad y selectividad, puesto que además, su aplicabilidad es para todo tipo de adiciones puzolánicas naturales o artificiales, como así lo demuestran los resultados obtenidos de los materiales puzolánicos naturales y artificiales seleccionados y analizados, en un rango de concentraciones del analito -contenido de alúmina reactiva, Al2O3r- (%)-, desde el 5 % hasta el 30 % en masa, rango éste que, por otra parte, comprende prácticamente TODAS las adiciones puzolanas naturales y artificiales existentes en el mercado transnacional y las aún por existir. Por consiguiente y de acuerdo con lo anterior, el nuevo método analítico, ya sea realizado mediante su variante I o la II, debido, - en primer lugar, a los fundamentados planteamientos relativos a su procedimiento experimental -modus operandi- el cual ha sido aplicado a una amplia gama de puzolanas naturales y artificiales, y - en segundo lugar, debido a la calidad de los resultados obtenidos con un grado de precisión y repetibilidad excelentes, ha demostrado poseer una gran utilidad científica -para investigación-, pero, sobre todo, técnica -para control de calidad de adiciones puzolánicas naturales y artificiales que se adicionan habitualmente al cemento Portland en fábrica y/o a sus hormigones y morteros en planta-, además de ser representativos los valores obtenidos mediante el mismo respecto a la más que probable durabilidad química que cada una de ellas puede llegarle a conferir al hormigón armado y en masa, mortero y pasta del que forme parte, así como también su cantidad adecuada de sustitución parcial de cada cemento Portland para conseguirla, acorde con sus propias prestaciones químico-físicas o físico-químicas que puede llegarle a conferir, según sea su carácter químico (alumínico, alumínico-silícico, silícico-alumínico, silícico-férrico-alumínico o silícico), forma y tamaño medio de su partícula. Por último, el nuevo método analítico ha demostrado cumplir además, con todos los requisitos de obligado cumplimiento que establece la norma ISO/IEC 17025 sobre la calidad y fiabilidad de nuevos métodos o procedimientos analíticos no normalizados todavía, para poder ser propuesto en un futuro próximo, ante la Comisión de AENOR correspondiente, con objeto de comenzar un expediente para su certificación y normalización. ________________________________________________________________________________ Both the subject of this research, its objectives, fundamentals, materials selected and experimental part to achieve, have all been promoted by the situation and the state of reinforced concrete constructions that began performing in Spain from 1975, with concrete and mortars cement containing fly ash up to 20 %, in principle, and later, up to 35 % to its content of Portland cement, which and against expected, demanded a need to improve their performance, especially due to an unexpectedly low level of durability of some works built with them, despite, however, its apparent benefits of all kinds are ascribed to them. Ultimately, the natural or artificial pozzolanic additions, such as fly ash specially, referred to above, have been used with regulation to manufacture cements and/or its derivatives, concretes, mortars, cement pastes, in the most industrialized countries. More than three decades ago, under the same conditions and identical construction mainly uses concretes and mortars plain Portland cement, besides coming, given that use of these waste materials, industrial by-products today for environmental and/or economic issues. For this reason, this Doctoral Thesis aims to answer properly and schematically (in the form of flow chart), the criteria to be taken into account when selection and characterization standardized for these active mineral additions, especially prior to choosing and use in the so-called Portland Cement (PC) pozzolan, or with fly ash or with calcined shales or with calcined pozzolans or with silica fume or PC mixed or pozzolanic cement or compound cement, for that such pathology problems will not occur when reinforced concretes nor mass concretes are used for building. Hence the very particular and special focus about this research, having confined only to the natural or artificial pozzolans, considering them all, regardless of their origin, approach as materials consisting of small crystalline fractions randomly distributed in a largely vitreous and/or amorphous matrix, which confers their reactivity with calcium hydroxide in the form of slaked lime or portlandite from PC. In turn, these vitreous and/or amorphous fractions consist in its greater part, by reactive silica, SiO2r-, reactive alumina, Al2O3r-, and reactive iron oxide, Fe2O3r-, which also receive, in conjunction, the specific name of "hydraulic factors" of the pozzolan. Usually, they all differs in quantity of their respective total contents of the SiO2 (%), Al2O3 (%) and Fe2O3 (%) determined the pozzolan by alkaline fusion by means of standard procedures. Of the three above-mentioned oxides reagents and from the technical point of view, the most important for its increased presence in every one of the natural or artificial pozzolans and also significance in the chemical durability that can get them to give the concrete mortar or cement paste which contain them, are SiO2r- and Al2O3r-. From the first two, the SiO2r- reacts with portlandite only, released in the hydration of the PC (and with Ca(OH)2), to form C-S-H gels, transformed in tobermorites or jennites later on, similar to C-S-H gels also originating from the alite and belite hydration in the CP. From the standardization criteria point of view, the presence of this silicic fraction in pozzolans is regulated at first, by the European standard EN 197-1, in general, also being referred by the EN 450-1:2006, in the context of the fly ash in addition to the concrete, as a "fine powder of spherical particles mainly crystalline form. It is from the combustion of pulverized coal, which have pozzolanic properties and is mainly composed of SiO2 and Al2O3". In addition and according to the EN 197-1 standard, the reactive silica content (which can be defined and determined in accordance with EN 197-1 standard or its UNE 80225 standard) must not be lower than 25 % of its mass. Meanwhile, considerable experimental studies by Talero and Talero et al, have shown that if the pozzolan is not adequate in quality nor quantity, the durability of cement that is part and, therefore, of its derivative products, concretes, mortars and pastes cement, can become abnormally low because its reactive alumina, Al2O3r- (%), content or tetra- or penta-coordinated alumina which involves itself in a very direct and totally mixed and conflicting results even at all aggressive chemical attack natural to produce to the concrete, mortar and paste with inadequate natural and/or artificial pozzolans, such as those from the selenitous land and waters (sulfates, strikes if the material itself concrete, mortar and paste that contain them, for rapid forming ettringite form, ett-rf, which can even cause rapid gypsum attack to said concrete). In contrast, sea spray and de-icing salts (chlorides strikes the reinforced steel concrete causing them electrochemical corrosion by "bite", although in that other chemical attack, such Al2O3r- causes rapid Friedel's salt formation, Fs-rf, too, to cause protector effect of the electrochemical corrosion of reinforcements for these chlorides), seawater (mutual aggressive action of chlorides and sulfates), carbonation, alkali-silica reaction, and, in addition, to influence the release of hydration heat, as well as in the rheological behavior of the pastes, etc., decreasing/shorting them thus their expected durability and sometimes even very seriously. But the most ironic thing is, that despite its referral totally opposed, compared to sulfates and chlorides, behaviour, - far not available is, a chemical analysis method for its quantitative determination, which is also relatively simple in operation, accurate, precise, rapid response, from a technical point of view for building (no more than 28 days), repeatable, reproducible, not involving danger to life safety of the people who need to manipulate and implement, economic, and also serve for both scientific research and technical side, and - has yet to be any chemical specification that sets maximum levels for Al2O3r-(%) in the natural or artificial pozzolan to be added to the cement and/or to the concrete that will be subject to a particularly aggressive chemical attack from those mentioned above, and in particular, to sulphates, chlorides or sea water. And for the sake of and justification of this need, it has to be said that the current Spanish Instruction for Structural Concrete EHE-08 does not provide any specification on "hydraulic factors" in general, nor the content of Al2O3r- (%) in fly ash, very particular, as Article 30º "Additions", or any other Article, although does provide, however, other chemical specifications lacking the necessary meaning in terms of the message Chemical Durability mentioned, nor the Article 37º which and for greater sake, is paradoxically entitled "Durability of the concrete and of their reinforcements". It has also not contemplated in the latest version just released from EN 197-1 standard entitled "Cement Part 1: Composition, specifications and conformity criteria for common cements". Nor, in EN 450-1:2006 entitled "Fly ash for concrete Part 1: Definitions, specifications and conformity criteria", nor by current Spanish Instruction for Cement Reception, RC-08, nor the ASTM C618-03 Standard either. The only chemical specification that both Standards, European and American, refer is one that says that the sum of the total contents of SiO2 (%), Al2O3 (%) and Fe2O3 (%) of natural and artificial pozzolan, must be greater than or equal to 70 % , defining pozzolans thus: "siliceous or aluminous and siliceous materials, which themselves do not have any cementitious value but finely divided and in the presence of moisture it reacts with calcium hydroxide at ordinary temperatures to form compounds possessing cementitious properties". Consequently and according to everything related before, the primary objective of this Doctoral Thesis has been: To design and start-up a new quantitative analytical method of technical utility (the maximum test duration is not more than 28 days), to determine the content of reactive alumina content, Al2O3r- (%), vitreous or amorphous alumina, of natural and artificial pozzolans. And once designed, validate at repeatability level and in accordance with appropriate statistical parameters with special emphasis on the acceptance criteria established by the American Association of Official Analytical Chemists (AOAC). And to achieve this, the innovation of this research has been based on the following general principles, namely: - All the alumina in any pozzolan, natural or artificial, that can be attacked, dissolved and leached by portlandite or calcium hydroxide, Ca(OH)2, in aqueous medium, is considered reactive alumina, Al2O3r-. - This aluminic fraction of natural or artificial pozzolan to analyze and study, has to be in such physical-chemical state that it can react in the presence of calcium hydroxide, sodium chloride and water status and to cause monochloro-aluminate hydrated calcium, C3A·CaCl2·10H2O or Friedel's salt. Moreover, such physical-chemical state of the pozzolan must be consistent with the definition of reactive alumina adopted in this research because of the actual performance of chemical durability that can reach confer on blended cements and their derivatives, concretes, mortars and pastes that are manufactured with the same. - The originality of this new analytical method, compared to the other methods for determining reactive alumina existing (collected in abbreviated form in the state of the art of this report), is the quantification of such aluminic fraction of natural or artificial pozzolans is performed by stoichiometric calculation based on this, in the chemical reaction of Friedel's salt formation after 28 days of the analysis of saline-basic hydration accelerated natural or artificial pozzolan also performed in this research, and the quantitative determination of the Friedel's salt has been performed by two instrumental analytical techniques known as thermogravimetric analysis (variant I), and Rietveld method with X-ray powder diffraction (variant II). - The chemical reaction of Friedel's salt formation after 28 days of accelerated saline-basic hydration of the selected natural and artificial pozzolan, was optimized to ensure that the single chemical compound of aluminium and chlorine formed was Friedel's salt only (dosing for this purpose in amount suitable chemical reagents: Ca(OH)2, NaCl and distilled water), and, on the other hand, maintaining the appropriate compromise between the highest yield from the chemical reaction (attack, dissolution and leaching in 28 days, all reactive alumina of pozzolan) and to accelerate the etching media, which were 40°C temperature, constant stirring and sealing the reactor. - The applicability and selectivity of the new analytical method, the subject of this Doctoral Thesis, was studied with a series of Spanish natural and artificial pozzolans, siliceous or siliceous and aluminous in nature, which were as follows: M0 (metakaolin 0), M1 (M0 with 50 % quartz), L and C (natural pozzolans of the Canary Islands), CV10 (fly ash 10), CV17 (fly ash 17), A (natural pozzolan of Almagro), O (natural pozzolan of Olot), and HS (silica fume). - All mineral admixtures were selected satisfied the physical and chemical requirements proposed to consider them as pozzolan, which was mandatory, so its Al2O3r- (%) content can determine by the new analytical method. These conditions were as follows: adequate degree of fineness of grind or average particle size (according to EN 451-2 standard), have been analyzed chemically (according to EN 196-2 or ASTM C311 standards), in order to determine their total contents of SiO2 (%), Al2O3 (%) and Fe2O3 (%), mainly, having also determined its reactive silica content, SiO2r- (%) (UNE 80225 standard), and fulfilled with testing of pozzolanicity or Frattini test (according to EN 196-5 standard) at 28 days age at least. The last criteria was mandatory until 1988, for any natural and artificial pozzolan to a factory intended to introduce cements in the manufacturing process of a new Portland cement type CEM IV pozzolanic additions, and with this Doctoral Thesis has made is to be used once again mandatory. And the results obtained using the new analytical method, of the Al2O3r- (%) content for each selected pozzolan, were as follows: - by its variant I: M0 29.9 % , M1 16.9 % , CV10 11.4 % , L 12.3 % , C 12.6 % , A 8.0 % , CV17 9.5 % and O 6.3 % of Al2O3r-, and - by its variant II: M0 30.7 % , M1 15.4 % , CV10 14.7% % , L 11.8 % , C 11.1 % , A 8.9 % , CV17 9.6 % and O 6.8 % of Al2O3r-. Finally, they would all be further contrasted by the calibration and validation of new analytical method, with reference values obtained from these same natural and artificial pozzolans, which had been given by the method of Florentin, consisting of attack, dissolve and leached with a basic attack (with Ca(OH)2 in aqueous medium and laboratory temperature, having also been its duration up to 1 year), followed by another acid attack (HCl, d = 1.12), all soluble aluminic fraction of pozzolan, and in particular their total content of reactive alumina, Al2O3r-(%), was this time as follows: M0 28.8 %, M1 16.7 %, CV10 9.7 %, L 11.2 %, C 12.2 %, A 13.0 %, CV17 10.6 % and O 9.5 % (and their siliceous and iron contents that are at par). This validation has shown on the new analytical method is more reliable than Florentin method, so it turns out to be entirely appropriate to get the results that have been tried by the same, besides providing them a relatively short space of time (28 days at most) and reasonably no high economic cost (unless mistake -free direct and indirect taxes, such economic cost would be between 800.00 - 900.00 €/pozzolan (most likely case), and about an one-third part around, in the event that the maximum age of the accelerated test is 7 days only (less likely case). So it is technically acceptable, to consider the range of possible variability of concentrations or contents pozzolan analyte with validation parameters such as: linearity (the results obtained are directly proportional to the instrumental response signal received), excellent sensitivity and accuracy, satisfactory repeatability values from the contents of each and Al2O3r- (%) each selected pozzolan, confirming therefore universal use. Finally, the advantages of the new analytical method over existing methods compiled from literature (Florentin method , the Lopez Ruiz method -HF and HNO3 40 % 2N-, the method of Murat and Driouche for clays -0.5M HF-, the method of Arjuan, Roy and Silbee for fly ash -HF 1 %- and its modification by Fernández-Jiménez et al -HF 1 %, 27Al MAS NMR and XRD (Rietveld method)-, and the method for determining the SiO2r-/Al2O3r- clay and fly ash ratio of Santaquiteria Ruiz et al -HF 1 %, NaOH 8M and ICP-AES-) are primarily and relatively short time get the result intended answer (28 days at most), its considerable lower cost, free from danger to the life safety of the people who need to manipulate and put in practice as well as its universality and selectivity, since it is applicable for all types of natural or artificial pozzolans, as it has been shown by the results of selected natural and artificial pozzolanic materials and analyzed in a range of analyte concentrations -reactive alumina, Al2O3r- (%) content- from 5 % to 30 % by mass, this range, on the other hand, includes virtually ALL existing transnational market in natural and artificial pozzolans and still exist. Therefore and in accordance with the above, the new analytical method is already performed by the variant I or II, because, - firstly, grounded to experimental approaches concerning its experimental procedure -"modus operandi"- which has been applied to a wide range of natural and artificial pozzolans, and - secondly, due to the quality of the results obtained with a great degree of accuracy and repeatability, it has been shown to possess significant scientific value in the research, but especially technical value -for quality control of natural and artificial pozzolans commonly added to Portland cement factory and/or directly to their concrete and mortar in plant-, and also be representative enough of the values obtained by the same probable chemical durability that each of them can reach out to give the concrete mortar and paste to which it belongs, as well as proper amount of partial replacement of Portland cement. To get in line with their own chemical-physical or physical-chemical features which can come to confer, as its chemical character (aluminic, silicic-aluminic, aluminic-silicic, aluminic-ferric-silicic or ferric-silicic), form and medium size of its particle is. Finally, the new analytical method has proven to meet all mandatory requirements established by ISO/IEC 17025 on the quality and reliability of new methods or analytical procedures are not standardized yet, in order to be considered appropriate this new analytical method, in this Doctoral Thesis it is to be proposed in the near future, before the corresponding AENOR (Spanish Association for Standardization and Certification) Commission, to start a procedure for certification and standardization.

Role of p38 mitogen-activated protein kinase in HIV type 1 production in vitro

The proinflammatory cytokines interleukin (IL)-1 and tumor necrosis factor (TNF) promote HIV type 1 viral replication in vitro. In the present studies, HIV production was increased in the macrophagic U1 cell line expressing the HIV genome after exposure to IL-1β, osmotic stress, or surface adhesion, suggesting a confluence of signaling pathways for proinflammatory cytokines and cell stressors. The p38 mitogen-activated protein kinase (MAPK) mediates both cytokine and stress responses; thus the role of this kinase in HIV production was investigated. HIV production as measured by p24 antigen correlated with changes in the expression of a specific (non-alpha) isoform of p38 MAPK. In the presence of a specific p38 MAPK inhibitor (p38 inh), IL-1β-induced HIV production was suppressed by more than 90% and IL-1β-induced IL-8 production was suppressed completely, both with IC50 of 0.01 μM. p38 inhibition blocked cell-associated p24 antigen and secreted virus to a similar extent. The p38 inh also decreased constitutive HIV production in freshly infected peripheral blood mononuclear cells by up to 50% (P < 0.05). Interruption of p38 MAPK activity represents a viable target for inhibition of HIV.

Multiple Genes Encoding the Conserved CCAAT-Box Transcription Factor Complex Are Expressed in Arabidopsis

The CCAAT motif is found in the promoters of many eukaryotic genes. In yeast a single complex of three proteins, termed HAP2, HAP3, and HAP5, binds to this sequence, and in mammals the three components of the equivalent complex (called variously NF-Y, CBF, or CP1) are also represented by single genes. Here we report the presence of multiple genes for each of the components of the CCAAT-binding complex, HAP2,3,5, from Arabidopsis. Three independent Arabidopsis HAP subunit 2 (AtHAP2) cDNAs were cloned by functional complementation of a yeast hap2 mutant, and two independent forms each of AtHAP3 and AtHAP5 cDNAs were detected in the expressed sequence tag database. Additional homologs (two of AtHAP3 and one of AtHAP5) have been identified from available Arabidopsis genomic sequences. Northern-blot analysis indicated ubiquitous expression for each AtHAP2 and AtHAP5 cDNA in a range of tissues, whereas expression of each AtHAP3 cDNA was under developmental and/or environmental regulation. The unexpected presence of multiple forms of each HAP homolog in Arabidopsis, compared with the single genes in yeast and vertebrates, suggests that the HAP2,3,5 complex may play diverse roles in gene transcription in higher plants.

Subcutaneous vaccination with irradiated, cytokine-producing tumor cells stimulates CD8+ cell-mediated immunity against tumors located in the "immunologically privileged" central nervous system.

Vaccination with cytokine-producing tumor cells generates potent immune responses against tumors outside the central nervous system (CNS). The CNS, however, is a barrier to allograft and xenograft rejection, and established tumors within the CNS have failed to respond to other forms of systemic immunotherapy. To determine what barriers the "immunologically privileged" CNS would pose to cytokine-assisted tumor vaccines and what cytokines would be most efficacious against tumors within the CNS, we irradiated B16 murine melanoma cells producing murine interleukin 2 (IL-2), IL-3, IL-4, IL-6, gamma-interferon, or granulocyte-macrophage colony stimulating factor (GM-CSF) and used these cells as subcutaneous vaccines against tumors within the brain. Under conditions where untransfected B16 cells had no effect, cells producing IL-3, IL-6, or GM-CSF increased the survival of mice challenged with viable B16 cells in the brain. Vaccination with B16 cells producing IL-4 or gamma-interferon had no effect, and vaccination with B16 cells producing IL-2 decreased survival time. GM-CSF-producing vaccines were also able to increase survival in mice with pre-established tumors. The response elicited by GM-CSF-producing vaccines was found to be specific to tumor type and to be abrogated by depletion of CD8+ cells. Unlike the immunity generated against subcutaneous tumors by GM-CSF, however, the effector responses generated against tumors in the CNS were not dependent on CD4+ cells. These data suggest that cytokine-producing tumor cells are very potent stimulators of immunity against tumors within the CNS, but effector responses in the CNS may be different from those obtained against subcutaneous tumors.

Expression of corticotropin-releasing factor in inflamed tissue is required for intrinsic peripheral opioid analgesia.

Immune cell-derived opioid peptides can activate opioid receptors on peripheral sensory nerves to inhibit inflammatory pain. The intrinsic mechanisms triggering this neuroimmune interaction are unknown. This study investigates the involvement of endogenous corticotropin-releasing factor (CRF) and interleukin-1beta (IL-1). A specific stress paradigm, cold water swim (CWS), produces potent opioid receptor-specific antinociception in inflamed paws of rats. This effect is dose-dependently attenuated by intraplantar but not by intravenous alpha-helical CRF. IL-1 receptor antagonist is ineffective. Similarly, local injection of antiserum against CRF, but not to IL-1, dose-dependently reverses this effect. Intravenous anti-CRF is only inhibitory at 10(4)-fold higher concentrations and intravenous CRF does not produce analgesia. Pretreatment of inflamed paws with an 18-mer 3'-3'-end inverted CRF-antisense oligodeoxynucleotide abolishes CWS-induced antinociception. The same treatment significantly reduces the amount of CRF extracted from inflamed paws and the number of CRF-immunostained cells without affecting gross inflammatory signs. A mismatch oligodeoxynucleotide alters neither the CWS effect nor CRF immunoreactivity. These findings identify locally expressed CRF as the predominant agent to trigger opioid release within inflamed tissue. Endogenous IL-1, circulating CRF or antiinflammatory effects, are not involved. Thus, an intact immune system plays an essential role in pain control, which is important for the understanding of pain in immunosuppressed patients with cancer or AIDS.

GSP-1 genes are linked to the grain hardness locus (Ha) on wheat chromosome 5D.

An important determinant of wheat grain quality is the hardness of the grain. The trait is controlled by a major locus, Ha, on the short arm of chromosome 5D. Purified starch granules from soft-grained wheats have associated with them 15-kDa polypeptides called grain softness proteins (GSPs) or "friabilins." Genes that encode one family of closely related GSP polypeptides - GSP-1 genes - were mapped using chromosome substitution lines to the group 5 chromosomes. An F2 population segregating for hard and soft alleles at the Ha locus on a near-isogenic background was used in a single-seed study of the inheritance of grain softness and of GSP-1 alleles. Grain softness versus grain hardness was inherited in a 3:1 ratio. The presence versus absence of GSPs in single seed starch preparations was coinherited with grain softness versus hardness. This showed that grain softness is primarily determined by seed, and not by maternal, genotype. In addition, no recombination was detected in 44 F2 plants between GSP-1 restriction fragment length polymorphisms and Ha alleles. Differences between hard and soft wheat grains in membrane structure and lipid extractability have been described and, of the three characterized proteins that are part of the mixture of 15-kDa polypeptides called GSPs, at least two, and probably all three, are proteins that bind polar lipids. The data are interpreted to suggest that the Ha locus may encode one or more members of a large family of lipid-binding proteins.

A synthetic inhibitor of the mitogen-activated protein kinase cascade.

Treatment of cells with a variety of growth factors triggers a phosphorylation cascade that leads to activation of mitogen-activated protein kinases (MAPKs, also called extracellular signal-regulated kinases, or ERKs). We have identified a synthetic inhibitor of the MAPK pathway. PD 098059 [2-(2'-amino-3'-methoxyphenyl)-oxanaphthalen-4-one] selectively inhibited the MAPK-activating enzyme, MAPK/ERK kinase (MEK), without significant inhibitory activity of MAPK itself. Inhibition of MEK by PD 098059 prevented activation of MAPK and subsequent phosphorylation of MAPK substrates both in vitro and in intact cells. Moreover, PD 098059 inhibited stimulation of cell growth and reversed the phenotype of ras-transformed BALB 3T3 mouse fibroblasts and rat kidney cells. These results indicate that the MAPK pathway is essential for growth and maintenance of the ras-transformed phenotype. Further, PD 098059 is an invaluable tool that will help elucidate the role of the MAPK cascade in a variety of biological settings.

Kitāb al-Tanbīh wa-al-tadhkīr fī-mā ilayhi al-marjiʹ wa-al-maṣīr / taʼlīf ʻAbd al-Wahhāb al-Shaʻrānī : manuscript, undated

بسم الله الرحمن الرحيم الفصل الاول الحمد لله الذي نثر على وجه عروس الارض ... :Incipit

Tuḥfat al-ʻIrāqayn : manuscript, 1604

Title supplied by cataloger.

(Table A1) Uranium and Thorium determination from IODP Site 310-M0007B

The Integrated Ocean Drilling Program (IODP) Expedition 310 recovered drill cores from the drowned reefs around the island of Tahiti (17°40'S, 149°30'W), many of which contained samples of massive corals from the genus Porites. Herein we report on one well-preserved fossil coral sample: a 13.6 cm long Porites sp. dated by uranium series techniques at 9523 ± 33 years. Monthly delta18O and Sr/Ca determinations reveal nine clear and robust annual cycles. Coral delta18O and Sr/Ca determinations estimate a mean temperature of ca. 24.3°C (ca. 3.2°C colder than modern) for Tahiti at 9.5 ka; however, this estimate is viewed with caution since potential sources of cold bias in coral geochemistry remain to be resolved. The interannual variability in coral delta18O is similar between the 9.5 ka coral record and a modern record from nearby Moorea. The seasonal cycle in coral Sr/Ca is approximately the same or greater in the 9.5 ka coral record than in modern coral records from Tahiti. Paired analysis of coral delta18O and Sr/Ca indicates cold/wet (warm/dry) interannual anomalies, opposite from those observed in the modern instrumental record.

The history of the lives of Abeillard and Heloisa : comprising a period of eighty-four years from 1079 to 1163 : with their genuine letters from the collection of Amboise /

The letters (v.2, p. [233]-368) are in English and Latin.

Epistola Pauli Angeli ad Saracenos : cum libello co[n]tra Alcoranu[m] : pro p[er]uida preuiaq[ue] dispositione conuersionis infideliu[m] ....

Mode of access: Internet.

Werke.

Greek and German.

The Lady's monthly museum, or Polite repository of amusement and instruction: being an assemblage of whatever can tend to please the fancy, interest the mind, or exalt the character of the British fair.

Mode of access: Internet.