El problema de diagenesis y metamorfismo en el grupo de Bokkeveld de Sud África y las Sierras Australes de la provincia de Buenos Aires

En base a la estratigrafía y tectónica del Grupo de Bokkeveld, suministrado por S0EK0R de Sud Africa, se han ubicado las muestras utilizadas en el presente trabajo. Las muestras de las Sierras Australes, fueron tomadas de los Grupos de Ventana y Pillahuincó, de uno de los perfiles realizados por T. Suero (1967). El estudio Petrográfico de las Rocas de Bokkeveld y S. de la Ventana, muestran una gran similitud y homogeneidad entre ellas. Deben considerarse como rocas Sedimentarias, por la presencia de montmorillonita y de minerales interestratificados de arcillas. Las plagioclasas presentan una composición demasiado básica para incluir las rocas dentro del metamorfismo de bajo rango. Lá presencia de epidoto en las formaciones Bonete y Tunas se considera de origen hidrotermal.The samples used in this study have been selected taking into account the stratigraphy and tectonic of the Bokkeveld Group, submitted by SOEKOR Co. The rocks from the Southern Hills, Buenos Aires, were obtained from Ventana and Pilla- huincd Groups, on the basis of the profile from T. Suero. The petrographic studies of the rocks of Bokkeveld and Ventana Hills, show that there is homogenity and similitude in them. They should be considered as sedimentary rocks, sincje there is montmorillonite and interstratified clay minerals in them. The plagioclases are too basic to include this rocks in the very low range of metamorphism. Epidote, in Bonete and Tunas Formations, should be considered of hydrothermal and not of metamorphic origin

SCADA and related technologies

Presented at SCADA and related technologies for irrigation district modernization: a USCID water management conference on October 26-29, 2005 in Vancouver, Washington.Includes bibliographical references.This paper presents an application of a SCADAPack Remote Terminal Unit to regulate the level in an irrigation canal prototype. The designed upstream level regulator consists of two Linear Quadratic Gaussian (LQG) controllers switched with fuzzy logic. The control scheme developed was implemented on "C" at a SCADAPack installed in a Mexican laboratory canal. The adequated closed-loop performance obtained suggests the evaluation of the developed scheme on field applications

Taphonomic considerations on pinworm prevalence in three Ancestral Puebloan latrines

For archaeological studies it is always necessary to consider taphonomic factors that could have influenced in ancient material preservation. Parasite eggs are usually highly degraded in ancient sites dated from all periods of time and taphonomic factors are mentioned to explain absence and low quantity of eggs found. In this study, we compare parasite egg recovery of three Great House latrines: two from Aztec Ruins (Rooms 219 and 225) and one from Salmon Ruins. We compared through statistical regression the recovery of eggs with the abundance of two classes of decomposers: mites and nematodes. These microorganisms have relation with nematode larvae and parasites remains degradation, respectively, mostly in moist environments. Pinworm was the only parasite found in the sites studied. Prevalences were 32.8% at Salmon Ruins, 72.7% at Aztec Ruins Room 225 and 14.3% at Room 219. Egg preservation was considered good at Salmon Ruins and Aztec Ruins Room 225. At Room 219, the eggs were badly preserved and there was a significant statistical correlation with mites (multiple r (18) =0.64/P=0.002). This correlation could indicate that mites could be involved in preservation, and consequently that pinworm prevalence in this latrine is underestimated. Abiotic factors such as humidity could have possibly favored the biological relation. Considering the extreme egg degradation at Room 219, it is not possible to strictly compare parasite data with other Ancestral Pueblo sites, even with Room 225, located at the same site. Room 225 prevalence is the highest found in Ancestral Pueblo sites until now. Taphonomic analysis shows that decomposers operated at different levels of severity, despite the latrines\u27 close location

General properties of overlap probability distributions in disordered spin systems. Toward Parisi ultrametricity

For a very general class of probability distributions in disordered Ising spin systems, in the thermodynamical limit, we prove the following property for overlaps among real replicas. Consider the overlaps among s replicas. Add one replica s+1. Then, the overlap q(a,s+1) between one of the first s replicas, let us say a, and the added s+1 is either independent of the former ones, or it is identical to one of the overlaps q(a,b), with b running among the first s replicas, excluding a. Each of these cases has equal probability 1/s.Comment: LaTeX2e, 11 pages. Submitted to Journal of Physics A: Mathematical and General. Also available at http://rerumnatura.zool.su.se/stefano/ms/ghigu.p

Puzolanas artificiales obtenidas por tratamiento térmico de arcillas de la provincia de Buenos Aires (1ª parte)

Considerando la necesidad creciente de utilizar cementos puzolánicos en hormigones, el LEMIT ha iniciado un estudio para la obtención de puzolanas artificiales, por tratamiento térmico de arcillas provenientes de las formaciones sedimentarias de la Serie de La Tinta en el sistema de Tandilia y de las sierras Australes de la Provincia de Buenos Aires. Para le realización del trabajo, se efectuó un muestreo representativo de arcillas; se procedió luego a su activación a diversas temperaturas. Las muestras así tratadas, se estudiaron por difracción de Rayos X, lo que permitió seguir las transformaciones de la estructura de las arcillas. Finalmente se realizaron ensayos de acuerdo a normas vigentes para este tipo de materiales. Las muestras ensayadas cumplen con los requisitos exigidos en las mismas.The increasing need for the use of pozzolanic cements has induced the LEMIT to start a research for obtaining artificial pozzolans by thermic treatment of clays from sedimentary sequences of the La Tinta Series and Southern Hills of Buenos Aires Province. After a representative sampling, clays were activated at different temperatures and then studied bv X-Ray diffraction to determine transformations of clay structures. Tests were also carried out in accordance with prevailing norms. The results obtained are highly satisfactory, as most treated samples fulfill the specifications of the norms

Comparison of the Spherical Averaged Pseudopotential Model with the Stabilized Jellium Model

We compare Kohn-Sham results (density, cohesive energy, size and effect of charging) of the Spherical Averaged Pseudopotential Model with the Stabilized Jellium Model for clusters of sodium and aluminum with less than 20 atoms. We find that the Stabilized Jellium Model, although conceptually and practically more simple, gives better results for the cohesive energy and the elastic stiffness. We use the Local Density Approximation as well as the Generalized Gradient Approximation to the exchange and correlation energies.Comment: 13 pages, latex, 8 figures, compressed postscript version available at http://www.fis.uc.pt/~vieir

Numerical Simulations of the 4D Edwards-Anderson Spin Glass with Binary Couplings

We present numerical results that allow a precise determination of the transition point and of the critical exponents of the 4D Edwards-Anderson Spin Glass with binary quenched random couplings. We show that the low T phase undergoes Replica Symmetry Breaking. We obtain results on large lattices, up to a volume $V=10^4$: we use finite size scaling to show the relevance of our results in the infinite volume limit.Comment: 18 pages + 17 figures, revised bibliography and minor typos. Added Journal Re

Estudio mineralógico de algunas calcedonias argentinas

El trabajo se realizó teniendo en cuenta la reacción de este mineral con el cemento portland, la cuál produce efectos perjudiciales en los hormigones. Se comprobó que en ciertos casos la reacción no se produce. Se investigan las causas de tal comportamiento. El material utilizado para el estudio proviene de los ríos Uruguay y Paraná, ya que son las principales fuentes de abastecimiento de agregados del Gran Buenos Aires. Las "calcedonias" estudiadas están compuestas por un agregado fino de cuarzo, calcedonia y ópalo. La proporción relativa de dichos minerales condiciona la reactividad de los mismos.This paper deals with the reaction between chalcedony and Portland cement. This reaction damages the structure of the reinforced concrete, when aggregates of this kind are used for that purpose. In certain cases the concerned reaction do not take place. For that reason a detailed study was carried out to determine the behavior of the materials. The aggregates used for this, study come from Paraná and Uruguay rivers; the sediments of this area supply enough material from the Gran Buenos Aires market. The so call "chalcedony" studies are mainly composed of fine quartz, chalcedony and opal. The relative amounts of these minerals are thought to affect the behavior of the aggregates when they are mixed with portland cement

Composición mineralógica de las arcillas de la serie de La Tinta, Prov. de Buenos Aires

This paper deals with the study of clay minerals from "La Tinta" series, which extends from Blanca Grande -in the middle of the Province of Buenos Aires- to Mar del Plata, in the Atlantic coast (300 km). The results obtained have shown the history of sedimentary deposition. At the same time, three zones of economic importance are defined: a caolinitic zone was found in the central part of the studied area; a second illitic-caolinitic zone surrounds the first area; and, at last, a illitic zone is located in the N.W, part of the area.En la provincia de Buenos Aires, a lo largo del cordón de Tandilia, se encuentran depositadas directamente sobre el basamento, un conjunto de rocas sedimentarias, compuestas por ortocuarcitas con intercalaciones de arcillas, a las cuales se ha dado la denominación de serie de "La Tinta". Se extienden desde las proximidades de Blanca Grande, en el centro de la Provincia, hasta Mar del Plata (300 km) El estudio mineralógico de las arcillas de esta formación ha permitido reconstruir la historia de su depositación y determinar tres zonas de valor económico: una zona caolinítica, en la parte central del cordón; una zona illito-caolinítica, rodeando a la primera, y una zona illítica en el extremo NW

Simulation of 3d Ising spin glass model using three replicas: study of Binder cumulants

We have carried out numerical simulations of the three-dimensional Ising spin glass model with first neighbour Gaussian couplings using three replicas for each sample of couplings. We have paid special attention to the measure of two types of Binder cumulant that can be constructed from the three possible overlaps between the replicas. We obtain new information about the possible phase transition and perform an initial analysis of the ultrametricity issue.Comment: 14 pages and 7 figures, available at http://chimera.roma1.infn.it/index_papers_complex.htm