Resumen Durante la década de 1950 Karlheinz Stockhausen adhirió a los principios modernistas promovidos por la Escuela de Darmstadt que dieron lugar al desarrollo del serialismo integral. En su búsqueda de renovación del lenguaje musical, Stockhausen intentó aplicar esta técnica a la composición de obras electrónicas en el laboratorio de la WDR (Westdeutscher Rundfunk) en Colonia. Este artículo indaga, por medio del concepto de mediación técnica propuesto por Bruno Latour, cómo el intercambio de propiedades entre humanos y no humanos propiciado por el laboratorio fue modificando el proyecto serial. Como resultado de ese proceso, Stockhausen compuso una serie obras que no pudieron ser completamente prefiguradas a priori , hecho que demandó la creación de nuevas formas de escucha y notación musical. A partir de ello, buscaremos caracterizar la práctica compositiva de Stockhausen desde una perspectiva no modernista, haciendo hincapié en el carácter híbrido y relacional de los eventos musicales.

Abstract During the 1950s Karlheinz Stockhausen adhered to the modernist principles promoted by the Darmstadt School that led to the development of integral serialism. In his pursuit of renovation of the musical language, Stockhausen tried to apply this technique to the composition of electronic works at the WDR (Westdeutscher Rundfunk) laboratory in Cologne. This article inquires, through the concept of technical mediation proposed by Bruno Latour, how the exchange of properties between humans and non-humans inside the laboratory modified the serial project. As a result of this process, Stockhausen composed a series of works that couldn’t be completely prefigured a priori , a fact that led to the creation of new forms of listening and musical notation. From that, we will seek to characterize Stockhausen’s compositional practice from a non-modernist perspective, emphasizing the hybrid and relational character of musical events.

ABSTRACT. The goat's milk is an excellent choice to replace cow’s milk for children and adults, who are allergic to cow’s milk. Both the proteins and the fat portion of goat’s milk are absorbed by the body faster than cow's milk. Visually it is not possible to differentiate cow’s milk from goat’s milk, which can be differentiated through odor and taste which generates some concern to consumers. The objective of this study were to evaluate the acceptability of goat’s milk, compared to cow’s milk by children and young adults between 06 and 21 years old, in public network of schools Bambuí-MG, living in different socioeconomic levels, in order to verify if there is difference, in acceptance, between these two types of milk and study if the age and socioeconomic status could influence the results. Samples were prepared with chocolate powder and subjected to sensory evaluation by a group of 330 students, who are milk consumers. The samples were evaluated for preference through the hedonic scale of 5 points, asking about the score of the consumers and the preference of each type of milk. The test was conducted in two public schools. the data were submitted to ANOVA and Tukey test for comparison of means. Although goat's milk has some compositional characteristics and different physicochemical properties of cow's milk, there was no difference between them, due to acceptability between students of the public high school and elementary school network. The mixture 50% goat milk + 50% cow's milk generated greater rejection of the sampled population, a fact justified by the formation of small clots when mixing the different types of milks. Conventional cow's milk can be replaced by goat's milk in school meals, regardless of the age group and socioeconomic status of students.

Abstract In reducing the grid orientation effect for the numerical solution of partial differential equations, interpolation functions play an important role when the advective transport of the governing equations is considered. This is due to the fact that, in general, the unknowns are evaluated in the vertices of the elements and such properties must be extrapolated to inner parts of the elements. First-order schemes, such as upwind, are the easiest methods to use for performing the extrapolation of the properties. However, such methods introduce a large amount of numerical diffusion in the solution. A few higher-order interpolation schemes, on the other hand, are capable of providing solutions free of numerical diffusion, increasing the accuracy of the method and reducing the computational efforts required. In this work, we investigate the TVD interpolation scheme for three-dimensional unstructured grids in conjunction with Element-based Finite Volume Method (EbFVM) using four types of elements: hexahedron, tetrahedron, prism and pyramid.

Lepus flavigularis Wagner 1844 (Tehuantepec jackrabbit), a species endemic to southern Oaxaca in Mexico, and is currently considered as the jackrabbit in greatest danger of extinction worldwide. In the locality of Santa María del Mar in Oaxaca, it inhabits open pastures, sharing habitat with domestic cattle (Bos taurus). We hypothesize that L. flavigularis prefers to establish its feeding and resting sites in pastures where cattle are present. Understanding interspecific relationships is of great importance to the establishment of appropriate management plans. We record radio-tagged and no radio-tagged jackrabbits that established their resting and feeding sites on pastures with presence and absence of cattle and a compositional analysis of habitat preference was conducted. This paper reports for the first time the preference of L. flavigularis to establish feeding (ʎ = 0.8010, P = 0.0020) and resting sites (ʎ = 0.6605, P = 0.016) in the pasture with the presence of cattle. Selection of these sites could be attributed to the fact that the presence of cattle can function as an alarm system against possible predators, while the cattle grazing could itself promote palatable species of Poaceae that form part of the diet of this leporid. This information is key to the establishment of future management plans for both species and their ecosystem. A long-term study is required in order to determine the feasibility of cattle and jackrabbit cohabitation. We propose that an efficient rotational grazing program, could contribute to the conservation of this jackrabbit population.

Lepus flavigularis Wagner 1844 (Liebre de Tehuantepec), es una especie endémica del sur de Oaxaca, México. Actualmente considerada como la liebre en mayor peligro de extinción en todo el mundo. En Santa María del Mar, en Oaxaca, la liebre habita en pastizales abiertos, compartiendo su hábitat con el ganado doméstico (Bos taurus); nuestra hipótesis es que L. flavigularis prefiere establecer sus sitios de alimentación y de descanso en potreros donde el ganado está presente. Se registró el número de liebres radio-marcadas y sin marcar que establecieron sus sitios de alimentación y de descanso en potreros con presencia y ausencia de ganado bovino y se llevó a cabo un análisis composicional de la preferencia de hábitat. L. flavigularis prefiere establecer sus sitios de alimentación (ʎ = 0.8010, P = 0.0020) y sitios de descanso (ʎ = 0,6605, P = 0,016) en potreros con presencia de ganado. La selección de estos sitios se puede atribuir al hecho de que la presencia de ganado puede funcionar como un sistema de alarma contra posibles depredadores, mientras que el pastoreo del ganado podría en sí promover especies palatables de Poaceae que forman parte de la dieta local de este leporido. Esta información es clave para la creación de planes de manejo para ambas especies y su ecosistema. Se requiere un estudio a largo plazo para determinar la viabilidad de la cohabitación de la liebre y el ganado. Proponemos que un programa de rotación de ganado eficiente podría contribuir a la conservación de esta población de liebres.

BACKGROUND: Current study has been designed to evaluate the chemical composition of essential and fixed oils from stem and leaves of Perovskia abrotanoides and antioxidant and antimicrobial activities of these oils. RESULTS: GC-MS analysis of essential oil identified 19 compounds with (E)-9-dodecenal being the major component in stem and hexadecanoic acid in leaves. In contrast, GC-MS analysis of fixed oil showed 40 constituents with α-amyrin the major component in stem and α-copaene in leaves. The antioxidant activity showed the highest value of 76.7% in essential oil from leaves in comparison with fixed oil from stem (45.9%) through inhibition of peroxidation in linoleic acid system. The antimicrobial assay tested on different microorganisms (e.g. E. coli, S. aureus, B. cereus, Nitrospira, S. epidermis, A. niger, A. flavus and C. albicans) showed the higher inhibition zone at essential oil from leaves (15.2 mm on B. cereus) as compared to fixed oil from stem (8.34 mm onS. aureus) and leaves (11.2 mm on S. aureus). CONCLUSIONS: The present study revealed the fact that essential oil analyzed from Perovskia abrotanoides stem and leaves could be a promising source of natural products with potential antioxidant and antimicrobial activities, as compared to fixed oil.

Un tema que ha recibido escaso tratamiento en los estudios dedicados a la única obra de Le Corbusier construida en Latinoamérica, la casa Curutchet en La Plata, Argentina -1948-1953-, es el papel del árbol contenido en aquella. Este ensayo pretende mostrar que el manejo dado por Le Corbusier al tema no es accidental y que la relación entre el árbol, el proyecto y la obra cuenta con antecedentes en algunos trabajos de dicho arquitecto que se remontan hasta la década de 1920. Para evidenciarlo se recurre al análisis compositivo de la obra y del proyecto, a la lectura del tratamiento dado al tema en las investigaciones precedentes y a la revisión de diversas publicaciones sobre la obra en mención.

An issue that has received little treatment in the studies devoted to the only built work of Le Corbusier built in Latin America, maison Curutchet in La Plata, Argentina (1948-1953), is the role of the tree contained in that building. This essay aims to show that the management given by Le Corbusier to that issue is not accidental and that the relationship between the tree, the project and the built work has precedents in some works of this architect that date back to the 1920s. To demonstrate this fact it appeals to the compositional analysis of the project and the work, reading of the treatment of the topic in the previous investigations and the review of several publications on the mentioned house.

Um tema que tem recebido pouco tratamento nos estudos devotados ao único trabalho de Le Corbusier construído na América Latina, Casa Curutchet em La Plata, Argentina (1948-1953), é o papel da árvore contido nesse edifício. Este ensaio aponta mostrar que o manejo dado por Le Corbusier ao tema não é acidental e que o relacionamento entre a árvore, o projeto e o trabalho construído tem precedentes em alguns trabalhos deste arquiteto que datam dos anos 20. Para demonstrar este fato, se apela à análise compositiva do projeto e do trabalho, à leitura do tratamento dado ao tema nas pesquisas precedentes e à revisão de diversas publicações na casa mencionada.

This work describes the sandstone composition and provenance of the Peñas Coloradas Formation (Late Paleocene-Eocene?) located in the eastern sector of the Golfo de San Jorge basin, in the Chubut Province. Sandy sections in the unit from the profiles of the localities of Punta Peligro, Estancia La Rosa and Cañadón Hondo (Fig. 1) were analyzed petrographically, together with the diffractometric analysis of sandy and shale levels. The obtained data were used to define detritic modes, classify sandstones, differentiate petrofacies, and to infer the possible source of materials, in a warm and humid paleoclimatic context. In this part of the basin, the Peñas Coloradas Formation is composed of thin bedded conglomerates and sandstones of variable grain sizes (fine to coarse) with intercalated mudstone beds, which show evidences of pedogenesis. They are composed by grey to reddish epiclastic and volcaniclastics, with an average thickness of 80 m and representing a fluvial system of high to moderate energy (Fig. 2). The paleontological record is represented by fossil woods suggesting a warm and humid weather (Brea et al., 2004, Brea and Zucol, 2006 and Raigemborn et al., 2006) and mammals remnants of Late Paleocene age belonging to the Carodnia Fauna (Simpson, 1935). The Golfo San Jorge extensional basin was developed during the Jurassic and Cretaceous in a cratonic setting (Hechem and Strelkov, 2002). An extensive marine flooding took place from Maastrichtian to Early Paleocene, when the Salamanca Formation was deposited (Uliana and Legarreta, 1999). During the late Paleocene, the sedimentation evolved into a continental environment with the deposition of the Río Chico Group: Peñas Coloradas, Las Flores and Koluél Kaike formations was characterized by recurrence of lacustrine and fluvial conditions (Legarreta and Uliana, 1994). Contemporarily, a bimodal calcoalcaline volcanism developed in the Pilcaniyeu Belt (Rapela and Kay, 1988). Medium to coarse sandstones with matrix < 15 % was used in order to analyze provenance using the Gazzi-Dickinson method (Ingersoll et al., 1984; Zuffa, 1985). At least 300 clasts were counted per thin section. The recognized components are shown in Table 1. The average composition of the plagioclases isandesine-oligoclase and that of the K-feldspar is sanidine and microcline. Scarce volcanic lithics show dissolution (Figure 3c), developing a pseudomatrix (Dickinson, 1970). Clay and siliceous cements are abundant in many sandstone samples (Figure 3a and b). Less commonly, cementation is by iron oxide and calcite. Sandstones from Peñas Coloradas Formation are not intensely altered diagenetically. The classification diagram of Folk et al. (1970) shows an average Q21F43L36 (Fig. 4 and Table 2). In general, the analyzed samples present a predominance of plagioclase over K-feldspar and relationships of Lv/L close to 1. These sandstones show increased proportions of quartz and feldspar, and decreases in the relative proportion of lithics with time. Two petrofacies were differentiated (Table 2). The petrofacies I (Q<28 %) are composed of feldespathic litharenites and lithic feldarenites (Q14F44L42), with high P/K relations, the volcanic lithics are very abundant, and variety with microlithic texture predominates (Fig. 3b and d). This petrofacies characterizes the lower levels of the Peñas Coloradas Formation. The petrofacies II (Q>28 %) is integrated by lithic feldarenites (Q36F40L24), showing a P/K relation smaller than in petrofacies I with more abundant feldspar than in lithic fragments (Fig. 3a and c). This petrofacies is observed in the upper sections of the Peñas Coloradas Formation. The X-Ray analysis (Table 3) was carried out in air-dried, glycolated and heated samples (550º C) over samples coming from shales (< 4 ìm fraction). Semi-quantitative estimations of contents of identified species were performed by measuring peak areas on glycolate preparations (Biscaye, 1965). The smectite is the most abundant clay mineral, with kaolinite, illite and interestratificated I/S. Clinoptilolite and amorphous silica (opal-CT) are present in all of the samples. This mineralogical association can be attributed to the alteration of ash (De Ros et al., 1997) under warm and humid climatic conditions, with certain seasonality (Dingle and Lavelle, 2000). Cross-bedding and orient trunks of the Peñas Coloradas Formation indicate a uniform axial sedimentary transport from NW and W to SE and W (Fig. 2). The provenance area is viewed in the diagrams QtFL (Fig. 4b) and QmFLt (Fig. 4c) (Dickinson and Suczek, 1979; Dickinson et al., 1983). The samples show magmatic arc provenance from transitional arc (petrofacies I) to dissected arc (petrofacies II), and they show increased proportions of quartz and feldspar. This compositional change may record the arc dissection (Dickinson et al., 1983), being the volcanic cover removed gradually, leading to the partial exposition of the batholithic rocks of the arc, during the latest stages. The characteristics of the petrofacies I indicate a supply from the volcanic cover of the magmatic arc (Valloni and Mezzadri, 1984). The petrofacies II displacement is related to the gradual removal of the volcanic cover and the partial exposition of the arc granitic roots (Marsaglia and Ingersoll, 1992). The absence of plutonic origin fragments could also be due to the fact that these are separate in their individual mineral components in the analyzed sandy fraction. At the same time, the partial dissolution and alteration observed in the majority of potassic feldspar grains may be attributed to their low chemical stability under humid and warm weather (Suttner et al., 1981). It is interesting to note that the proportion of K-feldspar in the QmPK diagram (Fig. 4d) does not vary significantly, indicating that the arc provenance was not exhumed deeply enough to expose its plutonic root (Yan et al., 2006). Petrography data from Peñas Coloradas Formation suggest that they were derived mainly form a magmatic arc, where the sedimentary-volcanic cover was removed gradually, leading to the partial exposition of the batholithic rocks during the latest stages. Paleocurrent indicators demonstrate that this arc was located in the west and northwest of the study area. Given the compositional characteristics of the Peñas Coloradas Formation and the important volcanic activity during the Paleocene in Patagonia, it may be deduced that the main part of the materials have been provided from the Paleocene-Eocene arc of Pilcaniyeu Belt (Rapela and Kay, 1988), situated to the northwest of the study area (Raigemborn, 2005). The latter was developed between 60 and 43 Ma in northern Patagonian (40 to 43ºS), represented by a bimodal calcoalcaline volcanism composed of basaltic to rhyolitic rocks with ignimbritic facies (Rapela et al., 1984), under a warm and humid but seasonal climate (Aragón and Romero, 1984). A minor contribution from Paleocene Plateau Basalt and older volcanic units is not ruled out, such as the Middle Jurassic of the Marifil Complex and Cretaceous of the Divisadero Group or equivalents, which crop out towards the W and NW of the study area.

Se estudian preliminarmente, desde el punto de vista composicional, niveles arenosos de la Formación Peñas Coloradas (unidad inferior del Grupo Río Chico) del Paleoceno superior-Eoceno?, en los perfiles de Punta Peligro, Estancia La Rosa y Cañadón Hondo, ubicados en el sector oriental de la cuenca del Golfo San Jorge (provincia del Chubut). A partir de las modas detríticas obtenidas se clasificaron las muestras como litoarenitas feldespáticas y feldarenitas líticas, con una moda promedio Q21F43L36. Así mismo se diferenciaron dos petrofacies a fin de inferir el área de aporte de los materiales. La petrofacies I (litoarenitas feldespáticas > feldarenitas líticas), de escaso contenido de cuarzo e importantes tenores de líticos volcánicos, caracteriza a los niveles inferiores de la unidad y se corresponde con una procedencia de arco magmático transicional (Q14F44L42). Por su parte los niveles superiores de la unidad se corresponden con la petrofacies II (feldarenitas líticas), donde los valores de cuarzo son mayores al 28 % y las proporciones de feldespatos más altas que las de fragmentos líticos, indicando un área de aporte de arco magmático disectado (Q36F40L24). Conjuntamente los análisis por difractometría de rayos X revelan la importante participación de esmectita, material amorfo (ópalo) y zeolitas, interpretados como el producto de la meteorización química, actuante bajo climas cálidos y húmedos, sobre materiales volcánicos inestables. La tendencia general observada en sentido estratigráfico, revela un enriquecimiento en el contenido de cuarzo y feldespato y una disminución de fragmentos líticos. La misma sugiere un aumento en la disección del arco hacia los términos superiores de la unidad, con la erosión gradual de la cubierta volcánica y la posterior exhumación, al menos somera, de las raíces plutónicas del arco. Las características composicionales y los datos de paleocorrientes medidos, sugieren un aporte principal de los materiales desde el arco volcánico de la Patagonia que se mantuvo activo durante el Paleoceno-Eoceno (Cinturón de Pilcaniyeu), ubicado al noroeste de la zona de estudio y desarrollado en un contexto de clima cálido y húmedo con cierta estacionalidad.

The main objective of this work is to present an analysis and brief discussion of experimental ionic conductivity s data in the binary alkali tellurite system, including on 47 glasses that extend the ionic conductivity range by more than 14 orders of magnitude in a wide compositional range. A 'universal' behavior is obtained, using log sigma or log sigmaT vs. E A/kB T, where E A is the activation enthalpy for conduction, kB is the Boltzmann constant and T is the absolute temperature. This finding further indicates the importance of a scaling factor F recently proposed, that is correlated to the free volume of glass composition. For a given value of E A/kB T, the difference between large and small values of sigma is only one order of magnitude in 87% of these glass systems. The influence of alkali content and temperature was minor on the pre-exponential terms, considering both expressions log10sigma and log10sigmaT. Indeed, the pre-exponential term sigma0 varies around an average value of 50 omega-1cm-1 considering different compositions in this system. The fact that s lies on these single 'universal' curves for so many ion-conducting binary tellurite glasses means that sigma is governed mainly by E A. The composition dependence of the activation enthalpy is explained in the context of the Anderson-Stuart theory.

Petrographic sandstone analysis of 192 thin sections belonging to the lower section of the Paganzo Group (Upper Carboniferous; Lagares, Malanzán, Loma Larga, Guan-dacol, Tupe, Punta del Agua and Río del Peñón Formations) cropping out in the Paganzo Basin (Figs. 1, 2) was carried out in order to define cementation styles (Primmer et al., 1997) and reveal the main controlling factors, such as clast composition, matrix content, sedimentary environments and burial depth. The lower sedimentary section of the Paganzo Group (200 to 1200 m thick) was deposited in alluvial fan, glacial, deltaic, marine shoreline, marine shelf and fluvial environments (Fig. 3). Three distinct structural and paleogeographical areas of the basin were distinguished and sampled: a) the eastern area (Olta and Malanzán valleys, Las Mellizas mine and Bum Bum localities, Fig. 1), corresponds to the stable foreland sector of the basin, dominated by thick fluvial deposits whose provenance region is the plutonic-metamorphic basement of the Sierras Pampeanas located to the east, and only registering a short marine event from the west. This region records minimum relative burial depths. b) the central area (Cuesta de Huaco and Cerro Guandacol localities, Fig. 1), is composed of thick continental deposits from the Sierras Pampeanas that alternate with two main marine episodes flooding the basin from the west; the latter carries fragments of fine marine sedimentary and volcanic rocks from the Precordillera. Burial depths in this area are intermediate. c) the western area (Punta del Agua locality, Fig. 1), transitional to the Río Blanco Basin, is composed of a thick conglomeratic and volcanic sequence followed by marine and deltaic sediments from the Precordillera but also including some fluvial deposits from the Sierras Pampeanas area. Maximum thickness of the postcar-boniferous sedimentary pile in this area accounts for maximum relative burial depths. These sandstones exhibit large textural and compositional variations (Tables 1 to 4), depending on basin floor lithologies, sedimentary environments and temporal changes of provenance areas. Petrographically, most of them are feldsarenites, subfeldsarenites and lithic feldsarenites, with subordinated feldspathic litharenites and litharenites (Fig. 4). Common cements include quartz and feldspar overgrowths, calcite as single phase or hematite-zoned, kaolinite, illite and chlorite; less frequent authigenic minerals are albite, microquartz, ankerite, hematite and gypsum. Petrographic characteristics seems to be the main control on cementation types in these sandstones (Fig. 9). Three main sandstone petrographic associations were recognized based on clast composition and matrix content (Table 5), and each one of them was assigned to a particular cementation style defined by cement distribution, textures and stratigraphy (Fig. 12). Feldspar-rich arenites (Fig. 12a) comprise feldsarenites, subfeldsarenites and lithic feldsarenites whose matrix content is less than 15% and show more feldspar than lithic fragments (F>L). They typically have high monocrystalline quartz percentages, K-feldspars dominant over plagioclases and scarce lithic fragments of plutonicmetamorphic affinity. Feldspar-rich arenites are cemented by abundant quartz and feldspar overgrowths, large kaolinite pore fillings related to feldspar breakdown, and late sparry pure or hematite-zoned calcite. Lithic-rich arenites (Fig. 12b) include litharenites, sublitharenites and feldspathic litharenites that have amatrix content of less than 15%, and lithic fragments predominate over feldspars (L>F). In spite of a common low total quartz content, significant proportions of chert are not unusual; plagioclases dominate over K-feldspar grains and a large variety of volcanic, plutonic-metamorphic and sedimentary lithic fragments can predominate. Lithic-rich arenites show a limited development of quartz and feldspar overgrowths, but radial fibrous and massive chlorite is abundant, particularly when basic and intermediate volcanic fragments are present; sparry calcite and rare micritic ankerite are late cementing phases. Muddy arenites (Fig. 12c) grouped all psamites with more than 15% of matrix, regardless of their composition. In muddy arenites the high matrix content has inhibited quartz and feldspar overgrowths (Fig. 5); illitic clays, hematite and micritic calcite dispersed into matrix micropores (pores between 4 and 62 ìm) constitute the more conspicuous cementing phases. Sedimentary environments have also played a significant role in cement distribution (Fig. 10) through their influence on the textural and compositional maturity of sandstones (Primmer et al., 1997; Stonecipher, 2000). Highly mature arenites from littoral marine and fluvial environments show maximum quartz and feldspar overgrowths development, while these cements are strongly inhibited in more immature arenites from alluvial fan and glacial environments. The local influence of sedimentary environments can also explain the high rate of quartz cement in mica-rich fine arenites from distal deltaic mouth bars or the origin of hematite concretions in high sinuosity fluvial deposits. An increasing burial depth in the basin from east to west is then correlated with a parallel rise of diagenetic temperatures, a fact that has also entered into cement formation and stability (Fig. 11). While kaolinite is abundant in the eastern area characterized by relatively low diagenetic temperatures (55-120°C), it progressively disappears towards the west, where a quartz, illite and chlorite-rich authigenic association reflects higher diagenetic temperatures (~125°C; Boles and Franks, 1979; Worden and Morad, 2000).Other external factors such as ash falls, dissolution of gypsum beds, local increase of diagenetic temperature caused by intrusives, or climatic changes have also resulted in cements of limited distribution (microquartz, some chlorite, gypsum veins, albite as mosaics, hematite as coatings), whose main characteristics show no relation with the clastic fraction.

El estudio petrográfico de 192 secciones delgadas de areniscas de distintas unidades formacionales de la sección inferior del Grupo Paganzo (Carbonífero superior; Formaciones Lagares, Malanzán, Loma Larga, Guandacol, Tupe, Punta del Agua y Río del Peñón) reveló que la composición de la fracción clástica y el contenido de matriz son los principales factores de control de la mineralogía y texturas autigénicas. El referido intervalo estratigráfico incluye depósitos de abanicos aluviales, glaciarios, deltaicos, marinos litorales, de plataforma y fluviales. Las areniscas se muestrearon en localidades de los tres ámbitos de la Cuenca Paganzo, definidos sobre la base de la estructura de la cuenca, ubicación paleogeográfica, áreas de procedencia, ambientes sedimentarios y grado de soterramiento de los sedimentos. Petrográficamente, las areniscas comprenden feldarenitas, subfeldarenitas y feldarenitas líticas, con litoarenitas feldespáticas y litoarenitas en forma subordinada. Los cementos más comunes son cuarzo y feldespato como crecimientos secundarios, calcita pura o zonada con hematita, caolinita, illita y clorita; cementos de albita, microcuarzo, ankerita, hematita y yeso son menos frecuentes o sólo abundantes en forma localizada. La distribución, textura y estratigrafía de los cementos permitieron reconocer tres «estilos de cementación» característicos que corresponden a diferentes tipos petrográficos de areniscas. Las arenitas de afinidad feldespática (feldarenitas, subfeldarenitas y feldarenitas líticas, con matriz<15% y F>L) muestran importante desarrollo de crecimientos secundarios de cuarzo y feldespatos; se destaca la caolinita como parches y existe en general una fase tardía de calcita esparítica, pura o zonada con hematita. Las arenitas de afinidad lítica (litoarenitas, sublitoarenitas y litoarenitas feldespáticas, con matriz<15% y L>F) muestran escasa participación de crecimientos secundarios de cuarzo y feldespato; la clorita fibrosa radial o masiva es abundante, seguida por una fase carbonática tardía de calcita esparítica pura o zonada con hematita, o raramente ankerita micrítica. En las arenitas fangosas (matriz>15%) los crecimientos secundarios se inhibieron ante la presencia de matriz, y son las arcillas illíticas, óxidos de hierro y calcita micrítica las fases más características. Los ambientes de sedimentación han influenciado los estilos de cementación a través del control ejercido sobre la madurez textural y composicional de las areniscas. El aumento regional en el grado de soterramiento hacia el oeste de la cuenca se refleja en el aumento de las temperaturas diagenéticas; las asociaciones de cementos poseen abundante caolinita en el este (T=55- 120°C) y cuarzo, illita y clorita dominantes hacia el oeste (T~125°C). Otros factores externos al sistema como lluvias de cenizas, disolución de bancos de yeso, aumento puntual de la temperatura diagenética por intrusivos o la aridización del clima generaron cementos de distribución acotada que no se encuentran controlados por la composición de la fracción clástica.

Médanos Grandes dunefield, which is located near Vallecito city at the southeast of San Juan province (Argentina), is one of the largest eolian depositional systems in Argentina. It is formed by draas together with transversal and longitudinal dunes and large blowouts. Alluvial plain deposits related to San Juan and Bermejo rivers, and the Pie de Palo and Valle Fértil hills sourround the eolian system (Fig. 1). Previous works are very scarce (Groeber, 1937; Rodríguez, 1966), being Regairaz et al. (1987) the ones who described the dunefield as made up of complex dunes. The present study can be divided in three steps. Firstly, remote sensing images analysis were carried out to define and describe geomorphic units. Secondly, granulometric and compositional studies allowed characterizing the deposits that formed the eolian bedforms. Finally, a tentative model of the eolian system evolution is also proposed. The positive relief is formed by two mountain belts, the Pie de Palo range to the north and the Valle Fertil one to the east. The former is composed of Precambrian-Early Paleozoic anfibolites, maffic and ultramaffic rocks, migmatites and gneisses (Pie de Palo Complex) and the latter (Valle Fértil Complex) by crystalline rocks as well together with sedimentary rocks of Cretaceous and Triassic ages. Low areas are covered by Pleistocene to recent alluvial fan, alluvial plain and eolian sediments (Fig. 1). The eolian deposits include sandsheets and dunefields with several kinds of bedforms that predominate at the southwest of the valley. Médanos Grandes dunefield shows several patterns of dunes and draas of different types, size, spacing and alignment. Based on these configurations five geomorphic units have been defined and mapped (Figs. 3 and 4). Geomorphic unit 1 (UG1), which formed the north part of the dunefield is considered to be the oldest. It is made up of 55-meter tall and up to 2000-meter spacing, transversal draas with superimposed dunes (Fig. 5). The draas orientation, as well as that of the superimposed dunes, suggests southwestern paleowinds during their formation. Geomorphic unit 2 (UG2) shows similar transversal draas, better developed and with their slipface looking to the southwest. Herein there are also minor dunes over the megaforms, but with an oblique alignment in relation to the draas (Fig. 6). Therefore these smaller bedforms are considered as younger deposits. Geomorphic unit 3 (UG3, Fig. 7 and 8) has conspicuos erosional features characterized by large circular and triangular blowouts. Interference of crest lines belonging to draas of UG1 and UG2 probably produced enough wind acceleration to remove sand grains and develop the described blowouts. Geomorphic unit 4 (UG4) includes 40-meter tall and 150-meter spacing, longitudinal dunes with small transversal dunes in the interdune areas (Fig. 9). In this case dune alignment suggests paleowind from the south-southeast. Finally, geomorphic unit 5 (UG5), the youngest, is composed of transversal, barchanoid and longitudinal dunes (Fig. 10) and is related to present winds from the south-southeast. Grain-size characteristics of 78 samples corresponding to the eolian deposits were obtained by dry sieving, at 0.25 ø intervals. Mean and sorting were calculated following momentum method, whereas skewness, kurtosis, 1 % percentil and amount of material lower than 53 μ by Folk and Ward's (1957) graphical formulas. Textural parameters show that draas and dunes are made up of very good sorted (s=0,45 ø), fine to very fine (x=2,88 ø) sands, with skewness of nearly zero (SK 1 =0,05, Tables 1 to 4). They have less than 1 % of material lower that 53 μ and the average 1% percentil corresponds to medium sand (1,87 ø). These characteristics are very similar to those of other eolian sediments studied by several authors (Ahlbrandt, 1979; Chaudri y Khan, 1980; Brookfield, 1992; Limarino y Martínez, 1992; Tripaldi et al., 1998; among others). Despite the fact that UG1 and UG2 grain size distributions are similar, when compared in detail they show interesting differences. UG2 is coarser than UG1 and has better sorting and lower amount of clay and silt. Although, these differences could be the consequence of the different supply areas that have both units, a selective deflation of fine sediments during the UG2 formation must not be discharged. Modal analyses of the sand grain composition show that the eolian sediments are dominated by lithic fragments (in order of importance: volcanites, schists, anfibolites, chert, sedimentites and limestones clasts) together with low to moderate percentages of feldspar and scarce amount of quartz (Fig. 13). This composition suggests two major areas of provenance: 1) the Precordillera-Cordillera Frontal area to the west where volcanites and limestones are frequent and 2) the Sierras Pampeanas area that includes the above mentioned Pie de Palo and Valle Fertil mountains composed of crystalline rocks. Médanos Grandes dunefield had a complex evolution as pointed out by the presence of different generations of dunes, each of them represented by the above described geomorphic units, that were built up under a diverse paleowind regimen. The geomorphic units are here tentatively correlated with the climatic stages proposed by Iriondo y Kröhling (1996) in the pampean plain (Fig. 14). According to those authors, during the isotopic stage 4 (between 77.000 and 60.000 years B.P.) arid conditions were established related with glacial advance at the Andes. It is likely that Médanos Grandes dunefield, with draas and dunes migrating to the northeast (UG1), were given rise during this period favored not only by the aridness but also by a high sediment supply. A second generation of dunes could be related to a subsequently arid period that occured, according to Iriondo y Kröhling (1996), between 36.000 and 15.000 years B.P (isotopic stage 2). Due to the irregular relief in the area, reworking of previous draas to form new megaform migrating to the southwest (UG2) was not complete and therefore an interference zone, characterized by the triangular pattern and blowouts of UG3, was established. During a third state, probably associated with the arid period in the upper Holocene (between 3.500 and 1.400 years B.P, Iriondo y Kröhling, 1996) longitudinal dunes (UG4) and transversal, longitudinal and barchan dunes (UG5) were formed. Although at the begining the eolian system was likely to be more extensive, at present Médanos Grandes dunefield, as well as Médanos de la Chacras dunefield that occured to the north (Fig. 14), could be considered a remaining because of fluvial erosion.

El campo eólico de Médanos Grandes, sudeste de la provincia de San Juan (Argentina), es uno de los más extensos del país y está formado por distintos tipos de dunas, principalmente transversales y longitudinales. Junto a éstas aparecen grandes megaformas eólicas o draas, de hasta 70 metros de altura y 2000 metros de espaciamiento. El análisis de imágenes satelitales permitió identificar cinco unidades geomorfológicas caracterizadas por geoformas de diferente morfología, tamaño, orientación y dirección de migración. En la unidad geomórfica 1 (UG1) se incluyen draas de crestas transversales (orientadas al azimut 150º), ligeramente sinuosas, con dunas menores sobreimpuestas. La disposición de sus caras de sotavento indica que este conjunto se desarrolló a partir de paleovientos del sudoeste. En la conformación de la UG2 aparecen también draas transversales con dunas asociadas, sin embargo en este caso la orientación de los primeros evidencia paleovientos del noreste. Por otro lado, las dunas menores se disponen de forma oblicua y se habrían, por lo tanto, formado con posterioridad. En la UG3, ubicada en el centro del campo eólico, se destaca la presencia de grandes hoyos de deflación, de hasta 1000 metros de diámetro y 50 metros de desnivel con respecto a las dunas adyacentes. Así mismo, esta unidad se caracteriza por un diseño enrejado de médanos, resultado de la interferencia de las crestas de los draas pertenecientes a las unidades 1 y 2. La UG4 comprende dunas longitudinales, de hasta 40 metros de altura y 150 metros de espaciamiento, que se asocian a pequeñas dunas transversales. La disposición de las dunas longitudinales, junto con la orientación de las caras de sotavento de las formas menores, indican paleovientos del sud-sudeste. Por último, la UG5 está integrada por dunas transversales, barjanoides y longitudinales, que ocupan la periferia del campo eólico aquí estudiado. Constituye la unidad más moderna y respondería también a vientos del sud-sudeste similares a los actuales. Las geoformas eólicas de Médanos Grandes están formadas por arenas finas (X= 2,88 ø), muy bien seleccionadas (s= 0,45 ø) y con distribuciones granulométricas unimodales y simétricas (SK 1 = 0,05). El percentil del 1 % corresponde a la arena mediana (1,87 ø) y el material inferior a 53 μ conforma en promedio el 1,05 % de las muestras. En cuanto a la composición de las arenas predominan los fragmentos líticos (clastos de volcanitas, mayormente ácidas y mesosilícicas, esquistos micáceos, anfibolitas, milonitas, chert, sedimentitas y calizas), junto a moderados porcentajes de feldespatos y muy baja proporción de cuarzo y minerales pesados. La presencia de geoformas con diferente morfología y orientación indica que el sistema eólico de Médanos Grandes es policíclico ya que en su conformación se sucedieron distintos episodios de crecimiento, bajo distintos patrones de vientos. Las unidades geomórficas identificadas pueden ser tentativamente correlacionadas con los estadios climáticos propuestos por autores anteriores para la región pampeana. Finalmente, en la actualidad el campo eólico de Médanos Grandes se halla parcialmente erodado debido a la acción fluvial, constituyendo probablemente un remanente de un extenso sistema eólico que cubría gran parte del valle del Bermejo.

The composition, richness, diversity, abundance and dominance in infracommunities of metazoan parasites found in 86 croaker Cilus gilberti (Abbott 1889) are compared between two samples taken off Talcahuano, Chile, with 15 years of difference. All hosts harboured parasites, and 26 taxa were collected. The prevalence of all taxa, and the abundance of 22 taxa were recorded. Most (69 %) taxa were found in both years. However, to compare between years, we just considered those 13 taxa occurring in at least 10 host individuals. Significant variations in composition but not in richness, abundance, diversity and dominance were found when infracommunities collected from croaker of similar body length were compared between years. Despite the fact that there are few antecedents on the subject, these results are similar to those reported in infracommunities of metazoan parasites of fishes and mammals in that there is high compositional variability and low aggregate variability. The extent to which this can be interpreted as indicating community compensation or stasis is discussed, considering that biological interactions could also be responsible for the observed pattern

Se comparan la composición, riqueza, diversidad, abundancia y dominancia en las infracomunidades de parásitos metazoos de 86 ejemplares de corvina Cilus gilberti (Abbott 1889), recolectados en dos muestras tomadas con 15 años de diferencia en la zona de Talcahuano, VIII región, Chile. Se pretende averiguar si estas características comunitarias se modifican o no sustantivamente entre años. Se recolectaron un total de 26 taxa, a los que se les determinó la prevalencia, aunque sólo a 22 se les determinó la abundancia. El 69 % de los 26 taxa ocurría en ambos años, sin embargo, al comparar la composición infracomunitaria entre años, sólo se consideró a aquellos 13 taxa que estaban en al menos 10 corvinas del total de 86 examinadas, y a hospedadores de similar longitud corporal. Hay variaciones significativas entre años en la composición de las infracomunidades de parásitos pero no en la riqueza, abundancia, diversidad y dominancia. Aunque los antecedentes son escasos, la observada relativamente alta variabilidad composicional y baja variabilidad agregada es similar a lo encontrado en infracomunidades de parásitos, tanto de peces como de mamíferos. Se discute la medida en que estos resultados representan compensación o estasis comunitaria, entre cuyas causas podrían estar las interacciones biológicas

Foram avaliados durante três anos os efeitos de tratamentos de fogo e pastejo sobre a dinâmica da vegetação de uma pastagem natural localizada em Santa Maria, na região da Depressão Central, Rio Grande do Sul. Foi considerada a hipótese de resiliência, resultado das espécies componentes da pastagem terem evoluído sob influência de tais distúrbios. O experimento foi composto por oito parcelas experimentais submetidas a combinações de níveis de pastejo (pastejado, excluído) e de fogo (queimado, não-queimado), em duas posições de relevo (encosta, baixada). A análise multivariada dos dados de composição de espécies foi baseada em ordenação e testes de aleatorização. A vegetação sob efeito de pastejo, independente da queima, apresentou trajetórias direcionais, enquanto sob exclusão as trajetórias foram caóticas. O efeito do pastejo parece ser determinante da dinâmica vegetacional (P=0,077).

The effect of fire and grazing treatments on vegetation dynamics was evaluated during three years on a natural grassland located in Santa Maria, in the region of "Depressão Central", Rio Grande do Sul, Brazil. A hypothesis of resilience resulting from the fact that the species of the grassland evolved under the influence of these disturbances was considered. The experimental setup was formed by eight plots subjected to combinations of grazing (grazed, ungrazed) and fire (burned, unburned) levels, on two relief positions (convex, concave slope). Multivariate analysis of compositional data used ordination and randomization testing. Vegetation under grazing tended to show directional trajectories of floristic composition change, while under grazing exclusion the trajectories could be considered chaotic, independently from the plots being burned or not. Grazing effect seems to be determinant of vegetacional dynamics (P=0.077).

Un total de veinte muestras de aceite fueron recolectadas en el Campo Orito localizado en la Cuenca del Putumayo al sur de Colombia, con el fin de establecer mediante la caracterización geoquímica de crudos la existencia de compartimentalización del yacimiento en la Formación Caballos, así como definir la relación genética de los hidrocarburos producidos en las Formaciones Caballos y Pepino y los fenómenos que ocasionaron cambios en la composición del crudo antes y después de la producción. Las muestras fueron sometidas a análisis de parámetros totales (bulk), cromatografía gaseosa de crudo total, cromatografía gaseosa de fracción liviana, biomarcadores e isótopos de carbono. Los resultados son visualizados a través de diagramas estrella, gráficos xy, dendogramas y mapas de isovalores. Se encontró que las diferencias en composición de los hidrocarburos producidos de la Formaciones Pepino y Caballos se deben a que los crudos fueron originados por rocas fuente diferentes y con distintos grados de madurez termal. Se definieron dos compartimentos Domo Norte y Domo Sur para el yacimiento en la Formación Caballos. La compartimentalización está obedeciendo a fallas que influyeron en el momento de llenado de la trampa y que han actuado como sellos parciales para aislar los diferentes sectores y ocasionar heterogeneidad en la composición del crudo. Mediante la integración de esta información geoquímica con los modelos estáticos y dinámico del yacimiento se ha definido la sectorización para orientar el estudio de simulación del campo y se han identificado sectores de interés para realizar perforación de desarrollo en el Domo Norte.

A total of twenty oil samples from the Onto Field in the Putumayo Basin at the South of Colombia were analyzed to define the genetic relationship of the hydrocarbons produced from the Caballos and Pepino Formations, to establish the compartmentalization in the reservoirs of the Caballos Formation, so as to study the phenomena that caused the compositional changes of crude before and after the production. The samples were analyzed for bulk parameters, whole oil gas chromatography, light fraction gas chromatography, biomarkers and carbon isotopes. The results are presented using star diagrams, crossplots, cluster diagrams and iso-value maps. It was found that the compositional differences of the produced hydrocarbons from the Pepino and Caballos Formations are produced by the fact that the crude were originated by different source rocks each one with different grades of thermal maturity. There were defined two compartments: North Dome and South Dome for the Caballos Formation reservoir. The compartmentalization is caused by faults that play a role when the trap was filled. They have acted as partial seals isolating the different sectors and causing heterogeneity in the crude composition. The integration of this geochemistry information with the static and dynamic models of the reservoir lead to define different sectors to guide the simulation study of the field. Also some sectors of interest have been identified to carry out development new drilling opportunities in the North Dome.

The provenance and sedimentary petrography of the quartz arenites from the Balcarce formation (Cam-Or) were analysed using the Basu et al. (1975, 1985) discrimination model based on undulosity and policrystallinity of detrital quartz on 35 samples from different outcrops in the basin (Fig. 1). The source material are low (80% of the samples) and medium to high rank (20% of the samples) metamorphic rocks which are widespread as underlying basement rocks (see Fig. 2). The polycrystalline quartz shows low dispersion while the undulosity shows a higher one. This fact has been interpreted as the effect of an extended and areally heterogeneous dynamic metamorphism in the source areas (mainly underlying basement). The quartz with undulosity seems to be proportional to the degree of cataclasys of the basement rocks. From bottom to top of the sequence, the polycrystalline quartz and the undulose quartz decrease and the non undulose quartz increases which suggests an increasing reworking that get rid of the most unstable varieties of quartz, that is to say the ones that had suffered lattice dislocation‘ Other elements like the basin type, source material, weathering, the low sedimentation rate, the shallow platform marine environment of deposition and the effect of tidal currents play an important role in the first cycle generation of orthoquartzites. If we consider the sedimentation rate, (total thickness of the unit/time of deposition) versus the relative increase in quartz content (considering the % of quartz in the source rock) from the graph of Suttner et al., 1981 (Fig. 3), we obtain a first cycle orthoquartzite from the underlying basement rocks of the Balcarce Fm. without considering the influence of the climate, which is very important due to the intense weathering of the source rocks (Marchese & Di Paola, 1975a; Zalba et al., 1992) that form important paleosurfaces. The main conclusions in this contribution are: * The Basu et al. (1975, 1985) discrimination model for quartz provenance applied to orthocuartzites does not show coherent results in our case, due to the characteristics and heterogeneous distribution of the source rocks (granitoids affected by dynamic metamorphism, mylonitic belts and migmatic rocks). *The proportion of quartz with undulosity shows a good correlation with the undulosiy of the basement rocks. This fact suggests that the process of reworking of the source material "in situ" played an important role in the generation of the Balcarce Fm. This intense reworking works against reliable results applying this model. * The marine environment favours the compositional changes leading to the great sedimentary maturity. * The intense weathering and the reworking of the grains in a shallow and tide dominated marine environment are the main causes of this maturity. The reworking causes, also, a change in the amounts of quartz types within the sequence. * A sedimentation rate of 10.9 m/Ma for the Balcarce Fm. was inferred. * This low sedimentation rate in a cratonic basin is enough to generate first cycle orthoquartzites. * We plan to apply this statistical methodology in order to recognize and correlate other orthoquartzites along the basin.

Se realizó el estudio petrográfico de los clastos de cuarzo de las ortocuarcitas de la Formación Balcarce, utilizando el modelo de discriminación de procedencia de Basu et al. (1975, 1985). La proporción de cuarzo ondulante, no ondulante y policristalino determinado en 35 muestras es coherente con el grado de cataclasis del basamento cristalino subyacente, lo que sugiere un origen por meteorización y retrabajo del mismo "in situ" para estas facies. Se observa, en general, de base a techo de la secuencia, un incremento de cuarzo no ondulante en detrimento del ondulante y policristalino. Este hecho se explica por el mayor retrabajo que elimina a las variedades de cuarzo más inestables, que son aquellas que han sufrido un proceso de dislocación de su red cristalina. Se analizaron los factores que habrían determinado la madurez de los sedimentos de la Fm. Balcarce a partir de un aporte mayoritario de material meteorizado del basamento más la adición de sedimentitas de ciclos anteriores en forma subordinada. Asimismo, se consideraron otros factores sedimentológicos determinantes como el tipo de cuenca cratónica, la tasa de sedimentación baja, el ambiente marino somero y la acción de las corrientes de marea.