Ephemeral Stage Research Articles

Constraining depositional evolution and reservoir compartmentalization in a mixed carbonate-siliciclastic lacustrine system: The Yacoraite formation, Salta Group, NW Argentina

The mixed carbonate-siliciclastic Yacoraite Formation, Salta Group in northern Argentina has been interest of recent studies searching for potential analogues for the South Atlantic pre-sal carbonates. Microbial lacustrine carbonates are important reservoir systems and their characteristics and stratigraphic packaging are a major factor impacting compartmentalization. This study provides sedimentological and facies analyses combined with petrographical, isotope geochemical and petrophysical analyses of lacustrine clastics and carbonates using an example from the Yacoraite Formation (Salta Group) in northern Argentina (Tres Cruces sub-basin).The Yacoraite Formation records the evolution of a lacustrine system responding to basin scale tectonic processes and climatic conditions and is interpreted as a microbially-related mixed carbonate clastic lacustrine system comprising 8 main Facies types, deposited in either a perennial or an ephemeral system. The most dominant architectural elements are: Sandstones with interbedded shales (F1), Shales with interbedded sandstones and siltstones (F2), Thick-bedded oolitic grainstone (F5), Thin-bedded oolitic grainstone-packstone (F6) and Stromatolite boundstone (F8). These facies types allow to differentiate two types of lacustrine environments: Perennial (Stage I) vs Ephemeral (Stage II) intercalated with episodes of continental plains deposition, arranged in three depositional sequences (Yacoraite I, II and III), each recording either transgressive or a regressive-transgressive trend.Carbonate and clastics are arranged in cycles during the Perennial l Stage suggesting that the depositional system responded in patterns attributable to reciprocal sedimentation, whereas, during the Ephemeral Stage 2, spatial coexistence of clastic and carbonate seem to be the case rather that cyclic vertical superposition.Thick-bedded oolitic grainstone and Stromatolites (F5 and F8 respectively) of the perennial lacustrine system show laterally continuous and thick beds with the best reservoir properties. Furthermore, the Sandstones with interbedded shales (F1) are characterized by intermediate values of porosity and permeability, which would not result in permeability barriers. On the other hand, Thin-bedded oolitic grainstone-packstone (F6) of the ephemeral lacustrine system are characterized by a high degree of heterogeneity due to their limited areal distribution and their complex spatial variability with Shales with interbedded sandstones and siltstones (F2).

Fasciola gigantica: Comparison of the tegumental ultrastructure in newly excysted metacercariae and in vitro penetrated juvenile flukes indicates intracellular sources of molecules with vaccinal and immunomodulatory potential

Using in vitro procedures to prepare newly excysted metacercariae and gut-penetrated juvenile Fasciola gigantica, the ultrastructural features of the tegumental syncytium and perikarya of these ephemeral stages in the host-invasion process were compared. The T0-type tegumental cells in newly excysted metacercariae are packed with stored T0 granules which, following transport to the surface membrane of the syncytium, discharge by exocytosis to maintain the glycocalyx. The T0 cells become depleted of T0 granules during the penetration process, shrink in size, and initiate autophagy in the cytoplasm to facilitate metamorphosis from a storage function to active biosynthesis. The novel products appear to include lysosomes which contribute to the autophagosomes, and T1 granules, necessary for maintenance of the glycocalyx and immunoprotection, as the invasion process continues into the host liver. Residual bodies, the end-products of autophagy, are eliminated from the apical membrane of the tegumental syncytium into the host-parasite interface. There they may present a transient source of parasite-derived molecules, including lysosomal cathepsin-type proteases, with potential for interaction with the host’s immune system, and so might be exploited as targets for vaccinal and immunomodulatory studies.

Alternative stable equilibria and critical thresholds created by fire regimes and plant responses in a fire‐prone community

Wildfire is a dominant disturbance in many ecosystems, and fire frequency and intensity are being altered as climates change. Through effects on mortality and regeneration, fire affects plant community composition, species richness, and carbon cycling. In some regions, changes to fire regimes could result in critical, non‐reversible transitions from forest to non‐forested states. For example, the Klamath ecoregion (northwest United States) supports extensive conifer forests that are initially replaced by hardwood chaparral following high‐severity fire, but eventually return to conifer forest during the fire‐free periods. Climate change alters both the fire regime and post‐fire recovery dynamics, potentially causing shrubland to persist as a stable (i.e. self‐renewing) vegetation stage, rather than an ephemeral stage. Here, we present a theoretical investigation of how changes in plant traits and fire regimes can alter the stability of communities in forest‐shrub systems such as the Klamath. Our model captures the key characteristics of the system, including life‐stage‐specific responses to disturbance and asymmetrical competitive interactions. We assess vegetation stability via invasion analysis, and conclude that portions of the landscape that are currently forested also can be stable as shrubland. We identify parameter thresholds where community equilibria change from stable to unstable, and show how these thresholds may shift in response to changes in life‐history or environmental parameters. For instance, conifer maturation rates are expected to decrease as aridity increases under climate change, and our model shows that this reduction decreases the fire frequencies at which forests become unstable. Increases in fire activity sufficient to destabilize forest communities are likely to occur in more arid future climates. If widespread, this would result in reduced carbon stocks and a positive feedback to climate change. Changes in stability may be altered by management practices.

“Why Are You Mixing what Cannot be Mixed?” Shared Devotions in the Monotheisms

This paper focuses on the religious mixture in Mediterranean history. Here people of different religions have long lived intermingled. More generally, as it is widely known since at least Braudel’s major work, the history of this region has been characterized by a long‐term proliferation of traffic, contacts, and borrowings. To what extent has this close interaction also influenced religious behaviour? By examining several occurrences of religious mixture in this region, the paper will show that syncretism is not necessarily an ephemeral stage preceding the repression or the assimilation of other groups, nor is it confined to some historical situations. A broad perspective illustrates a surprising dissemination and a substantial continuity of these manifestations. Even a rough inventory gives an idea about the variety of common devotions at the same sanctuary, where holy figures often operate as catalysts of mixture. Taken together, these mixed devotional manifestations belie the tightness often attributed to monotheisms in the Mediterranean. In order to better understand these interfaith manifestations we should move away from doctrinal and institutional discontinuity between religions, and concentrate on elements of theological and devotional continuity.

The Ephemeral Page Mee ts The Ephemeral stage: Comix in Performance

The Ephemeral Page Mee ts The Ephemeral stage: Comix in Performance

Patterns of Drug Escalation among Philadelphia Arrestees: An Assessment of the Gateway Theory

Ephemeral stages in the use of licit and illicit substances have been documented for several decades. Sophisticated analyses have repeatedly demonstrated that “gateway” substances, such as alcohol and tobacco, emphasize early roles in a drug-using pathway. Adolescents are unlikely to use marijuana without first using alcohol and tobacco, and will not use more serious drugs, such as cocaine and heroin, without first using marijuana. To date, however, most research has focused on non-deviant populations. In the current analysis, non-recursive path models are estimated on a population of 1,252 adult Philadelphia arrestees surveyed through the Arrestee Drug Abuse Monitoring (ADAM) Program. Analyses confirm patterns of drug escalation among arrestees with “soft,” “alternative,”and “hard” central nervous system (CNS) modifying drugs. Generalizability and intervention strategies are discussed.

Genesis and transformation of minerals in the formation of red (Alfisols) and black (Inceptisols and Vertisols) soils on Deccan basalt in the Western Ghats, India

SUMMARYSix noncalcareous pedons from the basaltic terrain of the Western Ghats in Maharashtra, India, were identified for the present study. Of these, two red‐soil pedons (Typic Haplustalfs) and one black‐soil pedon (Vertic Ustropept) are from the Bhimashankar plateau at an elevation of 1000 m above mean sea level, experiencing a humid (>5000 mm rainfall) tropical climate. The other three pedons of black soils (Typic Chromusterts and Typic Ustropept) are from the semi‐arid zone (500–1000 mm rainfall), at an elevation of 825–893 m.Clay mineralogical investigation indicated that interstratified smectite‐kaolin (Sm/K) is dominant in red soils whereas smectite is dominant in black soils. The Sm/K is formed by the transformation of montmorillonite, the first weathering product of Deccan basalts in a humid tropical climate. We suggest that the interstratification of kaolin with chloritized smectite may also be an important ephemeral stage during the transformation of smectite to kaolinite. The presence of zeolites provided sufficient bases to prevent the complete transformation of Sm/K to kaolinite. The presence of smectites and zeolites made the formation of black soils possible in microdepressions even in a tropical humid climate. The genesis of Sm/K and smectite in red and black soils, respectively, suggests that these soils formed through a progressive landscape reduction process. The presence of both Sm/K and smectite in black soil clays of semi‐arid climate suggests that the smectite of these soils was formed in an earlier humid climate.

Architectural innovation and experimentation at Ganj Dareh, Iran

Abstract Ganj Dareh is an early neolithic mound site in the central Zagros mountains of western Iran in which the mud‐based architecture is unusually well preserved. Level D, which was burnt, has clustered two‐story structures with many small cubicles. It reveals several methods of brick making and wall construction, as well as unusual mortice‐and‐tenon devices, ‘storage bins’ made of prefabricated clay slabs, and many ‘portholes’ and ‘plugs’ in the walls. Level D and later levels may represent an ephemeral stage of architectural experimentation in the Zagros at a time when there was still no strong commitment to food production. It suggests the early Zagros architecture was more complex and innovative than is usually thought.

Development of haustoria of Melampsora lini

An initial step in haustorium formation is the contact of a terminal intercellular mycelial cell with the wall of a host cell. The former differentiates to form a haustorial mother cell having a thickened wall in the region of contact. A penetration peg develops in the thickened region of the cell wall; it elongates, penetrates the host cell wall, and extends into the lumen of the host cell. A dark-staining region, the neck ring, develops in the wall of the penetration peg and persists throughout subsequent stages of development. The distal end of the penetration peg expands to form a somewhat spherical haustorial body. Subsequently, one to several lobes form on, and extend from, the body of the haustorium. The more ephemeral stages of development are the initiation of the spherical haustorial body and the elongation of the penetration peg. The less ephemeral stages are prepenetration and early postpenetration of the host cell wall and the intermediate stages of haustorial expansion.