139 research outputs found
A comment on âMetamorphic origin of anastomosing and wavy laminas overprinting putative microbial deposits from the 3.22 Ga Moodies Group (Barberton Greenstone Belt)â
Morphological adaptations of 3.22 Ga-old tufted microbial mats to Archean coastal habitats (Moodies Group, Barberton Greenstone Belt, South Africa)
Microbial life was well established and widespread by the Paleoarchean; however, the degree of evolutionary advancement such as microbial motility, intra- and inter-species interactions, phototropism, or oxygenic photosynthesis by that time remains highly debated. The 3.22 Ga Moodies Group in the Barberton Greenstone Belt (BGB, South Africa) are Earth's oldest well-preserved siliciclastic tidal deposits. They exhibit a unique assemblage of microbial mats, providing an excellent opportunity to decipher the morphological adaptations of microbial communities to different paleoenvironmental settings. The fossil mats are preserved as kerogenous laminations (0.5â1 mm thick) that can be traced laterally for âŒ15 km in a âŒ1000 m-thick succession of fine- to coarse-grained tidal sandstones and conglomerates. We here present a detailed stratigraphic and depositional facies analysis, documenting the association of the three principal mat morphotypes with specific environmental settings: (1) planar-type in coastal floodplain, (2) wavy-type in intertidal, and (3) tufted-type in upper inter- to supratidal facies. All mat types indicate a flourishing phototrophic biota; moreover, the tufted morphology suggests an intricate level of coordinated growth commonly known from cyanobacterial mats in modern environments
Evidence for cavity-dwelling microbial life in 3.22 Ga tidal deposits
Cavities are considered plausible and favorable habitats for life on early Earth. In such microenvironments, organisms may have found an adequate protection against the intense ultraviolet radiation that characterized the Archean ozone-free atmosphere. However, while there is clear evidence that benthic life existed in the Paleoarchean, the oldest traces of cavity-dwelling microbes (coelobionts) have been found in Neoarchean rocks. Here we present the results of a detailed investigation of early silicified cavities occurring in the oldest well-preserved siliciclastic tidal deposits, the 3.22 Ga Moodies Group of the Barberton Greenstone Belt (South Africa). Downward-growing microstromatolitic columns composed of kerogenous laminae are commonly present in planar, bedding-parallel, now silica-filled cavities that formed in sediments of the peritidal zone. In-situ ÎŽ13CPDB (PDBâPeedee belemnite) measurements of the kerogen range from â32.3â° to â21.3â° and are consistent with a biogenic origin. Scanning electron microscopy analysis of the silicified cavities shows well-preserved chains of cell-sized molds that are interpreted as fossil filamentous microorganisms. The geological context, the morphology of the microstromatolites, the ÎŽ13C composition of the kerogen, and the presence of microfossils all suggest that a microbial community inhabited the cavities. These results extend the geological record of coelobionts by âŒ500 m.y., supporting the view that cavities were among the first ecological niches to have been occupied by early microorganisms
Predictors of Depression in Very Young Children: A Prospective Study
There have been only a few previous population-based studies of symptoms of depression in young children. There are no previous population-based studies which examine the factors which might be casually associated with depression in very young children
Beyond chance? The persistence of performance in online poker
A major issue in the widespread controversy about the legality of poker and the appropriate taxation of winnings is whether poker should be considered a game of skill or a game of chance. To inform this debate we present an analysis into the role of skill in the performance of online poker players, using a large database with hundreds of millions of player-hand observations from real money ring games at three different stakes levels. We find that players whose earlier profitability was in the top (bottom) deciles perform better (worse) and are substantially more likely to end up in the top (bottom) performance deciles of the following time period. Regression analyses of performance on historical performance and other skill-related proxies provide further evidence for persistence and predictability. Simulations point out that skill dominates chance when performance is measured over 1,500 or more hands of play
Differential exposure and reactivity to interpersonal stress predict sex differences in adolescent depression
This study tested the hypothesis that higher rates of depression in adolescent girls are explained by their greater exposure and reactivity to stress in the interpersonal domain in a large sample of 15-year-olds. Findings indicate that adolescent girls experienced higher levels of total and interpersonal episodic stress, whereas boys experienced higher levels of chronic stress (academic and close friendship domains). Higher rates of depression in girls were explained by their greater exposure to total stress, particularly interpersonal episodic stress. Adolescent girls were also more reactive (more likely to become depressed) to both total and interpersonal episodic stress. The findings suggest that girls experience higher levels of episodic stress and are more reactive to these stressors, increasing their likelihood of becoming depressed compared to boys. Results were discussed in terms of girls' greater interpersonal focus and implications for understanding sex differences in depression
Morphotectonics of the central Muertos thrust belt and Muertos Trough (northeastern Caribbean)
Multibeam bathymetry data acquired during the 2005 Spanish R/V Hespérides cruise and reprocessed
multichannel seismic profiles provide the basis for the analysis of the morphology and deformation in the
central Muertos Trough and Muertos thrust belt. The Muertos Trough is an elongated basin developed where
the Venezuelan Basin crust is thrusted under the Muertos fold-and-thrust belt. Structural variations along the
Muertos Trough are suggested to be a consequence of the overburden of the asymmetrical thrust belt and by
the variable nature of the Venezuelan Basin crust along the margin. The insular slope can be divided into
three eastâwest trending slope provinces with high lateral variability which correspond to different accretion
stages: 1) The lower slope is composed of an active sequence of imbricate thrust slices and closed fold axes,
which form short and narrow accretionary ridges and elongated slope basins; 2) The middle slope shows a
less active imbricate structure resulting in lower superficial deformation and bigger slope basins; 3) The
upper slope comprises the talus region and extended terraces burying an island arc basement and an inactive
imbricate structure. The talus region is characterized by a dense drainage network that transports turbidite
flows from the islands and their surrounding carbonate platform areas to the slope basins and sometimes to
the trough. In the survey area the accommodation of the ongoing eastâwest differential motion between the
Hispaniola and the Puerto RicoâVirgin Islands blocks takes place by means of diffuse deformation. The asymmetrical development of the thrust belt is not related to the geological conditions in the foreland, but rather may be caused by variations in the geometry and movement of the backstop. The map-view curves of the thrust belt and the symmetry of the recesses suggest a main northâsouth convergence along the Muertos margin. The western end of the Investigator Fault Zone comprises a broad band of active normal faults which result in high instability of the upper insular slope
A modern network approach to revisiting the positive and negative affective schedule (PANAS) construct validity
Introduction: The factor structure of the Positive and Negative Affective Schedule (PANAS) is still a topic of debate. There are several reasons why using Exploratory Graph Analysis (EGA) for scale validation is advantageous and can help understand and resolve conflicting results in the factor analytic literature. Objective: The main objective of the present study was to advance the knowledge regarding the factor structure underlying the PANAS scores by utilizing the different functionalities of the EGA method. EGA was used to (1) estimate the dimensionality of the PANAS scores, (2) establish the stability of the dimensionality estimate and of the item assignments into the dimensions, and (3) assess the impact of potential redundancies across item pairs on the dimensionality and structure of the PANAS scores. Method: This assessment was carried out across two studies that included two large samples of participants. Results and Conclusion: In sum, the results are consistent with a two-factor oblique structure.Fil: Flores Kanter, Pablo Ezequiel. Universidad Empresarial Siglo XXI; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Garrido, Luis Eduardo. Pontificia Universidad CatĂłlica Madre y Maestra; RepĂșblica DominicanaFil: Moretti, Luciana SofĂa. Universidad Empresarial Siglo XXI; Argentina. Pontificia Universidad CatĂłlica Madre y Maestra; RepĂșblica Dominicana. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Medrano, Leonardo. Universidad Empresarial Siglo XXI; Argentina. Pontificia Universidad CatĂłlica Madre y Maestra; RepĂșblica Dominicana. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; Argentin
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