Evidence for Localized High Temperature Hydrothermal Fluid Flow within the Sub-Crater Environment of the Rochechouart Impact Structure: Observations from a Polymict Breccia Dike

Hypervelocity impacts into volatilebearing terrestrial targets can initiate hydrothermal circulation for a finite period of time; evidence for this is preserved in approximately one-third of impact structures on Earth [1, 2]. Hydrothermal environments can host extremophile life, and microbial communities have been found to colonize impact craters [3, 4]. The majority of impact structures on Earth have yet to be studied in great detail; many aspects of the post-impact environment such as the extent and duration hydrothermal circulation with respect to location within the structure as well as crater diameter, target composition and external influences, (paleogeography) are not fully understood. <p></p>We present evidence for high temperature hydrothermal fluid circulation within the sub-crater environment of the highly eroded, 23km diameter, Mesozoic Rochechouart impact structure located in west-central France [5]. This evidence is a new impact lithology that was found during a recent field campaign at a collection site located approximately 7.5km north-east of the structure's center. It is a highly porous, polymict lithic impact breccia dike containing carbonate mineralization found below the transient crater floor. Secondary hydrothermal mineral assemblages are diagnostic of a range of temperatures (>100°C to low temperature diagenetic).<p></p&gt

Evidence for an impact-induced biosphere from the δ34S signature of sulphides in the Rochechouart impact structure, France

The highly eroded 23 km diameter Rochechouart impact structure, France, has extensive evidence for post-impact hydrothermal alteration and sulphide mineralization. The sulphides can be divided into four types on the basis of their mineralogy and host rock. They range from pyrites and chalcopyrite in the underlying coherent crystalline basement to pyrites hosted in the impactites. Sulphur isotopic results show that δ34S values vary over a wide range, from -35.8‰ to +0.4‰. The highest values, δ34S -3.7‰ to +0.4‰, are recorded in the coherent basement, and likely represent a primary terrestrial sulphur reservoir. Sulphides with the lowest values, δ34S -35.8‰ to -5.2‰, are hosted within locally brecciated and displaced parautochthonous and autochthonous impactites. Intermediate δ34S values of -10.7‰ to -1.2‰ are recorded in the semi-continuous monomict lithic breccia unit, differing between carbonate-hosted sulphides and intraclastic and clastic matrix-hosted sulphides. Such variable isotope values are consistent with a biological origin, via bacterial sulphate reduction, for sulphides in the parautochthonous and autochthonous units; these minerals formed in the shallow subsurface and are probably related to the post impact hydrothermal system. The source of the sulphate is likely to have been seawater, penecontemporaneous to the impact, as inferred from the marginal marine paleogeography of the structure. In other eroded impact craters that show evidence for impact-induced hydrothermal circulation, indirect evidence for life may be sought isotopically within late-stage (≤120°C) secondary sulphides and within the shocked and brecciated basement immediately beneath the transient crater floor

Stable Isotope Studies of the Rochechouart Impact Structure: Sources of Secondary Carbonates and Sulphides within Allochthonous and Parautochthonous Impactites

Hypervelocity impacts are among the most ubiquitous processes to affect solid bodies within our solar system [1, 2]. Although they are notoriously devastating, citing responsibility for mass extinction events and global climate perturbations, impacts can also create temporary environments which are favorable for life to thrive, if there is enough water present in the target, and sufficient energy is released as heat [1, 2]. One-third of impact structures on Earth contain fossil impact-initiated hydrothermal systems, and they are therefore being explored as potential “cradles of life” on other solid planets and satellites in our solar system [1].<p></p> We are presenting a case for the evaluation of the Mesozoic Rochechouart impact structure in France as a once-habitable environment. Initial δ 13C, δ18O and δ 34S isotope data collected in 2014 from hydrothermal carbonates and sulphides within monomict lithic impact breccia, collected from a site located 7.5km from the center of the structure at Champagnac quarry, supports our hypothesis of a warm, wet environment; we also found evidence for metabolically reduced sulphate [3]. Similar mineral assemblages can be found throughout the structure, including allochthonous breccias and low to unshocked target material. In order to explore our hypothesis further, a larger sample set was collected from various lithologies within the Champagnac site containing sulphide and carbonate mineralization for δ 13C, δ18O and δ34S isotope analysis in January 2015. These results will allow us to determine the relationships between the many hydrothermal mineral assemblages within this area of the structure, and ask whether the isotopic compositions recorded in secondary sulphides and carbonates of the impactites are inherited from the target, or possibly represent colonization by thermophilic microbes during the post-impact hydrothermal period.<p></p&gt

Stable isotope studies of post impact hydrothermal deposits within the sub-crater environment of the Rochechouart structure

No abstract available

Stable isotope studies of post impact hydrothermal deposits within the sub-crater environment of the Rochechouart structure

No abstract available

A semantical approach to equilibria and rationality

Game theoretic equilibria are mathematical expressions of rationality. Rational agents are used to model not only humans and their software representatives, but also organisms, populations, species and genes, interacting with each other and with the environment. Rational behaviors are achieved not only through conscious reasoning, but also through spontaneous stabilization at equilibrium points. Formal theories of rationality are usually guided by informal intuitions, which are acquired by observing some concrete economic, biological, or network processes. Treating such processes as instances of computation, we reconstruct and refine some basic notions of equilibrium and rationality from the some basic structures of computation. It is, of course, well known that equilibria arise as fixed points; the point is that semantics of computation of fixed points seems to be providing novel methods, algebraic and coalgebraic, for reasoning about them.Comment: 18 pages; Proceedings of CALCO 200

Time of admission to the PICU and mortality

Objectives: To evaluate for any association between time of admission to the PICU and mortality. Design: Retrospective cohort study of admissions to PICUs in the Virtual Pediatric Systems (VPS, LLC, Los Angeles, CA) database from 2009 to 2014. Setting: One hundred and twenty-nine PICUs in the United States. Patients: Patients less than 18 years old admitted to participating PICUs; excluding those post cardiac bypass. Interventions: None. Measurements and Main Results: A total of 391,779 admissions were included with an observed PICU mortality of 2.31%. Overall mortality was highest for patients admitted from 07:00 to 07:59 (3.32%) and lowest for patients admitted from 14:00 to 14:59 (1.99%). The highest mortality on weekdays occurred for admissions from 08:00 to 08:59 (3.30%) and on weekends for admissions from 09:00 to 09:59 (4.66%). In multivariable regression, admission during the morning 06:00-09:59 and midday 10:00-13:59 were independently associated with PICU death when compared with the afternoon time period 14:00-17:59 (morning odds ratio, 1.15; 95% CI, 1.04-1.26; p = 0.006 and midday odds ratio, 1.09; 95% CI; 1.01-1.18; p = 0.03). When separated into weekday versus weekend admissions, only morning admissions were associated with increased odds of death on weekdays (odds ratio, 1.13; 95% CI, 1.01-1.27; p = 0.03), whereas weekend admissions during the morning (odds ratio, 1.33; 95% CI, 1.14-1.55; p = 0.004), midday (odds ratio, 1.27; 95% CI, 1.11-1.45; p = 0.0006), and afternoon (odds ratio, 1.17; 95% CI, 1.03-1.32; p = 0.01) were associated with increased risk of death when compared with weekday afternoons. Conclusions: Admission to the PICU during the morning period from 06:00 to 09:59 on weekdays and admission throughout the day on weekends (06:00-17:59) were independently associated with PICU death as compared to admission during weekday afternoons. Potential contributing factors deserving further study include handoffs of care, rounds, delays related to resource availability, or unrecognized patient deterioration prior to transfer

Planck scale effects in neutrino physics

We study the phenomenology and cosmology of the Majoron (flavon) models of three active and one inert neutrino paying special attention to the possible (almost) conserved generalization of the Zeldovich-Konopinski-Mahmoud lepton charge. Using Planck scale physics effects which provide the breaking of the lepton charge, we show how in this picture one can incorporate the solutions to some of the central issues in neutrino physics such as the solar and atmospheric neutrino puzzles, dark matter and a 17 keV neutrino. These gravitational effects induce tiny Majorana mass terms for neutrinos and considerable masses for flavons. The cosmological demand for the sufficiently fast decay of flavons implies a lower limit on the electron neutrino mass in the range of 0.1-1 eV.Comment: 24 pages, 1 figure (not included but available upon request), LaTex, IC/92/196, SISSA-140/92/EP, LMU-09/9

CO2-fertilisation enhances resilience to browsing in the recruitment phase of an encroaching savanna tree

CO2-fertilisation is implicated in the widespread and significant woody encroachment of savannas due to CO2-stimulated increases in below-ground reserves that enhance sapling regrowth after fire. However, the effect of CO2 concentration ([CO2]) on tree responses to the other major disturbance in savannas, herbivory, is poorly understood. Herbivory responses cannot be predicted from fire responses, as herbivore effects occur earlier during establishment and are moderated by plant palatability and defence rather than below-ground carbon accumulation. The relationship between herbivory and [CO2] is explored here using a widespread, strongly encroaching savanna tree, Vachellia karroo. Using greenhouse-grown seedlings under past—through to predicted future—[CO2] (180–1000 ppm) and field-grown seedlings under ambient [CO2], we assessed plant survival, growth, defence and palatability. Increasing [CO2] improves the tolerance of greenhouse-grown seedlings to herbivory by stimulating growth and allowing a critical size threshold associated with survival to be reached earlier, thereby decreasing the probability of fatal herbivory during the vulnerable recruitment phase. Elevated [CO2] also decreases the time taken to reach a second size threshold linked to accelerated recovery of field-grown seedlings following herbivory. Seedling growth responses to increasing [CO2] are nonlinear, suggesting that historic growth and survival enhancements are smaller than those predicted for the future. Increasing [CO2] is associated with greater resistance to herbivores (more branched shoot architecture) but not leaf palatability (C:N ratio) or defence (leaf tannins and spine density). Increasing V. karroo densities already constitute a major land management problem in southern African savannas. However, encroachment by this species, and likely other savanna tree species, may be greatly exacerbated under future [CO2], as tolerance to herbivory at the recruitment stage is further enhanced

A systematic review of gut microbiota composition in observational studies of major depressive disorder, bipolar disorder and schizophrenia

The emerging understanding of gut microbiota as ‘metabolic machinery’ influencing many aspects of physiology has gained substantial attention in the field of psychiatry. This is largely due to the many overlapping pathophysiological mechanisms associated with both the potential functionality of the gut microbiota and the biological mechanisms thought to be underpinning mental disorders. In this systematic review, we synthesised the current literature investigating differences in gut microbiota composition in people with the major psychiatric disorders, major depressive disorder (MDD), bipolar disorder (BD) and schizophrenia (SZ), compared to ‘healthy’ controls. We also explored gut microbiota composition across disorders in an attempt to elucidate potential commonalities in the microbial signatures associated with these mental disorders. Following the PRISMA guidelines, databases were searched from inception through to December 2021. We identified 44 studies (including a total of 2510 psychiatric cases and 2407 controls) that met inclusion criteria, of which 24 investigated gut microbiota composition in MDD, seven investigated gut microbiota composition in BD, and 15 investigated gut microbiota composition in SZ. Our syntheses provide no strong evidence for a difference in the number or distribution (α-diversity) of bacteria in those with a mental disorder compared to controls. However, studies were relatively consistent in reporting differences in overall community composition (β-diversity) in people with and without mental disorders. Our syntheses also identified specific bacterial taxa commonly associated with mental disorders, including lower levels of bacterial genera that produce short-chain fatty acids (e.g. butyrate), higher levels of lactic acid-producing bacteria, and higher levels of bacteria associated with glutamate and GABA metabolism. We also observed substantial heterogeneity across studies with regards to methodologies and reporting. Further prospective and experimental research using new tools and robust guidelines hold promise for improving our understanding of the role of the gut microbiota in mental and brain health and the development of interventions based on modification of gut microbiota