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

Optimal conclusive teleportation of a d-dimensional unknown state

We formulate a conclusive teleportation protocol for a system in d-dimensional Hilbert space utilizing the positive operator valued measurement at the sending station. The conclusive teleportation protocol ensures some perfect teleportation events when the channel is only partially entangled, at the expense of lowering the overall average fidelity. We find the change of the fidelity as optimizing the conclusive teleportation events and discuss how much information remains in the inconclusive parts of the teleportation.Comment: 7 pages, 1 figure; figure correcte

Treatment of mixed (fresh and salt) wastewater

Hong Kong has the geographical advantage of being situated on the coast and therefore it is possible to use dual water supply systems (fresh + sea water systems in two separate distribution networks) for potable and non-potable uses. From the sea water supply system, about three quarters of the population in Hong Kong is supplied with salt water for toilet flushing. The seawater is extracted from the sea directly and pumped by pumping stations located near the shore and supplied to the households. The used toilet flushing water (saline wastewater) is discharged into the sewerage system which conducts the mixed (fresh + salt) wastewater into the STW (sewage treatment works). The salt concentration of the mixed wastewater is between 5,000 mg/l to 6,000 mg/l, about one-fifth of seawater salt concentration, in Hong Kong

Asymmetric quantum channel for quantum teleportation

There are a few obstacles, which bring about imperfect quantum teleportation of a continuous variable state, such as unavailability of maximally entangled two-mode squeezed states, inefficient detection and imperfect unitary transformation at the receiving station. We show that all those obstacles can be understood by a combination of an {\it asymmetrically-decohered} quantum channel and perfect apparatuses for other operations. For the asymmetrically-decohered quantum channel, we find some counter-intuitive results; one is that teleportation does not necessarily get better as the channel is initially squeezed more and another is when one branch of the quantum channel is unavoidably subject to some imperfect operations, blindly making the other branch as clean as possible may not result in the best teleportation result. We find the optimum strategy to teleport an unknown field for a given environment or for a given initial squeezing of the channel.Comment: 4pages, 1figur

Effects of stoichiometry, purity, etching and distilling on resistance of MgB2 pellets and wire segments

We present a study of the effects of non-stoichiometry, boron purity, wire diameter and post-synthesis treatment (etching and Mg distilling) on the temperature dependent resistance and resistivity of sintered MgB2 pellets and wire segments. Whereas the residual resistivity ratio (RRR) varies between RRR \~ 4 to RRR > 20 for different boron purity, it is only moderately affected by non-stoichiometry (from 20% Mg deficiency to 20% Mg excess) and is apparently independent of wire diameter and presence of Mg metal traces on the wire surface. The obtained set of data indicates that RRR values in excess of 20 and residual resistivities as low as rho{0} ~ 0.4 mu Ohm cm are intrinsic material properties of high purity MgB2

Virtual Community Informatics: A Review and Research Agenda

Divergent opinions exist on the basic understanding of the concept, virtual community. This study offers a working definition by examining different definitions, and proposes adoption of virtual community classifications. It also includes a summary of research conducted in the field. The research categorizes the different stages in virtual community growth to show the transition of research in this area. The results illustrate a paucity of technology development studies. We also investigate the extent of the adoption of informatics in these communities using a survey 200 virtual communities. The results indicate that discussion forum is the most popular tool adopted in virtual communities. The integration of the research review and tool adoption survey contributes to the generation of an agenda to direct future virtual community research