The extensive hydrocarbon-mediated fixation of hydrothermal gold in the Witwatersrand Basin, South Africa

Abstract There is a close spatial relation between high-grade gold mineralization in the Witwatersrand basin and carbonaceous nodules, veins and seams. Hydrocarbons thus may well have been essential in ore genesis. We have sampled four major gold-, uranium- and hydrocarbon-bearing ore horizons, namely the Carbon Leader, Vaal, B and Black reefs, to determine the role of hydrocarbons in the accumulation and hydrothermal fixation of gold. Our multipronged approach included high-resolution scanning and transmission electron microscopy (SEM, TEM), nanotomography with video clips, and geochemical modeling. Post-depositional hydrothermal activity at the peak of regional metamorphism produced an assemblage of quartz, phyllosilicates, brannerite, crandallite, florencite, monazite and gold in all four reefs. The gold, hydrocarbons and associated mineral assemblages are closely related on the micro to nano scale. Gold deposition occurred in interstices, as fracture fillings in detrital minerals, and on the surface of migrated solid hydrocarbon residues. The spherical to elliptical inclusions in the gold consist of an outer pyrobitumen phase and a central void space, partially associated with nanometric gold, uraninite, coffinite and silica. The hydrocarbon-bearing inclusion likely formed by the entrapment of a fossil liquid oil precursor during gold precipitation. The oil was subsequently thermally altered and converted into the final pyrobitumen and gaseous residues. Geochemical calculations to simulate the interaction of an invading hot hydrothermal fluid with the hydrocarbons in the reefs reveal that a very small amount of hydrocarbons will drastically decrease the aqueous solubility of gold and hence cause its instant precipitation. We extend our genetic model for the epigenetic formation of gold in the Witwatersrand. Regional metamorphism promoted the extensive and likely basin-wide circulation of hydrothermal fluids; these were capable of mobilizing substantial amounts of gold. The liquid, gaseous and solid hydrocarbons in the reefs acted as efficient chemical traps for the concentration of gold. Being strong chemical reductants, they caused the rapid precipitation and accumulation of gold on the surface of the fossil oil droplets and already solidified hydrocarbons. The release of the gases from accessible hydrocarbons into the sediments away from their source buffered the redox state of the hydrothermal solutions even at a considerable distance from the pyrobitumen seams and veins, likely resulting in the deposition of gold in the absence of visible hydrocarbons. Although our findings do not explain the ultimate origin and exceptional endowment of gold in the Witwatersrand, we do provide intriguing evidence for the large-scale hydrothermal mobilization, accumulation and fixation of gold mediated by hydrocarbons during post-depositional metamorphism

An in vivo evaluation of Brilliant Blue G in animals and humans

Background/Aims: To evaluate the retinal toxicity of Brilliant Blue G (BBG) following intravitreal injection in rat eyes and examine the biocompatibility and the staining properties in humans.Methods: BBG was injected into the 11 rat eyes to evaluate toxic effects with balanced salt solution (BSS) serving as control. Retinal toxicity was assessed by retinal ganglion cell (RGC) counts and by light microscopy 7 days later. In addition, BBG was applied during vitrectomy for macular hole (MH) (n = 15) or epiretinal membranes (ERM) (n = 3) in a prospective, non-comparative consecutive series of patients. Before and after surgery, all patients underwent a complete clinical examination including measurement of best corrected visual acuity (VA) and intraocular pressure, perimetry, fundus photography and optical coherence tomography. Patients were seen 1 day before surgery and then in approximately four weeks intervals.Results: No significant reduction in RGC numbers and no morphological alterations were noted. A sufficient staining of the internal limiting membrane (ILM) was seen in patients with MH, while the staining pattern in ERM cases was patchy, indicating that parts of the ILM were peeled off along with the ERM in a variable extent. All MHs could be closed successfully. VA improved in 10 eyes (56%; 8/15 MH patients, 2/3 ERM patients), was unchanged in four eyes (22%; all MH patients) and was reduced in four eyes (22%; 3/15 MH, 1/3 ERM). No toxic effects attributable to the dye were noted during patient follow-up. The ultrastructure of tissue harvested during surgery was unremarkable.Conclusion: Brilliant Blue provides a sufficient and selective staining of the ILM. No retinal toxicity or adverse effects related to the dye were observed in animal and human studies. The long-term safety of this novel dye will have to be evaluated in larger patient series and a longer follow-up

On the Estimation of True State Dependence in the Persistence of Innovation

This paper explores the persistence often found in firms’ innovation and advances current research by investigating its actual nature. Previous studies have aimed at disentangling true state dependence from spurious state dependence by using a random effects (RE) dynamic panel probit approach, thereby imposing strong conditions on the underlying structure of the unobserved heterogeneity. Building on recent advances in the econometric literature, which allows for true fixed effects estimation of dynamic nonlinear panel data models, we demonstrate that relaxing the assumptions on the unobserved heterogeneity can have a considerable effect on the estimates of true state dependence. While we confirm the existence of a strong persistence of innovation in firms, we however find that true state dependence only explains about half of the persistent behaviour displayed by firms; this is in contrast to the popular RE methodology that attributes 70% to 100% of persistence to true state dependence. Our results suggest that policy programs aimed at encouraging initial innovations alone are useful but may not possess a long-term stimulating effect on innovation activity

The role of NPOs and international actors in the national innovation system: A network-based approach

This paper conducts an explorative analysis of the UK's nanotechnology research collaboration network to understand the contributions of the different institutions in the development and generation of knowledge. Framed in the National Innovation System (NIS) and the Triple Helix (TH) model literature, this paper makes use of social network analysis (SNA) tools to identify the role and involvement of different institutional actors in the interactions and collaborations within the nanotechnology network. Building on the traditional university–industry–government three-helix interaction model, our paper includes two extra dimensions in the model to account for the increase in international collaboration and the increasingly important role of non-profit organizations (NPOs) in knowledge generation. In this way, our paper responds to recent calls to adapt the traditional NIS models to reflect the new realities of scientific collaboration

Mapping the entrepreneurial university literature: a text mining approach

Since the introduction of the concept of entrepreneurial university in 1980s, the number of studies has dramatically increased, in particular since 2015. This had made the literature on the entrepreneurial university complex, fragmented and difficult to navigate. This paper provides a comprehensive review of all topics covered in the body of literature on the entrepreneurial university and identifies the most salient topics and papers within this literature, making use of text-mining techniques. Our paper employs topic modelling that reveals the underlying semantic structure of texts to identify the different underlying. Our study systematically analyses 1,110 papers over the period 1983–2020 using the Latent Dirichlet Allocation algorithm. Our analysis shows that the entrepreneurial university is fragmented around different topics that are very diverse. We find a total of 20 differentiated topics. Our study suggests that topics related to the overarching theme of academic entrepreneurship, in particular to commercialisation of research and the triple helix model are very popular within the entrepreneurial university literature. Finally, our analysis reveals that case-study type of research is losing momentum, giving path to nascent topics of research in the areas of entrepreneurial capability and university-industry alliances, which are becoming very popular within the entrepreneurial university literature

Belastungen von Kindern, Jugendlichen und Eltern in der Corona-Pandemie

Die Studie beschäftigt sich mit den psychosozialen Belastungen von Eltern, Kindern und Jugendlichen während der Lockdown-Phasen in Deutschland seit Beginn der Corona-Pandemie. Der Fokus liegt hierbei auf den Auswirkungen der Kontaktbeschränkungen und Schulschließungen auf den mentalen und psychischen Gesundheitszustand. Vor allem für Kinder und Jugendliche sind in dieser Zeit viele alltagssichernde Strukturen weggebrochen, welche langfristige Konsequenzen für ihr persönliches Wohlbefinden und ihre Entwicklung nach sich ziehen könnten. Die zugrundeliegenden Daten sind zum einen Metadaten, welche den aktuellen Forschungsstand zu diesem Thema wiedergeben. Zudem erfolgen auch eigene Analysen mit längsschnittlichen und repräsentativen Daten des deutschen Beziehungs- und Familienpanels pairfam und deren COVID-19-Zusatzbefragung. Diese Befunde dienen dazu einen Überblick über die Lage von Eltern, Kindern und Jugendlichen zu geben, um letztlich adäquate politische und gesellschaftliche Maßnahmen und Handlungsempfehlungen ableiten zu können

THE TOOLS AND MONTE CARLO WORKING GROUP Summary Report from the Les Houches 2009 Workshop on TeV Colliders

This is the summary and introduction to the proceedings contributions for the Les Houches 2009 "Tools and Monte Carlo" working group.Comment: 144 Pages. Workshop site http://wwwlapp.in2p3.fr/conferences/LesHouches/Houches2009/ . Conveners were Butterworth, Maltoni, Moortgat, Richardson, Schumann and Skand

Falsification Of The Atmospheric CO2 Greenhouse Effects Within The Frame Of Physics

The atmospheric greenhouse effect, an idea that many authors trace back to the traditional works of Fourier (1824), Tyndall (1861), and Arrhenius (1896), and which is still supported in global climatology, essentially describes a fictitious mechanism, in which a planetary atmosphere acts as a heat pump driven by an environment that is radiatively interacting with but radiatively equilibrated to the atmospheric system. According to the second law of thermodynamics such a planetary machine can never exist. Nevertheless, in almost all texts of global climatology and in a widespread secondary literature it is taken for granted that such mechanism is real and stands on a firm scientific foundation. In this paper the popular conjecture is analyzed and the underlying physical principles are clarified. By showing that (a) there are no common physical laws between the warming phenomenon in glass houses and the fictitious atmospheric greenhouse effects, (b) there are no calculations to determine an average surface temperature of a planet, (c) the frequently mentioned difference of 33 degrees Celsius is a meaningless number calculated wrongly, (d) the formulas of cavity radiation are used inappropriately, (e) the assumption of a radiative balance is unphysical, (f) thermal conductivity and friction must not be set to zero, the atmospheric greenhouse conjecture is falsified.Comment: 115 pages, 32 figures, 13 tables (some typos corrected