Effect of weathering product assemblages on Pb bioaccessibility in mine waste: implications for risk management

General assessments of orebody types and associated mine wastes with regards to their environmental signature and human health hazards are needed to help managing present and historical mine waste facilities. Bioaccessibility tests and mineralogical analysis were carried out on mine waste from a systematic sampling of mine sites from the Central Wales orefield, UK. The bioaccessible Pb widely ranged from 270 to 20300 mg/kg (mean 7250 mg/kg; median 4890 mg/kg) and the bioaccessible fraction from 4.53 % to >100 % (mean 33.2 %; median 32.2 %), with significant (p=0.001) differences among the mine sites. This implies sensitivity of bioaccessibility to site-specific conditions and suggests caution in the use of models to assess human health impacts generalised on the basis of the mineral deposit type. Mineralogical similarities of the oxidation products of primary galena provided a better control over the observed Pb bioaccessibility range. The higher Pb bioaccessibility (%) was related to samples containing cerussite, irrespective of the presence of other Pb minerals in the mineral assemblage; lower Pb bioaccessibility resulted where anglesite was the main Pb mineral phase and cerussite was absent. A solubility diagram for the various Pb minerals in the waste was derived using PHREEQC model and the experimental Pb concentration measured in the simulated gastric solution compared with the equilibrium modelling results. For samples containing cerussite, the model well predicted the soluble Pb concentrations measured in the experimental simulated gastric solution, indicative of the carbonate mineral phase control on the Pb in solution for these samples and little kinetic control on the dissolution of cerussite. On the contrary, most mine waste samples containing dominant anglesite and or plumbojarosite (no cerussite) had lower solution Pb values, falling at or below the anglesite and plumbojarosite solubility equilibrium concentrations, implying kinetic or textural factors hindering the dissolution

Switching on Flowers: Transient LEAFY Induction Reveals Novel Aspects of the Regulation of Reproductive Development in Arabidopsis

Developmental fate decisions in cell populations fundamentally depend on at least two parameters: a signal that is perceived by the cell and the intrinsic ability of the cell to respond to the signal. The same regulatory logic holds for phase transitions in the life cycle of an organism, for example the switch to reproductive development in flowering plants. Here we have tested the response of the monocarpic plant species Arabidopsis thaliana to a signal that directs flower formation, the plant-specific transcription factor LEAFY (LFY). Using transient steroid-dependent LEAFY (LFY) activation in lfy null mutant Arabidopsis plants, we show that the plant’s competence to respond to the LFY signal changes during development. Very early in the life cycle, the plant is not competent to respond to the signal. Subsequently, transient LFY activation can direct primordia at the flanks of the shoot apical meristem to adopt a floral fate. Finally, the plants acquire competence to initiate the flower-patterning program in response to transient LFY activation. Similar to a perennial life strategy, we did not observe reprogramming of all primordia after perception of the transient signal, instead only a small number of meristems responded, followed by reversion to the prior developmental program. The ability to initiate flower formation and to direct flower patterning in response to transient LFY upregulation was dependent on the known direct LFY target APETALA1 (AP1). Prolonged LFY or activation could alter the developmental gradient and bypass the requirement for AP1. Prolonged high AP1 levels, in turn, can also alter the plants’ competence. Our findings shed light on how plants can fine-tune important phase transitions and developmental responses

Die Wirkung der Familiarität in Abhängigkeit vom Kontext

Die bloße Darbietung von ursprünglich unbekannten Objekten kann dazu führen, dass die Objekte eine zunehmend positive Wirkung haben. Dieser sogenannte Mere-exposure-Effekt wie auch gegenläufige Effekte einer Abnahme der Beliebtheit wiederholt gezeigter Objekte bilden das Thema der Arbeit. Im Mittelpunkt steht die Frage, inwieweit Tendenzen der Beliebtheitszunahme wie auch der Beliebtheitsabnahme durch die wiederholte Präsentation von Stimuli unterschiedlich ausfallen, wenn der jeweilige Bewertungskontext eher bekannt oder unbekannt ist. Es wird angenommen, dass mehr oder weniger häufig gezeigte Objekte vor allem dann eine besonders positive oder auch negative Wirkung haben, wenn sie auf dem Hintergrund von deutlich weniger häufig oder nicht gezeigten Objekten zu bewerten sind. Diese Annahme einer unterschiedlichen Wirkung der Familiarität in Abhängigkeit vom Kontext wurde im Rahmen von drei am Computer durchgeführten Experimenten empirisch geprüft. Als Untersuchungsgegenstand dienten chinesische Schriftzeichen, die zunächst in unterschiedlicher Häufigkeit dargeboten wurden und anschließend zu beurteilen waren. Variiert wurden in erster Linie die Darbietungshäufigkeit und die Komplexität der Schriftzeichen sowie die Familiarität des jeweiligen Bewertungskontexts. Dabei war zu beobachten, dass sowohl Tendenzen der Beliebtheitszunahme wie auch solche der Beliebtheitsabnahme von Objekten mit zunehmender Darbietungshäufigkeit in Abhängigkeit von der Kontextfamiliarität unterschiedlich ausfallen. Eine besonders positive oder auch negative Bewertung von häufig präsentierten Schriftzeichen zeigt sich vor allem dann, wenn die den Kontext bildenden Zeichen unbekannt sind. Diese Befunde können als erster Beleg dafür betrachtet werden, dass Effekte der Familiarität auf die Wirkung von Objekten davon abhängig sind, wie bekannt oder unbekannt der jeweilige Bewertungskontext ist

TwinLife survey methodology and fieldwork outcomes. Telephone survey of wave 1 subsample b (CATI 1b)

Lesaar S, Prussog-Wagner A, Hess D. TwinLife survey methodology and fieldwork outcomes. Telephone survey of wave 1 subsample b (CATI 1b). TwinLife Technical Report Series. Vol 09 v1.0.0. Bielefeld: Project TwinLife "Genetic and social causes of life chances" (Universität Bielefeld / Universität des Saarlandes); 2020.Presented by infas Institut für angewandte Sozialwissenschaft Gmb

TwinLife survey methodology and fieldwork outcomes. Face-to-face survey of wave 2 (F2F 2a/b)

Lesaar S, Prussog-Wagner A, Hess D. TwinLife survey methodology and fieldwork outcomes. Face-to-face survey of wave 2 (F2F 2a/b). TwinLife Technical Report Series. Vol 10 v1.0.0. Bielefeld: Project TwinLife "Genetic and social causes of life chances" (Universität Bielefeld / Universität des Saarlandes); 2020.Presented by infas Institut für angewandte Sozialwissenschaft Gmb

Einführung von Dreiecken in der Unterstufe

Die vorliegende Diplomarbeit widmet sich einer Untersuchung zum Vergleich der Lerneffizienz von Unterrichtsmethoden: Frontalunterricht, offenes Lernen. Diese wird anhand des Themas „Einführung von Dreiecken“ durchgeführt. Zunächst geht es darum die Unterrichtsmethode Frontalunterricht mit all ihren Vor- und Nachteilen genauer zu beschreiben. Anschließend werden die verschiedenen Unterrichtsformen von offenem Lernen vorgestellt und kurz erläutert. In weiterer Folge wird die offene Unterrichtsform „Stationenbetrieb“ hinsichtlich ihrer Lernchancen, Schwierigkeiten, Gestaltung, Planung und Durchführung genauer beschrieben. Im Zuge einer empirischen Untersuchung einer zweiten Klasse eines Gymnasiums konnte schließlich anhand des Themenschwerpunktes „Einführung von Dreiecken“ die lerneffizientere Unterrichtsmethode herausgefunden werden. Die offene Unterrichtsform “Stationenbetrieb” zeigte dabei die besseren Ergebnisse.The current thesis is dedicated to a study to compare the more efficient teaching method: frontal or open learning. This is determined on the basis of the subject “Introduction of Triangles”. First, the frontal teaching method is described in more detail with all its advantages and disadvantages. Then the different forms of teaching for open learning will be presented and briefly discussed. Subsequently, the open form of instruction, called “station operation”, is described with regards to further planning and implementation and its learning opportunities, difficulties, design. In an empirical study of a second class in a “Gymnasium”, the more efficient teaching method was detected based on the subject matter “Introduction of Triangles”. The open form of instruction "station operation" showed better results

Chromophore-bearing NH_2-terminal domains of phytochromes A and B determine their photosensory specificity and differential light lability

In early seedling development, far-red-light-induced deetiolation is mediated primarily by phytochrome A (phyA), whereas red-light-induced deetiolation is mediated primarily by phytochrome B (phyB). To map the molecular determinants responsible for this photosensory specificity, we tested the activities of two reciprocal phyA/phyB chimeras in diagnostic light regimes using overexpression in transgenic Arabidopsis. Although previous data have shown that the NH_2-terminal halves of phyA and phyB each separately lack normal activity, fusion of the NH_2-terminal half of phyA to the COOH-terminal half of phyB (phyAB) and the reciprocal fusion (phyBA) resulted in biologically active phytochromes. The behavior of these two chimeras in red and far-red light indicates: (i) that the NH2-terminal halves of phyA and phyB determine their respective photosensory specificities; (ii) that the COOH-terminal halves of the two photoreceptors are necessary for regulatory activity but are reciprocally inter-changeable and thus carry functionally equivalent determinants; and (iii) that the NH_2-terminal halves of phyA and phyB carry determinants that direct the differential light lability of the two molecules. The present findings suggest that the contrasting photosensory information gathered by phyA and phyB through their NH_2-terminal halves may be transduced to downstream signaling components through a common biochemical mechanism involving the regulatory activity of the COOH-terminal domains of the photoreceptors

Red-bed bleaching in a CO2 storage analogue: insights from Entrada Sandstone fracture-hosted mineralization

Improving our ability to predict the interactions between CO2 and reservoir rocks at geological time scales is of key importance if carbon capture and storage (CCS) is to have a role in climate-change mitigation, particularly in the light of likely regulatory requirements. Understanding and identifying the relevant geological processes over long time scales can be obtained only at natural-analogue sites. At one such site, in the Salt Wash Graben area of Utah, USA, widespread bleaching affects the Middle Jurassic red-bed “wet dune” Entrada Sandstone. Previous work has proposed a genetic link between the bleaching and spatially concomitant recent and modern CO2-rich fluids. The results presented here challenge some of the previous models and come from a detailed petrographic examination of mineralized fractures in the Entrada Sandstone that are centered in vertical extensions to the bleaching. These fractures typically contain complex mineralization assemblages. Pyrite was a paragenetically early phase, identifiable from common pseudomorphs of mixed iron oxides and oxyhydroxides that rarely contain relict pyrite. The pyrite contains up to 3 wt% arsenic. The volume of fracture-adjacent bleached sandstone is sufficient to have been the source of iron for the pyrite originally present in the fracture. The pyrite pseudomorphs occur at the center of fracture- and pore-filling cements that comprise intergrowths of hematite–goethite–jarosite–gypsum, an assemblage that suggests that their formation resulted from the oxidative alteration of pyrite, a genetic link supported by the arsenic present in the iron-bearing minerals. The presence of jarosite and proximal removal of earlier, sandstone-hosted carbonates are consistent with, and indicative of, the low-pH conditions associated with pyrite oxidation reactions. Calcite- and gypsum-cemented fractures crosscut, and contain fragments of, the pyrite-pseudomorphic and -oxidation assemblages, proving that they postdate pyrite formation and its subsequent oxidation, and that pyrite oxidation was not a result of modern weathering reactions. In outcrop, some calcite- and gypsum-cemented fractures link with travertine deposits associated with the modern and recent CO2-rich fluids. The mineral assemblages observed here, and the paragenetic sequence that we have inferred, suggest that the fracture-associated bleaching patterns result from the fracture-fed movement of sulfur-bearing reducing fluids, with hydrogen sulfide the most likely bleaching agent. We conclude that bleaching adjacent to fractures is not genetically related to modern CO2-bearing fluids despite the spatial relationship. The bleaching was already present when the modern fluids utilized the same fracture-based fluid pathways. We suggest that the more widespread regional bleaching formed contemporaneously with the fracture bleaching and followed similar mechanisms. This study highlights the complexity of interpreting analogue sites and the importance of using field and petrographic observations to unravel textures and events that are juxtaposed spatially but not temporally