University of Western Australia

About: University of Western Australia is a education organization based out in Perth, Western Australia, Australia. It is known for research contribution in the topics: Population & Poison control. The organization has 29613 authors who have published 87405 publications receiving 3064466 citations. The organization is also known as: UWA & University of WA.

Sediment-Hosted Lead-Zinc Deposits in Earth History

Abstract: Sediment-hosted Pb-Zn deposits can be divided into two major subtypes. The first subtype is clastic-dominated lead-zinc (CD Pb-Zn) ores, which are hosted in shale, sandstone, siltstone, or mixed clastic rocks, or occur as carbonate replacement, within a CD sedimentary rock sequence. This subtype includes deposits that have been traditionally referred to as sedimentary exhalative (SEDEX) deposits. The CD Pb-Zn deposits occur in passive margins, back-arcs and continental rifts, and sag basins, which are tectonic settings that, in some cases, are transitional into one another. The second subtype of sediment-hosted Pb-Zn deposits is the Mississippi Valley-type (MVT Pb-Zn) that occurs in platform carbonate sequences, typically in passive-margin tectonic settings. Considering that the redox state of sulfur is one of the major controls on the extraction, transport, and deposition of Pb and Zn at shallow crustal sites, sediment-hosted Pb-Zn ores can be considered a special rock type that recorded the oxygenation of Earth’s hydrosphere. The emergence of CD and MVT deposits in the rock record between 2.02 Ga, the age of the earliest known deposit of these ores, and 1.85 to 1.58 Ga, a major period of CD Pb-Zn mineralization in Australia and India, corresponds to a time after the Great Oxygenation Event that occurred at ca 2.4 to 1.8 Ga. Contributing to the abundance of CD deposits at ca 1.85 to 1.58 Ga was the following: (1) enhanced oxidation of sulfides in the crust that provided sulfate to the hydrosphere and Pb and Zn to sediments; (2) development of major redox and compositional gradients in the oceans; (3) first formation of significant sulfate-bearing evaporites; (4) formation of red beds and oxidized aquifers, possibly containing easily extractable Pb and Zn; (5) evolution of sulfate-reducing bacteria; and (6) formation of large and long-lived basins on stable cratons. Although MVT and CD deposits appeared for the first time in Earth history at 2.02 Ga, only CD deposits were important repositories for Pb and Zn in sediments between the Great Oxygenation Event, until after the second oxidation of the atmosphere in the late Neoproterozic. Increased oxygenation of the oceans following the second oxidation event led to an abundance of evaporites, resulting oxidized brines, and a dramatic increase in the volume of coarse-grained and permeable carbonates of the Paleozoic carbonate platforms, which host many of the great MVT deposits. The MVT deposits reached their maximum abundance during the final assembly of Pangea from Devonian into the Carboniferous. This was also a time for important CD mineral deposit formation along passive margins in evaporative belts of Pangea. Following the breakup of Pangea, a new era of MVT ores began with the onset of the assembly of the Neosupercontinent. A significant limitation on interpreting the secular distribution of the deposits is that there is no way to quantitatively evaluate the removal of deposits from the rock record through tectonic recycling. Considering that most of the sedimentary rock record has been recycled, most sediment-hosted Pb-Zn deposits probably have also been destroyed by subduction and erosion, or modified by metamorphism and tectonism, so that they are no longer recognizable. Thus, the uneven secular distribution of sediment-hosted Pb-Zn deposits reflects the genesis of these deposits, linked to Earth’s evolving tectonic and geochemical systems, as well as an unknown amount of recycling of the sedimentary rock record.

Young Children Understand That Looking Leads to Knowing (So Long as They Are Looking into a Single Barrel)

Abstract: 3 experiments were conducted to investigate the claim made by Wimmer, Hogrefe, and Perner that 3-4-year-old children do not understand that people gain knowledge about something by looking at it. The first experiment involved a simple forced-choice procedure in which children had to judge which of 2 assistants knew what was inside a box when one of the assistants had looked inside and the other had lifted it up. In this experiment, the children did realize that the assistant who had looked in the box knew its contents. The second experiment followed the Wimmer et al. procedure, but with a simpler question form. The children were just asked to state whether someone knew what was in the box. Again, the children were able to work out that a person who had looked in a box knew what was inside it. In the third experiment, a direct comparison was made between the simpler question and the more complex, double-barreled question asked by Wimmer et al. The children found the more complex question considerably harder. The results of these experiments suggest that, in contrast to the claims made by Wimmer et al., 3- and 4-year-old children do understand that looking leads to knowing, and that their difficulty in the Wimmer et al. study was mainly with the form of the question that they were asked.

Activation of Protease-Activated Receptor (PAR)-1, PAR-2, and PAR-4 Stimulates IL-6, IL-8, and Prostaglandin E2 Release from Human Respiratory Epithelial Cells

Abstract: Epithelia from many tissues express protease-activated receptors (PARs) that play a major role in several different physiological processes In this study, we examined their capacity to modulate IL-6, IL-8, and PGE 2 production in both the A459 and BEAS-2B cell lines and primary human bronchial epithelial cells (HBECs) All three cell types expressed PAR-1, PAR-2, PAR-3, and PAR-4, as judged by RT-PCR and immunocytochemistry Agonist peptides corresponding to the nascent N termini of PAR-1, PAR-2, and PAR-4 induced the release of cytokines from A549, BEAS-2B, and HBECs with a rank order of potency of PAR-2 > PAR-4 > PAR-1 at 400 μM PAR-1, PAR-2, and PAR-4 also caused the release of PGE 2 from A549 and HBECs The PAR-3 agonist peptide was inactive in all systems tested PAR-1, PAR-2, or PAR-4, in combination, caused additive IL-6 release, but only the PAR-1 and PAR-2 combination resulted in an additive IL-8 response PAR peptide-induced responses were accompanied by changes in intracellular calcium ion concentrations However, Ca 2+ ion shutoff was ∼2-fold slower with PAR-4 than with PAR-1 or PAR-2, suggesting differential G protein coupling Combined, these data suggest an important role for PAR in the modulation of inflammation in the lung

Mechanisms of Cl- transport contributing to salt tolerance

Abstract: Mechanisms of Cl(-) transport in plants are poorly understood, despite the importance of minimizing Cl(-) toxicity for salt tolerance. This review summarizes Cl(-) transport processes in plants that contribute to genotypic differences in salt tolerance, identifying key traits from the cellular to whole-plant level. Key aspects of Cl(-) transport that contribute to salt tolerance in some species include reduced net xylem loading, intracellular compartmentation and greater efflux of Cl(-) from roots. We also provide an update on the biophysics of anion transport in plant cells and address issues of charge balance, selectivity and energy expenditure relevant to Cl(-) transport mechanisms. Examples are given of anion transport systems where electrophysiology has revealed possible interactions with salinity. Finally, candidate genes for anion transporters are identified that may be contributing to Cl(-) movement within plants during salinity. This review integrates current knowledge of Cl(-) transport mechanisms to identify future pathways for improving salt tolerance.