Final Narrative

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Rietveld refinement of the crystal structures of Rb2X Si5O12 (X = Ni, Mn)

The synthetic leucite silicate framework mineral analogues Rb2XSi5O12 {X = Ni [dirubidium nickel(II) pentasilicate] and Mn [dirubidium manganese(II) pentasilicate]} have been prepared by high-temperature solid-state synthesis. The results of Rietveld refinements, using X-ray powder diffraction data collected using Cu K[alpha] X-rays, show that the title compounds crystallize in the space group Pbca and adopt the cation-ordered structure of Cs2CdSi5O12 and other leucites. The structures consist of tetrahedral SiO4 and XO4 units sharing corners to form a partially substituted silicate framework. Extraframework Rb+ cations sit in channels in the framework. All atoms occupy the 8c general position for this space group. In these refined structures, silicon and X atoms are ordered onto separate tetrahedrally coordinated sites (T-sites). However, the Ni displacement parameter and the Ni—O bond lengths suggest that for the X = Ni sample, there may actually be some T-site cation disorder

Up for Grabs: The State of Fossils Protection in (Recently) Unprotected National Monuments

On December 4, 2017, President Trump removed 2 million acres of land from the Bears Ears and Grand Staircase-Escalante national monuments. President Trump justified the reductions in part by claiming that many of the objects contained in the original monuments were already protected by other federal laws, and that the protections previously afforded to sixty-three percent of the land in the two original monuments were “unnecessary for the care and management of the objects to be protected within the monument[s].” This article explains why, contrary to the President’s assertions, plant and invertebrate fossils on the more than two million acres of land that were excluded from the monuments now receive less protection than when they were included in the monuments

HDAC inhibitors increase NRF2-signaling in tumour cells and blunt the efficacy of co-adminstered cytotoxic agents

The NRF2 signalling cascade provides a primary response against electrophilic chemicals and oxidative stress. The activation of NRF2-signaling is anticipated to have adverse clinical consequences; NRF2 is activated in a number of cancers and, additionally, its pharmacological activation by one compound can reduce the toxicity or efficiency of a second agent administered concomitantly. In this work, we have analysed systematically the ability of 152 research, pre-clinical or clinically used drugs to induce an NRF2 response using the MCF7-AREc32 NRF2 reporter. Ten percent of the tested drugs induced an NRF2 response. The NRF2 activators were not restricted to classical cytotoxic alkylating agents but also included a number of emerging anticancer drugs, including an IGF1-R inhibitor (NVP-AEW541), a PIM-1 kinase inhibitor (Pim1 inhibitor 2), a PLK1 inhibitor (BI 2536) and most strikingly seven of nine tested HDAC inhibitors. These findings were further confirmed by demonstrating NRF2-dependent induction of endogenous AKR genes, biomarkers of NRF2 activity. The ability of HDAC inhibitors to stimulate NRF2-signalling did not diminish their own potency as antitumour agents. However, when used to pre-treat cells, they did reduce the efficacy of acrolein. Taken together, our data suggest that the ability of drugs to stimulate NRF2 activity is common and should be investigated as part of the drug-development process

Rietveld refinements of the crystal structures of Rb2XSi5O12 (X = Mn, Ni)

Poster Number: CCG06 Synthetic analogues of the silicate framework mineral leucite (KAlSi2O6) with the stoichiometry Rb2XSi5O12 (X = Mn, Ni) have been prepared by high temperature solid-state synthesis. Ambient temperature X-ray powder diffraction data have been collected on these samples. Analysis of these powder diffraction data show that these samples both consist of single phases [1] isostructural with the Pbca cation-ordered framework leucite structure of Cs2CdSi5O12 [2]. Rietveld refinement [3] shows that for X = Mn this crystal structure has complete Mn and Si cation order over the tetrahredrally coordinated sites (T-sites) in the silicate framework. However, for X = Ni, Rietveld refinement suggests that there may be some Ni and Si cation T-site cation disorder

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