An X-ray magnetic circular dichroism (XMCD) study of Fe ordering in a synthetic MgAl<inf>2</inf>O<inf>4</inf>-Fe<inf>3</inf>O<inf>4</inf> (spinel-magnetite) solid-solution series: Implications for magnetic properties and cation site ordering

© 2016 by Walter de Gruyter Berlin/Boston. Fe L2,3-edge XAS and XMCD studies have been used to unravel structural trends in the MgAl2O4-Fe3O4 solid solution where thermodynamic modeling has presented a challenge due to the complex ordering arrangements of the end-members. Partitioning of Fe3+ and Fe2+ between tetrahedral (Td) and octahedral (Oh) sites has been established. In the most Fe-rich samples, despite rapid quenching from a disordered state, FeTd2+ is not present, which matches the ordered, inverse spinel nature of end-member magnetite (Mgt) at room temperature. However, in intermediate compositions Al and Mg substantially replace Fe and small amounts of FeTd2+ are found, stabilized, or trapped by decreasing occurrence of the continuous nearest neighbor Fe-Fe interactions that facilitate charge redistribution by electron transfer. Furthermore, in the composition range ~Mgt0.4-0.9, XAS and XMCD bonding and site occupancy data suggest that nanoscale, magnetite-like Fe clusters are present. By contrast, at the spinel-rich end of the series, Mgt0.17 and Mgt0.23 have a homogeneous long-range distribution of Fe, Mg, and Al. These relationships are consistent with the intermediate and Fe-rich samples falling within a wide solvus in this system such that the Fe-clusters occur as proto-nuclei for phases that would exsolve following development of long-range crystalline order during slow cooling. Unit-cell edges calculated from the spectroscopy-derived site occupancies show excellent agreement with those measured by X-ray powder diffraction on the bulk samples. Calculated saturation magnetic moments (Ms) for the Fe-rich samples also show excellent agreement with measured values but for the most Mg-rich samples are displaced to slightly higher values; this displacement is due to the presence of abundant Mg and Al disrupting the anti-parallel alignment of electron spins for Fe atoms.We thank Richard Pattrick and Vicky Coker for help in collecting XMCD on these samples at the Daresbury SRS and subsequently at the Advanced Light Source (ALS), Berkeley. The ALS is supported by the Director, Office of Science, Office of Basic Energy Sciences (OBES) of the U.S. Department of Energy (DOE) under Contract No. DE-AC02-05CH11231 and we thank Elke Arenholz for her assistance. RJH acknowledges funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement No. 320750. KMR gratefully acknowledges support from the DOE OBES Chemical Sciences, Geosciences, and Biosciences Division, through the Geosciences Program at Pacific Northwest National Laboratory. We also thank Gerrit van der Laan and Nick Telling for help with XMCD data analysis; David Plant carried out the electron microprobe analyses at Manchester and Paul Schofield provided information on the natural magnesian spinel. We also thank two anonymous referees for constructive comments

Impact of the Diamond Light Source on research in Earth and environmental sciences: current work and future perspectives.

Diamond Light Source Ltd celebrated its 10th anniversary as a company in December 2012 and has now accepted user experiments for over 5 years. This paper describes the current facilities available at Diamond and future developments that enhance its capacities with respect to the Earth and environmental sciences. A review of relevant research conducted at Diamond thus far is provided. This highlights how synchrotron-based studies have brought about important advances in our understanding of the fundamental parameters controlling highly complex mineral–fluid–microbe interface reactions in the natural environment. This new knowledge not only enhances our understanding of global biogeochemical processes, but also provides the opportunity for interventions to be designed for environmental remediation and beneficial use

Dense breast stromal tissue shows greatly increased concentration of breast epithelium but no increase in its proliferative activity

INTRODUCTION: Increased mammographic density is a strong risk factor for breast cancer. The reasons for this are not clear; two obvious possibilities are increased epithelial cell proliferation in mammographically dense areas and increased breast epithelium in women with mammographically dense breasts. We addressed this question by studying the number of epithelial cells in terminal duct lobular units (TDLUs) and in ducts, and their proliferation rates, as they related to local breast densities defined histologically within individual women. METHOD: We studied deep breast tissue away from subcutaneous fat obtained from 12 healthy women undergoing reduction mammoplasty. A slide from each specimen was stained with the cell-proliferation marker MIB1. Each slide was divided into (sets of) areas of low, medium and high density of connective tissue (CT; highly correlated with mammographic densities). Within each of the areas, the numbers of epithelial cells in TDLUs and ducts, and the numbers MIB1 positive, were counted. RESULTS: The relative concentration (RC) of epithelial cells in high compared with low CT density areas was 12.3 (95% confidence interval (CI) 10.9 to 13.8) in TDLUs and 34.1 (95% CI 26.9 to 43.2) in ducts. There was a much smaller difference between medium and low CT density areas: RC = 1.4 (95% CI 1.2 to 1.6) in TDLUs and 1.9 (95% CI 1.5 to 2.3) in ducts. The relative mitotic rate (RMR; MIB1 positive) of epithelial cells in high compared with low CT density areas was 0.59 (95% CI 0.53 to 0.66) in TDLUs and 0.65 (95% CI 0.53 to 0.79) in ducts; the figures for the comparison of medium with low CT density areas were 0.58 (95% CI 0.48 to 0.70) in TDLUs and 0.66 (95% CI 0.44 to 0.97) in ducts. CONCLUSION: Breast epithelial cells are overwhelmingly concentrated in high CT density areas. Their proliferation rate in areas of high and medium CT density is lower than that in low CT density areas. The increased breast cancer risk associated with increased mammographic densities may simply be a reflection of increased epithelial cell numbers. Why epithelium is concentrated in high CT density areas remains to be explained

Physiology and biochemistry of reduction of azo compounds by Shewanella strains relevant to electron transport chain

Azo dyes are toxic, highly persistent, and ubiquitously distributed in the environments. The large-scale production and application of azo dyes result in serious environmental pollution of water and sediments. Bacterial azo reduction is an important process for removing this group of contaminants. Recent advances in this area of research reveal that azo reduction by Shewanella strains is coupled to the oxidation of electron donors and linked to the electron transport and energy conservation in the cell membrane. Up to date, several key molecular components involved in this reaction have been identified and the primary electron transportation system has been proposed. These new discoveries on the respiration pathways and electron transfer for bacterial azo reduction has potential biotechnological implications in cleaning up contaminated sites

Synthesis of an ordered mesoporous carbon with graphitic characteristics and its application for dye adsorption

An ordered mesoporous carbon (OMC) was prepared by a chemical vapor deposition technique using liquid petroleum gas (LPG) as the carbon source. During synthesis, LPG was effectively adsorbed in the ordered mesopores of SBA-15 silica and converted to a graphitic carbon at 800 °C. X-ray diffraction and nitrogen adsorption/desorption data and high-resolution transmission electron microscopy (HRTEM) of the OMC confirmed its ordered mesoporous structure. The OMC was utilized as an adsorbent in the removal of dyes from aqueous solution. A commercial powder activated carbon (AC) was also investigated to obtain comparative data. The efficiency of the OMC for dye adsorption was tested using acidic dye acid orange 8 (AO8) and basic dyes methylene blue (MB) and rhodamine B (RB). The results show that adsorption was affected by the molecular size of the dye, the textural properties of carbon adsorbent and surface-dye interactions. The adsorption capacities of the OMC for acid orange 8 (AO8), methylene blue (MB) and rhodamine B (RB) were determined to be 222, 833, and 233 mg/g, respectively. The adsorption capacities of the AC for AO8, MB, and RB were determined to be 141, 313, and 185 mg/ g, respectively. The OMC demonstrated to be an excellent adsorbent for the removal of MB from wastewater.Web of Scienc

Tagging single-nucleotide polymorphisms in candidate oncogenes and susceptibility to ovarian cancer

Low–moderate risk alleles that are relatively common in the population may explain a significant proportion of the excess familial risk of ovarian cancer (OC) not attributed to highly penetrant genes. In this study, we evaluated the risks of OC associated with common germline variants in five oncogenes (BRAF, ERBB2, KRAS, NMI and PIK3CA) known to be involved in OC development. Thirty-four tagging SNPs in these genes were genotyped in ∼1800 invasive OC cases and 3000 controls from population-based studies in Denmark, the United Kingdom and the United States. We found no evidence of disease association for SNPs in BRAF, KRAS, ERBB2 and PIK3CA when OC was considered as a single disease phenotype; but after stratification by histological subtype, we found borderline evidence of association for SNPs in KRAS and BRAF with mucinous OC and in ERBB2 and PIK3CA with endometrioid OC. For NMI, we identified a SNP (rs11683487) that was associated with a decreased risk of OC (unadjusted Pdominant=0.004). We then genotyped rs11683487 in another 1097 cases and 1792 controls from an additional three case–control studies from the United States. The combined odds ratio was 0.89 (95% confidence interval (CI): 0.80–0.99) and remained statistically significant (Pdominant=0.032). We also identified two haplotypes in ERBB2 associated with an increased OC risk (Pglobal=0.034) and a haplotype in BRAF that had a protective effect (Pglobal=0.005). In conclusion, these data provide borderline evidence of association for common allelic variation in the NMI with risk of epithelial OC

Biological decolorization of xanthene dyes by anaerobic granular biomass

Biodegradation of a xanthene dyes was investigated for the first time using anaerobic granular sludge. On a first screening, biomass was able to decolorize, at different extents, six azo dye solutions: acid orange 7, direct black 19, direct blue 71, mordant yellow 10, reactive red 2 and reactive red 120 and two xanthene dyes—Erythrosine B and Eosin Y. Biomass concentration, type of electron donor, induction of biomass with dye and mediation with activated carbon (AC) were variables studied for Erythrosine B (Ery) as model dye. Maximum color removal efficiency was achieved with 4.71 g VSS L−1, while the process rates were independent of the biomass concentration above 1.89 g VSS L−1. No considerable effects were observed when different substrates were used as electron donors (VFA, glucose or lactose). Addition of Ery in the incubation period of biomass led to a fivefold increase of the decolorization rate. The rate of Ery decolorization almost duplicated in the presence of commercial AC (0.1 g L−1 AC0). Using different modified AC samples (from the treatment of AC0), a threefold higher rate was obtained with the most basic one, \textAC\textH2ACH2, as compared with non-mediated reaction. Higher rates were obtained at pH 6.0. Chemical reduction using Na2S confirmed the recalcitrant nature of this dye. The results attest that decolorization of Ery is essentially due to enzymatic and adsorption phenomena.This work was supported by the PTDC/AMB/69335/2006 project grants (Fundacao para a Ciencia e Technologia, FCT, Portugal), BRAIN project (ID 6681, European Social Found and Romanian Government and the grant of the Romanian National Authority for Scientific Research, CNCS-UEFISCDI, project number PN-II-ID-PCE-2011-3-0559, Contract 265/2011

Cationic Amino Acid Transporter-2 Regulates Immunity by Modulating Arginase Activity

Cationic amino acid transporters (CAT) are important regulators of NOS2 and ARG1 activity because they regulate L-arginine availability. However, their role in the development of Th1/Th2 effector functions following infection has not been investigated. Here we dissect the function of CAT2 by studying two infectious disease models characterized by the development of polarized Th1 or Th2-type responses. We show that CAT2−/− mice are significantly more susceptible to the Th1-inducing pathogen Toxoplasma gondii. Although T. gondii infected CAT2−/− mice developed stronger IFN-γ responses, nitric oxide (NO) production was significantly impaired, which contributed to their enhanced susceptibility. In contrast, CAT2−/− mice infected with the Th2-inducing pathogen Schistosoma mansoni displayed no change in susceptibility to infection, although they succumbed to schistosomiasis at an accelerated rate. Granuloma formation and fibrosis, pathological features regulated by Th2 cytokines, were also exacerbated even though their Th2 response was reduced. Finally, while IL-13 blockade was highly efficacious in wild-type mice, the development of fibrosis in CAT2−/− mice was largely IL-13-independent. Instead, the exacerbated pathology was associated with increased arginase activity in fibroblasts and alternatively activated macrophages, both in vitro and in vivo. Thus, by controlling NOS2 and arginase activity, CAT2 functions as a potent regulator of immunity

The changing form of Antarctic biodiversity

Antarctic biodiversity is much more extensive, ecologically diverse and biogeographically structured than previously thought. Understanding of how this diversity is distributed in marine and terrestrial systems, the mechanisms underlying its spatial variation, and the significance of the microbiota is growing rapidly. Broadly recognizable drivers of diversity variation include energy availability and historical refugia. The impacts of local human activities and global environmental change nonetheless pose challenges to the current and future understanding of Antarctic biodiversity. Life in the Antarctic and the Southern Ocean is surprisingly rich, and as much at risk from environmental change as it is elsewher

High Resistance of Plasmodium falciparum to Sulphadoxine/Pyrimethamine in Northern Tanzania and the Emergence of dhps Resistance Mutation at Codon 581

BACKGROUND: Sulphadoxine-pyrimethamine (SP) a widely used treatment for uncomplicated malaria and recommended for intermittent preventive treatment of malaria in pregnancy, is being investigated for intermittent preventive treatment of malaria in infants (IPTi). High levels of drug resistance to SP have been reported from north-eastern Tanzania associated with mutations in parasite genes. This study compared the in vivo efficacy of SP in symptomatic 6-59 month children with uncomplicated malaria and in asymptomatic 2-10 month old infants. METHODOLOGY AND PRINCIPAL FINDINGS: An open label single arm (SP) standard 28 day in vivo WHO antimalarial efficacy protocol was used in 6 to 59 months old symptomatic children and a modified protocol used in 2 to 10 months old asymptomatic infants. Enrolment was stopped early (87 in the symptomatic and 25 in the asymptomatic studies) due to the high failure rate. Molecular markers were examined for recrudescence, re-infection and markers of drug resistance and a review of literature of studies looking for the 581G dhps mutation was carried out. In symptomatic children PCR-corrected early treatment failure was 38.8% (95% CI 26.8-50.8) and total failures by day 28 were 82.2% (95% CI 72.5-92.0). There was no significant difference in treatment failures between asymptomatic and symptomatic children. 96% of samples carried parasites with mutations at codons 51, 59 and 108 in the dhfr gene and 63% carried a double mutation at codons 437 and 540. 55% carried a third mutation with the addition of a mutation at codon 581 in the dhps gene. This triple: triple haplotype maybe associated with earlier treatment failure. CONCLUSION: In northern Tanzania SP is a failed drug for treatment and its utility for prophylaxis is doubtful. The study found a new combination of parasite mutations that maybe associated with increased and earlier failure. TRIAL REGISTRATION: ClinicalTrials.gov NCT00361114