A multi-modal approach to measuring particulate iron speciation in buoyant hydrothermal plumes

Processes active within buoyant hydrothermal plumes are expected to modulate the flux of elements, such as Fe, to the deep ocean; however, they are yet to be described in a comprehensive manner through observations or models. In this study, we compare observed particulate Fe (pFe) speciation with thermodynamic (equilibrium) reaction path modeling for three vent fields in the Eastern Lau Spreading Center (ELSC). At each site, particles were collected from the buoyant rising portion of hydrothermal plumes using in situ filtration with a Remotely Operated Vehicle. Filter bound particles were analyzed by synchrotron micro-probe X-ray fluorescence mapping (XRF), X-ray diffraction (XRD), XRF spectroscopy, and X-ray absorption near edge structure (XANES) spectroscopy at the Fe 1 s edge, as well as XRF-based chemical speciation mapping for Fe. For buoyant plumes of the ELSC, diversity in solid-state chemistry was high, and poorly crystalline, meta-stable phases were common. We demonstrate that to fully describe the crystalline-to-noncrystalline character of plume pFe, a multi-modal XRD-XANES analytical approach is needed. We found that an equilibrium modeling approach worked well for pyrite but performed poorly for important families of meta-stable pFe, namely Fe (oxyhydr)oxides and monosulfides. Based on our findings, we recommend future field expeditions strategically explore sites representing a diversity of site-specific conditions to better capture the full range of processes active in plumes. We also recommend development of kinetic models, as well as expansion of thermodynamic databases to better reflect the solid-state composition of plumes. These steps should allow oceanographers to understand the processes controlling Fe speciation in plumes well enough to create realistic models of hydrothermal fluxes to the ocean

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The genetic architecture of the human cerebral cortex

The cerebral cortex underlies our complex cognitive capabilities, yet little is known about the specific genetic loci that influence human cortical structure. To identify genetic variants that affect cortical structure, we conducted a genome-wide association meta-analysis of brain magnetic resonance imaging data from 51,665 individuals. We analyzed the surface area and average thickness of the whole cortex and 34 regions with known functional specializations. We identified 199 significant loci and found significant enrichment for loci influencing total surface area within regulatory elements that are active during prenatal cortical development, supporting the radial unit hypothesis. Loci that affect regional surface area cluster near genes in Wnt signaling pathways, which influence progenitor expansion and areal identity. Variation in cortical structure is genetically correlated with cognitive function, Parkinson's disease, insomnia, depression, neuroticism, and attention deficit hyperactivity disorder

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Proceedings of the 3rd Biennial Conference of the Society for Implementation Research Collaboration (SIRC) 2015: advancing efficient methodologies through community partnerships and team science

It is well documented that the majority of adults, children and families in need of evidence-based behavioral health interventionsi do not receive them [1, 2] and that few robust empirically supported methods for implementing evidence-based practices (EBPs) exist. The Society for Implementation Research Collaboration (SIRC) represents a burgeoning effort to advance the innovation and rigor of implementation research and is uniquely focused on bringing together researchers and stakeholders committed to evaluating the implementation of complex evidence-based behavioral health interventions. Through its diverse activities and membership, SIRC aims to foster the promise of implementation research to better serve the behavioral health needs of the population by identifying rigorous, relevant, and efficient strategies that successfully transfer scientific evidence to clinical knowledge for use in real world settings [3]. SIRC began as a National Institute of Mental Health (NIMH)-funded conference series in 2010 (previously titled the “Seattle Implementation Research Conference”; $150,000 USD for 3 conferences in 2011, 2013, and 2015) with the recognition that there were multiple researchers and stakeholdersi working in parallel on innovative implementation science projects in behavioral health, but that formal channels for communicating and collaborating with one another were relatively unavailable. There was a significant need for a forum within which implementation researchers and stakeholders could learn from one another, refine approaches to science and practice, and develop an implementation research agenda using common measures, methods, and research principles to improve both the frequency and quality with which behavioral health treatment implementation is evaluated. SIRC’s membership growth is a testament to this identified need with more than 1000 members from 2011 to the present.ii SIRC’s primary objectives are to: (1) foster communication and collaboration across diverse groups, including implementation researchers, intermediariesi, as well as community stakeholders (SIRC uses the term “EBP champions” for these groups) – and to do so across multiple career levels (e.g., students, early career faculty, established investigators); and (2) enhance and disseminate rigorous measures and methodologies for implementing EBPs and evaluating EBP implementation efforts. These objectives are well aligned with Glasgow and colleagues’ [4] five core tenets deemed critical for advancing implementation science: collaboration, efficiency and speed, rigor and relevance, improved capacity, and cumulative knowledge. SIRC advances these objectives and tenets through in-person conferences, which bring together multidisciplinary implementation researchers and those implementing evidence-based behavioral health interventions in the community to share their work and create professional connections and collaborations

Large nickel isotope fractionation caused by surface complexation reactions with hexagonal birnessite

Manganese oxides are an important sink for Ni in the ocean. To explore the potential of Ni stable isotopes as a geochemical tracer, we conducted two types of sorption reactions between Ni and hexagonal birnessite in 0.05 M NaNO3 media: one where we varied pH from 5 to 8 (constant initial Ni concentration = 170 μmol/L), and a second where we varied the initial dissolved Ni concentration from 17 to 426 μmol/L (constant pH = 7.7). Isotopic measurements were made on both the solid phase and the supernatant solutions to determine the Ni isotope fractionation factors (∆60/58Nimin-aq = δ60/58Nimin − δ60/58Niaq) between the mineral and aqueous phases. Nickel extended X-ray absorption fine structure (EXAFS) spectroscopy showed Ni in two distinct bonding environments: one where Ni atoms incorporate into the MnO2 sheet and a second where Ni atoms associate with the mineral surface sharing oxygens with 3 Mn tetrahedra (TCS, triple corner sharing). As pH and net negative surface charge increase, the coordination of Ni shifts to higher proportions of incorporation. The number of structural vacancies in birnessite, which are locations for TCS coordination of Ni, are controlled by pH and increase with decreasing pH. These vacancies are preferentially occupied by lighter Ni isotopes leading to fractionation factors, ∆60/58Nimin-aq, ranging from −2.76‰ (lowest TCS) to −3.35‰ (maximum TCS). These Ni isotopic fractionation factors are among the largest observed in natural geological and biological materials to date. Our findings reveal a relationship between Ni coordination environment and pH that may ultimately be used as an isotopic geochemical tracer of past ocean conditions. However, the results are inconsistent with current isotopic fractionation factors for marine ferromanganese deposits relative to seawater and point to unaddressed processes that modify Ni isotopic fractionation for ferromanganese deposits. Further research is needed to develop Ni as an isotopic tracer

Reactivity of Uranium and Ferrous Iron with Natural Iron Oxyhydroxides.

Determining key reaction pathways involving uranium and iron oxyhydroxides under oxic and anoxic conditions is essential for understanding uranium mobility as well as other iron oxyhydroxide mediated processes, particularly near redox boundaries where redox conditions change rapidly in time and space. Here we examine the reactivity of a ferrihydrite-rich sediment from a surface seep adjacent to a redox boundary at the Rifle, Colorado field site. Iron(II)-sediment incubation experiments indicate that the natural ferrihydrite fraction of the sediment is not susceptible to reductive transformation under conditions that trigger significant mineralogical transformations of synthetic ferrihydrite. No measurable Fe(II)-promoted transformation was observed when the Rifle sediment was exposed to 30 mM Fe(II) for up to 2 weeks. Incubation of the Rifle sediment with 3 mM Fe(II) and 0.2 mM U(VI) for 15 days shows no measurable incorporation of U(VI) into the mineral structure or reduction of U(VI) to U(IV). Results indicate a significantly decreased reactivity of naturally occurring Fe oxyhydroxides as compared to synthetic minerals, likely due to the association of impurities (e.g., Si, organic matter), with implications for the mobility and bioavailability of uranium and other associated species in field environments

Influence of Chelating Agents on Biogenic Uraninite Reoxidation by Fe(III) (Hydr)oxides

Microbially mediated reduction of soluble U­(VI) to U­(IV) with subsequent precipitation of uraninite, UO_2(S), has been proposed as a method for limiting uranium (U) migration. However, microbially reduced UO₂ may be susceptible to reoxidation by environmental factors, with Fe­(III) (hydr)­oxides playing a significant role. Little is known about the role that organic compounds such as Fe­(III) chelators play in the stability of reduced U. Here, we investigate the impact of citrate, DFB, EDTA, and NTA on biogenic UO₂ reoxidation with ferrihydrite, goethite, and hematite. Experiments were conducted in anaerobic batch systems in PIPES buffer (10 mM, pH 7) with bicarbonate for approximately 80 days. Results showed EDTA accelerated UO₂ reoxidation the most at an initial rate of 9.5 μM day^–1 with ferrihydrite, 8.6 μM day^–1 with goethite, and 8.8 μM day^–1 with hematite. NTA accelerated UO₂ reoxidation with ferrihydrite at a rate of 4.8 μM day^–1; rates were less with goethite and hematite (0.66 and 0.71 μM day^–1, respectively). Citrate increased UO₂ reoxidation with ferrihydrite at a rate of 1.8 μM day^–1, but did not increase the extent of reaction with goethite or hematite, with no reoxidation in this case. In all cases, bicarbonate increased the rate and extent of UO₂ reoxidation with ferrihydrite in the presence and absence of chelators. The highest rate of UO₂ reoxidation occurred when the chelator promoted both UO₂ and Fe­(III) (hydr)­oxide dissolution as demonstrated with EDTA. When UO₂ dissolution did not occur, UO₂ reoxidation likely proceeded through an aqueous Fe­(III) intermediate with lower reoxidation rates observed. Reaction modeling suggests that strong Fe­(II) chelators promote reoxidation whereas strong Fe­(III) chelators impede it. These results indicate that chelators found in U contaminated sites may play a significant role in mobilizing U, potentially affecting bioremediation efforts