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Redox reactions control the mobility and bioavailability of selenium (Se) in biogeochemical systems, both modern and ancient. Se isotope ratio measurements (e.g., 82Se/76Se) have been developed to enhance understanding of biogeochemical transformations and transport of Se. Stable isotope ratios of many elements are known to be powerful indicators of redox reactions, and shifts in 82Se/76Se have been observed for Se reduction reactions. However, Se isotope shifts caused by naturally relevant oxidation reactions have not been published. Here, we report Se isotope fractionation factors for oxidation of Se(IV) by birnessite. Experiments were conducted at pH = 4.0 and 5.5, with two types of birnessite of contrasting composition at two concentrations of suspended birnessite. The results are consistent with a single 82Se/76Se fractionation factor, for all times during all experiments, of 0.99767 (±0.0035 2 s.d.). Expressed as ε, the fractionation is 2.33‰ (±0.08‰).

Selenium (Se) isotope fractionation has been widely used for constraining redox conditions and microbial processes in both modern and ancient environments, but our knowledge of the controls on fractionation during microbial reduction of Se-oxyanions is based on a limited number of studies. Here we complement and expand the currently available pure culture data for Se isotope fractionation by investigating for the first time six phylogenetically diverse, mesophilic, and non-respiring bacterial strains that reduce Se-oxyanions to elemental Se [Se(0)]. Experiments were performed with either selenate [Se(VI)] or selenite [Se(IV)] at lower, more environmentally-relevant Se (9–47 μM) and carbon (500 μM) concentrations than previously investigated. Enterobacter cloacae SLD1a-1, Desulfitobacterium chlororespirans Co23 and Desulfitobacterium sp. Viet-1 were incubated with Se(VI) and Se(IV). Geobacter sulfurreducens PCA, Anaeromyxobacter dehalogenans FRC-W and Shewanella sp. (NR) were examined for their ability reducing Se(IV) to Se(0). Our data confirm that microbial reduction of both Se-oxyanions is accompanied by large kinetic isotopic fractionation (reported as 82/76e = 1000×(82/76α-1) in ‰). Under our experimental conditions, microbial reduction of Se(VI) shows consistently greater isotope fractionation (e = −9.2‰ to −11.8‰) than reduction of Se(IV) (e = −6.2 to −7.8‰) confirming the difference in metabolic pathways for the reduction of the two Se-oxyanions. For Se(VI), an inverse relationship between normalized cell specific reduction rate (cSRR) and Se isotope fractionation suggests that the kinetic isotope effect for Se(VI) reduction is governed by an enzymatically-specific pathway related to the bacterial strain-specific physiology. In contrast, the lack of correlation between normalized cSRR and isotope fractionation for Se(IV) reduction indicates a non-enzyme specific pathway which is dominantly extracellular. Our study highlights the importance to understand microbially-mediated Se isotope fractionation depending on Se species, and cell-specific reduction rates before Se isotope ratios can become a fully applicable tool to interpret Se isotopic changes in modern and ancient environments.

Biostimulation to induce reduction of soluble U(VI) to relatively immobile U(IV) is an effective strategy for decreasing aqueous U(VI) concentrations in contaminated groundwater systems. If oxidation of U(IV) occurs following the biostimulation phase, U(VI) concentrations increase, challenging the long-term effectiveness of this technique. However, detecting U(IV) oxidation through dissolved U concentrations alone can prove difficult in locations with few groundwater wells to track the addition of U to a mass of groundwater. We propose the 238U/235U ratio of aqueous U as an independent, reliable tracer of U(IV) remobilization via oxidation or mobilization of colloids. Reduction of U(VI) produces 238U-enriched U(IV), whereas remobilization of solid U(IV) should not induce isotopic fractionation. The incorporation of remobilized U(IV) with a high 238U/235U ratio into the aqueous U(VI) pool produces an increase in 238U/235U of aqueous U(VI). During several injections of nitrate to induce U(IV) oxidation, 238U/235U consistently increased, suggesting 238U/235U is broadly applicable for detecting mobilization of U(IV).

Bulk δ82/76Se values of representative marine shales from the Paleoarchean to the present day vary between approximately −3 and + 3 ‰ with only local deviations beyond this range. This muted Se isotope variability in the shale record contrasts with the relatively large fractionations associated with abiotic and microbial Se oxyanion reduction seen in experimental studies. Long-term temporal trends in the bulk shale data do not directly correlate with changes in redox conditions of the global ocean, although a minor but significant shift towards more negative formation-averaged δ82/76Se values appears to track oxygenation of the deep ocean at the end of the Proterozoic. We hypothesize that extensive δ82/76Se variability in the shale data was suppressed due to the early emergence of biological assimilatory uptake and the resulting persistence of low seawater Se concentrations, coupled with small authigenic Se outputs throughout most of geological time. In the modern ocean, Se is an essential micronutrient with a relatively short residence time of about 11,500 yrs. The marine Se cycle is dominated by assimilation into biomass and subsequent recycling in the water column and surface sediments, i.e. processes that result in only minimal isotopic fractionation. We suggest that similar processes dominated back through the geological record to Archean times. Our model shows that paleoceanographic information could in principle be extracted from proxy data on the Se isotopic composition of seawater, once isotopic differences can be readily discerned between individual sedimentary Se pools.

Advancements in missile technology have made cruise missile capability available worldwide. Current US naval weapon systems lack full interoperability across multiple platforms and full integration of detection, control, and engagement processes against incoming targets. The key to defeating future threats to our military assets is in gaining additional reaction time. This can be accomplished by leveraging collective sensor detection data throughout the battlespace, utilizing the FORCEnet data resources to evaluate the threat, and engaging the threat with a tiered defense. The objective of this capstone project is to address the above issues through the use of Open Architecture (OA) within a FORCEnet environment. This report focuses on the development of a conceptual architecture for Cruise Missile Defense (CMD) that combines FORCEnet architecture requirements with Program Executive Office of Integrated Warfare Systems (PEO IWS)'s OA functional architecture technical requirements. Further, this conceptual architecture is compared with PEO IWS's functional architecture via a series of systems engineering diagrams. These diagrams culminate in a simulation model that analyzes and determines the validity of the conceptual architecture. Results from the simulation model show that the conceptual architecture performed significantly better than PEO IWS's. These results are attributed to the addition of a re-engagement loop called Observe-Orient-Decide-Act (OODA). http://archive.org/details/openrchitectures109456930

Selenium poisoning is a significant health problem in parts of Punjab, India, which is an area of intense agricultural productivity. To determine the complex soil dynamics that control distribution of Se in this area, we measured concentrations and δ(82/76)Se of bulk Se and individual Se pools in four soil profiles. This was compared against δ(82/76)Se of crops and groundwater used for irrigation. The isotopic composition of bulk Se and component Se pools reveal spatial heterogeneity. The bulk δ(82/76)Se show progressively lower values with increasing soil depth indicating the preferential migration of isotopically lighter Se downward through the soil profile. The δ(82/76)Se of water-soluble Se is isotopically heavier than δ(82/76)Se of adsorbed Se, suggesting Se isotope fractionation by reduction prior to scavenging by reactive minerals in the soil. The organically bound Se is isotopically lighter than water-soluble Se and correlates with the C/N ratio at different soil depths. Thus, Se immobilization by redox cycling controls the biogeochemical Se cycle in the soil. Se isotope ratios help to trace biochemical processes of Se in agricultural seleniferous soils and provide an important assessment for better soil management mitigating Se concentrations of ecotoxicological levels.

The Lexical Grid (LexGrid) enables the integration of terminologies and ontologies through a common model, services, and tools. The LexGrid Editor is a prototype terminology authoring and maintenance tool designed for this environment. This demonstration will present an overview of the Editor’s functional capabilities in relation to technologies offered by the LexGrid platform. We will also demonstrate additional proof of concept work, such as integration of technology provided by the Protégé Ontology Management System.

Archeological investigations were conducted at 36FA404, the New Geneva Pottery Waster/Loading Dock Site. Field work consisted of both manually and mechanically excavated test units and trenches. Portions of the waster dump used by the New Geneva potters in the final two decades of the nineteenth century and into the early years of the twentieth century were excavated on Lot 167. Excavations on Lot 166 recovered artifacts associated with the Arthur Robbins’ pottery (circa 1907-1914). The artifacts were used as backfill for railroad construction. Along the Monongahela River shore a buried in situ deposit of ceramics was found and appears to date, like the deposits on Lot 167, from the final twenty years of the nineteenth century and into the first decade of the twentieth century. No documentary or archeological evidence was found indicating that a wharf or dock was present at 36FA404. Archeological evidence of the location of Ford Street was discovered in one of the excavation units, and a drain-like feature was found running parallel to the street. The road was used in the movement of pottery between the kilns and the Monongahela River. Over 66,000 artifacts were recovered from the current and previous investigations conducted at the site. Diagnostic and non-diagnostic stoneware and redware sherds, along with significant amounts of kiln furniture and misfired ceramics were found throughout the site, as well as small amounts of non-pottery related artifacts, such as glass containers, refined ceramics, nails, bone, spikes, and leather. Brick, slag,and coal in abundance were also recovered. The archeological and historical evidence has yielded data related to the production and transport of New Geneva stoneware. Historical records suggest that the upper Monongahela River potteries produced a somewhat limited range of vessel types, but may have been known for the large capacity jars and chums they manufactured. Later potters at the site produced predominantly jug forms, and the archeological record contained numerous examples of these vessels. The distribution of New Geneva stonewares seems to have been throughout the local region, and into the Ohio and Mississippi River valleys. By the end of the nineteenth century, as production failed to keep up with mechanized pottery factories located in the vicinity of Pittsburgh, the New Geneva potters apparently chose to produce for an increasingly local clientele. The New Geneva Pottery Waster/Loading Dock Site (36FA404) is recommended eligible for the National Register of Historic Places for the data it contains pertaining to the nineteenth and early twentieth century ceramic industry in New Geneva and due to its association with the New Geneva Pottery Site (36FA91) located across Route 166, and with the New Geneva Historic District, which is listed on the National Register of Historic Places. The site consists of the redeposited waster debris and secondary deposition resulting from the construction of the railroad overpass and incidental breakage during transport. Although the site is considered significant as an archeological resource contributing to the New Geneva Historic District, no additional archeological field work is recommended. Archeological investigations at the site recovered artifact assemblages and related data that constitute a sample of the range and variety of data available from the site. Accordingly, it is our opinion that the planned construction activities will have no adverse effect upon significant archeological resources at Site 36FA404.

Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte. Subdirección General de Coordinación Bibliotecaria, 2013 Sign.: A6, a4, B-Z6, 2A-2Z6, 3A-3S6, 3T4, 3V-3X2, 3Y4. Segunda obra con pag. y port. propias. Port. a dos tintas, fileteada y con viñeta xil. Texto con apostillas marginales. Il. xil. a lo largo del texto.