Alkali oxide-tantalum, niobium and antimony oxide ionic conductors

The phase equilibrium relations of four systems were investigated in detail. These consisted of sodium and potassium antimonates with antimony oxide and tantalum and niobium oxide with rubidium oxide as far as the ratio 4Rb2O:llB2O5 (B=Nb, Ta). The ternary system NaSbO3-Sb2O4-NaF was investigated extensively to determine the actual composition of the body centered cubic sodium antimonate. Various other binary and ternary oxide systems involving alkali oxides were examined in lesser detail. The phases synthesized were screened by ion exchange methods to determine mobility of the mobility of the alkali ion within the niobium, tantalum or antimony oxide (fluoride) structural framework. Five structure types warranted further investigation; these structure types are (1) hexagonal tungsten bronze (HTB), (2) pyrochlore, (3) the hybrid HTB-pyrochlore hexagonal ordered phases, (4) body centered cubic antimonates and (5) 2K2O:3Nb2O5. Although all of these phases exhibit good ion exchange properties only the pyrochlore was prepared with Na(+) ions as an equilibrium phase and as a low porosity ceramic. Sb(+3) in the channel interferes with ionic conductivity in this case, although relatively good ionic conductivity was found for the metastable Na(+) ion exchanged analogs of RbTa2O5F and KTaWO6 pyrochlore phases

Classification of hyperspectral imagery with neural networks: comparison to conventional tools

Efficient exploitation of hyperspectral imagery is of great importance in remote sensing. Artificial intelligence approaches have been receiving favorable reviews for classification of hyperspectral data because the complexity of such data challenges the limitations of many conventional methods. Artificial neural networks (ANNs) were shown to outperform traditional classifiers in many situations. However, studies that use the full spectral dimensionality of hyperspectral images to classify a large number of surface covers are scarce if non-existent. We advocate the need for methods that can handle the full dimensionality and a large number of classes to retain the discovery potential and the ability to discriminate classes with subtle spectral differences. We demonstrate that such a method exists in the family of ANNs. We compare the maximum likelihood, Mahalonobis distance, minimum distance, spectral angle mapper, and a hybrid ANN classifier for real hyperspectral AVIRIS data, using the full spectral resolution to map 23 cover types and using a small training set. Rigorous evaluation of the classification accuracies shows that the ANN outperforms the other methods and achieves ?90% accuracy on test data

Effects of Salinity Changes on the Photodegradation and Ultraviolet-Visible Absorbance of Terrestrial Dissolved Organic Matter

We performed laboratory studies to determine the effects of salinity on the photodegradation of dissolved organic matter (DOM) from the Great Dismal Swamp, Virginia, an important source of terrestrial DOM to the lower Chesapeake Bay. Samples were created by mixing Great Dismal Swamp water (ionic strength approximate to 0 mol L-1) with modified artificial seawater solutions of differing salinities while keeping the final dissolved organic carbon (DOC) concentration constant. These samples were then irradiated for 24 h in a light box providing ultraviolet (UV) light similar to that of natural sunlight. Light absorbance and DOC concentrations decreased after photoexposure, whereas dissolved inorganic carbon (DIC) concentrations increased. Variations in salinity affected both DIC production and UV absorption, with the higher salinity samples showing lower DIC production and less photobleaching. Addition of an iron chelator eliminated the relationship between photochemistry and salinity by reducing both photobleaching and DIC production at low salinities. As terrigenous DOM transits through an estuary, its photochemical reactivity and optical properties may change significantly as a function of salinity, probably as a result of changes in DOM conformation or changes in iron-DOM photochemistry, or both

From widespread faulting to localised rifting: Evidence from K-Ar fault gouge dates from the Norwegian North Sea rift shoulder

Although seismic and stratigraphic well information put tight constraints on rift basin evolution, eroded rift shoulders commonly expose polydeformed prerift basement whose deformation history may be difficult to constrain. In this work, we apply K-Ar dating of fault gouge samples from 18 faults to explore the brittle deformation of the well-exposed eastern rift margin to the northern North Sea rift. We find evidence of clay gouge formation since the Late Devonian, with distinct Permian and Jurassic fault activity peaks that closely match early stages of the two well-established North Sea rift phases. A marked decay in fault density away from the rift margin confirms a close relationship between rifting and onshore faulting. The results show that initial rift-related extension affected a much wider area than the resulting offshore rift. Hence our data support a rift model where strain is initially distributed over a several 100 km wide region, as a prelude to the development of the ~150–200 km wide Permo-Triassic northern North Sea rift as defined by large marginal faults. Towards the end of the second rift phase, strain localises even more strongly to the 25–50 km wide Viking Graben. Interestingly, a period of early widespread extension is seen for both phases of North Sea rifting and may be a general characteristic of continental rifting. The documented prerift faulting and fracturing of the basement since the Devonian weakened the basement and probably facilitated the widespread initial extension that subsequently localised to form the northern North Sea rift, with further localisation to its relatively narrow central part (Viking Graben).publishedVersio

A mechanism for assembly of complexes of vitronectin and plasminogen activator inhibitor-1 from sedimentation velocity analysis

Plasminogen activator inhibitor-1 (PAI-1) and vitronectin are cofactors involved in pathological conditions such as injury, inflammation, and cancer, during which local levels of PAI-1 are increased and the active serpin forms complexes with vitronectin. These complexes become deposited into surrounding tissue matrices, where they regulate cell adhesion and pericellular proteolysis. The mechanism for their co-localization has not been elucidated. We hypothesize that PAI-1-vitronectin complexes form in a stepwise and concentration-dependent fashion via 1:1 and 2:1 intermediates, with the 2:1 complex serving a key role in assembly of higher order complexes. To test this hypothesis, sedimentation velocity experiments in the analytical ultracentrifuge were performed to identify different PAI-1-vitronectin complexes. Analysis of sedimentation data invoked a novel multisignal method to discern the stoichiometry of the two proteins in the higher-order complexes formed (Balbo, A., Minor, K. H., Velikovsky, C. A., Mariuzza, R. A., Peterson, C. B., and Schuck, P. (2005) Proc. Natl. Acad. Sci. U. S. A. 102, 81-86). Our results demonstrate that PAI-1 and vitronectin assemble into higher order forms via a pathway that is triggered upon saturation of the two PAI-1-binding sites of vitronectin to form the 2:1 complex. This 2:1 PAI-1-vitronectin complex, with a sedimentation coefficient of 6.5 S, is the key intermediate for the assembly of higher order complexes

Three-dimensional coherent X-ray diffraction imaging of a ceramic nanofoam: determination of structural deformation mechanisms

Ultra-low density polymers, metals, and ceramic nanofoams are valued for their high strength-to-weight ratio, high surface area and insulating properties ascribed to their structural geometry. We obtain the labrynthine internal structure of a tantalum oxide nanofoam by X-ray diffractive imaging. Finite element analysis from the structure reveals mechanical properties consistent with bulk samples and with a diffusion limited cluster aggregation model, while excess mass on the nodes discounts the dangling fragments hypothesis of percolation theory.Comment: 8 pages, 5 figures, 30 reference