The Influence of Slope Breaks on Lava Flow Surface Disruption

Changes in the underlying slope of a lava flow impart a significant fraction of rotational energy beyond the slope break. The eddies, circulation and vortices caused by this rotational energy can disrupt the flow surface, having a significant impact on heat loss and thus the distance the flow can travel. A basic mechanics model is used to compute the rotational energy caused by a slope change. The gain in rotational energy is deposited into an eddy of radius R whose energy is dissipated as it travels downstream. A model of eddy friction with the ambient lava is used to compute the time-rate of energy dissipation. The key parameter of the dissipation rate is shown to be rho R(sup 2/)mu, where is the lava density and mu is the viscosity, which can vary by orders of magnitude for different flows. The potential spatial disruption of the lava flow surface is investigated by introducing steady-state models for the main flow beyond the steepening slope break. One model applies to slow-moving flows with both gravity and pressure as the driving forces. The other model applies to fast-moving, low-viscosity, turbulent flows. These models provide the flow velocity that establishes the downstream transport distance of disrupting eddies before they dissipate. The potential influence of slope breaks is discussed in connection with field studies of lava flows from the 1801 Hualalai and 1823 Keaiwa Kilauea, Hawaii, and 2004 Etna eruptions

Ross River Virus Disease Reemergence, Fiji, 2003–2004

We report 2 clinically characteristic and serologically positive cases of Ross River virus infection in Canadian tourists who visited Fiji in late 2003 and early 2004. This report suggests that Ross River virus is once again circulating in Fiji, where it apparently disappeared after causing an epidemic in 1979 to 1980

The Arabidopsis NPR1/NIM1 Protein Enhances the DNA Binding Activity of a Subgroup of the TGA Family of bZIP Transcription Factors

The Arabidopsis NPR1 gene is essential in activating systemic, inducible plant defense responses. To gain a better understanding of NPR1 function, we conducted a yeast two-hybrid screening procedure and identified a differential interaction between NPR1 and all known members of the Arabidopsis TGA family of basic leucine zipper transcription factors. In the electrophoretic mobility shift assay, NPR1 substantially increased the binding of TGA2 to its cognate promoter element (as-1) as well as to a positive salicylic acid–inducible element (LS7) and a negative element (LS5) in the promoter of the pathogenesis-related PR-1 gene. Proteins encoded by npr1 mutants interacted poorly with TGA2 and did not substantially increase TGA2 binding to the as-1, LS5, or LS7 elements, thus establishing a link between the loss of disease resistance and the loss of TGA2 interaction and NPR1-enhanced DNA binding. Coupled with observations that the DNA binding activity of TGA factors is deregulated in npr1 plants, the results suggest that NPR1-mediated DNA binding of TGA2 is critical for activation of defense genes

A Hybrid Model for Leveed Lava Flows: Implications for Eruption Styles on Mars

Many cehannelized lava flows on the plains of Mars have substantial embanking margins and levees inferred to have been stationary while the central channel was active. Levee formation can be attributed to two end-member processes during emplacement; construction during passage of the flow front and growth along the entire length of the flow while it is active. It is shown here that the amount of lava that can be deposited by the flow front alone is limited. Estimates of the levee volume for many Mars plains flows exceed this limit and must have formed by processes that continued after the passage of the front. Experimental studies of analogous laboratory flows also indicate a combination of both modes of emplacement. A model that combines both modes of levee formation. is presented, including a method for estimating volumetric flow rate, eruption duration, and viscosity. Six lava flows on the plains of the Tharsis volcanic province are used as illustrative examples. Crustal thicknesses for the six flows examined range from 9 to 23 m. Estimated emplacement times required to cool crusts of these thicknesses range from I year to 10 years. Correspondini viscosities are on the order of 10 5-106 Pa s. Effusion rates range from 25 to 840 m 3 s - and are all within the range of terrestrial observations. Therefore, the large leveed plains flows on Mars are not dramatically different in eruption rate or lava viscosity from large terrestrial analogs

Additional file 1: of Barriers, supports, and effective interventions for uptake of human papillomavirus- and other vaccines within global and Canadian Indigenous peoples: a systematic review protocol

PRISMA-P Checklist. (DOCX 39 kb