Local problem-based <Emphasis Type="Italic">a posteriori</Emphasis> error estimators for discontinuous Galerkin approximations of reactive transport

We consider adaptive discontinuous Galerkin (DG) methods for solving reactive transport problems in porous media. To guide anisotropic and dynamic mesh adaptation, a posteriori error estimators based on solving local problems are established. These error estimators are efficient to compute and effective to capture local phenomena, and they apply to all the four primal DG schemes, namely, symmetric interior penalty Galerkin, nonsymmetric interior penalty Galerkin, incomplete interior penalty Galerkin, and the Oden–Babuška-Baumann version of DG. Numerical results are provided to illustrate the effectiveness of the proposed error estimators.     

X‐ray fluorescence measurements of the surface elemental composition of asteroid 433 Eros

Abstract— We report major element ratios determined for the S‐class asteroid 433 Eros using remote‐sensing x‐ray fluorescence spectroscopy with the near‐Earth asteroid rendezvous Shoemaker x‐ray spectrometer (XRS). Data analysis techniques and systematic errors are described in detail. Data acquired during five solar flares and during two extended “quiet Sun” periods are presented; these results sample a representative portion of the asteroid's surface. Although systematic uncertainties are potentially large, the most internally consistent and plausible interpretation of the data is that Eros has primitive Mg/Si, Al/Si, Ca/Si and Fe/Si ratios, closely similar to H or R chondrites. Global differentiation of the asteroid is ruled out. The S/Si ratio is much lower than that of chondrites, probably reflecting impact‐induced volatilization and/or photo‐ or ion‐induced sputtering of sulfur at the surface of the asteroid. An alternative explanation for the low S/Si ratio is that it reflects a limited degree of melting with loss of an FeS‐rich partial melt. Size‐sorting processes could lead to segregation of Fe‐Ni metal from silicates within the regolith of Eros; this could indicate that the Fe/Si ratios determined by the x‐ray spectrometer are not representative of the bulk Eros composition.     

Galactic mass determinations from incomplete rotation curves

Given an incomplete rotation curve of a spiral galaxy, various assumptions about the Galaxy beyond the last observed point are made: (A) the force falls off as 1/r ², (B) the mass density is zero, and (C) the mass density falls off as 1/r ³. The msss distributions obtained from each of these assumptions are all well behaved, and it is impossible to choose the correct curve from considerations of the resulting mass distributions alone. The correct mass distribution in the disk system of a galaxy cannot be deduced from an incomplete rotation curve.     

Spatio-temporal pattern of viral meningitis in Michigan, 1993-2001

To characterize Michigans high viral meningitis incidence rates, 8,803 cases from 1993–2001 were analyzed for standard epidemiological indices, geographic distribution, and spatio-temporal clusters. Blacks and infants were found to be high-risk groups. Annual seasonality and interannual variability in epidemic magnitude were apparent. Cases were concentrated in southern Michigan, and cumulative incidence was correlated with population density at the county level (r=0.45, p<0.001). Kulldorffs Scan test identified the occurrence of spatio-temporal clusters in Lower Michigan during July–October 1998 and 2001 (p=0.01). More extensive data on cases, laboratory isolates, sociodemographics, and environmental exposures should improve detection and enhance the effectiveness of a Space-Time Information System aimed at prevention.The authors gratefully acknowledge Dr. Duane Newton, former manager of the Virology Section, Michigan Department of Community Health Bureau of Laboratories, for his provision of data on viral isolates. We also appreciate the contributions of Drs. Leah Estberg and Dunrie Greiling for ClusterSeer support, Scott Swan for his assistance with ArcView GIS, and Dr. Edward L. Ionides for his advice on time series analysis. We are grateful to Dr. Pierre Goovaerts and two anonymous reviewers for their insightful comments on an earlier draft of this paper. This project was supported in part by a grant from the National Oceanic and Atmospheric Administrations Joint Program on Climate Variability and Human Health, a consortium including the EPA, NASA, NSF, and EPRI (NA16GP2361) to MLW.     

Communication,Partnerships, and the Role of Social Science: Conservation Delivery in a Brave New World

Abstract

The Saginaw Bay Regional Conservation Partnership Program (RCPP) in Michigan is an innovative conservation effort organized to address water quality impairments involving a unique collaboration between conservation organizations, agronomists, universities, commodity groups, and agribusinesses. We track the evolution and adaptation of the Saginaw Bay RCPP, and the collaboration among the traditional and nontraditional conservation partners. Our reflections are organized around three key lessons: vertical and horizontal communication challenges; contextual and structural constraints; barriers that remain between private and public sector entities for this and alternative conservation-delivery models. Lessons from this evaluation will inform the design of future collaborative/multi-stakeholder watershed management efforts. We also demonstrate that rather than being used as an ad-hoc approach, social science evaluation was integrated into conservation planning and practice, hence increasing the salience and legitimacy of the conservation social science in collaborative watershed management.     

Distribution and geological control of mud volcanoes and other fluid/free gas seepage features in the Mediterranean Sea and nearby Gulf of Cadiz

Existing knowledge on the distribution of mud volcanoes (MVs) and other significant fluid/free gas-venting features (mud cones, mud pies, mud-brine pools, mud carbonate cones, gas chimneys and, in some cases, pockmark fields) discovered on the seafloor of the Mediterranean Sea and in the nearby Gulf of Cadiz has been compiled using regional geophysical information (including multibeam coverage of most deepwater areas). The resulting dataset comprises both features proven from geological sampling, or in situ observations, and many previously unrecognized MVs inferred from geophysical evidence. The synthesis reveals that MVs clearly have non-random distributions that correspond to two main geodynamic settings: (1) the vast majority occur along the various tectono-sedimentary accretionary wedges of the Africa-Eurasia subduction zone, particularly in the central and eastern Mediterranean basins (external Calabrian Arc, Mediterranean Ridge, Florence Rise) but also along its westernmost boundary in the Gulf of Cadiz; (2) other MVs characterize thick depocentres along parts of the Mesozoic passive continental margins that border Africa from eastern Tunisia to the Levantine coasts, particularly off Egypt and, locally, within some areas of the western Mediterranean back-arc basins. Meaningfully accounting for MV distribution necessitates evidence of overpressured fluids and mud-rich layers. In addition, cross-correlations between MVs and other GIS-based data, such as maps of the Messinian evaporite basins and/or active (or recently active) tectonic trends, stress the importance of assessing geological control in terms of the presence, or not, of thick seals and potential conduits. It is contended that new MV discoveries may be expected in the study region, particularly along the southern Ionian Sea continental margins.