Mesophilic microorganisms build terrestrial mats analogous to Precambrian microbial jungles.

Development of Archean paleosols and patterns of Precambrian rock weathering suggest colonization of continents by subaerial microbial mats long before evolution of land plants in the Phanerozoic Eon. Modern analogues for such mats, however, have not been reported, and possible biogeochemical roles of these mats in the past remain largely conceptual. We show that photosynthetic, subaerial microbial mats from Indonesia grow on mafic bedrocks at ambient temperatures and form distinct layers with features similar to Precambrian mats and paleosols. Such subaerial mats could have supported a substantial aerobic biosphere, including nitrification and methanotrophy, and promoted methane emissions and oxidative weathering under ostensibly anoxic Precambrian atmospheres. High C-turnover rates and cell abundances would have made these mats prime locations for early microbial diversification. Growth of landmass in the late Archean to early Proterozoic Eons could have reorganized biogeochemical cycles between land and sea impacting atmospheric chemistry and climate.

A high-resolution chemical and structural study of framboidal pyrite formed within a low-temperature bacterial biofilm.

A novel, anaerobically grown microbial biofilm, scraped from the inner surface of a borehole, 1474 m below land surface within a South African, Witwatersrand gold mine, contains framboidal pyrite. Water flowing from the borehole had a temperature of 30.9 degrees C, a pH of 7.4, and an Eh of -50 mV. Examination of the biofilm using X-ray diffraction, field emission gun scanning electron microscope equipped for energy dispersive X-ray microanalysis demonstrated that the framboids formed within a matrix of bacteria and biopolymers. Focused ion beam sectioning of framboids followed by NEXAFS measurements using both scanning transmission X-ray microscopy and X-ray photoelectron emission microscopy revealed that the pyrite crystals grew within an organic carbon matrix consisting of exopolysaccharides and possibly extracellular DNA, which is intuitively important in sulfide mineral diagenesis. Growth of individual pyrite crystals within the framboid occurred inside organic templates confirms the association between framboidal pyrite and organic materials in low-temperature diagenetic environments and the important role of microenvironments in biofilms in regulating geochemical cycles.

Resource absorption in a health service system.

This paper considers the use of treatment resources in a health service system. The particular aspect of system use which is identified is resource absorption - excessive use by a small subset of users and unmet need by others. A dynamic stochastic model for health status with treatment interventions is formulated and the distribution of accumulated treatment time (service) is developed. The characterization of heavy tails in the distribution, the essential feature of resource absorption, is based on the Lorenz curve and an Index of Resource Absorption is defined for any feasible Lorenz curve. The index is applied to the use of psychiatric hospital resources in a Province of Canada.

Physician practice style variations.

This article studies the variation in physician practice style among geographic regions and across time. A physician practice profile is defined and a simple model for profile variation is developed. Ratios are calculated for the components of the profile--ambulatory visit rate, hospitalization rate and length of hospitalization--and studied in terms of adaptation to resource constraint and nonspecific style. The methods are applied to hospital use in the Census Metropolitan Areas of Canada.

Randomness and order in the topology of settlement systems.

"The frequency distribution of settlement links forms the basis of a linear programming methodology which can be utilized to analyze the structure of settlement systems. The resulting index of system topology is compared to a more conventional measure, Geary's contiguity coefficient, which may be applied when the problem is conceptualized as one of spatial autocorrelation on a k-color map. The index of linkage similarity that is introduced appears to have a useful advantage over the Geary measure. The Geary and linkage similarity indices are used to examine the topology of four Canadian and two hypothetical settlement systems."

Self-sufficiency in a regional hospital system.

This article considers measures that indicate the degree of regionalization within a hospital system. In particular, regional independence is characterized with a "self-sufficiency" index. The basis of these measures is the use of facilities in one region by residents of another region, that is, interregional flows. Examples of the use of the suggested measure in the Nova Scotia hospital system are presented.