Microbial nitrogen dynamics in south central Chilean agricultural and forest ecosystems located on an Andisol

The natural soil N supply in volcanic soils (Andisols) can be a significant source of plant-available N for agro-ecosystems. Nevertheless, intensive farming systems in south Chile apply high fertilization rates, which lead to high production costs and involve a risk for adverse ecosystem effects. In order to achieve sustainable land management, a better understanding of the processes that govern soil N availability and loss, and their external drivers, is required. In this study, we selected a winter-cropland, a summer crop-winter fallow rotation, and a forest, used as a reference ecosystem. Gross N transformations (¹⁵N isotope dilution) and microbial community structure (phospho-lipid fatty acid analysis) in the topsoil were determined. Gross N mineralization was about ten times lower in the agro-ecosystems than in the forest, while gross nitrification was low in all sites. Gross N immobilization equalized or exceeded the gross inorganic N production in all sites. Microbial biomass was 3–5 times more abundant in the forest than in the agro-ecosystems. A positive relationship between the ratio fungi/bacteria and total microbial biomass was observed in these Andisols. We suggest that the reduction in fungal biomass induced a lower extracellular enzyme production and limited soil organic matter depolymerisation in the agro-ecosystems. We conclude that soil N cycling was unable to provide a significant N input for the croplands, but also the risk for ecosystem N losses was low, even under fallow soil conditions. Current fertilization practices appropriately anticipated the soil N cycling processes, but further research should indicate the potential of alternative land management to reduce fertilizer cost.     

Turning Social Relations into Space: Property,Law and the Plaza of Santa Fe,New Mexico

In this article, a series of controversies in and over the central Plaza of Santa Fe, New Mexico, USA is examined. The complex and contradictory dynamics of law and property as they intersect to shape and define a critical public space that is the symbolic heart of Santa Fe's landscape are explored. It is argued that laws and regulations that determine the activities that may occur in the Plaza, that restrict some actions, or that adjudicate ownership disputes literally shape the lands to which they pertain. It is shown that one purpose of law is to negotiate just how the social relations that are property get transformed into the regulated space that is property.     

Submicrometer Aerosol Mass Distributions of Emissions from Boilers,Fireplaces, Automobiles,Diesel Trucks,and Meat-Cooking Operations

The predominant peak in the mass distribution emitted from each source measured in this study occurs at or below about 0.2 μm in particle diameter, whereas the Los Angeles atmospheric aerosol contains peaks at a variety of sizes in the range between 0.1 and 1.0 μm in particle diameter, including peaks at sizes larger than 0.2 μm. This suggests that considerable modification of the primary aerosol size distribution occurs because of subsequent processes in the atmosphere. The data presented here are intended for use in defining the size distribution of the primary combustion source effluent for use with mathematical models of the evolution of the atmospheric aerosol size distribution.     

Water Uptake by NaCl Particles Prior to Deliquescence and the Phase Rule

Using an environmental transmission electron microscope (ETEM), we show that a significant amount of water, far exceeding the multilayers caused by surface adsorption, is reversibly associated prior to deliquescence with substrate-supported NaCl particles (dry diameters of ～ 40 nm to 1.5 μ m; ～ 18°C). We hypothesize that the water is present as an aqueous solution containing dissolved Na and Cl ions. Water uptake occurs at relative humidities (RH) as low as 70%, and the resulting liquid layer coating the particles is stable over extended times if the RH is held constant. We exposed CaSO ₄ and CaSO ₄ · 2H ₂ O particles to elevated RH values in the ETEM to show that chemically nonspecific condensation of gas-phase water on the TEM substrate does not explain our observations. Furthermore, damage to the NaCl surface induced by the electron beam and small fluctuations in RH do not seem to contribute to or otherwise affect water uptake. We have similar observations of water association for other alkali halide particles, including NaBr and CsCl, prior to deliquescence. To explain the observations, we derive the phase rule for this geometry and show that it allows for the coexistence of liquid, solid, and vapor for the binary NaCl/H ₂ O system across a range of RH values. The derivation includes the effects of heterogeneous pressure because of the Laplace-Young relations for the subsystems. Furthermore, in view of the lever rule and the absence of similar observations for free-floating pure NaCl aerosol particles, we hypothesize that the surface energy necessary to support these effects is provided by sample-substrate interactions. Thus, the results of this study may be relevant to atmospheric systems in which soluble compounds are associated with insoluble materials.     

KINETIC AND STRUCTURAL STUDIES OF CALCIUM-BASED SORBENTS FOR HIGH-TEMPERATURE COAL-GAS DESULFURIZATION

ABSTRACT

The absorption of H₂S by large particles of limestone, dolomitic limestone and dolomite (average mass-radius of 0·40 mm) was tested under simulated coal gases. Below the calcination temperature of CaCO₃ (about 900^°C under 1 bar of CO₂), complete conversion of the calcium carbonate to calcium sulfide can only be achieved with dolomite. Above the calcination temperature of CaCO₃, the conversion to CaS is complete for all three sorbents in about one hour when 10,000 ppm H₂S is present in the gas phase. Large particles of limestone thus appear to be a suitable sorbent for high-temperature coal-gas desulfurization (above about 900 ^°C). A mathematical model based on the kinetic information collected in this work predicts the desulfurization performance of a packed or moving bed of limestone particles. Finally, a low-temperature regeneration scheme for the spent sorbent (CaS) in which sulfur can be subsequently recovered as the element is suggested.     

Depressive symptoms among American Indian adolescents: Psychometric characteristics of the Center for Epidemiologic Studies Depression Scale (CES-D).

The psychometric characteristics of the Center for Epidemiologic Studies Depression Scale (CES–D) were investigated with American Indian boarding school students (N?=?188; Grades 9–12). The CES–D showed good internal consistency (α?=?.82). Its dimensional structure was different from that described for adults, both Indian and non-Indian. Of the Indian students, 58% were classified as depressed, using the standard cutoff score of 16 or more, consistent with past studies of this age group. Alternative scoring methods were considered, based on persistence of symptoms as well as derived Diagnostic and Statistical Manual of Mental Disorders (DSM-III) and Research Diagnostic Criteria algorithms. Major gender differences were observed in the prevalence of reported symptoms as well as patterns of endorsement for certain CES–D items. The CES–D should be used with caution with American Indian adolescents, given the observed variation in its dimensional structure and uncertainty regarding appropriate cutoff scores. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Prevention, Identification, and Cognitive Determinants of Math Difficulty.

This study examined the efficacy of preventive 1st-grade tutoring in mathematics, estimated the prevalence and severity of mathematics disability, and explored pretreatment cognitive characteristics associated with mathematics development. Participants were 564 first graders, 127 of whom were designated at risk (AR) for mathematics difficulty and randomly assigned to tutoring or control conditions. Before treatment, all participants were assessed on cognitive and academic measures. Tutoring occurred 3 times weekly for 16 weeks; treatment fidelity was documented; and math outcomes were assessed. Tutoring efficacy was supported on computation and concepts/applications, but not on fact fluency. Tutoring decreased the prevalence of math disability, with prevalence and severity varying as a function of identification method and math domain. Attention accounted for unique variance in predicting each aspect of end-of-year math performance. Other predictors, depending on the aspect of math performance, were nonverbal problem solving, working memory, and phonological processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social–cognitive alternatives to dissociation theories of hypnotic involuntariness.

Three social–cognitive models are presented as alternatives to dissociation theories of hypnotic involuntariness. In Model I, people are seen as intentionally enacting responses without being aware of the volitional quality of their acts. In Model II, hypnotic behaviors are seen as prepared responses that are triggered directly by suggestion. The first model corresponds to E. R. Hilgard's (1986) neodissociation theory and the second to K. S. Bowers's (1992) theory of dissociated control, but without positing dissociative mechanisms as explanatory constructs. These constructs are replaced by a consideration of the automaticity that is inherent in commonplace intentional behavior and the degree to which subjective experience is affected by beliefs and expectations. Finally, a composite model reconciling the contradictions between the two prior social–cognitive models is presented. (PsycINFO Database Record (c) 2010 APA, all rights reserved)