Comparison of Filter and Wall Deposits From Samplers Used to Collect Airborne Lead-Containing Dusts at Field Sites

Pairs of Institute of Occupational Medicine (IOM) and 37 mm closed face cassette samplers (CFC) were deployed where occupational exposures to lead-containing dusts were known to occur. Discrete particle analyses of wall and filter deposits were performed by Scanning Electron Microscopy—Energy Dispersive X-ray Spectrometry (SEM-EDX). From the elemental composition and projected area diameter of each particle a density, volume, and mass were calculated, and a mass-weighted size distribution for each filter and corresponding wall deposit determined. Comparison of pairs of wall and filter mass-weighted size distributions by Mann–Whitney statistical analysis shows that in only 3 of 72 examples from either sampler were the distributions significantly different that suggests that the mechanisms of particle deposition on the sampler walls for particles in this size range (0.5 μm through 20 μm) do not differ for the different samplers. Furthermore, in only 4 of 33 sampler pairs did the IOM and CFC results differ. Although these results originate from several distinct processes characterized by different chemical and physical dust generation mechanisms, they suggest that in these environments the measurement of “total dust” by the CFC and inhalable dust by the IOM will be very similar when both samplers are processed the same way with respect to the including or excluding wall deposits with the filter catch. However, these results may not be applicable to environments where larger particles exist.     

Stable isotope tracing of trout hatchery carbon to sediments and foodwebs of limestone spring creeks

Limestone springs support productive ecosystems and fisheries, yet aquaculture may modify or impair these ecosystems. We determined trout hatchery organic contribution to spring creek sediments and foodwebs with natural abundance stable isotope methods. Hatchery feed, waste, and trout were significantly enriched in delta(13)C relative to autotrophs and wild fish. Spring creek sediments were enriched in delta(13)C toward the hatchery endmember relative to reference streams without hatcheries and relative to a larger larger-order, spring-influenced stream. Contribution of hatchery C to spring creek sediments was greatest during March and associated with greatest sediment %C. Contribution of hatchery C to pollution-tolerant isopod diet was 39-51% in a stream receiving limestone spring water via hatchery effluent. Isopods of one spring creek also relied on hatchery-derived C within one month of hatchery closure. Four years later, less pollution pollution-tolerant amphipods dominated and consumed non-vascular over vascular autotrophs (86%). Isopods of a second spring creek with an active hatchery did not appear to be using hatchery matter directly, but were enriched in delta(34)S relative to a spring creek tributary with no hatchery influence. Isopods in both of these streams were relatively enriched in delta(15)N, indicating general nutrient enrichment from surrounding agricultural land use. The contribution of hatchery vs. wild fish in diet of herons and egrets was traced with delta(13)C of guano. These birds were strongly dependent on stocked trout in a spring creek with a recently closed state trout hatchery, and also near another large, state-run hatchery. Heron dependence on hatchery fish in the spring creek decreased with time since hatchery closure. Use of stable isotope natural abundance techniques in karst spring creeks can reveal stream impairment due to aquaculture, specific C sources to bio-indicating consumers, losses of farmed fish to predation, and potential exposure of higher order consumers to contaminants associated with aquaculture.     

NMR Evidence for C<Subscript>60</Subscript> Configurational Fluctuations Around Na Sites in Na<Subscript>2</Subscript>CsC<Subscript>60</Subscript>

The ²³Na nuclear magnetic resonance (NMR) spectrum, spin-lattice and spin–spin relaxation, as well as spin echo double resonance (SEDOR) are investigated in the ternary alkali fulleride compound Na₂CsC₆₀ in the temperature range of 10–300 K. The NMR line associated with the tetrahedral sodium site is split below 170 K (T and T′ lines) similarly to Rb₃C₆₀ although the crystal structures of these two materials are different. SEDOR measurements prove that the T and T′ sites are microscopically close. The merger of the two lines at about 170 K is attributed to motional narrowing resulting from a site exchange due to angular reorientations of the C₆₀ molecules. The exchange dynamics inferred from the spectra, spin–spin relaxation, and spin-lattice relaxation are all consistent and agree with inelastic neutron scattering, supporting our proposal that the observed T-T′ splitting originates from different local fullerene configurations around the tetrahedral alkaline sites.     

Singular Band Behavior of the Extended Emery Model for the Superconducting Cuprates

Mean field slave-boson approximation is performed on the extended Emery model for the CuO₂ conducting plane. The model is parameterized by Cu–O charge transfer energy _pd , copper–oxygen overlap t ₀, oxygen–oxygen overlap t', and Coulomb interaction U on the copper site taken as infinite. Special emphasis is placed on the role of t in the renormalization trends of the effective band parameters _pf and t, replacing _pd and t ₀, at small doping . It is shown that small, negative t expands the range of stability of the metallic phase, changing, in the second order of the perturbation theory, the nature of the metal–insulator transition point. In the nonperturbative limit, t modifies strongly the renormalization of _pf , making it saturate at the value of 4t. Finite doping suppresses the insulating state approximately symmetrically with respect to its sign. The regime _pf 4t fits very well the ARPES spectra of Y123, Bi2212, and LSCO and also explans, in the latter case, the evolution of the FS with doping accompanied by the spectral weight-transfer from the oxygen to the resonant band.     

Identifying the Right Stuff: Selecting and Training On-Scene Emergency Commanders

This paper examines the selection and training of on-scene commanders who have responsibility for managing an emergency at the scene of the event, be it a fire, a riot, a battle or an aircraft with a technical problem in flight. It presents a selective review of the findings of a study, commissioned by the Offshore Safety Division of the UK Health and Safety Executive, which examined the selection, training and competence assessment of individuals with emergency command responsibilities in a range of military, public service and commercial organisations. It identifies a set of generic characteristics and competencies for on-scene commanders and considers how these are identified in the selection process. This is followed by a discussion of training and formal competence assessment. These issues have increasing relevance not only for the military and civil protection agencies but also in an industrial context for site managers, particularly in chemical, petroleum and nuclear plants and in large entertainment venues.     

HYPERTEXT TOOLS FOR KNOWLEDGE WORKERS

Connections and networking. These two words probably best represent the milieu of the 1980s, They'll continue to be significant throughout the 1990s, but in a much different context. These concepts are the essentials of hypertext—a computerized form of information variously characterized as nonlinear prose, interactive print, or dynamic text. Proponents maintain that hypertext will revolutionize information systems, causing designers of information to reexamine widely held beliefs and practices relating to publishing, text and screen design, information access and retrieval, user support, and documentation management.     

Development and Characterization of a Novel Soil Amendment Based on Biomass Fly Ash Encapsulated in Calcium Alginate Microspheres

Biomass fly ash (BFA) from a biomass cogeneration plant was encapsulated into calcium alginate microspheres (ALG/Ca) and characterized. An FTIR analysis indicated that BFA loading weakened molecular interactions between ALG/Ca constituents (mainly hydrogen bonding and electrostatic interactions), thus changing the crosslinking density. SEM and AFM analyses revealed a wrinkled and rough surface with elongated and distorted granules. The in vitro release of BFA’s main components (K, Ca, and Mg) was controlled by diffusion through the gel-like matrix, but the kinetics and released amounts differed significantly. The smaller released amounts and slower release rates of Ca and Mg compared to K resulted from the differences in the solubility of their minerals as well as from the interactions of divalent cations with alginate chains. The physicochemical properties of the novel microsphere formulation reveal significant potential for the prolonged delivery of nutrients to crops in a safe manner.     

Individual, Sexual, Seasonal, and Temporal Variation in the Amount of Sagebrush Lizard Scent Marks

Although many animals deposit scent marks, previous studies have focused almost entirely on rodents or on the chemical structure of the signal. Here, we study the quantity and temporal pattern of chemical deposition by the territorial sagebrush lizard Sceloporus graciosus, measuring both femoral pore and fecal deposits. Specifically, we tested whether variation in deposition is a good cue of individual and sexual identity and/or whether it is more closely associated with body size and reproductive state, indicators of physiological condition. The results support the latter hypothesis. We found that although the amount of fluid deposited on a single perch (rarely quantified in mammals) carries little information on individual or sexual identity, it reflects the physiological condition and reproductive state of individual lizards and is replenished on a roughly weekly cycle, potentially providing additional information on the producer's activity level. The amount of deposition may thus provide important information to chemical receivers making mate choice and territorial defense decisions. The results further suggest that seasonal increases in gland production allow lizards to mark more sites rather than to influence the quality of the signal on a single perch.