Determining the influence and effects of manufacturing variables on sulfur dioxide cells

A survey of the Li/SO2 manufacturing community was conducted to determine where variability exists in processing. The upper and lower limits of these processing variables might, by themselves or by interacting with other variables, influence safety, performance, and reliability. A number of important variables were identified and a comprehensive design experiment is being proposed to make the proper determinations

Effects of Resident Species on Recruitment into a Community: Larval Settlement Versus Post-Settlement Mortality in the Oyster Crassostrea virginica

Laboratory and field experiments revealed that a variety of species of common, sessile invertebrates, including barnacles, ascidians, and bryozoans, affected the settlement and post-settlement abundance of the oyster Crassostrea virginica (Gmelin). While the nature of the effects varied, most species both reduced oyster settlement by covering and removing substrate available for attachment, and increased settlement on adjacent surfaces. The solitary ascidians Ciona intestinalis (L.) and Styela clava (Herdman), were found to be predators of oyster larvae. Post-settlement survivorship and growth were also strongly affected by the presence of sessile species. In most cases the effects were negative and correlated with the abundances of the species. Data suggest that competition for planktonic food was the mostly likely cause of reduced growth and survivorship. For many resident species, the combination of reduced oyster settlement on their own exposed surfaces, increased settlement on substrate adjacent to them, and decreased post-settlement survivorship in their presence resulted in these species having little effect on net recruitment. These results demonstrate the need for distinguishing interactions among benthic invertebrate populations during the period from settlement to recruitment

Effects of Inter-Specific Density and Food Supply on Survivorship and Growth of Newly Settled Benthos

Using a laboratory model system comprised of newly settled oysters Crassostrea virginica and established fouling species (Botrylloides sp. initially, and others including Styela clava and Ciona intestinalis as the experiment progressed), we tested how differences in food supply and competitor density may affect post-settlement surivorship and growth of sessile marine invertebrates over a 44 d period. After 15 d, results were mixed but indicated that both food and density conditions affected growth and survivorship significantly, with some suggestion of high food levels ameliorating high density effects However, 44 d after settlement, oysters had reduced survivorship and growth when competitors were present regardless of food level. This study suggests that localized food depletion by juveniles and/or adults of resident species may have a negative effect on recruitment in fouling communities, even when space is not limiting

Molecular Imaging of Petroleum Asphaltenes by Scanning Tunneling Microscopy: Verification of Structure from 13C and Proton Nuclear Magnetic Resonance Data

Scanning tunneling microscopy (STM) was used to verify the molecular structure of Maya asphaltene which had been derived from combined 13C and proton nuclear magnetic resonance (NMR) experiments. Petroleum asphaltenes are known to contain large polynuclear aromatic centers with aliphatic sidechains. Average molecular models of Maya asphaltenes were derived using studies which included combined proton and 13C NMR data to determine total aromatic carbon content and the ratio of peripheral to internal aromatic ring carbons. These parameters permitted estimating the average number of aromatic rings per condensed cluster. These Maya asphaltenes were imaged by scanning tunneling microscopy (STM) in a dilute solution of tetrahydrofuran on highly oriented pyrolytic graphite. The sizes and structures of the asphaltenes as observed by STM are in reasonable agreement with these average molecular models. We observed asymmetric structures whose largest dimension averaged 10.4 Å ± 1.9 Å from 24 separate images. The condensed ring portions of three representative NMR derived molecular models yielded an average dimension of 11.1 Å ± 1.4 Å

Parasite infections in a social carnivore: Evidence of their fitness consequences and factors modulating infection load

There are substantial individual differences in parasite composition and infection load in wildlife populations. Few studies have investigated the factors shaping this heterogeneity in large wild mammals or the impact of parasite infections on Darwinian fitness, particularly in juveniles. A host's parasite composition and infection load can be shaped by factors that determine contact with infective parasite stages and those that determine the host's resistance to infection, such as abiotic and social environmental factors, and age. Host–parasite interactions and synergies between coinfecting parasites may also be important. We test predictions derived from these different processes to investigate factors shaping infection loads (fecal egg/oocyte load) of two energetically costly gastrointestinal parasites: the hookworm Ancylostoma and the intracellular Cystoisospora, in juvenile spotted hyenas (Crocuta crocuta) in the Serengeti National Park, in Tanzania. We also assess whether parasite infections curtail survival to adulthood and longevity. Ancylostoma and Cystoisospora infection loads declined as the number of adult clan members increased, a result consistent with an encounter‐reduction effect whereby adults reduced encounters between juveniles and infective larvae, but were not affected by the number of juveniles in a clan. Infection loads decreased with age, possibly because active immune responses to infection improved with age. Differences in parasite load between clans possibly indicate variation in abiotic environmental factors between clan den sites. The survival of juveniles (<365 days old) to adulthood decreased with Ancylostoma load, increased with age, and was modulated by maternal social status. High‐ranking individuals with low Ancylostoma loads had a higher survivorship during the first 4 years of life than high‐ranking individuals with high Ancylostoma loads. These findings suggest that high infection loads with energetically costly parasites such as hookworms during early life can have negative fitness consequences

Suppression of cross-hatched polariton disorder in GaAs/AlAs microcavities by strain compensation

Zinc-blende semiconductor heterostructures grown in the [001] direction with a small lattice mismatch accommodate stress by developing a cross-hatch dislocation pattern. In GaAs based planar microcavitiesgrown by molecular beam epitaxy, this pattern creates a potential landscape for exciton-polaritons, causing scattering and localization. We report here on suppressing the cross-hatch by introducing strain-compensating AlP layers into the center of the low index AlAs layers of the distributed Bragg reflectors. We observe a reduction of the cross-hatch dislocation density by at least one order of magnitude for 1.1 nm thick AlP layers, which correspond to an effective AlAs0.985P0.015 low index layer. These compensated structures show a remaining polariton disorder potential in the 10 μeV range

High-energy spectroscopic study of the III-V nitride-based diluted magnetic semiconductor Ga1−x_{1-x}Mnx_{x}N

We have studied the electronic structure of the diluted magnetic semiconductor Ga$_{1-x}$Mn$_{x}$N ($x$ = 0.0, 0.02 and 0.042) grown on Sn-doped $n$-type GaN using photoemission and soft x-ray absorption spectroscopy. Mn $L$-edge x-ray absorption have indicated that the Mn ions are in the tetrahedral crystal field and that their valence is divalent. Upon Mn doping into GaN, new state were found to form within the band gap of GaN, and the Fermi level was shifted downward. Satellite structures in the Mn 2$p$ core level and the Mn 3$d$ partial density of states were analyzed using configuration-interaction calculation on a MnN$_{4}$ cluster model. The deduced electronic structure parameters reveal that the $p$-$d$ exchange coupling in Ga$_{1-x}$Mn$_{x}$N is stronger than that in Ga$_{1-x}$Mn$_{x}$As.Comment: 6pages, 10figures. To be published to Phys. Rev.