Hydrogen in stishovite, with implications for mantle water content

Stishovite, the highest pressure polymorph of silicon dioxide, may be an important mineral in some regions of the Earth's mantle. Fourier transform infrared spectroscopy has been used to determine the hydrogen content of synthetic stishovite. The concentration of hydrogen depends on the aluminum content of the sample and reaches a maximum of 549 +/- 23 hydrogen atoms per 10(6) silicon atoms for an Al(2)O(3) content of 1.51 percent by weight. Stishovite could be a storage site for water in deep subducting slabs and in regions of the mantle that are too hot for hydrous minerals to be stable.     

From sequence to chromosome: the tip of the X chromosome of D. melanogaster

One of the rewards of having a Drosophila melanogaster whole-genome sequence will be the potential to understand the molecular bases for structural features of chromosomes that have been a long-standing puzzle. Analysis of 2.6 megabases of sequence from the tip of the X chromosome of Drosophila identifies 273 genes. Cloned DNAs from the characteristic bulbous structure at the tip of the X chromosome in the region of the broad complex display an unusual pattern of in situ hybridization. Sequence analysis revealed that this region comprises 154 kilobases of DNA flanked by 1.2-kilobases of inverted repeats, each composed of a 350-base pair satellite related element. Thus, some aspects of chromosome structure appear to be revealed directly within the DNA sequence itself.     

Lectin binding and the carbohydrate moieties present on Newcastle disease virus strains

Lectin-binding profiles were developed for 14 strains of Newcastle disease virus in order to determine the carbohydrate moieties associated with hemagglutination and to establish whether there are any associations between the carbohydrates present on the virus envelope and virulence. All strains of Newcastle disease virus were bound by concanavalin A. Other lectins bound the viruses differentially, but there was no pattern of binding that could be associated with viral virulence. The binding of virus by Lens culinaris lectin was associated with the elution rate of the virus from chicken erythrocytes. Strains that elute rapidly from chicken erythrocytes were not bound by Lens culinaris lectin. The sugar alpha-D-N-acetylglucosamine inhibited the adsorption of Lens culinaris lectin to the strains that were "slow eluters" from chicken erythrocytes.     

Prevalence of respiratory diseases and their association with growth rate and space in randomly selected swine herds.

The prevalence and extent of respiratory tract lesions were measured in 1425 pigs from 27 randomly selected herds in the summer of 1982 and winter of 1983. About 75% of pigs had lesions of enzootic pneumonia, approximately 60% had atrophic rhinitis and approximately 11% had pleuropneumonia and/or pleuritis. Individual pig growth rate was recorded on two of the farms, and it was found that the correlations between growth rate and severity of enzootic pneumonia lesions were positive on one farm and negative on the other. Negative correlations between severity of turbinate atrophy and growth rate existed in one of the two herds. Extent of pneumonia and severity of turbinate atrophy were poorly related in individual pigs but herd averages were moderately and positively correlated. Prevalence of diffuse pleuritis and of pleuropneumonia were positively related, as were the extent of pneumonia and prevalence of localized pleuritis. Prevalence of pleuropneumonia was strongly correlated with increased days-to-market. A method of estimating the average days-to-market using weekly herd data (inventory) was developed.     

Management and housing factors associated with piglet preweaning mortality

The purposes of this study were to establish piglet preweaning mortality rates on representative Ontario pig farms and to examine possible relationships between preweaning mortality and various management and environmental factors. Thirty randomly sampled farrow-to-finish herds were surveyed over a two year period. Mean preweaning mortality in liveborn pigs of 18.5±5.8 and 18.7±5.4 was recorded in the first and second years of the survey, respectively. Preweaning mortality was correlated positively with still-birth rate (r₁=0.31, p₁<0.1 (Year 1), and (r₂=0.37, p₂<0.05 (Year 2)) and with weaner pig mortality in the second year (r₂=0.37, p₂<0.05). Preweaning mortality was negatively correlated with herd size (r₁=−0.30, p₁<0.1 and (r₂=−0.31, p₂<0.1), crate utilization (r₁=−0.52, p₁<0.01 and (r₂=−0.53, p₂<0.01), and positively correlated with the number of farrowing crates per room (r₁ and r₂=0.52, p<0.05).

There was no relationship observed between preweaning mortality and housing and management characteristics such as the use of bedding or no bedding, batch farrowing versus continuous farrowing and single-use compared to multi-use farrowing rooms.

It was felt that stockmanship was an important modifier of environmental effects.

     

The effect of post-fire stand age on the boreal forest energy balance

Fire in the boreal forest renews forest stands and changes the ecosystem properties. The successional stage of the vegetation determines the radiative budget, energy balance partitioning, evapotranspiration and carbon dioxide flux. Here, we synthesize energy balance measurements from across the western boreal zone of North America as a function of stand age following fire. The data are from 22 sites in Alaska, Saskatchewan and Manitoba collected between 1998 and 2004 for a 150-year forest chronosequence. The summertime albedo immediately after a fire is about 0.05, increasing to about 0.12 for a period of about 30 years and then averaging about 0.08 for mature coniferous forests. A mature deciduous (aspen) forest has a higher summer albedo of about 0.16. Wintertime albedo decreases from a high of 0.7 for 5- to 30-year-old forests to about 0.2 for mature forests (deciduous and coniferous). Summer net radiation normalized to incoming solar radiation is lower in successional forests than in more mature forests by about 10%, except for the first 1–3 years after fire. This reduction in net radiative forcing is about 12–24 W m⁻² as a daily average in summer (July). The summertime daily Bowen ratio exceeds 2 immediately after the fire, decreasing to about 0.5 for 15-year-old forests, with a wide range of 0.3–2 for mature forests depending on the forest type and soil water status. The magnitude of these changes is relatively large and may affect local, regional and perhaps global climates. Although fire has always determined stand renewal in these forests, increased future area burned could further alter the radiation balance and energy partitioning, causing a cooling feedback to counteract possible warming from carbon dioxide released by boreal fires.