CHARACTERIZATION OF VARIOUS BITUMEN SAMPLES FROM TAR SANDS

ABSTRACT

We have investigated twenty three bitumen samples obtained using different separation methods such as: ultracentrifugation, Dean-Stark extraction, solvent extraction employing vigorous agitation, hot water separation and the Solvent Extraction Spherical Agglomeration technique. These samples were extracted from oil sand feedstocks of different grades, Suncor sludge pond tailings and mineral agglomerates obtained from the Solvent Extraction Spherical Agglomeration process. All of the bitumen samples were examined on a comparative basis using various analytical techniques. These included: fractionation into asphaltenes and maltenes; elemental analyses; molecular weight determination using vapour pressure osmometry and gel permeation chromatography, infrared, proton and 13C nuclear magnetic resonance spectroscopy. Proton and ¹³C n.m.r. spectroscopic data were used to determine the distribution of various types of hydrogens and carbons in the samples. These data were also used to derive various molecular parameters in order to investigate average molecular structures of different bitumen samples and some of their asphaltene fractions.     

High-order harmonic generation from metal plasmas using 1 kHz laser pulses

High-order harmonic generation in laser-produced plasma was demonstrated on metal surfaces using a high pulse repetition rate laser (1?kHz). It was found that if sufficiently thick bulk targets were used thermal conduction was sufficient to prevent any deterioration in the metal plasma plume production at this repetition rate. Under appropriate conditions harmonic yields were found to remain stable for >10⁵ laser shots without the need to move the target. The high repetition rate allowed both short and long electron trajectories to be clearly identified during harmonic generation from the metal plasmas.     

Harmful recessive effects on fertility detected by absence of homozygous haplotypes

Five new recessive defects were discovered in Holsteins, Jerseys, and Brown Swiss by examining haplotypes that had a high population frequency but were never homozygous. The method required genotypes only from apparently normal individuals and not from affected embryos. Genotypes from the BovineSNP50 BeadChip (Illumina, San Diego, CA) were examined for 58,453 Holsteins, 5,288 Jerseys, and 1,991 Brown Swiss with genotypes in the North American database. Haplotypes with a length of ≤75 markers were obtained. Eleven candidate haplotypes were identified, with the earliest carrier born before 1980; 7 to 90 homozygous haplotypes were expected, but none were observed in the genomic data. Expected numbers were calculated using either the actual mating pattern or assuming random mating. Probability of observing no homozygotes ranged from 0.0002 for 7 to 10⁻⁴⁵ for 90 expected homozygotes. Phenotypic effects were confirmed for 5 of the 11 candidate haplotypes using 14,911,387 Holstein, 830,391 Jersey, and 68,443 Brown Swiss records for conception rate. Estimated effect for interaction of carrier service sire with carrier maternal grandsire ranged from −3.0 to −3.7 percentage points, which was slightly smaller than the −3.9 to −4.6 percentage points expected for lethal recessives but slightly larger than estimated effects for previously known lethal alleles of −2.5 percentage points for brachyspina and −2.9 percentage points for complex vertebral malformation. Conception rate was coded as a success only if the gestation went to term or the cow was confirmed to be pregnant. Estimated effect of carrier interaction for stillbirth rate based on 10,876,597 Holstein and 25,456 Jersey records was small. Thus, lethal effects may include conception, gestation, and stillbirth losses. Carrier frequency has been >20% for many years for the confirmed defect in Jerseys and is currently 16% for the defect in Brown Swiss. The 3 defects discovered in Holsteins have carrier frequencies of 2.7 to 6.4% in the current population. For previously known defects, map locations and lack of homozygotes were consistent with the literature and lethal recessive inheritance, but numbers of expected homozygotes for some were small because of low frequency. Very large genotypic and phenotypic data sets allow efficient detection of smaller and less frequent effects. Haplotype tests can help breeders avoid carrier matings for such defects and reduce future frequencies.     

An assessment of sampling methods and microbiological hygiene indicators for process verification in poultry slaughterhouses

Studies to determine the appropriateness of the use of populations of indicator bacteria on poultry carcasses for process verification were undertaken in commercial slaughterhouses. Samples were collected from neck skin by excision or from whole carcass rinses and were examined for a range of presumptive process hygiene indicator bacteria. Coefficients of variation were calculated for each bacterial indicator and were significantly lower in excised samples, indicating more reproducible bacterial recovery by this sampling method. Total viable counts of aerobic bacteria, Enterobacteriaceae, and Pseudomonas in samples collected by excision had the lowest coefficients of variation when compared with other indicators and were therefore used for further study. The uncertainties associated with the quantification of each bacterial indicator were calculated and were lowest overall for total viable counts of aerobic bacteria. In general, uncertainty was higher for lower bacterial numbers. Results of microbiological testing on pooled excised neck skin samples were not significantly different from the mean of individually analyzed samples. Bacterial numbers increased by 1 log unit when cultures were stored under chilled conditions typical of those used for transporting samples to external laboratories, but the increases were not significant for Pseudomonas and aerobic bacteria when storage time was less than 17 h. Weak relationships were identified between bacterial indicator numbers and duration of processing, although cleanliness of the processing environment diminished visibly during this time. In the plants visited for this study, there was a poor relationship between presumptive bacterial indicator numbers and process hygiene. Consequently, bacterial analyses for process verification purposes may be of limited value.     

Measurement of Campylobacter numbers on carcasses in British poultry slaughterhouses

An assessment of the proposed new International Organization for Standardization quantitative method for Campylobacter was undertaken on poultry carcass samples collected after the chilling phase of processing. Using a critical differences method, we determined the uncertainty associated with log-transformed Campylobacter numbers by dual analyses of 346 samples collected from 22 processing plants located throughout the United Kingdom. Overall, using log-transformed Campylobacter numbers that ranged between -1 and 5 log, we calculated the expanded measurement of uncertainty (EMU) to be 3.889 for the new method. The EMU changed when ranges of bacterial numbers were grouped for analyses. For low numbers of Campylobacter (< 1 log), the EMU was calculated to be 5.622. There was less measurement error with higher bacterial numbers because the EMU was found to be 0.612 for samples containing Campylobacter numbers of 3 log or above. The draft method was used to measure numbers of Campylobacters on poultry carcasses collected from 18 United Kingdom processing plants in summer and winter. Numbers were significantly lower in winter. We conclude that, although the new method is adequate at quantifying high numbers of Campylobacter on poultry carcasses, further development is required to improve the measurement of small numbers of this causative agent of foodborne illness.