Currently, two commercial plants, operating in the Athabasca region of Alberta, produce approximately 20 percent of Canada's petroleum requirements from oil sands. Surface mined oil sand is treated in a water based separation process that yields large volumes of clay tailings with poor settling and compaction characteristics. Clay particles, suspended in the pond water, interact with salts, dissolved from the oil sands ore, to produce mature fine tailings (MFT) containing only 20 to 50 w/w% solids. As a result, large sedimentation ponds are required to produce enough process water to recycle for the plant. Tailings pond dykes can only be constructed during a short summer season. Consequently, the capability to predict production rate and final volume of MFT is essential for mine planning and tailings disposal operations.

Previous research has demonstrated that a small fraction of nano sized clay particles (20 to 300 nm) effectively controls the bulk properties of MFT. These particles are present in the original ore and become mobilized into the water phase during the oil separation process. In this work, the nano sized particles have been separated from the bulk tailings and subjected to a fundamental study of their flocculation behavior in model tailings water.

Photon correlation spectroscopy and a deuterium NMR method were used to follow particle flocculation and gelation processes. These results were correlated with particle settling data measured under the same conditions. It was determined that the nano particles form fractal flocs that eventually interact to give a thixotropic gel. The ultimate sediment volume produced is almost entirely dependent on the original concentration of nano particles while the rate of water release is governed primarily by electrolyte concentration.

During processing of Athabasca oil sands, the finely divided solids form an aqueous suspension, which ultimately stabilizes as a gel-like structure retaining up to 90% of the process water. This gelling phenomenon is believed to be caused by colloidal inorganic components. Kaolinite and mica are the main crystalline minerals in these colloidal solids; swelling clays are present in only trace amounts. Non-crystalline components are more concentrated in the finer fraction of the solids. Although the surfaces of the colloidal solids are virtually free of Fe, some contamination with polar organic matter is observed.

Pompe disease results from lysosomal acid α-glucosidase deficiency, which leads to cardiomyopathy in all infantile-onset and occasional late-onset patients. Cardiac assessment is important for its diagnosis and management. This article presents unpublished cardiac findings, concomitant medications, and cardiac efficacy and safety outcomes from the ADVANCE study; trajectories of patients with abnormal left ventricular mass z score at enrolment; and post hoc analyses of on-treatment left ventricular mass and systolic blood pressure z scores by disease phenotype, GAA genotype, and “fraction of life” (defined as the fraction of life on pre-study 160 L production-scale alglucosidase alfa). ADVANCE evaluated 52 weeks’ treatment with 4000 L production-scale alglucosidase alfa in ≥1-year-old United States of America patients with Pompe disease previously receiving 160 L production-scale alglucosidase alfa. M-mode echocardiography and 12-lead electrocardiography were performed at enrolment and Week 52. Sixty-seven patients had complete left ventricular mass z scores, decreasing at Week 52 (infantile-onset patients, change −0.8 ± 1.83; 95% confidence interval −1.3 to −0.2; all patients, change −0.5 ± 1.71; 95% confidence interval −1.0 to −0.1). Patients with “fraction of life” <0.79 had left ventricular mass z score decreasing (enrolment: +0.1 ± 3.0; Week 52: −1.1 ± 2.0); those with “fraction of life” ≥0.79 remained stable (enrolment: −0.9 ± 1.5; Week 52: −0.9 ± 1.4). Systolic blood pressure z scores were stable from enrolment to Week 52, and no cohort developed systemic hypertension. Eight patients had Wolff–Parkinson–White syndrome. Cardiac hypertrophy and dysrhythmia in ADVANCE patients at or before enrolment were typical of Pompe disease. Four-thousand L alglucosidase alfa therapy maintained fractional shortening, left ventricular posterior and septal end-diastolic thicknesses, and improved left ventricular mass z score.

Trial registry: ClinicalTrials.gov Identifier: NCT01526785 https://clinicaltrials.gov/ct2/show/NCT01526785.

Social Media Statement: Post hoc analyses of the ADVANCE study cohort of 113 children support ongoing cardiac monitoring and concomitant management of children with Pompe disease on long-term alglucosidase alfa to functionally improve cardiomyopathy and/or dysrhythmia.

The Athabasca oil sands deposit in Alberta contains ~5 x 109 m3 of bitumen accessible by surface mining. During bitumen separation from the mined ore, ultra-fine (<300 nm) aluminosilicate clays only a few layers thick (U/F) are mobilized and become dispersed in the process water. In this water containing dissolved salts from natural deposits, U/F are capable of forming thixotropic gels. The consequence of this is the production of large volumes of mature fine tailings (MFT) with a high water holding capacity. For mine planning purposes, the objective of predicting and possibly mitigating MFT formation requires an understanding of the colloidal behaviour of U/F particles in salt solutions. In this work, photon correlation spectroscopy and the deuterium NMR method are used to provide an insight into the U/F floc formation process. These results are correlated with conventional analysis of settling data.

Anaerobic bacteria were identified in live drilling muds and cores from nine different North Sea and Irish Basin oilfields, varying in depth from 3500 to 15000 ft, and at temperatures up to 150°C. The anaerobic bacteria may be introduced into the reservoir during drilling operations or injection of water, but in many cases the bacteria are indigenous to the oilfield reservoirs. Confirmation of the indigenous anaerobic bacteria was made using molecular biology techniques (16S rDNA sequence analysis), comparing microbial populations present in the blank drilling mud as supplied to wellsite, in the live drilling mud taken during coring, and in the live core. The role of anaerobic bacteria in oilfield diagenesis is not fully understood, though pyrite precipitation, and exopolymer and H2S gas production were noted in this study, up to temperatures of 95°C.

In this article, we challenge the conclusion that the preferences of members of Congress are best represented as existing in a low-dimensional space. We conduct Monte Carlo simulations altering assumptions regarding the dimensionality and distribution of member preferences and scale the resulting roll call matrices. Our simulations show that party polarization generates misleading evidence in favor of low dimensionality. This suggests that the increasing levels of party polarization in recent Congresses may have produced false evidence in favor of a low-dimensional policy space. However, we show that focusing more narrowly on each party caucus in isolation can help researchers discern the true dimensionality of the policy space in the context of significant party polarization. We re-examine the historical roll call record and find evidence suggesting that the low dimensionality of the contemporary Congress may reflect party polarization rather than changes in the dimensionality of policy conflict.

We present a high resolution polarimetry and variability study of the M87 jet using VLA and HST data taken during 2002 to 2008. Both data-sets have an angular resolution as high as 0.06”, which is 2-3 times better than previous observations. New morphological details are revealed in both the optical and radio, which can help to reveal the energetic and magnetic field structure of the jet. By comparing the data with previously published HST and VLA observations, we show that the jet's morphology in total and polarized light is changing significantly on timescales of ~1 decade. We compare the evolution of the inner jet (particularly the nucleus and knot HST-1), when our observations overlap with the multi-wavelength monitoring campaigns conducted with HST and Chandra. We use these data to comment on particle acceleration and main emission processes.

Field emission (FE) measurements are reported from carbon nanotube (CNT) fibers and laser-patterned free standing films fabricated by direct online condensation from a floating catalyst chemical vapor deposition reactor. Fiber and film cathodes showed stable emission in the 1–2 mA current (I) range at maximum cathode temperatures less than 1000 °C; film cathodes show localized heating at the triangular tips and higher maximum temperatures than the fibers. Fowler–Nordheim (FN) analysis indicated a change in the morphology of the emitters with increasing external electrical field (E ext). Fiber cathode I–E ext data are interpreted as FN emission from the fiber tip which is eventually limited by space-charge effects. At higher E ext, FN emission from the fiber sidewall occurs. The single fiber cathode stopped emitting abruptly when field induced self-heating effects became significant. For CNT films, self-heating effects can destroy a portion of the film, but FE can still occur from other areas.

There is limited understanding of the effects of normal and abnormal aging on gist-based memory in relation to the massive evidence regarding detail-based memory. This void is striking given the widely accepted view that memory is rarely veridical, but most often abstracted. The present study examined the effects of healthy advanced aging and mild Alzheimer's disease (AD) on three distinct forms of gist. Two of these gist forms involved a passage: transformed gist (global generalised meaning of a passage) and main-idea gist (main points of a passage). The third gist form involved a word list: categorical gist (clustering of words according to semantic categories during list recall). These gist forms were assessed in immediate and delayed recall conditions. A total of 36 participants were included: 12 cognitively healthy young seniors (65–79 years), 12 cognitively healthy old seniors (80–95 years), and 12 young seniors with mild AD (65–79 years). The findings revealed that age and dementia did not equally affect all three forms of gist. Specifically, transformed gist was relatively maintained in the cognitively healthy senior groups as compared to the other two gist forms (main-idea gist and categorical gist), whereas all three gist forms were impaired in individuals with AD. The present study suggests that transformed gist operates differently than detail-based memory in the cognitively healthy senior groups. These findings have important theoretical implications in terms of informing existing models on the interrelationship between gist and detail-based memory and clinical implications in diagnosis of AD.

Although the relationship between education and cognitive status is well-known, evidence regarding whether education moderates the trajectory of cognitive change in late life is conflicting. Early studies suggested that higher levels of education attenuate cognitive decline. More recent studies using improved longitudinal methods have not found that education moderates decline. Fewer studies have explored whether education exerts different effects on longitudinal changes within different cognitive domains. In the present study, we analyzed data from 1014 participants in the Victoria Longitudinal Study to examine the effects of education on composite scores reflecting verbal processing speed, working memory, verbal fluency, and verbal episodic memory. Using linear growth models adjusted for age at enrollment (range, 54–95 years) and gender, we found that years of education (range, 6–20 years) was strongly related to cognitive level in all domains, particularly verbal fluency. However, education was not related to rates of change over time for any cognitive domain. Results were similar in individuals older or younger than 70 at baseline, and when education was dichotomized to reflect high or low attainment. In this large longitudinal cohort, education was related to cognitive performance but unrelated to cognitive decline, supporting the hypothesis of passive cognitive reserve with aging. (JINS, 2011, 17, 1039–1046)