Geoscience at the nanometre scale: review of analytical transmission electron microscopy applications

This paper describes applications of analytical Transmission Electron Microscopy (TEM) in the geosciences. The topics include: 1) sulphide-mineral oxidation; 2) trace-metal attenuation by secondary Mn oxides; 3) silicate weathering; 4) transition-metal valence in minerals; and 5) secondary Hg minerals in stream sediments. The main advantage of the analytical TEM is the ability to obtain images, chemical information, and electron diffraction patterns at the nanometre scale. With such high spatial resolution, it is possible to observe physical and chemical features in samples that cannot be resolved with most other techniques. This information can lead to significant improvement in our understanding of the system under investigation. Sample preparation techniques that are used in each study are also described in this paper. The preparation of samples for TEM analysis can be challenging because of the heterogeneity commonly encountered in geological materials, the fragility of some geological samples (e.g., low-temperature minerals), and the need to maintain spatial relationships present in the samples. The sample preparation techniques presented are specific to the needs of the study and the appropriateness of these methods is demonstrated by the high quality analytical TEM data that are obtained. RÉSUMÉ Cet exposé décrit des applications de la microscopie électronique à transmission analytique dans les sciences de la terre. Les aspects étudiés comprennent : 1) l'oxydation des minéraux sulfurés; 2) l'atténuation des métaux-traces par des oxydes de Mn secondaires; 3) la silicatisation météorique; 4) la valence des métaux de transition dans les minéraux; et 5) les minéraux de Hg secondaires dans les sédiments fluviatiles. Le principal avantage qu'offre la MET analytique est la possibilité d'obtenir des images, des données chimiques et des figures de diffraction des électrons à l'échelle nanométrique. Une résolution spatiale aussi élevée permet l'observation dans les échantillons de propriétés physiques et chimiques impossibles à éclaircir au moyen de la majorité des autres techniques. De tels renseignements peuvent mener à une amélioration marquée de notre compréhension du système à l'étude. Cet exposé décrit en plus les techniques de préparation des échantillons utilisées lors de chaque étude. La préparation des échantillons à une analyse MET peut s'avérer compliquée en raison de l'hétérogénéité que présentent communément les matières géologiques, de la fragilité de certains échantillons géologiques (p. ex. minéraux à basse température) et de la nécessité de maintenir les liens spatiaux présents dans les échantillons. Les techniques de préparation des échantillons présentées sont propres aux besoins de l'étude; les données de haute qualité obtenues des analyses MET témoignent de la pertinence de ces méthodes. [Traduit par la rédaction

Current-induced transition from particle-by-particle to concurrent intercalation in phase-separating battery electrodes

Many battery electrodes contain ensembles of nanoparticles that phase-separate on (de)intercalation. In such electrodes, the fraction of actively intercalating particles directly impacts cycle life: a vanishing population concentrates the current in a small number of particles, leading to current hotspots. Reports of the active particle population in the phase-separating electrode ​lithium iron phosphate (​LiFePO4; ​LFP) vary widely, ranging from near 0% (particle-by-particle) to 100% (concurrent intercalation). Using synchrotron-based X-ray microscopy, we probed the individual state-of-charge for over 3,000 ​LFP particles. We observed that the active population depends strongly on the cycling current, exhibiting particle-by-particle-like behaviour at low rates and increasingly concurrent behaviour at high rates, consistent with our phase-field porous electrode simulations. Contrary to intuition, the current density, or current per active internal surface area, is nearly invariant with the global electrode cycling rate. Rather, the electrode accommodates higher current by increasing the active particle population. This behaviour results from thermodynamic transformation barriers in ​LFP, and such a phenomenon probably extends to other phase-separating battery materials. We propose that modifying the transformation barrier and exchange current density can increase the active population and thus the current homogeneity. This could introduce new paradigms to enhance the cycle life of phase-separating battery electrodes

Process/economic strategy for upgrading shale oil

A prime difficulty with the production of transportation fuels from Western US shale oil is the high heteroatom content, especially nitrogen. Nitrogen containing molecules are known to have high market value for non-fuel uses. Selective extraction of nitrogen-containing molecules from shale oil recovers these potentially valuable components while upgrading the remaining shale oil for refining to transportation fuels. A thermodynamically logical separation process sequence consisting of primarily distillation and liquid-liquid extraction has been shown effective in selective isolation of polar heteroatom-containing molecules. The polar fraction may be processed for the production of chemical intermediates and specialty chemicals of high value. Projected material balances show an overall product split of 80% refinery feed and 20% polar products. Based on product values and composition, a preliminary economic analysis yields 30% internal rate of return. A summary of the economic strategy, process results and promising products will be presented

Report of the Scientific Council Meeting 01 -15 June 2017

Council met at the Sobey Building, Saint Mary’s University, Halifax, NS, Canada, during 01 – 15 June 2017, to consider the various matters in its Agenda. Representatives attended from Canada, Denmark (in respect of Faroe Islands and Greenland), the European Union (France, Germany (via WebEx), Portugal, Spain, the United Kingdom and the European Commission), Japan, the Russian Federation and the United States of America. Observers from the Ecology Action Centre and Dalhousie University were also present. The Executive Secretary, Scientific Council Coordinator and other members of the Secretariat were in attendance. The Executive Committee met prior to the opening session of the Council to discuss the provisional agenda and plan of work. The Council was called to order at 1000 hours on 01 June 2017. The provisional agenda was adopted with modification. The Scientific Council Coordinator was appointed the rapporteur. The Council was informed that the meeting was quorate and authorization had been received by the Executive Secretary for proxy votes from the European Union, Denmark (in respect of Faroe Islands and Greenland), Iceland, Japan, Republic of Korea, and Norway. The opening session was adjourned at 1200 hours on 01 June 2017. Several sessions were held throughout the course of the meeting to deal with specific items on the agenda. The Council considered adopted the STACFEN report on 8 June 2017, and the STACPUB, STACFIS and STACREC reports on 15 June 2017. The concluding session was called to order at 0830 hours on 15 June 2017. The Council considered and adopted the report the Scientific Council Report of this meeting of 01 -15 June 2017. The Chair received approval to leave the report in draft form for about two weeks to allow for minor editing and proof-reading on the usual strict understanding there would be no substantive changes. The meeting was adjourned at 1430 hours on 15 June 2017. The Reports of the Standing Committees as adopted by the Council are appended as follows: Appendix I - Report of the Standing Committee on Fisheries Environment (STACFEN), Appendix II - Report of Standing Committee on Publications (STACPUB), Appendix III - Report of Standing Committee on Research Coordination (STACREC), and Appendix IV - Report of Standing Committee on Fisheries Science (STACFIS). The Agenda, List of Research (SCR) and Summary (SCS) Documents, and List of Representatives, Advisers and Experts, are given in Appendix V-VII. The Council’s considerations on the Standing Committee Reports, and other matters addressed by the Council follow in Sections II-XV

Shale Oil Value Enhancement Research. Quarterly Report, December 1, 1994 - February 28, 1995

Objectives for the Quarter were: Perform six-stage extraction of total shale oil using the dual solvent system; complete modifications to the extraction unit to extract +400 `C fraction; conduct hydrodealkylation experiments on the shale oil fractions; complete cost and economic analysis for both schemes; and continue marketing efforts aimed at identifying additional majors as candidate partners for commercialization. Accomplishments for each task is described

Simulations of extensional flow in microrheometric devices

We present a detailed numerical study of the flow of a Newtonian fluid through microrheometric devices featuring a sudden contraction–expansion. This flow configuration is typically used to generate extensional deformations and high strain rates. The excess pressure drop resulting from the converging and diverging flow is an important dynamic measure to quantify if the device is intended to be used as a microfluidic extensional rheometer. To explore this idea, we examine the effect of the contraction length, aspect ratio and Reynolds number on the flow kinematics and resulting pressure field. Analysis of the computed velocity and pressure fields show that, for typical experimental conditions used in microfluidic devices, the steady flow is highly three-dimensional with open spiraling vortical structures in the stagnant corner regions. The numerical simulations of the local kinematics and global pressure drop are in good agreement with experimental results. The device aspect ratio is shown to have a strong impact on the flow and consequently on the excess pressure drop, which is quantified in terms of the dimensionless Couette and Bagley correction factors. We suggest an approach for calculating the Bagley correction which may be especially appropriate for planar microchannels

Shale Oil Value Enhancement Research. Quarterly Report, June 1 - August 31, 1993

All tasks are on schedule, or ahead of schedule. Particular progress has been made in identifying industrial entities, commodities and specialty products of target interest for shale oil-derived products. There is clearly a major emphasis worldwide on new chemicals and shale oil-derived structures are similar to many of these chemicals of interest. Details of the mathematical modeling, programming and algorithm development have progressed with excellent results. Considerable effort will be required to interface these with the output of the gc/ms but we are receiving excellent support from Hewlett Packard in this regard. The ability to concentrate particularly valuable compounds with reasonable projected cost processes continues to show promise. In one system, a single-stage extraction recovered 87% of the total nitrogen in an extract representing only 33% of the fraction. Special attention is being paid to both nitrogen types and oxygen types. The raffinates from the polar solvent extractions will be evaluated for their oil and wax contents. All of the start-up infrastructure is now in place. Subcontracts have been initiated and equipment and supplies have been procured. We are now planning a major push to reach some general findings by early in 1994. From these findings, we will be prepared to focus on experimental verification of process design needed for the second program phase

Defining Metrics for Short Term Success After LVAD Implant: An Analysis of the Society of Thoracic Surgeons Intermacs Registry

Purpose: While clinical trials evaluating left ventricular assist device (LVAD) technology typically use composite outcomes to assess efficacy, composite outcomes including patient reported outcomes (PROs) have not been utilized as benchmarks for LVAD implant center performance improvement initiatives or quality ranking. The objective of the study was to assess the feasibility of generating a patient composite outcome measure including PROs from a real world registry. Methods: Short term (ST, 180 days) adverse events (AEs) and mortality were tallied for Intermacs patients undergoing LVAD implant between 1/2012 and 12/2019. ST postoperative events included mortality on first device and frequencies of stroke, reoperation (device malfunction/other), right heart failure (RHF), prolonged respiratory failure, and/or dialysis on first device. Logistic regression was used to generate odds ratios for mortality for each AE. Separately, the EuroQOL visual analog scale (VAS) was assessed at baseline and 180 days in ST survivors. Results: Of 20,115 patients, 37% suffered at least one event, most commonly death, reoperation and stroke (Table, column A). Stroke, prolonged respiratory failure, and dialysis attributed the most to ST mortality (Table, column B). Of the 16725 patients alive at 180 days, 43% completed a VAS with 82.0% showing VAS improvement. Renal failure and RHF contributed most to failure to improve VAS (Figure). Conclusion: Assessment of a ST composite outcome metric after LVAD implant from a real world data source is feasible but limited by incomplete PRO reporting. ST adverse events display differential effects on mortality and PROs that can be used in development of global rank outcome scores. While reoperation is common, stroke, prolonged respiratory failure and renal failure conferred highest risks of ST deaths within Intermacs. Assessment of PROs should become a priority for LVAD centers to allow the field to generate a complete assessment of patient-centered outcomes

Suppression of Phase Separation in LiFePO4 Nanoparticles During Battery Discharge

Using a novel electrochemical phase-field model, we question the common belief that LixFePO4 nanoparticles separate into Li-rich and Li-poor phases during battery discharge. For small currents, spinodal decomposition or nucleation leads to moving phase boundaries. Above a critical current density (in the Tafel regime), the spinodal disappears, and particles fill homogeneously, which may explain the superior rate capability and long cycle life of nano-LiFePO4 cathodes.Comment: 27 pages, 8 figure