To better inform the subsurface scientist on the expected performance of parallel simulators, this work investigates performance of the reactive multiphase flow and multicomponent biogeochemical ...transport code PFLOTRAN as it is applied to several realistic modeling scenarios run on the Jaguar supercomputer. After a brief introduction to the code's parallel layout and code design, PFLOTRAN's parallel performance (measured through strong and weak scalability analyses) is evaluated in the context of conceptual model layout, software and algorithmic design, and known hardware limitations. PFLOTRAN scales well (with regard to strong scaling) for three realistic problem scenarios: (1) in situ leaching of copper from a mineral ore deposit within a 5‐spot flow regime, (2) transient flow and solute transport within a regional doublet, and (3) a real‐world problem involving uranium surface complexation within a heterogeneous and extremely dynamic variably saturated flow field. Weak scalability is discussed in detail for the regional doublet problem, and several difficulties with its interpretation are noted.
Key Points
Scientists must better understand the benefit of high-performance computing
PFLOTRAN's scalability is exceptional on multiple realistic subsurface problems
Understanding PFLOTRAN's scalability better educates on expected performance
Energy-related carbon emissions from UK manufacturing have fallen, between 1990 and 2007, by approximately 2% per annum. This reduction could be caused by a number of effects that can act to increase ...or decrease the level of emissions. Decomposition analysis has been used to separate the contributions of changes in output, industrial structure, energy intensity, fuel mix and electricity emission factor to the reduction in carbon emissions. The primary reason for the fall in emissions was found to be a reduction in energy intensity. The manufacturing sector was also split into two subsectors: the energy-intensive (EI) subsector, and the non-energy-intensive (NEI) subsector. The NEI subsector, somewhat surprisingly, was found to have made greater relative reductions in its energy-related carbon emissions over the study period. This was principally due to much greater relative improvements in energy intensity. There is evidence that the EI subsector had made greater relative improvements in energy intensity in the period preceding 1990, and so this may have limited improvements post 1990.
•Heat recovery opportunities from UK industry were evaluated.•Surplus heat availability was based on previous work.•Various technologies to utilise the recovered heat were examined.•Greatest ...potential shown for heat use on-site and its conversion to electricity.•Transportation of heat shows potential, but will require the existence of networks.
A database of the heat demand, and surplus heat available, at United Kingdom industrial sites involved in the European Union Emissions Trading System, was used to estimate the technical potential of various heat recovery technologies. The options considered were recovery for use on-site, using heat exchangers; upgrading the heat to a higher temperature, using heat pumps; conversion of the heat energy to fulfill a chilling demand, using absorption chillers; conversion of the heat energy to electrical energy, using Rankine cycles; and transport of the heat to fulfill an off-site heat demand. A broad analysis of this type, which investigates a large number of sites, cannot accurately identify site level opportunities. However the analysis can provide an indicative assessment of the overall potential for different technologies. The greatest potential for reusing this surplus heat was found to be recovery at low temperatures, utilising heat exchangers; and in conversion to electricity, mostly using organic Rankine cycle technology. Both these technologies exist in commercial applications, but are not well established, support for their development and installation could increase their use. The overall surplus heat that was technically recoverable using a combination of these technologies was estimated at 52PJ/yr, saving 2.2MtCO2e/yr in comparison to supplying the energy outputs in a conventional manner. It is thought that a network and market for trading in heat and the wider use of district heating systems could open considerable potential for exporting heat from industrial sites to other users.
Carbon capture and storage (CCS) facilities coupled to power plants provide a climate change mitigation strategy that potentially permits the continued use of fossil fuels whilst reducing the carbon ...dioxide (CO
2) emissions. This process involves three basic stages: capture and compression of CO
2 from power stations, transport of CO
2, and storage away from the atmosphere for hundreds to thousands of years. Potential routes for the capture, transport and storage of CO
2 from United Kingdom (UK) power plants are examined. Six indicative options are evaluated, based on ‘Pulverised Coal’, ‘Natural Gas Combined Cycle’, and ‘Integrated (coal) Gasification Combined Cycle’ power stations. Chemical and physical CO
2 absorption capture techniques are employed with realistic transport possibilities to ‘Enhanced Oil Recovery’ sites or depleted gas fields in the North Sea. The selected options are quantitatively assessed against well-established economic and energy-related criteria. Results show that CO
2 capture can reduce emissions by over 90%. However, this will reduce the efficiency of the power plants concerned, incurring energy penalties between 14 and 30% compared to reference plants without capture. Costs of capture, transport and storage are concatenated to show that the whole CCS chain ‘cost of electricity’ (COE) rises by 27–142% depending on the option adopted. This is a significant cost increase, although calculations show that the average ‘cost of CO
2 captured’ is £15/tCO
2 in 2005 prices the current base year for official UK producer price indices. If potential governmental carbon penalties were introduced at this level, then the COE would equate to the same as the reference plant, and make CCS a viable option to help mitigate large-scale climate change.
► Potential routes for carbon capture and storage (CCS) from UK power plants are examined, including six indicative options. ► Chemical and physical CO
2 absorption techniques were studied with realistic transport possibilities to North Sea EOR sites or depleted gas fields. ► CO
2 capture is shown to reduce emissions by over 90%, although incurring energy penalties between 14 and 30% depending on the CCS chain. ► Whole CCS chain ‘cost of electricity’ is estimated to rise by 27–142%, depending on the option selected. ►The corresponding average ‘cost of CO
2 captured’ is £15/tCO
2.This will determine the viability of CCS with market carbon prices.
Suspension culture remains a popular modality, which manipulates mechanical culture conditions to maintain the specialized features of cultured cells. The rotating-wall vessel is a suspension culture ...vessel optimized to produce laminar flow and minimize the mechanical stresses on cell aggregates in culture. This review summarizes the engineering principles, which allow optimal suspension culture conditions to be established, and the boundary conditions, which limit this process. We suggest that to minimize mechanical damage and optimize differentiation of cultured cells, suspension culture should be performed in a solid-body rotation Couette-flow, zero-headspace culture vessel such as the rotating-wall vessel. This provides fluid dynamic operating principles characterized by 1) solid body rotation about a horizontal axis, characterized by colocalization of cells and aggregates of different sedimentation rates, optimally reduced fluid shear and turbulence, and three-dimensional spatial freedom; and 2) oxygenation by diffusion. Optimization of suspension culture is achieved by applying three tradeoffs. First, terminal velocity should be minimized by choosing microcarrier beads and culture media as close in density as possible. Next, rotation in the rotating-wall vessel induces both Coriolis and centrifugal forces, directly dependent on terminal velocity and minimized as terminal velocity is minimized. Last, mass transport of nutrients to a cell in suspension culture depends on both terminal velocity and diffusion of nutrients. In the transduction of mechanical culture conditions into cellular effects, several lines of evidence support a role for multiple molecular mechanisms. These include effects of shear stress, changes in cell cycle and cell death pathways, and upstream regulation of secondary messengers such as protein kinase C. The discipline of suspension culture needs a systematic analysis of the relationship between mechanical culture conditions and biological effects, emphasizing cellular processes important for the industrial production of biological pharmaceuticals and devices.
Transcranial magnetic stimulation (TMS) is a non-invasive brain stimulation technique used to study human neurophysiology. A single TMS pulse delivered to the primary motor cortex can elicit a motor ...evoked potential (MEP) in a target muscle. MEP amplitude is a measure of corticospinal excitability and MEP latency is a measure of the time taken for intracortical processing, corticofugal conduction, spinal processing, and neuromuscular transmission. Although MEP amplitude is known to vary across trials with constant stimulus intensity, little is known about MEP latency variation. To investigate MEP amplitude and latency variation at the individual level, we scored single-pulse MEP amplitude and latency in a resting hand muscle from two datasets. MEP latency varied from trial to trial in individual participants with a median range of 3.9 ms. Shorter MEP latencies were associated with larger MEP amplitudes for most individuals (median
r
= − 0.47), showing that latency and amplitude are jointly determined by the excitability of the corticospinal system when TMS is delivered. TMS delivered during heightened excitability could discharge a greater number of cortico-cortical and corticospinal cells, increasing the amplitude and, by recurrent activation of corticospinal cells, the number of descending indirect waves. An increase in the amplitude and number of indirect waves would progressively recruit larger spinal motor neurons with large-diameter fast-conducting fibers, which would shorten MEP onset latency and increase MEP amplitude. In addition to MEP amplitude variability, understanding MEP latency variability is important given that these parameters are used to help characterize pathophysiology of movement disorders.
With the suitable selection of a gold catalyst as well as the appropriate control of the reaction conditions, various new gold‐catalyzed cyclizations of 2‐alkynyl benzaldehyde with acyclic or cyclic ...vinyl ethers have been developed. Acetal‐tethered dihydronaphthalene and isochromenes were obtained from the reactions of 2‐alkynyl benzaldehydes with acyclic vinyl ethers under mild conditions. And, more interestingly, the gold‐catalyzed reactions of 2‐alkynyl benzaldehyde with a cyclic vinyl ether afforded the bicyclo2.2.2octane derivative involving two molecules of cyclic vinyl ethers. These products contain interesting substructures that have been found in many biologically active molecules and natural products. In addition, a gold‐catalyzed homo‐dimerization of 2‐phenylethynyl benzaldehyde 1 a was observed when the reaction was carried out in the absence of vinyl ether, affording a set of separable diastereomeric products. Plausible mechanisms for these transformations are discussed; a gold‐containing benzopyrylium was regarded as the crucial intermediate by which a number of these new transformations took place.
The (mild) Midas touch: The gold‐catalyzed reactions of 2‐alkynyl benzaldehydes with acyclic or cyclic vinyl ethers afforded acetal‐tethered dihydronaphthalene 1, isochromene 2, and bicyclo2.2.2octane 3 under mild reaction conditions (see scheme). Plausible mechanisms for the formations of these interesting compounds are discussed.
Maintaining executive functions, including planning, inhibition, and decision-making skills, is important for autonomy and activities of daily living. There is a growing body of evidence linking ...social determinants and cognitive aging, but less is known about the potential role of social determinants in changes in executive functioning over time. Using data from the Canadian Longitudinal Study on Aging (CLSA), a large cohort of mid-aged and older adults, we examined changes in executive function over a 3-year period. Specifically, we focused on the role of social determinants (i.e., social positioning, social support, education) in explaining these changes. Executive function was measured at baseline and follow-up 3 years later using the Mental Alteration Test (MAT). We computed a reliable change index (RCI) and used a multiple linear regression model to examine the associations between known correlates and change in executive function over the 3-year period (
= 29,344). Older age, higher household income, and greater educational attainment predicted declines in executive function. Health factors (e.g., depression symptoms, physical activity levels) and many social determinants (sexual orientation, gender identity, race, and perceived social standing) were not associated with change in executive function. These results suggest that social determinants of health may be related to initial differences in cognitive functioning (i.e., cross-sectional differences) rather than more rapid cognitive aging.
•Our paper investigates how prices are determined on peer-to-peer markets.•We analyze whether experience and reputation in sharing economy platforms have the same impact as in traditional markets.•We ...provide the first empirical analysis of the world's leading intercity carsharing platform, BlaBlaCar.•We show that more-experienced drivers on BlaBlaCar set lower prices and sell more seats than less-experienced drivers.•We find evidence of discrimination against drivers of a minority group (Arabic drivers) that sell less seats on Blablacar.
We examine how price and demand are determined on peer-to-peer platforms and whether experience and reputation have the same impact as in traditional markets. We use data from the world's leading intercity carsharing platform, BlaBlaCar, which connects drivers with empty seats to riders. We find that pricing decisions evolve as drivers gain experience with the platform. More-experienced drivers set lower prices and, controlling for price, sell more seats. Our interpretation is that more-experienced drivers on BlaBlaCar learn to lower their prices as they gain experience; accordingly, more-experienced drivers earn more revenue per trip. In total, our results suggest that peer-to-peer markets such as BlaBlaCar share some characteristics with other types of peer-to-peer markets such as eBay but remain a unique and rich setting in which there are many new insights to be gained.
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