On buoyant convection in binary solidification

We consider the problem of nonlinear steady buoyant convection in horizontal mushy layers during the solidification of binary alloys. We investigate both cases of zero vertical volume flux and constant pressure, referred to as impermeable and permeable conditions, respectively, at the upper mush???liquid interface. We analyze the effects of several parameters of the problem on the stationary modes of convection in the form of either hexagonal cells or non-hexagonal cells, such as rolls, rectangles and squares. [More ...]published or submitted for publicationis not peer reviewe

Long-term Perspectives for Carbon Capture in Power Plants: Scenarios for the 21st Century

The report analyzes the role of fossil-fired power plants equipped with carbon capture systems in long-term scenarios of the global energy system representing technological change as an endogenous process. Within this framework the impacts of a technology policy is illustrated that requires over time an increasing fraction of fossil-fired power generation to incorporate carbon capture technologies. In particular, we examine the potential costs and the contribution that such a policy could offer in reducing energy-related carbon dioxide emissions and highlight some of the technologies that may play a role in doing so. The analysis is carried out with the global energysystems optimization MESSAGE model (Messner and Strubegger 1995) considering endogenous technology learning for fossil power plants and the corresponding carbon capture technologies, such that they experience cost reductions as a function of accumulated capacity installations. The report describes two baseline scenarios: (1) including learning for fossil power plants and (2) the other with no learning. In addition, the analysis examines three cases that are based on a technology policy that enforces an increasing share of fossil fuel power plants with carbon capture, distinguishing between future worlds assuming: (1) no learning for fossil systems, (2) learning just for the carbon capture component, and (3) full learning for the reference plants as well as for the carbon capture systems. The analysis shows that the introduction of a policy for carbon capture and storage would lead to considerable reductions in carbon emissions in the electricity sector and major changes in the power generation mix. Technologies are chosen, that provide the most cost-effective combination between electricity generation and carbon capture, fostering the penetration of advanced fossil technologies. In particular, coal gasification systems such as, IGCC power plants and high temperature fuel cells, and in addition gas-fired combined cycle power plants appear as the most attractive fossil-fired electricity generation options

Electron impact ionization of Ar10+

Total and single differential cross sections have been calculated for electron impact ionization of Ar10+(1s22s22p4)3Pe using a method that combines the distorted-wave Born approximation and R-matrix theory. In this method, the incident/scattered electron is described by the distorted-wave Born approximation, while both the initial bound state and the final continuum states are expanded in terms of an R-matrix basis. Eight states of the final Ar11+ ion are considered, namely 1s22s22p3 4So 2Do 2Po and 1s2 2s2p4 4Pe 2De 2Se 2Pe 2Po . Up to the 24- pole components of the interaction with ionizing electron were included, giving ten distinct Ar10+ continuum symmetries. We calculated single differential cross sections summed over final ionic states, as a function of the energy loss. These cross sections exhibit considerable structure due to autoionizing resonances. Total cross sections for production of Ar11+ in each of the eight states are presented for impact energies from threshold energy at 19.8 au to 200 au. Our theoretical values for the total cross section are in good agreement with recent experimental results.Total and single differential cross sections have been calculated for electron impact ionization of Ar10+(1s22s22p4)3Pe using a method that combines the distorted-wave Born approximation and R-matrix theory. In this method, the incident/scattered electron is described by the distorted-wave Born approximation, while both the initial bound state and the final continuum states are expanded in terms of an R-matrix basis. Eight states of the final Ar11+ ion are considered, namely 1s22s22p3 4So 2Do 2Po and 1s2 2s2p4 4Pe 2De 2Se 2Pe 2Po . Up to the 24- pole components of the interaction with ionizing electron were included, giving ten distinct Ar10+ continuum symmetries. We calculated single differential cross sections summed over final ionic states, as a function of the energy loss. These cross sections exhibit considerable structure due to autoionizing resonances. Total cross sections for production of Ar11+ in each of the eight states are presented for impact energies from threshold energy at 19.8 au to 200 au. Our theoretical values for the total cross section are in good agreement with recent experimental results

Access to Modern Energy: Assessment and Outlook for Developing and Emerging Regions

This report provides a high-level assessment of the progress to date, past policies and programs, and future scenarios related to modern energy access developed within the framework of the Global Energy Assessment (GEA). Providing universal access to modern energy for all is a goal increasingly discussed in international and national policy settings. Developing solutions to this challenge is one of the chief aims of policy makers, and for this reason this report attempts to synthesize a multitude of strategic insights that have resulted from the GEA analysis of this issue. The overarching objective of the report is to provide guidance on how to facilitate the achievement of universal access to clean-combusting cooking fuels and stoves, and rural electrification by 2030. Focus is given to assessing the situation at global and regional levels, as well as to the types of policies and measures that will be needed to ensure a successful household transition to modern energy in the next decades. Of particular note are the assessment of key success factors for enhancing access at a regional level, and estimation of investments required and impacts of achieving a 2030 universal modern energy access target. This report is complemented by two interactive, web-based analytical tools, which have been developed in support of this study: (1) the IIASA Energy Access Tool (Energy-ENACT), which permits the assessment of alternative future policy scenarios, including an estimation of investment needs and impacts at the global and regional scales; and (2) the GEA Scenario Database, which documents the full suite of GEA pathways in great detail, allowing the user to explore the consequences of different supply and demand-side technology choices for the feasibility and costs of reaching multiple energy objectives at both the global and regional levels

Comparison between seasonal pumped-storage and conventional reservoir dams from the water, energy and land nexus perspective

Renewable sources of energy are providing an increasing share of the electricity generation mix, but their intermittency drives a need for energy storage. At the same time, water resources are increasingly scarce due to changes in demand, such as from population growth, supply side pressures such as climate change and governance challenges relating to poor management. Large storage reservoirs are used for water management and for energy storage. However, some existing and proposed hydropower reservoirs require vast areas of land and have considerable social and environmental impacts. Growing concerns on water and energy storage from a water-energy-land nexus approach motivated this study. Our objective is to compare how energy and water storage services, such as hydropower generation, electricity grid and water management, are provided with Seasonal Pumped-Storage (SPS) and Conventional Reservoir Dams (CRD) plants. Our case study region is Brazil, a country with extensive hydropower capacity and development plans, for which we compare the cost, land requirement and social impacts between CRD and potential SPS plants. Whilst seasonal pumped-storage have higher capital costs than conventional reservoir dams, given the much lower land requirements and evaporative losses, they are a valuable water and energy storage alternative especially in locations with plain topography and high evaporation. Results show that if Sobradinho CRD was built today it would result in a $USD 1.46 billion loss, on the other hand, Muquém SPS plant would result in a$USD 0.67b revenue

Der Nutzen liegt auf der Hand

Im September 2011 präsentierte UN-Generalsekretär Ban Ki-moon die Initiative „Sustainable Energy for All“ mit drei globalen Zielen, die bis 2030 erreicht werden sollen. Erhebliche Investitionen werden dafür notwendig sein. Nach den Ergebnissen einer weltweiten Studie erscheint ihre Umsetzung jedoch machbar

Chronic effects of aerobic exercise on gene expression of LOX-1 receptor in the heart of rats fed with high fat diet

Objective(s): Lectin-like low density lipoprotein receptor (LOX-1) has pivot role in vascular complications, which is upregulated in numerous pathological conditions. Since exercise has beneficial effects in prevention of hyperlipidemic complications, present study examined protective effects of aerobic exercise through reduction of LOX-1 expression in heart during dyslipidemia. Materials and Methods: Four groups of rats were used (N=25): Normal, Normal and exercise, High fat and High fat and exercise. High fat diet (HFD) was made by adding 10 animal oil, 2 cholesterol and 0.5 colic acid to standard rodent chow. Exercise protocol consisted of swimming 1 hr/day, and 5 days/week for 8 weeks. Plasma lipids were evaluated at the end of experiment, 48 hr after final session of exercise. At the end, rats were sacrificed and heart was removed for determination of malondialdehyde (MDA) content, and LOX-1 expression. Results: HFD meaningfully changed lipid profile (>50), but chronic exercise had no significant effects on lipid profile. LOX-1 expression was significantly increased in heart of rats fed with HFD, while swimming exercise considerably reduced gene expression of LOX-1. MDA content was significantly enhanced in rats fed with HFD (4.37±0.6 nmol/mg, P<0.01) compared to normal group (1.56±0.48 nmol/mg), whereas swimming exercise decreased MDA level of heart in rats fed with HFD (2.28±0.32, P<0.01). Conclusion: Findings indicated that swimming exercise is able to diminish heart expression of LOX-1 receptor concomitant reduction of oxidative stress. Since these parameters are involved in generation of dyslipidemic complications, swimming exercise is a good candidate to reduce these complications. Copyright 2015, Mashhad University of Medical Sciences , All Rights Reserved

The prevalence of atrial fibrillation in Greenland:a register-based cross-sectional study based on disease classifications and prescriptions of oral anticoagulants

    Previous studies of the prevalence of atrial fibrillation (AF) in Greenland are based on either single-point electrocardiograms (ECGs) or patients admitted with stroke. This study estimates the prevalence of AF based on disease classifications in the electronic medical record system (EMR) and prescriptions of oral anticoagulants (OACs). Patients given a diagnose classification code for AF or atrial flutter or prescribed the vitamin K antagonist Warfarin or the direct-acting oral anticoagulant Rivaroxaban were identified in the EMR. Descriptive data and selected laboratory values were extracted, and a minimum CHA(2)DS(2)-VASc score was calculated for the 790 patients identified in the EMR (66% men). A total prevalence of AF of 1.4% was found in the general population (1.8% among men and 1.0% among women), with a significantly lower prevalence among women younger than 70 years. There was a significant increase in AF-prevalence with advancing age (p<0.001) for both men and women. A minimum CHA(2)DS(2)-VASc was estimated and app. 10% of the patients may be undertreated with OACs. The prevalence of AF found in this study is higher than that found in previous studies in Greenland and comparable to the prevalence found in other Western countries, indicating that AF is common in Greenland

The IIASA Energy Access Tool (Energy-ENACT)

Researchers from the Energy Program at the International Institute for Applied Systems Analysis (IIASA), building on work carried out within the framework of the Global Energy Assessment (GEA), have developed an interactive web-based scenario analysis tool that permits assessment of different policies for achieving universal access to modern energy by 2030. This software, known as the IIASA Energy-ENACT tool, is designed to assist national and regional policy makers and analysts in their strategic policy planning processes. The tool extends work undertaken for the GEA and, as such, is built on an extensive set of energy access scenarios to visualise costs and benefits of specific policy choices and their impacts. This document serves as an introduction to the Energy-ENACT tool and as a brief manual for the typical user