Nonnegative solutions of parabolic operators with low-order terms

We develop the harmonic analysis approach for parabolic operator with one order term in the parabolic Kato class on $C^{1,1}$-cylindrical domain $\Omega$. We study the boundary behaviour of nonnegative solutions. Using these results, we prove the integral representation theorem and the existence of nontangential limits on the boundary of $\Omega$ for nonnegative solutions. These results extend some first ones proved for less general parabolic operators

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

Assessment of Alternative Hydrogen Pathways: Natural Gas and Biomass

Achieving large-scale changes to develop a sustained hydrogen economy requires a large amount of planning and cooperation at national and international levels alike. ECS developed a long-term hydrogen-based scenario (B1-H2) of the global energy system to examine the future perspectives of fuel cells (Barreto et al., 2002). That earlier study, done with the collaboration and support of the Tokyo Electric Power Company (TEPCO), illustrated the key role of hydrogen towards a clean and sustainable energy future. In an affluent, low-population-growth, equity and sustainability-oriented world, hydrogen technologies experience substantial but plausible performance and costs improvements and diffuse extensively. Fuel cells and other hydrogen-using technologies play a major role in a transformation towards a more flexible, less vulnerable, distributed energy system that meets energy needs in a cleaner, more efficient and cost-effective way. This profound structural transformation of the global energy system brings substantial improvements in energy intensity and an accelerated decarbonizaton of the energy mix, resulting in relatively low climate impacts. In order to understand the future potential of hydrogen, in this report we compare the two main hydrogen production alternatives from natural gas and biomass as identified in the above-mentioned (B1-H2) scenario in more detail. The first alternative, steam reforming of natural gas, is a well-established technology and the most common and current method to produce hydrogen (Ogden, 1999a). The second technology, biomass gasification, is still in its infancy. A small number of demonstration facilities are in place. Many issues still have to be addressed before the technology can be expected to reach an adequate technical performance and hence become economically competitive (Milne et al., 2002). Nevertheless, biomass-based systems are a very promising option for ensuring the sustainability of a future hydrogen-supply system. The report includes a comparative analysis of both systems and their potential for carbon mitigation via CO2 capture and sequestration. Estimates of the hydrogen costs for alternative production chains are presented, and the competitiveness of the systems under alternative CO2 taxes are analyzed. Both technologies appear as economically attractive and environmentally compatible options for shaping a sustainable hydrogen economy and contributing to the mitigation of greenhouse gas emissions in the long term

Technological progress towards sustainable development

The purpose of this paper is twofold. First, to present an analysis of a comprehensive set of global energy scenarios that has been undertaken to identify key energy technologies for achieving sustainable development. Secondly, to describe tools that could aid policy makers using insights in the dynamics of technological progress to promote the development of promising technologies throughresearch and development (R&D) and procurement. As an operational working definition of sustainable development we use the following four criteria: (1) Economic growth sustains throughout the whole time horizon; (2) socio-economic inequity among world regions is reduced "significantly" during this century; (3) reserves-to-production (R/P) ratios of exhaustible primary energy carriers do not decrease substantially from today's values; and (4) short- to medium-term environmental impacts (e.g., acidification) are reduced towards meeting critical loads and carbon emissions at the end of the century are below today's levels. Applying these criteria in an analysis of a representative set of global economy-energy-environment scenarios shows that in sustainable-development scenarios, hydrogen fuel cells and solar photovoltaic cells emerge as key technologies in the long run. Natural gas technologies, in particular fuel cells and combined-cycle power plants, could provide for an efficient medium-term transition to these key technologies. The question then becomes which policies can promote the development of these technologies. We think that an important tool to tackle this question is provided by an improved concept of technological learning. According to that concept, technological progress, expressed as specific technology cost, is a regular function of not only cumulative installed capacity but also of R&D expenditures. This tool can assist in determining how much money should be spent for which energy technology on procurement (capacity expansion) and how much money for R&D. The results of first model runs aiming at eventually formulating policy guidance are presented

A Model of Noncommunicable Diseases Determinants in Iran; a Qualitative Study

Aims: Non-communicable diseases have become an emerging pandemic globally with disproportionately higher rates in developing countries. This study aimed to design a representative model of non-communicable diseases determinants in Iran according to the viewpoint of experts. Participants & Methods: The statistical population of this qualitative study was experts and academic member informants, who were worked at Kashan, Esfahan and Tehran Universities of Medical Sciences in March to June 2016. 20 participants were selected through purposeful sampling method. Experts were asked to explain their opinion regarding to the most effective factors of noncommunicable disease in developing countries. Findings: Social, environmental, and physiological factors, besides the life style were affecting factors on non-communicable diseases in developing countries. Conclusion: Social, environmental, and physiological factors, besides the life style are affecting factors on non-communicable diseases in developing countries

Aviram-Ratner rectifying mechanism for DNA base pair sequencing through graphene nanogaps

We demonstrate that biological molecules such as Watson-Crick DNA base pairs can behave as biological Aviram-Ratner electrical rectifiers because of the spatial separation and weak hydrogen bonding between the nucleobases. We have performed a parallel computational implementation of the ab-initio non-equilibrium Green's function (NEGF) theory to determine the electrical response of graphene---base-pair---graphene junctions. The results show an asymmetric (rectifying) current-voltage response for the Cytosine-Guanine base pair adsorbed on a graphene nanogap. In sharp contrast we find a symmetric response for the Thymine-Adenine case. We propose applying the asymmetry of the current-voltage response as a sensing criterion to the technological challenge of rapid DNA sequencing via graphene nanogaps

Quantifying the potential for reservoirs to secure future surface water yields in the world's largest river basins

Surface water reservoirs provide us with reliable water supply, hydropower generation, flood control and recreation services. Yet, reservoirs also cause flow fragmentation in rivers and lead to flooding of upstream areas, thereby displacing existing land-use activities and ecosystems. Anticipated population growth and development coupled with climate change in many regions of the globe suggests a critical need to assess the potential for future reservoir capacity to help balance rising water demands with long-term water availability. Here, we assess the potential of large-scale reservoirs to provide reliable surface water yields while also considering environmental flows within 235 of the world’s largest river basins. Maps of existing cropland and habitat conservation zones are integrated with spatially-explicit population and urbanization projections from the Shared Socioeconomic Pathways (SSP) to identify regions unsuitable for increasing water supply by exploiting new reservoir storage. Results show that even when maximizing the global reservoir storage to its potential limit (~4.3-4.8 times the current capacity), firm yields would only increase by about 50% over current levels. However, there exist large disparities across different basins. The majority of river basins in North America are found to gain relatively little firm yield by increasing storage capacity, whereas basins in Southeast Asia display greater potential for expansion as well as proportional gains in firm yield under multiple uncertainties. Parts of Europe, the United States and South America show relatively low reliability of maintaining current firm yields under future climate change, whereas most of Asia and higher latitude regions display comparatively high reliability. Findings from this study highlight the importance of incorporating different factors, including human development, land-use activities, and climate change, over a time span of multiple decades and across a range of different scenarios when quantifying available surface water yields and the potential for reservoir expansion