Showing papers on "Energy source published in 2002"

Environmental and Natural Resource Economics

Abstract: 1. Visions of the Future. 2. Valuing the Environment: Concepts. 3. Valuing the Environment: Methods. 4. Property Rights, Externalities, and Environmental Problems. 5. Sustainable Development: Defining the Concept. 6. The Population Problem. 7. The Allocation of Depletable and Renewable Resources. 8. Depletable, Non-recyclable Energy Resources: Oil, Gas, Coal and Uranium. 9. Recyclable Resources: Minerals, Paper, Glass, etc. 10. Replenishable but Depletable Resources: Water. 11. Reproducible Private-Property Resources: Agriculture. 12. Storable, Renewable Resources: Forests. 13. Renewable Common-Property Resources: Fisheries and Other Species. 14. Generalized Resource Scarcity. 15. Economics of Pollution Control: An Overview. 16. Stationary-Source Local Air Pollution. 17. Regional and Global Air Pollutants: Acid Rain and Atmospheric Modification. 18. Mobile -Source Air Pollution. 19. Water Pollution. 20. Toxic Substances. 21. Environmental Justice. 22. Development, Poverty, and the Environment. 23. The Quest for Sustainable Development. 24. Visions of the Future Revisited.

Advanced Technology Paths to Global Climate Stability: Energy for a Greenhouse Planet

Abstract: Stabilizing the carbon dioxide-induced component of climate change is an energy problem. Establishment of a course toward such stabilization will require the development within the coming decades of primary energy sources that do not emit carbon dioxide to the atmosphere, in addition to efforts to reduce end-use energy demand. Mid-century primary power requirements that are free of carbon dioxide emissions could be several times what we now derive from fossil fuels (approximately 10(13) watts), even with improvements in energy efficiency. Here we survey possible future energy sources, evaluated for their capability to supply massive amounts of carbon emission-free energy and for their potential for large-scale commercialization. Possible candidates for primary energy sources include terrestrial solar and wind energy, solar power satellites, biomass, nuclear fission, nuclear fusion, fission-fusion hybrids, and fossil fuels from which carbon has been sequestered. Non-primary power technologies that could contribute to climate stabilization include efficiency improvements, hydrogen production, storage and transport, superconducting global electric grids, and geoengineering. All of these approaches currently have severe deficiencies that limit their ability to stabilize global climate. We conclude that a broad range of intensive research and development is urgently needed to produce technological options that can allow both climate stabilization and economic development.

The state of the art of electric and hybrid vehicles

Abstract: In a world where environment protection and energy conservation are growing concerns, the development of electric vehicles (EV) and hybrid electric vehicles (HEV) has taken on an accelerated pace. The dream of having commercially viable EVs and HEVs is becoming a reality. EVs and HEVs are gradually available in the market. This paper will provide an overview of the present status of electric and hybrid vehicles worldwide and their state of the art, with emphasis on the engineering philosophy and key technologies. The importance of the integration of technologies of automobile, electric motor drive, electronics, energy storage, and controls and also the importance of the integration of society strength from government, industry, research institutions, electric power utilities, and transportation authorities are addressed. The challenge of EV commercialization is discussed.

Equivalent consumption minimization strategy for parallel hybrid powertrains

Abstract: Hybrid vehicles use at least two energy sources for their propelling. Usually an electric motor is used with an IC engine. Hybrid vehicles are expected to be less polluting and to have a lower fuel consumption than conventional vehicles. This paper presents an algorithm which chooses the power split between the motor and the engine in order to minimize the fuel consumption. First of all, the prototype built at the LAMIH is presented, then the equivalent consumption minimization strategy is described. First results show that a 17.5% of fuel reduction can be achieved for the CEN speed cycle.

A large-cavity zeolite with wide pore windows and potential as an oil refining catalyst

Abstract: Crude oil is an important feedstock for the petrochemical industry and the dominant energy source driving the world economy, but known oil reserves will cover demand for no more than 50 years at the current rate of consumption1. This situation calls for more efficient strategies for converting crude oil into fuel and petrochemical products. At present, more than 40% of oil conversion is achieved using catalysts based on faujasite; this zeolite requires extensive post-synthesis treatment to produce an ultrastable form2,3, and has a large cavity accessible through four 0.74-nm-wide windows and thus limits the access of oil molecules to the catalytically active sites. The use of zeolites with better accessibility to their active sites should result in improved catalyst efficiency. To date, two zeolites with effective pore diameters exceeding that of faujasite have been reported4,5, but their one-dimensional pore topology excludes use in oil refining. Similarly, zeolites with large pores and a three-dimensional pore topology have been reported6,7,8, but in all these materials the pore openings are smaller than in faujasite. Here we report the synthesis of ITQ-21, a zeolite with a three-dimensional pore network containing 1.18-nm-wide cavities, each of which is accessible through six circular and 0.74-nm-wide windows. As expected for a zeolite with this structure, ITQ-21 exhibits high catalytic activity and selectivity for valuable products in preliminary oil refining tests.

Fatty Acid Oxidation Disorders

Abstract: ▪ Abstract Genetic disorders of mitochondrial fatty acid β-oxidation have been recognized within the last 20 years as important causes of morbidity and mortality, highlighting the physiological significance of fatty acids as an energy source. Although the mammalian mitochondrial fatty acid-oxidizing system was recognized at the beginning of the last century, our understanding of its exact nature remains incomplete, and new components are being identified frequently. Originally described as a four-step enzymatic process located exclusively in the mitochondrial matrix, we now recognize that long-chain-specific enzymes are bound to the inner mitochondrial membrane, and some enzymes are expressed in a tissue-specific manner. Much of our new knowledge of fatty acid metabolism has come from the study of patients who were diagnosed with single-gene autosomal recessive defects, a situation that seems to be further evolving with the emergence of phenotypes determined by combinations of multiple genetic and environ...

Biodiesel from palmoil—an analysis of its properties and potential

Abstract: If the agricultural products market is limited and much of agricultural land is not utilized as is the case in many countries in the world at present, then agriculture should be directed to the production of new alternative products. The land can be used to produce non-food products including biodiesels for the domestic energy market to diminish imports. Much research has been done on biodiesels over the last 20 yr after the oil crisis in 1973. At present, concern about environmental regulations has been the major reason to look for alternative fuel. A significant level in terms of physico-chemical properties of biodiesel has been obtained but there is a lack of full or partial replacement of fossil fuel that needs to be discussed. This paper presents the experimental results carried out to evaluate the effect of anticorrosion additive in biodiesel (from palm oil) on diesel engines, performance, emissions and wear characteristics. This biodiesel is defined as the methyl ester of palm oil also known as palm oil diesel. The results of this investigation will be used to find compatible lubricant for biodiesel engine.

Dominance of autochthonous autotrophic carbon in food webs of heterotrophic rivers

Abstract: This paper addresses the river heterotrophy paradox, “How can animal biomass within riverine food webs be fueled primarily by autochthonous autotrophic production if the ecosystem as a whole is heterotrophic?”. Reviewed, stable isotope data from tropical, temperate, and arctic rivers provide evidence consistent with the revised riverine productivity model (RPM): “The primary, annual energy source supporting overall metazoan production and species diversity in mid- to higher-trophic levels of most rivers (≥4th order) is autochthonous primary production entering food webs via algal-grazer and decomposer pathways”. The revised RPM does not conflict with the heterotrophy paradox because: (a) the decomposer (microbial loop) food pathway processes most of the transported, allochthonous and autochthonous carbon and, with algal respiration in some cases, is primarily responsible for a river's heterotrophic state (P/R<1); but (b) biomass production of mid- to higher-trophic levels is principally supported by an algal-grazer (phytoplankton and benthic microalgae) pathway that is only weakly linked to the decomposer pathway. The reason the algal-grazer pathway supports the majority of metazoan biomass is that allochthonous carbon is mostly recalcitrant, whereas carbon from autochthonous primary production, though much less plentiful, is commonly more labile (easier to assimilate), contains more energy per unit mass, and is typically preferred by metazoa.

Lead telluride as a thermoelectric material for thermoelectric power generation

Abstract: The specialized applications of thermoelectric generators are very successful and have motivated a search for materials with an improved figure of merit Z, and also for materials which operate at elevated temperatures. Lead telluride, PbTe, is an intermediate thermoelectric power generator. Its maximum operating temperature is 900 K. PbTe has a high melting point, good chemical stability, low vapor pressure and good chemical strength in addition to high figure of merit Z. Recently, research in thermoelectricity aims to obtain new improved materials for autonomous sources of electrical power in specialized medical, terrestial and space applications and to obtain an unconventional energy source after the oil crises of 1974. Although the efficiency of thermoelectric generators is rather low, typically ∼5%, the other advantages, such as compactness, silent, reliability, long life, and long period of operation without attention, led to a wide range of applications. PbTe thermoelectric generators have been widely used by the US army, in space crafts to provide onboard power, and in pacemakers batteries. The general physical properties of lead telluride and factors affecting the figure of merit have been reviewed. Various possibilities of improving the figure of merit of the material have been given, including effect of grain size on reducing the lattice thermal conductivity λ L . Comparison of some transport properties of lead telluride with other thermoelectric materials and procedures of preparing compacts with transport properties very close to the single crystal values from PbTe powder by cold and hot-pressing techniques are discussed.

Evolution of "51 Pegasus b-like" planets

Abstract: About one-quarter of the extrasolar giant planets discovered so far have orbital distances smaller than 0.1 AU. These "51 Peg b-like" planets can now be directly characterized, as shown by the planet transiting in front the star HD 209458. We review the processes that affect their evolution. We apply our work to the case of HD 209458b, whose radius has been recently measured. We argue that its radius can be reproduced only when the deep atmosphere is assumed to be unrealistically hot. When using more realistic atmospheric temperatures, an energy source appears to be missing in order to explain HD 209458b's large size. The most likely source of energy available is not in the planet's spin or orbit, but in the intense radiation received from the parent star. We show that the radius of HD 209458b can be reproduced if a small fraction (∼1%) of the stellar flux is transformed into kinetic energy in the planetary atmosphere and subsequently converted to thermal energy by dynamical processes at pressures of tens of bars.

Star formation from galaxies to globules

Abstract: The origin of the empirical laws of galactic scale star formation is considered in view of the self-similar nature of interstellar gas and the observation that most local clusters are triggered by specific high-pressure events. The empirical laws suggest that galactic scale gravity is involved in the first stages of star formation, but they do not identify the actual triggering mechanisms for clusters in the final stages. Many triggering processes satisfy the empirical laws, including turbulence compression and expanding shell collapse. The self-similar nature of the gas and associated young stars suggests that turbulence is more directly involved, but the energy source for this turbulence is not clear, and the small-scale morphology of gas around most embedded clusters does not look like a random turbulent flow. Most clusters appear to be triggered by other nearby stars. Such a prominent local influence makes it difficult to understand the universality of the Kennicutt and Schmidt laws on galactic scales. A unified view of multiscale star formation avoids most of these problems. The Toomre and Kennicutt surface density thresholds, along with the large-scale gas and star formation morphology, imply that ambient self-gravity produces spiral arms and giant cloud complexes and at the same time drives much of the turbulence that leads to self-similar structures. Localized energy input from existing clusters and field supernovae drives turbulence and cloud formation too, while triggering clusters directly in preexisting clouds. The hierarchical structure in the gas made by turbulence ensures that the triggering time scales with size, thereby giving the Schmidt law over a wide range of scales and the size-duration correlation for young star fields. Reanalysis of the Schmidt law from a local point of view suggests that the efficiency of star formation is determined by the fraction of the gas above a critical density of around 105 m(H2) cm-3. Such high densities probably result from turbulence compression in a self-gravitating gas, in which case their mass fraction can be estimated from the density distribution function that results from turbulence. For Wada & Norman's lognormal function that arises in whole-galaxy simulations, the theoretically predicted mass fraction of star-forming material is the same as that observed directly from the galactic Schmidt law and is ~10-4. The unified view explains how independent star formation processes can combine into the empirical laws while preserving the fractal nature of interstellar gas and the pressurized, wind-swept appearance of most small-scale clouds. Likely variations in the relative roles of these processes from region to region should not affect the large-scale average star formation rate. Self-regulation by spiral instabilities and star formation ensures that most regions are in a marginally stable state in which turbulence limits the mass available for star formation and the overall rate is independent of the nature of the energy sources. In this sense, star formation is saturated to its largest possible value given the fractal nature of the interstellar medium.

Selfgravity and QSO disks

Abstract: It is well known that the outer parts of QSO accretion disks are prone to selfgravity if heated solely by orbital dissipation. Such disks might be expected to form stars rather than accrete onto the black hole. The arguments leading to this conclusion are reviewed. Conversion of a part of the gas into high-mass stars or stellar-mass black holes, and the release of energy in these objects by fusion or accretion, may help to stabilize the remaining gas. If the disk extends beyond a parsec, however, more energy is probably required for stability than is available by turning half the gas into high-mass stars. Small black holes are perhaps marginally viable energy sources, with important implications (not pursued here) for the QSO spectral energy distribution, the metallicity of the gas, microlensing of QSO disks, and perhaps gravitational-wave searches. Other possible palliatives for selfgravity include accretion driven by nonviscous torques that allow near-sonic accretion speeds and hence lower surface densities for a given mass accretion rate. All such modes of accretion face major theoretical difficulties, and in any case merely postpone selfgravity. Alternatively, thin disks may not exist beyond a thousand Schwarzshild radii or so (0.01 parsec), in which case QSOs must be fueled by gas with small specific angular momentum.

ORIGINAL COMMUNICATION The paradoxical nature of hunter-gatherer diets: meat-based, yet non-atherogenic

Abstract: Objective: Field studies of twentieth century hunter-gathers (HG) showed them to be generally free of the signs and symptoms of cardiovascular disease (CVD). Consequently, the characterization of HG diets may have important implications in designing therapeutic diets that reduce the risk for CVD in Westernized societies. Based upon limited ethnographic data (n ¼ 58 HG societies) and a single quantitative dietary study, it has been commonly inferred that gathered plant foods provided the dominant energy source in HG diets. Method and Results: In this review we have analyzed the 13 known quantitative dietary studies of HG and demonstrate that animal food actually provided the dominant (65%) energy source, while gathered plant foods comprised the remainder (35%). This data is consistent with a more recent, comprehensive review of the entire ethnographic data (n ¼ 229 HG societies) that showed the mean subsistence dependence upon gathered plant foods was 32%, whereas it was 68% for animal foods. Other evidence, including isotopic analyses of Paleolithic hominid collagen tissue, reductions in hominid gut size, low activity levels of certain enzymes, and optimal foraging data all point toward a long history of meat-based diets in our species. Because increasing meat consumption in Western diets is frequently associated with increased risk for CVD mortality, it is seemingly paradoxical that HG societies, who consume the majority of their energy from animal food, have been shown to be relatively free of the signs and symptoms of CVD. Conclusion: The high reliance upon animal-based foods would not have necessarily elicited unfavorable blood lipid profiles because of the hypolipidemic effects of high dietary protein (19 ‐ 35% energy) and the relatively low level of dietary carbohydrate (22 ‐ 40% energy). Although fat intake (28 ‐ 58% energy) would have been similar to or higher than that found in Western diets, it is likely that important qualitative differences in fat intake, including relatively high levels of MUFA and PUFA and a lower o-6=o-3 fatty acid ratio, would have served to inhibit the development of CVD. Other dietary characteristics including high intakes of antioxidants, fiber, vitamins and phytochemicals along with a low salt intake may have operated synergistically with lifestyle characteristics (more exercise, less stress and no smoking) to further deter the development of CVD.

Evolution of "51Peg b-like" Planets

Abstract: About one-quarter of the extrasolar giant planets discovered so far have orbital distances smaller than 0.1 AU. These ``51Peg b-like'' planets can now be directly characterized, as shown by the planet transiting in front the star HD209458. We review the processes that affect their evolution. We apply our work to the case of HD209458b, whose radius has been recently measured. We argue that its radius can be reproduced only when the deep atmosphere is assumed to be unrealistically hot. When using more realistic atmospheric temperatures, an energy source appears to be missing in order to explain HD209458b's large size. The most likely source of energy available is not in the planet's spin or orbit, but in the intense radiation received from the parent star. We show that the radius of HD209458b can be reproduced if a small fraction (~1%) of the stellar flux is transformed into kinetic energy in the planetary atmosphere and subsequently converted to thermal energy by dynamical processes at pressures of tens of bars.

The paradoxical nature of hunter-gatherer diets: meat-based, yet non-atherogenic

Abstract: Objective: Field studies of twentieth century hunter-gathers (HG) showed them to be generally free of the signs and symptoms of cardiovascular disease (CVD). Consequently, the characterization of HG diets may have important implications in designing therapeutic diets that reduce the risk for CVD in Westernized societies. Based upon limited ethnographic data (n=58 HG societies) and a single quantitative dietary study, it has been commonly inferred that gathered plant foods provided the dominant energy source in HG diets. Method and Results: In this review we have analyzed the 13 known quantitative dietary studies of HG and demonstrate that animal food actually provided the dominant (65%) energy source, while gathered plant foods comprised the remainder (35%). This data is consistent with a more recent, comprehensive review of the entire ethnographic data (n=229 HG societies) that showed the mean subsistence dependence upon gathered plant foods was 32%, whereas it was 68% for animal foods. Other evidence, including isotopic analyses of Paleolithic hominid collagen tissue, reductions in hominid gut size, low activity levels of certain enzymes, and optimal foraging data all point toward a long history of meat-based diets in our species. Because increasing meat consumption in Western diets is frequently associated with increased risk for CVD mortality, it is seemingly paradoxical that HG societies, who consume the majority of their energy from animal food, have been shown to be relatively free of the signs and symptoms of CVD. Conclusion: The high reliance upon animal-based foods would not have necessarily elicited unfavorable blood lipid profiles because of the hypolipidemic effects of high dietary protein (19–35% energy) and the relatively low level of dietary carbohydrate (22–40% energy). Although fat intake (28–58% energy) would have been similar to or higher than that found in Western diets, it is likely that important qualitative differences in fat intake, including relatively high levels of MUFA and PUFA and a lower ω-6/ω-3 fatty acid ratio, would have served to inhibit the development of CVD. Other dietary characteristics including high intakes of antioxidants, fiber, vitamins and phytochemicals along with a low salt intake may have operated synergistically with lifestyle characteristics (more exercise, less stress and no smoking) to further deter the development of CVD.

Molecular Hydrogen as an Energy Source for Helicobacter pylori

Abstract: The gastric pathogen Helicobacter pylori is known to be able to use molecular hydrogen as a respiratory substrate when grown in the laboratory We found that hydrogen is available in the gastric mucosa of mice and that its use greatly increased the stomach colonization by H pylori Hydrogenase activity in H pylori is constitutive but increased fivefold upon incubation with hydrogen Hydrogen concentrations measured in the stomachs of live mice were found to be 10 to 50 times as high as the H pylori affinity for hydrogen A hydrogenase mutant strain is much less efficient in its colonization of mice Therefore, hydrogen present in animals as a consequence of normal colonic flora is an energy-yielding substrate that can facilitate the maintenance of a pathogenic bacterium

Influence of the Protein Digestion Rate on Protein Turnover in Young and Elderly Subjects

Abstract: It has long been recognized that numerous dietary parameters, such as the amount and type of protein and nonprotein energy sources, affect protein metabolism. More recently, we demonstrated that the protein digestion rate is an independent factor regulating postprandial protein gain. Indeed, in young men, using a non-steady-state approach and intrinsically labeled milk protein fractions [whey protein (WP) and casein (CAS)] we showed that a slow digested dietary protein (CAS) induced a greater protein gain than a fast one (WP). The mechanisms of this gain also differed according to the protein rate of digestion. WP stimulated amino acid oxidation and protein synthesis without modifying proteolysis, whereas CAS increased amino acid oxidation and protein synthesis to a lesser extent and strongly inhibited proteolysis. These results led to the concept of "slow" and "fast" protein and were confirmed by further experiments during which the meals tested presented different digestion rates but were otherwise identical in terms of amino acid profile. We also analyzed the effects of fat and carbohydrates added to CAS and WP. Our preliminary results suggest that added nonprotein energy sources to CAS and WP attenuated the differences in both the protein digestion rate and protein gain. Finally, and in contrast to young subjects, a "fast" protein may be more beneficial than a "slow" one in elderly subjects, to limit body protein loss. However, long-term studies are needed to confirm this age-related effect.

Bacterial chemotaxis toward environmental pollutants: role in bioremediation.

Abstract: The increasing release of organic pollutants by industries cause many health-related problems. However, increased awareness of the harmful effects of environmental pollution has led to a dramatic increase in research on various strategies that may be employed to clean up the environment. It is now realized that microbial metabolism provides a safer, more efficient, and less expensive alternative to physicochemical methods for pollution abatement (27). In the past few decades, a vast range of xenobiotic compounds have been found to be susceptible to microbial mineralization. In most instances where mineralization has been demonstrated, the catabolic pathway and its regulation have also been determined. Bacterial chemotaxis, movement under the influence of a chemical gradient, either toward (positive chemotaxis) or away (negative chemotaxis) from the gradient helps bacteria to find optimum conditions for their growth and survival. However, this aspect has received little attention, even though some microorganisms with the chemotactic ability toward different xenobiotic compounds have been isolated and characterized (8, 19, 23, 41, 53). In many cases, the chemoattractant is a compound that serves as carbon and energy source, whereas a chemorepellent is toxic for the bacteria. We describe here recent discoveries in bacterial chemotaxis toward pollutants and how they may be explored and exploited for bioremediation applications.