Showing papers on "Energy source published in 2015"

Reducing the energy cost of human walking using an unpowered exoskeleton

Abstract: With efficiencies derived from evolution, growth and learning, humans are very well-tuned for locomotion. Metabolic energy used during walking can be partly replaced by power input from an exoskeleton, but is it possible to reduce metabolic rate without providing an additional energy source? This would require an improvement in the efficiency of the human-machine system as a whole, and would be remarkable given the apparent optimality of human gait. Here we show that the metabolic rate of human walking can be reduced by an unpowered ankle exoskeleton. We built a lightweight elastic device that acts in parallel with the user's calf muscles, off-loading muscle force and thereby reducing the metabolic energy consumed in contractions. The device uses a mechanical clutch to hold a spring as it is stretched and relaxed by ankle movements when the foot is on the ground, helping to fulfil one function of the calf muscles and Achilles tendon. Unlike muscles, however, the clutch sustains force passively. The exoskeleton consumes no chemical or electrical energy and delivers no net positive mechanical work, yet reduces the metabolic cost of walking by 7.2 ± 2.6% for healthy human users under natural conditions, comparable to savings with powered devices. Improving upon walking economy in this way is analogous to altering the structure of the body such that it is more energy-effective at walking. While strong natural pressures have already shaped human locomotion, improvements in efficiency are still possible. Much remains to be learned about this seemingly simple behaviour.

The future of organic photovoltaics

Abstract: Increasing global demand for energy, along with dwindling fossil fuel resources and a better understanding of the hidden costs associated with these energy sources, have spurred substantial political, academic, and industrial interest in alternative energy resources. Photovoltaics based on organic semiconductors have emerged as promising low-cost alternatives for electricity generation that relies on sunlight. In this tutorial review we discuss the relevance of these organic photovoltaics beginning with some of the economic drivers for these technologies. We then examine the basic properties of these devices, including operation and materials requirements, in addition to presenting the development of the field from a historical perspective. Potential future directions are also briefly discussed. This tutorial review is intended to be an essential overview of the progress of the field, in addition to aiding in the discussion of the future of OPV technologies.

Functional Roles of Fatty Acids and Their Effects on Human Health

Abstract: A variety of fatty acids exists in the diet of humans, in the bloodstream of humans, and in cells and tissues of humans. Fatty acids are energy sources and membrane constituents. They have biological activities that act to influence cell and tissue metabolism, function, and responsiveness to hormonal and other signals. The biological activities may be grouped as regulation of membrane structure and function; regulation of intracellular signaling pathways, transcription factor activity, and gene expression; and regulation of the production of bioactive lipid mediators. Through these effects, fatty acids influence health, well-being, and disease risk. The effects of saturated, cis monounsaturated, ω-6 and ω-3 polyunsaturated, and trans fatty acids are discussed. Although traditionally most interest in the health impact of fatty acids related to cardiovascular disease, it is now clear that fatty acids influence a range of other diseases, including metabolic diseases such as type 2 diabetes, inflammatory diseases, and cancer. Scientists, regulators, and communicators have described the biological effects and the health impacts of fatty acids according to fatty acid class. However, it is now obvious that within any fatty acid class, different members have different actions and effects. Thus, it would seem more appropriate to describe biological effects and health impacts of individual named fatty acids, although it is recognized that this would be a challenge when communicating outside of an academic environment (eg, to consumers).

Dietary gut microbial metabolites, short-chain fatty acids, and host metabolic regulation.

Abstract: During feeding, the gut microbiota contributes to the host energy acquisition and metabolic regulation thereby influencing the development of metabolic disorders such as obesity and diabetes. Short-chain fatty acids (SCFAs) such as acetate, butyrate, and propionate, which are produced by gut microbial fermentation of dietary fiber, are recognized as essential host energy sources and act as signal transduction molecules via G-protein coupled receptors (FFAR2, FFAR3, OLFR78, GPR109A) and as epigenetic regulators of gene expression by the inhibition of histone deacetylase (HDAC). Recent evidence suggests that dietary fiber and the gut microbial-derived SCFAs exert multiple beneficial effects on the host energy metabolism not only by improving the intestinal environment, but also by directly affecting various host peripheral tissues. In this review, we summarize the roles of gut microbial SCFAs in the host energy regulation and present an overview of the current understanding of its physiological functions.

The decomposition of energy-related carbon emission and its decoupling with economic growth in China

Abstract: In order to find the efficient ways to reduce carbon emission intensity in China, we utilize the LMDI method to decompose the changes of China׳s carbon emissions and carbon emission intensity from 1996 to 2010, from the perspectives of energy sources and industrial structure respectively. Then we introduce the decoupling index to analyze the decoupling relationship between carbon emissions and economic growth in China. The results indicate that, on the one hand, economic growth appeared as the main driver of carbon emissions increase in the past decades, while the decrease of energy intensity and the cleaning of final energy consumption structure played significant roles in curbing carbon emissions; meanwhile, the secondary industry proved the principal source of carbon emissions reduction among the three industries and had relatively higher potential. On the other hand, when the decoupling relationship is considered, most years during the study period saw the relative decoupling effect between carbon emissions and economic growth, which indicated that the reduction effect of inhibiting factors of carbon emissions was less than the driving effect of economic growth, and the economy grew with increased carbon emissions; there appeared the absolute decoupling effect in 1997, 2000 and 2001, which implied that the economy grew while carbon emissions decreased; whereas no decoupling effect was identified in 2003 and 2004.

Global Prospects, Progress, Policies and Environmental Impact of Solar Photovoltaic Power Generation

Abstract: Global energy demand and environmental concerns are the driving force for use of alternative, sustainable, and clean energy sources. Solar energy is the inexhaustible and CO2-emission-free energy source worldwide. The Sun provides 1.4 � 10 5 TW power as received on the surface of the Earth and about 3.6 � 10 4 TW of this power is usable. In 2012, world power consumption was 17 TW, which is less than 3.6 � 10 4 TW. Photovoltaic (PV) cells are the basic element for converting solar energy into electricity. PV cell technologies, energy conversion efficiency, economic analysis, energy policies, environmental impact, various applications, prospects, and progress have been comprehensively reviewed and presented in this paper. This work compiles the latest literature (i.e. journal articles, conference proceedings, and reports, among others) on PV power generation, economic analysis, environmental impact, and policies to increase public awareness. From the review, it was found that PV is an easy way to capture solar energy where PV based power generation has also rapidly increased.

Flexible thermoelectric materials and device optimization for wearable energy harvesting

Abstract: In this paper, we review recent advances in the development of flexible thermoelectric materials and devices for wearable human body-heat energy harvesting applications. We identify various emerging applications such as specialized medical sensors where wearable thermoelectric generators can have advantages over other energy sources. To meet the performance requirements for these applications, we provide detailed design guidelines regarding the properties of the material, device dimensions, and gap fillers by performing realistic device simulations with important parasitic losses taken into account. For this, we review recently emerging flexible thermoelectric materials suited for wearable applications, such as polymer-based materials and screen-printed paste-type inorganic materials. A few examples among these materials are selected for thermoelectric device simulations in order to find optimal design parameters for wearable applications. Finally we discuss the feasibility of scalable and cost-effective manufacturing of thermoelectric energy harvesting devices with desired dimensions.

Direct-drive inertial confinement fusion: A review

Abstract: The direct-drive, laser-based approach to inertial confinement fusion (ICF) is reviewed from its inception following the demonstration of the first laser to its implementation on the present generation of high-power lasers. The review focuses on the evolution of scientific understanding gained from target-physics experiments in many areas, identifying problems that were demonstrated and the solutions implemented. The review starts with the basic understanding of laser–plasma interactions that was obtained before the declassification of laser-induced compression in the early 1970s and continues with the compression experiments using infrared lasers in the late 1970s that produced thermonuclear neutrons. The problem of suprathermal electrons and the target preheat that they caused, associated with the infrared laser wavelength, led to lasers being built after 1980 to operate at shorter wavelengths, especially 0.35 μm—the third harmonic of the Nd:glass laser—and 0.248 μm (the KrF gas laser). The main physics areas relevant to direct drive are reviewed. The primary absorption mechanism at short wavelengths is classical inverse bremsstrahlung. Nonuniformities imprinted on the target by laser irradiation have been addressed by the development of a number of beam-smoothing techniques and imprint-mitigation strategies. The effects of hydrodynamic instabilities are mitigated by a combination of imprint reduction and target designs that minimize the instability growth rates. Several coronal plasma physics processes are reviewed. The two-plasmon–decay instability, stimulated Brillouin scattering (together with cross-beam energy transfer), and (possibly) stimulated Raman scattering are identified as potential concerns, placing constraints on the laser intensities used in target designs, while other processes (self-focusing and filamentation, the parametric decay instability, and magnetic fields), once considered important, are now of lesser concern for mainline direct-drive target concepts. Filamentation is largely suppressed by beam smoothing. Thermal transport modeling, important to the interpretation of experiments and to target design, has been found to be nonlocal in nature. Advances in shock timing and equation-of-state measurements relevant to direct-drive ICF are reported. Room-temperature implosions have provided an increased understanding of the importance of stability and uniformity. The evolution of cryogenic implosion capabilities, leading to an extensive series carried out on the 60-beam OMEGA laser [Boehly et al., Opt. Commun. 133, 495 (1997)], is reviewed together with major advances in cryogenic target formation. A polar-drive concept has been developed that will enable direct-drive–ignition experiments to be performed on the National Ignition Facility [Haynam et al., Appl. Opt. 46(16), 3276 (2007)]. The advantages offered by the alternative approaches of fast ignition and shock ignition and the issues associated with these concepts are described. The lessons learned from target-physics and implosion experiments are taken into account in ignition and high-gain target designs for laser wavelengths of 1/3 μm and 1/4 μm. Substantial advances in direct-drive inertial fusion reactor concepts are reviewed. Overall, the progress in scientific understanding over the past five decades has been enormous, to the point that inertial fusion energy using direct drive shows significant promise as a future environmentally attractive energy source.

Networks of triboelectric nanogenerators for harvesting water wave energy: a potential approach toward blue energy.

Abstract: With 70% of the earth’s surface covered with water, wave energy is abundant and has the potential to be one of the most environmentally benign forms of electric energy. However, owing to lack of effective technology, water wave energy harvesting is almost unexplored as an energy source. Here, we report a network design made of triboelectric nanogenerators (TENGs) for large-scale harvesting of kinetic water energy. Relying on surface charging effect between the conventional polymers and very thin layer of metal as electrodes for each TENG, the TENG networks (TENG-NW) that naturally float on the water surface convert the slow, random, and high-force oscillatory wave energy into electricity. On the basis of the measured output of a single TENG, the TENG-NW is expected to give an average power output of 1.15 MW from 1 km2 surface area. Given the compelling features, such as being lightweight, extremely cost-effective, environmentally friendly, easily implemented, and capable of floating on the water surface, ...

Hydrogen: A sustainable fuel for future of the transport sector

Abstract: Mobility (transport of people and goods) is a socio-economic reality and need for which is bound to grow in the coming years. Modes of transport should be safe, economic and reasonably environmental friendly. Hydrogen could be ideal as a synthetic energy carrier for transport sector as its gravimetric energy density is very high, abundantly available in combined form on the earth and its oxidation product (water) does not contribute to greenhouse gas emissions. However, its sustainable production from renewable resources economically, on-board storage to provide desirable driving range, usage in durable energy conversion devices and development of infrastructure for its delivery remain significant challenges. In this article, recent developments in the field of production, storage, transport and delivery of hydrogen along with environmental and safety aspects of its use as an energy carrier are presented. Almost any energy source can be used to produce hydrogen. Presently, non-renewable sources dominate hydrogen production processes but the need of the hour is to develop and promote the share of renewable sources for hydrogen production to make it completely sustainable. Hydrogen may be used as fuel for almost any application, where fossil fuels are used presently and would offer immediate benefits over the conventional fuels, if produced from renewable sources. For achieving a successful "hydrogen economy" in the near future, the technical and economic challenges associated with hydrogen must be addressed quickly. Finding feasible solutions to different challenges may take some time but technological breakthrough by way of on-going efforts do promise hydrogen as the ultimate solution for meeting our future energy needs for the transport sector.

Biomass pyrolysis—A review of modelling, process parameters and catalytic studies

Abstract: Biomass as a form of energy source may be utilized in two different ways: directly by burning the biomass and indirectly by converting it into solid, liquid or gaseous fuels. Pyrolysis is an indirect conversion method, and can be described in simpler terms as a thermal decomposition of biomass under oxygen-depleted conditions to an array of solid, liquid and gaseous products, namely biochar, bio-oil and fuel gas. However, pyrolysis of biomass is a complex chemical process with several operational and environmental challenges. Consequently, this process has been widely investigated in order to understand the mechanisms and kinetics of pyrolysis at different scales, viz. particle level, multi-phase reacting flow, product distribution and reactor performance, process integration and control. However, there are a number of uncertainties in current biomass pyrolysis models, especially in their ability to optimize process conditions to achieve desired product yields and distribution. The present contribution provides a critical review of the current status of mathematical modelling studies of biomass pyrolysis with the aim to identify knowledge gaps for further research and opportunities for integration of biomass pyrolysis models of disparate scales. Models for the hydrodynamic behaviour of particles in pyrolysis, and their interaction with the reactive flow and the effect on the performance of the reactors have also been critically analyzed. From this analysis it becomes apparent that feedstock characteristics, evolving physical and chemical properties of biomass particles and residence times of both solid and gas phases in reactors hold the key to the desired performance of the pyrolysis process. Finally, the importance of catalytic effects in pyrolysis has also been critically analyzed, resulting in recommendations for further research in this area especially on selection of catalysts for optimal product yields under varying operating conditions.

Colloidal matter: Packing, geometry, and entropy

Abstract: BACKGROUND Colloids consist of solid or liquid particles, each about a few hundred nanometers in size, dispersed in a fluid and kept suspended by thermal fluctuations. Whereas natural colloids are the stuff of paint, milk, and glue, synthetic colloids with well-controlled size distributions and interactions are a model system for understanding phase transitions. These colloids can form crystals and other phases of matter seen in atomic and molecular systems, but because the particles are large enough to be seen under an optical microscope, the microscopic mechanisms of phase transitions can be directly observed. Furthermore, their ability to spontaneously form phases that are ordered on the scale of visible wavelengths makes colloids useful building blocks for optical materials such as photonic crystals. Because the interactions between particles can be altered and the effects on structure directly observed, experiments on colloids offer a controlled approach toward understanding and harnessing self-assembly, a fundamental topic in materials science, condensed-matter physics, and biophysics. ADVANCES In the past decade, our understanding of colloidal self-assembly has been transformed by experiments and simulations that subject colloids to geometrical or topological constraints, such as curved surfaces, fields, or the shapes of the particles themselves. In particular, advances in the synthesis of nonspherical particles with controlled shape and directional interactions have led to the discovery of structural transitions that do not occur in atoms or molecules. As a result, colloids are no longer seen as a proxy for atomic systems but as a form of matter in their own right. The wide range of self-assembled structures seen in colloidal matter can be understood in terms of the interplay between packing constraints, interactions, and the freedom of the particles to move—in other words, their entropy. Ongoing research attempts to use geometry and entropy to explain not only structure but dynamics as well. Central to this goal is the question of how entropy favors certain local packings. The incompatibility of these locally favored structures with the globally favored packing can be linked to the assembly of disordered, arrested structures such as gels and glasses. OUTLOOK We are just beginning to explore the collective effects that are possible in colloidal matter. The experimentalist can now control interactions, shapes, and confinement, and this vast parameter space is still expanding. Active colloidal systems, dispersions of particles driven by intrinsic or extrinsic energy sources rather than thermal fluctuations, can show nonequilibrium self-organization with a complexity rivaling that of biological systems. We can also expect new structural transitions to emerge in “polygamous” DNA-functionalized colloids, which have no equivalent at the molecular scale. New frameworks are needed to predict how all of these variables—confinement, activity, and specific interactions—interact with packing constraints to govern both structure and dynamics. Such frameworks would not only reveal general principles of self-assembly but would also allow us to design colloidal particles that pack in prescribed ways, both locally and globally, thereby enabling the robust self-assembly of optical materials.

A review on clean energy solutions for better sustainability

Abstract: Summary This paper focuses on clean energy solutions in order to achieve better sustainability, and hence discusses opportunities and challenges from various dimensions, including social, economic, energetic and environmental aspects. It also evaluates the current and potential states and applications of possible clean-energy systems. In the first part of this study, renewable and nuclear energy sources are comparatively assessed and ranked based on their outputs. By ranking energy sources based on technical, economic, and environmental performance criteria, it is aimed to identify the improvement potential for each option considered. The results show that in power generation, nuclear has the highest (7.06/10) and solar photovoltaic (PV) has the lowest (2.30/10). When nonair pollution criteria, such as land use, water contamination, and waste issues are considered, the power generation ranking changes, and geothermal has the best (7.23/10) and biomass has the lowest performance (3.72/10). When heating and cooling modes are considered as useful outputs, geothermal and biomass have approximately the same technical, environmental, and cost performances (as 4.9/10), and solar has the lowest ranking (2/10). Among hydrogen production energy sources, nuclear gives the highest (6.5/10) and biomass provides the lowest (3.6/10) in ranking. In the second part of the present study, multigeneration systems are introduced, and their potential benefits are discussed along with the recent studies in the literature. It is shown that numerous advantages are offered by renewable energy-based integrated systems with multiple outputs, especially in reducing overall energy demand, system cost and emissions while significantly improving overall efficiencies and hence output generation rates. Copyright © 2015 John Wiley & Sons, Ltd.

Stable Isotope Turnover and Half-Life in Animal Tissues: A Literature Synthesis

Abstract: Stable isotopes of carbon, nitrogen, and sulfur are used as ecological tracers for a variety of applications, such as studies of animal migrations, energy sources, and food web pathways. Yet uncertainty relating to the time period integrated by isotopic measurement of animal tissues can confound the interpretation of isotopic data. There have been a large number of experimental isotopic diet shift studies aimed at quantifying animal tissue isotopic turnover rate λ (%·day -1 , often expressed as isotopic half-life, ln(2)/λ, days). Yet no studies have evaluated or summarized the many individual half-life estimates in an effort to both seek broad-scale patterns and characterize the degree of variability. Here, we collect previously published half-life estimates, examine how half-life is related to body size, and test for tissue- and taxa-varying allometric relationships. Half-life generally increases with animal body mass, and is longer in muscle and blood compared to plasma and internal organs. Half-life was longest in ecotherms, followed by mammals, and finally birds. For ectotherms, different taxa-tissue combinations had similar allometric slopes that generally matched predictions of metabolic theory. Half-life for ectotherms can be approximated as: ln (half-life) = 0.22*ln (body mass) + group-specific intercept; n = 261, p<0.0001, r 2 = 0.63. For endothermic groups, relationships with body mass were weak and model slopes and intercepts were heterogeneous. While isotopic half-life can be approximated using simple allometric relationships for some taxa and tissue types, there is also a high degree of unexplained variation in our models. Our study highlights several strong and general patterns, though accurate prediction of isotopic half-life from readily available variables such as animal body mass remains elusive.

AMPK modulates Hippo pathway activity to regulate energy homeostasis.

Abstract: The Hippo pathway was discovered as a conserved tumour suppressor pathway restricting cell proliferation and apoptosis. However, the upstream signals that regulate the Hippo pathway in the context of organ size control and cancer prevention are largely unknown. Here, we report that glucose, the ubiquitous energy source used for ATP generation, regulates the Hippo pathway downstream effector YAP. We show that both the Hippo pathway and AMP-activated protein kinase (AMPK) were activated during glucose starvation, resulting in phosphorylation of YAP and contributing to its inactivation. We also identified glucose-transporter 3 (GLUT3) as a YAP-regulated gene involved in glucose metabolism. Together, these results demonstrate that glucose-mediated energy homeostasis is an upstream event involved in regulation of the Hippo pathway and, potentially, an oncogenic function of YAP in promoting glycolysis, thereby providing an exciting link between glucose metabolism and the Hippo pathway in tissue maintenance and cancer prevention.

Direct Power Generation from a Graphene Oxide Film under Moisture.

Abstract: An efficient moisture-electric-energy transformation is discovered by means of establishing an oxygen functional group gradient in a graphene oxide film. The moisture variation serves as an energy source to generate electric power with an energy-conversion efficiency of up to ≈62%. Based on this finding, a prototype power generator and a self-powered respiratory monitor are demonstrated under the stimulus of the human breath.

The economics of wave energy: A review

Abstract: Wave energy is arguably one of the most promising renewables. Less developed at present than other renewables, the existing models to estimate the costs of a wave energy project are often oversimplified, and the resulting scatter in the economic assessments weighs on the confidence of potential investors and constitutes therefore an impediment to the development of wave energy. Indeed, understanding the costs of wave energy is one of the main fields of research in marine renewable energy. In this context, the main objective of this paper is to review all the factors that must be considered in an economic analysis of wave energy, including a number of elements that are usually overlooked. In the process we characterise the direct and indirect costs of a wave farm – preliminary costs, construction, operation and maintenance and decommissioning cost – as well as its prospective incomes. For each of them a reference value is presented, together with a generic formula for its calculation. Moreover, the levelised cost, i.e., the production cost of an energy unit (1 kW h), is compared between various energy sources, and on these grounds conclusions on the profitability and competitiveness of wave energy are drawn. In sum, this work reviews the state of the art and sets the basis for a thorough economic analysis of wave energy.

Sugars in soil and sweets for microorganisms: Review of origin, content, composition and fate

Abstract: Sugars are the most abundant organic compounds in the biosphere because they are monomers of all polysaccharides. We summarize the results of the last 40 years on the sources, content, composition and fate of sugars in soil and discuss their main functions. We especially focus on sugar uptake, utilization and recycling by microorganisms as this is by far the dominating process of sugar transformation in soil compared to sorption, leaching or plant uptake. Moreover, sugars are the most important carbon (C) and energy source for soil microorganisms. Two databases have been created. The 1st database focused on the contents of cellulose, non-cellulose, hot-water and cold-water extractable sugars in soils (348 data, 32 studies). This enabled determining the primary (plant-derived) and secondary (microbially and soil organic matter (SOM) derived) sources of carbohydrates in soil based on the galactose + mannose/arabinose + xylose (GM/AX) ratio. The 2nd database focused on the fate of sugar C in soils (734 data pairs, 32 studies using 13 C or 14 C labeled sugars). 13 C and 14 C dynamics enabled calculating the: 1) initial rate of sugar mineralization, 2) mean residence time (MRT) of C of the applied sugars, and 3) MRT of sugar C incorporated into 3a) microbial biomass and 3b) SOM. The content of hexoses was 3–4 times higher than pentoses, because hexoses originate from plants and microorganisms. The GM/AX ratio of non-cellulose sugars revealed a lower contribution of hexoses in cropland and grassland (ratio 0.7–1) compare to forest (ratio 1.5) soils. 13 C and 14 C studies showed very high initial rate of glucose mineralization (1.1% min −1 ) and much higher rate of sugars uptake by microorganisms from the soil solution. Considering this rate along with the glucose input from plants and its content in soil solution, we estimate that only about 20% of all sugars in soil originate from the primary source – decomposition of plant litter and rhizodeposits. The remaining 80% originates from the secondary source – microorganisms and their residues. The estimated MRT of sugar C in microbial biomass was about 230 days, showing intense and efficient internal recycling within microorganisms. The assessed MRT of sugar C in SOM was about 360 days, reflecting the considerable accumulation of sugar C in microbial residues and its comparatively slow external recycling. The very rapid uptake of sugars by microorganisms and intensive recycling clearly demonstrate the importance of sugars for microbes in soil. We speculate that the most important functions of sugars in soil are to maintain and stimulate microbial activities in the rhizosphere and detritusphere leading to mobilization of nutrients by accelerated SOM decomposition – priming effects. We conclude that the actual contribution of sugar C (not only whole sugar molecules, which are usually determined) to SOM is much higher than the 10 ± 5% commonly measured based on their content.

Performance enhancement of solar collectors—A review

Abstract: Given rapid depletion of conventional energy sources and environmental degradation caused by their over exploitation, the renewable energy sources are believed to be the future. Technologies utilizing renewable energy sources differ significantly from one another, not only with regard to technical and economic aspects but also in relation to their reliability, maturity, and operational experience in utility scale conditions. Technologies used to harness solar energy have emerged as the most promising and mature since solar energy is abundant, freely available, and it has commercial potential too. This paper presents a review of advancements made in the field of solar thermal technology with a focus on techniques employed for its performance enhancement. It also covers the description of different types of solar collectors to facilitate the systematic understanding of solar thermal technology and the novel modifications realized in each category of solar collectors have been highlighted to promote the use of solar energy in routine activities. Performance enhancement techniques such as geometrical modifications on the absorber plate, use of solar selective coatings and nanofluids have been given a special attention.

Aviation biofuel from renewable resources: Routes, opportunities and challenges

Abstract: Air transport describes an inevitable part in the day to day life of the modern world. It is highly responsible for the worldwide social contacts and business developments. The use of petroleum fuels as energy source for air transport is not sustainable. Aviation is one of the leading contributors to the total greenhouse gas emissions. Also, the fossil fuel prices are becoming more volatile day by day. So it is very essential to introduce and industrialize alternative aviation fuels generated from renewable resources, especially biomass. A number of industrial commitments and collaborations have emerged to find alternative ways to reach bio aviation fuels. Research on the conversion of biomass based sources to bio jet fuels is of current interest. The main concern is the production of biojet fuel, from renewable resources, with relatively low greenhouse gas life cycle and sustainability with affordable price. The present paper overviews the opportunities and challenges in the development of alternative fuels for aviation. The production process, feedstock used and the most promising global projects are also reviewed.

Direct neuronal glucose uptake heralds activity-dependent increases in cerebral metabolism

Abstract: Metabolically, the brain is a highly active organ that relies almost exclusively on glucose as its energy source. According to the astrocyte-to-neuron lactate shuttle hypothesis, glucose is taken up by astrocytes and converted to lactate, which is then oxidized by neurons. Here we show, using two-photon imaging of a near-infrared 2-deoxyglucose analogue (2DG-IR), that glucose is taken up preferentially by neurons in awake behaving mice. Anaesthesia suppressed neuronal 2DG-IR uptake and sensory stimulation was associated with a sharp increase in neuronal, but not astrocytic, 2DG-IR uptake. Moreover, hexokinase, which catalyses the first enzymatic steps in glycolysis, was highly enriched in neurons compared with astrocytes, in mouse as well as in human cortex. These observations suggest that brain activity and neuronal glucose metabolism are directly linked, and identify the neuron as the principal locus of glucose uptake as visualized by functional brain imaging.