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Reduced carbon dioxide

A substantial fraction of the named enzymes are oxido-reductases, responsible for shuttling electrons along metabolic pathways that reduce carbon dioxide to sugar (in the case of plants), or reduce oxygen to water (in the case of mammals). The oxido-reductases that drive these processes involve a small set of redox active cofactors , that is, small chemical groups that gain or lose electrons. These cofactors include iron porjDhyrins, iron-sulfur clusters and copper complexes as well as organic species that are ET active. [Pg.2974]

The electrons undergo the equivalent of a partial oxidation process ia a dark reaction to a positive potential of +0.4 V, and Photosystem I then raises the potential of the electrons to as high as —0.7 V. Under normal photosynthesis conditions, these electrons reduce tryphosphopyridine-nucleotide (TPN) to TPNH, which reduces carbon dioxide to organic plant material. In the biophotolysis of water, these electrons are diverted from carbon dioxide to a microbial hydrogenase for reduction of protons to hydrogen ... [Pg.19]

Concerns about global climate change have led to extensive research and high-level international debates about the need for targets and timetables to reduce carbon dioxide emissions. Some policymakers believe that current uncertainties in how to approach the issue do notjustify an all-out effort to reduce carbon dioxide emission, while others feel that this is a crisis needing immediate attention. [Pg.478]

Transportation accounts for about one-fourth of the primary energy consumption in the United States. And unlike other sectors of the economy that can easily switch to cleaner natural gas or electricity, automobiles, trucks, nonroad vehicles, and buses are powered by internal-combustion engines burning petroleum products that produce carbon dioxide, carbon monoxide, nitrogen oxides, and hydrocarbons. Efforts are under way to accelerate the introduction of electric, fuel-cell, and hybrid (electric and fuel) vehicles to replace sonic of these vehicles in both the retail marketplace and in commercial, government, public transit, and private fleets. These vehicles dramatically reduce harmful pollutants and reduce carbon dioxide emissions by as much as 50 percent or more compared to gasoline-powered vehicles. [Pg.479]

The use of the lignin fraction is much more cumbersome currently the best-known chemical of a real commercial importance is vanillin, which is obtained by oxidation of the black liquor. Another example is a product called spray-dried lignosulfonate (as sodium salt) obtained from the older, acidic sulfite pulping process. It is sold as a commercial product primarily as a concrete additive for enhanced strength. Since the cement industry is one of the big contributors of carbon dioxide emissions (due to the production of calcium oxide from calcium carbonate), the use of this renewable, wood-derived product not only is fossil-carbon neutral in itself but also reduces carbon dioxide emission due to the diminished need for cement in large infrastructures made of concrete. [Pg.165]

One of the most straightforward methods to reduce carbon dioxide emissions is to enhance the fuel efficiency of engines. The three-way catalyst, although very successful at cleaning up automotive exhaust, dictates that engines operate at air-to-fuel ratios of around 14.7 1. Unfortunately, this is not the optimum ratio with respect to fuel efficiency, which is substantially higher under lean-burn conditions at A/F ratios of about 20 1, where the exhaust becomes rich in oxygen and NOx reduction is extremely difficult (Fig. 10.1). [Pg.391]

Iwasita T, Nart EC, Lopez B, Vielstich W. 1992. On the study of adsorbed species at platinum from methanol, formic acid and reduced carbon dioxide via in situ ETIR spectroscopy. Electrochim Acta 37 2361-2367. [Pg.458]

Methanogens, which reduce carbon dioxide to methane... [Pg.816]

Turning to the other major areas, the picture is clearer, at least in terms of the direchon of the impact. Nuclear power can help to reduce carbon dioxide emissions and thereby lessen the severity of predicted climate changes. It can also help ease the difficulties that will arise from the conflict between the shrinking of fossil fuel supplies and the rising material aspirations of a growing world population. [Pg.89]

Bronchiolar smooth muscle is sensitive to changes in carbon dioxide levels. Excess carbon dioxide causes bronchodilation and reduced carbon dioxide causes bronchoconstriction. Pulmonary vascular smooth muscle is sensitive to changes in oxygen levels excess oxygen causes vasodilation and insufficient oxygen (hypoxia) causes vasoconstriction. The changes in bronchiolar and vascular smooth muscle tone alter the amount of ventilation and perfusion in a lung unit to return the V/Q ratio to one. [Pg.263]

In a lung unit with low blood flow and high ventilation (alveolar dead space), the level of carbon dioxide is decreased and the level of oxygen is increased. The reduced carbon dioxide causes bronchoconstriction and a decrease in ventilation. The excess oxygen causes vasodilation and an increase in perfusion and, once again, the V/Q ratio is brought closer to one and gas exchange is improved. [Pg.263]

At elevated temperatures, the hydride reduces carbon dioxide or sodium hydrogen-carbonate to methane and ethane. The latter are probably the explosive reaction products produced when carbon dioxide extinguishers are used on LAH fires. [Pg.47]

Bosch A regenerative, two-stage process for reducing carbon dioxide to oxygen ... [Pg.44]

Much interest has recently been shown in artificial photosynthesis. Photosynthesis is a system for conversion or accumulation of energy. It is also interesting that some reactions occur simultaneously and continuously. Fujishima et al. [338] pointed out that a photocatalytic system resembles the process of photosynthesis in green plants. They described that there are three important parts of the overall process of photosynthesis (1) oxygen generation by the photolysis of water, (2) photophosphorylation, which accumulates energy, and (3) the Calvin cycle, which takes in and reduces carbon dioxide. The two reactions, reduction of C02 and generation of 02 from water, can occur simultaneously and continuously by a sonophotocatalytic reaction. [Pg.451]

Hydrogen fuel-based technologies hold great promise in reducing carbon dioxide and toxic air emissions from mobile sources in meeting current clean air standards and proposed greenhouse gas reductions. [Pg.175]

When a fuel cell consumes natural gas or other hydrocarbons, it produces some carbon dioxide, though much less than burned fuel. Advanced fuel cells using natural gas, for example, could potentially reduce carbon dioxide emissions by 60% compared to a conventional coal plant and by 25% compared to modern natural gas plants. [Pg.189]

Biofuels offer a number of technical and enviromnental benefits over conventional fossil fuels, which make them attractive as alternatives for the transport sector. The benefits include greenhouse gas reductions including reduced carbon dioxide emissions, which will contribute to domestic and international targets, the diversification of the fuel sector, biodegradability, sustainability, and an additional market for agricultural products. Biofuels help to protect and create jobs. Table 3.1 shows the major benefits of biofuels. [Pg.61]

Natural gas (NG) consists of 85-95% methane (CH ), which is the simplest hydrocarbon. NG is the cleanest burning alternative fuel. Exhaust emissions from NG vehicles are much lower than those from gasoline-powered vehicles. Combustion of NG reduces carbon dioxide content compared with diesel, but the lost efficiency when the Otto process is used means that carbon dioxide emissions increase. All in all combustion of NG in a gasoline engine gives rise to about as much carbon dioxide as the combustion of diesel in a diesel engine, measured in units of energy. [Pg.91]

Shackleton NJ, Hall MA, Line J, Gang S (1983) Carbon isotope data in core V19-30 confirm reduced carbon dioxide concentration in the ice age atmosphere. Nature 306 319-322 Shahar A, Young ED, Manning CE (2008) Equihbrium high-temperature Fe isotope fractionation between fayalite and magnetite an experimental calibration. Earth Planet Sci Lett 268 ... [Pg.270]

Piperidine alkaloids contain the piperidine nucleus. The structural development of this group of alkaloids in synthesis is presented in Figure 52. Here a is L-lysine and /3 is cadaverine. The basic ring of j3 is the same as in a, although the activity of PLP reduces carbon dioxide. The j3 is biogenic amine, neither a stable nor a poisonous compound... [Pg.95]

Potassium reduces carbon dioxide to carbon, carbon monoxide and potassium carbonate ... [Pg.735]

Rosenfeld, A. H., Kaarsberg, T. M. Romm, J. 2000. Technologies to reduce carbon dioxide emissions in the next decade. Physics Today, November, 29-34. [Pg.22]


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