Adsorption enhancement mechanisms of silica-titania nanocomposites for elemental mercury vapor removal

A novel nanocomposite that combines high-surface area silica with the photocatalytic properties of titania has been developed that allows for effective capture of elemental mercury vapor. The adsorption capability of the developed material has been found to improve after periods of photocatalytic oxidation. In this study, the mechanisms for adsorption enhancement were identified. BET nitrogen adsorption and mercury porosimetry were used to evaluate pore structure, and the results suggest that a decrease in contact angle was likely to be responsible for improved mercury capture over time. Contact angle measurements showed a significant change of more than 10 degrees, indicating greater attraction to mercury for the used pellets due to deposited mercuric oxide. ICP and TGA analyses showed that mercury was captured as both elemental mercury (Hg0) and mercuric oxide (HgO). In addition, it was shown that pellets used for nearly 500 h still showed greater than 90% removal efficiency and had an average capacity of 10 mg of Hg/g based on mass balance calculations, while some pellets had a capacity over 30 mg of Hg/g according to ICP and TGA analyses. Mercuric oxide doped pellets removed 100% of elemental mercury without pretreatment. The superior mercury removal efficiency combined with various advantages of the novel composite demonstrates its use as an effective alternative to conventional activated carbon injection technology.     

Composition and bioactive factor content of cowpea (Vigna unguiculata L. Walp) raw meal and protein concentrate

Analysis was done of the composition and bioactive factor content of whole meal, processed meal and protein concentrate from a cowpea cultivar (Vigna unguiculata L. Walp var. IT86D‐719) grown in Yucatan, Mexico and of changes in these parameters after soaking and dehulling. Both meals had a high protein content (247.53 and 257 g kg^?1 dry matter (DM) respectively). The protein concentrate was rich in protein (786 g kg^?1 DM) and lipids (58.47 g kg^?1 DM) and had an amino acid profile similar to that of the processed meal. The amino acid profiles of the meals almost covered human dietary requirements based on FAO/WHO/UNU‐suggested profiles but were deficient in sulphur amino acids. Trypsin inhibitor activity was high in both meals compared with levels found in previous studies. Trypsin inhibitor activity in the concentrate was not eliminated but was significantly reduced. Lectin activity, tannin levels, phytate levels and α‐amylase inhibitor activity were relatively low in the meals, and cyanogenic glucosides were not detected. Residual amounts of α‐amylase inhibitors, tannins and phytate were observed in the concentrate, and lectin activity was not detected. Results indicate that V. unguiculata L. Walp var. IT86D‐719 meals and protein concentrate are good potential foodstuffs in the Yucatan region. Copyright © 2006 Society of Chemical Industry     

Fossil fuel and wood combustion as recorded by carbon particles in Lake Erie sediments 1850-1998

Carbon particle analysis was performed on a dated sediment core from Lake Erie in order to explore the inputs of pollution from incomplete combustion of coal, oil, and wood. Carbon particles were isolated from the sediment by chemical digestion, and elemental carbon content was determined by CHN analysis. The type of carbon particle (from burning coal, oil, and wood) and particle size and relative abundance were determined using scanning electron microscopy on 100 particles from each core section. The elemental carbon content in the Lake Erie core ranges from 2.5 to 7.4 mg of carbon/g of sediment (1850-1998), and the maximum carbon content in the sediment occurs in the late 1960s to early 1970s. It is shown that particle mass is a better predictor than particle number of historical energy consumption records. This is especially clear for wood where variable particle volumes play a significant role in determining the record of elemental carbon mass from wood burning. Lake Erie core's content of total carbon and carbon particle type is in agreement with U.S. energy consumption records, except that a wood maximum occurs during 1905-1917, about 36 yr after the U.S. consumption maximum from 1870 to 1880.     

Different catalytic effects by copper and chromium on the formation and degradation of chlorinated aromatic compounds in fly ash

Fly ash from municipal solid waste incineration may catalytically enhance the formation and degradation of chlorinated aromatic compounds. The activities of three Deacon catalysts in this process were investigated in a statistically designed experiment. Chlorides of copper, chromium, and nickel were added to fly ash samples and the resulting samples heated at 300 degrees C for 2 h in an air atmosphere. The addition of copper increases the formation of all chlorinated aromatic compounds except the low chlorinated congeners of polychlorinated dibenzo-p-dioxins and dibenzofurans. The addition of chromium decreased the formation of most chlorinated aromatic compounds except the highest chlorinated species, where it was without effect. The addition of nickel did not show any significant effect. The outcome of the experiment can be interpreted as two competing processes: the chlorination of aromatic rings and the oxidation of carbon-carbon and carbon-oxygen bonds. The delicate balance between chlorination and oxidation could probably be further exploited to minimize both the emissions and the net production of chlorinated aromatic compounds from combustion.     

Is Ultra-Low Friction Needed to Prevent Wear of Diamond-Like Carbon (DLC)? An Alcohol Vapor Lubrication Study for Stainless Steel/DLC Interface

The effects of n-pentanol vapor on friction and wear of hydrogenated diamond-like carbon (DLC) films during sliding against a 440C stainless steel (SS) ball were investigated with a reciprocating pin-on-disc tribometer. Under dry sliding conditions, the friction coefficient is initially high (>0.2) for a so-called run-in period and then gradually subsequently decreases to an ultra-low value (<0.025). During the run-in period, a carbon transfer film is formed on the SS ball side, which seems to be the key for the ultra-low friction behavior. In n-pentanol vapor environments, the friction coefficient remained nearly constant at ~0.15 throughout the entire test cycles without any noticeable run-in period. Although the friction coefficient is high, there is no visible wear on rubbing surfaces when examined by optical microscopy, and the transfer film forming tendency on the SS ball side was much reduced. In humid environments, the wear prevention effect is not observed and transfer films do form on the ball side. These results imply that the n-pentanol layer adsorbed on DLC film from the vapor phase provides a molecularly thin lubrication layer which can prevent the substrate from wear.     

Tribological Properties of Greases Based on Biogenic Base Oils and Traditional Thickeners in Sapphire-Steel Contact

Friction and wear tests were performed with a number of greases based on biogenic esters and thickened with two metal soaps and a highly dispersed silica acid gel. The series of experiments was performed on a Nonotribometer in material combination of sapphire ball on steel disks with a range of normal loads from 1 up to 500 mN. Results directly show influences of the bulk grease components on frictional and wear behavior. Comparison of frictional and wear results makes manifest that, while in most combinations of base oil and thickener, the highest influence is found in the thickening agent, some combinations are mainly influenced by the base oil. All frictional results along with wear widths and depths as well as micrographs of the prevailing wear mechanisms are presented and discussed.     

Maximum a posteriori estimation of linear shape variation with application to vertebra and cartilage modeling

The estimation of covariance matrices is a crucial step in several statistical tasks. Especially when using few samples of a high dimensional representation of shapes, the standard maximum likelihood estimation (ML) of the covariance matrix can be far from the truth, is often rank deficient, and may lead to unreliable results. In this paper, we discuss regularization by prior knowledge using maximum a posteriori (MAP) estimates. We compare ML to MAP using a number of priors and to Tikhonov regularization. We evaluate the covariance estimates on both synthetic and real data, and we analyze the estimates' influence on a missing-data reconstruction task, where high resolution vertebra and cartilage models are reconstructed from incomplete and lower dimensional representations. Our results demonstrate that our methods outperform the traditional ML method and Tikhonov regularization.     

Oxygen consumption rate of permeabilized cells and isolated mitochondria from pork M. masseter and liver examined fresh and after freeze-thawing at different pH values

Abstract: The oxygen consumption rate (OCR) of 2 types of permeabilized tissues and their corresponding isolated mitochondria from porcine M. masseter and liver, resulting in 4 systems, was studied at different pH values (5.0 to 7.1) using fresh samples and samples frozen directly in liquid nitrogen (N₂) or air‐frozen at ?20°C. A protocol with the additive sequence rotenone–succinate–ADP (adenosine diphosphate)–cytochrome c–FCCP (carbonyl cyanide p‐trifluoromethoxyphenylhydrazone) was used to study respiration changes. The OCR of liver respiring on succinate (OCR _S ) was higher than that of muscle tissue. pH had a larger effect on OCR_S than freeze‐thawing. Low pH was associated with reduced OCR_S. The OCR_S of isolated muscle mitochondria appeared to be an underestimated relative to the OCR_S of permeabilized muscle cells. Increasing pH, following prior subjection to pH 5.0, showed partial reversibility of the OCR_S. The freeze‐thaw cycle increased the OCR_S when muscle systems were frozen and examined above pH 6.0; this effect was less apparent for liver tissue. A response to cytochrome c addition, indicating a defective outer mitochondrial membrane, was observed for all 4 systems. The response was, however, lowest for permeabilized cells. The ADP/FCCP additive pair indicated partial coupling for isolated liver and muscle mitochondria. These additives gave weak responses for the permeabilized liver cells while the OCR seemed to be inhibited for permeabilized muscle fibers when ADP/FCCP was added. Practical Application: The mitochondrial state is believed to be important for myoglobin reduction, development of flavor, and possibly other meat qualities. By monitoring the oxygen consumption in mitochondria and meat we can better understand and control such processes following freezing and thawing.     

Combined heat and power in the Swedish district heating sector—impact of green certificates and CO2 trading on new investments

Combined heat and power (CHP) has been identified by the EU administration as an important means of reducing CO₂-emissions and increasing the energy efficiency. In Sweden, only about one third of the demand for district heat (DH) is supplied from CHP. This share could be significantly larger if the profitability of CHP generation increased. The objective of this study was to analyse the extent to which the profitability for investments in new CHP plants in the Swedish DH sector have changed thanks to the recently implemented trading schemes for green certificates (TGCs) and CO₂ emissions (TEPs). The analysis was carried out using a simulation model of the Swedish DH sector in which the profitability of CHP investments for all DH systems, with and without the two trading schemes applied, is compared. In addition, a comparison was made of the changes in CHP generation, CO₂ emissions, and operation costs if investments are made in the CHP plant shown to be most profitable in each system according to the model. The study shows that the profitability of investments in CHP plants increased significantly with the introductions of TGC and TEP schemes. If all DH utilities also undertook their most profitable CHP investments, the results indicate a major increase in power generation which, in turn, would reduce the CO₂ emissions from the European power sector by up to 13 Mton/year, assuming that coal condensing power is displaced.     

Short-term impact of green certificates and CO2 emissions trading in the Swedish district heating sector

Swedish district-heating (DH) systems use a wide range of energy sources and technologies for heat-and-power generation. This provides the DH utilities with major flexibility in changing their fuel and technology mix when the economic conditions for generation change. Two recently introduced policy instruments have changed the DH utilities’ costs for generation considerably; the tradable green-certificate (TGC) scheme introduced in 2003 in Sweden, and the tradable greenhouse-gas emission permit (TEP) scheme introduced in the EU on January 1, 2005. The objective of this study is to analyse how these two trading schemes impact on the operation of the Swedish DH sector in terms of changes in CHP generation, CO₂ emissions, and operating costs. The analysis was carried out by comparing the most cost-effective operation for the DH utilities, with and without, the two trading schemes applied, using a model that handles the Swedish DH-sector system-by-system. It was found that the volume of renewable power generated in CHP plants only increased slightly owing to the TGC scheme. The TGC and the TEP schemes in force together, however, nearly doubled the renewable power-generation. CO₂ emissions from the DH sector may either increase or decrease depending on the combination of TGC and TEP prices. The overall CO₂ emissions from the European power-generation sector would, however, be reduced for all price combinations assuming that increased Swedish CHP generation replaces coal-condensing power (coal-fired plants with power generation only) in other European countries. The trading schemes also lower the operational costs of the DH sector since the cost increase owing to the use of more expensive fuels and the purchase of TEPs is outweighed by the increased revenues from sales of electricity and TGCs.