Carbon and life cycle implications of thermal recovery from the organic fractions of municipal waste

Purpose

The aim of this research was to determine the optimum way of recovering energy from the biodegradable fractions of municipal waste. A part-life cycle study was carried out on the following wastes: paper, food waste, garden waste, wood, non-recyclable mixed municipal waste and refuse-derived fuel. The energy recovery processes considered were incineration, gasification, combustion in dedicated plant, anaerobic digestion and combustion in a cement kiln.

Methods

The life cycle assessment (LCA) was carried out using WRATE, an LCA tool designed specifically for waste management studies. Additional information on waste composition, waste collection and the performance of the energy recovery processes was obtained from a number of UK-based sources. The results take account of the energy displaced by the waste to energy processes and also the benefits obtained by the associated recycling of digestates, metals and aggregates as appropriate.

Results and discussion

For all the waste types considered the maximum benefits in terms of climate change and non-renewable resource depletion would be achieved by using the waste in a cement kiln as a substitute fuel for coal. When considering the impacts in terms of human toxicity, aquatic ecotoxicity, acidification and eutrophication, direct combustion with energy recovery was the best option. The results were found to be highly sensitive to the efficiency of the energy recovery process and the conventional fuel displaced by the recovered energy.

Conclusions and recommendations

This study has demonstrated that LCA can be used to determine the benefits and burdens associated with recovering energy from municipal waste fractions. However, the findings were restricted by the lack of reliable data on the performance of waste gasification and anaerobic digestion systems and on the burdens arising from collecting the wastes. It is recommended that further work is carried out to address these data gaps.     

Time required for the restoration of normal heavy exercise VO2 kinetics following prior heavy exercise.

Prior heavy exercise markedly alters the O2 uptake (VO2) response to subsequent heavy exercise. However, the time required for VO2 to return to its normal profile following prior heavy exercise is not known. Therefore, we examined the VO2 responses to repeated bouts of heavy exercise separated by five different recovery durations. On separate occasions, nine male subjects completed two 6-min bouts of heavy cycle exercise separated by 10, 20, 30, 45, or 60 min of passive recovery. The second-by-second VO2 responses were modeled using nonlinear regression. Prior heavy exercise had no effect on the primary VO2 time constant (from 25.9 +/- 4.7 s to 23.9 +/- 8.8 s after 10 min of recovery; P = 0.338), but it increased the primary VO2 amplitude (from 2.42 +/- 0.39 to 2.53 +/- 0.41 l/min after 10 min of recovery; P = 0.001) and reduced the VO2 slow component (from 0.44 +/- 0.13 to 0.21 +/- 0.12 l/min after 10 min of recovery; P < 0.001). The increased primary amplitude was also evident after 20-45 min, but not after 60 min, of recovery. The increase in the primary VO2 amplitude was accompanied by an increased baseline blood lactate concentration (to 5.1 +/- 1.0 mM after 10 min of recovery; P < 0.001). Baseline blood lactate concentration was still elevated after 20-60 min of recovery. The priming effect of prior heavy exercise on the VO2 response persists for at least 45 min, although the mechanism underpinning the effect remains obscure.     

Prediction of the three-dimensional structure of aflatoxin of Aspergillus flavus by homology modelling

Aflatoxins are polyketide-derived secondary metabolites produced by Aspergillus spp. The toxic effects of aflatoxins have adverse consequences for human health and agricultural economics. The aflR gene, a regulatory gene for aflatoxin biosynthesis, encodes a protein containing a zinc-finger DNA-binding motif. AFLR-Protein three-dimensional model was generated using Robetta server. The modeled AFLR-Protein was further optimization and validation using Rampage. In the simulations, we monitored the backbone atoms and the C-α-helix of the modeled protein. The low RMSD and the simulation time indicate that, as expected, the 3D structural model of AFLR-protein represents a stable folding conformation. This study paves the way for generating computer molecular models for proteins whose crystal structures are not available and which would aid in detailed molecular mechanism of inhibition of aflatoxin.     

Cell turnover: flexible coupling meets the needs of development

The identification of Drosophila genes that inhibit proliferation while simultaneously promoting apoptosis--decreasing cell number--or that promote proliferation while simultaneously inhibiting apoptosis--increasing cell number--has revealed new ways that cell birth and death may be coupled to meet the needs of development.     

In vitro effect of a buffered chelating agent and neomycin or oxytetracycline on bacteria associated with diseases of fish

The antimicrobial agents used to treat bacterial fish diseases are archaic, and their uses may result in the emergence of drug-resistant bacterial strains. This study evaluated the in vitro antimicrobial activity of combinations of Tricide and neomycin or oxytetracycline on common disease-causing bacteria of fish and its possible use as an alternative treatment of these diseases. Tricide solutions containing of 8 mM United States Pharmacopeia (USP) disodium ethylenediaminetetraacetate dehydrate (chelator) and 20 mM USP 2-amino-2-hydroxymethyl-1,3-propanediol (buffer) potentate the antimicrobial action of neomycin and oxytetracycline when reacted in vitro with Aeromonas hydrophila, Streptococcus iniae, Pseudomonas aeruginosa, and Staphylococcus aureus. Serial passage of the test organisms in Tricide or Tricide and neomycin or oxytetracycline did not result in the development of resistant forms. Combinations of Tricide and neomycin or oxytetracycline reduced the amount of antibiotics necessary for fish therapy, render drug-resistant bacteria sensitive to antimicrobial therapy, may be used to decontaminate recently shipped fish, and should reduce the formation of antibiotic-resistant forms.     

Oxygen uptake kinetics in treadmill running and cycle ergometry: a comparison.

The purpose of the present study was to comprehensively examine oxygen consumption (VO(2)) kinetics during running and cycling through mathematical modeling of the breath-by-breath gas exchange responses to moderate and heavy exercise. After determination of the lactate threshold (LT) and maximal oxygen consumption (VO(2 max)) in both cycling and running exercise, seven subjects (age 26.6 +/- 5.1 yr) completed a series of "square-wave" rest-to-exercise transitions at running speeds and cycling power outputs that corresponded to 80% LT and 25, 50, and 75%Delta (Delta being the difference between LT and VO(2 max)). VO(2) responses were fit with either a two- (LT) exponential model. The parameters of the VO(2) kinetic response were similar between exercise modes, except for the VO(2) slow component, which was significantly (P < 0.05) greater for cycling than for running at 50 and 75%Delta (334 +/- 183 and 430 +/- 159 ml/min vs. 205 +/- 84 and 302 +/- 154 ml/min, respectively). We speculate that the differences between the modes are related to the higher intramuscular tension development in heavy cycle exercise and the higher eccentric exercise component in running. This may cause a relatively greater recruitment of the less efficient type II muscle fibers in cycling.     

Mapping the amino acid properties of constituent nucleoporins onto the yeast nuclear pore complex

Visualization of molecular structures aids in the understanding of structural and functional roles of biological macromolecules. Macromolecular transport between the cell nucleus and cytoplasm is facilitated by the nuclear pore complex (NPC). The ring structure of the NPC is large and contains several distinct proteins (nucleoporins) which function as a selective gate for the passage of certain molecules into and out of the nucleus. In this note we demonstrate the utility of a python code that allows direct mapping of the physiochemical properties of the constituent nucleoporins on the scaffold of the yeast NPC׳s cytoplasmic view. We expect this tool to be useful for researchers to visualize the NPC based on their physiochemical properties and how it alters when specific mutations are introduced in one or more of the nucleoporins. The code developed using Python is available freely from the authors.     

Modulation of ionizing radiation-induced apoptosis by bantam microRNA in Drosophila

In Drosophila, heterozygosity in the pro-apoptotic gene hid significantly reduces apoptosis that is induced by ionizing radiation (IR). Therefore, mechanisms that regulate Hid levels can potentially contribute to life-or-death decision of an irradiated cell. 3′UTR of hid mRNA contains 5 potential binding sites for bantam microRNA. Ectopic expression of ban attenuated apoptosis that results from ectopic expression of hid but the significance of this regulation under physiological conditions remained to be investigated. We report here that ban is needed to limit IR-induced apoptosis in larval imaginal discs. Using tubulin–EGFP ban sensors with ban consensus sequences in the 3′UTR, we find that EGFP decreases following IR, indicating that IR activates ban. Likewise, a tubulin–EGFP reporter with hid-3′UTR is repressed in irradiated discs and this repression requires ban consensus sites in the hid 3′UTR. ban mutant larvae show increased sensitivity to killing by IR, which is suppressed by a mutation in hid. These results can fit into a model in which IR activates ban and ban represses hid to limit IR-induced apoptosis. miRNAs have been shown previously to be induced by radiation but this is the first report that a miRNA is functionally important for radiation responses.