A missing error term in benefit-cost analysis

Benefit-cost models are frequently used to inform environmental policy and management decisions. However, they typically omit a random or pure error which biases downward any estimated forecast variance. Ex-ante benefit-cost analyses create a particular problem because there are no historically observed values of the dependent variable, such as net present social value, on which to construct a historically based variance as is the usual statistical approach. To correct this omission, an estimator for the random error variance in this situation is developed based on analysis of variance measures and the coefficient of determination, R(2). A larger variance may affect decision-maker's choices if they are risk averse, consider confidence intervals, exceedance probabilities, or other measures related to the variance. When applied to a model of the net benefits of the Clean Air Act, although the probability of large net benefits increases, the probability that the net present value is negative also increases from 0.2 to 4.5%. A framework is also provided to assist in determining when a variance estimate would be better, in a utility sense, than using the current default of a zero error variance.     

Resveratrol in human cancer chemoprevention--choosing the 'right' dose

There is now robust preclinical evidence to suggest that resveratrol possesses cancer chemopreventive properties. A series of clinical pilot studies has provided insights into its pharmacokinetics, and data on its human antineoplastic pharmacodynamics start to emerge. It is likely that resveratrol will be developed further in the clinic as a putative cancer chemopreventive agent. The question that remains unresolved is: What is the most suitable dose of resveratrol for effective cancer preventive intervention? Mechanistic studies in cells in vitro have almost invariably used concentrations of resveratrol in the 10^–5 to 10^–4 M range, which is much higher than those which can be achieved in the human biophase after consumption of doses up to 1 g. Many of the preclinical efficacy studies in rodent models of carcinogenesis have employed doses which are dramatically above those which can be ingested with the diet. New experimental paradigms need to be used to obtain information on pharmacological changes elicited by resveratrol when present at very low concentrations or when administered at dietary‐relevant doses.     

Dietary bioaccumulation of perfluorophosphonates and perfluorophosphinates in juvenile rainbow trout: evidence of metabolism of perfluorophosphinates

The perfluorophosphonates (PFPAs) and perfluorophosphinates (PFPiAs) are high production volume chemicals that have been observed in Canadian surface waters and wastewater environments. To examine whether their occurrence would result in contamination of organisms in aquatic ecosystems, juvenile rainbow trout (Oncorhynchus mykiss) were separately exposed to a mixture of C6, C8, and C10 monoalkylated PFPAs and a mixture of C6/C6, C6/C8, and C8/C8 dialkylated PFPiAs in the diet for 31 days, followed by 32 days of depuration. Tissue distribution indicated preferential partitioning to blood and liver. Depuration half-lives ranged from 3 to 43 days and increased with the number of perfluorinated carbons present in the chemical. The assimilation efficiencies (α, 7-34%) and biomagnification factors (BMFs, 0.007-0.189) calculated here for PFPAs and PFPiAs were lower than those previously observed for the perfluorocarboxylates (PFCAs) and perfluorosulfonates (PFSAs) in the same test organism. Bioaccumulation was observed to decreased in the order of PFSAs > PFCAs > PFPAs of equal perfluorocarbon chain length and was dependent on the charge of the polar headgroup. Bioaccumulation of the PFPiAs was observed to be low due to their rapid elimination via metabolism to the corresponding PFPAs. Here, we report the first observation of an in vivo cleavage of the carbon-phosphorus bond in fish, as well as, the first in vivo biotransformation of a perfluoroalkyl acid (PFAA). As was previously observed for PFCAs and PFSAs, none of the BMFs determined here for the PFPAs and PFPiAs were greater than one, which suggests PFAAs do not biomagnify from dietary exposure in juvenile rainbow trout.     

LC-MS–MS characterisation of curry leaf flavonols and antioxidant activity

Curry leaf (Murraya koenegii) is a common flavouring agent in Indian foods. This study characterised the flavonol profile of curry leaf extracted with different solvents and the relative antioxidant capacity of these extracts by quantifying phenolic constituents. Flavonols were extracted using ethanol, methanol, or acetone prior to identification and quantification using liquid chromatography coupled to atmospheric pressure chemical ionisation (APCI) mass spectrometry in tandem mode (LC-MS–MS) with negative ion detection. Major curry leaf flavonols included myricetin-3-galactoside, quercetin-O-pentohexoside, quercetin-3-diglucoside, quercetin-3-O-rutinoside, quercetin-3-glucoside, quercetin-3-acetylhexoside, quercetin-O-xylo-pentoside, kaempferol-O-glucoside, and kaempferol-aglucoside. Lag-time and TBARS tests demonstrated that curry leaf phenolics prevent cupric-ion induced oxidation of LDL. The best extraction yield was obtained with 80% ethanol. Acetone extracts provided better antioxidant activity expressed as increased lag-time formation, than did ethanol or methanol extracts. Curry leaf is a rich source of flavonols that have biological activity in vitro and further studies are warranted in regards to the potential health benefits and identification of the novel flavonols whose identities remain unknown.     

Net air emissions from electric vehicles: the effect of carbon price and charging strategies

Plug-in hybrid electric vehicles (PHEVs) may become part of the transportation fleet on time scales of a decade or two. We calculate the electric grid load increase and emissions due to vehicle battery charging in PJM and NYISO with the current generation mix, the current mix with a $50/tonne CO(2) price, and this case but with existing coal generators retrofitted with 80% CO(2) capture. We also examine all new generation being natural gas or wind+gas. PHEV fleet percentages between 0.4 and 50% are examined. Vehicles with small (4 kWh) and large (16 kWh) batteries are modeled with driving patterns from the National Household Transportation Survey. Three charging strategies and three scenarios for future electric generation are considered. When compared to 2020 CAFE standards, net CO(2) emissions in New York are reduced by switching from gasoline to electricity; coal-heavy PJM shows somewhat smaller benefits unless coal units are fitted with CCS or replaced with lower CO(2) generation. NO(X) is reduced in both RTOs, but there is upward pressure on SO(2) emissions or allowance prices under a cap.     

Degradation of LaSr2Fe2CrO9−δ solid oxide fuel cell anodes in phosphine-containing fuels

The performance and stability of La_0.9Sr_0.1Ga_0.8Mg_0.2O_3-δ-electrolyte supported solid oxide fuel cells with composite LaSr₂Fe₂CrO_9-δ-Gd_0.1Ce_0.9O₂ anodes were studied in wet H₂ and coal syngas containing phosphine impurity. Introduction of 5-20 ppm PH₃ into the fuels caused an initial slow cell performance degradation followed by a very rapid complete cell degradation that initiated within 11-24 h - earlier at higher PH₃ concentration. There was no recovery after removing PH₃ impurity from the fuels. Electrochemical impedance analysis suggested that the initial gradual performance degradation was due to conductivity loss of the oxide anode due to chemisorption and reaction of phosphine. X-ray diffraction analysis showed the formation of FeP_x and LaPO₄ compounds. The rapid degradation presumably occurred when most or all of the Fe initially present in the LaSr₂Fe₂CrO_9−δ was consumed. Thermodynamic calculations confirmed that Fe is highly reactive with PH₃ at 800 °C, even at concentrations below 1 ppm.     

Braking wind in Australia: A critical evaluation of the renewable energy target

This paper provides a critical evaluation of Australia’s new Renewable Energy Target (RET) program with respect to its capacity to support wind power development. Four structural flaws associated with the RET which undermine its effectiveness as a catalyst for technological change in the electricity sector are discussed: (i) the inclusion of waste coal mine gas (WCMG) as an eligible fuel source which acts as an indirect coal industry subsidy, (ii) program duration which is too short and ill-structured, (iii) a multiplier that is well-intended to support small-scale renewable technologies but which creates “phantom capacity”, and (iv) the capped target of 45,000 GWh which will stymie long-term wind power market investment. The paper concludes with recommendations which stress the importance of passing effective Carbon Pollution Renewable Scheme (CPRS) legislation to offset the weaknesses associated with the RET. If an effective CPRS cannot be implemented, the paper recommends that amendments be made to the RET to (i) remove WCMG from the list of approved alternative energy sources, and (ii) extend the RET targets to reach 120,000 GWh by 2030.     

The effect of electrode parameters on performance of a phosphoric acid-doped PBI membrane fuel cell

A study of the effect of electrode parameters in a phosphoric acid-doped polybenzimidazole (PBI) membrane fuel cell is reported. The influence of phosphoric acid and PBI content are described. High levels of PBI in the catalyst layer did not enhance electrode layer performance for both hydrogen oxidation or oxygen reduction. High levels of doping with phosphoric acid in the anode catalyst layer were beneficial to fuel cell performance. Anode polarisation data confirmed that PBI fuel cells could operate at 175 °C with carbon monoxide contents in the feed gas of 10% in volume. There was an optimum amount of acid doping that gave good performance for oxygen reduction in the cathode layer. The effect of a perfluorinated surfactant improved the oxygen reduction behaviour in the catalyst layer. The carbon in catalyst support and it's interaction with the electrolyte have a large influence on cell performance.     

Modeling dynamic stall on wind turbine blades under rotationally augmented flow fields

This paper presents an investigation of two well‐known aerodynamic phenomena, rotational augmentation and dynamic stall, together in the inboard parts of wind turbine blades. This analysis is carried out using the following: (1) the National Renewable Energy Laboratory's Unsteady Aerodynamics Experiment Phase VI experimental data, including constant as well as continuously pitching blade conditions during axial operation; (2) data from unsteady delayed detached eddy simulations (DDES) carried out using the Technical University of Denmark's in‐house flow solver Ellipsys3D; and (3) data from a reduced order dynamic stall model that uses rotationally augmented steady‐state polars obtained from steady Phase VI experimental sequences, instead of the traditional two‐dimensional, non‐rotating data. The aim of this work is twofold. First, the blade loads estimated by the DDES simulations are compared with three select cases of the N‐sequence experimental data, which serves as a validation of the DDES method. Results show reasonable agreement between the two data in two out of three cases studied. Second, the dynamic time series of the lift and the moment polars obtained from the experiments are compared with those from the dynamic stall model. This allowed the differences between the stall phenomenon on the inboard parts of harmonically pitching blades on a rotating wind turbine and the classic dynamic stall representation in two‐dimensional flow to be investigated. Results indicated a good qualitative agreement between the model and the experimental data in many cases, which suggests that the current two‐dimensional dynamic stall model as used in blade element momentum‐based aeroelastic codes may provide a reasonably accurate representation of three‐dimensional rotor aerodynamics when used in combination with a robust rotational augmentation model. Copyright © 2015 John Wiley & Sons, Ltd.