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Using a large dataset of well-level natural gas production from Wyoming, we evaluate the respective roles played by market signals and geological characteristics in natural gas supply. While we find well-level production of natural gas is primarily determined by geological characteristics, producers respond to market signals through drilling rates and locations. Using a novel fixed effects approach based on petroleum-engineering characteristics, we confirm that production decline rates tend to be larger for wells with larger peak-production rates. We also find that the price elasticity of peak production is negative, plausibly because firms drill in less productive locations as prices increase. Finally, we show that drilling is price inelastic, although the price elasticity of drilling increased significantly when new technologies began to be adopted in Wyoming. Our results indicate that the popular view that shale wells have larger decline rates than conventional wells can be at least partially explained by the pattern of falling natural gas prices.

The concept of reducing emissions of CO2 to the atmosphere by producing chemicals has been suggested by many people as a potential greenhouse gas mitigation option. The goal of such schemes is either: (i) fixation of CO2 in a chemical compound for a significant time, or, (ii) reduction of emissions by replacing an existing process with an alternative releasing less CO2. This paper describes a simple assessment procedure which can be used as a preliminary screen to test the validity of schemes for chemicals utilisation of CO2. The procedure is presented as a template (or worksheet); two summaries of its use are presented. The template gives research workers a decision methodology which leads to the proposed scheme either being rejected or accepted as being of sufficient potential to merit more detailed investigation. © 1997 Elsevier Science Ltd.

Two patients with ureteric fistulae who were unfit for reconstructive surgery were treated by renal ablation using intra-arterial ethanol, gelfoam fragments and in one case coils. In both cases the fistulae dried-up on the same day and both patients are well and normotensive a year later. Our conclusion is that renal ablation by arterial embolization with ethanol can be a valuable alternative to surgery to treat ureteric fistulae in patients who are poor surgical risks.

Abstract The influence of mounting setup on the wind flow field, temperature pattern, and electrical performance of building-integrated (BIPV) and building-applied (BAPV) photovoltaic modules was investigated using wind tunnel experiments. Tests were done with an inclined 3 × 2 module for four air gap thicknesses varying from 0 cm (BIPV) to 5.5 cm (BAPV) and five freestream approaching wind speeds from 1 to 5 m s−1. Wind speed and temperature were measured along the central line of the module, on the top (illuminated) as well as on the back (shaded) side. Short-circuit current and open-circuit voltage were determined from I-V measurements, and the maximum power was calculated. The wind and temperature patterns and the electrical performance were considerably affected by the mounting setup. The BAPV configurations were always better cooled by the wind than the BIPV setup because of the additional cooling in the air gap. Although a better cooling does not automatically guarantee a higher electrical performance, the BAPV configurations showed the highest performances in the test. In addition, the development of a boundary layer above and (in the case of BAPV) below the module and the trapping of heat into it, created a surface temperature gradient that significantly affected the electrical performance of the individual solar cells in the module. This is important because in most PV modules, solar cells are connected in series. Since the operational temperature influences mainly the open-circuit voltage, the open-circuit voltage of the whole module, and hereby the power output, will be determined by the behavior of each individual solar cell. In the tests reported here, the BAPV module with the thickest air gap (5.5 cm in this study) was the best performing configuration.

Regarding short-term reliability of composite power system, probability of critical event resulting in system failure within a short lead time is extremely low, which renders classical sequential Monte Carlo simulation method inefficient. In this paper, a cross-entropy-based three-stage sequential importance sampling (TSSIS) method is proposed to solve the low efficiency problem resulted from the low rate of component state transition during a fixed lead time. First, by assuming the system state transition process conforms to continuous time Markov chain, an analytical solution to optimal distorted component state transition rate to be used for sequential importance sampling is found by means of cross-entropy method. Second, TSSIS for a fixed lead time is constructed as follows: 1) acceleration of producing system state transitions; 2) enhanced learning to give optimal distorted transition rate; 3) compensation to the cost function. Case studies based on a reinforced Roy Billinton reliability test system and RTS-79 are carried out respectively for illustration of parameter settings of TSSIS as well as efficiency gain in comparison with the classical sequential Monte Carlo simulation method. The results demonstrate that given rational setting of parameters, TSSIS is of relatively high efficiency for sequential short-term reliability evaluation of composite power system.

In the past few decades, a competitive landscape, learned customers and rigorous regulations have forced manufacturing industries to focus on sustainability alongside operational efficiency. The main objective of the present study is to develop a systematic Green Lean Six Sigma (GLSS) framework for improvement in operational efficiency together with environmental and social sustainability. Further, the proposed framework was tested in a leading manufacturing company. The framework was designed with insights gained from the literature and industrial personnel and encompasses the systematic application of different tools of the Green paradigm, Lean, and Six Sigma, from the identification and assessment of the problem to the sustainment of the adopted measures. A systematic application of lifecycle assessment and social lifecycle assessment was used to assess environmental and societal performance. The sustainability focused GLSS framework enhances the environmental capability, process performance and provides a new perspective for researchers and practitioners to support GLSS projects to achieving higher sustainability dynamics.

This paper reports the application of a dehydrogenase enzyme mimic as a biomimetic sensor. The model compound investigated was a beta-cyclodextrin (beta-CD) derivative with a nicotinamide group attached to the secondary face of a beta-CD (Fig. 1g). It was envisaged that the nicotinamide group would act as the electron transfer agent and that the cyclodextrin would provide a suitable hydrophobic cavity for the reaction to take place in. Ethanol, propranalol, dopamine and acetone were used as substrates in backgrounds of hydrophilic and hydrophobic anions. Electrochemical and fluorescence techniques were used to study the catalytic effects in solution. It was found that the size of the analyte and the hydrophobicity of the anion affected the catalytic activity of the dehydrogenase mimic. Catalytic effects were most enhanced with ethanol and dopamine in presence of larger and more strongly solvated anions, SO4(2-) and H2PO4- which are excluded from the cavity. The molecule was also immobilised in a sol-gel matrix and investigated as a sol-gel electrochemical biomimetic sensor. Concentration dependence with increasing aliquots of ethanol was observed. These results indicated that a re-usable biomimetic sensor is indeed feasible.

Abstract Climate observations inform about the past and present state of the climate system. They underpin climate science, feed into policies for adaptation and mitigation, and increase awareness of the impacts of climate change. The Global Climate Observing System (GCOS), a body of the World Meteorological Organization (WMO), assesses the maturity of the required observing system and gives guidance for its development. The Essential Climate Variables (ECVs) are central to GCOS, and the global community must monitor them with the highest standards in the form of Climate Data Records (CDR). Today, a single ECV—the sea ice ECV—encapsulates all aspects of the sea ice environment. In the early 1990s it was a single variable (sea ice concentration) but is today an umbrella for four variables (adding thickness, edge/extent, and drift). In this contribution, we argue that GCOS should from now on consider a set of seven ECVs (sea ice concentration, thickness, snow depth, surface temperature, surface albedo, age, and drift). These seven ECVs are critical and cost effective to monitor with existing satellite Earth observation capability. We advise against placing these new variables under the umbrella of the single sea ice ECV. To start a set of distinct ECVs is indeed critical to avoid adding to the suboptimal situation we experience today and to reconcile the sea ice variables with the practice in other ECV domains.