Feedback control optimisation of ESR experiments

Numerically optimised microwave pulses are used to increase excitation efficiency and modulation depth in electron spin resonance experiments performed on a spectrometer equipped with an arbitrary waveform generator. The optimisation procedure is sample-specific and reminiscent of the magnet shimming process used in the early days of nuclear magnetic resonance -- an objective function (for example, echo integral in a spin echo experiment) is defined and optimised numerically as a function of the pulse waveform vector using noise-resilient gradient-free methods. We found that the resulting shaped microwave pulses achieve higher excitation bandwidth and better echo modulation depth than the pulse shapes used as the initial guess. Although the method is theoretically less sophisticated than simulation based quantum optimal control techniques, it has the advantage of being free of the linear response approximation; rapid electron spin relaxation also means that the optimisation takes only a few seconds. This makes the procedure fast, convenient, and easy to use. An important application of this method is at the final stage of the implementation of theoretically designed pulse shapes: compensation of pulse distortions introduced by the instrument. The performance is illustrated using spin echo and out-of-phase electron spin echo envelope modulation experiments. Interface code between Bruker SpinJet arbitrary waveform generator and Matlab is included in versions 2.2 and later of the Spinach library

Price Discovery in Emissions Permit Auctions

Auctions are increasingly being used to allocate emissions allowances (“permitsâ€) for cap and trade and common-pool resource management programs. These auctions create thick markets that can provide important information about changes in current market conditions. This paper reports a laboratory experiment in which half of the bidders experienced unannounced increases in their willingness to pay for permits. The focus is on the extent to which the predicted price increase due to the demand shift is reflected in sales prices under alternative auction formats. Price tracking is comparably good for uniform-price sealed-bid auctions and for multi-round clock auctions, with or without end-of-round information about excess demand. More price inertia is observed for “pay as bid†(discriminatory) auctions, especially for a continuous discriminatory format in which bids could be changed at will during a pre-specified time window, in part because “sniping†in the final moments blocked the full effect of the demand shock.auction, greenhouse gases, price discovery, cap and trade, emission allowances, laboratory experiment

An Experimental Analysis of Auctioning Emission Allowances Under a Loose Cap

The direct sale of emission allowances by auction is an emerging characteristic of cap-and-trade programs. This study is motivated by the observation that all of the major implementations of cap-and-trade regulations for the control of air pollution have started with a generous allocation of allowances relative to recent emissions history, a situation we refer to as a “loose cap.†Typically more stringent reductions are achieved in subsequent years of a program. We use an experimental setting to investigate the effects of a loose cap environment on a variety of auction types. We find that all auction formats studied are efficient in allocating emission allowances, but auction revenues tend to be lower relative to competitive benchmarks when the cap is loose. Regardless of whether the cap is tight or loose, the different auction formats tend to yield comparable revenues toward the end of a series of auctions. However, aggressive bidding behavior in initial discriminatory auctions yields higher revenues than in the other auction formats, a difference that disappears as bidders learn to adjust their bids closer to the cut-off that separates winning and losing bids.auction, carbon dioxide, greenhouse gases, allowance trading, Regional Greenhouse Gas Initiative, RGGI, cap and trade, Environmental Economics and Policy, Resource /Energy Economics and Policy,

Phosphate selective binding and sensing by halogen bonding tripodal copper( ii ) metallo-receptors in aqueous media †

Combining the potency of non-covalent halogen bonding (XB) with metal ion coordination, the synthesis and characterisation of a series of hydrophilic XB tripodal Cu(ii) metallo-receptors, strategically designed for tetrahedral anion guest binding and sensing in aqueous media is described. The reported metallo-hosts contain a tripodal C3-symmetric tris-iodotriazole XB donor anion recognition motif terminally functionalised with tri(ethylene glycol) and permethylated β-cyclodextrin functionalities to impart aqueous solubility. Optical UV-vis anion binding studies in combination with unprecedented quantitative EPR anion titration investigations reveal the XB Cu(ii) metallo-receptors exhibit strong and selective phosphate recognition over a range of other monocharged anionic species in competitive aqueous solution containing 40% water, notably outperforming a hydrogen bonding (HB) Cu(ii) metallo-receptor counterpart. Electrochemical studies demonstrate further the capability of the metallo-receptors to sense anions via significant cathodic perturbations of the respective Cu(ii)/Cu(i) redox couple

Raising a Small Flock of Sheep in Ohio

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