Microwave Penetration Depth and Quasiparticle Conductivity in PrFeAsO_1-y Single Crystals : Evidence for a Full-Gap Superconductor

In-plane microwave penetration depth $\lambda_{ab}$ and quaiparticle conductivity at 28 GHz are measured in underdoped single crystals of the Fe-based superconductor PrFeAsO$_{1-y}$ ($T_c\approx 35$ K) by using a sensitive superconducting cavity resonator. $\lambda_{ab}(T)$ shows flat dependence at low temperatures, which is incompatible with the presence of nodes in the superconducting gap $\Delta({\bf k})$. The temperature dependence of the superfluid density demonstrates that the gap is non-zero ($\Delta/k_BT_c\gtrsim 1.6$) all over the Fermi surface. The microwave conductivity below $T_c$ exhibits an enhancement larger than the coherence peak, reminiscent of high-$T_c$ cuprate superconductors.Comment: 4 pages, 3 figures. Version accepted for publication in Phys. Rev. Lett. For related results of hole-doped 122 system, see arXiv:0810.350

Ratepayer-funded energy-efficiency programs in a restructured electricity industry: Issues, options, and unanswered questions

Regulated utilities have, in the past, been responsible for {open_quotes}Public purpose{close_quotes} programs that contribute to the general social good, such as energy-efficiency programs. In several states, continuation of these programs has become a critical issue in forging the consensus required to proceed with restructuring. As a result of reviewing the restructuring process in several states, we expect this trend to continue, but do not believe a single, generic approach can or should be defined. Instead, we expect a variety of solutions based on considerations unique to individual states or regions. To help structure these discussions in states struggling with this issue, we pose a series of questions and describe a range of possible answers: (1) We encourage state public utility commissions and legislatures to provide clear guidance on goals. (2) Close attention to the primary objectives for energy efficiency is important because the objectives influence the choices of programs and activities to be supported. (3) We advocate that states adopt a pragmatic approach to resolving the potentially contentious issue of determining whether or not utilities should continue to have primary responsibility for program administration, management, and design. The approach we propose involves assessing a utility`s past performance, its cur-rent commitment to energy-efficiency activities, and the potential conflicts of interest presented, if the utility retains a central role in administering energy-efficiency programs after restructuring. (4) A state should first assess policy options to mitigate adverse incentives and conflicts of interest in the utility before examining the possibility of having a non-utility entity assume responsibility for designing and managing energy-efficiency activities. (5) If a state does pursue non-utility administration for ratepayer-funded energy-efficiency programs, explicit attention must be paid to governance and accountability issues