A high voltage square wave generator for Stark modulation

M.S.J. Quitman William

Elected Mayors: Leading Locally?

The directly elected executive mayor has been with us in England for more than a decade. Drawing inspiration from European and American experience (see Elcock and Fenwick, 2007) the elected mayor has appealed to both Labour and Conservative commentators in offering a solution to perceived problems of local leadership. For the Left, it offered a reinvigoration of local democracy, a champion for the locality who could stand up for the community: in one early pamphlet, a Labour councillor envisaged that an elected mayor could “...usher in a genuinely inclusive way of doing civic business as well as giving birth to an institution that encourages and values people” (Todd, 2000: 25). For the Right, it offered the opportunity to cut through the lengthy processes of local democratic institutions by providing streamlined high-profile leadership. Although inconsistent in their expectations of what the new role of executive mayor would bring, Left and Right shared a view that leadership of local areas was failing. Despite the very low turnout in referendums on whether to adopt the system, and the very small number of local areas that have done so, the prospect of more executive mayors, with enhanced powers, refuses to exit the policy arena

Retroactive Liability and Future Risk: The Optimal Regulation of Underground Storage Tanks

The optimal design of environmental liability policy focuses on two primary policy issues: the cleanup of existing sources of pollution and the definition and enforcement of policies to promote prospectively efficient environmental risk reduction. Through the analysis of a policy toward a pervasive environmental risk--leaking underground storage tanks--we analyze the effectiveness of an existing policy governing retroactive and prospective liability issues and suggest ways in which that policy can be improved. While we find some theoretical support for the public financing of UST cleanups, we also find the current system to be flawed in its implementation. In general, the paper argues that public financing of past pollution cleanup costs can lead to greater future risk deterrence by allowing firms to more fully internalize the costs of future environmental risks. However, if it is practically or politically impossible to limit public financing to retroactive liabilities alone, the deterrent effect of such a system is vastly reduced.

Liquid acrobatics

We experiment with injecting a continuous stream of gas into a shallow liquid, similar to how one might blow into a straw placed at the bottom of a near-empty drink. By varying the angle of the straw (here a metal needle), we observe a variety of dynamics, which we film using a high-speed camera. Most noteworthy is an intermediate regime in which cyclical jets erupt from the air-liquid interface and breakup into air-born droplets. These droplets trace out a parabolic trajectory and bounce on the air-liquid interface before eventually coalescing. The shape of each jet, as well as the time between jets, is remarkably similar and leads to droplets with nearly identical trajectories. The following article accompanies the linked fluid dynamics video submitted to the Gallery of Fluid Motion in 2008.Comment: Accompanies video submission to APS DFD 2008 Gallery of Fluid Motion, low http://ecommons.library.cornell.edu/bitstream/1813/11469/3/Bird_DFD2008_mpeg1.mpg , and high resolution http://ecommons.library.cornell.edu/bitstream/1813/11469/2/Bird_DFD2008_mpeg2.mp

How many metals does it take to fix N2? A mechanistic overview of biological nitrogen fixation

During the process of biological nitrogen fixation, the enzyme nitrogenase catalyzes the ATP-dependent reduction of dinitrogen to ammonia. Nitrogenase consists of two component metalloproteins, the iron (Fe) protein and the molybdenum-iron (MoFe) protein; the Fe protein mediates the coupling of ATP hydrolysis to interprotein electron transfer, whereas the active site of the MoFe protein contains the polynuclear FeMo cofactor, a species composed of seven iron atoms, one molybdenum atom, nine sulfur atoms, an interstitial light atom, and one homocitrate molecule. This Perspective provides an overview of biological nitrogen fixation and introduces three contributions to this special feature that address central aspects of the mechanism and assembly of nitrogenase

Pre-Assembeld Non-Load Bearing Interior Partition Panels

Gives an illustrated description of a design for pre-assembled interior partitioning walls created by the Small Homes Council aimed at realize the cost savings of using pre-fabricated materials in home construction.Lumber Dealers Research Counci

Nitrogenase: A nucleotide-dependent molecular switch

In the simplest terms, the biological nitrogen cycle is the reduction of atmospheric dinitrogen (N2) to ammonia with the subsequent reoxidation ammonia to dinitrogen (1). At the reduction level of ammonia, nitrogen incorporated into precursors for biological macromolecules such as proteins and nucleic acids. Reoxidation of ammonia to dinitrogen ("denitrification") by a variety of microbes (by way of nitrite and other oxidation levels of nitrogen) leads to the depletion of the "fixed," biologically usable, nitrogen pool. Besides the relatively small contribution from commercial ammonical fertilizer production, replenishing of the nitrogen pool falls mainly to a limited number of physiologically diverse microbes (e.g. eubacteria and archaebacteria; free-living and symbiotic; aerobic and anaerobic) that contain the nitrogenase enzyme system