Modal quantum theory

We present a discrete model theory similar in structure to ordinary quantum mechanics, but based on a finite field instead of complex amplitudes. The interpretation of this theory involves only the "modal" concepts of possibility and necessity rather than quantitative probability measures. Despite its simplicity, our model theory includes entangled states and has versions of both Bell's theorem and the no cloning theorem.Comment: Presented at the 7th Workshop on Quantum Physics and Logic, Oxford University (29-30 May 2010). Revised 1 Aug 2011 in response to referee comment

The Privatization of Correctional Institutions: The Tennessee Experience

Recently, the privatization of correctional institutions has been a topic of intense interest both in Tennessee and other parts of the Nation. In the hope that we might learn from the past, we undertook to examine Tennessee\u27s convict leasing practices of the nineteenth century. This Article summarizes that research and provides a narrative and analysis of the recent events regarding privatization of correctional institutions in Tennessee

On-demand single-photon state generation via nonlinear absorption

We propose a method for producing on-demand single-photon states based on collision-induced exchanges of photons and unbalanced linear absorption between two single-mode light fields. These two effects result in an effective nonlinear absorption of photons in one of the modes, which can lead to single photon states. A quantum nonlinear attenuator based on such a mechanism can absorb photons in a normal input light pulse and terminate the absorption at a single-photon state. Because the output light pulses containing single photons preserve the properties of the input pulses, we expect this method to be a means for building a highly controllable single photon source.Comment: 5 pages, 2 figures, to appear in PRA. To be published in PR

Calculation of steady and unsteady pressures at supersonic speeds with CAP-TSD

A finite difference technique is used to solve the transonic small disturbance flow equation making use of shock capturing to treat wave discontinuities. Thus the nonlinear effects of thickness and angle of attack are considered. Such an approach is made feasible by the development of a new code called CAP-TSD (Computational Aeroelasticity Program - Transonic Small Disturbance), and is based on a fully implicit approximate factorization (AF) finite difference method to solve the time dependent transonic small disturbance equation. The application of the CAP-TSD code to the calculation of low to moderate supersonic steady and unsteady flows is presented. In particular, comparisons with exact linear theory solutions are made for steady and unsteady cases to evaluate shock capturing and other features of the current method. In addition, steady solutions obtained from an Euler code are used to evaluate the small disturbance aspects of the code. Steady and unsteady pressure comparisons are made with measurements for an F-15 wing model and for the RAE tailplane model

Direct Evidence That the Reaction Intermediate of Metallo-β-lactamase L1 Is Metal Bound

In an effort to probe the structure of the reaction intermediate of metallo-β-lactamase L1 when reacted with nitrocefin and other β-lactams, time-dependent absorption and rapid-freeze-quench (RFQ) EPR spectra were obtained using the Co(II)-substituted form of the enzyme. When using nitrocefin as the substrate, time-dependent absorption spectra demonstrate that Co(II)-substituted L1 utilizes a reaction mechanism, similar to that of the native Zn(II) enzyme, in which a short-lived intermediate forms. RFQ-EPR spectra of this intermediate demonstrate that the binding of substrate results in a change in the electronic properties of one or both of the Co(II)\u27s in the enzyme that is consistent with a change in the coordination sphere of this metal ion. This observation provides evidence that the reaction intermediate is a metal-bound species. RFQ-EPR studies also demonstrate that other β-lactams, such as cephalothin, meropenem, and penicillin G, proceed through an electronically similar complex and that the role of metal is similar in all cases. EPR spectroscopy has also identified distinct product-bound species of L1, indicating that reversible product binding must be considered in all future kinetic mechanisms. Consideration of the time-dependent optical and EPR studies in light of available crystallographic information indicates the intimate involvement of the metal ion in the Zn2-binding site of L1 in the hydrolytic reaction

Merchant Capital and the Origins of the Barbados Sugar Boom, 1627-1672

This dissertation undertakes the first systematic study of the English merchants who financed the Barbados sugar boom in the mid-seventeenth century. It brings together archival material from the UK, USA, and the Caribbean to explore their involvement with Barbados in detail and put their commercial activity into metropolitan and global context. I trace how merchant capital was invested in the Barbadian economy during the 1640s, produced transformative social and economic changes on Barbados and in England over the next two decades, before being withdrawn in the 1660s and reinvested elsewhere. By placing the merchant financiers of the sugar boom and their trading networks at the centre of my analysis, I work at the intersection of three historiographical subfields which are usually studied separately: the history of early modern England, Caribbean history, and global history. Bringing these fields into conversation has revealed the importance of both political events occurring in the metropole and the expansion of the empire in other parts of the globe to the development of the Barbadian sugar industry. The capital which merchants used to finance the growth of plantation slavery was generated through a variety of domestic and global business activities, and the political and economic uncertainty caused by the English Civil War (1642-49) was a key reason why London merchants invested such large amounts of money in land and enslaved Africans in the colony during the 1640s. This results in an analysis of early modern empire that is more global than is usually seen in current studies of seventeenth-century colonialism. It encourages historians to conceptualise the constituent parts of the seventeenth-century English empire in America, West Africa, Asia, and the Mediterranean as an integrated whole

Preserving entanglement under decoherence and sandwiching all separable states

Every entangled state can be perturbed, for instance by decoherence, and stay entangled. For a large class of pure entangled states, we show how large the perturbation can be. Our class includes all pure bipartite and all maximally entangled states. For an entangled state, E, the constucted neighborhood of entangled states is the region outside two parallel hyperplanes, which sandwich the set of all separable states. The states for which these neighborhoods are largest are the maximally entangled ones. As the number of particles, or the dimensions of the Hilbert spaces for two of the particles increases, the distance between two of the hyperplanes which sandwich the separable states goes to zero. It is easy to decide if a state Q is in the neighborhood of entangled states we construct for an entangled state E. One merely has to check if the trace of EQ is greater than a constant which depends upon E and which we determine.Comment: Corrected first author's e-mail address. All the rest remains unchange

Indeterminate-length quantum coding

The quantum analogues of classical variable-length codes are indeterminate-length quantum codes, in which codewords may exist in superpositions of different lengths. This paper explores some of their properties. The length observable for such codes is governed by a quantum version of the Kraft-McMillan inequality. Indeterminate-length quantum codes also provide an alternate approach to quantum data compression.Comment: 32 page