Hyperfine-Induced Decay in Triple Quantum Dots

We analyze the effects of hyperfine interactions on coherent control experiments in triple quantum dots. By exploiting Hamiltonian symmetries and the SU(3) structure of the triple-dot system under pseudo-exchange and longitudinal hyperfine couplings, we provide analytic formulae for the hyperfine decay of triple-dot Rabi and dephasing experiments.Comment: 5 pages, 2 figure

The 2015 Debt Crisis

At the London G20 Summit, participants reaffirmed their commitment to the Millennium Development Goals (MDGs) and to increasing official development assistance (ODA). This aid will be important in helping the poorest countries meet the MDGs that were agreed before the crisis, but it will probably be insufficient to tackle the additional problems caused by the current economic downturn. (...)The 2015 Debt Crisis

Prosodic description: An introduction for fieldworkers

This article provides an introductory tutorial on prosodic features such as tone and accent for researchers working on little-known languages. It specifically addresses the needs of non-specialists and thus does not presuppose knowledge of the phonetics and phonology of prosodic features. Instead, it intends to introduce the uninitiated reader to a field often shied away from because of its (in part real, but in part also just imagined) complexities. It consists of a concise overview of the basic phonetic phenomena (section 2) and the major categories and problems of their functional and phonological analysis (sections 3 and 4). Section 5 gives practical advice for documenting and analyzing prosodic features in the field.National Foreign Language Resource Cente

The initial stages of cave formation: Beyond the one-dimensional paradigm

The solutional origin of limestone caves was recognized over a century ago, but the short penetration length of an undersaturated solution made it seem impossible for long conduits to develop. This is contradicted by field observations, where extended conduits, sometimes several kilometers long, are found in karst environments. However, a sharp drop in the dissolution rate of CaCO_3 near saturation provides a mechanism for much deeper penetration of reactant. The notion of a "kinetic trigger" - a sudden change in rate constant over a narrow concentration range - has become a widely accepted paradigm in speleogenesis modeling. However, it is based on one-dimensional models for the fluid and solute transport inside the fracture, assuming that the dissolution front is planar in the direction perpendicular to the flow. Here we show that this assumption is incorrect; a planar dissolution front in an entirely uniform fracture is unstable to infinitesimal perturbations and inevitably breaks up into highly localized regions of dissolution. This provides an alternative mechanism for cave formation, even in the absence of a kinetic trigger. Our results suggest that there is an inherent wavelength to the erosion pattern in dissolving fractures, which depends on the reaction rate and flow rate, but is independent of the initial roughness. In contrast to one-dimensional models, two-dimensional simulations indicate that there is only a weak dependence of the breakthrough time on kinetic order; localization of the flow tends to keep the undersaturation in the dissolution front above the threshold for non-linear kinetics.Comment: to be published in Earth and Planetary Science Letter

Scaling the Digital Divide: Home Computer Technology and Student Achievement

Assesses the effect of access to home computers and broadband Internet on students' math and reading test scores and its potential to close the achievement gap for the disadvantaged. Considers the role of parental monitoring

“Als wel the lord as the schepherde, He broghte hem alle in good accord”: Harmonious Materialism in the Confessio Amantis

Using R. F. Yeager\u27s analysis of the figure Arion as a starting point, this article argues that in the Confessio Amantis, John Gower shifts his impulse toward social correction from direct estates satire to a more subtle approach encoding his social critique in the love stories of the Confessio. Examples of this approach include a variety of tales from Book 5, and the Apollonius of Tyre story in Book 8. Details of the poem\u27s ending and later works like In Praise of Peace indicate that Gower still retained an interest in direct critique of social problems

Public School Choice And Integration: Evidence from Durham, North Carolina

Using evidence from Durham, North Carolina, we examine the impact of school choice programs on racial and class-based segregation across schools. Theoretical considerations suggest that how choice programs affect segregation will depend not only on the family preferences emphasized in the sociology literature but also on the linkages between student composition, school quality and student achievement emphasized in the economics literature. Reasonable assumptions about the distribution of preferences over race, class, and school characteristics suggest that the segregating choices of students from advantaged backgrounds are likely to outweigh any integrating choices by disadvantaged students. The results of our empirical analysis are consistent with these theoretical considerations. Using information on the actual schools students attend and on the schools in their assigned attendance zones, we find that schools in Durham are more segregated by race and class as a result of school choice programs than they would be if all students attended their geographically assigned schools. In addition, we find that the effects of choice on segregation by class are larger than the effects on segregation by race