Empirical Determination of Bang-Bang Operations

Strong and fast "bang-bang" (BB) pulses have been recently proposed as a means for reducing decoherence in a quantum system. So far theoretical analysis of the BB technique relied on model Hamiltonians. Here we introduce a method for empirically determining the set of required BB pulses, that relies on quantum process tomography. In this manner an experimenter may tailor his or her BB pulses to the quantum system at hand, without having to assume a model Hamiltonian.Comment: 14 pages, 2 eps figures, ReVTeX4 two-colum

The Political Economy of Failure: The Euro as an International Currency

How do international currencies get established and consolidated? What domestic and international political foundations support an international currency? And what kinds of macro-economic flows enable an international currency? In this essay we consider these perennial questions of modern IPE scholarship in reverse order to ask whether the euro could ever have become, or seek to become, a true international currency rivalling the US dollar, used not only for passive foreign exchange reserves but also as a major commercial currency outside the EU. We argue that the EU lacks the will, the ideas and the capacity to promote the euro into the status of an international currency. In this article, we concentrate on this final issue of capacity, as the will and ideas issues have already been well explored. Capacity is an issue coeval with, if not prior to, the first two issues. The EU's current institutional arrangements and its economic geography create macro-economic consequences that diminish the euro's capacity to operate as a top currency. These conflicts go beyond the well-recognized issue that the euro-zone is not an optimum currency area. Examining the euro's debilities sheds light not only on the euro's (in)capacity to rival the dollar as an international currency, but also on the future of both the euro and the dollar in the aftermath of the euro-zone crisis

Quadrupole moments of collective structures up to spin ̃65h in 157Er and 158Er: A challenge for understanding triaxiality in nuclei

The transition quadrupole moments, Qt, of four weakly populated collective bands up to spin ̃65h in 157,158Er have been measured to be ̃11 eb demonstrating that these sequences are associated with large deformations. However, the data are inconsistent with calculated values from cranked Nilsson-Strutinsky calculations that predict the lowest energy triaxial shape to be associated with rotation about the short principal axis. The data appear to favor either a stable triaxial shape rotating about the intermediate axis or, alternatively, a triaxial shape with larger deformation rotating about the short axis. These new results challenge the present understanding of triaxiality in nuclei

Non-yrast positive-parity structures in the γ-soft nucleus Er156

Weakly populated band structures have been established in Er156 at low to medium spins, following the Cd114(Ca48,6nγ) reaction at 215 MeV. High-fold γ-ray coincidence data were recorded in a high-statistics experiment with the Gammasphere spectrometer. Bands built on the second 0+ and 2+ (γ-vibrational) states have been established. A large energy staggering between the even- and odd-spin members of the γ-vibrational band suggests a γ-soft nature of this nucleus. An additional band is discussed as being based on a rotationally aligned (νh9/2,f 7/2)2 structure, coexisting with the systematically observed, more favorable (νi13/2)2 aligned structure seen in this mass region

Collective structures up to spin ∼ 65h in the N 90 isotones 158Er and 157Ho

A new collective band with high dynamic moment of inertia in 158Er at spins beyond band termination has been found in addition to the two previously reported ones. The measured transition quadrupole moments (Qt) of these three bands are very similar. These three bands have been suggested to possess a triaxial strongly deformed shape, based on comparisons with calculations using the cranked Nilsson-Strutinsky model and with tilted axis cranking calculations using the Skyrme-Hartree-Fock model. In addition, three collective bands with similar high dynamic moments of inertia, tentatively assigned to 157Ho, have been observed. Thus, it is suggested that all these structures share a common underlying character and that they are most likely associated with triaxial strongly deformed minima which are predicted to be close to the yrast line at spin 50 - 70h

E-assessment: past, present and future

This review of e-assessment takes a broad definition, including any use of a computer in assessment, whilst focusing on computer-marked assessment. Drivers include increased variety of assessed tasks and the provision of instantaneous feedback, as well as increased objectivity and resource saving. From the early use of multiple-choice questions and machine-readable forms, computer-marked assessment has developed to encompass sophisticated online systems, which may incorporate interoperability and be used in students’ own homes. Systems have been developed by universities, companies and as part of virtual learning environments. Some of the disadvantages of selected-response question types can be alleviated by techniques such as confidence-based marking. The use of electronic response systems (‘clickers’) in classrooms can be effective, especially when coupled with peer discussion. Student authoring of questions can also encourage dialogue around learning. More sophisticated computer-marked assessment systems have enabled mathematical questions to be broken down into steps and have provided targeted and increasing feedback. Systems that use computer algebra and provide answer matching for short-answer questions are discussed. Computer-adaptive tests use a student’s response to previous questions to alter the subsequent form of the test. More generally, e-assessment includes the use of peer-assessment and assessed e-portfolios, blogs, wikis and forums. Predictions for the future include the use of e-assessment in MOOCs (massive open online courses); the use of learning analytics; a blurring of the boundaries between teaching, assessment and learning; and the use of e-assessment to free human markers to assess what they can assess more authentically