Magnetic field inversions at 1 AU: comparisons between mapping predictions and observations

Large-scale magnetic field configurations are important for the transport of solar wind strahl electrons, which are suprathermal and directed along the field outward from the Sun. Strahl electrons are routinely used to infer not only the field configurations between the Sun and Earth but also local field structures, i.e., field inversions, where the magnetic field is locally folded back or inverted. Using solar wind data from ACE observations and a 2-D data-driven solar wind model with nonzero azimuthal magnetic field at the solar wind source surface, magnetic field lines are mapped between the Sun and Earth and beyond, in the solar equatorial plane. Standard verification metrics are used to assess, for five solar rotations at different phases of solar cycle 23, the performance of the mapping predictions for observed inversions, which are inferred from solar wind suprathermal electrons and magnetic fields measured by ACE. The probability of detection is consistently ≈0.70 across the different phases. The success ratio, the Hanssen-Kuipers skill score, and the Heidke skill score are ≈0.55–0.70 for the four rotations in the rising, solar maximum, and declining phases, but ≈0.35–0.60 for the rotation near solar minimum, during which almost half of the samples have undetermined field configurations. Our analyses confirm the persistence of inversions throughout solar cycle 23, suggest for most observed inversions a solar/coronal origin at the wind's source surface or below, and predict that inversions should be less common for larger heliocentric distance r ∼> 3 AU than for smaller r

'I would rather die': reasons given by 16-year-olds for not continuing their study of mathematics

Improving participation rates in specialist mathematics after the subject ceases to be compulsory at age 16 is part of government policy in England. This article provides independent and recent support for earlier findings concerning reasons for non- participation, based on free response and closed items in a questionnaire with a sample of over 1500 students in 17 schools, close to the moment of choice. The analysis supports findings that perceived difficulty and lack of confidence are important reasons for students not continuing with mathematics, and that perceived dislike and boredom, and lack of relevance, are also factors. There is a close relationship between reasons for non-participation and predicted grade, and a weaker relation to gender. An analysis of the effects of schools, demonstrates that enjoyment is the main factor differentiating schools with high and low participation indices. Building on discussion of these findings, ways of improving participation are briefly suggested

Exact Solutions of Regge-Wheeler Equation and Quasi-Normal Modes of Compact Objects

The well-known Regge-Wheeler equation describes the axial perturbations of Schwarzschild metric in the linear approximation. From a mathematical point of view it presents a particular case of the confluent Heun equation and can be solved exactly, due to recent mathematical developments. We present the basic properties of its general solution. A novel analytical approach and numerical techniques for study the boundary problems which correspond to quasi-normal modes of black holes and other simple models of compact objects are developed.Comment: latex file, 25 pages, 4 figures, new references, new results and new Appendix added, some comments and corrections in the text made. Accepted for publication in Classical and Quantum Gravity, 2006, simplification of notations, changes in the norm in some formulas, corrections in reference

Exploring supply management status, internal collaboration and operating performance

An important internal link in the supply chain is between supply managers and their internal customers. These individuals must collaborate to determine purchase specifications, develop sourcing strategies, ensure supplier performance, and maintain effective supplier relationships. Using power and social networking as the theoretical lenses, we develop and test a conceptual model examining the supply management function’s status, supply manager’s networking behavior, collaboration with the internal customer, and operating performance (lower cost, better quality, faster delivery, and consistent delivery). We also examine the mediating effect of collaboration and networking behavior on the positive effect of status and operating performance. Data gathered in an online survey of supply management professionals are examined using path analysis. Results show that without including the mediators, supply management status is directly related to all four operating performance measures. It is also positively related to collaboration with the internal customer and networking behavior. Contrary to expectations, the supply manager’s networking behavior is not related to collaboration with the internal customer. Collaboration is positively related to all four operating performance measures. However, the supply manager’s networking behavior is only related to one operating performance measure, better quality. Mediation analysis shows that supply management status has a direct effect on faster delivery performance beyond what is explained by collaboration and the supply manager’s networking behavior. The findings suggest that organizations should look for ways to elevate the status of the supply management function to improve internal collaboration and operating performance.Keywords: status, operating performance, supply management, networking, collaboration, internal custome

Negative Thermal Expansion Coefficient of Graphene Measured by Raman Spectroscopy

The thermal expansion coefficient (TEC) of single-layer graphene is estimated with temperature-dependent Raman spectroscopy in the temperature range between 200 and 400 K. It is found to be strongly dependent on temperature but remains negative in the whole temperature range, with a room temperature value of -8.0x10^{-6} K^{-1}. The strain caused by the TEC mismatch between graphene and the substrate plays a crucial role in determining the physical properties of graphene, and hence its effect must be accounted for in the interpretation of experimental data taken at cryogenic or elevated temperatures.Comment: 17 pagese, 3 figures, and supporting information (4 pages, 3 figures); Nano Letters, 201