The Polarization of Drifting Subpulses

Using new techniques based on the polarimetric fluctuation spectrum, the fluctuation behaviour of the polarization of individual pulses is examined in three pulsars that show drifting subpulses, allowing various aspects of the fluctuations to be quantified for the first time. Of the three pulsars studied, only PSR B0809+74 shows behaviour completely consistent with the superposition of orthogonal polarization modes (OPMs), and this only at 328 MHz and in superposition with an apparently randomly polarized component. The observed periodic pattern is decomposed into the sum of two orthogonally polarized, out-of-phase drift patterns, one of which shows a dramatic jump in subpulse phase near the leading edge of the pulse window. For PSR B0320+39 and PSR B0818$-$13, considerable periodic fluctuations away from OPM orientations are seen, a condition that also occurs in the trailing half of the pulse in PSR B0809+74 at 1380 MHz. In some cases the deviation is so strong that the periodic locus of the polarization vector in the Poincar\'{e} sphere is almost circular, in contrast to the strictly colinear states of superposed OPMs. Several possibilities are discussed for the physical origin of these patterns. The similarity between the subpulse patterns in one of the OPMs of PSR B0809+74 at 328 MHz to that of the total intensity signal at 1380 MHz supports a picture of superposed, out of phase drift patterns. To explain the full range of behaviour seen in the three pulsars, it must be possible to produce at least three arbitrarily polarized superposed patterns. While the data do not suggest a particular approach for the empirical decomposition of patterns into non-orthogonally polarized components, the specific, quantitative nature of the results should provide strong constraints for theoretically driven modelling.Comment: 11 pages, 6 figures (1 colour), accepted for publication in A&A. Abstract abridge

An economic assessment of the accession of the Central and Eastern European countries to the EU single market

In 2004 the European Union is due to incorporate 10 new members, mostly from theCentral and Eastern European Countries (CECs). Trade between the EU and CECs currently falls well short of that between EU countries, and if we assume this pattern reflects both tariffs and a resource cost due to regulatory differences, then 1997 trade patterns would imply such costs are 7-15% on trade between the EU and CECs. Elimination/harmonisation of remaining tariffs is likely to bring small welfare gains to new entrants. By contrast entry to the Single Market looks far more significant: after both tariff union and entry to the Single Market total trade volumes between the EU and CECs could rise by 50-100% (much more in some commodities), while welfare gains in the CECs could be of the order of 11.5-20%, larger than the previous two studies have suggested. Welfare gains within the EU are around 0.4% of GDP, with all regions gaining but Germany gaining most. Gains are greater where capital is fully mobile

Approach to the Continuum Limit of the Quenched Hermitian Wilson-Dirac Operator

We investigate the approach to the continuum limit of the spectrum of the Hermitian Wilson-Dirac operator in the supercritical mass region for pure gauge SU(2) and SU(3) backgrounds. For this we study the spectral flow of the Hermitian Wilson-Dirac operator in the range $0\le m\le 2$. We find that the spectrum has a gap for $0 < m \le m_1$ and that the spectral density at zero, $\rho(0;m)$, is non-zero for $m_1\le m\le 2$. We find that $m_1\to 0$ and, for $m \ne 0, \rho(0;m)\to 0$ (exponential in the lattice spacing) as one goes to the continuum limit. We also compute the topological susceptibility and the size distribution of the zero modes. The topological susceptibility scales well in the lattice spacing for both SU(2) and SU(3). The size distribution of the zero modes does not appear to show a peak at a physical scale.Comment: 19 pages revtex with 9 postscript figures included by eps

Search and the Path-Dependency of Trade.

This paper investigates the implications of imperfect information and matching/searching for international trade theory. I develop an illustrative model where firms find such partners by a search through successive matches. The consequences include linking today's import demand patterns to past changes in costs, protection and interest rates. Today's policy decisions will likewise affect future trade. Trade diversion from a preferential trading agreement may well persist as informational diversion well after the preferential agreement has been scrapped. This has important implications for the timing of trade liberalisation.Trade, Protection, Search, Outsourcing.

Geometry definition and grid generation for a complete fighter aircraft

Recent advances in computing power and numerical solution procedures have enabled computational fluid dynamicists to attempt increasingly difficult problems. In particular, efforts are focusing on computations of complex three-dimensional flow fields about realistic aerodynamic bodies. To perform such computations, a very accurate and detailed description of the surface geometry must be provided, and a three-dimensional grid must be generated in the space around the body. The geometry must be supplied in a format compatible with the grid generation requirements, and must be verified to be free of inconsistencies. This paper presents a procedure for performing the geometry definition of a fighter aircraft that makes use of a commercial computer-aided design/computer-aided manufacturing system. Furthermore, visual representations of the geometry are generated using a computer graphics system for verification of the body definition. Finally, the three-dimensional grids for fighter-like aircraft are generated by means of an efficient new parabolic grid generation method. This method exhibits good control of grid quality

Cell volume regulation in the proximal tubule of rat kidney proximal tubule cell volume regulation

We developed a dynamic model of a rat proximal convoluted tubule cell in order to investigate cell volume regulation mechanisms in this nephron segment. We examined whether regulatory volume decrease (RVD), which follows exposure to a hyposmotic peritubular solution, can be achieved solely via stimulation of basolateral K^+ and Cl^− channels and Na^+–HCO₃^− cotransporters. We also determined whether regulatory volume increase (RVI), which follows exposure to a hyperosmotic peritubular solution under certain conditions, may be accomplished by activating basolateral Na^+/H^+ exchangers. Model predictions were in good agreement with experimental observations in mouse proximal tubule cells assuming that a 10% increase in cell volume induces a fourfold increase in the expression of basolateral K+ and Cl− channels and Na+–HCO₃^− cotransporters. Our results also suggest that in response to a hyposmotic challenge and subsequent cell swelling, Na^+–HCO₃^− cotransporters are more efficient than basolateral K^+ and Cl^− channels at lowering intracellular osmolality and reducing cell volume. Moreover, both RVD and RVI are predicted to stabilize net transcellular Na^+ reabsorption, that is, to limit the net Na^+ flux decrease during a hyposmotic challenge or the net Na^+ flux increase during a hyperosmotic challenge.This research was supported by the National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases, via grant R01DK106102 to AT Layton. (R01DK106102 - National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases)Accepted manuscrip

The fall of Doha and the rise of regionalism? CEPS Policy Brief No. 111, September 2006

The indefinite prorogation of the WTO’s Doha trade talks in July suggests that the global appetite for multilateralism may now be seriously weakened. In this new Policy Brief, CEPS Senior Research Fellow David Kernohan and T. Huw Edwards of Loughborough University look at how a failed or significantly delayed Doha round (say till 2009 at the earliest) could affect the scope and structure of any eventual WTO deal. In particular, if a rise in regionalism in the interim is inevitable, they ask whether the EU should reassess its regional trade policy objectives? A move from a multilateral focus to a twinned regional-multilateral trade policy stance will have consequences, both for practical reasons of EC ‘institutional capacity’ and for strategic reasons, in terms of choice of partner/s. Either way, tough decisions will have to be made. Wherever possible, the authors argue that these tactical choices should be preceded by careful technical analysis of the choice of regional partners and trading groups, as well as on traditional ‘diplomatic’ methods of trade partner selection

Neuroimaging in Functional Movement Disorders.

PURPOSE OF REVIEW: Functional movement disorders are common and disabling causes of abnormal movement control. Here, we review the current state of the evidence on the use of neuroimaging in Functional movement disorders, particularly its role in helping to unravel the pathophysiology of this enigmatic condition. RECENT FINDINGS: In recent years, there has been a shift in thinking about functional movement disorder, away from a focus on high-level psychological precipitants as in Freudian conversion theories, or even an implicit belief they are 'put-on' for secondary gain. New research has emphasised novel neurobiological models incorporating emotional processing, self-representation and agency. Neuroimaging has provided new insights into functional movement disorders, supporting emerging neurobiological theories implicating dysfunctional emotional processing, self-image and sense of agency. Recent studies have also found subtle structural brain changes in patients with functional disorders, arguing against a strict functional/structural dichotomy