Low-temperature muon spin rotation studies of the monopole charges and currents in Y doped Ho2Ti2O7

In the ground state of Ho2Ti2O7 spin ice, the disorder of the magnetic moments follows the same rules as the proton disorder in water ice. Excitations take the form of magnetic monopoles that interact via a magnetic Coulomb interaction. Muon spin rotation has been used to probe the low-temperature magnetic behaviour in single crystal Ho2−xYxTi2O7 (x = 0, 0.1, 1, 1.6 and 2). At very low temperatures, a linear field dependence for the relaxation rate of the muon precession λ(B), that in some previous experiments on Dy2Ti2O7 spin ice has been associated with monopole currents, is observed in samples with x = 0, and 0.1. A signal from the magnetic fields penetrating into the silver sample plate due to the magnetization of the crystals is observed for all the samples containing Ho allowing us to study the unusual magnetic dynamics of Y doped spin ice

Population et urbanisation au Québec et au Canada, XIXe et XXe siècles

La croissance urbaine rapide de la fin du XIXe siècle et du premier tiers du XXe a suscité nombre de travaux sur un large éventail de sujets, notamment en rapport avec les processus démographiques associés à l'urbanisation: formation et évolution des populations des villes, transition démographique, structure et composition des ménages, rôles des membres des familles, logement, etc... Au Québec en particulier, les études sur les populations urbaines apparaissent plus fragmentaires. Si des recherches récentes ou en cours contribuent à une meilleure compréhension de l'urbanisation des Canadiens français (sinon de la franco-canadianisation des villes québécoises), il reste encore largement place pour des études englobantes de la croissance rapide qu'ont connue les villes entre 1860 et 1930. Ainsi est née l'idée d'un atelier sur cet objet éminemment complexe et interdisciplinaire que sont les populations urbaines du passé. Il visait à proposer quelques jalons quant aux pistes de recherche à explorer sur le sujet: jalons liés aux questionnements et problématiques, jalons méthodologiques sur les façons de faire, notamment par l'exploitation des données tirées des grandes séries documentaires tels les recensements nominatifs. Ce livret regroupe les contributions de quatre des huit conférenciers invités à lancer les échanges sur l'un ou l'autre des sujets proposés aux participants. Leur contenu offre diverses pistes susceptibles d'aider à mieux comprendre à échelle fine ce phénomène fondamental qu'est l'urbanisation des populations contemporaines

The Review of Economic Performance and Social Progress 2002: Towards a Social Understanding of Productivity

In this chapter, Richard Harris points out that a traditional view has been that there is an inherent conflict between economic efficiency and social equality, a view neatly summarized in the title of Okun's famous book, Equality and Efficiency: The Big Trade-off (1975). This view gained renewed currency in the policy debates of the 1990s, as commentators contrasted the economic performance of Europe and the U.S. in that decade. This view has been challenged both by cross-national empirical studies and by theoretical advances. Recent research seems to suggest that there is no efficiency-equity trade-off and that social policy and greater equality may actually contribute to higher productivity growth. Richard Harris surveys two streams of recent research that point in this direction. The chapter also examines new theoretical literature, especially the new endogenous growth theory that suggests that increases in inequality can hurt growth.Equity, Efficiency, Productivity, Labour Productivity, Labor Productivity, Growth, Income, Inequality, Equality, Social Policy, Education, Health, Welfare, Redistribution, Social Cohesion, Cohesion, Investment, Innovation, Competition, Living Standards

An Optical Velocity for the Phoenix Dwarf Galaxy

We present the results of a VLT observing program carried out in service mode using FORS1 on ANTU in Long Slit mode to determine the optical velocities of nearby low surface brightness galaxies. As part of our program of service observations we obtained long-slit spectra of several members of the Phoenix dwarf galaxy from which we derive an optical helio-centric radial velocity of -13 +/- 9km/s. This agrees very well with the velocity of the most promising of the HI clouds seen around Phoenix, which has a helio-centric velocity of -23 km/s, but is significantly different to the recently published optical heliocentric velocity of Phoenix of -52 +/- 6 km/s of Gallart et al. (2001).Comment: Aceepted for publication in MNRA

Standard SANC modules for NLO QCD Radiative Corrections to Single-top Production

It this paper we present the results obtained with the newly created Standard SANC modules for calculation of the NLO QCD corrections to single top production processes in s and t channels at the partonic level, as well as top-decays. The main aim of these results is to prove the correct work of modules. A comprehensive comparison with results of the CompHEP system is given, where possible. These modules are intended to be used in Monte Carlo generators for single top production processes at the LHC. As in our recent paper, devoted to the electroweak corrections to these processes, we study the regularization of the top-legs associated infrared divergences with aid of the complex mass of the top quark. A comparison of QCD corrections with those computed by the conventional method is presented both for top production and decays. For s channel production we give an analytic proof of equivalence of the two methods in the limit of low top width.Comment: 21 pages, 2 figures, 17 table

Potential Energy Surface for H_2 Dissociation over Pd(100)

The potential energy surface (PES) of dissociative adsorption of H_2 on Pd(100) is investigated using density functional theory and the full-potential linear augmented plane wave (FP-LAPW) method. Several dissociation pathways are identified which have a vanishing energy barrier. A pronounced dependence of the potential energy on ``cartwheel'' rotations of the molecular axis is found. The calculated PES shows no indication of the presence of a precursor state in front of the surface. Both results indicate that steering effects determine the observed decrease of the sticking coefficient at low energies of the H_2 molecules. We show that the topology of the PES is related to the dependence of the covalent H(s)-Pd(d) interactions on the orientation of the H_2 molecule.Comment: RevTeX, 8 pages, 5 figures in uufiles forma

Spin chirality on a two-dimensional frustrated lattice

The collective behavior of interacting magnetic moments can be strongly influenced by the topology of the underlying lattice. In geometrically frustrated spin systems, interesting chiral correlations may develop that are related to the spin arrangement on triangular plaquettes. We report a study of the spin chirality on a two-dimensional geometrically frustrated lattice. Our new chemical synthesis methods allow us to produce large single crystal samples of KFe3(OH)6(SO4)2, an ideal Kagome lattice antiferromagnet. Combined thermodynamic and neutron scattering measurements reveal that the phase transition to the ordered ground-state is unusual. At low temperatures, application of a magnetic field induces a transition between states with different non-trivial spin-textures.Comment: 7 pages, 4 figure

Self-affirmation improves performance on tasks related to executive functioning

Objectives: The current study explored the effect of self-affirmation on two aspects of performance that have been related to executive functioning: working memory (assessed by a 2-back task) and inhibition (assessed by a Stroop task). The goal was to establish whether self-affirmation improved performance on these tasks. Method: Participants (N = 83) were randomized to either a self-affirmation or a control task and then completed the computerized tasks, in a fixed sequence. Results: Self-affirmed participants performed better than non-affirmed participants on both tasks. Conclusion: Self-affirmation can improve aspects of performance related to executive functioning. This finding may help to explain the wide range of beneficial effects that self-affirmation can have on cognition and behavior