Michael Oakeshott: Religion, Politics and the Moral Life

Although students of Michael Oakeshott have special reason to be grateful to Timothy Fuller for this carefully selected volume of ten of Oakeshott’s early and mid-career essays, as well as for the scholarly introduction Fuller has provided, his book will also appeal to general readers concerned to grapple with the central issues of modern life and thought with which Oakeshott constantly wrestled. Four of the essays have never been previously published and six are now made available in a more accessible form

Extension du modèle de Hertz pour la prise en compte de la tension de surface dans les essais de nano-indentation des matériaux souples

International audienceThe contact between a spherical indenter and a solid is considered. A numerical finite element model (F. E. M) to taking into account the surface tension of the solid is presented and assessed. It is shown that for nano-indentation of soft materials, the surface tension of the solid influences significantly the reaction force due to indentation. The validity of the classical Hertz model is defined. In very good approximation, the force vs. indentation depth curve can be fitted by a power law function F = a d where F denotes the force acting on the indentor, d the indentation depth, a and b in ]1, 1.5] are constants depending on the materials and the size of the indentor.Le contact entre un indenteur sphérique et un solide élastique est considéré. Un modèle par éléments finis permettant de prendre en compte la tension de surface du solide est présenté et validé. Il est montré que pour la nano-indentation de matières souples, la tension de surface du solide peut influencer considérablement la courbe force vs. profondeur d’indentation. Il est ainsi définit quand le modèle de Hertz classique ne convient plus. En très bonne approximation, la courbe force vs. profondeur d’indentation peux être décrite par une croissance allométrique F = a  d où F désigne la force agissant sur l'indenteur, d la profondeur d’indentation, a et b dans ]1, 1.5] sont des constantes qui dépendent du matériau et du rayon de pointe

Emission spectra and intrinsic optical bistability in a two-level medium

Scattering of resonant radiation in a dense two-level medium is studied theoretically with account for local field effects and renormalization of the resonance frequency. Intrinsic optical bistability is viewed as switching between different spectral patterns of fluorescent light controlled by the incident field strength. Response spectra are calculated analytically for the entire hysteresis loop of atomic excitation. The equations to describe the non-linear interaction of an atomic ensemble with light are derived from the Bogolubov-Born-Green-Kirkwood-Yvon hierarchy for reduced single particle density matrices of atoms and quantized field modes and their correlation operators. The spectral power of scattered light with separated coherent and incoherent constituents is obtained straightforwardly within the hierarchy. The formula obtained for emission spectra can be used to distinguish between possible mechanisms suggested to produce intrinsic bistability.Comment: 18 pages, 5 figure

First Experience with in situ Helium Processing of the LEP Superconducting Modules

The helium processing technique has been used at CERN to improve the performance of the accelerating RF cavities with respect to field emission. It was extensively used in the vertical bare cavity tests to improve the superconducting cavities for the LEP Project. However this technique was rarely used on fully equipped production modules because of the risk of damaging the power couplers and its ceramic window by a possible glow discharges. First experience with helium processing on finished modules equipped with additional vacuum interlocks to protect the power couplers was acquired in the test area in October 1996. He processing was applied to three modules limited by field emission. Their overall performance was increased up to about 7 MV/m. Confident with these results, one module was processed in the LEP tunnel just before the shutdown 1996. The results obtained confirmed the feasibility of this method on a module already installed in the LEP tunnel and its efficiency in improving the performances. During the winter shutdown 1996-97, helium processing has been done separately on seven installed in LEP

Early Lifestyle Interventions in People with Impaired Glucose Tolerance in Northern Colombia: The DEMOJUAN Project

Background: The objective of the demonstration project for type 2 diabetes prevention in the Barranquilla and Juan Mina (DEMOJUAN) study was to investigate the extent to which it is possible to reach normal glucose metabolism with early lifestyle interventions in people at high risk of type 2 diabetes (prediabetes), compared with those who receive standard usual care. Methods: DEMOJUAN was a randomized controlled trial conducted in Juan Mina and Barranquilla, Northern Colombia. Eligible participants were randomized into one of three groups (control group, initial nutritional intervention, and initial physical activity intervention). The duration of the intervention was 24 months. The main study outcome in the present analysis was reversion to normoglycemia. Relative risks and their corresponding 95% confidence intervals were calculated for reversal to normoglycemia and T2D incidence. Results: There was no statistically significant association between the intervention groups and reversion to normoglycemia. The relative risk of reversion to normoglycemia was 0.88 (95% CI 0.70–1.12) for the initial nutritional intervention group participants and 0.95 (95% CI 0.75–1.20) for the initial physical activity intervention group participants. Conclusions: Our study did not find any statistically significant differences in reversion to normoglycemia or the development of type 2 diabetes between the intervention groups and the control group in this population

Emission of photon echoes in a strongly scattering medium

We observe the two- and three-pulse photon echo emission from a scattering powder, obtained by grinding a Pr$^{3+}$:Y$_2$SiO$_5$ rare earth doped single crystal. We show that the collective emission is coherently constructed over several grains. A well defined atomic coherence can therefore be created between randomly placed particles. Observation of photon echo on powders as opposed to bulk materials opens the way to faster material development. More generally, time-domain resonant four-wave mixing offers an attractive approach to investigate coherent propagation in scattering media

Frictionless bead packs have macroscopic friction, but no dilatancy

The statement of the title is shown by numerical simulation of homogeneously sheared packings of frictionless, nearly rigid beads in the quasistatic limit. Results coincide for steady flows at constant shear rate γ in the limit of small γ and static approaches, in which packings are equilibrated under growing deviator stresses. The internal friction angle ϕ, equal to 5.76 $\pm$ 0.22 degrees in simple shear, is independent on the average pressure P in the rigid limit. It is shown to stem from the ability of stable frictionless contact networks to form stress-induced anisotropic fabrics. No enduring strain localization is observed. Dissipation at the macroscopic level results from repeated network rearrangements, like the effective friction of a frictionless slider on a bumpy surface. Solid fraction Φ remains equal to the random close packing value ≃ 0.64 in slowly or statically sheared systems. Fluctuations of stresses and volume are observed to regress in the large system limit, and we conclude that the same friction law for simple shear applies in the large psystem limit if normal stress or density is externally controlled. Defining the inertia number as I = γ m/(aP), with m the grain mass and a its diameter, both internal friction coefficient $\mu$∗ = tan ϕ and volume 1/Φ increase as powers of I in the quasistatic limit of vanishing I, in which all mechanical properties are determined by contact network geometry. The microstructure of the sheared material is characterized with a suitable parametrization of the fabric tensor and measurements of connectivity and coordination numbers associated with contacts and near neighbors.Comment: 19 pages. Additional technical details may be found in v

Chemical and Physiological Interactions Between E-Liquid Constituents: Cause for Concern?

Studies of Electronic Nicotine Delivery Systems (ENDS) toxicity have largely focused on individual components such as flavour additives, base e-liquid ingredients (propylene glycol, glycerol), device characteristics (eg, model, components, wattage), use behaviour, etc. However, vaping involves inhalation of chemical mixtures and interactions between compounds can occur that can lead to different toxicities than toxicity of the individual components. Methods based on the additive toxicity of individual chemical components to estimate the health risks of complex mixtures can result in the overestimation or underestimation of exposure risks, since interactions between components are under-investigated. In the case of ENDS, the potential of elevated toxicity resulting from chemical reactions and interactions is enhanced due to high operating temperatures and the metallic surface of the heating element. With the recent availability of a wide range of e-liquid constituents and popularity of do-it-yourself creation of e-liquid mixtures, the need to understand chemical and physiological impacts of chemical combinations in ENDS e-liquids and aerosols is immediate. There is a significant current knowledge gap concerning how specific combinations of ENDS chemical ingredients result in synergistic or antagonistic interactions. This commentary aims to review the current understanding of chemical reactions between e-liquid components, interactions between additives, chemical reactions that occur during vaping and aerosol properties and biomolecular interactions, all of which may impact physiological health