Ratings of speed in real music as a function of both original and manipulated beat tempo

There is an apparent contradiction between the narrow range of tempi optimal for perceptual judgment and motor synchronization and the wide range of beat tempi found in real music. The relation between listeners' perception of speed and beat tempo was therefore investigated, both for real music excerpts (ME) and metronome sequences. Tempi ranged from 42 to 200 beats per minute (BPM), and some excerpts were further tempo manipulated in four levels from ±5 to ±20%. Regression analyses showed that speed was a shallower function of original tempo for fast (>150 BPM) and slow (<95 BPM) MEs than for MEs with intermediate tempi, describing a non-linear, sigmoid function. Manipulated tempo had twice as large an effect on speed as had original tempo. In contrast, speed was an almost linear function of tempo for metronome sequences. Taken together, these results show that the non-linearity stems from properties of the musical signal, rather than being a subjective perceptual effect. They indicate an inverse relation between tempo and relative event density in real music, and demonstrate that the perception of periodic signals is affected not only by the beat level, but also by faster and slower levels.     

Pseudogroups of isometries of ℝ and Rips’ theorem on free actions on ℝ-trees

We give a proof of Rips’ theorem that a finitely generated group acting freely on an ℝ-tree is a free product of free abelian groups and surface groups, using methods of dynamical systems and measured foliations.     

Spectroscopic signatures of VOC physisorption on microporous solids. Application for trichloroethylene and tetrachloroethylene adsorption on MFI zeolites

This paper presents an experimental infrared spectroscopic study of the physisorption of trichloroethylene (TCE) and tetrachloroethylene (PCE) on a self-supported high silica ZSM5 zeolite. The evolution of the shape, area, and location of vibration bands of both the adsorbent and the adsorbate is analyzed with respect to the number of sorbed molecules. The state of the adsorbed phase is characterized upon adsorption by comparing the location of the investigated vibration bands with the location of the corresponding vibration bands of the chloroalkenes in gaseous, liquid, and solid phases. The singular behavior of PCE with respect to TCE is seen from the modification of vibration bands of both the adsorbed phase and the adsorbent upon loading. The adsorption process proceeds by stages for PCE, whereas it appears continuous for TCE. Particular micropore loadings are evidenced at 4 and 6.5 molec.uc(-1) for PCE and at 6 molec.uc(-1) for TCE, in agreement with previous macroscopic and microscopic data. In addition, the presence of admolecules induces at least one emerging vibration band located at around 1715 cm(-1), mainly due to a contribution of the microporous surface of the adsorbent.     

Topologie de Gromov équivariante,structures hyperboliques et arbres réels

Résumé Les objets que nous étudions sont les espaces métriques munis d'une action par isométrie d'un groupe fixé . Nous définissons une «topologie» naturelle sur «l'ensemble» de ces espaces. Nous montrons un critère de compacité séquentielle par des méthodes inspirées des travaux de M. Gromov. Nous utilisons ce critère pour donner une preuve plus courte et plus géométrique de deux théorèmes: celui de M. Culler et J. Morgan sur la compacité de l'espace des arbres réels à petits stabilisateurs d'arêtes; et celui de J. Morgan sur la compactification de l'espace des structures hyperboliques sur une variété par des arbres réels à petits stabilisateurs d'arêtes.     

Vacancy migration energy in quenched Al-Mg0.01 alloy by positron annihilation

The isothermal recovery rates of vacancy-impurity complexes in an aluminium-1% magnesium alloy are measured in situ at eight temperatures from variations of colinear annihilation -rays versus time. These data analysed in terms of a time dependant ⁺-trapping model yield two apparent migration energies of 0.8 eV±0.1 eV and 0.9 eV±0.05 eV. The nature of the complexes is discussed and their binding energy is estimated.     

Effect of dental finishing instruments on the surface roughness of composite resins as elucidated by atomic force microscopy

Roughness increases significantly after finishing procedures. The aim of this study was to assess by the atomic force microscope (AFM) the effect of finishing instruments on the surface roughness of composite resins. A nanofiller composite resin (Filtek Supreme, 3MP) were selected. The finishing procedures were done with a 30-blade carbide bur (C) and a 30-M), and (3) finishing instrument (FM, PM, FC, FD, PC, PD). The mean surface roughness was evaluated by AFM in the contact mode. FM and PM groups were assessed statistically by the Student's T test, and FC, FD, PC, PD groups were submitted to variance analysis (ANOVA), both at 5% significance. The mean surface roughness values, in nanometers, were FM, 23.63 (b); FC, 283.88 (c); FD, 510.55 (d); PM, 12.52 (a); PC, 343.98 (c); PD, 531.64 (d). Microhybrid composite displayed less roughness than nanofiller composite in the absence of finishing procedures. The 30-blade carbide bur produced less roughness compared to the extra fine diamond bur.     

Unstable step meandering with elastic interactions.

We report on theoretical investigations of the influence of step interactions due to elasticity on unstable step meandering during molecular beam homoepitaxy. It is shown that elasticity causes coarsening of the cellular structure of the meander found in a previous work. The time dependence of step roughness is found to be robust, behaving as t(1/2). The lateral length scale coarsening is shown to be sensitive to the underlying physical mechanisms. In particular, the typical length follows the law t(alpha), with alpha = 1/6 or 1/4 depending on whether line diffusion is negligibly small or not.     

Positron trapping by defects in plastically deformed copper

When compared to current theories, positron lifetimes in plastically strained copper are indicative of diffusion limited positron trapping, with diffusion constant D₊ ≈ 4 × 10^?2 cm²/s in dislocations of effective capture radius $\text{r}{}_{\mathrm{<mtext>d</mtext>}}\text{≈ 70}\text{A}\text{?}$.     

Study of a perforated thin plate according to the relative sizes of its different parameters

We are interested in the study of a thin plate, periodicially perforated by cylindrical holes, the axes of which are perpendicular to the plane of the plate. A horizontal section of the plate specifies its geometry, and shows a periodicity in the order of ?. The thickness of the plate is equal to e. The ratio of material is small, and is characterized by the parameter δ, the thickness of the bars being equal to ?δ. In this paper, we study the dependence of displacements on e, ? and δ, and to give equivalent limits when e, then ?, and finally δ, tend towards zero. An interesting result obtained in this work is the negative Poisson coefficient of the final equivalent material. Although this coefficient is theoretically between ?½ and 1, most materials encountered in practice have a positive one.