Averaging rheological quantities in descriptions of soft glassy materials

Many mean-field models have been introduced to describe the mechanical behavior of glassy materials. They often rely on averages performed over distributions of elements or states. We here underline that averaging is a more intricate procedure in mechanics than in more classical situations such as phase transitions in magnetic systems. This leads us to modify the predictions of the recently proposed SGR model for soft glassy materials, for which we suggest that the viscosity should diverge at the glass transition temperature $T_g$ with an exponential form $\eta \sim \exp(\frac{A}{T-T_g})$.Comment: 4 pages, Latex, 1 eps figur

The energy spectrum of cosmic rays beyond the turn-down around 10^17 eV as measured with the surface detector of the Pierre Auger Observatory

We present a measurement of the cosmic-ray spectrum above 100 PeV using the part of the surface detector of the Pierre Auger Observatory that has a spacing of 750 m. An inflection of the spectrum is observed, confirming the presence of the so-called second-knee feature. The spectrum is then combined with that of the 1500 m array to produce a single measurement of the flux, linking this spectral feature with the three additional breaks at the highest energies. The combined spectrum, with an energy scale set calorimetrically via fluorescence telescopes and using a single detector type, results in the most statistically and systematically precise measurement of spectral breaks yet obtained. These measurements are critical for furthering our understanding of the highest energy cosmic rays

Reconstruction of events recorded with the surface detector of the Pierre Auger Observatory

Cosmic rays arriving at Earth collide with the upper parts of the atmosphere, thereby inducing extensive air showers. When secondary particles from the cascade arrive at the ground, they are measured by surface detector arrays. We describe the methods applied to the measurements of the surface detector of the Pierre Auger Observatory to reconstruct events with zenith angles less than 60o using the timing and signal information recorded using the water-Cherenkov detector stations. In addition, we assess the accuracy of these methods in reconstructing the arrival directions of the primary cosmic ray particles and the sizes of the induced showers

Élaboration et transformation d'alliages binaires à base de niobium à l'état de grande pureté

This paper concerns the preparation and the transformation of Nb-rich alloys made by melting high purity metals. Nb-Zr and Nb-Mo alloys have been prepared by electronbeam melting ; Nb-Ti alloy has been prepared by vacuum-arc melting. After cold-forging of the cast ingots, the alloys have been either cold-rolled until 1 mm thick, or cold-swaged until 0,3 mm diameter. Experimental conditions are precised.A partir de métaux très purs les alliages binaires suivants ont été élaborés par fusion par bombardement électroniques : Nb-Zr à 2,0, 3,85, 5,45 % at Zr et Nb-Mo à 5,3 % at Mo. Un alliage Nb-Ti à 4,65 % at Ti a été préparé au four à arc. Ces alliages, sous forme de lingots de 4 kg environ, présentent une bonne homogénéité. Leur pureté est supérieure à 99,97 %. Après forgeage en plats, ces alliages sont transformés à froid, soit par laminage jusqu'à 1 mm, soit par retreinte à l'état de fils jusqu'à 0,3 mm de diamètre. Les conditions opératoires sont précisées et on rend compte des difficultés rencontrées et de l'expérience acquise