排序方式: 共有86条查询结果,搜索用时 15 毫秒
61.
Dr. Frédéric Loosli Matthieu Najm Raymond Chan Dr. Evdokia Oikonomou Arnaud Grados Mathieu Receveur Dr. Jean‐François Berret 《Chemphyschem》2016,17(24):4134-4143
Viscoelastic liquids are characterized by a finite static viscosity and a yield stress of zero, whereas soft solids have an infinite viscosity and a non‐zero yield stress. The rheological nature of viscoelastic materials has long been a challenge and is still a matter of debate. Here, we provide for the first time the constitutive equations of linear viscoelasticity for magnetic wires in yield‐stress materials, together with experimental measurements by using magnetic rotational spectroscopy (MRS). In MRS, the wires were subjected to a rotational magnetic field as a function of frequency and the motion of the wire was monitored by using time‐lapse microscopy. The studied soft solids were aqueous dispersions of gel‐forming polysaccharide (gellan gum) at concentrations above the gelification point. It was found that soft solids exhibited a clear and distinctive signature compared with viscous and viscoelastic liquids. In particular, the average wire rotation velocity equaled zero over a broad frequency range. We also showed that the MRS technique is quantitative. The equilibrium elastic modulus was retrieved from the wire oscillation amplitudes, and agrees with polymer‐dynamics theory. 相似文献
62.
Tkaczyk S Tollefson K Tollestrup A Toyoda H Trischuk W de Troconiz JF Tseng J Turini N Ukegawa F Valls J Vejcik S Velev G Vidal R Vilar R Volobouev I Vucinic D Wagner RG Wagner RL Wahl J Wallace NB Walsh AM Wang C Wang CH Wang MJ Watanabe T Waters D 《Physical review letters》2000,84(23):5273-5278
We have searched for direct production of scalar top quarks at the Collider Detector at Fermilab in 88 pb(-1) of p&pmacr; collisions at sqrt[s] = 1.8 TeV. We assume the scalar top quark decays into either a bottom quark and a chargino or a bottom quark, a lepton, and a scalar neutrino. The event signature for both decay scenarios is a lepton, missing transverse energy, and at least two b-quark jets. For a chargino mass of 90 GeV/c(2) and scalar neutrino masses of at least 40 GeV/c(2), we find no evidence for scalar top production and present upper limits on the production cross section in both decay scenarios. 相似文献
63.
J.-F. Berret 《Colloid and polymer science》2009,287(7):801-810
We report on the formation of colloidal complexes resulting from the electrostatic co-assembly between anionic surfactants
and cationic polyelectrolytes or block copolymers. Combining light and X-ray scattering experiments with cryogenic transmission
and optical microscopy, we emphasize a feature rarely addressed in the formation of the electrostatic complexes, namely the
role of the mixing concentration on the microstructure. At low mixing concentration, electrostatic complexes made from cationic-neutral
copolymers and alkyl sulfate surfactants exhibit spherical core-shell microstructures. With increasing concentration, the
complexes undergo a sphere-to-cylinder transition, yielding elongated aggregates with diameter 50 nm and length up to several
hundreds of nanometers. From the comparison between homo- and diblock polymer phase behaviors, it is suggested that the unidimensional
growth is driven by the ability of the surfactant to self-assemble into cylindrical micelles when complexed with cationic
polymers. 相似文献
64.
65.
66.
J. F. Berret P. Doussineau A. Levelut W. Schön 《Zeitschrift für Physik B Condensed Matter》1988,70(4):485-490
Dielectric measurements have been performed at 1 and 10 GHz in (KBr)1–x
(KCN)
x
mixed crystals for cyanide concentrationsx=0.25 andx=0.50 in the temperature rangeT=1.7–150 K. The maxima of the real and imaginary parts of the dielectric constant falls into the Arrhenius straight lines obtained at lower frequencies. These dipolar lines cross over the so-called quadrupolar (acoustic) lines, in contradiction with theoretical predictions on the nature of the freezing. We also present a qualitative model which reinterprets the dipolar and quadrupolar freezings in terms of an individual and a collective processes.Associated with the Centre National de la Recherche Scientifique 相似文献
67.
68.
69.