780 research outputs found
Probability densities of a forced probe particle in glass: results from mode coupling theory and simulations of active microrheology
We investigate the displacements of a probe particle inside a glass, when a
strong external force is applied to the probe (active nonlinear microrheology).
Calculations within mode coupling theory are presented for glasses of hard
spheres and compared to Langevin and Brownian dynamics simulations. Under not
too strong forces where the probe remains trapped, the probe density
distribution becomes anisotropic. It is shifted towards the direction of the
force, develops an enhanced tail in that direction (signalled by a positive
skewness), and exhibits different variances along and perpendicular to the
force direction. A simple model of an harmonically trapped probe rationalizes
the low force limit, with strong strain softening setting in at forces of the
order of a few thermal energies per particle radius
Stimuli-responsive behavior of PNiPAm microgels under interfacial confinement
The volume phase transition of microgels is one of the most paradigmatic
examples of stimuli-responsiveness, enabling a collapse from a highly swollen
microgel state into a densely coiled state by an external stimulus. Although
well characterized in bulk, it remains unclear how the phase transition is
affected by the presence of a confining interface. Here, we demonstrate that
the temperature-induced volume phase transition of poly(N-isopropylacrylamide)
microgels, conventionally considered an intrinsic molecular property of the
polymer, is in fact largely suppressed when the microgel is adsorbed to an
air/liquid interface. We further observe a hysteresis in core morphology and
interfacial pressure between heating and cooling cycles. Our results, supported
by molecular dynamics simulations, reveal that the dangling polymer chains of
microgel particles, spread at the interface under the influence of surface
tension, do not undergo any volume phase transition, demonstrating that the
balance in free energy responsible for the volume phase transition is
fundamentally altered by interfacial confinement. These results imply that
important technological properties of such systems, including the
temperature-induced destabilization of emulsions does not occur via a decrease
in interfacial coverage of the microgels
A multi-level understanding of trust development in contexts of blurred organizational boundaries: the case of crowdfunding
Are trust development processes in settings of blurred organizational boundaries different from those in conventional organizational settings, and if so, how? Taking the crowdfunding campaigns of the Fin-Tech Monzo as examples of settings of blurred organizational boundaries, we analyze how the three main trust forms (individual, organizational, and institutional trust) emerge and interact in the campaigns’ online discourse and develop a process model that captures distinct trust development dynamics. We contribute to the trust literature by highlighting increased dynamics and co-existence of trust forms, and by showing that the validation of extra-organizational boundary spanners is crucial to compensate for a missing personal interaction in settings of blurred organizational boundaries. We also contribute to the crowdfunding literature and derive managerial implications
Asymptotic analysis of mode-coupling theory of active nonlinear microrheology
We discuss a schematic model of mode-coupling theory for force-driven active
nonlinear microrheology, where a single probe particle is pulled by a constant
external force through a dense host medium. The model exhibits both a glass
transition for the host, and a force-induced delocalization transition, where
an initially localized probe inside the glassy host attains a nonvanishing
steady-state velocity by locally melting the glass. Asymptotic expressions for
the transient density correlation functions of the schematic model are derived,
valid close to the transition points. There appear several nontrivial time
scales relevant for the decay laws of the correlators. For the nonlinear
friction coeffcient of the probe, the asymptotic expressions cause various
regimes of power-law variation with the external force, and two-parameter
scaling laws.Comment: 17 pages, 12 figure
BUBBLE CHAMBER SAFETY MEETING
A description is given of bubble chambers in use and those in the design stages. Safety factors in the design and operation of a bubble chamber are discussed. Data are presented on fatige and rupture tests on glass. Data are contained on the effects of liquid helium on the tensile properties of various stainless steels. (C.J.G.
Isothiourea-catalysed sequential kinetic resolution of acyclic (±)-1,2-diols
Authors thank the EPSRC Centre for Doctoral Training in Critical Resource Catalysis (CRITICAT, grant code EP/L016419/1, R.M.N.) for funding. We thank the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007–2013) ERC grant agreement no. 279850 (A.D.S.). A.D.S. thanks the Royal Society for a Wolfson Research Merit Award.The isothiourea-catalysed acylative kinetic resolution of a range of acyclic (±)-1,2-diols using 1 mol% of catalyst under operationally simple conditions is reported. Significantly, the bifunctional nature of (±)-1,2-diols was exploited in a sequential double kinetic resolution, in which both kinetic resolutions operate synergistically to provide access to highly enantioenriched products. The principles that underpin this process are discussed, and selectivity factors for the individual kinetic resolution steps are reported in a model system.PostprintPeer reviewe
COST STUDY OF A 100-Mw(e) DIRECT-CYCLE BOILING WATER REACTOR PLANT
A technical and economic evaluation is presented of a direct-cycle light- water boiling reactor designed for natural circulation and internal steam-water separation. The reference lOO-Mw(e) reactor power plant design evolved from the study should have the best chance (compared to similar plants) of approaching the 8 to 9 mill/kwh total power-cost level. (W.D.M.
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