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

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

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

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.