416 research outputs found
Ulta-slow relaxation in discontinuous-film based electron glasses
We present field effect measurements on discontinuous 2D thin films which are
composed of a sub monolayer of nano-grains of Au, Ni, Ag or Al. Like other
electron glasses these systems exhibit slow conductance relaxation and memory
effects. However, unlike other systems, the discontinuous films exhibit a
dramatic slowing down of the dynamics below a characteristic temperature .
is typically between 10-50K and is sample dependent. For the
sample exhibits a few other peculiar features such as repeatable conductance
fluctuations in millimeter size samples. We suggest that the enhanced system
sluggishness is related to the current carrying network becoming very dilute in
discontinuous films so that the system contains many parts which are
electrically very weakly connected and the transport is dominated by very few
weak links. This enables studying the glassy properties of the sample as it
transitions from a macroscopic sample to a mesocopic sample, hence, the results
provide new insight on the underlying physics of electron glasses.Comment: 4 pages, 4 figure
Confidence Cycles
We provide a model that rationalizes variations in confidence of rational agents, both in the time-series and the cross-section. Combining horizon-dependent risk aversion (“anxiety”) and selective memory, we show that over- and underconfidence can arise in the Bayesian equilibrium of an intra-personal game. In
the time-series, overconfidence is more prevalent when actual risk levels are high, while underconfidence occurs when risks are low. In the cross-section, more anxious agents are more prone to biased confidence and their beliefs fluctuate more, leading them to buy in booms and sell in crashes. Lastly, fluctuations in confidence can amplify boom-bust cycles
Horizon-Dependent Risk Aversion and the Timing and Pricing of Uncertainty
We address two fundamental critiques of established asset pricing models: that they (1) require a controversial degree of preference for early resolution of uncertainty; and (2) do not match the
term structures of risk premia observed in the data. Inspired by experimental evidence, we construct preferences in which risk aversion decreases with the temporal horizon. The resulting
model implies term structures of risk premia consistent with the evidence, including timevariations and reversals in the slope, without imposing a particular preference for early or late
resolutions of uncertainty or compromising on the ability to match standard moments in the returns distributions
Incarcerated vermiform appendix in a left-sided inguinal hernia
We report here of a patient with an incarcerated vermiform appendix occurring in a left-sided indirect inguinal hernia. Occasionally, appendices are found in a hernial sac; however, the finding of an incarcerated vermiform appendix in an inguinal hernia on the left side is very unusual and has only been previously described once. The patient suffering this rare entity underwent appendectomy and repair of the hernia and experienced an uneventful postoperative recovery. The possibility of the presence of a situs inversus, or malrotation, as an underlying cause for the observed pathology was excluded by x-ray examinatio
A first parameterization of the pore-structure dependent kinetic adsorption model for O2 adsorption in biomass conversion modeling
Mass transport properties of the oxidation and gasification agents O2, CO2, and H2O are highly relevant for the modeling of the conversion process of biomasses. Therefore, this study presents experimental investigations on the adsorption kinetics of O2 on a biomass char using a modified gravimetric sorption device. Based on this comprehensive set of adsorption kinetic data, a first parameterization of the pore-structure dependent kinetic adsorption (PSK) model for O2 adsorption is presented. This model intends to account for mass transport during biomass conversion in a more meaningful way as it is considered in conventional conversion models. With this parameterization, the model is capable of describing accurately the adsorption kinetics of O2 as a function of time, temperature, and pressure
Exploring Replica-Exchange Wang-Landau sampling in higher-dimensional parameter space
We considered a higher-dimensional extension for the replica-exchange
Wang-Landau algorithm to perform a random walk in the energy and magnetization
space of the two-dimensional Ising model. This hybrid scheme combines the
advantages of Wang-Landau and Replica-Exchange algorithms, and the
one-dimensional version of this approach has been shown to be very efficient
and to scale well, up to several thousands of computing cores. This approach
allows us to split the parameter space of the system to be simulated into
several pieces and still perform a random walk over the entire parameter range,
ensuring the ergodicity of the simulation. Previous work, in which a similar
scheme of parallel simulation was implemented without using replica exchange
and with a different way to combine the result from the pieces, led to
discontinuities in the final density of states over the entire range of
parameters. From our simulations, it appears that the replica-exchange
Wang-Landau algorithm is able to overcome this difficulty, allowing exploration
of higher parameter phase space by keeping track of the joint density of
states.Comment: Proceedings of CCP2014 will appear in Journal of Physics: Conference
Series (JPCS), published by the IO
Ultrasonic Treatment Enhanced Surface Modification of Titanium Oxide by Tailor-Made Surface-Active Polymers
The surface modification of titanium dioxide in aqueous dispersions of specially tailor-made periodic acrylic acid/isobutylene copolymers, poly(acrylic acid)/polystyrene graft copolymers, and hydrophobically modified polyethyleneoxide urethane (HEUR) by ultrasonic treatment was studied. The pigment surface modification by the above copolymers was comparatively investigated regarding conventional adsorption as contrasted to an ultrasonic treatment assisted procedure. The course and efficiency of the polymer adsorpption onto the pigment surface was quantified by electrokinetic sonic amplitude measurements. The higher efficiency of the pigment surface coating by the copolymers as achieved by ultrasonic treatment varies with the copolymer architecture and is a consequence of ultrasonically induced pigment surface activation
Creation of Coatings by Temperature-Controlled Polymer Deposition
In this paper, the results of the recent studies on application of lower critical solution temperature (LCST) phenomena of polymer solutions to the surface modification of flat and spherical substrates are reported. It was found that a controlled polymer deposition can be achieved upon prevailing of the LCST, a peculiar surface topology of polymer coating and particles those remarkably effective in stabilizing pigment dispersiions. Second, the finding is that the temperature induces polymer deposition as the coprecipitation of a finely dispersed component on the substrate surface. That goes along with the polymer deposition after exceeding of the LCST which in turn allows for the tailored surface modification of pigments in that particulate additiives can be incorporated into the surface modifying coating
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