Direct conversion of rheological compliance measurements into storage and loss moduli

We remove the need for Laplace/inverse-Laplace transformations of experimental data, by presenting a direct and straightforward mathematical procedure for obtaining frequency-dependent storage and loss moduli ($G'(\omega)$ and $G"(\omega)$ respectively), from time-dependent experimental measurements. The procedure is applicable to ordinary rheological creep (stress-step) measurements, as well as all microrheological techniques, whether they access a Brownian mean-square displacement, or a forced compliance. Data can be substituted directly into our simple formula, thus eliminating traditional fitting and smoothing procedures that disguise relevant experimental noise.Comment: 4 page

Active Microrheology of Networks Composed of Semiflexible Polymers. II. Theory and comparison with simulations

Building on the results of our computer simulation (ArXiv cond-mat/0503573)we develop a theoretical description of the motion of a bead, embedded in a network of semiflexible polymers, and responding to an applied force. The theory reveals the existence of an osmotic restoring force, generated by the piling up of filaments in front of the moving bead and first deduced through computer simulations. The theory predicts that the bead displacement scales like x ~ t^alfa with time, with alfa=0.5 in an intermediate- and alfa=1 in a long-time regime. It also predicts that the compliance varies with concentration like c^(-4/3) in agreement with experiment.Comment: 18 pages and 2 figure

An empirical investigation of the EOE gold options market

On April 2, 1981, the European Option Exchange introduced the first organized exchange trading of options on spot gold. We study this new market for three months at its inception and in a parallel period a year later via various tests of rational boundary conditions. Additionally, we use call-put parity to infer implied risk free rates (IRFR's). Deviations of the IRFR's from the prevailing risk free rate permit the possibility of arbitrage through positions known as forward and reverse conversions. Our tests are modified to allow for transaction costs to more fully address the question of market efficiency.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25742/1/0000302.pd

On inferring standard deviations from path dependent options

Path dependent option prices are employed to derive implied standard deviations of the underlying security price process without recourse to numerical procedures. We empirically illustrate our methodology by inferring the volatility of gold prices.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25893/1/0000456.pd

If You’re Going Through Hell, Keep Going: Nonlinear Effects of Financial Liberalization in Transition Economies

Copyright © Taylor & Francis Group, LLC. Did increasing the level and pace of financial liberalization during transition expose countries to crises? And if a crisis did strike, did liberalization do more harm or good? Using a database of 28 transition economies over 22 years, this article examines these questions across a host of economic outcomes, including savings and the size of the private sector. The results provide evidence that, while liberalization may initially increase the probability of a crisis, the prospect of a crisis drops dramatically at higher levels of financial openness. Moreover, the benefits of liberalization across several metrics outweigh the risks of these intermediate stages

Steady shear flow thermodynamics based on a canonical distribution approach

A non-equilibrium steady state thermodynamics to describe shear flows is developed using a canonical distribution approach. We construct a canonical distribution for shear flow based on the energy in the moving frame using the Lagrangian formalism of the classical mechanics. From this distribution we derive the Evans-Hanley shear flow thermodynamics, which is characterized by the first law of thermodynamics $dE = T dS - Q d\gamma$ relating infinitesimal changes in energy $E$, entropy $S$ and shear rate $\gamma$ with kinetic temperature $T$. Our central result is that the coefficient $Q$ is given by Helfand's moment for viscosity. This approach leads to thermodynamic stability conditions for shear flow, one of which is equivalent to the positivity of the correlation function of $Q$. We emphasize the role of the external work required to sustain the steady shear flow in this approach, and show theoretically that the ensemble average of its power $\dot{W}$ must be non-negative. A non-equilibrium entropy, increasing in time, is introduced, so that the amount of heat based on this entropy is equal to the average of $\dot{W}$. Numerical results from non-equilibrium molecular dynamics simulation of two-dimensional many-particle systems with soft-core interactions are presented which support our interpretation.Comment: 23 pages, 7 figure

The Viscoelastic Properties of Passive Eye Muscle in Primates. I: Static Forces and Step Responses

The viscoelastic properties of passive eye muscles are prime determinants of the deficits observed following eye muscle paralysis, the root cause of several types of strabismus. Our limited knowledge about such properties is hindering the ability of eye plant models to assist in formulating a patient's diagnosis and prognosis. To investigate these properties we conducted an extensive in vivo study of the mechanics of passive eye muscles in deeply anesthetized and paralyzed monkeys. We describe here the static length-tension relationship and the transient forces elicited by small step-like elongations. We found that the static force increases nonlinearly with length, as previously shown. As expected, an elongation step induces a fast rise in force, followed by a prolonged decay. The time course of the decay is however considerably more complex than previously thought, indicating the presence of several relaxation processes, with time constants ranging from 1 ms to at least 40 s. The mechanical properties of passive eye muscles are thus similar to those of many other biological passive tissues. Eye plant models, which for lack of data had to rely on (erroneous) assumptions, will have to be updated to incorporate these properties

Viscoelastic hinge formation in beams

A constitutive equation for nonlinear viscoelasticity is used to model the mechanical response of solid polymers such as polycarbonate. The nonlinearity arises from a reduced time variable which causes stress relaxation to occur faster as strain increases. This constitutive equation is used to study the consequences of the interaction of the acceleration of stress relaxation with strain and the spatial variation of strain within the context of the structural theory of beams undergoing small displacements.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41706/1/707_2005_Article_BF01182510.pd

Digitalized service multinationals and international business theory

Banalieva and Dhanaraj argue that digital service multinationals (DSMNCs) possess a new category of firm-specific advantage (FSA), the network advantage, and that, contrary to extant theory, they use networks as a mode of governance. I review the business models used by DSMNCs, compare them to non-digital ones, and explore what we can learn about them from extant IB theory. I conclude that network advantages are not a new category of FSAs, that networks are not a mode of governance, and that their use by DSMNCs is well explained by extant theory

The Viscoelastic Properties of Passive Eye Muscle in Primates. II: Testing the Quasi-Linear Theory

We have extensively investigated the mechanical properties of passive eye muscles, in vivo, in anesthetized and paralyzed monkeys. The complexity inherent in rheological measurements makes it desirable to present the results in terms of a mathematical model. Because Fung's quasi-linear viscoelastic (QLV) model has been particularly successful in capturing the viscoelastic properties of passive biological tissues, here we analyze this dataset within the framework of Fung's theory