Dynamical behavior of a complex fluid near an out-of-equilibrium transition: approaching simple rheological chaos

We report here an extensive study of sustained oscillations of the viscosity of a complex fluid near an out-of-equilibrium transition. Using well defined protocols, we perform rheological measurements of the onion texture near a layering transition in a Couette flow. This complex fluid exhibits sustained oscillations of the viscosity, on a large time scale (500s) at controlled stress. These oscillations are directly correlated to an oscillating microstrutural change of the texture of the fluid. We observe a great diversity of dynamical behavior and we show that there is a coupling with spatial effects in the gradient v direction. This is in agreement with a carefull analysis of the temporal series of the viscosity with the dynamical system theory. This analysis indicates that the observed dynamical responses do not strictly correspond to 3-dimensional chaotic states, probably because some spatio-temporal effects are present and are likely to play an important role.Comment: submitted to Phys. Rev.

Investigation of Metal and Organic Contaminant Distributions and Sedimentation Rates in Backwater Lakes along the Illinois River

Systematic sub-sampling of sediment cores in sections of uniform thickness is necessary in order to evaluate historic changes in sediment quality, to determine the vertical extent of contamination, and to measure sedimentation rates. With these objectives in mind, fourteen sediment cores were collected during March 2002 using the Illinois State Water Survey vibracorer. Concentrations of metals and total organic carbon were measured using standard techniques. Concentrations of chlorinated pesticides, phenolic compounds, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) were measured by gas chromatography/mass spectrometry (GC-MS). The concentrations of chlorinated pesticides, phenolic compounds and polychlorinated biphenyls (PCBs) were below the method detection limit in all sediment samples analyzed. However, there was a wide range in concentrations of polycyclic aromatic hydrocarbons (PAHs) which were detected in all sediment samples. Also, a wide range of metal concentrations was noted in the sediments evaluated. Lower concentrations of metals were found in the upper 0.5 m of sediment but concentrations were elevated at depths ranging from 1.0 m to 1.5 m. Sedimentation rates were estimated using cesium-137 radiometric dating on 14 vibracores. Sedimentation rates range from < 0.1 to 1.9 cm/yr, with an average of 0.9 cm/yr. These rates are comparable to those reported in previous studies.Illinois Sustainable Technology Centerpublished or submitted for publicationis peer reviewe

CLEAR: Covariant LEAst-square Re-fitting with applications to image restoration

In this paper, we propose a new framework to remove parts of the systematic errors affecting popular restoration algorithms, with a special focus for image processing tasks. Generalizing ideas that emerged for $\ell_1$ regularization, we develop an approach re-fitting the results of standard methods towards the input data. Total variation regularizations and non-local means are special cases of interest. We identify important covariant information that should be preserved by the re-fitting method, and emphasize the importance of preserving the Jacobian (w.r.t. the observed signal) of the original estimator. Then, we provide an approach that has a "twicing" flavor and allows re-fitting the restored signal by adding back a local affine transformation of the residual term. We illustrate the benefits of our method on numerical simulations for image restoration tasks

Mobilizing Public Will For Social Change

Examines the theory and strategies of "public will" campaigns and offers tangible criteria for their evaluation. It provides a rich inventory of strategies for use in mobilizing the public will through an integration of models of agenda building, social problem construction, issues management, social movements, media advocacy, and social capital. In addition, the paper provides cases and examples of public will campaigns directed at various social problems, along with criteria for evaluating these campaigns at various stages of a social problem's life cycle

Can an underestimation of opacity explain B-type pulsators in the SMC?

Slowly Pulsating B and $\beta$ Cephei are $\kappa$ mechanism driven pulsating B stars. That $\kappa$ mechanism works since a peak in the opacity due to a high number of atomic transitions from iron-group elements occurs in the area of $\log T \approx 5.3$. Theoretical results predict very few SPBs and no $\beta$ Cep to be encountered in low metallicity environments such as the Small Magellanic Cloud. However recent variability surveys of B stars in the SMC reported the detection of a significant number of SPB and $\beta$ Cep candidates. Though the iron content plays a major role in the excitation of $\beta$ Cep and SPB pulsations, the chemical mixture representative of the SMC B stars such as recently derived does not leave room for a significant increase of the iron abundance in these stars. Whilst abundance of iron-group elements seems reliable, is the opacity in the iron-group elements bump underestimated? We determine how the opacity profile in B-type stars should change to excite SPB and $\beta$ Cep pulsations in early-type stars of the SMC.Comment: 5 pages, 7 figures, to appear under electronic form in : Proceedings of the 4th HELAS International Conference: Seismological Challenges for Stellar Structur

Asteroseismology of Massive Stars : Some Words of Caution

Although playing a key role in the understanding of the supernova phenomenon, the evolution of massive stars still suffers from uncertainties in their structure, even during their "quiet" main sequence phase and later on during their subgiant and helium burning phases. What is the extent of the mixed central region? In the local mixing length theory (LMLT) frame, are there structural differences using Schwarzschild or Ledoux convection criterion? Where are located the convective zone boundaries? Are there intermediate convection zones during MS and post-MS phase, and what is their extent and location? We discuss these points and show how asteroseismology could bring some light on these questions.Comment: 10 pages, 5 figures, IAU Symposium 307, New windows on massive stars: asteroseismology, interferometry, and spectropolarimetry, G. Meynet, C. Georgy, J.H. Groh & Ph. Stee, ed

3D printing dimensional calibration shape: Clebsch Cubic

3D printing and other layer manufacturing processes are challenged by dimensional accuracy. Several techniques are used to validate and calibrate dimensional accuracy through the complete building envelope. The validation process involves the growing and measuring of a shape with known parameters. The measured result is compared with the intended digital model. Processes with the risk of deformation after time or post processing may find this technique beneficial. We propose to use objects from algebraic geometry as test shapes. A cubic surface is given as the zero set of a 3rd degree polynomial with 3 variables. A class of cubics in real 3D space contains exactly 27 real lines. We provide a library for the computer algebra system Singular which, from 6 given points in the plane, constructs a cubic and the lines on it. A surface shape derived from a cubic offers simplicity to the dimensional comparison process, in that the straight lines and many other features can be analytically determined and easily measured using non-digital equipment. For example, the surface contains so-called Eckardt points, in each of which three of the lines intersect, and also other intersection points of pairs of lines. Distances between these intersection points can easily be measured, since the points are connected by straight lines. At all intersection points of lines, angles can be verified. Hence, many features distributed over the build volume are known analytically, and can be used for the validation process. Due to the thin shape geometry the material required to produce an algebraic surface is minimal. This paper is the first in a series that proposes the process chain to first define a cubic with a configuration of lines in a given print volume and then to develop the point cloud for the final manufacturing. Simple measuring techniques are recommended.Comment: 8 pages, 1 figure, 1 tabl

The ontology of causal process theories

There is a widespread belief that the so-called process theories of causation developed by Wesley Salmon and Phil Dowe have given us an original account of what causation really is. In this paper, I show that this is a misconception. The notion of "causal process" does not offer us a new ontological account of causation. I make this argument by explicating the implicit ontological commitments in Salmon and Dowe's theories. From this, it is clear that Salmon's Mark Transmission Theory collapses to a counterfactual theory of causation, while the Conserved Quantity Theory collapses to David Fair's phsyicalist reduction of causation