Dynamics of Low Anisotropy Morphologies in Directional Solidification

We report experimental results on quasi-two-dimensional diffusion limited growth in directionally solidified succinonitrile with small amounts of poly(ethylene oxide), acetone, or camphor as a solute. Seaweed growth, or dense branching morphology, is selected by growing grains close to the $\{111\}$ plane, where the in-plane surface tension is nearly isotropic. The observed growth morphologies are very sensitive to small anisotropies in surface tension caused by misorientations from the $\{111\}$ plane. Different seaweed morphologies are found, including the degenerate, the stabilized, and the strongly tilted seaweeds. The degenerate seaweeds show a limited fractal scaling range and, with increased undercooling, suggests a transition from "fractal" to "compact" seaweed. Strongly tilted seaweeds demonstrate a significant twofold anisotropy. In addition, seaweed-dendrite transitions are observed in low anisotropy growth.Comment: 12 pages, 17 figures, submitted to Phys. Rev. E, reduced image quality for smaller file siz

Experimental Measures of Affine and Non-affine Deformation in Granular Shear

Through 2D granular Couette flow experiments, we probe failure and deformation of disordered solids under shear. Shear produces smooth affine deformations in such a solid and also irresversible so-called non-affine particle displacements. We examine both processes. We show that the non-affine part is associated with diffusion, and also can be used to define a granular temperature. Distributions for single particle non-affine displacements, \dri, satisfy P_1(\dri) \propto \exp [-|\dri/\Delta r|^{\alpha}] ($\alpha \stackrel{<}{\sim} 2$). We suggest that the shear band forms due to a radially outward diffusive flux/non-affine motion which is balanced in the steady state by inward diffusion due to density gradients.Comment: 4 pages, 5 figure

Transients in sheared granular matter

As dense granular materials are sheared, a shear band and an anisotropic force network form. The approach to steady state behavior depends on the history of the packing and the existing force and contact network. We present experiments on shearing of dense granular matter in a 2D Couette geometry in which we probe the history and evolution of shear bands by measuring particle trajectories and stresses during transients. We find that when shearing is stopped and restarted in the same direction, steady state behavior is immediately reached, in agreement with the typical assumption that the system is quasistatic. Although some relaxation of the force network is observed when shearing is stopped, quasistatic behavior is maintained because the contact network remains essentially unchanged. When the direction of shear is reversed, a transient occurs in which stresses initially decrease, changes in the force network reach further into the bulk, and particles far from the wheel become more mobile. This occurs because the force network is fragile to changes transverse to the force network established under previous shear; particles must rearrange before becoming jammed again, thereby providing resistance to shear in the reversed direction. The strong force network is reestablished after displacing the shearing surface $\approx 3d$, where $d$ is the mean grain diameter. Steady state velocity profiles are reached after a shear of $\leq 30d$. Particles immediately outside of the shear band move on average less than 1 diameter before becoming jammed again. We also examine particle rotation during this transient and find that mean particle spin decreases during the transient, which is related to the fact that grains are not interlocked as strongly.Comment: 7 pages, 11 figures, accepted to Eur. Phys. J. E, revised version based on referee suggestion

Who is teaching the kids to cook? Results from a nationally representative survey of secondary school students in New Zealand

Learning how to cook is an important skill for developing healthy eating behaviors. Moreover, involvement in home cooking may offer young people opportunities for skill building, identity development and social engagement with their families. Recently, there have been concerns that the current generation of young people may not have the opportunities to develop sufficient cooking skills. These concerns have been addressed by the initiation of numerous, localized interventions. Yet, little is known about where the current generation of young people learn cooking skills. The objective of this study was to describe where the current generation of young people report learning to cook, drawing on nationally representative data from New Zealand. Data were collected as part of Youth2012, a nationally representative survey of secondary school students (n = 8500) in New Zealand. Almost all students reported learning to cook and from multiple sources. Almost all students reported learning to cook from a family member (mother, father, or other family member), approximately 60% of students reported that they learned to cook from certain media (cookbooks, TV, or the Internet) and half of all students reported learning to cook at school. There were numerous differences in where students learned to cook by socio-demographic characteristics. Findings from the current research highlight the important role that families play in teaching young people to cook and will be useful for those working with young people to develop these skills

Oil Shale R & D -- A Bureau of Mines Program

Energy is one of our basic natural resources. Oil constitutes an important part of this resource but domestic production is dropping while imports are rising. Today, oil represents about one-half of the total energy consumed in this country, and demand is expected to grow at the rate of about 2 percent per year during the next 10 years. Increased reliance on imports can be reduced by synthetic fuels produced from the oil shale deposits of the Green River Formation in Colorado, Utah, and Wyoming. These deposits are so enormous (600 billion barrels in high- grade shale alone), that any limitations on production are set by economic, environmental, political, or technological constraints. According to the Project Independence Blueprint, a shale oil production of 1,000,000 barrels per day could be attained by the year 1985. This would meet the goal established by President Ford in his recent State-of-the- Union Message. This paper outlines the work that the Bureau of Mines is doing in oil shale mining research to further this goal. It describes the results of our first year\u27s contract research program, and our plans for the future. Oil shale research is part of the Bureau\u27s overall Advancing Mining Technology Program. The objectives of our program are to develop, test, and demonstrate improved low-cost mining and waste management methods and equipment that are capable of producing the large tonnages of oil shale and shale oil needed by the 1 980\u27s. Oil shale and associated minerals must be mined safely and economically, using methods that will allow maximum recovery of the mineral resource with acceptable environmental impact. The immediate objectives of the program are to assess the technical and economic feasibility of various surface and underground mining methods and of modified in situ extraction systems, evaluate the mineral resources, and determine the environmental impacts of an oil shale mining industry

American Dumpling Warrior

The author shares a humorous story on his attempt to study martial arts while teaching in China