Shear thickening of highly viscous granular suspensions

We experimentally investigate shear thickening in dense granular suspensions under oscillatory shear. Directly imaging the suspension-air interface, we observe dilation beyond a critical strain $\gamma_c$ and the end of shear thickening as the maximum confining stress is reached and the contact line moves. Analyzing the shear profile, we extract the viscosity contributions due to hydrodynamics $\eta_\mu$, dilation $\eta_c$ and sedimentation $\eta_g$. While $\eta_g$ governs the shear thinning regime, $\eta_\mu$ and $\eta_c$ together determine the shear thickening behavior. As the suspending liquid's viscosity varies from 10 to 1000 cst, $\eta_\mu$ is found to compete with $\eta_c$ and soften the discontinuous nature of shear thickening

Fish Habitat Utilization Patterns and Evaluation of the Efficacy of Marine Protected Areas in Hawaii: Integration of NOAA Digital Benthic Habitat Mapping and Coral Reef Ecological Studies

Over the past four decades, the state of Hawaii has developed a system of eleven Marine Life Conservation Districts (MLCDs) to conserve and replenish marine resources around the state. Initially established to provide opportunities for public interaction with the marine environment, these MLCDs vary in size, habitat quality, and management regimes, providing an excellent opportunity to test hypotheses concerning marine protected area (MPA) design and function using multiple discreet sampling units. NOAA/NOS/NCCOS/Center for Coastal Monitoring and Assessment’s Biogeography Team developed digital benthic habitat maps for all MLCD and adjacent habitats. These maps were used to evaluate the efficacy of existing MLCDs for biodiversity conservation and fisheries replenishment, using a spatially explicit stratified random sampling design. Coupling the distribution of habitats and species habitat affinities using GIS technology elucidates species habitat utilization patterns at scales that are commensurate with ecosystem processes and is useful in defining essential fish habitat and biologically relevant boundaries for MPAs. Analysis of benthic cover validated the a priori classification of habitat types and provided justification for using these habitat strata to conduct stratified random sampling and analyses of fish habitat utilization patterns. Results showed that the abundance and distribution of species and assemblages exhibited strong correlations with habitat types. Fish assemblages in the colonized and uncolonized hardbottom habitats were found to be most similar among all of the habitat types. Much of the macroalgae habitat sampled was macroalgae growing on hard substrate, and as a result showed similarities with the other hardbottom assemblages. The fish assemblages in the sand habitats were highly variable but distinct from the other habitat types. Management regime also played an important role in the abundance and distribution of fish assemblages. MLCDs had higher values for most fish assemblage characteristics (e.g. biomass, size, diversity) compared with adjacent fished areas and Fisheries Management Areas (FMAs) across all habitat types. In addition, apex predators and other targeted resources species were more abundant and larger in the MLCDs, illustrating the effectiveness of these closures in conserving fish populations. Habitat complexity, quality, size and level of protection from fishing were important determinates of MLCD effectiveness with respect to their associated fish assemblages. (PDF contains 217 pages

Functional Diversity

The question at the heari of this dissertation is, can it be different? The it is the way church is organized, worship happens, and the very flavor of the church in the United Methodist Church in Oregon and Idaho. Today, church is generally organized following the traditional Anglo experience. The hymns, food, and organizational patterns generally follow the patterns of the white, English-speaking majority in the churches. A different formula would be one that is more multicultural and multiethnic. In this dissertation, the different way of organizing and thinking of church is called functional diversity. Functional diversity is explored through the Wesleyan Quadrilateral, the traditional United Methodist formula for doing theology. The Wesleyan Quadrilateral looks at any theological issue through four lenses: Scripture, tradition, reason and experience. After exploring the Scriptural call to welcome strangers and aliens, listening to the theology of marginality as discussed by J. Y. Lee, discovering a time in the history of the church where diversity existed, and taking note of my own experience with diversity, this dissertation claims that there is another way, that the church can be different. Throughout this dissertation, I argue that the church is called to diversity and that diversity is a valid, biblically-sound way to build a church. In chapter one I introduce the idea of functional diversity. In chapter two I explore the biblical witness that calls the church to diversity as I key into the bible\u27s special concern for the strangers and the aliens. In chapter three I read the theology of marginality as imagined by J. Y. Lee and hear this as a call to diversity in the church. In chapter four I explore the time of the Egyptian monks of the third and fourth centuries and hear their monasteries and places of diversity. In chapter five I listen to my own experience and that of United Methodist Churches in Oregon and Idaho as the area has become more diverse. In chapter 6, I consider the idea ofmissiology and the teachings ofthe Church Growth movement. The Church Growth movement suggests that, rather than diversity, a church will grow best if it is filled with homogeneous ethnic units. I suggest that, while the teachings of the Church Growth movement are one biblically-principled way to grow churches, there are other, equally correct and biblically-principled ways to grow churches. Erwin McManus\u27 Mosaic Church is one such way. In the final chapter, I draw conclusions from the previous chapters and suggest that a functionally diverse church is the way I feel God calling me to grow churches

Shear thickening in densely packed suspensions of spheres and rods confined to few layers

We investigate confined shear thickening suspensions for which the sample thickness is comparable to the particle dimensions. Rheometry measurements are presented for densely packed suspensions of spheres and rods with aspect ratios 6 and 9. By varying the suspension thickness in the direction of the shear gradient at constant shear rate, we find pronounced oscillations in the stress. These oscillations become stronger as the gap size is decreased, and the stress is minimized when the sample thickness becomes commensurate with an integer number of particle layers. Despite this confinement-induced effect, viscosity curves show shear thickening that retains bulk behavior down to samples as thin as two particle diameters for spheres, below which the suspension is jammed. Rods exhibit similar behavior commensurate with the particle width, but they show additional effects when the thickness is reduced below about a particle length as they are forced to align; the stress increases for decreasing gap size at fixed shear rate while the shear thickening regime gradually transitions to a Newtonian scaling regime. This weakening of shear thickening as an ordered configuration is approached contrasts with the strengthening of shear thickening when the packing fraction is increased in the disordered bulk limit, despite the fact that both types of confinement eventually lead to jamming.Comment: 21 pages, 14 figures. submitted to the Journal of Rheolog

Prothymosin α is a component of a linker histone chaperone

AbstractLinker histone H1 binds with high affinity to naked and nucleosomal DNA in vitro but is rapidly exchanged between chromatin sites in vivo suggesting the involvement of one or more linker histone chaperones. Using permeabilized cells, we demonstrate that the small acidic protein prothymosin α (ProTα) can facilitate H1 displacement from and deposition onto the native chromatin template. Depletion of ProTα levels in vivo by siRNA-mediated mRNA degradation resulted in a decreased rate of exchange of linker histones as assayed by photobleaching techniques. These results indicate that ProTα is a component of a linker histone chaperone

Strain-stiffening in random packings of entangled granular chains

Random packings of granular chains are presented as a model polymer system to investigate the contribution of entanglements to strain-stiffening in the absence of Brownian motion. The chain packings are sheared in triaxial compression experiments. For short chain lengths, these packings yield when the shear stress exceeds a the scale of the confining pressure, similar to packings of spherical particles. In contrast, packings of chains which are long enough to form loops exhibit strain-stiffening, in which the effective stiffness of the material increases with strain, similar to many polymer materials. The latter packings can sustain stresses orders-of-magnitude greater than the confining pressure, and do not yield until the chain links break. X-ray tomography measurements reveal that the strain-stiffening packings contain system-spanning clusters of entangled chains.Comment: 4 pages, 4 figures. submitted to Physical Review Letter

Mass Inflation in the Loop Black Hole

In classical general relativity the Cauchy horizon within a two-horizon black hole is unstable via a phenomenon known as mass inflation, in which the mass parameter (and the spacetime curvature) of the black hole diverges at the Cauchy horizon. Here we study this effect for loop black holes -- quantum gravitationally corrected black holes from loop quantum gravity -- whose construction alleviates the $r=0$ singularity present in their classical counterparts. We use a simplified model of mass inflation, which makes use of the generalized DTR relation, to conclude that the Cauchy horizon of loop black holes indeed results in a curvature singularity similar to that found in classical black holes. The DTR relation is of particular utility in the loop black hole because it does not directly rely upon Einstein's field equations. We elucidate some of the interesting and counterintuitive properties of the loop black hole, and corroborate our results using an alternate model of mass inflation due to Ori.Comment: Latex 20 pages, 7 figure