Micromechanics of high temperature deformation and failure

The micromechanics of the constitutive behavior of elastoplastic materials at high temperatures was examined. The experimental work focused on the development of microscopic defects in superalloys (Waspaloy), especially the formation of voids at grain boundary carbides, and slip induced surface cracks within grains upon cyclic loading at high temperatures. The influence of these defects on the life expectancy of the material was examined. The theoretical work consists of two parts: (1) analytical description of the mechanisms that lead to defects observed experimentally; and (2) development of macroscopic elastoplastic nonlinear constitutive relations based on mechanical modeling

Hadronic Equation of State and Speed of Sound in Thermal and Dense Medium

The equation of state $p(\epsilon)$ and speed of sound squared $c_s^2$ are studied in grand canonical ensemble of all hadron resonances having masses $\leq 2\,$GeV. This large ensemble is divided into strange and non-strange hadron resonances and furthermore to pionic, bosonic and femionic sectors. It is found that the pions represent the main contributors to $c_s^2$ and other thermodynamic quantities including the equation of state $p(\epsilon)$ at low temperatures. At high temperatures, the main contributions are added in by the massive hadron resonances. The speed of sound squared can be calculated from the derivative of pressure with respect to the energy density, $\partial p/\partial \epsilon$, or from the entropy-specific heat ratio, $s/c_v$. It is concluded that the physics of these two expressions is not necessarily identical. They are distinguishable below and above the critical temperature $T_c$. This behavior is observed at vanishing and finite chemical potential. At high temperatures, both expressions get very close to each other and both of them approach the asymptotic value, $1/3$. In the HRG results, which are only valid below $T_c$, the difference decreases with increasing the temperature and almost vanishes near $T_c$. It is concluded that the HRG model can very well reproduce the results of the lattice quantum chromodynamics (QCD) of $\partial p/\partial \epsilon$ and $s/c_v$, especially at finite chemical potential. In light of this, energy fluctuations and other collective phenomena associated with the specific heat might be present in the HRG model. At fixed temperatures, it is found that $c_s^2$ is not sensitive to the chemical potential.Comment: 19 pages, 6 figures with 13 eps graph

Thermodynamics, transition dynamics, and texturing in polymer-dispersed liquid crystals with mesogens exhibiting a direct isotropic/smectic-A transition

Experimental and modeling/simulation studies of phase equilibrium and growth morphologies of novel polymer-dispersed liquid crystal (PDLC) mixtures of PS (polystyrene) and liquid crystals that exhibit a direct isotropic/smectic-A (lamellar) mesophase transition were performed for PS/10CB (decyl- cyanobiphenyl) and PS/12CB (dodecyl-cyanobiphenyl). Partial phase diagrams were determined using polarized optical microscopy (POM) and differential scanning calorimetry (DSC) for different compositions of both materials, determining both phase separation (liquid/liquid demixing) and phase ordering (isotropic/smectic-A transition) temperatures. The Flory-Huggins theory of isotropic mixing and Maier-Saupe-McMillan theory for smectic-A liquid crystalline ordering were used to computationally determine phase diagrams for both systems, showing good agreement with the experimental results. In addition to thermodynamic observations, growth morphology relations were found depending on phase transition sequence, quench rate, and material composition. Three stages of liquid crystal-rich domain growth morphology were observed: spherical macroscale domain growth ("stage I"), highly anisotropic domain growth ("stage II"), and sub-micron spheroid domain growth ("stage III"). Nano-scale structure of spheroidal and spherocylindrical morphologies were then determined via two-dimensional simulation of a high-order Landau-de Gennes model. Morphologies observed during stage II growth are typical of di- rect isotropic/smectic-A phase transitions, such as highly anisotropic "batonnets" and filaments. These morphologies, which are found to be persistent in direct isotropic/smectic-A PDLCs, could provide new functionality and applications for these functional materials.Comment: First Revision, 21 pages, 11 figures, submitted to Macromolecules as an article 17JUL200

THE EXPLOITATION OF COAL AS AN ENGINE FOR GROWTH IN EASTERN KENTUCKY - AN INPUT-OUTPUT STUDY

Resource /Energy Economics and Policy,

Negotiations for meaning in the context of a massively multiplayer online role-playing game

This study investigated negotiations for meaning as conditions for second language (L2) learning in the context of a massively multiplayer online role-playing game, World of Warcraft (WoW) (Blizzard Entertainment, 2004). Varonis and Gass’s (1985) and Smith’s (2003a) models were used to identify negotiation episodes during on-task and off-task talks among the participants while playing WoW. The participants were six non-native (NNS) and one native English speaker (NS). The NNSs were divided into two teams of three: Team 1 (T1) pre-intermediate and Team 2 (T2) upper-intermediate. The NS played the game with both teams. The study lasted for six months and resulted in 59.96 hours of recorded audio and nine hours of screen-recorded gaming sessions. Negotiation patterns were compared across the L2 proficiency levels and three different types of dyads. The results revealed that (a) T1 encountered more communication breakdowns, but T2 engaged in more negotiations, (b) T1 engaged in more complex negotiations, (c) breakdowns and negotiations occurred more during off-task talk, and (d) breakdowns were triggered more by the NS’s utterances in T1 and by NNSs’ utterances in T2. The results also showed the participants’ abundant L2 use to undertake authentically contextualized game-driven tasks, meticulous involvement in bi- and multi-lateral negotiations, and creative strategies to resolve incomprehension

The role of T regulatory lymphocytes in lymphoma

T regulatory cells play a crucial role in immunological unresponsiveness to selfantigens and in suppressing excessive immune responses deleterious to the host. T regulatory cells are produced in the thymus as a functionally mature subpopulation of T cells. They can be induced from naive T cells in the periphery and express their marker as a forkhead/winged helix transcription factor called FoxP3. In patients with lymphomas where T regulatory cells serve as suppressor anti-tumor cytotoxicity, decreased numbers of T regulatory cells are associated with a favorable prognosis. In contrast, in patients with lymphomas where T regulatory cells function as anti-tumor cytotoxic agents, enhanced numbers of T regulatory cells are associated with a favorable prognosis. Tumors actively promote the accumulation of these cells through several mechanisms that involve activation of naturally occurring T regulatory cells as well as conversion of non-T regulatory cells into T regulatory cells. Tumor-derived prostaglandin E2 can increase T regulatory cell activity and induce a regulatory phenotype in CD4+CD25+T cells. On the other hand, a balance between T regulatory and Th17 cells is essential for maintaining homeostasis of anti-tumor immunity. Accelerating processes such as increasing the amounts of IL-6 or IL-17 can enhance FoxP3 T regulatory cell expression and result in a lymphoma or inactivation of T cell CD4+. This effect is the reason for malignancy and a reduction in anti-tumor immune response. In this systematic review we intend to analyze this relationship. We have collected and analyzed the majority of recently published articles on the role of T regulatory cells as a review article