Experimental Divertor Similarity Database Parameters

A set of experimentally-determined dimensionless parameters is proposed for characterizing the regime of divertor operation. The objective is to be able to compare as unambiguously as possible the operation of different divertors and to understand what physical similarities and differences they represent. Examples from Alcator C-Mod are given.Comment: Plain Tex (8 pages) plus 5 postscipt figure

Dynamic buckling estimates

Dynamic buckling estimates for sensitive structures subjected to finite-time loadin

Phase Transitions in Ultra-Cold Two-Dimensional Bose Gases

We briefly review the theory of Bose-Einstein condensation in the two-dimensional trapped Bose gas and, in particular the relationship to the theory of the homogeneous two-dimensional gas and the Berezinskii-Kosterlitz-Thouless phase. We obtain a phase diagram for the trapped two-dimensional gas, finding a critical temperature above which the free energy of a state with a pair of vortices of opposite circulation is lower than that for a vortex-free Bose-Einstein condensed ground state. We identify three distinct phases which are, in order of increasing temperature, a phase coherent Bose-Einstein condensate, a vortex pair plasma with fluctuating condensate phase and a thermal Bose gas. The thermal activation of vortex-antivortex pair formation is confirmed using finite-temperature classical field simulations

An Exploratory Study of Forces and Frictions affecting Large-Scale Model-Driven Development

In this paper, we investigate model-driven engineering, reporting on an exploratory case-study conducted at a large automotive company. The study consisted of interviews with 20 engineers and managers working in different roles. We found that, in the context of a large organization, contextual forces dominate the cognitive issues of using model-driven technology. The four forces we identified that are likely independent of the particular abstractions chosen as the basis of software development are the need for diffing in software product lines, the needs for problem-specific languages and types, the need for live modeling in exploratory activities, and the need for point-to-point traceability between artifacts. We also identified triggers of accidental complexity, which we refer to as points of friction introduced by languages and tools. Examples of the friction points identified are insufficient support for model diffing, point-to-point traceability, and model changes at runtime.Comment: To appear in proceedings of MODELS 2012, LNCS Springe

Non-linear Plasma Wake Growth of Electron Holes

An object's wake in a plasma with small Debye length that drifts \emph{across} the magnetic field is subject to electrostatic electron instabilities. Such situations include, for example, the moon in the solar wind wake and probes in magnetized laboratory plasmas. The instability drive mechanism can equivalently be considered drift down the potential-energy gradient or drift up the density-gradient. The gradients arise because the plasma wake has a region of depressed density and electrostatic potential into which ions are attracted along the field. The non-linear consequences of the instability are analysed in this paper. At physical ratios of electron to ion mass, neither linear nor quasilinear treatment can explain the observation of large-amplitude perturbations that disrupt the ion streams well before they become ion-ion unstable. We show here, however, that electron holes, once formed, continue to grow, driven by the drift mechanism, and if they remain in the wake may reach a maximum non-linearly stable size, beyond which their uncontrolled growth disrupts the ions. The hole growth calculations provide a quantitative prediction of hole profile and size evolution. Hole growth appears to explain the observations of recent particle-in-cell simulations

Collisional Effects on Nonlinear Ion Drag Force for Small Grains

The ion drag force arising from plasma flow past an embedded spherical grain is calculated self-consistently and non-linearly using particle in cell codes, accounting for ion-neutral collisions. Using ion velocity distribution appropriate for ion drift driven by a force field gives wake potential and force greatly different from a shifted Maxwellian distribution, regardless of collisionality. The low-collisionality forces are shown to be consistent with estimates based upon cross-sections for scattering in a Yukawa (shielded) grain field, but only if non-linear shielding length is used. Finite collisionality initially enhances the drag force, but only by up to a factor of 2. Larger collisionality eventually reduces the drag force. In the collisional regime, the drift distribution gives larger drag than the shift distribution even at velocities where their collisionless drags are equal. Comprehensive practical analytic formulas for force that fit the calculations are provided.Comment: Fig 1. corrected in this versio

A Search for Lymphatic Tissue in the Mouse Pineal Gland

There is recent evidence that the pineal gland in some species may have lymphatic qualities during early post natal life. In this study the development and structure of the pineal complex in the CDF1 mouse is examined in fetal, neonatal, juvenile, and adult stages. The gland appears as an out growth of the dorsal wall of the third ventricle of the brain and at ten days gestation attains a mean size of 90 microns in the transverse and 35 microns in the median saggital plane. General and specific staining shows fetal and early post partum tissue to be compact and mitotic with scant vascularity and poorly developed connective tissue structure. Mitotic activity ceases around three weeks post partum marking the beginning of the juvenile period. Neuroglia become evident as cell volume increases throughout the juvenile stage. Parenchyma cells reach a size of 15 microns in the late juvenile and adult glands. In the adult the gland has grown to a mean diameter of 630 microns in the transverse by 390 microns in the median saggital plane. At this stage the gland is supported by an extremely fine connective tissue framework which is continuous with the capsule. There is no evidence of lymphatic aggregations or germinal centers as described in other species, although occasional lymphocytes are seen in the capsule of the gland and adjacent meningeal tissues of juvenile specimens

The Temporal Nature of the Acute Stress Response and its Impact on Explicit Learning

Acute stress is commonly experienced by many throughout their lives. Given the demanding lifestyle of many career paths, it\u27s important to gauge the influence of these stressors upon cognitive performance. The present dissertation focus\u27 upon explicit learning in attempts to explore one avenue of the stress-cognition relationship. The Trier Social Stress Test (TSST) was used as a lab stressor for Experiments 1 and 2, in which participants are asked to give a speech and complete a difficult math task in front of 2 evaluators trained to monitor non-verbal behavior. Experiment 1 investigates the dynamic stress response during the minutes following stress, and how changes in the physiological response influence cognitive task performance. Stress was measured cardiovascularly, hormonally and as a self-reported appraisal of the situation. Findings from Experiment 1 revealed a time point 55 min following stress in which participants\u27 task performance was enhanced compared to a non-stressed comparison condition. These results suggest explicit task performance can be facilitated given a sufficient length of time following stress. Experiment 2 was designed in attempts to replicate the delayed RB task enhancement following the TSST, and given suggestions from the extant literature, explore if this task enhancement is attributed to enhanced working memory (WM). WM was assessed using an n-back task. Results confirmed the delayed RB task enhancement 55 min after stress, however no effect was present for n-back task performance. Experiment 3 was designed to understand if the RB task enhancement extended for a number of hours following stress. Additionally, cold-pressor stress was used to assess if the delayed task enhancement was stressor specific. In this task, participants were asked to submerge their hand in ice-water for up to 3 min. Results revealed a marginal task enhancement following a similar delay as Experiments 1 & 2, however the enhanced task performance did not remain hours later. Taken together the present experiments suggest a time frame following a delay from stress in which explicit learning and more specifically RB category learning is enhanced, however it doesn\u27t seem as if this effect is due to the impact of stress on WM