Vector magnetic hysteresis of hard superconductors

Critical state problems which incorporate more than one component for the magnetization vector of hard superconductors are investigated. The theory is based on the minimization of a cost functional ${\cal C}[\vec{H}(\vec{x})]$ which weighs the changes of the magnetic field vector within the sample. We show that Bean's simplest prescription of choosing the correct sign for the critical current density $J_c$ in one dimensional problems is just a particular case of finding the components of the vector $\vec{J}_c$. $\vec{J}_c$ is determined by minimizing ${\cal C}$ under the constraint $\vec{J}\in\Delta (\vec{H},\vec{x})$, with $\Delta$ a bounded set. Upon the selection of different sets $\Delta$ we discuss existing crossed field measurements and predict new observable features. It is shown that a complex behavior in the magnetization curves may be controlled by a single external parameter, i.e.: the maximum value of the applied magnetic field $H_m$.Comment: 10 pages, 9 figures, accepted in Phys. Rev.

Internal Stress in a Model Elasto-Plastic Fluid

Plastic materials can carry memory of past mechanical treatment in the form of internal stress. We introduce a natural definition of the vorticity of internal stress in a simple two-dimensional model of elasto-plastic fluids, which generates the internal stress. We demonstrate how the internal stress is induced under external loading, and how the presence of the internal stress modifies the plastic behavior.Comment: 4 pages, 3 figure

A Random Keys Genetic Algorithm for Job Shop Scheduling

https://deepblue.lib.umich.edu/bitstream/2027.42/154143/1/39015099114574.pd

The Adiabatic Instability on Cosmology's Dark Side

We consider theories with a nontrivial coupling between the matter and dark energy sectors. We describe a small scale instability that can occur in such models when the coupling is strong compared to gravity, generalizing and correcting earlier treatments. The instability is characterized by a negative sound speed squared of an effective coupled dark matter/dark energy fluid. Our results are general, and applicable to a wide class of coupled models and provide a powerful, redshift-dependent tool, complementary to other constraints, with which to rule many of them out. A detailed analysis and applications to a range of models are presented in a longer companion paper.Comment: 4 pages, 1 figur

Cosmon dark matter?

We investigate if the fluctuations of the scalar field mediating quintessence -- the cosmon -- can play an important role in cosmology. Small fluctuations with short wavelength behave similar to a relativistic gas. In contrast, the contribution to the energy density from horizon size fluctuations may decrease less rapidly than radiation. We discuss the possibility that the cosmon fluctuations grow nonlinearly, form lumps and constitute the clustering dark matter of the universe. Cosmon dark matter would lead to interesting consequences for the equation of state and the coupling between quintessence and dark matter.Comment: Published version,correction in appendix A, 43 pages, LaTe

Live Cell Imaging Gas Control

The following document outlines the entire process for designing and manufacturing a Live Cell Imaging Gas Control subsystem in tandem with the Heated Stage subsystem to make a CO2 and temperature-controlled chamber for use with the Olympus IX73P2F Microscope. It highlights the current literature and patents surrounding live cell imaging and touches on the existing live cell imaging setups currently being used by other entities. Following this, it defines the scope of the project, key customer requirements, and engineering specifications to ensure the design meets all the needs of its users. This document includes project planning steps to establish important deadlines and a budget for project completion. As the project has progressed, additional documentation has been added such as morphologies of possible design functions, conjoint analyses, conceptual evaluations, and conceptual models for development of the final design. To note, these initial designs highlighting a drawer like chamber were soon dismissed as it would not allow imaging within the device due to objective focal length. The design evolved into the final chamber with a removable lid of a polysulfone chamber with aluminum base. The manufacturing process instructions and design history file show the exact steps taken to manufacture the chamber prototype. Similarly, circuitry diagrams and instructions on the Arduino controlled CO2 system are outlined. In depth test plans were outlined, including testing for the materials, chamber itself, CO2 control system, and fully combined system with the Heated Stage subsystem. Material testing showed that polysulfone, glass, and aluminum withstand autoclave sterilization and laboratory cleaning agents. Chamber testing highlighted the compact size and usability of the device with a multitude of culture vessels. CO2 control system testing showed that the control system effectively keeps CO2 concentration between 4.5% and 5.5% during imaging, with the system being able to re-establish CO2 concentration within 2 minutes of the lid removal, and the system establishes required CO2 concentration about 5 minutes after setup. The entire Live Cell Imaging Device was shown to keep cells alive compared to an ambient air flask for a period of 3 hours. Finally, this document outlines the next steps for this device, including finer tuning of the CO2 control system and increasing cellular viability in the chamber for longer periods of time with the addition of humidity control

Autonomous clustering using rough set theory

This paper proposes a clustering technique that minimises the need for subjective human intervention and is based on elements of rough set theory. The proposed algorithm is unified in its approach to clustering and makes use of both local and global data properties to obtain clustering solutions. It handles single-type and mixed attribute data sets with ease and results from three data sets of single and mixed attribute types are used to illustrate the technique and establish its efficiency

Field Induced Nodal Order Parameter in the Tunneling Spectrum of YBa2_2Cu3_3O7−x_{7-x} Superconductor

We report planar tunneling measurements on thin films of YBa$_2$Cu$_3$O$_{7-x}$ at various doping levels under magnetic fields. By choosing a special setup configuration, we have probed a field induced energy scale that dominates in the vicinity of a node of the d-wave superconducting order parameter. We found a high doping sensitivity for this energy scale. At Optimum doping this energy scale is in agreement with an induced $id_{xy}$ order parameter. We found that it can be followed down to low fields at optimum doping, but not away from it.Comment: 9 pages, 8 figures, accepted for publication in Phys. Rev.

Metallicities of M Dwarf Planet Hosts from Spectral Synthesis

We present the first spectroscopic metallicities of three M dwarfs with known or candidate planetary mass companions. We have analyzed high resolution, high signal-to-noise spectra of these stars which we obtained at McDonald Observatory. Our analysis technique is based on spectral synthesis of atomic and molecular features using recently revised cool-star model atmospheres and spectrum synthesis code. The technique has been shown to yield results consistent with the analyses of solar-type stars and allows measurements of M dwarf [M/H] values to 0.12 dex precision. From our analysis, we find [M/H] = -0.12, -0.32, and -0.33 for GJ 876, GJ 436, and GJ 581 respectively. These three M dwarf planet hosts have sub-solar metallicities, a surprising departure from the trend observed in FGK-type stars. This study is the first part of our ongoing work to determine the metallicities of the M dwarfs included in the McDonald Observatory planet search program.Comment: 13 pages, 2 figures, accepted for publication in ApJ