The velocity field of a system of unsteady cycloidal vorticies

An essential difference between two-dimensional and three-dimensional models of cycloidal rotors, the presence of unsteady trailing cycloidal vorticies in the wake, was studied. The velocity induced by these vorticies is the primary mechanism producing flow retardation for low span/radius ratio, finite blade number rotors. Results of using idealized rigid wake model of finite blade cycloidal rotors to investigate some cycloidal rotor problems are presented

Searching for an anomalous tˉqγ\bar t q \gamma coupling via single top quark production at a γγ\gamma\gamma collider

We investigate the potential of a high-energy $\gamma\gamma$ collider to detect an anomalous $\bar t q \gamma$ coupling from observation of the reaction $\gamma \gamma \to t\bar q$, $\bar t q$, where $q=c$ or $u$. We find that with $b$-tagging and suitable kinematic cuts this process should be observable if the anomalous coupling $\kappa/\Lambda$ is no less than about 0.05/TeV, where $\Lambda$ is the scale of new physics associated with the anomalous interaction. This improves upon the bound possible from observation of top decays at the Tevatron.Comment: 13 pages, RevTeX, 1 PS figur

Polyimides with pendant alkyl groups

The effect on selected polyimide properties when pendant alkyl groups were attached to the polymer backbone was investigated. A series of polymers were prepared using benzophenone tetracarboxylic acid dianhydride (BTDA) and seven different p-alkyl-m,p'-diaminobenzophenone monomers. The alkyl groups varied in length from C(1) (methyl) to C(9) (nonyl). The polyimide prepared from BTDA and m,p'-diaminobenzophenone was included as a control. All polymers were characterized by various chromatographic, spectroscopic, thermal, and mechanical techniques. Increasing the length of the pendant alkyl group resulted in a systematic decrease in glass transition temperature (Tg) for vacuum cured films. A 70 C decrease in Tg to 193 C was observed for the nonyl polymer compared to the Tg for the control. A corresponding systematic increase in Tg indicative of crosslinking, was observed for air cured films. Thermogravimetric analysis revealed a slight sacrifice in thermal stability with increasing alkyl length. No improvement in film toughness was observed

Generalized contact process with two symmetric absorbing states in two dimensions

We explore the two-dimensional generalized contact process with two absorbing states by means of large-scale Monte-Carlo simulations. In part of the phase diagram, an infinitesimal creation rate of active sites between inactive domains is sufficient to take the system from the inactive phase to the active phase. The system therefore displays two different nonequilibrium phase transitions. The critical behavior of the generic transition is compatible with the generalized voter (GV) universality class, implying that the symmetry-breaking and absorbing transitions coincide. In contrast, the transition at zero domain-boundary activation rate is not critical.Comment: 7 pages, 7 eps figures included, final version as publishe

An Economic Assessment of the Myanmar Rice Sector: Current Developments and Prospects

In this study, the Myanmar rice economy is described in the context of the current political situation and state of national economic development. The forces that are changing rice production and exports are identified; however, the rate of development involves a complex integration of government intervention and politics, as well as availability of resources. Probable scenarios for rice production and export are projected based on recent growth trends and expected infrastructure development. The Arkansas Global Rice Model is used to integrate the Myanmar rice sector with the global rice market in developing projections

A List of Wisconsin Springtails With New Records and Annotations (Hexapoda: Parainsecta: Collembola)

Twenty Collembola species new to Wisconsin were collected from soil at two agricultural sites in southern Wisconsin, including an undescribed species of Isotomidae. The state faunal list now contains 52 species representing seven families

Generating entanglement with low Q-factor microcavities

We propose a method of generating entanglement using single photons and electron spins in the regime of resonance scattering. The technique involves matching the spontaneous emission rate of the spin dipole transition in bulk dielectric to the modified rate of spontaneous emission of the dipole coupled to the fundamental mode of an optical microcavity. We call this regime resonance scattering where interference between the input photons and those scattered by the resonantly coupled dipole transition result in a reflectivity of zero. The contrast between this and the unit reflectivity when the cavity is empty allow us to perform a non demolition measurement of the spin and to non deterministically generate entanglement between photons and spins. The chief advantage of working in the regime of resonance scattering is that the required cavity quality factors are orders of magnitude lower than is required for strong coupling, or Purcell enhancement. This makes engineering a suitable cavity much easier particularly in materials such as diamond where etching high quality factor cavities remains a significant challenge

Chiral extrapolations for nucleon magnetic moments

Lattice QCD simulations have made significant progress in the calculation of nucleon electromagnetic form factors in the chiral regime in recent years. With simulation results achieving pion masses of order ~180 MeV, there is an apparent challenge as to how the physical regime is approached. By using contemporary methods in chiral effective field theory, both the quark-mass and finite-volume dependence of the isovector nucleon magnetic moment are carefully examined. The extrapolation to the physical point yields a result that is compatible with experiment, albeit with a combined statistical and systematic uncertainty of 10%. The extrapolation shows a strong finite-volume dependence; lattice sizes of L > 5 fm must be used to simulate results within 2% of the infinite-volume result for the magnetic moment at the physical pion mass.Comment: 7 pages, 12 figures, 1 tabl

Power Counting Regime of Chiral Effective Field Theory and Beyond

Chiral effective field theory complements numerical simulations of quantum chromodynamics (QCD) on a space-time lattice. It provides a model-independent formalism for connecting lattice simulation results at finite volume and a variety of quark masses to the physical world. The asymptotic nature of the chiral expansion places the focus on the first few terms of the expansion. Thus, knowledge of the power-counting regime (PCR) of chiral effective field theory, where higher-order terms of the expansion may be regarded as negligible, is as important as knowledge of the expansion itself. Through the consideration of a variety of renormalization schemes and associated parameters, techniques to identify the PCR where results are independent of the renormalization scheme are established. The nucleon mass is considered as a benchmark for illustrating this general approach. Because the PCR is small, the numerical simulation results are also examined to search for the possible presence of an intrinsic scale which may be used in a nonperturbative manner to describe lattice simulation results outside of the PCR. Positive results that improve on the current optimistic application of chiral perturbation theory beyond the PCR are reported.Comment: 18 pages, 55 figure