Identities in the Superintegrable Chiral Potts Model

We present proofs for a number of identities that are needed to study the superintegrable chiral Potts model in the $Q\ne0$ sector.Comment: LaTeX 2E document, using iopart.cls with iopams packages. 11 pages, uses eufb10 and eurm10 fonts. Typeset twice! vs2: Two equations added. vs3: Introduction adde

Impedance of a sphere oscillating in an elastic medium with and without slip

The dynamic impedance of a sphere oscillating in an elastic medium is considered. Oestreicher's formula for the impedance of a sphere bonded to the surrounding medium can be expressed simply in terms of three lumped impedances associated with the displaced mass and the longitudinal and transverse waves. If the surface of the sphere slips while the normal velocity remains continuous, the impedance formula is modified by adjusting the definition of the transverse impedance to include the interfacial impedance.Comment: 10 pages, 2 figure

Computing stationary free-surface shapes in microfluidics

A finite-element algorithm for computing free-surface flows driven by arbitrary body forces is presented. The algorithm is primarily designed for the microfluidic parameter range where (i) the Reynolds number is small and (ii) force-driven pressure and flow fields compete with the surface tension for the shape of a stationary free surface. The free surface shape is represented by the boundaries of finite elements that move according to the stress applied by the adjacent fluid. Additionally, the surface tends to minimize its free energy and by that adapts its curvature to balance the normal stress at the surface. The numerical approach consists of the iteration of two alternating steps: The solution of a fluidic problem in a prescribed domain with slip boundary conditions at the free surface and a consecutive update of the domain driven by the previously determined pressure and velocity fields. ...Comment: Revised versio

Diffusion, Fragmentation and Coagulation Processes: Analytical and Numerical Results

We formulate dynamical rate equations for physical processes driven by a combination of diffusive growth, size fragmentation and fragment coagulation. Initially, we consider processes where coagulation is absent. In this case we solve the rate equation exactly leading to size distributions of Bessel type which fall off as $\exp(-x^{3/2})$ for large $x$-values. Moreover, we provide explicit formulas for the expansion coefficients in terms of Airy functions. Introducing the coagulation term, the full non-linear model is mapped exactly onto a Riccati equation that enables us to derive various asymptotic solutions for the distribution function. In particular, we find a standard exponential decay, $\exp(-x)$, for large $x$, and observe a crossover from the Bessel function for intermediate values of $x$. These findings are checked by numerical simulations and we find perfect agreement between the theoretical predictions and numerical results.Comment: (28 pages, 6 figures, v2+v3 minor corrections

A note on leapfrogging vortex rings

In this paper we provide examples, by numerical simulation using the Navier-Stokes equations for axisymmetric laminar flow, of the 'leapfrogging' motion of two, initially identical, vortex rings which share a common axis of symmetry. We show that the number of clear passes that each ring makes through the other increases with Reynolds number, and that as long as the configuration remains stable the two rings ultimately merge to form a single vortex ring

Radiotherapy: Impact of quality of life and need for psychological care: Results of a longitudinal study

Background: In the framework of a prospective longitudinal study, the quality of life (QoL) and support requirements of patients from a university hospital department of radiotherapy were evaluated for the first time by means of established psychodiagnostic questionnaires. Patients and Methods: At first, 732 patients were screened, of whom 446 (60.9%) fulfilled the criteria for inclusion; 39.1% did not (refusals 21.0%, low Karnofsky performance status 6.6%, management problems 3.4%, language barriers 3.0%, cognitive restrictions 2.6%, death 2.5%). Disease-specific aspects of QoL (Functional Assessment of Cancer Treatment - General, FACT-G) and moderating variables {[}Social Support Scale (SSS), Disease Coping (FKV), Self-Assessment Depression Scale (SDS), and Self-Defined Care Requirements (BB)] were self-rated by patients with different tumor types before radiotherapy (T1), after radiotherapy (T2), and 6 weeks after the end of radiotherapy (T3). We studied 265 patients (157 male, 108 female; median age 58.6 years) with complete data of three time points. Results: In general, QoL of patients decreased significantly over all time points in all subscales. Social support was rated high and remained constant throughout the treatment. Apparent coping mechanisms were active problem-oriented coping, leisure activities, and self-support. The patients' depression proved to be an important and constant factor without significant changes. The support requirement is characterized by the need for more medical information and dialogue with a physician. Conclusions: Early specific support from personnel with radiotherapeutic skills, during the disease-coping process as well as during rehabilitation, should be a permanent component of an integrated radiooncological treatment schedule

Temperature dependence of nonlinear auto-oscillator linewidths: Application to spin-torque nano-oscillators

The temperature dependence of the generation linewidth for an auto-oscillator with a nonlinear frequency shift is calculated. It is shown that the frequency nonlinearity creates a finite correlation time, tau, for the phase fluctuations. In the low-temperature limit in which the spectral linewidth is smaller than 1/tau, the line shape is approximately Lorentzian and the linewidth is linear in temperature. In the opposite high-temperature limit in which the linewidth is larger than 1/tau, the nonlinearity leads to an apparent "inhomogeneous broadening" of the line, which becomes Gaussian in shape and has a square-root dependence on temperature. The results are illustrated for the spin-torque nano-oscillator.Comment: 4 pages, 1 figur

Turbulent Mixing in the Surface Layers of Accreting Neutron Stars

During accretion a neutron star (NS) is spun up as angular momentum is transported through its surface layers. We study the resulting differentially rotating profile, focusing on the impact this has for type I X-ray bursts. The predominant viscosity is likely provided by the Tayler-Spruit dynamo. The radial and azimuthal magnetic field components have strengths of ~10^5 G and ~10^10 G, respectively. This leads to nearly uniform rotation at the depths of interest for X-ray bursts. A remaining small shear transmits the accreted angular momentum inward to the NS interior. Though this shear gives little viscous heating, it can trigger turbulent mixing. Detailed simulations will be required to fully understand the consequences of mixing, but our models illustrate some general features. Mixing has the greatest impact when the buoyancy at the compositional discontinuity between accreted matter and ashes is overcome. This occurs at high accretion rates, at low spin frequencies, or may depend on the ashes from the previous burst. We then find two new regimes of burning. The first is ignition in a layer containing a mixture of heavier elements from the ashes. If ignition occurs at the base of the mixed layer, recurrence times as short as ~5-30 minutes are possible. This may explain the short recurrence time of some bursts, but incomplete burning is still needed to explain these bursts' energetics. When mixing is sufficiently strong, a second regime is found where accreted helium mixes deep enough to burn stably, quenching X-ray bursts. We speculate that the observed change in X-ray burst properties near one-tenth the Eddington accretion rate is from this mechanism. The carbon-rich material produced by stable helium burning would be important for triggering and fueling superbursts. (abridged)Comment: Accepted for publication in The Astrophysical Journal, 16 pages, 15 figure

Competition in Electricity Spot Markets. Economic Theory and International Experience.

The main purpose of this survey paper is to consider the attempts that have been ,ade to apply economic theory snd empirical methods to the analysis of electricity markets, and to evaluate them in light of theoretical considerations and empirical evidence. We describe the key features of the markets in England and Wales, Norway and Australia in order to allow for a comparison of design issues and evaluation of competitive performance