Nonequilibrium steady states of driven magnetic flux lines in disordered type-II superconductors

We investigate driven magnetic flux lines in layered type-II superconductors subject to various configurations of strong point or columnar pinning centers by means of a three-dimensional elastic line model and Metropolis Monte Carlo simulations. We characterize the resulting nonequilibrium steady states by means of the force-velocity / current-voltage curve, static structure factor, mean vortex radius of gyration, number of double-kink and half-loop excitations, and velocity / voltage noise spectrum. We compare the results for the above observables for randomly distributed point and columnar defects, and demonstrate that the three-dimensional flux line structures and their fluctuations lead to a remarkable variety of complex phenomena in the steady-state transport properties of bulk superconductors.Comment: 23 pages, IOP style, 18 figures include

Impact of new technology on timber harvesting costs: Evaluation methods and literature

Timber harvesting and transport are crucial components of the cost of delivered wood to forest products processing facilities. In fact, harvesting and delivering wood often costs more than the entire costs of growing wood until harvest. As such, timber harvesting research and development are important. Additionally, research in this area is worthwhile because efficiency gains, cost improvements, and environmental benefits due to timber harvesting research can be realized in a very short time period, rather than the decades-long wait required for research investments in timber growing. This paper provides an overview of the means of measuring the impact of new technology on timber harvesting costs. In recent years, there have been many efforts to increase research for developing better harvesting equipment and methods. In conjunction with these efforts, greater demands have been made for research efficiency and accountability (Silversides et al. 1988); several studies have therefore been completed to measure the impacts of timber harvesting research and development. These studies, other means of evaluating timber harvesting research, and suggestions for future evaluations are discussed

Costs and cost trends for forestry practices in the South

Cost estimates of practicing forestry in the South during 1986 and cost changes during the 1952-1986 period are presented in this report. Albert C. Worrell reported the original cost study in Forest Farmer in May 1953. His work was updated by James G. Yoho and Robert B. Fish in the November 1961 issue of Forest Farmer. Other revisions include James G. Yoho, George F . Dutrow, and James Moak (Forest Farmer, 1971); James Moak and Jim Kucera (Forest Farmer, 1975); James Moak, James Kucera, and W.F. Watson (Forest Farmer Manual, 1977); James Moak, W.F. Watson, and Paul Van Deusen (Forest Farmer Manual, 1980); James Moak, W.F. Watson, and Mark Watson (Forest Farmer Manual, 1983); and Thomas J. Straka and William F . Watson (Forest Farmer Manual, 1985). The present study is based on the results of a survey completed in 1986 and reports current costs for most forestry practices covered by previous surveys. It also provides tables with cost changes from 1952 to 1986 for\u27 specific commercial practices common in the South

It pays to know how your timber will be valued

You as a forest farmer can usually realize income from your timber investment in two ways. You can rent timberland for nontimber uses (usually hunting) , or you can lease or sell your interest in the timber. In most cases, greater returns result from selling timber outright

Primer on forestry investment

Most forest farmers know that growing timber is a good investment. Some forest farmers, however, and many new timberland investors may not fully understand the basic ingredients that make up a forestry investment. Like other ventures, forest farming involves costs and revenues, and rates of return can be calculated. These rates can be compared with interest rates for other investments, but forest farming is not exactly like your other investments. It has special qualities

Kinematic dynamo action in a sphere: Effects of periodic time-dependent flows on solutions with axial dipole symmetry

Choosing a simple class of flows, with characteristics that may be present in the Earth's core, we study the ability to generate a magnetic field when the flow is permitted to oscillate periodically in time. The flow characteristics are parameterised by D, representing a differential rotation, M, a meridional circulation, and C, a component characterising convective rolls. Dynamo action is sensitive to these flow parameters and fails spectacularly for much of the parameter space where magnetic flux is concentrated into small regions. Oscillations of the flow are introduced by varying the flow parameters in time, defining a closed orbit in the space (D,M). Time-dependence appears to smooth out flux concentrations, often enhancing dynamo action. Dynamo action can be impaired, however, when flux concentrations of opposite signs occur close together as smoothing destroys the flux by cancellation. It is possible to produce geomagnetic-type reversals by making the orbit stray into a region where the steady flows generate oscillatory fields. In this case, however, dynamo action was not found to be enhanced by the time-dependence. A novel approach is taken to solving the time-dependent eigenvalue problem, where by combining Floquet theory with a matrix-free Krylov-subspace method we avoid large memory requirements for storing the matrix required by the standard approach.Comment: 22 pages, 12 figures. Geophys. Astrophys. Fluid Dynam., as accepted (2004

Monoclonal antibodies against human astrocytomas and their reactivity pattern

The establishment of hybridomas after fusion of X63-Ag8.653 mouse myeloma cells and splenocytes from mice hyperimmunized against human astrocytomas is presented. The animals were primed with 5 × 106 chemically modified uncultured or cultured glioma cells. Six weeks after the last immunization step an intrasplenal booster injection was administrated and 3 days later the spleen cells were prepared for fusion experiments. According to the specificity analysis of the generated antibodies 7 hybridoma products (MUC 7-22, MUC 8-22, MUC 10-22, MUC 11-22, MUC 14-22, MUC 15-22 and MUC 2-63) react with gliomas, neuroblastomas and melanomas as well as with embryonic and fetal cells but do not recognize non-neurogenic tumors. The selected monoclonal antibodies (McAbs) of IgG1 and IgG2a isotypes are not extensively characterized but these antibodies have been demonstrated to be reactive with a panel of glioma cell lines with varying patterns of antigen distribution. Using the McAbs described above and a series of cryosections of glioma biopsies and paraffin sections of the same material as well as glioma cultures established from these, variable antigenic profiles among glioma cell populations could be demonstrated. From these results it is evident that there is not only a distinct degree of antigenic heterogeneity among and within brain tumors, but also that the pattern of antigenic expression can change continuously. Some of the glioma associated antigens recognized by the selected antibodies persist after fixation with methanol/acetone and Karnovsky's fixative and probably are oncoembryonic/oncofetal antigen(s). The data suggest that the use of McAbs recognizing tumor associated oncofetal antigens in immunohistochemistry facilitates objective typing of intracranial malignancies and precise analysis of fine needle brain/tumor biopsies in a sensitive and reproducible manner

Remarks on the stability of the Navier-Stokes equations supplemented with stress-free boundary conditions

The purpose of this note is to analyze the long term stability of the Navier-Stokes equations supplemented with the Coriolis force and the stress-free boundary condition. It is shown that, if the flow domain is axisymmetric, spurious stability behaviors can occur depending whether the Coriolis force is active or not