ASSET FIXITY, ASSET SPECIFICITY AND REGIONAL ECONOMIC CHANGE: HYPOTHESIS AND IMPLICATIONS

That asset specificity and asset fixity are impediments to economic adjustment is well understood in the literatures of industrial organization and agricultural economics. In this paper, we show that spatial factors can plausible be expected to be arguments in functions that define asset fixity and specificity and, hence, asset fixity may be systematically related to space. The implications with regard to differences across space in rates of adjustment to market signals suggest that the short run is longer in remote than in less remote places, which may prove useful in explaining the behavior of a spatial economic system during times of rapid technological change.Industrial Organization,

QED \otimes QCD Threshold Corrections at the LHC

We use the theory of YFS resummation to compute the size of the expected resummed soft radiative threshold effects in precision studies of heavy particle production at the LHC, where accuracies of 1 percent are desired in some processes. We find that the soft QED threshold effects are at the level of 0.3 percent whereas the soft QCD threshold effects enter at the level of 20 percent and hence both must be controlled to be on the conservative side to achieve such goals.Comment: 8 pages, no figures; improved text; improved refs. and tex

Extended Gas in Seyfert Galaxies: Near Infrared Observations of NGC 2110 and Circinus

We present results of near--IR long-slit spectroscopy in the J and K bands of the Seyfert 2 galaxies NGC 2110 and Circinus, investigating the gaseous distribution, excitation, reddening and kinematics. In NGC 2110, the emission line ratio [FeII]/Pa beta increases towards the nucleus (to ~ 7). The nuclear [Fe II]1.257 (microns) and Pa beta lines are broader (FWHM ~ 500 km/s) than the H2 (2.121) line (FWHM ~ 300 km/s). Both these results suggest that shocks, driven by the radio jet, are an important source of excitation of [Fe II]. The H2 excitation appears to be dominated by X-rays from the nucleus. In Circinus, both [FeII]/Pa beta and H2/Br gamma decrease from ~ 2 at 4 arcsec from the nucleus to nuclear values of ~ 0.6 and ~ 1, respectively, suggesting that the starburst dominates the nuclear excitation, while the AGN dominates the excitation further out (r > 2 arcsec). For both galaxies, the gaseous kinematics are consistent with circular rotation in the plane of the disk. Our rotation curves suggest that the nucleus (identified with the peak of the IR continuum) is displaced from the kinematic centre of the galaxies. This effect has been observed previously in NGC 2110 based on the kinematics of optical emission lines, but the displacement is smaller in the infrared, suggesting the effect is related to obscuration. The continuum J-K colours of the nuclear region indicate a red stellar population in NGC 2110 and a reddened young stellar population in Circinus. Right at the nucleus of both galaxies, the colours are redder, apparently a result of hot dust emission from the inner edge of a circumnuclear torus.Comment: 11 pages, 14 figures, accepted for publication in MNRA

The Virtual Correction to Bremsstrahlung in High-Energy e+ e- Annihilation: Comparison of Exact Results

We have compared the virtual corrections to single hard bremsstrahlung as calculated by S. Jadach, M. Melles, B.F.L. Ward and S.A. Yost to several other expressions. The most recent of these comparisons is to the leptonic tensor calculated by J.H. Kuhn and G. Rodrigo for radiative return. Agreement is found to within a part in 10^5 or better, as a fraction of the Born cross section, for most of the range of photon energies. The massless limits have been shown to agree analytically to NLL order.Comment: 7 pages, 2 figures. Presented by S.A. Yost at ICHEP 2004, International Conference on High Energy Physics, Beijing, August 16-22, 200

Field enhancement in subnanometer metallic gaps

Motivated by recent experiments [Ward et al., Nature Nanotech. 5, 732 (2010)], we present here a theoretical analysis of the optical response of sharp gold electrodes separated by a subnanometer gap. In particular, we have used classical finite difference time domain simulations to investigate the electric field distribution in these nanojunctions upon illumination. Our results show a strong confinement of the field within the gap region, resulting in a large enhancement compared to the incident field. Enhancement factors exceeding 1000 are found for interelectrode distances on the order of a few angstroms, which are fully compatible with the experimental findings. Such huge enhancements originate from the coupling of the incident light to the evanescent field of hybrid plasmons involving charge density oscillations in both electrodes.Comment: 4 pages, 3 figures, to appear in Physical Review

Task oriented nonlinear control laws for telerobotic assembly operations

The goal of this research is to achieve very intelligent telerobotic controllers which are capable of receiving high-level commands from the human operator and implementing them in an adaptive manner in the object/task/manipulator workspace. Initiatives by the authors at Integrated Systems, Inc. to identify and develop the key technologies necessary to create such a flexible, highly programmable, telerobotic controller are presented. The focus of the discussion is on the modeling of insertion tasks in three dimensions and nonlinear implicit force feedback control laws which incorporate tool/workspace constraints. Preliminary experiments with dual arm beam assembly in 2-D are presented

A comparison of operationally determined atmospheric densities from satellite orbit solutions and the exospheric temperature from the Jacchia-Roberts model

Operational orbit determination by the Flight Dynamics Division at the Goddard Space Flight Center has yielded a data base of orbit solutions covering the onset of solar cycle 22. Solutions for nine satellites include an estimated drag adjustment parameter (rho sub 1) determined by the Goddard Trajectory Determination System (GTDS). The rho sub 1 is used to evaluate correlations between density variations and changes in the following: 10.7-centimeter wavelength solar flux (F sub 10.7), the geomagnetic index A sub p, and two exospheric temperatures (T sub c and T sub infinity) adapted from the Jacchia-Roberts atmospheric density model in GTDS. T sub c depends on the daily and 81-day centered mean F sub 10.7; T sub infinity depends on T sub c and the geomagnetic index K sub p values. The highest correlations are between density and T sub infinity. Correlations with T sub c and F sub 10.7 are lower by 9 and 10 percent, respectively. For most cases, correlations with A sub p are considerably lower; however, significant correlations with A sub p were found for some high-inclination, moderate-altitude orbits. Results from this analysis enhance the understanding of the drag model and the accommodation of atmospheric density variations in the operational orbit determination support. The degree of correlation demonstrates the sensitivity of the orbit determination process to drag variations and to the input parameters that characterize aspects of the atmospheric density model. To this extent, the degree of correlation provides a measure of performance for methods of selecting or modeling the thermospheric densities using the solar F sub 10.7 and geomagnetic data as input to the process

Threshold Corrections in Precision LHC Physics: QED otimes QCD

With an eye toward LHC processes in which theoretical precisions of 1 percent are desired, we introduce the theory of the simultaneous YFS resummation of QED and QCD to compute the size of the expected resummed soft radiative threshold effects in precision studies of heavy particle production at the LHC. Our results show that both QED and QCD soft threshold effects must be controlled to be on the conservative side to achieve such precision goals.Comment: 4 pages, no figures; presented by B.F.L. Ward in DPF200