The Innovation Threshold

In this paper, we propose an economic model to analyse the sales out of new products. This model accounts for the fact that even among firms for which R&D is a permanent activity, a fraction of firms does not have sales of innovative products during a two-year observation period. We propose a model in which the fixed costs of introduction is a major concern in the decision making process. In a structural model we estimate the fixed costs of the market introduction of new products and explain subsequent sales of innovative products. We examine an indicator of innovative output, i.e. sales of products 'new to the firm'. We estimate fixed costs thresholds using data from the Dutch part of the Community Innovation Survey (CIS) from 1998. R&D intensity, competition and market structure have a positive impact on sales of new products. The most important factors to decrease the fixed costs threshold of introduction are product related R&D investments, R&D subsidies and knowledge spillovers.Innovation;Product R&D;Threshold model

Photon heat transport in low-dimensional nanostructures

At low temperatures when the phonon modes are effectively frozen, photon transport is the dominating mechanism of thermal relaxation in metallic systems. Starting from a microscopic many-body Hamiltonian, we develop a nonequilibrium Green's function method to study energy transport by photons in nanostructures. A formally exact expression for the energy current between a metallic island and a one-dimensional electromagnetic field is obtained. From this expression we derive the quantized thermal conductance as well as show how the results can be generalized to nonequilibrium situations. Generally, the frequency-dependent current noise of the island electrons determines the energy transfer rate.Comment: 4 pages, 3 Fig

Rectification of displacement currents in an adiabatic electron pump

Rectification of ac displacement currents generated by periodic variation of two independent gate voltages of a quantum dot can lead to a dc voltage linear in the frequency. The presence of this rectified displacement current could account for the magnetic field symmetry observed in a recent measurement on an adiabatic quantum electron pump by Switkes et al. [Science 283, 1905 (1999)].Comment: 2 pages, RevTeX; 1 figur

Endstates in multichannel spinless p-wave superconducting wires

Multimode spinless p-wave superconducting wires with a width W much smaller than the superconducting coherence length \xi are known to have multiple low-energy subgap states localized near the wire's ends. Here we compare the typical energies of such endstates for various terminations of the wire: A superconducting wire coupled to a normal-metal stub, a weakly disordered superconductor wire and a wire with smooth confinement. Depending on the termination, we find that the energies of the subgap states can be higher or lower than for the case of a rectangular wire with hard-wall boundaries.Comment: 10 pages, 7 figure

Third post-Newtonian accurate generalized quasi-Keplerian parametrization for compact binaries in eccentric orbits

We present Keplerian-type parametrization for the solution of third post-Newtonian (3PN) accurate equations of motion for two non-spinning compact objects moving in an eccentric orbit. The orbital elements of the parametrization are explicitly given in terms of the 3PN accurate conserved orbital energy and angular momentum in both Arnowitt, Deser, and Misner-type and harmonic coordinates. Our representation will be required to construct post-Newtonian accurate `ready to use' search templates for the detection of gravitational waves from compact binaries in inspiralling eccentric orbits. Due to the presence of certain 3PN accurate gauge invariant orbital elements, the parametrization should be useful to analyze the compatibility of general relativistic numerical simulations involving compact binaries with the corresponding post-Newtonian descriptions. If required, the present parametrization will also be needed to compute post-Newtonian corrections to the currently employed `timing formula' for the radio observations of relativistic binary pulsars.Comment: 33 pages, 1 figur

Intensity distribution of scalar waves propagating in random media

Transmission of the scalar field through the random medium, represented by the system of randomly distributed dielectric cylinders is calculated numerically. System is mapped to the problem of electronic transport in disordered two-dimensional systems. Universality of the statistical distribution of transmission parameters is analyzed in the metallic and in the localized regimes.In the metallic regime the universality of the transmission statistics in all transparent channels is observed. In the band gaps, we distinguish the disorder induced (Anderson) localization from the tunneling through the system due to the gap in the density of states. We show also that absorption causes rapid decrease of the mean conductance, but, contrary to the localized regime, the conductance is self-averaged with a Gaussian distribution

Changing with the tide: Semi-parametric estimation of preference dynamics

We contrast the discovered preference hypothesis against the theory of coherent arbitrariness in a split-sample stated choice experiment on flood-risk exposure. A semiparametric local multinomial logit model is developed as an alternative to the Swait and Louviere (1993) test procedure controlling for preference dynamics within and between samples. The proposed model supports the discovered preference hypothesis by means of a decaying starting point bias. The Swait and Louviere (1993) test procedure reaches a different conclusion. It rejects the assumption of stable preferences, but most preference dynamics tend to be smoothed out, causing a more erratic pattern of preference dynamics

Considerations on the feasibility of a directed fishery for Panga pterogymnus laniarius (Pisces: sparidae)

Recent assessments of the status of the panga Pterogymnus laniarius stock on the Agulhas Bank, South Africa, showed that catches could be sustained at considerably higher levels than those harvested at present. Although the stock could be successfully harvested using available fishing methods, the sympatry of this species with other commercial species, such as shallow-water Cape hake Merluccius capensis, Cape horse mackerel Trachurus trachurus capensis and other deep-reef species was of concern, because these species would form a significant bycatch in a panga-directed fishery. These findings highlight the problems of bycatch management and emphasize the need for creativity by both scientists and fishers in designing new and improved methods for selectively exploiting bycatch fish resources

The Finite Field Kakeya Problem

A Besicovitch set in AG(n,q) is a set of points containing a line in every direction. The Kakeya problem is to determine the minimal size of such a set. We solve the Kakeya problem in the plane, and substantially improve the known bounds for n greater than 4.Comment: 13 page