6,381 research outputs found
Competition, R&D, and the Cost of Innovation.
This paper proposes a model in the spirit of Aghion et al. (2005) that encompasses the magnitude of the impact of competition on R&D according to the cost of the innovation. The effect of competition on R&D is an inverted U-shape. However, the shape is flatter and competition policy is therefore less relevant for innovation when innovations are relatively costly. Intuitively, if innovations are costly for a firm, competitive shocks have to be significant to alter its innovation decisions. Empirical investigations using a unique panel dataset from the Banque de France show that an inverted U-shaped relationship can be clearly evidenced for the largest firms, but the curve becomes flatter when the relative cost of R&D increases. For large costs, the relationship even vanishes. Consequently, in sectors in which innovations are costly, policy changes have to be on a very large scale for an impact to be expected; at the extreme end, in certain sectors, the curve is so at that competition policy is not an appropriate tool for boosting the research effort of firms.Competition ; R&D ; Innovation.
Metastable helium molecules as tracers in superfluid liquid He
Metastable helium molecules generated in a discharge near a sharp tungsten
tip operated in either pulsed mode or continuous field-emission mode in
superfluid liquid He are imaged using a laser-induced-fluorescence
technique. By pulsing the tip, a small cloud of He molecules is
produced. At 2.0 K, the molecules in the liquid follow the motion of the normal
fluid. We can determine the normal-fluid velocity in a heat-induced counterflow
by tracing the position of a single molecule cloud. As we run the tip in
continuous field-emission mode, a normal-fluid jet from the tip is generated
and molecules are entrained in the jet. A focused 910 nm pump laser pulse is
used to drive a small group of molecules to the vibrational state.
Subsequent imaging of the tagged molecules with an expanded 925 nm probe
laser pulse allows us to measure the velocity of the normal fluid. The
techniques we developed demonstrate for the first time the ability to trace the
normal-fluid component in superfluid helium using angstrom-sized particles.Comment: 4 pages, 7 figures. Submitted to Phys. Rev. Let
Dynamics of Phase Transitions: The 3D 3-state Potts model
In studies of the QCD deconfining phase transition or cross-over by means of
heavy ion experiments, one ought to be concerned about non-equilibrium effects
due to heating and cooling of the system. In this paper we extend our previous
study of Glauber dynamics of 2D Potts models to the 3D 3-state Potts model,
which serves as an effective model for some QCD properties. We investigate the
linear theory of spinodal decomposition in some detail. It describes the early
time evolution of the 3D model under a quench from the disordered into the
ordered phase well, but fails in 2D. Further, the quench leads to competing
vacuum domains, which are difficult to equilibrate, even in the presence of a
small external magnetic field. From our hysteresis study we find, as before, a
dynamics dominated by spinodal decomposition. There is evidence that some
effects survive in the case of a cross-over. But the infinite volume
extrapolation is difficult to control, even with lattices as large as .Comment: 12 pages; added references, corrected typo
Calibration of liquid argon and neon detectors with
We report results from tests of Kr, as a calibration
source in liquid argon and liquid neon. Kr atoms are
produced in the decay of Rb, and a clear Kr
scintillation peak at 41.5 keV appears in both liquids when filling our
detector through a piece of zeolite coated with Rb. Based on this
scintillation peak, we observe 6.0 photoelectrons/keV in liquid argon with a
resolution of 6% (/E) and 3.0 photoelectrons/keV in liquid neon with a
resolution of 19% (/E). The observed peak intensity subsequently decays
with the Kr half-life after stopping the fill, and we
find evidence that the spatial location of Kr atoms in
the chamber can be resolved. Kr will be a useful
calibration source for liquid argon and neon dark matter and solar neutrino
detectors.Comment: 7 pages, 12 figure
Solvable Examples of Drift and Diffusion of Ions in Non-uniform Electric Fields
The drift and diffusion of a cloud of ions in a fluid are distorted by an
inhomogeneous electric field. If the electric field carries the center of the
distribution in a straight line and the field configuration is suitably
symmetric, the distortion can be calculated analytically. We examine the
specific examples of fields with cylindrical and spherical symmetry in detail
assuming the ion distributions to be of a generally Gaussian form. The effects
of differing diffusion coefficients in the transverse and longitudinal
directions are included
A 83Krm Source for Use in Low-background Liquid Xenon Time Projection Chambers
We report the testing of a charcoal-based Kr-83m source for use in
calibrating a low background two-phase liquid xenon detector. Kr-83m atoms
produced through the decay of Rb-83 are introduced into a xenon detector by
flowing xenon gas past the Rb-83 source. 9.4 keV and 32.1 keV transitions from
decaying 83Krm nuclei are detected through liquid xenon scintillation and
ionization. The characteristics of the Kr-83m source are analyzed and shown to
be appropriate for a low background liquid xenon detector. Introduction of
Kr-83m allows for quick, periodic calibration of low background noble liquid
detectors at low energy.Comment: Updated to version submitted to JINS
Surface-directed spinodal decomposition in the pseudobinary alloy (HfO_2)_x(SiO_2)_{1-x}
Hf silicate films (HfO_2)_{0.25}(SiO_2)_{0.75} with thicknesses in the range
4-20 nm were grown on silicon substrate by atomic layer deposition at 350
deg.C.The Hf distributions in as-grown and 800 deg.C annealed films were
investigated by high resolution transmission electron microscopy (HRTEM),
angle-resolved x-ray photoelectron spectroscopy (ARXPS) and medium energy ion
scattering (MEIS). HRTEM images show a layered structure in films thinner than
8 nm. The ARXPS data also reveal a non-uniform distribution of Hf throughout
the film depth. Diffusion of SiO_2 to the film surface after a longer time
anneal was observed by MEIS. All these observations provide evidence for
surface-directed spinodal decomposition in the pseudobinary
(HfO_2)_x(SiO_2)_{1-x} alloy system.Comment: 1o figures, one tabl
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