15,985 research outputs found
The Impact of Multinational Entry on Domestic Market Structure and R&D
We model the impact of different modes of multinational entry on the choices of domestic firms. Focusing on the competitive effects of foreign presence in the host country we demonstrate that greenfield investment will increase competition only if it is not countered by anti-competitive reactions on the part of the domestic firms. Considering also cross-border mergers and acquisitions the model, thus, provides two alternative explanations for the increase in concentration ratios in industries with mostly horizontal foreign direct investment. Moreover, foreign presence is shown to raise total investment in the local industry at the cost of crowding out domestic R&D.greenfield investment, cross-border mergers and acquisitions, host-country effects, market
Productivity is higher among some service firms when broadband becomes available, but not all. ESRI Research Bulletin 2019/04
Using internet services over broadband connections may help some firms become more productive, generating more output from a given amount of labour and capital equipment. However, there is mixed evidence internationally about how large this benefit has been in practice and which types of firms are most likely to improve their productivity by using these technologies. In this research we examine the effects of broadband availability on the productivity of service sector firms.
Some previous studies using region- or country-level data have reported large productivity effects of broadband on services, but it is hard for this type of study to prove that broadband is making firms more productive. For example, their results might partly be explained by factors that both make firms more productive and more likely to use broadband, rather than a causal link from one to the other. Studies using data on firms have tended to find little evidence that there are broad-based gains from this source.2 Our research tries to unpack the service sector to see whether there are identifiable groups of firms that register significant productivity gains after broadband becomes available to them.
Knowing more about how large and focused these benefits are should help policymakers predict the likely effects of programmes to bring high-speed broadband to less well-served areas
Quark confinement and color transparency in a gauge-invariant formulation of QCD
We examine a nonlocal interaction that results from expressing the QCD
Hamiltonian entirely in terms of gauge-invariant quark and gluon fields. The
interaction couples one quark color-charge density to another, much as electric
charge densities are coupled to each other by the Coulomb interaction in QED.
In QCD, this nonlocal interaction also couples quark color-charge densities to
gluonic color. We show how the leading part of the interaction between quark
color-charge densities vanishes when the participating quarks are in a color
singlet configuration, and that, for singlet configurations, the residual
interaction weakens as the size of a packet of quarks shrinks. Because of this
effect, color-singlet packets of quarks should experience final state
interactions that increase in strength as these packets expand in size. For the
case of an SU(2) model of QCD based on the {\em ansatz} that the
gauge-invariant gauge field is a hedgehog configuration, we show how the
infinite series that represents the nonlocal interaction between quark
color-charge densities can be evaluated nonperturbatively, without expanding it
term-by-term. We discuss the implications of this model for QCD with SU(3)
color and a gauge-invariant gauge field determined by QCD dynamics.Comment: Revtex, 23 pages; contains additional references with brief comments
on sam
Carfentrazone-ethyl Pond Dissipation and Efficacy on Floating Plants
Carfentrazone-ethyl (CE) is a reduced risk herbicide that
is currently being evaluated for the control of aquatic weeds.
Greenhouse trials were conducted to determine efficacy of
CE on water hyacinth (
Eichhornia crassipes
(Mart.) Solms-
Laub.), water lettuce (
Pistia stratiotes
L.), salvinia (
Salvinia
minima
Baker) and landoltia
(Landoltia punctata
(G. Mey.)
Les & D. J. Crawford
)
. CE controlled water lettuce, water hyacinth
and salvinia at rates less than the maximum proposed
use rate of 224 g ha
-1
. Water lettuce was the most susceptible
to CE with an EC
90
of 26.9 and 33.0 g ha
-1
in two separate trials.
Water hyacinth EC
90
values were calculated to be 86.2 to
116.3 g ha
-1
, and salvinia had a similar susceptibility to water
hyacinth with an EC
90
of 79.1 g ha
-1
. Landoltia was not adequately
controlled at the rates evaluated. In addition, CE was
applied to one-half of a 0.08 ha pond located in North Central,
Florida to determine dissipation rates in water and hydrosoil
when applied at an equivalent rate of 224 g ha
-1
. The
half-life of CE plus the primary metabolite, CE-chloropropionic
acid, was calculated to be 83.0 h from the whole pond,
and no residues were detected in water above the limit of
quantification (5 μg L
-1
) 168 h after treatment. CE dissipated
rapidly from the water column, did not occur in the sediment
above the levels of quantification, and in greenhouse
studies effectively controlled three species of aquatic weeds
at relatively low rates.(PDF contains 6 pages.
Quantum Gauge Equivalence in QED
We discuss gauge transformations in QED coupled to a charged spinor field,
and examine whether we can gauge-transform the entire formulation of the theory
from one gauge to another, so that not only the gauge and spinor fields, but
also the forms of the operator-valued Hamiltonians are transformed. The
discussion includes the covariant gauge, in which the gauge condition and
Gauss's law are not primary constraints on operator-valued quantities; it also
includes the Coulomb gauge, and the spatial axial gauge, in which the
constraints are imposed on operator-valued fields by applying the
Dirac-Bergmann procedure. We show how to transform the covariant, Coulomb and
spatial axial gauges to what we call
``common form,'' in which all particle excitation modes have identical
properties. We also show that, once that common form has been reached, QED in
different gauges has a common time-evolution operator that defines
time-translation for states that represent systems of electrons and photons.
By combining gauge transformations with changes of representation from
standard to common form, the entire apparatus of a gauge theory can be
transformed from one gauge to another.Comment: Contribution for a special issue of Foundations of Physics honoring
Fritz Rohrlich; edited by Larry P. Horwitz, Tel-Aviv University, and Alwyn
van der Merwe, University of Denver (Plenum Publishing, New York); 40 pages,
REVTEX, Preprint UCONN-93-3, 1 figure available upon request from author
Precision Measurements of Stretching and Compression in Fluid Mixing
The mixing of an impurity into a flowing fluid is an important process in
many areas of science, including geophysical processes, chemical reactors, and
microfluidic devices. In some cases, for example periodic flows, the concepts
of nonlinear dynamics provide a deep theoretical basis for understanding
mixing. Unfortunately, the building blocks of this theory, i.e. the fixed
points and invariant manifolds of the associated Poincare map, have remained
inaccessible to direct experimental study, thus limiting the insight that could
be obtained. Using precision measurements of tracer particle trajectories in a
two-dimensional fluid flow producing chaotic mixing, we directly measure the
time-dependent stretching and compression fields. These quantities, previously
available only numerically, attain local maxima along lines coinciding with the
stable and unstable manifolds, thus revealing the dynamical structures that
control mixing. Contours or level sets of a passive impurity field are found to
be aligned parallel to the lines of large compression (unstable manifolds) at
each instant. This connection appears to persist as the onset of turbulence is
approached.Comment: 5 pages, 5 figure
Do Domestic Firms Benefit from Foreign Presence and Competition in Irish Services Sectors? ESRI WP395. July 2011
This paper examines whether domestic firms benefit from foreign competition through imports and from the presence of foreign-owned firms via spillovers in three Irish market-services sectors between 2001 and 2007. Import competition enhances the productivity of domestic firms in two out of three market-services sectors (transport and business activities). The effects from foreign presence are more varied. Foreign presence enhances the productivity of domestic firms in one sector (transport) when using standard output-based measures of productivity. After taking into account the degree of absorptive capacity of the domestic firms this spillover effect only accrues
to domestic non-importers. Using input-based measures of productivity, the paper points to adverse effects of foreign presence as it is associated with lower capital-labour ratios and higher part-time-to-full-time employee ratios among domestic firms in wholesale and retail trade
Supersonic STOVL ejector aircraft from a propulsion point of view
A baseline supersonic STOVL ejector aircraft, its propulsion and typical operating modes is described, and important propulsion parameters are identified. Then a number of propulsion system changes are evaluated for improvement of the lift-off performance aft deflection of the ejector jet and heating of the ejector primary air either by burning or using the hot engine core flow. The possibility for cooling the footprint is illustrated for mixing or interchanging the fan and core flows, and in use of a core flow ejector. The application of a new engine concept the turbine bypass engine plus a turbocompressor to supply the ejector primary air, and thrust during takeoff combat are presented
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