2,577 research outputs found
A Research Note on Multinationality and Firm Performance: Nonparametric Frontier Analysis
This study provides a fresh insight into the examination of the comparison between multinationality and firm performance, measured through technical efficiency levels by overcoming methodological constraints and misunderstandings presented in earlier research. We estimate firmsâ efficiency levels in a production function-type framework through technical efficiency levels using nonparametric data envelopment analysis (DEA). We include firms from both developed and developing economies, from different national origins and with different sectoral characteristics, with a particular focus on knowledge-intensive business services (KIBS) and capital-intensive business services (CIBS). The study confirms for the case of KIBS the existence of the three-stage sigmoid (S-shaped) hypothesis between multinationality and firm performance measured through technical efficiency levels. Finally, the empirical findings reveal that CIBS exhibit only the first two stages, thus forming a âUâ-shape relationship. We propose the application of different firmsâ performance measurements, providing us with the ability to unpack a firmsâ managerial decision processes with regards to determining the optimised investment(s) in technology and research and development and with a particular focus on knowledge-intensive business services (KIBS) and capital-intensive business services (CIBS)
A new nanocrystalline diamond-based biosensor for the detection of cardiovascular risk markers
In this paper, a new method to probe associative interactions of C-reactive protein (CRP) antigen with CRP antibody immobilized on a gold-interdigitated diamond electrodes was investigated. The CRP antigen detection was performed by capacitive/dielectric-constant measurements. Our results showed that the dynamic detection range using optimized conditions for a given antibody concentration (100 ÎŒg/ml) was found to be in the range 25-800 ng/ml of CRP-antigen. Biosensor developed in this study can be potentially used for detection of elevated CRP levels in suspected subjects for early diagnosis
Production of Li, Be \& B from Baryon Inhomogeneous Primordial Nucleosynthesis
We investigate the possibility that inhomogeneous nucleosynthesis may
eventually be used to explain the abundances of \li6, \be9 and B in population
II stars. The present work differs from previous studies in that we have used a
more extensive reaction network. It is demonstrated that in the simplest
scenario the abundances of the light elements with constrain the
separation of inhomogeneities to sufficiently small scales that the model is
indistinguishable from homogeneous nucleosynthesis and that the abundances of
\li6, \be9\ and B are then below observations by several orders of magnitude.
This conclusion does not depend on the \li7 constraint. We also examine
alternative scenarios which involve a post-nucleosynthesis reprocessing of the
light elements to reproduce the observed abundances of Li and B, while allowing
for a somewhat higher baryon density (still well below the cosmological
critical density). Future B/H measurements may be able to exclude even this
exotic scenario and further restrict primordial nucleosynthesis to approach the
homogeneous model conclusions.Comment: 18 pages; Plain TeX; UMN-TH-1131/9
Accurate structure factors from pseudopotential methods
Highly accurate experimental structure factors of silicon are available in
the literature, and these provide the ideal test for any \emph{ab initio}
method for the construction of the all-electron charge density. In a recent
paper [J. R. Trail and D. M. Bird, Phys. Rev. B {\bf 60}, 7863 (1999)] a method
has been developed for obtaining an accurate all-electron charge density from a
first principles pseudopotential calculation by reconstructing the core region
of an atom of choice. Here this method is applied to bulk silicon, and
structure factors are derived and compared with experimental and Full-potential
Linear Augmented Plane Wave results (FLAPW). We also compare with the result of
assuming the core region is spherically symmetric, and with the result of
constructing a charge density from the pseudo-valence density + frozen core
electrons. Neither of these approximations provide accurate charge densities.
The aspherical reconstruction is found to be as accurate as FLAPW results, and
reproduces the residual error between the FLAPW and experimental results.Comment: 6 Pages, 3 figure
Effects of rapid prey evolution on predator-prey cycles
We study the qualitative properties of population cycles in a predator-prey
system where genetic variability allows contemporary rapid evolution of the
prey. Previous numerical studies have found that prey evolution in response to
changing predation risk can have major quantitative and qualitative effects on
predator-prey cycles, including: (i) large increases in cycle period, (ii)
changes in phase relations (so that predator and prey are cycling exactly out
of phase, rather than the classical quarter-period phase lag), and (iii)
"cryptic" cycles in which total prey density remains nearly constant while
predator density and prey traits cycle. Here we focus on a chemostat model
motivated by our experimental system [Fussmann et al. 2000,Yoshida et al. 2003]
with algae (prey) and rotifers (predators), in which the prey exhibit rapid
evolution in their level of defense against predation. We show that the effects
of rapid prey evolution are robust and general, and furthermore that they occur
in a specific but biologically relevant region of parameter space: when traits
that greatly reduce predation risk are relatively cheap (in terms of reductions
in other fitness components), when there is coexistence between the two prey
types and the predator, and when the interaction between predators and
undefended prey alone would produce cycles. Because defense has been shown to
be inexpensive, even cost-free, in a number of systems [Andersson and Levin
1999, Gagneux et al. 2006,Yoshida et al. 2004], our discoveries may well be
reproduced in other model systems, and in nature. Finally, some of our key
results are extended to a general model in which functional forms for the
predation rate and prey birth rate are not specified.Comment: 35 pages, 8 figure
Powerful Radio-Loud Quasars are Triggered by Galaxy Mergers in the Cosmic Bright Ages
While supermassive black holes are ubiquitous features of galactic nuclei,
only a small minority are observed during episodes of luminous accretion. The
physical mechanism(s) driving the onset of fueling and ignition in these active
galactic nuclei (AGN) are still largely unknown for many galaxies and
AGN-selection criteria. Attention has focused on AGN triggering by means of
major galaxy mergers gravitationally funneling gas towards the galactic center,
with evidence both for and against this scenario. However, several recent
studies have found that radio-loud AGN overwhelmingly reside in ongoing or
recent major galaxy mergers. In this study, we test the hypothesis that major
galaxy mergers are important triggers for radio-loud AGN activity in powerful
quasars during cosmic noon (1 < z < 2). To this end, we compare Hubble Space
Telescope WFC3/IR observations of the z > 1 3CR radio-loud broad-lined quasars
to three matched radio-quiet quasar control samples. We find strong evidence
for major-merger activity in nearly all radio-loud AGN, in contrast to the much
lower merger fraction in the radio-quiet AGN. These results suggest major
galaxy mergers are key ingredients to launching powerful radio jets. Given many
of our radio-loud quasars are blue, our results present a possible challenge to
the "blow-out" paradigm of galaxy evolution models in which blue quasars are
the quiescent end result following a period of red quasar feedback initiated by
a galaxy merger. Finally, we find a tight correlation between black hole mass
and host galaxy luminosity for these different high-redshift AGN samples
inconsistent with those observed for local elliptical galaxies.Comment: Published by Ap
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Universal detection of foot and mouth disease virus based on the conserved VP0 protein
Background: Foot and mouth disease virus (FMDV), a member of the picornaviridae that causes vesicular disease in ungulates, has seven serotypes and a large number of strains, making universal detection challenging. The mature virion is made up of 4 structural proteins, virus protein (VP) 1 â VP4, VP1-VP3 of which form the outer surface of the particle and VP4 largely contained within. Prior to mature virion formation VP2 and VP4 occur together as VP0, a structural component of the pre-capsid which, as a result of containing the internal VP4 sequence, is relatively conserved among all strains and serotypes. Detection of VP0 might therefore represent a universal virus marker.
Methods: FMDV virus protein 0 (VP0) was expressed in bacteria as a SUMO fusion protein and the SUMO carrier removed by site specific proteolysis. Rabbit polyvalent sera were generated to the isolated VP0 protein and their reactivity characterised by a number of immunoassays and by epitope mapping on peptide arrays.
Results: The specific VP0 serum recognised a variety of FMDV serotypes, as virus and as virus-like-particles, by a variety of assay formats. Epitope mapping showed the predominant epitopes to occur within the unstructured but highly conserved region of the sequence shared among many serotypes. When immunogold stained VLPs were assessed by TEM analysis they revealed exposure of epitopes on the surface of some particles, consistent with particle breathing hitherto reported for some other picornaviruses but not for FMDV.
Conclusion: A polyvalent serum based on the VP0 protein of FMDV represents a broadly reactive reagent capable of detection of many if not all FMDV isolates. The suggestion of particle breathing obtained with this serum suggests a reconsideration of the FMDV entry mechanism
Approximate k-state solutions to the Dirac-Yukawa problem based on the spin and pseudospin symmetry
Using an approximation scheme to deal with the centrifugal
(pseudo-centrifugal) term, we solve the Dirac equation with the screened
Coulomb (Yukawa) potential for any arbitrary spin-orbit quantum number
{\kappa}. Based on the spin and pseudospin symmetry, analytic bound state
energy spectrum formulas and their corresponding upper- and lower-spinor
components of two Dirac particles are obtained using a shortcut of the
Nikiforov-Uvarov method. We find a wide range of permissible values for the
spin symmetry constant C_{s} from the valence energy spectrum of particle and
also for pseudospin symmetry constant C_{ps} from the hole energy spectrum of
antiparticle. Further, we show that the present potential interaction becomes
less (more) attractive for a long (short) range screening parameter {\alpha}.
To remove the degeneracies in energy levels we consider the spin and pseudospin
solution of Dirac equation for Yukawa potential plus a centrifugal-like term. A
few special cases such as the exact spin (pseudospin) symmetry Dirac-Yukawa,
the Yukawa plus centrifugal-like potentials, the limit when {\alpha} becomes
zero (Coulomb potential field) and the non-relativistic limit of our solution
are studied. The nonrelativistic solutions are compared with those obtained by
other methods.Comment: 21 pages, 6 figure
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