17,338 research outputs found
How foreign firms achieve competitive advantage in the Chinese emerging economy: Managerial ties and market orientation
As China experience unprecedented changes in its social, legal, and economic institutions, on what should foreign firms focus more to overcome this challenge, managerial ties or market orientation? This study investigates how managerial ties and market orientation affect competitive advantage and, consequently, firm performance in China. On the basis of a survey of 179 foreign firms in China, we find that both managerial ties and market orientation can lead to firm success-but in different ways. Market orientation enhances firm performance by providing differentiation and cost advantages, whereas managerial ties improve performance through an institutional advantage (i.e., superiority in securing scarce resources and institutional support). Institutional advantage, in turn, leads to differentiation and cost advantages and consequently superior performance. © 2009 Elsevier Inc.postprin
When Can You Trust ‘Trust'? Calculative Trust, Relational Trust, and Supplier Performance
Our research empirically assesses two distinct bases for trust: calculative trust, based on a structure of rewards and penalties, versus relational trust, a judgment anchored in past behavior and characterized by a shared identity. We find that calculative trust and relational trust positively influence supplier performance, with calculative trust having a stronger association than relational trust. Yet, important boundary conditions exist. If buyers invest in supplier-specific assets or when supply side market uncertainty is high, relational trust, not calculative trust, is more strongly associated with supplier performance. In contrast, when behavioral uncertainty is high, calculative trust, not relational trust, relates more strongly to supplier performance. These results highlight the value of examining distinct forms of trust. Copyright © 2015 John Wiley & Sons, Ltd.postprin
Multi-Objective Big Data Optimization with jMetal and Spark
Big Data Optimization is the term used to refer to optimization problems which have to manage very large amounts of data. In this paper, we focus on the parallelization of metaheuristics with the Apache Spark cluster computing system for solving multi-objective Big Data Optimization problems. Our purpose is to study the influence of accessing data stored in the Hadoop File System (HDFS) in each evaluation step of a metaheuristic and to provide a software tool to solve these kinds of problems. This tool combines the jMetal multi-objective optimization framework with Apache Spark. We have carried out experiments to measure the performance of the proposed parallel infrastructure in an environment based on virtual machines in a local cluster comprising up to 100 cores. We obtained interesting results for computational e ort and propose guidelines to face multi-objective Big Data Optimization
problems.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
An adaptive technique for content-based image retrieval
We discuss an adaptive approach towards Content-Based Image Retrieval. It is based on the Ostensive Model of developing information needs—a special kind of relevance feedback model that learns from implicit user feedback and adds a temporal notion to relevance. The ostensive approach supports content-assisted browsing through visualising the interaction by adding user-selected images to a browsing path, which ends with a set of system recommendations. The suggestions are based on an adaptive query learning scheme, in which the query is learnt from previously selected images. Our approach is an adaptation of the original Ostensive Model based on textual features only, to include content-based features to characterise images. In the proposed scheme textual and colour features are combined using the Dempster-Shafer theory of evidence combination. Results from a user-centred, work-task oriented evaluation show that the ostensive interface is preferred over a traditional interface with manual query facilities. This is due to its ability to adapt to the user's need, its intuitiveness and the fluid way in which it operates. Studying and comparing the nature of the underlying information need, it emerges that our approach elicits changes in the user's need based on the interaction, and is successful in adapting the retrieval to match the changes. In addition, a preliminary study of the retrieval performance of the ostensive relevance feedback scheme shows that it can outperform a standard relevance feedback strategy in terms of image recall in category search
Controlling spin relaxation with a cavity
Spontaneous emission of radiation is one of the fundamental mechanisms by
which an excited quantum system returns to equilibrium. For spins, however,
spontaneous emission is generally negligible compared to other non-radiative
relaxation processes because of the weak coupling between the magnetic dipole
and the electromagnetic field. In 1946, Purcell realized that the spontaneous
emission rate can be strongly enhanced by placing the quantum system in a
resonant cavity -an effect which has since been used extensively to control the
lifetime of atoms and semiconducting heterostructures coupled to microwave or
optical cavities, underpinning single-photon sources. Here we report the first
application of these ideas to spins in solids. By coupling donor spins in
silicon to a superconducting microwave cavity of high quality factor and small
mode volume, we reach for the first time the regime where spontaneous emission
constitutes the dominant spin relaxation mechanism. The relaxation rate is
increased by three orders of magnitude when the spins are tuned to the cavity
resonance, showing that energy relaxation can be engineered and controlled
on-demand. Our results provide a novel and general way to initialise spin
systems into their ground state, with applications in magnetic resonance and
quantum information processing. They also demonstrate that, contrary to popular
belief, the coupling between the magnetic dipole of a spin and the
electromagnetic field can be enhanced up to the point where quantum
fluctuations have a dramatic effect on the spin dynamics; as such our work
represents an important step towards the coherent magnetic coupling of
individual spins to microwave photons.Comment: 8 pages, 6 figures, 1 tabl
Anisotropic Impurity-States, Quasiparticle Scattering and Nematic Transport in Underdoped Ca(Fe1-xCox)2As2
Iron-based high temperature superconductivity develops when the `parent'
antiferromagnetic/orthorhombic phase is suppressed, typically by introduction
of dopant atoms. But their impact on atomic-scale electronic structure, while
in theory quite complex, is unknown experimentally. What is known is that a
strong transport anisotropy with its resistivity maximum along the crystal
b-axis, develops with increasing concentration of dopant atoms; this
`nematicity' vanishes when the `parent' phase disappears near the maximum
superconducting Tc. The interplay between the electronic structure surrounding
each dopant atom, quasiparticle scattering therefrom, and the transport
nematicity has therefore become a pivotal focus of research into these
materials. Here, by directly visualizing the atomic-scale electronic structure,
we show that substituting Co for Fe atoms in underdoped Ca(Fe1-xCox)2As2
generates a dense population of identical anisotropic impurity states. Each is
~8 Fe-Fe unit cells in length, and all are distributed randomly but aligned
with the antiferromagnetic a-axis. By imaging their surrounding interference
patterns, we further demonstrate that these impurity states scatter
quasiparticles in a highly anisotropic manner, with the maximum scattering rate
concentrated along the b-axis. These data provide direct support for the recent
proposals that it is primarily anisotropic scattering by dopant-induced
impurity states that generates the transport nematicity; they also yield simple
explanations for the enhancement of the nematicity proportional to the dopant
density and for the occurrence of the highest resistivity along the b-axis
Common carp (Cyprinus carpio L.) alters its feeding niche in response to changing food resources: direct observations in simulated ponds
We used customized fish tanks as model fish ponds to observe grazing, swimming, and conspecific social behavior of common carp (Cyprinus carpio) under variable food-resource conditions to assess alterations in feeding niche. Different food and feeding situations were created by using only pond water or pond water plus pond bottom sediment or pond water plus pond bottom sediment and artificial feeding. All tanks were fertilized twice, prior to stocking and 2 weeks later after starting the experiment to stimulate natural food production. Common carp preferred artificial feed over benthic macroinvertebrates, followed by zooplankton. Common carp did not prefer any group of phytoplankton in any treatment. Common carp was mainly benthic in habitat choice, feeding on benthic macroinvertebrates when only plankton and benthic macroinvertebrates were available in the system. In the absence of benthic macroinvertebrates, their feeding niche shifted from near the bottom of the tanks to the water column where they spent 85% of the total time and fed principally on zooplankton. Common carp readily switched to artificial feed when available, which led to better growth. Common carp preferred to graze individually. Behavioral observations of common carp in tanks yielded new information that assists our understanding of their ecological niche. This knowledge could be potentially used to further the development of common carp aquaculture
Activation of Human Stearoyl-Coenzyme A Desaturase 1 Contributes to the Lipogenic Effect of PXR in HepG2 Cells
The pregnane X receptor (PXR) was previously known as a xenobiotic receptor. Several recent studies suggested that PXR also played an important role in lipid homeostasis but the underlying mechanism remains to be clearly defined. In this study, we found that rifampicin, an agonist of human PXR, induced lipid accumulation in HepG2 cells. Lipid analysis showed the total cholesterol level increased. However, the free cholesterol and triglyceride levels were not changed. Treatment of HepG2 cells with rifampicin induced the expression of the free fatty acid transporter CD36 and ABCG1, as well as several lipogenic enzymes, including stearoyl-CoA desaturase-1 (SCD1), long chain free fatty acid elongase (FAE), and lecithin-cholesterol acyltransferase (LCAT), while the expression of acyl:cholesterol acetyltransferase(ACAT1) was not affected. Moreover, in PXR over-expressing HepG2 cells (HepG2-PXR), the SCD1 expression was significantly higher than in HepG2-Vector cells, even in the absence of rifampicin. Down-regulation of PXR by shRNA abolished the rifampicin-induced SCD1 gene expression in HepG2 cells. Promoter analysis showed that the human SCD1 gene promoter is activated by PXR and a novel DR-7 type PXR response element (PXRE) response element was located at -338 bp of the SCD1 gene promoter. Taken together, these results indicated that PXR activation promoted lipid synthesis in HepG2 cells and SCD1 is a novel PXR target gene. © 2013 Zhang et al
The J-triplet Cooper pairing with magnetic dipolar interactions
Recently, cold atomic Fermi gases with the large magnetic dipolar interaction
have been laser cooled down to quantum degeneracy. Different from
electric-dipoles which are classic vectors, atomic magnetic dipoles are
quantum-mechanical matrix operators proportional to the hyperfine-spin of
atoms, thus provide rich opportunities to investigate exotic many-body physics.
Furthermore, unlike anisotropic electric dipolar gases, unpolarized magnetic
dipolar systems are isotropic under simultaneous spin-orbit rotation. These
features give rise to a robust mechanism for a novel pairing symmetry: orbital
p-wave (L=1) spin triplet (S=1) pairing with total angular momentum of the
Cooper pair J=1. This pairing is markedly different from both the He-B
phase in which J=0 and the He- phase in which is not conserved. It
is also different from the p-wave pairing in the single-component electric
dipolar systems in which the spin degree of freedom is frozen
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