11,254 research outputs found
Epidemiological Baseline of Influenza Virus in Wild Aquatic Birds in Hong Kong during the Pre-H5N1 Endemic Era
Influenza virus surveillance was conducted on wild ducks and shorebirds in Hong Kong at the Mai Po Nature Reserve to determine whether East Asian wild aquatic birds passing through or overwintering in Hong Kong are reservoirs of H5N1 influenza viruses and to establish an epidemiological baseline of influenza virus in wild aquatic birds during the pre-H5N1 endemic era. Three influenza viruses were isolated from 3178 faecal samples collected over three sampling periods from 1988 to 2001 during the southern and northern migration periods. The isolation rates and viruses were, respectively 0.08% (H10N5) in 1988 – 1990, 0.12% (H11N1) in 1998 and 0.09% (H3N8) in 1999 – 2001. Whereas tracheal and intestinal colon explants from representative shorebirds were susceptible to in vitro infection by the H10N5 virus, orally infected shorebirds were apparently not. Genetic analyses indicated that the nucleoprotein, matrix and nonstructural genes of the three viruses were related to those of aquatic bird viruses in Asia, but not to those of the human H5N1 virus. The present study provided epidemiological baseline information for future influenza virus surveillance in wild aquatic birds in southeast China
Coherence and Decoherence in Biological Systems: Principles of Noise Assisted Transport and the Origin of Long-lived Coherences
The quantum dynamics of transport networks in the presence of noisy
environments have recently received renewed attention with the discovery of
long-lived coherences in different photosynthetic complexes. This experimental
evidence has raised two fundamental questions: Firstly, what are the mechanisms
supporting long-lived coherences and secondly, how can we assess the possible
functional role that the interplay of noise and quantum coherence might play in
the seemingly optimal operation of biological systems under natural conditions?
Here we review recent results, illuminate them at the hand of two paradigmatic
systems, the Fenna-Matthew-Olson (FMO) complex and the light harvesting complex
LHII, and present new progress on both questions. In particular we introduce
the concept of the phonon antennae and discuss the possible microscopic origin
or long-lived electronic coherences.Comment: Paper delivered at the Royal Society Discussion Meeting
"Quantum-coherent energy transfer: implications for biology and new energy
technologies", 27 - 28 April 2011 at The Kavli Royal Society International
Centre, Buckinghamshire, UK. Accepted for publication in Philosophical
Transactions of the Royal Society
Experimental and analytical investigation of the variation of spray characteristics along a radial distance downstream of a pressure-swirl atomizer
The variation of spray characteristics along a radial distance downstream of a pressure-swirl atomizer was measured by laser light-scattering technology. An analytical model was developed to predict the variation of spray characteristics along the radial distance. A comparison of the predicted and experimental data showed excellent agreement. Therefore, the spray model proposed, although relatively simple, is correct and can be used, with some expansion and modification of the prepared model, to predict more complicated spray systems
Strategic Trade Policy in Bargaining over Managerial Delegation Competition
In this paper, we assess the influence of the generalized Nash bargaining model on strategic trade policies. In particular, how the trade policy and the bargaining process over managerial contract are strategically connected within the context of bargaining over the sales delegation model is analyzed. We explore the policy impacts in two different models: the export rivalry model and the import-competing model, and show that the introduction of managers' bargaining process leads to a decrease in the export subsidy and optimal tariff in different models.Bargaining Delegation
Privatization and the Environment in a Mixed Duopoly with Pollution Abatement
The purpose of this note is to re-examine whether privatization improves the environment or not in a mixed duopolistic model. In our model, both firms adopt pollution abatement technologies in response to the environmental tax imposed by the government. It is shown that privatization unambiguously reduces the pollution levels of firms. Namely, privatization does improve the environment. Moreover, by implementing partial-privatization policy, social welfare can be enhanced.Environmental Taxes; Mixed Oligopoly: Privatization
Surface location of sodium atoms attached to He-3 nanodroplets
We have experimentally studied the electronic excitation of
Na atoms attached to He droplets by means of laser-induced fluorescence as
well as beam depletion spectroscopy. From the similarities of the spectra
(width/shift of absorption lines) with these of Na on He droplets, we
conclude that sodium atoms reside in a ``dimple'' on the droplet surface. The
experimental results are supported by Density Functional calculations at zero
temperature, which confirm the surface location of sodium on He droplets,
and provide a microscopic description of the ``dimple'' structure.Comment: 4 pages, 5 figure
Phase-dependent exciton transport and energy harvesting from thermal environments
Non-Markovian effects in the evolution of open quantum systems have recently
attracted widespread interest, particularly in the context of assessing the
efficiency of energy and charge transfer in nanoscale biomolecular networks and
quantum technologies. With the aid of many-body simulation methods, we uncover
and analyse an ultrafast environmental process that causes energy relaxation in
the reduced system to depend explicitly on the phase relation of the initial
state preparation. Remarkably, for particular phases and system parameters, the
net energy flow is uphill, transiently violating the principle of detailed
balance, and implying that energy is spontaneously taken up from the
environment. A theoretical analysis reveals that non-secular contributions,
significant only within the environmental correlation time, underlie this
effect. This suggests that environmental energy harvesting will be observable
across a wide range of coupled quantum systems.Comment: 5 + 4 pages, 3 + 2 figures. Comments welcom
Highly efficient energy excitation transfer in light-harvesting complexes: The fundamental role of noise-assisted transport
Excitation transfer through interacting systems plays an important role in
many areas of physics, chemistry, and biology. The uncontrollable interaction
of the transmission network with a noisy environment is usually assumed to
deteriorate its transport capacity, especially so when the system is
fundamentally quantum mechanical. Here we identify key mechanisms through which
noise such as dephasing, perhaps counter intuitively, may actually aid
transport through a dissipative network by opening up additional pathways for
excitation transfer. We show that these are processes that lead to the
inhibition of destructive interference and exploitation of line broadening
effects. We illustrate how these mechanisms operate on a fully connected
network by developing a powerful analytical technique that identifies the
invariant (excitation trapping) subspaces of a given Hamiltonian. Finally, we
show how these principles can explain the remarkable efficiency and robustness
of excitation energy transfer from the light-harvesting chlorosomes to the
bacterial reaction center in photosynthetic complexes and present a numerical
analysis of excitation transport across the Fenna-Matthew-Olson (FMO) complex
together with a brief analysis of its entanglement properties. Our results show
that, in general, it is the careful interplay of quantum mechanical features
and the unavoidable environmental noise that will lead to an optimal system
performance.Comment: 16 pages, 9 figures; See Video Abstract at
http://www.quantiki.org/video_abstracts/09014454 . New revised version;
discussion of entanglement properties enhance
- âŠ