7,121 research outputs found
Managing animal health status information in the cattle market
The paper analyses the problem of information in the cattle market, particularly as it relates to the status of animal health, and discusses ways to limit it with the view to improving social surplus. Against this background, it aims to achieve three major objectives. Firstly, it describes the ways of improving the level of information through such schemes as Conventional Warranties and Third Party Certification and the different choices made by sellers and buyers in the presence of these schemes. Secondly, it studies the various ways by which these schemes make an impact on equilibria in different markets (i.e., the pooling market and the premium market), and, consequently, on the social surplus. Thirdly, it identifies the necessary conditions for a third party/public decision-maker to increase social surplus and reduce the negative externality caused by disease by managing and supporting Third Party Certification. The paper shows that product certification and product warranty cannot coexist because product warranty is suboptimal. It also shows that certification, and a possible supporting of certification or animal testing does not necessarily improve the safety of the trade.Asymmetric information, Third-Party certification, Disease Externalities, Livestock Production/Industries,
Decoherence suppression via environment preparation
To protect a quantum system from decoherence due to interaction with its
environment, we investigate the existence of initial states of the environment
allowing for decoherence-free evolution of the system. For models in which a
two-state system interacts with a dynamical environment, we prove that such
states exist if and only if the interaction and self-evolution Hamiltonians
share an eigenstate. If decoherence by state preparation is not possible, we
show that initial states minimizing decoherence result from a delicate
compromise between the environment and interaction dynamics.Comment: 4 pages, 2 figure
One-Way Quantum Computing in the Optical Frequency Comb
One-way quantum computing allows any quantum algorithm to be implemented
easily using just measurements. The difficult part is creating the universal
resource, a cluster state, on which the measurements are made. We propose a
radically new approach: a scalable method that uses a single, multimode optical
parametric oscillator (OPO). The method is very efficient and generates a
continuous-variable cluster state, universal for quantum computation, with
quantum information encoded in the quadratures of the optical frequency comb of
the OPO.Comment: v2: changed author order; 4 pages, 3 figures; supplemental movie
available at http://faculty.virginia.edu/quantum/torus.mo
Accelerating relativistic reference frames in Minkowski space-time
We study accelerating relativistic reference frames in Minkowski space-time
under the harmonic gauge. It is well-known that the harmonic gauge imposes
constraints on the components of the metric tensor and also on the functional
form of admissible coordinate transformations. These two sets of constraints
are equivalent and represent the dual nature of the harmonic gauge. We explore
this duality and show that the harmonic gauge allows presenting an accelerated
metric in an elegant form that depends only on two harmonic potentials. It also
allows reconstruction of the spatial structure of the post-Galilean coordinate
transformation functions relating inertial and accelerating frames. The
remaining temporal dependence of these functions together with corresponding
equations of motion are determined from dynamical conditions, obtained by
constructing the relativistic proper reference frame of an accelerated test
particle. In this frame, the effect of external forces acting on the observer
is balanced by the fictitious frame-reaction force that is needed to keep the
test particle at rest with respect to the frame, conserving its relativistic
linear momentum. We find that this approach is sufficient to determine all the
terms of the coordinate transformation. The same method is then used to develop
the inverse transformations. The resulting post-Galilean coordinate
transformations extend the Poincar\'e group on the case of accelerating
observers. We present and discuss the resulting coordinate transformations,
relativistic equations of motion, and the structure of the metric tensors
corresponding to the relativistic reference frames involved.Comment: revtex4, 21 page
Molecular and Ionic shocks in the Supernova Remnant 3C391
New observations of the supernova remnant 3C391 are in the H2 2.12 micron and
[Fe II] 1.64 micron narrow-band filters at the Palomar 200-inch telescope, and
in the 5-15 micron CVF on ISOCAM. Shocked H2 emission was detected from the
region 3C391:BML, where broad millimeter CO and CS lines had previously been
detected. A new H2 clump was confirmed to have broad CO emission, demonstrating
that the near-infrared H2 images can trace previously undetected molecular
shocks. The [Fe II] emission has a significantly different distribution, being
brightest in the bright radio bar, at the interface between the supernova
remnant and the giant molecular cloud, and following filaments in the radio
shell. The near-infrared [Fe II] and the mid-infrared 12-18 micron filter
images are the first images to reveal the radiative shell of 3C391. The
mid-infrared spectrum is dominated by bright ionic lines and H2 S(2) through
S(7). There are no aromatic hydrocarbons associated with the shocks, nor is
their any mid-infrared continuum, suggesting that macromolecules and very small
grains are destroyed. Comparing 3C391 to the better-studied IC443, both
remnants have molecular- and ionic-dominated regions; for 3C391, the
ionic-dominated region is the interface into the giant molecular cloud, showing
that the main bodies of giant molecular clouds contain significant regions with
densities 100 to 1000/cm^3 and a small filling factor with higher-density. The
molecular shocked region resolves into 16 clumps of H2 emission, with some
fainter diffuse emission but with no associated near-infrared continuum
sources. One of the clumps is coincident with a previously-detected OH 1720 MHz
maser. These clumps are interpreted as a cluster of pre-stellar, dense
molecular cores that are presently being shocked by the supernova blast wave
The Initial-Boundary Value Problem in General Relativity
In this article we summarize what is known about the initial-boundary value
problem for general relativity and discuss present problems related to it.Comment: 11 pages, 2 figures. Contribution to a special volume for Mario
Castagnino's seventy fifth birthda
Conformational flexibility influences structure–function relationships in tyrosyl protein sulfotransferase-2
Tyrosine sulfation is a very important posttranslational modification of proteins. It is catalyzed by tyrosylprotein sulfotransferase and recently became increasingly important for biomedicine and pharmacy. An important insight about structure–activity relationships of human tyrosylprotein sulfotransferase has been received by elucidating the crystal structure, but there is still no understanding about how conformational flexibility and dynamics which are fundamental protein properties influence structure–function relationships of the enzyme. In order to provide this missing but crucially important knowledge we performed a comprehensive atomistic molecular dynamics study which revealed that (i) the conformational flexibility influences sensitively key structural determinants and interactions between the enzyme, the substrate and the cofactor; (ii) a more open conformation adopted by the substrate for binding in TPST 2; (iii) the mutations of key residues related with catalysis and binding change alter the enzyme structure and influence important interactions between the enzyme, the cofactor and the substrate
Detection of Gravitational Lensing in the Cosmic Microwave Background
Gravitational lensing of the cosmic microwave background (CMB), a
long-standing prediction of the standard cosmolgical model, is ultimately
expected to be an important source of cosmological information, but first
detection has not been achieved to date. We report a 3.4 sigma detection, by
applying quadratic estimator techniques to all sky maps from the Wilkinson
Microwave Anisotropy Probe (WMAP) satellite, and correlating the result with
radio galaxy counts from the NRAO VLA Sky Survey (NVSS). We present our
methodology including a detailed discussion of potential contaminants. Our
error estimates include systematic uncertainties from density gradients in
NVSS, beam effects in WMAP, Galactic microwave foregrounds, resolved and
unresolved CMB point sources, and the thermal Sunyaev-Zeldovich effect.Comment: 27 pages, 20 figure
Extraction of coherent structures in a rotating turbulent flow experiment
The discrete wavelet packet transform (DWPT) and discrete wavelet transform
(DWT) are used to extract and study the dynamics of coherent structures in a
turbulent rotating fluid. Three-dimensional (3D) turbulence is generated by
strong pumping through tubes at the bottom of a rotating tank (48.4 cm high,
39.4 cm diameter). This flow evolves toward two-dimensional (2D) turbulence
with increasing height in the tank. Particle Image Velocimetry (PIV)
measurements on the quasi-2D flow reveal many long-lived coherent vortices with
a wide range of sizes. The vorticity fields exhibit vortex birth, merger,
scattering, and destruction. We separate the flow into a low-entropy
``coherent'' and a high-entropy ``incoherent'' component by thresholding the
coefficients of the DWPT and DWT of the vorticity fields. Similar thresholdings
using the Fourier transform and JPEG compression together with the Okubo-Weiss
criterion are also tested for comparison. We find that the DWPT and DWT yield
similar results and are much more efficient at representing the total flow than
a Fourier-based method. Only about 3% of the large-amplitude coefficients of
the DWPT and DWT are necessary to represent the coherent component and preserve
the vorticity probability density function, transport properties, and spatial
and temporal correlations. The remaining small amplitude coefficients represent
the incoherent component, which has near Gaussian vorticity PDF, contains no
coherent structures, rapidly loses correlation in time, and does not contribute
significantly to the transport properties of the flow. This suggests that one
can describe and simulate such turbulent flow using a relatively small number
of wavelet or wavelet packet modes.Comment: experimental work aprox 17 pages, 11 figures, accepted to appear in
PRE, last few figures appear at the end. clarifications, added references,
fixed typo
Precise calculation of transition frequencies of hydrogen and deuterium based on a least-squares analysis
We combine a limited number of accurately measured transition frequencies in
hydrogen and deuterium, recent quantum electrodynamics (QED) calculations, and,
as an essential additional ingredient, a generalized least-squares analysis, to
obtain precise and optimal predictions for hydrogen and deuterium transition
frequencies. Some of the predicted transition frequencies have relative
uncertainties more than an order of magnitude smaller than that of the g-factor
of the electron, which was previously the most accurate prediction of QED.Comment: 4 pages, RevTe
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