563 research outputs found
Why Environmental Liability Regimes in the United States, the European Community, and Japan Have Grown Synonymous With the Polluter Pays Principle
Significant concern about the harm to the environment caused by the disposal of hazardous wastes and detrimental materials abounds. In response, regulators around the globe have struggled to develop environmental liability regimes that effectively remediate contaminated sites. Regulators in the United States, the European Community, and Japan have addressed environmental contamination concerns by adopting the polluter pays principle as a core component of their domestic environmental liability regimes. The polluter pays principle demands that the polluter bear the burden of remediating the waste it generates. The impetus for adoption of the polluter pays principle in the United States, the European Community, and Japan is somewhat unclear. Certain sources and trends, however, have likely contributed to and informed the principle\u27s adoption. These sources include the prevalence of international treaties, the increasing availability of information concerning the environment, domestic and foreign laws that influence the conduct of other countries, nongovernmental organizations that exert pressure on regulatory bodies, bilateral and multilateral development institutions that condition their lending practices on the friendly treatment of the environment, and the growing standardization of environmental policies worldwide. This Note addresses these sources, and explores the manner in which they have influenced and encouraged the United States, the European Community, and Japan to embrace the polluter pays principle as an effective tool to achieve environmental waste remediation
AN ECONOMIC ANALYSIS OF GENETIC INFORMATION: LEPTIN GENOTYPING IN FED CATTLE
The use of genetic knowledge is widespread in crop production but is just recently being utilized in livestock production. This study investigates the economic value to feedlots of a polymorphism in the bovine leptin gene. Previous studies indicate that this polymorphism is associated with fat deposition. Since fed cattle are often priced on a grid that considers both yield and quality grades, fat deposition is an important factor in the value and profitability of fed cattle. Using data from 590 crossbred steers and heifers, we estimate growth curves for relevant biological traits, both with and without genotypic information. Using the resulting functions, we then simulate carcass traits to various days-on-feed and compute the associated profit under three price grids. Maximum profits are determined in an unconstrained profit maximization model and in a model that constrains cattle to be marketed in 45-head "potloads." Results indicate that leptin genotypic knowledge has little impact on optimal days-on-feed but may play a role in valuing feeder cattle. The differences in value of cattle varied by as much as $37 per head between genotypes.genetics, leptin genotype, beef cattle, value of information, Livestock Production/Industries,
Dark cloud cores and gravitational decoupling from turbulent flows
We test the hypothesis that the starless cores may be gravitationally bound
clouds supported largely by thermal pressure by comparing observed molecular
line spectra to theoretical spectra produced by a simulation that includes
hydrodynamics, radiative cooling, variable molecular abundance, and radiative
transfer in a simple one-dimensional model. The results suggest that the
starless cores can be divided into two categories: stable starless cores that
are in approximate equilibrium and will not evolve to form protostars, and
unstable pre-stellar cores that are proceeding toward gravitational collapse
and the formation of protostars. The starless cores might be formed from the
interstellar medium as objects at the lower end of the inertial cascade of
interstellar turbulence. Additionally, we identify a thermal instability in the
starless cores. Under par ticular conditions of density and mass, a core may be
unstable to expansion if the density is just above the critical density for the
collisional coupling of the gas and dust so that as the core expands the
gas-dust coupling that cools the gas is reduced and the gas warms, further
driving the expansion.Comment: Submitted to Ap
An Exploratory Look at Supermarket Shopping Paths
We present analyses of an extraordinary new dataset that reveals the path taken by individual shoppers in an actual grocery store, as provided by RFID (radio frequency identification) tags located on their shopping carts. The analysis is performed using a multivariate clustering algorithm not yet seen in the marketing literature that is able to handle data sets with unique (and numerous) spatial constraints. This allows us to take into account physical impediments (such as the location of aisles and other inaccessible areas of the store) to ensure that we only deal with feasible paths. We also recognize that time spent in the store plays an important role, leading to different cluster configurations for short, medium, and long trips. The resulting three sets of clusters identify a total of 14 canonical path types that are typical of grocery store travel, and we carefully describe (and cross-validate) each set of clusters These results dispel certain myths about shopper travel behavior that common intuition perpetuates, including behavior related to aisles, end-cap displays, and the racetrack. We briefly relate these results to previous research (using much more limited datasets) covering travel behavior in retails stores and other related settings
Inferring Quantum Network Topology using Local Measurements
Statistical correlations that can be generated across the nodes in a quantum
network depend crucially on its topology. However, this topological information
might not be known a priori, or it may need to be verified. In this paper, we
propose an efficient protocol for distinguishing and inferring the topology of
a quantum network. We leverage entropic quantities -- namely, the von Neumann
entropy and the measured mutual information -- as well as measurement
covariance to uniquely characterize the topology. We show that the entropic
quantities are sufficient to distinguish two networks that prepare GHZ states.
Moreover, if qubit measurements are available, both entropic quantities and
covariance can be used to infer the network topology. We show that the protocol
can be entirely robust to noise and can be implemented via quantum variational
optimization. Numerical experiments on both classical simulators and quantum
hardware show that covariance is generally more reliable for accurately and
efficiently inferring the topology, whereas entropy-based methods are often
better at identifying the absence of entanglement in the low-shot regime
Observations on the Formation of Massive Stars by Accretion
Observations of the H66a recombination line from the ionized gas in the
cluster of newly formed massive stars, G10.6-0.4, show that most of the
continuum emission derives from the dense gas in an ionized accretion flow that
forms an ionized disk or torus around a group of stars in the center of the
cluster. The inward motion observed in the accretion flow suggests that despite
the equivalent luminosity and ionizing radiation of several O stars, neither
radiation pressure nor thermal pressure has reversed the accretion flow. The
observations indicate why the radiation pressure of the stars and the thermal
pressure of the HII region are not effective in reversing the accretion flow.
The observed rate of the accretion flow, 0.001 solar masses/yr, is sufficient
to form massive stars within the time scale imposed by their short main
sequence lifetimes. A simple model of disk accretion relates quenched HII
regions, trapped hypercompact HII regions, and photo-evaporating disks in an
evolutionary sequence
Molecular Evolution in Collapsing Prestellar Cores
We have investigated the evolution and distribution of molecules in
collapsing prestellar cores via numerical chemical models, adopting the
Larson-Penston solution and its delayed analogues to study collapse. Molecular
abundances and distributions in a collapsing core are determined by the balance
among the dynamical, chemical and adsorption time scales. When the central
density n_H of a prestellar core with the Larson-Penston flow rises to 3 10^6
cm^{-3}, the CCS and CO column densities are calculated to show central holes
of radius 7000 AU and 4000 AU, respectively, while the column density of N2H+
is centrally peaked. These predictions are consistent with observations of
L1544. If the dynamical time scale of the core is larger than that of the
Larson-Penston solution owing to magnetic fields, rotation, or turbulence, the
column densities of CO and CCS are smaller, and their holes are larger than in
the Larson-Penston core with the same central gas density. On the other hand,
N2H+ and NH3 are more abundant in the more slowly collapsing core. Therefore,
molecular distributions can probe the collapse time scale of prestellar cores.
Deuterium fractionation has also been studied via numerical calculations. The
deuterium fraction in molecules increases as a core evolves and molecular
depletion onto grains proceeds. When the central density of the core is n_H=3
10^6 cm^{-3}, the ratio DCO+/HCO+ at the center is in the range 0.06-0.27,
depending on the collapse time scale and adsorption energy; this range is in
reasonable agreement with the observed value in L1544.Comment: 21 pages, 17 figure
Chromatographic identification and determination of organic acids in water
Reprinted from Analytical Chemistry, v.30, January, 1958.Bibliography: p. [44]
Oscillations of starless cores
If the split, asymmetric molecular spectral line profiles that are seen in
many starless cores are interpreted as indicative of global collapse or
expansion of the core then one possible implication is that most starless cores
have short lifetimes on the order of the collapse or sound crossing time scale.
An alternative interpretation of the line profiles as indicative of
perturbations on an underlying equilibrium structure leads to the opposite
implication, that many cores have long lifetimes. While evidence suggests that
some cores are collapsing on a free-fall time scale, we show that observations
of some other starless cores can be reproduced by a model of non-radial
oscillations about the equilibrium configuration of a pressure-bounded,
thermally-supported sphere (Bonnor-Ebert sphere). We model the oscillations as
linear perturbations following a standard analysis developed for stellar
pulsations and compare the column densities and molecular spectral line
profiles predicted from a particular model to observations of the Bok globule
B68.Comment: submitted to the Astrophysical Journa
Complete atrial-specific knockout of sodium-calcium exchange eliminates sinoatrial node pacemaker activity.
The origin of sinoatrial node (SAN) pacemaker activity in the heart is controversial. The leading candidates are diastolic depolarization by "funny" current (If) through HCN4 channels (the "Membrane Clock" hypothesis), depolarization by cardiac Na-Ca exchange (NCX1) in response to intracellular Ca cycling (the "Calcium Clock" hypothesis), and a combination of the two ("Coupled Clock"). To address this controversy, we used Cre/loxP technology to generate atrial-specific NCX1 KO mice. NCX1 protein was undetectable in KO atrial tissue, including the SAN. Surface ECG and intracardiac electrograms showed no atrial depolarization and a slow junctional escape rhythm in KO that responded appropriately to ÎČ-adrenergic and muscarinic stimulation. Although KO atria were quiescent they could be stimulated by external pacing suggesting that electrical coupling between cells remained intact. Despite normal electrophysiological properties of If in isolated patch clamped KO SAN cells, pacemaker activity was absent. Recurring Ca sparks were present in all KO SAN cells, suggesting that Ca cycling persists but is uncoupled from the sarcolemma. We conclude that NCX1 is required for normal pacemaker activity in murine SAN
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