7,156 research outputs found
Voluntary Environmental Agreements when Regulatory Capacity Is Weak
Voluntary agreements (VAs) negotiated between environmental regulators and industry are increasingly popular. However, little is known about whether they are likely to be effective in developing and transition countries, where local and federal environmental regulatory capacity is typically weak. We develop a dynamic theoretical model to examine the effect of VAs on investment in regulatory infrastructure and pollution abatement in such countries. We find that under certain conditions, VAs can improve welfare by generating more private-sector investment in pollution control and more public-sector investment in regulatory capacity than the status quo.voluntary environmental regulation, developing country
Does Disclosure Reduce Pollution? Evidence from India's Green Rating Project
Public disclosure programs that collect and disseminate information about firms’ environmental performance are increasingly popular in both developed and developing countries. Yet little is known about whether they actually improve environmental performance, particularly in the latter setting. We use detailed plant-level survey data to evaluate the impact of India’s Green Rating Project (GRP) on the environmental performance of the country’s largest pulp and paper plants. We find that the GRP drove significant reductions in pollution loadings among dirty plants but not among cleaner ones. This result comports with statistical and anecdotal evaluations of similar disclosure programs. We also find that plants located in wealthier communities were more responsive to GRP ratings, as were single-plant firms.public disclosure, pollution control, India, pulp and paper
The Magnetic Properties of Heating Events on High-Temperature Active Region Loops
Understanding the relationship between the magnetic field and coronal heating
is one of the central problems of solar physics. However, studies of the
magnetic properties of impulsively heated loops have been rare. We present
results from a study of 34 evolving coronal loops observed in the Fe XVIII line
component of AIA/SDO 94 A filter images from three active regions with
different magnetic conditions. We show that the peak intensity per unit
cross-section of the loops depends on their individual magnetic and geometric
properties. The intensity scales proportionally to the average field strength
along the loop () and inversely with the loop length () for a
combined dependence of . These loop properties are
inferred from magnetic extrapolations of the photospheric HMI/SDO line-of-sight
and vector magnetic field in three approximations: potential and two Non Linear
Force-Free (NLFF) methods. Through hydrodynamic modeling (EBTEL model) we show
that this behavior is compatible with impulsively heated loops with a
volumetric heating rate that scales as .Comment: Astrophysical Journal, in pres
Crystallization of the Wahnstr\"om Binary Lennard-Jones Liquid
We report observation of crystallization of the glass-forming binary
Lennard-Jones liquid first used by Wahnstr\"om [G. Wahnstr\"om, Phys. Rev. A
44, 3752 (1991)]. Molecular dynamics simulations of the metastable liquid on a
timescale of microseconds were performed. The liquid crystallized
spontaneously. The crystal structure was identified as MgZn_2. Formation of
transient crystallites is observed in the liquid. The crystallization is
investigate at different temperatures and compositions. At high temperature the
rate of crystallite formation is the limiting factor, while at low temperature
the limiting factor is growth rate. The melting temperature of the crystal is
estimated to be T_m=0.93 at rho=0.82. The maximum crystallization rate of the
A_2B composition is T=0.60+/-0.02.Comment: 4 pages, 4 figures; corrected typo
Herschel dust emission as a probe of starless cores mass: MCLD 123.5+24.9 of the Polaris Flare
We present newly processed archival Herschel images of molecular cloud MCLD
123.5+24.9 in the Polaris Flare. This cloud contains five starless cores. Using
the spectral synthesis code Cloudy, we explore uncertainties in the derivation
of column densities, hence, masses of molecular cores from Herschel data. We
first consider several detailed grain models that predict far-IR grain
opacities. Opacities predicted by the models differ by more than a factor of
two, leading to uncertainties in derived column densities by the same factor.
Then we consider uncertainties associated with the modified blackbody fitting
process used by observers to estimate column densities. For high column density
clouds (N(H) 10 cm), this fitting technique can
underestimate column densities by about a factor of three. Finally, we consider
the virial stability of the five starless cores in MCLD 123.5+24.9. All of
these cores appear to have strongly sub-virial masses, assuming, as we argue,
that CO line data provide reliable estimates of velocity dispersions.
Evidently, they are not self-gravitating, so it is no surprise that they are
starless.Comment: ApJ, Accepted. Minor typographical errors corrected and figures 6 & 7
updated in v
Exponential distributions of collective flow-event properties in viscous liquid dynamics
We study the statistics of flow events in the inherent dynamics in
supercooled two- and three-dimensional binary Lennard-Jones liquids.
Distributions of changes of the collective quantities energy, pressure and
shear stress become exponential at low temperatures, as does that of the event
"size" . We show how the -distribution controls the
others, while itself following from exponential tails in the distributions of
(1) single particle displacements , involving a Lindemann-like length
and (2) the number of active particles (with ).Comment: Accepter version (PRL
Strong pressure-energy correlations in liquids as a configuration space property: Simulations of temperature down jumps and crystallization
Computer simulations recently revealed that several liquids exhibit strong
correlations between virial and potential energy equilibrium fluctuations in
the NVT ensemble [U. R. Pedersen {\it et al.}, Phys. Rev. Lett. {\bf 100},
015701 (2008)]. In order to investigate whether these correlations are present
also far from equilibrium constant-volume aging following a temperature down
jump from equilibrium was simulated for two strongly correlating liquids, an
asymmetric dumbbell model and Lewis-Wahnstr{\"o}m OTP, as well as for SPC water
that is not strongly correlating. For the two strongly correlating liquids
virial and potential energy follow each other closely during the aging towards
equilibrium. For SPC water, on the other hand, virial and potential energy vary
with little correlation as the system ages towards equilibrium. Further proof
that strong pressure-energy correlations express a configuration space property
comes from monitoring pressure and energy during the crystallization (reported
here for the first time) of supercooled Lewis-Wahnstr{\"o}m OTP at constant
temperature
Synthetic metabolons for metabolic engineering.
Journal ArticleResearch Support, Non-U.S. Gov'tReviewThis is a pre-copyedited, author-produced PDF of an article accepted for publication in Journal of Experimental Botany following peer review. The definitive publisher-authenticated version J. Exp. Bot. (2014) 65 (8) pp. 1947-1954 is available online at: http://jxb.oxfordjournals.org/content/65/8/1947It has been proposed that enzymes can associate into complexes (metabolons) that increase the efficiency of metabolic pathways by channelling substrates between enzymes. Metabolons may increase flux by increasing the local concentration of intermediates, decreasing the concentration of enzymes needed to maintain a given flux, directing the products of a pathway to a specific subcellular location or minimizing the escape of reactive intermediates. Metabolons can be formed by relatively loose non-covalent protein-protein interaction, anchorage to membranes, and (in bacteria) by encapsulation of enzymes in protein-coated microcompartments. Evidence that non-coated metabolons are effective at channelling substrates is scarce and difficult to obtain. In plants there is strong evidence that small proportions of glycolytic enzymes are associated with the outside of mitochondria and are effective in substrate channelling. More recently, synthetic metabolons, in which enzymes are scaffolded to synthetic proteins or nucleic acids, have been expressed in microorganisms and these provide evidence that scaffolded enzymes are more effective than free enzymes for metabolic engineering. This provides experimental evidence that metabolons may have a general advantage and opens the way to improving the outcome of metabolic engineering in plants by including synthetic metabolons in the toolbox
Towards a Quantitative Comparison of Magnetic Field Extrapolations and Observed Coronal Loops
It is widely believed that loops observed in the solar atmosphere trace out
magnetic field lines. However, the degree to which magnetic field
extrapolations yield field lines that actually do follow loops has yet to be
studied systematically. In this paper we apply three different extrapolation
techniques - a simple potential model, a NLFF model based on photospheric
vector data, and a NLFF model based on forward fitting magnetic sources with
vertical currents - to 15 active regions that span a wide range of magnetic
conditions. We use a distance metric to assess how well each of these models is
able to match field lines to the 12,202 loops traced in coronal images. These
distances are typically 1-2". We also compute the misalignment angle between
each traced loop and the local magnetic field vector, and find values of
5-12. We find that the NLFF models generally outperform the potential
extrapolation on these metrics, although the differences between the different
extrapolations are relatively small. The methodology that we employ for this
study suggests a number of ways that both the extrapolations and loop
identification can be improved.Comment: Accepted for publication in Ap
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