581 research outputs found
On Bayesian and non-Bayesian estimation of a two-level CES production function for the Dutch manufacturing sector
In this paper maximum-likelihood estimates of the parameters of the two-level CES function, obtained by direct estimation of this function, are given. In addition the authors propose to show how a Bayesian analysis may help to find a solution to the difficulties related with, but not specific to, this particular estimation problem. It is shown that numerical integration of the posterior distribution may give an indication as to which parameter has to be pinpointed and at which value when multi-collinearity precludes unconditional maximization of the likelihood. It is suspected that this approach has a wider field of application
Trade liberalization and the allocation over domestic and foreign supplies: a case study for Spanish manufacturing
The purpose of the present paper is to investigate whether Spain's accession
to the European Union in 1986 caused a structural break in the allocation of total supplies of manufactures over domestic and foreign supplies. To that end we use the homogeneity-constrained Almost Ideal Demand System to
specify the long-run equilibrium relationships between the shares in total supplies and total real demand and relative prices and a first-order error correction mechanism in order to describe the adjustment process to equilibrium. Using a formal statistical test, it turns out that a
structural break actually occurred and led to a rather sharp decrease in the share of Spain and an increase in the shares of the other members of the European Union
Divergent effects of urban particulate air pollution on allergic airway responses in experimental asthma: a comparison of field exposure studies
Abstract
Background
Increases in ambient particulate matter of aerodynamic diameter of 2.5 μm (PM2.5) are associated with asthma morbidity and mortality. The overall objective of this study was to test the hypothesis that PM2.5 derived from two distinct urban U.S. communities would induce variable responses to aggravate airway symptoms during experimental asthma.
Methods
We used a mobile laboratory to conduct community-based inhalation exposures to laboratory rats with ovalbumin-induced allergic airways disease. In Grand Rapids exposures were conducted within 60 m of a major roadway, whereas the Detroit was located in an industrial area more than 400 m from roadways. Immediately after nasal allergen challenge, Brown Norway rats were exposed by whole body inhalation to either concentrated air particles (CAPs) or filtered air for 8 h (7:00 AM - 3:00 PM). Both ambient and concentrated PM2.5 was assessed for mass, size fractionation, and major component analyses, and trace element content. Sixteen hours after exposures, bronchoalveolar lavage fluid (BALF) and lung lobes were collected and evaluated for airway inflammatory and mucus responses.
Results
Similar CAPs mass concentrations were generated in Detroit (542 μg/m3) and Grand Rapids (519 μg/m3). Exposure to CAPs at either site had no effects in lungs of non-allergic rats. In contrast, asthmatic rats had 200% increases in airway mucus and had more BALF neutrophils (250% increase), eosinophils (90%), and total protein (300%) compared to controls. Exposure to Detroit CAPs enhanced all allergic inflammatory endpoints by 30-100%, whereas inhalation of Grand Rapids CAPs suppressed all allergic responses by 50%. Detroit CAPs were characterized by high sulfate, smaller sized particles and were derived from local combustion sources. Conversely Grand Rapids CAPs were derived primarily from motor vehicle sources.
Conclusions
Despite inhalation exposure to the same mass concentration of urban PM2.5, disparate health effects can be elicited in the airways of sensitive populations such as asthmatics. Modulation of airway inflammatory and immune responses is therefore dependent on specific chemical components and size distributions of urban PM2.5. Our results suggest that air quality standards based on particle speciation and sources may be more relevant than particle mass to protect human health from PM exposure.http://deepblue.lib.umich.edu/bitstream/2027.42/112357/1/12940_2012_Article_573.pd
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Ultrafast Rydberg-state dissociation in oxygen: Identifying the role of multielectron excitations
We investigated the fragmentation dynamics of highly excited states of molecular oxygen using femtosecond transient photoelectron spectroscopy. An extreme ultraviolet (XUV) pulse populates the autoionizing Rydberg series converging to O-2(+) c(4)Sigma(-)(u), and a femtosecond near-infrared (IR) pulse was used to photoionize these states as they dissociate. Monitoring the differential photoelectron spectra as a function of time delay allowed us to obtain the relaxation lifetimes of these Rydberg states. We observed a photoelectron signal corresponding to the formation of a 4p excited atomic oxygen fragment, which is not an expected dissociation product of the (O-2(+) c(4)Sigma(-)(u))nl sigma(g) Rydberg series. Analysis of the time-dependent photoelectron spectra and photoionization calculations indicate that this fragment results from a previously unexplored (O-2(+) (4)Pi(g))4p repulsive state and that, contrary to expectations, this multielectron excitation pathway presents a substantial cross section. Our study demonstrates that two-color time-resolved differential photoelectron spectroscopy is an excellent tool to study the fragmentation dynamics of such multielectron excited states, which are not easily probed by other means.US Army Research Laboratory; U.S. Army Research Office [W911NF-14-1-0383]; National Science Foundation (NSF) [PHY-1505556]; U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES) [DE-SC0018251]; US Department of Energy Chemical Sciences, Geosciences, and Biosciences Division [DE-AC02-05CH11231]This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
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