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521.
Masako Morishita Gerald J. Keeler Jacob D. McDonald James G. Wagner Li-Hao Young Satoshi Utsunomiya Rodney C. Ewing Jack R. Harkema 《Atmospheric environment (Oxford, England : 1994)》2009,43(10):1805-1813
Recent studies have attributed toxic effects of ambient fine particulate matter (aerodynamic diameter ≤ 2.5 μm; PM2.5) to physical and/or chemical properties rather than total mass. However, identifying specific components or sources of a complex mixture of ambient PM2.5 that are responsible for adverse health effects is still challenging. In order to improve our understanding of source-to-receptor pathways for ambient PM2.5 (links between sources of ambient PM2.5 and measures of biologically relevant dose), integrated inhalation toxicology studies using animal models and concentrated air particles (CAPs) were completed in southwest Detroit, a community where the pediatric asthma rate is more than twice the national average. Ambient PM2.5 was concentrated with a Harvard fine particle concentrator housed in AirCARE1, a mobile air research laboratory which facilitates inhalation exposure studies in real-world settings. Detailed characterizations of ambient PM2.5 and CAPs, identification of major emission sources of PM2.5, and quantification of trace elements in the lung tissues of laboratory rats that were exposed to CAPs for two distinct 3-day exposure periods were completed.This paper describes the physical/chemical properties and sources of PM2.5, pulmonary metal concentrations and meteorology from two different 3-day exposure periods—both conducted at the southwest Detroit location in July 2003—which resulted in disparate biological effects. More specifically, during one of the exposure periods, ambient PM2.5-derived trace metals were recovered from lung tissues of CAPs-exposed animals, and these metals were linked to local combustion point sources in southwest Detroit via receptor modeling and meteorology; whereas in the other exposure period, no such trace metals were observed. By comparing these two disparate results, this investigation was able to define possible links between PM2.5 emitted from refineries and incinerators and biologically relevant dose, which in turn may be associated with observed health effects. 相似文献
522.
Mark T. Young Emily J. Rayfield Casey M. Holliday Lawrence M. Witmer David J. Button Paul Upchurch Paul M. Barrett 《Die Naturwissenschaften》2012,99(8):637-643
Sauropod dinosaurs were the largest terrestrial herbivores and pushed at the limits of vertebrate biomechanics and physiology. Sauropods exhibit high craniodental diversity in ecosystems where numerous species co-existed, leading to the hypothesis that this biodiversity is linked to niche subdivision driven by ecological specialisation. Here, we quantitatively investigate feeding behaviour hypotheses for the iconic sauropod Diplodocus. Biomechanical modelling, using finite element analysis, was used to examine the performance of the Diplodocus skull. Three feeding behaviours were modelled: muscle-driven static biting, branch stripping and bark stripping. The skull was found to be ‘over engineered’ for static biting, overall experiencing low stress with only the dentition enduring high stress. When branch stripping, the skull, similarly, is under low stress, with little appreciable difference between those models. When simulated for bark stripping, the skull experiences far greater stresses, especially in the teeth and at the jaw joint. Therefore, we refute the bark-stripping hypothesis, while the hypotheses of branch stripping and/or precision biting are both consistent with our findings, showing that branch stripping is a biomechanically plausible feeding behaviour for diplodocids. Interestingly, in all simulations, peak stress is observed in the premaxillary–maxillary ‘lateral plates’, supporting the hypothesis that these structures evolved to dissipate stress induced while feeding. These results lead us to conclude that the aberrant craniodental form of Diplodocus was adapted for food procurement rather than resisting high bite forces. 相似文献
523.
Ji Young Park Peter C. Raynor Andrew D. Maynard Lynn E. Eberly Gurumurthy Ramachandran 《Atmospheric environment (Oxford, England : 1994)》2009,43(3):502-509
Recent research has suggested that the adverse health effects caused by nanoparticles are associated with their surface area (SA) concentrations. In this study, SA was estimated in two ways using number and mass concentrations and compared with SA (SAmeas) measured using a diffusion charger (DC). Aerosol measurements were made twice: once starting in October 2002 and again starting in December 2002 in Mysore, India in residences that used kerosene or liquefied petroleum gas (LPG) for cooking. Mass, number, and SA concentrations and size distributions by number were measured in each residence. The first estimation method (SAPSD) used the size distribution by number to estimate SA. The second method (SAINV) used a simple inversion scheme that incorporated number and mass concentrations while assuming a lognormal size distribution with a known geometrical standard deviation. SAPSD was, on average, 2.4 times greater (range = 1.6–3.4) than SAmeas while SAINV was, on average, 6.0 times greater (range = 4.6–7.7) than SAmeas. The logarithms of SAPSD and SAINV were found to be statistically significant predictors of the logarithm of SAmeas. The study showed that particle number and mass concentration measurements can be used to estimate SA with a correction factor that ranges between 2 and 6. 相似文献
524.
The realignment and reorganization of ESPR 总被引:1,自引:1,他引:0
525.
526.
Robert F. Young 《Journal of Environmental Planning and Management》2010,53(8):1051-1068
Urban sustainability literature calls for new governance relations to support green urban agendas. Privileging non-hierarchical relations, this literature fails to address the means by which organisations create these capacities. The author interviewed public, private and community environmental leaders in metropolitan Chicago regarding their disposition toward creating boundary spanning organisations (BSOs) in addressing the City's Environmental Action Agenda. Their responses reflect engaged efforts to enhance cross-boundary sharing of information, resources, and power. However, they also reflect the decisive role of central authority in initiating this process. These findings suggest the complexity of urban governance in transitions toward sustainability and the opportunities they provide to explore the implications of on-the-ground practice. 相似文献
527.
Jai-Young Lee Sun Young Youm Sang-Il Choi Byung-Taek Oh 《Journal of Material Cycles and Waste Management》2009,11(3):214-221
The present study investigated the reactivity and ability of permeable reactive barriers [zero-valent iron (ZVI)-barrier plus
biobarrier) to remove various contaminants (Cd, As, Zn, Cu, Mn, Cr, NO3
−, NH4
+, and CODcr) from synthetic leachate. Two different reactive materials were used in this study, namely ZVI and autoclaved lightweight
concrete (ALC). After 90 days of column operation, the contaminant profiles were determined along the length of the columns.
The heavy metals were extensively removed in the bio-ALC and sequential barriers (ZVI plus bio-ALC), however the removal efficiencies
for the heavy metals Zn and Cr in the ALC and bio-ALC barriers were comparatively low. Nitrate was completely removed (>99.9%)
in the ALC, bio-ALC, and sequential barriers. More than 50% of the produced ammonium and organic materials were removed in
the biologically reactive zone of the sequential barriers. The results of the present study suggest that sequential barriers
are one of the best solutions for in situ remediation and that they can be applied to clean up the leachate released from
landfills. 相似文献
528.
This study investigated the reforming characteristics and optimum operating condition of the high-temperature plasma torch (so called plasmatron) for hydrogen-rich gas (syngas) production. At the optimum condition, the composition of produced syngas was 45.4% hydrogen (H2), 6.9% carbon monoxide (CO), 1.5% carbon dioxide (CO2), and 1.1% acetylene (C2H2). The H2/CO ratio was 6.6, hydrogen yield was 78.8%, and the energy conversion rate was 63.6%. To obtain the optimum operating condition, parametric studies were carried out examining the effects of O2/CH4 ratio, steam/CH4 ratio, and Ni catalyst addition in reactor. When the steam/CH4 ratio was 1.23, the production of hydrogen was maximized and the methane conversion rate was 99.7%. The syngas composition was determined to be 50.4% H2, 5.7% CO, 13.8% CO2, and 1.1% C2H2. The H2/CO ratio was 9.7, hydrogen yield was 93.7%, and the energy conversion rate was 78.8%. Hydrogen production with catalyst was effective, compared with no catalyst. 相似文献
529.
Maxted AP Black CR West HM Crout NM McGrath SP Young SD 《Environmental pollution (Barking, Essex : 1987)》2007,150(3):363-372
The objectives of this study were to assess the potential for using Thlaspi caerulescens as a phytoextraction plant and develop a user-advice model, which can predict the frequency of phytoextraction operation required under prescribed conditions. Pot and field trials were conducted using soil collected from a dedicated sewage sludge disposal facility. Soil amendments (sulphuric acid, potassium chloride and EDTA) intended to increase Cd solubility were also tested. Predictive models of Cd and Zn uptake were developed which were able to reproduce the observed pH-dependence of Cd uptake with an apparent maximum around pH 6. Chemical treatments did not significantly increase the uptake of Cd. The periodic use of phytoextraction with T. caerulescens to maintain soils below statutory metal concentration limits, when modern sewage sludges are repeatedly applied, seems very attractive given the non-intrusive and cost-effective nature of the process. The major limitations lie with the large-scale husbandry of T. caerulescens. 相似文献
530.
To analyze polycyclic aromatic hydrocarbons (PAHs) at an urban site in Seoul, South Korea, 24-hr ambient air PM2.5 samples were collected during five intensive sampling periods between November 1998 and December 1999. To determine the PAH
size distribution, 3-day size-segregated aerosol samples were also collected in December 1999. Concentrations of the 16 PAHs
in the PM2.5 particles ranged from 3.9 to 119.9 ng m−3 with a mean of 24.3 ng m−3.An exceptionally high concentration of PAHs(∼120 ng m−3) observed during a haze event in December 1999 was likely influenced more by diesel vehicle exhaust than by gasoline exhaust,
as well as air stagnation, as evidenced by the low carbon monoxide/elemental carbon (CO/EC) ratio of 205 found in this study
and results reported by previous studies.
The total PAHs associated with the size-segregated particles showed unimodal distributions. Compared to the unimodal size
distributions of PAHs with modal peaks at < 0.12 μm measured in highway tunnels in Los Angeles (Venkataraman and Friedlander,
1994), four- to six-ring PAHs in our study had unimodal size distributions, peaking at the larger size range of 0.28–0.53
μm, suggesting the coagulation of freshly emitted ultrafine particles during transport to the sampling site. Further, the
fraction of PAHs associated with coarse particles(> 1.8 μm) increased as the molecular weight of the PAHs decreased due to
volatilization of fine particles followed by condensation onto coarse particles. 相似文献