Real-Time PM10 Emission Rates From Paved Roads by Measurement of Concentrations in the Vehicle\u27s Wake Using On-Board Sensors Part 1. SCAMPER Method Characterization

Based on emission factors derived from the AP-42 algorithm, particulate matter from paved roads has been estimated to be a major source of PM10 of geologic origin. This is an empirical formula based on upwind-downwind measurement of PM10 concentrations and is dependent solely on the silt loading of the pavement and the weight of vehicles. A number of upwind-downwind studies conducted in urban areas to validate this algorithm have been generally inconclusive because the PM10 concentration difference between upwind and downwind often is within the measurement uncertainty. In the approach presented here PM10 concentrations were measured directly behind a moving vehicle in order to improve the measurement sensitivity for estimating the emission rates for vehicles on paved roads. Optical sensors were used to measure PM10 concentrations with a time resolution of approximately 10 s. Sensors were mounted in the front of the vehicle and behind it in the well-mixed wake. A special inlet probe was designed to allow isokinetic sampling under varying speed conditions. As a first approximation the emission rate was calculated by multiplying the PM10 concentration difference between the front and rear of a moving vehicle by the frontal area of the vehicle. This technique is also useful for quickly surveying large areas and for investigating hot spots on roadways caused by greater than normal deposition of PM10 forming debris. The method is designated as SCAMPER: System for the Continuous Aerosol Measurement of Particulate Emissions from Roads. Part I describes SCAMPER development and Part II describes a comprehensive field testing of mobile methods

Association of FEV1 in asthmatic children with personal and microenvironmental exposure to airborne particulate matter.

Exposure to particulate matter (PM) air pollution has been shown to exacerbate children's asthma, but the exposure sources and temporal characteristics are still under study. Children's exposure to PM is likely to involve both combustion-related ambient PM and PM related to a child's activity in various indoor and outdoor microenvironments. Among 19 children with asthma, 9-17 years of age, we examined the relationship of temporal changes in percent predicted forced expiratory volume in 1 sec (FEV1) to personal continuous PM exposure and to 24-hr average gravimetric PM mass measured at home and central sites. Subjects were followed for 2 weeks during either the fall of 1999 or the spring of 2000, in a southern California region affected by transported air pollution. FEV(subscript)1(/subscript) was measured by subjects in the morning, afternoon, and evening. Exposure measurements included continuous PM using a passive nephelometer carried by subjects; indoor, outdoor home, and central-site 24-hr gravimetric PM2.5 (PM of aerodynamic diameter < 2.5 microm) and PM10; and central-site hourly PM10, nitrogen dioxide, and ozone. Data were analyzed with linear mixed models controlling for within-subject autocorrelation, FEV1 maneuver time, and exposure period. We found inverse associations of FEV1 with increasing PM exposure during the 24 hr before the FEV1 maneuver and with increasing multiday PM averages. Deficits in percent predicted FEV1 (95% confidence interval) for given PM interquartile ranges measured during the preceding 24-hr were as follows: 128 microg/m3 1-hr maximum personal PM, -6.0% (-10.5 to -1.4); 30 microg/m3 24-hr average personal PM, -5.9% (-10.8 to -1.0); 6.7 microg/m3 indoor home PM2.5, -1.6% (-2.8 to -0.4); 16 microg/m3 indoor home PM10, -2.1% (-3.7 to -0.4); 7.1 microg/m3 outdoor home PM2.5, -1.1% (-2.4 to 0.1); and 7.5 microg/m3 central-site PM2.5, -0.7% (-1.9 to 0.4). Stronger associations were found for multiday moving averages of PM for both personal and stationary-site PM. Stronger associations with personal PM were found in boys allergic to indoor allergens. FEV1 was weakly associated with NO2 but not with O3. Results suggest mixed respiratory effects of PM in asthmatic children from both ambient background exposures and personal exposures in various microenvironments

Production of He-4 and (4) in Pb-Pb collisions at root(NN)-N-S=2.76 TeV at the LHC

Results on the production of He-4 and (4) nuclei in Pb-Pb collisions at root(NN)-N-S = 2.76 TeV in the rapidity range vertical bar y vertical bar <1, using the ALICE detector, are presented in this paper. The rapidity densities corresponding to 0-10% central events are found to be dN/dy4(He) = (0.8 +/- 0.4 (stat) +/- 0.3 (syst)) x 10(-6) and dN/dy4 = (1.1 +/- 0.4 (stat) +/- 0.2 (syst)) x 10(-6), respectively. This is in agreement with the statistical thermal model expectation assuming the same chemical freeze-out temperature (T-chem = 156 MeV) as for light hadrons. The measured ratio of (4)/He-4 is 1.4 +/- 0.8 (stat) +/- 0.5 (syst). (C) 2018 Published by Elsevier B.V.Peer reviewe

Cooperative Agreement CR 827331-01-0 By

A new state-of-the-art indoor environmental chamber facility for the study of atmospheric processes leading to the formation of ozone and secondary organic aerosol (SOA) has been constructed and characterized. The chamber is designed for atmospheric chemical mechanism evaluation at low reactant concentrations under well-controlled environmental conditions. It consists of two collapsible 90 m 3 FEP Teflon film reactors on pressure-controlled moveable frameworks inside a temperature-controlled enclosure flushed with purified air. Solar radiation is simulated with either a 200 kW Argon arc lamp or multiple blacklamps. Results of initial characterization experiments, all carried out under dry conditions, concerning NOx and formaldehyde offgasing, radical sources, particle loss rates, and background PM formation are described. Results of initial single organic- NOx and simplified ambient surrogate- NOx experiments to demonstrate the utility of the facility for mechanism evaluation under low NOx conditions are summarized and compared with the predictions of the SAPRC-99 chemical mechanism. Overall, the results of the initial characterization and evaluation indicate that this new environmental chamber can provide high quality mechanism evaluation data for experiments with NOx levels as low as ~2 ppb, though the results indicate some problems with the gas-phase mechanism that need further study. Initia

Thin Stage I Primary Cutaneous Malignant Melanoma

Although wide surgical excision is the accepted treatment for thin malignant melanomas, there is reason to believe that narrower margins may be adequate. We conducted a randomized prospective study to assess the efficacy of narrow excision (excision with 1-cm margins) for primary melanomas no thicker than 2 mm. Narrow excision was performed in 305 patients, and wide excision (margins of 3 cm or more) was performed in 307 patients. The major prognostic criteria were well balanced in the two groups. The mean thickness of melanomas was 0.99 mm in the narrow-excision group and 1.02 mm in the wide-excision group. The subsequent development of metastatic disease involving regional nodes and distant organs was not different in the two groups (4.6 and 2.3 percent, respectively, in the narrow-excision group, as compared with 6.5 and 2.6 percent in the wide-excision group). Disease-free survival rates and overall survival rates (mean follow-up period, 55 months) were also similar in the two groups. Only three patients had a local recurrence as a first relapse. All had undergone narrow excision, and each had a primary melanoma with a thickness of 1 mm or more. The absence of local recurrence in the group of patients with a primary melanoma thinner than 1 mm and the very low rate of local recurrences indicate that narrow excision is a safe and effective procedure for such patients. (N Engl J Med 1988; 318:1159–62.) THE question of how much surrounding normal skin should be removed during the excision of primary melanomas of the skin has never been properly answered. For decades, wide excision (with margins of 3 to 5 cm) has been universally accepted as the treatment of choice. In 1977, however, Breslow and Macht1 reported that narrow resection margins may be satisfactory in the treatment of very thin melanomas. Subsequent reports2 3 4 5 6 7 8 9 10 11 have also supported the conservative surgical approach to local control of the primary tumor. Nevertheless, there are several points of disagreement, including how thick a primary melanoma can be and still be. © 1988, Massachusetts Medical Society. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe