The Experts below are selected from a list of 276 Experts worldwide ranked by ideXlab platform
R. A. Cary - One of the best experts on this subject based on the ideXlab platform.
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Elemental Carbon based method for monitoring occupational exposures to particulate diesel exhaust
Aerosol Science and Technology, 1996Co-Authors: M. Eileen Birch, R. A. CaryAbstract:ABSTRACT Diesel exhaust has been classified a probable human carcinogen, and the National Institute for Occupational Safety and Health (NIOSH) has recommended that employers reduce workers' exposures. Because diesel exhaust is a chemically complex mixture containing thousands of compounds, some measure of exposure must be selected. Previously used methods involving gravimetry or analysis of the soluble organic fraction of diesel soot lack adequate sensitivity and selectivity for low-level determination of particulate diesel exhaust; a new analytical approach was therefore needed. In this paper, results of investigation of a thermal-optical technique for analysis of the Carbonaceous fraction of particulate diesel exhaust are reported. With this technique, speciation of organic and Elemental Carbon is accomplished through temperature and atmosphere control, and by an optical feature that corrects for pyrolytically generated Carbon, or “char,” which is formed during the analysis of some materials. The therma...
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An in situ, Time-resolved analyzer for aerosol organic and Elemental Carbon
Aerosol Science and Technology, 1990Co-Authors: Barbara J. Turpin, R. A. Cary, J.j. HuntzickerAbstract:An in situ Carbon analyzer has been developed to investigate the aerosol chemistry of organic Carbon. Uncertainties because of sample handling and loss of organic Carbon during storage were eliminated by combining the sampling and analysis functions into a single instrument which could operate on a time cycle as short as 90 minutes. Carbon analysis was accomplished with a thermal-optical method with corrections made for the vapor adsorption artifact and for pyrolytic conversion of organic to Elemental Carbon during the Carbon analysis. Total aerosol Carbon uncertainties are 3.1% with detection limits of 0.2 μg of Carbon. The in situ Carbon analyzer was operated during the Carbonaceous Species Methods Comparison Study in Glendora, California, in the summer of 1986. Concentrations of total, organic, and Elemental Carbon showed strong diurnal variations with peaks occurring during the daylight hours. Comparison of the diurnal profile of organic Carbon with those of Elemental Carbon, a tracer for primary comb...
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Measurement of atmospheric Elemental Carbon: Real-time data for Los Angeles during summer 1987
Atmospheric Environment. Part A. General Topics, 1990Co-Authors: Karen M. Adams, Steven M. Japar, L. I. Davis, D. R. Finley, R. A. CaryAbstract:Two fundamentally different techniques for measuring atmospheric Elemental Carbon (EC) aerosol were compared to validate the methods. One technique, photoacoustic spectroscopy, was used to measure the optical absorption (2-514.5 nm) of in situ atmospheric aerosol in real time. This optical absorption can be converted to EC concentration using the appropriate value of the absorption cross- section for C, so that a comparison could be made with the second technique, thermal-optical analysis of filter-collected samples, which measures the collected EC by combustion. Solvent extraction of the filter samples prior to the thermal analysis procedure was required to minimize errors due to pyrolysis of organic Carbon. Excellent 1 : 1 correlation of atmospheric EC concentrations resulted for measurements by the photoacoustic method vs the thermal method over coincident sampling times. The linear regression gave y = 1.006 ( + 0.056) x + 0.27 ( _+ 0.56) with r = 0.945 ( n = 41 ), where y is the photoacoustic EC concentra- tion and x is the thermal Elemental Carbon concentration, both in #g m- 3. This data set was collected in Los Angeles as part of the Southern California Air Quality Study (SCAQS) during the summer 1987, and supplements the results of an earlier, more limited data set taken in Dearborn, MI. The diurnal variability of EC aerosol in Los Angeles during SCAQS, as determined by photoacoustic spectroscopy, is discussed. Key word index: Atmospheric Carbon, black Carbon, Elemental Carbon, particulate Carbon, photoacoustic, spectrophone, atmospheric optics, visibility, light absorption, optical absorption.
Johan Ström - One of the best experts on this subject based on the ideXlab platform.
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Observed metre scale horizontal variability of Elemental Carbon in surface snow
Environmental Research Letters, 2013Co-Authors: J. Svensson, Johan Ström, Margareta E Hansson, Heikki Lihavainen, V.-m. KerminenAbstract:Surface snow investigated for its Elemental Carbon (EC) concentration, based on a thermal–optical method, at two different sites during winter and spring of 2010 demonstrates metre scale horizontal variability in concentration. Based on the two sites sampled, a clean and a polluted site, the clean site (Arctic Finland) presents the greatest variability. In side-by-side ratios between neighbouring samples, 5 m apart, a ratio of around two was observed for the clean site. The median for the polluted site had a ratio of 1.2 between neighbouring samples. The results suggest that regions exposed to snowdrift may be more sensitive to horizontal variability in EC concentration. Furthermore, these results highlight the importance of carefully choosing sampling sites and timing, as each parameter will have some effect on EC variability. They also emphasize the importance of gathering multiple samples from a site to obtain a representative value for the area.
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Elemental Carbon deposition to Svalbard snow from Norwegian settlements and long-range transport
Tellus B, 2011Co-Authors: Borgar Aamaas, Carl Egede Bøggild, Frode Stordal, Terje Berntsen, Kim Holmen, Johan StrömAbstract:The impact on snow pack albedo from local Elemental Carbon (EC) sources in Svalbard has been investigated for the winter of 2008. Highly elevated EC concentrations in the snow are observed around t ...
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Elemental Carbon distribution in svalbard snow
Journal of Geophysical Research, 2009Co-Authors: S Forsstrom, Johan Ström, C A Pedersen, Elisabeth Isaksson, Sebastian GerlandAbstract:[1] The concentration of apparent Elemental Carbon (ECa, based on a thermal-optical method) in the snow was investigated in Svalbard (European Arctic) during spring 2007. The median ECa concentration of 81 samples was 4.1 μg l−1 and the values ranged from 0 to 80.8 μg l−1 of melt water. The median concentration is nearly an order of magnitude lower than the previously published data of equivalent black Carbon (BCe, based on an optical method), obtained from Svalbard snow in the 1980s. A systematic regional difference was evident: ECa concentrations were higher in east Svalbard compared to west Svalbard. The observations of snow ECa cover spatial scales up to several hundred kilometers, which is comparable to the resolution of many climate models. Measurements of atmospheric Carbonaceous aerosol (2002–2008) at Zeppelin station in Ny-Alesund, Svalbard, were divided to air mass sectors based on calculated back trajectories. The results show that air originating from the eastern sector contains more than two and half times higher levels of soot than air arriving from south to west. The observed east–west gradient of ECa concentrations in snow may be because of a combination of the atmospheric concentration gradient, the orographic effect of the archipelago, and the efficient scavenging of the Carbonaceous particles through precipitation.
Rebecca J Hopkins - One of the best experts on this subject based on the ideXlab platform.
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applications of lagrangian dispersion modeling to the analysis of changes in the specific absorption of Elemental Carbon
Atmospheric Chemistry and Physics, 2007Co-Authors: J C Doran, Jerome D Fast, James C Barnard, Alexander Laskin, Yury Desyaterik, Marry K Gilles, Rebecca J HopkinsAbstract:We use a Lagrangian dispersion model driven by a mesoscale model with four-dimensional data assimilation to simulate the dispersion of Elemental Carbon (EC) over a region encompassing Mexico City and its surroundings. The region was the study domain for the 2006 MAX-MEX experiment, which was a component of the MILAGRO campaign. The results are used to identify periods when biomass burning was likely to have had a significant impact on the concentrations of Elemental Carbon at two sites, T1 and T2, downwind of the city, and when emissions from the Mexico City Metropolitan Area (MCMA) were likely to have been more important. They are also used to estimate the median ages of EC affecting the specific absorption of light, α ABS , at 870 nm as well as to identify periods when the urban plume from the MCMA was likely to have been advected over T1 and T2. Median EC ages at T1 and T2 are substantially larger during the day than at night. Values of α ABS at T1, the nearer of the two sites to Mexico City, were smaller at night and increased rapidly after mid-morning, peaking in the mid-afternoon. The behavior is attributed to the coating of aerosols with substances such as sulfate or organic Carbon during daylight hours, but such coating appears to be limited or absent at night. Evidence for this is provided by scanning electron microscopy images of aerosols collected at the sampling sites. During daylight hours the values of α ABS did not increase with aerosol age for median ages in the range of 1–4 h. There is some evidence for absorption increasing as aerosols were advected from T1 to T2 but the statistical significance of that result is not strong.
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Applications of Lagrangian dispersion modeling to the analysis of changes in the specific absorption of Elemental Carbon
Atmospheric Chemistry and Physics Discussions, 2007Co-Authors: J C Doran, Jerome D Fast, James C Barnard, Alexander Laskin, Yury Desyaterik, Marry K Gilles, Rebecca J HopkinsAbstract:Abstract. We use a Lagrangian dispersion model driven by a mesoscale model with four-dimensional data assimilation to simulate the dispersion of Elemental Carbon (EC) over a region encompassing Mexico City and its surroundings, the study domain for the 2006 MAX-MEX experiment, which was a component of the MILAGRO campaign. The results are used to identify periods when biomass burning was likely to have had a significant impact on the concentrations of Elemental Carbon at two sites, T1 and T2, downwind of the city, and when emissions from the Mexico City Metropolitan Area (MCMA) were likely to have been more important. They are also used to estimate the median ages of EC affecting the specific absorption of light, αABS, at 870 nm as well as to identify periods when the urban plume from the MCMA was likely to have been advected over T1 and T2. Median EC ages at T1 and T2 are substantially larger during the day than at night. Values of αABS at T1, the nearer of the two sites to Mexico City, were smaller at night and increased rapidly after mid-morning, peaking in the mid-afternoon. The behavior is attributed to the coating of aerosols with substances such as sulfate or organic Carbon during daylight hours, but such coating appears to be limited or absent at night. Evidence for this is provided by scanning electron microscopy images of aerosols collected at the sampling sites. During daylight hours the values of αABS did not increase with aerosol age for median ages in the range of 1–4 h. There is some evidence for absorption increasing as aerosols were advected from T1 to T2 but the statistical significance of that result is not strong.
Sebastian Gerland - One of the best experts on this subject based on the ideXlab platform.
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Elemental Carbon distribution in svalbard snow
Journal of Geophysical Research, 2009Co-Authors: S Forsstrom, Johan Ström, C A Pedersen, Elisabeth Isaksson, Sebastian GerlandAbstract:[1] The concentration of apparent Elemental Carbon (ECa, based on a thermal-optical method) in the snow was investigated in Svalbard (European Arctic) during spring 2007. The median ECa concentration of 81 samples was 4.1 μg l−1 and the values ranged from 0 to 80.8 μg l−1 of melt water. The median concentration is nearly an order of magnitude lower than the previously published data of equivalent black Carbon (BCe, based on an optical method), obtained from Svalbard snow in the 1980s. A systematic regional difference was evident: ECa concentrations were higher in east Svalbard compared to west Svalbard. The observations of snow ECa cover spatial scales up to several hundred kilometers, which is comparable to the resolution of many climate models. Measurements of atmospheric Carbonaceous aerosol (2002–2008) at Zeppelin station in Ny-Alesund, Svalbard, were divided to air mass sectors based on calculated back trajectories. The results show that air originating from the eastern sector contains more than two and half times higher levels of soot than air arriving from south to west. The observed east–west gradient of ECa concentrations in snow may be because of a combination of the atmospheric concentration gradient, the orographic effect of the archipelago, and the efficient scavenging of the Carbonaceous particles through precipitation.
Isil Kerti - One of the best experts on this subject based on the ideXlab platform.
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Production of Al-Ti-C Grain Refiners with the Addition of Elemental Carbon and K 2 TiF 6
Light Metals 2011, 2011Co-Authors: Fatih Toptan, Isil Kerti, Sibel Daglilar, Ahmet Sagin, Omer F. Karadeniz, Aysin AmbarkutukAbstract:Al−Ti−B grain refiners are widely used as aluminum grain refiners. Despite the problems in application, Al−Ti−C refiners have an increasing demand in recent years. In the present work, Al-Ti-C grain refiners with different Ti:C ratios were produced by in-situ method with the addition of Elemental Carbon into the Al-Ti master alloy (master alloy method) and the addition of K2TiF6 and Elemental Carbon powder mixture into the commercially pure aluminum (flux method). The effects of production method and Ti:C ratio on the grain refinement process were investigated using Alcoa Cold finger Test and so optimum conditions were determined. The best performance was accomplished with the refiner produced at 1300°C with the master alloy method.
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Light Metals 2011 - Production of Al‐Ti‐C Grain Refiners with the Addition of Elemental Carbon and K2TiF6
Light Metals, 2011Co-Authors: Fatih Toptan, Isil Kerti, Sibel Daglilar, Omer F. Karadeniz, Ahmet S Agin, Aysin AmbarkutukAbstract:Al−Ti−B grain refiners are widely used as aluminum grain refiners. Despite the problems in application, Al−Ti−C refiners have an increasing demand in recent years. In the present work, Al-Ti-C grain refiners with different Ti:C ratios were produced by in-situ method with the addition of Elemental Carbon into the Al-Ti master alloy (master alloy method) and the addition of K2TiF6 and Elemental Carbon powder mixture into the commercially pure aluminum (flux method). The effects of production method and Ti:C ratio on the grain refinement process were investigated using Alcoa Cold finger Test and so optimum conditions were determined. The best performance was accomplished with the refiner produced at 1300°C with the master alloy method.
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Production of Al–Ti–C grain refiners with the addition of Elemental Carbon
Materials & Design, 2010Co-Authors: Berke Turgay Gezer, Fatih Toptan, Sibel Daglilar, Isil KertiAbstract:Abstract Grain refining process used in aluminium alloys, has an important role for preventing columnar, coarse grains and encouraging fine, equiaxed grain formation. Al–Ti–B grain refiners are widely used as aluminium grain refiners despite the problems in application Al–Ti–C refiners have an increasing demand in recent years. In the present work, Al–Ti–C grain refiners with different Ti:C ratios were produced by insitu method with the addition of Elemental Carbon. Microstructures were characterised by optic microscope and scanning electron microscope equipped with energy dispersive spectroscopy. The effects of temperature, holding time and Ti:C ratio on the grain refinement process were investigated and optimum conditions were determined.
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production of tic reinforced aluminum composites with the addition of Elemental Carbon
Materials Letters, 2005Co-Authors: Isil KertiAbstract:Abstract TiC reinforced Al matrix composites were produced by the additions of Elemental Carbon to both Al + 4%Ti and Al + 5%Ti alloys. It is shown that the microstructure, phase composition as well as fracture behavior of the composites produced are controlled by the processing parameters, such as temperature, amount of excess Carbon and duration. Composite microstructure subjected to 1300 °C for 15 min includes only TiC particles where the fracture occurs in a ductile manner whilst composites subjected to 1200 °C for 30 min contain Al 3 Ti and TiC particles which show mixed mode of fracture behavior where Al 3 Ti particles resulted in brittle fracture due to their coarser size.