Carbon Mass Fraction Research Articles

PM 1 /PM 2.5 /PM 10 Characteristics in the Urban Atmosphere of Taipei

Characteristics of PM 1 /PM 2.5 /PM 10 were evaluated in the ambient general (Chung-Shan) and traffic (Da-Tung) monitoring stations in the Taipei area. It was observed that average concentrations of PM 1 , PM 2.5 , and PM 10 were 14.0, 24.4, and 48.1 w g/m 3 in the Chung-Shan station, respectively. In the Da-Tung station, the mean levels of PM 1 , PM 2.5 , and PM 10 were 37.6, 42.8, and 61.5 w g/m 3 , respectively. In addition, it was found that PM 1 /PM 2.5 mass ratios could be as high as 0.90 in the traffic station. Regarding carbon profiles, it was observed that mass fractions of total carbon in PM 1 , PM 2.5 , and PM 10 were 0.58, 0.49, and 0.35 in the Chung-Shan station and 0.74, 0.66, and 0.53 in the Da-Tung station, respectively. It was clearly indicated that fine particles related to combustion sources play an important role in urban atmosphere. Further investigation is needed to evaluate chemical compositions and health effects of PM 1 .

A multicomponent sectional model applied to flame synthesis of nanoparticles

Sodium/halide flame synthesis and encapsulation (SFE) is a promising technique for producing nonoxide materials. The reaction produces nanoparticles of the core product and a condensable by-product (e.g., NaF). In this research, the SFE process was studied numerically for a spherically symmetric non-premixed flame in a low-pressure atmosphere of sodium vapor. Experimentally, this flame can be established in microgravity. A transient flame code incorporating detailed chemistry and transport processes was developed to perform the investigation. In addition, a two-component sectional method was developed and integrated into the flame code to simulate aerosol dynamics, including coagulation and condensation. For the simulation, the reaction of CF4 with Na was chosen such that solid carbon was the core product and NaF was the condensable by-product. the results show that near the reaction region, a large number of core particles form, yet condensation of the condensable species does not occur because of the high temperature. Slightly away from the reaction region toward the ambient, there is a narrow region within which rapid condensation of NaF occurs and a few large, heavily coated particles are formed. Most of the small core particles are not coated in this region, but instead are being scavenged by the large, heavily coated particles. Condensation is negligible further downstream because the concentration of the condensable species becomes too low. The simulation also shows that thermophoresis is important, especially at low pressure, to the distribution of particles and that the effect of sticking coefficient on NaF(1) is minimal. The effect of pressure also has been studied, and the results show that the mass fractions of carbon and NaF(1) are insensitive to pressure.

Micromechanical properties of carbon–silica aerogel composites

Materials’ endurance to mechanical stress is desirable from a technological point of view. In particular, in the case of silica aerogels, an improvement of the material elasticity is needed for some applications. Carbon–silica aerogel composites have been obtained and their mechanical properties, Young’s modulus, elastic parameter and hardness, have been evaluated with a dynamical, non-destructive microindentation technique. Large changes are found in Young’s modulus when only a small amount of carbon is added. This is clearly shown in the shape of the indentation curves as well as in the increase of the elastic parameter value, which evaluates the percentage of elasticity versus plasticity. Young’s modulus values obtained for carbon–silica aerogels show a similar variation with the carbon mass fraction to that predicted by a commonly used model for composite materials. The measured hardness values corresponding to the total elastoplastic deformation do not show such a prominent dependency on the carbon mass fraction as the elastic parameter and Young’s modulus do and they are similar to those measured for the pure-silica aerogel.

Temporally resolved species measurements in a flickering AIR-diluted, non-premixed natural gas flame by extractive sampling of flame gases and fourier transform ir analysis

Spatially and temporally resolved concentrations of carbon monoxide, carbon dioxide, methane, andacetylene are presented for a 10 Hz, acoustically forced, air-diluted natural gas flame with a fuel mixture equivalence ratio of 3.3. Samples were withdrawn from the flame using a modified quartz microprobe designed to minimize dead volume in the probe during the sampling event. Valve opening and closing were synchronized to the forcing waveform. Extracted gases were analyzed using on-line Fourier transform IR spectrometry. Concentrations were determined using a combination of singular value decomposition matrix techniques and fitting of rotational line sequences. In both techniques, samples were calibrated using data collected in a well-characterized methane/air diffusion flame supported on a Wolfhard-Parker slot burner. Because these four species comprise most of the carbon in the flame, their concentrations can be used to estimate the mass fraction of carbon and thus mixture fraction. Contour maps of all four species and mixture fraction are presented.

Sampling atmospheric carbonaceous aerosols using a particle trap impactor/denuder sampler.

A particle trap impactor/denuder system has been developed and tested for the sampling of ambient carbonaceous aerosols. Use of a particle trap impactor allows for a reduction of particle bounce and re-entrainment at high particle loadings, and operation at high volumetric flow rates is achieved without the use of oiled impaction substrates, thus facilitating the chemical and physical analysis of the organic compounds comprising the collected gas (G) and particle (P) phases. Honeycomb denuders have a greater density of channels for a given denuder cross-sectional area than parallel plate or annular denuders; for a given sampling flow rate, honeycomb denuders can be fabricated in more compact shapes and will have a greater amount of surface area for the collection of gases. Field testing of the sampler was conducted primarily at night to minimize the evaporation of organic carbon (OC) from collected particles, which can result from the heating of collected particles as ambient temperatures rise during the day. In side-by-side testing with an open-face filter pack sampler, the denuder system was found to minimize positive gas adsorption artifacts caused by the adsorption of gaseous OC to quartz filter fiber (QFF) surfaces. In the denuder sampler, negligible amounts of OC were observed on a QFF placed downstream of a particle-loaded QFF, suggesting that OC detected on the backup QFF in the filter pack sampler resulted primarily from the adsorption of ambient G-phase OC rather than OC evaporated from particles collected on the front filter. Equations are presented for the evaluation of the magnitude of positive and negative sampling artifacts. Analysis of these equations indicates that the mass of OC evaporated from filter-bound particles present downstream of a denuder depends on (i) the volume of OC-free gas passed through the filter, (ii) the P-phase concentration and the P/G partition coefficients (Kp) of the compounds comprising the P-phase OC, (iii) the temperature (T) (values of Kp are inversely proportional to T), and (iv) the mass fraction of carbon in the compounds comprising P-phase OC. For these reasons, the magnitude of evaporative losses of OC in denuder samplers may vary among different sampling events. In addition, a method utilizing gas chromatography/mass spectrometry has been developed for determination of inertial impactor collection efficiency and denuder particle transmission efficiency. Using this method, only a single extraction of the sampler components is necessary, thereby reducing the number of extractions and analyses over conventional approaches by at least a factor of 2.

Erratum

Environmental Toxicology and ChemistryVolume 20, Issue 10 p. 2403-2404 ERRATUMFree Access Erratum First published: 03 November 2009 https://doi.org/10.1002/etc.5620201036AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat LeBoeuf EJ, Weber WJ Jr. 1999. Reevaluation of general partitioning model for sorption of hydrophobic organic contaminants by soil and sediment organic matter. Environ Toxicol Chem 18:1617–1626. Frank-Dieter Kopinke and Anett Georgi of the Department of Remediation Research, Center for Environmental Research, Leipzig, Germany, have graciously called to our attention errors in the paper named above [1]. In response, we provide these corrections. Table 2 has been revised and should replace that in the original paper. This version reflects corrections to columns 2 (log(γ*1)), 4 (R2), and 10 (σp) that rectify the inconsistencies in the data contained therein. Column 2 corrections were necessitated by a transfer of data error, column 10 includes a correction to the spreadsheet calculations for σp, and column 4 corrections result from a reevaluation of the isotherm least-squares fit analysis. Equation 3 should be X = n1/n3, where n3 = number of moles of solution. The units of ρo appearing in Equation 7 should reflect the density of organic carbon within the polymer (g organic carbon/cm3), rather than the density of the polymer (g/cm3). The elemental composition of cellulose noted in Table 1 should be C: 44.4%, H: 6.2%, and O: 49.3%, reflecting an O/C ratio of 1.11. This correction results in a reduction in the correlation between the literature solubility parameter and O/C ratio for each of the natural sorbents from 0.971 to 0.903 (correlation: σp 3.3273(O/C atomic ratio) + 9.711). The lignin identified in Table 1 should be noted as organsolv, rather than alkali. Table Table 2. (revised). Flory-Huggins interaction parameters for phenanthrene sorption on several sorbents Sorbent Log(γ*1)a 1/m + 1 [-]b R2 ϕ*1 [-] χ* [-] μR*1 [KJ/mol] χH [-] σp Sorbent (references) [cal/cm3]0.5 σp Sorbent (from eq. 19, 20, 21) [cal/cm3]0.5 O/C [atomic ratio] [-] Cellulose 2.20 (0.07) 1.03 (0.04) 0.994 0.006 4.13 10.23 3.79 13.4–16.1c 13.6 1.11 Lignin (Organosolv) 1.55 (0.12) 0.80 (0.05) 0.980 0.028 2.75 6.82 2.41 10.8c 12.8 0.44 Peat humic acid 1.65 (0.04) 0.79 (0.02) 0.998 0.022 2.95 7.31 2.61 11.5d 12.9 0.64 Aldrich humic acid 1.24 (0.04) 0.84 (0.02) 0.998 0.057 2.16 5.35 1.82 11.5d 12.4 0.62 Green River kerogen 0.33 (0.12) 0.90 (0.06) 0.981 0.47 0.81 2.01 0.47 NA 11.1 0.19 Ohio Shale II kerogen 0.86 (0.20) 0.52 (0.10) 0.867 0.13 1.53 3.79 1.19 NA 11.9 0.23 Wyoming coal 0.76 (0.03) 0.62 (0.02) 0.997 0.17 1.37 3.40 1.02 10.69e 11.7 0.24 Illinois No. 6 coal 0.43 (0.05) 0.57 (0.02) 0.994 0.37 0.92 2.28 0.58 10.69e 11.3 0.17 PBMA 0.04 (0.17) 1.04 (0.06) 0.983 0.91 0.53 1.31 0.19 8.75f 9.0 0.33 PBIMA 0.43 (0.08) 1.06 (0.04) 0.996 0.37 0.91 2.25 0.57 8.70f 8.3 0.39 PIMA 0.68 (0.06) 1.04 (0.02) 0.998 0.21 1.25 3.10 0.90 8.65f 8.0 0.44 PMMA 2.72 (0.04) 0.84 (0.02) 0.998 0.002 5.29 13.11 4.96 11.08f 14.1 0.33 PPMA 0.92 (0.06) 0.57 (0.03) 0.991 0.12 1.62 4.02 1.27 10.0g 12.0 0.26 a 95% confidence interval for log(γ*1). b 95% confidence interval for 1/(m + 1) c [1]. d Estimated based on average literature values. e Estimated from carbon mass fraction [1]. f [2]. g Estimated from chemical functional group contribution method [3]. Again, we thank Dr. Kopinke and Dr. Georgi for their interest in our work and for providing us the opportunity to correct the inconsistencies in our paper. REFERENCES 1 Barton AFM: 1990. CRC Handbook of Polymer-Liquid Interaction Parameters and Solubility Parameters. CRC, Ann Arbor, MI, USA. 2 Barton AFM: 1983. CRC Handbook of Solubility Parameters and Other Cohesion Parameters. CRC, Boca Raton, FL, USA. 3 Salame M: 1986. Prediction of gas barrier properties of high polymers. Polymer Eng Sci 26: 1543– 1546. Volume20, Issue10October 2001Pages 2403-2404 ReferencesRelatedInformation

ERRATUM

Environmental Toxicology and ChemistryVolume 20, Issue 10 p. 2403-2404 ERRATUMFree Access Erratum First published: 03 November 2009 https://doi.org/10.1002/etc.5620201036AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat LeBoeuf EJ, Weber WJ Jr. 1999. Reevaluation of general partitioning model for sorption of hydrophobic organic contaminants by soil and sediment organic matter. Environ Toxicol Chem 18:1617–1626. Frank-Dieter Kopinke and Anett Georgi of the Department of Remediation Research, Center for Environmental Research, Leipzig, Germany, have graciously called to our attention errors in the paper named above [1]. In response, we provide these corrections. Table 2 has been revised and should replace that in the original paper. This version reflects corrections to columns 2 (log(γ*1)), 4 (R2), and 10 (σp) that rectify the inconsistencies in the data contained therein. Column 2 corrections were necessitated by a transfer of data error, column 10 includes a correction to the spreadsheet calculations for σp, and column 4 corrections result from a reevaluation of the isotherm least-squares fit analysis. Equation 3 should be X = n1/n3, where n3 = number of moles of solution. The units of ρo appearing in Equation 7 should reflect the density of organic carbon within the polymer (g organic carbon/cm3), rather than the density of the polymer (g/cm3). The elemental composition of cellulose noted in Table 1 should be C: 44.4%, H: 6.2%, and O: 49.3%, reflecting an O/C ratio of 1.11. This correction results in a reduction in the correlation between the literature solubility parameter and O/C ratio for each of the natural sorbents from 0.971 to 0.903 (correlation: σp 3.3273(O/C atomic ratio) + 9.711). The lignin identified in Table 1 should be noted as organsolv, rather than alkali. Table Table 2. (revised). Flory-Huggins interaction parameters for phenanthrene sorption on several sorbents Sorbent Log(γ*1)a 1/m + 1 [-]b R2 ϕ*1 [-] χ* [-] μR*1 [KJ/mol] χH [-] σp Sorbent (references) [cal/cm3]0.5 σp Sorbent (from eq. 19, 20, 21) [cal/cm3]0.5 O/C [atomic ratio] [-] Cellulose 2.20 (0.07) 1.03 (0.04) 0.994 0.006 4.13 10.23 3.79 13.4–16.1c 13.6 1.11 Lignin (Organosolv) 1.55 (0.12) 0.80 (0.05) 0.980 0.028 2.75 6.82 2.41 10.8c 12.8 0.44 Peat humic acid 1.65 (0.04) 0.79 (0.02) 0.998 0.022 2.95 7.31 2.61 11.5d 12.9 0.64 Aldrich humic acid 1.24 (0.04) 0.84 (0.02) 0.998 0.057 2.16 5.35 1.82 11.5d 12.4 0.62 Green River kerogen 0.33 (0.12) 0.90 (0.06) 0.981 0.47 0.81 2.01 0.47 NA 11.1 0.19 Ohio Shale II kerogen 0.86 (0.20) 0.52 (0.10) 0.867 0.13 1.53 3.79 1.19 NA 11.9 0.23 Wyoming coal 0.76 (0.03) 0.62 (0.02) 0.997 0.17 1.37 3.40 1.02 10.69e 11.7 0.24 Illinois No. 6 coal 0.43 (0.05) 0.57 (0.02) 0.994 0.37 0.92 2.28 0.58 10.69e 11.3 0.17 PBMA 0.04 (0.17) 1.04 (0.06) 0.983 0.91 0.53 1.31 0.19 8.75f 9.0 0.33 PBIMA 0.43 (0.08) 1.06 (0.04) 0.996 0.37 0.91 2.25 0.57 8.70f 8.3 0.39 PIMA 0.68 (0.06) 1.04 (0.02) 0.998 0.21 1.25 3.10 0.90 8.65f 8.0 0.44 PMMA 2.72 (0.04) 0.84 (0.02) 0.998 0.002 5.29 13.11 4.96 11.08f 14.1 0.33 PPMA 0.92 (0.06) 0.57 (0.03) 0.991 0.12 1.62 4.02 1.27 10.0g 12.0 0.26 a 95% confidence interval for log(γ*1). b 95% confidence interval for 1/(m + 1) c [1]. d Estimated based on average literature values. e Estimated from carbon mass fraction [1]. f [2]. g Estimated from chemical functional group contribution method [3]. Again, we thank Dr. Kopinke and Dr. Georgi for their interest in our work and for providing us the opportunity to correct the inconsistencies in our paper. REFERENCES 1 Barton AFM: 1990. CRC Handbook of Polymer-Liquid Interaction Parameters and Solubility Parameters. CRC, Ann Arbor, MI, USA. Google Scholar 2 Barton AFM: 1983. CRC Handbook of Solubility Parameters and Other Cohesion Parameters. CRC, Boca Raton, FL, USA. Google Scholar 3 Salame M: 1986. Prediction of gas barrier properties of high polymers. Polymer Eng Sci 26: 1543– 1546. Wiley Online LibraryCASWeb of Science®Google Scholar Volume20, Issue10October 2001Pages 2403-2404 ReferencesRelatedInformation

A model for the role of carbon on carbochlorination of TiO2

The carbochlorination of TiO2 is characterized by two successive reaction stages, named the first and the second stage. In both stages, reaction rate increases as carbon mass fraction increases. This kinetic effect of carbon was interpreted on the basis of a model developed to describe the rate of each reaction stage as a function of carbon mass fraction in TiO2-C powder mixture. The model considers, for both reaction stages, two global steps: [I] the formation of gaseous intermediates at the carbon surface and [II] the reaction of these intermediates with TiO2 to form the reaction products. The mathematical treatment from these steps involves the adaptation of the general model applied to catalytic gas-solid reactions. The first reaction stage occurs, for high carbon contents, under strong external chlorine transport control and, for low enough carbon content, under internal mixed control. The second reaction stage occurs out of external gaseous influence and a net chemical control operates, both at low temperatures and for the lowest carbon content. The intrinsic activation energies for the first and second reaction stages are 40 and 117 kJ-mol−1, respectively.

Optimal Control of Methane Conversion to Ethylene

An optimal control methodology is applied to the problem of finding the heat, hydrogen, and oxygen flux profiles for the homogeneous gas-phase conversion of methane to ethylene in a plug flow reactor. The calculations use a detailed reaction model for the oxidative pyrolysis of methane and a model for the growth of polycyclic aromatic hydrocarbons and soot particle nulceation and growth. The reactor designs show that distributed hydrogen and oxygen fluxes along the axis of the reactor improve ethylene yields to a greater extent than co-fed hydrogen and/or oxygen. The axial heat flux is shown to play a major role in the final yields of ethylene. The optimal residence times are 28−31 ms, and the optimal temperature profiles cover a range of 1200−1985 K. The simulation results show that for the conditions considered, C2H2 is formed initially and is converted to C2H4 by a controlled extraction of energy. Hydrogen addition is advantageous at both stages to reduce soot in the first half of the reactor and to shift the equilibrium toward ethylene in the second half. Oxygen aids in forming ethylene from the C2H5 and C2H3 intermediates and in the formation of hydrogen radicals. Ethylene carbon mass fractions of 0.64 have been achieved. The solutions, although not proven to be globally optimal, are of high quality.

Carbon and Hydrogen in Hot DB White Dwarfs

The roles played by carbon and hydrogen in helium atmosphere (DB) white dwarf evolution is not well understood. We present GHRS observations (centered at 1215 and 1335 A) of the hot helium white dwarfs PG 0112+104 (≈30,000 K) and GD 190 (≈23,000 K) and EUVE observations of the well-studied DB GD 358 (≈27,000 K) and revisit pre-COSTAR observations of GD 358. We detect Lyα and carbon absorption features in all three of our hot DB white dwarfs. Using the non-LTE model atmosphere code TLUSTY, we calculate carbon and hydrogen surface abundances and mass fractions. We discuss the implications of our analysis for two aspects of DB evolution. First, we find hydrogen surface abundances corresponding to mass fractions over an order of magnitude too low to explain the observed lack of helium atmosphere white dwarfs between 45,000 and 30,000 K unless we allow extensive mixing in DB atmospheres. Second, the photospheric carbon in all three objects cannot be explained by interstellar accretion or conventional convective dredge-up. We present evidence for substantial horizontal motions in two of our objects that may explain both the presence of carbon and the lower than predicted hydrogen surface abundance.

The Origin of the Diversity of Type I[CLC]a[/CLC] Supernovae and the Environmental Effects

Observations suggest that the properties of Type Ia supernovae (SNe Ia) may depend on environmental characteristics, such as the morphology, metallicity, and age of the host galaxies. The influence of these environmental properties on the resulting SNe Ia is studied in this Letter. First, it is shown that the carbon mass fraction X(C) in the C + O white dwarf SN Ia progenitors tends to be smaller for a lower metallicity environment and an older binary system. It is then suggested that the variation of X(C) causes the diversity in the brightness of SNe Ia: a smaller X(C) leads to a dimmer SN Ia. Further studies of the propagation of the turbulent flame are necessary to confirm this relation. Our model for the SN Ia progenitors then predicts that when the progenitors belong to an older population or to a low-metallicity environment, the number of bright SNe Ia is reduced, so that the variation in brightness among the SNe Ia is also smaller. Thus, our model can explain why the mean SN Ia brightness and its dispersion depend on the morphology of the host galaxies and on the distance of the SN from the center of the galaxy. It is further predicted that at higher redshift (z 1), both the mean brightness of SNe Ia and its variation should be smaller in spiral galaxies than in elliptical galaxies. These variations are within the range observed in nearby SNe Ia. Insofar as the variation in X(C) is the most important cause for the diversity among SNe Ia, the light-curve shape method that is currently used to determine the absolute magnitude of SNe Ia can also be applied to high-redshift SNe Ia.

Atmospheric particulate absorption and black carbon measurement

It is convenient to measure the optical attenuation A of the combination of a layer of atmospheric particulate matter and the quartz fiber filter on which it has been collected. The problem of relating A to the absorption and scattering coefficients k and s of the particulate matter itself is treated as a problem in diffuse reflectance spectroscopy using the KubelkaMunk theory. The results show that although, in general, A is a nonlinear function strongly dependent on both s and k, for a limited range of s and sample thickness d, A can be a practically linear function of k. Fortunately, this range includes that common to atmospheric particulate samples. Furthermore, it is shown that if the filter's reflectance is sufficiently high, A can be nearly independent of s. This is in agreement with experimental and, for the limiting case when the substrate filter reflectance is unity, theoretical results obtained by other researchers. Use of such measurements of A as a means of determining the black carbon mass loading C on a filter is also investigated. It is shown that when the black carbon mass fraction f(c) is high, as it is for samples collected in large urban areas, A is a predictable and practically linear function of C. However, when f(c) is low, as it is for many rural locations, then the slope of the function A(C) is strongly dependent on f(c), leading to possible overestimates of C. This problem can be alleviated by making the measurement of A at near-infrared wavelengths rather than in the visible spectrum.

Spectral analyses of WC stars in the LMC

Spectra of seven WC stars in the LMC are taken with the HST-FOS. They are analyzed by means of non-LTE models for spherically expanding atmospheres with complex model atoms of helium, carbon and oxygen taken into account. We find stellar luminosities in the range from 1051–56 L⊙. The stellar temperature T*, defined as the effective temperature related to the stellar core radius, is of the order of 100 kK. The atmospheric compositions show carbon mass fractions of about 0.4 and oxygen mass fractions in the range 0.1–0.5.

Effect of Linear-Dodecylbenzenesulfonate and Humic Acid on the Adsorption of Tricresyl Phosphate Isomers onto Clay Minerals

The adsorption of three tricresyl phosphate (TCP) isomers, o-, m-, and p-TCP, onto kaolin, alumina, and montmorillonite without coating or coated with linear-dodecylbenzenesulfonate (DBS) or humic acid was studied. The amount of TCP isomers adsorbed per unit mass of mineral followed the order alumina < kaolin < montmorillonite, but that per unit surface area of mineral was in the order kaolin < montmorillonite < alumina. The amount of TCP adsorbed was almost constant between pH 4 and 9. Higher adsorption per unit surface area on alumina might be due to the strong interaction between Al and phosphate oxygen (P0) of TCP. Adsorption of TCP isomers on kaolin and alumina followed the order o-TCP < m-TCP < p-TCP, depending on their steric hindrance. Adsorption of TCP isomers on kaolin and alumina was enhanced with an increase in DBS adsorbed. This might be due to the hydrophobic interaction of TCP isomers with DBS adsorbed on minerals. Similarly, the adsorption of TCP isomers was accelerated in the presence of humic acid. However, adsorptive capacity of TCP isomers on minerals coated with humic acid was smaller than that with DBS. This is possibly due to the difference in hydrophobicity between humic acid and DBS adsorbed. It was confirmed that the carbon-normalized adsorption coefficient (Koca) decreased with increasing carbon mass fraction of DBS and humic acid adsorbed on minerals.

A Mathematical Model of the Carbon Arc Reactor for Fullerene Synthesis

A mathematical model of the carbon arc process for the synthesis of fullerenes (C 60 , C 70 ) is developed. The two-dimensional model solves for the velocities, temperature, and total concentration of carbon species. The net emission coefficient method is used for the radiation term. The carbon species conservation equations consider the evaporation of carbon from the anode, cathode surface deposition, and carbon condensation. The thermodynamic and transport properties are calculated as a function of temperature and carbon mass fraction, using the method of Chapman–Enskog. Erosion rates used by the model are determined experimentally. Calculated fields of the velocities, temperatures, carbon mass fraction and current intensity are presented. Comparison is made of the behavior of the arc at 1 and 4 mm interelectrode gaps, and between operation in argon and in helium. The results of simulations provide a justification for the higher yields observed in helium compared to the argon case.

Airborne measurements of carbonaceous aerosols on the East Coast of the United States

In this paper we report results of aircraft measurements of mass concentrations of carbonaceous aerosols, total aerosol mass, and simultaneously determined light scattering and absorption coefficients onshore and offshore of the eastern coast of the United States. We describe the sampling and analytical methodology used to derive spatially resolved aerosol carbon concentrations and discuss these in the context of other concurrently collected data. The carbon mass was, on average, 50% of the total dry aerosol mass. The carbon mass fraction tended to increase with altitude, suggesting that ground‐based measurements can significantly underestimate the importance of carbon species in the column aerosol mass budget. The aerosol carbon mass was significantly correlated with aerosol light absorption, suggesting that the black and organic carbon components have, at least in part, common combustion sources. A regression of the light absorption coefficient onto carbon mass suggests that ∼10% of the carbon mass is in the form of black (light‐absorbing) carbon.

The dependence of the specific attenuation cross-section on black carbon mass fraction and particle size

The specific attenuation cross-section σ ATN which relates the attenuation of light by a particleloaden quartz fiber filter to the black carbon (BC) content of deposited fine dust is the most important parameter far optical BC determination using an aethalometer. A simple model is presented to describe the effects of light scattering particles on the specific attenuation cross-section. It is found that σ ATN varies with the BC fraction of total mass f according to δ ATN = σ abs + ( f −1 − 1) σ scat The average specific scattering cross-section σ scat depends on the light scattering dry fraction of fine dust particles, while the specific absorption cross-section σ abs is determined by the light absorbing BC particles. The application of the model to an externally mixed BC-NaCl aerosol shows excellent agreement between the proposed theory and our experiments. The suitability of the outlined model is confirmed by analyses of attenuation data sets obtained from several measuring sites in Germany. For the examined data sets the average attenuation cross-section σ ATN of ambient BC varies between 8 m 2 g −1 (rural sites) and 19 m 2 g −1 (street crossing). These variations can be explained by assuming a site-independent BC absorption cross-section σ abs = 4 m 2 g −1 which is derived from experiments with a BC test aerosol, and by varying the σ scat value from 0.45 m 2 g −1 (rural sites) to 1.2–1.4 m 2 g −1 (urban areas). Finally, the particle size dependence of the specific absorption cross-section σ abs is examined for a particle size range from 0.05 μm to 1.1 μm. As it is suggested by the fractal nature of BC particles no size dependence of σ abs with respect to the used BC test aerosol is found.

Fibrous metal–carbon composite structures as gas diffusion electrodes for use in alkaline electrolyte

The fabrication of novel fibre composite electrode structures and the performance assessments for oxygen reduction in alkaline electrolyte is reported. An array of 2μm diameter activated carbon fibres interlocked within a network of 2μm sinter-bonded metal fibres to form the composite structure was used. The resulting electrode structure is stable, highly conductive and can maintain void fraction exceeding 95%. Electrode physical properties including thickness, macroporosity, volume and mass fractions of constituent carbon and metal fibres have been controlled, characterized, and related to the electrode polarization in a KOH half cell. Comparisons have been made with a commercial Teflon-bonded gas diffusion electrode (GDE). It has been demonstrated that this novel method allows reproducible and low-cost fabrication of GDEs with the optimal balance between macropores for gas access, micropores for liquid access, and conductive paths for electron access.

Physiology of Saccharomyces cerevisiae during cell cycle oscillations

Synchronized populations of Saccharomyces cerevisiae CBS 426 are characterized by autonomous oscillations of process variables. CO 2 evolution rate, O 2 uptake rate and heat production rate varied by a factor of 2 for a continuous culture grown at a dilution rate of 0.10 h −1. Elemental analysis showed that the carbon mass fraction of biomass did not change. Since the reactor is not at steady state, the elemental and energy balances were calculated on cumulated quantities i.e. the integral of the reaction rates. It was possible to show that carbon, degree of reduction and energy balances matched. Application of simple mass balance principles for non-steady state systems indicated that oscillations were basically characterized by changes in biomass production rate. In addition, the amount of intermediates e.g. ethanol or acetate, produced or consumed was negligible. Growth rate was low during the S-phase (0.075 h −1) and high during the G2, M and G1 phases (0.125 h −1) for a constant dilution rate of 0.10 h −1. However, nitrogen, ash, sulfur and potassium content showed systematic increases during the S-phase (bud initiation). Cell component analyses showed that changes in cellular fractions during oscillations (storage carbohydrate content decreased during the S-phase) were due to changes in production rates, particularly for protein and carbohydrates. Nevertheless, using the data evaluation techniques for dynamic systems presented here, it was shown that storage carbohydrates are not consumed during the S-phase. Only the synthesis rate of the different cell components changed depending on position in cell cycle. The growth process may be divided into two phenomena: the formation of new cells during mitosis with a low yield, and size increase of new born cells with high yield. Both kinetic and stoichiometric coefficients varied with the position in the oscillation: the results showed that biomass structure changed and that specific growth rate, as well as biomass yield, varied by ± 25% during the oscillation.

Updated Opal Opacities

The reexamination of astrophysical opacities has eliminated gross discrepancies between a variety of observations and theoretical calculations; thus allowing for more detailed tests of stellar models. A number of such studies indicate that model results are sensitive to modest changes in the opacity. Consequently, it is desirable to update available opacity databases with recent improvements in physics, refinements of element abundance, and other such factors affecting the results. Updated OPAL Rosseland mean opacities are presented. The new results have incorporated improvements in the physics and numerical procedures as well as corrections. The main opacity changes are increases of as much as 20{percent} for Population I stars due to the explicit inclusion of 19 metals (compared to 12 metals in the earlier calculations) with the other modifications introducing opacity changes smaller than 10{percent}. In addition, the temperature and density range covered by the updated opacity tables has been extended. As before, the tables allow accurate interpolation in density and temperature as well as hydrogen, helium, carbon, oxygen, and metal mass fractions. Although a specific metal composition is emphasized, opacity tables for different metal distributions can be made readily available. The updated opacities are compared to other work. {copyright} {ital 1996 Themore » American Astronomical Society.}« less