Search

Abstract: Nucleation mode particles were investigated for their morphology using TEM and the presence or absence of solid cores was addressed. At cold start idle nucleation particles were observed in the exhaust of a diesel passenger car. These particles occurred with both low and high S fuel and were only partly volatile in a thermodenuder, which indicates that the composition was not sulfate and as derived from TEM/EDX (transmission electron microscopy/energy dispersive X-ray analysis) probably not ash. It could be high boiling hydrocarbons, or primary soot particles. With all fuels at warm idle no nucleation particles and only soot particles were observed in the SMPS and the TEM. With 3.0×1011 s−1 the total soot particle number during idle was much less than during driving, e.g. at 120kmh−1 the emission rate was 6.7×1012 s−1. At high load and high S fuel 10–20nm nucleation particles were observed by SMPS and TEM. A thermodenuder at 280°C and TEM showed that all nucleation particles were volatile. EDX gave a weak S-signal only. Some nucleation particles contained smaller spots (1–3nm) with a very high contrast, which might be due to heavy elements. However, under the electron beam of the TEM these spots disappeared and EDX analysis was not possible. With low S fuel at 120kmh−1 only soot particles and no nucleation particles were observed. [Copyright &y& Elsevier]

In-situ measurements of various properties of traffic-related aerosol particles have been performed with a mobile laboratory. The measured aerosol quantities include particle chemical composition (sulfate, nitrate, total organic matter, ammonium, black carbon) as well as particle size distributions covering diameters from 10 to 300nm, and total particle number density. Additionally, gas phase emissions (CO2, NO, NO2) were monitored. We performed six measurement drives in the vicinity of the city of Aachen (population ca. 260,000) at 50.8°N, 6.1°E in Germany on motorways, rural roads, and in the inner city of Aachen in June 2005. The results indicate that the main influence of traffic on the aerosol properties results in soot particles coated with organic matter, having a modal diameter around 100nm (“soot mode”). The abundance of these particles was found to be highest in the inner city traffic. Nucleation mode particles (around 30nm) have been observed occasionally during truck chasings on motorways. These particles consisted mainly of organic compounds but included possibly also a sulfuric acid core. Data observed under “motorway background” conditions were similar to the rural regional road data. Highest number concentrations have been observed during truck chasings. Comparison between non-refractory (here with respect to 600°C) and total particle volume indicated a higher contribution of refractory material under all traffic-influenced conditions compared to rural road data. Fuel specific emission ratios were derived for a subset of 18 truck-chasing experiments, yielding (8.3±5.8)×1015 kg−1 for particle number, 224±136mgkg−1 for black carbon, 125±125mgkg−1 for organic matter, 17±12gkg−1 for NO and 18±14gkg−1 for NO x (mean values and standard deviations). [Copyright &y& Elsevier]

The idea of a multiverse – an ensemble of universes – has received increasing attention in cosmology, both as the outcome of the originating process that generated our own Universe, and as an explanation for why our Universe appears to be fine-tuned for life and consciousness. Here we carefully consider how multiverses should be defined, stressing the distinction between the collection of all possible universes, and ensembles of really existing universes that are essential for an anthropic argument. We show that such realized multiverses are by no means unique. A proper measure on the space of all really existing universes or universe domains is needed, so that probabilities can be calculated, and major problems arise in terms of realized infinities. As an illustration we examine these issues in the case of the set of Friedmann–Lemaître–Robertson–Walker universes. Then we briefly summarize scenarios such as chaotic inflation, which suggest how ensembles of universe domains may be generated, and we point out that the regularities which must underlie any systematic description of truly disjoint multiverses must imply some kind of common generating mechanism. Finally, we discuss the issue of testability, which underlies the question of whether multiverse proposals are really scientific propositions. [ABSTRACT FROM AUTHOR]

Within the framework of the AIDA soot aerosol campaign diesel soot particles, spark generated soot particles, and aerosol mixtures were characterized with respect to their chemical state using different surface sensitive analysis methods. A comparison between diesel soot and graphite spark generated soot revealed a significant difference in the chemical composition of the particle surfaces. No distinct change from external to internal mixing could be detected by single particle mass spectrometry for mixtures of diesel soot and (NH4)2SO4 aerosol since the spectra of diesel soot and (NH4)2SO4 aerosol were surprisingly similar due to sulfate on the surface of diesel soot particles and traces of carbon impurities on ammonium sulfate particles. In addition to the expected formation of new particles a considerable change of the soot particle surface was detected while exposing diesel soot or spark generated soot to α-pinene and ozone, indicating a surface layer formed by oxidation products of α-pinene. However, the oxygen-containing hydrocarbon fragments detected by single particle mass spectrometry were distinctly different for the two soot types, which can be explained by either the different product adsorption or ionization behavior. Depositions of α-pinene reaction products on the surface could be confirmed by QMS-SIMS and XPS for particles of both types of soot. Due to the high mass resolution of TOF-SIMS acidic derivatives were identified as reaction products of α-pinene and ozone. The analytical methods applied in this work elucidated the different properties of spark generated soot compared to diesel soot. Therefore, spark generated soot should only be used with care as a general diesel soot surrogate. [Copyright &y& Elsevier]

A single-particle mass spectrometer (LAMPAS-2) was operated at an Autobahn (high-speed highway with significant heavy-duty diesel traffic), an urban and a rural site in the vicinity of Aachen (Germany). The single-particle mass spectra could be classified into eight classes, representing different types of mineral particles, inorganic salt particles, and carbonaceous aerosol particles. At all three sites characteristic patterns of diesel exhaust particles with and without secondary compounds (ammonium sulfate/nitrate) were observed. The relative contribution of diesel soot to the number of 0.5 μm particles was 23% or 35% at the rural and the Autobahn site, respectively. The absolute number of diesel exhaust particles was three times larger at the Autobahn site. At the urban site the diesel exhaust particle contribution ranged from 10% to 35%, depending on the local operation of heavy-duty construction vehicles. Elemental carbon and carbonaceous particles made up the majority number of the 0.5 μm particles, and showed a decreasing percentage towards 2 μm particle size. As expected mineral-soil-derived particles showed the reverse size distribution. The data sets were also analyzed using a reference pattern obtained from exhaust particles of a light-duty diesel vehicle as a fingerprint. A similar trend of the contribution to the diesel-exhaust-like particle class was found, although the absolute numbers were somewhat different. On-line single-particle mass spectrometry proved to be a promising tool to identify individual particles if characteristic reference spectra were available. [Copyright &y& Elsevier]

The article offers information on cost estimation accuracy in healthcare industry by healthcare professionals. It mentions factors contributing to coast estimation accuracy involves deficient education or training, and poor availability of cost information. It also mentions importance of log (deviation) that normalize data distribution in studies involving cost analysis estimation and avoid systematic bias towards overestimation.

Abstract: Various types of combustion-related particles in the size range between 100 and 850nm were analyzed with an aerosol mass spectrometer and a differential mobility analyzer. The measurements were performed with particles originating from biomass burning, diesel engine exhaust, laboratory combustion of diesel fuel and gasoline, as well as from spark soot generation. Physical and morphological parameters like fractal dimension, effective density, bulk density and dynamic shape factor were derived or at least approximated from the measurements of electrical mobility diameter and vacuum aerodynamic diameter. The relative intensities of the mass peaks in the mass spectra obtained from particles generated by a commercial diesel passenger car, by diesel combustion in a laboratory burner, and by evaporating and re-condensing lubrication oil were found to be very similar. The mass spectra from biomass burning particles show signatures identified as organic compounds like levoglucosan but also others which are yet unidentified. The aerodynamic behavior yielded a fractal dimension (D f) of 2.09±0.06 for biomass burning particles from the combustion of dry beech sticks, but showed values around three, and hence more compact particle morphologies, for particles from combustion of more natural oak. Scanning electron microscope images confirmed the finding that the beech combustion particles were fractal-like aggregates, while the oak combustion particles displayed a much more compact shape. For particles from laboratory combusted diesel fuel, a D f value of 2.35 was found, for spark soot particles, D f ≈2.10. The aerodynamic properties of fractal-like particles from dry beech wood combustion indicate an aerodynamic shape factor χ that increases with electrical mobility diameter, and a bulk density of 1.92gcm−3. An upper limit of χ ≈1.2 was inferred for the shape factor of the more compact particles from oak combustion. [Copyright &y& Elsevier]

Mass spectrometric measurements of size and composition of diesel exhaust particles have been performed under various conditions: chassis dynamometer tests, field measurements near a German motorway, and individual car chasing. Nucleation particles consisting of volatile sulfate and organic material could be detected both at the chassis dynamometer test facility and during individual car chasing. We found evidence that if nucleation occurs, sulfuric acid/water is the nucleating agent Low-volatile organics species condense only on the preexisting sulfuric acid/water clusters. Nucleation was found to depend strongly on various parameters such as exhaust dilution conditions, fuel sulfur content and engine load. The latter determines the fraction of the fuel sulfur that is converted to sulfuric acid. The organic compounds (volatile and low- volatile) condense only on preexisting particles, such as both sulfuric acid nucleation particles and larger accumulation mode soot particles. On the latter, sulfuric acid also condenses, if the conditions for nucleation are not given. The overall ratio of sulfate to organic (volatile and low- volatile) is also strongly dependent on the engine load. It was found that the production of nucleation particles even at high engine load can be suppressed by using low- sulfur fuel. [ABSTRACT FROM AUTHOR]