Comparison of concentrations and size distributions of fungal spores in buildings with and without mould problems

Concentrations and types of airborne fungal spores and their aerodynamic sizes were studied in nine buildings with mould problems and in matched reference buildings in order to characterize the exposure in buildings with mould problems. Samples were taken with Andersen six-stage impactors in the autumn and winter. In winter, total concentrations of fungal spores in buildings with mould problems were twice those in reference buildings, even though all concentrations were quite small. In the autumn, the differences were less obvious due to the masking effect of outdoor air fungi. Also, the compositions of fungal genera differed in buildings with mould problems from that in reference buildings. The difference was most significant in the size range 2.1-4.7 μm. The size distribution of fungal spores in dwellings with mould problems skewed towards larger particles than in reference dwellings. The observed differences in size distribution indicate differences in airborne behaviour of fungal spores and, consequently, in respiratory exposure.     

Effects of Compression and Filler Particle Coating on the Electrical Conductivity of Thermoplastic Elastomer Composites

Elastomeric polymers can be filled with metallic micro- or nanoparticles to obtain electrical conductivity, in which the conductivity is largely determined by the intrinsic conductivity of and contact resistance between the particles. Electrons will flow through the material effectively when the percolation threshold for near-neighbor contacts is exceeded and sufficiently close contacts between the filler particles are realized for electron tunneling to occur. Silver-coated glass microparticles of two types (fibers and spheres) were used as fillers in a thermoplastic elastomer composite based on styrene–ethylene–butylene–styrene copolymer, and the direct-current (DC) resistance and radiofrequency impedance were significantly reduced by coating the filler particles with octadecylmercaptan. Not only was the resistance reduced but also the atypical positive piezoresistivity effect observed in these elastomers was strongly reduced, such that resistivity values below 0.01 Ω cm were obtained for compression ratios up to 20%. In the DC measurements, an additional decrease of resistivity was obtained by inclusion of π-extended aromatic compounds, such as diphenylhexatriene. Some qualitative theories are presented to illuminate the possible mechanisms of action of these surface coatings on the piezoresistivity.     

Characterization of diesel particles: effects of fuel reformulation, exhaust aftertreatment, and engine operation on particle carbon composition and volatility

Diesel exhaust particles are the major constituent of urban carbonaceous aerosol being linked to a large range of adverse environmental and health effects. In this work, the effects of fuel reformulation, oxidation catalyst, engine type, and engine operation parameters on diesel particle emission characteristics were investigated. Particle emissions from an indirect injection (IDI) and a direct injection (DI) engine car operating under steady-state conditions with a reformulated low-sulfur, low-aromatic fuel and a standard-grade fuel were analyzed. Organic (OC) and elemental (EC) carbon fractions of the particles were quantified by a thermal-optical transmission analysis method and particle size distributions measured with a scanning mobility particle sizer (SMPS). The particle volatility characteristics were studied with a configuration that consisted of a thermal desorption unit and an SMPS. In addition, the volatility of size-selected particles was determined with a tandem differential mobility analyzer technique. The reformulated fuel was found to produce 10-40% less particulate carbon mass compared to the standard fuel. On the basis of the carbon analysis, the organic carbon contributed 27-61% to the carbon mass of the IDI engine particle emissions, depending on the fuel and engine operation parameters. The fuel reformulation reduced the particulate organic carbon emissions by 10-55%. In the particles of the DI engine, the organic carbon contributed 14-26% to the total carbon emissions, the advanced engine technology, and the oxidation catalyst, thus reducing the OC/EC ratio of particles considerably. A relatively good consistency between the particulate organic fraction quantified with the thermal optical method and the volatile fraction measured with the thermal desorption unit and SMPS was found.     

Modernity and Die Historical Perspectivism of Nietzsche and Loos

In recent years, the increasingly diminished structure and role of architecture in society has seemed to represent, at least in part, the failure of modern thought to sustain a sufficiently robust conceptualization of cultural phenomena in general, and architecture in particular. This article addresses two fundamental questions: (1) what is the nature of this theoretical cul-de-sac in which architecture now finds itself? and (2) is there a way forward that will resuscitate the stature and mission of architecture? The first question is addressed through the analysis of how the exclusively “subjectivist” philosophical tradition of modern thought has led to an impoverished understanding of architecture. The second question leads to the suggestion that a truly “culturalist” perspective would serve to sustain a more responsible and powerful role for architecture.     

Dispersion studies on a solid waste refuse incinerator

The dispersion of the emissions of a municipal solid waste incinerator in eastern Helsinki has been studied by analysing birch leaf (Betula pubescent) and grass (mainly couch‐grass, Elymys repens) samples collected from the neighbourhood of the incinerator. The elemental concentrations of 17 elements were analyzed by the PIXE method. The incinerator was closed down in March 1983 because of the then measured high emissions. In the birch leaf samples collected in September 1982 (before the shut‐down) elemental concentrations of 11 elements varied strongly as a function of distance from the incinerator. In the respective samples collected in September 1983 (after the shut‐down) no clear distance versus concentration dependence was obtained for any elements.     

Characterization of the Gent Stacked Filter Unit PM10 Sampler

ABSTRACT

An integral part of several International Atomic Energy Agency sponsored coordinated research programmes involving the sampling and analysis of ambient airborne particules was the development of a PM₁₀ sampler. Each participant was provided with such a sampler so that comparable samples would be obtained by each of the participating groups. Thus, in order to understand the characteristics of this sampler, we undertoke several characterization studies in which we examined the aerodynamic collection characteristics of the impactor inlet and the reproducibility of the sample mass collection. One of the samplers machined in Belgium was compared with one built from the same design in the U.S. and comparable results were obtained. The sampler was operated side-by-side with a commercial PM₁₀ beta gauge and an IMPROVE-design 2.5 μm cut-point cyclone. Although the sampler was not wind tunnel tested as required for certification as a reference sampler, it does provide a collection efficiency that generally follows the guidelines for a PM₁₀ sampler.     

Particle emission from gasoline powered vehicles: Emission, deposition and re-emission under different traffic density situations

Particle emission, re-emission and deposition from a gasoline fueled car were investigated during driving conditions in streets. The measurement facility was carried on a trailer behind the testcar. Filter collection and sedimentation samplers were used for particle collection. Measurements were performed in different environmental and meteorological situations.

Particle emission was also measured in laboratory conditions at temperatures of + 20 and − 20°C using gasoline and diesel engines.

The elemental composition of the particle samples was analyzed by the PIXE-method and the composition data by a statistical cluster-method. The results for re-emission and condensation growth of aerosols were compared with theoretical calculations.

The re-emission fraction in summer conditions was obtained to be over 70% in high traffic densities and about 50% in low densities. The condensation growth was about four times higher in the cold air than in the warm weather.