Processing of Soot by Controlled Sulphuric Acid and Water Condensation—Mass and Mobility Relationship

The effects of atmospheric processing on soot particle morphology were studied in the laboratory using the Differential Mobility Analyzer-Aerosol Particle Mass Analyzer (DMA-APM) and the DMA-DMA (Tandem DMA) techniques. To simulate atmospheric processing, combustion soot agglomerates were altered by sulphuric acid vapor condensation, relative humidity (RH) cycling, and evaporation of the sulphuric acid and water by heating. Primary investigated properties were particle mobility size and mass. Secondary properties, derived from these, include effective density, fractal dimension, dynamic shape factor, and the mass fraction of condensed material. A transformation of the soot particles to more compact forms occurs as sulphuric acid and water condense onto fresh soot. The particle mass increases and initially the mobility diameter decreases, indicating restructuring of the soot core, likely due to surface tension forces. For a given soot source and condensing liquid, the degree of compaction depends strongly on the mass (or volume) fraction of condensed material. For water and sulphuric acid condensing on combustion soot, a mass increase of 2–3 times is needed for a transformation to spherical particles. In the limit of spherical particles without voids, the effective density then approaches the inherent material density, the fractal dimension approaches 3 and the dynamic shape factor approaches 1. Our results indicate that under typical atmospheric conditions, soot particles will be fully transformed to spherical droplets on a time scale of several hours. It is expected that the morphology changes and addition of soluble material to soot strongly affect the optical and hygroscopic properties of soot.     

Effect of Humidity on Constant Output and Breath Enhanced Nebulizer Designs When Tested in the EN 13544-1 EC Standard

Aqueous aerosols produced by nebulizers used in clinical situations can rapidly change size as the patient inhales. This is caused by air with a relative humidity (RH) lower than inside the nebulizer being entrained and mixed with nebulized aerosol during the inhalation maneuver. A way to assess the change in size is to measure the aerosol in a test method that reflects the clinical situation. The EC standard, EN 13544-1, offers a first step towards this assessment. In this paper we have tested two nebulizer designs, one conventional constant output nebulizer and one breath-enhanced nebulizer, using the proposed standard in order to assess the effect of the relative humidity of entrained ambient air on nebulized aerosol size properties. The results indicate that aerosol size from the conventional nebulizer is greatly affected by the RH of the entrained air, while the breath-enhanced nebulizer is not affected. The results agree with theoretical expectations of how the entrained air interacts with nebulized aerosol. In the breath-enhanced nebulizer, the air is passed through the nebulizer interior and becomes saturated with moisture drawn from the relatively large nebulizer reservoir solution. With the conventional constant output nebulizer, ambient air is drawn over the nebulizer and draws its moisture from the relatively small volume of nebulized aerosol released from the nebulizer. For the conventional nebulizer design, we found a large decrease in measured nebulized aerosol size with decreasing relative humidity--3.1 w m MMAD at 75% RH fell to 1.9 w m MMAD at 20% RH. For the breath-enhanced nebulizer design, the MMAD was stable between a similar humidity range. The results indicate that aerosol size is dependent on relative humidity of the entrained air for the constant output jet nebulizer design that has no air entrainment through the nebulizer. We found no significant effect of ambient humidity of entrained air on nebulized aerosol size from the breath-enhanced nebulizer design.     

Phase-Field Modeling of Sigma-Phase Precipitation in 25Cr7Ni4Mo Duplex Stainless Steel

Phase-field modeling is used to simulate the formation of sigma phase in a model alloy mimicking a commercial super duplex stainless steel (SDSS) alloy, in order to study precipitation and growth of sigma phase under linear continuous cooling. The so-called Warren–Boettinger–McFadden (WBM) model is used to build the basis of the multiphase and multicomponent phase-field model. The thermodynamic inconsistency at the multiple junctions associated with the multiphase formulation of the WBM model is resolved by means of a numerical Cut-off algorithm. To make realistic simulations, all the kinetic and the thermodynamic quantities are derived from the CALPHAD databases at each numerical time step, using Thermo-Calc and TQ-Interface. The credibility of the phase-field model is verified by comparing the results from the phase-field simulations with the corresponding DICTRA simulations and also with the empirical data. 2D phase-field simulations are performed for three different cooling rates in two different initial microstructures. A simple model for the nucleation of sigma phase is also implemented in the first case. Simulation results show that the precipitation of sigma phase is characterized by the accumulation of Cr and Mo at the austenite-ferrite and the ferrite-ferrite boundaries. Moreover, it is observed that a slow cooling rate promotes the growth of sigma phase, while a higher cooling rate restricts it, eventually preserving the duplex structure in the SDSS alloy. Results from the phase-field simulations are also compared quantitatively with the experiments, performed on a commercial 2507 SDSS alloy. It is found that overall, the predicted morphological features of the transformation and the composition profiles show good conformity with the empirical data.

     

Application of interrupted cooling experiments to study the mechanism of bainitic ferrite formation in steels

New interrupted cooling experiments have been designed to study the kinetics of bainitic ferrite formation starting from a mixture of austenite and bainitic ferrite. It is found that the kinetics of bainitic ferrite formation during the cooling stage is determined by the isothermal holding time. The formation rate of bainitic ferrite at the beginning of the cooling decreases with increasing prior isothermal holding time. An unexpected stagnant stage during the cooling stage appears when the isothermal holding time increases to a critical point. There are two reasons for the occurrence of the stagnant stage: (i) a solute spike in front of the interface; and (ii) kinetic transition. A so-called Gibbs energy balance approach, in which the dissipation of Gibbs energy due to diffusion inside the interface and interface friction is assumed to be equal to the available chemical driving force, is applied to theoretically explain the stagnant stage. A kinetics transition from a fast growth mode without diffusion of Mn and Si inside the austenite–bainitic ferrite interfaces to a slow growth mode with diffusion inside the interface is predicted. The stagnant stage is caused by the transition to a slow growth mode. The Gibbs energy balance approach describes the experimental observations very well.     

Environmental life cycle assessment of a pre‐fragmented high explosive grenade

Organisations today face increasing environmental constraints, e.g. in the form of legal and customer requirements; the defence sector is no exception. There is a need to evaluate and limit environmental effects of defence activities and materiel. In this study we used quantitative Life Cycle Assessment (LCA) and a method for simplified LCA (the Material, Energy, Chemicals and Others (MECO) method) to assess the environmental impacts of a grenade. The aims of the study are to identify aspects in the grenade's life‐cycle that have the largest environmental impact, suggest improvement possibilities, make a comparison between different approaches for waste management of munitions, and to perform a demonstrative case for the application of LCA to munitions. Significant environmental aspects of the grenade's life‐cycle include use of metals, use of fossil fuels, and detonation outdoors. The study shows that an LCA can be used to analyse environmental impacts from munitions. The simplified LCA gave information that is complementary to the quantitative LCA. Copyright © 2005 Society of Chemical Industry     

Does waterborne citalopram affect the aggressive and sexual behaviour of rainbow trout and guppy?

Citalopram is one of several selective serotonin reuptake inhibitors (SSRIs) commonly found in treated sewage effluents. Accordingly, there are concerns about possible adverse effects of SSRIs on aquatic organisms, particularly behavioural effects similar to those associated with SSRI use in humans. Rainbow trout fry and adult male guppies were therefore exposed to waterborne citalopram, ranging from environmentally relevant to high concentrations (1, 10, 100 μg/L) for 3-7 days. Under these experimental conditions citalopram does not appear to cause significant effects on aggression in rainbow trout fry or on sexual behaviour in male guppies. This may be explained by a relatively low uptake of citalopram from water to fish.     

An improved assessment method for the temperature dependence of yield strength values

In Europe work is in progress to establish new standards for materials and it is very important that accurate data are used as a basis for property values in these standards. In addition reliable evaluation methods must be employed when the values are derived. A systematic evaluation method for yield strengths at elevated temperatures has been developed which is a modification of the ISO 2605/111 (ENV22605-3) procedure. The method has been applied to a number of steel types and has proven to provide values in good accordance with experimental data. Comparisons with existing national and international standards showed the importance of using experimental values when establishing new standards. The method is intended for use in the standard developments by the European Committee for Iron and Steel Standardisation (ECISS).     

Nuclear microscopy in biomedical analysis with special emphasis on clinical metal biology

Nuclear microscopy based upon developments in high energy ion beam techniques is by now an accepted technique in many fields of research. The advancements into the biomedical field have, however, been slower than expected. A major factor explaining this tendency is the availability of nuclear microscopy. This paper reviews briefly the biomedical work using nuclear microscopy that has been carried out since the 4^th International Conference on Nuclear Microprobe Technology and Applications held in Shanghai. Nuclear microscopy of isolated individual blood cells from patients adversely affected by metal exposure from dental amalgam has been performed both before and after removal of the metallic fillings. The elemental profile of blood cells was more or less normalised after treatment. Some of these results will be presented to illustrate a medical application. Results from bulk analysis by ICP-MS of erythrocytes and plasma before and after treatment will also be presented to illustrate the difference in information content between these two approaches as well as the need for complementary information in solving biomedical problems. As part of a larger study of acute porphyria, nuclear microscopy of blood cells was included among the 78 laboratory tests. The approach in this study was unbiased in the sense that no hypothesis was formulated as to which laboratory parameters would be the most explanatory for health or disease. Multivariate discriminant analysis was applied to the large amounts of data acquired. This approach led to the hypothesis that oxidative stress increased the synthesis of manganese-dependent superoxide dismutase in the mitochondria of polymorphonuclear leukocytes, explaining the increase of manganese in these cells. Antioxidant therapy was therefore applied to a couple of patients with porphyria, however, without clinical success.