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Laboratory experiments have been carried out to elucidate the role of surfactants on the primary marine aerosol production of submicron marine aerosols. A synthetic surfactant SDS was used in conjunction with artificially generated seawater, and the resultant bubble-mediated aerosol produced was observed. At 23°C, the aerosol distribution resulting from the use of surfactant-free seawater comprised three modes: (1) a dominant accumulation mode at 110 nm; (2) an Aitken mode at 45 nm; and (3) a third mode, at 300 nm, resulting from forced bursting of bubbles. The forced bursting occurs when bubbles fail to burst upon reaching the surface and are later shattered by splashing associated with breaking waves and/or wind pressure at the surface. At 4°C, the accumulation mode diameter was reduced to 85 nm, the Aitken mode diameter was reduced to <30 nm and the 300 nm mode diameter was reduced to 200 nm. With the addition of SDS, the relative importance of the mode resulting from forced bursting increased dramatically. The laboratory results were compared to the observed seasonality of North Atlantic marine aerosol where a progression from mode radii minima in winter to maxima in summer is seen. The bimodality and the seasonality in modal diameter can be mostly explained by a combination of the three modes observed in the laboratory and their variation as a function of sea-surface temperature and seawater surfactant concentration. These results indicate that submicron primary aerosol modes would on a first approximation result from bubble bursting processes, although evidences of additional secondary processes leading, during summer, to a higher amplitude of the Aitken mode and mode 2 smoothed into mode 3 still need to be investigated. Copyright 2006 by the American Geophysical Union.

An algorithm for the retrieval of the aerosol optical thickness over land and over water from Global Ozone Monitoring Experiment (GOME) data is presented. The cloud fraction in the GOME pixels is determined using the Fast Retrieval Scheme for Clouds From the Oxygen A Band (FRESCO) algorithm. Surface contributions to the top of atmosphere reflectance are determined from the GOME surface reflectance database. The aerosol retrieval algorithm uses lookup tables that were created using the radiative transfer model 6S. The algorithm allows retrieving the aerosol types characterized by Angstrom coefficients in the range from -0.1 to 2.8; i.e., the range of values observed by the AERONET ground-based measurements. Validation of the algorithm done using the AERONET Sun photometer data for 12 sites in Europe and Africa, for the year 1997, shows very good agreement. The correlation coefficient between the satellite retrieval and AERONET data for the wavelength of 440 nm is 97%, and for 670 nm it is 94%. Validation of the algorithm for the year 2000 was done for a few sites with similar results. The algorithm has been successfully tested over an island influenced by Saharan dust (i.e., Cape Verde, 16oN, 22oW and over a site located near the Saharan desert (i.e., Bondoukoui, 11oN, 3oW). For other sites located near the Saharan desert such as Bidi Bahn (14oN, 2oW) and Banizombou (13oN, 2oE), the agreement was very good at 440 nm. The algorithm has not been tested over other bright surfaces such as ice-covered regions. Examples of the spatial distribution of the aerosol optical thickness over Europe, north Africa, and the North Atlantic for the year 1997 and 2000 are presented.

Maintenance and operations of road safety equipment and infrastructure ensure that all safety related elements of the road system are operating as they were designed, tested, and approved. Maintenance of road equipment should not only be considered as the repair of broken or damaged equipment, but also as a potential monitoring system for the road network. This overlooked aspect of maintenance and operations is a central theme for the following sections.

The European Commission Directorate General for Transportation and Energy (DGTREN) sponsored a research project to investigate the best practice guidelines for roadside infrastructure. The RISER consortium has compiled the following document which is a synthesis of existing practice in Europe with additional information collected from accident and human behaviour studies. Several technical reports developed in the RISER project were the basis for this document and can provide more technical information. The information contained in this document should be used in conjunction with the document 'European Best Practice for Roadside Design: Guidelines for Maintenance and Operations of Roadside Infrastructure'.

Chemical analysis is one of the most important parts within an energetic material lifecycle. It starts with the qualification and quantification of the raw materials and/or the intermediate materials used for the manufacturing of the final product. When the product is finished there is quality control and finally after functioning or demilitarisation components will end-up in the environment.

ln order to provide a quantitative basis for pretreatment and therapy of intoxications with sulfur mustard the toxicokinetics of this agent as well as its major DNA-adducts are being studied in male hairless guinea pigs for the intravenous, respiratory and percutaneous routes. A highly sensitive method for bioanalysis of the intact agent in blood and tissues was developed, involving gas chromatography with automated thermodesorption injection and mass-spectrometric detection. Deuterated sulfur mustard is used as the internal standard. The absolute detection limit is 700 fg for sulfur mustard, which corresponds with a detection limit in blood of ca. 5 pg/ml. DNA-adducts are measured via the previously developed immuno-slot-blot method, using antibodies directed against the adduct of sulfur mustard to guanine. The intravenous 96-h LD50 of sulfur mustard in the hairless guinea pig was determined and appeared to be 8.2 mg/kg. The intravenous toxicokinetics of this dose in the hairless guinea pig are characterized by a very rapid distribution phase and a very slow elimination phase. A rapid adduct formation occurs in blood and lung, and subsequently in other organs. The adduct levels in lung were remarkably high. A considerable repair of the adducts is observed within 6 h. However, at 2 days after administration of sulfur mustard adducts are still detectable in most of the organs studied. The intravenous toxicokinetics of sulfur mustard were also studied in the marmoset at a dose corresponding with 1 LD50 in the hairless guinea pig. The results obtained sofar will be discussed.

Orbital manoeuvring is the next challenge in the development of cubesats. In this study a propulsion system for a cubesat with the main purpose of providing orbit manoeuvring and formation flying has been designed. This propulsion system is basically a cold gas system but it does not use a pressurised tank to store the gas, instead the propellant is chemically stored in cool gas generators. By storing the propellants chemically bounded in a solid material the system has no leakage, is unpressurised and can be stored for a long time without attendance. This advanced technology, developed by TNO, has already been used for a propulsion system, which will fly on the PR0BA2 mission and provides a good opportunity to store propellant in a volume efficient way. Based on this propulsion system, needed changes and improvements of the system have been investigated in order to make it suitable for cubesats. This all led to a preliminary design of a scaled down system which has been designed using requirements for formation flying and which has the capability of being adaptive to any requirements and cubesat configuration due to its modular design principle. The system is capable to store as much gas as a normal tank solution by using only 1/6 of the volume. Within this study a development model has been built and tested. The successful tests verified the design of the micro gas generators and provide a promising basis for further steps.

This paper explores factors that influence the user experience when using utilitarian websites. A theoretical model for the user experience of utilitarian websites is proposed and investigated. This model is an extension of the Technology Acceptance Model (TAM). The effects of perceived ease of use, perceived usefulness, perceived enjoyment, perceived visual aesthetics, internet anxiety and internet playfulness on the behavioural intention to use were examined. Most of these factors were adapted from earlier literature. The paper also introduces a new construct, perceived interactivity. A web survey was conducted, yielding a sample size of 147. The results confirmed 8 of the original 14 hypotheses. Perceived enjoyment and perceived visual aesthetics showed to be important factors in shaping the user experience.

In the study the effect of scaling the material structure on the fracture behaviour of concrete is investigated. Next to this the size effect of concrete fracture strength and fracture energy is studied. The fracture mechanism of concrete made with different size aggregates are tested numerically. A lattice type fracture model is adopted to simulate the fracture mechanisms in concrete. The heterogeneity of the concrete is implemented using a regular pattern of circular particles on top of the lattice of beams. The results obtained show that with the model a structural size effect is obtained, which his however partly an artefact of the model. Furthermore a dependency of strength, fracture energy and brittleness of the aggregate size is found. © 2005 Materials Research Society.

We present a method to give single band intensified nightvision imagery a natural day-time color appearance. For input, the method requires a true color RGB source image and a grayscale nightvision target image. The source and target image are both transformed into a perceptually decorrelated color space. In this color space a best matching source pixel is deter mined for each pixel of the target image. The matching criterion uses the first order statistics of the luminance distribution in a small window around the source and target pixels. Once a best matching source pixel is found, its chromaticity values are assigned (transferred) to the target pixel while the original luminance value of the target pixel is retained. The only requirement of the method is that the compositions of the source and target scenes resemble each other.

Vibrotactile displays covering the torso present spatial information in an intuitive way since the stimuli are directly mapped to the body coordinates; left is left, front is front, etc. The present study investigated the direction in the horizontal plane to which a specific torso location is mapped using a 15 tactor linear display. Participants indicated the observed external direction of a localized vibration by positioning a remotely controlled cursor. The results show that the observed direction is toward the midsagittal plane (i.e. the navel or the spine) compared to the tactor direction. This bias is consistent over the observers tested, and up to 10° for the oblique directions. Inspection of the response patterns revealed that observers did not use the body midaxis as the origin for the observed direction, but used two spatially separated internal reference points, one for each body half. Therefore, the use of a torso-related transfer function in applications that require a high level of precision is suggested. The variability of the responses also depends on the tactor direction. It is higher for the left-right direction and lower for the fore-aft direction, which may be caused by the spine and navel acting as anchor points. The present results are relevant for tactile navigation displays

The area of tactile and haptic interactions has produced a number of exemplar systems and an even greater number of research papers. The time has come to systematize the knowledge that has been gained in order to produce guidance. The Ergonomics of Tactile and Haptic Interactions symposium provides an analysis of some of the complexities of tactile/haptic interactions and provides a number of ergonomic insights on how they should be designed and evaluated. Papers in this symposium present a model for analyzing and designing the complexities of tactile/haptic interactions, a research-based understanding of and guidance on the many dimensions of tactile/haptic encoding, application-based guidance on designing and utilizing tactile/haptic interaction techniques, and insights on how international standards are providing a compendium of ergonomic guidance in designing and evaluating tactile/haptic interactions.

In the context of detecting ‘paralinguistic events’ with the aim to make classification of the speaker’s emotional state possible, a detector was developed for one of the most obvious ‘paralinguistic events’, namely laughter. Gaussian Mixture Models were trained with Perceptual Linear Prediction features, pitch&energy, pitch&voicing and modulation spectrum features to model laughter and speech. Data from the ICSI Meeting Corpus and the Dutch CGN corpus were used for our classification experiments. The results showed that Gaussian Mixture Models trained with Perceptual Linear Prediction features performed best with Equal Error Rates ranging from 7.1%-20.0%.

How do induced brightness and darkness signals from local and remote surfaces interact to determine the final achromatic color percept of a target surface? An emerging theory of achromatic color perception posits that brightness and darkness percepts are computed by weighting and summing the induction signals generated at edges in a scene. This theory also characterizes how neighboring edges interact to modulate the gain of brightness and darkness signals induced from one another. Here we assess evidence for this edge integration theory by means of computational modeling and a psychophysical experiment. We quantitatively show how local and remote edge induction signals in disk-ring displays give rise to either contrast or assimilation effects. Spatial integration of same-polarity edge signals supports a contrast effect, whereas integration of opposite-polarity signals supports an assimilation effect, particularly when the remote induction signal is much stronger than the local induction signal. The results confirm a key prediction of edge integration theory, namely, that strong assimilation effects can lead subjects to ignore the polarity of local edge information when setting achromatic color matches. The conditions necessary for strong assimilation effects are also associated with greater difficulty in setting matches, suggesting that caution is required when interpreting matching data in terms of gain control. We describe several avenues for further study of contrast, assimilation, and gain control. Keywords: contrast, assimilation, brightness, darkness, integration, edge