Radioactive contamination in Croatia by phosphate fertilizer production

The contents of natural radionuclides (radium, uranium and potassium) were measured in the area of a phosphate fertilizer factory in central Croatia, as a part of extended and still ongoing monitoring program of radioactive contamination of human environment in Croatia that is performed by the Radiation Protection Unit of the Institute for Medical Research and Occupational Health in Zagreb. Activity concentrations in all analysed media (waste water, trickling water from piezometers, phosphogypsum deposit and final products) considerably fluctuated, especially in phosphogypsum and waste water. Mean (226)Ra activity concentration in waste phosphogypsum was measured to be 483+/-190 Bqkg(-1). Based on that value, it was estimated that 4 million m(3) of phosphogypsum that have been deposited up to now contain about 4.3 x 10(12) Bq, i.e. about 200 g of (226)Ra. However, effective dose for an adult that would be incurred by consumption of water from nearby wells was estimated to be 5.3+/-1.3 microSv. The results show that (226)Ra activities cause effective doses, which are below the recommended maximum as the estimated annual (226)Ra effective dose does not exceed 0.1 mSv as recommended by the World Health Organization.     

Urinary mercury in adults in Poland living near a chloralkali plant

We conducted a study within the framework of the interdisciplinary European Mercury Emission from Chloralkali Plants (EMECAP) project to assess exposure to mercury (Hg) and the contribution of Hg emissions from a mercury cell chloralkali plant to urinary mercury (U-Hg) in adults living near the plant. We collected data from questionnaires and first morning urine samples from 75 subjects living near the Tarnow plant in Poland and 100 subjects living in a reference area. Median U-Hg was 0.32 mug/g creatinine (microg/gC) and 0.20 microg/gC, respectively. The median U-Hg was also higher in the amalgam-free subjects living near the plant (0.26 microg/gC) than in the reference group (0.18 microg/gC), but no such association was found in a multivariate analysis. There was a statistically significant positive association between U-Hg and number of teeth with amalgams, a negative association with age and a tendency towards higher U-Hg in female subjects. In the amalgam-free subjects there were statistically significant effects of female sex and fish consumption, and a negative association with age. The additional long-term average air Hg concentration from the plant, based on EMECAP environmental measurements and modelling, was estimated to be 1-3.5 ng/m(3) for the residential study area and should have a very small effect on U-Hg. The other Hg emission sources such as coal combustion facilities located nearby should be taken into account in assessing the overall impact of air Hg on U-Hg in this area.     

The effect of different pollutants exposure on the pigment content of pigmented macrophage aggregates in the spleen of Vardar chub (Squalius vardarensis Karaman, 1928)

Pigmented macrophage aggregates (MAs) are known to change under influence of various factors, such as aging, season, starvation, and/or pollution. In this study, changes in the pigment content of the MAs in the spleen of Vardar chub (Squalius vardarensis, Karaman) (n = 129) collected in spring and autumn, from three rivers with different pollution impact was examined: Zletovska River (metals), Kriva River (metals and municipal wastewater), and Bregalnica River (municipal wastewater). Collected data revealed increased relative volume and number of MAs containing hemosiderin under the influence of metals, significant in autumn (p < .05). In chub exposed to metals combined with municipal wastewater, significant increase of lipochrome accumulation in MAs in autumn, melanin in MAs in fish captured in the spring season, and number of splenic MAs containing combination of melanin and lipochrome was noted. Volumes and number of MAs containing combination of hemosiderin and lipochrome increased in spleen of fish captured in autumn from both Zletovska River and Kriva River, most likely due to the contribution of hemosiderin and lipochrome, respectively. Values measured for the various pigments in splenic MAs in fish captured from Bregalnica River, were overall closer to the values measured for fish captured from Kriva River. Notably, melanin and lipochrome are more likely to be found in fish from waters influenced by municipal wastewater (organic pollution) and hemosiderin in fish spleen from water influenced by mining activity (heavy metals pollution).     

Distributed Computation Multi-agent System

This article addresses a formal model of a distributed computation multi-agent system. This model has evolved from the experimental research on using multi-agent systems as a ground for developing fuzzy cognitive maps. The main paper contribution is a distributed computation multi-agent system definition and mathematical formalization based on automata theory. This mathematical formalization is tested by developing distributed computation multi-agent systems for fuzzy cognitive maps and artificial neural networks – two typical distributed computation systems. Fuzzy cognitive maps are distributed computation systems used for qualitative modeling and behavior simulation, while artificial neural networks are used for modeling and simulating complex systems by creating a non-linear statistical data model. An artificial neural network encapsulates in its structure data patterns that are hidden in the data used to create the network. Both of these systems are well suited for formal model testing. We have used evolutionary incremental development as an agent design method which has shown to be a good approach to develop multi-agent systems according to the formal model of a distributed computation multi-agent system.     

Issues and approaches in the design of collective autonomous agents

The problem of synthesizing and analyzing collective autonomous agents has only recently begun to be practically studied by the robotics community. This paper overviews the most prominent directions of research, defines key terms, and summarizes the main issues. Finally, it briefly describes our approach to controlling group behavior and its relation to the field as a whole.     

Automated Derivation of Primitives for Movement Classification

We describe a new method for representing human movement compactly, in terms of a linear super-imposition of simpler movements termed primitives. This method is a part of a larger research project aimed at modeling motor control and imitation using the notion of perceptuo-motor primitives, a basis set of coupled perceptual and motor routines. In our model, the perceptual system is biased by the set of motor behaviors the agent can execute. Thus, an agent can automatically classify observed movements into its executable repertoire. In this paper, we describe a method for automatically deriving a set of primitives directly from human movement data.We used movement data gathered from a psychophysical experiment on human imitation to derive the primitives. The data were first filtered, then segmented, and principal component analysis was applied to the segments. The eigenvectors corresponding to a few of the highest eigenvalues provide us with a basis set of primitives. These are used, through superposition and sequencing, to reconstruct the training movements as well as novel ones. The validation of the method was performed on a humanoid simulation with physical dynamics. The effectiveness of the motion reconstruction was measured through an error metric. We also explored and evaluated a technique of clustering in the space of primitives for generating controllers for executing frequently used movements.     

Tablet game-supported speech therapy embedded in children’s popular practices

Modern speech-language pathology practices (SLPPs) have adopted tablet games in recent years. Research is needed to take advantage of the potential benefits tablets can offer and to explore the factors that influence its introduction. This paper discusses a survey that was conducted to investigate the factors that influence speech-language pathologists’ (SLPs) beliefs and the actual use of tablets in SLPPs. The results of the survey, conducted among Slovenian SLPs, indicated that their most positive beliefs concerning tablets relate to social influence. Specifically, the beliefs relate to children’s interest and practice with tablets and have a significant impact on the decision-making of SLPs concerning introducing tablets in therapy. Conversely, SLPs’ most negative beliefs relate to the conditions for facilitating tablet use, particularly the lack of Slovenian applications. This paper discusses a separate case study that was conducted in which tablet game-supported therapy was introduced to a group of 44 children. The case study results indicated that the children accepted the use of tablet games for therapy purposes and the games had a positive impact on the children’s motivation and satisfaction.     

Evaluating fault tolerance approaches in multi-agent systems

A multi-agent system (MAS) is a distributed system that consists of multiple agents working together to solve mutual problems. Even though MASs are well suited for the development of complex distributed systems, the number of real-world usages is still small. One of the main reasons for this is that MASs are very fragile. In a typical, large-scale MAS, the rate of failure grows with the number of hosts, the number of deployed agents, and the duration of the agent’s task execution. For this reason, numerous approaches have been introduced to deal with aspects of failure handling. However, the absence of centralized control and a large number of individual intelligent components makes it difficult to detect and treat errors. The risk of uncontrollable fault propagation is high and can seriously impact on system performance. There are two important factors that limit the usage of MASs: (1) existing fault tolerance (FT) approaches are not generic, as they focus on and improve specific issues of FT; and (2) despite the plethora of available FT approaches and theories, there is a remarkable lack of general metrics, tools, benchmarks, and experimental methods for formal validation and comparison of existing or newly developed FT approaches. As FT approaches in MASs become a well-established field, the need for generalized, standardized evaluation of FT approaches emerges as imperative. In this paper, we first present a detailed overview of existing FT solutions, approaches, and techniques in agent platform hosted MASs. From that overview, we derive the commonalities in existing research. Next, we present the main contribution of our paper: an evaluation methodology, with a set of metrics, for comparing FT approaches in MASs. We adopt an engineering perspective on the problem, defining a methodology and metrics that are both implementation- and domain-independent. The metrics are formalized with an acyclic directed graph. By using our methodology, evaluators can select an appropriate FT approach for targeted MAS application, thus improving MAS usability, stability, and development speed. In order to show the viability of our approach, a case study that compares two FT approaches for a targeted MAS is presented. The case study results show that our methodology can be used for selecting an appropriate FT approach for the targeted MAS.