New phenothiazine-containing monomers and polymers

Summary Three new phenothiazine-containing electrono-donor monomers: methacryloyl-2-hydroxyethyl-2-(N-phenothiazinyl)propionate (i) acryloyl-2-hydroxyethyl-2-(N-phenothiazinyl) propionate (ii) and 2-(N-phenothiazinyl) propionic acid vinyl ester (iii) were synthesized and radically polymerized. The ionization potentials of poly(i), poly(iii) and of the model for the structural unit of the acrylic polymers: acetyl-2-hydroxyethyl-2-(N-phenothiazinyl) propionate determined with two small acceptors were discussed in terms of sterical hindrances.     

Very long chain PUFA in murine testicular triglycerides and cholesterol esters

Very long chain (VLC) PUFA of the n−6 and n−3 series are known to occur in mammalian testis. The aim of this work was to characterize further two testicular lipid classes with VLCPUFA, cholesterol esters (CE) and total triglycerides (TG) in rat and mouse testis. The VLCPUFA predominating in these lipids were a series of n−6 pentaenes and tetraenes with 24 to 32 carbons, including small amounts of odd-chain PUFA, 28∶5n−6 and 24∶5n−6 prevailing in CE and TG, respectively. Most of the VLCPUFA of TG were concentrated in a small fraction of TG, made up by 1-O-alkyl-2,3-DAG. This TG subclass was absent altogether from the TG of sexually immature testis. The TG and the CE with VLCPUFA only occurred in testis of adult fertile animals. The proportion of VLCPUFA in total TG and CE was higher in rodents than in other mammals. In the n−6 PUFA-rich adult mouse testis, the amounts of testicular triacylglycerols decreased significantly after consumption of fish oil for 2 wk. Whereas 18∶2n−6 was significantly reduced, the amounts of 22∶5n−6 and longer n−6 PUFA were less affected in all mamor testicular lipids including PC and PE, where they were unchanged. The 1-O-alkyl-2,3-DAG and their n−6 VLCPUFA were virtually unaffected by the diet. The VLCPUFA-containing molecular species of CE and TG may represent a form of storage of cholesterol and polyenoic FA required to sustain spermatogenesis. Via chain-shortening, VLCPUFA stored in the neutral lipids may serve as precursors of the major C₂₂ PUFA typical of cell membrane glycerophospholipids, protecting testicular cells against shifts in FA composition induced by dietary changes.     

Conformational transitions in poly(butyl methacrylate)

Summary Temperature dependence of viscosity data was investigated on poly(butyl methacrylate) fractions in dilute solution. A discontinuity in intrinsic viscosity was observed in the 25°C–35°C temperature range. Sharp changes of unperturbed dimensions were visualized from this behaviour. The phenomenon can be accounted for by assuming conformational changes of the chain in different solvents.     

The dynamic contact area of elastomers at different velocities

The friction in tribo-systems that contain viscoelastic materials, such as elastomers, is relevant for a large number of applications. Examples include tyres, hoses, transmission and conveyor belts. To quantify the friction in these applications, one must first understand the contact behaviour of such viscoelastic materials, both in static and in dynamic situations. This work discusses an experimental study into the change of the contact area with the sliding velocity and relates the change in contact area with the mechanical properties of the elastomer. The results show that for a tribo-system containing an elastomer, there is a threshold velocity, above which the size of the contact area significantly reduces.     

A coherence maximisation process for solving normative inconsistencies

Norms can be used in multi-agent systems for defining patterns of behaviour in terms of permissions, prohibitions and obligations that are addressed to agents playing a specific role. Agents may play different roles during their execution and they may even play different roles simultaneously. As a consequence, agents may be affected by inconsistent norms; e.g., an agent may be simultaneously obliged and forbidden to reach a given state of affairs. Dealing with this type of inconsistency is one of the main challenges of normative reasoning. Existing approaches tackle this problem by using a static and predefined order that determines which norm should prevail in the case where two norms are inconsistent. One main drawback of these proposals is that they allow only pairwise comparison of norms; it is not clear how agents may use the predefined order to select a subset of norms to abide by from a set of norms containing multiple inconsistencies. Furthermore, in dynamic and non-deterministic environments it can be difficult or even impossible to specify an order that resolves inconsistencies satisfactorily in all potential situations. In response to these two problems, we propose a mechanism with which an agent can dynamically compute a preference order over subsets of its competing norms by considering the coherence of its cognitive and normative elements. Our approach allows flexible resolution of normative inconsistencies, tailored to the current circumstances of the agent. Moreover, our solution can be used to determine norm prevalence among a set of norms containing multiple inconsistencies.     

A visual analytics framework for spatio-temporal analysis and modelling

To support analysis and modelling of large amounts of spatio-temporal data having the form of spatially referenced time series (TS) of numeric values, we combine interactive visual techniques with computational methods from machine learning and statistics. Clustering methods and interactive techniques are used to group TS by similarity. Statistical methods for TS modelling are then applied to representative TS derived from the groups of similar TS. The framework includes interactive visual interfaces to a library of modelling methods supporting the selection of a suitable method, adjustment of model parameters, and evaluation of the models obtained. The models can be externally stored, communicated, and used for prediction and in further computational analyses. From the visual analytics perspective, the framework suggests a way to externalize spatio-temporal patterns emerging in the mind of the analyst as a result of interactive visual analysis: the patterns are represented in the form of computer-processable and reusable models. From the statistical analysis perspective, the framework demonstrates how TS analysis and modelling can be supported by interactive visual interfaces, particularly, in a case of numerous TS that are hard to analyse individually. From the application perspective, the framework suggests a way to analyse large numbers of spatial TS with the use of well-established statistical methods for TS analysis.     

Educational affordances of PDAs: A study of a teacher’s exploration of this technology

This paper reports on a case study of a teacher from a technical education institution who explored the educational affordances of PDA technology over a period of six months. Based on this teacher’s perspectives, the study was designed to inform our own understanding of educational affordances of this new and emerging technology. Understanding of educational affordances is important in the context of planning a suitable intervention to support pedagogically effective integration of PDA technology. The study explicated a set of five affordances of PDA technology: as a multimedia-access tool, connectivity tool, capture tool, representational tool and analytical tool. We call on further research to expand this set into a more comprehensive collage of educational affordances of PDA technology.     

Classification of slice-based VBR video traffic and estimation of link loss by exceedance

Classification of a video stream is an essential preliminary step to estimate the bit loss when the video stream is transmitted over a communication network. In this paper, we classify the video frames by the average frame size and estimate the bit loss for each class when the bitrate exceeds the capacity of the bottleneck link. The video stream under study is encoded using the explicit slice-based H.264/AVC encoding scheme. This scheme reduces the burstiness of regular H.264/AVC encoded video by removing the traditional GOP structure. Instead, a repetitive combination of intracoded and predicted slices is employed, thereby introducing a specific dependence structure in the video data. We consider a bufferless model of the communication system and evaluate the channel capacity required to give a maximum allowed loss rate for each class.Due to the high variability, non-stationarity and non-homogeneity of the underlying video data, the obtained classes are checked regarding the dependence and distribution structure of the data. The high quantiles of the losses are estimated for each class.     

Functional polysiloxanes

Summary Carboxyester- and carboxyamido-terminated polydimethylsiloxanes were obtained through the reaction of cyclic anhydrides (succinic, maleic and phthalic anhydride) with hydroxypropyl- and aminoalkyl-terminated polydimethylsiloxanes, respectively. The reactivity of the starting compounds and the influence of the reaction conditions on the characteristics of the final products are discussed.Part 1: Eur. Polym. J., in press     

Chemical synthesis of some Schiff base-type polymers containing pyrrole units

Summary The synthesis of three Schiff-base type monomers containing pyrrole units was performed. Their polymerization was carried out by chemical oxidation with (NH₄)₂S₂O₈. Some preliminary thermal and electrical properties were determined.