The optimal stimulation pattern for skeletal muscle is dependent on muscle length

Stimulation patterns can be optimized by maximizing the force-time integral (FTI) per stimulation pulse of the elicited muscle contraction. Such patterns, providing the desired force output with the minimum number of pulses, may reduce muscle fatigue, which has been shown to correlate to the number of pulses delivered. Applications of electrical stimulation to use muscle as a controllable biological actuator may, therefore, be improved. Although muscle operates over a range of lengths, optimized patterns have been determined only at optimal muscle length. In this study, the patterns with up to four pulses that produced the highest isometric FTI were determined at 10 muscle lengths for 11 rabbit tibialis anterior muscles. The interpulse intervals (IPIs) used ranged from 4 to 54 ms. At high muscle length, the optimal stimulation pattern consisted of an initial short IPI (doublet) followed by longer IPIs, in agreement with previous studies. However, at low length, the third pulse still elicited more than linear summation (triplet); furthermore, the relative enhancement of the FTI per pulse was considerably larger at low length than at high length, suggesting that optimal stimulation patterns are length dependent.     

Distributed Context Retrieval and Consistency Control in Pervasive Computing

The challenge of saturating all phases of pervasive service provision with context-aware functionality lies in coping with the complexity of maintaining, retrieving and distributing context information. To efficiently represent and query context information a sophisticated modelling scheme should exist. To distribute and synchronise context knowledge in various context repositories across a multitude of administrative domains, streamlined mechanisms are needed. This paper elaborates on an innovative context management framework that has been designed to cope with free-text and location based context retrieval and efficient context consistency control. The proposed framework has been incorporated in a multi-functional pervasive services platform, while most of the mechanisms it employs have been empirically evaluated.     

What are users’ intentions towards real money trading in massively multiplayer online games?

This study investigates user behaviour in massively multiplayer online games from the perspective of their intentions to engage in real money trading. Players who engage in real money trading purchase resources instead of spending time to acquire them in the game. This behaviour influences not just their own gaming experience, but those of other players as well as the operator??s revenues. We present an online survey which targets the players of World of Warcraft. Players?? relationships with real money trading are investigated using insights from behavioural economics. We propose a model which includes a set of behavioural determinants grounded in empirical research on online games. The study??s findings indicate that a player??s social status and the disinhibiting effects of online play are positive influences on players?? intentions to engage in real money trading, while perceived fairness, anticipated regret and uncertainty about the seller??s behaviour are negative influences. Interestingly, neither the perceived enjoyment nor the potential punishments influence intentions.     

Boys’ and girls’ ICT beliefs: Do teachers matter?

This exploratory study took place in the context of middle school information science in Greece, to examine possible relations between boys’ and girls’: value and efficacy beliefs about computers and information science; perceived parental support; perceived teacher expectations; and perceptions of the nature of information science instruction. The participants of the study were 301 (135 male and 166 female) students who responded to a self-report questionnaire. Regression analysis showed that perceived teacher expectations were positively associated with students’ ability beliefs, perceptions of learning activities as creative and personally meaningful was a significant predictor of students’ interest in computing, and perceived parental support was related to both value and efficacy beliefs. Unlike previous research, the findings of this study did not support the conclusion that boys have more positive ICT self-efficacy and value beliefs than girls. They indicated however, that boys’ and girls’ beliefs are differentially affected by parents, teachers, and school IS instruction.     

Dropout prediction in e-learning courses through the combination of machine learning techniques

In this paper, a dropout prediction method for e-learning courses, based on three popular machine learning techniques and detailed student data, is proposed. The machine learning techniques used are feed-forward neural networks, support vector machines and probabilistic ensemble simplified fuzzy ARTMAP. Since a single technique may fail to accurately classify some e-learning students, whereas another may succeed, three decision schemes, which combine in different ways the results of the three machine learning techniques, were also tested. The method was examined in terms of overall accuracy, sensitivity and precision and its results were found to be significantly better than those reported in relevant literature.     

Synthesis of ferronickel slag-based geopolymers

This paper deals with the synthesis of geopolymers utilizing ferronickel slag as raw material. The utilized slag is produced in the Greek plant LARCO during the pyrometallurgical treatment of laterites for the production of ferronickel, specifically at the step of the reductive smelting in electric arc furnaces. The performed work includes the optimization of the slag-based geopolymeric system through the study of the effect of the synthesis parameters on the mechanical properties of the produced materials. The structure of geopolymers was determined with X-ray diffractometry (XRD), Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The obtained results showed that the ferronickel slag is an excellent raw material for the production of inorganic polymers using the geopolymerization technology. The materials produced under the optimum synthesis conditions were compact and rigid and presented high compressive strength (118 MPa), as well as extremely low water absorption (0.7–0.8%).     

Consumer behaviour in the mobile telecommunications’ market: The individual’s adoption decision of innovative services

Research in the adoption of innovative services in mobile communications markets has not offered a comprehensive explanation of how the individual makes a choice. This article proposes a theoretical framework for the analysis of the adoption decision of innovative mobile services such as mobile TV. The decision to adopt the service can be viewed as a choice based on two cognitive processes of reasoning and referencing, as postulated in behavioural decision making. The framework has both theoretical and practical value. From a theoretical perspective, it illustrates the manner in which referencing and reasoning influence the individual’s decision to adopt innovative services in the mobile telecommunications market. From a practical perspective the framework offers a market analysis tool which can generate useful insights for the vendors.     

New method for improving accuracy of 24-hour continuous intragastric pH-metry. Reflections on physiological and pharmacological studies

Continuous 24-hr intragastric pH-metry was prospectively performed in 801 subjects with different clinical conditions using two pH electrodes placed closely adjacent. The aim was to assess the in situ repeatability of the test and to verify whether the removal of artifacts, interference, and noise usually superimposed onto the fundamental signal recorded by the measuring apparatus improves the clinical usefulness of experimental data. The following debugging/filtering procedure was used: first, pH recordings of each channel were amended separately from artifacts, then they underwent 7 min windowed median interference debugging, and finally Wiener noise filtering was applied. Afterwards, the 24-hr mean pH profile was obtained in each subject by averaging the pH tracings of the two channels every minute (1440 data points/24 hr). The efficiency of this procedure was assessed at each step by evaluating the difference among groups using the O'Brien test, a distribution-free nonparametric method well-suited for evaluating differences among groups allocated onto a two-way layout. The differences among groups calculated from raw pH data of the single channels can be very misleading, in that it is possible to find that they are significant on one channel and not significant on the other channel. Conversely, the significance of the differences among groups increases progressively at each step of the above debugging/filtering procedure applied to raw pH profiles of each channel. Seven minutes was shown to be the most suitable time lag for windowed median removal of interference.(ABSTRACT TRUNCATED AT 250 WORDS)