Modeling how incoming knowledge,persistence, affective states,and in-game progress influence student learning from an educational game

This study investigated the relationships among incoming knowledge, persistence, affective states, in-game progress, and consequently learning outcomes for students using the game Physics Playground. We used structural equation modeling to examine these relations. We tested three models, obtaining a model with good fit to the data. We found evidence that both the pretest and the in-game measure of student performance significantly predicted learning outcome, while the in-game measure of performance was predicted by pretest data, frustration, and engaged concentration. Moreover, we found evidence for two indirect paths from engaged concentration and frustration to learning, via the in-game progress measure. We discuss the importance of these findings, and consider viable next steps concerning the design of effective learning supports within game environments.     

Survival of infectious Poliovirus-1 in river water compared to the persistence of somatic coliphages, thermotolerant coliforms and Poliovirus-1 genome

The microbiological quality of water is currently assessed by search for fecal bacteria indicators. There is, however, a body of knowledge demonstrating that bacterial indicators are less resistant to environmental factors than human pathogenic viruses and therefore underestimate the viral risk. As river water is often used as a resource for drinking water production, it is particularly important to obtain a valid estimation of the health hazard, including specific viral risk. This work was conducted to compare the survival of infectious Poliovirus-1 used as a pathogenic virus model to the persistence of, on the one hand, thermotolerant coliforms commonly used as indicators and on the other hand, to somatic coliphages and Poliovirus-1 genome considered as potential indicators. We studied the behavior of infectious Poliovirus-1 and the three (potential) indicators of viral contamination in river water at three different temperatures (4 degrees C,18 degrees C and 25 degrees C). This experiment was performed twice with river water sampled at two different periods, once in winter and once in summer. Our results showed that the survival of thermotolerant coliforms can be 1.5-fold lower than infectious Poliovirus-1. In contrast, under all our experimental conditions, somatic coliphages and Poliovirus-1 genome persisted longer than infectious Poliovirus-1, surviving, respectively, 2-6-fold and about 2-fold longer than infectious Poliovirus-1. According to our results exclusively based on survival capacity, somatic coliphages and viral genome, unlike thermotolerant coliforms appear to be better indicators of viral contamination in river water. Moreover, the disappearance of viral genome is well-correlated to that one of infectious virus irrespective of the conditions tested.     

Long-run urban dynamics: understanding local housing market change in London

Abstract

Recently, a literature has emerged using empirical techniques to study the evolution of international cities over many centuries; however, few studies examine long-run change within cities. Conventional models and concepts are not always appropriate and data issues make long-run neighbourhood analysis particularly problematic. This paper addresses some of these points. First, it discusses why the analysis of long-run urban change is important for modern urban policy and considers the most important concepts. Second, it constructs a novel data set at the micro level, which allows consistent comparisons of London neighbourhoods in 1881 and 2001. Third, the paper models some of the key factors that affected long-run change, including the role of housing. There is evidence that the relative social positions of local urban areas persist over time but, nevertheless, at fine spatial scales, local areas still exhibit change, arising from aggregate population dynamics, from advances in technology, and also from the effects of shocks, such as wars. In general, where small areas are considered, long-run changes are likely to be greater, because individuals are more mobile over short than long distances. Finally, the paper considers the implications for policy.     

Cyber-harassment victimization in Portugal: Prevalence,fear and help-seeking among adolescents

Cyber-harassment is one of today's problems in adolescent health. This study aimed to determine the prevalence of cyber-victimization among Portuguese adolescents. It also explored its nature, patterns and victim's reactions of fear and help-seeking. A representative sample of 627 adolescents, aged 12–16, enrolled in schools from northern Portugal and Azores answered an online survey. Cyber-victimization was widely experienced by these adolescents, mainly among older adolescents. Results evidenced a high prevalence rate of adolescents (66.1%) double involved as both cyber-victim and cyber-aggressor. Although not all adolescents reported fear (37%) or sought help (45.9%), persistent victimization increased fear. In turn, fear increased help-seeking behaviors. Cyber-victims were more afraid encountering unknown cyber-aggressors (vs. acquainted) and when victimized by older males (vs. younger females cyber-aggressors). Younger girls reported more fear and more help-seeking behaviors while older boys were more often victim-aggressors. The subgroup of victim-aggressors was both the target of a higher diversity of cyber-victimization behaviors than the victim-only subgroup and also engaged in fewer help-seeking behaviors. Those adolescents who sought help considered it helpful. Implications for educational, social and political practices are discussed.     

Ethanol consumption in Brazil: Empirical facts based on persistence,seasonality and breaks

This paper investigates the consumption of sugar cane ethanol in Brazil for the time period from January 2000 to December 2012. We examine ethanol and gasoline consumption along with the price ratio series. Two important features of the data are analyzed, in particular, its degree of persistence and the seasonality. The results show that the two series of consumption are fractionally integrated with orders of integration smaller than 1 implying that shocks in the series will disappear in the long run. On the other hand, the price ratio series displays an order of integration higher than 1 implying lack of mean reversion behavior. This suggests that strong policy measures must be adopted on prices in the event of shocks since they do not recover by themselves in the long run.     

Biological activity and persistence of four essential oils towards the main pest of stored cowpeas, Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)

The use of essential oils extracted from native aromatic plants is perceived as a promising alternative to protect stored cowpeas in West Africa. However the optimal conditions for their efficiency remain to be determined. A study was therefore carried out to compare the biological activity and temperature-related persistence of four selected essential oils towards Callosobruchus maculatus, the main pest of stored cowpeas. Essential oil extracted from Ocimum americanum proved to be very toxic towards C. maculatus adults (LC₅₀ = 0.23 μl/l) while the oils from Hyptis suaveolens, Hyptis spicigera and Lippia multiflora exhibited higher LC₅₀ values (1.30 μl/l; 5.53 μl/l and 6.44 μl/l respectively). The persistence of the biological activity of the four oils was variable and that from O. americanum was most persistent. Fourteen days post-application, this oil was still as active on C. maculatus adults as it was immediately after its application. Exposure of this oil to a high temperature, close to temperatures occurring during storage in Burkina Faso in the dry season, however, resulted in a rapid decrease in its efficacy. Our results emphasize the need to take into account environmental factors such as temperature to optimize the use of promising essential oils for controlling stored-product pests in West Africa.     

How exciting can a signal really be?

The rate of parameter convergence in a number of adaptive estimation schemes is related to the smallest eigenvalue of the average information matrix determined by the regression vector. Using a very simple examples, we illustrate that the input signals that maximize this minimum eigenvalue may be quite different from the input signals that optimize more classical input design criteria, e.g. D-optimal criterion.     

Adaptive extremum-seeking control of nonisothermal continuous stirred tank reactors

In this paper, we present an adaptive extremum-seeking control scheme for nonisothermal continuous stirred tank reactors. We assume limited knowledge of the reaction kinetics. An adaptive learning technique is introduced to construct an optimum-seeking algorithm that drives the system states to optimal equilibrium concentrations of the reaction mixture. Lyapunov's stability theorem is used in the design of the extremum-seeking controller structure and the development of the parameter-learning laws. Under mild assumptions, the resulting controller is an output-feedback controller. The performance of the technique is demonstrated with the van de Vusse reaction system.     

Solution properties and kinetics of aggregation of an alkyl-substituted poly(p-phenylene)

Freshly prepared solutions of poly(2,5-di-n-dodecyl-1,4-phenylene) (PPP 12) in toluene are metastable at room temperature with regard to a process which leads to the formation of aggregates composed of up to 100 individual macromolecules. This aggregation process has an induction period of more than 10 h at room temperature. The kinetics of aggregation was investigated by making use of a fast capillary membrane osmometer. Aggregation follows an Avrami-Evans type formalism and suggests that clusters of a lyotropic liquid crystalline phase of the polymer are formed of the same type as observed in the melt. The long induction period of aggregate formation in dilute solution in toluene allows to apply conventional techniques of molar mass determination like membrane osmometry and size-exclusion chromatography (SEC). A relationship [η] = 1.94 × 10⁻³ M^0.94 was found for PPP 12 in toluene at 20 °C and a persistence length of 15.6 nm was derived applying the Bohdanecky-formalism. This gives evidence of the worm-like nature of the non-aggregated PPP 12 in dilute solution.