Understanding the Properties of the BitTorrent Overlay

In this paper, we conduct extensive simulations to understand the properties of the overlay generated by BitTorrent. We start by analyzing how the overlay properties impact the efficiency of BitTorrent. We focus on the average peer set size (i.e., average number of neighbors), the time for a peer to reach its maximum peer set size, and the diameter of the overlay. In particular, we show that the later a peer arrives in a torrent, the longer it takes to reach its maximum peer set size. Then, we evaluate the impact of the maximum peer set size, the maximum number of outgoing connections per peer, and the number of NATed peers on the overlay properties. We show that BitTorrent generates a robust overlay, but that this overlay is not a random graph. In particular, the connectivity of a peer to its neighbors depends on its arriving order in the torrent. We also show that a large number of NATed peers significantly compromise the robustness of the overlay to attacks. Finally, we evaluate the impact of peer exchange on the overlay properties, and we show that it generates a chain-like overlay with a large diameter, which will adversely impact the efficiency of large torrents

Swarming Overlay Construction Strategies

Swarming peer-to-peer systems play an increasingly instrumental role in Internet content distribution. It is therefore important to better understand how these systems behave in practice. Recent research efforts have looked at various protocol parameters and have measured how they affect system performance and robustness. However, the importance of the strategy based on which peers establish connections has been largely overlooked. This work utilizes extensive simulations to examine the default overlay construction strategy in BitTorrent systems. Based on the results, we identify a critical parameter, the maximum allowable number of outgoing connections at each peer, and evaluate its impact on the robustness of the generated overlay. We find that there is no single optimal value for this parameter using the default strategy. We then propose an alternative strategy that allows certain new peer connection requests to replace existing connections. Further experiments with the new strategy demonstrate that it outperforms the default one for all considered metrics by creating an overlay more robust to churn. Additionally, our proposed strategy exhibits optimal behavior for a well-defined value of the maximum number of outgoing connections, thereby removing the need to set this parameter in an ad-hoc manner

Beta-Endorphin Receptors on Equine Lymphocytes: Relationship to Immune Function and Exercise.

Current evidence suggests that endogenous opioids are released in response to various stressors and that these opioids interact with cells of the immune system, and modulate immune function. However, data substantiating this are conflicting. Therefore, this study endeavored to clarify the role of beta-endorphin (BE) in exercise and immune function. Beta-endorphin exhibited a diurnal rhythm in the horse with peak plasma levels occurring at 0900 hours. Analgesia, tachycardia and mydriasis were also observed at this time, mimicking the effects of morphine in the horse. Therefore, subsequent experiments were performed at 0900 hours during times of increased basal opioid activity. Beta-endorphin levels were increased in response to maximal exercise in the horse. The BE response to exercise was attenuated by physical conditioning and was correlated with exercise intensity. Analgesia was noted in unfit horses but not in fit horses after a standardized exercise bout, suggesting that unfit horses experience greater stress when exercised. Naloxone administration resulted in prolonged increases in BE levels following exercise in fit and unfit horses. Naloxone administration also reversed the analgesia noted in fit horses following a more intense exercise bout, but caused hyperalgesia in unfit horses. These results suggest that BE release is controlled through autoreceptors at the hypothalamic or pituitary level and that chronic exercise causes a downregulation of opioid receptors. Specific, saturable receptors for beta-endorphin were identified on equine lymphocytes which appeared to be a mu/delta receptor complex, with a K\sb{\rm d} of 17 pM and B\sb{\rm max} of 0.538 fmoles/10\sp6 cells. Acute exercise resulted in an increased affinity and decreased number of receptors, while chronic exercise resulted in a decreased affinity of the receptor for the ligand. Beta-endorphin suppressed the proliferative response of equine lymphocytes to mitogens through interaction with opioid receptors. Naloxone also suppressed the proliferative response, presumably through opioid receptors. In conclusion, BE modulates equine immune function through interaction with opioid receptors on equine lymphocytes. Beta-endorphin is also a possible mediator of the effects of acute and chronic exercise on equine immune function, as demonstrated by up- and downregulation of opioid receptors on equine lymphocytes

Organization and Parental Perceptions of Electronic Payments by Selected Seventh-day Adventist (SDA) International Schools in Thailand

This research explored the use of electronic payments by selected Seventh-day Adventist International Schools in Thailand and investigated the factors that affected parental perceptions of these payments. A Descriptive Research Design approach was utilized. Questionnaires and interviews were used to collect the data. A statistical software package was used to analyze the data, and stepwise multiple regression was applied to test the hypotheses. The 319 parents who had previously made electronic payments to the schools and eight Finance Department staff members at the schools were selected as respondents. Frequencies, percentages, means, standard deviations, and multiple regression (stepwise multiple regression analysis) were utilized for data analysis.The results indicated that the factors of benefits, trust, self-efficacy, ease of use, and security were rated at the “High” level. The highest mean score was benefits (4.16), followed by selfefficacy (3.91), ease of use (3.89), trust (3.81), and security (3.55), respectively. Also, all factors – except for self-efficacy – were related to parental perceptions of e-payments at the 0.05 level of significance. Findings from group interviews of the finance staff at each school revealed that the factors of ease of use, trust, security, and benefits affected their perceptionsof electronic transactions for both receiving and disbursing funds

Network Effects on Learning during Disasters: The Case of Australian Bushfires

Understanding factors that enhance or diminish learning levels of individuals and teams is significant for achieving both individual (low level) and organisational (high level) goals. In this study, the effect of social network factors at all levels of analysis (actor level, dyadic level and network level) on learning attitudes of emergency personnel in emergency events is investigated. Based on social network concepts of structural holes and strength of weak ties, and the social influence model of learning, a conceptual model is developed. To test and validate the model, data was collected from the transcripts of the 2009 Victorian Bushfires Royal Commission reports in conjunction with the 2008 Australian Inter-Service Incident Management System (AIIMS) survey. Secondly, network measures were applied for exploring the association with learning from a sample of people working within Incident Management Teams, combat roles and coordination centres across Australia and New Zealand. Empirical results suggest that social network factors at all levels of analysis (actor, dyadic and network levels) of emergency personnel play a crucial role in individual and team learning. The contextual implication from the quantitative and qualitative findings of this research is that when approaches for improving the emergency response at an interpersonal level are contemplated, the importance of social structure, position and relations in the networks of emergency personnel needs to be considered carefully as part of the overall individual and organisation-level goals. With this model of learning-related work activity, based on network connectedness, emergency staff members can strengthen their capacity to be flexible and adaptable. The findings of this study may be appreciated by emergency managers or administrators for developing an emergency practice culture to optimise individual and team learning and adaptability within an emergency management context

DEVELOPING A MODEL OF TEACHING READING COMPREHENSION FOR EFL STUDENTS

This study aimed at designing a model of teaching reading comprehension based on the objectives of teaching reading at the senior high school and  the teachers’ understanding of the school curriculum and to describe the implementation of the model. The subject consisted of 24 teachers, 167 students of five SMAs (senior high schools) in South Sulawesi, Indonesia. This developmental study had five steps: analysis, design, development, implementation, and evaluation. The result indicates that the model significantly increases the reading comprehension of EFL students (M= -14.43114), t(166) = -16.155, p <.05. The teachers and students stated that the learning condition, teaching and learning process, reading comprehension, instructional reading materials, and teachers’ teaching performance were well established. This interactive model improved the reading comprehension of the students significantly. Thus, it is an alternative model of teaching reading for EFL students

Burnout among workers in emergency Departments in Palestinian hospitals: prevalence and associated factors

Background: Working in Emergency Departments (EDs) entails high work pressure and stress due to witnessing human suffering and the unpredictable nature of the work. This environment puts personnel at risk of burnout. This analysis aims to assess burnout levels and associated risk factors among health workers in EDs in Palestinian hospitals. Also, it examines the association between burnout and workplace violence, as well as with job turnover. Methods: Cross-sectional design utilising a self-administered questionnaire was used to collect data from all workers at 14 EDs; 8 from the West Bank and 6 from the Gaza Strip. Burnout was measured using Maslach Burnout Inventory-Human Services Survey. Results: A total of 444 workers (response rate 74.5%) participated: 161(36.3%) nurses, 142(32.0%) physicians and 141(31.7%) administrative personnel. Results showed high levels of burnout among EDs workers; 64.0% suffered from high emotional exhaustion, 38.1% from high depersonalization and 34.6% from low personal accomplishment. In addition, high levels of emotional exhaustion (72.3%) was significantly prevalent among physicians compared to nurses (69.8%) and administrative workers (51.4%) (p < 0.05). In comparison, high levels of depersonalization was significantly prevalent among nurses (48.8%) compared to physicians (32.1%) and administrative workers (31.9%) (p < 0.05). However, there were no significant differences in the levels of personal accomplishment burnout among the three groups (p > 0.05). Moreover, high degree of burnout was more prevalent among EDs workers in the West Bank than among those working in the Gaza Strip (OR 2.02, 95% CI = 1.11–3.69, p = 0.019), and higher among younger workers (aged ≤30 years old) than their older counterparts (OR 2.4, 95% CI = 1.302–4.458, p = 0.005). Exposure to physical violence was significantly associated with having a high degree of burnout (OR 2.017 95% CI = 1. 121–3.631, p = 0.019), but no association was observed with regards to exposure to verbal violence (p > 0.05). Finally, burnout was significantly associated with workers’ intention to leave work at EDs (p < 0.05). Conclusions: Burnout is considerably prevalent among EDs’ workers, especially nurses and physicians. Burnout is positively associated with job turnover intention and also with exposure to workplace violence. Therefore, there is a need for prevention and management strategies to address occupational burnout and reduce negative consequences on workers, patients and organisations