Emergence of Equilibria from Individual Strategies in Online Content Diffusion

Social scientists have observed that human behavior in society can often be modeled as corresponding to a threshold type policy. A new behavior would propagate by a procedure in which an individual adopts the new behavior if the fraction of his neighbors or friends having adopted the new behavior exceeds some threshold. In this paper we study the question of whether the emergence of threshold policies may be modeled as a result of some rational process which would describe the behavior of non-cooperative rational members of some social network. We focus on situations in which individuals take the decision whether to access or not some content, based on the number of views that the content has. Our analysis aims at understanding not only the behavior of individuals, but also the way in which information about the quality of a given content can be deduced from view counts when only part of the viewers that access the content are informed about its quality. In this paper we present a game formulation for the behavior of individuals using a meanfield model: the number of individuals is approximated by a continuum of atomless players and for which the Wardrop equilibrium is the solution concept. We derive conditions on the problem's parameters that result indeed in the emergence of threshold equilibria policies. But we also identify some parameters in which other structures are obtained for the equilibrium behavior of individuals

Analysis of Buffer Starvation with Application to Objective QoE Optimization of Streaming Services

Our purpose in this paper is to characterize buffer starvations for streaming services. The buffer is modeled as an M/M/1 queue, plus the consideration of bursty arrivals. When the buffer is empty, the service restarts after a certain amount of packets are \emph{prefetched}. With this goal, we propose two approaches to obtain the \emph{exact distribution} of the number of buffer starvations, one of which is based on \emph{Ballot theorem}, and the other uses recursive equations. The Ballot theorem approach gives an explicit result. We extend this approach to the scenario with a constant playback rate using T\`{a}kacs Ballot theorem. The recursive approach, though not offering an explicit result, can obtain the distribution of starvations with non-independent and identically distributed (i.i.d.) arrival process in which an ON/OFF bursty arrival process is considered in this work. We further compute the starvation probability as a function of the amount of prefetched packets for a large number of files via a fluid analysis. Among many potential applications of starvation analysis, we show how to apply it to optimize the objective quality of experience (QoE) of media streaming, by exploiting the tradeoff between startup/rebuffering delay and starvations.Comment: 9 pages, 7 figures; IEEE Infocom 201

Reactivity of OH and CH3OH between 22 and 64 K: Modelling the gas phase production of CH3O in Barnard 1b

In the last years, ultra-low temperature chemical kinetic experiments have demonstrated that some gas-phase reactions are much faster than previously thought. One example is the reaction between OH and CH3OH, which has been recently found to be accelerated at low temperatures yielding CH3O as main product. This finding opened the question of whether the CH3O observed in the dense core Barnard 1b could be formed by the gas-phase reaction of CH3OH and OH. Several chemical models including this reaction and grain-surface processes have been developed to explain the observed abundance of CH$_3$O with little success. Here we report for the first time rate coefficients for the gas-phase reaction of OH and CH3OH down to a temperature of 22 K, very close to those in cold interstellar clouds. Two independent experimental set-ups based on the supersonic gas expansion technique coupled to the pulsed laser photolysis-laser induced fluorescence technique were used to determine rate coefficients in the temperature range 22-64 K. The temperature dependence obtained in this work can be expressed as k(22-64 K) = (3.6+/-0.1)e-12 (T/ 300)^(-1.0+/-0.2) cm3 molecule-1 s-1. Implementing this expression in a chemical model of a cold dense cloud results in CH3O/CH3OH abundance ratios similar or slightly lower than the value of 3e-3 observed in Barnard 1b. This finding confirms that the gas-phase reaction between OH and CH3OH is an important contributor to the formation of interstellar CH3O. The role of grain-surface processes in the formation of CH3O, although it cannot be fully neglected, remains controversial.Comment: Accepted for publication in The Astrophysical Journa

Stress among Mansoura (Egypt) baccalaureate nursing students

Background: Over the last years, details regarding levels of stress and sources of stress have emerged in studies of nursing students in Western population To date, there only few similar reports on clinical stress, anxiety, depression among the Arab population .This study was conducted to examine the level of perceived stress among baccalaureate Mansoura nursing students and to highlight the possible predicting factors. Methods: In this cross- sectional study, Data were obtained from 373 students using a self-administered questionnaire, including questions on sociodemographics, list of possible stressors, perceived stress, physical wellbeing factors, anxiety and depressive symptoms. Results: Prevalence of high stress level, anxiety and depression were 40.2%, 46.6% and 27.9%, respectively. On average each student reported a mean of 4.6 stressors and academic pressures were the most frequent stressors .In regression analysis the number of stressors and global sickness index score were predictors of high stress level. Conclusion: These findings call for introduction of stress management programs and psychiatric care into nursing health services of the University.Key words: Nursing students, stress, Depression, Anxiety, Arab culture, Egyp

Curing Hepatitis C in Liver Transplant Recipients Is Associated with Changes in Immunosuppressant Use.

Background and aimsAll-oral interferon-free antivirals are highly effective in treating recurrent hepatitis C (HCV) infection in liver transplant (LT) recipients. The aim of the study was to assess immunosuppression needs after achieving a sustained viral response (SVR).MethodsWe compared immunosuppression needs before and after achieving a SVR in adult LT recipients treated for recurrent HCV infection with all-oral direct acting agents.ResultsWe identified 52 liver LT treated recipients who achieved a SVR. The median (25th and 75th percentile interquartile range [IQR]) age was 62 years (57.75, 65). Most recipients received tacrolimus (TAC) for their immunosuppressant regimen. After achieving SVR, there was no statistically significant difference in daily dose of TAC unadjusted per weight (p > 0.05). However, there was a statistically significant decrease in daily dose of TAC adjusted per weight, serum levels of TAC, and the product of glomerular filtration rate and TAC. No statistically significant differences in cyclosporine unadjusted/adjusted per weight daily dose or serum levels were noted.ConclusionsImmunosuppression needs were increased for those patients treated with TAC but not cyclosporine. LT recipients prescribed TAC require close monitoring after treatment completion to avoid potential risk of acute rejection

Edge detection algorithm based on quantum superposition principle and photons arrival probability

The detection of object edges in images is a crucial step employed in a vast amount of computer vision applications, for which a series of different algorithms has been developed in the last decades. This paper proposes a new edge detection method based on quantum information, which is achieved in two main steps: (i) an image enhancement stage that employs the quantum superposition law and (ii) an edge detection stage based on the probability of photon arrival to the camera sensor. The proposed method has been tested on synthetic and real images devoted to agriculture applications, where Fram & Deutsh criterion has been adopted to evaluate its performance. The results show that the proposed method gives better results in terms of detection quality and computation time compared to classical edge detection algorithms such as Sobel, Kayyali, Canny and a more recent algorithm based on Shannon entropy

Slotted Aloha as a stochastic game with partial information

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