5 research outputs found

    Free Riding, Altruism, and Cooperation on Peer-to-Peer File-Sharing Networks

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    Researchers have acknowledged the existence of free-riding in peer-to-peer networks. Krishnan et al. (2002a) provide a plausible game theoretic explanation for the sustenance of cooperation in P2P networks and their ability to tolerate free-riding. Our paper investigates this issue further using a computational model. We find the Krishnan et al. (2002a) model to hold true only for a restricted set of assumptions. We argue that, in general, aggregation of individualsā€™ utility is necessary to explain the ability of P2P systems to tolerate free- riders. From our experiments we observe that the stability of the network is sensitive to the underlying incentive structure of individual users. We suggest a detailed incentive structure for users participating on the P2P network and examine this incentive structure in light of existing data of P2P usage. The findings of this paper should be useful to researchers and practitioners for policy making, network design, regulating growth, and deploying novel business models on P2P file sharing networks

    Breast Cancer Metastasis Suppressor-1 Differentially Modulates Growth Factor Signaling*Sāƒž

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    That metastatic tumor cells grow in selective non-native environments suggests an ability to differentially respond to local microenvironments. BRMS1, like other metastasis suppressors, halts ectopic growth (metastasis) without blocking orthotopic tumor formation. BRMS1-expressing tumor cells reach secondary sites but do not colonize distant tissues, compelling the hypothesis that BRMS1 selectively restricts the ability of tumor cells to respond to exogenous regulators in different tissues. Here we report that BRMS1 expression in metastatic human breast cancer cells leads to a selective reduction in epidermal growth factor receptor expression and downstream (AKT) signaling. Signaling through another receptor tyrosine kinase, hepatocyte growth factor receptor (c-Met), remains unaltered despite reduced levels of the signaling intermediate phosphatidylinositol (4,5)-bisphosphate. Interestingly, reduced downstream calcium signaling is observed following treatment with platelet-derived growth factor, consistent with decreased phosphatidylinositol (4,5)-bisphosphate. However, platelet-derived growth factor receptor expression is unaltered. Thus, BRMS1 differentially attenuates cellular responses to mitogenic signals, not only dependent upon the specific signal received, but at varying steps within the same signaling cascade. Specific modulation of signaling responses received from the microenvironment may ultimately dictate which environments are permissive/restrictive for tumor cell growth and provide insights into the biology underlying metastasis

    Metastasis Suppressors and Their Roles in Breast Carcinoma

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