On game theoretic peer selection for resilient peer-to-peer media streaming

Peer-to-peer (P2P) media streaming quickly emerges as an important application over the Internet. A plethora of approaches have been suggested and implemented to support P2P media streaming. In our study, we first classified existing approaches and studied their characteristics by looking at three important quantities: number of upstream peers (parents), number of downstream peers (children), and average number of links per peer. In existing approaches, peers are assigned with a fixed number of parents without regard to their contributions, measured by the amount of outgoing bandwidths. Obviously, this is an undesirable arrangement as it leads to highly inefficient use of the P2P links. This observation motivates us to model the peer selection process as a cooperative game among peers. This results in a novel peer selection protocol such that the number of upstream peers of a peer is related to its outgoing bandwidth. Specifically, peers with larger outgoing bandwidth are given more parents, which make them less vulnerable to peer dynamics. Simulation results show that the proposed protocol improves delivery ratio using similar number of links per peer, comparing with existing approaches under a wide range of system parameters. © 2009 IEEE.published_or_final_versio

Wireless cache invalidation schemes with link adaptation and downlink traffic

Providing on-demand data access in client-server wireless networks is an important support to many interesting mobile computing applications. Caching frequently accessed data by mobile clients can conserve wireless bandwidth and battery power, at the expense of some system resources to maintain cache consistency. The basic cache consistency strategy is the use of periodic invalidation reports (IRs) broadcast by the server. Recently, IR-based approaches have been further improved by using additional updated invalidation reports (UIRs) (i.e., the IR+UIR algorithm) to reduce the long query latency. However, the performance of the IR+UIR approach in a practical system is still largely unknown. Specifically, previous results are based on two impractical simplifying assumptions: 1 ) broadcast traffic is error-free and 2) no other downlink traffic (e.g., voice) exists in the system. The first assumption is clearly unrealistic as signal propagation impairments (e.g., multipath fading) and, hence, packet reception failures are inevitable in a practical situation. The second assumption is also inapplicable in real life because mobile devices are usually multipurposed (e.g., a mobile phone equipped with a browser may be used for Web surfing while having a phone conversation). In this paper, we first study the performance of the IR+UIR approach under a realistic system model: The quality of the wireless channel is time-varying, and there are other downlink traffics in the system. Our simulation results show that query delay significantly increases as a result of broadcast error and the additional downlink traffics experience longer delay due to extended broadcast period. Exploiting link adaptation (i.e., transmission rate is adjusted dynamically according to channel quality), we then propose three schemes to tackle these two problems. Our results indicate that the proposed schemes outperform IR+UIR under a wide range of system parameters.published_or_final_versio

Design and analysis of channel adaptive wireless cache invalidation strategies with downlink traffic

In this paper, we study the performance of the IR+UIR wireless data cache Invalidation approach under a realistic system model: the quality of the wireless channel Is time-varying; and there are other downlink traffics in the system. Our analysis and simulation results show that query delay significantly increases as a result of broadcast error and the additional downlink traffics experience longer delay due to extended broadcast period. Exploiting link adaptation (i.e., transmission rate is adjusted dynamically according to channel quality), we then propose three schemes to tackle these two problems. Our results Indicate that the proposed schemes outperform IR+UIR under a wide range of system parameters.published_or_final_versio

A game theoretic approach to energy efficient cooperative cache maintenance in MANETs

There have been an increasingly large number of mobile handsets equipped with dual or multiple network interfaces. The server interface (e.g., GPRS, EDGE, UMTS) is responsible for communicating with the network operator, while the peer interfaces (e.g., Bluetooth, IEEE 802.11) are used to connect with other computing devices. However, they are usually used separately. In this paper, we investigate the use of both network interfaces to support energy efficient data applications among mobile clients. Specifically, we proposed a fully distributed protocol for mobile handsets to form cooperative groups to maintain cache consistency with minimal communication with the network operator. Our proposed protocol takes advantage of the low power consumption and high data rate of the peer interface. The aim is to reduce the use of the server interface, which is typically slower and involves higher power consumption. Furthermore, we also consider the presence of selfish clients. It is shown that groups formed by the proposed protocol constitutes a pure Nash Equilibrium. This suggests that our protocol is robust even in the presence of selfish clients. Simulation results confirm that, given the same energy resource, mobile clients running the proposed protocol complete more queries, experience longer lifetime and achieve smaller query latency. © 2005 IEEE.published_or_final_versio

Game theoretic power aware wireless data access

The paper examines the following wireless data access scenario: a number of clients are interested in a set of data items kept at the server. A client sends a query request to inform the server of its desired data item. The server replies in the common broadcast channel. We first define a utility function that considers the client's power consumption in transmit, receive and idle modes. Specifically, utility is expressed as the number of queries that can be completed given a fixed energy source. Based on the utility function, we formulate our power aware wireless data access scheme as a non-cooperative game, called the WDA game. From our theoretical analysis, we show that clients are not always necessary to send query requests to the server. Instead, each client determines the request probability without any explicit communication with one another. Furthermore, we design and evaluate the server and client algorithms for the WDA game. Simulation results confirm that our proposed scheme, compared with a simple always-request one, increases the utility and lifetime of every client while reducing the number of requests sent, at the cost of a slightly larger average query delay.published_or_final_versio

Study of extracellular matrix for the culture of human embryonic stem cells

Poster Session 2: abstract no. 718Background: The development of clinical grade human embryonic stem cells (hESC) suitable for cell therapy requires defined components for hESC culture. We hypothesize that the feeder cells used for hESC culture produce extracellular matrix molecules supporting the growth of hESC. Materials and Methods: The profiles of mRNA and extracellular matrix production of two human feeder cell lines, human foreskin fibroblast (hFF-1) and human lung fibroblast (WI-38) were correlated with their ability to maintain the pluripotency of a hESC line, BG01V. The mRNA expression profile and matrix production were determined by Affymetrix microarray chip and liquid chromatography/mass spectrometry/mass spectrometry analysis, respectively. Results: Using a morphological grading system, hFF-1 but not WI-38 supported the pluripotency of BG01V. The observation was supported by over-expression of early differentiation markers KRT-8 and -18 mRNA in BG01V cells cultured on WI-38, though the mRNA expression of pluripotent markers Nanog, Oct4 and TRA-1-81 in BG01V cultured with hFF-1 and WI-38 was similar. Microarray analysis showed that the expression of 530 transcripts was 2-fold higher (P<0.05) in hFF-1 than in WI-38. The microarray data were validated by real-time PCR on 12 differentially expressed genes related to secretory and extracellular matrix molecules. Proteomic profiling of the extracellular matrix molecules also demonstrated differences between the two feeder cell lines. Both microarray and proteomic analysis identified sulfatase 1 (SUFL1) and chemokine (C-X-C Motif) ligand 12 (CXCL12) were higher in hFF-1. Conclusion: The difference in the ability of feeder cells in maintaining the pleuripotency of hESC may be related to the differential secretion of matrix molecules by the feeder cells.published_or_final_versio

An evaluative study on the effectiveness of a parent-child parallel group model

Objective; To examine the effectiveness of a parent-child parallel group model that attempted to reduce parent-adolescent conflict. Method: A single group research design with pretest, posttest, and follow-up assessments was employed. Results: Results showed that the level of mother-adolescent conflict at posttest was lower than the level at pretest. The findings, based on the target problem rating, indicated that after the group intervention, both the mothers and adolescents perceived that the problems they had identified in the mother-child relationship had become less severe. The findings, based on subjective outcome measures, were also positive. Conclusion: The present study provides some evidence to support the effectiveness of the parallel group intervention for social work practice.preprin

Longitudinal predictors of Chinese word reading and spelling among elementary grade students.

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The core components of reading instruction in Chinese

The present study aimed at identifying core components of reading instruction in Chinese within the framework of the tiered intervention model. A curriculum with four teaching components of cognitive-linguistic skills was implemented in a Program school for 3 years since Grade 1. The findings showed that the Tier 1 intervention was effective in enhancing the literacy and cognitive-linguistic skills of children in the Program school. The positive effects were maintained at the end of Grade 2. Progress in both word-level and text-level cognitive-linguistic skills predicted significantly progress in reading comprehension. Based on the present findings, the four core reading components in Chinese were proposed-oral language, morphological awareness, orthographic skills, and syntactic skills. Comparing the Big Five in English and the four core components in Chinese reflects different cognitive demands for reading diverse orthographies. © 2011 Springer Science+Business Media B.V.postprin

Clinical features, management, and prognostic factors of status epilepticus in Chinese

Poster PresentationINTRODUCTION: Status epilepticus (SE) is a neurological emergency with significant mortality and morbidity. There are currently limited data regarding the causes and outcomes of SE in our locality, and identification of prognostic factors, especially those available at presentation, could lower risk of under- or over-treatment in SE. METHODS: We retrospectively studied the clinical characteristics, management, and clinical outcome of adults diagnosed with incident SE, excluding episodes due to cerebral anoxia, at a regional hospi…published_or_final_versio