Kihyun Pyun

Chronic activation of sigma-1 receptor evokes nociceptive activation of trigeminal nucleus caudalis in rats

Primary headache disorders, including migraine, are thought to be mediated by prolonged nociceptive activation of the trigeminal nucleus caudalis (TNC), but the precise mechanisms are poorly understood. Our past studies demonstrated that sigma-1 receptors (Sig-1R) facilitate spinal nociceptive transmission in several pain models. Based on these findings, this study asked if chronic activation of Sig-1R by intracisternal administration of the selective Sig-1R agonist, PRE084, produced TNC neuronal activation as a migraine trigger in rats. A single infusion of PRE084 (10, 50, 100, 500 nmol) significantly increased the number of Fos immunoreactive neurons (Fos-IR) in TNC, which BD1047 (a Sig-1R antagonist) reversed. Chronic infusion of PRE084 (100 nmol for 1, 3, 7 and 14 days) time-dependently elevated Fos-IR in TNC. The number of Fos-IR elevation from day 7 of infusion was comparable with a single capsaicin infusion as a headache model. Increase in face grooming/scratching behavior was evident from day 7, and peaked at day 14 of chronic PRE084 infusion, which was correlated with ΔFosB elevation and phosphorylation of extracellular signal-regulated kinase, and the NMDA receptor NR1 subunit in TNC. Following 14 days of PRE084 infusion, the number of Fos-IR increased until day 7 after final infusion. Moreover, by day 14, Fos-IR associated with PRE084 infusion was significantly reversed by NMDA receptor antagonist MK801, rather than BD1047. These findings indicated that chronic activation of Sig-1R could evoke prolonged neuronal activation in the trigeminovascular system.

A New Packet Marking Scheme for Fairness Improvement of AF Services in DiffServ Network

This paper presents a new scheme based on average transmission rate, using the achieved rate and fairness of each flow to provide fairly marking for Assured Forwarding services in DiffServ network. A record unit and a promotion/demotion probability generator are added to the conventional traffic conditioner. Hence the impacts of Round Trip Time, UDP/TCP interactions, and different target rates can be mitigated effectively by proposed scheme. A simulation and a performance evaluation of the proposed scheme are also presented.

A Hierarchical Deficit Round-Robin Scheduling Algorithm for a High Level of Fair Service

For the last several decades, many researches have been performed to distribute bandwidth fairly between sessions. In this problem, the most important challenge is to realize a scalable implementation and high fairness simultaneously. Here high fairness means that bandwidth is distributed fairly even in short time intervals. Unfortunately, existing scheduling algorithms either are lack of scalable implementation or can achieve low fairness. In this paper, we propose a scheduling algorithm that can achieve feasible fairness without losing scalability. The proposed algorithm is a Hierarchical Deficit Round-Robin (H-DRR). While H-DRR requires a constant time for implementation, the achievable fairness is similar to that of Packet-by-Packet Generalized Processor Sharing (PGPS) algorithm. PGPS has worse scalability since it uses a sorted-priority queue requiring O(logN) implementation complexity where N is the number of sessions.

The service curve service discipline for the rate-controlled EDF service discipline in variable-sized packet networks

Guaranteed service will provide high quality services to real-time applications, e.g., audio or video, over packet networks such as the Internet. To support guaranteed service, a service discipline must guarantee a delay bound to each session. In addition, a preferred service discipline should achieve high network utilization and good scalability. The service disciplines studied so far have problems in achieving these two objectives at the same time. Generalized processor sharing (GPS) service disciplines can have low network utilization. Rate-controlled (RC) service disciplines have difficulty in scalability because of regulators. For service curve (SC) service disciplines, both the network utilization and the scalability depend on the adopted SC. To date, there have been no studies on an SC which can make an SC discipline achieve these two objectives. We propose a new service discipline based on SC service disciplines. The proposed discipline achieves these two goals in a variable-sized packet environment. We show that the discipline can achieve the network utilization achievable by the RC service disciplines. We further show that our SC requires O(1) complexity for deadline calculation. Different from the RC service disciplines, the SC service discipline with our SC does not need regulators at all. Thus, it has better scalability than the RC service disciplines and is work-conserving. We also show that the proposed SC makes SC service disciplines have strictly higher network utilization than the GPS service disciplines including the multi-rate service discipline.

A New Packet Marking Scheme with Fairness Guarantee for DiffServ Network

Conventional works for the AF (assured forwarding) service in the differentiated services (DiffServ) have no sufficient consideration on the fairness of bandwidth share based the target rate and the impact of RTT and UDP. In order to solve these problems, we proposed a new packet marking scheme with fairness guarantee. The proposed scheme based on average transmission rate, using the achieved rate and fairness of each flow to provide fairly marking for assured forwarding services in DiffServ network. By adding a record unit and a promotion/demotion probability generator to the conventional traffic conditioner, the impacts of RTT, UDP/TCP interactions, and different target rates can be mitigated effectively. The performance of the proposed scheme, compared with TSW3CM, is evaluated with the ns-2 simulator.

Groupers for deterministic guaranteed service in an FH-OFDM wireless system

Groupers are proposed to guarantee strict delay bounds of a large number of real-time sessions in advanced wireless networks that adopt adaptive modulation techniques. We show that the number of admitted sessions is increased significantly, if groupers are used.