• Title/Summary/Keyword: Transport Mechanism

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Role of Endogenous Transport Systems for the Transport of Basic and Acidic Drugs at Blood-Brain Barrier (염기성 및 산성 약물의 혈액-뇌관문 투과에 관여하는 내인적 수송계)

  • Kang, Young-Sook
    • Journal of Pharmaceutical Investigation
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    • v.23 no.1
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    • pp.1-9
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    • 1993
  • The endothelial cell of brain capillary called the blood-brain barrier (BBB) has carrier-mediated transport systems for nutrients and drugs. The mechanism of the BBB transport of basic and acidic drugs has been reviewed and examined for endogenous transport systems in BBB in WKY and SHRSP. Acidic drugs such as salicylic acid and basic drugs such as eperisone are taken up in a carrier mediated manner through the BBB via the monocarboxylic acid and amine transport systems. The specific dysfunction for the choline transport at the BBB in SHRSP would affect the function of the brain endothelial cell and brain parenchymal cell. The utilization of the endogenous transport systems of monocarboxylic acid and amine could be promising strategy for the effective drug delivery to the brain.

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Effect of Scutellaria Baicalensis Georgi Extraction (SbGE) on H2O2-induced Inhibition of Phosphate Transport in Renal Epithelial Cells (황금약침액(黃芩藥鍼液)이 신장상피세포(腎臟上皮細胞)에서의 H2O2에 의한 인산염(燐酸鹽) 운반(運搬)의 억제(抑制)에 미치는 영향(影響))

  • Cho, Eun-jin;Youn, Hyoun-min;Jang, Kyung-jeon;Song, Choon-bo;Ahn, Chang-beobm
    • Journal of Acupuncture Research
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    • v.19 no.4
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    • pp.190-199
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    • 2002
  • Objective : This study was performed to determine if Scutellaria balicalensis Georgi extract (SbGE) prevents oxidant-induced membrane transport dysfunction in renal tubular cells. Methods : Membrane transport function was estimated by measuring $Na^+$-dependent inorganic phosphate transport in opossum kidney (OK) cells. $H_2O_2$ inhibited phosphate transport in a dose-dependent manner. Results : The inhibitory effect of $H_2O_2$ was significantly prevented SbGE over concentration range of 0.005-0.05%. $H_2O_2$ caused ATP depletion, which was prevented by SbGE. $H_2O_2$ induced the loss of mitochondrial function as evidenced by decreased MTT reduction and its effect was prevented by SbGE. The $H_2O_2$-induced inhibition of phosphate transport was not affected by a potent antioxidant DPPD, but the inhibition was prevented by an iron chelator deferoxamine, suggesting that $H_2O_2$ inhibits $Na^+$-dependent phosphate transport via an iron-dependent nonperoxidative mechanism in renal tubular cells. Conclusion : These data suggest that SbGE may exert the protective effect against oxidant-induced membrane transport dysfunction by a mechanism similar to iron chelators in renal epithelial cells. However, furher studies should be carried out to find the active ingredient(s) of SbGE that exerts the protective effect.

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A Study on the Reliable Transport Mechanism for delivering realtime video and audio data in Internet Broadcasting Applications (다수이용자를 지원하는 인터넷방송을 위한 신뢰적인 영상 및 음성 전송방법에 관한 연구)

  • 김용회;이현태;오용선
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2001.05a
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    • pp.378-382
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    • 2001
  • There are some technical problems in current internet-broadcasting. The load of server rises in proportion to user connection. And the inefficient usage of network bandwidth deteriorates quality of services and doesn't transport multimedia data in real time. To overcome above problems, multicast transport technology is applied to real-time multimedia data transport. But the reliability problem is still remained. This paper provides an efficient design of internet broadcasting server. We propose an multimedia data transport algorithm using adaptive encoding by grouping users according to similar connection environment. Performance evaluations show that the mechanism decreases the load of server and improves the quality of services.

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A Top-down based Control Tree Construction Mechanism for Reliable Multicast Transport Protocols (신뢰적인 멀티캐스트 전송 프로토콜을 위한 Top-Down 기반의 제어 트리 구축 방안)

  • Kim, Eun-Sook;Koh, Seok-Joo;Kang, Shin-Gak;Choe, Jong-Won
    • Journal of KIISE:Information Networking
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    • v.28 no.4
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    • pp.611-620
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    • 2001
  • To meet the requirements of reliable service for various applications, a Reliable Multicast Transport Protocol should be implemented over IP Multicast where currently best-effort service is provided. Among the current researches, hierarchical tree-based mechanism has been proposed and actively studied. This mechanism is known to provide high scalability as well as reliability, but needs an additional tree configuring mechanism for building an efficient logical tree in transport layer. Bottom-up approach has been used for creating such a tree. This method has benefits from parallel tree construction for receivers, while it has some drawbacks such that it does not guarantee a loop-free tree and brings heavy message overhead during tree creation process. Therefore, this paper proposes a top-down based mechanism for constructing a control tree, which can guarantee loop-freeness by step-wise mannered tree building. From experimental simulations, it shows that the proposed mechanism has less message overhead. It is recommended that the bottom-up and the proposed top-down will be selectively used in real networks, according to the requirements of the concerned multicast applications.

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A Real-time Traffic Control Scheme for ATM network:RCT (ATM망을 위한 실시간 트래픽 제어 기법:RCT)

  • Lee, Jun-Yeon;Lee, Hae-Wan;Kwon, Hyeog-In
    • The Transactions of the Korea Information Processing Society
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    • v.4 no.11
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    • pp.2822-2831
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    • 1997
  • A B-ISDN network based on ATM must support several kinds of transport services with different traffic characteristics and service requirements. There is neither link-by-link flow control nor error control in the ATM layer. For different services, different flow/error controls could be performed at the AAL layer or at a higher Iayer(e.g. transport layer). In traditional data networks, the window now control mechanism combined with error control was used prevalently. But, the window flow control mechanism might be useless in ATM networks because the propagation delay is too large compared with the transmission rate. In this paper, we propose a simple flow control mechanism, called RCT(Rate Control for end-to-end Transport), for end-to-end data transport. The RCT shows acceptable performance when the average overload period is bounded by a certain time.

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Performance Analysis of Error and Congestion Control Algorithm in Transport Layer Mobility Support Approach (트랜스포트 계층 이동성 지원 방안에서의 오류 및 혼잡제어 알고리즘 성능분석)

  • Jang, Moon-Jeong;Lee, Mee-Jeong
    • The KIPS Transactions:PartC
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    • v.12C no.5 s.101
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    • pp.733-740
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    • 2005
  • In this paper, we propose an approach to transport layer mobility support leveraging the SCTP extension dubbed dynamic address reconfiguration in IPv6 networks. Timing issues related to the end-to-end address management, and a novel error recovery mechanism associated with a handover are discussed. The proposed error recovery mechanism is analyzed and compared to that of the plain SCTP to show that it reduces the handover latency and error recovery time.

Error Adaptive Transport Protocol in Variable Error Rate Environment for Wireless Sensor Networks

  • Dang, Quang-Bui;Hwang, Won-Joo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.32 no.4B
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    • pp.208-216
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    • 2007
  • Wireless Sensor Networks (WSNs) are characterized by low capacity on each nodes and links. Wireless links have high bit error rate (BER) parameter that changes frequently due to the changes on network topology, interference, etc. To guarantee reliability in an error-prone environment, a retransmission mechanism can be used. In this mechanism, the number of retransmissions is used as a parameter that controls reliability requirement level. In this paper, we propose an Error Adaptive Transport Protocol (EATP) for WSNs that updates the number of retransmissions regularly to guarantee reliability during bit error rate changes as well as to utilize energy effectively. The said algorithm uses local information, thus, it does not create overhead problem.

Electrical characteristics of Au/3C-SiC/Si/Al Schottky, diode (Au/3C-SiC/Al 쇼터키 다이오드의 전기적 특성)

  • Shim, Jae-Cheol;Chung, Gwiy-Sang
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.11a
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    • pp.65-65
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    • 2009
  • High temperature silicon carbide Schottky diode was fabricated with Au deposited on poly 3C-SiC thin film grown on p-type Si(100) using atmospheric pressure chemical vapor deposition. The charge transport mechanism of the diode was studied in the temperature range of 300 K to 550 K. The forward and reverse bias currents of the diode increase strongly with temperature and diode shows a non-ideal behavior due to the series resistance and the interface states associated with 3C-SiC. The charge transport mechanism is a temperature activated process, in which, the electrons passes over of the low barriers and in turn, diode has a large ideality factor. The charge transport mechanism of the diode was analyzed by a Gaussian distribution of the Schottky barrier heights due to the Schottky barrier inhomogeneities at the metal-semiconductor interface and the mean barrier height and zero-bias standard deviation values for the diode was found to be 1.82 eV and $s_0$=0.233 V, respectively. The interface state density of the diode was determined using conductance-frequency and it was of order of $9.18{\times}10^{10}eV^{-1}cm^{-2}$.

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A Study on the Transport Mechanism of a SCH Quantum-Well Laser Diode and on the Modulation Characteristics (SCH 양자우물 레이저 다이오드의 수송기구와 변조응답 특성에 관한 연구)

  • Kim, Jong-Gi;Jeong, Jea-Yong;Suh, Chung-Ha
    • Journal of the Institute of Electronics Engineers of Korea TE
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    • v.37 no.1
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    • pp.27-34
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    • 2000
  • In this paper, carrier transport mechanism and modulation response for SCH(Separate Confinement Heterostructure) SQW(Single Quantum Well) laser diodes were studied. In order to explain carrier transport mechanism, both carrier density and current density were calculated. The recombination current density in the quantum well as a function of the SCH length was also calculated. For the modulation response, linearizing the rate equation, we calculated the bandwidth, relaxation oscillation frequency, damping factor, and the K-factor.

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Electroconvective Instability on Undulated Ion-selective Surface (파상형 이온 선택 표면상의 전기와류 불안정성)

  • Lee, Hyomin
    • Korean Chemical Engineering Research
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    • v.57 no.5
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    • pp.735-742
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    • 2019
  • In this work, the electrokinetic interactions between the undulated structure of an ion-selective membrane and electroconvective instability has been studied using numerical analysis. Using finite element method, electric field-ionic species transport-flow field were analyzed by fully-coupled manner. Through the numerical study, the Dukhin's mode as the mechanism of undulated surface for the electroconvective instability were proven. The Dukhin's mode which competes with Rubinstein's mode has roles of (i) decreasing transition voltage to overlimiting regime and (ii) non-linearly increasing of overlimiting current. Also, (iii) the mixing efficiency is enhanced by removal mechanism of high-frequency Fourier mode of the electroconvective instability. Conclusively, the undulated ion-selective surface would provide energy-efficient mechanism for ion-selective transport systems such as electrodialysis, electrochemical battery, etc.