• 산업공학
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• 제16권2호
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• pp.195-200
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• 2003

In this paper, the selective use of RTS and CTS frames is considered to analyze the capacity of IEEE 802.11 WLAN (Wireless Local Area Network). The RTS and CTS frames are used to transmit the data frames longer than dot11RTSThreshold according to IEEE 802.11 specification. The analysis of the optimal RTS-CTS threshold is derived to maximize the capacity of IEEE 802.11 WLAN. And, numerical examples are also presented for IEEE 802.11 a and b WLANs.

• Asian Pacific Journal of Cancer Prevention
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• 제16권9호
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• pp.3697-3701
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• 2015

Background: Cholangiocarcinoma (CHCA) is serious public health problem in Thailand, especially in the northeastern and northern regions. CHCA is known as one of the most aggressive malignant tumors associated with local invasion and a high rate of metastasis. A crucial step in the invasion process is the proteolytic degradation of the extracellular matrix (ECM) and basal membranes, for which several studies have shown a critical role played by matrix metalloproteinase-11 (MMP-11). Objective: This study aim to detect MMP-11 expression in CHCA specimens and any correlation with survival time. Materials and Methods: A retrospective analysis was conducted of 30 patients with CHCA in Rajvithi hospital, who had undergone immunohistochemical staining of MMP-11. Relationships between clinicopathological data and MMP-11 expression in CHCA specimens were analyzed by the ${\chi}^2$ test or Fisher's exact test. The estimated survival and the survival differences were analyzed by the Kaplan-Meier method and the log-rank test, respectively. Results: MMP-11 expression was found in 15 specimens (50%). The overall mean survival time is 237.0 days (95% CI 135.4-338.5, SD 271.9). Specimens with a positive MMP-11 had an average survival time of 136.7 days (95%CI 50.3-223.1, SD 156.0). Survival differences was signficant for the positive and negative MMP-11(p=0.022), but not well differentiated tumor and moderate to poor differentiated tumor (p=0.755), CA19-9 level of >1,000 and <1,000 (p=0.488), and between advanced and non-advanced staging (p=0.388). Conclusions: The positive MMP-11 expression indicates poor prognosis in CHCA specimens.

• 한국통신학회논문지
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• 제31권4A호
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• pp.412-420
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• 2006

다양한 형태의 트래픽이 등장하면서 각 트래픽이 요구하는 서비스 품질을 모두 만족시키기 위한 패킷 스케줄링 연구에 대한 중요성이 커지고 있다. IEEE 802.11 위원회에서는 이러한 요구에 부응하기 위해 IEEE 802.11e 규격을 제정하여 모든 트래픽을 4가지로 분류한 뒤 각 트래픽 별로 차등화된 서비스를 제공하고 있다. 그리고 IEEE 802.11a/g규격에서는 물리계층에서의 전송속도를 무선 단말기 당 최대 54 Mbps까지 지원하고 있다. 하지만 무선 채널환경에서는 전체 대역폭이 제한되어 있기 때문에 주어진 대역폭 내에서 전송효율을 최대화시키는 문제는 항상 풀어야 하는 과제이다. 따라서 본 연구에서는 전송오류가 발생하는 무선통신 환경 하에서 동작하는 무선 LAN 단말기가 패킷 전송을 위해 CSMA-CA 기반으로 동작함에 있어서 CW(Contention Window) 값을 현재 무선채널 상태에 따라 달리 설정함으로써 서비스 처리량(Throughput)을 더욱 극대화할 수 있는 패킷 스케줄링 기법을 제안하였다. 제안된 알고리즘을 NS-2 네트워크 시뮬레이터를 이용하여 성능평가를 수행하였고, 수치 결과를 통해 제안한 알고리즘이 기존 IEEE 802.11e의 성능을 더욱 향상시킬 수 있음을 보였다.

• 한국재료학회지
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• 제15권2호
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• pp.97-105
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• 2005

[ $11\AA$ ] tobermorite$(5CaO{\cdot}6SiO_2{\cdot}5H_2O)$ is synthesized from the mixtures of calcium hydroride and quartz using alumina in a molar ratio $Ca(OH)_2/SiO_2$ of 0.8 at $180^{\circ}C$ for 8 and 24 hrs under saturated steam pressure. The influence of alumina on the formation of $11\AA$ tobermorite was investigated by X-ray diffraction, differential thermal analysis and infrared spectroscopy. $11\AA$ tobermorite containing increasingly larger amounts of aluminum showed a shift of the basal spacing from 11.3 to $11.6\AA$. In general, there was a direct linear relation between the basal spacing and added content of alumina. The differential thermal analysis curves showed that $11\AA$ tobermorite with increasing alumina contents exhibited the exothermic peak at high temperature, namely $11\AA$ tobermorite containing aluminum gave a sharp exothermic peak at temperature around $850\~860^{\circ}C$ in the case of $S_3\~S_5$. The absorption band at $1607\~1620cm^{-1}$ is attributed to the bending vibration of water, and the position of the main O-H stretching and Si-O lattice vibration of $11\AA$ tobermorite at 3500 and $965cm^{-1}$ respectively is not altered. Consequently the existence of alumina accelerates the crystallization of $11\AA$ tobermorite, and that the aluminum ion appears to substitute for the silicon ion in $11\AA$ tobermorite structure. Al-containing tobermorite is distinguished from Al-free tobermorite.

• 한국자기공명학회논문지
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• 제9권1호
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• pp.1-20
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• 2005

Vanadium-incorporated aluminophophate molecular sieve VH-SAPO-11 has been studied by electron spin resonanace (ESR) and electron spin echo modulation (ESEM) spectroscopies to determine the vanadium locatin and interaction with various adsorbate molecules. As-synthsized VH-SAPO-11 contains only vanady1 species with distored octahral coordination. After calcinations in $O_2$ and exposure to moisture, only species A is observed with reduced intensities. Species A is suggested as a VO$(H_2O)_2^{2+$} complex coordinate to three framwork oxygen bonded to aluminum. When calcined, hydrate VH-SAPO-11 is dehydrated at elevated temperature, species A loses it water ligands and transforms to $VO^{2+}$ ions coordinated to three framework oxygens (species B). Species B reduces its intensities significantly after treatment with $O_2$at high temperature, thus suggesting oxidation of $v^{4+}$to $v^{5+}$. When dehydrated VH-SAPO-11 contacts with $D_2O$ at room temperature, the ESR signal of species A is observed. This species assumed as a $VO(O_f)_3(D_2O)_2$, by considering 3 framework oxygens. Adsorption of deuterated methanol on dehydrated VH-SAPO-11 results in another new vanadium species D, which is identified as a $VO(CD_{3}OH)$ complex. When deuterated ethanol is adsorbed on dehydrated VH-SAPO-11, another new vanadium species E identified as a $VO(C_{2}H_{5}OD)^{2+}$, is observed. When deuterated propanol is adsorbed on dehydrated VH-SAPO-11, a new vanadium species F identified as a $VO(C_{3}H_{7}OD)$, is observed. Possible coordination geometries of these various complexes are discussed.

• 조명전기설비학회논문지
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• 제22권6호
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• pp.116-126
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• 2008

본 논문에서는 2.4[GHz]와 5[GHz]로 동작하는 Dual-band WLAN 송신기의 설계에 대하여 기술한다. Dual-band WLAN 송신기는 2.4[GHz] 대역과 5[GHz] 대역에서 각각 동작할 수 있도록 설계되었다. 이중대역의 구조를 갖는 송신 부는 2.4[GHz] 과 5[GHz] 주파수에서 동작하는 증폭기와 두 개의 VCO(Voltage Controlled Oscillator)또는 주파수 가변 범위가 매우 넓은 VCO를 사용해야 한다. 이 문제는 크기와 소비전력으로 나타나며, 이를 해결하기 위하여 이중대역 송신 모듈을 제안하였다. 이 송신부는 단일 송신 블럭을 사용하여 입력되는 주파수와 인가하는 바이어스 전압에 따라, IEEE 802.11b/g의 2.4[GHz] 대역신호에 대해서는 증폭기로 동작하고 IEEE로 802.11a의 5.8[GHz] 대역신호는 주파수 체배 방식을 이용하여 출력신호를 얻도록 설계하였다. 출력스펙트럼은 중심주파수에서 각각 +11[GHz], +20[MHz], +30[MHz] offset인 주파수에서 적응형 방식이 아닌 경우와 비교하여 4[dB], 6[dB], 16[dB]의 ACPR특성이 향상되었으며, IEEE 802.11a 무선 랜 송신스펙트럼 마스크 규격을 만족하였다.

• 한국산학기술학회논문지
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• 제12권1호
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• pp.312-317
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• 2011

캡사이신 채널로 알려진 바닐로이드 수용체 TRPV1 (캡사이신채널, Transient Receptor Potential Vanilloid 1)은 통증발현에서 중요한 역할을 하는 것으로 알려져 있다. 하지만 TRPV1의 활성조절에 관여하는 단백질에 대하여는 알려진 바가 많지 않다. 최근 rat TRPV1과 직접적으로 결합하는 단백질을 탐색하여 mouse Rab11-FIP3 (rab11-family interaction protein 3)가 rat TRPV1과 직접적으로 결합한다는 것이 보고되었다. Rab11은 여러 가지의 세포내 이동에 관여하는 것으로 보고되었다. 그러므로 Rab11-FIP3과의 결합을 통해 TRPV1의 세포막으로의 이동에 관여할 것으로 추측할 수 있다. 본 연구에서는 전에 보고된 연구가 mouse와 rat 이라는 다른 종의 단백질끼리의 결합이기 때문에 같은 종에서의 상호작용을 확인하고 Rab11-FIP3의 TRPV1의 세포막으로의 이동에서의 역할을 알아보고자 현재까지 동정되지 않은 rat의 Rab11-FIP3의 유전자를 GenBank 서열을 바탕으로 rat 뇌의 RNA 로부터 cDNA 를 클로닝하여 유전자를 분리하고 TRPV1 과의 관계를 세포생물학적으로 알아보았다. 연구결과 rat의 Rab11-FIP3는 489개의 아미노산 서열을 가지고 있으며 human과는 80%, mouse와는 90% 이상 아미노산 서열의 상동성을 보였다. 조직별 분포는 심장, 뇌, 간, 콩팥, 정소에서 발현되고 있는 것을 northern blot assay와 western blot assay 로 확인하였다. rat 의 뇌조직에서 TRPV1 과 Rab11-FIP3 단백질이 결합하여 colocalize 하는 것을 면역화학방법으로 확인하였다. 이 결합은 같은 family 의 TRPV2 와는 결합하지 않는 특이적 결합이므로 Rab11-FIP3 가 TRPV1 과 상호작용하여 세포막으로의 이동에 관여할 것이라는 것을 시사한다.

• 대한방사성의약품학회지
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• 제2권2호
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• pp.123-131
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• 2016

Increasing clinical demand for carbon-11 labeled radiopharmaceuticals has triggered technological advances in fields of radiochemistry and automated modules. Even though carbon-11 has a short half-life ($t_{1/2}=20.4min$), the consecutive second production of carbon-11 labeled radiopharmaceutical in one $^{11}C$-synthetic module should be delayed at least over 4 h to avoid the high radiation exposure. We herein aimed to produce two different carbon-11 labeled radiopharmaceuticals ([$^{11}C$]PIB and [$^{11}C$]methionine) by sharing of [$^{11}C$]methylation source in one $^{11}C$-synthetic module. The synthesis of $^{11}C$-labeling reagents ($[^{11}C]CH_3I$ or $[^{11}C]CH_3OTf$) is fully automated using the commercial TRACERlab $FX_{C-pro}$ module and is readily adaptable to $^{11}C$-labeling reactor for [$^{11}C$]PIB as well as another $^{11}C$-labeling apparatus for [$^{11}C$]methionine via the three-way valve. After completing the [$^{11}C$]PIB production, the re-synthesized $[^{11}C]CH_3I$ was passed through the three-way valve connected the polyetheretherketone (PEEK) line and loaded into the C18 Sep-Pak cartridge including the methionine precursor. The labeled product [^${11}C$]methionine was purified by a simple cartridge separation and reformulated into saline. The radiochemical yield of [$^{11}C$]PIB and [$^{11}C$]methionine were $5.3{\pm}0.6%$ and $18.7{\pm}0.8%$ (n.d.c.), respectively, with over 97% of radiochemical purity. The specific activity of [$^{11}C$]PIB was over $110GBq/{\mu}mol$. Total production time of two radiopharmaceuticals needs about 2 h from $1^{st}$ beam irradiation including quality control tests. Final [$^{11}C$]PIB and [$^{11}C$]methionine were satisfied all quality control test standards.

• The Korean Journal of Physiology and Pharmacology
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• 제18권5호
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• pp.391-396
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• 2014

Although interleukin-11 (IL-11) has been reported to be elevated in hypoxic tumors and has been associated with a poor prognosis in various cancers, little is known about its precise role in promoting metastasis in hypoxic tumors. In the present study, the molecular mechanism underlying the effects of IL-11 on MDA-MB-231 breast cancer cells migration and invasion in relation to metastasis under hypoxic conditions has been defined. Inhibition of IL-11 expression or function using small interfering RNA (siRNA) or a neutralizing antibody attenuated hypoxic MDA-MB-231 breast cancer cell migration and invasion through down-regulation of matrix metalloproteinases (MMPs) and activation of epithelial-to-mesenchymal transition (EMT) related gene expression. In addition, hypoxia-induced IL-11 increased STAT3 phosphorylation and STAT3 knockdown suppressed hypoxic MDA-MB-231 breast cancer cell invasion due to reduced MMP levels and reprogrammed EMT-related gene expression. These results suggest that one of the hypoxic metastasis pathways and the regulation of this pathway could be a potential target for novel cancer therapeutics.

• Journal of Applied Biological Chemistry
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• 제43권2호
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• pp.101-103
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• 2000

The synthesis and resolution of ($\pm$)-10,11-dihydroxydibenzosuberenone 3, a potential pharmaceutical compound, is described. It was synthesized from the 5H-dibenzo[a,d]cycloheptene-5-one (dibenzosuberenone) 1, and converted to diastereomeric isomers using (R)-(+)-$\alpha$-methylbenzylamine. Optical resolution of ($\pm$)-10,11-dihydroxydibenzosuberenone 3 was possible by fractional recrystallization of the diastereomer formed in ethanol. The optical resolution of 10,11-dihydroxydibenzosuberenone through formation of its phosphoamidates 5 using the (R)-(+)-$\alpha$-methylbenzylamine was achieved. These compounds provided the optical rotation of [${\alpha}]=-64.3$ for (-)-10,11-dihydroxy-dibenzosuberenone and [${\alpha}]=+61.3$ for (+)-10,11-dihydroxydibenzosuberenone. The (-)- and (+)-enantiomers were prepared in five steps from dibenzosuberenone with overall yields of 11.66% and 9.38%, respectively.