• Journal of KIISE
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• v.42 no.10
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• pp.1254-1267
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• 2015

Recently, excessive installations of APs have caused WLAN interference, and many techniques have been suggested to solve this problem. The AP aggregation technique serves to reduce active APs by moving station connections to a certain AP. Since this technique forcibly moves station connections, the transmission performance of some stations may deteriorate. The AP transmit power control technique may cause station disconnection or deterioration of transmission performance when power is reduced under a certain level. The combination of these two techniques can reduce interference through AP aggregation and narrow the range of interferences further through detailed power adjustment. However, simply combining these techniques may decrease the probability of power adjustment after aggregation and increase station disconnections upon power control. As a result, improvement in performance may be insignificant. Hence, this study suggests a scheme to combine the AP aggregation and the AP transmit power control techniques in OpenFlow-based WLAN to ameliorate the disadvantages of each technique and to reduce interferences efficiently by performing aggregation for the purpose of increasing the probability of adjusting transmission power. Simulations reveal that the average transmission delay of the suggested scheme is reduced by as much as 12.8% compared to the aggregation scheme and by as much as 18.1% compared to the power control scheme. The packet loss rate due to interference is reduced by as much as 24.9% compared to the aggregation scheme and by as much as 46.7% compared to the power control scheme. In addition, the aggregation scheme and the power control scheme decrease the throughput of several stations as a side effect, but our scheme increases the total data throughput without decreasing the throughput of each station.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.7
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• pp.653-660
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• 2013

This paper deals with the problem of unfairness among uplink TCP (Transmission Control Protocol) flows associated with frame aggregation employed in IEEE 802.11n WLANs (Wireless Local Area Networks). When multiple stations have uplink TCP flows and transmit TCP data packets to an AP (Access Point), the AP has to compete for channel access with stations for the transmission of TCP ACK (acknowledgement) packets to the stations. Due to this contention-based channel access, TCP ACKs tend to be accumulated in the AP's downlink buffer. We show that the frame aggregation in the MAC (Medium Access Control) layer increases TCP ACK losses in the AP and leads to the serious unfair operation of TCP congestion control. To resolve this problem, we propose the TAC (TCP ACK Compression) mechanism operating at the top of the AP's interface queue. By exploiting the properties of cumulative TCP ACK and frame aggregation, TAC serves only the representative TCP ACK without serving redundant TCP ACKs. Therefore, TAC reduces queue occupancy and prevents ACK losses due to buffer overflow, which significantly contributes to fairness among uplink TCP flows. Also, TAC enhances the channel efficiency by not transmitting unnecessary TCP ACKs. The simulation results show that TAC tightly assures fairness under various network conditions while increasing the aggregate throughput, compared to the existing schemes.

• Journal of Microbiology and Biotechnology
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• v.23 no.6
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• pp.818-825
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• 2013

We isolated and functionally characterized the ${\alpha}$- and ${\beta}$-subunits (ApCpnA and ApCpnB) of a chaperonin from Aeropyrum pernix K1. The constructed vectors pET3d-ApCpnA and pET21a-ApCpnB were transformed into E. coli Rosetta (DE3), BL21 (DE3), or CodonPlus (DE3) cells. The expression of ApCpnA (60.7 kDa) and ApCpnB (61.2 kDa) was confirmed by SDS-PAGE analysis. Recombinant ApCpnA and ApCpnB were purified by heat-shock treatment and anion-exchange chromatography. ApCpnA and ApCpnB were able to hydrolyze not only ATP, but also CTP, GTP, and UTP, albeit with different efficacies. Purified ApCpnA and ApCpnB showed the highest ATPase, CTPase, UTPase, and GTPase activities at $80^{\circ}C$. Furthermore, the addition of ApCpnA and ApCpnB effectively protected citrate synthase (CS) and alcohol dehydrogenase (ADH) from thermal aggregation and inactivation at $43^{\circ}C$ and $50^{\circ}C$, respectively. In particular, the addition of ATP or CTP to ApCpnA and ApCpnB resulted in the most effective prevention of thermal aggregation and inactivation of CS and ADH. The ATPase activity of the two chaperonin subunits was dependent on the salt concentration. Among the ions we examined, potassium ions were the most effective at enhancing the ATP hydrolysis activity of ApCpnA and ApCpnB.

• Journal of Microbiology and Biotechnology
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• v.21 no.2
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• pp.212-217
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• 2011

${\alpha}$ and ${\beta}$-subunits (ApCpnA and ApCpnB) are group II chaperonins from the hyperthermophilic archaeum Aeropyrum pernix K1, specialized in preventing the aggregation and inactivation of substrate proteins under conditions of transient heat stress. In the present study, the cooperativity of ${\alpha}$- and ${\beta}$-subunits from the A. pernix K1 was investigated. The ApCpnA and ApCpnB chaperonin genes were overexpressed in E. coli Rosetta and Codonplus (DE3), respectively. Each of the recombinant ${\alpha}$- and ${\beta}$-subunits was purified to 92% and 94% by using anionexchange chromatography. The cooperative activity between purified ${\alpha}$- and ${\beta}$-subunits was examined using citrate synthase (CS), alcohol dehydrogenase (ADH), and malate dehydrogenase (MDH) as substrate proteins. The addition of both ${\alpha}$- and ${\beta}$-subunits could effectively protect CS and ADH from thermal aggregation and inactivation at $43^{\circ}C$ and $50^{\circ}C$, respectively, and MDH from thermal inactivation at $80^{\circ}C$C and $85^{\circ}C$. Moreover, in the presence of ATP, the protective effects of ${\alpha}$- and ${\beta}$-subunits on CS from thermal aggregation and inactivation, and ADH from thermal aggregation, were more enhanced, whereas cooperation between chaperonins and ATP in protection activity on ADH and MDH (at $85^{\circ}C$) from thermal inactivation was not observed. Specifically, the presence of both ${\alpha}$- and ${\beta}$- subunits could effectively protect MDH from thermal inactivation at $80^{\circ}C$ in an ATP-dependent manner.

• Korean journal of applied entomology
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• v.62 no.4
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• pp.245-253
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• 2023

A control technique using mass-trapping was developed against thrips infesting hot peppers cultivating in greenhouses. It was essential to develop effective lure(s) attracting thrips for the control technique. Especially, mass-trapping using aggregation pheromone (AP) of the thrips was not much effective in open field cultivating hot peppers. This study aimed to develop a new lure to enhance the attractiveness of AP-based mass-trapping. In addition, this study was designed to investigate the decrease of attractiveness of the AP-based mass-trapping in the open field conditions. Methyl isonicotinate (MIN) as a new lure was assessed by the laboratory olfactometry and showed its attractiveness to thrips and its mixture effect with AP to attract the thrips. These results led us to test the AP+MIN mixture in the open field conditions cultivating hot peppers. The mixture significantly enhanced the mass-trapping efficacy in the open field conditions. Especially, the significant increase of the captured numbers was found in the western flower thrips, Frankliniella occidentalis. Furthermore, the increase of the AP concentration in the mass-trapping significantly increased the captured numbers in F. occidentalis and other thrips occurring in the hot pepper field. This study demonstrated the difference in the AP-based mass-trapping efficacy of the thrips between greenhouse and open field conditions. It also showed the increase of mass-trapping efficacy by increasing AP concentration in the trap. Especially, this study proposes a high efficient mass-trapping technology by the addition of MIN to AP especially against F. occidentalis.

• Korean journal of applied entomology
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• v.48 no.1
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• pp.73-79
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• 2009

Male adults of bean bug, Riptortus clavatus Thunberg (Heteroptera: Alydidae), release aggregation pheromone (AP) which consists of (E)-2-hexenyl (Z)-3-hexenoate (E2HZ3H), (E)-2-hexenyl (E)-2-hexenoate (E2HE2H), and tetradecyl isobutyrate (TI). Variation in the pheromonal secretion were checked by the factors of age, mating status, seasons, body weight and time in a day. There were no significant differences in the amounts of AP secretion by mating, body weight, and time in a day. Higher amount of AP was detected from older males than younger ones. The amount of AP detected was higher in the males collected from April to September than in those collected during October. No AP was detected in the males of November and December. These phenomena in the AP secretion were discussed in relation to food exploitation and reproductive diapause of the bean bug.

• Journal of Microbiology and Biotechnology
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• v.20 no.3
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• pp.542-549
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• 2010

In the present study, overexpression, purification, and characterization of Aeropyrum pernix K1 chaperonin B in E. coli were investigated. The chaperonin $\beta$-subunit gene (ApCpnB, 1,665 bp ORF) from the hyperthermophilic archaeon A. pernix K1 was amplified by PCR and subcloned into vector pET21a. The constructed pET21a-ApCpnB (6.9 kb) was transformed into E. coli BL21 Codonplus (DE3). The transformant cell successfully expressed ApCpnB, and the expression of ApCpnB (61.2 kDa) was identified through analysis of the fractions by SDS-PAGE (14% gel). The recombinant ApCpnB was purified to higher than 94% by using heat-shock treatment at $90^{\circ}C$ for 20 min and fast protein liquid chromatography on a HiTrap Q column step. The purified ApCpnB showed ATPase activity and its activity was dependent on temperature. In the presence of ATP, ApCpnB effectively protected citrate synthase (CS) and alcohol dehydrogenase (ADH) from thermal aggregation and inactivation at $43^{\circ}$ and $50^{\circ}$, respectively. Specifically, the activity of malate dehydrogenase (MDH) at $85^{\circ}$ was greatly stabilized by the addition of ApCpnB and ATP. Coexpression of pro-carboxypeptidase B (pro-CPB) and ApCpnB in E. coli BL21 Codonplus (DE3) had a marked effect on the yield of pro-CPB as a soluble and active form, speculating that ApCpnB facilitates the correct folding of pro-CPB. These results suggest that ApCpnB has both foldase and holdase activities and can be used as a powerful molecular machinery for the production of recombinant proteins as soluble and active forms in E. coli.

• Journal of Life Science
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• v.32 no.7
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• pp.501-509
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• 2022

Pollen corrected from Quercus species is abundant in Korea and has been used to treat anemia and inflammation of the prostate gland. It is also used for hemostasis in oriental medicine. In this study, the ethanol extract of the acorn pollen and its subsequent organic solvent fractions using hexane, ethylacetate, butanol, and water residue were prepared, and their antioxidant, anti-thrombosis, and hemolysis activities were evaluated. The ethylacetate fraction of acorn pollen (EF-AP) showed the highest polyphenol content (225.0 mg/g) and strong antioxidant activity among the solvent fractions. The RC₅₀ of EF-AP against DPPH, ABTS, and nitrite radicals was 72.2, 27.7, and 62.6 ㎍/ml, respectively. The blood coagulation activities of the all-solvent fractions determined by thrombin time, prothrombin time, and activated partial thromboplastin time were negligible up to 5 mg/ml. Platelet aggregation inhibitory activities were observed in the EF-AP, butanol fraction, and water residue, whereas hexane fraction induced strong platelet aggregation. The EF-AP has no hemolysis activity against human RBC up to 1 mg/ml. UPLC/MS/MS analysis of the EF-AP revealed that rutin, isoquercitrin, and astragalin are major compounds for antioxidant and anti-thrombosis activities. Our results suggest that EF-AP could be developed as a noble antioxidant and anti-thrombosis agent.

• Korean journal of applied entomology
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• v.47 no.2
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• pp.141-147
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• 2008

Male adults of bean bug, Riptortus clavatus Thunberg (Heteroptera: Alydidae), release aggregation pheromone (AP) attracting both sexes of adult and nymphs, which its egg parasite, Ooencyrtus nezarae (Hymenoptera: Encyrtidae) exploits the pheromone to find host. The AP consists of three components; (E)-2-hexenyl (Z)-3-hexenoate (E2HZ3H), (E)-2-hexenyl (E)-2-hexenoate (E2HE2H), and tetradecyl isobutyrate (TI). We analyzed composition of the pheromone components of bean bugs from different geo graphical locations of Korea and Japan. The attractiveness of different blends of AP components to R. clavatus was also tested in the fields in Jinju, Korea and in Kumamoto, Japan. Composition ratios (E2HZ3H: E2HE2H:TI) of the AP of Jinju and Iksan populations were 1:1.4:0.2 and 1:0.8:0.2, and those of Tsukuba and Kumamoto populations were 1:2.8:0.2 and 1:1.5:0.1, respectively. In field tests, traps baited with ratio of 1:1:1 (E2HZ3H:E2HE2H:TI=16.7:16.7:16.7mg/rubber septum) and 1:1:0.5(E2HZ3H:E2HE2H:TI= 20:20:10mg/rubber septum) attracted significantly greater number of adult bugs than that of 1:5:1 (E2HZ3H:E2HE2H:TI=7.1:35.7:7.1mg/rubber septum).

• Preventive Nutrition and Food Science
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• v.18 no.3
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• pp.181-187
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• 2013

Artemisia princeps Pampanini (AP) has been used as a traditional medicine in Korea, China and Japan and reported to exhibit various beneficial biological effects including anti-inflammatory, antioxidant, anti-atherogenic and lipid lowering activities; however, its antiplatelet and anticoagulant properties have not been studied. In the present study, we evaluated the effects of an ethanol extract of Artemisia princeps Pampanini (EAP) and its major flavonoids, eupatilin and jaceosidin, on platelet aggregation and coagulation. To determine the antiplatelet activity, arachidonic acid (AA)-, collagen- and ADP (adenosine diphosphate)-induced platelet aggregation were examined along with serotonin and thromboxane A2 ($TXA_2$) generation in vitro. The anticoagulant activity was determined by monitoring the activated partial thromboplastin time (aPTT) and prothrombin time (PT) in vitro. The data showed that EAP and its major flavonoids, eupatilin and jaceosidin, significantly reduced AA-induced platelet aggregation and the generation of serotonin and $TXA_2$, although no significant change in platelet aggregation induced by collagen and ADP was observed. Moreover, EAP significantly prolonged the PT and aPTT. The PT and/or aPTT were significantly increased in the presence of eupatilin and jaceosidin. Thus, these results suggest that EAP may have the potential to prevent or improve thrombosis by inhibiting platelet activation and blood coagulation.