• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.281-281
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• 2010

Very low refractive index (<1.4) materials have been proved to be the key factor improving the performance of various optical components, such as reflectors, filters, photonic crystals, LEDs, and solar cell. Highly porous SiO2 are logically designed for ultralow refractive index materials because of the direct relation between porosity and index of refraction. Among them, ordered macroporous SiO2 is of potential material since their theoretically low refractive index ~1.10. However, in the conventional synthesis of ordered macroporous SiO2, the time required for the crystallization of organic nanoparticles, such as polystyrene (PS), from colloidal solution into well ordered template is typical long (several days for 1 cm substrate) due to the low interaction between particles and particle - substrate. In this study, polystyrene - polyacrylic acid (PS-AA) nanoparticles synthesized by miniemulsion polymerization method have hydrophilic polyacrylic acid tails on the surface of particles which increase the interaction between particle and with substrate giving rise to the formation of PS-AA film by simply spin - coating method. Less ordered with controlled thickness films of PS-AA on silicon wafer were successfully fabricated by changing the spinning speed or concentration of colloidal solution, as confirmed by FE-SEM. Based on these template films, a series of macroporous SiO2 films whose thicknesses varied from 300nm to ~1000nm were fabricated either by conventional sol - gel infiltration or gas phase deposition followed by thermal removal of organic template. Formations of SiO2 films consist of interconnected air balls with size ~100 nm were confirmed by FE-SEM and TEM. These highly porous SiO2 show very low refractive indices (<1.18) over a wide range of wavelength (from 200 to 1000nm) as shown by SE measurement. Refraction indices of SiO2 films at 633nm reported here are of ~1.10 which, to our best knowledge, are among the lowest values having been announced.

• Journal of Photoscience
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• v.1 no.1
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• pp.47-52
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• 1994

Effects of HgCl$_2$-treatment on electron transport, chlorophyll a fluorescence and its quenching were studied using isolated barley (Hordeum vulgare L. cv. Albori) chloroplasts. Depending on the concentration of HgCI$_2$, photosynthetic oxygen-evolving activities of photosystem II (PS II) were greatly inhibited, whereas those of photosystem I (PS I) were slightly decreased. The inhibitory effects of HgCl$_2$ on the oxygen-evolving activity was partially restored by the addition of hydroxyamine, suggesting the primary inhibition site by HgCl$_2$2-treatment is close to the oxidizing site of PS tl associated with water-splitting complex. Addition of 50 $\mu$M HgCI$_2$ decreased both photochemical and nonphotochemical quenching of chlorophyll fluorescence. Especially, energy dependent quenching (qE) was completely disappeared by HgCl$_2$-treatment as observed by NH$_4$CI treatment. In the presence of HgCI$_2$, F'o level during illumination was also increased. These results suggest that pH gradient across thylakoid membrane can not be formed in the presence of 0 $\mu$M HgCl$_2$. In addition, antenna pigment composition might be altered by HgCl$_2$-treatment.

• BMB Reports
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• v.35 no.5
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• pp.459-464
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• 2002

Fusogenic liposomes that incorporate Sendai virus envelope proteins, so-called Sendai virosomes, have been developed for in vitro and in vivo genetic modification of animal cells. In this study, several different virosomes of varying lipid compositions were formulated and their in vitro gene-transfer efficiencies compared. The virosomes were prepared by quantitative reconstitution of the Sendai envelope, fusion (F) and hemagglutinin-neuraminidase (HN) proteins into liposomal vesicles. Virosomes that contained luciferase reporter genes were tested in 293 transformed human kidney cells. F/HN-virosomes that were prepared with an artificial Sendai viral envelope (ASVE-virosomes) or phosphatidylserine (PS-virosomes) exhibited an 8- or 6-fold higher gene-transfer efficiency than cationic liposomes that were made with 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP). F/HN-virosomes that were prepared with phosphatidic acid (PA-virosomes) instead of PS were less efficient in gene transfer than either ASVE- or PS-virosomes. In addition, the genetransfer capability of ASVE- and PS-virosomes was maximal at a $Ca^{2+}$ concentration of 510 mM. These results suggest that the incorporated lipid components significantly affect the in vitro gene transfer that is mediated by Sendai F/HN-virosomes.

• Journal of Oriental Neuropsychiatry
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• v.11 no.1
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• pp.19-36
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• 2000

Alzheimer's disease (AD) is progressive neurodegenerative disease, which is pathologically characterized by neuritic plaques and neurofibrillary tangles associated with the acetylcholinesterase, apolipoprotein E and butylcholinesterase, and by mutations in the presenilin genes PS1 and PS2, and amyloid precursor proteins (APPs) overexpression. The present research is to examine the inhibition effect of KBT on PS1, PS2 and APPs overexpression by detected to Western blotting. To verify the Effects of KBT on cognitive deficits further, we tested it on the scopolamine (1 mg/kg)-induced amnesia model of the mice using the Morris water maze tests, and there was ameliorative effects of memory impairment as a protection to scopolamine. KBT only partially blocked the increase in blood serum level of acetylcholinesterase and Uric acid induced by scopolamine, whereas blood glucose level was shown to attenuate the amnesia induced by scopolamine and inreased extracellular serum level compared with only scopolamine injection. In conclusion, studies of KBT that has been know as anti-choline and inhibition ablilities of APPs overexpression, this could also be used further as a important research data for a preventive and promising symptomatic treatment for Alzheimer's disease.

• Journal of Oriental Neuropsychiatry
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• v.12 no.1
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• pp.151-167
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• 2001

Alzheimer's disease(AD) is a progressive neurodegenerative disease, which is pathologically characterized by neuritic plaques and neurofibrillary tangles associated with the acetylchohnesterase, apolipoprotein E and butylcholinesterase, and by mutations in the presenilin genes PS1 and PS2, and amyloid precursor proteins (APPs)'s overexpression. The present research is to examine the inhibition effect of BYCNT on PS-1, PS-2 and APPs's overexpression by detected to Western blotting. To verify the effects of BYCNT on cognitive deficits further, we tested it on the scopolamine(1mg/kg)-induced amnesia model of the mice using the Morris water maze tests, and there was ameliorative effects of memory impairment as a protection from scopolamine. BYCNT only partially blocked the increase in blood serum level of acetylcholinesterase and Uric acid induced by scopolamine, whereas blood glucose level was shown to attenuate the amnesia induced by scopolamine and inreased extracellular serum level compared with only scopolamine injection. In conclusion, studies of BYCNT that has been known as anti-choline and inhibition ablilities of APPs overexpression, this could also be used further as a important research data for a preventive and promising symptomatic treatment for Alzheimer's disease.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.688-698
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• 2018

Quasi Z-Source Multilevel Inverter (QZMLI) topology has attracted grid connected Photovoltaic (PV) systems in recent days. So there is a remarkable research thrust in switching techniques and control strategies of QZMLI. This paper presents the mathematical analysis of Phase shift- Pulse Width Amplitude Modulation (PS-PWAM) for QZMLI and emphasizes on the advantages of the technique. The proposed technique uses the maximum and minimum envelopes of the reference waves for generation of pulses and proportion of it to generate shoot-through pulses. Hence, it results in maximum utilization of input voltage, lesser switching loss, reduced Total Harmonic Distortion (THD) of the output voltage, reduced inductor current ripple and capacitor voltage ripple. Due to these qualities, the QZMLI with PS-PWAM emerges to be the best suitable for PV based grid connected applications compared to Phase shift-Pulse Width Modulation (PS-PWM). The detailed math analysis of the proposed technique has been disclosed. Simulation has been performed for the proposed technique using MATLAB/Simulink. A prototype has been built to validate the results for which the pulses were generated using FPGA /SPARTAN 3E.

• Korean Journal of Environmental Agriculture
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• v.17 no.1
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• pp.5-10
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• 1998

The microbial degradation, photosensitizer-mediated photolysis, and bioceramic- accelerated degradation of the herbicide imazapyr were investigated using four types of soil. 1. Seven strains of microorganisms isolated from the soil A and the active sludge collected from the waste water disposal plant in CheongJu did not give any distinct degradation products in pure culture. When imazapyr (10ppm) was incubated for 14days with each of the 6strains of the known bacteria, they did not produce any noticeable products, either, suggesting that imazapyr was degraded very little by microorganisms in aqueous media. Meanwhile, when 50ppm of imazapyr was incubated in soil A and B for 6months, a degradation product of m/z 279 was detected. It turned out to be 2-[(1-carbamoyl-1,2-dimethylpropyl)carbamoyl]nicotinic acid, which was formed by the hydrolytic cleavage of the imidazolinone ring and by tautomerism. When imazapyr was exposed to sunlight, degradation rates were 14.6% under the control and 66.0, 76.5, 26.7, and 90.0% in the presence of PS-1 (100ppm), PS-1 (200ppm), PS-2(100ppm), and PS-3(100ppm), respectively, and a degradation product of m/z 149 was tentatively identified in the treatment of PS-1. 2. When soil C and D treated with bioceramic were incubated for 7weeks, the $^{14}C$-activities of $^{14}CO_2$ evolved were 2.03 and 1.12% of the originally applied ones, respectively, whereas those in control soils without bioceramic were 1.88 and 0.82% showing no significant defferences.After 5 weeks, however,the differences in the amounts of $^{14}CO_2$ between the two treatments increased gradually, suggesting the bioceramic effect.

• Journal of Positioning, Navigation, and Timing
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• v.6 no.3
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• pp.125-133
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• 2017

Time comparison is necessary for the verification and synchronization of the clock. Two-way satellite time and frequency (TWSTFT) is a method for time comparison over long distances. This method includes errors such as atmospheric effects, satellite motion, and environmental conditions. Ionospheric delay is one of the significant time comparison error in case of the carrier-phase TWSTFT (TWCP). Global Ionosphere Map (GIM) from Center for Orbit Determination in Europe (CODE) is used to compare with Bernese. Thin shell model of the ionosphere is used for the calculation of the Ionosphere Pierce Point (IPP) between stations and a GEO satellite. Korea Research Institute of Standards and Science (KRISS) and Koganei (KGNI) stations are used, and the analysis is conducted at 29 January 2017. Vertical Total Electron Content (VTEC) which is generated by Bernese at the latitude and longitude of the receiver by processing a Receiver Independent Exchange (RINEX) observation file that is generated from the receiver has demonstrated adequacy by showing similar variation trends with the CODE GIM. Bernese also has showed the capability to produce high resolution IONosphere map EXchange (IONEX) data compared to the CODE GIM. At each station IPP, VTEC difference in two stations showed absolute maximum 3.3 and 2.3 Total Electron Content Unit (TECU) in Bernese and GIM, respectively. The ionospheric delay of the TWCP has showed maximum 5.69 and 2.54 ps from Bernese and CODE GIM, respectively. Bernese could correct up to 6.29 ps in ionospheric delay rather than using CODE GIM. The peak-to-peak value of the ionospheric delay for TWCP in Bernese is about 10 ps, and this has to be eliminated to get high precision TWCP results. The $10^{-16}$ level uncertainty of atomic clock corresponds to 10 ps for 1 day averaging time, so time synchronization performance needs less than 10 ps. Current time synchronization of a satellite and ground station is about 2 ns level, but the smaller required performance, like less than 1 ns, the better. In this perspective, since the ionospheric delay could exceed over 100 ps in a long baseline different from this short baseline case, the elimination of the ionospheric delay is thought to be important for more high precision time synchronization of a satellite and ground station. This paper showed detailed method how to eliminate ionospheric delay for TWCP, and a specific case is applied by using this technique. Anyone could apply this method to establish high precision TWCP capability, and it is possible to use other software such as GIPSYOASIS and GPSTk. This TWCP could be applied in the high precision atomic clocks and used in the ground stations of the future domestic satellite navigation system.

• Polymer(Korea)
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• v.33 no.5
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• pp.458-462
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• 2009

We have synthesized ABC linear triblock copolymers, i.e., polystyrene-b-poly(ethylene oxide)-b-polylactide, via sequential anionic and ring-opening polymerizations. In the first anionic polymerization step, styrene was polymerized in cyclohexane using sec-butyllithium as the initiator. Poly (styryl) lithium was hydroxylated by the addition of ethylene oxide, and the subsequent protonation with methanolic HCl. In the second anionic polymerization step, potassium naphthalenide was used to deprotonate the hydroxyl group of the PS to generate the macroinitiator of PS-$O^-K^+$. Polymerization of ethylene oxide was performed in THF and terminated with methanolic HCl. In the ring-opening polymerization step, the PS-b-PEO-$AlEt_2$ macroinitiator was prepared from an $AlEt_3$/pyridine system in THF, and the polymerization of lactide was performed at $90^{\circ}C$. The resulting block copolymers showed well-defined molecular weights and narrow molecular weight distributions as revealed by $^1H$- NMR spectroscopy and gel permeation chromatography (GPC).

• Applied Chemistry for Engineering
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• v.25 no.6
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• pp.581-585
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• 2014

We conducted investigation on the hybridization of poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) (PEDOT : PSS) with graphene derivative (G-PSS), which has been prepared by wrapping reduced graphene oxide (RGO) with PSS. In situ polymerization of PEDOT/PSS in the presence of G-PSS afforded the PEDOT/PSS and graphene hybrid (GP). The analysis of XPS, IR and Raman spectroscopies for GP showed that PEDOT/PSS was successfully synthesized and hybridized with graphene. Compared to the G-PSS, GP showed an enhanced electrical conductivity of $4.46{\times}10^2S/m$ with a good wter-dispersity.