• Journal of Environmental Health Sciences
• /
• v.30 no.2
• /
• pp.115-122
• /
• 2004

A glassy carbon electrode(GCE) modified with nafion-DTPA (diethylene triamine-pentaacetic acid)-glycerol is used for the highly selective and sensitive determination of a trace amount of Cu(II). Various experimental parameters, which influenced the response of nafion-DTPA-glycerol modified electrode to Cu(II), are optimized. The Copper(II) is accumulated on the electrode surface by the formation of the complex in an open circuit, and the resulting surface is characterized by medium exchange, electrochemical reduction, and differential pulse voltammetry(DPV). The electrochemical response is evaluated with respect to concentration of modifier, pH and preconcentration time, quiet time, copper(II) concentration, and other variables. A linear range is obtained in the concentration range 1.0${\times}$10$^{-8}$ M-1.0${\times}$10$^{-6}$ MCu(II) with 7 min preconcentration time. The detection limit(3s) is as low as 2.36${\times}$10$^{-8}$ M (1.50 ppb).

• BMB Reports
• /
• v.28 no.6
• /
• pp.533-537
• /
• 1995

The detection with lucigenin under physiological conditions is selective for ${\cdot} O_{2}^{-}$, for it can be accepted that lucigenin indicates actual intramembranal $\cdot O_{2}^{-}- formation$. Lucigenin chemiluminescence (CL) was elicited from the plasma membrane (PM) only by addition of reduced pyridine nucleotide. NADPH was preferred to NADH in PM and hepatocytes. This specificity was masked by $NAD(P)^+$ inhibition. The half maximum rate of CL increase was obtained with 1.5 ${\mu}m$ NADH or 55 ${\mu}m$ NADPH in hepatocytes and 6 ${\mu}m$ NADH or 30 ${\mu}m$ NADPH in plasma membranes. Measurement of these NADPH values required the presence of a NADPH-regenerating system. With NADPH the maximal rate obtained was 10 fold higher than with NADH. NADPH and NADH could produce CL when having access from either side of the membrane. They seemed to react with the identical acceptor because NADH-induced CL was also inhibited by $NADP^+$. The characteristics of ${\cdot}O_{2}^{-}-formation$ produced by pyridine nucleotide will be discussed.

• Journal of ILASS-Korea
• /
• v.9 no.4
• /
• pp.67-76
• /
• 2004

Diode laser absorption sensors are advantageous because they may provide fast, sensitive, absolute, and selective measurements of species concentration. These systems are very attractive for practical applications owing to its compactness, reasonable cost, robustness, and ease of use. In addition, diode lasers we fiber-optic compatible and thus enable simultaneous measurements of multiple species along a line-of-sight. Recent advances of room-temperature, near-IR and visible diode laser sources for telecommunication, optical data storage applications make it possible to be applied for combustion diagnostics based on diode laser absorption spectroscopy. Therefore, combined with fiber-optics and high sensitive detection strategies, compact and portable sensor systems are now appearing for variety of applications. The objectives of this research are to develop new gas sensing system and to verify feasibility of this system. Wavelength modulation spectroscopy has been demonstrated in these experiments and has a bright prospect to this diode laser system.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.8
• /
• pp.2256-2260
• /
• 2013

A new quinoline-based acylhydrazone (1) has been synthesized and applied as a fluorescent probe. Probe 1 exhibits high selectivity and sensitivity to $Cu^{2+}$ with fluorescence "ON-OFF" behavior in HEPES buffered (1‰ DMSO, HEPES 20 mM, pH = 7.4) solution. The on-site generated 1-$Cu^{2+}$ complex displays excellent selectivity to sulfide ions with fluorescence "OFF-ON" performance through copper displacement approach.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.15 no.4
• /
• pp.324-330
• /
• 1990

In this paper, the hybrid ARQ system involving the single error correcting and double error detection (127, 119) cyclic Hamming codes and the SR(selective repeat) ARQ schemes with a finite receiver buffer has been designed and constructed. The system performance has been analyzed and simulated. As a result of the simulation, it has been shown that the transmitter retransmitted those data blocks that were detected in errors especially the request signal errors using two retransmission. The system performance was measured by throughput efficiency due to channel error effects.

• Journal of Communications and Networks
• /
• v.9 no.2
• /
• pp.167-176
• /
• 2007

In multimedia communication systems, efficient transmission system design should incorporate the use of matching unequal error protection (UEP), since source coders exhibit unequal bit error sensitivity. In this paper, we present UEP schemes which exploit differences in bit error protection levels in orthogonal frequency division multiplexing (OFDM) systems over frequency selective fading channels. We introduce an UEP scheme which improves the link performance with multiple transmit and receive antennas. Especially, we propose a new receiver structure based on two stage Maximum Likelihood detection (MLD) schemes which can approach the performance of a full search MLD receiver with much reduced computational complexity. In the performance analysis, we derive a generalized pairwise error probability expression for the proposed UEP schemes. Simulation results show that the proposed schemes achieve a significant performance gain over the conventional equal error protection (EEP) scheme.

• The KIPS Transactions:PartC
• /
• v.12C no.2 s.98
• /
• pp.229-234
• /
• 2005

We propose a fuzzy logic-based buffer management algorithm to improve internet traffic over ATM-GFR service. The proposed algorithm employs the strategies of early congestion detection and selective packet discard to achieve its design goals. A key feature of proposed algorithm is its ability to accept or drop a new incoming packet dynamically based on buffer condition and load rate of VCs. This is achieved by using fuzzy logic controller for the production of a drop factor. Simulation results show that proposed scheme significantly has improved fairness and TCP throughput compared with previous schemes.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2000.02a
• /
• pp.155-155
• /
• 2000

Adsorption of alkali metals on a silicon surface has attracted much attention due to its importance in metal-semiconductor interface technology, In particular, the bonding nature of alkali metal to silicon substrate has been a focus of fundamental research efforts. We examined the adsorbed layer of Cs on a Si(111)-(7$\times$) surface by reactive ion scattering (RIS) of hyperthermal Cs+ beams. RIS from a Cs-adsorbed surface gives rise to Cs, representing pickup of surface Cs by Cs projectile. The Cs intensity is proportional to surface coverage of Cs at a high substrate temperature (473 K), while it varies anomalously with Cs coverage at low temperatures (130-170 K). This observation indicates that RIS selectively detects metallic Cs on surface, but discriminates ionic Cs. Transition from ionic to metallic Cs adlayer is driven by thermal diffusion of Cs and their clustering process.

• Korean Journal of Veterinary Service
• /
• v.28 no.2
• /
• pp.113-119
• /
• 2005

We surveyed the distribution of Listeria spp in intestinal contents of slaughtered cattle from Daegu between March and October 2003. Fourteen Listeria spp were isolated from a total of 100 samples. Two samples contained only L innocua and other six samples contained both L monocytogenes and L innocua. Of the 99 samples positive to esculin reaction in Fraser broth, Listeria spp were isolated only from $8\%$ of the samples. Three selective plating medium were examined for detection of Listeria species including Enhanced hemolysis agar, Oxford agar and Palcam agar, It was found that Enhanced hemolysis agar was more effective than Oxford agar and Palcam agar, and that L monocytogenes needed 48 hour growth to give positive reaction.

• Bulletin of the Korean Chemical Society
• /
• v.11 no.2
• /
• pp.124-126
• /
• 1990

The potentiometric response behavior of a polypyrrole(PPy) coated Pt electrode to nitrate ion has been studied. The electrode shows a nernstian behavior with a slope of 59 mV over 0.50 M to $1.0{\times}10^{-3}M\;NO_3\;^-$ and a detection limit of $1.0{\times}10^{-4}M\;NO_3\;^-$. The response of the electrode is fast and the selectivities for $I^-,\;ClO_4\;^-,\;and\;IO_4\;^-$ are found to be improved. The effect of pH on the potential response to $NO_3\;^-$ is compared with the existing nitrate ion selective electrodes.