• Toxicological Research
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• v.30 no.3
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• pp.179-184
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• 2014

Xenobiotics causing a variety of toxicity in biological systems could be classified as two types, inorganic and organic chemicals. It is estimated that the organic xenobiotics are responsible for approximately 80~90% of chemical-induced toxicity in human population. In the class for toxicology, we have encountered some difficulties in explaining the mechanisms of toxicity caused especially by organic chemicals. Here, a simple flowchart was introduced for explaining the mechanism of toxicity caused by organic xenobiotics, as the central dogma of molecular biology. This flowchart, referred to as a central dogma, was described based on a view of various aspects as follows: direct-acting chemicals vs. indirect-acting chemicals, cytochrome P450-dependent vs. cytochrome P450-independent biotransformation, reactive intermediates, reactivation, toxicokinetics vs. toxicodynamics, and reversibility vs. irreversibility. Thus, the primary objective of this flowchart is to help better understanding of the organic xenobiotics-induced toxic mechanisms, providing a major pathway for toxicity occurring in biological systems.

• Bulletin of the Korean Chemical Society
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• v.24 no.8
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• pp.1135-1140
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• 2003

The kinetics and mechanism of the pyridinolysis $(XC_5H_4N)$ of Y-aryl phenyl isothiocyanophosphates (1;$(YC_6H_4O)\;(C_6H_5O)$P(=O)NCS) are investigated in acetonitrile at 55.0 ℃. The Hammett plots for substituent (Y) variations in the substrate (log k₂ vs σY) exhibit a convex upward biphasic type with breaks at Y = H. For electron-donating Y groups the Hammett coefficients, ρY, are positive and cross-interaction constant ρXY is negative, while those for electron-withdrawing Y groups ρY values are negative with a positive ρXY. These results are interpreted to indicate mechanistic change at the breakpoint (σY = 0) from a concerted to a stepwise mechanism with rate-limiting expulsion of the $^-NCS$ group from a trigonal bipyramidal pentacoordinated (TBP-5C) intermediate. Biphasic plots of log k₂ vs σX or $pK_a$(X) with steeper slopes for the more basic nucleophiles are obtained suggesting an equatorial nucleophilic attack in contrast to an apical attack for the less basic nucleophiles with smaller magnitude of ρX or βx.

• Bulletin of the Korean Chemical Society
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• v.26 no.9
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• pp.1354-1358
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• 2005

Nano- and microstructured indium nitride crystals were synthesized by the reaction of indium oxide ($In_2O_3$) powder and its pellet with ammonia in the temperature range 580-700 ${^{\circ}C}$. The degree of nitridation of $In_2O_3$ to InN was very sensitive to the nitridation temperature. The formation of zero- to three-dimensional structured InN crystals demonstrated that $In_2O_3$ is nitridated to InN via two dominant parallel routes (solid ($In_2O_3$)-to-solid (InN) and gas ($In_2O$)-to-solid (InN)). The growth of InN crystals with such various morphologies was explained by the vapor-solid (VS) mechanism where the degree of supersaturation of In vapor determines the growth morphology and the vapor was mainly by the reaction of $In_2O$ with ammonia and partially by sublimation of solid InN. The pellet method was proven to be useful to obtain homogeneous InN nanowires.

• Korean Journal of Applied Biomechanics
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• v.17 no.4
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• pp.73-82
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• 2007

The purpose of this study was to qualitatively analyze coordination pattern of joints and segments during Dwichagi in Taekwondo and present a point of difference as compared with the previous study on Dolryeochagi in Taekwondo. By the utilization of three-dimensional cinematography, the angles of individual joints and segments of six male Taekwondo experts during Dwichagi were calculated by using Euler's angle. The used coordination variables were angle vs. angle plots between adjacent joints and segments and angle vs. angular velocity plots of individual joints and segments, respectively. It was observed during Dwichagi that in-phase coordination and spring-like rotational control mechanism of the lower and upper trunk were transferred into straight spring-like control mechanism of lower leg passing through flexion-extension and the fixation of degree-of-freedom of lower trunk and hip joint alternatively. This comparative study that coordination variables were used seems to be more useful research direction to deeply understand basic control mechanisms of Taekwondo kicking techniques when compared with the previous studies that defined Dwichagi as a thrust movement pattern merely based on biomechanical variables of a kicking leg.

• Journal of the Semiconductor & Display Technology
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• v.9 no.2
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• pp.1-6
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• 2010

Star-like ZnO nanostructures were grown on SI(100) substrates with carbon(C) catalyst by employing vapor-solid(VS) mechanism. The morphologies and structure of ZnO nanostructures were investigated by Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and Raman spectrum, Photoluminescence spectrum. The results demonstrated that the as-synthesized products consisted of star-like ZnO nanostructure with hexagonal wurtzite phase. Nanostructures grown at 1100 were mainly star-like in structure with diameters of 500 nm. The legs of the star-like nanostructures were preferentially grown up along the [0001] direction. A vapor.solid (VS) growth mechanism was proposed to explain the formation of the star-like structures. Photoluminescence spectrum exhibited a narrow emission band peak around 380 nm and a broad one around 491 nm. Raman spectrum of the ZnO nanostructures showed oxygen defects in ZnO nanostructures due to the existence of Ar gas during the growth process, leading to the dominant green band peak in the PL spectrum.

• The Korean Journal of Physiology and Pharmacology
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• v.18 no.5
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• pp.411-418
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• 2014

Vascular remodelling is an adaptive mechanism, which counteracts pressure changes in blood circulation. Nicotine content in cigarette increases the risk of hypertension. The exact relationship between nicotine and vascular remodelling still remain unknown. Current study was aimed to determine the effect of clinically relevant dosage of nicotine (equivalent to light smoker) on aortic reactivity, oxidative stress markers and histomorphological changes. Twelve age-matched male Sprague-Dawley rats were randomly divided into two groups, i.e.: normal saline as control or 0.6 mg/kg nicotine for 28 days (i.p., n=6 per group). On day-29, the rats were sacrificed and the thoracic aorta was dissected immediately for further studies. Mean arterial pressure (MAP) and pulse pressure (PP) of nicotine-treated vs. control were significantly increased (p<0.05). Nicotine-treated group showed significant (p<0.05) increase tunica media thickness, and decrease in lumen diameter, suggesting vascular remodelling which lead to prior hypertension state. The phenylephrine (PE)-induced contractile response in nicotine group was significantly higher than control group ($ED_{50}=1.44{\times}10^5M$ vs. $4.9{\times}10^6M$) (p<0.05~0.001). However, nicotine-treated rat showed significantly lower endothelium-dependent relaxation response to acetylcholine (ACh) than in control group ($ED_{50}=6.17{\times}10^7M$ vs. $2.82{\times}10^7M$) (p<0.05), indicating loss of primary vascular function. Malondialdehyde (MDA), a lipid peroxidation marker was significantly higher in nicotine group. Superoxide dismutase (SOD) enzymatic activity and glutathione (GSH) were all reduced in nicotine group (p<0.05) vs. control, suggesting nicotine induces oxidative imbalance. In short, chronic nicotine administration impaired aortic reactivity, probably via redox imbalance and vascular remodelling mechanism.

• The Journal of Information Systems
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• v.28 no.4
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• pp.1-25
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• 2019

Purpose The purpose of this study is to investigate cognitive mechanism of goal relations (Single-goal vs. Multiple-goals) and to-do list (Packing vs. Unpacking) and also verify the role of self-efficacy in the perspective of motivation belief. The perspective of cognitive mechanism is related to the effects of how the relations of multitasking environments affects to facilitating relation or conflicting relations. In pursuit of a single goal, judgement of task importance can be facilitated by unpacking effect due to relations of strongly associated project components including to-do list. On the other hands, in pursuit of multiple goals, judgement of task importance can be conflicted due to mutually exclusive relations of multiple goals. Additionally, the cognitive mechanism can be regulated from the role of self-efficacy, which contributes to motivation belief on how much a person is confident in achieving given tasks. In the end this research is to identify self-efficacy as boundary condition in inhibiting the effects of facilitation and conflict. Design/methodology/approach This study conducted Two-way ANOVA (Packing/ Unpacking * Single-goal/ Multiple-goals) to explore the effects of cognitive mechanism on task importance. After that we performed Three-way ANOVA, 2 (To-do list: Packing/ Unpacking) * 2 (Goal relation: Single-goal/ Multiple-goals) * 2 (Self-efficacy: Low self-efficacy/ High self-efficacy) to verify the role of self-efficacy between goal relations and to-do list. Findings In the cognitive mechanism, the task importance is not significantly different between in packed and in unpacked condition in pursuit of a single goal. But multitasking with multiple goals causes goal conflict, which means packed condition indicates significantly higher task importance than unpacked condition. Additionally, for a group with low self-efficacy unpacking leads to conflicting relation, which implies that packed condition is more efficient strategy than packed condition. On the other hands, in pursuit of mulitple goals, either packing or unpacking has no distinctive effects on task importance. However, participants with high self-efficacy are no longer affected by facilitating relation and conflicting relation as well in pursuit of either a single goal or multiple goals as well.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.272-280
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• 2003

A definite shut-in pressure in hydraulic fracturing techniques is needed for obtaining the correct information on the in-situ stress regimes in rock masses. The relation between the behaviour of hydraulically induced fractures and the condition of remote stress is considered to be major reasons of an ambiguous shut-in pressure in hydraulic fracturing pressure-time history curves. This paper describes the results of a series of numerical analyses carried out using UDEC(Universal Distinct Element Code, Itasca), which is based on the discrete element method, to compare several methods for determining the shut-in pressure during hydraulic fracturing. The fully coupling of hydraulic and mechanical analysis was applied, and the effects of four different discontinuity geometries in numerical modelling have been investigated for this purpose. The effects of different remote stress regimes and different physical properties on hydraulic fracture propagation have been also analyzed. Several methods for obtaining shut-in pressure from the ambiguous shut-in curves have been applied to all the numerical models. The graphical intersection methods, such as (P vs. t) method, (P vs. log(t)) method, (log(P) vs. log(t)) method, give smaller values of the shut-in pressure than the statistical method, (dP/dt vs. P). Care should be taken in selecting a method for shut-in pressure, because there can be existed a stress anomaly around the wellbore and fracturing from the wellbore by a constant flow rate may have a more complicate mechanism.

• Korean Journal of Materials Research
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• v.13 no.10
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• pp.668-672
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• 2003

The ZnO nanorods were synthesized using vapor-solid (VS) method on sodalime glass substrate without the presence of metal catalyst. ZnO nanorods were prepared thermal evaporation of Zn powder at $500^{\circ}C$. As-fabricated ZnO nanorods had an average diameter and length of 85 nm and 1.7 $\mu\textrm{m}$. Transmission electron microscopy revealed that the ZnO nanorods were single crystalline with the growth direction perpendicular to the (101) lattice plane. The influences of reaction time on the formation of the ZnO nanorods were investigated. The photoluminescence measurements showed that the ZnO nanorods had a strong ultraviolet emission at around 380 nm and a green emission at around 500 nm.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.2
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• pp.371-378
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• 2004

As an agent is applied into various fields, it is suggested as the paradigm of new application technology in the area of computer communication. However, the mobile agent brines the problem of security on an agent due to mobility. This study proposals the mobile agent protection protocol framework for more effective protection and safety. The designed Framework of protocol uses the public ky, the private key and the digital signature in PKI environment based on JAVA. This is the mechanism accomplishing safely the work of an agent by tracking the pattern of execution and the mobility plan through the VS(verification server). This also secures the suity and the flawlessness of an agent through the VS guaranteeing safety from malicious attacks.