• Toxicological Research
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• v.30 no.4
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• pp.267-276
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• 2014

Exposures to lead (Pb) are associated with neurological problems including psychiatric disorders and impaired learning and memory. Pb can be absorbed by iron transporters, which are up-regulated in hereditary hemochromatosis, an iron overload disorder in which increased iron deposition in various parenchymal organs promote metal-induced oxidative damage. While dysfunction in HFE (High Fe) gene is the major cause of hemochromatosis, the transport and toxicity of Pb in Hfe-related hemochromatosis are largely unknown. To elucidate the relationship between HFE gene dysfunction and Pb absorption, H67D knock-in Hfe-mutant and wild-type mice were given drinking water containing Pb 1.6 mg/ml ad libitum for 6 weeks and examined for behavioral phenotypes using the nestlet-shredding and marble-burying tests. Latency to nestlet-shredding in Pb-treated wild-type mice was prolonged compared with non-exposed wild-types (p < 0.001), whereas Pb exposure did not alter shredding latency in Hfe-mutant mice. In the marble-burying test, Hfe-mutant mice showed an increased number of marbles buried compared with wild-type mice (p = 0.002), indicating more repetitive behavior upon Hfe mutation. Importantly, Pb-exposed wild-type mice buried more marbles than non-exposed wild-types, whereas the number of marbles buried by Hfe-mutant mice did not change whether or not exposed to Pb. These results suggest that Hfe mutation could normalize Pb-induced behavioral alteration. To explore the mechanism of repetitive behavior caused by Pb, western blot analysis was conducted for proteins involved in brain dopamine metabolism. The levels of tyrosine hydroxylase and dopamine transporter increased upon Pb exposure in both genotypes, whereas Hfe-mutant mice displayed down-regulation of the dopamine transporter and dopamine D1 receptor with D2 receptor elevated. Taken together, our data support the idea that both Pb exposure and Hfe mutation increase repetitive behavior in mice and further suggest that these behavioral changes could be associated with altered dopaminergic neurotransmission, providing a therapeutic basis for psychiatric disorders caused by Pb toxicity.

• Journal of fish pathology
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• v.21 no.2
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• pp.107-117
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• 2008

The pharmacokinetic properties of oxytetracycline (OTC) were studied after dipping and oral administration to cultured olive flounder, Paralichthys olivaceus (600 g). Plasma concentrations of OTC were determined after oral dosage (50, 100 and 200 mg/kg body weight) and dipping (50, 100 and 200 ppm, 1 h) in olive flounder (average 600 g, 23±1℃). Plasma samples were taken at 3, 5, 10, 15, 24, 32, 48, 72, 120, 168 and 240 h post-dose. In oral dosage of 50, 100 and 200 mg/kg, the peak plasma concentrations of OTC, which attained at 3 h post-dose, were 0.34, 0.44 and 1.18 ㎍/㎖, respectively. In dipping of 50, 100 and 200 ppm, those of OTC which also observed at 5 h post-dose, were 0.43, 0.38 and 0.64 ㎍/㎖, respectively. Plasma concentrations of OTC were not measurable at 240 h post-dose in all experiments. The kinetic profile of absorption, distribution and elimination of OTC in plasma were analyzed fitting to a one-compartment model by WinNonlin program. The following parameters were calculated for a single dosage of 50, 100 and 200 mg/kg body weight, respectively: AUC (the area under the concentration-time curve)=31.40, 28.07 and 32.97 ㎍∙h/㎖; T1/2 (half-life)􀆫0.89, 1.12 and 0.43 h; Tmax (time for maximum concentration)= 5.25, 3.70 and 7.30 h, Cmax (maximum concentration)=0.25, 0.38 and 0.61 ㎕/㎖. Following dipping at 50, 100 and 200 ppm, these parameters were AUC􀆫15.51, 14.63 and 19.72 ㎍∙h/㎖; T1/2= 0.75, 0.41 and 0.74 h; Tmax=4.90, 7.08 and 4.68 h, Cmax=0.40, 0.32 and 0.46 ㎕/㎖.

• Advances in environmental research
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• v.9 no.2
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• pp.135-150
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• 2020

Many industries, such as textiles, chemical refineries, leather, plastics and paper, use different dyes in various process steps. At the same time, these industrial sectors are responsible for discharging contaminants that are harmful and toxic to humans and microorganisms by introducing synthetic dyes into wastewater. Of these dyes, methylene blue dye, which is classified as basic dyes, is accepted as a model dye. For this reason, methylene blue dye was selected in the study and its removal from the water was studied. In this study, two efficient biosorbents were developed from chitosan and sunflower waste, an agro-industrial waste and modified using iron nanoparticles. The biosorption efficiency was evaluated for methylene blue (MB) dye removal from aqueous solution under various parameters such as treating agent, solution pH, biosorbent dosage, contact time, initial dye concentration and temperature. We investigated the kinetic properties of dye removal from water for Chitosan-Sunflower (CS), Chitosan-Sunflower-Nanoiron (CSN). When the wavelength of MB dye was spectrophotometrically scanned, the maximum absorbance was determined as 660 nm. For the core shell biosorbents we obtained, we found that the optimum time for removal of MB from wastewater was 60 min. The pH of the best pH was determined as 5 in the studied pH. The most suitable temperature for the experiment was determined as 30℃. SEM-EDAX, TEM, XRD, and FTIR techniques were used to characterize biosorbents produced and modified in the experimental stage and to monitor the change of biosorbent after dye removal. The interactions of the paint with the surface used for removal were explained by these techniques. It was calculated that 80% of CS and 88% of CSN removed MB in optimum conditions. Also, the absorption of MB dye onto the surface was investigated by Langmiur and Frendlinch isotherms and it was determined from the results that the removal was more compatible with Langmiur isotherm.

• Bulletin of the Korean Chemical Society
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• v.16 no.12
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• pp.1193-1203
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• 1995

In this work, we focused on the setup of the tools for the analysis of the final rotational state distribution of photofragments in vibrational predissociations of triatomic van der Waals molecules A-B2. We found that reflection principle used for the direct photodissociation processes can also be applied to find out the final rotational state distributions for indirect photodissociation processes. The quantity which represents the strength of rovibrational coupling between the quasi-bound state and the final state is reflected into the mirror of the classical angular momentum function, instead of the initial state before light absorption used in the reflection principle of direct processes. The sign change in the first derivative of the interaction potential with respect to the bond distance of B2 is found to be the source of the binodal structures in the final rotational distributions of photofragments in the model system studied in this work. In MQDT analysis, short range eigenchannel basis functions were found to be localized in angle, in the previous work [Lee, C.W. Bull. Korean Chem. Soc. 1995, 16, 957.] and may be called angle functions. Angle functions enjoy simple geometrical structures which have simple functional relations with the final state distributions of photofragments. Two processes take place along the angle functions which resemble the quasi-bound state and dominate over other processes. Two such angle functions are found to be not only localized angularly but also localized either one of ends of B2 in motions along the bond of B2. These dominating photodissociation processes, however, cancel each other. This cancellation causes photodissociation to depend sensitively on the interaction potential at other angles than the dominant one. Part of potential surface where much larger torque exists can now play an important role in photodissociation. MQDT also enables us to see which processes play important roles after cancellation. This is done by examining the amounts of time delayed by asymptotic eigenchannels.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.5
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• pp.95-100
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• 2014

In hypersonic aircraft, increase of aerodynamic heat and engine heat leads heat loads in airframe. It could lead structural change of aircraft's component and malfunctioning. Endothermic fuels are liquid hydrocarbon fuels which are able to absorb the heat load by undergoing endothermic reactions. In this study, exo-tetrahydrodicyclopentadiene was selected as a model endothermic fuel and experiments on endothermic properties were investigated with pore structure controlled zeolite catalyst using metal deposition. We secured the catalyst that had better endothermic performance than commercial catalyst. The object of this study is inspect catalyst properties which have effect on heat absorption improvement. Synthetic catalyst could be applied to system that use exo-THDCP as endothermic fuel instead of other commercial catalyst.

• Journal of Aerospace System Engineering
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• v.12 no.1
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• pp.1-9
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• 2018

In this study, a hybrid control method that adjusts for the existing force control technique has been presented for consideration. The proposed hybrid control technique does away with the chattering phenomenon occurring in existing force control technique and provides high shock absorption efficiency. In order to design the controller for the landing gear with MR damper, the equation of motion of the landing gear was derived. The hybrid controller was designed after constructing a simulation model using Recur-Dyne, multi-body dynamic analysis software. The hybrid controller can reduce the maximum strut force and displacement based on the skyhook controller, and is able to get the high efficiency by making it work for the additional force control technique. In addition, an effective switching control technique and input shaping technique was applied to prevent the chattering in the drop simulation. Finally, the performance of the landing characteristics was evaluated throughout the various drop simulations.

• Archives of Pharmacal Research
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• v.29 no.4
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• pp.318-322
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• 2006

Many quaternary ammonium salts are incompletely absorbed after their oral administration and may also be actively secreted into the intestine. However, the underlying mechanism(s) that control the transport of these cations across the intestinal epithelium is not well understood. In this study, the mechanism of absorption of quaternary ammonium salts was investigated using Caco-2 cell monolayers, a human colon carcinoma cell line. Tributylmethylammonium (TBuMA) was used as a model quaternary ammonium salts. When TBuMA was administrated at a dose of 13.3 imole/kg via iv and oral routes, the AUC values were $783.7{\pm}43.6\;and\;249.1{\pm}28.0{\mu}mole\;min/L$ for iv and oral administration, indicating a lower oral bioavailability of TBuMA $(35.6\%)$. The apparent permeability across Caco-2 monolayers from the basal to the apical side was 1.3 times (p<0.05) greater than that from the apical to the basal side, indicating a net secretion of TBuMA in the intestine. This secretion appeared to be responsible for the low oral bioavailability of the compound, probably mediated by p-gp (p-glycoprotein) located in the apical membrane. In addition, the uptake of TBuMA by the apical membrane showed a $Na^+$ dependency. Thus, TBuMA appears to absorbed via a $Na^+$ dependent carrier and is then secreted via p-gp related carriers.

• Tribology and Lubricants
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• v.35 no.4
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• pp.222-228
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• 2019

As rubber products such as O-rings, which are also known as packings or toric joints, come in regular, long term contact with liquid fuel, they can eventually swell, become mechanically weakened, and occasionally crack; this diminishes both their usefulness and intrinsic lifetime and could cause leaks during the steady-state flow condition of the fuel. In this study, we evaluate the lifetime of such products through compression set tests of FKM, a family of fluorocarbon elastomer materials defined by the ASTM international standard D141; these materials have great compression, sunlight, and ozone resistance as well as a low gas absorption rate. In this process, O-rings are immersed in the liquid fuel of airtight containers that can be expressed as a compression set, and the liquid fuel leakage in a flow rig tester at variable temperatures over 12 months is investigated. Using the Power Law model, our study determined a theoretical O-ring lifetime of 2,647 years, i.e. a semi-permanent lifespan, by confirming the absence of liquid fuel leakage around the O-ring assembled fittings. These results indicate that the FKM O-rings are significantly compatible for fuel tests to evaluate long-term sealing conditions.

• International Area Studies Review
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• v.15 no.2
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• pp.175-196
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• 2011

The developing countries have a lot of dormant resources, attempting the take-off of economic growth. The theory of 'vent for surplus' and Lewis model provide a good cornerstones to analyze the effect of export, FDI and domestic production on employment. This paper attempts to do empirical test to figure out what factor is significant as the determinant of Chinese employment. For this test, the estimation equations are derived from the Cobb-Douglas production function. The results are that the domestic production affects the most positive employment, compared to FDI and export. Unlikely general expectation, export doesn't have an substantial effect on employment in China. It is also found that the absorption of technology through export is lower than that of FDI in terms of the effect of technology on employment. So it is suggested that the employment policy should be shifted toward the increase of domestic production by using FDI rather than by promoting export industry. to reduce the internal imbalance.

• Journal of Aerospace System Engineering
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• v.15 no.1
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• pp.7-18
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• 2021

A semi-active MR damper landing gear is a damper that generates a fluid damping force and a magnetic field control damping force when the MR fluid passes through annular flow paths. In the case of MR fluid passing through annular flow paths, an incompletely developed flow inevitably occurs, causing an error in calculating damper inner forces including the fluid damping force. This error results in an inaccurate design of damper structural parameters and control gain selection, resulting in deterioration of dynamic characteristics and shock absorption performance of the landing gear. In this paper, we derived a mathematical model of an MR damper landing gear considering additional damping force generated in the entrance region of annular flow paths of the MR damper. If the mathematical modeling derived from this paper is applied to the design and optimization process of an MR damper landing gear, excellent performance of the MR damper landing gear is expected.