• Journal of Pharmaceutical Investigation
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• v.18 no.4
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• pp.175-180
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• 1988

The role and effect of aluminum tristearate in microencapsulation were investigated based on the dispersion system of ethambutol hydrochloride in acetone-liquid paraffin. Eudragit RS was used as a wall-forming material. Eudragit RS microcapsules prepared using aluminum tristearate were uniform, free-flowing particles. The phase diagram of ethambutol hydrochloride-Eudragit RS-aluminum tristearate indicated that spherical microcapsules ranging from 250 to 1400 ${\mu}m$ in diameter could be prepared only in a very limited region. Instrumental analysis using an energy dispersive-type X-ray microanalyser and a scanning electron microscope showed that aluminum tristearate was localized near the surface of microcapsules. From these results, it was presumed that aluminum tristearate reduced the phase tension between Eudragit microcapsules and liquid paraffin. The dissolution rates of ethambutol hydrochloride from Eudragit RS microcapsules were consideraly lower than those from ethambutol hydrochloride powders and decreased as the amount of aluminum tristearate decreased.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.159-164
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• 2000

The fracture behaviors of aluminum foils and sheet papers were analyzed on the basis of linear elastic fracture mechanics(LEFM). The fracture loads of the similarly shaped specimens were calculated by dimensional analysis. The actual fracture loads were measured using the simple tension equipment. The predicted fracture loads were compared with the experimental results.

• The Korean Journal of Pharmacology
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• v.26 no.1
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• pp.13-23
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• 1990

Methylene Blue (MeB) and gentian violet $(10^{-6}{\sim}10^{-4}\;M)$ produced contractions in isolated thoracic aortic preparations of rabbits in a dose-dependent fashion, while other dyes, evans blue and eosine yellowish, did not affect the basal tension in the same range of doses. Porcine mesenteric arterial rings also responded to MeB with dose-dependent contractions. Single dose of $10^{-4}$ M MeB produced a biphasic response: contraction followed by relaxation. The contraction developed slowly within $2{\sim}4$ min and peaked in about 20 minutes and then slowly relaxed to the basal level. Tyramine $(10^{-4}\;M)$ also induced contraction but it developed faster and was more persistent than that of MeB. While the tyramine-induced tension was reproducible, the MeB-induced one wat not reiterable until 3 to 5 hours after washing out the MeB. Adding $10^{-4}$ M MeB further potentiated the contraction induced by $10^{-4}$ M tyramine. However, the MeB contraction was not affected by further addition or tyramine. Both tyramine- and MeB-induced tensions were abolished or significantly inhibited by pretreatment with various drugs acting on the sympathetic nervous system. The tyramine-induced tension was more sensitive to guanethidine and 6-hydroxydopamine than the MeB-induced tension, while the latter was more sensitive to $Ca^{2+}-free$ PSS and reserpine. But they have similar sensitivity to prazosin. The MeB-induced tension was significantly inhibited but not abolished by 6-hydroxydopamine pretreatment. However, either tyramine or 6-hydroxydopamine could not affect the basal tension of the ring that MeB once had been tested. These results suggest that MeB-induced contractions of rabbit thoracic aorta and porcine mesenteric artery result from a release of endogenous norepinephrine from adrenergic nerve endings and are dependent in part on extracellular calcium, and that the potency of MeB to release or to deplete norepinephrine is greater than that of either tyramine or 6-hydroxydopamine.

• Journal of Microbiology and Biotechnology
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• v.12 no.3
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• pp.431-436
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• 2002

Effects of fertilizer additions for oil degradation were examined in sand seashore mesocosms. Within 37 days, up to $85\%$ removal was achieved by the addition of slow-release type fertilizer (SRF) with the initial degradation rate of 423.3 mg oil $(kg sand)^-1\;day^-1$. The removal was mostly of biological origin based on the changes of $C_17$ /pristane and $C_18$/phytane ratios from 2.60 to 0.81 and from 3.55 to 1.29, respectively. The addition of oleophilic fertilizer (Inipol EAP22) was less effective and resulted in the removal of $64\%$ of the added oil ($3\%$, v/v) with a lower initial degradation rate. Petroleum-degrading bacteria had achieved a value of $1{\times}10^8$ CFU $(g sand)^-1$ at Day 3 and this peak exactly coincided with the initial degradation in the SRF-treated mesocosm. In this mesocosm, surface tension values were decreased drastically during Days 3 and 8, suggesting that microbially-produced surface-active agents actively enhanced the oil degradation rate and cell proliferation. Although the Inipol-treated mesocosm appeared to show significantly enhanced oil degradation compared to that of the untreated control mesocosm, Inipol was found to be less effective than SRF in enhancing a true oil-degrader when compared under similar experimental conditions.

• The Korean Journal of Physiology and Pharmacology
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• v.4 no.3
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• pp.197-210
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• 2000

Suppressive role of $Na^+-Ca^{2+}$ exchange in myocardial tension generation was examined in the negative frequency-force relationship (FFR) of electric field stimulated left atria (LA) from postnatal developing rat heart and in the whole-cell clamped adult rat ventricular myocytes with high concentration of intracellular $Ca^{2+}$ buffer (14 mM EGTA). LA twitch amplitudes, which were suppressed by cyclopiazonic acid in a postnatal age-dependent manner, elicited frequency-dependent and postnatal age-dependent enhancements after $Na^+-reduced,\;Ca^{2+}-depleted$ (26 Na-0 Ca) buffer application. These enhancements were blocked by caffeine pretreatment with postnatal age-dependent intensities. In the isolated rat ventricular myocytes, stimulation with the voltage protocol roughly mimicked action potential generated a large inward current which was partially blocked by nifedipine or $Na^+$ current inhibition. 0 Ca application suppressed the inward current by $39{\pm}4%$ while the current was further suppressed after 0 Na-0 Ca application by $53{\pm}3%.$ Caffeine increased this inward current by $44{\pm}3%$ in spite of 14 mM EGTA. Finally, the $Na^+$ current-dependent fraction of the inward current was increased in a stimulation frequency-dependent manner. From these results, it is concluded that the $Ca^{2+}$ exit-mode (forward-mode) $Na^+-Ca^{2+}$ exchange suppresses the LA tension by extruding $Ca^{2+}$ out of the cell right after its release from sarcoplasmic reticulum (SR) in a frequency-dependent manner during contraction, resulting in the negative frequency-force relationship in the rat LA.

• Journal of Chest Surgery
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• v.28 no.2
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• pp.156-161
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• 1995

Although there are many kinds of method in treatment of tracheal stenosis, tracheal resection and primary anastomosis can be performed for management of various kinds of tracheal stenosis because it is considered the most anatomical ideal therapeutic modality. During a 10-year period we performed 18 tracheal resection on 18 patients with no operative mortality and some morbidity. 13 patients had tracheal stenosis caused by endotracheal intubation [eight patients or tracheostomy [five patients ; and five patients caused by a variety of neoplastic lesions [four primary and one secondary . The length of tracheal stenosis were various from 1.5cm to 5.5cm and site of tracheal stenosis were cervical[17patients and thoracic [one patient . Operative techniques were tracheal resection and primary anastomosis[18 patients and additional procedures were cricoid cartilage reconstruction with costal cartilage [one patient , primary repair of esophagus[one patient and suprahyoid laryngeal release technique[eight patients without any complications. We have eight complications; tracheal restenosis were developed in five patients[growth of grannulation tissue at anastomotic site in three patients, delayed restenosis in two patients , anastomotic disruption in one patient, hoarseness and pneumonia in each of two patients. We managed tracheal complications with T-tube insertion in two patients, permanent tracheostomy in three patients and insertion of Gianturco tracheal stent in one patient, but tracheal stent did not reveal good result because it caused persistent production of sputum. We concluded that it is necessary to access full length of normal trachea including suprahyoid laryngeal release technique to avoid anastomotic tension in tracheal surgery and develope new ideal techniques to manage postoperative tracheal complications, because we suppose tracheal complications are developed due to anastomotic tension.

• Steel and Composite Structures
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• v.43 no.1
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• pp.19-30
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• 2022

The static strength and fatigue crack resistance of the aircraft skin structures depend on the materials used and joint type. Most of the commercial aircraft's skin panel structures are made from aluminium alloy and carbon fibre reinforced epoxy. In this study, the fatigue resistance of four joint configurations (metal/metal, metal/composite, composite/composite and composite/metal) with riveted, adhesive bonded, and hybrid joining techniques are investigated with experiments and finite element analysis. The fatigue tests were tension-tension because of the typical nature of the loads on aircraft skin panels susceptible of experimenting fatigue. Experiment results suggest that the fatigue life of hybrid joints is superior to adhesive bonded joints, and these in turn much better than conventional riveted joints. Thanks to the fact that, for hybrid joints, the adhesive bond provides better load distribution and ensures load-carrying capacity in the event of premature adhesive failure while rivets induce compressive residual stresses in the joint. Results from FE tool ABAQUS analysis for adhesive bonded and hybrid joints agrees with the experiments. From the analysis, the energy release rate for adhesive bonded joints is higher than that of hybrid joints in both opening (mode I) and shear direction (mode II). Most joints show higher energy release rate in mode II. This indicates that the joints experience fatigue crack in the shear direction, which is responsible for crack opening.

• Polymer(Korea)
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• v.29 no.3
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• pp.260-265
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• 2005

The initial burst of drug release is an important role in the controlled delivery of drug having hish toxicity and narrow therapeutic ranges. Nanosphere composed of monolayer could not achieve precisely controlled drug release because of the initial burst of drug on surface. In this study, double layered nanosphere was prepared for sustained drug delivery without initial burst. Double layered nanosphere composed of dextran and PLGA was fabricated by using conventional W/O/W double emulsion method. To control surface tension on the outer layer of nanospheres, PVA was used as a surfactant. Release behavior of dextran as model drug was observed as the $3{\times}1$mm wafers formed by compression mould in the deionized water for 7 days. Double layered nanosphere has sustained release behavior, in contast to single layered nanospheres. such as mechanical mixture and dextran nanospheres. Especially, nanosphere containing PVA $0.2\%$ has shown nearly the zero-order release profile. As a result of this study, double layered nanospheres has more sustained release profile of drug without the initial burst and the release behavior of dexoan on tile double layered nanospheres was controlled by the contents of PVA as a surfactant.

• Journal of Ginseng Research
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• v.20 no.2
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• pp.133-138
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• 1996

Rabbit corpus cavernosal smooth muscle strips submaximally precontracted with phenylephrine (5$\times$$10^6$ M) and treated with increasing concentrations of Korean ginseng (1, 5, 10, 20, 30, 40 mg/ml) showed tension decrease concentration-dependently (1 mg/ml: 1.7%, 5 mg/ml: 10.2%, 10 mg/ml: 22.7%, 20 mg/ml: 44.0%, 30 mg/ml: 65.2%, 40 mg/ml: 95.6%). Relaxations to Korean ginseng were inhibited significantly by endothelial disruption, by pretreatment with methylene blue, pyrogallol, L-NNA and atropine. Pretreatment of the muscle strips with ginseng caused concentration-related inhibition of a phenylephrine induced contraction, and in calcium-free high potassium depolarizing solution, decreased basal tension as well as inhibited contraction induced by Caclr. Korean ginseng also produced the reduction of responses to depolarizing medium(50, 40, 60 mM KCI). With these results we can confirm the relaxation effect of ginseng at a dose dependent on the cavernosal smooth muscle and suggest that its action is mediated by multiple action mechanisms that include increasing the release of nitric oxide from the corporal sinusoids. Increasing intracellular calcium sequestration, and a hyperpolarizating action.

• Geomechanics and Engineering
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• v.23 no.6
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• pp.587-600
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• 2020

Shear-induced instability of jointed rock mass has greatly threatened the safety of underground openings. To better understand the failure mechanism of surrounding rock mass under shear, the flawed specimens containing a circular opening and two open joints are prepared and used to conduct direct shear tests. Both experimental and numerical results show that joint inclination (β) has a significant effect on the shear strength, dilation, cracking behavior and stress distribution around flaws. The maximum shear strength, occurring at β=30°, usually corresponds to a unifrom stress state around joint and an intense energy release. However, a larger joint inclination, such as β=90°~150°, will cause a more uneven stress distribution and a stronger stress concentration, thus a lower shear strength. The stress distribution around opening changes little with joint inclination, while the magnitude varys much. Both compression and tension around opening will be greatly enhanced by the 30°-joints. In addition, a higher normal stress tends to enhance the compression and suppress the tension around flaws, resulting in an earlier generation and a larger proportion of shear cracks.