• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.26 no.1
• /
• pp.59-72
• /
• 2000

In this study, the rate of bone formation and the pattern of bone to implant contact surface around HA coated implant and pure Ti implant inserted into the irradiated tibia of rabbit were compared. Sixteen mongrel mature male rabbits were used as experimental animal. Each rabbit received 15 Gy of irradiation. Four weeks after irradiation, two holes were prepared on the tibia of each rabbit for placement of HA coated type and pure Ti type implants. Prior to implant placement, one group received steroid irrigation and the control group was similarly irrigated with normal saline. This was immediately followed by placement of the two different types of implants. Postoperatively, tetracycline was injected intramuscularly for 3 days. For fluorescent labelling, 3 days of intramuscular alizarine red injection was given. 2 weeks before sacrifice, followed by intramuscular calcein green on the last 3 days before specimen collection. Each rabbit was sacrificed on the second, fourth, sixth and eighth week after the implantation. The specimens were observed by the light microscope and the fluorescent microscope. The results were as follows; 1. All implants inserted into the irradiated tibia of rabbit were free from clinical mobility and no signs of bony resorption were noted around the site of implant placement. 2. Under the light microscope, new bone formation proceeded faster around implants that received steroid irrigation compared to the control group irrigated with saline. Bone to implant contact surface was greater in the steroid irrigated group than the saline irrigated group. Therefore, better initial stabilization was observed in the group pretreated with steroid irrigation. 3. Under the light microscope. HA coated implants showed broader bone to implant contact surface than pure Ti implants, and HA coated implants had better bone healing pattern than pure Ti implants. 4. In the steroid pretreated group, acceleration of bone formation was demonstrated by fluorescent microscopy around the 2, 4 weeks group and the 6 weeks HA coated implant group. The difference in the rate of bone formation proved to be statistically significant(P<0.05). Faster bone formation was noted in the saline irrigated group in the 6 weeks pure Ti implants and 8 weeks group. The difference was not statistically significant(P<0.05). 5. For the rabbits that were sacrificed on the second and fourth week after the implant placements, the rates of bone formation around HA coated implants proceeded faster than those around pure Ti implants under the fluorescent microscopy. For the rabbits that were sacrificed on the sixth week after the implant placements, the rates of bone formation around pure Ti implants proceeded faster than those around HA coated implants under the fluorescent microscopy. But this result did not show statistical significance (P<0.05) For the rabbits that were sacrificed on the eighth week after the implant placements, the rates of bone formation around HA coated implants proceeded faster than those around pure Ti implants under the fluorescent microscopy. This result was statistically significant (P<0.05).

• Tuberculosis and Respiratory Diseases
• /
• v.46 no.4
• /
• pp.481-488
• /
• 1999

Background: The routine application of the combined regimen of corticosteroid-antituberculosis therapy to the tuberculous pleurisy remains controversial. Steroid therapy to tuberculous pleurisy could be effective on the acceleration of absorption of pleural effusion and symptom improvement, but there has been debate about the effect of prednisolone on the prevention of pleural adhesion. So we studied the efficacy of combined regimen of prednisolone-antituberculosis therapy on the absorption of pleural effusion and prevention of pleural adhesion. Method: A prospective, randomized study was performed in 82 patients, 50 patients(non-steroid group) were treated with only antituberculosis regimen for 6 months and in 32 patients(steroid group) prednisolone(30mg/day) were administered in addition to antituberculosis regimen for one months and tapered for another month. The amount of pleural effusion was compared at the beginning of treatment, 2nd month, 6th month and final visit with chest X-ray findings which were graded from grade 0(complete absorption) to grade 6(near total haziness). Results: The amount of pleural effusion of steroid group at 2nd month, 6th month and final visit was lesser than that of non-steroid group(P<0.05). The incidence of the complete absorption of the pleural effusion was 3/32(9.4%) in steroid group, 1/50(2%) in non-steroid group at 2nd month after treatment; and 12/32(37.5%) in steroid group, 6/50(12%) in non-steroid group at 6th month after treatment(P<0.05). At final observation, the incidence of residual pleural thickening was 15/32(47%) in steroid group and 37/50(74%) in non-steroid group(P<0.05). No serious side effects were noted during the treatment with prednisolone. Conclusion: The administration of prednisolone in conjunction with antituberculosis chemotherapy improved the absorption of pleural effusion and decreased the residual pleural thickening.

• Tuberculosis and Respiratory Diseases
• /
• v.46 no.6
• /
• pp.846-855
• /
• 1999

Background : Secondary pulmonary hypertension is an important final endpoint in patients with chronic hypoxic lung disease, accompanied by deterioration of pulmonary hemodynamics. The clinical diagnosis of pulmonary hypertension and/or cor pulmonale could be difficult, and simple noninvasive evaluation of pulmonary artery pressures has been an relevant clinical challenge for many years. Doppler echocardiography might to be a more reliable method for evaluating pulmonary hemodynamics in such patients in terms of the accuracy, reproducibility and easiness for obtaining an appropriate echocardiographic window than M-mode echocardiography. The aim of this study was to assess echocardiographic parameters associated with pulmonary arterial hypertension, defined by increasing right ventricular systolic pressure(RVSP), calculated from trans-tricuspid gradient in patients with chronic hypoxic lungs. Method : We examined 19 patients with chronic hypoxic lung disease, suspected pulmonary hypertension under the clinical guidelines by two dimensional echocardiography via the left parasternal and subcostal approach in a supine position. Doppler echocardiography measured RVSP from tricuspid regurgitant velocity in continuous wave with 2.5MHz transducer and acceleration time(AT) on right ventricular outflow tract in pulsed wave for the estimation of pulmonary arterial pressure. Results : On echocardiography, moderate to severe degree of pulmonary arterial hypertension was defined as RVSP more than 40mmHg, presenting tricuspid regurgitation. Increased right ventricular endsystolic diameter and shortened AT were noted in the increased RVSP group. Increased RVSP was correlated negatively with the shortening of AT. Other clinical data, including pulmonary functional parameters, arterial blood gas analysis and M mode echocardiographic parameters were not changed significantly with the increased RVSP. Conclusion : These findings suggest that shortened AT on pulsed doppler can be useful when quantifying pulmonary arterial pressure with increased RVSP in patients with chronic lung disease with hypoxemia. Doppler echocardiography in pulmonary hypertension of chronic hypoxic lungs is an useful option, based on noninvasiveness under routine clinical practice.

• Membrane Journal
• /
• v.6 no.3
• /
• pp.157-165
• /
• 1996

Polysulfone(PS) membranes were prepared from homogeneous PS solutions by the phase inversion technique. When propionic acid(PA) was added into a casting solution of n-methylpyrrolidone(NMP) and PS, precipitation rate of the solution film was accelerated. This kind of acceleration was consistent, even though a precipitating nonsolvent was changed from water to isopropanol. These phenomena were caused by decrease of nonsolvent tolerance in the casting solution due to addition of PA. PS powder was prepared by precipitation of a 3wt% solution in dimethylformamide(DMF) using ethanol as nonsolvent. Gas adsorption analysis of the powder showed that the capillary condensation sites were found in the powder structure. Membranes prepared from PS solution(15wt%) in NMP had the following characteristics of gas adsorption and water permeation. In gas adsorption analysis, the membrane precipitated using isopropanol showed low uptake of nitrogen gas and the capillary condensation sites were not found. On the contrary, a significant amount of the capillary condensation sites was found in the membrane coagulated by water, which was related to increase of nitrogen uptake. tn the membrane prepared froin the solution including PA, an increase of the Henry's law sites and the Langmuir sites was not found clearly. However, the capillary condensation sites were significantly increased, and the water transport also increased.

• The Korean Journal of Pharmacology
• /
• v.11 no.2
• /
• pp.29-40
• /
• 1975

1. Sites of the cardioaccelerating action of nicotine, DMPP, McN-A-343, AHR-602, tyramine, angiotensin and neostigmine were investigated in spinal rabbits. 2. The cardioaccelerating action of the above substances was substantially weak in reserpine-pretreated rabbits. The accelerating action was scarcely observed after propranolol administration. 3. Tetrodotoxin and guanethidine did not affect the cardioacceleration due to nicotine, DMPP, tyramine and isoproterenol, but they markedly weakened that due to McN-A-343, AHR-602, angiotensin and neostigmine. 4. Chlorisondamine blocked the cardioacceleration by nicotine and DMPP; atropine that by McN-A-343 and AHR-602. 5. Appropriate doses of isoproterenol, nicotine, DMPP, McN-A-343, tyramine, angiotensin and neostigmine, when administered into the right auricle, produced almost the same degree of cadia acceleration as when they were given to the right ear vein. AHR-602 did not produce significant cardioacceleration through this route. 6. Nicotine, DMPP and neostigmine when injected into the right auricle produced marked cardioacceleration, whereas they produced little action when injected into the left ventricle. Isoproterenol and tyramine produced more marked effect by the intraauricular route than the intraventricular one. 7. McN-A-343, AHR-602 and angiotensin produced more marked cardioacceleration by the intraventricular administration than the intraauricular one. The intraventricular AHR-602 produced marked cardioacceleration. 8. It is inferred that the sites of cardioaccelerating action of nicotine, DMPP, and tyramine will be either the terminals of the adrenergic nerves or the extraneuronal stores of norepinephrine and that of McN-A-343, AHR-602, angiotensin and neostigmine will be the adrenergic neurons in the heart. The sites on which nicotine, DMPP, tyramine and neostigmine will act are chiefly distributed in the auricular tissues and those on which McN-A-343, AHR-602, and angiotensin act chiefly in the ventricular tissues.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.34 no.6
• /
• pp.643-651
• /
• 2001

Paddlewheel-driven circulation in a culture pond has been simulated based on the depth integrated 2 dimensional hydrodynamic model. Acceleration by paddlewheel is expressed as shaft force divided by water mass discharged by paddlewheel blades. The model has been calibrated and applied to culture ponds as following steps:- i) The model predicted velocities at every 10 m along longitudinal direction from the paddlewheel. The model was calibrated comparing the results with the measured values at mass correction factor $\alpha$ and dimensionless eddy viscosity constant $\gamma$, respectively, in a range $15\~20$ and 6. ii) Wind shear stress was simulated under conditions of direction $0^{\circ}C,\;90^{\circ}C\;and\;180^{\circ}C$ and speed 0.0, 2.5, 5.0 and 7.5 m/s. Change rate of current speed was <$1\%$ at wind in parallel or opposite direction to the paddlewheel-driven jet flow, while $4\%$ at orthogonal angle. iii) The model was then applied to 2 culture ponds located at the Western coast of Korea. The measured and predicted currents for the ponds were compared using the regression analysis. Analysis of flow direction and speed showed correlation coefficients 0.8928 and 0.6782 in pond A, 0.8539 and 0.7071 in pond B, respectively. Hence, the model is concluded to accurately predict circulation driven by paddlewheel such that it can be a useful tool to provide pond management strategy relating to paddlewheel operation and water quality.

• Geophysics and Geophysical Exploration
• /
• v.10 no.3
• /
• pp.183-190
• /
• 2007

The site effects of seismic stations were evaluated by conducting a simultaneous inversion of the stochastic point-source ground-motion model (STGM model; Boore, 2003) parameters based on the accumulated dataset of horizontal shear-wave Fourier spectra. A model parameter $K_0$ and frequency-dependent site amplification function A(f) were used to express the site effects. Once after a H/V ratio of the Fourier spectra was used as an initial estimate of A(f) for the inversion, the final A(f) which is considered to be the result of combined effect of the crustal amplification and loca lsite effects was calculated by averaging the log residuals at the site from the inversion and adding the mean log residual to the H/V ratio. The seismic stations were classified into five classes according to $logA_{1-10}^{max}$(f), the maximum level of the site amplification function in the range of 1 Hz < f < 10 Hz, i.e., A: $logA_{1-10}^{max}$(f) < 0.2, B: 0.2 $\leq$ $logA_{1-10}^{max}$(f) < 0.4, C: 0.4 $\leq$ $logA_{1-10}^{max}$(f) < 0.6, D: 0.6 $\leq$ $logA_{1-10}^{max}$(f) < 0.8, E: 0.8 $\leq$ $logA_{1-10}^{max}$(f). Implication of the classified result was supported by observing a shift of the dominant frequency of average A(f) for each classified stations as the class changes. Change of site classes after moving seismic stations to a better site condition was successfully described by the result of the station classification. In addition, the observed PGA (Peak Ground Acceleration)-values for two recent moderate earthquakes were well classified according to the proposed station classes.

• Journal of the Korea Concrete Institute
• /
• v.27 no.2
• /
• pp.127-136
• /
• 2015

To evaluate the effects of limestone powder and silica fume on the properties of high-strength high-volume ground granulated blast-furnace slag (GGBFS) blended cement concrete, this study investigated the rheology, strength development, hydration and pozzolanic reaction characteristics, porosity and pore size distribution of high-strength mortars with the water-to-binder ratio of 20, 50 to 80% GGBFS, up to 20% limestone powder, and up to 10% silica fume. According to test results, compared with the Portland cement mixture, the high-volume GGBFS mixture had much higher flow due to the low surface friction of GGBFS particles and higher strength in the early age due to the accelerated cement hydration by increase of free water; however, because of too low water-to-binder ratio and cement content, and lack of calcium hydroxide content, the pozzolanic reactio cannot be activated and the long-term strength development was limited. Limestone powder did not affect the flowability, and also accelerate the early cement hydration. However, because its effect on the acceleration of cement hydration is not greater than that of GGBFS, and it does not have hydraulic reactivity unlikely to GGBFS, compressive strength was reduced proportional to the replacement ratio of limestone powder. Also, silica fume and very fine GGBFS lowered flow and strength by absorbing more free water required for cement hydration. Capillary porosities of GGBFS blended mortars were smaller than that of OPC mortar, but the effect of limestone powder on porosity was not noticeable, and silica fume increased porosity due to low degree of hydration. Nevertheless, it is confirmed that the addition of GGBFS and silica fume increases fine pores.

• Journal of the Korea Concrete Institute
• /
• v.24 no.3
• /
• pp.293-303
• /
• 2012

Recently, as construction technology improved, concrete structures not only became larger, taller and longer but were able to perform various functions. However, if extreme loads such as impact, blast, and fire are applied to those structures, it would cause severe property damages and human casualties. Especially, the structural responses from extreme loading are totally different than that from quasi-static loading, because large pressure is applied to structures from mass acceleration effect of impact and blast loads. Therefore, the strain rate effect and damage levels should be considered when concrete structure is designed. In this study, the low velocity impact loading test of steel fiber reinforced concrete (SFRC) slabs including 0%~1.5% (by volume) of steel fibers, and strengthened with two types of FRP sheets was performed to develop an impact resistant structural member. From the test results, the maximum impact load, dissipated energy and the number of drop to failure increased, whereas the maximum displacement and support rotation were reduced by strengthening SFRC slab with FRP sheets in tensile zone. The test results showed that the impact resistance of concrete slab can be substantially improved by externally strengthening using FRP sheets. This result can be used in designing of primary facilities exposed to such extreme loads. The dynamic responses of SFRC slab strengthened with FRP sheets under low velocity impact load were also analyzed using LS-DYNA, a finite element analysis program with an explicit time integration scheme. The comparison of test and analytical results showed that they were within 5% of error with respect to maximum displacements.

• Journal of the Korean earth science society
• /
• v.23 no.4
• /
• pp.357-368
• /
• 2002

In this study we have tried to explain the barrel-shaped morphology for young supernova remnants considering the dynamical effects of the ejecta. We consider the magnetic field amplification resulting from the Rayleigh-Taylor instability near the contact discontinuity. We can generate the synthetic radio image assuming the cosmic-ray pressure and calculate the azimuthal intensity ratio (A) to enable a quantitative comparison with observations. The postshock magnetic field are amplified by shearing, stretching, and compressing at the R-T finger boundary. The evolution of the instability strongly depends on the deceleration of the ejecta and the evolutionary stage of the remnant. the strength of the magnetic field increases in the initial phase and decreases after the reverse shock passes the constant density region of the ejecta. However, some memory of the earlier phases of amplification is retained in the interior even when the outer regions turn into a blast wave. The ratio of the averaged magnetic field strength at the equator to the one at the pole in the turbulent region can amount to 7.5 at the peak. The magnetic field amplification can make the large azimuthal intensity ratio (A=15). The magnitude of the amplification is sensitive to numerical resolution. This mens the magnetic field amplification can explain the barrel-shaped morphology of young supernova remnant without the dependence of the efficiency of the cosmic-ray acceleration on the magnetic field configuration. In order for this mechanism to be effective, the surrounding magnetic field must be well-ordered. The small number of barrel-shaped remnants may indicate that this condition rarely occurs.