• The Korean Journal of Physiology
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• 제18권1호
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• pp.19-35
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• 1984

Since the first report of Drury and $Szent-Gy{\ddot{o}}rgyi$ in 1929, the inhibitory influences of adenosine on the heart have repeatedly been described by many investigators. These studies have shown that adenosine and adenine nucleotides have overall depressant effects, similar to those of acetylcholine. Heart beats become slow and weak. It is also well known that adenosine is a potent endogenous coronary vasodilator. Many investigations on the working mechanisms of adenosine have been focused mainly on the effects of the coronary blood flow. However, the cellular mechanisms underlying the inhibitory action of adenosine on sinus node are not well understood yet. Thus, this study was undertaken to examine the behavior of rabbit SA node under influence of adenosine. In these series of experiments three kinds of preparations were used: whole atrial pair, left atrial strip, and isolated SA node preparations. The electrical activity of SA node was recorded with conventional glass microelectrodes 30 to 50 $M{\Omega}$. The preparations were superfused with bicarbonate-buffered Tyrode solution of pH 7.35 and aerated with a gas mixture of $3%\;CO_2-97%\;O_2$ at $35^{\circ}C$. In whole atrial pair, adenosine suppressed sinoatrial rhythm in a dose-dependent manner. Effect of adenosine on atrial rate appeared at the concentration of $10^{-5}M$ and was enhanced in parallel with the increase in adenosine concentration. Inhibitory action of adenosine on pacemaker activity was more prominent in the preparation pretreated with norepinephrine, which can steepen the slope of pacemaker potential by increasing permeability of $Ca^{+2}$. Calcium ions in perfusate slowly produced a marked change in sinoatrial rhythm. Elevation of the calcium concentration from 0.3 to 8 mM increased the atrial rate from 132 to 174 beats/min, but over 10 mM $Ca^{+2}$ decreased. The inhibitory effect of adenosine on sinoatrial rhythm developed very rapidly. Atrial rate was recovered promptly from the adenosine-induced suppression by the addition of norepinephrine, but extra $Ca^{+2}$ was less suitable to restore the suppression of atrial rate. Adenosine suppressed also atrial contractility in the same dosage range that restricted pacemaker activity, even in the reserpinized preparation. In isolated SA node preparation, spontaneous firing rate of SA node at $35^{\circ}C$(mean{\pm}SEM, n=16) was $154{\pm}3.3\;beats/min. The parameters of action potentials were: maximum diastolic potential(MDP), $-73{\pm}1.7\;mV: overshoot(OS), $9{\pm}1.4\;mV: slope of pacemaker potential(SPP), $94{\pm}3.0\;mV/sec. Adenosine suppressed the firing rate of SA node in a dose-dependent manner. This inhibitory effect appeared at the concentration of $10^{-6}M$ and was in parallel with the increase in adenosine concentration. Changes in action potential by adenosine were dose-dependent increase of MDP and decrease of SPP until $10^{-4}M$. Above this concentration, however, the amplitude of action potential decreased markedly due to the simultaneous decrease of both MDP and OS. All these effects of adenosine were not affected by pretreatment of atropine and propranolol. Lowering extra $Ca^{2+}$ irom 2 mM to 0.3 mM resulted in a marked decrease of OS and SPP, but almost no change of MDP. However, increase of perfusate $Ca^{2+}$ from 2 mM to 6 or 8 mM produced a prominent decrease of MDP and a slight increase of OS and SPP. Dipyridamole(DPM), which is known to block the adenosine transport across the cell membrane, definately potentiated the action of adenosine. The results of this experiment suggest that adenosine suppressed pacemaker activity and atrial contractility simultaneously and directly, by decreasing $Ca^{2+}-permeability$ of nodal and atrial cell membranes.

• 대한핵의학회지
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• 제20권1호
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• pp.17-24
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• 1986

Authors enumerate various malignant and benign cases which showed soft tissue uptake of $^{99m}Tc-MDP$. We hope it might be a help in understanding and interpreting bone scans. Among 10,361 $^{99m}Tc-MDP$ bone scans underwent from April, 1981 to March, 1986, 344 (3.3%) showed abnormal soft tissue uptake, which included 126 malignancies, 5 benign tumors, and 153 nontumorous diseases. Neuroblastoma(23.3%) and malignant fibrous histiocytoma(22.2%) showed highest positive uptake rate among various malignancies. We also illustrated typical cases according to possible mechanisms.

• 로봇학회논문지
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• 제17권1호
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• pp.76-85
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• 2022

One of the most fundamental challenges when designing controllers for dynamic systems is the adjustment of controller parameters. Usually the system model is used to get the initial controller, but eventually the controller parameters must be manually adjusted in the real system to achieve the best performance. To avoid this manual tuning step, data-driven methods such as machine learning were used. Recently, reinforcement learning became one alternative of this problem to be considered as an agent learns policies in large state space with trial-and-error Markov Decision Process (MDP) which is widely used in the field of robotics. However, on initial training step, as an agent tries to explore to the new state space with random action and acts directly on the controller parameters in real systems, MDP can lead the system safety-critical system failures. Therefore, the issue of 'safe exploration' became important. In this paper we meet 'safe exploration' condition with Control Barrier Function (CBF) which converts direct constraints on the state space to the implicit constraint of the control inputs. Given an initial low-performance controller, it automatically optimizes the parameters of the control law while ensuring safety by the CBF so that the agent can learn how to predict and control unknown and often stochastic environments. Simulation results on a quadrotor UAV indicate that the proposed method can safely optimize controller parameters quickly and automatically.

• 대한핵의학회지
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• 제15권2호
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• pp.1-9
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• 1981

Bone scans with $^{99m}Tc-MDP$ (methylene diphosphonate) were obtained and analysed in 574 patients with biopsy-proven malignancy, who visited Seoul National University Hospital from April, 1979 to June, 1931. Clinical staging was done in all patients without bone scan information and compared with bone scan to determine the predictive value of bone scanning. 1. Primary site of the maligancies were lung in 152, breast in 97, stomach in 43, colon in 15, esophagus in 9, liver and pancreas in 11, kidney in 14, bladder in 27, prostate in 22, thyroid in 20, skin in 11, bone in 9, head and neck in 36, ovary and uterus in 17, hematopoietic and lymphoretic ular system in 33, nervous system in 10, and others in 9 cases. Primary site was not defined in 39 cases. 2. Bone scans were positive in 186 cases (32.4%), which, included 48 cases (31.6%) of lung cancer, 27 cases (27.8%) of breast cancer, 12 cases(28%) of stomach cancer, 6 cases(40%) of colon cancer, 6 cases(43%) of kidney tumor, 4 cases(15%) of bladder cancer, 14 cases(64%) of prostate cancer, 3 cases(15%) of thyroid cancer and 66 other cases. 3. Bone scans were suspicious in 64 cases (11.2%) which included 29 cases (19.1%) of lung cancer, 10 cases (10.3%) of breast cancer, 4 cases (9.3%) of stomach cancer, one case (7%) of colon cancer, 3 cases(11%) of bladder cancer, 2 cases(10%) of thyroid cancer and 15 other cases. 4. Out of 121 cases with early stage of malignancy (which included 20 cases of lung cancer in stage I, II, 38 cases of breast cancer, 13 cases of stomach cancer, 8 cases of kidney tumor, 14 cases of thyroid cancer in stage $I{\sim}III$, and 6 cases of colon cancer, 14 cases of bladder cancer, 8 cases of prostate cancer in stage $A{\sim}C$, bone scans were positive in 5 cases (4.1%) which included 3 cases of lung cancer one case of breast cancer and one case of prostate cancer, and considered as further advanced stage. Out of 121 cases with early stage of malgnancy, bone scans were suspicious in 21 cases (17.4%) which inlcuded 9 cases of lung cancer, 4 cases of breast cancer, 2 cases of stomach cancer, one case of colon cancer, 3 cases of bladder cancer, and 2 cases of thyroid cancer. From these results, we concluded bone scan was useful in detecting bone metastasis in patients of early stage of malignancy, determining prognosis and establishing therapentic plan.

• The Journal of Advanced Prosthodontics
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• 제10권5호
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• pp.374-380
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• 2018

PURPOSE. The effect of silica-based glass-ceramic liners on the tensile bond strength between zirconia and resin-based luting agent was evaluated and compared with the effect of 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-containing primers. MATERIALS AND METHODS. Titanium abutments and zirconia crowns (n = 60) were fabricated, and the adhesive surfaces of the specimens were treated by airborne-particle abrasion. The specimens were divided into 5 groups based on surface treatment: a control group, 2 primer groups (MP: Monobond Plus; ZP: Z Prime Plus), and 2 liner groups (PL: P-containing Liner; PFL: P-free Liner). All specimens were cemented with self-adhesive resin-based luting agent. After 24-hour water storage and thermocycling (5,000 cycles, $5^{\circ}C/55^{\circ}C$), the tensile bond strength was measured using a universal testing machine. Failure mode analysis and elemental analysis on the bonding interface were performed. The data were analyzed using Kruskal-Wallis test, Dunn's post hoc test, and Fisher's exact test. RESULTS. The liner groups and primer groups showed significantly higher tensile bond strengths than that of the control group (P<.05). PFL showed a significantly higher tensile bond strength than the primer groups (P<.05). The percentage of mixed failure was higher in the primer groups than in the control group (P<.001), and all the specimens showed mixed failure in the liner groups (P<.001). A chemical reaction area was observed at the bonding interface between zirconia and liner. CONCLUSION. The application of liner significantly increased the tensile bond strength between zirconia and resin-based luting agent. PFL was more effective than MDP-containing primers in improving the tensile bond strength with the resin-based luting agent.

• The Journal of Advanced Prosthodontics
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• 제10권3호
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• pp.205-210
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• 2018

PURPOSE. The purpose of this study was to evaluate the efficiency of a gas-phase fluorination method under different fluorination periods through using two resin cements. MATERIALS AND METHODS. 84 zirconia specimens in dimensions of $5mm{\times}5mm{\times}2mm$ were prepared and surface treated with $50{\mu}m$ aluminum oxide particles or gas phase fluorination for 2 min, 5 min, or 10 min. One specimen in each group was surface analyzed under scanning electron microscope. The remaining specimens were bonded to composite cylinders in dimensions of 2 mm diameter and 3 mm high with Panavia SA Plus or Variolink N. Then, the specimens were stored in $37^{\circ}C$ distilled water for 24 hours and shear bond strength test was applied at a speed of 1 mm/min. RESULTS. The highest shear bond strength values were observed in the samples fluorinated for 5 minutes and cemented with Panavia SA Plus. Variolink N did not elicit any statistical differences between surface treatments. Panavia SA Plus resin cement and Variolink N resin cements featured statistically significant difference in shear bond strength values only in the case of 5 minutes of fluorination treatment. CONCLUSION. According to the results of this study, application of 5 minutes of fluorination with 10-methacryloyloxydecyl dihydrogen phosphate monomer (MDP) containing Panavia SA Plus resin cement increased the resin bond strength of zirconia. Fluorination of the zirconia surface using conventional resin cement, Variolink N, did not lead to an increase in bond strength.

• The Journal of Advanced Prosthodontics
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• 제10권4호
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• pp.308-314
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• 2018

PURPOSE. Plasma activation of hydrophobic zirconia surfaces might be suitable to improve the bond strength of luting materials. The aim of this study was to analyze the influence of nonthermal argon-plasma on the shear bond strength (SBS) between zirconia and different combinations of 10-MDP adhesive systems and luting composites after artificial aging. MATERIALS AND METHODS. Two hundred forty Y-TZP specimens were ground automatically with $165{\mu}m$ grit and water cooling. Half of the specimens received surface activation with nonthermal argon-plasma. The specimens were evenly distributed into three groups according to the adhesive systems ([Futurabond U, Futurabond M, Futurabond M + DCA], VOCO GmbH, Germany, Cuxhaven) and into further two subgroups according to the luting materials ([Bifix SE, Bifix QM], VOCO GmbH). Each specimen underwent artificial aging by thermocycling and water storage. SBS was measured in a universal testing machine. Statistical analysis was performed using ANOVA and $Scheff{\grave{e}}$ procedure with the level of significance set to 0.05. RESULTS. Surface activation with nonthermal plasma did not improve the bond strength between zirconia and the tested combinations of adhesive systems and luting materials. The plasma-activation trended to reveal higher bond strength if the self-etch luting material (Bifix SE) was used, irrespective of the adhesive system. CONCLUSION. Plasma-activation seems to be suitable to improve bond strength between zirconia and self-etch resin materials. However, further research is necessary to identify the influence of varying plasma-parameters.

• 대한핵의학회지
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• 제33권6호
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• pp.475-483
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• 1999

목적: 안구보충물로 사용된 hydroxyapatite 내로의 섬유혈관증식은 이물질 반응으로 인한 염증의 동반없이 의안의 운동성을 유지시키기 위한 운동성 나사못을 삽입하는데 중요한 역할을 한다. 안구보충물 삽입술 후에 섬유혈관증식의 정도를 알아보는데 Tc-99m MDP를 이용한 평면영상과 단면영상에서 정성적 평가와 정량적 평가의 비교분석을 함으로서 완전한 섬유혈관증식을 예측하는데 단면영상의 유용성을 알아보고자 하였다. 대상 및 방법: 안구 제거술후 hydroxyapatite를 이용하여 안구보충술을 시행받고 $197{\pm}81$일 후에 골신티그라피를 시행받은 17명의 환자(남:녀=12:5, 연령; $50.4{\pm}17.5$세)의 18예를 대상으로 하였다. 골신티그라피는 Tc-99m MDP 740 MBq를 정맥주사 후 4시간 경과뒤에 이중헤드 감마카메라(ECAM, Siemens, Germany)로 안면부 평면영상을 얻은 후 이어서 단면영상을 얻었다. 평면영상과 단면영상에서의 안구보충물의 방사능 섭취가 비교(nasal bridge)보다 약한 경우를 grade 1, 비슷한 경우를 grade 2, 강한 경우를 grade 3로 평가하였고, 정상안구에 대한 안구보충물의 섭취비를 정량적으로 구하여 운동성 나사못 삽입술 후 시행된 세극등 검사에서 염증반응의 동반 없이 완전한 섬유혈관증식을 보인 환자 군과 염증 반응의 동반과 함께 불완전한 섬유혈관증식을 보인 환자 군으로 나누어 비교 분석하였다. 결과: 평면영상에서 grade 1은 9예, grade 2가 1예, grade 3가 2예로 충분한 섬유혈관증식을 의미하는 grade 2와 3를 보인 경우가 9예 (50%) 이었으나 단면영상에서는 grade 1이 6예, grade 2가 4예, grade 3가 8예로 평면영상에 비하여 grade 2와 3를 보이는 경우가 12예(61%) 이었다. 정성적 평가에 의한 완전한 섬유혈관증식을 예측하는 데 있어서 평면영상은 예민도가 60% (9/15),특이도 100% (3/3), 양성예측률 100% (9/9), 음성예측률 33.3% (3/9), 정확도 66.7% (12/18) 이었고 단면영상은 예민도 80% (12/15), 특이도 100% (3/3), 양성예측률 100% (12/12), 음성예측률 50% (3/6), 정확도 83.3% (15/18) 이었다. 정량적으로 구한 안구보충물 내의 방사능 섭취비는 평면영상에서 grade 1은 $1.19{\pm}0.10$, grade 2는 $2.16{\pm}0.43$, grade 3는 $3.57{\pm}0.74$로 grade가 높을수록 정량적 섭취비가 유의하게 증가하였다(p<0.001). 단면영상에서 grade 1은 $3.06{\pm}1.22$, grade 2는 $3.71{\pm}0.83$, grade 3는 $12.49{\pm}4.31$로 grade가 높을수록 정량적 섭취비가 유의하게 증가하였다(p<0.001). 완전한 섬유혈관증식을 보인 환자 군과 불완전한 섬유혈관증식을 보인 환자군으로 나누어 정량적으로 측정한 방사능 섭취비를 비교시 평면영상에서는 $1.96{\pm}0.87$ 대 $1.17{\pm}0.08$로 유의한 차이를 보이지 않았으나 단면영상에서는 $8.44{\pm}5.45$ 대 $2.20{\pm}0.87$로 유의한 차이를 보였다 (p<0.05). 결론: 안구보충물 삽입 후 섬유혈관증식을 평가할 때 평면영상에 비하여 단면영상이 섬유혈관증식 정도를 평가하는데 보다 도움을 주었다.

• Clinical and Experimental Reproductive Medicine
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• 제36권1호
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• pp.63-70
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• 2009

목 적: 본 연구는 전향적 무작위 배정법 연구로 40세 이상의 불임여성의 자연주기에서 소량의 재조합난포자극호르몬을 이용한 최소자극법의 효과를 성선자극호르몬분비호르몬길항제 다회투여법과 비교 분석하고자 한다. 연구방법: 불임크리닉을 방문하였던 환자들 중 나이가 40세 이상인 75명 환자들을 대상으로 시행하였다. 연구군은 최소자극법으로 37명, 대조군은 성선자극호르몬분비호르몬길항제 다회투여법으로 38명의 환자들로 구성되었으며 모두 체외수정시술을 시행 받았다. 주기 취소율, 난포자극호르몬 종 사용량과 일수, 성숙난자의 수, 이식된 배아의 수, 배아이식 주기당 임신율, 착상율 등을 비교하였으며, 통계학적인 방법은 평균값의 비교를 위하여 Student's t-test를 이용하였고 분율의 비교를 위하여 ${\chi}^2$ 검정, Fisher's exact test를 사용하였으며, p값이 0.05 미만인 경우에 통계학적으로 유의하다고 판정하였다. 결 과: 두 군간의 대상 환자들의 기본적인 특성은 차이가 없었다. rhFSH의 투여기간과 총용량에서 연구군의 경우 4.5${\pm}$1.2일, 632.2${\pm}$123.7 IU로 대조군에서의 11.3${\pm}$2.7일, 3124.6${\pm}$452.1 IU에 비하여 통계학적으로 유의하게 낮은 값을 보였고, 주기 취소율은 연구군에서 16.2%, 대조군에서 5.3%로 통계적으로 유의성은 없었다. 회수된 난자의 수, 성숙한 제 2감수분열 중기 상태의 난자의 수 및 수정된 난자의 수, 양질의 배아수, 배아이식된 배아의 수에 있어서 대조군에 비해서 연구군에서 통계적으로 유의하게 낮았다. 배란유도를 시작한 주기당 임상적 임신율과 배아이식 주기당 임상적임신율은 연구군의 경우 각각 10.8%와 13.4%로 대조군에서 13.2%와 13.9%에 비하여 다소 낮긴 하였으나 통계학적으로 유의성은 없었다. 착상율, 자연유산율에서는 두 군간의 차이가 없었다. 결 론: 40세 이상의 고령 여성에서 체외수정술을 시행하고자 할 때 배란유도의 방법으로 GnRH antagonist와 성선자극호르몬을 이용한 최소자극법은 성선자극호르몬분비호르몬길항제 다회투여법과 비교하여 임신율이 감소하지 않으며 비용면에서 효율적이고 효과적인 방법이다.

• The Journal of Advanced Prosthodontics
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• 제1권1호
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• pp.41-46
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• 2009

STATEMENT OF PROBLEM. The poor chemical bonding of a denture base resin to cast titanium framework often introduces adhesive failure and increases microleakage. PURPOSE. This study evaluated the shear bond strengths of a heat cure denture base resin to commercially pure titanium, Ti-6Al-4V alloy and a cobalt-chromium alloy using two adhesive primers. MATERIAL AND MATHODS. Disks of commercially pure titanium, Ti-6Al-4V alloy and a cobalt-chromium alloy were cast. Specimens without the primer were also prepared and used as the controls. The shear bond strengths were measured on a screw-driven universal testing machine. RESULTS. The primers significantly(P < .05) improved the shear bond strengths of the heat cure resin to all metals. However, the specimens primed with the Alloy $primer^{(R)}$(MDP monomer) showed higher bond strength than those primed with the MR $bond^{(R)}$(MAC-10 monomer) on titanium. Only adhesive failure was observed at the metal-resin interface in the non-primed specimens, while the primed specimens showed mixed failure of adhesive and cohesive failure. CONCLUSIONS. The use of appropriate adhesive metal primers makes it possible not only to eliminate the need for surface preparation of the metal framework before applying the heat cure resins, but also reduce the need for retentive devices on the metal substructure. In particular, the Alloy $primer^{(R)}$, which contains the phosphoric acid monomer, MDP, might be clinically more acceptable for bonding a heat cure resin to titanium than a MR $bond^{(R)}$, which contains the carboxylic acid monomer, MAC-10.