• Korean Journal of Veterinary Research
• /
• v.43 no.4
• /
• pp.587-595
• /
• 2003

The aim of this study was to investigate trazodone's effect on vasorelaxation and blood pressure lowering and to examine its underlying mechanism of action in isolated thoracic aorta and anesthesized rats. Precontracted aortic rings with high KCl were relaxed with trazodone, at concentrations of $50{\mu}M$ or greater. However, precontracted rings with phenylephrine (PE) were relaxed with trazodone, at concentrations of $0.03{\mu}M$ or greater, in a concentration-dependent manner. These relaxant effects of trazodone on endothelium intact rat aortic rings were significantly greater than those on denuded rings. The trazodone-induced relaxations were suppressed by nitric oxide synthase (NOS) inhibitors, N(G)-nitro-L-arginine (L-NNA) and N(omega)-nitro-L-arginine methyl ester (L-NAME), guanylate cyclase inhibitors, methylene blue and 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), a $Ca^{2+}$-activated $K^+$ channel blocker, tetrabutylammonium (TBA), a $Ca^{2+}$ channel blocker, nifedipine, $Na^+$ channel blockers, lidocaine and procaine, and removal of extracellular $Na^+$, but not by aminoguanidine, 2-nitro-4-carboxyphenyl-n, n-diphenylcarbamate (NCDC), indomethacin, glibenclamide and clotrimazole. In vivo, infusion of trazodone elicited significant decrease in arterial blood pressure. Trazodone-induced decrease in blood pressure was markedly inhibited by pretreatment of intravenous injection of saponin, L-NNA, methylene blue, TBA, lidocaine or nifedipine. These findings suggest that the endothelium-dependent relaxation and decrease in blood pressure induced by trazodone is mediated by release of NO from the endothelium, activation of TBA-sensitive $Ca^{2+}$-activated $K^+$ channels or inhibition of $Ca^{2+}$ entry through voltage-gated channel.

• Applied Chemistry for Engineering
• /
• v.9 no.4
• /
• pp.561-564
• /
• 1998

The radial distribution functions of a linear spheroidal type gas molecule $C_2H_4$ were calculated by using the Stockmayer molecular molel, which assumed the $C_2H_4$ molecule as simple quadrupolar molecule. To examine the validity of the calculated radial distribution of $C_2H_4$ gas, the density dependent pressures of $C_2H_4$ gas at several temperatures were calculated and compared with literarily known experimental pressure data of $C_2H_4$ gas. The temperatures examined was 50, 100 and $150^{\circ}C$ and the densities were up to $0.02/{\AA}^3$ (maximum pressure = 1500 atm). The radial distribution function expression used was derived by Yoon, Hacura, and Baglin (YHB) with Baker and Henderson's perturbation theory. The calculated results by a computer showed that the $C_2H_4$ pressures calculated agreed well with the experimental values within ${\pm}5%$ of error range. This indicated that the YHB radial distribution function expression is good enough to obtain various physical quantities sensitive to density such as pressure with resonable accuracy.

• Journal of the Korean Society of Safety
• /
• v.34 no.1
• /
• pp.40-44
• /
• 2019

Experimental studies have been carried out to investigate characteristics of gas explosion using a multi layered water gel barrier in a vented explosion chamber. The chamber is consisted of 1600 mm in length, with a square cross-section of $100{\times}100mm^2$. The gel concentration of inner layer of MLWGB ranged from 10% to 90% with intervals of 10% by weight of gel. Displacement of the MLWGB was photographed with a measured using a high-speed video camera, and pressure development was measured using a data acquisition system. It was found that MLWGBs with 10 ~ 20% inner layer concentrations were ruptured during the explosions. As the concentrations of inner layer increased from 30% to 90%, the barriers were not ruptured. As the gel concentrations of the inner layer increased, the displacement increased toward the chamber exit and the pressure decreased for the ruptured barriers. It was found that the pressure attenuation obtained from the MLWGB was higher than that of the single water gel barrier. For the cases of non-ruptured barriers, the pressure inside the chamber less increased with increasing gel concentrations of the inner layer. It was also found that the displacement moved back into the chamber for non-ruptured MLWGBs, and it was sensitive to the gel concentrations.

• Journal of the Optical Society of Korea
• /
• v.8 no.2
• /
• pp.83-89
• /
• 2004

A variable optical attenuator with a bending-sensitive fiber (BSF) that can be used in optical networks is developed. The refractive index profile of the BSF is divided into four regions which are inner core, center dip of inner core, outer core and clad. The 3-dimensional finite difference beam propagation method (3D FD-BPM) is utilized to find the characteristics of the BSF, so the mode profile of the BSF and optical power attenuation according to the bending are investigated, and the equivalent model of the BSF is made. By using this equivalent model of the BSF, the BSF is fabricated, and the refractive index profile of the BSF is measured, which is similar to refractive index profile of the proposed BSF. The fabricated variable optical fiber attenuator (VOFA) consists of the BSF in a rectangular rubber ring with a fixed bend radius (BR) in a steady state. The VOFA using the proposed BSF was able to attenuate the optical power by more than about －38 ㏈ at certain wavelengths (1540∼1560 nm) based on adjusting the mechanical pressure applied to the upper surface of the rectangular rubber ring with the bent BSF. In addition, the proposed VOFA produced an insertion loss of 0.68 ㏈, polarization dependent loss (PDL) of about 0.5 ㏈, and return loss of less than －60 ㏈.

• Progress in Superconductivity
• /
• v.11 no.1
• /
• pp.36-41
• /
• 2009

Superconducting quantum phenomena are getting attention from the field of metrology area. Following its first successful application of Josephson effect to voltage standard, piconewton force standard was suggested as a candidate for the next application of superconducting quantum effects in metrology. It is predicted that a micron-sized superconducting Nb ring in a strong magnetic field gradient generates a quantized force of the order of sub-piconewtons. In this work, we studied the design and fabrication of Nb superconducting quantum interference device (SQUID) on an ultra-thin silicon cantilever. The Nb SQUID and electrodes were structured on a silicon-on-insulator (SOI) wafer by dc magnetron sputtering and lift-off lithography. Using the resulting SOI wafer, we fabricated V-shaped and parallel-beam cantilevers, each with a $30-{\mu}m$-wide paddle; the length, width, and thickness of each cantilever arm were typically $440{\mu}m,\;4.5{\mu}m$, and $0.34{\mu}m$, respectively. However, the cantilevers underwent bending, a technical difficulty commonly encountered during the fabrication of electrical circuits on ultra-soft mechanical substrates. In order to circumvent this difficulty, we controlled the Ar pressure during Nb sputtering to minimize the intrinsic stress in the Nb film and studied the effect of residual stress on the resultant device.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.228.2-228.2
• /
• 2014

Characteristics of high Fermi velocity, high mechanical strength, and transparency offer tremendous advantages for using graphene as a promising transparent conducting material [1] in electronic devices. Although graphene is a prospective candidate for touch sensor with strong mechanical properties [2] and flexibility, only few investigations have been carried out in the field of sensor as a device form. In this study, we suggest ultra-highly sensitive and transparent graphene touch sensor fabricated by single layer graphenes. One of the graphene layers is formed in the top panel as a disconnected graphene beam transferred on PDMS, and the other of the graphene layer is formed with line-patterning on the bottom panel of triple structure PET/PI/SiO2. The touch sensor shows characteristics of flexible. Its transmittance is approximately 75% where transmittance of the top panel and the bottom panel are 86.3% and 87%, respectively, at 550 nm wavelength. Sheet resistance of each graphene layer is estimated as low as $971{\Omega}/sq$. The results show that the conductance change rate (${\Delta}C/C0$) is $8{\times}105$ which depicts ultra-high sensitivity. Moreover, reliability characteristic confirms consistent behavior up to a 100-cycle test.

• Journal of the Korean Society of Food Culture
• /
• v.17 no.3
• /
• pp.289-298
• /
• 2002

This study was conducted to find sensitive indicator of food intake and specific food group related to cognitive function and to analyze the pathway among factors affecting food intake and cognitive function of the aged. 179 people over 50 years old were investigated and all the data were analyzed by SPSS 10.0 package. Food frequency was more sensitive indicator to show the relationship between food intake and cognitive function of the aged than the numbers of standard amount of food eaten. Consumption of grains and starch, meat, fish, eggs and beans were strongly related to cognitive function of the aged and intake of vegetables and fruits also have relationship with it. Moreover, the more frequent eating the carbohydrate and the protein, the higher the cognitive level of the aged. Age, education period, income, blood pressure, duration after retirement, frequency of physical activity and BMI were correlated with food intake and cognitive function of the aged. Among them, age and frequency of physical activity were most strongly correlated with food intake, and education period with cognitive function of them. This investigation shows that more stable intake of carbohydrate and protein containing foods need to be supplied to low income aged and the importance of physical activity of the aged must be emphasized with food intake for better life of the aged.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.32 no.6
• /
• pp.454-462
• /
• 2008

Since operating conditions are significantly different for heating and cooling mode operations in a $CO_2$ heat pump system, it is difficult to optimize the performance of the $CO_2$ cycle. In addition, the performance of a $CO_2$ heat pump is very sensitive to outdoor temperature and gascooler pressure. In this study, the cooling and heating performances of a variable speed $CO_2$ heat pump with a twin-rotary compressor were measured and analyzed with the variations of EEV opening and compressor frequency. As a result, the cooling and heating COPs were 2.3 and 3.0, respectively, when the EEV opening was 22%. When the optimal EEV openings for heating and cooling were 28% and 16%, the cooling and heating COPs increased by 3.3% and 3.9%, respectively, over the COPs at the EEV opening of 22%. Beside, the heating performance was more sensitive to EEV opening than the cooling performance. As the compressor speed decreased by 5 Hz, the cooling COP increased by 2%, while the heating COP decreased by 8%.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.8 no.6
• /
• pp.1325-1331
• /
• 2007

In order to investigate the cooling capacity of an air-conditioner applying a variable capacity compressor and the temperature characteristics on a condenser and an evaporator, the experiment on the operation characteristics of the air-conditioner was performed along a compressor operation ratio and an indoor/outdoor temperatures, under a cooling operation mode. The system characteristics were measured by the psychrometric calorimeter. The cooling capacity increased with decreasing the outdoor temperature and increasing the indoor temperature. Also, it increased with increasing the compressor operation ratio. The temperature of the condenser was more sensitive for the variation of the outdoor temperature and the temperature of the evaporator was more sensitive for the variation of the indoor temperature. The operation characteristics of the cycle used in this present were also analyzed by a pressure-enthalpy chart.

• Analytical Science and Technology
• /
• v.36 no.6
• /
• pp.281-290
• /
• 2023

Zidovudine is an antiretroviral agent prescribed for the prevention and treatment of human immunodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS). It is typically recommended to be used in combination with other antiretroviral drugs. Zidovudine has the potential to generate N-nitrosodimethylamine (NDMA) in the presence of dimethylamine and nitrite salt under acidic reaction conditions during the drug manufacturing process. NDMA is a potent human carcinogen that may be detected in drug substances or drug products. An analytical method was developed to determine NDMA in pharmaceuticals including zidovudine using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The analysis involved reversed-phase chromatography on a Kinetex F5 column with a mobile phase comprising water-acetonitrile mixtures. The detection of positively charged ions was conducted using atmospheric pressure chemical ionization (APCI). The calibration curve demonstrated excellent linearity (r = 0.9997) across the range of 1-50 ng/mL with a highly sensitive limit of detection (LOD) at 0.3 ng/mL. The developed method underwent thorough validation for specificity, linearity, accuracy, precision, robustness, and system suitability. This sensitive and specific analytical method was applied for detecting NDMA in zidovudine drug substance and its formulation currently available in the market, indicating its suitability for drug quality management purposes.