• Biomolecules & Therapeutics
• /
• 제3권2호
• /
• pp.149-153
• /
• 1995

Nitric oxide (NO) has been regarded as one of the neurotransmitters of nonadrenergic, noncholinergic (NANC) nerve stimulation in rabbit corpus cavernosum, rat gastric fundus and human intestine. PIANO (photo-induced adequate nitric oxide) is a very useful tool to investige the role of NO in various smooth muscles where NO is a mediator. The present study was undertaken to compare the physiological responses of the rat gastric smooth muscle in response to NANC nerve stimulation and to PIANO. Photolysis of L-NAME, D-NAME and streptozotocin (572) by UV light in the bathing medium caused relaxation of rat gastric fungus that contracted with carbachol, but was resistant to tetrodotoxin (TTX, 1 $\mu$M). Electrical stimulation (20 V, 2~32 Hz, 0.2 msec, 10s) of the gastric fundus, in the presence of atropine and guanethidine, induced frequency-dependent, TTX-sensitive relaxation. Sodium nitroprusside (1 nM-10 $\mu$M), a NO donor, mimicked the relaxations observed after NANC-stimulation or PIANO. Furthermore, PIANO caused UV light exposure time-dependent increase of CGMP in rat gastric fungus strips. These results provide another evidence indirectly that NO is one of the mediators of the NANC inhibitory nerve stimulation in the rat gastric fundus.

• 한국음향학회:학술대회논문집
• /
• 한국음향학회 1999년도 학술발표대회 논문집 제18권 1호
• /
• pp.224-227
• /
• 1999

A high power deep-water sonar transducer of FFR (Free Flooded Ring) type has been designed using a coupled FE-BEM. The present sonar transducer is composed of rectangular piezoelectric ceramics and pie-shaped steels (or the advantage of simple fabrication. The dynamics of the sonar transducer is modelled in three dimensions and is analyzed with external electrical excitation conditions. Different results are available such as steady-state frequency response for TX and RX displacement modes, directivity patterns, back-scattering patterns, bandwidths, transmitting voltage responses and receiving sensitivity responses. The TV response shows a very high acoustic pressure of 150 dB/lV (ref $1{\mu}Pa$ at 1m) at 1900 Hz. This ultra high power response of the sonar transducer indicates a new possibility of the sonar transducer development.

• 대한화학회지
• /
• 제56권4호
• /
• pp.424-430
• /
• 2012

Densities, viscosities, refractive indices and speed of sounds of the binary mixtures of Acetophenone with Ethylchloroacetate were measured over the entire mole fractions at (303.15, 313.15 and 323.15) K. From these experimental results, excess molar volume $V^E$, viscosity deviation ${\Delta}{\eta}$, refractive index deviation ${\Delta}n_D$, deviations in speed of sound ${\Delta}u$, deviations in isentropic compressibility ${\Delta}k_s$ and excess intermolecular free length ${\Delta}L_f$ were calculated. The viscosity data have been correlated with the equations of Grunberg and Nissan, Hind et al., Tamura and Kurata, Katti and Chaudri, Sedgwick, Krishnan-Laddha and McAllister. The thermo physical properties under study were fit to the Jouyban-Acree model. The excess values were correlated using Redlich-Kister polynomial equation to obtain their coefficients and standard deviations. It was found that in all cases, the data obtained fitted with the values correlated by the corresponding models very well. The results are interpreted in terms of molecular interactions occurring in the solution.

• Bulletin of the Korean Chemical Society
• /
• 제28권3호
• /
• pp.397-402
• /
• 2007

Restenosis after percutaneous coronary intervention (PCI) continues to be a serious problem in clinical cardiology. To solve this problem, drug eluting stents (DES) with antiproliferative agents have been developed. Variable local drug delivery systems in the context of stenting require the development of stent manufacture, drug pharmacology and coating technology. We have worked on a system that integrates electrophoretic deposition (EPD) technology with the polymeric nanoparticles in DES for local drug delivery and a controlled release system. The surface morphology and drug loading amount of DES by EPD have been investigated under different operational conditions, such as operation time, voltage and the composition of media. We prepared poly-D,L-lactide-co-glycolic acid (PLGA) nanoparticles embedded with curcumin, which was done by a modified spontaneous emulsification method and used polyacrylic acid (PAA) as a surfactant because its carboxylic group contribute negative charge to the surface of CPNPs (?53.5 ± 5.8 mV). In the process of ‘trial and error' endeavors, we found that it is easy to control the drug loading amount deposited onto the stent while keeping uniform surface morphology. Accordingly, stent coating by EPD has a wide application to the modification of DES using various kinds of nanoparticles and drugs.

• Journal of the Korean Wood Science and Technology
• /
• 제23권4호
• /
• pp.46-53
• /
• 1995

The anatomy of Korean diffuse-porous woods, 36 families, 75 genera, 145 species, 215 specimens was described and analyzed. Sixteen wood anatomical characters, habit and phenology factors were determined by simple correlation and principal component analysis. Strong positive correlations were found between vessel element length and fiber length, ray width and ray height, simple pits of fiber wall and paratracheal parenchyma distribution. The results of principal component analysis (PCA) disclose the primitive characteristics and the direction of xylem evolution of Korean diffuse-porous woods. The xylem evolution scenario for Korean dicotyledonous woods is considered to be developed in the direction of decreasing trends of vessel frequency, vessel element length, and length/diameter(L/D) ratio of vessel element but increasing trends of vessel diameter, fiber length/vessel element length(F/V) ratio, libriform wood fibers, simple perforation, and homogeneous ray composition. Increase of vessel diameter and decrease of vessel frequency seem to be related to the improvement of conductive efficiency, and increase of the vessel element length and occurrence of scalariform perforation in vessel element may be related to enhanced of conductive safety. Also the libriform wood fibers and ray features appear to have relationship with mechanical support and nutrient metabolism, respectively.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1995년도 추계학술대회 논문집 학회본부
• /
• pp.348-351
• /
• 1995

A modified silicon direct bonding method has been developed alloying an intimate contact between grooved and smooth mirror-polished oxide-free silicon wafers. A regular set of grooves was formed during preparation of heavily doped $p^+$-type grid network by oxide-masking und boron diffusion. Void-free bonded interfaces with filing of the grooves were observed by x-ray diffraction topography, infrared, optical. and scanning electron microscope techniques. The presence of regularly formed grooves in bending plane results in the substantial decrease of dislocation over large areas near the interface. Moreover two strongly misoriented waters could be successfully bonded by new technique. Diodes with bonded a pn-junction yielded a value of the ideality factor n about 1.5 and the uniform distribution of series resistance over the whole area of horded pn-structure. The suitability of the modified technique was confirmed by I - V characteristics of power diodes and reversly switched-on dynistor(RSD) with a working area about $12cm^2$. Both devices demonstrated breakdown voltages close to the calculation values.

• Journal of Microbiology and Biotechnology
• /
• 제8권3호
• /
• pp.270-276
• /
• 1998

Extracellular ${\alpha}$-glucosidase was purified to homogeneity from moderately thermophilic Bacillus sp. DG0303. The thermostable ${\alpha}$-glucosidase was purified by ammonium sulfate fractionation, ion-exchange chromatography, preparative polyacrylamide gel electrophoresis (PAGE), and electroelution. The molecular weight of the enzyme was estimated to be 60 kDa by SDS-PAGE. The optimum temperature for the action of the enzyme was at $60^{\circ}C$. It had a half-life of 35 min at $60^{\circ}C$. The enzyme was stable at the pH range of 4.5~7.0 and had an optimum pH at 5.0. The enzyme preparation did not require any metal ion for activity. The thermostable ${\alpha}$-glucosidase hydrolyzed the ${\alpha}$-1,6-linkages in isomaltose, isomaltotriose, and panose, and had little or no activity with maltooligosaccharides and other polysaccharides. The $K_m$ (mM) for p-nitrophenyl-${\alpha}$-D-glucopyranoside (pNPG), panose, isomaltose, and isomaltotriose were 4.6, 4.7, 40.8, and 3.7 and the $V_{max}$(${\mu}mol{\cdot}min^-1$$mg^-1$) for those substrates were 5629, 1669, 3410, and 1827, respectively. The N-terminal amino acid sequence of the enzyme was MERVWWKKAV. Based on its substrate specificity and catalytic properties, the enzyme has been assigned to be an oligo-1,6-glucosidase.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 C
• /
• pp.950-952
• /
• 1999

In this paper, we are studied a electrical properties study with P.D.GEORGE/STER LING Co. P.B 302-LV-2 POLYBUTADIENE RESIN which is used for VPI(Vacuum Pressure Impregnation)processing of field magnet and armature of traction motor in Korean national railroad at present was carried out its FT-IR (Fourier Transform Infra-Red) volume resistivity characteristics. The varnishes were experimented with the temperature range form $25[^{\circ}C]$ to $180[^{\circ}C]$ and applied voltage were supplied at 100, 250, 500, 1,000[V]. In this condition, the volume resistivity for specimens were measured. From the above study, the following data obtained for volume resistivity. It can be confirmed that velume resistivity with the increase of temperature is lower rapidly from room temperature to $130[^{\circ}C]$, and it is lower slowly at temperature higher than $130[^{\circ}C]$. Volume resistivity value is higher, according as the specimen is thick gradually. As the applied voltage is higher in the same temperature, volume resistivity value is lower.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2002년도 하계학술대회 논문집 C
• /
• pp.1840-1842
• /
• 2002

고전압 대 전류를 필요로 하는 펄스 파워 시스템에서 스위치는 중요한 소자중의 하나이다. 펄스 트랜스포머를 이용하여 고전압 펄스를 만드는 회로에서 대전류 스위칭에는 대부분 스파크 갭 스위치나 싸이라트론을 사용하는데 높은 펄스 반복 율과 긴 수명을 제공하기 위해서는 반도체 스위치를 사용해야한다. 고전압 대전류 펄스파워 시스템에 적합한 반도체 스위치의 스위칭 특성과 제어방식에 관한 연구를 수행하였다 실험에 사용한 스위치는 20 kV, 12.6 kA, 12 ${\mu}s$의 펄스 스위칭이 가능한 ABB사의 반도체스위치 스택 (5SPR-26L4508-8-WC)이다. 실험회로는 콘덴서에 충전을 완료한 다음 스위치와 인덕터를 통하여 방전하도록 구성하였다. 8개의 직렬 연결된 스위치는 광케이블을 사용하여 병렬구동하고, 고주파 스위칭 전류전원을 사용하여 고전압 절연을 하면서 게이트 구동전력을 전달하도록 하였다. 본 논문에서는 스위치 전압과 방전전류를 관측하여 반도체 스위치의 특성을 조사하였다.

• Preventive Nutrition and Food Science
• /
• 제7권2호
• /
• pp.123-127
• /
• 2002

Ninety nine extracts from Korean plants were screened for their inhibitory activities on human immunodeficiency virus (HIV) type 1 pretense by an HPLC method. The pretense inhibitory activities were determined by incubating the extracts in reaction mixtures containing pretense and substrate (His-Lys-Ala-Arg-Val-Leu-(p-NO$_2$- Phe)-Glu-Ala-Nle-Ser-NH$_2$) to perform proteolytic cleavage reactions. Of the extracts tested, the water extracts of Viburnum awabuki (stem and leaves) and Distylium racemosum (leaves) had the highest pretense inhibitory activities at a concentration of 100ug/mL. Activity-guided fractionation, revealed that the n-butanol fraction of the V. awabuki extract and the ethyl acetate fraction from the D. racemosum extract had the greatest inhibitory activity on HIV-1 pretense.