• Bulletin of the Korean Chemical Society
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• v.15 no.9
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• pp.729-732
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• 1994

The acid-promoted cleavage of the E-and Z-isomers of 1-phenyl-6-neopentyl-1,3,4-trimethyl-1-silacyclohe x-3-ene(II) under various conditions gave clean and nearly quantitative formation of the ring-opened 2,3,7,7-tetramethyl-5-(X)silyl-1-octene products (X=OMe, Cl, OH). The possible mechanism for the formation of the ring-opened products was suggested that the initial protonation of II at C-4 would give a carbocation oriented so that they are ${\beta}$ to the silicon atom, and the subsequent nucleophilic attack at silicon would give rise to the observed products (VI, VII, VIII).

• Journal of the Korean Electrochemical Society
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• v.9 no.2
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• pp.64-69
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• 2006

Cathode materials of Al-doped $Li(Ni_{1/3}Co_{1/3}Mn_{1/3-x}Al_x)O_2$ (x=0.0, 0.005, 0.01 0.05) for lithium ion batteries were synthesized with ultra-sonic spray pyrolysis method and single-step heat treatment. No secondary phases were found in all synthesized powders. The intensity ratio of $I_{003}\;to\;I_{104}$, however, slightly decreased and the particle size increased with the Al contents. The cells with bare, 0.5 and 1.0 at% Al-doped powders showed the initial discharge capacities of 182, 180 and $184mAhg^{-1}$ in a voltage range of $3.0\sim4.5V$ at 1C rate, and the capacity retentions of 81, 77 and 78% at the end of 30 cycles, respectively. But in the voltage range of $3.0\sim4.6V$, the Al-doping significantly enhanced the cycle stability. For example, the discharge capacity after 50 cycles was maintained to 70% in the 0.5 at% Al-doped sample compared to only 30% in no doped sample. The improvement of the cycle stability was thought to be due to $Mn^{3+}$ ion decrease as the Al doping from the XPS analysis results.

• Bulletin of the Korean Chemical Society
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• v.19 no.9
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• pp.897-906
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• 1998

A new synthesis has been developed for 1-thia-4,7-diazacyclononane and the complexation behavior of a particular derivative has been explored. The pentadentate ligand 4,7-bis(2-pyridylmethyl)-l-thia-4,7-diazacyclononane ([9]$N_2SPY_2$) and its iron(Ⅱ) and manganese(Ⅱ) complexes were prepared and characterized. Magnetic moments of 5.17 and 5.90 μB respectively, indicate that the iron(Ⅱ) and manganese(Ⅱ) complexes are high spin. Charge transfer transitions (d-π*) occur for [Fe(Ⅱ)([9]$N_2SPY_2)(X)]^{n+}$at 27027, 25000, and 24390 cm-1 for X=$H_2O$, Cl-, and OH-, respectively. In acetonitrile solution, the cyclic voltammogram of the manganese(Ⅱ) complex exhibits a redox couple at 0.92 V vs. NHE while the redox potentials for [Fe(Il)([9]$N_2SPY_2)(X)]^{n+}$ are 0.70, 0.66, and 0.37 V vs. NHE for X=$H_2O$, Cl-, and OH-, respectively. The d-π* charge transfer energy and Fe(Ⅱ)/Fe(Ⅲ) redox potential for [Fe(Ⅱ)([9]$N_2SPY_2)(X)]^{n+}$ increase in the same order: $H_2O>Cl^- >OH^-$. The crystal structures of the iron(Ⅱ) and manganese(Ⅱ) complexes reveal that the metal ions are sixcoordinate, binding to four nitrogen atoms and a sulfur atom from the pentadentate ligand, as well as a chloride anion, with the chloride and sulfur atoms in cis positions. The two metals have similar coordination geometries, which are closer to trigonal prismatic than octahedral. In both iron and manganese complexes, the M-N($sp_3$) trans to Cl- is 0.07 Å longer than the one cis to Cl- , and M-N($sp^2$) trans to S is 0.05 longer than the one cis to S atom.

• Journal of Life Science
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• v.13 no.1
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• pp.118-127
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• 2003

$\rho$-Fluorophenylalanine (FPA), a phenylalanine analog, is able to induce apoptotic cell death of human acute leukemia Jurkat T cells. To better understand the mechanism by which FPA induces apoptotic cell death, the effect of ectopic expression of antiapoptotic proteins, Bcl-2 and Bcl-xL, on FPA-induced apoptosis was investigated by employing lurkat T cells transfected with Bcl-2 gene (JT/Bcl-2) or Bcl-xL gene (1/Bcl-xL) and Jurkat T cells transfected with vector (JT/Neo or J/Neo). When Jurkat T cells, JT/Neo or J/Neo, were exposed to FPA at concentrations ranging from 0.63 to 5.0 mM, the cell viability determined by MTT assay declined in a dose-dependent manner. In addition, apoptotic DNA fragmentation along with several apoptotic events such as caspase-8 activation, Bid cleavage, mitochondrial cytochrome c release, caspase-9 activation, caspase-3 activation, and degradation of PARP was induced. However, the FPA-induced cytotoxic effect, activation of caspase-8, and cleavage of Bid were significantly abrogated by ectopic expression of Bcl-2 or Bcl-xL. At the same time, there was marked reduction in the level of cytochrome c release from mitorhondria, caspase-9 activation, caspase-3 activation, and degradation of PARP. These results indicate that caspase-8 activation, Bid cleavage, and mitochondrial cytochrome c release with subsequent activation of the caspase cascade are negatively regulated by Bcl-2 or Bcl-xL, and are thus required for FPA-induced apoptosis in Jurkat T cells

• Journal of IKEEE
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• v.23 no.1
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• pp.181-187
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• 2019

In this paper, we demonstrated a power amplifier monolithic microwave integrated circuit (MMIC) for X-band radar applications. It utilizes commercial $0.25{\mu}m$ GaN-based high electron mobility transistor (HEMT) technology and delivers more than 20 W of output power. The developed GaN-based power amplifier MMIC has small signal gain of over 22 dB and saturated output power of over 43.3 dBm (21.38 W) in a pulse operation mode with pulse width of $200{\mu}s$ and duty cycle of 4% over the entire band of 9 to 10 GHz. The chip dimensions are $3.5mm{\times}2.3mm$, generating the output power density of $2.71W/mm^2$. Its power added efficiency (PAE) is 42.6-50.7% in the frequency bandwidth from 9 to 10 GHz. The developed GaN-based power amplifier MMIC is expected to be applied in a variety of X-band radar applications.

• Clinical and Experimental Pediatrics
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• v.45 no.12
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• pp.1484-1490
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• 2002

Purpose : The purpose of this study was to look at prevalences of abnormal serum aminotransferase levels and abnormal serum total cholesterol levels among adolescents with obesity in Seoul area. Methods : Body mass index[$BMI(kg/m^2)$], serum aspartate aminotransferase(AST) alanine aminotransferase( ALT), and total cholesterol levels were measured in 26,876 adolescents(male : 13,287, female : 13,589) of first grade of high school in Seoul between the ages of 15 and 16 years, enrolled in a large health examination survey by Seoul School Health Center(SSHC) in 2001. Obesity was defined as BMI more than 95th percentile for age and sex and normal weight was defined as BMI between 25th percentile and 75th percentile for age and sex. Abnormal levels of AST, ALT and total cholesterol were defined as more than 95th percentile for age and sex. Results : The BMI at 95th percentile was 28.7 in males and 26.9 in females. The prevalence of abnormal AST levels was higher in obesity group than in normal weight group. In males, those were 23.7% and 3.7%, respectively(P<0.01, $x^2-value$ : 529.2). In females, those were 11.8% and 4.9 %, respectively(P<0.01, $x^2-value$ : 56.3). The prevalence of abnormal ALT levels was significantly higher in the obesity group compared with the normal weight group. In males, those were 33.9% and 1.7%, respectively(P<0.01, $x^2-value$ : 1,693.4). In females, those were 22.3% and 3.9%, repectively(P<0.01, $x^2-value$ : 397.6). The prevalence of abnormal total cholesterol levels was higher in the obesity group than in the normal weight group. In males, those were 16.8% and 3.5%, respectively(P<0.01, $x^2-value$ : 268.3). In females, those were 9.0% and 5.4%, respectively(P<0.01, $x^2-value$ : 14.2). Conclusion : This study revealed that the prevalences of abnormal AST, ALT and total cholesterol level were higher in the obese group than in the normal weight group.

• The Journal of the Korea Contents Association
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• v.9 no.3
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• pp.250-255
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• 2009

This study performed and evaluated the performance test in 40 general X-ray units among diagnostic X-ray units, which were being used in hospitals of gyeongsangnam-do gimhae-si through X-ray tube variable limiting device ability test, the light field and X-ray field alignment test and collimation and beam alignment test of diagnostic X-ray unit. The results are as followings: In a variable beam limiting device ability test, the result of maximum X-ray field test showed that 4(10%) of were incongruent while the result of minimum X-ray field test represented that 5(12.5%) of were incongruent. The result of the light field and X-ray field alignment test showed 23(57.5%) of were within 2% of maximum permissible level and the other 17(42.5%) units were misalignment. The result of beam alignment test represented that 11(27.5%) coincided and another 11(27.5%) within $0.5^{\circ}$ respectively, 10(25%) were $0.6^{\circ}-1.5^{\circ}$ intervals, 7(17.5%) were $1.6^{\circ}-3^{\circ}$ and 1(2.5%) were more than $3^{\circ}$.

• Korean Journal of Environment and Ecology
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• v.32 no.4
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• pp.413-424
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• 2018

The study analyzed the effects of topographic structures and altitude in mountainous parks in Mt. Namsan in Gyeongju on the generation of anions. The temperature was at ridge ($9.82^{\circ}C$) > valley ($8.44^{\circ}C$), the relative humidity valley (59.01 %) > ridge (58.64 %), the solar radiation ridge ($34.40W/m^2$) > valley($14.69W/m^2$), the wind speed ridge (0.63m/s) > valley(0.37m/s), and the negative ion valley($636.81ea/cm^3$) > ridge($580.04ea/cm^3$). In the valley, the correlation with altitude was verified for the temperature, relative humidity, solar radiation, and negative ion generation in the valley. The relative humidity, solar radiation, and negative ion indicated a positive correlation while the temperature had a negative correlation. In the ridge, the correlation with altitude was verified for the temperature, relative humidity, wind speed, solar radiation, and negative ion generation. The relative humidity, solar radiation, and negative ion generation indicated a positive correlation while the temperature and wind speed had a negative correlation. The regression analysis showed the prediction equation of y=-0.006x+9.663 (x=altitude, y=temperature) in the valley and y=-0.009x+11.595 (x=altitude, y=temperature) in the ridge for the temperature, y=0.027x+53.561 (x=altitude, y=relative humidity) in the valley and y=0.008x+56.646 (x=altitude, y=relative humidity) in the ridges for the relative humidity, and y=0.027x+53.561 (x=altitude, y=negative Ion generation) in the valley and y= 0.008x+56.646 (x=altitude, y=negative Ion generation) in the ridge for the negative ion generation.

• Korean Journal of Materials Research
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• v.14 no.9
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• pp.627-633
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• 2004

Lithium titanate whiske($Li_{x}Ti_{4}O_9$) was prepared by an ion-exchange reaction. To this end, the initial material, potassium tetratitanate ($K_{2}Ti_{4}O_9{\cdot}nH_{2}O$) was prepared by calcination of a mixture of $K_{2}CO_3\;and\;TiO_2$ with a molar ratio of 2.8 at $1050^{\circ}C$ for 3 h, followed by boiling water treatment of the calcined products for 10 h. Fibrous potassium tetratitanate could be transformed into layered hydrous titanium dioxide ($H_{2}Ti_{4}O_9{\cdot}nH_{2}O$) through an exchange of $K^{+}\;with\;H^{+}$ using 0.075 M HCl. Also, lithium titanate whisker was finally prepared as $Li^{+}\;and\;H^{+}$ ions were exchanged by adding 20 mL of a mixture solution of LiOH and $LiNO_3$ to 1g whisker and stirring for $5\~15$ days. The average length and diameter of the $Li_{x}Ti_{4}O_9$ whiskers were $10\~20{\mu}m\;and\;1\~3{\mu}m$, respectively.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.6
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• pp.553-557
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• 1999

In order to investigate the optical properties of the $Al_XGa_{1-X}N/GaN$ thin film grown by metalorganic chemical vapor deposition (MOCVD) method, the photoluminescene (PL), photocurrent (PC) and persistent photoconductivity (PPC) measurements were carried out at room temperature. The band gap of the $A1_x$$Ga_{1-x}$N/GaN was determined to 3.70 eV by the PL and PC measurements. The PC measurement on the light illumination from the top of the $A1_x$$Ga_{1-x}$N/GaN thin film provides peaks at 3.70, 3.43, and around 2.2 eV. The PC spectrum by the illumination passing through from the substrate of the sample can be shown at 3.43 eV together with a broad tail band from the GaN band edge to around 2.23 eV. The photocurrent quenching and anomalous PPC decay observed in PPC measurements indicate that metastable electron states are fomed in the band gap of GaN layer to trap electrons which can be tunneled the potential barrier for long recovery time.