• Journal of the Korean Ceramic Society
• /
• v.34 no.11
• /
• pp.1165-1172
• /
• 1997

ZrB2 powders were prepared from a mixture of ZrO2, B2O3 and Mg by self-propagating high temperature synthesis method. The combustion product was successfully obtained from a mixture of ZrO2:B2O3:Mg=1:2:8.5 molar ratio. By-product, MgO was effectively removed by leaching with 1M HCl solution at 9$0^{\circ}C$ for over 5hours. After leaching, the Mg content was 0.86~1.42 wt%, and the mean particle size was 4.72${\mu}{\textrm}{m}$. The addition of 7.5 wt%(14Ni:1.0C) as a sintering aid greatly densified ZrB2 bodies compared with that of only Ni. The ZrB2 sintered bodies containing 7.5 wt%(14Ni:1.0C) was 94.3% of the theoretical density. In this case, ZrB2 existed as a major phase and had a bend strength of 300 MPa and a vickers hardness of 2000 kg/$\textrm{mm}^2$.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.13 no.4
• /
• pp.318-330
• /
• 2013

This paper presents a high-linearity low-noise small-size programmable gain amplifier (PGA) based on a new low-noise low-distortion differential amplifier and a proposed reconfiguration technique. The proposed differential amplifier combines an inverter-based differential pair with an adaptive biasing circuit to reduce noise and distortion. The reconfiguration technique saves the chip size by half by utilizing the same differential pair for the input transconductance and load-stage, interchangeably. Fabricated in $0.18-{\mu}m$ CMOS, the proposed PGA shows a dB-linear control range of 21dB in 16 steps from -11 dB to 10 dB with a gain error of less than ${\pm}0.33$ dB, an IIP3 of 7.4~14.5 dBm, a P1dB of -7~1.2 dBm, a noise figure of 13dB, and a 3-dB bandwidth of 270MHz at the maximum gain, respectively. The PGA occupies a chip area of $0.04mm^2$ and consumes only 1.3 mA from the 1.8 V supply.

• Water for future
• /
• v.29 no.4
• /
• pp.139-147
• /
• 1996

The stream morphological characteristics of river basin has a close correlation with the hydrological and hydraulic characteristics of the basin. This study was conducted to suggest a river width formula for medium rivers of central area in Korea. As a result, The following conclusions are made: (1) The model for the stream-width to be applied to the medium rivers of central area in Korea is developed as suggestion model-a function of the design flood discharge-of which the formula is $B=1.532A^{0.644.}$; (2) The model for the stream-sidth to be applied to the medium rivers of central area in Korea is developed as suggestion model-a function of the watershed Area-of which the formula is $B=12.392A^{0.511}$; (3) The model for the stream-width to be applied to the medium rivers of central area in Korea is developed as suggestion model-a function of the stream length of which the formual is $B=10.509l^{0.852}$.

• Journal of Korea Foresty Energy
• /
• v.19 no.1
• /
• pp.1-6
• /
• 2000

This study was carried out to investigate the growth responses of Pinus densiflora seedlings to enhanced UV-B environment for 16 weeks in the field condition. The seedlings were treated with one of three levels of UV-B dosages - ambient UV-B, ambient + 3.2, and ambient + 5.2 KJ m$^{-2}$day$^{-1}$ and the irradiation was performed at the stage before the germination, the fully expanded cotyledon, and the primary needles grown more than 0.8cm in length of the seedlings, respectively. Enhanced UV-B irradiation reduced the height and the root collar diameter growth, and dry mass production of the seedling, and T/R ratio was increased by the UV-B treatment. Difference in seedling growth was observed by difference in time of the UV-B treatment. Among the seedlings which were treated with ambient - 3.2 KJ m$^{-2}$day$^{-1}$, height and root collar diameter growth was relatively high in the seedling received the UV-B treatment at the stage before the germination. The lowest dry mass production was observed in the seedlings received the UV-B at stage of cotyledon both in two levels of enhanced UV-B treatment. Chlorophyll concentration was reduced by enhanced UV-B irradiation, and chlorophyll a/b ratio was increased by the UV-B treatment.

• Biomolecules & Therapeutics
• /
• v.18 no.4
• /
• pp.463-468
• /
• 2010

T-cell activation depends on signals received by the T-cell receptor and CD28 co-stimulatory receptor. Since B7.1 and B7.2 molecules expressed on the surface of antigen presenting cells provide co-stimulatory signals through CD28 to T-cells, an inhibitor of CD28-B7.1/B7.2 binding has been proposed as a therapeutic agent for suppression of excessive T-cell activity. Although anti-B7.1/B7.2 antibodies are known to block B7.1 and B7.2 molecules, their effects on intracellular events in antigen presenting cells remain unclear. In this study, anti-B7.1/B7.2 antibodies decreased secretion of nitric oxide and pro-inflammatory cytokines such as TNF-$\alpha$, IL-$1{\beta}$, and IL-12 in LPS-activated RAW264.7 macrophage-like cells and peritoneal macrophages. Moreover, anti-B7.1/B7.2 antibodies inhibited $I{\kappa}B{\alpha}$ phosphorylation and down-regulated expression of co-stimulatory molecules including B7.1, B7.2, and PD-L1 in LPS-stimulated peritoneal macrophages. These findings suggest that CTLA4-Ig and anti-B7.1/B7.2 antibodies may be candidates to treat chronic inflammatory diseases and autoimmune responses caused by excessive activation of both T-cells and macrophages.

• IMMUNE NETWORK
• /
• v.15 no.3
• /
• pp.161-166
• /
• 2015

Early growth response (Egr)-1 is a $Cys_2-His_2-type$ zincfinger transcription factor. It has been shown to induce survival and proliferation of immature and mature B cells, respectively, but its role in the differentiation of B cells into plasma cells remains unclear. To examine the effects of Egr-1 deficiency on the activation of B cells, naive B cells from $Egr1^{-/-}$mice and their wild-type (WT) littermates were activated to proliferate and differentiate, and then assayed by FACS. Proportions of cells undergoing proliferation and apoptosis did not differ between $Egr1^{-/-}$ and WT mice. However, $Egr1^{-/-}$ B cells gave rise to fewer plasma cells than WT B cells. Consistently, $Egr1^{-/-}$ mice produced significantly lower titer of antigen-specific IgG than their WT littermates upon immunization. Our results demonstrate that Egr-1 participates in the differentiation program of B cells into plasma cells, while it is dispensable for the proliferation and survival of mature B cells.

• East Asian mathematical journal
• /
• v.17 no.2
• /
• pp.233-237
• /
• 2001

The authors aim at presenting summation formulas of Appell's function $F_1$: $$F_1(a;b,b';1+a+b-b'+i;1,-1)\;(i=0,\;{\pm}1,\;{\pm}2,\;{\pm}3,\;{\pm}4,\;{\pm}5)$$, which, for i=0, yields a known result due to Srivastava.

• Korean Journal of Medicinal Crop Science
• /
• v.11 no.5
• /
• pp.385-391
• /
• 2003

The influences of the extracts from Cinnamomi Cortex, Eucommiae Cortex, Puerariae Radix, Lycii Fructus, Zizyphi Fructus, Schisandrae Fructus, Mume Fructus, Chaenomelis Fructus on mycelial growth and aflatoxin $B_1$ production from Aspergillus parasiticus were analyzed. The pH of the culture media were reduced to below pH 4 by all the herbal extracts after 3 days incubation. However, the pH of the culture media increased above pH 6 after 6 days incubation using the extracts from Cinnamomi Cortex, Eucommiae Cortex, Puerariae Radix and Lycii Fructus. The mycelial growth of A. parasiticus was increased over the amount of the control. Puerariae Radix produced the largest amount of mycelial growth and Chaenomelis Fructus produced the smallest amount of mycelial growth. The productions of aflatoxin $B_1$ from A. parasticus culture were increased by the extracts of Puerariae Radix and Zizyphi Fructus, while inhibited by the extracts of Cinnamomi Cortex, Eucommiae Cortex, Lycii Fructus, Schisandrae Fructus, Mume Fructus and Chaenomelis Fructus. In particular, the extracts of Cinnamomi Cortex, Lycii Fructus and Schisandrae Fructus almost inhibited the production of aflatoxin $B_1$. The production of the total protein from Cinnamomi Cortex, which produced much less aflatoxin $B_1$, and Puerariae Radix, which produced a great deal of aflatoxin $B_1$ from A parasticus were slightly higher than the production of the total protein of the control medium.

• Annals of Clinical Neurophysiology
• /
• v.8 no.1
• /
• pp.78-80
• /
• 2006

Miller-Fisher syndrome, Guillain-Barre syndrome with ophthalmoplegia, Bickerstaff s brainstem encephalitis and acute ophthalmoplegia share some clinical features, and common anti-GQ1b IgG antibody and these are introduced as anti-GQ1b antibody syndrome. These syndromes mostly present with paralysis of extraocular muscles and internal ophthalmoplegia rarely occurs. We report a case of acute isolated bilateral internal ophthalmoplegia associated with anti-GQ1b IgG antibody.

• Bulletin of the Korean Chemical Society
• /
• v.26 no.1
• /
• pp.63-71
• /
• 2005

Equilibrium geometries, electronic structures, and energies of borocarbon clusters (binary compounds of carbon and boron), an unexplored class of molecules with highly unusual characteristics and potential for further development, have been investigated by means of B3LYP/6-311+G$^*$ density functional theory computations. A large number of B$_7$C${_1}^{1-}$, B$_6C_2$, and B$_5C_{3}\,^{1+}$ clusters with planar and non-planar monocyclic and polycyclic rings, as well as cage structures, have been systematically studied. Unexpectedly, planar forms are predicted not only to be the most stable structures, but also, in many cases, to have unprecedented planar heptacoordinate boron (p-heptaB) and planar heptacoordinate carbon (p-heptaC) arrangements. All these pheptaB and p-heptaC have 6π electrons and are aromatic according to the nucleus independent chemical shift (NICS). This novel bonding pattern is analyzed in terms of natural bond orbital (NBO) analysis. For virtually all possible B$_7$C${_1}^{1-}$, B$_6C_2$, and B$_5C_{3}\,^{1+}$ combinations, the p-heptaB arrangements are the more stable than other type structures.