• Bulletin of the Korean Chemical Society
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• v.34 no.8
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• pp.2325-2329
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• 2013

Second-order rate constants $k_N$ have been measured for reactions of benzyl 2-pyridyl thionocarbonate (4b) and t-butyl 2-pyridyl thionocarbonate (5b) with a series of cyclic secondary amines in MeCN at $25.0{\pm}0.1^{\circ}C$. The $k_N$ values for the reactions of 4b and 5b have been compared with those reported previously for the corresponding reactions of benzyl 2-pyridyl carbonate (4a) and t-butyl 2-pyridyl carbonate (5a) to investigate the effect of changing the electrophilic center from C=O to C=S on reactivity and reaction mechanism. The thiono compound 4b is more reactive than its oxygen analogue 4a. The Br${\o}$nsted-type plots for the reactions of 4a and 4b are linear with ${\beta}_{nuc}=0.57$ and 0.37, respectively. The reactions of 4a were previously reported to proceed through a concerted mechanism, while those of 4b in this study have been concluded to proceed through a stepwise mechanism with formation of an intermediate being the rate-determining step on the basis of the ${\beta}_{nuc}$ value of 0.37. Enhanced polarizability upon changing the C=O in 4a by C=S has been suggested to be responsible for the reactivity order and the contrasting reaction mechanisms. In contrast, the reactivity of 5a and 5b is similar, but they are much less reactive than 4a and 4b. Furthermore, the reactions of 5a and 5b have been concluded to proceed through the same mechanism (i.e., a concerted mechanism) on the basis of linear Bronsted-type plots with ${\beta}_{nuc}=0.45$ or 0.47. It has been concluded that the strong steric hindrance exerted by the t-Bu in 5a and 5b causes a decrease in their reactivity and forces the reactions to proceed through a concerted mechanism.

• Journal of the Korean Chemical Society
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• v.44 no.5
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• pp.435-440
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• 2000

The reaction of 2-methoxycarlmethylen-l,2-dihydro-4H-pyrido[2,3-b]pyrazin-3-one(5) with hydrazine hydrate and ethylenediamine gave 2-hydrazinocarbonylmethylene-1,2-dihydro-4H-pyrido[2,3-b]pyrazin-3-one(6) and 2-aminoethylcarbamethylene-1,2-dihydro-4H-pyrido[2,3-b]pyrazin-3-one(7), res-pectively. The reaction of compound 6 or 7 with substituted benzaldehydes or heteroaryl aldehydes afforded pyrido[2,3-b]pyrazines(8-13). Some pyrin the enamine, methylene imine and enaminol forms in solution. The tau-tomer ratios were determined by the H NMR.

• Journal of the Korean Mathematical Society
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• v.59 no.4
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• pp.757-774
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• 2022

Let a and b be positive even integers. An even [a, b]-factor of a graph G is a spanning subgraph H such that for every vertex v ∈ V (G), d_H(v) is even and a ≤ dH(v) ≤ b. Let κ(G) be the minimum size of a vertex set S such that G - S is disconnected or one vertex, and let σ₂(G) = min_uv∉E(G) (d(u)+d(v)). In 2005, Matsuda proved an Ore-type condition for an n-vertex graph satisfying certain properties to guarantee the existence of an even [2, b]-factor. In this paper, we prove that for an even positive integer b with b ≥ 6, if G is an n-vertex graph such that n ≥ b + 5, κ(G) ≥ 4, and σ₂(G) ≥ ${\frac{8n}{b+4}}$, then G contains an even [4, b]-factor; each condition on n, κ(G), and σ₂(G) is sharp.

• Membrane Journal
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• v.19 no.3
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• pp.228-236
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• 2009

ABA type triblock copolymer of poly(hydroxyl ethyl acrylate )-b-polystyrene-b-poly(hydroxyl ethyl acrylate), i.e. PHEA-b-PS-b-PHEA, was synthesized throughatom transfer radical polymerization (ATRP). This block copolymer was thermally crosslinked with 4,5-imidazole dicarboxylic acid (IDA) via the esterification between the -OH groups of PHEA in block copolymer and the -COOH groups of IDA. Upon doping with ${H_3}{PO_4}$ to form imidazole-${H_3}{PO_4}$ complexes, the proton conductivity of membranes continuously increased with increasing ${H_3}{PO_4}$ content. The PHEA-b-PS-b-PHEA/IDA/${H_3}{PO_4}$ polymer membrane with [HEA]:[IDA]:[${H_3}{PO_4}$]=3:4:4 exhibited a maximum proton conductivity of 0.01 S/cm at $100^{\circ}C$ under anhydrous conditions. Thermal gravimetric analysis (TGA) shows that the PHEA-b-PS-b-PHEA/IDA/${H_3}{PO_4}$ complex membranes were thermally stable up to $350^{\circ}C$, indicating their applicability in fuel cells.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.8 no.2
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• pp.95-99
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• 2014

Binaural interaction can recognize the same intensity sound by stimulating two ears alternatively, and it can be record auditory brainstem responses (ABR). However, We needs to be researched about binaural interaction in asymmetric binaural acoustic stimulation. 17 normal young hearing university students were participated. Clicks were presented at the intensity of 90 dB nHL to one ear and the click intensity was increased from 0 to 90 dB nHL with a separation of 10 dB to another ear, simultaneous. BI waveform was obtained by subtracting the sum of the asymmetrically evoked potentials from the binaurally evoked potentials; i.e. BI = B - (L + R). Latency and amplitude was measured 'peak to following trough' of IV-V complex of BI waveform. Threshold of BIC (t-BIC) was obtained using amplitude depend on stimulus intensities (paired sample t-test). Latency shifted in 4.65, 4.63, 4.57, 4.58, 4.62, 4.6, 4.48, 4.36, 4.23 ms for peak, 5.57, 5.51, 5.51, 5.59, 5.61, 5.55, 5.44, 5.28, 5.19 ms for trough, and amplitude shifted in .0.32, -0.3, -0.34, -0.32, -0.42, -0.53, -0.54, -0.61, $-0.67{\mu}V$ from 0 to 90 dB nHL in every 10 dB, respectively. t-BIC was observed 40 dB nHL(p=.001).

• The Korean Journal of Ecology
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• v.27 no.2
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• pp.93-98
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• 2004

Decay rate and nutrient dynamics during decomposition of oak (Quercus acutissima) branches were investigated for 33-months in Kongju, Korea. After 33-months, remaining weight of B₁, B₂ and B₃ was 44.5%, 58.5% and 55.37%, respectively. Decomposition constant (k) for B₁, B₂ and B₃ was 0.294/yr, 0.195/yr, 0.215/yr, respectively. N concentration in decomposing oak branches increased in all diameter classes. After 33-months, remaining N in B₁, B₂ and B₃ was 101.2%, 91.9%, 104.4%, respectively. P concentration in decomposing oak branches increased in B₁ and B₂, and there was no immobilization period. After 33-months, remaining P in B₁, B₂ and B₃ was 57.2%, 74.4%, 53.9%, respectively. K concentration in decomposing oak branches decreased significantly. Remaining K in B₁, B₂ and B₃ was 7.7%, 17.1% and 17.2%, respectively, which was significantly lower than other nutrients. Ca concentration in decomposing oak branches increased in B₂ and B₃. After 33-months, remaining Ca in B₁, B₂ and B₃ was 58.5%, 47.8% and 75.2%, respectively. Initial concentration of Mg in oak branch was higher in smaller diameter class. After 33-months, remaining Mg in B₁, B₂ and B₃ was 44.3%, 57.9% and 47.7%, respectively.

• The Korean Journal of Physiology and Pharmacology
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• v.16 no.4
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• pp.265-271
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• 2012

HoxB4, a homeodomain-containing transcription factor, is involved in the expansion of hematopoietic stem cells and progenitor cells in vivo and in vitro, and plays a key role in regulating the balance between hematopoietic stem cell renewal and cell differentiation. However, the biological activity of HoxB4 in other cells has not been reported. In this study, we investigated the effect of overexpressed HoxB4 on cell survival under various conditions that induce death, using the Ba/F3 cell line. Analysis of phenotypical characteristics showed that HoxB4 overexpression in Ba/F3 cells reduced cell size, death, and proliferation rate. Moreover, the progression from early to late apoptotic stages was inhibited in Ba/F3 cells subjected to HoxB4 overexpression under removal of interleukin-3-mediated signal, leading to the induction of cell cycle arrest at the G2/M phase and attenuated cell death by Fas protein stimulation in vitro. Furthermore, apoptotic cell death induced by doxorubicin-treated G2/M phase cell-cycle arrest also decreased with HoxB4 overexpression in Ba/F3 cells. From these data, we suggest that HoxB4 may play an important role in the regulation of pro-B cell survival under various apoptotic death environments.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.12
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• pp.6239-6244
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• 2012

Background: The basal cell carcinoma (BCC) is the most common non-melanoma skin cancer (NMSK). BCC might develop because of the faulty cell cycle arrest. $p15^{INK4b}$ is a tumor suppressor gene, involved in cell cycle arrest and inactivated in most human cancers. The role of $p15^{INK4b}$ protein expression in the genesis of BCC is as yet unknown. In a previous study we showed the absence of $p15^{INK4b}$ expression in the majority of tissue microarray cores of cutaneous squamous cell carcinoma (SCCs), another type of non-melanoma skin cancer, indicating that $p15^{INK4b}$ could possibly be involved in the pathogenesis of cutaneous SCC. The aim of this study was to investigate $p15^{INK4b}$ protein expression in BCCs. Materials and Method: Protein expression of $p15^{INK4b}$ in 35 cases of BCC tissue arrays and 19 cases of normal human skin tissue was studied using an immunohistochemical approach. Results: The expression of $p15^{INK4b}$ was not significantly different in the BCC cases as compared with normal human skin (p=0.356; p>0.05). In addition, there were no significant relationship between clinicopathologic variables of patients (age and sex) and $p15^{INK4b}$ protein expression. Conclusions: Our finding may indicate that $p15^{INK4b}$ protein expression does not play a role in the genesis of BCC.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.5
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• pp.3011-3015
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• 2013

Objective: This study aimed to investigate the expression of B7-H4 in human thyroid cancer and determine any association with patient clinicopathological parameters and survival. Methods: B7-H4 expression in 64 clinical thyroid cancer specimens was assessed with immunohistochemistry. Moreover, B7-H4 mRNA expression in 10 fresh resected specimens were evaluated by the reverse transcription-polymerase chain reaction (RT-PCR). Immunohistochemical staining of CD3 was performed to assess the number of tumor infiltrating T lymphocytes (TILs) in thyroid cancers. Results: Positive B7-H4 immunohistochemical staining was observed in 61 out of 64 (95.3%) specimens of thyroid cancer tissues. Significantly more B7-H4 mRNA copies were found in thyroid cancer tissue than that adjacent normal tissue. Moreover, B7-H4 expression in human thyroid cancer tissues was significantly correlated with patient TNM stages and extrathyroidal extension (P<0.05), being inversely correlated with the number of TILs (P<0.05). The overall survival rate of the patients with higher B7-H4 expression was significantly worse than that of the patients with lower B7-H4 expression. Conclusions: This present study suggests that high B7-H4 expression is associated with cancer progression, reduced tumor immunosurveillance and worse patient outcomes in human thyroid cancer.

• Journal of Powder Materials
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• v.20 no.3
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• pp.215-220
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• 2013

In the present work, 6061 Al-$B_4C$ sintered composites containing different $B_4C$ contents were fabricated and their characteristic were investigated as a function of sintering temperature. For this, composite powders and their compacts with $B_4C$ various contents from 0 to 40 wt.% were fabricated using a planetary ball milling equipment and cold isostatic pressing, respectively, and then they were sintered in the temperature ranges of 580 to $660^{\circ}C$. Above sintering temperature of $640^{\circ}C$, real density was decreased due to the occurrence of sweat phenomena. In addition, it was realized that sinterability of 6061Al-$B_4C$ composite material was lowered with increasing $B_4C$ content, resulting in the decrease in its real density and at the same time in the increment of porosity.