• Bulletin of the Korean Mathematical Society
• /
• v.51 no.5
• /
• pp.1241-1257
• /
• 2014

We consider a class of hypoelliptic operators of the following type $$L=\sum_{i,j=1}^{p_0}a_{ij}{\partial}^2_{x_ix_j}+\sum_{i,j=1}^{N}b_{ij}x_i{\partial}_{x_j}-{\partial}_t$$, where ($a_{ij}$), ($b_{ij}$) are constant matrices and ($a_{ij}$) is symmetric positive definite on $\mathbb{R}^{p_0}$ ($p_0{\leqslant}N$). By establishing global Morrey estimates of singular integral on the homogenous space and the relation between Morrey space and weak Morrey space, we obtain the global weak Morrey estimates of the operator L on the whole space $\mathbb{R}^{N+1}$.

• Journal of Applied Biological Chemistry
• /
• v.48 no.2
• /
• pp.101-104
• /
• 2005

DXS catalyzes the first step of MEP pathway. Escherichia coli disruptants defective in dxs were constructed by insertional mutation and characterized. Selected disruptant, DXM3, was auxotrophic for DX or ME. Putative class 1 DXS ORF from Ginkgo biloba was shown to rescue DXM3 grown without DX or ME supplementation. The putative ORF was thus confirmed as DXS1. The disruptant was demonstrated to be useful for DSX screening.

• Journal of Information Display
• /
• v.9 no.3
• /
• pp.16-22
• /
• 2008

A novel class of conjugated dendritic molecules bearing N-hexyl-substituted carbazoles as peripheral groups and various conjugative aromatic cores was synthesized through Heck coupling and the Horner-Emmons reaction. A multilayered structure of ITO/PEDOT:PSS (30 nm)/emitting material (50 nm)/BCP (10 nm)/$Alq_3$ (10 nm)/LiF (1 nm)/Al (100 nm) was employed to evaluate the synthesized dendritic materials. The electroluminescence spectrum of the multilayered device made of 3Cz predominantly exhibited blue emissions. Similar emissions were observed in the PL spectra of it's the device's thin film. The multilayered devices made of 3Cz, 3BCz, and 4BCz showed luminance values of 6,250 cd $m^{-2}$ at 24 V, 3,000 cd $m^{-2}$ at 25 V, and 1,970 cd $m^{-2}$ at 36 V, respectively. The smallest molecule, 3Cz, which bore three carbazole peripheral groups, exhibited a blue-like emission with CIE 1931 chromaticity coordinates of x = 0.17 and y = 0.21.

• Bulletin of the Korean Chemical Society
• /
• v.30 no.12
• /
• pp.2899-2904
• /
• 2009

Esterification is an important class of reactions in the preparation of perfumery and flavor chemicals, wherein homogeneous, solid acidic, and superacidic catalysts are normally used. Now, an efficient and selective protocol for protection of various functionalized alcohols employing carboxylic acids as protecting agents is realized through the catalytic mediation of simple heteropolyoxometallates. In this methodology, water is the only by-product and notably the aspect of effluent treatments does not arise. The advantages include the operational simplicity, recycle ability of the catalyst and mild reaction conditions. The present catalytic system may be a potential candidate not only for laboratory practice but also for commercial applications and offers an environmentally safer alternative to the existing processes.

• Journal of the Korean Chemical Society
• /
• v.60 no.1
• /
• pp.69-81
• /
• 2016

The purpose of this study was to find out the validation of instructional strategies using the Advanced Laboratory Equipment (ALE class) by investigating science high school students’ perception on ALE in chemistry classrooms and to consider the need for development of teaching materials on ALE class. 7 sessions of ALE including experiments with innovative equipment were developed and applied to 21 students in D Science High School. At the end of the sessions, questionnaire was given to the students. We also collected qualitative data by interviewing 9 students who participated in the questionnaire. We analyzed the data collected by In-depth interviews and students’ experimental reports. The result showed that ALE class was effective to enhance students’ understanding of learning concepts because the experimental time was shortened in real time data processing. Some students showed creative performance on solving scientific problems by using everyday materials in experimental process and developed perceptions of practical inquiry. Through this process, students’ positive attitudes and interests in science and heuristic inquiry skills were also enhanced. Developing ALE lesson materials will be helpful for students to understand science and technology and the domain of science in broader contexts.

• Journal of Ginseng Research
• /
• v.44 no.1
• /
• pp.14-23
• /
• 2020

Ginseng has been used as a popular herbal medicine in East Asia for at least two millennia. However, 20(R)-ginseng saponins, one class of important rare ginsenosides, are rare in natural products. 20(R)-ginseng saponins are generally prepared by chemical epimerization and microbial transformation from 20(S)-isomers. The C20 configuration of 20(R)-ginseng saponins are usually determined by ¹³C NMR and X-ray single-crystal diffraction. 20(R)-ginseng saponins have antitumor, antioxidative, antifatigue, neuroprotective, and osteoclastogenesis inhibitory effects, among others. Owing to the chemical structure and pharmacological and stereoselective properties, 20(R)-ginseng saponins have attracted a great deal of attention in recent years. In this study, the discovery, identification, chemical epimerization, microbial transformation, pharmacological activities, and metabolism of 20(R)-ginseng saponins are summarized.

• Parasites, Hosts and Diseases
• /
• v.45 no.3
• /
• pp.239-243
• /
• 2007

Many allergists are currently focusing on the development of new diagnostic tools, and are attempting to improve both the sensitivity and specificity. A multiple allergen simultaneous test-chemiluminescent assay (MAST-CLA) is one of the most popular diagnostic tools used in the Republic of Korea. However, there remains controversy among allergists with regard to the cut-off point for a positive result. The present study was conducted in order to determine the validity of MAST-CLA as compared with that of the skin prick test, with particular emphasis on arthropod allergens, on the basis of percentage agreement rates and k-values, and also to suggest the optimal positive cutoff points using receiver operating characteristic (ROC) curves. The study was conducted with 97 subjects (54 men, 43 women). Optimal individual cut-off points were calculated as follows; class II for Dermatophagoides farinae, class I for Dermatophagoides pteronyssinus, and trace for a cockroach mix. These findings suggest that attempting to apply optimal individual cut-off points will be a good way of improving diagnostic tests, particularly MAST-CLA.

• Biomedical Science Letters
• /
• v.10 no.2
• /
• pp.137-142
• /
• 2004

The peroxisome proliferator-activated receptor $\gamma$ (PPAR${\gamma}$) is the molecular target for a class of drugs, the antidiabetic thiazolidnediones (TZDs). The heterodimer of PPAR${\gamma}$ with retinoid X receptor (RXR) plays a central role in the regulation of adipogenesis and insulin sensitization. We synthesized two chemicals, DANA87 and DANA88, sharing structural characteristics with TZDs. Given this structural similarity, it was hypothesized that DANA87 and DANA88 may act as PPAR$\gamma$ ligands. In transient transfection assays, DANA87 and DANA88 caused slight increases in the endogenous expression of a luciferase reporter gene containing the PPAR responsive element in 3T3-L1 preadipocytes. However, DANA87 and DANA88 significantly inhibited troglitazone-induced reporter gene activation when cells were treated with a combination of DANA87 or DANA 88 and troglitazone, one of the TZDs that activate PPAR$\gamma$. These results suggest that DANA87 and DANA88 are not only weak agonists of PPAR${\gamma}$ transactivation, but also competitively antagonize troglitazone-induced PPAR$\gamma$ reporter activity.

• Journal of Microbiology and Biotechnology
• /
• v.25 no.5
• /
• pp.629-636
• /
• 2015

Chemical investigation of the actinobacterial isolate Pseudonocardia endophytica VUK-10 has led to the segregation of two known bioactive compounds, namely 4-(2-acetamidoethyl) phenyl acetate and 4-((1, 4-dioxooctahydropyrrolo [1, 2-a] pyrazin-3-yl) methyl) phenyl acetate. The strain was isolated from a sediment sample of the Nizampatnam mangrove ecosystem, south coastal Andhra Pradesh, India. The chemical structure of the active compounds was established on the basis of spectroscopic analysis, including ¹H NMR and ¹³C NMR spectroscopies, FTIR, and EIMS. The antimicrobial and cytotoxic activities of the bioactive compounds produced by the strain were tested against opportunistic and pathogenic bacteria and fungi and on MDA-MB-231, OAW, HeLa, and MCF-7 cell lines. The compounds exhibited antimicrobial activities against gram-positive and gram-negative bacteria and fungi and also showed potent cytotoxic activity against MDA-MB-231, OAW, HeLa, and MCF-7 cell lines. This is the first example for this class of bioactive compounds isolated from Pseudonocardia of mangrove origin.

• Journal of the Korean Chemical Society
• /
• v.46 no.5
• /
• pp.450-468
• /
• 2002

As the computer is popularized in individual and society, it is using in a many of area. In particular, there are many materials to learn a science knowledge using multimedia through computer. Many of them are web-based learning materials, which are developed by Java or Flash. Since the technology of the representation, storage, com-putation and communication in computer make progress, the environment of education is also developed. Especially, the internet and VR technology will cause the education to change. A key feature of VR is real-time interactivity, in that the computer is able to detect student input and instantaneously modify the virtual world. It is reported that using the VR simulation in chemistry education can increase student engagement in class, promote understanding of basic chem-ical principles, and augment laboratory experience. In this study, application way of the virtual reality technology in chemistry education is examined.