• Journal of the Korean Ceramic Society
• /
• v.41 no.11
• /
• pp.864-871
• /
• 2004

Porous pseudo-boehmite gel was prepared through the aging process of amorphous aluminum hydroxides gel precipitated by the hydrolysis reaction of dilute NaOH solution and AlCl$_3$ solution. In this study, the synthesis method was studied on porous pseudo-boehmite gel having maximum pore volume, as being investigated the changes of crystal structure, infrared rays absorption spectrum, BET surface area and pore structure when the hydrolysis reaction is controlled in the range of pH 7.6~11.6 and the aging process is hold up for 2~24 h at 60~10$0^{\circ}C$. We could find that the gel precipitates deposited in in range of pH 7.6~9.6 were developed into porous pseudo-boehmite which surface area was 250~357 $m^2$/g, pore volume was 0.4~0.7 cc/g and average pore size was 58~l14$\AA$. However, the gel precipitates deposited in range of pH 10.6~11.6 were developed into bayerite which pore volume was very little.

• Nuclear Engineering and Technology
• /
• v.51 no.8
• /
• pp.2005-2012
• /
• 2019

This work investigated the radiation attenuation characteristics of three series of tellurite glass systems with the following compositions: 30PbO-10ZnO-xTeO₂-(60-x)B₂O₃ where x = 10, 30, 40, 50 and 60 mol%, xBaO-xB₂O₃-(100-2x)TeO₂ with x = 15-40 mol% and 50ZnO-(50-x)P₂O₅-xTeO₂, where x = 0, 10, .40 mol%. The results revealed that the attenuation parameters in all the samples decrease with increase in the energy, which implied that all the samples have better interaction with gamma photons at low energies and thus higher photon attenuating efficiency. From the three systems, the samples coded as PbZnBTe60, BaBTe70 and ZnPTe40 have the lowest half value layer values and accordingly have superior photon attenuation efficacy. The maximum effective atomic number values were found for energy less than 0.1 MeV particularly near the K-edges absorption of the heavy atomic number elements such as Te, Ba and Pb. At the lowest energy, the Z_eff values are found in the range of 62.33-66.25, 49.43-50.81 and 24.99-35.83 for series 1-3 respectively. Also, we found that the density of the glass remarkably affects the photon attenuation ability of the selected glasses. The mean free path results showed that the PbO-ZnO-TeO₂-B₂O₃ glass system has better radiation shielding efficiency than the glass samples in series 2 and 3.

• The Journal of Natural Sciences
• /
• v.19 no.1
• /
• pp.45-55
• /
• 2008

Alzheimer's disease is charaterized by the acetylcholine depletion, amyloid b-protein aggregation and neurofibrillary tangles. The prevention of the breakdown of acetylcholine by acetylcholinesterase (AChE) inhibitor has the best clinically therapeutic efficacy for Alzheimer's disease patients. To develop new antidementia alternative drugs or nutraceuticals, methanol extracts of Sorghum bicolor was screened from various extracts of cereals and legumes as a potent AChE inhibitor-containing extract in previous paper. In this paper, physicochemical properties of the methanol extracts was investigated. The methanol extracts was soluble by water, methanol and DMSO and had 215 nm and 282nm of maximum absorption spectra. It was also stable at 20-$100^{\circ}C$ and pH 2.0-10.0 for 1 hr. Test product was prepared by using methanol extracts from Sorghum bicolor and changes of its quality during storge at $20^{\circ}C$ and $40^{\circ}C$ were investigated. It was very stable for 8 weeks at $40^{\circ}C$.

• Journal of the East Asian Society of Dietary Life
• /
• v.15 no.4
• /
• pp.465-474
• /
• 2005

This study was conducted to estimate the contents of heavy metals 'mercury(Hg), cadmium(Cd), lead(Pb), arsenic(As), zinc(Zn), copper(Cu), chrome(Cr) and manganese(Mn)' in root vegetables which were produced in Korea. The levels of heavy metals were determined using a mercury analyzer, an ICP(inductively coupled plasma spectrometer) and an AAS(atomic absorption spectrophotometer) after wet digestion. The values of heavy metals 'mean(minimum-maximum)' mg/kg(ppm) in root vegetables (radish, turnip, carrot, ginger, edible burdock, taro, Chinese yam, east indian lotus) were as follows ; Hg : 0.0019(0.0002${\~}$0.0062), Cd : 0.0088(ND${\~}$0.0402), Pb : 0.021(ND${\~}$0.1070), As : 0.0401(ND${\~}$0.1732), Zn : 1.865(0.4186${\~}$6.9319), Cu : 0.648 (0.1826${\~}$4.0172), Cr : 0.121(0.0132${\~}$1.2030), and Mn : 2.730(0.0477${\~}$10.0468) mg/kg. These results showed that Hg were generally similar to and Cd was lower but Ph, As, Zn, Co, Mn were little higher than the levels of those reported contents in root vegetables on retail markets in Korea. Although the tolerable limit of Cd and Hg is not set in a regulation of WHO/FAO, the tested mean levels(Pb, As, Zn, Cu) were lower than the regulated ones of WHO/FAO, Pb '0.1-2.0', As '1.0', Zn '5.0', and Cu 0.1${\~}$50 mg/kg from vegetables. Therefore, root vegetables sold in the retail markets were evaluated as safe in terns of the heavy metal contents.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.1
• /
• pp.105-110
• /
• 2012

A europium (III)-sensitized, spectrofluorimetric (FL) method is presented for the determination of sparfloxacin (SPAR) using an anionic surfactant, sodium dodecyl benzene sulphonate (SDBS). The method is based on the strong fluorescence (FL) enhancement of SPAR after the addition of $Eu^{3+}$ ions as fluorescence probes. The experimental results indicated that the FL intensity of the SPAR-$Eu^{3+}$ system was enhanced markedly by SDBS. The maximum FL emission signal was obtained at about 615 nm when excited at 372 nm. The experimental conditions that affected the FL intensity of the SPAR-$Eu^{3+}$-SDBS system were optimized systematically. The enhanced FL intensity of the system exhibited a good linear relationship with the SPAR concentration over the range of $1.5{\times}10^{-9}-1.2{\times}10^{-7}mol\;L^{-1}$ with a correlation coefficient (r) of 0.9987. The limit of detection ($3{\delta}$) was $4.15{\times}10^{-10}mol\;L^{-1}$ with a relative standard deviation (RSD) of 1.65%. This method was successfully applied for the determination of SPAR in pharmaceuticals, and human serum and urine samples with higher sensitivity, wide dynamic range and better stability. The possible interaction mechanism of the system is also discussed in detail by ultraviolet absorption spectra and FL spectra.

• The Research Journal of the Costume Culture
• /
• v.18 no.2
• /
• pp.371-381
• /
• 2010

The pine needles can be used for four seasons in normal living and it can be taken friendly everywhere as it is distributed over 50% in Korea. The pine needles consist of vitamins, protein, minerals, essential oil and enzyme related to antimicrobial activity. It has effect like high blood pressure, neuralgia and hanged over by terpene, glucokinin, rutin, apigenic acid and tannin. Also the extract of them can be used for dyeing of fabrics. However, the extract components and effects of them are not well known yet. Therefore, the purpose of this study was to investigate the volatile components of the pine needles extract and functionality. The pine needles extract was dyed into various fabrics(nylon, silk, wool and soybean) and mordanted with Al, Cu, Cr, Fe and Sn. The extracted aroma compounds were compared by gas chromatography-mass spectrometry. The major volatile compounds of pine needles verified by using SPME were alpha-pinene, beta-pinene, beta-phellandrene, caryophyllene, ethanon, benzen. A total of 15 compounds were identified by using the SPME fibers. In the UV-visible spectra, the maximum absorption of wavelength of the pine needles ethanol extract appeared at 460, 630nm for chlorophyll component and at 237, 281nm for tannin component with the pine needles distilled water extract. Most of sample showed high antibacterial effect in none mordant but wool fabric showed high antibacterial effect in mordants. The result of UV block test showed a superior ability of blocking ultraviolet ray infiltration in all sample.

• Bulletin of the Korean Chemical Society
• /
• v.25 no.3
• /
• pp.365-372
• /
• 2004

Two simple, rapid and sensitive spectrophotometric methods for the determination of three fluoroquinolones, namely levofloxacin, norfloxacin and ciprofloxacin have been performed either in pure form or in their tablets. In the first method, levofloxacin and norfloxacin are directly treated with bromocresol green (BCG) in dichloromethane while ciprofloxacin is allowed to react with the same dye in aqueous acidic buffer. Highly yellow colored complex species were formed instantaneously in case of levofloxacin and norfloxacin or after extraction into dichloromethane for ciprofloxacin. The formed complexes are quantified spectrophotometrically at their absorption maxima at 411 nm for levofloxacin and 412 nm for norfloxacin and ciprofloxacin. The second method involves the reaction of levofloxacin with ${\rho}$-chloranilic acid ( ${\rho}$-CA) and norfloxacin with tetracyanoethylene (TCNE) in acetonitrile to give complexes with maximum absorbance at 521 and 333 nm for the two drugs, respectively. Adopting the first procedure, calibration graphs were linear over the range 1- 20 ${\mu}g\;mL^{-1}$ with mean percentage recoveries of 100.41 ${\pm}$ 0.72, 99.99 ${\pm}$ 0.54 and 100.23 ${\pm}$ 0.91 for the theree drugs, respectively. For the second procedure, the concentration ranges were 15-250 ${\mu}g\;mL^{-1}$ for levofloxacin using ${\rho}$-CA and 0.8-16 ${\mu}g\;mL^{-1}$ for norfloxacin using TCNE with mean percentage recoveries of 99.88 ${\pm}$ 0.45 and 100.26 ${\pm}$ 0.68 for the two drugs, respectively. The proposed methods were successfully applied to determine these drugs in their tablet formulations and the results compared favorably to that of reference methods. The proposed methods are recommended for quality control and routine analysis.

• Proceedings of the Korea Crystallographic Association Conference
• /
• 2003.05a
• /
• pp.8-8
• /
• 2003

Electron-phonon interaction plays a significant role in forming of colossal magnetoresistance effect (CMR). Polaron formation was observed by neutron diffraction and by extended X-ray absorption fine structure (EXAFS) analysis. Local probe as given by the EXAFS is a useful method to study the polaronic charge and its dependence on temperature and ions size. Here we present the EXAFS study of polaronic charge in La/sub 0.7/Ca/sub 0.3-X/Ba/sub X/MnO₃ compositions. The single phase La/sub 0.7/Ca/sub 0.3-X/Ba/sub X/MnO₃ manganites (x=0; 0.03; 0.06, ..., 0.3) were prepared by ceramic technology [1]. The Curie temperature was determined by extrapolation of the temperature dependence of the magnetization (down to zero magnetization). EXAFS experiments were carried out at the 7C EC beam line of the Pohang Light Source (PLS) in Korea. The atomic pair distribution functions (PDF) were obtained by re-regularization method [2] from filtered spectra. The PDF for the x=0.3 sample showed a single peak function and for x=0.0, 0.03, 0.06, 0.09, 0.12 compositions were asymmetric in agreement with a small Jahn-Teller elongation of two (short and long) bonds of the MnO/sub 6/ octahedron. Dispersion, σ/sub Min-O//sup 2/, and asymmetry, σ/sub Min-O//sup 3/, of the Mn-O bond distances varied significantly with x and showed a maximums at x=0.09. The maximum of σ/sub Min-O//sup 2/ is caused by increase of dynamic rms displacements of the Mn-O distances near the T/sub C/. The observed x dependence of σ/sub Min-O//sup 3/ reflects the reduction of charge carriers mobility at approaching to T/sub C/ from low as well as high temperatures.

• Journal of the Korean Magnetics Society
• /
• v.22 no.6
• /
• pp.210-215
• /
• 2012

The absorption performance of a metal-backed single layered electromagnetic wave absorber is optimized at matching conditions of thickness and frequency indicating the maximum returns loss of incidence electromagnetic wave in the contour map. These matching conditions are obtained by applying the electromagnetic impedance to the transmission line theory, which depend on the complex permeability and complex permittivity of absorber material. The magnetic materials with high permeability can enhance the matching thickness condition to the wide frequency range based on the decrease of permeability with frequency and it can be used as a wideband electromagnetic wave absorber material. Therefore, the magnetic materials with higher saturation magnetization and lower permittivity than NiZn ferrite can be applied to the wideband electromagnetic wave absorber in order to satisfy the newly enforcing the electromagnetic compatibility regulation in the future.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.105-106
• /
• 2013

Surface plasmon resonance (SPR) is classified into the propagating surface plasmon (PSP) excited on flat metal surfaces and the local surface plasmon (LSP) excited by metalnanoparticles. It is known that fluorescence signals are enhanced by these two SPR-fields.On the other hand, fluorescence is quenched by the energy transfer to metal (FRET). Bothphenomena are controlled by the distance between dyes and metals, and the degree offluorescence enhancement is determined by the correlation. In this study, we determined thecondition to achieve the maximum fluorescence enhancement by adjusting the distance of ametal nanoparticle 2D sheet and a quantum dots 2D sheet by the use of $SiO_2$ spacer layers. The 2D sheets consisting of myristate-capped Ag nanoparticles (AgMy nanosheets) wereprepared at the air-water interface and transferred onto hydrophobized gold thin films basedon the Langmuir-Schaefer (LS) method [1]. The $SiO_2$ sputtered films with different thickness (0~100 nm) were deposited on the AgMy nanosheet as an insulator. TOPO-cappedCdSe/CdZnS/ZnS quantum dots (QDs, ${\lambda}Ex=638nm$) [2] were also transferred onto the $SiO_2$ films by the LS method. The layered structure is schematically shown in Fig. 1. The result of fluorescence measurement is shown in Fig. 2. Without the $SiO_2$ layer, the fluorescence intensity of the layered QD film was lower than that of the original QDs layer, i.e., the quenching by FRET was predominant. When the $SiO_2$ thickness was increased, the fluorescence intensity of the layered QD film was higher than that of the original QDs layer, i.e., the SPR enhancement was predominant. The fluorescence intensity was maximal at the $SiO_2$ thickness of 20 nm, particularly when the LSPR absorption wavelength (${\lambda}=480nm$) was utilized for the excitation. This plasmonic nanosheet can be integrated intogreen or bio-devices as the creation point ofenhanced LSPR field.