• Bulletin of the Korean Chemical Society
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• 제31권7호
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• pp.1875-1880
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• 2010

A dicycle pyrazoline derivative, 1-phenyl-5-(p-fluorophenyl)-3,4-($\alpha$-p-fluoro-tolylenecyclohexano) pyrazoline, was synthesized and characterized by elemental analysis, IR, UV-vis, fluorescence spectra and X-ray single crystal diffraction. Density function theory (DFT) calculations were performed by using B3LYP method with 6-$311G^{**}$ basis set. The optimized geometry can well simulate the molecular structure. Vibrational frequencies were predicted, assigned and compared with the experimental values, which suggest that B3LYP/6-$311G^{**}$ method can well predict the IR spectra. Both the experimental electronic absorption spectra and the predicted ones by B3LYP/6-$311G^{**}$ method reveal three electron-transition bands, with the theoretical ones having some red shifts compared with the experimental data. Natural bond orbital analyses indicate that the absorption bands are mainly derived from the contribution of n $\rightarrow\pi^*$ and $\pi\rightarrow\pi^*$ transitions. Fluorescence spectra determination shows that the title compound can emit blue-light at about 478 nm. On the basis of vibrational analysis, the thermodynamic properties of title compound at different temperature have been calculated, revealing the correlations between $C^0_{p,m}$, $S^0_m$, $H^0_m$ and temperature.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.542-547
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• 2001

A non-intrusive Planar Laser-Induced Fluorescence(PLIF) technique was applied to study the turbulent mixing process in a Rushton turbine reactor. Instantaneous and ensemble averaged concentration fields are obtained by measuring the fluorescence intensity of Rhodamine B tracer excited by a thin Nd:Yag laser sheet illuminating the whole center plane of the stirred tank. The gray level images captured by a 14-bit cooled CCD camera can be transformed to the local concentration values using a calibration matrix. The dye injection point was selected at the tank wall with three quarter height (3/4H) from the tank bottom to observe the mixing characteristics in upper bulk flow region. There exist distinct two time scales: the rapid decay of mean concentration in each region after the dye infusion reflects the large scale mixing while the followed slow decay reveals the small scale mixing. The temporal change of concentration probability functions conjectures the two sequential processes in the batch type mixing. An inactive column of water existed above the impeller disk, in which the fluid rotates with the shaft but is isolated from the mean bulk flow.

• 대한기계학회논문집B
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• 제26권8호
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• pp.1145-1152
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• 2002

A non-intrusive Planar Laser-Induced Fluorescence(PLIF) technique was applied to study the turbulent mixing process in a Rushton turbine reactor. Instantaneous and ensemble averaged concentration fields was obtained by measuring the fluorescence intensity of Rhodamine B tracer excited by a thin Nd:Yag laser sheet illuminating the whole center plane of the stirred tank. The gray level images captured by a 14-bit cooled CCD camera could be transformed to the local concentration values using a calibration matrix. The dye injection point was selected at the tank wall with three quarter. height (3/4H) from the tank bottom to observe the mixing characteristics in upper bulk flow region. There exist distinct two time scales: the rapid decay of mean concentration after the dye infusion reflects the large scale turbulent mixing while the fellowed slow decay reveals the small scale molecular mixing. The temporal change of concentration variance field conjectures the two sequential processes for the batch type mixing. An inactive column of water is existed above the impeller disk, in which the fluid rotates with the shaft but is isolated from the mean bulk flow.

• Journal of Photoscience
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• 제12권2호
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• pp.87-93
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• 2005

A new assay technique to distinguish between pure compounds and the isomeric mixtures has been suggested using single molecule (SM) fluorescence detection technique. Since the number of emission spots in a fluorophorespread film prepared from a genuine dye solution was determined by experimental condition, the deviation of spot numbers from the expected values could be considered to be an indication of lower purity of the sample solution. The lower limit of sample concentration for this assay was determined to be $5{\times}10^{-10}$ M to show uniform number of expected spots within 10% uncertainties in our experimental condition. An individual fluorescence intensity distribution for a mixture of isomers having doubly different emissivities was simulated by adding distributions obtained from Cy3 and nile red (NR) independently. The result indicated that the mixture could be identified from the pure compounds through the difference in the number of Gaussian functions to fit the distribution. This new assay technique can be applied to the purity test for synthetic biofluorophores which are usually prepared in small quantities not enough for classical ensemble assays.

• Food Science and Biotechnology
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• 제18권4호
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• pp.978-984
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• 2009

An analytical method for the simultaneous determination of 9 quinolones (QNs) in porcine, chicken, and bovine muscles was developed and validated using liquid chromatography-fluorescence detector (LC-FLD). The samples were extracted using a liquid-liquid extraction (LLE) process. Chromatographic separation was achieved on a reverse phase $C_8$ column with a gradient elution using a mobile phase of 200 mM ammonium acetate buffer (pH 4.5) and acetonitrile (ACN). The proposed method was validated according to the Food and Drug Administration (FDA) guideline for bioanalytical assay procedures. Recoveries of QNs were 83.1-111.9% with relative standard deviations (RSDs) below 15%. Linearity within a range of 30-500 ${\mu}g/kg$ was obtained with the correlation coefficient ($R^2$) of 0.9967-0.9999. The limits of detection (LOD) were 1-16 ${\mu}g/kg$. These values were lower than the maximum residues limits (MRLs) established by the European Union (EU). The present method was successfully applied to determine QNs in edible muscles.

• 한국환경과학회지
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• 제13권4호
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• pp.359-365
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• 2004

The change of chlorophyll fluorescence parameters, O-J-I-P transients and psbA gene expression were investigated in the leaves of Crinum asiaticum var. japonicum on the natural condition in winter, in order to elucidate physiological responses of photosystem II (PS II) activity to winter stresses. The photochemical efficiencies of PS II, Fv/Fm, were significantly low in winter, contrary to its high value in summer. The values of I -qN and I-qP were lower in midday than at dawn or night both in summer and winter, although their decrease in midday was less in winter than in summer. In the O-J-I-P transients, the fluorescence intensity of J, I, P-step decreased remarkably depending on temperature drop in winter. And the D I reaction center protein of PS II decreased in late winter more than in early winter, concomitantly with relatively high content of description products of psbA gene in midday. These results indicate that low temperature in winter causes irreversible damage to PS II and subsequently leads to cell death.

• Journal of Astronomy and Space Sciences
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• 제35권1호
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• pp.7-18
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• 2018

We have investigated the intensities and full width at half maximum (FWHM) of the high dispersion spectroscopic N III emission lines of AG Peg, observed with the Hamilton Echelle Spectrograph (HES) in three different epochs at Mt. Hamilton's Lick Observatory. The earlier theoretical Bowen line study assumed the continuum fluorescence effect, presenting a large discrepancy with the present data. Hence, we analyzed the observed N III lines assuming line fluorescence as the only suitable source: (1) The O III and N III resonance line profiles near ${\lambda}$ 374 were decomposed, using the Gaussian function, and the contributions from various O III line components were determined. (2) Based on the theoretical resonant N III intensities, the expected N III Bowen intensities were obtained to fit the observed values. Our study shows that the incoming line photon number ratio must be considered to balance at each N III Bowen line level in the ultraviolet radiation according to the observed lines in the optical zone. We also found that the average FWHM of the N III Bowen lines was about $5km{\cdot}s^{-1}$ greater than that of the O III Bowen lines, perhaps due to the inherently different kinematic characteristics of their emission zones.

• Structural Monitoring and Maintenance
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• 제9권3호
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• pp.259-270
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• 2022

This study explores the use of the recently developed "strain-sensing smart skin" (S⁴) method for noncontact strain measurements on cement-based samples. S⁴ sensors are single-wall carbon nanotubes dilutely embedded in thin polymer films. Strains transmitted to the nanotubes cause systematic shifts in their near-infrared fluorescence spectra, which are analyzed to deduce local strain values. It is found that with cement-based materials, this method is hampered by spectral interference from structured near-infrared cement luminescence. However, application of an opaque blocking layer between the specimen surface and the nanotube sensing film enables interference-free strain measurements. Tests were performed on cement, mortar, and concrete specimens with such modified S⁴ coatings. When specimens were subjected to uniaxial compressive stress, the spectral peak separations varied linearly and predictably with induced strain. These results demonstrate that S⁴ is a promising emerging technology for measuring strains down to ca. 30 𝜇𝜀 in concrete structures.

• Bulletin of the Korean Chemical Society
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• 제4권1호
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• pp.45-47
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• 1983

In order to standardize the ${\sigma}^*,\;{\rho}^*$ is taken as unity for the benzoic acids by analogy with the fact that ${\rho}$ of benzoic acids in the ground state is taken as unity. The $pK_{\alpha}^*$ of many benzoic acid derivatives are determined by UV spectroscopy and fluorescence spectral analysis whenever possible. The ${\sigma}^*$ constants are derived from the Hammett equation utilizing these $pK_{\alpha}^*$ values and the $pK_{\alpha}^*$ of the benozic acid derivatives showed better correlationship with ${\sigma}^*$ than ${\sigma},\;{\sigma}^+\;and\;{\sigma}^-$ as expected. From these ${\sigma}^*$ values, ${\rho}^*$ of the phenol derivatives was calculated to be 1.28. The new standardized ${\sigma}^*$ values are calculated from the $pK_{\alpha}^*$ values of phenols since more accurate and abundant data are available for phenols than the benzoic acid derivatives.

• Bulletin of the Korean Chemical Society
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• 제29권1호
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• pp.197-201
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• 2008

Conformational heterogeneity of directly linked multiporphyrin arrays with larger molecular length retards their utilities in practical applications such as two-photon absorption and molecular photonic wire. In this regard, here we adopted a way to overcome the conformational heterogeneity through hydrogen bonding by selective binding of meso aryl substituents of porphyrins (host) with urea (guest) to form helical structure. Using steady-state and time-resolved spectroscopy, we observed the enhanced fluorescence quantum yield by ~1.8 to 2.4 times, enhanced anisotropy values and the disappearance of fast fluorescence decay component in the host-guest helical forms. In addition, the enhanced nonlinear optical responses of helical arrays infer the extended inter-porphyrin electronic coupling due to a significant change in dihedral angle between the neighboring porphyrin moieties. The current host-guest strategy will provide a guideline to improve the structural homogeneity of the photonic wire.