• Mass Spectrometry Letters
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• 제14권4호
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• pp.147-152
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• 2023

The increasing demand for two-dimensional imaging analysis using optical or electronic microscopic techniques has led to an increase in the use of simple one-dimensional and two-dimensional mass spectrometry imaging. Among these imaging methods, secondary-ion mass spectrometry (SIMS) has the best spatial resolution using a primary ion beam with a relatively insignificant beam diameter. Until recently, SIMS, which uses high-energy primary ion beams, has not been used to analyze molecules. However, owing to the development of cluster ion beams, it has been actively used to analyze various organic molecules from the surface. Researchers and commercial SIMS companies are developing cluster ion beams to analyze biological samples, including amino acids, peptides, and proteins. In this study, a water droplet ion beam for surface analysis was realized. Water droplets ions were generated via electrospraying in a vacuum without desolvation. The generated ions were accelerated at an energy of 10 keV and collided with the target sample, and secondary ion mass spectra were obtained for the generated ions using ToF-SIMS. Thus, the proposed water droplet ion-beam device showed potential applicability as a primary ion beam in SIMS.

• 한국염색가공학회지
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• 제12권1호
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• pp.52-60
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• 2000

In the prior studies, we reported that the dye uptakes of C. I. Disperse Violet 1 on polyester fiber in hexane and cyclohexane were higher than those in the other solvents, as the number of carbon atoms of alkanes decreased, the dye uptake increased, and the logarithmic plot of the dye uptakes vs. the solubilities of the dye showed that the dye uptakes are inversely proportional to the solubilities. In this study, for Interpretation of dyeing behavior of C. I. Disperse Violet 1 on polyester in alkanes, the thremodynamic parameters of dyeing, such as standard affnity, heat of dyeing(enthalpy change), entropy change, diffusion coefficient, and activation energy of diffusion, were obtained from isotherms and dyeing rates at different temperature. As the number of carbon atoms of alkanes increased, the standard affinity decreased, but the heat of dyeing(enthalpy change) and the entropy change showed larger negative values. These results mean that as the number of carbon atoms of alkanes increases, the dye uptake decreases, but both the fraction of the dye molecules dyed at relatively highly aligned or compact region of polyester fiber and the regularity of dye aggregates in the fiber become increased. As the number of carbon atoms of alkanes increased, the diffusion coefficient decreased, but the activation energy of diffusion increased. In the alkane of larger number of carbon atoms, because the solubility of the dye is higher, the desorption rate of the dye is faster and the diffusion coefficient is smaller than those in the smaller alkanes. But the energy required to separate the dye molecules from the alkane molecules is much higher because the interaction between the alkane molecule and the dye molecule become strong with the number of carbon atoms.

• Toxicological Research
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• 제31권2호
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• pp.97-104
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• 2015

The skin exposure to solar irradiation and photoreactive xenobiotics may produce abnormal skin reaction, phototoxicity. Phototoxicity is an acute light-induced response, which occurs when photoreacive chemicals are activated by solar lights and transformed into products cytotoxic against the skin cells. Multifarious symptoms of phototoxicity are identified, skin irritation, erythema, pruritis, and edema that are similar to those of the exaggerated sunburn. Diverse organic chemicals, especially drugs, are known to induce phototoxicity, which is probably from the common possession of UV-absorbing benzene or heterocyclic rings in their molecular structures. Both UVB (290~320 nm) and UVA (320~400 nm) are responsible for the manifestation of phototoxicity. Absorption of photons and absorbed energy (hv) by photoactive chemicals results in molecular changes or generates reactive oxygen species and depending on the way how endogenous molecules are affected by phototoxicants, mechanisms of phototoxcity is categorized into two modes of action: Direct when unstable species from excited state directly react with the endogenous molecules, and indirect when endogeneous molecules react with secondary photoproducts. In order to identify phototoxic potential of a chemical, various test methods have been introduced. Focus is given to animal alternative test methods, i.e., in vitro, and in chemico assays as well as in vivo. 3T3 neutral red uptake assay, erythrocyte photohemolysis test, and phototoxicity test using human 3-dimensional (3D) epidermis model are examples of in vitro assays. In chemico methods evaluate the generation of reactive oxygen species or DNA strand break activity employing plasmid for chemicals, or drugs with phototoxic potential.

• 천문학회보
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• 제44권1호
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• pp.70.4-70.4
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• 2019

Complex organic molecules (COMs) are increasingly observed in the environs of young stellar objects (YSOs), including hot cores/corinos around high-mass/low-mass protostars and protoplanetary disks. It is widely believed that COMs are first formed in the ice mantle of dust grains and subsequently released to the gas by thermal sublimation at high temperatures (T>100 K) in strong stellar radiation fields. In this paper, we report a new mechanism that can desorb COMs from icy grain mantles at low temperatures (T<100K), which is termed rotational desorption. The rotational desorption process of COMs comprises two stages: (1) ice mantles on suprathermally rotating grains spun-up by radiative torques (RATs) are first disrupted into small fragments by centrifugal stress, and (2) COMs and water ice then evaporate rapidly from the tiny fragments (i.e., radius a <1nm) due to thermal spikes or enhanced thermal sublimation due to increased grain temperature for larger fragments (a>1 nm). We discuss the implications of rotational desorption for releasing COMs and water ice in the inner region of protostellar envelopes (hot cores and corinos), photodissociation regions, and protoplanetary disks (PPDs). In shocked regions of stellar outflows, we find that nanoparticles can be spun-up to suprathermal rotation due to supersonic drift of neutral gas, such that centrifugal force can be sufficient to directly eject some molecules from the grain surface, provided that nanoparticles are made of strong material. Finally, we find that large aggregates (a~ 1-100 micron) exposed to strong stellar radiations can be disrupted into individual icy grains via RAdiative Torque Disruption (RATD) mechanism, which is followed by rotational desorption of ice mantles and evaporation of COMs. In the RATD picture, we expect some correlation between the enhancement of COMs and the depletion of large dust grains in not very dense regions of YSOs.

• Journal of Ginseng Research
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• 제48권4호
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• pp.366-372
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• 2024

Background: The biological activity and pharmacological effects of rare ginsenosides have been proven to be superior to those of the major ginsenosides, but they are rarely found in ginseng. Methods: Ginsenoside Rb1 was chemically transformed with the involvement of methanol molecules by a synthesized heterogeneous catalyst 12-HPW@MeSi, which was obtained by the immobilization of 12-phosphotungstic acid on a mesoporous silica framework. High-performance liquid chromatography coupled with mass spectrometry was used to identify the transformation products. Results: A total of 18 transformation products were obtained and identified. Methanol was found to be involved in the formation of 8 products formed by the addition of methanol molecules to the C-24 (25), C-20 (21) or C-20 (22) double bonds of the aglycone. The transformation pathways of ginsenoside Rb1 involved deglycosylation, addition, elimination, cycloaddition, and epimerization reactions. These pathways could be elucidated in terms of the stability of the generated carbenium ion. In addition, 12-HPW@MeSi was able to maintain a 60.5% conversion rate of Rb1 after 5 cycles. Conclusion: Tandem and high-resolution mass spectrometry analysis allowed rapid and accurate identification of the transformation products through the characteristic fragment ions and neutral loss. Rare ginsenosides with methoxyl groups grafted at the C-25 and C-20 positions were obtained for the first time by chemical transformation using the composite catalyst 12-HPW@MeSi, which also enabled cyclic heterogeneous transformation and facile centrifugal separation of ginsenosides. This work provides an efficient and recyclable strategy for the preparation of rare ginsenosides with the involvement of organic molecules.

• 한국인쇄학회지
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• 제23권1호
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• pp.77-97
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• 2005

Organic light-emitting diodes(OLEDs) have received considerable attention since they were first reported by Tang. Novel organic fluorescent materials have been reported on synthesis and application of new organic light-emitting materials. Despite of much recent progress, fabrication of full-color OLEDs still remained to be done. Many method have been proposed to full-color OLEDs displays such as using separated red, green and blue emitters, stacking separate rad, green and blue emitter, using a white emitter with individually pattered color filters, microcavity structures and using a blue emitter with individually patterned fluorescent materials. The last method has much attention because of easy fabrication of OLEDs and low-priced fabrication. This paper reports the optical and electrical characteristics of OLEDs using novel molecules containing biphenyl structure. Optical properties of biphenyl derivatives doped with poly(9-vinyl carbazole)(PVK) are measured and found Forster energy transfer process in the blends. And devices were fabricated as ITO/PEDOT/PVK doped with biphenyl derivatives/$Alq_3$/Li:Al and I-V-L characteristics and EL efficiency of devices were examined.

• 한국환경과학회지
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• 제22권10호
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• pp.1263-1271
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• 2013

Graphene oxide (GO)-titania composites have emerged as an attractive heterogeneous photocatalyst that can enhance the photocatalytic activity of $TiO_2$ nanoparticles owing to their potential interaction of electronic and adsorption natures. Accordingly, $TiO_2$-GO mixtures were synthesized in this study using a simple chemical mixing process, and their heterogeneous photocatalytic activities were investigated to determine the degradation of airborne organic pollutants (benzene, ethyl benzene, and o-xylene (BEX)) under different operational conditions. The Fourier transform infrared spectroscopy results demonstrated the presence of GO for the $TiO_2$-GO composites. The average efficiencies of the $TiO_2$-GO mixtures for the decomposition of each component of BEX determined during the 3-h photocatalytic processes were 26%, 92%, and 96%, respectively, whereas the average efficiencies of the unmodified $TiO_2$ powder were 3%, 8%, and 10%, respectively. Furthermore, the degradation efficiency of the unmodified $TiO_2$ powder for all target compounds decreased during the 3-h photocatalytic processes, suggesting a potential deactivation even during such a short time period. Two operational conditions (air flow entering into the air-cleaning devices and the indoor pollution levels) were found to be important factors for the photocatalytic decomposition of BEX molecules. Taken together, these results show that a $TiO_2$-GO mixture can be applied effectively for the purification of airborne organic pollutants when the operating conditions are optimized.

• 환경위생공학
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• 제13권1호
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• pp.16-25
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• 1998

Laboratory-scale experiment using anaerobic fluidized bed reactor was carried out to investigate the prehydrolysis step with caustic soda on the treatment efficiency of anaerobic sludge treatment, since the overall rate-limiting step for the complete anaerobic digestion of sludge was the hydrolysis step by extracellular bacterial enzymes of insoluble polymeric molecules. Reactors received a sludge which had not been pretreated, a 50-50 mixture of pretreated and untreated sludge, and the fully pretreated sludge. Hydraulic retention time of 10, 5, 2.5 days and 1 day were applied with an respective equivalent organic loading rate of 1.17, 2.23, 4.17, 11.24 gCOD/L/d. Reactor with the untreated sludge did not archieve adequate digestion even at the HRT of 5 days, and reactor, which received the 50-50 mixture, operated well at the HRT of 5 days, but began to show signs of unstable digestion at the HRT of 2.5 days. While, reactor, which was fed the hydrolyzed sludge, operated reasonably well at the 2.5 days, but was showing somewhat decrease in removal efficiencies. Results, therefore, have substantiated that the limiting reaction in the anaerobic treatment process is hydrolysis. The soluble COD did not significantly accumulate in the reactor as organic acid form, even when they were highly stressed. It was believed that this resistance to a build-up of organic acids and soluble COD behavior was mainly due to the maintenance of the methane bacteria in the fixed-film system which prevents washout as the organic loading increased. The anaerobic fluidized bed reactor was therefore effective for the digestion of waste activated sludge at short HRT.

• 한국환경농학회지
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• 제3권1호
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• pp.22-29
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• 1984

토양(土壤)에 의한 linuron, bentazon, trifluralin 및 butachlor의 흡착(吸着)을 나타내는데 있어서 Freundlich adsorption isotherm이 사용되었으며, 실험결과(實驗結果)를 요약(要約)하면 아래와 같다. 토양(土壤)에 의한 linuron의 흡착(吸着)은 토양성분중(土壤成分中) 유기물(有機物)의 함량(含量)과 직접적인 관계(關係)가 있으며, 유기물(有機物)의 함량(含量)이 증가(增加)함에 따라 linuron의 흡착(吸着)도 증가(增加)하였다. Bentazon은 토양유기물(土壤有機物)이나 점토(粘土)의 함량(含量)에 따라 뚜렷한 상관(相關)이 없었으며, 오히려 유기물함양(有機物含量)이 증가(增加)됨에 따라 흡착(吸着)은 감소(減少)하는 경향(傾向)이었다. 이러한 현상은 bentazon이 토양용액중(土壤溶液中)에서 음하전(陰荷電)을 띠어 bentazon분자(分子)와 음하전(陰荷電)을 띤 토양표면간(土壤表面間)의 반발현상(反撥現象) 때문인 것으로 추정(推定)되었다. Trifluralin과 butachlor는 토양유기물함량(土壤有機物含量) 및 C.E.C.와 매우 높은 상관성(相關性)을 보였으나, 점토함량(粘土含量)과는 뚜렷한 경향(傾向)이 없었다. 각 공시농약(供試農藥)에 대한 흡착(吸着)은 trifluralin이 가장 많았고 다음으로는 linuron, butachlor, bentazon순(順) 이었다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2000년도 제1회 학술대회 논문집
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• pp.205-206
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• 2000

The capacitance-temperature (C-T) measurement technique is proposed in the present work to investigate the thermal stability of organic and polymeric thin films for organic electroluminescent display (OELD). The single layer devices with the individual materials were subjected to the C-T measurement, prior to the examination of the complete OELD. The single layer devices with the small molecules destroyed below $180\;^{\circ}C$ depending on the kinds of materials. However, the device with the hole-transporting polyimide did not show any relaxation up to $200\;^{\circ}C$. The small molecule based OELDs failed to emit light after annealing, whereas that with the hole-transporting polyimide worked well in spite of large reduction in intensity.