• Korean Journal of Environmental Agriculture
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• v.33 no.4
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• pp.344-349
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• 2014

BACKGROUND: Purpose of the study was to establish the extinction coefficients of chlorophyll a and b in N,N-dimethylformamide(DMF) and Dimethylsulfoxide(DMSO) solvents and to find out the conditions of optimal extraction temperature and time in citrus leaves. METHODS AND RESULTS: Chlorophyll a and b standards were dissolved in DMF and DMSO. Extinction coefficients of chlorophyll pigments were determined and their contents were quantified using spectrophotometer. Chlorophyllous pigments of citrus(Citrus unshiu Marc. cv. Okitsu wase) leaves were extracted at 25, 40, 60 and $80^{\circ}C$ for 4, 6, 8, 24 and 48 hours to determine the optimal extraction condition. CONCLUSION: The extinction coefficients of chlorophyll a(Chl a) and chlorophyll b(Chl b) of DMF extracts for high extinction wavelength were 663.8 and 647.2 nm. Similarly, the high extinction wavelength of DMSO extracts were 665.8 and 649.0 nm for chl a and b respectively. Chl a, Chl b and total chlorophyll content of DMF extracts were Chl a = $12.10A_{663.8}-2.74A_{647.2}$, Chl b = $21.94A_{647.2}-5.06A_{663.8}$ and total $Chl=19.193A_{647.2}+7.04A_{663.8}$. Similarly, Chl a, Chl b and total Chl of DMSO extracts were Chl a = $14.53A_{665.8}-5.40A_{649.0}$, Chl b = $26.98A_{649.0}-7.11A_{665.8}$ and total $Chl=21.58A_{649.0}+7.43A_{665.8}$. The chlorophyll extracts of DMF and DMSO were very stable in dark. High chlorophyll contents of citrus leaves were found at $80^{\circ}C$ extraction for 6 hours in DMF and at $80^{\circ}C$ extraction for 24 hours in DMSO. However, the chlorophyll content was decreased significantly after 8 hours in DMF extraction while it was remained up to 30 hours in DMSO extraction.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.24 no.3
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• pp.345-352
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• 2014

Objectives: This study is aimed to describe the current situation about urinary biomarker N-methylformamide(NMF) for workers exposed to N,N-dimethylformamide(DMF) according to industrial classification. Materials: Special health examination records of the workers who had undergone urinary biological monitoring in 2013 were collected. The numbers and percentage of workers, whose urinary NMF values were above the limit of detection(LOD) and above the biological exposure index(BEI) were calculated. Health relatedness with DMF as judged by their doctors was also described. All description was classified according to the $9^{th}$ Korean Standard Industrial Classification(KSIC). Results: It appeared that most workers exposed to DMF belong to manufacturing section(80.7%). The geometric mean(GM) values of urinary NMF were 6.25 mg/L, 3.54, and 3.86 for the manufacturing section, professional, scientific and technical activities section, and for the construction section respectively. In detail, it seemed that division of textiles(except apparel) (GM 7.51 mg/L), division of leather, luggage and footwear(11.59 mg/L), and division of rubber and plastic products(6.89 mg/L) were highly exposed to DMF with a high percentage of workers with urinary NMF values above BEI. This was probably due to the effect of skin absorption that the division of leather, luggage and footwear showed the highest urine NMF GM. Conclusions: It seemed that workers in manufacture industries such as textile, leather, luggage, footwear, rubber and plastic products were highly exposed to DMF. So, efforts should be focused on those industries in order to effectively diminish worker's exposure. Further studies to compare DMF air-monitoring with bio-monitoring according to industrial classification should be considered.

• The Journal of Korean Society for School & Community Health Education
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• v.2 no.1
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• pp.31-40
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• 2001

A study of fluoride effects on teeth of school children was conducted in order to determine the usefulness of fluoride for preventing dental caries. Nine hundred and thirty six(936) elementary school children were selected from Chongju where children drank fluoridated water. Eight hundred and thirty six(836) from Seoul where children applied fluoride topically, and eight hundred and three(803) from Kumi where the children drank non fluoridated water(control). DMFs of school children were compared by the sources of fluoride. This study was conducted from May 1, through June 15, 2000. The results are summarized as follows; 1. The DMF rate of male school children topically applying fluoride was 51.4%, that of female children was 56.1%, and that of both males and females was 54.0%, The DMF rate of male children of control group was 72.4%, that of females was 77.5% and that of both males and females was 74.8%. 2. The DMF rate of male children drinking fluoridated tap water was 56.1%, that of females was 54.1%, and that of both males and females was 55.5%. The rates of control group were 72.4% for males, 77.5% for females and 74.8% for male and female children respectively. 3. The difference of DMF rates between the group of children who drank fluoridated water and applied fluoride topically, and control group was statistically significant. 4. The difference of DMF rates between the children who drank fluoridated water and the children who applied fluoride topically were not statistically significant. 5. The difference of DMFT rates between 5th graders who applied fluoride topically and the 5th graders of control group was not statistically significant. However, the difference of DMFT rates of the 6th graders who applied fluoride topically and the same graders of control group were statistically significant. The difference of DMF rates between 5th and 6th graders who drank fluoridated tap water and the same graders of control group was statistically significant. 6. The difference of DMFT rates between children drinking fluoridated tap water and children applying fluoride topically was statistically significant.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.5 no.1
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• pp.104-118
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• 1995

This study was performed to evaluate factors affecting desorption of organic solvents collected on charcoal tube and to find out the optimum condition. Desorption efficiency for polar analytes was improved when several polar desorption solvents such as methanol, dimethylformamide(DMF), 2-(2-butoxyethoxy)ethanol were added to carbon disulfide($CS_2$). The best improvement was achieved when 10% dimethylformamide(DMF) in $CS_2$ was used as desorption solvent. During storage of polar analytes, recovery was greatly reduced. Especially, the recovery of cyclohexanone was decreased to 18.1 % after a month storage at $34^{\circ}C$. After two weeks storage, recovery of polar analytes was sharply decreased. Water adsorbed on charcoal interfered the recovery of polar analytes but didn't interfere that one of nonpolar solvent, toluene. When 10% DMF in $CS_2$ was used as desorption solvent, the effect of water on recovery was decreased, comparing with Desorption efficiency increased when analyte loading increased, and usage of 10% DMF in $CS_2$ decreased the loading effect. Increasing volume of desorption solvent was not effective to improve desorption efficiency of analytes when 10% DMF was used. Continuous shaking and sonication is not helpful to increase the desorption efficiency of analytes except cyclohexanone using 10% DMF. When silica gel used as adsorbent, methanol was better desorbent than dimethylsulfoxide. Analytes adsorbed on silica gel showed high recovery in low concentration and less affected by humidity. On the basis of this study, the following conclusions have been drawn. To improve the recovery of polar organic materials in air samples, it is necessary to analyze samples as soon as possible after they were collected. Otherwise, samples must be stored at low temperature. Using two components of desorption solvents, such as 10% DMF in $CS_2$, the effects of loading and humidity decreased for polar analytes such as methyl ethyl ketone and methyl isobutyl ketone. When work place has high humidity with low concentration of polar organic solvents, silica gel can be used as adsorbent, because it produces quantitative recovery for polar analytes at this condition. But it should be noted that high humidity makes breakthrough easy in silica gel samples.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.1
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• pp.22-28
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• 2010

Approximate analysis for a building installed with a friction damper is performed to get insight of its dynamic behavior. Energy balance equation is used to have a closed analytical form solution of dynamic magnification factor(DMF). It is found out that DMF is dependent on friction force ratio and resonance frequency. Approximation of DMF and equivalent damping ratio of a friction damper is proposed with such assumption that the building with a friction damper shows harmonic steady-state response and narrow banded response behavior near resonance frequency. Linear transfer function from input external force to output building displacement is suggested from the simplified DMF equation. Root mean square of a building displacement is derived under earthquake-like random excitation. Finally, design procedure of a friction damper is proposed by finding friction force corresponding to target control ratio. Numerical analysis is carried out to verify the proposed design procedure.

• Journal of the korean academy of Pediatric Dentistry
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• v.21 no.2
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• pp.463-468
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• 1994

The purpose of this study was evaluation of the oral health of cerebral palsied children by considering the DMFT index. The 31 cerebral palsied children(Male 20, Female 11) participated in the study, and mean age was 11.3 years. All patient were examined for determination of decayed tooth, missing tooth, filled tooth. For children with only deciduous dentition, the dmf system was used; for children with only permanent dentition, the DMF system was used; for children with mixed dentition, a combination of two systems(dmf and DMF) was used. The results were as follows: 1. In the deciduous dentition, dmft index was 11.60.(dt rate ; 83.62%, mt rate ; 12.07%, ft rate ; 4.31 %) 2. In the mixed dentition, DMFT index was 12.25 and dmft index was 10.75.(DT rate ; 90.00 %, MT rate ; 0 %, FT rate ; 10.00 %, dt rate ; 60.53 %, mt rate ; 28.95 %, ft rate ; 10.52 % ) 3. In the permanent dentition, DMFT index was 8.16.(DT rate ; 87.77 %, MT rate ; 11.51 %, FT rate ; 0.72 %)

• Clean Technology
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• v.9 no.3
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• pp.145-151
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• 2003

This study shows the evaluation and consulting for pollution prevention of dye production by cleaner production methodology. Especially, this study intended to investigate the methods for reduction of process water and recovery of organic solvent (DMF), and to modify the process for higher qualified products in the acid dye production by cleaner production methodology. This methodology, consisting of 7 sequential phases (business leadership decision to start, problem definition, evaluation of the screened options, option selection for implementation, implementation, monitoring and sustainable implementation), is based on initial developments in the USA and Western Europe. Reduction of process water over 25%, recovery of DMF and solubility enhancement of acid dye over 2 times were achieved.

• Journal of the Korean Chemical Society
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• v.31 no.6
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• pp.486-490
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• 1987

The effect of the hydrogen-bonding between thioacetamide (TA) and amides (N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA) and N,N-dimethylpropionamide (DMP)) on the hindered rotation of N-C(S) bond of TA was investigated by the nmr spectroscopy. The $^1H$-nmr spectrum of $NH_2$ group in TA was distinctly separated into two peaks with increasing the amount of $CCl_4$ and the effect of amides on the peak separation was in the order of DMF < DMA < DMP. Those phenomena were interpreted in terms of hydrogen-bonding between TA and amide.

• Journal of Ceramic Processing Research
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• v.18 no.11
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• pp.810-814
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• 2017

Proton exchange membrane fuel cells (PEMFCs) are some of the most efficient electrochemical energy sources for transportation applications because of their clean, green, and high efficiency characteristics. The optimization of catalyst layer morphology is considered a feasible approach to achieve high performance of PEMFC membrane electrode assembly (MEA). In this work, we studied the effect of the solvent on the catalyst layer of PEMFC MEAs fabricated using the electrostatic spray deposition method. The catalyst ink comprised of Pt/C, a Nafion ionomer, and a solvent. Two types of solvent were used: isopropyl alcohol (IPA) and dimethylformamide (DMF). Compared with the catalyst layer prepared using IPA-based ink, the catalyst layer prepared with DMF-based ink had a dense structure because the DMF dispersed the Pt/C-Nafion agglomerates smaller and more homogeneously. The size distribution of the agglomerates in catalyst ink was confirmed through Dynamic Light Scattering (DLS) and the microstructure of the catalyst layer was compared using field emission scanning electron microscopy (FE-SEM). In addition, the electrochemical investigation was performed to evaluate the solvent effect on the fuel cell performance. The catalyst layer prepared with DMF-based ink significantly enhanced the cell performance (1.2 A cm-2 at 0.5 V) compared with that fabricated using IPA-based ink (0.5 A cm-2 at 0.5 V) due to the better dispersion and uniform agglomeration on the catalyst layer.

• Polymer(Korea)
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• v.39 no.3
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• pp.394-402
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• 2015

Modification of polyacrylonitrile (PAN) films by using hydroxylamine (HA) and hydrazine to produce hydroxyl and amine groups, respectively, and to introduce cross-linking of PAN polymers was studied. Modified PAN films obtained by HA and/or hydrazine treatment including a successive or a simultaneous process were analyzed by the degree of conversion, water and N,N'-dimethylformamide (DMF) swelling ratio, FTIR spectra, atom content, and thermal analysis data. PAN films reacted with HA showed increased hydrophilicity and low dimensional stability in water. Hydrazine treatment gave PAN films high dimensional stability of low DMF swelling. Although the DMF swelling ratio of the modified PAN films was dramatically decreased by the successive treatment of hydrazine and HA, the introduction of the hydrophilic functional groups was limited due to the cross-linking. Simultaneous treatment of HA and hydrazine was the most effective method to increase hydrophilicity of PAN films with a high dimensional stability.