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11.
Chutima Kranrod Supitcha Chanyotha Nares Chankow Shinji Tokonami Tetsuo Ishikawa 《Journal of Radioanalytical and Nuclear Chemistry》2013,296(2):625-630
A new portable type cascade impactor has been developed to determine the activity size distribution of radon and thoron progeny in a natural environment more efficiently. The modified impactor consists of 4 stages with a back up filter stage for the collection of aerosol samples. The aerosol cut points in the impactor are set for 10, 2.5, 1 and 0.5 μm at a flow rate of 4 L min?1. Five CR-39 chips were used as alpha detectors for each stage. In order to separate α particles emitted from radon and thoron progeny, CR-39 detectors are covered with aluminum-vaporized Mylar films. The thickness of each film is adjusted to allow α particles emitted from radon and thoron progeny to reach the CR-39 detectors. The technique has been successfully tested in field studies, particularly inside a mineral treatment industry in Thailand to estimate doses in the working environment. The dose calculations by lung dose evaluation program showed that activity median aerodynamic diameters played a significant role in determining the particle size distributions of the attached radon and thoron progeny. The dose conversion factor determined from short term measurements due to exposure from the inhalation of thoron and its progeny was found to be 4 times higher than comparable values for radon and its progeny. The effective dose for workers exposed to radon is about 4–6 times higher than thoron. 相似文献
12.
Chutima SrisitthiratkulVoraluck Pongsorrarith Narupol Intasanta 《Applied Surface Science》2011,257(21):8850-8856
While chemical and biological attacks pose risk to human health, clean air is of scientific, environmental and physiological concerns. In the present contribution, the potential use of nanosilver-decorated titanium dioxide (TiO2) nanofibers for toxin decomposition with antimicrobial activity and self-cleaning properties was investigated. Titanium dioxide nanofibers were prepared through sol-gel reaction followed by an electrospinning process. Following the Japan Industrial Standard (JIS) protocol, decompositions of nitrogen oxide (NOx) and volatile organic compound (VOC) by the TiO2 nanofibers suggested that these materials were capable of air treatment. To further enhance their anti-microbial activity, silver nanoparticles were decorated onto the TiO2 nanofibers’ surfaces via photoreduction of silver ion in the presence of the nanofibers suspension. Furthermore, tests of photocatalytic activity of the samples were performed by photodegrading methylene blue in water. The nanofibrous membranes prepared from these nanofibers showed superhydrophilicity under UV. Finally, the possibility of using these hybrid nanofibers in environmental and hygienic nanofiltration was proposed, where the self-cleaning characteristics was expected to be valuable in maintenance processes. 相似文献
13.
Kanchana Uraisin Supavita Janya Chutima Phechkrajang Nathawut Choengchan Warawut Tiyapongpattana Víctor Cerdà 《International journal of environmental analytical chemistry》2016,96(9):886-903
This work presents a novel method for simultaneous spectrophotometric determination of phosphate and silicate by using a cross injection analysis (CIA) coupled with the use of partial least squares (PLS) for data evaluation. The detection principle is based on the well-known ‘molybdenum blue’ method. The molybdate ions in the presence of stannous chloride in acidic medium give phosphomolybdenum blue and silicomolybdenum blue as products. In this work, all the liquids, including sample and reagents were simultaneously introduced into a CIA platform by using two peristaltic pumps for controlling the x-channel and y-channel flow which was automatically manipulated by using in-house control board. Crossflow provides sufficient mixing inside the platform prior detection of the absorption spectra of blue complexes in the wavelength of 400–900 nm. Since spectra of the blue colour product of phosphate and silicate are resemblant, these two analytes therefore reciprocally interfere with one another. This results in difficulty in simultaneous analysis of phosphate and silicate. In this work, PLS was utilised as assistor of CIA system for simultaneous analysis of phosphate and silicate using molybdenum blue reaction without using any modification of reagents and addition of selective masking agent. The calibration ranges are 0.1–6 mgP L?1 and 5–100 mgSi L?1 for phosphate and silicate, respectively. By using CIA coupled with PLS for data evaluation, the analysis of two analytes was achieved within 1.5 min with only single injection. The developed system was applied to natural water samples and the system was validated with the conventional methods. By statistical paired t-test, there was no evidence of significant difference at 95% confidence level (tstat = 2.28, tcritical = 2.31 and tstat = 0.62, tcritical = 2.31 for phosphate and silicate, respectively). This implied that the chemometrics-assisted CIA system was successfully developed for simultaneous spectrophotometric determination of phosphate and silicate. 相似文献
14.
Pohmakotr M Yotapan N Tuchinda P Kuhakarn C Reutrakul V 《The Journal of organic chemistry》2007,72(13):5016-5019
Functionalized gamma-lactams are found to be crucial intermediates in the synthesis of biologically important natural products. We herein described a highly diastereoselective synthesis of beta-carboxy-gamma-lactams and their ethyl ester derivatives, in high yields with high diastereomeric ratio, via the Mukaiyama-aldol type reaction of 2,5-bis(trimethysilyloxy)furan with imines, employing Sc(OTf)(3) as a catalyst. 相似文献
15.
Chooprayoon S Kuhakarn C Tuchinda P Reutrakul V Pohmakotr M 《Organic & biomolecular chemistry》2011,9(2):531-537
A concise asymmetric synthesis of (+)-swainsonine (ent-1) is described starting from 2, which was readily prepared from commercially available l-glutamic acid. The method features installation of the indolizidine ring via an intramolecular cyclisation of α-sulfinyl carbanion as a key step. (+)-Swainsonine was obtained in 11.8% overall yield in 10 steps. 相似文献
16.
The syntheses of indolizidine alkaloids, i.e., (±)-coniceine, (±)-indolizidine 167B, (±)-5-butylindolizidine and (±)-monomorine I via Pummerer cyclization are described. The key step is the transformation of lactam sulfoxide to bicyclic lactam via the Pummerer cyclization. 相似文献
17.
Darunee Soorukram Jaray PanmuangPatoomratana Tuchinda Chutima KuhakarnVichai Reutrakul Manat Pohmakotr 《Tetrahedron》2014
A stereoselective approach to secolignans is described. The key synthetic strategy involves an asymmetric aldol reaction to control the creation of the stereogenic center at the β-carbon of the target secolignans. In the present work, peperomin C and its analogues, i.e., 2,6-didehydropeperomin C and 2-epi-peperomin C were successfully synthesized in good yields with high stereoselectivities. 相似文献
18.
Charoensak Muangkaew Praewpan Katrun Patcharaphon Kanchanarugee Manat Pohmakotr Vichai Reutrakul Darunee Soorukram Thaworn Jaipetch Chutima Kuhakarn 《Tetrahedron》2013
A convenient method for 1,2-acetoxysulfenylation of alkenes using disulfide promoted by (diacetoxyiodo)benzene (PhI(OAc)2, DIB)/KI was developed. The reaction is highly regioselective for styrene derivatives while aliphatic alkenes lead to a mixture of two regioisomers. 相似文献
19.
Quynh N. Bach Sakchai Hongthong Lien T. Quach Lieu V. Pham Thuc V. Pham Chutima Kuhakarn 《Natural product research》2020,34(17):2518-2523
AbstractRhodomyrtone was isolated from the leaves of Rhodomyrtus tomentosa (Aiton) Hassk grown in Vietnam using chromatographic methods. Its chemical structure was confirmed by means of spectroscopic data analysis. The pH drop measurement, enzyme activity assays and fluorescence stain were used to examine rhodomyrtone anticaries activity. It was found that rhodomyrtone suppressed acid production by Streptococcus mutans, a major cariogenic agent in human by inhibiting enzyme activities responsible for acid production and tolerance, including membrane bound enzymes F-ATPase and phosphotransferase system (PTS), as well as glycolysis enzymes glyceraldehyphosphate dehydrogenase (GAPDH) and pyruvate kinase (PK) in cytoplasm with the IC50 values of 24?μM, 19?μM, 23?μM and 28?μM, respectively. Moreover, 50?μM rhodomyrtone reduced biofilm biomass formed by S. mutans up to 59% (p?<?0.05). Fluorescent images indicated that cells on the biofilms were significantly killed. Thus, rhodomyrtone is a new and potential anticaries agent against S. mutans. 相似文献
20.
Chutima Vanichvattanadecha Pitt Supaphol Ratana Rujiravanit 《Macromolecular Symposia》2008,264(1):121-126
N-Maleoyl chitosan (N-MC), a water-soluble derivative of chitosan, was synthesized by N-carboxyacylation of chitosan and maleic anhydride. N-MC films were prepared by solvent casting and kept in a desiccator for different time intervals in order to obtain N-MC films with different degrees of cross-linking. The swelling characteristic of N-MC films was investigated. When the ageing time increased from 5 to 30 d, the swelling of the N-MC films decreased from ∼475 to ∼160% and the weight loss decreased from ∼25 to ∼8%, corresponding to the increase in the cross-linking density from 0.86 × 10−6 to 8.97 × 10−6 mol · cm−3. Additionally, the swelling behavior of the N-MC films was influenced by changes in either the pH or the ionic strength of the media. 相似文献