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1.
Ritthiruangdej P Kasemsumran S Suwonsichon T Haruthaithanasan V Thanapase W Ozaki Y 《The Analyst》2005,130(10):1439-1445
Near-infrared (NIR) transflectance spectra in the region of 1100-2500 nm were measured for 100 Thai fish sauces. Quantitative analyses of total nitrogen (TN) content, pH, refractive index, density and brix in the Thai fish sauces and their qualitative analyses were carried out by multivariate analyses with the aid of wavelength interval selection method named searching combination moving window partial least squares (SCMWPLS). The optimized informative region for TN selected by SCMWPLS was the region of 2264-2428 nm. A PLS calibration model, which used this region, yielded the lowest root mean square error of prediction (RMSEP) of 0.100% w/v for the PLS factor of 5. This prediction result is significantly better than those obtained by using the whole spectral region or informative regions selected by moving window partial least squares regression (MWPLSR). As for pH, density, refractive index and brix, the 1698-1722, and 2222-2258 nm regions, the 1358-1438 nm region, the 1774-1846, and 2078-2114 nm regions, and the 1322-1442, and 2000-2076 nm regions were selected by SCMWPLS as the optimized regions. The best prediction results were always obtained by use of the optimized regions selected by SCMWPLS. The lowest RMSEP for pH, density, refractive index and brix were 0.170, 0.007 g cm(-3), 0.0079 and 0.435 degrees Brix, respectively. Qualitative models were developed by using four supervised pattern recognitions, linear discriminant analysis (LDA), factor analysis-linear discriminant analysis (FA-LDA), soft independent modeling of class analog (SIMCA), and K neareat neighbors (KNN) for the optimized combination of informative regions of the NIR spectra of fish sauces to classify fish sauces into three groups based on TN. All the developed models can potentially classify the fish sauces with the correct classification rate of more than 82%, and the KNN classified model has the highest correct classification rate (95%). The present study has demonstrated that NIR spectroscopy combined with SCMWPLS is powerful for both the quantitative and qualitative analyses of Thai fish sauces. 相似文献
2.
Koonchira Buaban Weerachai Phutdhawong Thongchai Taechowisan Waya S. Phutdhawong 《Molecules (Basel, Switzerland)》2021,26(1)
A series of tetrahydro-ß-carbolines substituted with an alkyl or acyl side chain was synthesized and screened for its antifungal activity against plant pathogenic fungi (Bipolaris oryzae, Curvularia lunata, Fusarium semitectum, and Fusarium fujikuroi). The structure activity relationship revealed that the substituent at the piperidine nitrogen plays an important role for increasing antifungal activities. In this series, 2-octyl-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole (3g) displayed potent antifungal activities with a minimum inhibitory concentration of 0.1 μg/mL, including good inhibitory activity to the radial growth of fungus at a concentration of 100 μg/mL compared to amphotericin B. 相似文献
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A novel chemiluminescence (CL) microfluidic system incorporating a molecularly imprinted polymer (MIP) preconcentration step was used for the determination of chloramphenicol in honey samples. The MIP was prepared by using chloramphenicol as the template, diethylaminoethyl methacrylate (DAM) as the function monomer, ethylene glycol dimethacrylate (EGDMA) as the cross-linking monomer, 2, 2′-dimethoxy-2-phenylacetophenone (DMPA) as the free radical initiator and toluene and dodecanol as the solvent. The MIP was pre-loaded into a 10 mm long, 2 mm wide and 150 μm deep channel in a planar glass microfluidic device. When the sample containing chloramphenicol was introduced into the microfluidic device it was first preconcentrated on the MIP then detected by an enhancement effect on the chemiluminescence reaction of tris(2, 2′-bipyridyl) ruthenium(II) with cerium(IV) sulphate in sulphuric acid. A micro-syringe pump was used to pump the reagents. The CL intensity was linear in relationship to the chloramphenicol concentrations from 1.55 × 10−4 to 3.09 × 10−3 μmol L−1 (r2 = 0.9915) and the detection limit (3σ) and the quantitation limit (10σ) were found to be 7.46 × 10−6 and 2.48 × 10−5 μmol L−1, respectively. This method offered a high selectivity and sensitivity for quantitative analysis of chloramphenicol in the honey samples. 相似文献
4.
Maria G. Corradini Veronique Stern Thongchai Suwonsichon Micha Peleg 《Rheologica Acta》2000,39(5):452-460
Samples of commercial tomato paste, low fat mayonnaise and mustard about 6–8 mm thick were squeezed to 0.8 mm at various
speeds between 5 mm min−1 and 25 mm min−1 between Teflon-coated parallel plates 127 mm in diameter using an Instron UTM Model 5542. All the log force vs log height
relationships had a clearly identified linear region. This indicated that a dominant squeezing flow regime was achieved at
about 3 mm height, and that the machine has the proper stiffness to perform the tests. The stress level at a pre-selected
height in this region is a measure of consistency, sensitive enough to distinguish between products of different brands. The
residual stress after relaxation for about 2 min was on order of 10–50% of the initial stress, an indication that all three
foods have a considerable structural integrity. In all three products there was a considerable discrepancy between the observed
rate effects and predictions based on a pseudoplastic (power law) model. It could be described by the empirical relation (Fv1 − FR)/(Fv2 − FR)=(V1/V2)m where Fv1 and Fv2 are the forces at the given displacement reached at speeds v1 and v2 respectively, FR is the residual force after relaxation (found to be practically rate independent), and m is a constant of the order of 0.15–0.33,
independent of the compression velocities ratio but characteristic of the food and brand. The calculated elongational viscosity
was not a unique function of biaxial strain rate. To a certain extent, this was probably due to imperfect lubrication. But
it was also a manifestation of these products considerable structural integrity which cannot be accounted for by models developed
for ideal liquids.
Received: 1 November 1999 Accepted: 2 May 2000 相似文献
5.
Weerachai Phutdhawong Apiwat Chuenchid Thongchai Taechowisan Jitnapa Sirirak Waya S. Phutdhawong 《Molecules (Basel, Switzerland)》2021,26(6)
A series of novel coumarin-3-carboxamide derivatives were designed and synthesized to evaluate their biological activities. The compounds showed little to no activity against gram-positive and gram-negative bacteria but specifically showed potential to inhibit the growth of cancer cells. In particular, among the tested compounds, 4-fluoro and 2,5-difluoro benzamide derivatives (14b and 14e, respectively) were found to be the most potent derivatives against HepG2 cancer cell lines (IC50 = 2.62–4.85 μM) and HeLa cancer cell lines (IC50 = 0.39–0.75 μM). The activities of these two compounds were comparable to that of the positive control doxorubicin; especially, 4-flurobenzamide derivative (14b) exhibited low cytotoxic activity against LLC-MK2 normal cell lines, with IC50 more than 100 μM. The molecular docking study of the synthesized compounds revealed the binding to the active site of the CK2 enzyme, indicating that the presence of the benzamide functionality is an important feature for anticancer activity. 相似文献
6.
Chanakan Winyakul Weerachai Phutdhawong Poomipat Tamdee Jitnapa Sirirak Thongchai Taechowisan Waya S. Phutdhawong 《Molecules (Basel, Switzerland)》2022,27(13)
2,5-Diketopiperazine derivatives, consisting of benzylidene and alkylidene substituents at 3 and 6 positions, have been considered as a core structure for their antiviral activities. Herein, the novel N-substituted 2,5-Diketopiperazine derivatives were successfully prepared and their antiviral activities against influenza virus were evaluated by monitoring viral propagation in embryonated chicken eggs. It was found that (3Z,6Z)-3-benzylidene-6-(2-methyl propylidene)-4-substituted-2,5-Diketopiperazines (13b–d), (3Z,6E)-3-benzylidene-6-(2-methylpropyli dene)-1-(1-ethyl pyrrolidine)-2,5-Diketopiperazine (14c), and Lansai-C exhibited negative results in influenza virus propagation at a concentration of 25 µg/mL. Additionally, molecular docking study revealed that 13b–d and 14c bound in 430-cavity of neuraminidase from H5N2 avian influenza virus and the synthesized derivatives also strongly interacted with the key amino acid residues, including Arg371, Pro326, Ile427, and Thr439. 相似文献
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Manisara Phiriyawirut Puriphat Saenpong Suradet Chalermboon Ruangdet Sooksakoolrut Nikorn Pochanajit Leartprakit Vuttikit Apichate Thongchai Pitt Supaphol 《Macromolecular Symposia》2008,264(1):59-66
Isotactic poly(propylene) (iPP)/wood sawdust composite containing 30 wt.% of the natural fibers was first prepared by melt-mixing in a twin screw extruder and later molded into various shaped specimens by injection molding machine. The effect of natural weathering, water immersion, and gamma-ray irradiation on mechanical properties of the specimens were studied. All of the tensile properties were improved with initial increase in the exposure time of natural weathering of up to 30 days and decreased afterwards. Similarly, the tensile strength and the Young's modulus of the composite increased with initial increase in the radiation dosage and decreased afterwards. On the contrary, the tensile strength and the elongation at break of the composite were unchanged after having been immersed in water for the first 15 days, but increased slightly afterwards. The alteration in these properties were postulated to be a result of the interplay between the cross-linking and the chain scission reactions that occurred during natural weathering and gamma-ray irradiation and the plasticizing effect of the absorbed water molecules during water immersion. 相似文献
10.
Tuntiwachwuttikul P Pootaeng-on Y Pansa P Srisanpang T Taylor WC 《Chemical & pharmaceutical bulletin》2003,51(12):1423-1425
Two new sulfur-containing compounds, trans-3-methylsulfonyl-2-propenol (1) and trans-3-methylsulfinyl-2-propenol (2) were isolated together with trans-3-methylthioacrylamide (3), entadamide A (4) and entadamide C (5) from the leaves of Clinacanthus siamensis. The structures were established on the basis of the spectroscopic data. The compounds were tested for antimalarial and antimycobacterial activity. 相似文献