Discrimination of the cultivar,growing region,and geographical origin of rice (<Emphasis Type="Italic">Oryza sativa</Emphasis>) using a mass spectrometer-based electronic nose

The objective of this study was to discrimination the cultivar, growing region, and geographical origin of rice (Oryza sativa) using a mass spectrometry-based electronic nose (MSE-nose). The inside-needle dynamic extraction (INDEX) system was used to concentrate the samples for MSEnose, following which the ion fragment data obtained were used to perform discriminant function analysis. Discriminant functions 1 and 2 readily separated all 16 cultivars of rice sampled. It was also confirmed that MSE-nose could distinguish the region in which rice cv. Chucheong and Koshihikari were grown, likely due to variation in environmental factors, such as soil and climate. Finally, it was confirmed that MSE-nose could be used to detect the geographical origin of rice, discrimination Korea rice from Japanese rice. Therefore, this simple and rapid technique is of value for discriminating the cultivar, growing region, and geographical origin of rice.     

Major Phytochemical Composition of 3 Native Korean Citrus Varieties and Bioactive Activity on V79-4 Cells Induced by Oxidative Stress

ABSTRACT:  Three citrus varieties grown in Korea, namely, Yuza ( Citrus junos  Sieb ex Tanaka), Kjool ( Citrus unshiu  Marcow), and Dangyooja ( Citrus grandis  Osbeck), were evaluated for their dietary fiber, total phenolics, total flavonoids, and total carotenoids as well as individual flavonoids composition. The biochemical characteristics of citrus varieties were examined by the antioxidant capacity (731 to 1221 μmol of Trolox equivalent/g), total phenolic (334 to 411 mg of chlorogenic acid equivalent/100 g), total flavonoid contents (214 to 281 mg of catechin equivalent/100 g), and total carotenoid contents (63 to 84 mg/100 g). Six flavonoids, including naringin, naringenin, hesperidin, hesperetin, neohesperidin, and luteolin, were tentatively identified. Naringin, hesperidin, and neohesperidin were the predominant flavonoids in 3 citrus varieties. Among the citrus varieties studied, Yuza showed higher antioxidant activity, total phenolics, total carotenoids, and lower superoxide radical scavenging assay (SRSA) IC₅₀ values than other varieties. Furthermore, Korean citrus showed higher protective effect on gap-junction intercellular communication (GJIC) as compared to vitamin C and luteolin.     

Isolation and identification of antioxidative compounds and their activities from Suaeda japonica

The ethyl acetate (EtOAc) and chloroform (CHCl₃) layers obtained after solvent fractionation of a H₂O suspension of powdered Suaeda japonica juice showed higher 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicalscavenging activity than other layers. Eighteen compounds were purified and isolated from the EtOAc and CHCl₃ layers using chromatography following DPPH radicalscavenging assay. These compounds were identified as dihydroferulic acid methyl ester (1), pyrocatechol (2), syringic acid (3), apigenin (4), isorhamnetin (5), kaempferol (6), dihydroferulic acid (7), vanillic acid (8), 4-hydroxybenzoic acid (9), acetophlorglucine (10), homoeriodictyol (11), naringenin (12), quercetin (13), luteolin (14), 9-epiblumenol C (15), scopoletin (16), dihydroisorhamnetin (17), and chrysoeriol (18). The structures of these compounds were determined by mass spectrometry and nuclear magnetic resonance analyses. The isolated compounds were newly identified from this plant. Compounds 13 and 14 exhibited higher DPPH radical-scavenging activity and an inhibition effect against ferric ion-induced lipid oxidation of rat liver when compared to α-tocopherol and other compounds.     

喷墨油墨流变性能对其印刷适性的影响

喷墨印刷是一种可直接出版的印刷方式.喷墨印刷之所以能够实现,依靠的是油墨流体稳定、精准喷墨的印刷性能.本文通过观察墨滴形成的动态过程,研究喷墨印刷适性与油墨流变性能之间的内在联系.油墨的印刷适性是依照Ohnesorge(Oh)值的倒数Z来进行度量的,而Oh值与油墨的黏度、表面张力及浓度有关.考虑到墨滴的成形、定位的精准性及允许的最高喷墨频率,将Z值的可印刷范围重新定义在4～14之间.     

Two novel glycosyl cinnamic and benzoic acids from korean black raspberry (Rubus coreanus) wine

Korean black raspberry (Rubus coreanus) wine was solvent-fractionated with n-hexane, ethyl acetate, and n-butanol and the n-butanol layer was purified by various column chromatographic procedures, including Amberlite XAD-2, Sephadex LH-20, and octadecylsilane resins as well as high performance liquid chromatography. Two novel glycosyl cinnamic and benzoic acids were isolated and their structures were (E)-8-O-β-d-glucopyranosylcinnamic acid (1) and 3′-[O-β-d-glucopyranosyl)(1″→6′)-α-d-psicofuranosyl] benzoate (2) based on the spectroscopic data obtained by high resolution fast-atom bombardment mass spectroscopy and nuclear magnetic resonance analyses.     

The onset of natural convection in a horizontal fluid layer heated isothermally from below

The onset of buoyancy-driven convection in an initially quiescent fluid layer confined between two horizontal plates is analyzed theoretically. In case of isothermal heating it is well known that convective motion sets in when the Rayleigh number Ra exceeds 1708. For Ra > 1708, there are three characteristic times t_c, t_D and t_u which represent respectively, the critical time to mark the onset of intrinsic instability, the detection time of motion, and the undershoot time in a plot of the heating rate versus time. These characteristic times are analyzed by employing the numerical method under the single mode of instabilities and fitting some experimental t_u-values. The new measures to represent t_c and t_D are suggested, based on the growth rates of fluctuations. It is interesting that t_c is the invariant but the predicted t_D- and t_u-values are dependent upon the magnitude of initial conditions forced. It is shown that for the isothermally heated system of a large Prandtl number the relation of t_u ? 7t_c agrees well with the available experimental t_u-values for Ra > 10⁵ and t_D is located between t_c and t_u. This paper removes the confusion among the characteristic times, t_c, t_D and t_u in the literature on stability. Also the boundary-layer instability model is discussed in order to analyze turbulent thermal convection heat transfer characteristics in the fully developed state, based on the present numerical predictions.     

Using hydrogen activated by microwave plasma vs. molecular hydrogen for hydrogen storage in tungsten disulfide inorganic nanotubes

In this work we investigate the inorganic nanotubes of layered tungsten disulfide, as material for hydrogen storage. These nanotubes may allow hydrogen to be either chemi- or physisorbed inside their crystalline structure (in between the layers), inside hollow core of nanotubes, on the surface or in the open interstitial pore spaces of nanotubes' powder mesh. While exposure to molecular hydrogen was found to have measurable but limited absorption rate – up to 0.13 wt.%, the exposure to hydrogen activated by microwave (MW) plasma resulted in much higher value of adsorbed hydrogen of ∼1 wt.%. These observations could be attributed to more effective interaction of activated vs. molecular hydrogen with nanotubes surface due to the strong chemisorption of activated hydrogen compared to weaker physisorption of molecular hydrogen. We report here the results of such exposures and analyze the absorption and diffusion of hydrogen by different methods: adsorption–desorption curves obtained by pressure–composition–temperature isotherm measurements, and hydrogen depth profiles measured by Secondary Ion Mass Spectroscopy. We found that 5 min exposure to MW plasma at 400 W and 60 Torr (causing local heating up to ∼100 °C) results in substantial hydrogen retention, though some etching of the substrate material may occur during such treatment.     

Successive laser-induced breakdowns in atmospheric pressure air and premixed ethane–air mixtures

Two successive focused laser pulses are employed to experimentally simulate laser-induced breakdown plasmas at high repetition rates. We find that energy absorption of the second laser pulse by the plasma produced by the first laser pulse is enhanced slightly when the time interval between the pulses is shorter than several tens of nanoseconds but falls to almost zero when the time interval is between a few hundreds of nanoseconds and several tens of microseconds. This behavior is attributed to gas heating by the first breakdown event. In premixed ethane–air mixtures, we identify another strong reduction in the second laser pulse absorption when this pulse coincides with the heat released by combustion, typically milliseconds after the first laser pulse. The fuel–air equivalence ratio (?) and base flow speed are also varied in this study. The results show that the window of reduced absorption coinciding with heat release due to combustion is narrowed when the base flow speed is increased, and also under fuel lean and fuel rich conditions. These results suggest that the use of pulsed high frequency laser breakdowns for premixed combustion stabilization is optimized when laser pulse repetition rates below a certain frequency (e.g., 500 Hz at the conditions that ? is 1 and the base flow speed is 4.9 m/s) to maximize laser energy coupling and for improved anchoring of the flame base.     

Comparison of antibiogram, staphylococcal enterotoxin productivity, and coagulase genotypes among Staphylococcus aureus isolated from animal and vegetable sources in Korea

Staphylococcal food poisoning is caused by enterotoxin-producing Staphylococcus aureus. We investigated the prevalence of such organisms in samples of bovine mastitic milk (n = 714), raw meat (n = 139), and vegetables (n = 616). We determined the degrees of relatedness of isolates as indicated by antibiogram, staphylococcal enterotoxin (SE) productivity, and coagulase gene restriction fragment length polymorphism analysis. We examined 297 S. aureus isolates and found SE production in 57 (31.8%), 4 (7.8%), and 49 (73.1%) isolates from raw milk, raw meat, and vegetables, respectively. A high proportion of the isolates obtained from milk produced more than two types of toxins (mainly SEA, SEB, and/or SEC), whereas isolates from raw meat and vegetables primarily produced SEA alone. Most isolates were sensitive to cephalothin (97.6%), gentamicin (80.8%), erythromycin (79.5%), and tetracycline (72.7%), but were resistant to penicillin (90.2%) and ampicillin (88.9%). The proportion of antibiotic-resistant isolates differed according the source of the bacteria; the milk and vegetable isolates were more resistant to penicillin and ampicillin than were the meat isolates (P < 0.05), whereas tetracycline resistance was limited to the milk and vegetables isolates. The coagulase genotypes (I to XII) varied with the source of the organism, and only a few genotypes prevailed in each source: II (42.4%) and IV (24%) types in isolates from milk, IX (35.3%) and XI (45%) from raw meat, and III (40.3%) and XII (32.8%) from vegetables. These findings suggest that remarkable differences exist in antibiogram, SE productivity, and coagulase genotypes, resulting in limited clonal transmission of S. aureus into various food sources. As enterotoxin production only occurs when S. aureus grows to high numbers, staphylococcal food poisoning can be prevented by proper refrigeration.     

Microbial evaluation of minimally processed vegetables and sprouts produced in Seoul, Korea

The aim of this study was to evaluate the microbial quality of some minimally processed vegetables. A total of 345 samples of minimally processed vegetables were acquired at a department store, a local supermarket, and a restaurant in Seoul, Korea. Samples were tested for microorganism distributions and for the presence of pathogenic bacteria. The aerobic mesophilic counts ranged between 2.0 and 9.7 log CFU/g, with the highest count recorded from the sprouts. Counts of psychrotrophic microorganisms were as high as those of the mesophilic microorganisms. Total coliform populations between 1.0 and 8.8 log CFU/g were found in 98.3% of the samples. Microbiological counts for fresh-cut fruits were very low. Sprouts were highly contaminated with microorganisms and showed a high incidence of Escherichia coli and Clostridium perfringence. Salmonella species and Listeria monocytogenes were detected in 1.5 and 0.3% of samples, respectively. E. Coli O157:H7 and Yersinia enterocolitica were not detected in any of the samples.