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排序方式: 共有6397条查询结果,搜索用时 15 毫秒
991.
Thomas Schneider Benjamin L. Oyler Sung Hwan Yoon Tao Liang Gloria S. Yen David P. A. Kilgour Erik Nilsson David R. Goodlett 《Food Analytical Methods》2018,11(9):2447-2454
Rapid food product analysis is of great interest for quality control and assurance during the production process. Conventional quality control protocols require time and labor-intensive sample preparation for analysis by state-of-the-art analytical methods. To reduce overall cost and facilitate rapid qualitative assessments, food products need to be tested with minimal sample preparation. We present a novel and simple method for assessing food product compositions by mass spectrometry using a novel surface acoustic wave nebulization method. This method provides significant advantages over conventional methods requiring no pumps, capillaries, or additional chemicals to enhance ionization for mass spectrometric analysis. In addition, the surface acoustic wave nebulization–mass spectrometry method is ideal for rapid analysis and to investigate certain compounds by using the mass spectra as a type of species-specific fingerprint analysis. We present for the first time surface acoustic wave nebulization-generated mass spectra of a variety of fermented food products from a small selection of vinegars, wines, and beers. 相似文献
992.
Enzyme assisted extraction of Undaria pinnatifida was performed using five proteases (Alcalase, Flavourzyme, Neutrase, Trypsin and Protamex) and six carbohydrases (AMG, Dextrozyme, Maltogenase, Promozyme, Viscozyme and Celluclast) in order to acquire extracts rich in antioxidants. Antioxidant activity of the extracts was investigated using electron spin resonance (ESR) spectroscopy on 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl and superoxide radicals. Extracts exhibited strong radical scavenging activity on DPPH and hydroxyl radical, and activity increased with increasing extract concentration. In contrast to DPPH and hydroxyl radical scavenging activity, extracts showed weak scavenging activity on superoxide radical. Extracts exhibited weak radical scavenging activity compared to vitamin C as a reference compound. However, they are still a good source of antioxidant materials that are safe for consumption and show water-soluble properties. 相似文献
993.
Jun Hwan Kim Byoung Oon Lee Chan Bock Lee Seung Hyun Jee Young Soo Yoon 《中国稀土学报(英文版)》2012,30(6):599-603
The intermetallic compounds formation at interface between rare earth elements and clad material were investigated to demonstrate the effects of rare earth elements on fuel-cladding chemical interaction(FCCI)behavior.Mischmetal(70Ce-30La)and Nd were prepared as rare earth elements.Diffusion couple testing was performed on the rare earth elements and cladding(9Cr2W steel)near the operation temperature of(sodium-cooled fast reactor)SFR fuel.The performance of a diffusion barrier consisting of Zr and V metallic foil against the rare earth elements was also evaluated.Our results showed that Ce and Nd in the rare earth elements and Fe in the clad material interdiffused and reacted to form intermetallic species according to the parabolic rate law,describing the migration of the rare earth element.The diffusion of Fe limited the reaction progress such that the entire process was governed by the cubic rate law.Rare earth materials could be used as a surrogate for high burnup metallic fuels,and the performance of the barrier material was demonstrated to be effective. 相似文献
994.
The objective of this study was to model the effect of drying temperatures (52, 57, and 63 degrees C) and predrying treatments on the inactivation of Listeria monocytogenes on beef jerky. Before drying, beef slices were inoculated with a 10-strain composite of L. monocytogenes and then treated with the following: (i) nothing (C), (ii) traditional marinade (M), or (iii) dipping in 5% acetic acid solution for 10 min, followed by M (AM). In addition, sequential stresses (exposure to 10% NaCl, followed by an adjustment of the pH to 5.0 and, subsequently, a water bath at 45 degrees C) were applied to the inocula before beef contamination and drying at 63 degrees C. Surviving L. monocytogenes were determined on tryptic soy agar plus 0.6% yeast extract (TSAYE) and on PALCAM agar at 0, 2, 4, 6, 8, and 10 h during drying. Data were modeled by a linear regression (treatment AM) and a logistic-based equation capable of fitting biphasic inactivation curves without initial shoulder (treatments C and M). The total log reductions expressed as the CFU per square centimeter of L. monocytogenes (3.9 to 5.1) for the samples treated with M (3.5 to 5.4) when compared with C were similar, whereas AM-treated samples had higher (6.1 to 6.8) reductions. All survival curves were characterized by an initial rapid decrease in populations within the first 2 h, which was followed by a secondary death phase at a lower rate. No significant (P > or = 0.05) differences in inactivation were observed due to drying temperatures in the range (52 to 63 degrees C) tested. Inactivation differences between recovered counts of stressed and unstressed cells were significant (P < 0.05) in PALCAM but not in TSAYE. The acidified predrying treatment (AM) had higher pathogen inactivation during drying than other treatments, regardless of drying temperature. The models developed may be useful in designing effective drying processes for beef jerky. 相似文献
995.
We present a method for glucose prediction from mid-IR spectra by independent component analysis (ICA). This method is able to identify pure, or individual, absorption spectra of constituent components from the mixture spectra without a priori knowledge of the mixture. This method was tested with a two-component system consisting of an aqueous solution of both glucose and sucrose, which exhibit distinct but closely overlapped spectra. ICA combined with principal component analysis was able to identify a spectrum for each component, the correct number of components, and the concentrations of the components in the mixture. This method does not need a calibration process and is advantageous in noninvasive glucose monitoring since expensive and time-consuming clinical tests for data calibration are not required. 相似文献
996.
997.
Yoon TH Benzerara K Ahn S Luthy RG Tyliszczak T Brown GE 《Environmental science & technology》2006,40(19):5923-5929
Synchrotron-based soft X-ray spectromicroscopy was used to probe nanometer-scale chemical heterogeneities of black carbon (BC) materials, including anthracite coal, coke, and activated carbon (AC), and to study their impact on the partitioning of one type of polychlorinated biphenyls (PCB-166: 2,3,4,4',5,6 hexachloro biphenyl) onto AC particles. Various carbon species (e.g., aromatic, ketonic/ phenolic, and carboxylic functional groups) were found in all of the BC materials examined, and impurities (e.g., carbonate and potassium ions in anthracite coal) were identified in nanometer-scale regions of these samples. We show that these chemical heterogeneities in AC particles influence their sorption of hydrophobic organic compounds (HOCs). PCB-166 was found to accumulate preferentially on AC particles with the highest content of aromatic functionalities. These new findings from X-ray spectromicroscopy have the following implications for the role of BC materials in the environment: (1) the functional groups of BC materials vary on a 25-nanometer scale, and so does the abundance of the HOCs; (2) molecular-level characterization of HOC sorption preferences on AC will lead to an improved understanding of AC sorption properties for the remediation of HOCs in soils and sediments. 相似文献
998.
Leem CH Kim WT Ha JM Lee YJ Seong HC Choe H Jang YJ Youm JB Earm YE 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2006,364(1842):1223-1243
In recent studies, we recorded transiently activated outward currents by the application of three-step voltage pulses to induce a reverse mode of Na+-Ca2+ exchange (NCX). We found that these currents were mediated by a Ca2+-activated Cl- current. Based on the recent reports describing the atrial Ca2+ transients, the Ca2+ transient at the subsarcolemmal space was initiated and then diffused into the cytosolic space. Because the myocardium in the pulmonary vein is an extension of the atrium, the Ca2+-activated Cl- current may reflect the subsarcolemmal Ca2+ dynamics. We tried to predict the subsarcolemmal Ca2+ dynamics by simulating these current traces. According to recent reports on the geometry of atrial myocytes, we assumed that there were three compartments of sarcoplasmic reticulum (SR): a network SR, a junctional SR and a central SR. Based on these structures, we also divided the cytosolic space into three compartments: the junctional, subsarcolemmal and cytosolic spaces. Geometry information and cellular capacitance suggested that there were essentially no T-tubules in these cells. The basic physical data, such as the compartmental volumes, the diffusion coefficients and the stability coefficients of the Ca2+ buffers, were obtained from the literature. In the simulation, we incorporated the NCX, the L-type Ca2+ channel, the rapid activating outward rectifier K+ channel, the Na+-K+ pump, the SR Ca2+-pump, the ryanodine receptor, the Ca2+-activated Cl- channel and the dynamics of Na+, K+, Ca2+ and Cl-. In these conditions, we could successfully reconstruct the Ca2+-activated Cl- currents. The simulation allowed estimation of the Ca2+ dynamics of each compartment and the distribution of the Ca2+-activated Cl- channel and the NCX in the sarcolemma on the junctional or subsarcolemmal space. 相似文献
999.
Liquid-ordered (L(O)) domains reconstituted in model membranes have provided a useful platform for in vitro studies of the lipid-raft model, in which signalling membrane molecules are thought to be compartmentalized in sphingolipid- and cholesterol-rich domains. These in vitro studies, however, have relied on an uncontrolled phase-separation process that gives a random distribution of L(O) domains. Obviously, a precise control of the size and spatial distribution of the L(O) domains would enable a more systematic large-scale in vitro study of the lipid-raft model. The prerequisite for such capability would be the generation of a well-defined energy landscape for reconstituting the L(O) domain without disrupting the two-dimensional (2D) fluidity of the model membrane. Here we report controlling the reconstitution of the L(O) domains in a spatially selective manner by predefining a landscape of energy barriers using topographic surface modifications. We show that the selective reconstitution spontaneously arises from the 2D brownian motion of nanoscale L(O) domains and signalling molecules captured in these nanodomains, which in turn produce a prescribed, concentrated downstream biochemical process. Our approach opens up the possibility of engineering model biological membranes by taking advantage of the intrinsic 2D fluidity. Moreover, our results indicate that the topographic configuration of cellular membranes could be an important machinery for controlling the lipid raft in vivo. 相似文献
1000.
A water quality model applicable to rice paddies was developed using field data from 1999-2002. Use of the Dirac delta function efficiently explained the nutrient-concentration characteristics of ponded water. The model results agreed reasonably well with the observed data. The ponded-water quality was influenced primarily by fertilization; nutrient concentration was especially high during early cultivation periods. Reducing surface drainage during the fertilization period may substantially reduce nonpoint source loading from paddies. Increased weir heights and shallow irrigation methods were evaluated by the model as practical methods for reducing nutrient loading from paddies. These methods were effective in reducing surface drainage and are suggested as "best management practices" (BMPs) if applied based on site-specific paddy conditions. 相似文献