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排序方式: 共有430条查询结果,搜索用时 15 毫秒
41.
介绍了原子吸收分光光度法分析镍硅铜合金中的镍,硅钼蓝光度法测定镍硅铜合金中的硅含量的方法,并对不同的溶样酸、不同空白液、不同分析方法进行了筛选。 相似文献
42.
A u.v. method, recommended for use in surveys of the operation of swimming pools, depends on measuring the difference in absorbance at 225 nm between basified and acidified aliquots of sample and comparing with values obtained for standard solutions of cyanuric acid similarly treated. Also described is a High Performance Liquid Chromatography (HPLC) method which would be advantageous for large numbers of samples and for other analytical applications where cyanuric acid must be separated before quantitation by measuring the u.v. absorbance. Turbidimetric methods based on the precipitation of melamine cyanurate are less precise but still useful for pool-side monitoring of cyanuric acid levels. The performance of commercial test kits based on this principle should be checked by a controlling laboratory. 相似文献
43.
A. D. Levin 《Measurement Techniques》2005,48(2):161-165
Quantitative estimates of the components of the error associated with the spectral characteristics of interference light filters, the curving of the surface of a liquid in a crater of the microplotter due to its motion, and capillary effects are given. Methods of identifying and limiting these errors are proposed.__________Translated from Izmeritelnaya Tekhnika, No. 2, pp. 40–42 February, 2005. 相似文献
44.
Tory L. Parker Sarah T. Esgro Samantha A. Miller Lauren E. Myers Rustin A. Meister Stoyan A. Toshkov Nicki J. Engeseth 《Food chemistry》2010
Papaya does not sufficiently maintain desired fresh fruit quality when shipped long distances due to an easily bruised soft skin and a short shelf life. This leads to both a large supply of pulp from unsightly fruit that is never shipped and low sales due to blemished fruit. Unfortunately, traditional preservation methods (pasteurisation) negatively alter papaya’s fresh flavour. Thus to effectively utilise available papaya pulp, processing requires an approach that enables retention of papaya’s natural flavours without excessive heat. Papaya fruit (Carica papaya L., var.’s Rainbow (yellow-fleshed) and SunUp (red-fleshed)) were pulped, diluted, and processed with mild heat (80 °C, 5 min), irradiation (5 kGy or 7.5 kGy) or combinations of both. Irradiation resulted in a significant reduction in ascorbic acid content. Mild heat treatment significantly reduced pectinesterase activity and microbiological viability. Irradiation followed by heat further enhanced destruction of Listeria innocua and Clostridium sporogenes and retained the flavour and a nutritional profile closest to untreated controls. The product was microbiologically safe with acceptable enzyme levels and would be shippable under refrigeration. 相似文献
45.
In this article, morphological modification of Saccharum spontaneum L, a natural fiber through graft copolymerization with methylmethacrylate using ferrous ammonium sulfate—potassium per sulfate redox initiator has been reported. Different reaction parameters such as reaction temperature, time, initiator molar ratio, monomer concentration, pH and solvent were optimized to get maximum graft yield (144%). The graft copolymers thus formed were characterized by Fourier transform infrared, scanning electron microscopy, X‐ray diffraction and thermogravimetric, differential thermal analysis, and differential thermogravimetric techniques. Graft copolymer has been found to be more moisture resistant and also showed higher chemical and thermal resistance. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
46.
The action spectra of Bacillus subtilis spores (ATCC6633) and Salmonella typhimurium LT2 were characterized using physical radiometry for irradiance measurements and a multiple target model to interpret the inactivation kinetics. The observed action spectrum of B. subtilis spores deviated significantly from the relative absorbance spectrum of the DNA purified from the spores, but matched quite well with the relative absorbance spectrum of decoated spores. The action spectrum of B. subtilis spores determined in this study was statistically different from those reported in previous studies. On the other hand, the action spectrum of S. typhimurium bacteria matched quite well with the relative absorbance spectrum of DNA extracted from vegetative cells, except in the region below 240 nm. It is concluded that the common use of the relative DNA absorbance spectrum as a surrogate for the germicidal action spectrum can result in systematic errors when evaluating the performance of a polychromatic UV light reactors using bioassays. For example, if the weighted germicidal fluence (UV dose) calculated using the relative DNA absorbance spectrum as the germicidal weighting factor is found to be 40 mJ cm−2 for a medium pressure lamp UV reactor, that calculated using the relative action spectrum of B. subtilis spores, as determined in this study, would be 66 mJ cm−2. 相似文献
47.
Liliana Jimenez Emilio Alarcón Colleen Trevithick-Sutton Niket GandhiJuan C. Scaiano 《Food chemistry》2011
The effect of γ-radiation on green onion DNA integrity, phenol content, oxygen radical absorbance capacity, employing pyrogallol red and fluorescein as probes, as well as ascorbic acid content has been evaluated. Measurements using thiazole orange-DNA fluorescence and agarose gel electrophoresis show that γ-radiation does not lead to an apparent DNA change in green onion. However, it was readily cleaved upon irradiation from the previously isolated nucleic acid. Furthermore, green onion exposure to γ-radiation produces slight increases in the polyphenol concentrations (163–188 μM Trolox eq.) and a decrease in the oxygen radical absorbance using fluorescein (from 245 to 200 Trolox eq.) Interestingly, a high ascorbic acid content (364 μM), which decreases by 40% after γ-ray exposure was measured by using pyrogallol-red-based oxygen radical absorbance capacity induction times from green onion aqueous extracts. Thus, our results suggest that ascorbic acid present in green onion plays a fundamental role in the plant antioxidant response toward γ-radiation exposure, while polyphenols remain largely unchanged, as revealed from oxygen radical absorbance capacity, employing pyrogallol red. 相似文献
48.
49.
Using black coatings and materials with high light absorbance that are capable of absorbing photons at visible and longer wavelengths is a very effective way to reduce unwanted stray light, also known as optical noise, within optical equipment. These lights can be greatly reduced to a reasonable level by functional and performable black coatings that are modified to absorb incident light as much as possible by their specific pigments. In the present work, several carbonaceous pigments were synthesized for the first time from wasteful materials and their optical properties in the visible and near‐infrared ranges studied. First, MCM‐48 and SBA‐15 were synthesized at different conditions and were then used as templates for carbonaceous products. SSS‐1 (the carbonic pigment synthesized by the mixture of sucrose and sodium silicate), SSS‐2 (the carbonic pigment synthesized by the mixture of sawdust and sodium silicate), and mesoporous carbon pigments (CMK‐3 and CMK‐1 with different levels of saturations) were synthesized. Finally, their structure, morphology, and optical properties were investigated by X‐ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE‐SEM), and Diffuse Reflectance Spectroscopy (DRS). The results indicated that the SSS‐1 pigment had a lower reflectance (below 1%) than carbon black (about 2.5%) in the visible region despite it being more cost‐effective than carbon black. The mesoporous pigments showed very high light absorbance in the visible region (about 2.5%). Compared with other black pigments, the CMK‐1 was the blackest synthesized material with a very low reflectance (about 0.05% in visible region), making it an ideal candidate as a super black pigment for reducing unwanted stray light within optical equipment. 相似文献
50.