Optical studies of pure and gelatin‐doped poly(vinyl alcohol) films irradiated with fast neutrons

The ultraviolet (UV) and infrared (IR) spectra of pure poly(vinyl alcohol) (PVA) and gelatin–doped PVA films with concentrations (2, 5, 7, 10, and 15 wt %) were studied before and after irradiation with neutron fluences in the range of 10⁵–10⁸ n/cm². The obtained data revealed that the addition of gelatin and neutron irradiation causes structural variation in the PVA network. The analysis of the UV spectra showed that the increase of dopant concentration above 5 wt % gelatin makes the sample less resistant to a degradation effect caused by neutron irradiation. It was also found that the intensity of the band at 210 nm increases by increasing dopant concentration. Careful examination of the infrared spectra indicated that the induced percent crystallinity of the sample containing 5 wt % gelatin has more stability than the other doped samples. Neutron irradiation also results in the appearance of new absorption bands and irregular change in the absorbance of some IR bands. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1395–1406, 1999     

防腐剂与抗磨剂的竞争吸附效应

利用含有防腐剂的润滑油和轴承珠进行模拟吸附实验,通过紫外光谱的测量方法对吸附实验前后的润滑油进行吸光度测量,发现了吸附实验前后润滑油紫外吸光度的区别, 利用郎伯-贝尔原理对润滑油与轴承珠接触界面膜中的吸附量进行了计算,证实了防腐剂在摩擦副表面的吸附作用;对含有抗磨剂和防腐剂的润滑油进行吸附实验,并测量了实验前后润滑油的紫外吸光度,发现了相同防腐剂质量分数、不同抗磨剂质量分数润滑油紫外吸光度有较大区别;通过紫外光谱测量和界面膜中防腐剂吸附量的计算方法,表征了抗磨剂对防腐剂在摩擦副表面吸附量的定性影响规律 ,证实了抗磨剂与防腐剂的竞争吸附关系。     

Optical properties of polymeric materials for concentrator photovoltaic systems

As part of our research on materials for concentrator photovoltaics (CPV), we are evaluating the optical properties and solar radiation durability of a number of polymeric materials with potential in CPV applications. For optical materials in imaging or non-imaging optical systems, detailed knowledge of the wavelength-dependent complex index of refraction is important for system design and performance, yet optical properties for many polymeric systems are not available in the literature. Here we report the index of refraction, optical absorbance, haze, and Urbach edge analysis results of various polymers of interest for CPV systems. These values were derived from ellipsometry and from using a VUV-VASE and transmission based absorbance spectroscopy on thick film samples.Fluoropolymers such as poly(tetrafluoroethylene-co-hexafluoropropylene) (Teflon^® FEP), poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether) (Teflon^® PFA) and poly(ethylene-co-tetrafluoroethylene) (Teflon^® ETFE Film) have desirable optical and physical properties for optical applications in CPV. Ethylene backbone polymers such as polyvinylbutyral (PVB) sheet (e.g., DuPont^TM PV5200), and ethylene co-polymers such as poly(ethylene-co-vinyl acetate) (EVA) (e.g., DuPont^TM Elvax^® PV1400), and poly(ethylene-co-methacrylic acid metal salt) ionomer sheet (e.g., DuPont^TM PV5300) have applications as encapsulants in crystalline silicon (c-Si) and other flat plate PV applications. These materials are available with both a wide variety of polymer compositions and additive packages which affect their optical properties such as the UV absorption edge. Even materials such as DuPont’s Kapton^® polyimide films, which are used behind the PV cell for their electrically insulating properties, have optical requirements, and we have also characterized these materials.The detailed optical properties of these materials will be useful in the design of the geometrical optics of a CPV system and optimization of the system’s optical throughput. This information will also provide insights into the system’s optical absorption. This is important, for example in the UV, where this absorption can impact the radiation durability of the materials.     

食品着色剂诱惑红在不同pH值介质中吸光度变化的研究

食品着色剂诱惑红（AlluraRed）是七十年代美国经过严格毒理学研究及安全性评估后推出的一种毒性小、安全性高、色光鲜艳，已在世界各国批准使用并将逐渐取代其他红色谱食用合成色素的食品、药品、化妆品着色剂新品种。在食品、药品、化妆品、饲料、玩具等行业中有越来越大的用途。本文研究了诱惑红在不同pH值介质中的吸光度的变化，其结果有助于着色剂诱惑红在各领域中的更广泛应用。     

络合-分光光度法测定食品级石蜡中的痕量铅

食品级石蜡中的铅与双硫腙能够生成红色络合物,采用分光光度法测定络合溶液的吸光度,建立溶液的吸光度与铅含量回归方程。实验证明,络合溶液在波长510nm处有最大吸收峰,当溶液中铅质量分数在0～10 0mg/kg内,铅含量与吸光度成良好的线性关系,检出限为0 1mg/kg。该方法适用于食品级石蜡、微晶蜡中铅的测定。     

The wind potential impact on the maximum wind energy penetration in autonomous electrical grids

According to long-term wind speed measurements the Aegean Archipelago possesses excellent wind potential, hence properly designed wind energy applications can substantially contribute to fulfill the energy requirements of the island societies. On top of this, in most islands the electricity production cost is extremely high, while significant insufficient power supply problems are often encountered, especially during the summer. Unfortunately, the stochastic behaviour of the wind and the important fluctuations of daily and seasonal electricity load pose a strict penetration limit for the contribution of wind energy in the corresponding load demand. The application of this limit is necessary in order to avoid hazardous electricity grid fluctuations and to protect the existing thermal power units from operating near or below their technical minima. In this context, the main target of the proposed study is to present an integrated methodology able to estimate the maximum wind energy penetration in autonomous electrical grids on the basis of the available wind potential existing in the Aegean Archipelago area. For this purpose a large number of representative wind potential types have been investigated and interesting conclusions have been derived.     

Reconsidering the quantitative analysis of organic carbon concentrations in size exclusion chromatography

The evaluation of the molecular size distribution of natural organic matter (NOM) in aquatic environments via size exclusion chromatography (SEC) is important for the understanding of environmental processes such as nutrient cycling and pollutant transport as well as of technical water treatment processes. The use of organic carbon (OC) detectors has become popular in recent studies due to improved availability and quantification possibilities, which supposedly are superior to those of ultraviolet (UV) detectors. A set of 12 NOM samples was used to demonstrate the limitations of online OC detection (OCD) when analyzing complex aquatic organic matter. A novel evaluation approach for SEC data is introduced by combining the information from UV absorbance (UVA) and OCD chromatograms as well as offline total OC (t-OC) and dissolved OC-specific UVA (SUVA) measurements. It could be shown that about 70% of certain OC components were not detected with the OCD system used in this study. For the investigated samples, these types of carbon accounted for up to 72% of the t-OC, i.e. for such NOM samples quantification by OCD is not possible or at least highly questionable. The addition of an oxidant improved the overall oxidation efficiency only slightly. Most likely NOM that predominantly consists of polysaccharides and features a nominal molecular weight of 150 kg/mol or more was responsible for low OCD yields. For future applications, a further improvement of the OCD system would be worthwhile so that quantitative analytical data on the molecular size distribution of NOM and its structural characteristics such as the SUVA distribution can be obtained.     

Thermal, Optical, and Electrical Properties of Gel Grown ZMTC

The bimetallic thiocyanate of the group IIB divalent d¹⁰ ions Zn²⁺ and Hg²⁺ having unique characteristics: The pale color and high thermal stability—Zinc Mercury tetrathiocyanate (ZMTC) is chosen for growth and study. ZMTC is grown in silica gel by chemical reaction method and characterized by single crystal XRD, FTIR, FT-Raman, UV-Vis-NIR, NLO, TGA/DTG, DSC, AC conductivity, and dielectric studies. It has wide transparency window and possesses high second harmonic generation efficiency. Its thermal stability is very high. The dielectric permittivity of this material is very low.     

Effect of γ-radiation on green onion DNA integrity: Role of ascorbic acid and polyphenols against nucleic acid damage

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.     

Some of the most significant changes in the Fourier transform infrared spectra of edible oils under oxidative conditions

The oxidation of a broad collection of commercial edible oils, including extra virgin olive, olive, sesame, sunflower, corn, unknown seed, soybean, safflower, rapeseed, peanut and walnut oils, was monitored by Fourier transform infrared spectroscopy. Samples were kept in a convection oven with air circulating at 70 °C. Duplicate spectra were collected each day of the experiment by applying a film of pure oil between two KBr disks. The frequency and absorbance of each infrared band were automatically registered by a macro program. Ratios between absorbances of different bands of the spectra were calculated. Changes in frequency values of different bands and in ratios between absorbances of some bands allow different stages of the oxidation process to be distinguished as well as determining their oxidative stability in a simple and fast way, showing the usefulness of this technique in monitoring oil oxidation processes. © 2000 Society of Chemical Industry