Using mass defect plots as a discovery tool to identify novel fluoropolymer thermal decomposition products

Fire events involving halogenated materials, such as plastics and electronics, produce complex mixtures that include unidentified toxic and environmentally persistent contaminants. Ultrahigh‐resolution mass spectrometry and mass defect filtering can facilitate compound identification within these complex mixtures. In this study, thermal decomposition products of polychlorotrifluoroethylene (PCTFE, [–CClF–CF₂–]_n), a common commercial polymer, were analyzed by Fourier transform ion cyclotron resonance mass spectrometry. Using the mass defect plot as a guide, novel PCTFE thermal decomposition products were identified, including 29 perhalogenated carboxylic acid (PXCA, X = Cl,F) congener classes and 21 chlorine/fluorine substituted polycyclic aromatic hydrocarbon (X‐PAH, X = Cl,F) congener classes. This study showcases the complexity of fluoropolymer thermal decomposition and the potential of mass defect filtering to characterize complex environmental samples. Copyright © 2014 John Wiley & Sons, Ltd.     

波长色散X射线荧光光谱法快速测定纺织面料中的铬、镍、铜

建立波长色散X射线荧光光谱快速检测纺织面料中铬、镍、铜的方法。利用树脂将标准贴衬织物复合到玻璃熔片上,在制备好的织物样片上滴加铬、镍、铜标准溶液,采用波长色散X射线荧光光谱仪检测。根据元素滴加量的变化建立校准曲线,铬、镍、铜3种元素的含量分别在0~853,0~853,0~1 706μg/g范围内与荧光强度呈良好的线性关系,相关系数r2大于0.99。方法回收率为95.0%~98.8%,测定结果的相对标准偏差为3.2%~4.8%(n=6)。利用该方法检测纺织面料中重金属元素含量,方法简便,结果准确,检测成本低。     

基于布尔集线器的线速多播自路由交换结构

现有的组播交换结构均是从单播交换结构发展而来,而目前的各种单播交换结构都存在各自的技术瓶颈,当被应用于组播交换时,既不能突破原交换结构的技术局限,又限制了组播交换的性能,因此现有的组播交换结构基本都不具备大规模可扩展的能力。本文提出基于分配格理论的线速组播交换结构,它不仅能满足大规模可扩展和线速组播要求,而且具有低时延、无抖动,不需要排队缓存等性能优势。本文分析并证明了该组播交换结构既能实现最优化的组播,又支持具有优先级的组播,从而在时延上保证了组播QoS(quality of service)。     

激光对棉织物雕印印花强力损失的研究

近年来,激光雕刻工艺开始逐步应用于纺织面料、皮革等材料,对各种面料的雕割、镂花、蚀刻等激光处理开拓了面料再造与图案设计的新途径。然而,激光雕印时,对织物的强力易造成损伤,本文系统地研究了棉织物在激光雕印印花时的强力变化,探讨了不同克重棉织物在BMP、PLT两种图片格式下激光雕印印花后强力与激光速度的关系以及激光雕印后织物强力与激光速度百分率、激光能量百分率之间的关系,以便于推进纺织面料的激光雕印印花的发展。结果表明：BMP图片格式下激光雕印,当激光速度大于1 200 m/min时,基本能保证棉织物的撕破和断裂强力下降率均低于20%。PLT图片格式下激光雕印,棉织物的强力下降率随激光速度百分率的下降而下降,随激光能量百分率的下降而变缓。     

一种新型光子晶体的光学特性研究

本文提出了一种非对称一维各向异性掺杂光子晶体,通过传输矩阵法研究了这种新型光子晶体的光学特性,通过数值模拟得出:光通过该结构光子晶体后TE波和TM波缺陷模的透过率及中心波长位置随缺陷层介质的光学厚度、缺陷层两侧周期数的非对称性的变化规律,两种偏振光波能完全分开,缺陷层介质的光学厚度及掺杂层两侧的周期数层差越大,缺陷模的透过率越小,当光学厚度及层差达到某一极限值时,将产生完全光子禁带,这是对称结构光子晶体所不具备的光学特性,其光学特性将为光子器件的转换制作及应用提供理论依据。     

Self‐Compensated Insulating ZnO‐Based Piezoelectric Nanogenerators

Remarkable enhancement of piezoelectric power output from a nanogenerator (NG) based on a zinc oxide (ZnO) thin film is achieved via native defect control. A large number of unintentionally induced point defects that act as n‐type carriers in ZnO have a strong influence on screening the piezoelectric potential into a piezoelectric NG. Here, additional oxygen molecules bombarded into ZnO lead to oxygen‐rich conditions, and the n‐type conductivity of ZnO is decreased dramatically. The acceptor‐type point defects such as zinc vacancies created during the deposition process trap n‐type carriers occurring from donor‐type point defects through a self‐compensation mechanism. This unique insulating‐type ZnO thin film‐based NGs (IZ‐NGs) generates output voltage around 1.5 V that is over ten times higher than that of an n‐type ZnO thin film‐based NG (around 0.1 V). In addition, it is found that the power output performance of the IZ‐NG can be further increased by hybridizing with a p‐type polymer (poly(3‐hexylthiophene‐2,5‐diyl):phenyl‐C₆₁‐butyric acid methyl ester) via surface free carrier neutralization.     

Effects of defect states on the performance of CuInGaSe2 solar cells

Device modeling has been carried out to investigate the effects of defect states on the performance of ideal CulnGaSe2 （CIGS） thin film solar cells theoretically. The varieties of defect states （location in the band gap and densities） in absorption layer CIGS and in buffer layer CdS were examined. The performance parameters： open-circuit voltage, short-circuit current, fill factor, and photoelectric conversion efficiency for different defect states were quantitatively analyzed. We found that defect states always harm the performance of CIGS solar cells, but when defect state density is less than 10 14 cm-3 in CIGS or less than 10 18 cm-3 in CdS, defect states have little effect on the performances. When defect states are located in the middle of the band gap, they are more harmful. The effects of temperature and thickness are also considered. We found that CIGS solar cells have optimal performance at about 170 K and 2 μm of CIGS is enough for solar light absorption.     

划痕型缺陷对光场质量的影响

为了研究高功率激光系统中划痕型缺陷对光场质量的影响,采用分步傅里叶算法对非线性近轴波动方程进行求解,模拟分析了不同划痕参数（长度、宽度、深度）下,元件内部、光束近场、元件后传输光场以及光束远场的光强分布情况。数值模拟结果表明：随着划痕长度、宽度或深度的增加,元件内部以及元件后传输光场的峰值强度和对比度均会相应增强;光束近场的光强对比度也会略微增大;对于光束远场的强度分布,与划痕宽度方向所对应的频谱能量会不断增强。该项研究工作可以为划痕检验标准的制定提供一定的定量分析依据。     

Electromagnetic-Interference-Shielding Effectiveness of Lyocell-Based Carbon Fabrics Carbonized at Various Temperatures

Lyocell is a biodegradable filament yarn obtained by directly dissolving cellulose in a mixture of N-methylmorpholine-N-oxide and a non-toxic solvent. Therefore, herein, lyocell fabrics were employed as eco-friendly carbon-precursor substitutes for use as electromagnetic interference (EMI) shielding materials. First, a lyocell fabric treated with polyacrylamide via electron beam irradiation reported in a previous study to increase carbon yields and tensile strengths was carbonized by heating to 900, 1100, and 1300 °C. The carbonization transformed the fabric into a graphitic crystalline structure, and its electrical conductivity and EMI shielding effectiveness (SE) were enhanced despite the absence of metals. For a single sheet, the electrical conductivities of the lyocell-based carbon fabric samples at the different carbonization temperatures were 3.57, 5.96, and 8.91 S m⁻¹, leading to an EMI SE of approximately 18, 35, and 82 dB at 1.5–3.0 GHz, respectively. For three sheets of fabric carbonized at 1300 °C, the electrical conductivity was 10.80 S m⁻¹, resulting in an excellent EMI SE of approximately 105 dB. Generally, EM radiation is reduced by 99.9999% in instances when the EMI SE was over 60 dB. The EMI SE of the three lyocell-based carbon fabric sheets obtained at 1100 °C and that of all the sheets of the sample obtained at 1300 °C exceeded approximately 60 dB.     

Green Tea Catechins Attenuate Neurodegenerative Diseases and Cognitive Deficits

Neurodegenerative diseases exert an overwhelming socioeconomic burden all around the globe. They are mainly characterized by modified protein accumulation that might trigger various biological responses, including oxidative stress, inflammation, regulation of signaling pathways, and excitotoxicity. These disorders have been widely studied during the last decade in the hopes of developing symptom-oriented therapeutics. However, no definitive cure has yet been discovered. Tea is one of the world’s most popular beverages. The same plant, Camellia Sinensis (L.).O. Kuntze, is used to make green, black, and oolong teas. Green tea has been most thoroughly studied because of its anti-cancer, anti-obesity, antidiabetic, anti-inflammatory, and neuroprotective properties. The beneficial effect of consumption of tea on neurodegenerative disorders has been reported in several human interventional and observational studies. The polyphenolic compounds found in green tea, known as catechins, have been demonstrated to have many therapeutic effects. They can help in preventing and, somehow, treating neurodegenerative diseases. Catechins show anti-inflammatory as well as antioxidant effects via blocking cytokines’ excessive production and inflammatory pathways, as well as chelating metal ions and free radical scavenging. They may inhibit tau protein phosphorylation, amyloid beta aggregation, and release of apoptotic proteins. They can also lower alpha-synuclein levels and boost dopamine levels. All these factors have the potential to affect neurodegenerative disorders. This review will examine catechins’ neuroprotective effects by highlighting their biological, pharmacological, antioxidant, and metal chelation abilities, with a focus on their ability to activate diverse cellular pathways in the brain. This review also points out the mechanisms of catechins in various neurodegenerative and cognitive diseases, including Alzheimer’s, Parkinson’s, multiple sclerosis, and cognitive deficit.