The Photodecomposition of 1,l-Dichloro-2,2-bis(5′-chloro-2′-methoxyphenyl)ethylene (MPE), an Analogue of DDE

The solution-phase photodecomposition of l, l-dichloro-2,2-bis(5′-chloro-2′-methoxy-phenyl)ethylene (MPE) has been studied at an excitation wavelength of 313 nm in the presence of O₂ as well as in vacuum-degassed solutions. Only two non-volatile compounds are produced: 2,5-dichloro-3-(5′-chloro-2′-methoxyphenyl)benzofuran (BFD) and a minor product which was not identified. The BFD represents approximately 90% of the total non-volatiles. The volatile products were identified as CH₃Cl, CH₄ and HC1, with CH₃C1 being approximately 99.9 % of the total volatiles. Photolyses were carried out in C₆H₁₂ and CCI₄ solvents, the same products being observed in both solvents. Variation of MPE concentration has little or no effect on the relative quantum yield of decomposition. The photodecomposition of MPE does not follow the same pathway as the photodecomposition of DDE.     

Dimensional considerations on the mechanical properties of 3D printed polymer parts

Additive manufacturing offers a useful and accessible tool for prototyping and manufacturing small volume functional parts. Polylactic acid (PLA) and thermoplastic polyurethane (TPU) are amongst the most commonly used materials. Characterising 3D printed PLA and TPU is potentially important for both designing and finite element modelling of functional parts. This work explores the mechanical properties of additively manufactured PLA/TPU specimens with consideration to design parameters including size, and infill percentage. PLA/TPU specimens are 3D-printed in selected ISO standard geometries with 20%, 60%, 100% infill percentage. Tensile and compression test results suggest that traditional ISO testing standards might be insufficient in characterising 3D printed materials for finite element modelling or application purposes. Infill percentage in combination to design size, may significantly affect the mechanical performance of 3D printed parts. Dimensional variation may cause inhomogeneity in mechanical properties between large and small cross section areas of the same part. The effect was reduced in small cross section parts where reducing the nominal infill had less effect on the resulting specimens. The results suggest that for 3D printed functional parts with significant dimensional differences between sections, the material properties are not necessarily homogeneous. This consideration may be significant for designers using 3D printing for applications, which include mechanical loading.     

片段化森林中檵木幼苗种内叶经济性状变异及其驱动因子

在异质性生境中,种内功能性状变异有助于植物对环境的适应,进而影响种群更新、群落构建和生态系统过程。探讨了种内叶经济性状的变异及受生境异质性的塑造情况。以千岛湖片段化生境中的常见种檵木（Loropetalum chinense）的幼苗为研究对象,测定了200株檵木幼苗个体水平的7个叶经济性状（比叶面积SLA、叶全碳量C、叶全氮量N等）及其对应的生境因子（郁闭度、土壤全碳量、土壤全氮量等）,采用相关性检验、主成分分析和线性混合效应模型等方法探讨片段化森林中檵木幼苗的种内叶经济性状变异及生境异质性对该变异的驱动作用。结果显示：（1） 在7个叶经济性状所构成的21对相关性分析中,有12对显著相关。经主成分分析降维后,主成分1（PC1）占性状总变异的43.02%,主要与比叶面积、叶绿素浓度、叶全氮量呈正相关,与叶干物质质量分数和叶碳氮比呈负相关,体现了檵木的种内叶经济谱,可反映叶片的最大光合效率。（2）片段化对生境条件和叶经济性状均有影响。岛屿森林群落的郁闭度显著低于大陆。相对于大陆,岛屿中的檵木幼苗趋向于更小的PC1值（缓慢投资-收益策略）;大岛边缘较大岛内部偏向于更小的PC1值。（3）生境因子中,郁闭度对PC1具有显著正效应。研究表明,片段化生境中的檵木在幼苗阶段存在叶经济谱,生境片段化可通过影响生境条件进而改变檵木幼苗的叶经济性状。随着生境片段化程度的加剧,檵木幼苗的叶经济性状逐渐向缓慢投资-收益策略靠拢。     

Seasonal Variability of a Caryophyllane Chemotype Essential Oil of Eugenia patrisii Vahl Occurring in the Brazilian Amazon

Eugenia patrisii Vahl is a native and non-endemic myrtaceous species of the Brazilian Amazon. Due to few botanical and phytochemical reports of this species, the objective of the present work was to evaluate the seasonal variability of their leaf essential oils, performed by GC and GC-MS and chemometric analysis. The results indicated that the variation in oil yields (0.7 ± 0.1%) could be correlated with climatic conditions and rainy (R) and dry seasons (D). (E)-caryophyllene (R = 17.1% ± 16.0, D = 20.2% ± 17.7) and caryophyllene oxide (R = 30.1% ± 18.4, D = 14.1% ± 19.3) are the major constituents and did not display significant differences between the two seasons. However, statistically, a potential correlation between the main constituents of E. patrisii essential oil and the climatic parameters is possible. It was observed that the higher temperature and insolation rates and the lower humidity rate, which are characteristics of the dry season, lead to an increase in the (E)-caryophyllene contents, while lower temperature and insolation and higher humidity, which occur in the rainy season, lead to an increase in the caryophyllene oxide content. The knowledge of variations in the E. patrisii essential oil composition could help choose the best plant chemical profile for medicinal purposes.     

Development and characterization of a magnetic bead-quantum dot nanoparticles based assay capable of Escherichia coli O157:H7 quantification

The development and characterization of a magnetic bead (MB)-quantum dot (QD) nanoparticles based assay capable of quantifying pathogenic bacteria is presented here. The MB-QD assay operates by having a capturing probe DNA selectively linked to the signaling probe DNA via the target genomic DNA (gDNA) during DNA hybridization. The signaling probe DNA is labeled with fluorescent QD₅₆₅ which serves as a reporter. The capturing probe DNA is conjugated simultaneously to a MB and another QD₆₅₅, which serve as a carrier and an internal standard, respectively. Successfully captured target gDNA is separated using a magnetic field and is quantified via a spectrofluorometer. The use of QDs (i.e., QD₅₆₅/QD₆₅₅) as both a fluorescence label and an internal standard increased the sensitivity of the assay. The passivation effect and the molar ratio between QD and DNA were optimized. The MB-QD assay demonstrated a detection limit of 890 zeptomolar (i.e., 10⁻²¹ mol L⁻¹) concentration for the linear single stranded DNA (ssDNA). It also demonstrated a detection limit of 87 gene copies for double stranded DNA (dsDNA) eaeA gene extracted from pure Escherichia coli (E. coli) O157:H7 culture. Its corresponding dynamic range, sensitivity, and selectivity were also presented. Finally, the bacterial gDNA of E. coli O157:H7 was used to highlight the MB-QD assay's ability to detect below the minimum infective dose (i.e., 100 organisms) of E. coli O157:H7 in water environment.     

线性随机桁架结构的平稳随机响应分析

研究了随机桁架结构的平稳随机响应问题。同时考虑结构的物理参数、几何尺寸的随机性，从结构平稳随机响应在频域上的表达式出发，利用求解随机变量函数矩的方法，导出了随机桁架结构在平稳随机激励下位移响应均方值的均值、均方差和变异系数的计算表达式。通过算例考察了随机荷载激励下结构物理参数、几何尺寸的随机性对结构随机响应的影响。     

低压闪蒸液滴形态和温度变化的研究

将液滴在常压下突然置于低压环境中,液滴由最初的平衡状态变成过热状态,发生闪蒸.本文实验研究了低压闪蒸液滴内部形态和温度的变化,系统描述了液滴闪蒸过程中的各种形态变化,总结了稳态闪蒸和稳态结冰过程中环境压力和初始温度对温度变化的影响.实验结果表明液滴闪蒸分六种形态.稳态闪蒸中环境压力越低,液滴的最终温度也越低;液滴的初始温度越高,降到最低温度的时间越长.稳态结冰过程中,液滴初始温度增加,液滴结冰温度和结冰回升最高温度也随之增加;液滴的结冰温度和回升最高温度随环境压力的增高而减小.     

名义上无水硬玉矿物中“水”的热变异行为研究

以硬玉岩中名义上无水硬玉矿物为研究对象,通过常温和变温红外光谱测量,确定硬玉矿物结构水表征及变温过程热变异行为。研究结果显示：由M-OH伸缩振动所致的红外吸收谱带集中于3 700～3 600,3 570～3 520,3 500～3 300及3 230～3 140 cm-1波数范围内,但在不同的硬玉岩中具有不同的红外吸收。变温过程中,该吸收谱带基本在500 ℃左右相对吸收强度出现较为明显的减弱,且结构水含量也逐渐下降,进一步表征硬玉矿物中的“水”是以结构水的形式进入晶格。但此M-OH伸缩振动所致的吸收谱带、结构水含量和指纹谱均在850 ℃附近出现较为明显的变化,预示该温度硬玉矿物的成分已出现变异。硬玉矿物中“水”的热变异行为为进一步了解水分子的赋存状态与结合方式及其成岩机制提供一定的佐证。     

基于全变分正则化的高能闪光照相消模糊图像重建算法

 针对高能闪光照相投影图像消模糊难度大的问题,提出了一种基于全变分正则化的消模糊图像重建算法,该算法根据闪光照相的成像特点,将客体的纵向截面作为一个整体来进行建模,并在重建方程中考虑了模糊因素,然后采用全变分范数作为正则项,构建了用于消模糊图像重建的展平泛函,将消模糊图像重建问题转化为能量泛函极小化问题,通过固定点迭代算法求解图像重建问题的最小化解。数值模拟结果表明：该算法由于考虑了闪光照相成像时的图像模糊因素,在重建时能够较好地消除模糊对重建结果的影响,在抑制噪声的同时能较好地保持图像的边缘信息,有利于提高重建图像的质量。