Fragmentation pathways of deprotonated ortho-hydroxybenzyl alcohol

The ortho, meta, and para isomers of hydroxybenzyl alcohol can be unequivocally distinguished by the collision-induced dissociation mass spectra of their anions. The presence of a prominent peak at m/z 121 for an elimination of a dihydrogen molecule renders the ortho-isomer spectrum markedly different from those of its meta and para congeners. Investigations carried out with deuterium-labeled isotopologues of the ortho isomer verified that the labile hydrogen atom on the hydroxyl group and one of the benzylic hydrogen atoms are specifically removed in the formation of the m/z 121 ion. The ortho-isomer spectrum also showed a prominent peak at m/z 93. Experimental data indicated that the m/z 93 product ion originates either from a two-step H₂and CO elimination mechanism or from a direct loss of a HCHO molecule from the precursor anion. The intensity ratio of the m/z 93 and 94 peaks in the spectrum recorded from the m/z 124 ion generated from a sample of o-hydroxybenzyl alcohol dissolved in D₂O supported the notion that the direct HCHO loss is the more dominant pathway for the generation of the phenolate ion under low activation conditions. In contrast, the two-step mechanism becomes the more dominant pathway under high collisional activation conditions. The spectrum also showed a weak peak at m/z 105 for a water loss. Based on computational data, the m/z 105 ion generated in this way appears to be a composite generated from a common ion-neutral complex intermediate in which a hydroxyl anion is positioned equidistantly between one of the benzylic hydrogens and a nearby hydrogen atom of the benzene ring. Upon activation, the complex dissociates to form either a phenide or a quinone methide anion. The reaction forming a carbon dioxide adduct under ion-mobility conditions was used to support the proposed water-loss mechanism.     

An exact algorithm for a resource allocation problem in mobile wireless communications

We consider a challenging resource allocation problem arising in mobile wireless communications. The goal is to allocate the available channels and power in a so-called OFDMA system, in order to maximise the transmission rate, subject to quality of service constraints. Standard MINLP software struggled to solve even small instances of this problem. Using outer approximation, perspective cuts and several implementation “tricks”, we are able to solve realistic instances in about one minute. A novel ingredient of our algorithm is what we call pre-emptive cut generation: the generation of cutting planes that are not violated in the current iteration, but are likely to be violated in subsequent iterations.     

Degradation of β-Carbolines Harman and Norharman in Edible Oils during Heating

The β-carbolines, mainly including harman and norharman, are a group of naturally occurring, plant-derived alkaloids, and are also considered as nonpolar heterocyclic aromatic amines. Sesame seed oils contain a high level of β-carbolines (harman and norharman). In China, sesame seed oil blends are one of the most popular types of vegetable oils blends, which can be used as cooking oils or frying oils. Thus, it is meaningful to investigate the degradation of β-carbolines (harman and norharman) in sesame seed oil blends as frying oils during heating. In this work, the loss of harman and norharman in different types of sesame seed oil blends have been investigated. The results showed that the degradation of harman and norharman were dependent both on the type of oil blends, heating temperature and time. Harman and norharman were more degraded during heating (150 °C, 180 °C) in oleic acid-rich oil blends compared to polyunsaturated acid-rich oil blends. Mechanistic investigation suggested that the reduction in harman and norharman in oil blends during heating was mainly due to the oxidative degradation reaction between β-carbolines and lipid oxidation products. Therefore, the contents of β-carbolines (harman and norharman) in sesame seed oil blends when used as frying oils and heated can be decreased with prolonged cooking time.     

1,1—二甲基—3—丁烯基环戊二烯基稀土二氯化物的合成

１，１－二甲基－３－丁烯基环戊二烯基稀土二氯化物的合成林进张萍王昭煜＊（河北师范大学化学系石家庄０５００１６）关键词烯基环戊二烯基，稀土二氯化物，配合物，合成１９９７－０８－０６收稿，１９９７－１２－０５修回河北省自然科学基金资助课题环戊二烯基轻稀土...     

徒骇河聊城大学段水质情况的检测

徒骇河是流经聊城地区的一条主要河流,将其作为研究对象,在不同地点取样,对其水质进行了实验检测。结果显示,徒骇河水质只符合国家Ⅳ或Ⅴ类水的标准,即一般工业或农业用水及景观用水等。因此,长期饮用此水或用于灌溉农田都会对居民及农作物甚至当地的生态环境带来严重的负面影响。     

Absorption enhancement of thin film solar cells using back binary metallic grating

We reported in this work that light absorption can be significantly enhanced in an a-Si thin film solar cell with a nano binary metallic grating patterned on the bottom side. The enhancement is mainly due to combination of several kinds of optical modes. Cavity mode, at the transverse and longitudinal cavities and surface plasmon mode, propagating along the interface of silicon and silver are the main modes contributing to the enhancement. Some key parameters including grating period, width, height and active layer thickness are optimized. The integrated absorption rate of the optimized system reaches 76.55 % for the wavelength range from 300 to 950 nm under AM1.5G spectrum.     

Controllable synthesis of graphene sheets with different numbers of layers and effect of the number of graphene layers on the specific capacity of anode material in lithium-ion batteries

High quality graphene sheets are synthesized through efficient oxidation process followed by rapid thermal expansion and reduction by H₂. The number of graphene layers is controlled by tuning the oxidation degree of GOs. The higher the oxidation degree of GOs is getting, the fewer the numbers of graphene layers can be obtained. The material is characterized by elemental analysis, thermo-gravimetric analysis, scanning electron microscopy, atomic force microscopy, transmission electron microscopy and Fourier transform infrared spectroscopies. The obtained graphene sheets with single, triple and quintuplicate layers as anode materials exhibit a high reversible capacity of 1175, 1007, and 842 mA h g⁻¹, respectively, which show that the graphene sheets with fewer layers have higher reversible capacity.     

钢丝软轴是怎样传递扭矩的

 详细分析了钢丝软轴传递扭矩的原理,结果表明: 包轴的套管的协同工作起着至关重要的作用.     

外周天线色素分子间的能量传递

依据外周天线LHCII的吸收光谱和解叠谱,将LHCII中大量的色素分子分为4类色素分子团,建立了色素分子团的能量传递模型,并分别在436nm、480nm激励光下,对它的荧光光谱进行了研究,436nm和480nm激励下的荧光光谱相比要弱,可能是由于436nm激励下,受激的一部分色素分子的振动自由度比较大,产生了激发态到基态的无辐射内转换,使得能量传递几率降低.同时也说明,不同色素分子间的能量传递几率是不同的.     

确定疲劳极限的外推法

提出了利用成组法的结果代替升降法确定疲劳极限的外推法。首先给出以疲劳极限为参量的S－N曲线的数学表达式。然后将四组成组法的试验结果代入上式，得到四个等式。从这四个等式中消去其它的材质参量，即可得到求解疲劳极限的超越方程。在求得疲劳极限后，再根据上述试验结果以最小二乘法拟合上述其它材质参量。利用该方法可进一步做出完整的中值S－N曲线，这就大大地节约了疲劳试验的机时与疲劳试验费用。