Ultrasonic characterisation of flour-water systems: a new approach to investigate dough properties

The viscoelastic properties of dough are of great interest in the baking industry as they affect the quality of the final product. In this work, the viscoelastic properties of dough were investigated using ultrasonic techniques and then compared with traditional methods. It has been shown that ultrasonics provides a non-destructive, rapid and low cost technique for the measurement of physical food characteristics. A common protocol for dough preparation was used for each type of measurement. Experimental results on more than 30 different flour quality and dough processing were presented. The measurements were correlated and compared with traditional dough quality tests. In addition, the capability of ultrasound measurements for discriminating flours for different purposes was also studied, showing the potential of ultrasound as an alternative measurement method to discriminate types of flours for different purposes.     

两跳蚤移行路径长度比较

讨论有关文献在谈到曲线弧长公式时所提出的一个关于两跳蚤移行路径长度的问题.通过理论推导并借助图形分析显示,只是在一些离散的特殊时刻,两跳蚤移行的摆线长度才相等.     

Realization of all Dold's congruences with stability

The main goal of this paper is to prove that for each n>2, every sequence of integers satisfying Dold's congruences is realized as the sequence of fixed point indices of the iterates of an orientation preserving Rn-homeomorphism at an isolated stable fixed point. We use Conley index techniques even though stable fixed points are not isolated invariant sets.     

电炮加载下芳纶蜂窝夹芯板的动力响应

研究了方形钛-芳纶蜂窝夹芯板在电炮驱动的高速聚酯飞片撞击加载下的动力响应,给出了面板和蜂窝芯层在不同冲击速度下的变形及失效模式。采用VISAR(velocity interferometer system for any reflector)测速技术测量了后面板中心点的速度时程,分析了芳纶蜂窝夹芯板的动态响应过程,讨论了冲击速度对夹芯板动力响应和抗冲击能力的影响。研究结果表明,低波阻抗的芳纶蜂窝破碎行为阻断了应力波向后面板的传播途径,破碎的蜂窝和塑形大变形的前面板吸收了高速冲击的大部分能量,充分发挥了钛合金的高强度和芳纶蜂窝的缓冲吸能特性,提高了夹芯板整体的防护能力。     

5-甲基-2-(2'-吡啶基)苯并咪唑及甘氨酸根铜(Ⅱ)配合物的合成、DNA结合及抗癌活性

利用溶剂缓慢挥发法合成了以5-甲基-2-(2′-吡啶基)苯并咪唑为主配体的铜(Ⅱ)混配配合物[Cu(HPBM)(Gly)(H_2O)]ClO_4·0.5H_2O(HPBM=5-甲基-2-(2′-吡啶基)苯并咪唑,Gly=甘氨酸根)。采用元素分析、红外光谱、紫外可见光谱、摩尔电导率测定和ESIMS等手段对配合物进行了表征。应用电子吸收光谱、荧光光谱、粘度测定及分子对接等方法揭示了配合物主要以沟槽结合的方式与DNA作用。应用MTT法测定了配合物对Eca-109、HeLa和A549细胞株的体外细胞毒活性,其IC50值范围为6.4～8.5μmol·L~(-1)。尤为重要的是,通过AO/EB双染法、单细胞凝胶电泳、线粒体膜电位及细胞周期测定分析等揭示了配合物通过DNA结合及线粒体功能失调途径诱导Eca-109细胞凋亡。     

MWCNT‐modified Electrode for Voltammetric Determination of Allura Red and Brilliant Blue FCF in Isotonic Sport Drinks

A fast and simple electrochemical sensor is presented for the determination of allura red and brilliant blue in isotonic sport drinks, using a glassy carbon electrode modified with multi‐walled carbon nanotubes. The electrochemical behavior of the colorants was studied by cyclic and differential pulse voltammetry in 0.1 M PBS, pH 7.0. The solution pH, the amount of nanomaterial on the surface of the electrode and the accumulation time of each colorant were optimized. Under the optimal conditions, the sensor exhibited a linear response to allura red and brilliant blue with detection limits of 7 μg L^?1 and 52 μg L^?1, respectively. The sensor was applied to the analysis of commercial isotonic sports drinks that contain individual or mixed colorants, showing good sensitivity and reproducibility. The results were compared with a chromatographic method showing that the levels of colorants are low and did not show a risk for a consumer's health.     

Elucidation of artefacts in proton transfer reaction time‐of‐flight mass spectrometers

We present an effective procedure to differentiate instrumental artefacts, such as parasitic ions, memory effects, and real trace impurities contained in inert gases. Three different proton transfer reaction mass spectrometers were used in order to identify instrument‐specific parasitic ions. The methodology reveals new nitrogen‐ and metal‐containing ions that up to date have not been reported. The parasitic ion signal was dominated by [N₂]H⁺ and [NH₃]H⁺ rather than by the common ions NO⁺ and O₂⁺. Under dry conditions in a proton transfer reaction quadrupole interface time‐of‐flight mass spectrometer (PTR‐QiTOF), the ion abundances of [N₂]H⁺ were elevated compared with the signals in the presence of humidity. In contrast, the [NH₃]H⁺ ion did not show a clear humidity dependency. On the other hand, two PTR‐TOF1000 instruments showed no significant contribution of the [N₂]H⁺ ion, which supports the idea of [N₂]H⁺ formation in the quadrupole interface of the PTR‐QiTOF. Many new nitrogen‐containing ions were identified, and three different reaction sequences showing a similar reaction mechanism were established. Additionally, several metal‐containing ions, their oxides, and hydroxides were formed in the three PTR instruments. However, their relative ion abundancies were below 0.03% in all cases. Within the series of metal‐containing ions, the highest contribution under dry conditions was assigned to the [Fe(OH)₂]H⁺ ion. Only in one PTR‐TOF1000 the Fe⁺ ion appeared as dominant species compared with the [Fe(OH)₂]H⁺ ion. The present analysis and the resulting database can be used as a tool for the elucidation of artefacts in mass spectra and, especially in cases, where dilution with inert gases play a significant role, preventing misinterpretations.     

单光束多组分温室气体的腔衰荡光谱同步检测

腔衰荡光谱技术(CRDS)作为一种具有高灵敏度高光谱分辨率的检测方法已被广泛用于痕量气体检测。而目前基于CRDS痕量气体检测多针对单一气体进行测量或通过多个激光器产生的多光束进行多种组分气体浓度测量。利用DFB激光器波长可调谐特性,通过强弱吸收峰结合,使用单光束实现了多种温室气体的腔衰荡光谱技术同步检测。由于大气中水汽和二氧化碳浓度较高,为实现同一衰荡系统对三种温室气体的同步测量,在平衡吸收损耗的基础上,选取1 653~1 654 nm内甲烷的强吸收峰与水汽、二氧化碳的弱吸收峰进行测量。通过光谱叠加反演矩阵,分别得到甲烷、水汽、二氧化碳的浓度。在计算测量灵敏度过程中发现,通过去除衰荡过程初期的部分数据点(过滤区间),会对噪声等效吸收系数产生影响。多数情况下,在测量灵敏度计算方面,列文伯格-马夸尔特算法(L-M)会优于离散傅里叶变换法(DFT);但当衰荡曲线的单指数性下降时,上述结论不一定成立。搭建了一个低精细度(F≈6×103)衰荡腔对上述结论进行了实验验证。相较于用于测量温室气体浓度的高精细度衰荡腔(F≈1×105),低精细度衰荡腔的衰荡速率较快,衰荡曲线的单指数性明显低于高精细度衰荡腔。实验表明,在过滤区间长度较短时,采用DFT算法计算得到的噪声等效吸收系数会小于L-M算法得到的结果。当过滤区间长度增加时,L-M算法得到的结果优于DFT算法。在受过滤区间长度影响方面,DFT算法的波动性要明显小于L-M算法。根据Allan方差分析,在512次采样平均(约8 s)下的最小噪声等效吸收系数进行计算,该CRDS装置测量灵敏度为2.4×10-10 cm-1。在25 ℃标准大气压下,对应甲烷、水汽、二氧化碳的测量灵敏度分别为0.64 ppbv,3.5 ppmv和4.0 ppmv。基于该CRDS装置,通过单光束多波长测量方法,利用光谱叠加反演矩阵,测得大气中甲烷、水汽、二氧化碳浓度分别为2.018,3 654和526 ppmv;而采用经典CRDS单波长测量得到的甲烷、水汽、二氧化碳浓度分别为2.037,3 898和630 ppmv。通过与温控调节波长,逐点扫描得到的光谱吸收曲线进行对比,采用多波长测量得到气体浓度进行复合拟合的光谱曲线残差小于单波长测量得到气体浓度进行简单拟合的光谱曲线残差。     

Entropic Kullback-Leibler type distance measures for quantum distributions

Entropic distance measures for quantum mechanical probability distributions, which are characterized by nodal structure and symmetry holes, are considered. We illustrate how the Kullback-Leibler (KL) distance is not well defined in some instances and propose instead the use of the cumulative residual Kullback-Leibler (CRKL) distance. The KL and CRKL measures are compared and contrasted for some representative quantum mechanical systems: The particle in an infinite well, the harmonic oscillator, and hydrogenic systems. We present cases where CRKL can be used to obtain distances whereas KL cannot be used, and also highlight examples where the KL and CRKL measures yield different behaviors and interpretations. An extension of the CRKL definition is obtained for application to harmonic oscillator systems defined over [−∞, ∞]. Distance measures for two-variable (particle) distributions are also considered to address generalizations of the mutual information correlation measure. The use of CRKL in measuring distances between orbitals is also discussed.     

二对甲基苄基锡芳甲酰腙配合物的合成、晶体结构及生物活性

将二对甲基苄基二氯化锡分别与2-[(4-硝基-苯甲酰基)-亚肼基]-3-苯基-丙酸或2-[(噻吩-2-羰基)-亚肼基]-3-苯基-丙酸反应,合成了2个以Sn_2O_2四元环为中心对称的二对甲基苄基锡配合物(C1、C2),通过元素分析、IR、~1H NMR、~(13)C NMR、~(119)Sn NMR、HRMS以及X-射线单晶衍射等表征了配合物的结构。测试了配合物C1、C2对癌细胞NCI-H460、HepG2、MCF7的体外抑制活性,结果表明,配合物C1、C2对3种癌细胞都有较好的抑制作用,C1略优于C2。通过紫外光谱、荧光光谱、粘度法测试配合物C1与小牛胸腺DNA的相互作用方式,结果均显示配合物C1与小牛胸腺DNA的作用是插入结合,并且作用效果较强;凝胶电泳研究表明,配合物C1能够有效地将超螺旋DNA pBR322切割成缺刻型DNA。