The Application of Diffusing-Wave Spectroscopy to Monitor the Phase Behavior of Emulsion-Polysaccharide Systems

Droplet aggregation is an important cause of instability in emulsions because it may, on one hand, lead to an increased creaming rate, resulting in fast separation of a concentrated emulsion phase (creamed layer). On the other hand, it may also lead to the formation of a stabilizing, droplet-based network. Early detection of instability is often difficult due to the high turbidity and viscosity of more concentrated food emulsions. The applicability of diffusing-wave spectroscopy (DWS) for monitoring droplet aggregation and creaming was studied using a model system consisting of a protein-stabilized emulsion, to which a soluble polymer ("thickener") was added. This addition leads to an increased solvent viscosity and may induce droplet aggregation. In addition, the redistribution process of emulsion droplets in aggregating concentrated emulsions was directly observed by confocal scanning laser microscopy (CSLM). By DWS the decrease of the droplet mobility caused by the viscosity increase of the continuous phase could be separated from the effect of droplet aggregation. Moreover, a distinction could be made between aggregation, leading to increased creaming rates and that leading to the formation of a stabilizing droplet network. The potential of DWS for in situ measurement of the stability of concentrated emulsions is discussed. Copyright 2000 Academic Press.     

邻苯二酚显色树脂相分光光度法同时测定地下水中微量铁(Ⅲ)和钼(Ⅵ)

研究了铁（Ⅲ）和钼（Ⅵ）与邻苯二酚在ｐＨ ６．２０ 微酸性介质中反应生成的有色配合物与７１７型强碱性阴离子交换树脂的交换吸附,探讨了树脂相分光光度法同时测定铁（Ⅲ）和钼（Ⅵ）的实验条件。铁（Ⅲ）和钼（Ⅵ）树脂相有色配合物的最大吸收波长分别为５２０ ｎｍ 和４００ ｎｍ ,表观摩尔吸光系数ε为４．１×１０４ Ｌ／（ｍ ｏｌ·ｃｍ ）和９．０×１０４ Ｌ／（ｍ ｏｌ·ｃｍ ）,符合Ｂｅｅｒ定律的范围为０～２．２ ｍ ｇ·Ｌ－ １和０～１．６ ｍ ｇ·Ｌ－ １。此法用于地下水中微量铁和钼的测定,相对标准偏差为３．３ ％ 和３．２ ％ 。     

甘氨酸钙络合物的熔融法合成及表征

以甘氨酸和氢氧化钙为原料,采用熔融法合成了甘氨酸钙络合物,最佳合成条件为:原料摩尔比n甘氨酸:nCa(OH)2=2:1,在熔融状态下,反应温度150℃左右,反应时间40min,并通过元素分析、红外光谱、X-射线粉末衍射、差热-热重等实验手段对该络合物进行了表征,确定其化学式为Ca(NH2CH2COO)2,所得产品的产率达94.1%.     

外电场下的TCNQ电子转移过程研究

自制了紫外/拉曼两用的电化学薄层池。观测到了TCNQ在外电场作用下转变为TCNQ－而后又转变为TCNQ2－的紫外-可见吸收光谱变化的电子转移过程, 并且当有氧气存在时, TCNQ2－又被氧化而形成DCTC－的过程。还观测到了TCNQ在外电场作用下转变为TCNQ－的傅里叶变换拉曼光谱发生频移的电子转移过程。     

利用有限域上奇异伪辛几何构作具有仲裁的认证码

利用有限域上奇异伪辛几何构作了一个新的具有仲裁的认证码,计算了这个码的参数,当发方编码规则和收方解码规则按等概率分布选取时,计算出各种攻击成功的概率.     

Ca0．80Zn0．20Te晶体的生长及性能研究

用本实验室合成的Ca0．80Zn0．20Te多晶料为原料，采用改进的布里奇曼法在镀碳和未镀碳的石英安瓿中生长出Ca0．80Zn0．20Te晶锭。使用X射线衍射仪对合成产物及晶锭进行了分析，生长晶体的X射线衍射峰尖锐，摇摆谱对称，表明晶锭的结晶性能较好；用IRPrestige-21红外光谱仪分析了晶体的红外透射光谱，测试结果表明安瓿镀碳后生长的晶体位错密度小，均匀性较好，电阻率优于未镀碳安瓿生长的晶体；晶体的蚀坑密度在10^3-10^4cm^-2之间，比未镀碳安瓿生长的晶体低1个数量级。     

Crystal structure,spectroscopy and magnetism of binuclear complexes of mercury and lanthanides; the Ln(NCS)(HMPA)4(μ-SCN)2HgCl(SCN) type

A series of lanthanide compounds of type Ln(NCS)(HMPA)₄,(μ-SCN)₂HgCl(SCN) (Ln = Pr, Nd, Eu) were synthesized and grown in the form of single crystals.

The crystal structure of the neodymium complex was determined by X-ray diffraction. Its space group is Cc, with the following unit cell parameters; a = 17.338(3) Å, b = 15.795(3) Å, c = 21.828(4) Å, β = 107.65(3)°. The structure has an unexpected architecture in which one Cl^? ion, four SCN^? ions, and four oxygen atoms of HMPA groups are engaged in the metal ion coordination.

The binuclear complex is composed of two types of subunits; seven coordinated Nd (III) and four coordinated Hg (II). The results obtained were compared with the earlier published data on the crystal structures of polynuclear complexes with ions of the IIa group (Zn or Cd). Luminescence, excitation of luminescence and absorption spectra of lanthanide (Pr, Nd, Eu) single crystals, as well as vibrational IR and Raman spectra at 293, 77 and 4K, were recorded. Non-trivial results of reabsorption of the d-level of Pr(III) emission by ³H₄ → ³ P_J, ₁D² transitions were observed with simultaneous detection of emission from the ³P₀ level after excitation in the UV region. The experimental oscillator strengths of the transitions were determined from the absorption spectra and parametrized in terms of the Judd-Ofelt intensity parameters Ω_λ (λ = 2, 4, 6).

Satisfactory results for the calculation with low errors of estimation of the parameters were obtained for a crystal of the Nd-Hg compound, which reproduced the intensities of the electronic transitions well. Positive values of Ω_λ were evaluated for Pr(III) after including the ³H₄ → ³F₂ hypersensitive transition (obeying selection rules δJ = 2, δL = 2) in the calculations.

Based on the above results, the radiative rate constant can be determined. Strong vibronic components were found in the low temperature spectra for both types of ligands involved in metal ion coordination. The vibronic transitions are mainly associated with modes of groups directly coordinated to the metal ions. Electron-phonon coupling including the resonant vibronic effect was analysed based on IR and Raman data.

Magnetic susceptibility measurements were carried out down to 1.7 K. Correlation of the spectra and magnetic properties with details of the structure of the title compound was studied.     

轴对称压—弯下圆板中圆脱层的后屈曲扩展

本文分析了周边承受轴对称压一弯载荷的圆板中薄圆脱层的后屈曲扩展.运用基于四阶龙格-库塔积分公式的打靶法得到无量纲形式Von Karman非线性方程组的单参数解族.利用与路径无关的M积分导出能量释放率表达式并给出相应的数值解.文中还探讨了分叉、跳跃及扩展的可能性.     

Microwave heating of ceramic composites

The microwave heating of a ceramic composite is modelled andanalysed. The composite consists of many small ceramic particlesembedded in a ceramic cement. The composite is assumed to bewell insulated, and each particle is assumed to be in imperfectthermal contact with the surrounding cement. Based on thesetwo assumptions an asymptotic theory exploiting the small Biotnumber and small non-dimensional contact conductance is developed.Our asymptotic theory yields a set of nonlinear partial differentialequations which govern the temperature in the composite. Theseare reduced to a set of coupled nonlinear ordinary differentialequations in which the surface area of each particle entersas a parameter. Recent experiments with such composites haveshown that the steady-state temperature of the composite isstrongly dependent upon the radii of the embedded particles.Our model captures this effect. In fact, our analysis showsthat the assumption of imperfect thermal contact between theparticles and the ceramic cement is essential for this trendto be established.