1,2-和1,4-萘醌248 nm激光光解的瞬态吸收光谱研究

利用纳秒级激光光解动态吸收光谱装置,研究了1,2-和1,4-萘醌中性水溶液的瞬态吸收光谱.发现1,2-萘醌及1,4-萘醌被光电离后形成的阳离子自由基在380nm均有最大吸收,但1,4-萘醌阳离子自由基在衰变过程中又形成了两种新的活性粒子,它们的最大吸收分别位于410和580nm,分析表明:410nm属于1,4-萘醌脱氢自由基的吸收,而580nm很可能归属由于电子转移而形成的瞬态产物.进一步研究发现,1,2-萘醌在中性水溶液中能被248nm激光单光子电离.     

氧与次溴酸反应理论研究

用密度函数理论(DFT)对氧原子与次溴酸HOBr在势能面上的反应进行了研究,用B3LYP方法计算了势能面上各驻点物种的参数、能量等.结果表明:O与HOBr在势能面上有两个通道,简单可概括为摘H和摘Br反应,两通道的产物相同,均为HO、BrO.计算出反应热为42.3kJ/mol,根据等链反应特点,得到HOBr的生成热为-41.4kJ/mol.     

紫外-可见光谱-偏最小二乘法测定渣油四组分含量

用已建立的渣油聚类和识别模型将渣油分为坟渣油、减压渣油和加氢渣油,用紫外－可见光谱－偏最小二乘法（ＵＶ－ＰＬＳ）分别建立了这３种渣油的饱和烃、芳烃、胶质和沥青质四组分测定模型。该方法的测定结果与经典洗脱色谱法（ＥＣ）的结果相吻合。与ＥＣ方法相比,该方法具有快速、操作简单、不需分离,重复性好等特点。     

Cd（Ⅱ）与HSA或BSA的结合平衡研究

用平衡透析法详细研究了生理pH(7.43)条件下Cd(Ⅱ)与HSA或BSA的结合平衡.通过非线性最小二乘法拟合Bjerrum方程,首次报道了Cd(Ⅱ)-HSA和Cd(Ⅱ)-BSA体系的逐级稳定常数值,其K_1～K_3的数量级均为10~4;Hill系数和自由能偶合定量分析表明Cd(Ⅱ)与HSA或BSA的结合均产生在类似体系中少见的强的正协同效应,且Cd(Ⅱ)与HSA结合产生的正协同效应大于BSA;Scatchard图分析表明,Cd(Ⅱ)在HSA和BSA中均有3个强结合部位.通过Cd(Ⅱ)与Cu(Ⅱ),Zn(Ⅱ)或Ca(Ⅱ)等竞争结合HSA或BSA的结果,进一步讨论了Cd(Ⅱ)在HSA或BSA中强结合部位的可能位置和(或)配体.     

高浓度杂多酸溶液催化性能的研究1: 一种新型异丁烷/丁烯烷 基化催化剂

在异丁烷、丁烯烷基化反应中研究了一种由杂多酸和醋酸组成的新型液体催化剂的催化性能,醋酸作为溶剂对杂多酸具有共协效应,系统研究了形成活性相的条件,杂多酸结晶水含量对活性相的形成和催化活性均有显著影响,这一催化体系具有与硫酸可比的催化活性。     

Preparation and Characterization of Aluminum Alkoxides and their Application to Ring‐Opening Polymerization of ϵ‐Caprolactones

The reaction of 2‐methoxybenzyl alcohol with one molar equiv of R₂AIX in diethyl ether at 0°C gives [(2‐MeOC₆H₄CH₂‐μ‐O)AlRX]₂ ( 1 : R = Et, X = Cl, 2 : R = X = Et). In addition, 2,4‐di‐tert‐butylphenol reacts with ⁱBu₃Al affording a four‐coordinated aluminum compound [(μ‐2,4‐^tBu₂‐C₆H₄O)Al(ⁱBu)₂]₂ ( 4 ). Single crystal X‐ray structure analysis of 4 shows a C_2h‐symmetry with a planar Al₂O₂ core. Ring‐opening polymerization (ROP) of caprolactones initiated by 1, 4 and [(μ‐OCH₂C₆H₄OMe)Al(ⁱBu)₂]₂ ( 3 ) is performed and polyesters with narrow molecular weight distributions were obtained from the “living” ROP of caprolactones. ¹H NMR spectroscopic studies of PCL reveal that the initiator of 1 and 3 is through the Al‐OAr function, but the initiator of 4 is through the Al‐ ⁱBu group.     

Nurses allocation models for maternal and child health services

Maternal and Child Health (MCH) centres in Hong Kong offer, for children aged below six and women of childbearing age, a comprehensive range of health services regularly performed by nurses of different ranks. While each rank has its specific duties, nurses of a higher rank can step down to the work of a more junior rank when necessary. However, cross-regional deployments of nurses occur less frequently. We develop goal programming models of ‘optimal’ MCH nurses allocation. The presence and absence of nurses’ ‘cross-over’ of work functions are explicitly considered. The results show that more equitable manpower levelling can be achieved, with flexibility (in the longer term) on cross-regional deployment of nurses as a possible way of operational improvement when the entire MCH service is taken as a whole.     

Electrospinning of Hyaluronic Acid (HA) and HA/Gelatin Blends

Summary: In the present study, electrospinning of hyaluronic acid (HA) and hyaluronic acid/gelatin (HA‐GE) blends in N,N‐dimethylformamide (DMF)/water‐mixed solvents have been investigated. When the volume ratio of DMF to water was in the range of 1.5–0.5, HA solutions could be electrospun into fibrous membranes successfully. The average diameter of HA fibers was about 200 nm. The HA‐GE composite nanofibrous membranes with varied HA/GE weight ratio in the range of 100/20–100/100 have also been successfully fabricated. The average diameter of HA‐GE fibers was in the range of 190–500 nm. The decrease in surface tension could promote fiber formation. Thus, an introduction of DMF that could decrease the surface tension distinctively, without significant change or increase in viscosity of the solution, could bypass the use of blowing‐assisted electrospinning. Our postulated picture is that the lower surface tension could help the ejection of stream with relatively high viscosity and reduce or prevent the droplet formation during the spinning process.

HA/GE (100/80) nanofibrous membrane produced by electrospinning.     

A Rapid Process for Producing Cellulose Multi‐Filament Fibers from a NaOH/Thiourea Solvent System

Summary: Cellulose was dissolved rapidly in 9.5 wt.‐% NaOH and 4.5 wt.‐% thiourea aqueous solution pre‐cooled to −5 °C to prepare a transparent solution. Novel cellulose multi‐filament fibers were spun successfully, for the first time, from the cellulose dope on an extended laboratory scale. The results from ¹³C NMR, scanning electron microscopy and wide angle X‐ray diffraction (WAXD) patterns indicated that the fibers exhibited cellulose II character and possessed a circular cross‐section and smooth surface. The tensile strength of the novel fibers reached 1.9–2.2 cN · dtex⁻¹. 2D WAXD and SAXS patterns revealed that, with a drawing progress, the orientation factor increased and mechanical properties were improved.

SEM micrographs of the novel multi‐filament fibers spun from cellulose solution in a NaOH/thiourea aqueous system pre‐cooled to −5 °C on an extended laboratory scale.     

Synchronization and parameter identification of one class of realistic chaotic circuit

In this paper, the synchronization and the parameter identification of the chaotic Pikovsky--Rabinovich (PR) circuits are investigated. The linear error of the second corresponding variables is used to change the driven chaotic PR circuit, and the complete synchronization of the two identical chaotic PR circuits is realized with feedback intensity k increasing to a certain threshold. The Lyapunov exponents of the chaotic PR circuits are calculated by using different feedback intensities and our results are confirmed. The case where the two chaotic PR circuits are not identical is also investigated. A general positive Lyapunov function V, which consists of all the errors of the corresponding variables and parameters and changeable gain coefficient, is constructed by using the Lyapunov stability theory to study the parameter identification and complete synchronization of two non-identical chaotic circuits. The controllers and the parameter observers could be obtained analytically only by simplifying the criterion dV/dt<0 (differential coefficient of Lyapunov function V with respect to time is negative). It is confirmed that the two non-identical chaotic PR circuits could still reach complete synchronization and all the unknown parameters in the drive system are estimated exactly within a short transient period.