Slow quenching for a one-dimensional kinetic Ising model: Residual energy and domain growth

A one-dimensional kinetic Ising model with Glauber dynamics subjected to a slow continuous quench to zero temperature is studied. For a rather general class of cooling schemes, described by a time-dependent temperatureT(t), the mean domain sizeL(t) is calculated along with the residual energye _res (r) as a function of the cooling rater. If the attempt frequency =₀ exp(–/kT), entering into the transition rates, is temperature dependent (i.e., the barrier is non-zero), the asymptotic growth ofL(t) is given byL()–L(t)~exp[–/kT(t)]. For this case the residual energy exhibits a power-law behaviore _res(r) ~r ^{/2(1 + )} forr small, where =4J/ andJ is the nearest neighbor coupling constant. For =0 and for certain cooling schemes the residual energy is zero andL(t)~t1/2, independent ofr.     

脱乙酰基对天然魔芋葡甘聚糖分子形貌的影响

通过原子力显微镜直接观察魔芋葡甘聚糖（KGM）分子的三维结构形貌，KGM水溶液铺展在经Ca^2 处理的云母片上，干燥固定后，可获得稳定，重复的图像，实验结果表明，稀溶液中KGM分子具有伸展的螺旋链状结构，单股的长度达200－400nm，厚度为1．0nm，宽度为35．0－35．2nm，脱乙酰后分子链卷曲成直径约40－50nm,厚3．5－5．0nm的弹性圆台状。     

Vibrational assignment, <Emphasis Type="Italic">ab initio</Emphasis> calculation and normal coordinate analysis of 2,2′-biquinoline

The vibrational wavenumbers and the fundamental modes of 2,2′-biquinoline were obtained by density functional theory (DFT) with the B3LYP functional using the 6-31G(d,p) basis set. The calculated wavenumbers were scaled by a single factor of 0.965 to correct them for vibrational anharmonicity, but the force constants were overestimated. Normal coordinate analysis of the molecule was also carried out by using the force field of the quinoline molecule and the force field parameters of quinoline are shown to be transferable to 2,2′-biquinoline. The potential energy distribution associated with the normal modes is also given. The theoretical wavenumbers are found to be in good agreement with the experimental data.     

有机磷酸酯类化合物气相色谱定量结构保留关系研究

采用分子电性距离矢量(MEDV)表征有机磷酸酯类化合物的分子结构,运用多元线性回归建立定量结构-色谱保留关系(QSRR)模型,同时采用逐步回归结合统计检测对模型进行变量筛选,建立了35个有机磷酸酯类化合物在3种不同固定相(OV-101,DB-1701和DB-WX)上气相色谱保留指数(RI)与MEDV的定量相关模型.在3种固定相上的QSRR模型的建模计算值复相关系数(R)、留一法(leave-one-out)交互校验复相关系数(QCV)分别为0.998 0和0.995 1(OV-101);0.996 3和0.989 6(DB-1701);0.993 7和0.984 1(DB-WX),表明模型具有良好估计能力与稳定性.     

苯丙氨酸改性树枝状聚赖氨酸的合成及表征

以双芴甲氧羰基赖氨酸(Di- Fmoc -Lysine)为支化单元采用固相多肽合成技术制备了一种树枝状聚赖氨酸.该聚合物表面活性氨基通过与芴甲氧羰基苯丙氨酸(Fmoc- Phe)反应获得表面完全替代的苯丙氨酸改性树枝状聚赖氨酸.产物的分子量和结构经MS和NMR进行了表征.研究结果表明,利用该方法得到的产物分子量单一,是一种潜在的理想非病毒治疗载体.     

划痕试验法对特殊薄膜系结合力的检测与评价

简要介绍了划痕试验法测量表面薄膜与基体结合力的测试原理和实验方法，讨论了影响临界载荷Lc测量值准确性的主要因素，通过对薄膜系的分类以及大量实际测量数据的总结和分析，认为被测薄膜以及基体的物理化学特性对临界载荷的测量具有重要的影响，单纯从声发射信号的变化来确定临界载荷的方法有可能存在较大误差，分析和讨论了某些特殊薄膜系的声发射信号与其实际临界载荷值之间存在较大偏差的现象和原因，并提出了针对不同膜系，合理利用声发射曲线，摩擦力斜率以及显微观测来正确判定临界载荷的必要性。     

Characterization of Ultrathin Films of Cellulose Esters

The adsorption of cellulose acetate (CA), cellulose acetate propionate (CAP) and cellulose acetate butyrate (CAB) from solutions prepared in acetone onto silicon wafers led to ultrathin films, which were characterized by ellipsometry, atomic force microscopy (AFM) and contact angle measurements. The polysaccharides films were characterized in the air just after their formation and after annealing at temperatures higher than their glass transition temperature or melt temperature. The films thickness close to 2 nm and surface roughness did not vary significantly upon annealing. AFM images revealed the presence of small clumps dispersed on a homogeneous layer, which covered completely the Si wafers. Such topographic details were also observed after annealing. However, upon annealing the films surfaces changed from hydrophilic to hydrophobic, evidencing molecular re-orientation at the solid–air interface. The adhesion of bovine serum albumin (BSA) and lipase onto the cellulose esters films was quantified in order to evaluate the possibility of applying such films as selective support for biomolecules.     

镧对含锡、锑残余元素的34CrNi3Mo钢热塑性的改善作用

采用Gleeble-1500热模拟机测定了不同含量的残余元素锡、锑及稀土镧对低氧、低硫的34CrNi3Mo钢热塑性的影响;采用SEM及EDS手段研究了稀土镧对不同锡、锑含量的钢断裂方式的影响及在其中形成夹杂物的情况。结果表明,用稀土金属可以改善低氧、低硫钢中残余元素对钢性能的危害;镧可以和钢中较低含量的锑作用生成镧锑金属间化合物,并且发现了少量的镧锡金属间化合物。     

Properties of ITO films prepared by reactive magnetron sputtering

Indium tin oxide (ITO) thin films were deposited by mid frequency pulsed dual magnetron sputtering using a metallic alloy target with 10 wt.% tin in an atmosphere of argon and oxygen. The aim of the work was to study the interdependence of structural, electrical and optical properties of ITO films deposited in the reactive and transition target mode, respectively. The deposition rate in the transition mode exceeds the deposition rate in the reactive mode by a factor of six, a maximum value of 100 nm·m min⁻¹ could be achieved. This corresponds to a static deposition rate of 200 nm min⁻¹. The lowest electrical resistivity of 1.1·10⁻³ Ω cm was measured at samples deposited in the high oxygen flow range in the transition mode. The samples show a good transparency in the visible range corresponding to extinction coefficients being below 10⁻². X-ray diffraction was used to characterise crystalline structure as well as film stress. ITO films prepared in the transition mode show a slightly preferred orientation in (211) direction, whereas films deposited in the reactive mode are strongly (222) oriented. Compared to undoped In₂O₃ all samples have an enlarged lattice. The lattice strain perpendicular to the surface is about 0.8% and 2.0% for films grown in the transition and the reactive mode, respectively. Deposition in the transition mode introduces a biaxial film stress in the range of −300 MPa, while stress in reactive mode samples is −1500 MPa.     

Surface forces in foam films from ABA block copolymer: a dynamic method study

The thinning of foam films from aqueous solutions of an ABA triblock copolymer of polyethylene oxide and polypropylene oxide (average molecular weight 14,000 g/mol) is studied experimentally. The dependence of the surface forces on film thickness is obtained by the dynamic method of Scheludko and Exerowa.The total surface force measured in foam films (radius 60–70 m) from 10^–5 M (0.014 wt%) polymer solution with 0.1 M NaCl is positive at thicknesses from about 800 down to 460 . The electrostatic repulsion is negligible while the contribution of van der Waals attraction is small (within 15%). Therefore a positive surface force component predominates. Most probably it arises from steric interactions between the hydrophilic polyethylene oxide tails of the polymer. The dynamic method appears to be a suitable technique for exploring the stabilization of foam films from ABA copolymers.