Phase studies of surfactant–water systems

Significant advances have been made in establishing phase behavior of a number of nonionic, cationic, anionic, catanionic and fluorinated surfactants in water. An interest in phase equilibria existing at sub-ambient temperatures is developing. The study of cubic, intermediate, defective lamellar and sponge phases is an active field of research at present. Further work is needed in exploring thermodynamic stability of rigid nanodisks and densely packed vesicles. Colloidal aspects, thermodynamic and volumetric properties of the surfactant-containing systems deserve special attention.     

1-苯氧基乙酰基-4-(邻硝基苯甲酰基)氨基硫脲及其相关杂环化合物的合成研究

芳氧基乙酸及其衍生物对植物有很强的生理活性,广泛用作除莠剂和植物生长调节剂［１,２］．１,４－二酰基取代的氨基硫脲及其杂环衍生物亦有多种生物活性［３］．若将上述两类具有生物活性的基团聚集于同一分子中,实现其活性叠加,同时改变取代基,有望获得具有更高生物活性的物质．基于此,我们在以前工作［４］的基础上,以ＰＥＧ－４００为催化剂,在固－液相转移条件下,用邻硝基苯甲酰氯与硫氰酸铵反应,首先制得邻硝基苯甲酰基异硫氰酸酯（Ⅰ）,不经分离,Ⅰ直接与芳氧基乙酰肼加成得到了１－芳氧基乙酰基－４－（邻硝基苯甲酰基…     

Application of Cryptand/Polystyrene Drift-Type Phase Transfer Catalysts for Reduction of Ketones

A drift-type phase transfer catalyst, cryptand-22, adsorbed on poly(styrene/diviny benzene)-sulfonic resin was prepared and applied to catalyze the reduction of ketones, e.g., acetophenone, benzophenone and benzaldehyde with NaBH₄ as a reducing agent. Before the reaction, cryptand-22 was adsorbed on the sulfonic resin with ion-pairing, resin-SO₃^{? +}NH-cryptand-22. The ion-pairs can be destroyed by adjusting the basicity of the reaction solution with NaOH and the cryptand can be released from the resin into the reaction solution as a homogeneous catalyst during the reaction period. After the reaction, the cryptand catalyst can be readsorbed on the resin by adjusting the acidity of the solution with HCl and can be readily recovered by filtration like a heterogeneous catalyst. The draft-type cryptand catalyst exhibited better catalytic ability than some common crown ethers, e.g., 15-crown-5, benzo-15-crown-5, 12-crown-4 and dibenzo-18-crown-6 for the reduction of acetophenone with NaBH₄. Effects of solvents, pH of solutions, concentration of the catalyst, reducing agents and resin property on the reduction of ketones were investigated and discussed. The reaction mechanism of the cryptand catalyzed reduction was also studied.     

Reliability of ak-out-of-n system with repair and retrial of failed units

We consider ak-out-of-n system with repair. Life times of components are independent exponentially distributed random variables with parameter λ _i when the number of working units isi. Failed units are taken for repair to a station, manned by a single server, having no waiting room. The failed units are brought to an orbit, if the server is found to be busy, for retrial. Reliability of the system is computed in the following three situations: (i) Cold system (ii) Warm system and (iii) Hot system. Several other system characteristics are derived.     

Computer simulation studies of magnetic phase transitions

The advancements which have been made in the use of computer simulations to study magnetic-phase transitions and critical phenomena are reviewed. We describe how the use of a combination of sophisticated Monte Carlo simulation algorithms and reweighting (histogram) techniques have allowed the determination of the static critical behavior with unprecedented precision. The study of “dynamic” critical behavior in simple spin models by both Monte Carlo and spin dynamics methods is also reviewed. Recent estimates for dynamic critical exponents are given including those for true dynamics.     

Ground state of a Bose-Einstein condensate which scatters coherently laser radiation

We present a self-consistent method of taking into account back action of a laser radiation to a Bose-Einstein condensate of neutral atoms. The light is coherently scattered inside the degenerate atomic sample, thus its intensity and, consequently, the atomic ground level AC Stark shift are spatially varying. This leads to a small deformation of the atomic cloud and, if the external radiation is abruptly switched off, to generation of collective excitations. Received 8 May 1999 and Received in final form 11 October 1999     

Continuous phase transition in a disordered eight-states Potts model

We investigate the two-dimensional eight-states ferromagnetic Potts model in the Voronoi-Delaunay tessellation. In this study, we assume that the coupling factor J varies with the distance r between the first neighbors as , with . The disordered system is simulated applying the single-cluster Monte-Carlo update algorithm and the reweighting technique. We find that this model displays a first-order phase transition if , in agreement with previous recent studies. For and 1.0, a typical second order transition is observed and the critical exponents for magnetization and susceptibility are calculated. Received 19 May 1999 and Received in final form 2 June 1999     

Contouring of artwork surface by fringe projection and FFT analysis

In the present work, we propose a simple optical method to perform profilometry on works of art. The method is based on the projection of a Ronchi grating onto the surface to be analyzed. When viewed at an angle different from the projection angle, the grid pattern appears deformed by the surface shape. This pattern is digitized, by a high-resolution CCD camera, and then processed using a Fourier transform analysis. The technique is free from the errors caused by higher harmonic components of the grating pattern. Furthermore, the method relies on very simple equipment and it is therefore suitable for in situ measurements. Theoretical details and examples of the technique in operation are given.     

苯乙烯基吡啶类液晶化合物的分子结构及相变过程的光谱研究

通过本乙烯基吡啶和不同脂肪羧酸间的氢键作用构成液晶的方法具有合成路线灵活、简便、易于变化的特点,本文通过变温红外光谱对做为质子受体的苯乙烯基吡啶粉液晶化合物的分子结构和相变过程中分子排列的变化进行了研究,结果表明在液晶分子中象羰基这样的偶极矩较大的极性基团,对分子所处的相态分子间的相互排列比较敏感。在红外光谱中羰基伸缩振动的变化可以看作是液晶分子相态转变的标志。