Photochemistry of furans. Photochemical transformations of some substituted 2-phenyl-3-furylacrylic acids

A number of new substituted 2-phenyl-3-furylacrylic acids (1–14) were synthesized by modified Perkin reaction and separated into their E-and Z-isomers and identified by spectroscopic methods. E-isomers were UV-irradiated under aerobic conditions to give several types of photoproducts, ie substituted naphtho[2,1-b]furancarboxylic acids (B), 2,3-epoxy-2,3-dihydrofuro[3,2-b]pyran-5-ones (C), 7a - hydroxy - 3a,7a - dihydrofuro[3,2 - b]pyran - 5 - ones (D) and 7a - hydroperoxy - 3a,7a - dihydrofuro[3,2 - b]pyran - 5 - one (E) were recognized. The type of product and yield are strongly substituent-dependent.     

Anti-proton scheme of β-disintegration

The author considers the possibility of generalizing known schemes of-decay by means of the anti-proton reaction.     

Arrays of Charged (±2π)-Twist Disclinations in Ferroelectric Liquid Crystals

The notion of an electrostatic charge of (±2)-twist disclinations is used to approximate the evaluation of the electrostatic interaction energy among disclinations forming arrays in finite samples of ferroelectric chiral smectic C liquid crystals. Screening effects of free charges in a material surrounding the disclination are taken into account by introducing a phenomenological depolarisation factor.The electrostatic interaction energy is important in chiral smectic C materials with high values of the spontaneous polarisation when screening effects of free charges are small. Then the electrostatic interaction leads to elimination of disclinations from the sample. When there is a high concentration of free charges in the sample (smaller value of depolarisation factor), the electrostatic interaction energy is of the order of the elastic interaction energy of disclinations what influences the equilibrium of disclination arrays in the sample. Two disclination configurations are considered. In the Brunet-Williams configuration the disclinations of opposite topological charge have also the opposite electrostatic charge so their attraction is augmented. This attraction can be balanced by the helical structure in the central part of the sample when the sample thickness is rather high.On the contrary, in the Glogarová-Pavel configuration the disclinations of opposite topological charge have the electrostatic charge of the same sign. The equilibrium in this configuration is either a balance of elastic attraction and electrostatic repulsion if elastic and Coulomb forces are of the same order or it is governed by the value of the anchoring energy when electrostatic interaction prevails over the elastic one.     

Mechanical characterisation of a viscoplastic material sensitive to hydrostatic pressure

The present paper deals with the characterisation of the static mechanical behaviour of an energetic material all along its lifespan. The material behaviour is viscoplastic, damageable and sensitive to hydrostatic pressure. For such materials, existing models have generally been developed in the framework of transient dynamic behaviour. These models are not suitable for a static study. Therefore a specific experimental protocol and an associated model are developed. Characterisation is derived from both uniaxial compressive, tensile tests and triaxial tests. Plastic behaviour is described by means of a parabolic yield criterion and a new hardening law. Non-associated plastic flow rule and isotropic damage complete the model. The performance of the model is illustrated through the simulation of various loading paths.     

Mechanism of inclusion chaining in SmC* free-standing films

The self-assembly of colloidal inclusions has recently been shown in smectic C* freely suspended films. In such 2D systems, the organization of the inclusions is qualitatively explained by elastic interactions induced by the disruption of the orientational order in the SmC* host phase. The interaction between resulting inclusion-defect pairs exhibits a dipolar character. We have developed a simplified model representing every inclusion and its companion hyperbolic defect by (+1)- and (-1)-wedge disclination lines, respectively. A finite anchoring energy has been introduced to explain the coalescence of the thinnest inclusions. Our model enables us to explain the chaining of the thickest inclusions and confirms the inclusion size dependence on the stability of the chains.     

STRONG CODING THEOREM AND ASYMPTOTIC ERROR EXPONENT OF ARBITRARILY VARYING SOURCE

ＳＴＲＯＮＧＣＯＤＩＮＧＴＨＥＯＲＥＭＡＮＤＡＳＹＭＰＴＯＴＩＣＥＲＲＯＲＥＸＰＯＮＥＮＴＯＦＡＲＢＩＴＲＡＲＩＬＹＶＡＲＹＩＮＧＳＯＵＲＣＥ符方伟，沈世镒）￥ＦｉＦａｎｇｗｅｉ；ＳｈｅｎＳｉｙｉ（Ｄｅｐｔ．ｏｆＭａｔｈ．，ＮａｎｋａｉＵｎｉｖ．，Ｔ...     

Size-dependent magnetic properties of CoFe2O4 nanoparticles prepared in polyol

Highly crystalline CoFe(2)O(4) nanoparticles with different diameters ranging from 2.4 to 6.1 nm have been synthesized by forced hydrolysis in polyol. The size can be controlled through adjusting the nominal water/metal molar ratio. X-ray diffraction, transmission electron microscopy, x-ray absorption spectroscopy and (57)Fe M?ssbauer spectrometry were employed to investigate the structure and the microstructure of the particles produced. Magnetic measurements performed on these particles show that they are superparamagnetic with a size-dependent blocking temperature. At 5 K, high saturation magnetization (~85 emu g(-1)) approaching that of the bulk was found for the larger particles, whereas a very large coercivity (14.5 kOe) is observed for the 3.5 nm sized particles.     

The interplay of iron(II) spin transition and polymorphism

The mononuclear compound (1) [Fe(II)(L)(2)](BF(4))(2) (L = 4-ethynyl-2,6-bis(pyrazol-1-yl)pyridine) was prepared and structurally as well as magnetically characterised. The crystallisation revealed the formation of two polymorphs--the orthorhombic 1A and the tetragonal form 1B. A third, intermediate phase 1C was found exhibiting a different orthorhombic space group. Reversibility of the phase transition between 1A and 1C was studied by variable-temperature single-crystal and powder X-ray diffraction studies, while an irreversible phase transition was observed for the transition of 1B→1C. The magnetic studies show that the 1A?1C transition is accompanied by a very abrupt spin transition (ST) with 8 K hysteresis width (T(1/2)(↓) = 337 K, T(1/2)(↑) = 345 K). The ST was confirmed by M?ssbauer spectroscopy as well as by DSC studies. In contrast, the 1B polymorph remained low-spin up to 420 K. In conclusion, a full cycle of intertwined phase- and spin-conversions of three polymorphs could be proven following the general scheme 1B→1C?1A.     

聚苯胺改性技术的研究新进展

导电聚合物由于有很大的应用前景而引起了很多研究者的兴趣。在导电聚合物中,聚苯胺由于具有很高的导电性、热稳定性、容易制备等性质而受到了格外的关注。但是聚苯胺同样有缺点,例如应用范围狭小、很难进行加工等。为了提高聚苯胺的加工性能,乳液聚合是一种有效的改性方法。本文讨论了用乳液聚合或反相乳液聚合合成聚苯胺以及聚苯胺的共聚物,同时也报道了聚苯胺与其它物质复合共混和掺杂的研究结果,并且研究了它们的结构以及各方面的性能。通过改性,可使得聚苯胺的加工性得到很好的改善。     

On the stereoselectivity of nitrone addition to (R)4-0-benzyl-4-lide

The title reaction was investigated for both known achiral and new chiral optically pure nitrones. In all cases, formation of only two diastereomeric cycloadducts was observed.Department of Organic Chemistry, Slovak Technical University, 812 37 Bratislava, Slovak Republic. Department of Organic Chemistry, University of Stuttgart, D-70569 Stuttgart, Germany. Published in Khimiya Geterotsiklicheskikh Soedinenii No. 10, pp. 1350–1352. October, 1995. Original article submitted August 24, 1995.