摘要:

The problem of photosynthetic reaction centers has been a subject of intensive study during recent years. The interest in this subject is due to the high quantum and energetic efficiency of transforming light energy into the electrochemical potential. Up until now, grown crystals, suitable for structural investigation, provided information for only a few types of reaction centers. The reaction centers of multiheme cytochrome C complex fromRhodopseudomonas viridis1,2andRhodobacter sphaeroidasR-263,4are the most convenient for study.

ISSN:1058-725X    

DOI:10.1080/10587259208037514

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The deuterium Zeeman spin-lattice relaxation times TIZin 4,4′-di-n-heptylazobenzene (HB), 4,4′-di-n-heptylazoxybenzene (HAB), and 4,4′-di n-octylazoxybenzene (OAB) deuterated on the aromatic rings and on the first methylene group of the chains were measured at 10 and 46.04 MHz by means of the inversion-recovery technique. Measurements were made throughout the mesomorphic range and also in the isotropic phase. The relaxation rates show a discontinuity at the isotropic-nematic transition for all deuterons not ascribable to the onset of orientational order. The trends of InR are linear within the different phases except near phase transitions, and allow to obtain apparent activation energies for the overall motions of the different C—D bonds.

ISSN:1058-725X    

DOI:10.1080/10587259208037515

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

We present Monte Carlo simulations of nematic droplets with toroidal boundary conditions (TBC) and various anchoring strengths and we investigate the orientational order and the molecular organizations in these systems that mimic polymer dispersed liquid crystals (PDLC).

ISSN:1058-725X    

DOI:10.1080/10587259208037516

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Quasiequilibrium states of the liquid crystalline system with added small ferromagnetic particles are discussed. Possible flexomagnetoelectrical effects and a helical twisting under the combined action of electric and magnetic fields are described.

ISSN:1058-725X    

DOI:10.1080/10587259208037517

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The formation of quasiequilibrium modulated structures with large spatial periods in the ferroelectric chiral smectics C with large magnitudes of the spontaneous polarization is discussed. The specific features of such structures are related to the nonequilibrium process of charge transfer, to the formation of orientational defects and polarization inhomogeneities stabilized by free charge carriers.

ISSN:1058-725X    

DOI:10.1080/10587259208037518

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

According to the model of optical reorientation of the molecular director, we report a study of the effect of temperature variations on the nonlinear optical behavior of a homeotropic liquid crystal cell. We show that the model is in good agreement with our experimental data obtained for the K18 nematic liquid crystal. By numerical simulation we also show what is the role played by the different material parameters in determining the temperature behavior.

ISSN:1058-725X    

DOI:10.1080/10587259208037519

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Optical properties of the mixture of cholesteryl-n-nonanoate (CN) and n-nonyloxybenzoic acid (NOBA) in weight proportion 7:3 have been investigated. As it was early found by us (Ukranian Fiz. Zhurn.,35, 221 (1990)) this mixture possesses a new liquid-crystalline helical smectic A (SmA*) phase between the low-temperature smectic A (SmA) and high-temperature cholesteric (Ch) phases. It is shown experimentally that there are three temperature regions of the optical Bragg diffraction for the mixture. The first two regions correspond to the different states of the SmA* phase and the third one corresponds to the Ch phase. Inside each region the temperature dependence of the Bragg reflection wavelength γ is in exellent agreement with an empirical formula γ = γ0+a/(T − T*)2, whereT* = 82.4°C is the temperature of the SmA − SmA* transition and γ0as well asaare constant within each region but differ for different regions.

ISSN:1058-725X    

DOI:10.1080/10587259208037520

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The thermotropic and solution photoisomerization properties of a class of polyacrylates containing differently methyl-substituted azobenzene groups are presented. Methyl-substitution inhibits the tendency to crystallize and causes a dramatic decrease in the stability of the established nematic phases. These effects result from a restriction of the packing capability of the mesogenic groups and a reduction of their length-to-breadth ratio. In dilute solution all polymeric samples undergotrans-to-cisphotoisomerization of the azo group upon irradiation in the absorption region of the π → π* electronic transitions. Photoisomerization rate constants are very similar and of the same order of magnitude as those observed for other polymeric systems containing the unsubstituted azobenzene chromophore.

ISSN:1058-725X    

DOI:10.1080/10587259208037521

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A new universal approach to the description of the formation of the supramolecular structures in surfactant solutions based on the Landau theory of phase transitions with coupled order parameters has been proposed. It has been shown that the specific interaction of amphiphiles with random inhomogeneities of the solvent may lead to a particular type of phase transition: spontaneous aggregation process as well as following formation of lyotropic liquid crystalline phases.

ISSN:1058-725X    

DOI:10.1080/10587259208037522

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Thermodynamic data referring to a new homologous series of fluorinated alkoxy-benzylidene-anilines are presented. Phase diagrams show the presence of smectic A and/or B phases determined by thermal microscopy and X-ray diffraction techniques. Interdigitated structures are not present in these smectic phases. Trends in clearing temperatures are briefly discussed in comparison with those for thep-alkoxy-benzylidene-p'-alkoxy-anilines in order to clarify the role of the fluorine atom.

ISSN:1058-725X    

DOI:10.1080/10587259208037523

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor