Abstract The activation field for the switching time (τ1/2) in the truly ferroelectric liquid crystal 8SI* (CE8; ΔS-(+)-4-(2′-methylbutyl) phenyl-4′-n-octylbiphenyl-4 carboxylate) has been studied for various surface conditions of the transparent electrode (SnO2), in order to understand the memory effect, the polarization reversal mechanism and its surface effect. We prepared five different surfaces, namely one coated with polyvinyl alcohol (PVA) and the other four by scratching N-times(N = 0, 10, 20 and 30) with a paste made of Cr2O3 powder (about 0·1 μm). The number and the area of scratches on the electrode surface obviously increase with N. The polarization reversal processes are influenced by this treatment. τ1/2 decreases with increasing N, but no change is observed in the contrast of the light transmittance. Two different activation fields, Ea1, for the applied field E > E0 and Ea2 for E < E0 are observed, where E0 is a certain field depending on the sample. Here Ea1 is much larger than Ea2; typically Ea1, = 260 kV cm?1 and Ea2 = 144 kV cm?1 for N = 0. This means that nucleation for the higher field needs a large activation energy which therefore has strong barriers. In contrast with this, nucleation for the low field occurs easily. Changing a surface condition, Ea2 clearly decreases with increasing N although Ea1 is almost independent of the surface scratching. This may suggest that Ea1 corresponds to the activation field for the bulk pinning and nucleation, and Ea2 for the surface pinning. The PVA treatment gives an intermediate influence between N = 0 and 10. 相似文献
The phase behaviour of the binary systems 4′-n-tetradecyloxy-3′-nitrobiphenyl-4-carboxylic acid (ANBC-14)-n-alkane (n-tetradecane or n-hexadecane) was investigated by differential scanning calorimetry, polarizing optical microscopy, and X-ray diffraction. The phase behaviour was a function of temperature (T) and the effective carbon number of the system (n*), where n* involves carbon atoms both from the alkoxy group of ANBC-14 and from the n-alkane added. ANBC-14 shows no cubic phase, but the addition of n-alkane induced cubic phases when n*≧c. 15. An interesting point is that the type of cubic phase is Ia3dfor 15≦n*≦17, while an Im3m type is formed for 18≦n*≦20. Furthermore, for n* = 22, two types of cubic phase, one with Im3m symmetry in the low temperature region and the other with Ia3d in the high temperature region, were observed both on heating and cooling. The phase diagram with respect to T and n* is very similar to that of pure one-component ANBC-n, which is a function of T and the number of carbon atoms in the alkoxy group n. 相似文献
There is growing awareness that circadian clocks are closely related to the intracellular redox state across a range of species. As the redox state is determined by the exchange of the redox species, electrochemically controlled extracellular electron transfer (EC‐EET), a process in which intracellular electrons are exchanged with extracellular electrodes, is a promising approach for the external regulation of circadian clocks. Herein, we discuss whether the circadian clock can be regulated by EC‐EET using the cyanobacterium Synechococcus elongatus PCC7942 as a model system. In vivo monitoring of chlorophyll fluorescence revealed that the redox state of the plastoquionone pool could be controlled with EC‐EET by simply changing the electrode potential. As a result, the endogenous circadian clock of S. elongatus cells was successfully entrained through periodically modulated EC‐EET by emulating the natural light/dark cycle, even under constant illumination conditions. This is the first example of regulating the biological clock by electrochemistry. 相似文献
We studied the stepwise formation constants (β) of water-soluble diglycolamide (DGA) and dioxaoctanediamide (DOODA) for the mutual separation of Ln in a solvent extraction system. TODGA (N,N,N?,N?-tetraoctyl-diglycolamide) and DOODA(C8) (N,N,N?,N?-tetraoctyl-dioxaoctanediamide) exhibit opposite behaviors in extracting both light and heavy Ln through Ln-patterns. Metal complexes of two- and three-folding with water-soluble DOODA and DGA, respectively, were found, and each β value was calculated using distribution ratios. Taking β, their distribution ratio, D, and separation factor, SF, values into consideration, the suitable separation conditions (aqueous phase: 30 mM DOODA(C2) in 1 M HNO3; organic phase: 0.1 M TODGA in n-dodecane) of multistage extraction (10?×?10 extraction using aqueous and organic phases, including one sample solution) were determined. In this study, La, Pr, and Nd were mainly present in the aqueous phase, whereas Sm–Dy existed in the organic phase. Although these two groups can be easily separated into two phases, the resolution, Rs, values provide for little mutual separation between La–Nd and Sm–Dy under the present conditions.
In 1989, Asahi Kasei commercialized a porous hollow fiber membrane filter (Planova?) made of cuprammonium regenerated cellulose, making it possible for the first time in the world to “remove viruses from protein solutions by membrane filtration”. Planova has demonstrated its usefulness in separating proteins and viruses. Filters that remove viruses from protein solutions, i.e., virus removal filters (VFs), have become one of the critical modern technologies to assure viral safety of biological products. It has also become an indispensable technology for the future. The performance characteristics of VFs can be summarized in two points: 1) the virus removal performance increases as the virus diameter increases, and 2) the recovery rate of proteins with molecular weights greater than 10,000 exceeds the practical level. This paper outlines the emergence of VF and its essential roles in the purification process of biological products, requirements for VF, phase separation studies for cuprammonium cellulose solution, comparison between Planova and other regenerated cellulose flat membranes made from other cellulose solutions, and the development of Planova. The superior properties of Planova can be attributed to its highly interconnected three-dimensional network structure. Furthermore, future trends in the VF field, the subject of this review, are discussed.
We study the infrared stability of global symmetries. It is shown that small orthogonal groups O(N) (N < 4) are infrared attractive, while their direct products are unstable. We also discuss the stability of simple supersymmetric models and the role of auxiliary fields. 相似文献