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51.
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S Zhou YA Nastishin MM Omelchenko L Tortora VG Nazarenko OP Boiko T Ostapenko T Hu CC Almasan SN Sprunt JT Gleeson OD Lavrentovich 《Physical review letters》2012,109(3):037801
Using a magnetic Frederiks transition technique, we measure the temperature and concentration dependences of splay K_{1}, twist K_{2}, and bend K_{3} elastic constants for the lyotropic chromonic liquid crystal sunset yellow formed through noncovalent reversible aggregation of organic molecules in water. K_{1} and K_{3} are comparable to each other and are an order of magnitude higher than K_{2}. At higher concentrations and lower temperatures, K_{1} and the ratios K_{1}/K_{3} and K_{1}/K_{2} increase, which is attributed to elongation of self-assembled lyotropic chromonic liquid crystal aggregates, a feature not found in conventional thermotropic and lyotropic liquid crystals formed by covalently bound units of a fixed length. 相似文献
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A network with its arc lengths as imprecise number, instead of a real number, namely, interval number and triangular fuzzy
number is considered here. Existing ideas on addition and comparison between two imprecise numbers of same type are introduced.
To obtain a fuzzy shortest path from a source vertex to all other vertices, a common algorithm is developed which works well
on both types of imprecise numbers under consideration. In the proposed algorithm, a decision-maker is to negotiate with the
obtained fuzzy shortest paths according to his/her view only when the means are same but the widths are different of the obtained
paths. Otherwise, a fuzzy optimal path is obtained to which the decision-maker always satisfies with different grades of satisfaction.
All pairs fuzzy shortest paths can be found by repeated use of the proposed algorithm. 相似文献
55.
To evaluate the functional difference of the pars recta and pars oblique during speech production, the electromyographic activities of these muscles were measured in thyroidectomized patients. The hooked wire electrodes were inserted into the normal side of the bellies of the pars recta and pars oblique bundles. Two kinds of sentences were used to obtain pitch changes, a simple interrogative sentence and a complex sentence with stress contrasts. The pars recta and pars oblique were simultaneously activated for initial lengthening and tensing of vocal folds to produce speech. The pars oblique might be initially more active than the pars recta at the initial task of speech and the pars recta might be more active at the pitch elevation in the interrogative sentence and the stress contrast of the complex sentence. The maximum electromyographic activity range of the pars recta and pars oblique seemed to be nearly equal. These results demonstrated that the patterns of electrical activities of the two bellies are different during speech and the combined activities of the pars recta and pars oblique are important in the adjustment of the vocal fold length during speech. 相似文献
56.
O. D. Lavrentovich 《Pramana》2003,61(2):373-384
Much of the modern understanding of orientational order in liquid crystals (LCs) is based on polarizing microscopy (PM). A
PM image bears only two-dimensional (2D) information, integrating the 3D pattern of optical birefringence over the path of
light. Recently, we proposed a technique to image 3D director patterns by fluorescence confocal polarizing microscopy (FCPM).
The technique employs the property of LC to orient the fluorescent dye molecules of anisometric shape, added in small quantities
to the LC. In LC, smooth director deformations do not alter mass density of the material. Thus the density of dye is also
uniform across the sample, except, perhaps, near the surfaces or at the cores of topological defects. In polarized light,
the measured fluorescence signal is determined by the spatial orientation of the molecules rather than by dye concentration
(as in regular biological samples stained with tissue-specific dyes). The contrast is enhanced when both excitation and detection
of fluorescence light are performed in polarized light. This short review describes the essence of FCPM technique and illustrates
some of its applications, including imaging of Frederiks electric-field induced effect in a nematic LC and defects such as
dislocations in cholesteric LCs. 相似文献
57.
Christopher J. Woolverton Corresponding author Erin Gustely Lanfang Li Oleg D. Lavrentovich 《Liquid crystals》2013,40(4):417-423
The primary objective of this research was to test the hypothesis that lyotropic chromonic liquid crystals (neutral grey, red 14, blue 27, cromolyn) are not toxic to bacteria as compared with surfactant‐based lyotropic (CPCl and CsPFO) or thermotropic (5CB and E7) liquid crystals. Biocompatibility of most liquid crystals is currently unknown and is required for the development of systems interfacing liquid crystals and biological systems. Potential liquid crystal toxicity was evaluated by two methods. The first examined bacterial survival measured by bacterial growth over 24 hours, after exposure to various liquid crystals. The second toxicity method evaluated liquid crystal effects on bacterial membrane permeability using two fluorescent dyes. Three different types of bacteria were evaluated to assess bacterial structure differences with respect to liquid crystal toxicity. The results of this study indicate that lyotropic chromonic liquid crystals are not toxic to bacteria, whereas thermotropic and surfactant‐based lyotropic liquid crystals are toxic to one or more forms of bacteria. We conclude that lyotropic chromonic liquid crystals may be the preferred material in designing liquid crystal‐based systems that interact with biological systems, especially in the use of liquid crystal‐based biosensors. 相似文献
58.
Redox reaction between 6-acetonylisoxanthopterin (H2pte) and [MoVIO2 (ssp)] [ssp = anion of 2-(salicylideneamino) benzenethiol] in CH3OH-C2H5OH medium produces a new mixed ligand compound [MoIV (ssp) (Hpte) (OCH3)] (1). It has been characterized by elemental analysis, ESMS data, UV-Vis, IR,1HNMR (1D and 2D) spectroscopy and cyclic voltammetry. Kinetics of formation of this compound as well as that of its reaction
with pyridine N-oxide have been followed spectrophotometrically. Both the reactions follow substrate saturation kinetics and
involve metal-centred oxygen atom transfer process. Large negative values of entropy of activation indicate the operation
of associative mechanism. 相似文献
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