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111.
ABSTRACTThe field of liquid crystals is truly multidisciplinary with numerous examples of virtuous circles of interaction between chemistry, physics, theory and engineering resulting in breakthroughs in both fundamental understanding and novel applications. This paper, written to mark John Goodby’s 65th birthday, offers a personal perspective of the synergy between chemistry and physics from a collaboration that has spanned three decades. The first part of the paper reviews some of the physics insights that resulted from chiral liquid crystals fundamental to understanding structures in ferroelectric, ferrielectric and antiferroelectric systems. The second part of the paper describes some of the remarkable consequences of the anomalous elasticity and flexoelectricity found in the nematic phases of bent-core materials. In particular, we present unusual bowing of disclination lines in the nematic phase of a bent-core material in the presence of a field. Finally, the paper summarises some future prospects relating for bent-core materials. The paper by no means captures the amazing breadth of contribution that John’s chemistry has made to the subject, but aims to exemplify how his generous collaborative approach coupled with innovative chemistry and physical insight has led to paradigm changes in our subject. 相似文献
112.
A stereOselective conversion of 1,8- and 1,5-diethoxy-9,10-anthraquinone to 1,8- and 1,5-diketo----perhydroanthracenes by successive sodium borohydride, metal-ammonia, and catalytic reductions is described. 相似文献
113.
Singular Value Decomposition (SVD) is a powerful tool in linear algebra and has been extensively applied to Signal Processing,
Statistical Analysis and Mathematical Modeling. We propose an extension of SVD for both the qualitative detection and quantitative
determination of nonlinearity in a time series. The method is to augment the embedding matrix with additional nonlinear columns
derived from the initial embedding vectors and extract the nonlinear relationship using SVD. The paper demonstrates an application
of nonlinear SVD to identify parameters when the signal is generated by a nonlinear transformation. Examples of maps (Logistic
map and Henon map) and flows (Van der Pol oscillator and Duffing oscillator) are used to illustrate the method of nonlinear
SVD to identify parameters. The paper presents the recovery of parameters in the following scenarios: (i) data generated by
maps and flows, (ii) comparison of the method for both noisy and noise-free data, (iii) surrogate data analysis for both the
noisy and noise-free cases. The paper includes two applications of the method: (i) Mathematical Modeling and (ii) Chaotic
Cryptanalysis. 相似文献
114.
115.
Soumya Menon Santhoshkumar Jayakodi Kanti Kusum Yadav Prathap Somu Mona Isaq Venkat Kumar Shanmugam Amballa Chaitanyakumar Nagaraj Basavegowda 《Molecules (Basel, Switzerland)》2022,27(21)
The potentiality of nanomedicine in the cancer treatment being widely recognized in the recent years. In the present investigation, the synergistic effects of chitosan-modified selenium nanoparticles loaded with paclitaxel (PTX-chit-SeNPs) were studied. These selenium nanoparticles were tested for drug release analysis at a pH of 7.4 and 5.5, and further characterized using FTIR, DLS, zeta potential, and TEM to confirm their morphology, and the encapsulation of the drug was carried out using UPLC analysis. Quantitative evaluation of anti-cancer properties was performed via MTT analysis, apoptosis, gene expression analysis, cell cycle arrest, and over-production of ROS. The unique combination of phytochemicals from the seed extract, chitosan, paclitaxel, and selenium nanoparticles can be effectively utilized to combat cancerous cells. The production of the nanosystem has been demonstrated to be cost-effective and have unique characteristics, and can be utilized for improving future diagnostic approaches. 相似文献
116.
117.
The stepwise synthesis of amino terminal pentapeptide of alamethicin, Z-Aib-Pro-Aib-Ala-Aib-OMe, by the dicyclohexylcarbodiimide mediated couplings leads to extensive racemization at the Ala and Pro residues. Racemization is largely suppressed by the use of additives like N-hydroxysuccinimide and 1-hydroxybenzotriazole. The presence of diastereomeric peptides may be detected by the observation of additional methyl ester and benzylic methylene signals in the 270 MHz 1H NMR spectra. Unambiguous spectral assignment of the signals to the diastereomers has been carried out by the synthesis and NMR studies of the D-Ala tetra and pentapeptides. The racemization at Pro is of particular relevance in view of the reported lack of inversion at C-terminal Pro on carboxyl activation. 相似文献
118.
G. Saberwal S. Thennarasu V. M. Dhople M. V. Jagannadham R. Nagaraj 《Journal of Chemical Sciences》1994,106(5):1109-1121
Studies in our laboratory have been directed towards understanding the mechanism of action of two hydrophobic toxins, pardaxin
comprising 33 residues and δ-toxin comprising 26 residues. Since isolation of these peptides in large amounts from natural
sources is not convenient, we have explored synthetic approaches to get these peptides as well as their analogs. We have used
chemistry specific to fluorenylmethoxycarbonyl (Fmoc) andt-butyloxycarbonyl (Boc) amino acids. Synthesis specific for Fmoc amino acids was carried out manually as well as on a semi-automated
continuous flow peptide synthesizer. Synthesis specific for Boc amino acids was carried out manually. The protocols used by
us have yielded 15–33 residue peptides which are of high purity. Even in peptides where heterogeneity was present, pure peptide
could be obtained in good yields using simple gradients in fast performance liquid chromatography. The synthesis of pardaxin,
δ-toxin and several analogs should help in identifying the molecular determinants of biological activity. 相似文献
119.
R Nagaraj 《Journal of Chemical Sciences》1987,98(5-6):479-485
Proteins destined for regions other than the cytoplasm in cells have to cross at least one membrane barrier before reaching
their proper destination. Almost all such proteins are initially biosynthesized as precursors with signal sequences at the
amino terminus. Signal sequences are essential and also sufficient for proteins to be targeted to membranes and also for translocation
across membranes. One striking feature that is clearly evident amongst signal sequences of secretory proteins is a positively
charged amino terminus followed by a region comprising 10–12 very hydrophobic amino acids. The structural and physico-chemical
properties of signal sequences have been analysed. On the basis of the analyses it is proposed that the structural feature
of a positively charged amino terminal region followed by a hydrophobic stretch of amino acids, rather than a conformational
one, is recognised by components of the cells export machinery. It is also postulated that signal sequences insert in the
lipid bilayer of the translocation competent membrane after targeting. The presence of the signal sequence results in the
formation of local ‘defects’ in the bilayer which have a role in translocation of proteins across membranes. 相似文献
120.