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11.
We report on the results of experiments on polarization switching in a ferroelectric TGS crystal during injection of electron beams from a scanning electron microscope under a surface layer. A series of models reflecting the polarization switching dynamics of a ferroelectric crystal under the action of an injected charge is constructed. The implementation of these models is based on the principles of evolution of domain structures taking into account analysis of possible polarization switching mechanisms for ferroelectric samples. A mathematical model developed using these principles demonstrates qualitative similarity of model current pulses and those obtained experimentally in the injection mode. 相似文献
12.
Dr. Lidiya A. Maslovskaya Dr. Andrei I. Savchenko Carly J. Pierce Dr. Glen M. Boyle Dr. Victoria A. Gordon Dr. Paul W. Reddell Prof. Peter G. Parsons Prof. Craig M. Williams 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(6):1525-1534
Investigation of the Australian rainforest plant Croton insularis revealed seven new cis-, two new trans-cyclopropane casbanes, and the first trans-cyclopropane seco-casbane. The relative configuration of the cyclopropane moiety for all compounds (EBC-182, 217, 218, 220, 343, 357, 358, 361, 365, 373; EBC=EcoBiotics Compound) was assigned using 13C NMR data. Comparison of the experimental electronic circular dichroism (ECD) spectra with the theoretical curves, calculated by TD-DFT at the B3LYP/6-31+G**//B3LYP/6-31+G** level, in conjunction with NOE data afforded the absolute configuration. EBC-180, 181 and 220 displayed potent activity against cervical carcinoma (HeLa cells). 相似文献
13.
The specific contrast of scanning electron microscope (SEM) images of ferroelectric domains observed in the pyrocurrent (pyroprobe)
mode is analyzed. Calculations taking into account both the nonuniform heating of domains and the heat diffusion via the domain
walls and the crystal boundaries are performed. It is established that the heat diffusion smears the domain images of small
domains. Along with the probe diameter, the scan rate is shown to be an important factor determining the character of the
SEM image contrast. A decrease in the scan rate may appreciably lower the resolution even in case of a fairly thin probe. 相似文献
14.
A. G. Maslovskaya 《Russian Physics Journal》2010,53(1):36-43
A spatial nonstationary temperature distribution in a model ferroelectric specimen exposed to electron beams of a scanning
electron microscope (SEM) is simulated. A solution to the problem on the effect of focused heat sources having different configurations
on a single ferroelectric crystal and crystal with electrodes deposited on its faces is presented. The model is based on the
finite-difference method. A program for calculating temperature fields and maximum overheating temperature for preset specimen
characteristics and experimental parameters of different scanning electron microscopes is suggested. 相似文献
15.
Lidiya A. Maslovskaya Andrei I. Savchenko Elizabeth H. Krenske Carly J. Pierce Victoria A. Gordon Paul W. Reddell Peter G. Parsons Craig M. Williams 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(27):7126-7129
EBC‐219 ( 4 ), isolated from Croton insularis (Baill), was established by spectroscopic and DFT methods as the first member of a new diterpene skeletal class, uniquely defined by the presence of a bicyclo[10.2.1] bridgehead olefin. The proposed biogenetic pathway to 4 from the co‐isolated natural products EBC‐131 ( 1 ), EBC‐180 ( 2 ) and EBC‐181 ( 3 ) is highly likely. EBC‐180 ( 2 ) and EBC‐181 ( 3 ) showed moderate to strong cytotoxic activity against various cancer cell lines. 相似文献
16.
Glushonok G. K. Glushonok T. G. Maslovskaya L. A. Shadyro O. I. 《Russian Journal of General Chemistry》2003,73(7):1027-1031
The state of hydroxyacetone in neutral aqueous solutions was studied by 1H and 13C NMR and UV spectroscopy. In the concentration range 0.1-1.41 M, 96-98% of hydroxyacetone exists in the carbonyl form. The content of the hydrated form of hydroxyacetone is 2-4%. No dimeric and polymeric species were detected. 相似文献
17.
Using the method of dynamic pyroeffect, polar properties of surface layers of nominally pure triglycinesulfate (TGS) crystals
prepolarized in an electrostatic field are experimentally investigated. The results on the pyrocoefficient distribution over
the crystal thickness modeled using the experimental dependences are reported. The model relies on the solution to the first-order
integral Fredholm equation by the method of Tikhonov’s regularization. 相似文献
18.
In this paper we prove the possibility of the use of the penalty method for grid matching in mixed finite element methods. We consider the Hermann-Johnson scheme for biharmonic equation. The main idea is to construct a perturbed problem with two parameters which play roles of penalties. The perturbed problem is built by the replacement of essential conditions on the interface in the mixed variational statement with natural conditions that contain parameters. The perturbed problem is discretized by the finite element method. We estimate the norm of the difference between a solution of the discrete perturbed problem and a solution of the initial problem; the obtained estimates depend on the step and the penalties. We give recommendations for the choice of penalties depending on the step. 相似文献
19.
Products of reactions of tert-butylated pyrocatechols with alkyl radicals were studied. The major products formed upon -irradiation of deaerated solutions of 4-tert-butyl- and 3,5-di-tert-butylpyrocatechol in hexane and cyclohexane are monoalkyl ethers, which were identified by NMR spectroscopy (1H, 13C, 1H-1H NOESY technique) and gas chromatography-mass spectrometry. 相似文献
20.
A. G. Maslovskaya T. K. Barabash 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2012,6(1):37-43
The features of polarization reversal processes of ferroelectric crystals are analyzed under the condition that electron beams
of a scanning electron microscope are injected into the subsurface layer of a sample. The proposed mathematical model describes
the dynamics of the polarization switching of a ferroelectric crystal using the injection contact technique. The simulation
relies on the basic principles of scale invariance in domain structure evolution. The polarization switching current of ferroelectric
crystals is investigated as the dynamic characteristic of a finite medium exhibiting fractal behavior. The application of
fractal and multifractal analysis of a time series enables us to calculate the fractal dimension of the polarization reversal
process under injection conditions. 相似文献