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991.
Caiyun Xiong Xiaolin Nie Yixue Peng Xun Zhou Yangtao Fan Hu Chen Yanhui Liu 《理论物理通讯》2021,73(7):75602
Knots are discovered in biophysical systems, such as DNA and proteins. Knotted portions in knotted DNA are significantly bent and their corresponding bending angles are comparable with or larger than the sharp bending angle resulting in flexible defects. The role of flexible defects in the interplay of supercoiling and knotting of circular DNA were predicted by a Monte Carlo simulation. In knotted DNA with a particular knot type, a flexible defect noticeably enhances the supercoiling of the knotted DNA and the decreasing excitation energy makes the knotted portion more compact. A reduction in twist rigidity and unwinding of flexible defects are incorporated into the numerical simulations, so that interplay of supercoiling and knotting of circular DNA is studied under torsional conditions. Increasing unwinding not only results in a wider linking number distribution, but also leads to a drift of the distribution to lower values. A flexible defect has obvious effects on knotting probability. The summation of equilibrium distribution probability for nontrivial knotted DNA with different contour length does not change with excitation energy monotonically and has a maximum at an intermediate value of excitation energy around 5 kBT. In the phase space of knot length and gyration radius of knotted DNA, knot length does not anticorrelate with its gyration radius, which is attributed to the flexible defect in the knotted portion, which leads to the release of bending energy and inhibited the competition between entropy and bending energy. 相似文献
992.
993.
The dimensionless third-order nonlinear Schrödinger equation (alias the Hirota equation) is investigated via deep leaning neural networks. In this paper, we use the physics-informed neural networks (PINNs) deep learning method to explore the data-driven solutions (e.g. bright soliton, breather, and rogue waves) of the Hirota equation when the two types of the unperturbated and perturbated (a 2% noise) training data are considered. Moreover, we use the PINNs deep learning to study the data-driven discovery of parameters appearing in the Hirota equation with the aid of bright solitons. 相似文献
994.
Based on the beyond-mean-field Skyrme–Hartree–Fock model, impurity effects of the Λhyperon in the hypernuclear systems ${}_{\,{\rm{\Lambda }}}^{25}$ Mg and ${}_{\,{\rm{\Lambda }}}^{29}$ Si are investigated, respectively. Four cases, in which the Λhyperon occupies the single-particle orbitals ${\rm{\Lambda }}$[000]${\tfrac{1}{2}}^{+}$, ${\rm{\Lambda }}$[110]${\tfrac{1}{2}}^{-}$, ${\rm{\Lambda }}$[101]${\tfrac{3}{2}}^{-}$ and ${\rm{\Lambda }}$[101]${\tfrac{1}{2}}^{-}$, are focused. In each case, the potential energy surface and the energy curves projected on certain angular momenta are employed to show the influence of the Λhyperon on the nuclear core. Beside the shrinkage effect that is induced by the Λhyperon occupying the sΛ orbital, it is found that the Λhyperon on the pΛ orbital, ${\rm{\Lambda }}$[110]${\tfrac{1}{2}}^{-}$, drives the nuclear core toward a prolate shape, while the ones on the other two pΛ orbitals, ${\rm{\Lambda }}$[101]${\tfrac{3}{2}}^{-}$ and ${\rm{\Lambda }}$[101]${\tfrac{1}{2}}^{-}$, drive the nuclear core toward an oblate shape. The energy spectra and the corresponding intra-band E2 transition rates for the rotational bands are given as a prediction for future experiments. 相似文献
995.
根据通电的环向场(TF)线圈在磁场作用下将产生侧向力和径向力,提出了抗扭转支撑结构方案。该方案能够降低这两种力对 TF 线圈的影响,并且保证线圈连接面的紧密接触和绝缘层不会发生相对错动。对抗扭转支撑结构进行计算分析,确定该结构的受力方式以及传力路径。结果表明,在实验运行以及极端工况下结构的应力、位移能够到达设计要求,通过疲劳计算得出抗扭转支撑结构能满足 20 年以上的实验运行,能够保证 HL-2M装置安全、平稳和可靠的运行。 相似文献
996.
通过数值计算评估了 HL-2M 装置磁测量传感器安装精度的要求,其中磁通环坐标(R, Z)的安装偏差
要求达到±2.0mm 以内,磁探针的(R, Z)偏差要求在±1.0mm 以内、角度偏差在±0.1°以内。定位安装采用高精度激
光跟踪仪和关节测量臂结合,设备定位精度在±0.3mm。根据不同种类的磁测量传感器的定位安装特点,优化设
计了包括磁通环、磁探针阵列、逆磁同心圆等的定位结构,将 HL-2M 磁测量传感器的安装精度控制到在±0.5mm
水平。 相似文献
997.
Thressa C. Stadtman 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):199-216
Abstract Some enzymes known to contain selenium are enumerated. In four of them which catalyze coupled oxidation-reduction reactions the selenium occurs exclusively in the form of selenocysteine residues. Their structure and function are described in detail. Two other bacterial enzymes which contain selenium in the form of a labile, readily dissociable component are also described. Results on the isolation, identification and structure determination of selenium-containing amino acid transfer ribonucleic acids are presented. These seleno-t RNA's are shown to contain either 5-methyl-aminomethyl-2-selenouridine or other 2-selenouridine derivatives. The role of selenium in a glutamate iso-accepter species is discussed. 相似文献
998.
A. A. F. Wasfy M. S. Amine M. M. H. Arief S. G. Donia A. A. Aly 《Phosphorus, sulfur, and silicon and the related elements》2013,188(5):1359-1368
4-(5,5-Dioxodibenzothiophen-2-yl)-4-oxo-2-butenoic acid ( 1 ) was condensed with compounds containing active methylene groups under Michael reaction conditions to form the Michael adducts 2a-c , 3a-c , and 4a-b . The behavior of Michael adduct towards the action of hydrazine hydrate was investigated. The compounds were tested for biological properties. 相似文献
999.
Azaiez Ben Akacha Salim Barkallah Belgacem Baccar 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):163-166
Abstract Under the normal conditions, the reaction of hydrazine and methylhydrazine with OO-diethyl 1 oxoalkane phosphonates 1 proceeds by cleavage of the phosphorus-carbon bond and leads to the formation of diethylphosphite 2 and N-acylhydrazide 3 . A procedure has been developed for the synthesis of new primary hydrazone of OO-diethyl 1-oxoalkane phosphonates 4 . A mechanism is proposed. The structure of those compounds 4 was confirmed by NMR and IR spectroscopy. 相似文献
1000.
N. Iranpoor H. Firouzabadi H. Bahador A. Jamalian 《Phosphorus, sulfur, and silicon and the related elements》2013,188(9):1972-1978
Silicaphosphite (silphos), [PCl3-n(SiO2)n], as a heterogeneous phosphorous compound, catalyzes the thiocyanation of benzylic alcohols and silyl and THP ethers in the presence of I2 and NH4SCN in refluxing CH3CN. The produced silphos oxide byproduct can be easily separated by a simple filtration. Silphos is also used for the efficient and selective deprotection of silyl and THP-ethers to their corresponding alcohols. 相似文献