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激光针灸理论与光剂量选择 总被引:3,自引:0,他引:3
激光针灸和传统针灸由于物理过程的差异其治疗机理不同。应用生物能量模型定量讨论激光热作用效应,利用几何光学模型解释光作用力的产生及其作用。根据光子中医理论和物理学基本原理,从理论角度探讨激光针灸作机理,并分析影响激光针灸作用的基本因素和最佳治疗光剂量。 相似文献
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生物医学与虚拟现实技术、计算机仿真技术的结合是现代科学与技术的一个重要发展趋势。为了解决角膜热成形术中的预测性及可控制性问题,本文针对角膜的特性进行医学虚拟研究,分析其变形机理;利用有限元方法,模拟了激光作用于眼角膜时的温度场分布情况,给出了不同参数下的激光作用时角膜的温度场分布曲线和穿透深度的比较;仿真结果表明,激光能量对角膜组织穿透深度影响很大,为角膜热成形术的研究提供了定性的基础,在减少实验费用、提高手术的预测性方面有非常重要的价值。 相似文献
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本研究应用激光拉曼散射光谱技术探讨SiO_2了诱发膜损伤效应以及柠檬酸铝抗损伤效应的机理。提出SiO_2的作用机理主要是与膜脂极性头部基团-N~+(CH_3)_3的相互作用及其对脂双层有序结构的破坏;而柠檬酸铝的抗损伤作用机理主要是通过铝与SiO_2颗粒表面的结合,从而阻断SiO_2与膜的直接相互作用,在一定程度上维持了膜的结构和功能。 相似文献
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本文是利用分子间相互作用的势能函数研究核酸的胞嘧啶碱基、腺嘌呤碱基与水的相互作用。方法上采用改进的分子相互作用势,并把能量贡献中的氢键项作为修正项处理,并应用BFGS 变尺度法进行最优化处理。研究结果表明:碱基(胞嘧啶,腺嘌呤)与水相互作用能的极小值及其最优的水合作用位置与精确的量子力学ab initio 法所得的结果接近,但在方法上得到了很大的简化。 相似文献
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James E. Olson Walter Schimmerling G. Craig Gundy Cornelius A. Tobias 《Cell biochemistry and biophysics》1981,3(4):349-371
Electrophysiological and ultrastructural effects of focused laser radiation on neurons from neonatal rat cerebellum in tissue
culture are reported. Action potentials were elicited by an extracellular current pulse train. The stimulator voltage required
for half-maximum response frequency was measured as a function of the energy delivered by a single laser pulse. Above a “threshold”
laser energy, the cell response to stimulation became negligible for all stimulator voltages. Electron micrographs of cells
revealed that the mitochondria are preferentially damaged at an energy comparable to the electrophysiological threshold. The
damaged mitochondria showed swollen matrix space and disrupted cristae membranes. Higher laser energies resulted in damage
to other cytoplasmic structures. The results are consistent with a model that assumes that light interaction with the nerve
cells proceeds by local heating of the mitochondria and nearby structures and leads to an increased conductance of the membrane
to some ionic species. 相似文献
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The importance of tight hydrophobic core packing in stabilizing proteins found in thermophilic organisms has been vigorously disputed. Here, portions of the cores found in three thermophilic homologues were transplanted into the core of staphylococcal nuclease, a protein of modest stability. Packing of the core was evaluated by comparing interaction energy of the three mutants to the comprehensive mutant library built up previously at these same sites in staphylococcal nuclease. It was found that the interaction energy of one thermophilic sequence is extraordinarily favorable and the interaction energies of other two transplanted thermophilic sequences are good, comparable to the interaction energies of mutant cores based on cores found in mesophilic homologues. As expected when transferring just a portion of the core sequence, the mutant proteins were destabilized overall relative to wild-type staphylococcal nuclease. The overall conclusion is that improvement of packing interactions is a mechanism to confer stability employed in some proteins from thermophiles, but not all. 相似文献
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H. Ruhl S. V. Bulanov T. E. Cowan T. V. Liseĭkina P. Nickles F. Pegoraro M. Roth W. Sandner 《Plasma Physics Reports》2001,27(5):363-371
Results from particle-in-cell simulations of the three-dimensional regime of proton acceleration in the interaction of laser radiation with a thin spherical target are presented. It is shown that the density of accelerated protons can be several times higher than that in conventional accelerators. The focusing of fast protons created in the interaction of laser radiation with a spherical target is demonstrated. The focal spot of fast protons is localized near the center of the sphere. The conversion efficiency of laser energy into fast ion energy attains 5%. The acceleration mechanism is analyzed and the electron and proton energy spectra are obtained. 相似文献
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D Lerche 《Biorheology》1984,21(4):477-492
On the basis of a recently developed biophysical model of cell-cell interaction, including electrostatic, electrodynamic, steric and bonding/bridging interaction energies the influence of different fixed charge (dissociated groups of the glycocalyx) density distributions in red blood cell (RBC) glycocalyces on the total free interaction energy was investigated. An analytical equation of electrostatic free energy on the basis of the linear Poisson-Boltzmann approach taking into account arbitrary distributions of fixed glycocalyx charges was obtained and corresponding free electrostatic energies of three example distributions were calculated. The electrodynamic, steric and bonding/bridging energies were computed as usual. It was shown that the free energy as a function of interaction distances strongly depends on the charge distribution and, correspondingly, the "weight" of this energy term in the total free interaction energy balance equation. Generally, it can be stated that as more charges are assumed to be fixed in the outer layer of RBC glycocalyx as more important becomes the electrostatic energy in contrast to the remaining three terms. 相似文献
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The energetics of the mechanism of proton transfer from a hydronium ion to one of the water molecules in its first solvation shell are studied using density functional theory and the Møller–Plesset perturbation (MP2) method. The potential energy surface of the proton transfer mechanism is obtained at the B3LYP and MP2 levels with the 6-311++G** basis set. Many-body analysis is applied to the proton transfer mechanism to obtain the change in relaxation energy, two-body, three-body and four-body energies when proton transfer occurs from the hydronium ion to one of the water molecules in its first solvation shell. It is observed that the binding energy (BE) of the complex decreases during the proton transfer process at both levels of theory. During the proton transfer process, the % contribution of the total two-body energy to the binding energy of the complex increases from 62.9 to 68.09% (39.9 to 45.95%), and that of the total three-body increases from 25.9 to 27.09% (24.16 to 26.17%) at the B3LYP/6-311++G** (MP2/ 6-311++G**) level. There is almost no change in the water–water–water three-body interaction energy during the proton transfer process at both levels of theory. The contribution of the relaxation energy and the total four-body energy to the binding energy of the complex is greater at the MP2 level than at the B3LYP level. Significant differences are found between the relaxation energies, the hydronium–water interaction energies and the four-body interaction energies at the B3LYP and MP2 levels. 相似文献
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Quantum and molecular dynamics study for binding of macrocyclic inhibitors to human alpha-thrombin
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Molecular dynamics simulations followed by quantum mechanical calculation and Molecular Mechanics Poisson-Boltzmann Surface Area (MM-PBSA) analysis have been carried out to study binding of proline- and pyrazinone-based macrocyclic inhibitors (L86 and T76) to human alpha-thrombin. Detailed binding interaction energies between these inhibitors and individual protein fragments are calculated using DFT method based on a new quantum mechanical approach for computing protein-ligand interaction energy. The analysis of detailed interaction energies provides insight on the protein-ligand binding mechanism. Study shows that T76 and L86 bind to thrombin in a very similar "inhibition mode" except that T76 has relatively weaker binding interaction with Glu(217). The analysis from quantum calculation of binding interaction is consistent with the MM-PBSA calculation of binding free energy, and the calculated free energies for L86/T76-thrombin binding agree well with the experimental data. 相似文献
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D. T. Edmonds 《European biophysics journal : EBJ》1985,13(1):31-35
Electric dipoles placed side by side attract each other if antiparallel and repel each other if parallel. The hydrophobic -helical sections of proteins that span membranes are known to possess large electric dipole moments. The first part of the paper consists of a calculation of the interaction energies between such helices including screening effects. Interaction energies remain comparable with a typical thermal energy of KT up to separations of order 20 Å. In addition it is shown that, due solely to its dipole moment, an -helix which completely spans the membrane has an energy up to 5 KT lower than one which terminates within the membrane width. The second part of the paper describes the electrical interaction of the charge structure of a membrane channel and the protein helices that surround the pore. The gating charge transfer that is measured when a voltage sensitive ion channel switches, means that the dipole moment of the ion channel changes. This in turn results in a change in the radial forces that act between the pore and the -helices that surround it. A change in these radial forces which tend to open or to close the pore constitutes an electrically silent gating mechanism that must necessarily act subsequent to the gating charge transfer. The gating mechanism could consist of the radial translation of the neighbouring proteins or in their axial rotation under the influence of the torque that would act on a pair of approximately equidistant but oppositely directed -helices. An attempt to calculate the interaction energy of a typical pore and a single -helix spanning the membrane results in an energy of many times KT. 相似文献
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The molecular forces that drive structural transitions between the open and closed states of channels and transporters are not well understood. The gate of the OmpA channel is formed by the central Glu52-Arg138 salt bridge, which can open to form alternate ion pairs with Lys82 and Glu128. To gain deeper insight into the channel-opening mechanism, we measured interaction energies between the relevant side chains by double-mutant cycle analysis and correlated these with the channel activities of corresponding point mutants. The closed central salt bridge has a strong interaction energy of -5.6 kcal mol(-1), which can be broken by forming the open-state salt bridge Glu52-Lys82 (DeltaDeltaG(Inter) = -3.5 kcal mol(-1)) and a weak interaction between Arg138 and Glu128 (DeltaDeltaG(Inter) = -0.6 kcal mol(-1)). A covalent disulfide bond in place of the central salt bridge completely blocks the channel. Growth assays indicate that this gating mechanism could physiologically contribute to the osmoprotection of Escherichia coli cells from environmental stress. 相似文献
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Shalabi AS 《Journal of molecular modeling》2002,8(10):314-326
The twofold potential of F+ color centers at the low coordinated surfaces of SrO for providing tunable laser activity and adsorption properties for atomic halogens (F, Cl and Br) has been investigated using ab initio electronic structure calculations. SrO clusters of variable sizes were embedded in simulated Coulomb fields that closely approximate the Madelung fields of the host surfaces and the nearest neighbor ions to F+ were allowed to relax to equilibrium. Based on Stokes shifted optical transition bands and horizontal shifts along the configuration coordinate diagrams, the F+ laser activity was found to decrease as the coordination number of the surface ions decreases from 5 (flat) to 4 (edge) to 3 (corner). An attempt has been made to explain this result in terms of Madelung potentials and optical-optical conversion efficiencies. All relaxed excited states are deep below the conduction bands of the perfect ground states, implying that F+ is a laser-suitable defect. The most laser active flat surface is the least probable for relaxed excited state orientational destruction of F+. The excited state at the edge has the highest energy, implying exciton (energy) transfer to the flat and edge sites. F+ relaxation and defect-formation energies increase with increasing surface coordination number. The Glasner-Tompkins relation between the fundamental optical absorption of F+ in solids and the fundamental absorption of the host crystals can be generalized to include the low coordinated surfaces of SrO. The F+ color center changes the nature of halogen-surface interaction (adsorption energies) from physical adsorption to chemical adsorption. The halogen-surface interactions increase with increasing electronegativity of the halogen. The calculated adsorption energies can be explained in terms of surface electrostatic potentials, and the covalent spin pairing mechanism plays a dominant role in determining adsorbate-substrate interactions. 相似文献
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S. V. Kuznetsov 《Plasma Physics Reports》2012,38(2):116-125
The process of trapping and acceleration of nonmonoenergetic electron bunches by a wake wave excited by a laser pulse in a
plasma channel is investigated. The electrons are injected into the vicinity of the maximum of the wakefield potential with
a velocity lower than the wave phase velocity. The study is aimed at utilizing specific features of a wakefield with substantially
overlapped focusing and accelerating phases for achieving monoenergetic electron acceleration. Conditions are found under
which electrons in a finite-length nonmonoenergetic bunch are accelerated to high energies, while the energy spread between
them is minimal. The effect of energy grouping of electrons makes it possible to obtain compact high-energy electron bunches
with a small energy spread during laser plasma acceleration. 相似文献