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131.
《Acta Crystallographica. Section C, Structural Chemistry》2017,73(10):803-809
Specific short contacts are important in crystal engineering. Hydrogen bonds have been particularly successful and together with halogen bonds can be useful for assembling small molecules or ions into crystals. The ionic constituents in the isomorphous 3,5‐dichloropyridinium (3,5‐diClPy) tetrahalometallates 3,5‐dichloropyridinium tetrachloridozincate(II), (C5H4Cl2N)2[ZnCl4] or (3,5‐diClPy)2ZnCl4, 3,5‐dichloropyridinium tetrabromidozincate(II), (C5H4Cl2N)2[ZnBr4] or (3,5‐diClPy)2ZnBr4, and 3,5‐dichloropyridinium tetrabromidocobaltate(II), (C5H4Cl2N)2[CoBr4] or (3,5‐diClPy)2CoBr4, arrange according to favourable electrostatic interactions. Cations are preferably surrounded by anions and vice versa ; rare cation–cation contacts are associated with an antiparallel dipole orientation. N—H…X (X = Cl and Br) hydrogen bonds and X …X halogen bonds compete as closest contacts between neighbouring residues. The former dominate in the title compounds; the four symmetrically independent pyridinium N—H groups in each compound act as donors in charge‐assisted hydrogen bonds, with halogen ligands and the tetrahedral metallate anions as acceptors. The M —X coordinative bonds in the latter are significantly longer if the halide ligand is engaged in a classical X …H—N hydrogen bond. In all three solids, triangular halogen‐bond interactions are observed. They might contribute to the stabilization of the structures, but even the shortest interhalogen contacts are only slightly shorter than the sum of the van der Waals radii. 相似文献
132.
《Advanced Optical Materials》2017,5(5)
Surface plasmonic tweezers and electrostatic forces can be employed as complementary methods for trapping and detecting molecules with high sensitivity and selectivity. The hotspots—localized regions of highly concentrated electromagnetic fields with large gradients—give rise to both the plasmonic tweezer effect and the surface‐enhanced Raman scattering (SERS) effect. So naturally, combining plasmonic tweezers and SERS makes for an ideal label‐free method for trapping and detecting molecules. Here, the trapping effect of the plasmonic tweezer is demonstrated by using the unique graphene–Au pyramid hybrid platform. While very powerful, the force associated with plasmonic tweezers is a short‐range effect (<50 nm from the spot of peak intensity). The electrostatic force, on the other hand, has long‐range interaction extending to beyond micrometers, which can guide molecules toward the hotspots. The authors present experimental evidence showing the combination of plasmonic tweezers and electrostatic forces by using an integrated electrostatic cell. Using the combined platform, trapping of single molecules in dilute solution is observed. These observations indicate a new approach for enhancing SERS sensitivity. It also offers a realistic possibility for precisely positional control of biomolecules, allowing the study of the properties of single biomolecules. 相似文献
133.
《Journal of computational chemistry》2017,38(2):65-80
Our Fuzzy‐Border (FB) continuum solvent model has been extended and modified to produce hydration parameters for small molecules using POlarizable Simulations Second‐order Interaction Model (POSSIM) framework with an average error of 0.136 kcal/mol. It was then used to compute pK a shifts for carboxylic and basic residues of the turkey ovomucoid third domain (OMTKY3) protein. The average unsigned errors in the acid and base pK a values were 0.37 and 0.4 pH units, respectively, versus 0.58 and 0.7 pH units as calculated with a previous version of polarizable protein force field and Poisson Boltzmann continuum solvent. This POSSIM/FB result is produced with explicit refitting of the hydration parameters to the pK a values of the carboxylic and basic residues of the OMTKY3 protein; thus, the values of the acidity constants can be viewed as additional fitting target data. In addition to calculating pK a shifts for the OMTKY3 residues, we have studied aspartic acid residues of Rnase Sa. This was done without any further refitting of the parameters and agreement with the experimental pK a values is within an average unsigned error of 0.65 pH units. This result included the Asp79 residue that is buried and thus has a high experimental pK a value of 7.37 units. Thus, the presented model is capable or reproducing pK a results for residues in an environment that is significantly different from the solvated protein surface used in the fitting. Therefore, the POSSIM force field and the FB continuum solvent parameters have been demonstrated to be sufficiently robust and transferable. © 2016 Wiley Periodicals, Inc. 相似文献
134.
《等离子体物理论文集》2017,57(9):404-413
A generalized response (dielectric) function for twisted electrostatic waves is derived for an un‐magnetized self‐gravitating thermal dusty plasma, whose constituents are the Boltzmann‐distributed electrons and positive ions in the presence of negatively charged micrometre‐sized massive dust particulates. For this purpose, a set of Vlasov–Poisson coupled equations is solved along with the perturbed Laguerre–Gauss distribution function, as well as the electrostatic and gravitational potentials in the limit of paraxial approximation. For plane wave solution, the wavefronts of the dust‐acoustic (DA ) wave are assumed to have a constant phase with electric and gravitational field lines propagating straight along the propagation axis. On the other hand, non‐planar wave solutions show helical (twisted) wavefronts, in which field lines spiral around the propagation axis owing to the azimuthal velocity component to account for the finite orbital angular momentum (OAM ) states. The dispersion relation and damping rate for twisted DA waves are studied both analytically and numerically. It is shown that finite OAM states, the dust to electron temperature ratio, and dust self‐gravitation effects significantly affect the linear dispersion and Landau damping frequencies. In particular, the phase speed of twisted DA waves is reduced with the variation of the twist parameter η (= k /lqϕ ), dust concentration δ (= nd 0/ni 0), and dust self‐gravitation α (= ωJd /ωpd ). The relevance of our findings to interstellar dust clouds is also discussed for micrometre‐sized massive dust grains. 相似文献
135.
Shanshan Jin Yunfeng Jiang Kaixiang Zhao Caiyong Zou Yajun Zhao Li Zhang Zhi Fang 《Plasma Processes and Polymers》2023,20(11):e2300063
Plasma bacteria decontamination devices for the inner surface of medical tubes have to consider more practical application problems, such as the processing compatibility for medical tubes of variable scales, a reasonable and effective design model for plasma electrode parameters, and so on. This paper proposes a novel multisegment-casing ring-ring jet (MSC-RRJ) without embedding the electrode into the target tube, obtaining the variable tube length processing capability. And through establishing an effective design model based on electric field distribution properties, ensuring the electric field strength margin in each segment of MSC-RRJ to achieve the processing capability of variable tube diameters. A prototype device is developed based on the proposed MSC-RRJ electrode and design method being verified by killing Staphylococcus aureus and Escherichia coli. 相似文献
136.
对于静电场,由普遍的格林互易定理得出特殊情形下的格林互易定理.应用该定理推导出均匀带电圆环的数种在形式上互不相同的静电势分布解式. 相似文献
137.
测绘模拟静电场的等K0面分布及多用途T型数字电桥仪 总被引：3，自引：0，他引：3
介绍了用测量归一化等电势面来测绘模拟静电场的方法以及相应的测量仪器——多用途T型数字电桥仪。 相似文献
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