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161.
Coakley WT Bazou D Morgan J Foster GA Archer CW Powell K Borthwick KA Twomey C Bishop J 《Colloids and surfaces. B, Biointerfaces》2004,34(4):221-230
An ultrasonic standing wave trap [Langmuir 19 (2003) 3635] in which the morphologies of 2-D latex–microparticle aggregates, forming a pressure node plane, were characterised has been applied here to different cell suspensions with increasing order of specificity of cross-linking molecule, i.e. polylysine with chondrocytes; wheat germ agglutinin (WGA) with erythrocytes and surface receptors on neural cells. The outcome of initial cell–cell contact, i.e. whether the cells stuck at the point of contact (collision efficiency=1) or rolled around each other (collision efficiency=0), was monitored in situ by video-microscopy. The perimeter fractal dimensions (FD) of 2-D hexagonally symmetric, closely packed aggregates of control erythrocytes and chondrocytes were 1.16 and 1.18, respectively while those for the dendrititc aggregates formed initially by erythrocytes in 0.5 μg/ml WGA and chondrocytes in 20 μg/ml polylysine were 1.49 and 1.66. The FDs for control and molecularly cross-linked cells were typical of reaction-limited aggregation (RLA) and transport diffusion-limited aggregation (DLA), respectively. The FDs of the aggregates of cross-linked cells decreased with time to give more closely packed aggregates without clear hexagonal symmetry. Suspensions of neural cells formed dendritic aggregates. Spreading of inter-cellular membrane contact area occurred over 15 min for both erythrocyte and neural cell dendritic aggregates. The potential of the technique to characterise and control the progression of cell adhesion in suspension away from solid substrata is discussed. 相似文献
162.
We have determined the dynamic dipole (α1), quadrupole (α2), octupole (α3), and dipole–dipole–quadrupole (B) polarizabilities and the second hyperpolarizability tensor (γ) for the helium atom in its lowest triplet state (23S). We have done so for both real and imaginary frequencies: in the former case, for a range of frequencies (ω) between zero and the first electronic-transition frequency, and in the latter case for a 32-point Gauss–Legendre grid running from zero to ?ω = 20 Eh. We have also determined the dispersion-energy coefficients C6, C8, and C10 for the systems H(12S)? He(23S), He(11S)? He(23S), and He(23S)? He(23S) and the C, C, C, C, and C coefficients for the interaction He(23S)? H2(X1∑). Our values of the higher-order multipolar polarizabilities and of γ for the 23S state of helium are, we believe, the first to be published. © 1993 John Wiley & Sons, Inc. 相似文献
163.
A series of indicators have been prepared by condensing pyromellitic dianhydride with various phénols. Color changes and pH ranges have been determined, both in visible light and in ultraviolet light, for those indicators that fluoresce. Of particular interest is the indicator prepared using oxine as the phenolic compound, since there is a possibility in this case of complex formation through the nitrogens of the condensed oxine groups. 相似文献
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Roger Bishop Ian G. Dance Stephen C. Hawkins Tony Lipari 《Journal of inclusion phenomena and macrocyclic chemistry》1984,2(1-2):75-83
The discovery thatexo-2,exo-6-dihydroxy-2,6-dimethylbicyclo [3.3.1]nonane (2) forms novel multimolecular canal-type inclusion complexes has led to a systematic study of related molecular structures. This synthetic programme has shown that diol (2) is the prototype of a family of host diols all with the same crystallographic space groupP3121, but with distinctly different canal shapes and dimensions. The structures of the first four members of this new family of hosts are described and contrasted. 相似文献
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Mixtures of oppositely charged nanoparticles (NPs) precipitate sharply only at the point of NP electroneutrality. This behavior-reminiscent of the threshold precipitation of inorganic ions-is specific to the nanoscale and can be attributed to the formation of like-charged NP clusters stabilized in solution by mutual electrostatic repulsions. NP titrations based on this phenomenon provide a uniquely accurate tool for measuring charges tethered onto nanoscopic objects and for studying the thermodynamics of surface reactions at the nanoscale. 相似文献
169.
Previously determined nonadiabatic wave functions for H2+ (containing several hundred terms) are analyzed by using natural orbitals. This is the first time that the natural orbital concept has been applied to other than purely electronic wave functions. We find that the natural orbital expansion converges rapidly and that five or six terms are sufficient to reproduce the exact expectation values. Several plots are given of the orbitals so found and these allow a visualization of the somewhat abstract nonadiabatic wave function in a format more reminiscent of everyday quantum-mechanical pictures. 相似文献
170.