Spheroids, dynamics

Resolution at tire atomic level of surfactant packing in micelles is difficult to obtain experimentally. This difficulty is based on tire fundamentally amoriDhous packing tliat is obtained as a result of tire surfactants being driven into a spheroidal assembly in order to minimize surface or interfacial free energy. It is also based upon tire dynamical nature of micelles and tire fact tliat tliey have relatively short lifetimes, often of tire order of microseconds to milliseconds, and tliat individual surfactant monomers are coming and going at relatively rapid rates. 

A modified version of the TAB model, called dynamic drop breakup (DDB) model, has been used by Ibrahim et aU556l to study droplet distortion and breakup. The DDB model is based on the dynamics of the motion of the center of a half-drop mass. In the DDB model, a liquid droplet is assumed to be deformed by extensional flow from an initial spherical shape to an oblate spheroid of an ellipsoidal cross section. Mass conservation constraints are enforced as the droplet distorts. The model predictions agree well with the experimental results of Krzeczkowski. 311 ... 

The dynamics of rigid, isolated spheroids was first analyzed for the case of shear flow by Jeffery[95]. When subject to a general linear flow with velocity gradient tensor G, the time rate of change of the unit vector defining the orientation of the symmetry axis of such a particle will have the following general form,... 

Three main tendencies have been underlined in recent studies of structure and action mechanism ofbacterial photosynthetic reaction centers. The crystallographic structure of the reaction centers from Rps. viridis and Rb. spheroids was initially determined to be 2.8 and 3 A resolutions (Michel and Deisenhofer et al., 1985 Allen et al., 1986). Resolution and refinement of these structures have been subsequently extended to 2.2, 2.3 and 2.6 A. (Rees et al., 1989 Stowell et al., 1997, Fyfe and Johns, 2000 Rutherford and Faller, 2001). Investigations of the electronic structure of donor and acceptor centers in the ground and exited states by modern physical methods with a combination ofpico-and femtosecond kinetic techniques have become more precise and elaborate. Extensive experimental and theoretical investigations on the role of orbital overlap and protein dynamics in the processes of electron and proton transfer have been done. All the above-mentioned research directions are accompanied by extensive use of methods of sit-directed mutagenesis and substitution of native pigments for artificial compounds of different redox potential. 

Ibrahim et al. [12] proposed the Droplet Deformation Breakup (DDB) model, which is based on the drop s dynamics in terms of the motion of the center-of-mass of the half-droplet. It is assumed that the liquid drop is deformed due to a pure extensional flow from an initial spherical shape of radius r into an oblate spheroid having an ellipsoidal cross-section with major semi-axis a and minor semi-axis b. The internal energy of the half-drop comes from the sum of its kinetic and potential energies, E, expressed as follows ... 

The a-dispersion exhibited by cell suspensions could basically be explained by rather complementary mechanisms, formally described by different microscopic models of cell systems, as the ones based either on displacement of counter-ions (Gheorghiu, 1993, 1994) or on shape effects (e.g., exhibited by clusters of interconnected cells as shown by Vrinceanu and Gheorghiu, 1996 Asami et al., 1999 Gheorghiu et al., 2002, 2010). These studies described both a and P dispersions based on unitary microscopic models. The reports emphasizing shape effect on the impedance spectra of (non)spheroidal living cells in suspension have also supported application of time-based impedance spectroscopy assays to noninvasively assess cell dynamics (e.g., cell-cycle progression). 

Measurement methods based on droplet deformation use either the shape change ratio or droplet dynamics, when they flow into a microchannel with an expanded or narrowed structure. For example, with the gradual broadening of the flowing chamber, the droplet velocity decreases, which causes round droplets to become spheroid, as shown in Fig. 6B (Hudson et al, 2005). During the ensuing time, the evolution of the deformation ratio of droplet D, defined by Eq. (4), is a function of interfacial tension, which can be used to measure the dynamic interfacial tension. 

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