Alternating phases

HORACE used alternating phases of classification (which topological or physicochemical features are required for a reaction type) and generalization (which features are allowed and can be eliminated) to produce a hierarchical classification of a set of reaction instances. 

Computer simulations of bulk liquids are usually performed by employing periodic boundary conditions in all three directions of space, in order to eliminate artificial surface effects due to the small number of molecules. Most simulations of interfaces employ parallel planar interfaces. In such simulations, periodic boundary conditions in three dimensions can still be used. The two phases of interest occupy different parts of the simulation cell and two equivalent interfaces are formed. The simulation cell consists of an infinite stack of alternating phases. Care needs to be taken that the two phases are thick enough to allow the neglect of interaction between an interface and its images. An alternative is to use periodic boundary conditions in two dimensions only. The first approach allows the use of readily available programs for three-dimensional lattice sums if, for typical systems, the distance between equivalent interfaces is at least equal to three to five times the width of the cell parallel to the interfaces. The second approach prevents possible interactions between interfaces and their periodic images. 

From a mechanical point of view the polymer may be regarded as a composite consisting of an alternative stiff (crystalline) and soft-compliant (disordered) elements. Given the geometrical arrangement of these two alternating phases and the hardness value of both of them, the arising question is to predict the hardness value of the material. On the other hand, it is known that density is a crystallinity parameter... 

One problem associated with COSY spectra is the dispersive character of the diagonal peaks, which can obliterate the cross-peaks lying near the diagonal. Moreover, if the multiplets are resolved incompletely in the crosspeaks, then because of their alternating phases an overlap can weaken their intensity or even cause them to disappear. In double-quantum filtered COSY spectra, both the diagonal and the cross-peaks possess antiphase character, so they can be phased simultaneously to produce pure 2D absorption line... 

The cardiac cycle is the period of time from beginning of one heart beat to beginning of the next. As such, it consists of two alternating phases ... 

PHEMA solubility decreases with increasing ion concentration. As a result, Mikos et al. used salt solutions of varying ionic strength to dilute the reaction mixtures (Liu et al., 2000). It was noted that increasing the ion content of the aqueous solution to 0.7M, interconnected macropores were obtained at 60 vol% water. Surfactants may also be used to control the network pore structure. However, not much work has been done in this area, since surfactants typically work to reduce the surface repulsions between the two phases and form a uniform emulsion. These smaller emulsion droplets when gelled will create a network with an even smaller porous structure. Yet, this is still a promising area of exploration, since it may be possible to form alternate phase structures such as bicontinuous phases, which would be ideal for cellular invasion. 

Spurred by our desire to avoid use of expensive dipolau aprotic solvents in nucleophilic aromatic substitution reactions, we have developed two alternative phase transfer systems, which operate in non-polar solvents such as toluene, chlorobenzene, or dichlorobenzene. Poleu polymers such as PEG are Inexpensive and stable, albeit somewhat inefficient PTC agents for these reactions. N-Alkyl-N, N -Dialkylaminopyridinium salts have been identified as very efficient PTC agents, which are about 100 times more stable to nucleophiles than Bu NBr. The bis-pyridinium salts of this family of catalysts are extremely effective for phase transfer of dianions such as bis-phenolates. 

The driving fields in nonlinear coherent microscopy can be dressed with alternative phase profiles. One of the simplest phase masks is a one-dimensional r-phase step across the transverse Gaussian beam profile. The resulting phase pattern resembles... 

As indicated, a single mean-field parameter amf is included as the proportionality factor. It is noteworthy that the numerical value of amf is unimportant to the condensation phenomenon itself, so that even an infinitesimally small value (e.g., of order 10-6 a.u.), is sufficient to reward thermodynamic condensation and yield an alternative phase of greatly reduced V under appropriate conditions of temperature and pressure. 

Alternatively, the reaction may be carried out in a mixture of two immiscible solvents. The contact area between the phases may be increased by agitation. Phase transfer reagents, in particular quaternary ammonium compounds, are useful aids in many two-phase reactions. Also, crown ethers are very effective in overcoming phase contact problems however, their usefulness is limited by high price. (Open-chain polyoxyethylene compounds often give a crown ether effecf and may constitute practically interesting alternative phase transfer reagents.)... 

It was quantitatively interpreted (Rice et al., 1977) as originating from bond alternation phase oscillations (in contrast to the bond alternation amplitude oscillations mentioned in subsection 4.8.2D). The vibrational absorption lines labeled 2 to 10 are directly related to the Ag Raman lines of TCNQ. The broad peak above 1600 cm originates from the single electron transition across the gap, and the indented line shape of mode 2 is a consequence of Fano interference between the single electron continuum and the phonon mode. The line intensities are determined by the respective electron - vibration coupling constants. 

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