Cooperative transitions

Fe(trim)2](PhC00)(C104) continuous transition, cooperativity [30]... 

In Chapter 7, Mano and Dionisio describe how electrical methods, and particularly dielectric relaxation spectroscopy (DRS) and thermally stimulated depolarisation current (TSDS) techniques, play a major role as tools for e2q)loring molecular mobility. DRS enables molecular relaxational processes (both slow and fast) to be studied. For example, the localized motions of glass formers in the glassy state give rise to local fluctuations of the dipole vector that are the origin of the secondary relaxation processes detected by dielectric relaxation spectroscopy, while above, but near, the glass transition, cooperative motions result in a distinguishably different relaxation process (the a-relaxation). 

Figure 5.6. Modulus-temperature curves for several polyurethanes in comparison with various classes of polymer (A) Schematic curve for a linear amorphous polymer (B) schematic curve for a crosslinked polymer (C) schematic curve for a semicrystalline polymer (D) poly(ester urethane),Estane 5740-100 (E) poly(ester urethane),Estane 5740-070. Note that the polyurethanes exhibit two distinct glass transitions. (Cooper and Tobolsky, 1966u.)...

Transit Capacity and Quality of Service Manual, 2nd ed. 2006. http //www.trb.org/ Publications/Blurbs/Transit Capacity and Quality of Service Manual 2nd 153590. aspx (accessed August 18, 2010). Transportation Research Board. Transit Cooperative... 

The ordered phase of systems undergoing a structural phase transition (cooperative Jahn-Teller effect) can be treated in complete analogy to the magnetically ordered phase. In order to demonstrate this we start out from the magneto-elastic interactions as given by eq. (17.32) and add to it an interaction which is described by the hamiltonian... 

We consider a finite space, which contains the NA sample and is in contact with a bath of water or water vapor. That allows one to maintain the r.h. in the experimental space at a constant level and change it when necessary. Such a scheme corresponds to the real experiments with wet NA samples. A NA molecule is simulated by a sequence of units of the same type. Thus, in the present study, we consider the case of a homogeneous NA or the case where averaging over the unit type is possible. Every unit can be found in the one of three conformational states unordered. A- or B- conformations. The units can reversibly change their conformational state. A unit corresponds to a nucleotide of a real NA. We assume that the NA strands do not diverge during conformational transitions in the wet NA samples [18]. The conformational transitions are considered as cooperative processes that are caused by the unfavorable appearance of an interface between the distinct conformations. 

Ivanov, V.I., Minchenkova, L.E., Minyat, E.E., Schyolkina, A.K. Cooperative transitions in DNA with no separation of strands. Cold Spring Harbor Symposia on Quantitative Biology 47 (1983) 243-250... 

Porschke, D., Eigen, M. Cooperative nonenzymic base recognition. HI. Kinetics of the helix-coil transition of the oligoribouridylic oligoriboadenylic acid system and of oligoriboadenylic acid alone at acidic pH. J. Mol. Biol. 62 (1971) 361-381... 

Because of the large difference in tp between successive molecular layers, each layer becomes complete at a relative pressure (plp°)g which is determined by the value of rp/kT for that layer, viz integral values). Each layer will therefore give rise to a step, such that the riser corresponds to the cooperative build-up of the layer and the tread to the transition between the layer and the next higher one. 

The transition between the T and R states of hemoglobin is also deeply involved in the Bohr effect and cooperativity. Therefore stabilization of either of the two stmctures should diminish these effects, which have important physiologic consequences. The clinical consequences of stabilization are not known. 

This model of classical cooperative transitions has been speculated about as an alternative to tunneling. No confirmation for such a scheme exists now. The possibility of representing the experimental form of k(T) as... 

On the other hand, the formation of the high pressure phase is preceded by the passage of the first plastic wave. Its shock front is a surface on which point, linear and two-dimensional defects, which become crystallization centers at super-critical pressures, are produced in abundance. Apparently, the phase transitions in shock waves are always similar in type to martensite transitions. The rapid transition of one type of lattice into another is facilitated by nondilTusion martensite rearrangements they are based on the cooperative motion of many atoms to small distances. ... 

The sharpness of the transition in pure lipid preparations shows that the phase change is a cooperative behavior. This is to say that the behavior of one or a few molecules affects the behavior of many other molecules in the vicinity. The sharpness of the transition then reflects the number of molecules that are acting in concert. Sharp transitions involve large numbers of molecules all melting together. 

Effective computation requires both the storage and transmission of information. If correlations between. separated sites aie too small, the sites evolve essentially independently of one another and little or no transmission of information takes place. On the other hand, if the correlations are too strong, distant sites may cooperate so strongly so as to effectively mimic each others behavior this, too, is not conducive to effective computation. It is only within the transition region that information can propagate freely over long distances without appreciable decay. 

Stereoelectronic effects and nonbonded interactions are non-cooperative in the reactions of (E)-allylboronates and x-heteroatom-substituted aldehydes. Thus, while transition state 8 experiences the fewest nonbonded interactions (gauche pentane type, to the extent that X has a lower steric requirement than R3), transition state 9 is expected to benefit from favorable stereoelectronic activation (Felkin-type)58f. This perhaps explains why the reaction of 2,3-[iso-propylidenebis(oxy)]propanal and ( >2-butenylboronate proceeds with a modest preference (55%) by way ol transition state 9. This result is probably a special case, how ever, since C-3 of 2.3-[isopropylidenebis(oxy)]propanal is not very stcrically demanding in 9 owing to the acetonide unit that ties back the oxygen substituent, thereby minimizing interactions with the... 

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