Disordering cooperative

Samanin, R and Grignaschi, G (1996) Role of 5-hydroxytryptamine receptor subtypes in satiety and animal models of eating disorders. In Drug Receptor Subtypes and Ingestive Behaviour (Eds Cooper, SJ and Clifton, PG), Academic Press, London, pp. 39-58. 

The case of isotactic polypropylene (iPP) presents some differences with respect to those just discussed. While both sPP and PET adopt in their mesophases disordered, extended, essentially non-helical conformations, iPP is characterized by a unique, relatively well ordered, stable chain structure with three-fold helical symmetry [18,19,36]. More accurately we can state that an iPP chain segment can exist in the mesophase either as a left handed or as the enantiomeric right-handed three-fold helix. The two are isoener-getic and will be able to interconvert only through a rather complex, cooperative process. From a morphological point of view Geil has reported that thin films of mesomorphic iPP quenched from the melt to 0 °C consist of... 

Both clusters in Fig. 5.31 exhibit considerable cooperative proton-ordering that distinguishes them from many alternative proton-disordered (and destabilized) isomeric forms that could be imagined. For example, the 24-mer (Fig. 5.31 (a)) has two fully cooperative W6C-like caps as well as a fully cooperative 12-ring girdle, ... 

Figure 2.48 Possible cooperative mechanism of crystal-crystal transition from (a) trans planar form III of sPP into (c) isochiral helical form II. Transition occurs through formation of (b) intermediate conformationally disordered modifications containing kink bands, characterized by helical sequences having same chirality (R = right-handed helix). Formation of helical sequences of opposite chirality (right- and left-handed) produces (if) steric interactions between neighboring chains.

The variation of order with temperature is shown in Figure 9.10. As the temperature is raised, a high degree of order remains until close to the transition temperature, where the disorder is induced rapidly. This cooperative behaviour is due to the fact that the energy associated with the disordering becomes progressively less as the disorder takes place. The transition is of second order. No short-range order remains above the transition temperature. 

A low AH for a cooperative cluster rotation allows excitation of a cluster of atoms from normal to saddle-point positions. Such an excitation may, in turn, lower the energy of the saddle-point sites relative to the normal sites, thus effectively introducing a AHg(T) that collapses in a smooth transition. At temperatures T> T, the mobile ions become disordered over the normal and saddle-point sites. Such a situation appears to be illustrated by stoichiometric LijN and PbFj (Goodenough, 1984). 

To understand whether cognitive function and mood disorders are cooperatively influenced by genetic factors in AD and to know the potential impact that conventional neuroprotection can exert on mood disorders, we studied the effect of the therapeutic CNLA protocol on anxiety in AD and the differential APOE- and ACE-related responses distinguishing the influence of monogenic and bigenic variants on emotional conditions. 

Many biological polymers display a cooperative transition from an ordered to disordered state [34] including the helix coil transitions observed for both peptides [35] and nucleic acids [36]. Synthetic systems that are able to undergo a cooperative helix coil transition can complement biopolymer studies and are of potential interest for density-responsive materials. 

We have demonstrated in this contribution that the structural order-disorder transitions in the KDP family are by far more complex than a pseudo-spin model, for example, could describe. Geometrical constraints and couphng to the soft mode, as well as cluster formation of nanometric size, indicate that here the conventional picture of cooperative phenomena has to be revised. 

Cambodia s City of Guns. The Economist, October 24, 1998, p. 40. Describes the situation of Cambodia s capital, Phnom Penh, where decades of civil war have left the population with 50,000 guns. Afraid of crime and disorder, most people have refused the government s request that the guns be turned in. The article suggests that the government must offer real security and reduce corruption before the populace will cooperate. 

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