Molecular origin

Cieplak M, Smith E D and Robbins M O 1994 Molecular origins of friction the force on adsorbed layers Science 256 1209... 

What distinguishes water from ordinary organic solvents and justifies the term hydrophobic interaction is the molecular origin of the effect, being entropy driven in pure water at room temperature and resulting primarily from the strong water-water interactions. 

In the hope of having done away with these misunderstandings, we now address the molecular origin of the hydrophobic hydration as well as the hydrophobic interaction. Note that comprehension of hydrophobic hydration is a prerequisite for understanding hydrophobic interactions, since hydrophobic interactions always involve a (partial) reversal of the hydrophobic hydration. 

The various elastic and viscoelastic phenomena we discuss in this chapter will be developed in stages. We begin with the simplest the case of a sample that displays a purely elastic response when deformed by simple elongation. On the basis of Hooke s law, we expect that the force of deformation—the stress—and the distortion that results-the strain-will be directly proportional, at least for small deformations. In addition, the energy spent to produce the deformation is recoverable The material snaps back when the force is released. We are interested in the molecular origin of this property for polymeric materials but, before we can get to that, we need to define the variables more quantitatively. 

Now let us examine the molecular origin of Molecular polarity may be the result of either a permanent dipole moment p or an induced dipole moment ind here the latter arises from the distortion of the charge distribution in a molecule due to an electric field. We saw in Chap. 8 that each of these types of polarity are sources of intermolecular attraction. In the present discussion we assume that no permanent dipoles are present and note that the induced dipole moment is proportional to the net field strength at the molecule ... 

This chapter has given an overview of the structure and dynamics of lipid and water molecules in membrane systems, viewed with atomic resolution by molecular dynamics simulations of fully hydrated phospholipid bilayers. The calculations have permitted a detailed picture of the solvation of the lipid polar groups to be developed, and this picture has been used to elucidate the molecular origins of the dipole potential. The solvation structure has been discussed in terms of a somewhat arbitrary, but useful, definition of bound and bulk water molecules. 

An essential requirement for device applications is that the orientation of the molecules at the cell boundaries be controllable. At present there are many techniques used to control liquid crystal alignment which involve either chemical or mechanical means. However the relative importance of these two is uncertain and the molecular origin of liquid crystal anchoring remains unclear. Phenomenological models invoke a surface anchoring energy which depends on the so-called surface director , fij. In the case where there exists cylindrical symmetry about a preferred direction, hp the potential is usually expressed in the form of Rapini and Popoular [48]... 

Kopka, M.L, C. Yoon, D. Goodsell, P. Pjura, and R.E. Dickerson. The molecular origin of DNA drug specificity in ne-tropsin and distamycin. Proc. Natl. Acad. Sci. USA 1985, 82, 1376-1380. 

Note that both acetogenins and styryl-lactones are cytotoxic for mammalian cells, as the result of distinct biochemical pathways, which, however, have their molecular origin near or in the mitochondrial membrane and/or the mitochondrial respiratory system (61,62). Acetogenins were first characterized as the active principles responsible for... 

Molecular Origins of the Resonance Raman Twisting Modes of... 

MOLECULAR ORIGINS OF THE RESONANCE RAMAN TWISTING MODES OF ANTENNA XANTHOPHYLLS... 

Needless to say, an analysis which will finally allow one to nail down all rates, activation parameters, and equilibrium constants requires a large amount of precise and reliable kinetic data from appropriate experiments, including the determination of isotope effects and the like, as well as a rather sophisticated treatment and solution of the complete kinetic scheme. Then a comparison is necessary between various organosilanes with different types of C-H and C-Si bonds as well as the comparison between the dtbpm and the dcpm ligand systems, not to speak of model calculations in order to understand the molecular origin of the kinetic and thermodynamic numbers. We are presently in the process of solving these problems. 

Cronin J (1998) Clues from the origin of the Solar System meteorites. In Brack A (Ed.) The Molecular Origins of Life. Cambridge University Press, p 119-146 Cronin J, Pizzarello S (2000) Orig Life Evol Biosphere 30 209 Dalgamo A (1991) Nature 353 502 Delsemme (1984) Orig Life Evol Biosphere 14 51... 

Maurette M (1998) Micrometeorites on the early earth. In Brack A (Ed.) The Molecular Origins of Life. Cambridge University Press p 147... 

Holm NG, Andersson EM (1998) Hydrothermal Systems. In Brack A (Ed.) The Molecular Origins of Life. Cambridge University Press, p 86 Hoffmann U (1968) Angew Chem 80 736, Int Ed 7 681 Horita J, Bemdt ME (1999) Science 285 1055 Huber C, Wachtershauser G (1997) Science 276 245 Huber C, Wachtershauser G (1998) Science 281 670 Huber C, Wachtershauser G (2006) Science 314 630 Huber C, Eisenreich W, Hecht S, Wachtershauser G (2003) Science 301 938 Kaschke M, Russell MJ, Coll WJ (1994) Orig Life Evol Biosphere 24 43 Keefe AD, Miller SL, Me Donald G, Bada J (1995) Proc Natl Acad Sd USA 92 11904 Keefe AD, Newton GL, Miller SL (1995) Nature 373 683... 

Schopf JW (1998) Tracing the Roots of the Universal Tree of Life. In Brack A (Ed) The Molecular Origins of Life. Cambridge University Press, pp 336-362 Schopf JW (1999) Cradle of Life. Princeton University Press, Princeton Schopf JW, Kudryavtsev AB, Agresti DG, Wdowiak TJ, Czaja AD (2002a) Nature 416 73... 

Attempts to interpret the corresponding build-up curves according to the Lipari-Szabo approach lead to inconsistent results (for instance, order parameters greater than unity). This indicates that these remote correlations are probably not of infra-molecular origin but would rather arise from znfer-molecular dipolar interactions which could become significant when some contacts exist between neighbouring aliphatic chains. This... 

Dynamic Mechanical Properties. The dynamic mechanical properties of branched and linear polyethylene have been studied in detail and molecular interpretation for various transitions have already been given, although not necessarily agreed upon in terras of molecular origin.(52-56) Transitions for conventional LDPE (prepared by free radical methods) when measured at low frequencies, are located around +70°C, -20°C and -120°C and are assigned to o, 5, and y transitions respectively. (53) Recently Tanaka et al. have reported the dynamic mechanical properties for a sample of HB which was also prepared by anionic polymerization, but contrary to our system the hydrogenation of the polybutadiene was carried out by a coordinate type catalyst.(12) The transitions reported for such a polymer at 35 Hz are very similar to those of LDPE.(12)... 

Characterization of Limited Chain Extensibility. The molecular origin of the unusual properties of bimodal PDMS networks having been elucidated at least to some extent, it is now possible to utilize these materials in a variety of applications. The first involves the interpretation of limited chain extensibility in terms of the configurational characteristics of the PDMS chains making up the network structure (5,12,13). 

In addition to its practical importance, Tx has important theoretical implications for the understanding of the molecular origin of polymer mechanical behavior (3,4,6,35,42-45) and plays a central role in establishing the framework, mentioned above, which relates the properties of different polymers to each other (3 46.47). 

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