The simple model and method proposed here provide a satisfactory description of the correlations between atomic fluctuations. Furthermore, this is achieved within computation times at least one order of magnitude shorter than commonly used molecular approaches.

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A single-parameter harmonic Hamiltonian based on local packing density and contact topology is proposed for studying residue fluctuations in native proteins. The internal energy obeys an equipartition law, and free energy changes result from entropy fluctuations only. Frequency -wave-number maps show communication between residues involved in slow and fast modes. Fast modes are strongly localized, resulting from the geometric irregularity of the structure. Comparison with experiments shows that slow and fast modes are associated, respectively, with function and stability. Specifically, domain motions and folding cores of HIV-1 protease are accurately identified. [S0031-9007(98)

Rubber elasticity is an important sub-field of polymer science. This book is in many ways a sequel to the authors' previous, more introductory book, Rubberlike Elasticity: A Molecular Primer (Wiley-Interscience, 1988), and will in some respects replace the now classic book by L.R.G. Treloar, The Physics of Rubber Elasticity (Oxford, 1975). The present book has much in common with its predecessor, in particular its strong emphasis on molecular concepts and theories. Similarly, only equilibrium properties are covered in any detail. Though this book treats much of the same subject matter, it is a more comprehensive, more up-to-date, and somewhat more sophisticated treatment.

The theory of elasticity of polymer networks is reformulated with greater generality and improved concision. In particular, the domains of constraint that, due to entanglements and steric requirements of real polymer chains, impede fluctuations of the junctions are introduced in a way that admits of a more rapid attenuation of these constraints than affine transformation of them with strain would allow. Illustrative calculations are presented on the contribution of the constraints to the stress in uniaxial deformation as a function of the extension ratio and the degree of dilation. The calculated reduced force is decidedly nonlinear with the reciprocal of the extension ratio.

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Catalytic palladium (Pd) nanoparticles on electrospun copolymers of acrylonitrile and acrylic acid (PAN-AA) mats were produced via reduction of PdCl2 with hydrazine. Fiber mats were electrospun from homogeneous solutions of PAN-AA and PdCl2 in dimethylformamide (DMF). Pd cations were reduced to Pd metals when fiber mats were treated in an aqueous hydrazine solution at room temperature. Pd atoms nucleate and form small crystallites whose sizes were estimated from the peak broadening of X-ray diffraction peaks. Two to four crystallites adhere together and form agglomerates. Agglomerate sizes and fiber diameters were determined by scanning and transmission electron microscopy. Spherical Pd nanoparticles were dispersed homogeneously on the electrospun nanofibers. The effects of copolymer composition and amount of PdCl 2 on particle size were investigated. Pd particle size mainly depends on the amount of acrylic acid functional groups and PdCl2 concentration in the spinning solution. Increasing acrylic acid concentration on polymer chains leads to larger Pd nanoparticles. In addition, Pd particle size becomes larger with increasing PdCl 2 concentration in the spinning solution. Hence, it is possible to tune the number density and the size of metal nanoparticles. The catalytic activity of the Pd nanoparticles in electrospun mats was determined by selective hydrogenation of dehydrolinalool (3,7-dimethyloct-6-ene-1-yne-3-ol, DHL) in toluene at 90°C. Electrospun fibers with Pd particles have 4.5 times higher catalytic activity than the current Pd/Al 2O3 catalyst.