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Showing 1 - 11 of 11 matches in All Departments
Viscoelasticandtransportpropertiesofpolymersintheliquid(solution,melt)or liquid-like (rubber) state determine their processing and application to a large extent and are of basic physical interest [1-3]. An understanding of these dynamic properties at a molecular level, therefore, is of great importance. However,thisunderstandingiscomplicatedbythefactsthatdi?erentmotional processes may occur on di?erent length scales and that the dynamics are governed by universal chain properties as well as by the special chemical structure of the monomer units [4,5]. The earliest and simplest approach in this direction starts from Langevin equations with solutions comprising a spectrum of relaxation modes [1-4]. Special features are the incorporation of entropic forces (Rouse model, [6]) which relax uctuations of reduced entropy, and of hydrodynamic interactions (Zimm model, [7]) which couple segmental motions via long-range back ow elds in polymer solutions, and the inclusion of topological constraints or entanglements (reptation or tube model, [8-10]) which are mutually imposed within a dense ensemble of chains. Another approach, neglecting the details of the chemical structure and concentratingontheuniversalelementsofchainrelaxation,isbasedondynamic scalingconsiderations[4,11].Inparticularinpolymersolutions,thisapproach o?ers an elegant tool to specify the general trends of polymer dynamics, although it su?ers from the lack of a molecular interpretation. A real test of these theoretical approaches requires microscopic methods, which simultaneously give direct access to the space and time evolution of the segmental di?usion. Here, quasi-elastic scattering methods play a crucial role sincetheyallowthemeasurementofthecorrespondingcorrelationfunctions.In particular,thehigh-resolutionneutronspinecho(NSE)spectroscopy[12-15]is very suitable for such investigations since this method covers an appropriate range in time (0.005)t/ns)40) and space (r/nm [15). Furthermore, the possibilityoflabellingbyhydrogen-deuteriumexchangeallowstheobservation of single-chain behavior even in the melt.
With contributions by Clarke, G.; Lang, R.E.; McKinley, M.J.; Merrick, L.P.; Rascher, W.; Richter, D.; Sofroniew, M.; Unger, T.; Weindl, A.
Across the world, soils are managed with an intensity and at a geographic scale never before attempted, yet we know remarkably little about how and why managed soils change through time. Understanding Soil Change explores a legacy of soil change in south-eastern North America, a region of global ecologic, agricultural and forestry significance: from the acidic soils of primary hardwood forests that covered the region until about 1800, through the marked transformations affected by long-cultivated cotton, to contemporary soils of rapidly growing and intensively managed pine forests. These well-documented records significantly enrich the science of ecology and pedology, and provide valuable lessons for land management throughout the world. The book calls for the establishment of a global network of soil-ecosystem studies, like the invaluable Calhoun study on which the book is based, to provide further information on sustainable land management, vital as human demands on soil continue to increase.
A. Radulescu, L.J. Fetters, D. Richter: Polymer Driven Wax Crystal Control Using Partially Crystalline Polymeric Materials.- F.R. Costa, M. Saphiannikova, U. Wagenknecht, G. Heinrich: Layered Double Hydroxide Based Polymer Nanocomposites.- S. Aoshima, S. Kanaoka: Synthesis of Stimuli-Responsive Polymers by Living Polymerization: Poly(N-Isopropylacrylamide) and Poly(Vinyl Ether)s.-
Across the world, soils are managed with an intensity and at a geographic scale never before attempted, yet we know remarkably little about how and why managed soils change through time. Understanding Soil Change explores a legacy of soil change in southeastern North America, from the acidic soils of primary hardwood forests that covered the region until about 1800, through the marked transformations affected by long-cultivated cotton, to contemporary soils of rapidly growing and intensively managed pine forests. These well documented records significantly enrich the science of ecology and pedology, and provide valuable lessons for land management throughout the world. The book calls for the establishment of a global network of soil-ecosystem studies, like the invaluable Calhoun study on which the book is based, to provide further information on sustainable land management, vital as human demands on soil continue to increase.
mRNA Formation and Function presents a compendium of techniques
geared exclusively toward the understanding of RNA metabolism. It
will be particularly useful because a number of different organisms
and systems are employed.
The 1990's are an important decade, because the gynaecologist in the 1990's has to develop a new profile. A gynaecology without psychosomatics cannot offer an adequate answer to the modern needs of women. European Symposium on Psychosomatic Obstetrics and Gynaecology - in the framework of a young, dynamic tradition - was planned by European researchers on Psychosomatic Obstetrics and Gynaecology (Leuven, Belgium; September, 1997). cancer (peri)menopausal and elderly woman needs and demands Therapeutical strategie
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