How Dilute are Dilute Solutions in Extensional Flows?

Submitted to J. Rheol.We investigate the concentration-dependence of the characteristic relaxation time of dilute polymer solutions in transient uniaxial elongational flow. A series of monodisperse polystyrene solutions of five different molecular weights (1.8×10^6 ≤ M ≤ 8.3×10^6 g/mol) with concentrations spanning five orders of magnitude were dissolved in two solvents of differing solvent quality (diethyl phthalate and oligomeric styrene). Optical measurements of the rate of filament thinning and the time to break-up in each fluid are used to determine the characteristic relaxation time. A lower sensitivity limit for the measurements was determined experimentally and confirmed by comparison to numerical calculations. Above this sensitivity limit we show that the effective relaxation time of moderately dilute solutions (0.01 ≤ c/c* ≤ 1) in transient extensional flow rises substantially above the fitted value of the relaxation time extracted from small amplitude oscillatory shear flow and above the Zimm relaxation time computed from kinetic theory and intrinsic viscosity measurements. This effective relaxation time exhibits a power-law scaling with the reduced concentration (c/c*) and the magnitude of the exponent varies with the thermodynamic quality of the solvent. This scaling appears to be roughly consistent to that predicted when the dynamics of the partially elongated and overlapping polymer chains are described within the framework of blob theories for semi-dilute solutions.NASA Microgravity Fluid Dynamic

Town and Country in the Southern Carmel: Report on the Landscape Archaeology Project at Dor (LAPD)

This report deals with the results of a project of landscape archaeology in the hinterland of Tel Dor (Tanturah) in the northern coastal plain of Israel. An introduction to previous research made in the region is followed by a description of the survey methods employed during the project and the characteristics of the five geographical subunits investigated (Zones I–V) The patterning of settlement remains and the chronology of landscape features forms the main part of the article, with information on changes occurring in the Dor landscape from the Chalcolithic through to Ottoman periods. Brief mention is made regarding groups of features examined, such as wells, cisterns, aqueducts, fields, oil presses, wine presses, columbaria, quarries and burial caves. Reports are given on the pottery from the Chalcolithic and Early Bronze Age I, the Middle Bronze Age IIA, and the Roman and Byzantine periods. Appendices also deal with Chalcolithic basalt vessels, Hellenistic stamped amphora handles, Ottoman copper lids and a nineteenth-century Arabic inscription from Tanturah