This paper employs data from selected sample survey areas in the northern Fertile Crescent to demonstrate how initial urbanization developed along several pathways. The first, during the Late Chalcolithic period, was within a dense pattern of rural settlement. There followed a profound shift in settlement pattern that resulted in the formation of large walled or ramparted sites ('citadel cities') associated with a more dynamic phase of urbanization exemplified by short cycles of growth and collapse. By the later third millennium BC, the distribution of larger centres had expanded to include the drier agropastoral zone of northern and central Syria, termed here the 'zone of uncertainty'. This configuration, in turn, formed the context for Middle Bronze Age settlement, and the pattern of political rivalries and alliances that typified the second millennium BC. Evidence is marshalled from archaeological surveys and landscape analyses to examine these multiple paths to urbanization from the perspectives of (a) staple production within major 123J World Prehist (2014) 27:43-109 DOI 10.1007/s10963-014-9072-2 agricultural lowlands; (b) the shift towards higher risk animal husbandry within climatically marginal regions; (c) changes in local and inter-regional networks (connectivity); and (d) ties and rights to the land. Textile production forms the core of the proposed model, which emphasizes how the demand for wool and associated pasture lands opened up new landscapes for agro-pastoral production and settlement. The resultant landscapes of settlement are then compared with the picture in the southern Levant where a more restricted zone of uncertainty may have limited the opportunities for agro-pastoral production.

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Monte Carlo simulations are used to study the effect of confinement on a crystal of point particles interacting with an inverse power law potential proportional, variantr;{-12} in d=2 dimensions. This system can describe colloidal particles at the air-water interface, a model system for experimental study of two-dimensional melting. It is shown that the state of the system (a strip of width D ) depends very sensitively on the precise boundary conditions at the two "walls" providing the confinement. If one uses a corrugated boundary commensurate with the order of the bulk triangular crystalline structure, both orientational order and positional order is enhanced, and such surface-induced order persists near the boundaries also at temperatures where the system in the bulk is in its fluid state. However, using smooth repulsive boundaries as walls providing the confinement, only the orientational order is enhanced, but positional (quasi-)long range order is destroyed: The mean-square displacement of two particles n lattice parameters apart in the y direction along the walls then crosses over from the logarithmic increase (characteristic for d=2 ) to a linear increase with n (characteristic for d=1 ). The strip then exhibits a vanishing shear modulus. These results are interpreted in terms of a phenomenological harmonic theory. Also the effect of incommensurability of the strip width D with the triangular lattice structure is discussed, and a comparison with surface effects on phase transitions in simple Ising and XY models is made.

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We investigate the nature of the ordered phase for a model of colloidal particles confined within a quasi-one-dimensional (Q1D) strip between two parallel boundaries, or walls, separated a distance D in two dimensions (2D). Using Monte Carlo simulations we find that at densities typical of the bulk 2D triangular solid the order in the D1D strip is determined by the nature of the boundaries. While the order is enhanced for a suitably corrugated boundary potential, for a uniformly repulsive smooth boundary potential ordering normal to the walls is enhanced ("layering"), but destroyed parallel to the wall.

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The variation in the glass transition temperature of thin polymeric films represents a phenomenon yet to be fully explained. To date, it is widely agreed that it is linked to the interfaces that the film forms with the air and the supporting substrate. Herein, we address one of the main issues regarding the viscoelastic behavior of the region near the free interface of thick polystyrene films where a reduction in the glass transition temperature is expected to occur. We have measured, as a function of the temperature, the elastic and viscous responses of polystyrene films with molecular weights above and below the critical value for the occurrence of molecular entanglement. The experiments have been carried out by means of scanning probe microscopy in a configuration combining the acquisition of force versus distance and indentation versus time curves. We show that the viscoelastic behavior of polystyrene films with thickness down to 30 nm can be successfully evaluated in the time scale from tenths to tens of seconds. In particular, we observe that the viscoelastic behavior of thick film surfaces has a similar dependence from the temperature as the viscoelastic behavior of the bulk, independently if the molecular weight is above or below the critical value. We estimate that the region at the free interface with a reduced glass transition temperature, if present, has a thickness below 3 nm.

Ordering phenomena in colloidal dispersions exposed to external one-dimensional, periodic fields or under confinement are studied systematically by Monte Carlo computer simulations. Such systems are useful models for the study of monolayers on a substrate. We find that the interaction with a substrate potential completely changes the miscibility of a binary, hard disc mixture at low external field amplitudes. The underlying ordering mechanisms leading to this laser-induced de-mixing differ, depending on which components interact with the substrate potential. Generic effects of confinement on crystalline order in two dimensions are studied in a model system of point particles interacting via a potential ∝ r −12. The state of the system (a strip of width D) depends very sensitively on the precise boundary conditions at the two confining walls. Commensurate, corrugated boundary conditions enhance both orientational order and positional order. In contrast, smooth repulsive boundaries enhance only the orientational order and destroy positional (quasi-)long range order. As external fields have a strong impact on the elastic behaviour of colloidal crystals there is a need to analyse the elastic response in such systems for the field-free case first. To this aim we study the strain-strain correlation functions in a two-dimensional crystal formed by super-paramagnetic colloids, as monitored by standard video microscopy.