448 research outputs found
A methodological approach to the study of archaeological cereal meals: a case study at Çatalhöyük East (Turkey)
This paper presents an integrated methodology for the analysis of archaeological remains of cereal meals, based on scanning electronic microscopic analyses of microstructures of charred food fragments from Neolithic Çatalhöyük (Turkey). The remains of cereal foods as ‘bread-like’ or ‘porridge-like’ small charred lumps of various amalgamated plant materials are frequently recovered from Neolithic and later archaeological sites in southwest Asia and Europe. Cereal food remains have recently attracted interest because the identification of their plant contents, the forms of food that they represent and the methods used in their creation can provide unique information about ancient culinary traditions and routine food processing, preparation and cooking techniques. Here, we focus on three methodological aspects: (1) the analysis of their composition; (2) the analysis of their microstructure to determine preparation and cooking processes; (3) the comparison with experimental reference materials. Preliminary results are presented on the botanical composition and cooking processes represented by the charred cereal preparations found at Neolithic Çatalhöyük (Turkey), for example cereals processed into bread, dough and/or porridge
Investigating early agriculture, plant use and culinary practices at Neolithic Jarmo (Iraqi Kurdistan)
The site of Jarmo in Iraqi Kurdistan has yielded key archaeological evidence which supports its interpretation as a large PPNB village. As such, it is the perfect candidate for the study of early agriculture, plant uses, food preparation and cooking practices. In order to explore these, new excavations and intensive sampling and flotation for the recovery of archaeobotanical remains were carried out in 2012 and 2014. This study presents the results from the analysis of the newly recovered archaeobotanical assemblage from Jarmo which has provided invaluable information about early crop agriculture and plant use. Furthermore, the in-depth study of recovered remains of archaeological food by high-resolution microscopy has shed light on culinary traditions and dietary choices during the Neolithic in the Central Zagros Area
Nonlinear localized modes in two-dimensional electrical lattices
We report the observation of spontaneous localization of energy in two
spatial dimensions in the context of nonlinear electrical lattices. Both
stationary and traveling self-localized modes were generated experimentally and
theoretically in a family of two-dimensional square, as well as hon- eycomb
lattices composed of 6x6 elements. Specifically, we find regions in driver
voltage and frequency where stationary discrete breathers, also known as
intrinsic localized modes (ILM), exist and are stable due to the interplay of
damping and spatially homogeneous driving. By introduc- ing additional
capacitors into the unit cell, these lattices can controllably induce traveling
discrete breathers. When more than one such ILMs are experimentally generated
in the lattice, the interplay of nonlinearity, discreteness and wave
interactions generate a complex dynamics wherein the ILMs attempt to maintain a
minimum distance between one another. Numerical simulations show good agreement
with experimental results, and confirm that these phenomena qualitatively carry
over to larger lattice sizes.Comment: 5 pages, 6 figure
Vortex Structures Formed by the Interference of Sliced Condensates
We study the formation of vortices, vortex necklaces and vortex ring
structures as a result of the interference of higher-dimensional Bose-Einstein
condensates (BECs). This study is motivated by earlier theoretical results
pertaining to the formation of dark solitons by interfering quasi
one-dimensional BECs, as well as recent experiments demonstrating the formation
of vortices by interfering higher-dimensional BECs. Here, we demonstrate the
genericity of the relevant scenario, but also highlight a number of additional
possibilities emerging in higher-dimensional settings. A relevant example is,
e.g., the formation of a "cage" of vortex rings surrounding the
three-dimensional bulk of the condensed atoms. The effects of the relative
phases of the different BEC fragments and the role of damping due to coupling
with the thermal cloud are also discussed. Our predictions should be
immediately tractable in currently existing experimental BEC setups.Comment: 8 pages, 6 figures (low res). To appear in Phys. Rev. A. Full
resolution preprint available at:
http://www-rohan.sdsu.edu/~rcarrete/publications
Guiding chemical pulses through geometry: Y-junctions
We study computationally and experimentally the propagation of chemical
pulses in complex geometries.The reaction of interest, CO oxidation, takes
place on single crystal Pt(110) surfaces that are microlithographically
patterned; they are also addressable through a focused laser beam, manipulated
through galvanometer mirrors, capable of locally altering the crystal
temperature and thus affecting pulse propagation. We focus on sudden changes in
the domain shape (corners in a Y-junction geometry) that can affect the pulse
dynamics; we also show how brief, localized temperature perturbations can be
used to control reactive pulse propagation.The computational results are
corroborated through experimental studies in which the pulses are visualized
using Reflection Anisotropy Microscopy.Comment: submitted to Phys. Rev.
Discrete breathers in a nonlinear electric line: Modeling, Computation and Experiment
We study experimentally and numerically the existence and stability
properties of discrete breathers in a periodic nonlinear electric line. The
electric line is composed of single cell nodes, containing a varactor diode and
an inductor, coupled together in a periodic ring configuration through
inductors and driven uniformly by a harmonic external voltage source. A simple
model for each cell is proposed by using a nonlinear form for the varactor
characteristics through the current and capacitance dependence on the voltage.
For an electrical line composed of 32 elements, we find the regions, in driver
voltage and frequency, where -peaked breather solutions exist and
characterize their stability. The results are compared to experimental
measurements with good quantitative agreement. We also examine the spontaneous
formation of -peaked breathers through modulational instability of the
homogeneous steady state. The competition between different discrete breathers
seeded by the modulational instability eventually leads to stationary
-peaked solutions whose precise locations is seen to sensitively depend on
the initial conditions
Polarized States and Domain Walls in Spinor Bose-Einstein Condensates
We study spin-polarized states and their stability in anti-ferromagnetic
states of spinor (F=1) quasi-one-dimensional Bose-Einstein condensates. Using
analytical approximations and numerical methods, we find various types of
polarized states, including: patterns of the Thomas-Fermi type; structures with
a pulse-shape in one component inducing a hole in the other components; states
with holes in all three components; and domain walls. A Bogoliubov-de Gennes
analysis reveals that families of these states contain intervals of a weak
oscillatory instability, except for the domain walls, which are always stable.
The development of the instabilities is examined by means of direct numerical
simulations.Comment: 7 pages, 9 figures, submitted to Phys. Rev.
A quasi-diagonal approach to the estimation of Lyapunov spectra for spatio-temporal systems from multivariate time series
We describe methods of estimating the entire Lyapunov spectrum of a spatially
extended system from multivariate time-series observations. Provided that the
coupling in the system is short range, the Jacobian has a banded structure and
can be estimated using spatially localised reconstructions in low embedding
dimensions. This circumvents the ``curse of dimensionality'' that prevents the
accurate reconstruction of high-dimensional dynamics from observed time series.
The technique is illustrated using coupled map lattices as prototype models for
spatio-temporal chaos and is found to work even when the coupling is not
strictly local but only exponentially decaying.Comment: 13 pages, LaTeX (RevTeX), 13 Postscript figs, to be submitted to
Phys.Rev.
Impact of anisotropy on vortex clusters and their dynamics
We investigate the effects of anisotropy on the stability and dynamics of
vortex cluster states which arise in Bose-Einstein condensates. Sufficiently
strong anisotropies are shown to stabilize states with arbitrary numbers of
vortices that are highly unstable in the isotropic limit. Conversely,
anisotropy can be used to destabilize states which are stable in the isotropic
limit. Near the linear limit, we identify the bifurcations of vortex states
including their emergence from linear eigenstates, while in the strongly
nonlinear limit, a particle-like description of the dynamics of the vortices in
the anisotropic trap is developed. Both are in very good agreement with
numerical results. Collective modes of stabilized many vortex cluster states
are demonstrated.Comment: 6 pages, 6 figure
Symmetry Breaking in Linearly Coupled Dynamical Lattices
We examine one- and two-dimensional (1D and 2D) models of linearly coupled
lattices of the discrete-nonlinear-Schr{\"{o}}dinger type. Analyzing ground
states of the systems with equal powers in the two components, we find a
symmetry-breaking phenomenon beyond a critical value of the squared -norm.
Asymmetric states, with unequal powers in their components, emerge through a
subcritical pitchfork bifurcation, which, for very weakly coupled lattices,
changes into a supercritical one. We identify the stability of various solution
branches. Dynamical manifestations of the symmetry breaking are studied by
simulating the evolution of the unstable branches. The results present the
first example of spontaneous symmetry breaking in 2D lattice solitons. This
feature has no counterpart in the continuum limit, because of the collapse
instability in the latter case.Comment: 9 pages, 9 figures, submitted to Phys. Rev. E, Apr, 200
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