19,243 research outputs found
Fluvial dynamics and watermills location in Basilicata (Southern Italy)
Watermills (grain mills, waulk mills, olive mills, sawmills and
threshing machines) operated in the Basilicata Region from the Roman
Period until the early decades of the twentieth century, representing an
important feature of waterways that is today almost totally forgotten. Using
documentary sources, ancient maps and field survey it is possible to
catalogue and identify the location of these ancient hydraulic structures.
Watermills were usually placed far enough away from the river to avoid
inundation during floods, and near natural knickpoints or artificial steps
in the river long profile that were created by mill engineers. Mill construction
often had significant impacts on a rivers morphology, because
it was necessary to divert the river discharge towards the mill wheel, to
drive the grain-grinding mechanism. Watermill typological variations
have been examined in relation to variations in river pattern to assess
the ways in which the hydrographic and hydrological settings of the Basilicata
Region have affected mill siting and operation. Most Basilicata
watermills were built with a horizontal water-wheel and a tower. The
characteristics of the tower and the associated hydraulic structures varied
according to the environmental setting. Finally, mill positions define
also the locations on the river system that have already been used
to exploit hydraulic power and thus could be useful for future use in the
micro-hydroelectric secto
Firewood, food and niche construction : the potential role of Mesolithic hunter-gatherers in actively structuring Scotland's woodlands.
Over the past few decades the potential role of Mesolithic hunter–gatherers in actively constructing their own niches, through the management of wild plants, has frequently been discussed. It is probable that Mesolithic hunter–gatherers systematically exploited specific woodland resources for food and fuel and influenced the ‘natural’ abundance or distribution of particular species within Mesolithic environments. Though there has been considerable discussion of the pollen evidence for potential small-scale human-woodland manipulation in Mesolithic Scotland, the archaeobotanical evidence for anthropogenic firewood and food selection has not been discussed in this context. This paper assesses the evidence for the active role of Mesolithic hunter–gatherer communities in systematically exploiting and managing woodlands for food and fuel in Scotland. While taphonomic factors may have impacted on the frequency of specific species in archaeobotanical assemblages, it is suggested that hunter–gatherers in Mesolithic Scotland were systematically using woodland plants, and in particular hazel and oak, for food and fuel. It is argued that the pollen evidence for woodland management is equivocal, but hints at the role of hunter–gatherers in shaping the structure of their environments, through the maintenance or creation of woodland clearings for settlement or as part of vegetation management strategies. It is proposed that Mesolithic hunter–gatherers may have actively contributed to niche construction and that the systematic use of hazel and oak as a fuel may reflect the deliberate pruning of hazel trees to increase nut-yields and the inadvertent – or perhaps deliberate – coppicing of hazel and oak during greenwood collection
Electronic polarons in an extended Falicov-Kimball model
We examine the one-dimensional spinless Falicov-Kimball model extended by a
hybridization potential between the localized and itinerant electron states.
Below half-filling we find a crossover from a mixed-valence metal to an
integer-valence phase separated state with increasing on-site Coulomb
repulsion. This crossover regime is characterized by local competition between
the strong- and weak-coupling behaviour, manifested by the formation of an
electronic polaron liquid. We identify this intermediate-coupling regime as a
charge-analogy of the Griffiths phase; a phase diagram is presented and
discussed in detail.Comment: RevTex, 10 pages, 1 figure; revised discussio
Valley polarization and susceptibility of composite fermions around nu=3/2
We report magnetotransport measurements of fractional quantum Hall states in
an AlAs quantum well around Landau level filling factor nu = 3/2, demonstrating
that the quasiparticles are composite Fermions (CFs) with a valley degree of
freedom. By monitoring the valley level crossings for these states as a
function of applied symmetry-breaking strain, we determine the CF valley
susceptibility and polarization. The data can be explained well by a simple
Landau level fan diagram for CFs, and are in nearly quantitative agreement with
the results reported for CF spin polarization.Comment: to appear in Phys. Rev. Let
Observation of Quantum Hall Valley Skyrmions
We report measurements of the interaction-induced quantum Hall effect in a
spin-polarized AlAs two-dimensional electron system where the electrons occupy
two in-plane conduction band valleys. Via the application of in-plane strain,
we tune the energies of these valleys and measure the energy gap of the quantum
Hall state at filling factor = 1. The gap has a finite value even at zero
strain and, with strain, rises much faster than expected from a single-particle
picture, suggesting that the lowest energy charged excitations at are
"valley Skyrmions".Comment: 4 pages, 3 figure
Systematic Inclusion of High-Order Multi-Spin Correlations for the Spin- Models
We apply the microscopic coupled-cluster method (CCM) to the spin-
models on both the one-dimensional chain and the two-dimensional square
lattice. Based on a systematic approximation scheme of the CCM developed by us
previously, we carry out high-order {\it ab initio} calculations using
computer-algebraic techniques. The ground-state properties of the models are
obtained with high accuracy as functions of the anisotropy parameter.
Furthermore, our CCM analysis enables us to study their quantum critical
behavior in a systematic and unbiased manner.Comment: (to appear in PRL). 4 pages, ReVTeX, two figures available upon
request. UMIST Preprint MA-000-000
Demixing can occur in binary hard-sphere mixtures with negative non-additivity
A binary fluid mixture of non-additive hard spheres characterized by a size
ratio and a non-additivity parameter
is considered in infinitely many
dimensions. From the equation of state in the second virial approximation
(which is exact in the limit ) a demixing transition with a
critical consolute point at a packing fraction scaling as
is found, even for slightly negative non-additivity, if
. Arguments concerning the stability of the
demixing with respect to freezing are provided.Comment: 4 pages, 2 figures; title changed; final paragraph added; to be
published in PRE as a Rapid Communicatio
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