260 research outputs found
The context and nature of the evidence for metalworking from mid 4th Millennium Yali (Nissyros)
Two crucibles with copper adhering (and one lead rivet) have been found on Yali (Nissyros) dating to the Final Neolithic, mid-4th millennium BCE. This is important and rare evidence for the earliest phase of Aegean metallurgy, now recognized as emerging in circumstances of high mobility and variable technological preference and practice. The finds are presented here through a study of their context, typology and chemical and lead isotope analysis. The results show that the crucibles come from the main settlement on the island; they were locally made, using a clay recipe deliberately tailored to the needs of metalworking. The copper was pure, with low levels of naturally occurring arsenic. The copper and lead came from the same source which, on current evidence, appears to be to Kythnos. The community on Yali was in contact with a broader Aegean where multiple metallurgical technologies are known. The presence of tin ore, or its product, might be indicated. Though small in scale, there are some parallels with the nature and technology of metallurgical activities in the succeeding Early Bronze Age
Dielectric spectra analysis: reliable parameter estimation using interval analysis
Dielectric spectroscopy is an extremely versatile method for characterizing the molecular dynamics over a large range of time scales. Unfortunately, the extraction of model parameters by data fitting is still a crucial problem which is now solved by our program S.A.D.E. S.A.D.E. is based on the algorithm S.I.V.I.A. which was proposed and implemented by Jaulin in order to solve constraint satisfaction problems. The problem of dielectric data analysis is reduced to a problem of choosing the appropriate physical model. In this article, Debye relaxations were used and validated to fit the relaxations of a DGEBA prepolymer and the polarization of the spectrometer electrodes. The conductivity was evaluated too
A large class of non constant mean curvature solutions of the Einstein constraint equations on an asymptotically hyperbolic manifold
We construct solutions of the constraint equation with non constant mean
curvature on an asymptotically hyperbolic manifold by the conformal method. Our
approach consists in decreasing a certain exponent appearing in the equations,
constructing solutions of these sub-critical equations and then in letting the
exponent tend to its true value. We prove that the solutions of the
sub-critical equations remain bounded which yields solutions of the constraint
equation unless a certain limit equation admits a non-trivial solution.
Finally, we give conditions which ensure that the limit equation admits no
non-trivial solution.Comment: remark on the equivalence between the existence of a solution to the
Lichnerowicz equation and to the prescribed scalar curvature equation added,
reference [BPB09] added, to appear in Commun. Math. Phy
Life path analysis: scaling indicates priming effects of social and habitat factors on dispersal distances
1. Movements of many animals along a life-path can be separated into repetitive ones within home ranges and transitions between home ranges. We sought relationships of social and environmental factors with initiation and distance of transition movements in 114 buzzards Buteo buteo that were marked as nestlings with long-life radio tags.
2. Ex-natal dispersal movements of 51 buzzards in autumn were longer than for 30 later in their first year and than 35 extra-natal movements between home ranges after leaving nest areas. In the second and third springs, distances moved from winter focal points by birds that paired were the same or less than for unpaired birds. No post-nuptial movement exceeded 2 km.
3. Initiation of early ex-natal dispersal was enhanced by presence of many sibs, but also by lack of worm-rich loam soils. Distances travelled were greatest for birds from small broods and with relatively little short grass-feeding habitat near the nest. Later movements were generally enhanced by the absence of loam soils and short grassland, especially with abundance of other buzzards and probable poor feeding habitats (heathland, long grass).
4. Buzzards tended to persist in their first autumn where arable land was abundant, but subsequently showed a strong tendency to move from this habitat.
5. Factors that acted most strongly in ½-km buffers round nests, or round subsequent focal points, usually promoted movement compared with factors acting at a larger scale. Strong relationships between movement distances and environmental characteristics in ½-km buffers, especially during early ex-natal dispersal, suggested that buzzards became primed by these factors to travel far.
6. Movements were also farthest for buzzards that had already moved far from their natal nests, perhaps reflecting genetic predisposition, long-term priming or poor habitat beyond the study area
On the Behavior of the Effective QCD Coupling alpha_tau(s) at Low Scales
The hadronic decays of the tau lepton can be used to determine the effective
charge alpha_tau(m^2_tau') for a hypothetical tau-lepton with mass in the range
0 < m_tau' < m_tau. This definition provides a fundamental definition of the
QCD coupling at low mass scales. We study the behavior of alpha_tau at low mass
scales directly from first principles and without any renormalization-scheme
dependence by looking at the experimental data from the OPAL Collaboration. The
results are consistent with the freezing of the physical coupling at mass
scales s = m^2_tau' of order 1 GeV^2 with a magnitude alpha_tau ~ 0.9 +/- 0.1.Comment: 15 pages, 4 figures, submitted to Physical Review D, added
references, some text added, no results nor figures change
New data on the ichthyosaur Platypterygius hercynicus and its implications for the validity of the genus
The description of a nearly complete skull from the late Albian of northwestern France
reveals previously unknown anatomical features of Platypterygius hercynicus (Kuhn 1946),
and of European Cretaceous ichthyosaurs in general. These include a wide frontal forming the
anteromedial border of the supratemporal fenestra, a parietal excluded from the parietal
foramen, and the likely presence of a squamosal, inferred from a very large and deep facet on
the quadratojugal. The absence of a squamosal has been considered as an autapomorphy of
the genus Platypterygius for more than ten years and has been applied to all known species by
default, but the described specimen casts doubt on this putative autapomorphy. Actually, it is
shown that all characters that have been proposed previously as autapomorphic for the genus
Platypterygius are either not found in all the species currently referred to this genus, or are
also present in other Ophthalmosauridae. Consequently, the genus Platypterygius must be
completely revised.Peer reviewe
Еволюція рослинного світу в природному і культигенному середовищі
У ході засідань Міжнародної наукової конференції “Еволюція рослинного світу в природному і культигенному середовищі”, присвяченої 200-річчю від Дня народження Чарльза Дарвіна, обговорено актуальні питання еволюційної теорії, ботаніки, фізіології рослин, інтродукції, генетики й селекції, екології, збереження і примноження глобального та локального біорізноманіття, лісових культур і фітомеліорації та інших біологічних наук.В ходе заседаний Международной научной конференции “Эволюция растительного мира в естественной и культигенной среде”, посвященной 200-летию со дня рождения Чарльза Дарвина, обсуждены актуальные вопросы эволюционной теории, ботаники, физиологии растений, интродукции, генетики и селекции, экологии, сохранения и приумножения глобального и локального биоразнообразия, лесных культур и фитомелиорации и других биологических наук.During meetings of the International scientific conference “Evolution of the natural and cultivated plants” to devoted a 200-year from the day of birth of Charles Darwin topical problems of the evolutional theory are discussed, including botany, physiology of plants, introduction of plants, genetics and breeding of plants, ecology, preventing the loss of global and loca biodiversity, arboriculture, forest-growing and other biological sciences
Some ideas about quantitative convergence of collision models to their mean field limit
We consider a stochastic -particle model for the spatially homogeneous
Boltzmann evolution and prove its convergence to the associated Boltzmann
equation when . For any time we bound the distance between
the empirical measure of the particle system and the measure given by the
Boltzmann evolution in some homogeneous negative Sobolev space. The control we
get is Gaussian, i.e. we prove that the distance is bigger than
with a probability of type . The two main ingredients are first a
control of fluctuations due to the discrete nature of collisions, secondly a
Lipschitz continuity for the Boltzmann collision kernel. The latter condition,
in our present setting, is only satisfied for Maxwellian models. Numerical
computations tend to show that our results are useful in practice.Comment: 27 pages, references added and style improve
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