48 research outputs found
High-precision radiocarbon dating of the construction phase of Oakbank Crannog, Loch Tay, Perthshire
Many of the Loch Tay crannogs were built in the Early Iron Age and so calibration of the radiocarbon ages produces
very broad calendar age ranges due to the well-documented Hallstatt plateau in the calibration curve. However, the
large oak timbers that were used in the construction of some of the crannogs potentially provide a means of improving the precision of the dating through subdividing them into decadal or subdecadal increments, dating them to high precision and wiggle-matching the resulting data to the master <sup>14</sup>C calibration curve. We obtained a sample from 1 oak timber from Oakbank Crannog comprising 70 rings (Sample OB06 WMS 1, T103) including sapwood that was complete to the bark edge. The timber is situated on the northeast edge of the main living area of the crannog and as a large and strong oak pile would have been a useful support in more than 1 phase of occupation and may be related to the earliest construction phase of the site. This was sectioned into 5-yr increments and dated to a precision of approximately ±8–16 <sup>14</sup>C yr (1 σ). The wiggle-match predicts that the last ring dated was formed around 500 BC (maximum range of 520–465 BC) and should be taken as indicative of the likely time of construction of Oakbank Crannog. This is a considerable improvement on the estimates based on single <sup>14</sup>C ages made on oak samples, which typically encompassed the period from around 800–400 BC
D-branes and the Standard Model
We perform a systematic study of the Standard Model embedding in a D-brane
configuration of type I string theory at the TeV scale. We end up with an
attractive model and we study several phenomenological questions, such as gauge
coupling unification, proton stability, fermion masses and neutrino
oscillations. At the string scale, the gauge group is U(3)_color x U(2)_weak x
U(1)_1 x U(1)_bulk. The corresponding gauge bosons are localized on three
collections of branes; two of them describe the strong and weak interactions,
while the last abelian factor lives on a brane which is extended in two large
extra dimensions with a size of afew microns. The hypercharge is a linear
combination of the first three U(1)s. All remaining U(1)s get masses at the TeV
scale due to anomalies, leaving the baryon and lepton numbers as
(perturbatively) unbroken global symmetries at low energies. The conservation
of baryon number assures proton stability, while lepton number symmetry
guarantees light neutrino masses that involve a right-handed neutrino in the
bulk. The model predicts the value of the weak angle which is compatible with
the experiment when the string scale is in the TeV region. It also contains two
Higgs doublets that provide tree-level masses to all fermions of the heaviest
generation, with calculable Yukawa couplings; one obtains a naturally heavy top
and the correct ratio m_b/m_tau. We also study neutrino masses and mixings in
relation to recent solar and atmospheric neutrino data.Comment: 42 pages, Latex2e, 6 figures, final version to be published in Nucl.
Phys.
Scottish Crannogs Underwater excavation of artificial islands with special reference to Oakbank Crannog, Loch Tay
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