Population expansion in the North African Late Pleistocene signalled by mitochondrial DNA haplogroup U6

Background <br/> The archaeology of North Africa remains enigmatic, with questions of population continuity versus discontinuity taking centre-stage. Debates have focused on population transitions between the bearers of the Middle Palaeolithic Aterian industry and the later Upper Palaeolithic populations of the Maghreb, as well as between the late Pleistocene and Holocene. <br/> Results Improved resolution of the mitochondrial DNA (mtDNA) haplogroup U6 phylogeny, by the screening of 39 new complete sequences, has enabled us to infer a signal of moderate population expansion using Bayesian coalescent methods. To ascertain the time for this expansion, we applied both a mutation rate accounting for purifying selection and one with an internal calibration based on four approximate archaeological dates: the settlement of the Canary Islands, the settlement of Sardinia and its internal population re-expansion, and the split between haplogroups U5 and U6 around the time of the first modern human settlement of the Near East. <br/> Conclusions <br/> A Bayesian skyline plot placed the main expansion in the time frame of the Late Pleistocene, around 20 ka, and spatial smoothing techniques suggested that the most probable geographic region for this demographic event was to the west of North Africa. A comparison with U6's European sister clade, U5, revealed a stronger population expansion at around this time in Europe. Also in contrast with U5, a weak signal of a recent population expansion in the last 5,000 years was observed in North Africa, pointing to a moderate impact of the late Neolithic on the local population size of the southern Mediterranean coast

A review of the relationship between eggshell colour and water vapour conductance

This review brings together the available literature that examines the effect of variations in pigmentation on the gas conductance of avian eggshells. Pheasant and Houbara bustard eggs provide some evidence that shell abnormalities can impact upon colour and conductance. By contrast, data from wild birds suggest that neither the degree of maculation or intensity of ground colour impact upon gas conductance. Those studies that purport to show variation in rates of water loss in eggs with different degrees of pigmentation may have been confounded by variation in nest humidity. This emerging field of research remains very much in its infancy

Simulations of metastable decay in two- and three-dimensional models with microscopic dynamics

We present a brief analysis of the crossover phase diagram for the decay of a metastable phase in a simple dynamic lattice-gas model of a two-phase system. We illustrate the nucleation-theoretical analysis with dynamic Monte Carlo simulations of a kinetic Ising lattice gas on square and cubic lattices. We predict several regimes in which the metastable lifetime has different functional forms, and provide estimates for the crossovers between the different regimes. In the multidroplet regime, the Kolmogorov-Johnson-Mehl-Avrami theory for the time dependence of the order-parameter decay and the two-point density correlation function allows extraction of both the order parameter in the metastable phase and the interfacial velocity from the simulation data.Comment: 14 pages, 4 figures, submitted to J. Non-Crystalline Solids, conference proceeding for IXth International Conference on the Physics of Non-Crystalline Solids, October, 199

An Anglo-Saxon execution cemetery at Walkington Wold, Yorkshire

This paper presents a re-evaluation of a cemetery excavated over 30 years ago at Walkington Wold in east Yorkshire. The cemetery is characterized by careless burial on diverse alignments, and by the fact that most of the skeletons did not have associated crania. The cemetery has been variously described as being the result of an early post-Roman massacre, as providing evidence for a ‘Celtic’ head cult or as an Anglo-Saxon execution cemetery. In order to resolve the matter, radiocarbon dates were acquired and a re-examination of the skeletal remains was undertaken. It was confirmed that the cemetery was an Anglo-Saxon execution cemetery, the only known example from northern England, and the site is set into its wider context in the paper

Revisiting the Tradespace Exploration Paradigm: Structuring the Exploration Process

A number of case applications of tradespace exploration have further extended the types of analyses and knowledge insights that can be gained about tradeoffs between design choices and perceived utility and cost of alternatives. These extensions include application beyond its heritage aerospace domain to the transportation domain, comparing distinct concepts on a common tradespace, considering the impact of changing needs and contexts over time, evaluation of alternatives in a “light effort” manner. In parallel with these case applications, a formalization of the tradespace exploration process has emerged, using a question-driven approach to ensure the knowledge generated is practical and useful to decision makers. These questions are introduced and applied to three example space systems in order to illustrate insights gained in answering the questions. The insights include identifying “good” designs, the strengths and weakness of selected alternatives across a tradespace, limiting constraints and requirements that could allow for less expensive solutions. Additionally, advanced insights include understanding the sensitivities of designs to changes in contexts and needs, and consideration of the differential impact of uncertainty across a set of alternatives with potential opportunities for risk mitigation.Massachusetts Institute of Technology. Engineering Systems Division (Systems Engineering Advancement Research Initiative (SEAri)

alpha'-exact entropies for BPS and non-BPS extremal dyonic black holes in heterotic string theory from ten-dimensional supersymmetry

We calculate near-horizon solutions for four-dimensional 4-charge and five-dimensional 3-charge black holes in heterotic string theory from the part of the ten-dimensional tree-level effective action which is connected to gravitational Chern-Simons term by supersymmetry. We obtain that the entropies of large black holes exactly match the alpha'-exact statistical entropies obtained from microstate counting (D=4) and AdS/CFT correspondence (D=5). Especially interesting is that we obtain agreement for both BPS and non-BPS black holes, contrary to the case of R^2-truncated (four-derivative) actions (D-dimensional N=2 off-shell supersymmetric or Gauss-Bonnet) were used, which give the entropies agreeing (at best) just for BPS black holes. The key property of the solutions, which enabled us to tackle the action containing infinite number of terms, is vanishing of the Riemann tensor \bar{R}_{MNPQ} obtained from torsional connection defined with \bar{\Gamma} = \Gamma - H/2. Morover, if every monomial of the remaining part of the effective action would contain at least two Riemanns \bar{R}_{MNPQ}, it would trivially follow that our solutions are exact solutions of the full heterotic effective action in D=10. The above conjecture, which appeared (in this or stronger form) from time to time in the literature, has controversial status, but is supported by the most recent calculations of Richards (arXiv:0807.3453 [hep-th]). Agreement of our results for the entropies with the microscopic ones supports the conjecture. As for small black holes, our solutions in D=5 still have singular horizons.Comment: 28 pages; v2: minor changes, references added; v3: extended discussion on small black holes in sec. 5.4, more references added, accepted in JHE

Using the Wigner-Ibach Surmise to Analyze Terrace-Width Distributions: History, User's Guide, and Advances

A history is given of the applications of the simple expression generalized from the surmise by Wigner and also by Ibach to extract the strength of the interaction between steps on a vicinal surface, via the terrace width distribution (TWD). A concise guide for use with experiments and a summary of some recent extensions are provided.Comment: 11 pages, 4 figures, reformatted (with revtex) version of refereed paper for special issue of Applied Physics A entitled "From Surface Science to Device Physics", in honor of the retirements of Prof. H. Ibach and Prof. H. L\"ut

The One-loop Open Superstring Massless Five-point Amplitude with the Non-Minimal Pure Spinor Formalism

We compute the massless five-point amplitude of open superstrings using the non-minimal pure spinor formalism and obtain a simple kinematic factor in pure spinor superspace, which can be viewed as the natural extension of the kinematic factor of the massless four-point amplitude. It encodes bosonic and fermionic external states in supersymmetric form and reduces to existing bosonic amplitudes when expanded in components, therefore proving their equivalence. We also show how to compute the kinematic structures involving fermionic states.Comment: 38 pages, harvmac TeX, v2: fix typo in (4.2) and add referenc

Rapid increase in coral cover on an isolated coral reef, the Ashmore Reef National Nature Reserve, north-western Australia

Against a background of coral reef ecosystem decline, understanding the propensity for coral communities to recover after acute disturbances is fundamental to forecasting and maintaining resilience. It may be expected that offshore reef ecosystems are less affected by anthropogenic disturbances compared with reefs closer to population centres, but that recovery may be slower on isolated reefs following disturbances. To test the hypothesis that community recovery is slow in isolated locations, we measured changes in coral cover and relative abundance of coral genera over a 4 year period (200509) at Ashmore Reef, north Western Australia, following severe bleaching. The percent cover of hard coral tripled, from 10.2% (±1.46 s.e.) in 2005 to 29.4% (±1.83 s.e.) in 2009 in all habitats (exposed and lagoonal) and depth zones (25 and 810m), and the percent cover of soft corals doubled, from 4.5% (+0.63 s.e.) in 2005 to 8.3% (+1.4 s.e.) in 2009. Significant shifts in the taxonomic composition of hard corals were detected. Our results imply that coral recovery in isolated locations can occur rapidly after an initial delay in recruitment, presumably through the interacting effects of self-recruitment and reduced exposure to additive impacts such as coastal pollution

Eureka and beyond: mining's impact on African urbanisation

This collection brings separate literatures on mining and urbanisation together at a time when both artisanal and large-scale mining are expanding in many African economies. While much has been written about contestation over land and mineral rights, the impact of mining on settlement, notably its catalytic and fluctuating effects on migration and urban growth, has been largely ignored. African nation-states’ urbanisation trends have shown considerable variation over the past half century. The current surge in ‘new’ mining countries and the slow-down in ‘old’ mining countries are generating some remarkable settlement patterns and welfare outcomes. Presently, the African continent is a laboratory of national mining experiences. This special issue on African mining and urbanisation encompasses a wide cross-section of country case studies: beginning with the historical experiences of mining in Southern Africa (South Africa, Zambia, Zimbabwe), followed by more recent mineralizing trends in comparatively new mineral-producing countries (Tanzania) and an established West African gold producer (Ghana), before turning to the influence of conflict minerals (Angola, the Democratic Republic of Congo and Sierra Leone)