Luminescence investigations at Quendale (Broo Peninsula, Shetland)

This report is concerned with optically stimulated luminescence (OSL) investigations of sediment samples collected from ongoing University of Southern Maine archaeological excavations at the Links of Quendale, southern Shetland, investigating the early-modern township of Broo. 11 sediment samples were submitted to the luminescence laboratory at SUERC for OSL dating by Ian Simpson. This report summaries the protocols, and laboratory analysis, employed in quartz single aliquot regenerative (SAR) OSL dating, as used to construct an OSL chronology for wind-blown sands in proximity to the Broo excavations, in association with archaeological structures (5 samples), and for sands in the coastal and inland dune systems (6 samples). The chronology established for the inland sands, in contexts associated with the Broo 2 building and enclosure, spans from AD1540 ± 40 (SUTL2441) through to AD1810 ± 25 (SUTL2519), encompassing the archaeological period of interest. The dates obtained for sands within the enclosed and unenclosed areas to the immediate east and southwest of the excavated Broo site, are AD1760 ± 30 - AD1760 ± 25, and AD1810 ± 25 (SUTL2517-2518 and 2519, respectively), are consistent with the expectation that the clean sands which infill these structures, post-date the period in which the Broo township was abandoned. The coastal sand accumulations, as so far dated, yielded luminescence ages of 2380 ± 230 BC (SUTL2526), 1510 ± 270 BC (SUTL2527), AD 1030 ± 80 (SUTL2528), AD 1690 ± 50 (SUTL2529), AD 1720 ± 20 (SUTL2530) and a mixed-age sample with youngest component at AD 1955 ± 15 (SUTL2531), implying periods of sand mobilisation, synchronous with sand deposition in Orkney and northern Scotland, in the late Neolithic, the Early Bronze Age, the Norse period, the early-modern, and modern periods. This work suggests that the present-day physio-geographical setting of the Quendale Links, comprised of the coastal sand barrier, and the inland dune fields, is a product of a prolonged history of sand mobilisation, erosion and deposition from the Neolithic to the present day. Furthermore, the emerging temporal framework, coupled with the spatial distribution of dune forms across the Links, raises questions as to whether Little Ice Age storms were responsible for deposition, or erosive destruction of older dune-forms, and the re-mobilisation of this sediment. To test these ideas, profiling methods, both field- and laboratory- based, could be employed to obtain a more complete temporal and spatial characterisation of the dune systems and excavated sequences. Further OSL sampling and dating would be needed to define the vertical and lateral chronostratigraphies of the environmental features in the landscape and their relationships to archaeological structures

Spitzer observations of extragalactic H II regions - III. NGC 6822 and the hot star, H II region connection

Using the short-high module of the Infrared Spectrograph on the Spitzer Space Telescope, we have measured the [S IV] 10.51, [Ne II] 12.81, [Ne III] 15.56, and [S III] 18.71-micron emission lines in nine H II regions in the dwarf irregular galaxy NGC 6822. These lines arise from the dominant ionization states of the elements neon (Ne$^{++}$, Ne$^+$) and sulphur (S$^{3+}$, S$^{++}$), thereby allowing an analysis of the neon to sulphur abundance ratio as well as the ionic abundance ratios Ne$^+$/Ne$^{++}$ and S$^{3+}$/S$^{++}$. By extending our studies of H II regions in M83 and M33 to the lower metallicity NGC 6822, we increase the reliability of the estimated Ne/S ratio. We find that the Ne/S ratio appears to be fairly universal, with not much variation about the ratio found for NGC 6822: the median (average) Ne/S ratio equals 11.6 (12.2$\pm$0.8). This value is in contrast to Asplund et al.'s currently best estimated value for the Sun: Ne/S = 6.5. In addition, we continue to test the predicted ionizing spectral energy distributions (SEDs) from various stellar atmosphere models by comparing model nebulae computed with these SEDs as inputs to our observational data, changing just the stellar atmosphere model abundances. Here we employ a new grid of SEDs computed with different metallicities: Solar, 0.4 Solar, and 0.1 Solar. As expected, these changes to the SED show similar trends to those seen upon changing just the nebular gas metallicities in our plasma simulations: lower metallicity results in higher ionization. This trend agrees with the observations.Comment: 22 pages, 13 figures. To be published in MNRAS. reference added and typos fixed. arXiv admin note: text overlap with arXiv:0804.0828, which is paper II by Rubin et al. (2008

Europeanization of sub-arctic environments : perspectives from Norse Greenland's outer fjords

Acknowledgements The authors gratefully acknowledge the financial support of the Leverhulme Trust Footprints on the Edge of Thule Programme Award. ECL acknowledges the support of the Weissman International Internship Program, the Department of Earth and Planetary Sciences and the Department of Anthropology at Harvard. We would also like to thank George McLeod (University of Stirling) for manufacturing soil thin sections.Peer reviewedPostprin

Evaluation of a weighting approach for performing sensitivity analysis after multiple imputation.

BACKGROUND: Multiple imputation (MI) is a well-recognised statistical technique for handling missing data. As usually implemented in standard statistical software, MI assumes that data are 'Missing at random' (MAR); an assumption that in many settings is implausible. It is not possible to distinguish whether data are MAR or 'Missing not at random' (MNAR) using the observed data, so it is desirable to discover the impact of departures from the MAR assumption on the MI results by conducting sensitivity analyses. A weighting approach based on a selection model has been proposed for performing MNAR analyses to assess the robustness of results obtained under standard MI to departures from MAR. METHODS: In this article, we use simulation to evaluate the weighting approach as a method for exploring possible departures from MAR, with missingness in a single variable, where the parameters of interest are the marginal mean (and probability) of a partially observed outcome variable and a measure of association between the outcome and a fully observed exposure. The simulation studies compare the weighting-based MNAR estimates for various numbers of imputations in small and large samples, for moderate to large magnitudes of departure from MAR, where the degree of departure from MAR was assumed known. Further, we evaluated a proposed graphical method, which uses the dataset with missing data, for obtaining a plausible range of values for the parameter that quantifies the magnitude of departure from MAR. RESULTS: Our simulation studies confirm that the weighting approach outperformed the MAR approach, but it still suffered from bias. In particular, our findings demonstrate that the weighting approach provides biased parameter estimates, even when a large number of imputations is performed. In the examples presented, the graphical approach for selecting a range of values for the possible departures from MAR did not capture the true parameter value of departure used in generating the data. CONCLUSIONS: Overall, the weighting approach is not recommended for sensitivity analyses following MI, and further research is required to develop more appropriate methods to perform such sensitivity analyses

Functional conservation of Pax6 regulatory elements in humans and mice demonstrated with a novel transgenic reporter mouse

<p>Abstract</p> <p>Background</p> <p>The Pax6 transcription factor is expressed during development in the eyes and in specific CNS regions, where it is essential for normal cell proliferation and differentiation. Mice lacking one or both copies of the <it>Pax6 </it>gene model closely humans with loss-of-function mutations in the <it>PAX6 </it>locus. The sequence of the Pax6/PAX6 protein is identical in mice and humans and previous studies have shown <it>structural </it>conservation of the gene's regulatory regions.</p> <p>Results</p> <p>We generated a transgenic mouse expressing green fluorescent protein (GFP) and neomycin resistance under the control of the entire complement of human <it>PAX6 </it>regulatory elements using a modified yeast artificial chromosome (YAC). Expression of GFP was studied in embryos from 9.5 days on and was confined to cells known to express Pax6. GFP expression was sufficiently strong that expressing cells could be distinguished from non-expressing cells using flow cytometry.</p> <p>Conclusion</p> <p>This work demonstrates the <it>functional </it>conservation of the regulatory elements controlling <it>Pax6/PAX6 </it>expression in mice and humans. The transgene provides an excellent tool for studying the functions of different <it>Pax6/PAX6 </it>regulatory elements in controlling Pax6 expression in animals that are otherwise normal. It will allow the analysis and isolation of cells in which <it>Pax6 </it>is activated, irrespective of the status of the endogenous locus.</p

Spitzer reveals what's behind Orion's Bar

We present Spitzer Space Telescope observations of 11 regions SE of the Bright Bar in the Orion Nebula, along a radial from the exciting star theta1OriC, extending from 2.6 to 12.1'. Our Cycle 5 programme obtained deep spectra with matching IRS short-high (SH) and long-high (LH) aperture grid patterns. Most previous IR missions observed only the inner few arcmin. Orion is the benchmark for studies of the ISM particularly for elemental abundances. Spitzer observations provide a unique perspective on the Ne and S abundances by virtue of observing the dominant ionization states of Ne (Ne+, Ne++) and S (S++, S3+) in Orion and H II regions in general. The Ne/H abundance ratio is especially well determined, with a value of (1.01+/-0.08)E-4. We obtained corresponding new ground-based spectra at CTIO. These optical data are used to estimate the electron temperature, electron density, optical extinction, and the S+/S++ ratio at each of our Spitzer positions. That permits an adjustment for the total gas-phase S abundance because no S+ line is observed by Spitzer. The gas-phase S/H abundance ratio is (7.68+/-0.30)E-6. The Ne/S abundance ratio may be determined even when the weaker hydrogen line, H(7-6) here, is not measured. The mean value, adjusted for the optical S+/S++ ratio, is Ne/S = 13.0+/-0.6. We derive the electron density versus distance from theta1OriC for [S III] and [S II]. Both distributions are for the most part decreasing with increasing distance. A dramatic find is the presence of high-ionization Ne++ all the way to the outer optical boundary ~12' from theta1OriC. This IR result is robust, whereas the optical evidence from observations of high-ionization species (e.g. O++) at the outer optical boundary suffers uncertainty because of scattering of emission from the much brighter inner Huygens Region.Comment: 60 pages, 16 figures, 10 tables. MNRAS accepte

Review of the quarter's economic trends [April 1980]

This brief paper surveys recent world and UK economic data and reveals that there are some signs to suggest that the world economy will withstand the 1979 oil price shock better than it did in 1973/74. The main difference is that the 1979 price rise was not super-imposed on as severe an inflation as that which occurred on the previous occasion. The present rate of increase in the world prices should not reach the levels of the last cycle when the twelve month increase in manufacturing prices peaked at 23%. Advance warning by US economists that 1979 was going to be a year of difficulty did not go unnoticed by businessmen in that country who took steps in 1978 to avoid a repetition of the inventory boom and bust cycle which had proved so costly in the recession of 1973/74. Also, consumer expectations are adjusting towards a continuing rise in the price of oil. In the UK real GDP is expected to fall by 2½% from mid-year 1980. Thereafter, it is assumed to grow at an average annual rate of 1% for the next four years

The tax and price index

A feature of this year's Budget was the shift in emphasis from direct taxation to indirect taxation. The annual yield of income tax has been reduced by £4½ billion while that of direct taxes was increased by a similar amount. It must be acknowledged that the new tax and price index has a number of deficiencies. It is only applicable to a proportion of the population, namely those who pay tax and whose gross income is less than £10,000 per annum. It takes no account of the social wage, nor of changes in benefits, such as the recent restructuring of child allowance. It smoothes out tax payments over a full year even though, for administrative reasons, these may fluctuate widely from month to month. This brief paper explores some of these deficiencies in more detail and assess their impact on taxation

The Scottish economy [October 1979]

The previous two issues of this Commentary have both indicated that the Scottish economy has been performing poorly since the mid 1970's. This is true in both an absolute and a relative sense. Manufacturing production only increased by 1.2% between 1976 and 1978 and, after dropping below 1975 levels in the first quarter of 1979, is unlikely to show any substantial improvement for the year as a whole. In an international context the 1975-1978 performance can best be described as appalling. Over the same period industrial production in Eire grew by 28%, in Japan and the US by 23% and in West Germany and France by 15%. Inertia in developing new markets and lack of competitiveness in existing markets both contributed substantially to the virtual stagnation of Scottish output. Because the problems are so diverse, so too must be the solutions

The complex radio and X-ray structure in the nuclear regions of the active galaxy NGC1365

We present a multiwavelength analysis of the prominent active galaxy NGC1365, in particular looking at the radio and X-ray properties of the central regions of the galaxy. We analyse ROSAT observations of NGC1365, and discuss recent ASCA results. In addition to a number of point sources in the vicinity of NGC1365, we find a region of X-ray emission extending along the central bar of the galaxy, combined with an emission peak near the centre of the galaxy. This X-ray emission is centred on the optical/radio nucleus, but is spatially extended. The X-ray spectrum can be well fitted by a thermal plasma model, with kT=0.6-0.8keV and a low local absorbing column. The thermal spectrum is suggestive of starburst emission rather than emission from a central black-hole. The ATCA radio observations show a number of hotspots, located in a ring around a weak radio nucleus. Synchrotron emission from electrons accelerated by supernovae and supernova remnants (SNRs) is the likely origin of these hotspots. The radio nucleus has a steep spectrum, indicative perhaps of an AGN or SNRs. The evidence for a jet emanating from the nucleus is at best marginal. The extent of the radio ring is comparable to the extended central X-ray source.Comment: 13 pages, 5 figures, to be published in MNRA