158 research outputs found

    A game of two halves: Looking for evidence for both embedded and direct procurement in a simulated dataset

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    The concepts of embedded and direct procurement have become weighted with extra baggage over the years. In embedded procurement, lithics are obtained along with other resources, while direct procurement involves a deliberate trip to the source for the sole purpose of obtaining that raw material. Lewis Binford suggested that direct procurement means something went wrong (a sign of poor planning), and that embedded procurement is the norm. Other authors found valid reasons why direct procurement could be deliberate, planned, and beneficial. Regardless, the two have often been seen as diametrically opposed, and applied to interpretations of mobility and lithic procurement as if they are mutually exclusive of one another. They have also been variously conflated with expedient and curated technology, the use of local vs. exotic raw materials, and so on. The often site-centric vision of archaeologists (we find it hard to see that people may have been passing through a site, not based there and going out and coming back), can further confuse the issue. The most important problem, however, is: how can we tell the difference between embedded and direct procurement from the stone tools collected at an archaeological site? We created the scenario of a site with various proportions of stone tools from different sources. In order to not influence the site characteristics through a priori expectations, we randomly assigned source qualities and percentages in the assemblage, along with the distances and directions of each source relative to the site. Then each author analysed those data from one of two points of view: LW convinced in advance that the evidence supported embedded lithic procurement, and PM equally certain that a direct strategy was apparent. In both cases, the authors felt they had sufficient “justification” to bolster their point of view and build a strong case for their raw material procurement strategy. This exercise gave some insight into the usefulness and limitations of these two concepts as heuristic devices, as they continue to be a major influence on anyone trying to interpret lithic procurement

    Uncertainty in Signals of Large-Scale Climate Variations in Radiosonde and Satellite Upper-Air Temperature Datasets

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    There is no single reference dataset of long-term global upper-air temperature observations, although several groups have developed datasets from radiosonde and satellite observations for climate-monitoring purposes. The existence of multiple data products allows for exploration of the uncertainty in signals of climate variations and change. This paper examines eight upper-air temperature datasets and quantifies the magnitude and uncertainty of various climate signals, including stratospheric quasi-biennial oscillation (QBO) and tropospheric ENSO signals, stratospheric warming following three major volcanic eruptions, the abrupt tropospheric warming of 1976–77, and multidecadal temperature trends. Uncertainty estimates are based both on the spread of signal estimates from the different observational datasets and on the inherent statistical uncertainties of the signal in any individual dataset. The large spread among trend estimates suggests that using multiple datasets to characterize large-scale upperair temperature trends gives a more complete characterization of their uncertainty than reliance on a single dataset. For other climate signals, there is value in using more than one dataset, because signal strengths vary. However, the purely statistical uncertainty of the signal in individual datasets is large enough to effectively encompass the spread among datasets. This result supports the notion of an 11th climate-monitoring principle, augmenting the 10 principles that have now been generally accepted (although not generally implemented) by the climate community. This 11th principle calls for monitoring key climate variables with multiple, independent observing systems for measuring the variable, and multiple, independent groups analyzing the data

    Tuberculosis Microepidemics among Dispersed Migrants, Birmingham, UK, 2004-2013

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    MIRU-VNTR typing was supported by the Public Health England National TB Strain Typing Project. M.M. is funded by the UK Clinical Research Collaboration Modernising Medical Microbiology Consortium. C.B. is funded by the Heart of Birmingham Primary Care Trust and Public Health England

    Linking micellar structures to hydrogelation for salt-triggered dipeptide gelators

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    Some functionalised dipeptides can form hydrogels when salts are added to solutions at high pH. We have used surface tension, conductivity, rheology, optical, confocal and scanning electron microscopy, 1H NMR and UV-Vis spectroscopy measurements to characterise fully the phase behaviour of solutions of one specific gelator, 2NapFF, at 25 °C at pH 10.5. We show that this specific naphthalene–dipeptide undergoes structural transformations as the concentration is increased, initially forming spherical micelles, then worm-like micelles, followed by association of these worm-like micelles. On addition of a calcium salt, gels are generally formed as long as worm-like micelles are initially present in solution, although there are structural re-organisations that occur at lower concentrations, allowing gelation at lower than expected concentration. Using IR and SANS, we show the differences between the structures present in the solution and hydrogel phases

    The state of the Martian climate

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    60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes

    A quantification of uncertainties in historical tropical tropospheric temperature trends from radiosondes

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    The consistency of tropical tropospheric temperature trends with climate model expectations remains contentious. A key limitation is that the uncertainties in observations from radiosondes are both substantial and poorly constrained. We present a thorough uncertainty analysis of radiosonde‐based temperature records. This uses an automated homogenization procedure and a previously developed set of complex error models where the answer is known a priori. We perform a number of homogenization experiments in which error models are used to provide uncertainty estimates of real‐world trends. These estimates are relatively insensitive to a variety of processing choices. Over 1979–2003, the satellite‐equivalent tropical lower tropospheric temperature trend has likely (5–95% confidence range) been between −0.01 K/decade and 0.19 K/decade (0.05–0.23 K/decade over 1958–2003) with a best estimate of 0.08 K/decade (0.14 K/decade). This range includes both available satellite data sets and estimates from models (based upon scaling their tropical amplification behavior by observed surface trends). On an individual pressure level basis, agreement between models, theory, and observations within the troposphere is uncertain over 1979 to 2003 and nonexistent above 300 hPa. Analysis of 1958–2003, however, shows consistent model‐data agreement in tropical lapse rate trends at all levels up to the tropical tropopause, so the disagreement in the more recent period is not necessarily evidence of a general problem in simulating long‐term global warming. Other possible reasons for the discrepancy since 1979 are: observational errors beyond those accounted for here, end‐point effects, inadequate decadal variability in model lapse rates, or neglected climate forcings
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