Image analysis of charcoal fragments to explore Holocene fire - vegetation dynamics in Northern Europe

Many sedimentary deposits are vital archives of fire-vegetation-climate records. Developing a better understanding of these relationships has relevance to understanding the impact of changes in climatic conditions, such as the increase in summer temperatures that is forecast for the next fifty years and beyond. Charcoal fragments can be used as a proxy for fire events however there is no standard method for their isolation from sediments or standard quantification unit. Many of the fire histories for the U.K. focus on a narrow temporal range and use a variety of quantification units to overcome methodological difficulties in comparing and compiling records. Statistical techniques can be employed to compile records; however, this leads to a reduction in the sensitivity of the data in detecting low impact disturbances such as ground fire and the light impact of early Mesolithic tribes. For this thesis, an image analysis method has been devised and robustly tested through analysis of macrocharcoal fragments. This method is initially used to explore the fire-vegetation-climate history of an upland ombrotrophic bog, Robinsons Moss, Peak District, U.K. in a multiproxy study covering the last 8200 years. The analysis is then extended to determine the local fire history for upland sites in and around the Peak District region using the Landscape Reconstruction Algorithm devised by Sugita (2007 a, b) in an empirical data-driven approach that does not require data transformation of charcoal records and the subsequent loss of sensitivity in the results. Four sites in northern Europe are used to explore the wider spatial fire- vegetation-climate relationships. This is achieved by using the new method for charcoal fragment analysis combined with the quantitative fire – vegetation response technique, redundancy analysis. Results show that the percentage of the variance in the vegetation dynamics explained by fire for sites within the Peak District and also for the sites in Denmark, Germany and Sweden does not exceed 30% for the last 13,500 years. Although fire is not the dominant driver at the sites explored in this thesis, it does have a substantial impact on the vegetation dynamics and soil chemistry. The results from this research implies that climate is more likely to have long-term control over vegetation dynamics at these sites

Is anterior release effective to increase flexibility in idiopathic thoracic scoliosis? Assessment by traction films

With the advent of thoracoscopy, anterior release procedures in adolescent idiopathic scoliosis (AIS) have come into more frequent use, however, the indication criteria for an anterior release in thoracic AIS are still controversial in the literature. To date, few studies have assessed the influence on spinal flexibility and no study has so far been able to show a beneficial effect on the correction rate as compared to a single posterior procedure. The objective of this study was to evaluate the influence of thoracic disc excision on coronal spinal flexibility. Six patients (5 females, 1 male) with AIS and a mean age of 15.6 years (range 13–20 years) underwent an open anterior thoracic release prior to posterior instrumentation. Cotrel dynamic traction along with radiographs of the whole spine including traction films were conducted pre- and postoperatively and were evaluated retrospectively. The mean preoperative thoracic curve was 89.7° ± 15.4° (range 65°–110°). The flexibility rate in Cotrel traction was 22.8 ± 8.1%. After performance of the anterior release the thoracic curve showed a mean increase of coronal correction by 5.5° ± 5.0° as assessed by traction radiographs. The flexibility index changed by 6.2 ± 5.6%. After posterior instrumentation the thoracic curve was corrected to a mean of 36.5° ± 10.1° (correction rate 59.6%). Disc excision in idiopathic thoracic scoliosis only slightly increased spinal flexibility as assessed by traction films. In our view a posterior release with osteotomy of the concave ribs (concave thoracoplasty, CTP) is more effective in increasing spinal flexibility. According to our clinical experience, an anterior release prior to posterior instrumentation in AIS should only be considered in hyperkyphosis, coronal imbalance or massive curves

Microscopic Charcoal Signal in Archaeological Contexts

The recovery of archaeological wood charcoals from combustion features provides insights into the exploitation and use of wood fuel resources and past landscapes. The quality of our interpretation based on wood charcoals, however, depends on reliable information about the charcoal assemblages resulting from taphonomy. Charcoal is very fragile in comparison to other combustion residues such as burnt bones. In archaeological contexts, charcoal can easily be fragmented into small pieces (<0.25 mm) due to their fragile property. The investigation of small fragments and particles is particularly important for the interpretation of combustion residues when large pieces of charcoal are rare or apparently absent in archaeological sites, which is mainly true for many European Palaeolithic sites. Here, archaeologists get incomplete information when only the largest pieces and fragments are considered. In this chapter, we present a method for extracting and quantifying charcoal pieces, fragments, and particles. This approach can be considered as a strategy to minimize the impact of sample incompleteness and biases related to combustion residues in archaeological contexts. We further provide (1) a definition of what the charcoal signal means in an archaeological context; (2) an overview of taphonomy that causes charcoal fragmentation; (3) a review of charcoal sampling, extraction, observation and quantification protocols; (4) a manual (pictures and descriptions) for the observation of charcoal, from large pieces to the smallest particles; and (5) a discussion about why the charcoal signal is useful for archaeologists. By taking into account the consequences of taphonomy, the microscopic charcoal analysis in archaeological contexts provides a reliable assessment of firewood and fuel management practices and the related resilience of societies through time. The microscopic charcoal analysis can further offer additional information about the intensity of taphonomical processes and dating