Identification of cellulose nitrate X-ray film for the purpose of conservation: Organic elemental analysis

Cellulose nitrate was widely used as a film base for photography, cinematography, and radiography in the first half of the twentieth century. Its stability is inherently poor and subject to environmental storage conditions. The risk of fire and the cross-infection effect on the cellulose acetate film stored at the same location necessitate that cellulose nitrate is identified within collections and stored separately. Not only medical archives, but also museums using radiography in their research may hold a sizeable amount of historical X-ray films. The Natural History Museum, London has been using film for X-radiography since before World War II. This suggests that some of the X-ray materials in its collections have a cellulose nitrate rather than ‘safety’ (cellulose acetate or polyester) film base. X-ray sheets rarely contain information related to their composition so science-based identification methods must be used. We propose the determination of nitrogen content in the film by organic elemental analysis (OEA) as a reliable method for the identification of films (X-ray, photographic, or cinematographic) with a cellulose nitrate base. Though it is a destructive method, the sample size required is small (<1?mg). This method does not require any sample preparation apart from weighing the samples and wrapping them in tin foil. OEA proved to be more accurate than the ‘float’ test in trichloroethylene and quicker and more straightforward to perform than infrared spectroscopy.     

Teaching Assistants managing behaviour – who knows how they do it? A review of literature

This article reflects on the specific challenges facing teaching assistants (TAs) when managing behaviour. It considers the variety of existing research into this area, and why the paucity of specific research is problematic. It discusses how difficulties in access to training, its availability, the levels of preparation for lessons, the lack of guidance on teacher and TA working relationships, all impact on the way TAs manage behaviour. The article also highlights some of the conflicts inherent within broader issues which impact, either positively or negatively, on TAs ability to manage behaviour, including TA role definition, deployment and the wider pedagogical aspects of their evolving role.