Artefacts stored

Figure 22 Pulse sequence of the HMBC-RELAY experiment. Filled and open bars represent 90° and 180° pulses, respectively. All other phases are set as x, excepted otherwise stated. A two-phase cycle x, —x is used for the pulse phases (j>, and

More detailed modeling exposes some weaknesses, for example, the need to use coarse monolithic catalyst structure to achieve reasonable reheat periods without excessive pressure drops. The cycle time of approximately 4 minutes is somewhat short for practical purposes. The cold spot formation in the reaction phase (Figure 14) and the resultant inability of the reaction to distribute itself over the catalyst to utilize the stored heat optimally is probably a modeling artefact caused by too low literature values for the activation energy, possibly reflecting an incorrectly interpreted film transport limitation. 

The Fenton reaction (1) was not used here to avoid any artefacts due to reactions of Fe with any organic acids formed. The reaction took place in an aqueous-phase simulation chamber, which consisted of a 450 mL Pyrex vessel. Unbuffered aqueous solutions were continuously stirred and maintained at 298 0.2 K. The light source was a 300 W xenon arc lamp (see Monod, et al. (2005) for further details on the apparatus). The initial concentrations of NMP and H2O2 were 5x10 and 1x10 mol L, respectively. During the reaction, aliquots of the solution were sampled at regular time intervals with an automatic sampler, and stored at 0 °C for further analysis. 

The V A remained at Westwood for several years after the departure of the British Museum and, by 1954, concern was expressed that over 2,000,000 worth of artefacts were still stored in the quarry. The repository was finally vacated in 1957, although maintenance was continued well into the 1960s. Considering the incalculable value of the material interred in the quarry, security staff was modest, consisting of a Keeper or Deputy Assistant, with one warder by day, and one warder accompanied by one Wiltshire Police Constable at night. 

Figure 41 (a) Read out from photorefractive recording of fhe alphabet E on a plane from bits spaced at 5.6 pm. (b) The same region of the film after the pattern has been erased by UV exposure, (c) after a pattern of alphabet F was written on the previously erased space, (d)-(f) Read outs from three-dimensionally recorded images of alphabets A , B , and C spaced 20 pm axially from each other [97]. The artefacts 1 and 2 in Figures 41(a)-(c) indicate that the data is written at the same area in the film after erasing the previously written data. The images of the three-dimensionally stored data are... 

Throughout the whole process of specimen preparation, strict care should be taken to limit the exposure of the samples to air as this may allow carbonation to occur. Samples should always be stored in a desiccator. Ideally, fracture surfaces should be prepared and coated immediately before observation. In order to have a representative study of a single sample, the surface of at least six grains should be analysed. Any feature observed only once should not be considered representative of the sample as it is likely an artefact. 

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