Artefacts treated

Alternatively (or initially) the mixture is treated as a whole and tested in its crude state. The advantage of this strategy includes the relevancy of the tested sample to its environmental counterpart, decreased potential for artefact formation, and inclusion of combined effects of chemicals in the mixture. Moreover if the mixture is representative of others in its class (e.g., diesel emissions from different sources would share certain characteristics), it may be possible to extrapolate results across samples. This method also circumvents the labor-intensive process of individual testing of multiple chemicals. But sometimes a complex mixture is too cytotoxic to be tested directly in a bioassay. Furthermore, it may be incompatible with the test system because of the physical matrix. Other disadvantages include the inability to specify the constituent of the mixture responsible for the toxicity, as well as potential masking effects (e.g., the masking of mutagenicity by cytotoxicity). 

The analogy with sides of coins suggests a symmetry between the social and the technical, and that they should each be treated in the same way. This is the method of actor-network theory , in which non-human artefacts and humans are regarded alike as actants in the same sociotechnical realm.5... 

A puzzling reaction was recorded in a small hospitalized Canadian population of elderly subjects treated for scabies with a single dose of ivermectin (150-200 micrograms/kg). Within 6 months, 15 of the 47 patients had died. All those who died had developed a sudden change in behavior, with lethargy, anorexia, and listlessness before death (31). The effect may have been an artefact with some extraneous cause, and it is notable that other groups using this treatment for scabies have not recorded similar reactions. 

This short and very limited review gives an idea of the wide variety and complexity of the problems encountered in the study of protonated hydrates. This selection of topics is illustrative of the new possibilities offered by the present developments of theoretical treatments and shows the progress realised in this field, especially within the last few years. Besides the improvement of the accuracy of some of the methods used, in particular to treat the correlation contribution to the intermolecular energies, other categories of methods of lower accuracy bring other kinds of information. This has been exemplified by the results obtained from Monte Carlo and Molecular Dynamics calculations based on the use of DFT or analytical potentials. Though great care must be taken to the possibility of artefacts due to the approximations included in these treatments, such work is complementary to more accurate determinations. We can expect all these methods to be more and more coupled in the near future. 

Interpreting the results of phthalate determinations in soil may be rather difficult. Even if blank values are really under control, phthalate contents, especially DEHP, may be caused by some artefacts, even the presence of pieces of plastics in the sample. If large samples have been pre-treated by milling, such an artefact may be difficult to recognise. Therefore, a different strategy should be considered and taking a number of small size samples that can be visually inspected may be a better choice. In any case the analyst should have a close look at the contents of the sample container in taking the required portion for... 

For the determination of dissolved metal concentrations, water samples have to be passed through a membrane filter of 0.45 J.m pore size. The filtration should be done in the field in order to prevent artefacts due to adsorption to the container walls. If expected metal concentrations are far below the suggested EQS it would be possible to analyse whole water samples and compare the results for the total content with the EQS for die dissolved fraction. In such cases, samples shall be acidified in the field and sample containers shall be pre-treated accordingly. 

For transportation of the artefact it is essential to maintain treatment initiated in the field. If the items cannot be moved in their storage tanks, they must be packed as mentioned for the large artefacts above, i. e. use sawdust, etc. If by the smell of the corrosion products (presence of hydrogen sulfide gas), microbial corrosion of the artefact is suspected, it would be advisable to add a biocide in order to minimise this type of attack until it can be treated in the laboratory. 

By using boiled water, the dissolved oxygen is expelled and hence, there should be no corrosion as the cathode reactant has been eliminated from the electrolyte. Unless the boiled water is kept in sealed containers, air (oxygen) will slowly dissolve into the water and corrosion of the metal or alloy will re-commence. As an alternative, using hot demineralised or distilled water will reduce the concentration of dissolved oxygen and hence corrosion, but this must be counter-balanced by the rise in reaction rates with temperature. In open conservation tanks, a temperature of 70°C is required to notice a significant reduction in rates of corrosion of metals. Small copper alloy artefacts from the Mary Rose were treated in this way using water at 80°C for 30 days. At the end of this period, the chloride levels in the water dropped to below 1 ppm. 

The anodes that have been used include stainless steels, mild steel, lead and platinised titanium, while typical electrolytes for ferrous materials have been 0.5 M sodium hydroxide, 0.2 M sodium carbonate, 0.5 M sodium sesquicar-bonate and tap water. For bronze cannons recovered from the Mary Rose, both sodium hydroxide and sodium carbonate electrolytes were employed while pewter artefacts (plates) from the same ship were treated in similar electrolytes or in a 0.5% solution of EDTA as a sodium salt in alkaline solution. 

The hydrogen reduction conservation process was first employed in Sweden in 1964 for ferrous artefacts recovered from the Swedish warship, the Vasa. The method was further developed at Portsmouth to treat the large number of finds recovered from the Solent and land-based archaeological sites within the Wessex region. The principle of the process is to heat the artefact in an atmosphere of hydrogen in order to sublime off the volatile chlorides and at the same time reduce the oxides, hydroxides, chlorides and eventually to the metallic state. The volume change associated with the reduction of the iron compounds is sufficiently high to enable the release of deeply-buried chlorides particularly at the metal/corrosion product interface. 

The major criticism of this method of conservation is that the metallurgical structure of the artefact has been altered by heating the artefact to elevated temperatures. For this reason, relatively few artefacts with derived microstructures such as knives, axes, etc., were treated in the furnace at Portsmouth. If hydrogen treatment was the method selected for these, the operating temperature was reduced to 350°C and the process time extended in order to minimise the alteration to the microstructure. Nevertheless, this method is one of the best and quickest methods for the removal of the chloride ions. Guns from the Mary Rose were fully conserved within 2-3 weeks and even after exposure to the atmospheric conditions for nearly 30 years, they still show no sign of breakdown. 

Dehydration techniques and methods involving in situ polymerisation are not considered suitable for anything other than small wooden artefacts. Freeze drying offers the conservator a safe method of drying small PEG-treated objects while air drying is more suited to the drying of larger structures, such as intact ships if the condition allows it. 

Rubin GD (2000) Data explosion the challenge of multide-tector-row CT. Eur J Radiol 36(2) 74-80 Seemann MD, Heuschmid M, Vollmar J, Kuttner A, Schober W, Schafer JF, Bitzer M, Claussen CD (2003) Virtual bronchoscopy comparison of different surface rendering models. Technol Cancer Res Treat 2(3) 273-279 Zou Y, Sidky EY, Pan X (2004) Partial volume and aliasing artefacts in helical cone-beam CT. Phys Med Biol 49 2365-2375... 

Patients treated with endovascular methods need angiographic follow-up. But coil artefacts preclude the use of CTA in these patients. MRA is clearly an... 

---