Radioactivity contact contamination from

The source and drain contacts of the examined OFETs were deposited by thermal evaporation of Au as described above for deposition of the radiotracers. Deposition of the contacts was not performed in the same chamber as the radio-tracer deposition in order to avoid contamination of the sample with radioactive isotopes. Patterning of the contact stractures was obtained using a stainless steel shadow mask. By deposition of Au an array of nine contacts was formed. The contact area of the Au was 50 x 50 pm and the distance between the contacts varied from 300 pm to 3290 pm. Three Au contact arrays with a thickness of 50 nm were deposited onto a 40 nm Pc film at a substrate temperature of 75 °C. The first contact array (Array 1 in the following) was deposited at a rate of 0.8 nm/min. For the second set of contacts (Array 2 in the following) first a submonolayer of Au was deposited very slowly (< 1 ML/h) on top of the Pc film in order to allow strong diffusion. Afterwards, the contacts were deposited at the same rate of 0.8 nm/min as the first set. The third array (Array 3 in the following) was deposited at 0.8 nm/min with the substrate at room temperature. 

There are studies to suggest safer construction materials with the lowest possible risk on health for the indoor environment, mainly to decrease the effect of second factor (chemical contaminants from indoor sources) listed above [7, 8]. Most of these are natural , or in other words, they are green . However, one should also consider the fact that, all natural things are not safe. A number of natural materials can contain VOC and hence can pose hazards to health as well. Radon is an example, it is a natural material, which is radioactive and exists almost everjrwhere in the house. In addition, allergic reactions to the odours from cedar furniture, a natural material, are very common. The risk is always low if a certain agent remains in the building product that does not affect occupants through respiration and physical contact. 

Along with many other authors, LeRoy and Koksoy have drawn-attention to a common source of error in the studies of the mineral content of lichens. It is difficult to avoid the contamination of the samples by the substratum, because of the close contact of the species with it and even the decaying of the lower parts of the thallus. Other sources of error that they mentioned are the composition of surface and near-surface water, age of the thalli, the contamination from the atmosphere, and soil that was not removed from the thalli during cleaning for the experiments. Radioactive fallout, also mentioned as a possibility, is of secondary importance with respect to inactive nuclides, because the absolute mass of a certain radionuclide representing a rather high radiation effect is usually vanishingly small compared with the inactive mass of that element. 

Radioactive substances (radionuclides) are known health hazards that emit energetic waves and/or particles that can cause both carcinogenic and noncarcinogenic health effects. Radionuclides pose unique threats to source water supplies and chemical processing, storage, or distribution systems because radiation emitted from radionuclides in chemical or industrial waste systems can affect individuals through several pathways by direct contact with, ingestion or inhalation of, or external exposure to, the contaminated waste stream. While radiation can occur naturally in some cases due to the decay of some minerals, intentional and nonintentional releases of... 

The list of potentially hazardous materials includes drugs, food additives, preservatives, ores, pesticides, dyes, detergents, lubricants, soaps, plastics, extracts from plant and animal sources, plants and animals that are toxic by contact or consumption, and industrial intermediates and waste products from production processes. Some of the information refers to materials of undefined composition. The chemicals included are assumed to exhibit the reported toxic effect in their pure state unless otherwise noted. However, even in the case of a supposedly pure chemical, there is usually some degree of uncertainty as to its exact composition and the impurities that may be present. This possibility must be considered in attempting to interpret the data presented because the toxic effects observed could in some cases be caused by a contaminant. Some radioactive materials are included but the effect reported is the chemically produced effect rather than the radiation effect. 

Routes of entry for radioactive materials are much the same as for poisons. However, the radioactive source or material does not have to be directly contacted for radiation exposure to occur. Exposure occurs from the radiation being emitted from the radioactive source. Once a particulate radioactive material enters the body, it is dangerous because the source now becomes an internal source rather than an external one. You cannot protect yourself by time, distance, or shielding from a source that is inside your body. Contact with or ingestion of a radioactive material does not make you radioactive. Contamination occurs with radioactive particles, but with proper decontamination, these can be successfully removed. After they are removed, they cannot cause any further damage to the body. 

Bradley then constructed an apparatus for measuring the force required to separate two silica spheres from adhesive contact (see Fig. 4.12). The rig could be evacuated to remove moisture and other contamination. Heaters were used to bake the glass and a radioactive source ionized the gas to leak away any stray charges. The silica balls were heated to incandescence immediately before the measurements. A deflection was applied to the bottom sphere until it detached from the upper sphere, giving the results shown in Fig. 4.13. 

A person who is contaminated externally by a radioisotope can contaminate another person by contact (cf transmission of a persistent chemical hazard such as sulphur mustard). Radioactive contamination is therefore transmissible either from person to person or from a contaminated surface to a person. This poses a hazard to emergency responders... 

The gel-forming prop>erties of smectites also are used in forming impermeable barriers around land-fills or contaminated soils. However when such materials are heated under humid conditions as may occur in the close vicinity of high level radioactive waste, the contact of wet steam with the smectites can cause the mineral to change from hydrophilic to hydrophobic, which results in the loss of the gel-forming capacity and thus the low permeability of the day Uner will be lost (Coutme, 1985 Bish et ai, 1999). 

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