Exposure systems

To achieve smaller dimensions there are systems that use x-rays instead of optical photons (150). These systems require a collimated x-ray source which is often expensive. Additionally, systems have been developed that use ion beams to expose the resist. Either an x-ray or ion beam system requires specialized resists and exposure systems. 

Concerning adherent cells there are few studies in the literature. Some of them deal with the influence of stirrer speed on microcarrier cultures. Most studies using defined forces are from medical research. These studies, as well as those with production cells, use different types of exposure systems based on the parallel plate theory. They investigate the influence of stress on cell morphology and viability which is most important for arteriosclerosis research. 

ACUTE EXPOSURE Systemic Pig few d (NS) (F) Gastro 15.0 (diarrheic digestive disturbance) Wetterau etal. 1964... 

Duration of exposure System Effect Blood lead levels at which effect was observed (ug/dL) Reference... 

There are three general types of data contained in three data files. These are illustrated for the exterior hardboard exposure system in Table III. The first file contains the information about the substrate. This includes an identification number for the panel, the date, the location and type of exposure to which the panel was subjected, the manufacturer of the substrate, the trade name, and the results of a series of standard test to evaluate the properties of the substrate. This information allows correlations to be made between the performance of the coating and the particular properties... 

Analysis of nitroaromatics found by treating diesel fuel with NO2 (column A) compared to nitroaromatics found in extracts of filters of exhaust from a diesel engine (column B) or in extracts of diesel soot deposited in a dilution tunnel of an animal exposure system (13). 

Frosolono and Currie (1985) investigated the effect of phosgene on the pulmonary surfactant-system (PSS) in groups of six to 14 rats exposed to phosgene at 1 ppm for 4 h. The exposure system and parameters were similar to those described in Section 3.2.1 (Hatch et al. 1986). The actual chamber concentration was 1.0 0.06 ppm. Animals were sacrificed immediately after exposure, or on postexposure days 1, 2, or 3. Pulmonary edema was present immediately after exposure and persisted through day 3. Phosphatidylinositol levels were significantly (p<0.05) decreased compared with controls immediately after exposure only. Phosphatidylserine and phosphatidylethanolamine levels were significantly increased compared with controls on days 1, 2, and 3 postexposure. Phosphatidylcholine levels were increased at all time points compared with controls. 

Concentration time curves for -hexane in a closed exposure system indicated that metabolism in rats was proportional to air concentration up to about 300 ppm (Filser et al. 1987). Metabolism was nonlinear above 300 ppm and appeared to be saturated at concentrations 3,000 ppm. 

A 0.4 m thick SPP layer was exposed to X-rays followed by a flood exposure using near UV radiation. The resist was then dip-developed in a 0.8 wt% TMAH solution for 60 s at 25 °C. We used two x-ray exposure systems to evaluate the characteristics of the SPP resist. One is SR-114 which has a source composed of a molybdenum rotating anode with a 0.54 nm Mo-La characteristic line. The exposure was carried out in air. The other has a synchrotron radiation source with a central wavelength of 0.7 nm (KEK Photon Factory Beam Line, BL-1B). The exposure was carried out in vacuum (<10-4 Pa). A positive resist, FBM-G,15) was used as a standard, because its sensitivity only weakly depends on the ambient. 

The main criteria for the design and operation of any dynamic (as opposed to static) inhalation exposure system are the following... 

Ulrich, C.E., Klonne, D.R. and Church, S.V (1984). Automated exposure system for metered-dose aerosol pharmaceuticals. Toxicologist 4 48. 

Study, SPE sampling of >6>C-associated residues cannot be ruled out. Also, no data are available on the potential of the surficial retention of colloids or DOC by the SPE sorbent. These factors would lead to an overestimation of dissolved concentrations. Other sampling equipment may also yield inaccurate measurements of dissolved concentrations. Pre-equilibration of laboratory exposure systems is a separate issue related to attainment of steady-state water concentrations in the exposure system prior to initiation of the test. Clearly, the issue of DOC or colloidally sorbed contaminants deserves additional discussion. 

Figure 38. Schematic of an electron beam exposure system.

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