Direct-Contact Tests

Where surfaces are flat and smooth, agar plates filled with the appropriate media can be pressed directly against the sanitized surface. In theory. 

Various tapes have been used in a manner similar to agar plates. In this case, tape is applied to surface and subsequently reapplied to the agar surface. 

---

A direct contact test has been developed for solid samples. A solid-phase assay eliminates the need for soil extracts and utilizes whole sediments and soils. In the current procedure the solid sample is suspended in 2% NaCl. Dilutions of the stock suspension are measured to determine the EC50 and ECjo at 5 and 15 minute contact times. For this the homogenized sample and photobacterial suspension mixture are incubated. The suspended solid material is then centrifuged out and hght emission of the supernatant determined [24-26,32]. 

Monitoring of the manufacturing process of perfluoralkyl-alkenes the test results of the extractables are inconspicuous the direct contact tests show no... 

Three in vitro biological tests exist the agar diffusion test, the direct contact test, and the elution test. Each test evaluates the interaction of the polymer with... 

Delivery of antibiotics from such formulations resulted in suppressed bacterial growth, and thus antibacterial activity, in an in vivo rabbit model. Furthermore, these formulations have proven to be effective in an agar diffusion test, direct contact test, mouse model, and rabbit osteomyelitis model without disturbing normal bone ingrowth. 

Direct contact test L-929 mammalian fibroblast cells Prepare monolayer cell culture and place the flat surface of samples and controls in contact with the agar surface Size of the zone around or under sample... 

Tests on extracts L929 elution test Neutral red uptake test Colony formation test 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and related tests Direct contact test Indirect contact test Agar diffusion test Filter diffusion... 

For the direct contact tests, materials with at least one flat surface need to be nsed, although the materials can have various shapes, sizes, or physical states (eg, liquid, solid, and gel). An important factor to consider is that the sterility of the sample mnst be maintained throughout the test procedure as, for example, bacterial contamination can lead to false evaluation of cytotoxicity. In this regard, the effect of sterilization on... 

In contrast to placing the testing material directly on a monolayer of cells as in the direct contact test, the agar diffusion assays use a monolayer of cells with a semisolid agar or agarose overlay (3-4imn) on which the material sample is placed (Fig. 7.23). Agarose is... 

For direct contact tests, HSFB were seeded onto polyurethane disks. After 3-5-72 hours incubation, cell survival was evaluated as described for cytotoxicity tests. 

Table 2. Cytocompatibility of PUs direct contact tests. Data are reported as % vs control, tissue culture polystyrene.

In many industries a non-contact testing of vibrating parts of the various equipment is needed. To prevent the destruction of large aggregates rotating and moving in various directions with the large speed, the parameters of vibrations should be measured very carefully. Besides, vibrations reduce considerably the equipment s duration of life. 

Concern for personnel exposure to hydrazine has led to several innovations in packaging to minimize direct contact with hydrazine, eg, Olin s E-Z dmm systems. Carbohydrazide was introduced into this market for the same reason it is a soHd derivative of hydrazine, considered safer to handle because of its low vapor pressure. It hydrolyzes to release free hydrazine at elevated temperatures in the boiler. It is, however, fairly expensive and contributes to dissolved soHds (carbonates) in the water (193). In field tests, catalyzed hydrazine outperformed both hydrazine and carbohydrazide when the feedwater oxygen and iron levels were critical (194). A pubUshed comparison is available (195) of these and other proposed oxygen scavengers, eg, diethyUiydroxylarnine, ydroquinone, methyethylketoxime, and isoascorbic acid. 

Tests have shown that citric acid is not corrosive to skin but is a skin and ocular irritant (50). Eor these reasons it is recommended that individuals use appropriate personal protection to cover the hands, skin, eyes, nose, and mouth when in direct contact with citric acid solutions or powders. 

As in normal potentiometry one uses and indicator electrode versus a reference electrode, the electrodes should, especially in pH measurements, be those recommended by the supplier of the pH meter in order to obtain a direct reading of the pH value displayed. In redox or other potential measurements any suitable reference electrode of known potential can be applied. However, a reference electrode is only suitable if a junction potential is excluded, e.g., an Ag-AgCl electrode in a solution of fixed Ag+ concentration or a calomel electrode in a saturated KC1 solution as a junction in many instances a direct contact of Cl" with the solution under test (possibly causing precipitation therein) is not allowed, so that an extra or so-called double junction with KN03 solution is required. Sometimes micro-electrodes or other adaptations of the surface are required. 

R D Focus. This database service [66] provides information on over 7000 drugs in active development. The service monitors the development, efficacy, and status of pharmaceuticals from early clinical testing through to launch. Data are gathered through direct contact with manufacturers and research organizations. It appraises both the scientific and commercial aspects of drug development and is searchable by product, by phase, by mechanism of action, and by country. R D Focus product is commercially available in several formats. 

It is demonstrated in the pilot tests that TCE can be removed by 99% for the direct contact exposure route within 3 to 5 yr using the vapor extraction system. The potential for fugitive losses of air contaminants would be minimal under good control conditions. A countercurrent packed tower air stripper (13.72 m tall and 1.22 m in diameter) would be used to treat the extracted groundwater to meet the performance goal of 5 pg/L TCE concentration. The exhaust air would be discharged through carbon beds for adsorption. 

Plants, fruits, vegetables, and grains should be quarantined until tested and determined to be safe to consume. In addition to a direct contact hazard, some G-series agents can translocate from roots to other areas (e.g., leaves, fruits, etc.) of some plants and may pose an ingestion hazard. 

---