Disc test

Purification of Antibiotic 66-40 — Dissolve 28 g of crude Antibiotic 66-40 in 100 ml of distilled water and charge to an anion exchange adsorption column (Dowex 1 X2) in the hydroxyl form. Slurry 2,000 g of the resin in water in to a column 2yj in diameter and 36 "high. Elute the column with distilled water at a rate of about 23 ml/min collecting 100 ml fractions and monitor with a conductivity meter and by disc testing against Staphylococcus aureus. 

Some of the brisant primers emit pressure pulses of sufficient magnitude to give measurable results in either the sand test or the Pb-disc test. Although many of these quantities are related to some aspects of primer performance, insofar as output is concerned, no general quantitative relationship of overall value has been-developed which can be used as a means of acceptance... 

Both the Pb disc test and the steel dent test are of particular significance to stab detonators. As a matter of illustration, the steel dent test (Ref 10) consists of firing a detonator in direct end-on contact with a steel block. The depth of the dent produced is a measure of output. The depth, or better, the volume of the dent correlates well with initiation effectiveness. The low-rate detonation, which crushes nearly as much sand as high-order detonation, makes no dent in a steel plate. It has been demonstrated that the depth of the dent is proportionate to the excess of pressure over the yield strength of the steel of the dent block, integrated over the volume of the detonation head. It has been found that a detonator of 0.190-inch diameter or larger, which produces a dent 0.010 of an inch deep in a mild steel block, will initiate a lead of Tetryl or RDX under favorable conditions. Specification requirements for detonators to be used in fuses are usually at least 0.015 to 0.020 inch in depth, and many produce dents up to 0.060 inch deep... 

The work function of the rubbing surfaces and the electron affinity of additives are interconnected on the molecular level. This mechanism has been discussed in terms of tribopolymerization models as a general approach to boundary lubrication (Kajdas 1994, 2001). To evaluate the validity of the anion-radical mechanism, two metal systems were investigated, a hard steel ball on a softer steel plate and a hard ball on an aluminum plate. Both metal plates emit electrons under friction, but aluminum produced more exoelectrons than steel. With aluminum, the addition of 1% styrene to the hexadecane lubricating fluid reduced the wear volume of the plate by over 65%. This effect considerably predominates that of steel on steel. Friction initiates polymerization of styrene, and this polymer formation was proven. It was also found that lauryl methacrylate, diallyl phthalate, and vinyl acetate reduced wear in an aluminum pin-on-disc test by 60-80% (Kajdas 1994). 

The depth of the dent is a measure of the output. The test applies only to components producing dents greater than 0.005 and smaller than 0.100 inch in depth. A drop-ball apparatus similar to the one employed in lead-disc test, is used here. A new block is used for each test. A complete description of the procedure is given as Test No 303 in MIL-STD-331 d ) Explosive Component Output Measurement by Steel Dent. The test is similar to the A1 dent test. It applies only to components producing dents greater than 0.005 and smaller than 0.100 inch in depth. A complete description of the procedure is given as Test No 301.1 in MIL-STD-331... 

Detonator Output Measurement by Lead Disc Test 302 is also briefly described in Vol 4, p D1092-R... 

Shallow convex tablets (jin) containing 300 mg HPMC K15M and 1% magnesium stearate were prepared by direct compression. Disintegration tests were performed in triplicate, using the BP 1988 method, in 600 ml of media at 37°C using discs. Tests were run for a maximum of 2 h. 

There are basically two forms of parallel plate compression plastimeter (a) with both compression plates much larger than the test piece (Figure 6.2(a), plate test) and (b) with one or both plates of approximately the same diameter as the test piece (Figure 6.2(b), disc test). 

Figure 6-2. Forms of parallel plate compression test for plasticity, (a) Plate test (b) Disc test. Broken lines and shading show position of upper plate and shape of test piece after...

ISO previously had two methods for relaxation in compression, a general method using disc test pieces and a method using ring test pieces mainly for tests in liquids. The use of rings reflects the importance of O ring seals and allows the maximum surface area of test piece to be exposed to a test liquid. However, these have now been combined into one standard, IS033845. 

In ISO 815, two sizes of disc test piece are allowed, either 29 mm in diameter and 12.5 mm thick or 13 mm in diameter and 6.3 mm thick, the same as used for creep. The larger size is preferred for low set materials because of the greater accuracy. The measurements of test piece thickness are made using a flat foot and not with a domed foot as was earlier practice (see Section 2.1 in Chapter 7). 

The DIN method is given in ISO 464954. The principle of the machine is illustrated in Figure 11.5 a disc test piece in a suitable holder is traversed across a rotating drum covered with a sheet of the abradant, which is why it is also called the rotary drum abrader. In this way, there is a relatively large area of abradant, each part of which is passed over in turn by the test piece, so that wear of the abradant is uniform and relatively slow. In the standard method there is no provision for changing conditions from those specified, other than a lower force for soft rubbers, but it would be possible to use other abradant cloths or papers and to vary the force on the test piece. The degree of slip is 100% and it would be inconvenient to test in the presence of a lubricant. Although not versatile, the method is very convenient and rapid and well suited to quality control. 

The international standard method given in ISO 8147 uses a disc test piece 3 0.1 mm thick and between 35 and 40 mm in diameter, bonded to metal plates which are approximately 0.1 mm less in diameter than the rubber. The slightly smaller size of the metals is intended to prevent the rubber tearing from the edges of the metals during test. 

To the neutralized filtrate, add sufficient oxalic acid to precipitate calcium and filter. Reneutralize the filtrate with ammonium hydroxide. Charge the filtrate onto a cationic exchange adsorption column containing 1,500 to 2,000 g of IRC-50 Amberlite in its ammonium form. Discard the eluate, wash the resin with water, and elute with 2N ammonium hydroxide. Collect 400 ml fractions and monitor by disc testing with S. aureus ATCC-6538P. Combine active fractions and evaporate to dryness under vacuum obtaining about 28 g of crude Antibiotic 6640 having an activity of about 500 mcm/g. 

Bonded Molybdenum Disulphide Film at Low Contact Stress in a Pin-on-Disc Test (Ref. 179)... 

Fig. 11.4 Disc test with inhibition zones around two (1,2) of five discs. While the zone around disc 1 is clear and easy to measure, that around disc 2 is indistinct. While none of the antimicrobials in discs 3,4 or 5 appear to inhibit the bacterium, synergy (as evidenced by inhibition of growth between the discs) is evident with the antimicrobials in discs 3 and 5. Slight antagonism of the drug in disc 1 by that in disc 3 is evident.

These are really modifications of the earlier cup or ditch-plate procedures where filter-paper discs impregnated with the antimicrobial replace the antimicrobial-filled cups or wells. For disc tests, standard suspensions (e.g. 0.5 McFarland standard) of log phase growth cells are prepared and inoculated onto the surface of appropriate agar plates to form a lawn. Commercially available filter-paper discs containing known concentrations of antimicrobial agent (it is possible to prepare your own discs for use with novel drugs) are then placed on... 

Although there are subtle variations of the disc test used in some countries, the basic principles behind the tests remain similar and are based on the original work of Bauer and colleagues. Some techniques employ a control bacterial isolate on each plate so that comparisons between zone sizes around the test and control bacterium can be ascertained (i.e. a disc potency control). Provided that discs are maintained and handled as recommended by the manufacturer, the value of such controls becomes debatable and probably unnecessary. Con-... 

Perhaps the most convenient and presently accepted method of determining bacterial MICs, however, is the E (Epsilometer)-test. Basically this is performed in a similar manner to the disc test except that nylon strips that have a linear gradient of antimicrobial lyophilized on one side are used instead of the filter-paper impregnated antimicrobial discs. On the other side of the nylon strip are a series... 

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