Indicator Time Test

The occurrence of stress-corrosion cracking in the martensitic steels is very sensitive to the magnitude of the applied stress. For instance, a 13% chromium martensitic steel tested in boiling 35% magnesium chloride solution (125.5°C) indicated times to failure that decreased abruptly from more than 25(X)h to less than 0.1 h as the applied stress was increased from 620 MPa to about 650 MPa (Fig. 8.25). However, the effects of stress on time to failure are not always so dramatic. For instance, in the same set of experiments times to failure for a 17Cr-2Ni martensitic steel gradually decreased from more than 800 h to about 8 h as the applied stress was increased from 500 MPa to 800 MPa. 

A solution of iodine in aqueous iodide has an intense yellow to brown colour. One drop of 0.05M iodine solution imparts a perceptible pale yellow colour to 100 mL of water, so that in otherwise colourless solutions iodine can serve as its own indicator. The test is made much more sensitive by the use of a solution of starch as indicator. Starch reacts with iodine in the presence of iodide to form an intensely blue-coloured complex, which is visible at very low concentrations of iodine. The sensitivity of the colour reaction is such that a blue colour is visible when the iodine concentration is 2 x 10 " 5 M and the iodide concentration is greater than 4x 10 4M at 20 °C. The colour sensitivity decreases with increasing temperature of the solution thus at 50 °C it is about ten times less sensitive than at 25 °C. The sensitivity decreases upon the addition of solvents, such as ethanol no colour is obtained in solutions containing 50 per cent ethanol or more. It cannot be used in a strongly acid medium because hydrolysis of the starch occurs. 

In these cultured VSMCs, about 56% of the SR released Ca2+ only in response to CPA (and, presumably, InsP3), and about 22% only in response to Caf only about 15% of the SR responded to both CPA and Caf. Moreover, the same stores could be refilled and re-emptied during a 30-60 min period (the longest times tested). These results indicate that the SR Ca2+ stores are organized into (at least) two classes of small compartments that are relatively stable. It is noteworthy that similar results have been reported in other cell types, including neurons and astrocytes (Golovina... 

A search of the available literature failed to produce evidence that methylphenidate has been used by the military to counteract fatigue in operational environments. However, the U.S. Navy has conducted laboratory studies in which military personnel were administered 10 mg methylphenidate or 37.5 mg pemoline during 64 hr of continuous wakefulness. The results indicated that methylphenidate did not produce improvements in objective and subjective sleepiness, or in straightforward measures of performance (27,46). However, when the performance data from a choice-reaction-time test were analyzed for trial-to-trial variance, methylphenidate was found to decrease the variance compared to placebo on the first of 2 days of sleep deprivation. The effect did not continue into the second day (51). As was the case with the vigilance studies (above), the nonsignificant or relatively small effects of methylphenidate may have resulted from the low dosage that was studied. 

Although the effects of caffeine on some aspects of performance may be difficult to establish, the impact of this compound on tasks requiring vigilance or sustained attention is clearer. Lieberman et al. (110) evaluated the impact of 32-, 64-, 128-, and 256-mg doses of caffeine on a four-choice visual reaction time test (10 min), a continuous-performance task (variable duration), and the Wilkinson auditory vigilance test (1 hr). Results indicated that every dose of caffeine improved four-... 

These results were further elaborated by measuring the silane loss over short leaching times for samples cured in air and under vacuum.35 Dehydrated mesoporous silica gel was modified with APTS or APDMS in dry toluene (1 % v/v silane/toluene). Curing was performed for variable times in air at 383 K or under vacuum at 423 K. For UV tests the modified silica was stirred in a salicylic aldehyde/ethanol solution. At indicated times a Sml sample was taken, centrifuged and the supernatant was measured at 404 nm. The loss curves of APTS for variably cured samples are displayed in figure 9.17. The position and profile of the absorbance curves are indicative for the stability of the coating under study. 

FIG. 13.48 Small-strain tensile creep of rigid PVC. Left short-time tests (t < 1000 s) at a te of 2 h after quenches from 90 °C to various temperatures (f/fe < 0.13). The master curve at 20 °C was obtained by time-temperature superposition (compare Section 13.4.8) the dashed curves indicate the master curves at other temperatures. Right, long-term tests (t = 2 x 106 s, fe = 1/2 h, t/te = 1100). The dashed lines are the master curves at 20 and 40 °C for a te of 1/2 h they were derived from the left-hand diagram. From Struik (1977,1978). Courtesy of the author and of Elsevier Science Publishers. 

Figure 24-7 Tear breakup time test. (A) Immediately after several complete bUnks, there is homogeneous tear film stained with sodium fluorescein. (B) Randomly formed dry spot signals conclusion of the test and indicates instability of the tear film.

In vivo toxicity tests involve the direct exposure (via appropriate exposure routes) of hving animals to variable doses of toxins over time, followed by measurement of toxic effects or exposure indicators. Inhalation tests either expose the subject animals to known concentrations of particles in an airstream, or utihze direct intratracheal implantation of the particles in the subject animals (e.g., studies summarized in Johnson and... 

Pregnant women have provided a striking illustration of subcutaneous fat (Taggart ei ai, 1967). The pinch test or, more accurately the skinfold lest, was performed on 84 women during the course of their pregnancy Data were taken at the indicated times, i.e, from week 10 of the pregnancy until 8 weeks after birth (Figure 7.1). Skinfold measurements were acquired at various sites of the body. 

FIGURE 6.33 Lipase-catalyzed release of fatty acids. This study, conducted in a series of test tubes, compared the action of normal lipase on two different substrates. The substrates were VLDLs from two different people, that is, VLDLs from a normal subject (O, ) and VLDLs from a patient with hypertriglyceridemia (A,A). Lipase was added to the test tubes containing a solution of VLDLs. The test tubes were incubated for the indicated times (0 to 45 min) to allow catalytic action. Then the amoimts of free fatty acids liberated were determined. The results demonstrate a steady increase in free fatty acids from the normal VLDLs but no detectable release from the abnormal VLDLs. ITie entire protocol was repeated with an identical amount of normal HDLs added to each test tube before incubation. The results demonstrate that the HDL supplement provoked a slight increase in the rate of liberation of fatty acids from the normal VLDLs ( ) but a dramatic increase in fatty acid liberation from the abnormal VLDLs (A). (Redrawn with permission from Brecken-ridge et al, 1978.)... 

Upon arrival, the sample should be logged in the laboratory record book indicating time of arrival, sample temperature, and pH. The sample should in all cases be analyzed for residual chlorine and, if present, oxidized with sodium thiosulfate before it is employed for toxicity evaluation. A portion of the sample should also be removed for alkalinity and hardness analyses. Often it is necessary to coarse filter the sample to remove floe or suspended debris before testing however, this practice may reduce the sample s toxicity. The remainder of the sample should be kept at 4°C for a period not exceeding 72 h after initial sample collection. It is desirable to employ two separate 24 h composite samples for performing a 96 h acute larval fathead minnow test. This would allow renewal after 48 h exposure. In the 7 day tests with Ceriodaphnia and Pimephales, three separate 24 h composite samples should be employed for daily renewal of the various exposure solutions. Toxicity data summary sheets should include daily routine physico-chemical measurements and sample information. It is essential that good laboratory practices be used in all aspects of sample collection, treatment, and analysis to obtain quality and defensible results. 

Figure 10.7 (a) Failure lines for grouted and ungrouted granular soils, (b) Drained triaxial test results for silicate grouted coarse and medium sands. (From Ref. 11.15.) (c) Typical stress-strain curve from unconfined compression test on chemically grouted sand, (d) Compression versus time data for creep test on chemically grouted sand, under constant load, (e) Failure time versus percent of unconfined compression failure load. (+) indicates unconfined compression tests, and ( ) indicates triaxial tests with S3 = 25% of Si. 

The pattern used for cutting test specimens is shown in Figure 3. The property values given in this report are mean values of the number of specimens indicated times two since each board was duplicated. Densities were measured on all thickness swell, internal bond (IB) and bending modulus specimens before those respective tests were run. 

Fig. 7.67 Correlation of EPR test values on type 316 stainless steel with ASTM A 262E test for susceptibility to intergranular corrosion. Circles indicate time-temperature treatments prior to test. Numbers at points are EPR values (Pa) of the same steel. C-curve defines times beyond which steel does not pass ASTM A 262E. Redrawn from Ref 105...

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