Arrival-Time Gauges

These are some of the oldest, yet still the most useful gauges in shock-wave research. They contribute mainly to shock-velocity measurements. In some cases, these gauges alone can provide accurate Hugoniot equation-of-state 

Arrival time gauges alone can lead to equation-of-state data in other ways, as well, but they are most often used in conjunction with other gauges to be described later. Three different arrival time gauges are discussed below. 

Fiber-Optic Pins. In one version of the fiber-optic pin (Benjamin et al., 1984), a small microballoon, 0.25 mm in diameter, filled with a noble gas such as argon or xenon is attached to the end of an optical fiber. When the pin is impacted, the shock heats the gas in the microballoon producing a flash which is channeled to a recording system via optical fibers. Some of the useful features of this pin are 

Shock Luminescence. Some transparent materials give off copious amounts of light when shocked to a high pressure, and thus they can serve as shock arrival-time indicators. A technique used by McQueen and Fritz (1982) to measure arrival times of release waves is based on the reduction of shock-induced luminescence as the shock pressure is relieved. Bromoform, fused quartz, and a high-density glass have been used for their shock luminescence properties. 

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The gauge records eimbient pressure Pq. At arrival time ta, the pressure rises quite abruptly (discontinuously, in an ideal wave) to a peak value Pj + Pq. The pressure then decays to ambient in total time tg + T+, drops to a partial vacuum of amplitude Pj, and eventually returns to Po in total time tg + T+ + T. The quantity P is usually termed the peak side-on overpressure, or merely the peak overpressure. The portion of the time history above initial ambient pressure is called the positive phase, of duration T+. That portion below Po, of amplitude Ps and duration T, is called the negative phase. 

Many different proteins exist in a single cell. A detailed study of the properties of any one protein requires a homogeneous sample consisting of only one kind of molecule. The separation and isolation, or purification, of proteins constitutes an essential first step to further experimentation. In general, separation techniques focus on size, charge, and polarity—the sources of differences between molecules. Many techniques are performed to eliminate contaminants and to arrive at a pure sample of the protein of interest. As the purification steps are followed, we make a table of the recovery and purity of the protein to gauge our success. Table 5.1 shows a typical purification for an enzyme. The percent recovery column tracks how much of the protein of interest has been retained at each step. This number usually drops steadily during the purification, and we hope that by the time the protein is pure, sufficient product will be left for study and characterization. The specific activity column compares the purity of the protein at each step, and this value should go up if the purification is successful. 

The tube is created with a squared cross section, 10 pm wide. The driver and driven section have equal lengths. The driver and driven sections are separated by a membrane, and the test section is prefilled with the test gas during fabrication. The top side of the tube is made of a plate comprising direct-sensing piezoelectric gauges, used for timing the arrival of pressure waves. 

According to the pressure records under the layer of PUR foam (curves 3,4), the reflection process inside the foam is fitted satisfactorily by numerical simulation. After the arrival of the expansion wave R at the end of shock tube, numerical and natural pressure time histories are significantly different. Wall pressure minimum (t 8) in simulation is only 50% from gauge data. This fact probably is caused by gas filtration through pores. 

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