Dwell-time length

In PD, prewarmed dialysate is instilled into the peritoneal cavity where it dwells for a specified length of time (usually one to several hours, depending on the type of PD) to adequately clear metabolic waste products. At the end of the dwell time, the dialysate is drained and replaced with fresh dialysate. The continuous nature of PD provides for a more physiologic removal of waste products from the bloodstream, which mimics endogenous renal function by decreasing the fluctuations seen in serum concentrations of the waste products. Similarly, water is removed at a more constant rate, lessening the fluctuations in intravascular fluid balance and providing for more hemodynamic stability. 

The toasting step is now frequently carried out by passing the branches through a perforated rotating metal cylinder in an inclined position over an open fire. The cylinders used are about 2 to 2.5 m in diameter and 4 m in length. Dwell time is very short. The process is called sepecadora . 

The dwell time is the time spent acquiring data at each of the channels which make up a peak in the mass spectrum. The length of time is measured in fractions of a millisecond, and will ultimately affect the frequency with which data is acquired at each mass. This will have a bearing on the final precision of the isotope ratio because of the influence of various sources of noise on the analytical signal. 

Based on the assumption of a 30 second dwell time, an oven length of 150 feet is indicated. An oven 6 feet wide by 2 feet deep is assumed with end openings of 0.5 feet by 6 feet. The total surface area of the oven is 2570 square feet. The end openings are 6 square feet in area. Based upon heat loss figures of 0.3 BTU/ft /hr and 54 BTU/ft /hr respectively for the oven surface and its end openings, the respective heat loss figures for the oven are 409,000 and 172,000 BTU/hr for an ambient temperature of 70 F. 

Fig. 17.12. Unfolding data obtained from ubiquitin, Ubig, polyproteins at a constant pulling force of 110 pN. (a) The length versus time traces show 20 nm stepwise increases in length each time a single protein domain unfolds. The time of occurrence of the unfolding events (At) is probabilistic, (b) Histogram of unfolding dwell times is measured at 110 pN. The dashed line is a single exponential fit with an unfolding rate, fc, of 0.6 s [10,18]. The solid line is a stretched exponential fit with p(t) = exp[—(fct) ] with b = 0.7...

Mechanical Definitions of dwell and contact times disregard material properties and concentrate on press and punch geometry (Fig. 17). Contact time can be defined as the time the punch is in contact with the compression wheel. Dwell time is defined as the time the flat portion of punch head is in contact with the compression wheel (time at maximum punch displacement, or time when the punch does not move in vertical direction). In dwell time calculations, the length of the punch head flat and horizontal component of punch speed (as determined by RPM and pitch circle diameter) are used. In case of a round head tooling, the dwell time, as defined here, is zero. But it should be kept in mind that mechanical definition is given here as a convention, a yardstick, or a common measure, to compare press speeds for different presses, and its absolute value is meaningless. A proposed convention to quantify linear speed of a press is to use an... 

The only reliable means to overcome these problems in punch-and-die presses is to employ hydraulic actuation of the punch(es) (Fig. 8.95b). The timing of the punch strokes as well as the rate of increasing or decreasing pressure and the dwell time can be easily adjusted. In addition, hydraulic presses typically feature overload protection by gas filled accumulators and, because there is no physical limit to the length of the stroke, densification ratios can be very high, thus allowing successful compaction of large amounts of feed even if its initial bulk density is low. 

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