Pulsatile pump

A schematic ofa pilot plant is shown in Figure 11.5. The pilot plant was 1500 mm wide, 900 mm long and 1500 mm high. Figure 11.6 shows the internal structure of the pilot plant in which 20 microreactors were set up in a constant-temperature bath. The inside of the pilot plant has a lower and upper step structure and it is composed of a flow control system, temperature and reaction control system and monitoring system. The flow control system consisted of non-pulsatile pumps and tanks in the lower step and electromagnetic valves and needle valves in the upper step. The withstand... 

The behaviour of the fluid around the valve can be studied using the steady flow device for the visualization of the flow patterns. With the steady flow device only the behaviour in condition of systolic peak is observable, but it is already a good indication. A pulsatile pump for the visualization of the flow patterns in pulsatile flow condition is being designed. 

Pulsatile Pump Another adjunctive maneuver that is employed to reduce local toxicity and enhance distribution is to place a pulsatile pump in-line with the infusate. The conventional flow rate for intraarte-... 

Sikdar et al. (2004) have used vascular ultrasound to record arterial wall vibrations from ex vivo 3.1 mm lamb arteries that have been partially ligated to model a 40% stenosis. Flow is provided from a pulsatile pump to match flow in a human artery. The apparatus was used to generate stenosis-induced sounds and were recorded by both ultrasound recording of vascular sounds and a fiber-optic microphone. To illustrate the frequency content microphone records a Fourier transform was applied to the microphone data to provide spectral data for both the ultrasound and Doppler records. 

Therapeutic control of AH cells. GnRH is used in hypothalamic infertility in women to stimulate FSH and LH secretion and to induce ovulation. For this purpose, it is necessary to mimic the physiologic intermittent "pulsatile" release (approx, every 90 min) by means of a programmed infusion pump. 

GnRH can stimulate pituitary function and is used to treat infertility caused by hypothalamic hypogonadotropic hypogonadism in both sexes. A portable battery-powered programmable pump and intravenous tubing allows pulsatile GnRH therapy every 90 minutes. 

Flow rate. The flow rate from the pump should be accurate, regardless of the system in which the pump is used. This means that the flow rate actually produced by the pump is the same as that dialled up on the front panel, and that this should not be affected by the rest of the HPLC system (for constant flow pumps, at least). The flow rate should be reproducible and practically free of pulsations. Pulsatile flow can limit the sensitivity of HPLC assays, resulting in a rhythmic variation in the apparent refractive index of the mobile phase flowing through the detector, which ultimately manifests itself in the chromatogram as baseline noise. Various means are employed to attempt to eliminate flow pulsation (see section 5.3). 

Other problems with pneumatic intensifier pumps include the fact that access to the high pressure seals for inspection and maintenance is usually quite restricted, by nature of their design. Because of the way they operate, the flow they produce is inherently highly pulsatile in nature and they also tend to be extremely noisy in use. For these reasons, pumps of this type are not used in general analytical HPLC. However, pneumatic intensifier pumps have found a niche in the packing of HPLC columns, where the intermittent nature of the function and their ability to deliver very high pressures compensate somewhat for their shortcomings in the analytical field. 

A potential drawback of the reciprocating piston pump may by now be apparent. As only the forward stroke of the piston drives eluent through the column, then during the return stroke, flow through the chromatographic system ceases. This makes the flow from a single, unmodified reciprocating piston inherently pulsatile. 

Fig. 12 Diffusion micropump, (a) Schematic set-up. (b) Operating principle, (c) Pump characteristics (1) peristaltic mode, (2) pulsatile mode. Reproduced from (Richter et al. 2009a) by permission of The Royal Society of Chemistry...

The pump can operate in two different modi (Fig. 12b). A peristaltic operation provides a continuous and relatively homogeneous pumping while a pulsatile operation of the pump is realised by a complete emptying of the pump chamber. 

Leyendecker, G.L., L. Wildt M. Hansmann. 1980. Pregnancies following intermittent (pulsatile) administration of GnRH by means of a portable pump ( Zyklomat ) A new approach to the treatment of infertility in hypothalamic amenorrhea. J. Clin. Endocr. Metab. 51 1214-16. 

Cells are cultivated in shaken suspension in nutrient medium and harvested during exponential growth (cell density not higher than 5 X 10 /mL). The cells are washed three times in PB, adjusted in the buffer to 1 x 10 /mL, and 30 mL of the suspension are shaken in 100-mL Erlenmeyer flasks. In strain AX3 the development needs to be stimulated by cAMP pulses, and in strain AX2 the development is enhanced by pulsatile stimulation. For this, cAMP is dropped into the cell suspension every 6 min to 200 nM final concentration at each pulse (for instance, 16 p,L droplets of 4 X 10 M cAMP) applied through a pump, e.g., the peristalsis-ftee pump listed up under Subheading 2.3, item 9 or a medical perfusor pump. 

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