Underfill theory

This is the presence of excess fluid in the peritoneal cavity, leading to a swollen abdomen (Figure 4.3). The accumulation of ascitic fluid represents a state of sodimn excess in the body. Patients often present with hyponatraemia, but this is thought to be due to the dilutional effect of excess water rather than to low sodium. There are three theories of the cause of ascites formation. The underfill theory suggests that there is a reduction in circulating plasma volume as a result of accumulation in the splanchnic area due to vascular dilatation in portal hypertension. This activates the plasma renin, aldosterone and sympathetic nervous systems, which leads to sodium and water retention by the kidneys. 

To explain the complex mechanisms of ascites formation, four hypotheses have been developed in the light of experimental and clinical findings (i.) underfill theory, (2.) overflow theory, (5.) lymph imbalance theory, and 4.) vasodilation theory, (s. fig. 16.6)... 

Underfill theory According to the underfill theory (S. Sherlock et al., 1963), the development of ascites is set off by mechanical factors and physical mechanisms ( imbalance of the Starling forces ). As a result, the effective plasma volume is reduced (so-called volume deficiency concept). 

Lymph imbalance theory The lymph imbalance theory (C.L. Witte et al., 1980) (16) contradicts the classical concepts of underfill and overflow. This theory is based... 

Adhesives used to fill spaces underneath a flip-chip device or BGA package must flow readily and rapidly when dispensed at the edges of the chip in order to completely fill the gap and free space surrounding the solder bumps. To be effective, the adhesive must be drawn into the narrow space by capillary action. The theory behind underfilling is based on capillary-flow behavior between closely spaced parallel plates (Fig. 2.5) by considering the drop in pressure (p) across a liquid-vapor interface ... 

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