In this Article. In this Article. A solitary pulmonary nodule (SPN) is a single abnormality in the lung that is smaller than 3 cm in diameter. Generally, a pulmonary nodule must grow to at least 1 cm in diameter before it can be seen on a chest X-ray.
Osmosis is the scientific process of transferring fluid between molecules. When molecules move in and out of a cell to achieve the same concentration of something, like salt, on both sides, then osmosis is happening.
Osmosis is diffusion through a membrane. The membrane acts as a barrier between two solutions of different concentration. One substance (usually water) travels from an area of high concentration to one of low concentration. Osmosis can be compared to the examples of diffusion given above involving perfume and ink.