Individual images of stained or unstained particles are very noisy, and so hard to interpret. The trains were made of maple and were often left unpainted and unstained. Quantitative phase contrast microscopy is primarily used to observed unstained living cells. Dark field microscopy is a technique for improving the contrast of unstained, transparent specimens. Unstained cells cannot be seen with a light microscope. The methylene blue is reduced in viable cells, leaving them unstained. The single nucleus sometimes is visible in unstained preparations. Her support of troops personifies the "unstained patriotic American womanhood our boys are fighting for". Traditionally wooden boards are made of unstained light and dark brown woods. In such cases, wear easily reveals unstained wood. Hansen observed a number of nonrefractile small rods in unstained tissue sections. Mid- to late-war chests were unstained with black painted lettering. However, when unstained, the nucleus is visible and it usually has two lobes. The professional models are usually made from more select grenadilla wood, and are usually unstained. In 2008, X-ray imaging of an unstained virus was demonstrated.