Phosphatidylcholine (lecithin, PC) and cholesterol (Ch) were chosen for the study because they are present in biological membranes and they fulfil essential functions in lively organisms.
They apparently do not represent age-related acquired atrophy of capillaries because they are present at all ages and do not progressively increase with normal aging.
The fusion glycoproteins have been difficult to study because they are present in a labile, metastable form at the surface of infectious virions.
In recent years, researchers have focused on mucins as possible tumor markers because they are present in abnormally high levels in multiple types of cancer.
These elements were chosen because they are present in significant amounts in commercially available zinc ingots, and at the tested temperature aluminum is completely soluble in zinc while lead and zinc form an emulsion.
Crystallins are named as such because they are present in the crystal-clear lens.
Titanite, perovskite, and vesuvianite were not included in the analysis because they are present only in small amounts.
Nickel and vanadium are particularly noticed because they are present in high concentrations and have the most detrimental effects on the cracking performance of the FCC catalyst.
Due to the mineralogical and electrochemical properties of many soils, some essential mineral nutrients are unavailable to plants because they are present in insoluble forms [105].
Among different fixed orthodontic appliances, wires could play a significant role in enamel demineralization because they are present throughout the period of orthodontic treatment.
The H2, H3 and H4 centers are important because they are present in many natural diamonds and their optical absorption can be strong enough to alter the diamond color (H3 or H4 – yellow, H2 – green).
