Vitamin K antagonists (VKA) are a group of substances that reduce blood clotting by reducing the action of vitamin K. They are used as anticoagulant medications in the prevention of thrombosis, and in pest control, as rodenticides. 1  1 Mechanism of action.  2 Coumarins (4-hydroxycoumarins)
Calculate the average atomic mass of oxygen. Solution: ((15.994915*99.757) + (16.999132*0.038) + (17.999160*0.205))/100 = 15.999405 . Using our equation for determining average atomic mass, we see that the average atomic mass for oxygen is 15.999405 amu. If we check the periodic table, we will see that our average atomic mass is the same as the atomic mass indicated on the element oxygen. Ã
(This is the most commonly asked question) Oxygen levels are commonly measured by two techniques. The first is a blood gas in which a blood sample is taken directly from an artery. This is the most accurate assessment of oxygen. The normal oxygen level using this technique is 80-100 (mmHg). The second technique is bloodless and is called pulse oximetry. The result here is not a direct measurement of oxygen but rather represents the percentage of hemoglobin that is saturated with oxygen.