1 For best results from your flask, before use, pre-fill for about 3 minutes, using either hot water for hot drinks or cold water for chilled drinks. 2  Never use a microwave or conventional oven to pre-heat your flask.  If your flask has not been used for some time, rinse with warm water to remove any residual odours.
2. : the degree to which something is prevalent; especially: the percentage of a population that is affected with a particular disease at a given time.
Cancer prevalence is defined as the number of living people who have ever been diagnosed with cancer. It includes people diagnosed with cancer in the past as well those who were recently diagnosed. Cancer prevalence is determined by how often a cancer occurs (incidence) and by how long people normally live after diagnosis (survival). This means prevalence counts are highest for the most common cancers with the longest survival.