The goal was to eliminate undesirable character traits. Any unexpected or undesirable behavior is a symptom. Bias in surveys is undesirable, but often unavoidable. Regulations ensure that all housing units are expensive enough to prevent access by undesirable groups. Boiling the wort ensures its sterility, helping to prevent contamination with undesirable microbes. It also helps prevent ants from concentrating on an undesirable trail. The imagined outcomes are either positive/desirable, negative/undesirable, or neutral. Aggressive behavior toward humans is uncharacteristic of the breed and highly undesirable. Exciton recombination is undesirable and higher levels lead to an inefficient photocatalyst. Then war is considered to be necessary though undesirable but means. Risk is often measured as the expected value of an undesirable outcome. Banning DEAs might not be as effective at deterring undesirable users. Those lists include the names of authors whose works were deemed as undesirable. This was necessary in order to keep out undesirable people and stray animals. Safety pharmacology specialises in detecting and investigating potential undesirable effects of drugs.