The Net (substance) The Net (substance) The Net, in alchemy, is an alloy of copper and iron, whose crystal structure induces a network pattern on its surface. It was described in the 17th century by Sir Isaac Newton. Newton produced the substance by following what he regarded as a recipe, encoded in classical mythology, for part of the process of achieving the philosopher's stone. The relevant myth involved the god Vulcan finding his wife Venus (alchemical symbol for copper) in bed with the god Mars (alchemical symbol for iron) Newton's interpretation rested on typical alchemical associations, construing Vulcan as a stand-in for fire,
Substance use disorder Substance use disorder A substance use disorder (SUD), also known as a drug use disorder, is a medical condition in which the use of one or more substances leads to a clinically significant impairment or distress. Substance use disorders are characterized by an array of mental, physical, and behavioral symptoms that may cause problems related to loss of control, strain to one's interpersonal life, hazardous use, tolerance, and withdrawal. Drug classes that are involved in SUD include alcohol, opioids, stimulants, tobacco, hallucinogens, phencyclidine, inhalants, and sedatives. Worldwide 275 million people were estimated to have used an illicit drug in 2016.