New World Gold: Cultural Anxiety and Monetary Disorder in Early Modern Spain (2010). External links

"Gold" . Encyclopædia Britannica. Vol. 11 (11th ed.). 1911. Chemistry in its element podcast (MP3) from the Royal Society of Chemistrys Chemistry World: Gold www.rsc.org
Gold at The Periodic Table of Videos (University of Nottingham)
Getting Gold 1898 book, www.lateralscience.co.uk
Technical Document on Extraction and Mining of Gold at the Wayback Machine (archived 7 March 2008), www.epa.gov
Gold element information - rsc.org
Three of the major opioid receptors include mu, kappa, delta, and nociception, each playing a role in eliciting the effects associated with opioids. An opioid overdose results from over-activation of these receptors, which can cause permanent brain damage from cerebral hypoxia or neurotoxicity.Mu receptors have an analgesic effect on the brain, and are found in various parts of the nervous system including the cerebral cortex and thalamus. They can be found in the nucleus accumbens, the pleasure centre of the brain, as well as the amygdala. Kappa receptors, in the hypothalamus, produce a similar analgesic effect. They bind with dynorphins to stimulate anti-reward effects —dysphoria— and other negative effects of withdrawal. While mu receptors are the source of addiction, kappa receptors contribute to continued abuse. They generate dysphoria in response to increasing stress levels via corticotropin-releasing factor (CRF). This increases erratic shifts in mood during withdrawal period and can prompt relapse. Delta receptors, found in the basal ganglia of the limbic system, have been shown to reduce anxiety by binding with enkephalins, although this requires further research. The most recent addition to these receptors are nociception opioid receptors. Although they have been determined to be receptors to certain ligands from opioids, their role has not yet fully understood.When opioids are ingested, the ligand binds to these constitutively active receptors to reduce neural activity. This is accomplished by inhibiting adenylyl cyclase and cyclic AMP, which are necessary for communication within the central nervous system.