Emperor Zhang's (r. 75–88 AD) reign came to be viewed by later Eastern Han scholars as the high point of the dynastic house. Subsequent reigns were increasingly marked by eunuch intervention in court politics and their involvement in the violent power struggles of the imperial consort clans. With the aid of the eunuch Zheng Zhong (d. 107 AD), Emperor He (r. 88–105 AD) had Empress Dowager Dou (d. 97 AD) put under house arrest and her clan stripped of power. This was in revenge for Dou's purging of the clan of his natural mother—Consort Liang—and then concealing her identity from him. After Emperor He's death, his wife Empress Deng Sui (d. 121 AD) managed state affairs as the regent empress dowager during a turbulent financial crisis and widespread Qiang rebellion that lasted from 107 to 118 AD.
Who was prevented from leaving their house?
Empress Dowager Dou

The Charaka Samhita, thought to have been written between 300 and 500 AD, mentions a metal which, when oxidized, produces pushpanjan, thought to be zinc oxide. Zinc mines at Zawar, near Udaipur in India, have been active since the Mauryan period. The smelting of metallic zinc here, however, appears to have begun around the 12th century AD. One estimate is that this location produced an estimated million tonnes of metallic zinc and zinc oxide from the 12th to 16th centuries. Another estimate gives a total production of 60,000 tonnes of metallic zinc over this period. The Rasaratna Samuccaya, written in approximately the 13th century AD, mentions two types of zinc-containing ores: one used for metal extraction and another used for medicinal purposes.
What process occurred around the 12th century?
smelting of metallic zinc

A party may claim that a treaty should be terminated, even absent an express provision, if there has been a fundamental change in circumstances. Such a change is sufficient if unforeseen, if it undermined the “essential basis” of consent by a party, if it radically transforms the extent of obligations between the parties, and if the obligations are still to be performed. A party cannot base this claim on change brought about by its own breach of the treaty. This claim also cannot be used to invalidate treaties that established or redrew political boundaries.[citation needed]
What might result in a party to a treaty claiming a treaty should be terminated even absent an express provision for its termination?
a fundamental change in circumstances