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On 7 June 1981, the Israeli air force destroyed Iraq's sole nuclear reactor, in order to impede Iraq's nuclear weapons program. The reactor was under construction just outside Baghdad. Following a series of PLO attacks in 1982, Israel invaded Lebanon that year to destroy the bases from which the PLO launched attacks and missiles into northern Israel. In the first six days of fighting, the Israelis destroyed the military forces of the PLO in Lebanon and decisively defeated the Syrians. An Israeli government inquiry – the Kahan Commission – would later hold Begin, Sharon and several Israeli generals as indirectly responsible for the Sabra and Shatila massacre. In 1985, Israel responded to a Palestinian terrorist attack in Cyprus by bombing the PLO headquarters in Tunis. Israel withdrew from most of Lebanon in 1986, but maintained a borderland buffer zone in southern Lebanon until 2000, from where Israeli forces engaged in conflict with Hezbollah.

When did the Israeli air force destroy Iraq's sole nuclear reactor?
Answer: 7 June 1981
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The earthquake also provided opportunities for researchers to retrofit data in order to model future earthquake predictions. Using data from the Intermagnet Lanzhou geomagnetic observatory, geologists Lazo Pekevski from the Ss. Cyril and Methodius University of Skopje in Macedonia and Strachimir Mavrodiev from the Bulgarian Academy of Sciences attempted to establish a "time prediction method" through collecting statistics on geomagnetism with tidal gravitational potential. Using this method, they were said to have predicted the time of the 2008 Sichuan earthquake with an accuracy of ±1 day. The same study, however, acknowledges the limitation of earthquake prediction models, and does not mention that the location of the quake could be accurately predicted.

What did they try to establish?
Answer: time prediction method
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Archival descriptions of the permanent holdings of the federal government in the custody of NARA are stored in Archival Research Catalog (ARC). The archival descriptions include information on traditional paper holdings, electronic records, and artifacts. As of December 2012, the catalog consisted of about 10 billion logical data records describing 527,000 artifacts and encompassing 81% of NARA's records. There are also 922,000 digital copies of already digitized materials.

Where are archival descriptions of holdings under the custody of NARA stored?
Answer:
Archival Research Catalog (ARC)