Answer the question at the end by quoting:

Dafydd Rhys "Dave" Williams OC (born May 16, 1954) is a Canadian physician, public speaker and a retired CSA astronaut. Williams was a mission specialist on two space shuttle missions. His first spaceflight, STS-90 in 1998, was a 16-day mission aboard Space Shuttle Columbia dedicated to neuroscience research. His second flight, STS-118 in August 2007, was flown by Space Shuttle Endeavour to the International Space Station.
In January 1995, Williams was selected to join the 1995 international class of NASA mission specialist astronaut candidates. He reported to the Johnson Space Center in March 1995 and completed training and evaluation in May 1996. On completing basic training, he was assigned to work technical issues for the payloads/habitability branch of the astronaut office. From July 1998 to November 2002, Williams served as Director of the Space and Life Sciences directorate with responsibility for research in both physical and biomedical space sciences at the Johnson Space Center (JSC). With this appointment, he became the first non-American to hold a senior management position within NASA. Overall crew medical safety was one of his principal concerns, in addition to flight medical operations and JSC occupational and environmental health. His programs were directed toward protecting astronauts from the hazards of the space environment, including space radiation and microgravity, in addition to maintaining their medical, physical, and psychological well-being while aloft and on return to Earth. His other oversight responsibilities were in the fields of telemedicine, 3-D tissue culture/regeneration in microgravity, the curatorial management of extraterrestrial materials, and of qualifying humans for very long space journeys and ensuring their safe return to Earth. Williams served as an aquanaut on the first NEEMO (NASA Extreme Environment Mission Operations) crew aboard the Aquarius underwater laboratory in October 2001. During this mission, he was thrilled to shake hands underwater with Canadian underwater explorer Joe MacInnis. Williams was originally scheduled to command NEEMO 7 in October 2004, but was replaced by back-up crewmember and fellow CSA astronaut Robert Thirsk due to Williams undergoing review of a temporary medical issue. In April 2006, Williams commanded the NEEMO 9 mission. During this eighteen-day mission, the six-person crew developed lunar surface exploration procedures and telemedical technology applications.

What caused him to join NASA?

In January 1995, Williams was selected to join the 1995 international class of NASA mission specialist astronaut candidates.

Answer the question at the end by quoting:

Celtic art is associated with the peoples known as Celts; those who spoke the Celtic languages in Europe from pre-history through to the modern period, as well as the art of ancient peoples whose language is uncertain, but have cultural and stylistic similarities with speakers of Celtic languages. Celtic art is a difficult term to define, covering a huge expanse of time, geography and cultures. A case has been made for artistic continuity in Europe from the Bronze Age, and indeed the preceding Neolithic age; however archaeologists generally use "Celtic" to refer to the culture of the European Iron Age from around 1000 BC onwards, until the conquest by the Roman Empire of most of the territory concerned, and art historians typically begin to talk about "Celtic art" only from the La Tene period (broadly 5th to 1st centuries BC) onwards. Early Celtic art is another term used for this period, stretching in Britain to about 150 AD.
From the 5th to the mid-9th centuries, the art of the Picts is primarily known through stone sculpture, and a smaller number of pieces of metalwork, often of very high quality; there are no known illuminated manuscripts. The Picts shared modern Scotland with a zone of Irish cultural influence on the west coast, including Iona, and the Anglo-Saxon kingdom of Northumbria to the south. After Christianization, Insular styles heavily influenced Pictish art, with interlace prominent in both metalwork and stones. Pictish stones are assigned by scholars to 3 classes. Class I Pictish stones are unshaped standing stones incised with a series of about 35 symbols which include abstract designs (given descriptive names such as crescent and V-rod, double disc and Z-rod, 'flower' and so on by researchers); carvings of recognisable animals (bull, eagle, salmon, adder and others), as well as the Pictish Beast, and objects from daily life (a comb, a mirror). The symbols almost always occur in pairs, with in about one-third of cases the addition of the mirror, or mirror and comb, symbol, below the others. This is often taken to symbolise a woman. Apart from one or two outliers, these stones are found exclusively in north-east Scotland from the Firth of Forth to Shetland. Good examples include the Dunnichen and Aberlemno stones (Angus), and the Brandsbutt and Tillytarmont stones (Aberdeenshire). Class II stones are shaped cross-slabs carved in relief, or in a combination of incision and relief, with a prominent cross on one, or in rare cases two, faces. The crosses are elaborately decorated with interlace, key-pattern or scrollwork, in the Insular style. On the secondary face of the stone, Pictish symbols appear, often themselves elaborately decorated, accompanied by figures of people (notably horsemen), animals both realistic and fantastic, and other scenes. Hunting scenes are common, Biblical motifs less so. The symbols often appear to 'label' one of the human figures. Scenes of battle or combat between men and fantastic beasts may be scenes from Pictish mythology. Good examples include slabs from Dunfallandy and Meigle (Perthshire), Aberlemno (Angus), Nigg, Shandwick and Hilton of Cadboll (Easter Ross). Class III stones are in the Pictish style, but lack the characteristic symbols. Most are cross-slabs, though there are also recumbent stones with sockets for an inserted cross or small cross-slab (e.g. at Meigle, Perthshire). These stones may date largely to after the Scottish takeover of the Pictish kingdom in the mid 9th century. Examples include the sarcophagus and the large collection of cross-slabs at St Andrews (Fife). The following museums have important collections of Pictish stones: Meigle (Perthshire), St Vigeans (Angus) and St Andrew's Cathedral (Fife) (all Historic Scotland), the Museum of Scotland, Edinburgh (which also exhibits almost all the major pieces of surviving Pictish metalwork), the Meffan Institute, Forfar (Angus), Inverness Museum, Groam House Museum, Rosemarkie and Tarbat Discovery Centre, Portmahomack (both Easter Ross) and Tankerness House Museum, Kirkwall, Orkney.

Were they in Scotland?
The Picts shared modern Scotland with a zone of Irish cultural influence on the west coast,