Arnold has been acquired by Hornby, just like some other European brands of the 'old days' such as Rivarossi, Jouef and Lima.
You can find them on the German Hornby website:
www.hornby.de, or on the Hornby International website:
http://arnold.hornbyinternational.comAnyRail includes their 1:160 (N) track library, although it still uses the old part numbers.
David.