As for Amitai -- I don't have any previous knowledge of this particular name being used for girls, but people who should know have told me that in
Israel during the past 20 years a whole host of formerly exclusively male names have been given to girls. The phenomenon of giving daughters formerly male names has been even more popular there than it has been in the English speaking world, according to my correspondents.
The Penguin Book of Hinud Names by Maneka Gandhi claims that Niraj meant "to illuminate, irradiate" and that Bina means "lute".