further from the same text:
"
It is now generally accepted that the Proto-Semitic aspectual system
is to be reconstructed to resemble that found in Akkadian. This system
contains two prefixal forms, one *ya-prus 'he separated' (perfective),
and another, *ya-paras 'he is separating' (imperfective). The third
prefix conjugation exists only in Akkadian as the perfect form
i-p-t-aras 'he has separated'. Its Proto-Semitic status has been
proposed by Voigt (1987) on the basis of further evidence from Berber
and Bedawye (North Cushitic). Of fundamental importance for the later
developments in Semitic is the ambivalence of the reconstructed
'middle-perfect' form *ya-p-t-aras (intransitive *ya-q-t-arVb 'he is
close' and 'he got close') between the perfect and the mediopassive
perfective (cf. Bubenik 2003).
"
cf
http://www.dabis.at/Anwender.htm/Alscher/afroasia.htm
Akkadian, preterite singular
a-
ta-
i-
PIE, perfect singular
*-h2-e -> *-a
*-th2-e -> *-ta
*-Ø-e -> *-e
Torsten