sci-misc/mendeleydesktop-1.13.7 is unavailable from the upstream website.
I'm dumping it right now
+*mendeleydesktop-1.13.8 (12 Apr 2015) + + 12 Apr 2015; Michael Weber <xmw@gentoo.org> +mendeleydesktop-1.13.8.ebuild, + -mendeleydesktop-1.13.7.ebuild: + Version bump +