GaMnAs: layers, wires and dots

Thin layers of GaMnAs ferromagnetic semiconductor grown by molecular beam epitaxy on GaAs(001) substrates were studied. To improve their magnetic properties the post-growth annealing procedures were applied, using the surface passivation layers of amorphous arsenic. This post growth treatment effectively increases the ferromagnetic-to-paramagnetic phase transition temperature in GaMnAs, and provides surface-rich MnAs layer which can be used for formation of low dimensional structures such as superlattices. If the surface rich MnAs layer consists of MnAs dots, then it is possible to grow Mn-doped GaAs nanowiresComment: 15 pages, 14 figures. To be published in Proc. XXXVII International School on the Physics of Semiconducting Compounds "Jaszowiec 2008", June 2008, Polan

Transition of Governance in a Mature Open Software Source Community: Evidence from the Debian Case

As flourishing, productive open source software (OSS) communities mature, they have to introduce a variety of governance mechanisms to manage the participation of their members and to coordinate the launch of new releases. In contrast to other modes of governance of OSS communities, the Debian community introduced new mechanisms of informal administrative control based on a constitution, elected leaders and new functions attributed to interactive communication channels (like mailing lists or IRC channels) that can provide for community effects (and feedback). We show that these control mechanisms were introduced as a response to emerging innovative opportunities due the usage of source packages and heterogeneous learning processes by different groups within the Debian community.Open Source Software community, Governance Mechanism, Debian Community

Conditional Preference for Flexibility: Eliciting Beliefs from Behavior

Following Kreps (1979), we consider a decision maker with uncertain beliefs about her own future taste. This uncertainty leaves the decision maker with preference for flexibility: When choosing among menus containing alternatives for future choice, she weakly prefers larger menus. Existing representations accommodating this choice pattern cannot distinguish tastes (indexed by a subjective state space) and beliefs (a probability measure over the subjective states) as different concepts, making it impossible to relate parameters of the representation to choice behavior. We allow choice among menus to depend on exogenous states, interpreted as information. Our axioms yield a representation that uniquely identifies beliefs, provided the impact of information on choice is rich. The result is suggested as a choice theoretic foundation for the assumption, commonly made in the incomplete contracting literature, that contracting parties, who know each other's ranking of contracts, also share beliefs about each others future tastes in the face of unforeseen contingencies.Preference for Flexibility; Uniqueness; Contracts; Subjective Uncertainty