Rapid synthesis of hydrogen bond templated handcuff rotaxanes.

The rapid synthesis of hydrogen bond templated handcuff rotaxanes is described. The isolated rotaxanes were characterized by NMR and IR spectroscopies and high resolution mass spectrometry. This report represents a rare demonstration of preparing (2)handcuff [2]rotaxanes by covalently linking separate axles threaded through the rings of a bis-macrocycle by use of the copper catalyzed azide-alkyne cycloaddition (CuAAC) reaction.

Study of the Natural Auger Suppression Mechanism in Heterostructures through Heteroboundary Engineering.

Planar superlattice devices revolutionized our approach to solid-state technology by reducing the Shockley-Read-Hall losses to negligible levels. Despite these achievements, significant efficiency losses are found in current devices presumably caused by the Auger recombinations. This work present the theoretical considerations of the Auger recombination suppression through heterostructure engineering. It is found that Auger recombinations are suppressed through the heterobarrier-carrier interactions. It is shown that a minima in Auger recombinations exists in type-II and III heterostructures, and can be reached through proper conduction and valence band alignments. Furthermore, the careful consideration of the heterostructure enables natural Auger suppression for high operating temperatures. Dark current based on the optimized heterostructure was computed and found to be over an order of magnitude below the currently reported measurements for the superlattice and QD devices. This research provides crucial information about the underlying physics behind the Auger recombination, enabling future superlattice and quantum dot device optimization.

Evaluation of Whatsapp for Promoting Social Presence in a First Year Undergraduate Radiography Problem-Based Learning Group.

The article reports the findings of an analysis into student postings on a mobile instant messaging service (WhatsApp) established to develop social presence in a small group of first-year undergraduate radiography students. The analysis was carried out using a validated and reported tool specifically designed to identify categories of social presence, developed using the Community of Enquiry theoretical model. The students themselves undertook the analysis, which enhanced validity due to participant verification of findings. Six hundred posts (approximately 10% of the total year's messages) were analysed at key points in the first-year student journey. In conclusion, WhatsApp was able to provide students with a platform to demonstrate all the characteristics relevant for the development of social presence. In addition, its immediacy appeared to offer benefits over embedded social media platforms such as discussion boards.