Ola Bratteli and his diagrams

This article discusses the life and work of Professor Ola Bratteli (1946--2015). Family, fellow students, his advisor, colleagues and coworkers review aspects of his life and his outstanding mathematical accomplishments.Comment: 18 pages, 15 figure

Self-reducing copper nanocrystals : how surface chemistry affects sintering

Copper nanocrystals (Cu NC) are actively investigated as substitutes for costly silver nanocrystals in conductive inks. However, to be of any use for printed conductors, oxidation of Cu NCs to non-conductive copper oxides must be avoided. Here, we analyze the interplay between the Cu NC surface termination, oxidation suppression and bulk copper formation through thermal annealing using 3 nm Cu NCs synthesized via thermal decomposition of copper formate in oleylamine (OLA). By adapting the method introduced by Sun et al,1 we obtain stable Cu NC dispersions that do not oxidize when stored under inert atmosphere, while showing a rapid conversion into copper oxide when exposed to air or deposited to form a thin NC film. Using solution 1H NMR spectroscopy, we demonstrate that as-synthesized Cu NCs are capped by OLA. OLA is tightly bound at NMR time scales, yet slowly desorbes during storage of the Cu dispersions, a process that is accelerated by oxygen exposure. Addition of carboxylic acids leads to the displacement of OLA from the Cu NCs and the formation of a denser ligand shell, probably consisting of dissociated carboxylic acids. We demonstrate that carboxylic acid ligands make Cu NCs more oxidation proof and facilitate the conversion of films of oxidized Cu NCs into a dense copper film. This offers the prospects of using colloidal Cu NCs as main constituent in conductive, nano-copper inks for applications in printed electronics

Ola de la Vida:a social play game

Ola de la Vida (ODLV) is a three-player cooperative game which was produced over the course of 48 hours within Global Game Jam in January 2017, at the Abertay University Jam Site.The Game is a playful intervention (an objects or events which seek to bring people together through play) that aims to invite players to form temporary relationships with their co-players through physical contact, collaboration and coaching during play in a co-located context (i.e. where all players are present in the same play space). The game also seeks to expand the play experience beyond the three players to the wider audience by inviting spectatorship through play as performance.The game was designed by Mona Bozdog, Lynn Parker, Danny Parker, and Alex Pass. Since its inception, it has undergone significant development to enhance its usability (through tutorials) and its features to enhance the development of a community of play, including the introduction of clear player scores and high scores for the game. Lynn Parker contributed to the design of physical interactions within the game, the enhancement of usability through tutorials and scores and the creation of digital art for the game in partnership with Alex Pass.Ola De La Vida as a practice as research work offers design insight into use of spectatorship to create a temporary community around a game and to enhance the facilitation of discussion between active players, previous players, spectators, and semi-spectators. The work builds on the varying levels of participation in play, proposing semi-spectatorship: where players are active in a game but have a critical distance afforded to them by the design of the game which offers them and their co-players (where appropriate) potential benefits in play

Steven Bornstein, Associate Professor of Communication Sciences and Disorders, College of Health and Human Services, Travels to Rusia

Professor Steven Bornstein traveled to Russia in November 2008 to present a paper at Mari-State University in Yoshkar-Ola, Russia, on the effects of hearing loss on oral language and speech development

Hardness of Vertex Deletion and Project Scheduling

Assuming the Unique Games Conjecture, we show strong inapproximability results for two natural vertex deletion problems on directed graphs: for any integer $k\geq 2$ and arbitrary small $\epsilon > 0$, the Feedback Vertex Set problem and the DAG Vertex Deletion problem are inapproximable within a factor $k-\epsilon$ even on graphs where the vertices can be almost partitioned into $k$ solutions. This gives a more structured and therefore stronger UGC-based hardness result for the Feedback Vertex Set problem that is also simpler (albeit using the "It Ain't Over Till It's Over" theorem) than the previous hardness result. In comparison to the classical Feedback Vertex Set problem, the DAG Vertex Deletion problem has received little attention and, although we think it is a natural and interesting problem, the main motivation for our inapproximability result stems from its relationship with the classical Discrete Time-Cost Tradeoff Problem. More specifically, our results imply that the deadline version is NP-hard to approximate within any constant assuming the Unique Games Conjecture. This explains the difficulty in obtaining good approximation algorithms for that problem and further motivates previous alternative approaches such as bicriteria approximations.Comment: 18 pages, 1 figur

Cosmic Magnetic Fields from Particle Physics

I review a number of particle-physics models that lead to the creation of magnetic fields in the early universe and address the complex problem of evolving such primordial magnetic fields into the fields observed today. Implications for future observations of the Cosmic Microwave Background (CMB) are briefly discussed.Comment: 8 pages, 1 figure, talk presented at the 7th International Symposium on Particles, Strings and Cosmology (PASCOS-99) at Granlibakken, Lake Tahoe, 10-16 Dec 1999, to appear in the proceeding