Strong geometric frustration in model glassformers

We consider three popular model glassformers, the Kob-Andersen and Wahnstr\"om binary Lennard-Jones models and weakly polydisperse hard spheres. Although these systems exhibit a range of fragilities, all feature a rather similar behaviour in their local structure approaching dynamic arrest. In particular we use the dynamic topological cluster classification to extract a locally favoured structure which is particular to each system. These structures form percolating networks, however in all cases there is a strong decoupling between structural and dynamic lengthscales. We suggest that the lack of growth of the structural lengthscale may be related to strong geometric frustration.Comment: 14 pages, Accepted by J. Non-Crystalline Solids, 7th International Discussion Meeting on Relaxation in Complex Systems Proceeding

Ultrafast electroabsorption dynamics in an InAs quantum dot saturable absorber at 1.3 mu m

The authors report a direct measurement of the absorption dynamics in an InAs p-i-n ridge waveguide quantum dot modulator. The carrier escape mechanisms are investigated via subpicosecond pump-probe measurements at room temperature, under reverse bias conditions. The optical pulses employed are degenerate in wavelength with the quantum dot ground state transition at 1.28 mu m. The absorption change recovers with characteristic times ranging from 62 ps (0 V) to similar to 700 fs (-10 V), showing a decrease of nearly two orders of magnitude. The authors show that at low applied fields, this recovery is attributed to thermionic emission while for higher applied fields, tunneling becomes the dominant mechanism. (c) 2006 American Institute of Physics.</p

Identification of structure in condensed matter with the topological cluster classification

We describe the topological cluster classification (TCC) algorithm. The TCC detects local structures with bond topologies similar to isolated clusters which minimise the potential energy for a number of monatomic and binary simple liquids with $m\leq13$ particles. We detail a modified Voronoi bond detection method that optimizes the cluster detection. The method to identify each cluster is outlined, and a test example of Lennard-Jones liquid and crystal phases is considered and critically examined.Comment: 28 pages, 28 figure

Structural changes in gill DNA reveal the effects of contaminants on Puget Sound fish.

Structural differences were identified in gill DNA from two groups of English sole collected from Puget Sound, Washington, in October 2000. One group was from the industrialized Duwamish River (DR) in Seattle and the other from relatively clean Quartermaster Harbor (QMH). Chemical markers of sediment contamination [e.g., polynuclear aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs)] established that the DR was substantially more contaminated than QMH. The levels of these chemicals in the sediments of both sites were consistent with levels of cytochrome P450 1A (CYP1A) expression in the gills of English sole from the same sites. Structural differences in gill DNA between the groups were evinced via statistical models of Fourier transform-infrared (FT-IR) spectra. Marked structural damage was found in the gill DNA of the DR fish as reflected in differences in base functional groups (e.g., C-O and NH2) and conformational properties (e.g., arising from perturbations in vertical base stacking interactions). These DNA differences were used to discriminate between the two fish groups through principal components analysis of mean FT-IR spectra. In addition, logistic regression analysis allowed for the development of a "DNA damage index" to assess the effects of contaminants on the gill. The evidence implies that environmental chemicals contribute to the DNA changes in the gill. The damaged DNA is a promising marker for identifying, through gill biopsies, contaminant effects on fish

Single addition of an allyl amine monomer enables access to end-functionalized RAFT polymers via native chemical ligation

A novel method for the introduction of a single protected amine-functional monomer at the chain end of RAFT polymers has been developed. This monomer addition, in concert with native chemical ligation, facilitated the development of a simple and versatile method for the end-functionalisation of polymers with peptides

The effect of attractions on the local structure of liquids and colloidal fluids

We revisit the role of attractions in liquids and apply these concepts to colloidal suspensions. Two means are used to investigate the structure; the pair correlation function and a recently developed topological method. The latter identifies structures topologically equivalent to ground state clusters formed by isolated groups of 5 < m < 13 particles, which are specific to the system under consideration. Our topological methodology shows that, in the case of Lennard-Jones, the addition of attractions increases the system's ability to form larger (m>8) clusters, although pair-correlation functions are almost identical. Conversely, in the case of short-ranged attractions, pair correlation functions show a significant response to adding attraction, while the liquid structure exhibits a strong decrease in clustering upon adding attractions. Finally, a compressed, weakly interacting system shows a similar pair structure and topology.Comment: 22 page

Rapid Additive-Free Selenocystine–Selenoester Peptide Ligation

We describe an unprecedented reaction between peptide selenoesters and peptide dimers bearing N-terminal selenocystine that proceeds in aqueous buffer to afford native amide bonds without the use of additives. The selenocystine-selenoester ligations are complete in minutes, even at sterically hindered junctions, and can be used in concert with one-pot deselenization chemistry. Various pathways for the transformation are proposed and probed through a combination of experimental and computational studies. Our new reaction manifold is also showcased in the total synthesis of two proteins

Making collaboration work: application of a conceptual design stages protocol for pre-BIM stages.

This paper presents the application of a Conceptual Design Stages Protocol during feasibility stages within a multidisciplinary design team, for the purpose of bridging the gap between ideas generation and their representation in later and more advanced design stages. Increased effort during the early and conceptual design is a prerequisite for effective and sustainable overall design and construction. Consequently, shift of the effort towards feasibility stages aims to tackle problems with workflow, education and organisation of design teams at the very beginning of a project. Furthermore, the application of an organised process during conceptual design could further support a multi-party agreement, hence enhancing the potentials of collaboration and coordination for the entirety of a project. This paper demonstrates the Conceptual Design Stages Protocol as an organised process encompassing different professionals, technologies and means for communication that has been tested in a conceptual stage study and the outcomes have been incorporated within BIM. The impact of this Protocol on designers cognitive, physical, perceptual and collaborative actions is presented and the first pre-BIM Protocol is established. This was a paper presented at the International Conference on Building Information Modelling (BIM) in Design, Construction and Operations, held in Bristol, 9-11 September 2015

Travelling and sticky affects: : Exploring teens and sexualized cyberbullying through a Butlerian-Deleuzian- Guattarian lens

In this paper we combine the thinking of Deleuze and Guattari (1984, 1987) with Judith Butler’s (1990, 1993, 2004, 2009) work to follow the rhizomatic becomings of young people’s affective relations in a range of on- and off-line school spaces. In particular we explore how events that may be designated as sexual cyberbullying are constituted and how they are mediated by technology (such as texting or in/through social networking sites). Drawing on findings from two different studies looking at teens’ uses of and experiences with social networking sites, Arto in Denmark, and Bebo in the UK, we use this approach to think about how affects flow, are distributed, and become fixed in assemblages. We map how affects are manoeuvred and potentially disrupted by young people, suggesting that in the incidences discussed affects travel as well as stick in points of fixation. We argue that we need to grasp both affective flow and fixity in order to gain knowledge of how subjectification of the gendered/classed/racialised/sexualised body emerges. A Butlerian-Deleuzian-Guattarian frame helps us to map some of these affective complexities that shape sexualized cyberbully events; and to recognize technologically mediated lines of flight when subjectifications are at least temporarily disrupted and new terms of recognition and intelligibility staked out. Keywords