Star-shaped hexaaryltriindoles small molecules: Tuning molecular properties towards solution processed organic light emitting devices

We present a series of differently substituted star-shaped hexaaryltriindoles with tunable light-emitting properties. The deep blue emission is unchanged by donor peripheral substituents while an increasing acceptor character produces a reduction of the optical gap, an increased Stokes shift and eventually leads to the appearance of a new electronic level and to the simultaneous deep blue (413 nm) and green (552 nm) emission in solution. Quenching by concentration increases with the acceptor character but is lower as the tendency of these compounds to aggregate is stronger. Solution processed thin films present optical and morphological qualities adequate for device fabrication and similar electronic structure compared to solutions with an emission range from 423 nm up to 657 nm (red), demonstrating the possibility of tuning the energy levels by chemical functionalization. We have fabricated and characterized single-layer solution processed organic light emitting diodes (OLED) to investigate the influence on transport and emission properties of the substituting species. We analyzed the I–V response using a single-carrier numerical model that includes injection barriers and non-uniform electric-field across the layer. As a result, we obtained the electric field dependence of the mobility for each device. Best results are obtained on the most electron rich derivative functionalized with six donor methoxy groups. This material shows the highest emission efficiency in solid state, due to aggregation-induced enhancement, and better transport properties with the highest mobility and a very low turn-on voltage of 2.8 V. The solution processed OLED devices produce stable deep blue (CIE coordinates (0.16, 0.16)) to white (CIE coordinates (0.33, 0.3)) emission with similar luminous efficiencies.     

Making and negotiating value: design and collaboration with community led groups

ABSTRACT

Value in collaborative design research and practice can be understood fundamentally as relationships, materials, processes, contexts, and outcomes that are subjects of and for negotiation. We argue for conceptions of value that move beyond traditional ‘outcomes’ based measurements to reimagine and rearticulate value itself as co-created, emerging from negotiation, relationality and immersion in specific contexts. These understandings of value, we argue, are not rooted in or always knowable through designers’ experiences, even as designers participate in creating them. Using case studies from our research we suggest that value in design collaboration emerges as a question: value to whom, and to what end? We propose that addressing these questions ethically through co-design requires actively engaged, grounded work with collaborators based in three principles: being present for the work, participant making, and co-creating capacity for collaborators to ‘go off and do their thing’.     

Broadband and knowledge intensive firm clusters: Essential link or auxiliary connection?

This study evaluates the relationship between the spatial distribution of broadband providers and the presence of knowledge intensive firm clusters in US counties. Results highlight this relationship is heterogeneous and localized. In some places, broadband appears to be an essential link that enables knowledge firms to strategically locate in lower cost counties and in close proximity to major knowledge centres. In other places, the availability of broadband Internet connections are unable the negative externalities associated with locations in more remote areas of the country. From a policy perspective, this suggests that broadband should be viewed as a key component, but not the only component, of comprehensive local economic development plans.     

Images of native Americans

Abstract

This interesting volume explores the photographic environment and output of four Anglo women who had extended photographic relationships with Native American people: Kate Cory, an artist and collector who lived with the Hopi people for many years; Mary Shaffer; who travelled amongst the Stoney and Metis of Alberta, Canada; Jane Gay, who assisted ethnographer Alice Fletcher and documented land allotment and the effects of the Dawes Act on the Nez Percé people; Grace Nicholson, who set up commercial enterprises trading in art and cultural objects. None of the women was primarily a photographer. Their photographic work was always an adjunct to other purposes, to record encounters commercial, artistic or ethnographic, but at the same time the work functioned as a key articulation of their relationships with Native peoples. All four women, in their different ways, looked to Native American peoples as a way of defining and experiencing their own identities and spirituality and all four shared a commitment to and engagement with these peoples.     

Temperature dependency of linear viscoelastic properties of a commercial low-fat soft cheese after frozen storage

The temperature dependency of linear viscoelastic properties of a commercial low-fat soft cheese containing microparticulated whey protein as fat replacer was studied considering the effect of freezing. After thawing, cheeses were held at 6 °C during 48 days for ripening. Refrigerated cheeses (stored at 6 °C for 48 days) were used as control samples. Frequency sweeps (0.01-10 Hz) in the linear viscoelastic region at 10, 20, 30, 40, and 50 °C were performed. Activation energies for complex viscosity at 1 Hz were obtained from an Arrhenius-type equation. Also, the time-temperature superposition method, the modified Cole-Cole analysis and the weak gel model for foods were used to compare the behavior of frozen and refrigerated cheeses. The results obtained in this work indicated that the viscoelastic properties of the studied cheeses obtained at different temperatures were influenced by freezing.     

Analyzing growth and mortality in a subtropical urban forest ecosystem

Information on urban tree growth, mortality and in-growth is currently being used to estimate urban forest structure changes and ecosystem services such as carbon sequestration. This study reports on tree diameter growth and mortality in 65 plots distributed among four land use categories, which were established in 2005/2006 in Gainesville, Florida, USA and were re-measured in 2009. Models for mortality and in-growth models were developed by grouping species into hardwoods and softwoods. Annual change in tree diameter at breast height growth was analyzed using three tree species groups based on potential height and longevity. Additionally, the four most common tree species in the study area were modeled to explore factors affecting tree growth. The average annual mortality rate in the city was 9.97%. Trees located in Institutional land use/land cover (LULC) had the highest annual mortality rate (19.2%/yr), and commercial had the lowest (3.1%/yr). Overall, growth rates for the study area (0.70 cm/yr) and residential LULC (0.80 cm/yr) were comparable to other studies. Growth rates for trees in forested areas were higher (0.56 cm/yr) than those previously reported. Individual species-level growth rates such as those for Juniperus virginiana (1.24 cm/yr) and Quercus virginiana (1.08 cm/yr) were different than other species values reported in other studies. Maintenance activities, site conditions, soil properties, tree characteristics, and LULC significantly influenced urban tree growth, mortality, and in-growth. Results can be used to better understand urban forest ecosystem structure and services in medium sized, subtropical cities and to make better decisions regarding planting and maintenance strategies.     

In vitro comparative evaluation of monolayered multipolymeric films embedded with didanosine-loaded solid lipid nanoparticles: a potential buccal drug delivery system for ARV therapy

Drug delivery via the buccal route has emerged as a promising alternative to oral drug delivery. Didanosine (DDI) undergoes rapid degradation in the gastrointestinal tract, has a short half-life and low oral bioavailability, making DDI a suitable candidate for buccal delivery. Recent developments in buccal drug delivery show an increased interest toward nano-enabled delivery systems. The advantages of buccal drug delivery can be combined with that of nanoparticulate delivery systems to provide a superior delivery system. The aim of this study was to design and evaluate the preparation of novel nano-enabled films for buccal delivery of DDI. Solid lipid nanoparticles (SLNs) were prepared via hot homogenization followed by ultrasonication and were characterized before being incorporated into nano-enabled monolayered multipolymeric films (MMFs). Glyceryl tripalmitate with Poloxamer 188 was identified as most suitable for the preparation of DDI-loaded SLNs. SLNs with desired particle size (PS) (201?nm), polydispersity index (PDI) (0.168) and zeta potential (?18.8?mV) were incorporated into MMFs and characterized. Conventional and nano-enabled MMFs were prepared via solvent casting/evaporation using Eudragit RS100 and hydroxypropyl methylcellulose. Drug release from the nano-enabled films was found to be faster (56% versus 20% in first hour). Conventional MMFs exhibited higher mucoadhesion and mechanical strength than nano-enabled MMFs. SLNs did not adversely affect the steady state flux (71.63?±?13.54?µg/cm²?h versus 74.39?±?15.95?µg/cm²?h) thereby confirming the potential transbuccal delivery of DDI using nano-enabled MMFs. Nano-enabled buccal films for delivery of DDI can be successfully prepared, and these physico-mechanical studies serve as a platform for future formulation optimization work in this emerging field.     

Can imageability help us draw the line between storage and composition?

Language requires both storage and composition. However, exactly what is retrieved from memory and what is assembled remains controversial, especially for inflected words. Here, “imageability effects” is introduced as a new diagnostic of storage and a complement to frequency effects. In 2 studies of past-tense morphology, more reliable imageability and frequency effects were found on irregulars than on regulars. An interaction with sex was also observed: Males but not females showed more reliable frequency and imageability effects for irregulars than for regulars; females but not males showed signs of storage for regulars, particularly among higher frequency forms. Overall, the findings validate imageability effects as another diagnostic of storage and suggest that the line between storage and computation is not a simple function; rather, it depends upon the interplay of both item- and subject-specific factors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)