White organic light-emitting diodes with an ultra-thin premixed emitting layer

We described an approach to achieve fine color control of fluorescent White Organic Light-Emitting Diodes (OLED), based on an Ultra-thin Premixed emitting Layer (UPL). The UPL consists of a mixture of two dyes (red-emitting 4-di(4'-tert-butylbiphenyl-4-yl)amino-4'-dicyanovinylbenzene or fvin and green-emitting 4-di(4'-tert-butylbiphenyl-4-yl)aminobenzaldehyde or fcho) premixed in a single evaporation cell: since these two molecules have comparable structures and similar melting temperatures, a blend can be evaporated, giving rise to thin films of identical and reproducible composition compared to those of the pre-mixture. The principle of fine color tuning is demonstrated by evaporating a 1-nm-thick layer of this blend within the hole-transport layer (4,4'-bis[N-(1-naphtyl)-N-phenylamino]biphenyl (\alpha-NPB)) of a standard fluorescent OLED structure. Upon playing on the position of the UPL inside the hole-transport layer, as well as on the premix composition, two independent parameters are available to finely control the emitted color. Combined with blue emission from the heterojunction, white light with Commission Internationale de l'Eclairage 1931 color coordinates (0.34, 0.34) was obtained, with excellent color stability with the injected current. The spectrum reveals that the fcho material does not emit light due to efficient energy transfer to the red-emitting fvin compound but plays the role of a host matrix for fvin, allowing for a very precise adjustment of the red dopant amount in the device

White Organic Light-Emitting Diodes with fine chromaticity tuning via ultrathin layer position shifting

Non-doped white organic light-emitting diodes using an ultrathin yellow-emitting layer of rubrene (5,6,11,12-tetraphenylnaphtacene) inserted on either side of the interface between a hole-transporting NPB (4,4'-bis[N-(1-naphtyl)-N-phenylamino]biphenyl) layer and a blue-emitting DPVBi (4,4'-bis(2,2'-diphenylvinyl)-1,1'-biphenyl) layer are described. Both the thickness and the position of the rubrene layer allow fine chromaticity tuning from deep-blue to pure-yellow via bright-white with CIE coordinates (x= 0.33, y= 0.32), a external quantum efficiency of 1.9%, and a color rendering index of 70. Such a structure also provides an accurate sensing tool to measure the exciton diffusion length in both DPVBi and NPB (8.7 and 4.9 nm respectively)

"Can we agree on that"? Plurality, power and language in participatory research

Participatory epidemiology (PE) is a method that gathers data from groups through focus group interviews and participatory visual and scoring exercises. The method is often used in poor communities in low-income countries where it is hard to obtain conventional epidemiological data. This paper draws on research on the public sphere and democratic deliberation, along with research on language and interpretation, to suggest how PE research could be better equipped to account for diversity in local knowledge, include minority views and acknowledge power dynamics. These aspects are discussed under the three themes of 'plurality', 'power' and 'language'. A review of highly-cited PE literature suggests that PE research engages with plurality and power to a very limited extent, and only marginally more so with language and translation. Examples are taken from the authors' own PE research on African swine fever in -Uganda, classical swine fever in Germany, peste des petits ruminants (PPR) in Eastern Europe, and Ugandan pastoralists' understanding of cattle disease to provide more detail as to why conventional PE studies might fail to record issues of plurality, power and language, and also to suggest how this can be addressed. With reference to the literature on the public sphere and democratic deliberation, and on language and interpretation, this paper concludes with some suggestions as to how to take plurality, power and language into greater consideration in PE studies in future, thus improving the validity and reliability of PE data

Enhanced production of coherent pulsed radiation at 125 nm: the route towards a tabletop VUV laser

A novel approach is used to enhance by nearly two orders of magnitude the conversion efficiency of a 125 nm-coherent source, based on four-wave mixing in room-temperature mercury vapor. Saturation issues are observed and discussed

African swine fever in Uganda

In the last decade millions of people have been able to leave poverty, increasing the regional demand for meat and livestock products. In combination with reforms in market and agricultural policy, this has led to an increase in pig production in sub-Saharan Africa, most notably in Uganda. The growing pig sector could be an important contributor to poverty reduction among smallholder pig keepers. However, the growing pig population has been followed by an increase in African swine fever (ASF) incidence. ASF is a contagious, typically very lethal, haemorrhagic, viral disease of domestic pigs. The overall goal of this doctoral project was to develop the understanding of ASF epidemiology in the smallholder setting in Uganda. Four studies were conducted in two districts in northern Uganda among smallholder farmers, other pig production value-chain actors, and a medium-sized farm. The studies included group- and individual interviews as well as biological and environmental sampling and testing for the virus. Data were analysed using semi-qualitative and quantitative methods. The thesis concluded that ASF was endemic in the study area, and that outbreaks could be detected using retrospective and real-time farmer reports. ASF outbreaks were associated with activities of humans, such as trade in pigs and pig products and free-range management systems. ASF outbreaks had long-term negative social and economic impact for pig production value-chain actors on all investigated levels in the value chain. For smallholder farmers, the impact was aggravated with increasing herd size. Trade and consumption of sick and dead pigs were commonly used as coping strategies. Farm-level biosecurity was insufficient for ASF protection and awareness of control methods did not guarantee their implementation. The continuous ASF transmission in the study area was not driven by lack of knowledge, but rather by cultural circumstances, taboos and poverty. Therefore, in order for control methods to be successfully and sustainably implemented, they need to be developed in participation with the communities, adapted to the local context, socially acceptable, flexible, and cost-effective

Two-scale convergence for locally-periodic microstructures and homogenization of plywood structures

The introduced notion of locally-periodic two-scale convergence allows to average a wider range of microstructures, compared to the periodic one. The compactness theorem for the locally-periodic two-scale convergence and the characterisation of the limit for a sequence bounded in $H^1(\Omega)$ are proven. The underlying analysis comprises the approximation of functions, which periodicity with respect to the fast variable depends on the slow variable, by locally-periodic functions, periodic in subdomains smaller than the considered domain, but larger than the size of microscopic structures. The developed theory is applied to derive macroscopic equations for a linear elasticity problem defined in domains with plywood structures.Comment: 22 pages, 4 figure

Measurement of XUV-absorption spectra of ZnS radiatively heated foils

Time-resolved absorption of zinc sulfide (ZnS) and aluminum in the XUV-range has been measured. Thin foils in conditions close to local thermodynamic equilibrium were heated by radiation from laser-irradiated gold spherical cavities. Analysis of the aluminum foil radiative hydrodynamic expansion, based on the detailed atomic calculations of its absorption spectra, showed that the cavity emitted flux that heated the absorption foils corresponds to a radiation temperature in the range 55 60 eV. Comparison of the ZnS absorption spectra with calculations based on a superconfiguration approach identified the presence of species Zn6+ - Zn8+ and S5+ - S6+. Based on the validation of the radiative source simulations, experimental spectra were then compared to calculations performed by post-processing the radiative hydrodynamic simulations of ZnS. Satisfying agreement is found when temperature gradients are accounted for

Diverging Discourses: Animal Health Challenges and Veterinary Care in Northern Uganda

People in northern Uganda are currently rebuilding their lives after a lengthy period of conflict. To facilitate this, the Ugandan government and donors have promoted investment in pigs as an important strategy for generating income quickly and ensuring livelihood security. In this context, animal health issues are an acknowledged challenge, creating uncertainty for animal owners who risk losing both their animals and income. This paper draws on policy documents guiding the veterinary sector, interviews with faculty staff at Makerere University and with veterinarians and paraprofessionals in northern Uganda, and ethnographic fieldwork in smallholder communities. The aims of this study were to contribute to an understanding of the structure of veterinary support and its dominant development narratives in policy and veterinary education and of the way in which dominant discourses and practices affect smallholders' ability to treat sick animals. Particular attention was paid to the role of paraprofessionals, here referring to actors with varied levels of training who provide animal health services mainly in rural areas. The results suggest that veterinary researchers, field veterinarians and government officials in agricultural policy share a common discourse in which making smallholders more business-minded and commercializing smallholder production are important elements in reducing rural poverty in Uganda. This way of framing smallholder livestock production overlooks other important challenges faced by smallholders in their livestock production, as well as alternative views of agricultural development. The public veterinary sector is massively under-resourced; thus while inadequately trained paraprofessionals and insufficient veterinary support currently present a risks to animal health, paraprofessionals fulfill an important role for smallholders unable to access the public veterinary sector. The dominant discourse framing paraprofessionals as "quacks" tends to downplay how important they are to smallholders by mainly highlighting the negative outcomes for animal healthcare resulting from their lack of formalized training. The conclusions of this study are that both animal health and smallholders' livelihoods would benefit from closer collaboration between veterinarians and paraprofessionals and from a better understanding of smallholders' needs