72 research outputs found
Electrode Materials, Thermal Annealing Sequences, and Lateral/Vertical Phase Separation of Polymer Solar Cells from Multiscale Molecular Simulations
The nanomorphologies of the bulk heterojunction (BHJ) layer of polymer solar cells are extremely sensitive to the electrode materials and thermal annealing conditions. In this work, the correlations of electrode materials, thermal annealing sequences, and resultant BHJ nanomorphological details of P3HT:PCBM BHJ polymer solar cell are studied by a series of large-scale, coarse-grained (CG) molecular simulations of system comprised of PEDOT:PSS/P3HT:PCBM/Al layers. Simulations are performed for various configurations of electrode materials as well as processing temperature. The complex CG molecular data are characterized using a novel extension of our graph-based framework to quantify morphology and establish a link between morphology and processing conditions. Our analysis indicates that vertical phase segregation of P3HT:PCBM blend strongly depends on the electrode material and thermal annealing schedule. A thin P3HT-rich film is formed on the top, regardless of bottom electrode material, when the BHJ layer is exposed to the free surface during thermal annealing. In addition, preferential segregation of P3HT chains and PCBM molecules toward PEDOT:PSS and Al electrodes, respectively, is observed. Detailed morphology analysis indicated that, surprisingly, vertical phase segregation does not affect the connectivity of donor/acceptor domains with respective electrodes. However, the formation of P3HT/PCBM depletion zones next to the P3HT/PCBM-rich zones can be a potential bottleneck for electron/hole transport due to increase in transport pathway length. Analysis in terms of fraction of intra- and interchain charge transports revealed that processing schedule affects the average vertical orientation of polymer chains, which may be crucial for enhanced charge transport, nongeminate recombination, and charge collection. The present study establishes a more detailed link between processing and morphology by combining multiscale molecular simulation framework with an extensive morphology feature analysis, providing a quantitative means for process optimization
Tuning intermolecular interactions in di-octyl substituted polyfluorene via hydrostatic pressure
Polyfluorenes (PFs) represent a unique class of poly para-phenylene based
blue-emitting polymers with intriguing structure-property relationships. Slight
variations in the choice of functionalizing side chains result in dramatic
differences in the inter- and intra-chain structures in PFs. We present
photoluminescence (PL) and Raman scattering studies of bulk samples and thin
films of dioctyl-substituted PF (PF8) under hydrostatic pressure. The bulk
sample was further thermally annealed at 1.9 GPa. The PL vibronics of the as-is
sample red-shift at an average rate of 26 meV/GPa. The thermally annealed
sample is characterized by at least two phase transitions at 1.1 GPa and 4.2
GPa, each of which has a different pressure coefficient for PL vibronics. The
Huang-Rhys factor, a measure of the electron-phonon interaction, is found to
increase with increasing pressures signaling a higher geometric relaxation of
the electronic states. The Raman peaks harden with increasing pressures; the
intra-ring C-C stretch frequency at 1600 cm has a pressure coefficient
of 7.2 cm/GPa and exhibits asymmetric line shapes at higher pressures,
characteristic of a strong electron-phonon interaction. The optical properties
of PF8 under high pressure are further contrasted with those of a branched side
chain substituted PF.Comment: 22 pages, 10 figure
A Research Agenda for Helminth Diseases of Humans: Social Ecology, Environmental Determinants, and Health Systems
In this paper, the Disease Reference Group on Helminth Infections (DRG4), established in 2009 by the Special Programme for Research and Training in Tropical Diseases (TDR), with the mandate to review helminthiases research and identify research priorities and gaps, focuses on the environmental, social, behavioural, and political determinants of human helminth infections and outlines a research and development agenda for the socioeconomic and health systems research required for the development of sustainable control programmes. Using Stockols' social-ecological approach, we describe the role of various social (poverty, policy, stigma, culture, and migration) and environmental determinants (the home environment, water resources development, and climate change) in the perpetuation of helminthic diseases, as well as their impact as contextual factors on health promotion interventions through both the regular and community-based health systems. We examine these interactions in regard to community participation, intersectoral collaboration, gender, and possibilities for upscaling helminthic disease control and elimination programmes within the context of integrated and interdisciplinary approaches. The research agenda summarises major gaps that need to be addressed
The Repeal of the Glass-Steagall Act and the Federal Reserve's Extraordinary Intervention During the Global Financial Crisis
Electrode Materials, Thermal Annealing Sequences, and Lateral/Vertical Phase Separation of Polymer Solar Cells from Multiscale Molecular Simulations
Multi-trait genome-wide association study identifies new loci associated with optic disc parameters
A new avenue of mining published genome-wide association studies includes the joint analysis of related traits. The power of this approach depends on the genetic correlation of traits, which reflects the number of pleiotropic loci, i.e. genetic loci influencing multiple traits. Here, we applied new meta-analyses of optic nerve head (ONH) related traits implicated in primary open-angle glaucoma (POAG); intraocular pressure and central corneal thickness using Haplotype reference consortium imputations. We performed a multi-trait analysis of ONH parameters cup area, disc area and vertical cup-disc ratio. We uncover new variants; rs11158547 in PPP1R36-PLEKHG3 and rs1028727 near SERPINE3 at genome-wide significance that replicate in independent Asian cohorts imputed to 1000 Genomes. At this point, validation of these variants in POAG cohorts is hampered by the high degree of heterogeneity. Our results show that multi-trait analysis is a valid approach to identify novel pleiotropic variants for ONH
Separated shear layers behind two-dimensional square-edged bodies
SIGLEAvailable from British Library Document Supply Centre- DSC:D39296/82 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Personalized Detection of Anxiety Provoking News Events using Semantic Network Analysis
In the age of hyper-connectivity, 24/7 news cycles, and instant news alerts via social media, mental health researchers don\u27t have a way to automatically detect news content which is associated with triggering anxiety or depression in mental health patients. Using the Associated Press news wire, a semantic network was built with 1,056 news articles containing over 500,000 connections across multiple topics to provide a personalized algorithm which detects problematic news content for a given reader. We make use of Semantic Network Analysis to surface the relationship between news article text and anxiety in readers who struggle with mental health disorders. Based on a reader\u27s anxiety profile collected by the network, a personalized dataset can be established to better understand the type of news that impacts a reader\u27s mental health in a negative way. This study can benefit two groups. The first group is the mental health community who can use our approach to understand the impact of news content on those combating anxiety disorders and depression. The second group is for readers of news content in general who might not be aware of the type of news topics they are sensitive to. The insight from the Semantic Network should provide more information about specific triggers of anxiety that were previously unknown
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