140,262 research outputs found
Correlating Structure with Optoelectronic Functionality in Polymer:Fullerene Blend Films
No full textIn this thesis the influence of processing conditions on the structure and optoelectronic properties of conjugated polymer:methanofullerene blend thin-films has been investigated. These conditions strongly impact upon the efficiency with which blend films may produce a photocurrent when fabricated into an Organic Photovoltaic (OPV) device. Using the model system P3HT:PCBM, it is shown that films undergo a three-stage drying process upon casting. Heterogeneous growth of P3HT crystallites occurs once the solid fraction in the film exceeds 50 wt%. Measurements from spectroscopic ellipsometry (SE) and grazing-incidence wide-angle X-ray scattering (GIWAXS) suggest a correspondence between enhanced polymer crystallinity and the strength of the π-π* electronic transition in the polymer absorption spectrum. In-situ measurements of a blend during thermal annealing evidence the evolution of residual solvent loss upon heating, volume relaxation, phase separation and increased electronic conjugation of P3HT upon cooling. The glass transition of P3HT:PCBM blend films, measured in a thin-film geometry, is found to correlate with the minimum effective annealing temperature for improving the power conversion efficiency of thermally annealed OPVs. As-cast films with 20 to 60 wt% PCBM exhibit two glass transitions, an observation that may indicate the existence of two compositionally distinct amorphous phases. Studies on a different polymer:fullerene blend system (PCDTBT:PC71BM), indicate a greater miscibility between materials compared to blends of P3HT:PCBM. In this system, thermal annealing is found to result in increased disorder in the polymer phase of the film, and also to drive excessive phase separation of PC71BM. It is argued that thermal annealing is unlikely to be an appropriate treatment for optimising the efficiency of OPVs based on PCDTBT:PC71BM blends. Finally, Helium Ion Microscopy (HeIM) is used to image the chemical composition of OPV applicable blend films with nanometer resolution, providing a powerful technique to correlate film morphology with device functionality in a range of organic opto-electronic devices
Aspirin-loaded P(3HO)/P(3HB) blend films: potential materials for biodegradable drug-eluting stents
No full textPoly(3-hydroxyoctanoate)/poly(3-hydroxybutyrate), P(3HO)/P(3HB), blend films loaded with aspirin were prepared, and the influence of aspirin loading on the surface properties, mechanical, thermal and degradation properties were investigated. Scanning electron microscopy images revealed that the addition of aspirin introduced a new topography on the surface of the blend films. Aspirin contributed to the increase in the hydrophilic nature of the blend films compared with the unloaded blend films. This was complemented by a considerable increase in the total protein adsorption in the aspirin-loaded blend films. The percentage cell viability was higher in the aspirin-loaded blend films compared with the unloaded blend films. There was a decrease in the tensile strength and the Young’s modulus with the addition of the aspirin. However, the percentage elongation at break, a measure of elasticity, was higher in the aspirin-loaded films, indicating an increase in their flexibility compared with the unloaded blend films. There was a decrease in the melting temperature (T m), glass transition temperature (T g) and the crystallization temperature (T c) due to the decrease in the crystallinity of the aspirin-loaded blend films in comparison with the unloaded blend films. Finally, controlled release of aspirin was observed without any burst release, and 96·6% release was achieved within 25 d, ideal for the development of biodegradable drug-eluting stents
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Buticulotrema Blend, Dronen & McEachran 1993
No full textGenus Buticulotrema Blend, Dronen & McEachran, 1993 urn:lsid:zoobank.org:act: 7331 E 813 - 20 EA- 4 F03-B 5 BC- 6215801 AE 23 D The only species in this genus Buticulotrema stenauchenus Blend, Dronen & McEachran, 1993, is reported from the macrourid fishes, the western softhead grenadier Malacocephalus occidentalis Goode & Bean, the common Atlantic grenadier Nezumia aequalis (Günther) and the glasshead grenadier Hymenocephalus italicus Giglioli, in the deep-waters of the Gulf of Mexico (Blend et al. 1993, Blend in Klimpel et al. 2001).Published as part of Bray, R. A., Waeschenbach, A., Dyal, P., Littlewood, D. T. J. & Morand, S., 2014, New digeneans (Opecoelidae) from hydrothermal vent fishes in the south eastern Pacific Ocean, including one new genus and five new species, pp. 73-87 in Zootaxa 3768 (1) on page 82, DOI: 10.11646/zootaxa.3768.1.5, http://zenodo.org/record/28562
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A Novel Blend of Dietary Ingredients Mitigates Blood and Breath Ethanol Levels After Acute Alcohol Intake
No full textMichael B La Monica, Betsy Raub, Shelley Hartshorn, Ashley Gustat, Jodi Grdic, Jennifer Sandrock The Center for Applied Health Sciences, Canfield, OH, USACorrespondence: Michael B La Monica, The Center for Applied Health Sciences, 6570 Seville Dr, Canfield, OH, 44460, USA, Email [email protected]: Various ingredients have been postulated to attenuate the cognitive and physiological effects of alcohol and next-day hangovers. However, few studies have focused on ingredients that may mitigate the acute effects of alcohol. Thus, the aim of this study was to determine if a novel blend of dietary ingredients would attenuate blood (BAC) and breath (BrAC) ethanol levels after acute alcohol ingestion.Methods: Thirty-five individuals participated in this double-blind, randomized, crossover clinical trial (#NCT06106620). Participants completed screening and two testing visits. During testing, participants consumed 100mL of alcohol immediately followed by either the supplement blend (SS) or a flavor-matched placebo (PL). BrAC, BAC, and biomarkers related to alcohol metabolism [acetaldehyde, alcohol dehydrogenase, aldehyde dehydrogenase (ALDH)] were made prior to and 30-, 45-, 60-, 90-, 120-, 180-, and 240-min post ingestion, whereas vital signs, urine volume, and subjective mood ratings were made prior to alcohol consumption and 60-, 120-, 180-, and 240-min post.Results: SS had lower BrAC during the entire post-consumption period (p ≤ 0.05, d = 0.57– 1.07) and lower BAC at 30-, 60-, and 180-min (p ≤ 0.05) post-consumption vs PL. SS had a lower (p ≤ 0.05) area under the curve (AUC, d = 0.71) and concentration maximum (Cmax, d = 0.58) for ethanol, and a higher AUC (d = 0.45, d = 0.54, respectively) and Cmax (d = 0.38, d = 0.47, respectively) than PL for acetaldehyde and ALDH levels. Urine output was greater in SS vs PL at 60-min post consumption (p 0.10).Discussion: Overall, SS was effective in reducing BrAC, BAC, and enhancing subjective mood ratings over a 4-hr post alcohol-consumption period vs PL. Thus, SS may mitigate the negative effects induced by acute alcohol intake.Keywords: alcohol metabolism, antioxidants, acetaldehyde, alcohol dehydrogenase, aldehyde dehydrogenas
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Transient Absorption Imaging of P3HT:PCBM Photovoltaic Blend: Evidence For Interfacial Charge Transfer State
No full textSolution-processed bulk heterojunction (BHJ) based on electron-donor (D) polymer and acceptor (A) fullerene is a promising technology for organic photovoltaics. Geminate charge recombination is regarded as one of the main loss mechanisms limiting device performances. This stems from the dynamics of the initial charge transfer state (CTS), which depend on the blend morphology, the molecular conformation, and the energetics of the D:A interface. Here we study the photophysics of a crystalline phase-separated blend of regioregular poly(3-hexylthiophene) (P3HT) with [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM) with a coarsened morphology, by mapping the transient absorption signal with submicrometer space and subpicosecond time resolution. At the P3HT:PCBM interface, we detect a long-lived photoinduced dynamic that we assign to a peculiar coherent CTS forming in similar to 10 ps, not affected by geminate recombination and characterized by a different polarization with respect to the one in the usual polydispersed blend. Quantum chemical calculations on supramolecular P3HT:PCBM complexes confirm the presence of low-lying and highly polarized CTS, validating the experimental findings
Some New Concepts of Shape Memory Effect of Polymers
No full textIn this study some new concepts regarding certain aspects related to shape memory polymers are presented. A blend of polylactic acid (PLA) (80%) and polybutylene succinate (PBS) (20%) was prepared first by extrusion, then by injection molding to obtain the samples. Tensile, stress-relaxation and recovery tests were performed on these samples at 70 °C. The results indicated that the blend can only regain 24% of its initial shape. It was shown that, this partial shape memory effect could be improved by successive cycles of shape memory tests. After a fourth cycle, the blend is able to regain 82% of its shape. These original results indicated that a polymer without (or with partial) shape memory effect may be transformed into a shape memory polymer without any chemical modification. In this work, we have also shown the relationship between shape memory and property memory effect. Mono and multi-frequency DMA (dynamic mechanical analyzer) tests on virgin and 100% recovered samples of polyurethane (PU) revealed that the polymer at the end of the shape memory tests regains 100% of its initial form without regaining some of its physical properties like glass transition temperature, tensile modulus, heat expansion coefficient and free volume fraction. Shape memory (with and without stress-relaxation) tests were performed on the samples in order to show the role of residual stresses during recovery tests. On the basis of the results we have tried to show the origin of the driving force responsible for shape memory effect
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