Solvatochromism On Regiochemically Substituted Poly(hexylthiophenes)

Poly (3, 3″-dihexylterthiophene) and poly (3′,4′-dihexylterthiophene) have been synthesized and studied with respect to their solvatochromic properties. While both polymers in chloroform solution have maximum absorption at approximately the same wavelength, they behave differently with respect to changes observed on their UV-visible spectra when the quality of the solvent is changed. A microscopic model for the solvation of both polymers has been developed based on semi-empirical quantum chemical calculations. The results are consistent with a high degree of conformational disorder in the 3′, 4′-substituted polymer even in the solid state, leading to chains of short conjugation length, and thus less sensitive to solvation effects. In 3,′3″-substituted polythiophene on the other hand, the substituents impose smaller torsional barriers, similar to the ones found in regioregular poly (3-hexylthiophene). A rod-to-coil like transition is thus expected to occur as a function of solvent quality.8401/03/15811812Faid, K., Fréchette, M., Ranger, M., Mazerolle, L., Lévesque, I., Leclerc, M., Chen, T., Rieke, D., (1995) Chem. Mater., 7, pp. 1390-1396Yoshino, K., Nakajima, S., Sugimoto, R., (1987) Jpn. J. Appl. Phys., 26, pp. L1038-L1039Rughooputh, S.D.D.V., Heeger, A.J., Wudl, F., (1987) J. Polym. Sci. Polym. Phys Ed., 25, pp. 1071-1078MOPAC Program, Version 6.0, , QCPE # 455Dos Santos, M.C., Bohland Filho, J., (1995) Proc. Int. Symp. on Optical Science, Engeneering, and Instrumentation SPIE ', 95 (2528), p. 153Dixon, R.W., Leonard, J.M., Hehre, W.J., (1993) Israel J. Chem., 33, p. 427SPARTAN Package Version 4.0, , Wavefunction Inc., 18401 Von Karmam Ave. # 370 Irvine, CA 9 2715 US

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical science. © The Author(s) 2019. Published by Oxford University Press