The nature of singlet exciton fission in carotenoid aggregates.

Singlet exciton fission allows the fast and efficient generation of two spin triplet states from one photoexcited singlet. It has the potential to improve organic photovoltaics, enabling efficient coupling to the blue to ultraviolet region of the solar spectrum to capture the energy generally lost as waste heat. However, many questions remain about the underlying fission mechanism. The relation between intermolecular geometry and singlet fission rate and yield is poorly understood and remains one of the most significant barriers to the design of new singlet fission sensitizers. Here we explore the structure-property relationship and examine the mechanism of singlet fission in aggregates of astaxanthin, a small polyene. We isolate five distinct supramolecular structures of astaxanthin generated through self-assembly in solution. Each is capable of undergoing intermolecular singlet fission, with rates of triplet generation and annihilation that can be correlated with intermolecular coupling strength. In contrast with the conventional model of singlet fission in linear molecules, we demonstrate that no intermediate states are involved in the triplet formation: instead, singlet fission occurs directly from the initial 1B(u) photoexcited state on ultrafast time scales. This result demands a re-evaluation of current theories of polyene photophysics and highlights the robustness of carotenoid singlet fission.This work was supported by the EPSRC (UK) (EP/G060738/ 1), the European Community (LASERLAB-EUROPE, grant agreement no. 284464, EC’s Seventh Framework Programme; and Marie-Curie ITN-SUPERIOR, PITN-GA-2009-238177), and the Winton Programme for the Physics of Sustainability. G.C. acknowledges support by the European Research Council Advanced Grant STRATUS (ERC-2011-AdG No. 291198). J.C. acknowledges support by the Royal Society Dorothy Hodgkin Fellowship and The University of Sheffield’s Vice- Chancellor’s Fellowship scheme.This is the final published version. It was first made available by ACS at http://pubs.acs.org/doi/abs/10.1021/jacs.5b01130

Evaluation of websites for biomedical postgraduate courses in Spanish

El objeto de este trabajo es la creación de una herramienta para la evaluación de la calidad de la información contenida en los sitios web de Postgrado de ámbito biosanitario en las universidades españolas. Se ha diseñado y desarrollado una hoja de evaluación (checklist) que ha sido validada y aplicada a los 131 sitios web de Postgrado con Mención de Calidad de tema biosanitario de las universidades españolas. Se han analizado las valoraciones obtenidas por los sitios web y se han aplicado técnicas de clustering y de análisis de componentes principales. Los datos recogidos por la checklist permiten establecer un ranking según la calidad de la información de los sitios web. Además, se observa la existencia de tres grandes grupos de sitios web según sus características y prestaciones. La aplicación de las herramientas diseñadas indica que los sitios web alcanzan valores aceptables, si bien presentan algunos defectos comunes. No obstante, se constata la existencia de varios niveles de calidad de los mismos.The aim of this work is to create a tool for assessing the quality of the information on postgraduate course websites at Spanish universities. An evaluation checklist was developed and applied to the 131 websites of postgraduate biomedical courses with quality accreditation in Spanish universities. The website evaluations were analysed with the application of clustering and principal component analysis techniques. While the average of all the sites is ‘acceptable’ there remain some clear weaknesses in aspects such as accessibility, lack of an internal search engine, or forms - for obtaining the views of current students and lecturers- and evaluation tests - for analysing the results. The tool developed provides a new instrument for evaluating postgraduate course websites. This evaluation enables website comparison, helps identify their strengths and weaknesses, and facilitates their improvement

CD73 controls Myosin II-driven invasion, metastasis, and immunosuppression in amoeboid pancreatic cancer cells

Pancreatic ductal adenocarcinoma (PDAC) has a very poor prognosis because of its high propensity to metastasize and its immunosuppressive microenvironment. Using a panel of pancreatic cancer cell lines, three-dimensional (3D) invasion systems, microarray gene signatures, microfluidic devices, mouse models, and intravital imaging, we demonstrate that ROCK–Myosin II activity in PDAC cells supports a transcriptional program conferring amoeboid invasive and immunosuppressive traits and in vivo metastatic abilities. Moreover, we find that immune checkpoint CD73 is highly expressed in amoeboid PDAC cells and drives their invasive, metastatic, and immunomodulatory traits. Mechanistically, CD73 activates RhoA–ROCK–Myosin II downstream of PI3K. Tissue microarrays of human PDAC biopsies combined with bioinformatic analysis reveal that rounded-amoeboid invasive cells with high CD73–ROCK–Myosin II activity and their immunosuppressive microenvironment confer poor prognosis to patients. We propose targeting amoeboid PDAC cells as a therapeutic strategy.The work was supported by Barts Charity MGU0418 (R.S., O.M., J.M., S.G., and V.S.-M.), Organ-on-a-Chip Network and Emulate Proof of Concept Awards (R.S. and V.S.-M.), Cancer Research UK (CRUK) C33043/A24478 (O.M., L.K., and V.S.-M.), Pancreatic Cancer Research UK Fund (C.M.W.), National Centre for the 3Rs (S.L. and A.B.), The National Institute for Health Research (NIHR) Biomedical Research Centre based at Guy’s and St Thomas’ NHS Foundation Trust and King’s College London and/or the NIHR Clinical Research Facility (H.L.), and Grant Atracción de Talento Investigador 2019-T1/BMD-13642 funded by Comunidad de Madrid (J.L.O.).Peer reviewe

Inorganic Mass Spectrometry

To establish a method for sensitive, accurate, and precise determination of Se in real samples, isotope dilution analysis using high-power nitrogen microwave-induced plasma mass spectrometry (N 2 MIP-IDMS) was conducted. In this study, freeze-dried human blood serum (Standard Reference Material, NIES No. 4) provided by NIES (National Institute for Environmental Studies) was used as a real sample. The measured isotopes of Se were 78 Se and 80 Se which are the major isotopes of Se. The appropriate amount of a Se spike solution was theoretically calculated by using an error multiplication factor (F) and was confirmed experimentally for the isotope dilution analysis. The mass discrimination effect was corrected for by using a standard Se solution for the measurement of Se isotope ratios in the spiked sample. However, the sensitivity for the detection of Se was not so good and the precision of the determination was not improved (2-3%) by N 2 MIP-IDMS with use of the conventional nebulizer. Therefore, a hydride generation system was connected to N 2 MIP-IDMS as a sample introduction system (HG-N 2 MIP-IDMS) in order to establish a more sensitive detection and a more precise determination of Se. A detection limit (3σ) of 10 pg mL -1 could be achieved, and the RSD was less than 1% at the concentration level of 5.0-10.0 ng mL -1 by HG-N 2 MIP-IDMS. The analytical results were found to be in a good agreement with those obtained by the standard addition method using conventional Ar ICPMS. It is well-known that Se is an essential element for all mammals. Se deficiency leads to deficiency syndromes, for example, Keshan disease, which is known for cardiac insufficiency that occurred in children and pregnant women in China. Problems also occur if the concentration of Se is too high; for example, gastroenteric disorders, dermatitis, and neurotic disorders are caused by excessive intake of Se. Moreover, it is well-known that the range of permissive intake amounts of Se is very narrow for human beings. Therefore, it is restricted as a toxic element in environmental standards. There are several sources of environmental Se pollution: the processes of Se refinement and the production processes of Se-containing products. For these reasons, the accurate and precise determination of trace levels of Se in environmental and biological samples is required, and studies of Se determination have been reported by several groups. [1][2][3][4][5][6][7][8][9][10][11] Because Ar ICPMS can measure multiple elements at a concentration range from ng mL -1 to fg mL -1 , it has widespread use in the determination of trace elements in various samples. 12-25 However

Evaluation of preconcentration methods for the determination of trace amounts of rare earth elements by x-ray fluorescence analysis using a conventional x-ray tube system and a synchrotron radiation source

Trace amounts of rare earth elements (REE) were preconcentrated by chemofiltration methods using the organic reagents o-(3,6-disulfo-2-hydroxy-1-naphthylazo)benzenearsonic acid (Thorin) and 2,2 '-(1,8-dihydroxy-3,6-disulfonaphthylene-2,7-bisazo)bisbenzenearsonic acid (Arsenazo III) as complexing agents for the REE. The resulting specimens (thin film) were then analyzed by an x-ray fluorescence method using two different instruments: a conventional x-ray tube system and a synchrotron radiation source. The results from these two systems were compared with respect to radiation damage, accuracy, detection limits and ease of analysis. Copyright (C) 2001 John Wiley & Sons, Ltd.30530831