TY - JOUR A1 - Khan, Muhammad S. A1 - Al-Mandhary, Muna R. A. A1 - Al-Suti, Mohammed K. A1 - Al-Battashi, Fathiya R. A1 - Al-Saadi, Sultan A1 - Bjernemose, Jens K. A1 - Mahon, Mary F. A1 - Chawdhury, Nazia A1 - Yonus, Muhammad A1 - Köhler, Anna A1 - Teat, Simon J. A1 - Marseglia, Elizabeth A. A1 - Tedesco, Emilio A1 - Feeder, Neil A1 - Ahrens, Birte A1 - Raithby, Paul R. T1 - Synthesis, characterisation and optical spectroscopy of platinum(II) di-ynes and poly-ynes incorporating condensed aromatic spacers in the backbone Y1 - 2004 U6 - https://doi.org/10.1039/B405070C SN - 1477-9226 ER - TY - JOUR A1 - Hayer, Anna A1 - Khan, A. L. T. A1 - Friend, Richard H. A1 - Köhler, Anna T1 - Morphology dependence of the triplet excited state formation and absorption in polyfluorene Y1 - 2005 ER - TY - JOUR A1 - Zhang, Ning A1 - Hayer, Anna A1 - Al-Suti, Mohammed K. A1 - Al-Belushi, Rayya A. A1 - Khan, Muhammad S. A1 - Köhler, Anna T1 - The effect of delocalization on the exchange energy in meta- and para-linked Pt-containing carbazole polymers and monomers N2 - A series of novel platinum-containing carbazole monomers and polymers was synthesized and fully characterized by UV-VIS absorption, luminescence, and photoinduced absorption studies. In these compounds, a carbazole unit is incorporated into the main chain via either a para- or a meta-linkage. We discuss the effects of linkage and polymerization on the energy levels of S-1, T-1, and T-n. The S-1-T-1 splitting observed for the meta-linked monomer (0.4 eV) is only half of that in the para-linked monomer (0.8 eV). Upon polymerization, the exchange energy in the para- linked compound reduces, yet still remains larger than in the meta-linked polymer. We attribute the difference in exchange energy to the difference in wave function overlap between electron and hole in these compounds. (c) 2006 American Institute of Physics Y1 - 2006 UR - http://scitation.aip.org/getpdf/servlet/ GetPDFServlet?filetype=pdf&id=JCPSA6000124000024244701000001&idtype=cvips&doi=10.1063/1.2200351&prog=normal U6 - https://doi.org/10.1063/1.2200351 ER - TY - JOUR A1 - Sandee, A. J. A1 - Williams, Charlotte K. A1 - Evans, N. R. A1 - Davies, J. E. A1 - Boothby, C. E. A1 - Köhler, Anna A1 - Friend, Richard H. A1 - Holmes, Andrew B. T1 - Solution-processible conjugated electrophosphorescent polymers Y1 - 2004 ER - TY - JOUR A1 - Hayer, Anna A1 - Köhler, Anna A1 - Arisi, E. A1 - Bergenti, I. A1 - Dediu, A. A1 - Taliani, C. A1 - Al-Suti, Mohammed K. A1 - Khan, Muhammad S. T1 - Polymer light-emitting diodes with spin-polarised charge injection. Y1 - 2004 SN - 0379-6779 ER - TY - JOUR A1 - Kohler, A. A1 - Ohrnberger, Matthias A1 - Scherbaum, Frank A1 - Stange, S. A1 - Kind, F. T1 - Ambient vibration measurements in the Southern Rhine Graben close to Basle N2 - This study presents results of ambient noise measurements from temporary single station and small-scale array deployments in the northeast of Basle. H/V spectral ratios were determined along various profiles crossing the eastern masterfault of the Rhine Rift Valley and the adjacent sedimentary rift fills. The fundamental H/V peak frequencies are decreasing along the profile towards the eastern direction being consistent with the dip of the tertiary sediments within the rift. Using existing empirical relationships between H/V frequency peaks and the depth of the dominant seismic contrast, derived on basis of the lambda/4-resonance hypothesis and a power law depth dependence of the S-wave velocity, we obtain thicknesses of the rift fill from about 155 m in the west to 280 in in the east. This is in agreement with previous studies. The array analysis of the ambient noise wavefield yielded a stable dispersion relation consistent with Rayleigh wave propagation velocities. We conclude that a significant amount of surface waves is contained in the observed wavefield. The computed ellipticity for fundamental mode Rayleigh waves for the velocity depth models used for the estimation of the sediment thicknesses is in agreement with the observed H/V spectra over a large frequency band Y1 - 2004 SN - 1593-5213 ER - TY - JOUR A1 - Köhler, Thomas A1 - Wetzstein, A. A1 - Schilde, Patrick T1 - Möglichkeiten der organisationalen Unterstützung räumlich verteilter Arbeits- und Lernprozesse Y1 - 2003 ER - TY - JOUR A1 - Kohler, Ulrich A1 - Kreuter, Frauke A1 - Stuart, Elizabeth A. T1 - Nonprobability Sampling and Causal Analysis JF - Annual review of statistics and its application N2 - The long-standing approach of using probability samples in social science research has come under pressure through eroding survey response rates, advanced methodology, and easier access to large amounts of data. These factors, along with an increased awareness of the pitfalls of the nonequivalent comparison group design for the estimation of causal effects, have moved the attention of applied researchers away from issues of sampling and toward issues of identification. This article discusses the usability of samples with unknown selection probabilities for various research questions. In doing so, we review assumptions necessary for descriptive and causal inference and discuss research strategies developed to overcome sampling limitations. KW - causal inference KW - generalizability KW - self-selection KW - nonprobability sampling KW - validity KW - measurement error KW - heterogeneous treatment effects KW - big data Y1 - 2018 U6 - https://doi.org/10.1146/annurev-statistics-030718-104951 SN - 2326-8298 SN - 2326-831X VL - 6 SP - 149 EP - 172 PB - Annual Reviews CY - Palo Alto ER - TY - JOUR A1 - Struszczyk, Marcin Henryk A1 - Loth, Fritz A1 - Köhler, L. A. A1 - Peter, Martin G. T1 - Characterization of chitosan Y1 - 1998 ER - TY - JOUR A1 - Peter, Martin G. A1 - Köhler, L. A. T1 - Chitin und Chitosan : nachwachsende Rohstoffe aus dem Meer Y1 - 1996 ER - TY - JOUR A1 - Batista, Rita A. A1 - Moreno-Romero, Jordi A1 - Qiu, Yichun A1 - van Boven, Joram A1 - Santos-Gonzalez, Juan A1 - Figueiredo, Duarte Dionisio A1 - Köhler, Claudia T1 - The MADS-box transcription factor PHERES1 controls imprinting in the endosperm by binding to domesticated transposons JF - eLife N2 - MADS-box transcription factors (TFs) are ubiquitous in eukaryotic organisms and play major roles during plant development. Nevertheless, their function in seed development remains largely unknown. Here, we show that the imprinted Arabidopsis thaliana MADS-box TF PHERES1 (PHE1) is a master regulator of paternally expressed imprinted genes, as well as of non-imprinted key regulators of endosperm development. PHE1 binding sites show distinct epigenetic modifications on maternal and paternal alleles, correlating with parental-specific transcriptional activity. Importantly, we show that the CArG-box-like DNA-binding motifs that are bound by PHE1 have been distributed by RC/Helitron transposable elements. Our data provide an example of the molecular domestication of these elements which, by distributing PHE1 binding sites throughout the genome, have facilitated the recruitment of crucial endosperm regulators into a single transcriptional network. Y1 - 2019 U6 - https://doi.org/10.7554/eLife.50541 SN - 2050-084X VL - 8 PB - eLife Sciences Publications CY - Cambridge ER - TY - JOUR A1 - Batista, Rita A. A1 - Figueiredo, Duarte Dionisio A1 - Santos-Gonzalez, Juan A1 - Köhler, Claudia T1 - Auxin regulates endosperm cellularization in Arabidopsis JF - Genes & Development N2 - The endosperm is an ephemeral tissue that nourishes the developing embryo, similar to the placenta in mammals. In most angiosperms, endosperm development starts as a syncytium, in which nuclear divisions are not followed by cytokinesis. The timing of endosperm cellularization largely varies between species, and the event triggering this transition remains unknown. Here we show that increased auxin biosynthesis in the endosperm prevents its cellularization, leading to seed arrest. Auxin-overproducing seeds phenocopy paternal-excess triploid seeds derived from hybridizations of diploid maternal plants with tetraploid fathers. Concurrently, auxin-related genes are strongly overexpressed in triploid seeds, correlating with increased auxin activity. Reducing auxin biosynthesis and signaling reestablishes endosperm cellularization in triploid seeds and restores their viability, highlighting a causal role of increased auxin in preventing endosperm cellularization. We propose that auxin determines the time of endosperm cellularization, and thereby uncovered a central role of auxin in establishing hybridization barriers in plants. KW - auxin KW - cellularization KW - endosperm KW - hybridization barrier KW - seed development KW - triploid block Y1 - 2019 U6 - https://doi.org/10.1101/gad.316554.118 SN - 0890-9369 SN - 1549-5477 VL - 33 IS - 7-8 SP - 466 EP - 476 PB - Cold Spring Harbor Laboratory Press CY - Cold Spring Harbor, NY ER -