Photochemische Reaktionen und Synthese heterotrimetallischer Verbindungen von Rh-Komplexen

Zur Darstellung der gewünschten trimetallischen Rh-Ti- und Rh-Zr-Komplexe mit verbrückten Tris(h5-cyclopentadienyl)silan-Liganden wurde eine neue Synthesestrategie entwickelt, wobei der verbrückende Ligand an einem monometallischen Precursor aufgebaut wird. Dafür wurden die Komplexe [{(C5H4)SiMeCl2}Rh(cod)] 2, dessen Struktur durch eine Einkristall-Röntgenbeugungsanalyse bestätig wurde, und [{(C5H4)SiMeCl2}Rh(CO)2] 3 als Precursoren hergestellt. Mit zwei Äquivalenten [(C5H5)MgBr] 5 werden die beiden Cl-Atome gegen Cyclopentadien ersetzt, wobei die Verbindung [{(C5H4)SiMe(C5H5)2}Rh(cod)] 4 gebildet wird. Deprotonierung von 4 liefert den Komplex [MeSi(C5H4)3{Rh(cod)}Li2] 6. Das Dilithiosalz 6 diente als Ausgangsverbindung für die heterotrimetallischen Komplexe [MeSi(C5H4)3{CpZrCl2}2{Rh(cod)}] 7, [MeSi(C5H4)3{Cp?ZrCl2}2{Rh(cod)}] 8 und [MeSi(C5H4)3{t-BuCpZrCl2}2{Rh(cod)}] 9, die alle drei mittels einer Salzeliminierungsreaktion mit zwei Äquivalenten RCpZrCl3×DME-Addukt synthetisiert wurden. Aufgrund von Nebenreaktionen konnte die entsprechende Rh-Ti-Spezies [MeSi(C5H4)3{Cp?TiCl2}2{Rh(cod)}] 10 nicht in reiner Form erhalten werden. Durch UV-Bestrahlung können [TpMe,PhRh(CO)2] 11 und [TpMe,PhRh(CO)(PPh3)] 12 intramolekular an einem der drei Phenylringe C?H-aktiviert werden, wobei die oktaedrisch koordinierten Komplexe [HB(Me,Phpy)2(MeC3HN2C6H4)Rh(CO)H] 13 bzw. [HB(Me,Phpy)2(MeC3HN2C6H4)Rh(PPh3)H] 14 mit sehr guten Ausbeuten von 81 % bzw. 97 % erhalten werden. Die intramolekularen C-H-Aktivierungen der Verbindungen 11 und 12 sind beide reversible Reaktionen. Leitet man Kohlenmonooxid in die Lösung der Komplexe 13 bzw. 14 ein, finden die Rückreaktionen statt, und die Edukte 11 bzw. 12 werden zurückgebildet. Die Verbindungen 13 und 14 liegen in Lösung als 5-fach koordinierte Spezies mit einem fluktuierenden Verhalten vor, wie durch temperaturabhängige NMR-Untersuchungen gezeigt werden konnte. 13 und 14 wurden durch 1H-, 13C-, 31P-NMR, MS, IR und Röntgenstrukturanalyse charakterisiert. Beim Versuch den Komplex 13 zu kristallisieren, erhielt man überraschend Kristalle einer zweikernigen Verbindung [{HB(Me,Phpy)2(MeC3HN2C6H4)Rh}2(m-k1:k2-CO3)(CO)] 15, in der die beiden Rh-Atome durch ein Carbonat m2-k2: k1 verbrückt sind. Diese Art der Carbonatverbrückung ist bisher beispiellos. Untersuchungen zeigen, dass das Carbonat durch Oxidation mit Sauerstoff aus 13 entstanden ist. Die UV-Bestrahlung von [CpRh(C2H4)2] mit Pyridin liefert in einer schrittweisen Aufbaureaktion die Verbindungen [CpRh(C2H4)(C5H5N)] 16, [(CpRh)2(m-CHCH3)( m-H)( m-C5H4N)] 17 und den dreikernigen Rhodiumkomplex [Cp3Rh3(m3-h2:h2:h2-C5H5N)] 18. In Lösung beobachtet man für 18 eine 60°-Oszillation des Pyridinringes über dem Rhodiumdreieck, an das er m3-h2:h2:h2 koordiniert ist. Dieser dynamische Prozess wurde durch Tieftemperatur-NMR-Spektroskopie an 18 in d8-Toluol eingehend untersucht. Aus der Koaleszenz der Cp-Signale erhält man DG¹238K = 48.30 kJ/mol. Die Linienformanalyse liefert die weiteren Werte DH¹ = 57.15 ± 4.65 kJ/mol und DS¹ = 44.71 ± 19.47 J/molK. Die Struktur der Verbindung [Cp3Rh3(m3-h2:h2:h2-C5H5N)] 18 konnte durch eine Röntgenbeugungsanalyse eindeutig belegt werden, sie stellt das erste Beispiel für eine synfacial verbrückende m3-h2:h2:h2-Koordination eines Pyridinliganden dar. Durch NMR-Untersuchung der betreffenden BF3-Addukte konnten gezeigt werden, dass die Lewis-Basizität von 18 gegenüber der von freiem Pyridin stark verringert ist

Controlling periodic Fano resonances of quantum acoustic waves with a giant atom coupled to microwave waveguide

Nanoscale Fano resonances, with applications from telecommunications to ultra-sensitive biosensing, have prompted extensive research. We demonstrate that a superconducting qubit, jointly coupled to microwave waveguides and an inter-digital transducer composite device, can exhibit acoustic Fano resonances. Our analytical framework, leveraging the Taylor series approximation, elucidates the origins of these quantum acoustic resonances with periodic Fano-like interference. By analyzing the analytical Fano parameter, we demonstrate that the Fano resonances and their corresponding Fano widths near the resonance frequency of a giant atom can be precisely controlled and manipulated by adjusting the time delay. Moreover, not just the near-resonant Fano profiles, but the entire periodic Fano resonance features can be precisely modulated from Lorentz, Fano to quasi-Lorentz shapes by tuning the coupling strength of the microwave waveguide. Our analytical framework offers insights into the control and manipulation of periodic Fano resonances in quantum acoustic waves, thereby presenting significant potential for applications such as quantum information processing, sensing, and communication.Comment: 13 pages, 5 figure

BIOADI: a machine learning approach to identifying abbreviations and definitions in biological literature

BACKGROUND: To automatically process large quantities of biological literature for knowledge discovery and information curation, text mining tools are becoming essential. Abbreviation recognition is related to NER and can be considered as a pair recognition task of a terminology and its corresponding abbreviation from free text. The successful identification of abbreviation and its corresponding definition is not only a prerequisite to index terms of text databases to produce articles of related interests, but also a building block to improve existing gene mention tagging and gene normalization tools. RESULTS: Our approach to abbreviation recognition (AR) is based on machine-learning, which exploits a novel set of rich features to learn rules from training data. Tested on the AB3P corpus, our system demonstrated a F-score of 89.90% with 95.86% precision at 84.64% recall, higher than the result achieved by the existing best AR performance system. We also annotated a new corpus of 1200 PubMed abstracts which was derived from BioCreative II gene normalization corpus. On our annotated corpus, our system achieved a F-score of 86.20% with 93.52% precision at 79.95% recall, which also outperforms all tested systems. CONCLUSION: By applying our system to extract all short form-long form pairs from all available PubMed abstracts, we have constructed BIOADI. Mining BIOADI reveals many interesting trends of bio-medical research. Besides, we also provide an off-line AR software in the download section on http://bioagent.iis.sinica.edu.tw/BIOADI/

Sequence features involved in the mechanism of 3' splice junction wobbling

Background Alternative splicing is an important mechanism mediating the diversified functions of genes in multicellular organisms, and such event occurs in around 40-60% of human genes. Recently, a new splice-junction wobbling mechanism was proposed that subtle modifications exist in mRNA maturation by alternatively choosing at 5'- GTNGT and 3'- NAGNAG, which created single amino acid insertion and deletion isoforms. Results By browsing the Alternative Splicing Database information, we observed that most 3' alternative splice site choices occur within six nucleotides of the dominant splice site and the incidence significantly decreases further away from the dominant acceptor site. Although a lower frequency of alternative splicing occurs within the intronic region (alternative splicing at the proximal AG) than in the exonic region (alternative splicing at the distal AG), alternative AG sites located within the intronic region show stronger potential as the acceptor. These observations revealed that the choice of 3' splice sites during 3' splicing junction wobbling could depend on the distance between the duplicated AG and the branch point site (BPS). Further mutagenesis experiments demonstrated that the distance of AG-to-AG and BPS-to-AG can greatly influence 3' splice site selection. Knocking down a known alternative splicing regulator, hSlu7, failed to affect wobble splicing choices. Conclusion Our results implied that nucleotide distance between proximal and distal AG sites has an important regulatory function. In this study, we showed that occurrence of 3' wobble splicing occurs in a distance-dependent manner and that most of this wobble splicing is probably caused by steric hindrance from a factor bound at the neighboring tandem motif sequence

Impacts of Two Types of El Niño and La Niña Events on Typhoon Activity

The HadISST (Hadley Centre Sea Ice and Sea Surface Temperature) dataset is used to define the years of El Niño, El Niño Modoki, and La Niña events and to find out the impacts of these events on typhoon activity. The results show that the formation positions of typhoon are farther eastward moving in El Niño years than in La Niña years and much further eastward in El Niño Modoki years. The lifetime and the distance of movement are longer, and the intensity of typhoons is stronger in El Niño and in El Niño Modoki years than in La Niña years. The Accumulated Cyclone Energy of typhoon is highly correlated with the Oceanic Niño Index with a correlation coefficient of 0.79. We also find that the typhoons anomalously decrease during El Niño years but increase during El Niño Modoki years. Besides, there are two types of El Niño Modoki, I and II. The intensity of typhoon in El Niño Modoki I years is stronger than in El Niño Modoki II years. Furthermore, the centroid position of the Western Pacific Warm Pool is strongly related to the area of typhoon formation with a correlation coefficient of 0.95

Finding Related Publications: Extending the Set of Terms Used to Assess Article Similarity.

Recommendation of related articles is an important feature of the PubMed. The PubMed Related Citations (PRC) algorithm is the engine that enables this feature, and it leverages information on 22 million citations. We analyzed the performance of the PRC algorithm on 4584 annotated articles from the 2005 Text REtrieval Conference (TREC) Genomics Track data. Our analysis indicated that the PRC highest weighted term was not always consistent with the critical term that was most directly related to the topic of the article. We implemented term expansion and found that it was a promising and easy-to-implement approach to improve the performance of the PRC algorithm for the TREC 2005 Genomics data and for the TREC 2014 Clinical Decision Support Track data. For term expansion, we trained a Skip-gram model using the Word2Vec package. This extended PRC algorithm resulted in higher average precision for a large subset of articles. A combination of both algorithms may lead to improved performance in related article recommendations

Pseudomonas aeruginosa sepsis with ecthyma gangrenosum and pseudomembranous pharyngolaryngitis in a 5-month-old boy

Pseudomonas aeruginosa infection that induced pseudomembranous laryngopharyngitis and ecthyma gangrenosum simultaneously in a healthy infant is rare. We reported on a previously healthy 5-month-old boy with initial presentation of fever and diarrhea followed by stridor and progressive respiratory distress. P. aeruginosa sepsis was suspected because ecthyma gangrenosum over the right leg was found at the emergency department, and the diagnosis was confirmed by the blood culture. Fiberscope revealed bacterial pharyngolaryngitis without involvement of the trachea. Because of early recognition and adequate treatment, including antimicrobial therapy, noninvasive ventilation, incision, and drainage, he recovered completely without any complications

Soft tagging of overlapping high confidence gene mention variants for cross-species full-text gene normalization

Abstract Background Previously, gene normalization (GN) systems are mostly focused on disambiguation using contextual information. An effective gene mention tagger is deemed unnecessary because the subsequent steps will filter out false positives and high recall is sufficient. However, unlike similar tasks in the past BioCreative challenges, the BioCreative III GN task is particularly challenging because it is not species-specific. Required to process full-length articles, an ineffective gene mention tagger may produce a huge number of ambiguous false positives that overwhelm subsequent filtering steps while still missing many true positives. Results We present our GN system participated in the BioCreative III GN task. Our system applies a typical 2-stage approach to GN but features a soft tagging gene mention tagger that generates a set of overlapping gene mention variants with a nearly perfect recall. The overlapping gene mention variants increase the chance of precise match in the dictionary and alleviate the need of disambiguation. Our GN system achieved a precision of 0.9 (F-score 0.63) on the BioCreative III GN test corpus with the silver annotation of 507 articles. Its TAP-k scores are competitive to the best results among all participants. Conclusions We show that despite the lack of clever disambiguation in our gene normalization system, effective soft tagging of gene mention variants can indeed contribute to performance in cross-species and full-text gene normalization.</p