Computational Study of Lawesson’s Reagent Mediated Fluorenone Dimerization Forming 9,9’-Bifluorenylidene

The ambition of this work is to start a path to the a priori rational design of high yield production for electron acceptors with finely tuned band gaps, from the comfort of an armchair. To this end, organic photovoltaics offer a cheap and sustainable means of manufacture using readily available materials and avoids the toxicity of some of the heavy metals used in first and second-generation solar cells such as cadmium. The microwave assisted Lawesson’s reagent mediated one-pot one-step solventless synthesis takes less than 3 minutes and results in an 84% yield of 9,9’-bifluorenylidene from two equivalents of fluorenone. While fullerenes have traditionally been the most widely used electron acceptors in organic photovoltaics, bifluorenylidenes have been gaining attention due to their superior absorption in the visible spectrum, highly tunable band gap and cheap/efficient synthesis. Using an analog system to study the reaction divided into two parts; intermediate formation and sulfur extrusion, a molecular pathway has been devised that fits the reaction conditions and explains differences in % yields of substituted 9,9’-bifluorenylidenes reported in a manner readily conducive to making predictions based on the substituents chosen in the 9-fluorenylidene scaffold

An Experimental Investigation in a Turbulent Channel Flow With a Thick Viscous Sublayer (Hot-Film Measurements in Oil)

In a turbulent channel-flow hot-film measurements have been made. To achieve a sublayer thickness of approximately 1 cm at y+ = 10, oil was used. The Reynolds numbers used for the investigations were 5,600 and 8,200 based on the channel-width of 22 cm and the channel center-line velocity. In the vicinity of the wall, y+ \u3c 0.1, the u\u27-fluctuations were found to be proportional to the wall distance, y+. The u\u27-values obtained with a hot-film probe for y+ \u3e 0.7 were all greater than those obtained with a hot-film wall probe, but extrapolation of the data from the movable hot-film probe to the wall gave good agreement with the data from the flush-mounted wall-film probe. The instantaneous values of the u\u27-fluctuations in the region 0 \u3c y+ \u3c 5 are very similar to the instantaneous values of the wall-gradient, but there is a time shift which is proportional to the wall distance, y+. Disturbances in the flow in this region were observed to be convected with a constant velocity toward the wall. The mean value of the convection velocity was found to be approximately equal to the friction velocity, uT. The Reynolds stress was found to be intermittent in the vicinity of the wall with high peak to mean ratios. It was found that the probability density of the instantaneous streamwise velocity is skewed for all y+ values except y+ ≈ 13. For y+ \u3c 13 the most probable instantaneous velocity is less than the mean velocity; for y+ \u3e 13 the opposite was found

Ad-hoc-AG Boden

Die Ad-hoc-AG Boden ist ein Gremium des Bund-/Länderausschusses Bodenforschung, dessen Aufgabe die Herausgabe von Kartieranleitungen, von länderübergreifenden Kartenwerken und von einschlägigen Methoden zur Bewertung von Böden ist. Es wird die Historie der AG dargestellt, ferner wesentliche Produkte und Angebote in Buchhandel und im Interne

XRCC1 PLAYS DIVERSE ROLES IN DNA STRAND BREAK REPAIR AND HUMAN DISEASE

Microhomology-mediated end joining (MMEJ), an error-prone pathway for DNA double-strand break (DSB) repair, is implicated in genomic rearrangement and oncogenic transformation; however, its contribution to repair of radiation-induced DSBs has not been characterized. We used recircularization of a linearized plasmid to recapitulate DSB repair via MMEJ or nonhomologous end-joining (NHEJ). MMEJ was significantly enhanced in irradiated cells, independent of their radiation-induced arrest in the G2/M phase. MMEJ activation was dependent on XRCC1 phosphorylation by casein kinase 2 (CK2), enhancing XRCC1's interaction with the end resection enzymes MRE11 and CtIP. Both endonuclease and exonuclease activities of MRE11 were required for MMEJ. Furthermore, the XRCC1 co-immunoprecipitate complex (IP) displayed MMEJ activity in vitro, which was significantly elevated after irradiation. Our studies thus suggest that radiation-mediated enhancement of MMEJ in cells surviving radiation therapy may contribute to their radioresistance and could be therapeutically targeted. Homologous recombination (HR)-deficient cancers, especially those with mutations in BRCA1 or BRCA2, utilize alternative methods of DNA double-strand break (DSB) repair, in particular microhomology-mediated end joining (MMEJ), for repair of DSBs that arise in S/G2 cell cycle phases as a result of replication stress. Depletion of MMEJ factors, including XRCC1, PARP1, and POLQ, is synthetic lethal with BRCA2 deficiency. While POLQ and PARP1 have been well-studied in the context of HR-deficiency, whether XRCC1 participates in MMEJ in HR-deficient cancers is unknown. We used a variety of approaches to demonstrate XRCC1’s critical role in MMEJ in BRCA2-deficient cells, and discovered that XRCC1 forms an active repair complex with POLQ and MRE11 after replication stress that has MMEJ activity in vitro. Formation of this complex was suppressed by BRCA2. Moreover, XRCC1 contributed to replication fork restart and fork degradation in BRCA2-deficient cells. Expression of XRCC1 is altered in HR-deficient cancers, along with other DNA repair factors in the same region of chromosome 19. Collectively, these studies identify new roles for XRCC1 in HR-deficient cancers and suggest chemotherapeutic strategies targeting MMEJ complex formation

From isophthalamides to supramolecular dendrimers

Erstmals konnte ein supramolekulares Dendrimer mit Hilfe von orthogonalen Erkennungsdomänen aufgebaut und untersucht werden. Hierzu wurden im Rahmen dieser Dissertation viele verschiedene Erkennungsbausteine synthetisiert und mit den entsprechenden Bindepartnern in 1H-NMR-Titrationen, 1H-NMR-Diffusionsexperimenten und ITC-Messungen analysiert.Dabei konnte durch die Einführung von verzweigten Alkylketten, Ethylenglykolketten und Ethern bzw. Estern die Löslichkeit der einzelnen Bausteine erheblich erhöht werden. Zudem konnten verschiedene Isocyanursäure-Kerne erhalten werden. Die Synthese neuer Hamilton-Rezeptoren ermöglicht nun den Aufbau weiterer Dendrimere.In Zusammenarbeit mit FISCHMANN und SAGGIOMO konnte ein konkaver Bimakrozyklus erhalten werden, der in der Lage ist, Dimethylsulfoxid und Pyridin-N-oxid in organischen Lösungsmitteln zu binden. Durch die Entwicklung einer neuen Berechnungsmethode kann mit wenigen Experimenten eine Vielzahl von möglichen Gästen untersucht werden. Durch die Synthese eines tritopen Makrozyklus ist es erstmals gelungen, u. a. Calciumchlorid als Ionentriplett in einem organischen Lösungsmittel zu binden. Der Makrozyklus ist in der Lage, die Salze aus dem Feststoff in die Lösung zu extrahieren. Weitere Experimente zum Thema Löslich- und Mischbarkeiten konnten veranschaulichen, dass Vorhersagen zum Verhalten bei Extraktionsversuchen nicht immer möglich sind.For the first time, a supramolecular dendrimer with orthogonal recognition domains was built up. In this thesis, several different recognition motifs were synthesized and analyzed. Their binding was investigated by 1H NMR titration, 1H NMR diffusion experiments and ITC measurements. To increase the solubility of the building blocks, branched alkyl chains, ethylene glycol chains, ethers and esters were introduced. Furthermore, the synthesis of different isocyanuric acid cores and several Hamilton receptors made the construction of supramolecular dendrimers possible. A novel concave bimacrocycle was obtained in collaboration with FISCHMANN and SAGGIOMO. This receptor was able to bind dimethylsulfoxide and pyridine-N-oxide in organic solvents. A new calculation method was developed to scan several possible guests with little effort. A tritopic macrocycle was synthesized to bind calcium chloride as an ion triplet in organic solvents. This macrocycle was able to extract different salts into the solvent. Additional experiments on miscibility and solubility demonstrates the complex world of multi layer experiments

AC losses in Bi,Pb(2223) multifilamentary wires with square cross-section

We have fabricated prototype Bi,Pb(2223)/Ag superconduting multifilamentary wires with a square cross-section. The AC losses of these wires were measured, compared with those of tapes and also compared with the theory. Wires show largely reduced AC magnetic field losses at 47 Hz, compared to those of tapes in a perpendicular magnetic field. The effects of the twist pitch and of the use of the high resisitive barriers were also investigated. The results show that the use of a twist pitch of about 10 mm is sufficient for decoupling the filaments, and that the use of very short twist pitches does not further reduce the absolute value of the AC losses. The losses in the wires are still higher than those of tapes in a parallel magnetic field, but the results show that the square or round configurations are interesting for applications where a perpendicular component of the magnetic field cannot be avoided, or for applications in rotating magnetic fields.Comment: 8 pages, 11 figures, submitted to Physica

Regulation of Oxidized Base Repair in Human Chromatin by Posttranslational Modification

Base excision repair (BER) is the major pathway for the repair of oxidized bases and apurinic/apyrimidinic (abasic; AP) sites produced by reaction with reactive oxygen/nitrogen species (ROS/RNS). These metabolites are generated spontaneously by endogenous cellular processes and also by environmental agents. Because most of these lesions are promutagenic, linked to diverse disease-associated somatic mutations, as well as heritable single nucleotide polymorphisms (SNPs) in the normal human population, their prompt repair is warranted. Impairment of repair leading to mutation, a hallmark of cancer, underscores the essentiality of BER for maintaining genome integrity in humans and other mammals. In mammals, repair of oxidized bases and other BER substrates is initiated by DNA glycosylases (DGs), which excise the damaged bases and cleave the DNA strands at the resulting AP sites, followed by sequential end processing, gap-filling DNA synthesis, and ligation. In vitro BER performed with naked DNA substrates has been extensively studied, which delineates its basic mechanistic steps and subpathways. However, recent interest is directed to unraveling BER in cell chromatin, including its regulation via posttranslational modifications (PTMs), which occurs possibly in concert with nucleosome remodeling. Emerging reports on various PTMs of BER enzymes indicate that the PTMs, while dispensable for the enzymatic activity, regulate overall repair by modulating interactions with other repair proteins and chromatin factors, assembly of BER complexes, as well as turnover of the proteins, and may ultimately dictate the cellular phenotype. Here, we discuss recent advances in the BER field by reviewing the PTMs and how they regulate BER in chromatin

Bodenübersichtskarte 1:200.000 (BÜK 200) – Vorschlag einer Generallegendengliederung zur Diskussion in der Ad-hoc-AG Boden

Die BÜK 200 ist ein aus 55 Einzelblättern bestehendes Kartenwerk, das von den Staatlichen Geologischen Diensten der Länder und der Bundesanstalt für Geo-wissenschaften und Rohstoffe (BGR) in enger Kooperation erarbeitet wird. Die bodenkundlichen Datensätze werden unabhängig von den Kartenblättern in einer gemeinsamen Flächendatenbank gespeichert, die die Funktion einer Rahmenlegende (vorläufige Generallegende) hat. Der fortgeschrittene Arbeitsstand der BÜK 200 - Flächendatenbank erlaubt es erstmals, über Konzepte nachzudenken, die eine Überführung der Rahmenlegende in eine Generallegende (GL) ermöglichen. Dieser erste Vorschlag einer Generallegendengliederung wurde bei der DBG-Tagung als Beginn einer inhaltlichen Diskussion vorgestellt. Wie alle Entwicklungsschritte zur BÜK 200 ist auch dieser zunächst mit den Mitgliedern der Ad-hoc-AG Boden zu erörtern

Temporal Entropy Generation in the Viscous Layers of Laterally-converging Duct Flows

Since insight into entropy generation is a key to increasing efficiency and thereby reducing fuel consumption and/or waste and -- for wall-bounded flows -- most entropy is generated in the viscous layer, we examine the transient behavior of its dominant contributor there for a non-canonical flow. New measurements in oil flow are presented for the effects of favorable streamwise mean pressure gradients on temporal entropy generation rates and, in the process, on key Reynolds-stress-producing events such as sweep front passage and on the deceleration/outflow phase of the overall bursting process. Two extremes have been considered: (1) a high pressure gradient, nearing "laminarization," and (2), for comparison, a low pressure gradient corresponding to many earlier experiments. In both cases, the peak temporal entropy generation rate occurs shortly after passage of the ejection/sweep interface. Whether sweep and ejection rates appear to decrease or increase with the pressure gradient depends on the feature examined and the manner of sampling. When compared using wall coordinates for velocities, distances and time, the trends and magnitudes of the transient behaviors are mostly the same. The main effects of the higher pressure gradient are (1) changes in the time lag between detections -- representing modification of the shape of the sweep front and the sweep angle with the wall, (2) modification of the magnitude of an instantaneous Reynolds shear stress with wall distance and (3) enlarging the sweeps and ejections. Results new for both low and high pressure gradients are the temporal behaviors of the dominant contribution to entropy generation; it is found to be much more sensitive to distance from the wall than to streamwise pressure gradient