Control of the long-range self-organization of polycyclic aromatic hydrocarbons for device applications

Electronic devices based on organic semiconductors have gained increased attention in nanotechnology, especially applicable to the field of field-effect transistors and photovoltaic. A promising class of materials in this reseach field are polycyclic aromatic hydrocarbons (PAHs). Alkyl substitution of these graphenes results in the selforganization into one-dimensional columnar superstructures and provides solubility and processibility. The nano-phase separation between the π-stacking aromatic cores and the disordered peripheral alkyl chains leads to the formation of thermotropic mesophases. Hexa-peri-hexabenzocoronenes (HBC), as an example for a PAH, exhibits some of the highest values for the charge carrier mobility for mesogens, which makes them promising candidates for electronic devices. Prerequisites for efficient charge carrier transport between electrodes are a high purity of the material to reduce possible trapping sites for charge carriers and a pronounced and defect-free, long-range order. Appropriate processing techniques are required to induce a high degree of aligned structures in the discotic material over macroscopic dimensions. Highly-ordered supramolecular structures of different discotics, in particular, of HBC derivatives have been obtained by solution processing using the zone-casting technique, zone-melting or simple extrusion. Simplicity and fabrication of highly oriented columnar structures over long-range are the most essential advantages of these zone-processing methods. A close relation between the molecular design, self-aggregation and the processing conditions has been revealed. The long-range order achieved by the zone-casting proved to be suitable for field effect transistors (FET).

Synthesis, characterization and chemical modification of a cationic polyelectrolyte poly(methylene amine)

Polyamine polymers have attracted attention due to their ability to demonstrate pH dependent cationic nature and presence of highly reactive pendant amino groups. These amino groups make them suitable for a host of applications through cross-linking and derivatization. As a result the end use application of a polyamine is largely driven by the number of amino groups and the way they are attached to the polymer backbone. Thus, this piece of work describes the synthesis and investigation of properties of a novel aliphatic polyamine, poly(methylene amine); that carries maximum number of amino group on its backbone. The target polymer, poly(methylene amine); was synthesized via two major steps viz.1.synthesis of precursor polymers of poly(methylene amine) and 2. Hydrolysis of the precursor polymers to obtain poly(methylene amine). The precursor polymers poly (1,3-diacetylimidazole-2-one)(6) and poly(1,3-diformyldihydroimidazol-2-one)(7) were synthesized via radical polymerization of their respective monomers. The monomers were polymerized in bulk as well as in solution at different reaction conditions. The maximum molecular weights were achieved by polymerizing the monomers in bulk (Mn = 6.5 x 104 g/mol and Mw = 2.13 x 105 g/mol) of 6. The precursor polymers were hydrolyzed under strong reaction conditions in ethanol in presence of NaOH, LiCl at 170°C to yield poly(methylene amine). The process of hydrolysis was monitored by IR spectroscopy. The solution properties of poly(methylene amine) and its hydrochloride were investigated by viscosimetry and light scattering. The reduced viscosity of poly (methylene amine) hydrochloride as a function of polymer concentration demonstrated a behavior typical of cationic polyelectrolyte. With decrease in polymer concentration the reduced viscosity of poly(methylene amine) hydrochloride increased gradually. The dynamic light scattering studies also revealed behaviors of a polyelectrolyte. Poly(methylene amine) was reacted with electrophiles to yield novel materials. While the attachment of alkyl group onto the nitrogen would increase nucleophilicity, it would also impose steric hindrance. As a result the degree of substitution on poly(methylene amine) would be governed by both the factors. Therefore, few model reactions with electrophiles were performed on polvinylamine under similar reaction conditions in order to make a comparative evaluation. It was found that under similar reaction conditions the degree of substitution was higher in case of polyvinylamine in comparison with poly (methylene amine).This shows that the steric hindrance outweighs nucleophilicity while deciding degree of substitution of electrophiles on poly(methylene amine). The modification was further extended to its use as an initiator for ring opening polymerization of benzyloxy protected N-carboxyanhydride of z-Lysine. The resulting polymer had an interesting brush like architecture. The solid state morphology of this polymer was investigated by SAXS. The 2D-WAXS diffractograms revealed hexagonal morphology of peptide segments without formation of alpha helices.

Study of the genes involved in Naphthenic acids (NAs) degradation by Rhodococcus spp.

Naphthenic acids (NAs) are an important group of organic pollutants mainly found in hydrocarbon deposits. Although these compounds are toxic, recalcitrant, and persistent in the environment, we are just learning the diversity of microbial communities involved in NAs- degradation and the mechanisms by which NAs are biodegraded. Studies have shown that naphthenic acids are susceptible to biodegradation, which decreases their concentration and reduces toxicity. Nevertheless, little is still known about their biodegradability. The present PhD Thesis’s work is aimed to study the biodegradation of simple model NAs using bacteria strains belonging to the Rhodococcus genus. In particular, Rh. sp. BCP1 and Rh. opacus R7 were able to utilize NAs such as cyclohexane carboxylic acid and cyclopentane carboxylic acid as the sole carbon and energy sources, even at concentrations up to 1000 mg/L. The presence of either substituents or longer carboxylic acid chains attached to the cyclohexane ring negatively affected the growth by pure bacterial cultures. Moreover, BCP1 and R7 cells incubated in the presence of CHCA or CPCA show a general increase of saturated and methyl-substituted fatty acids in their membrane, while the cis-mono-unsaturated ones decrease, as compared to glucose-grown cells. The observed lipid molecules modification during the growth in the presence of NAs is suggested as a possible mechanism to decrease the fluidity of the cell membrane to counteract NAs toxicity. In order to further evaluate this toxic effect on cell features, the morphological changes of BCP1 and R7 cells were also assessed through Transmission Electron Microscopy (TEM), revealing interesting ultrastructural changes. The induction of putative genes, and the construction of a random transposon mutagenesis library were also carried out to reveal the mechanisms by which these Rhodococcus strains can degrade toxic compounds such as NAs.

Pulse or hyaline ring granuloma. Review of the literature on etiopathogenesis of oral and extraoral lesions

Since the late 1950s, reports on an unusual giant-cell granulomatous lesion affecting the jaws, lungs, stomach and intestines have been published. Histopathologically, the lesions showed the presence of structureless hyaline rings with multinucleated giant cells. The aim of this review was to summarize the literature on the etiopathogenesis of the so-called oral and extraoral pulse or hyaline ring granuloma. Literature was searched using PubMed and Medline. In addition, hand search was performed. Search words were oral and extraoral hyaline ring granuloma, giant-cell hyaline angiopathy, pulse granuloma and chronic periostitis. Numerous terms for hyaline ring granuloma have been introduced over time (1971-2008). One hundred seventy-three cases of oral hyaline ring granuloma have been retrieved from the literature. In the mandible, 72.3% occurred . Two theories for etiopathogenesis have been proposed: (1) the origin of the hyaline rings is due to a foreign material (pulse and legumes) having penetrated the oral mucosa or gastrointestinal tract and lungs (exogenous theory) and (2) the rings are due to hyaline degenerative changes in walls of blood vessels (endogenous theory). Experimental production of oral and extraoral hyaline ring granulomas is consistent with the exogenous origin. Particles or remains of leguminous cells having been implanted or aspirated into human tissues whether located to the oral cavity or throughout the entire digestive tract and respiratory system are thought to be causative. Pulse or hyaline ring granulomas are rare but are well-defined oral and extraoral lesions due to implantation of the cellulose moiety of plant foods in contrast to the starch components.

Debris-flow activity in abandoned channels of the Manival torrent reconstructed with LiDAR and tree-ring data

Hydrogeomorphic processes are a major threat in many parts of the Alps, where they periodically damage infrastructure, disrupt transportation corridors or even cause loss of life. Nonetheless, past torrential activity and the analysis of areas affected during particular events remain often imprecise. It was therefore the purpose of this study to reconstruct spatio-temporal patterns of past debris-flow activity in abandoned channels on the forested cone of the Manival torrent (Massif de la Chartreuse, French Prealps). A Light Detecting and Ranging (LiDAR) generated Digital Elevation Model (DEM) was used to identify five abandoned channels and related depositional forms (lobes, lateral levees) in the proximal alluvial fan of the torrent. A total of 156 Scots pine trees (Pinus sylvestris L.) with clear signs of debris flow events was analyzed and growth disturbances (GD) assessed, such as callus tissue, the onset of compression wood or abrupt growth suppression. In total, 375 GD were identified in the tree-ring samples, pointing to 13 debris-flow events for the period 1931–2008. While debris flows appear to be very common at Manival, they have only rarely propagated outside the main channel over the past 80 years. Furthermore, analysis of the spatial distribution of disturbed trees contributed to the identification of four patterns of debris-flow routing and led to the determination of three preferential breakout locations. Finally, the results of this study demonstrate that the temporal distribution of debris flows did not exhibit significant variations since the beginning of the 20th century.

Sugar modification as a means to increase the biological performance of oligonucleotides

Modification of the ribose unit in DNA and RNA profoundly influences the self-rcognition and the biological properties of the nucleic acids. Conformational restriction of the ribose units, as in LNA and tricyclo-DNA, has been identified as a powerful tool to increase DNA and RNA affinity as well as biological stability and antisense properties. Apart from that sugar modified DNA analogues, as homo-DNA, have shown to be orthogonal base-pairing systems which by virtue of non-crosscommunicating with the natural nucleic acids open novel applications in biotechnology.

Effects on cycle control and bodyweight of the combined contraceptive ring, NuvaRing, versus an oral contraceptive containing 30 microg ethinyl estradiol and 3 mg drospirenone

BACKGROUND: The objective of this study was to compare cycle control, cycle-related characteristics and bodyweight effects of NuvaRing with those of a combined oral contraceptive (COC) containing 30 microg of ethinyl estradiol and 3 mg of drospirenone. METHODS: A randomized, multicentre, open-label trial in which 983 women were treated (intent-to-treat population) with NuvaRing or the COC for 13 cycles. RESULTS: Breakthrough bleeding or spotting during cycles 2-13 was in general less frequent with NuvaRing than that with the COC (4.7-10.4%) and showed a statistically significant odds ratio of 0.61 (95% confidence interval: 0.46, 0.80) with longitudinal analysis. Intended bleeding was significantly better for all cycles with NuvaRing (55.2-68.5%) than that with the COC (35.6-56.6%) (P < 0.01). Changes from baseline in mean bodyweight and body composition parameters were relatively small for both groups with no notable between-group differences. CONCLUSION: NuvaRing was associated with better cycle control than the COC, and there was no clinically relevant difference between the two groups in bodyweight.

Synthesis of the bicyclo-[4.3.0]thymidyl nucleoside via Pd(II)-mediated ring expansion chemistry

A variety of modified nucleosides to improve antisense oligodeoxynucleotide properties such as target affinity, nuclease resistance, and pharmacokinetics were developed in the last two decades. In the context of conformational restriction we present here the synthesis of the [4.3.0]-bicyclo-DNA thymine monomer via Pd(II)-mediated ring expansion of an intermediate of the tricyclo-DNA synthesis.

Synthesis of bicyclo-DNA nucleosides with additional functionalization in the carbocyclic ring

Two novel bicyclo nucleoside isomers carrying the base thymine in the furanose ring and an ester substituent in the carbocyclic ring were synthesized from a common bicyclic sugar precursor via a cyclopropanation/fragmentation pathway in nine steps. The relative configuration of the ester substituent in both isomers as well as the anomeric configuration in one nucleoside was determined by 1H-NMR difference NOE spectroscopy.