Charge Transport Properties of a Metal-free Phthalocyanine Discotic Liquid Crystal

Discotic liquid crystals can self-align to form one-dimensional semiconducting wires, many tens of microns long. In this letter, we describe the preparation of semiconducting films where the stacking direction of the disc-like molecules is perpendicular to the substrate surface. We present measurements of the charge carrier mobility, applying temperature-dependent time-of-flight transient photoconductivity, space-charge limited current measurements, and field-effect mobility measurements. We provide experimental verification of the highly anisotropic nature of semiconducting films of discotic liquid crystals, with charge carrier mobilities of up to 2.8x10$^{-3}$cm$^2$/Vs. These properties make discotics an interesting choice for applications such as organic photovoltaics.Comment: 5 pages, 5 figure

Ancient pigs reveal a near-complete genomic turnover following their introduction to Europe

Archaeological evidence indicates that pig domestication had begun by ∼10,500 y before the present (BP) in the Near East, and mitochondrial DNA (mtDNA) suggests that pigs arrived in Europe alongside farmers ∼8,500 y BP. A few thousand years after the introduction of Near Eastern pigs into Europe, however, their characteristic mtDNA signature disappeared and was replaced by haplotypes associated with European wild boars. This turnover could be accounted for by substantial gene flow from local European wild boars, although it is also possible that European wild boars were domesticated independently without any genetic contribution from the Near East. To test these hypotheses, we obtained mtDNA sequences from 2,099 modern and ancient pig samples and 63 nuclear ancient genomes from Near Eastern and European pigs. Our analyses revealed that European domestic pigs dating from 7,100 to 6,000 y BP possessed both Near Eastern and European nuclear ancestry, while later pigs possessed no more than 4% Near Eastern ancestry, indicating that gene flow from European wild boars resulted in a near-complete disappearance of Near East ancestry. In addition, we demonstrate that a variant at a locus encoding black coat color likely originated in the Near East and persisted in European pigs. Altogether, our results indicate that while pigs were not independently domesticated in Europe, the vast majority of human-mediated selection over the past 5,000 y focused on the genomic fraction derived from the European wild boars, and not on the fraction that was selected by early Neolithic farmers over the first 2,500 y of the domestication process

Radiolabeling of Pluronic amphiphilic copolymer for adsorption studies.

A new pathway for the radiolabeling of Pluronic PE6800 was developed. In a first step, the CH(2)-OH end groups of the copolymer were substituted by tosylates; in a second step these were reduced by [3H]-NaBH(4) to obtain tritiated chain ends. The final product was shown to be a mixture of native, tosylated, and reduced Pluronic containing 1 tritium atom per 1110 Pluronic molecules. The labeling procedure did not affect the molecular weight distribution nor the adsorption isotherm of the copolymer on polystyrene plates. A plateau value of about 0.7 microg/cm(2) is reached at a concentration in solution of 500 microg/ml, i.e., much lower than the cmc. Upon drying, the Pluronic adsorbed layer reorganizes in particles with a size of about 30 to 60 nm which cover about 15% of the substratum surface. This observation is of great importance for the design of protein-resistant surfaces by adsorption of Pluronic

Fish δ13C and δ15N results from two Bronze/Iron Age sites (Tell Tweini & Sidon) along the Levantine coast

Stable isotope ratio measurements of fish remains from archaeological sites are relatively rare so here we report results of 201 fish remains from two Bronze and Iron Age sites along the Syrian (Tell Tweini) and Lebanese (Sidon) coast to document the inter- and intra-specific variation of the δ13C and δ15N isotope values. Due to poor preservation, successful isotopic results were only obtained from 42 specimens (21%). Our results were combined with previously published fish isotopic results from Sidon (n = 16) so that a total 58 specimens representing 16 different fish taxa are presented. A wide variation was observed between species that appears to be related to the ecology of the fish, in particular their salinity tolerance and feeding behaviour. The largest intra-specific variation was observed in mullets (Mugilidae) and seabreams (Sparidae) in both δ13C and δ15N values, and it appears, after comparison with published data from the Northern Aegean, some clustering occurs with location. However, the data clustering is not discrete enough to allow provenancing of fish remains from archaeological sites in this region. This large series of fish isotope values can also serve as an isotopic baseline for other studies, including the dietary reconstruction of Eastern Mediterranean human remains

Surface characterization of poly(methyl methacrylate) microgrooved for contact guidance of mammalian cells.

High-resolution patterns of grooves have been made in poly(methyl methacrylate) films, PMMA, by an electron-beam microlithographic process. The surface of films processed over a large width was characterized in terms of chemical composition (X-ray photoelectron spectroscopy (XPS). time of flight secondary ion mass spectroscopy), wettability (sessile drop) and topography (atomic force microscopy). Collagen adsorption was also studied (radiocounting, XPS) as such or in competition with Pluronic F68. The chemical alteration of the surface induced by the electron-beam irradiation disappeared after the dissolution involved in the development process. W138 human fibroblasts cultivated on microgrooved substrata (grooves 1 microm deep and 0.5-10 microm wide) showed a strong orientation parallel to the grooves. The contact guidance is induced by the topography of the surface and not by the alternation of zones with different physico-chemical properties. It may be explained in terms of probability of successful substratum contact by cell protrusions

Controlling the supramolecular organisation of adsorbed collagen layers.

The supramolecular organisation of collagen adsorbed on polymer substrates was investigated as a function of properties of the substrates (chemical nature, roughness) and of characteristics of the collagen solution (concentration, state of aggregation) as well as details of the preparation procedure (adsorption time, drying rate). Elongated structures are formed at the interface by assembly of collagen molecular segments protruding into the solution. This is favoured by using a hydrophobic and smooth substrate, by increasing the adsorbed amount and by increasing the adsorption time, even beyond stages at which the adsorbed amount does no longer vary. Collagen adsorbed at low amount on hydrophobic substrates strongly reorganises into a net-like pattern if drying is performed at low rate. This is due to dewetting and collagen displacement by the water meniscus. Applications derived from the control of collagen organisation are presented. Nanostructured polymer surfaces were created starting from a collagen template. The attachment and the cytoskeletal organisation of mammalian cells (MCF-7/6) were also shown to depend on collagen organisation