1,721,011 research outputs found
Morphological and electronic properties of the thin film phase of pentacene investigated by AFM and STM/STS
No full textWe investigated the morphological, structural and electronic properties of Pentacene thin films grown by vacuum thermal evaporation on different inert substrates at room temperature. The results of our AFM and STM analysis give an interplanar spacing of 1.54 nm corresponding to the (0 0 1) distance of the so-called "thin film phase". The STS measurements show an HOMO-LUMO gap of 2.2 eV. (c) 2005 Elsevier B.V. All rights reserved
Nanowire directed diffusion limited aggregation growth of nanoparticles
No full textA binary solution of germanium nanoparticles and nanowires was drop cast on a silicon oxide surface. We investigated the dynamic behavior of the drop drying, successfully verifying the Diffusion Limited Aggregation growth mediated by nanowire attractors. The directed growth of nanostructures could be useful in view of device design. (C) 2010 Elsevier B.V. All rights reserved
Conductivity of the thin film phase of Pentacene
No full textWe investigated the morphological, structural and transport properties of pentacene thin films (20 nm) grown by high vacuum thermal evaporation on patterned substrates with different interelectrodes distances. X-ray diffraction and atomic force microscopy show a structure in the so called "thin film phase" with 1-2 mu m sized grains. By means of in situ electrical measurements we found for these films a resistivity value of rho = 4.7 +/- 0.2 x 10(4) Omega m, that is an order of magnitude lower than the value reported to date in literature for single crystals of pentacene. This value is not affected by the presence of grain boundaries. The resistivity is further reduced by a factor 8.9 +/- 0.7, 14 +/- 1, 2.3 +/- 0.3 upon exposure to oxygen, nitrogen and ambient air, respectively. (C) 2006 Elsevier B.V. All rights reserved
On the formation and stability of chitosan/hyaluronan-based complex coacervates
Full text linkThis contribution is aimed at extending our previous findings on the formation and stability of chitosan/hyaluronan-based complex coacervates. Colloids are herewith formed by harnessing electrostatic interactions between the two polyelectrolytes. The presence of tiny amounts of the multivalent anion tripolyphosphate (TPP) in the protocol synthesis serves as an adjuvant “point-like” cross-linker for chitosan. Hydrochloride chitosans at different viscosity average molar mass, Mv, in the range 10,000–400,000 g/mol, and fraction of acetylated units, FA, (0.16, 0.46 and 0.63) were selected to fabricate a large library of formulations. Concepts such as coacervate size, surface charge and homogeneity in relation to chitosan variables are herein disclosed. The stability of coacervates in Phosphate Buffered Saline (PBS) was verified by means of scattering techniques, i.e., Dynamic Light Scattering (DLS) and Small-Angle X-ray Scattering (SAXS). The conclusions from this set of experiments are the following: (i) a subtle equilibrium between chitosan FA and Mv does exist in ensuring colloidal stability; (ii) once diluted in PBS, osmotic swelling-driven forces trigger the enlargement of the polymeric mesh with an ensuing increase of coacervate size and porosity
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
3D island growth of 6,13 Pentacenequinone on silicon oxide and gold
No full textWe investigated the morphological and structural properties of 6,13 Pentacenequinone thin films (5-50 nm) grown by vacuum thermal evaporation on SiO(2) substrates with pre-patterned gold electrodes at room temperature using atomic force microscopy, scanning electron microscopy and X-ray diffraction. The X-ray diffraction always revealed the coexistence of two different crystalline phases, namely the bulk crystal phase and the thin film phase. A comparison of the diffraction data with atomic force microscopy and scanning electron microscopy measurements allowed assigning needle-like (compact) crystallites to the thin film (bulk) phase. The needle-like crystallites started to grow on flat two-dimensional islands lying on an initial wetting layer of Pentacenequinone. This is observed both on the bare silicon oxide substrate and on the polycrystalline gold electrodes. (C) 2010 Elsevier B.V. All rights reserved
Surface evaluation of the effect of X-rays irradiation on parchment artefacts through AFM and SEM
No full textBio-deterioration poses a serious risk in the preservation of ancient parchments. The deteriorating effects of microorganism can affect the surface layers of a membrane sheet causing the total loss of the written text and/or the decorative apparatus of which it is the vehicle. In this work the use of the X-ray radiation performed by an experimental setup, designed at ENEA Frascati, is proposed to inhibit the microbial growth. In order to find the most suitable dose for this purpose and to evaluate the deteriorating effect produced by the irradiation, a series of modern parchment samples has been treated and analysed by means of two microscopic techniques, namely Atomic Force Microscopy and Scanning Electron Microscopy. The combined use of these techniques allows the assessment of alterations in the surface morphology and in the fibrillary networking of the collagen molecule within the parchment, thus enabling the evaluation of the applicability and suitability of the disinfection method proposed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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