1,721,009 research outputs found
Deposition of nano-crystalline graphite films by cathodic plasma electrolysis
No full textAtmospheric pressure plasma deposition (APPD) of nano-crystalline graphite films on titanium substrate from a predominantly ethanol liquid phase was carried out under varying applied voltage. A thorough study of the plasma electrolytic deposition mechanisms has been performed. The investigation of the composition, structural properties, and the morphology of these graphite coatings have been performed by visible and UV Raman spectroscopy, X-Ray Photoelectron Spectroscopy, Scanning Electron Microscopy and EDAX elemental analysis. The experimental evidence of the reduction of the work function and the enhancement of the plasma intensity with the presence of the carbon film has been reported. These properties make such nano-crystalline graphite coatings very attractive for the production of inexpensive cold cathodes for electronics and plasma devices
Structural changes in the cells of some bacteria during population growth: An FT-IR/ATR study
No full textStructural changes occurring in the cells of several bacteria during their growth curves have been investigated by Fourier transform infrared (FT-IR) spectroscopy using the sampling technique of attenuated total reflectance (ATR). Spectra reflect all of the components of the cells including the cell walls, cell membranes, internal structures and the cytoplasm. The bacteria studied were Bacillus stearothermophilus, Halobacterium salinarium, Halococcus morrhuae and Acetobacter aceti. All species showed significant spectral changes during their growth curves, indicating structural changes in the cells during increases in cell numbers. The major change for B. stearothermophilus was in the lipid content which was at a maximum during the exponential phase of the growth curve. For the halophiles H. salinarium and H. morrhuae the major change was that the concentration of sulfate ion in the cells varied during the growth curve and was at a maximum during the mid-part of the exponential phase of the growth curve. A. aceti cells showed increasing polysaccharide content during the growth curve as well as maximum lipid content during the exponential phase of growth
Rationalizing the SER spectra of bacteria
No full textThe SER spectra of riboflavin and FAD are identical and are resonance enhanced at 514 or 532 nm. Signals from FAD/ riboflavin dominated SER spectra whenever these compounds were present with proteins or bacteria. SER spectra of very different bacteria such as Pseudomonas. aeruginosa, Bacillu. subtilis and Geobacillus. stearothermophilus were dominated by signals from FAD, even when these bacteria were added to a preformed colloid. The SERS signal of FAD is greatly reduced at 785 nm, and SER spectra of bacteria excited at 785 nm are quite different than those collected at 514 or 532 nm. This supports the assignment of the peaks in the 514 nm SER spectra of bacteria to FAD rather to amino acids or N-acetylglucosamine. The SER spectra of certain mixes of adenine and FAD showed similar changes to those of bacteria when the excitation was changed from 514/532 nm to 785 nm. The ratio of colloid: bacteria was of critical important for obtaining good SER spectra, and the addition of sodium sulfate was also beneficial. Removal of EPS from bacteria before analysis facilitated interaction with the silver surface, and may be a useful step to include in identification protocols
Raman and Infrared Microspectroscopic Mapping of Plasma-Treated and Grafted Polymer Surfaces
No full textThe grafting of polystyrene (PS) onto a predominantly polypropylene (PP) substrate has been followed by Raman and infrared microspectroscopic mapping. For exactly the same 50 μm × 50 μm section of polymer surface, Raman spectra were obtained at 1 μm intervals for the substrate, the surface after plasma treatment, and the surface after PS grafting. Maps of the substrate were constructed, indicating the crystallinity variation across the surface and also the distribution of the minor component ethylene-propylene rubber (EPR). After plasma treatment, the crystallinity was found to decrease slightly. Infrared microspectroscopic maps of a larger plasma-treated surface were also obtained with the technique of attenuated total reflection. The spatial resolution of these maps was 50 μm, and they showed the distribution of the hydroxy groups introduced onto the surface by the plasma treatment. PS grafting was found to be heterogeneous. Increased concentrations of grafted PS showed some correlation with positions on the surface which had higher EPR after plasma treatment
Plasma Electrolytic Deposition of Titanium Dioxide Nanorods and Nano-particles
No full textA new plasma electrolytic deposition process working at atmospheric pressure has been developed for the growth of titanium dioxide coatings composed of nano-rods and nano-particles. By controlling the plasma discharge intensity, the treatment time and the initial titanium concentration in the liquid solution, we have been able to produce a large range of structures and morphologies that must be promising in various technological applications, from nano-electronics to solar cell technologies
Forensic analysis of fibres by vibrational spectroscopy
No full textFibres are extremely common. They can originate directly from human and animal hair, and also from textiles in the form of clothing, upholstery and carpets. Hair and textile fibres are relatively easily shed and transferred, which means that it is highly likely that fibres will be found at crime scenes. If such fibres are carefully characterised they can be of immense value in the forensic environment. Vibrational spectroscopy is one of the most important methods for the characterisation of natural and synthetic fibres. The vibrational spectrum, whether mid-IR or Raman, can be considered to be a fingerprint of the molecular structure of the fibre and as such has a very high information content
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
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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