1,721,141 research outputs found
Bacterial Expression Of An Artificial Gene For The Production Of Crm197 And Its Derivatives
No full textThe present invention relates to polynucleotide sequences comprising the SEQ ID N° 1 encoding CRM197 and optimised for its expression in E. coli. The invention consequently concerns a method for the production of CRM197 in E. coli via a fusion protein CRM197-tag
Silicon Oxide Surface Functionalization by Self-Assembled Nanolayers for Micro-Cantilever Transducers
No full textWe developed a functionalization procedure for silicon oxide surfaces used in microcantilever-based sensors dedicated to the detection of food contaminants in fluid matrices. In particular we focused on the determination of heavy metal ions and of agricultural pesticides. The surface functionalization was obtained by direct self-assembly of long chain molecules bearing at one end a complexing moiety for metal ions. The selected chelating molecule, the nitrilotriacetic acid (NTA), was immobilized onto silicon oxide surfaces using a three-step process involving the consecutive addition of an organosilane, glutaraldehyde and a NTA derivative solutions. The formation of the self-assembled nanostructure (SAN) at the surface was traced by means of quartz crystal microbalance with dissipation monitoring (QCM) measurements as a function of time. The results indicated that the functionalized molecule forms a rigid self-assembled film on silicon dioxide. Data analysis provided the layer thickness and the molecular orientation of the chemisorbed layers at the interface. The optimized procedure was tentatively applied to functionalize the silicon oxide outer surface of an array of microwells each containing four microcantilevers. Quantitative determination of the metal ions complexation at the surface was achieved adding the desired solution in the QCM measuring chamber and recording the adsorbed mass change as a function of concentration
On the macromolecular cellulosic network of paper: changes induced by acid hydrolysis studied by NMR diffusometry and relaxometry
No full textThe cellulosic network of artificially acidified paper has been studied by 2D NMR relaxometry, NMR diffusometry and NMR diffusion-diffraction. Results show that the acidifying treatment enlarges the macropore structure of paper increasing the pore connectivity and modifying the exchange between water populations localized in amorphous cellulose. Acidification damage suggests that simple breaking of the amorphous portion of fibrils occurs. Nevertheless, under a specific acidifying condition, a rearrangement in the cellulose network seems to take place, with a reduction of the average macropore size and a loss of pore connectivity. The identification of water populations by 2D relaxation maps allows for monitoring the changes in cellulose water mobility due to the depolymerization process. In general the relaxation and self-diffusion results confirm that water mobility increases with acidification
Bottom-up/top-down synthesis of stable zirconium hydroxide nanophases
Full text linkIt is well known that the structure of ZrO2 powder synthesized by low temperature calcination of
hydrous zirconia is strongly affected by the nature and properties of precursors. In the present paper,
we combined a precipitation/restructuring approach (bottom-up/top-down methodology) to produce
zirconium hydroxide nanoparticles that transform into stable nanophasic tetragonal zirconia by low
temperature calcination. The dimension and structure of precursors could be modulated by adjusting
pH. The synthetic route was investigated by Raman spectroscopy, X-Ray Diffraction, Small-Angle XRay
Scattering and High-Resolution Transmission Electron Microscopy. The zirconium hydroxide
nanoparticles represent the final product of the overall process, which starts as a bottom-up synthesis of
the hydroxide gel, followed by a top-down reorganization stage. During this rearrangement, the
evolving structure passes through a mass fractal that arises from the clustering of the primary
zirconium hydroxide nano-units
Surfactant-based photorheological fluids: effect of the surfactant structure
No full textThe effect of the surfactant structure on the mechanical and structural properties of surfactant based photorheo- logical fluids are presented in this paper. Cetyltrimethylammonium bromide (CTABr) mixed with trans-o-methoxy- cinnamic acid in a basic environment can form photosensitive systems. The driving force is the ability of surfactant molecules to form wormlike micelles in the presence of the anionic photosensitive additive. Taking into account that slight changes in the surfactant monomer’s structure can induce drastic modifications of the micellar aggregate features, the role the of the nature of the counterion (in the CTAX type surfactants) or the headgroup size (CTRABr type surfactants) and its influence on the mechanical properties of surfactant based photorheological fluids using trans- o-methoxycinnamic acid (trans-OMCA) as additive were investigated. Rheological studies reported in this paper show that the viscosity of these systems drastically varies only by changing the nature of the surfactant counterion. Moreover, by increasing the bulk simply by replacing the three methyl groups with three ethyl groups in the surfactant headgroup moiety, the viscosity drastically decreases. Highly photosensitive PR fluids can be further obtained using cetyltri- methylammonium trans-o-methoxycinnamate (CTAOMC) as surfactant at neutral pH. In addition to the complete rheological characterization carried out by means of the application of both a steady shear and a dynamic shear stress, a 1H NMR and NOESY study was also performed
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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