1,721,029 research outputs found
Print-Light-Synthesis of ruthenium oxide thin film electrodes for electrochemical sensing applications
Full text linkPrint-Light-Synthesis (PLS) combines the inkjet printing of a ruthenium precursor ink with the simultaneous photo-induced generation of ruthenium oxide films. During PLS, inkjet-printing generates on conductive as well as insulating substrates micrometer-thin reaction volumes that contain with high precision defined precursor loadings. Upon direct UV light irradiation, the Ru precursor converts to RuO 2 while all other ink components escape in the gas phase. No post PLS processes are required, and the as-obtained RuO 2 films can be immediately used as electrochemical devices. Two-dimensional RuO 2 patterns with micrometric resolution and highlycontrolled ruthenium loadings (few µg/cm 2) are realized. Thin RuO 2 films are generated on insulating substrates, such as polyimide, as well as individual RuO 2 particles on conductive substrates, such as graphene layers. The RuO 2 films are characterized by electron microscopy and spectroscopic techniques. The sensoristic applicability of the PLS-RuO 2 electrodes is demonstrated by potentiometric pH sensing in cell cultures and amperometric detection of L-cysteine. For pH sensing the RuO 2 film electrodes show Nernstian sensitivity. L-cysteine detection of RuO 2-modified graphene electrodes showed an electrocatalytical effect and resulted in the possibility of selectively detecting L-Cysteine also in presence of the interfering compound uric acid. ☆ This article is part of a special issue entitled: '11th SMCBS 2023 Workshop' published in Bioelectrochemistry.GR-LU
Soft-Probe-Scanning Electrochemical Microscopy reveals electrochemical surface reactivity of E. coli biofilms
Full text linkInvestigating and understanding dynamic biofilm growth mechanisms is challenging, often because state-of-the-art optical characterization tools provide limited information. Micrometric electrochemical imaging of Escherichia coli biofilms using Soft-Probe-Scanning Electrochemical Microscopy (Soft-Probe-SECM) is herein presented as a complementary technique. A soft microelectrode is scanned over biofilms in a gentle contact mode, which is essential to provide a constant working distance. The on-film reduction of an electro-active compound, here the oxidized form of ferrocene methanol, is used to create in situ biofilm metabolic activity maps by applying the feedback mode of SECM. SECM approach curves of identically grown biofilms suggest that the SECM-based detection of metabolic activity is surface-confined. The analysis could therefore be carried out on entire biofilms as well as on tape-stripped biofilm surface layers. The method is further capable of distinguishing between biofilms containing E. coli cells either with or without ampicillin-resistance. Finally, the SECM detection of the degradation of an E. coli biofilm in the presence of different gentamicin concentrations is presented
Electrostatic Spray Ionization Mass Spectrometry Imaging
Full text linkImaging samples on a surface by mass spectrometry (MS) requires the combination of MS detection with a scanning mode that enables localized desorption and ionization and/or detection of sample analytes with good spatial resolution. We have developed a new mass spectrometry imaging (MSI) method based on electrostatic spray ionization. It works under ambient conditions and can be applied to a wide range of molecules providing quantitative MS analysis even in the presence of salts in excess. 2D MS images of protein and peptide spots, inkjet-printed black dye patterns, and cells were obtained. The presented novel ambient ionization mass spectrometry imaging method can find many applications in analytical and bioanalytical chemistryLEPALCPP
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
Print-Light-Synthesis of Gold Thin Film Electrodes for Electrochemical Sensing
Full text linkThe one-step fabrication of gold films by inkjet printing of a gold precursor ink and its photochemical reduction by exposure to UV light is presented. Inkjet printing creates on a substrate with high control micrometer-thin reaction volumes in which upon direct high-intensity light irradiation, the gold precursor reduces to pure and well-adhered Au particles, while all other ink components escape in the gas phase, without the need for any further post-treatment. The Au precursor ink does neither contain stabilizing agents, such as polymers or surfactants, nor sacrificial compounds, such as photoinitiators, to initiate and accelerate the reduction. This economic and green process is known as Print-Light-Synthesis (PLS) and is herein used to create gold patterns of thin compact Au films and separated Au nanoparticles. Gold loadings are in the mu g cm(-2) range and precisely controlled, thanks to the inkjet printing parameters. The gold films are characterized by spectroscopic and electrochemical methods. Finally, the applicability of Au films as electrochemical sensors is demonstrated for the detection of 1,4-butanediol in comparison to a commercial screen-printed Au electrode. The PLS Au electrode shows a 20 times higher sensitivity and opens new possibilities for disposable electrode production.GR-LU
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
Probing Odorant-Mediated Receptor Activation
No full textMolecular interactions of odorants with their olfactory receptors (ORs) are of central importance for the mammalian olfactory system to detect and discriminate a large variety of odors with a limited set of receptors. How a particular OR binds and distinguishes different odorant molecules remains unknown on a structural basis as there is no three- dimensional OR structure available. Progress in the area of ligand assignment to specific receptors with the development of functional assays allowing efficient screening of numerous odorant compound libraries is essential for the understanding of the selectivity and sensitivity of odor detection. To improve our knowledge of an OR binding site environment, the first part of this thesis focused on the characterization of the molecular interactions of the mouse eugenol receptor (mOR-EG) which has been shown to be activated by a wide variety of odorants. Computer modeling based on the resolved 3D structure of the β2-adrenergic receptor and mutational studies on mOR-EG were used to determine the key amino acid residues responsible for specific OR-ligand recognition and to determine the localization and chemical properties of the putative ligand binding site. Activation of mOR-EG point mutants was monitored using a cAMP-induced reporter gene assay in Hana3A cells. These investigations were used to improve ligand docking in the binding site and further define a more precise model of the mOR-EG ligand-binding cavity. With the development of genome sequencing, the comparison of ortholog/paralog pairs is becoming increasingly important to study the molecular basis of OR specificity. Emphasis has thus been placed on the characterization of the mOR-EG’s mouse paralog mOR-EV and on its putative human ortholog hOR5D18. These two ORs have been functionally expressed in Hana3A cells and the visualization of both their overall- and cell-surface expression have been performed using different OR fusion proteins. New specific agonists for the mOR-EV have been identified (jasmone, rose oxyde and nootkatone) and first attempts to de-orphanize hOR5D18 have been carried out, by random screening a large panel of more than 250 odorant compounds coupling the OR activation to cAMP-induced reporter gene expression. Based on our knowledge of the mOR-EG ligand binding site, three important positions for ligand recognition that diverge between mOR-EG and mOR-EV were mutated in both receptors to increase their sequence identity. Comparison of their respective ligand repertoires has provided novel insight into the molecular determinants for odor detection and discrimination. Given the importance to assign ligands to their cognate receptors, we established a novel functional assay based on electrical impedance measurements. The detection of ligand-induced cell morphological changes during and after receptor stimulation has been used to quantify the activation of different GPCRs including mOR-EG with their respective ligands. This label-free technique is applicable for many different cell types as well as for endogenously expressed receptors and is suitable for screening large libraries of ORs and compounds. Odorants are generally small hydrophobic cell-membrane-permeable organic molecules with highly variable chemical structures and properties. Due to their large chemical diversity, it is likely that some of them might trigger other cellular processes apart from their "conventional" role in olfaction. The dual role of some odorants acting on the mOR-EG and/or the nuclear estrogen receptor α (ERα) has therefore been explored. Estrogenic effect of these odorants has been measured on ER endogenously expressing MCF7 cells, which represent a sensitive and well-established system for the detection of estrogenic activities, using a Luciferase reporter gene assay and different cell proliferation measuring methods. Finally, computational modeling and ligand docking have provided informations on the molecular recognition principles of odorants on two functionally non-related receptors and will therefore help for the evaluation of the potential risk of chemical compounds used in perfumery.LCPP
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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