1,720,957 research outputs found
Synthesis, X-ray structural analysis, antibacterial and DNA-binding studies of a lanthanum bis-(5,5′-dimethyl-2,2′-bipyridine) complex
No full textA new complex with the formula [La(5,5′-dmbpy) 2 (NO 3 ) 3 ] (a) [where (5,5′-dmbpy = 5,5′-dimethyl-2,2′-bipyridine)] has been synthesized. The compound was characterized by cyclic voltammetry, elemental analysis and spectroscopic methods (IR, UV–Vis, 1 H-NMR). Single crystals adapted for X-ray diffraction analysis were recorded by slow crystallization from a methanol solution. The complex is neutral being the lanthanum cation chelated by two bipyridine derivative neutral ligands and three bidentate nitrate groups. Electronic spectra show the transition of both ligand field and charge transfer bands. The fluorescence properties of the compound have been studied. The interactions of complex with FS-DNA (salmon sperm DNA) have been studied using UV–Vis, fluorescence spectroscopies and gel electrophoresis. The above-mentioned techniques were used in physiological buffer having pH 7.2. The binding constant (K b ) for interaction in (a) with DNA was obtained using UV–Vis spectroscopies (K b = 1.2 × 10 5 ) and fluorescence spectroscopies (K b = 1.50 × 10 5 ). The binding constant (K b ), the number of binding sites for each 1000 nucleotides (n) and the apparent bio molecular quenching constant (k q ) for FS-DNA were obtained through Stern–Volmer equation. Thermodynamic parameters data (∆H°, ΔS° and ΔG°) showed that hydrogen bonding and van der Waals interactions have an important function in the interaction of DNA–La(III) complex, and the binding mode is the groove binding. The DNA binding of La(III) complex is spontaneous as suggested by the negative ΔG°. Moreover, the DNA cleavage has been studied using agarose gel electrophoresis. The antibacterial effects of complex (a) have also been examined in vitro against standard bacterial strains
Screen-printed electrode modified with Co-NPs, as an electrochemical sensor for simultaneous determination of doxorubicin and dasatinib
No full textThe new metal complex of Co(II) (a1) and its nano-size, (a2), with NCS− and 5,5 ́-dimethyl-2,2 ́-bipyridine ligands have been synthesized. [Co(5,5 ́-dmbpy)3][Co(NCS)4] (a1) characterized through spectroscopic methods such as FTIR, UV–Vis, diffractometric analysis and elemental analysis. Nanoparticle (a2) has been identified with FTIR spectroscopy, also SEM, and XRD techniques. The size of the (a2) is about 86 nm. In this study, an electrochemical sensing platform for simultaneous detection of doxorubicin and dasatinib based on screen-printed electrode (SPE) modified with (a2) was prepared. The modified SPE, on the contrary to bare SPE, can considerably enhance activities of electrocatalytic towards oxidation of doxorubicin and dasatinib, followed by rising the anodic peak current. Peak currents obtained via differential pulse voltammetry (DPV) showed a linear enhancement as dasatinib concentration elevated and sensor detected in ranges more than that of the concentration limited area of 0.04–195.0 μM, detection limit equal to 12.0 nM (S/N = 3). DPV responses show that at the surface of modified SPE, obvious separation of the peak of doxorubicin and dasatinib oxidation has been reported from another with 400 mV potential difference between them. A lower limit of detection (LOD), higher sensitivity as well as stability resulted in an electrode that could be applied for analyzing different real compounds. Moreover, its functionality is favorable and desirable in analyzing biological fluids and drug compounds
Synthesis and characterization of bipyridine cobalt(ii) complex modified graphite screen printed electrode: an electrochemical sensor for simultaneous detection of acetaminophen and naproxen
No full textThe new Co(ii) compound [Co(5,5′-dmbpy)2(NCS)2] (a1) was prepared by reacting Co(NO3)2·6H2O, 5,5′-dimethyl-2,2′-bipyridine ligand, and Na(SCN). The nano-scale size of [Co(5,5′-dmbpy)2(NCS)2] (a1) was synthesized using sonochemical process. The size of the nanoparticles (a2) was ∼13 ± 2 nm. We have also provided a new platform of electrochemical sensing for simultaneous detection of acetaminophen and naproxen using (a2) surface modified graphite screen printed electrode (SPE) in 0.1 M phosphate buffer solution (PBS, pH 7.0). In contrast to bare SPE, the modified SPE could significantly improve the electrooxidation activity of acetaminophen along with the rise in the current of an anodic peak. The peak currents acquired using differential pulse voltammetry (DPV) raised linearly with the raising of acetaminophen concentration and the sensor had a detection range over the concentration range of 0.009-325.0 μM, with a detection limit of 5.0 nM (S/N = 3). In the case of naproxen peak, currents of naproxen oxidation at the modified SPE were linearly dependent on the naproxen amounts in the range of 1.0-500.0 μM. The detection limit (S/N = 3) was calculated to be 0.03 μM. The DPV responses show that the peaks of acetaminophen and naproxen oxidation were vividly separated from one other with a potential difference of 410 mV between them. The low detection limit, high sensitivity, and stability made the relevant electrode applicable for the analysis of acetaminophen and naproxen in real samples. Further, its practical applicability was reliable and desirable in the analysis of pharmaceutical compounds and biological fluids. The benefits of using this modified electrode for the determination of analytes are compared with other works in the manuscript. This journal i
A Novel Carbon Paste Electrode-Modified Electrocatalytic CO–Ce–NPs for Sulfite Detection: A Sonochemical Synthesis
No full textThe present study introduced a novel ion-pair complex of [Co(5,5 '-dmbpy)(3)][Ce(NO3)(6)] (a1) fabricated by the reaction of Co(NO3)(2)center dot 6H(2)O, Ce(NO3)(3)center dot 6H(2)O, NaNO3 and 5,5 '-dimethyl-2,2 '-bipyridine ligand. A sonochemical method was used to synthesize the nano-scale [Co(5,5 '-dmbpy)(3)][Ce(NO3)(6)] (a2). The sulfite was then detected and quantified on a carbon paste electrode (CPE) modified with ferrocene derivative and cobalt nanoparticles (Co-NPs). Scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) were employed to characterize the Co-NPs. The results showed a significant improvement in the electrocatalytic activity and electro-active surface area following the CPE surface modification with the ferrocene derivative and Co-NPs. The voltammetric detection of sulfite was performed successfully by the as-fabricated sensor in real samples, with the linear dynamic range and the limit of detection of 0.07-440.0 and 0.03 mu M, under optimal conditions, respectively
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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