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New types of surface treatment of boron-doped diamond electrodes for electroanalysis
Full text linkBorem dopované diamantové (BDD) elektrody představují jedinečný materiál s výjimečnými fyzikálními a elektrochemickými vlastnostmi, což je činí vysoce atraktivními pro aplikace v různých oblastech elektrochemie. Nicméně komplexní charakterizace a srovnání polykrystalických neleštěných (as-grown) a chemicky-mechanicky (CM) leštěných BDD elektrod s různými stupni dopování borem je v literatuře dosud nedostatečně pokryta. Proto byly v rámci první části předkládané disertační práce komplexně charakterizovány a porovnány as-grown a CM leštěné BDD elektrody s různou mírou dopování borem. Bylo potvrzeno, že CM leštění způsobuje morfologické změny povrchu BDD elektrod, což vedlo k rovnoměrnějšímu rozložení vodivosti napříč povrchem elektrody, rychlejší kinetice heterogenního přenosu elektronů pro redoxní sondy vnitřní sféry a k vyšším hodnotám kapacity dvojvrstvy ve srovnání s as-grown BDD elektrodami. Následně byl na vybraných as-grown a CM leštěných BDD elektrodách zkoumán vliv poměru povrchového sp2 /sp3 uhlíku na jejich elektrochemické vlastnosti. Bylo zjištěno, že inkorporace boru zvyšuje absorpci infračerveného záření, což snižuje potřebnou laserovou fluenci pro konverzi sp3 na sp2 uhlík. Dále bylo zjištěno, že při poměru konverze sp2 /sp3 vyšším než 10 % dochází k ovlivnění elektrochemických...Boron-doped diamond (BDD) electrodes represent a unique material with exceptional physical and electrochemical properties, making them highly attractive for applications in various areas of electrochemistry. However, a comprehensive characterization and comparison of polycrystalline unpolished also known as as-grown and chemically-mechanically (CM) polished BDD electrodes with different degrees of boron doping is still underrepresented in the literature. In the first part of this thesis, as-grown and CM polished BDD electrodes with varying boron doping levels were comprehensively characterized and compared. It was confirmed that CM polishing causes morphological changes to the surface of the BDD electrodes, resulting in a more uniform distribution of conductivity across the electrode surface, faster heterogeneous electron transfer kinetics for inner-sphere redox markers, and higher double-layer capacitance values compared to as-grown BDD electrodes. Subsequently, the influence of the surface sp2 /sp3 carbon ratio on electrochemical properties was investigated on selected as-grown and CM polished BDD electrodes. It was revealed that boron incorporation enhances the absorption of infrared radiation, which reduces the required laser fluence for the conversion of sp3 to sp2 carbon. It was further found...Department of Analytical ChemistryKatedra analytické chemiePřírodovědecká fakultaFaculty of Scienc
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
Novel Approaches in Electrochemical Determination of Xenobiotic Compounds and in Study of Their Interaction with DNA
No full textPresented Ph.D. Thesis is focused on the development of analytical methods applicable for determination of selected xenobiotic compounds and for monitoring DNA damage they can induce. The main attention has been paid to the development and testing of non-toxic electrode materials for preparation of miniaturized electrochemical devices and novel electrochemical DNA biosensors. 2-Aminofluoren-9-one (2-AFN) was selected as a model environmental pollutant, which belongs to the group of hazardous genotoxic substances. Its carcinogenic and mutagenic effects may represent a risk to living and working environment. 2-AFN has one oxo group, where the cathodic reduction occurs, and one amino group, where the anodic oxidation occurs. The voltammetric behavior of 2-AFN in the negative potential region was investigated at a mercury meniscus modified silver solid amalgam electrode (m-AgSAE) representing a non-toxic and more mechanically robust alternative to mercury electrodes. This working electrode was subsequently used for the development of a newly designed miniaturized electrode system (MES), which has many benefits as the possibility of simple field measurements, easy portability, and the measurement in sample volume 100 µL. Moreover, a glassy carbon electrode (GCE) was used for further investigation of..
Study of Genotoxicity of Organic Compounds Using DNA Biosensors
No full textProposed dissertation thesis presents novel hybrid electrochemical DNA biosensors based on distinct forms of pyrolytic graphite ("edge-plane" and "basal-plane") and their potential in terms of applicability in the field of DNA electrochemistry. Testing of the applicability of the presented bioanalytical tools was preceded by thorough optimization process involving selection of the optimal values for the most crucial operational parameters of the electrochemical DNA biosensors fabricated by means of electrostatic adsorption - deposition potential (Edep), deposition time (tdep), optimal DNA concentration for electrostatic adsorption (cg(DNA)), and possible involvement of convection during the adsorption procedure. Initially, applicability of presented bioanalytical tools was investigated in relation to monitoring DNA damage by utilization of triplet of external DNA damaging sources - UV light irradiation, one- electron oxidants, and hydroxy radicals. Outcome of the damaging processes was monitored directly (via monitoring changes in the redox signals of DNA) or indirectly (via monitoring changes in the redox signals of redox indicator) by the use of voltammetric methods - square- wave voltammetry (SWV), cyclic voltammetry (CV), linear-sweep voltammetry (LSV), and electrochemical impedance..
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
Development of Novel Electrochemical Methods Using Various Membrane Materials for Monitoring of Selected Anticancer Drugs and Phytochelatins
No full textPresent Ph.D. Thesis is focused on the development of electrochemical methods for determination of anticancer drugs using various types of membranes for their preliminary separation. Furthermore, this Thesis reports the study of transport mechanisms of heavy metals in the presence of phytochelatins across biological membranes. Sodium anthraquinone-2-sulphonate (AQS) was used as a model compound for its similar structure with anthraquinone-based (AQ-based) anticancer drugs (doxo/daunorubicin) and also due to its better availability. All these compounds can be easily electrochemically oxidized and/or reduced. Redox behaviour of AQS was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in a cathodic region on mercury meniscus modified (m-AgSAE) and polished silver solid amalgam (p-AgSAE) electrodes, Obtained results were used for the development of a micro-volume voltammetric cell (MVVC). Its applicability for voltammetric determination of anticancer drugs was verified by using doxorubicin (DX) as a model substance. The second part of this Thesis deals with therapeutic monitoring of anticancer drugs in the blood circulation of the patients. For pilot experiments, a liquid-flow system with dialysis catheter and amperometric detection was used. The flow rate of carrier..
New types of surface treatment of boron-doped diamond electrodes for electroanalysis
No full textBoron-doped diamond (BDD) electrodes represent a unique material with exceptional physical and electrochemical properties, making them highly attractive for applications in various areas of electrochemistry. However, a comprehensive characterization and comparison of polycrystalline unpolished also known as as-grown and chemically-mechanically (CM) polished BDD electrodes with different degrees of boron doping is still underrepresented in the literature. In the first part of this thesis, as-grown and CM polished BDD electrodes with varying boron doping levels were comprehensively characterized and compared. It was confirmed that CM polishing causes morphological changes to the surface of the BDD electrodes, resulting in a more uniform distribution of conductivity across the electrode surface, faster heterogeneous electron transfer kinetics for inner-sphere redox markers, and higher double-layer capacitance values compared to as-grown BDD electrodes. Subsequently, the influence of the surface sp2 /sp3 carbon ratio on electrochemical properties was investigated on selected as-grown and CM polished BDD electrodes. It was revealed that boron incorporation enhances the absorption of infrared radiation, which reduces the required laser fluence for the conversion of sp3 to sp2 carbon. It was further found..
Electrochemical biosensors with spatially separated enzymatic and detection parts for selective analysis in flow-through arrangement
No full textThis dissertation thesis presents the newly developed four highly reusable, stable as well as simple, and cost-effective electrochemical (bi)enzymatic biosensors for the selective and reliable determination of choline, acetylcholine, uric acid, and L-lactic acid in flow injection analysis. All biosensors are based on the concept of the spatial separation of the biorecognition part from detection one and amperometric monitoring of the enzymatically consumed oxygen via its four-electron reduction at the highly negative detection potential. In this way, the design of the biosensors includes an easily replaceable enzymatic mini-reactor(s) connected upstream to the flow cell that contains the appropriate silver amalgam-based transducer. The enzymatic mini-reactor based on choline oxidase, uricase, or lactate oxidase was used for choline, uric acid, or L-lactic acid biosensors, respectively. The acetylcholine bienzymatic biosensor includes the consequently connected choline oxidase- and acetylcholinesterase-based mini-reactors. The first part of this thesis focuses on the construction of two different silver amalgam-based electrodes. Specifically, this section discusses the fabrication of a silver solid amalgam electrode covered by mercury film operating in a wall-jet cell and also highlights the..
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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