The Multiple Voices of Frederick Douglass

In this rhetorical analysis of Frederick Douglass\u27 style, I argue that the power of his language comes from the multiplicity of voices arising from his work. I specifically concentrate on the Narrative of the Life of Frederick Douglass, an American Slave, Written by Himself (1845), as well as on some of the speeches he delivered soon after the book was published. Coming from a different culture, I was intrigued by my reaction to Douglass\u27 writing style. I find him a writer with very strong rhetorical skills which have a tremendous appeal to any reader. My personal response explores the reasons for Douglass\u27 success both as a writer and an orator. However, I especially focus on what fascinates me most about his use of language. Furthermore, I account for my choice of the Narrative and the specific speeches as the primary texts I am using. Influenced by other major figures and works in American literature, I distinguish among different voices that arise from Douglass\u27 prose. I am convinced that the Narrative echoes the voices of a southerner, a preacher, an orator, and an ex-slave. In the main body of my thesis, I demonstrate how each voice contributes to the writer\u27s fascinating personality, as well as to the creation of a strong relationship between Douglass and his audience. My discussion of the ex-slave\u27s voice serves as an overview of Douglass\u27 transition from the world of ignorance and slavery to that of literacy and freedom. At this point, I emphasize the techniques he uses in order to become a master of the language and, subsequently, a master of himself. In the last pages of this project, I focus on the American reader\u27s response to the Narrative. The reviews that the book received when it was published help me examine in detail the reactions of Douglass\u27 contemporary audience. In addition, I rely on the autobiographical nature of the Narrative, in order to point out the effect that the book has to the reader today. Finally, I discuss the issue of slavery as the main theme of the Narrative and as the main reason for Douglass\u27 appeal to the American reader of the twentieth century

Virtual laboratories during coronavirus (COVID ‐19) pandemic

Coronavirus (COVID‐19) disease is an emerging situation that brought challenges to all sectors, including academia and research. Undergraduate and postgraduate students in biochemistry and molecular biology have been affected significantly due to the recent laboratory closures. Experiments have been suspended for long causing extreme stress to the students. Virtual laboratory is a powerful educational tool that enables students to conduct experiments at the comfort of their home. An excellent opportunity to engage students with technology and in parallel to avoid unforeseen disruptions, as happened recently due to pandemic

Electrochemistry of Eugenol and its Metabolism on a Bare Screen-Printed Electrode

Eugenol is an essential oil widely used in pharmaceutical and food industry. However, the metabolism of eugenol leads to the formation of a highly reactive phenoxyl radical that can induce toxicity with macromolecules. Herein, a simple and a cost-effective methodology was described for the mimicry of eugenol metabolism. Electrochemical measurements were recorded on bare screen-printed electrodes (SPEs) and the generated metabolites were collected and detected by electrospray ionization (ESI)/Mass spectrometry (MS). The reactive intermediate was successfully formed illustrating a cheaper alternative towards the mimicry of human metabolism

Development of a microfluidic device with a screen printed electrode for studies on phase II metabolism

Simulating human metabolism by electrochemistry (EC) and mass spectrometry (MS) provides an alternative approach to the existing in vitro and in vivo methodologies. Herein, screen printed electrodes (SPEs) were investigated as potent electrochemical tools with the aim of developing a microfluidic device with a SPE. The proposed chip could be used as a primary screening tool for phase II glutathione (GSH) adducts.The reusability of SPEs was investigated with solvent treatment, mechanical polishing, and electrochemical activation. However, damages to the three-electrode configuration and lack of reproducibility prevented the effective removal of deposited material. Thus, SPEs were used as single-shot sensors for micking phase I and phase II metabolism.The electrochemical reactions of dopamine, raloxifene, eugenol, and doxorubicin were examined initially on a bare SPE. Similar kinetics and reaction mechanisms were obtained as in previous studies with a glassy carbon electrode, confirming that SPEs can be used as cheaper alternatives. Controlled potential electrolysis (CPE) at the optimized potential was recorded for 30 min, in the presence of GSH, and subsequent offline MS permitted the detection of the corresponding GSH adducts of dopamine and raloxifene.Dopaminoquinone and raloxifene di-quinone methide were generated via dehydrogenation and reacted covalently with GSH. However, the GSH adducts for eugenol and doxorubicin were not formed, leading to the generation of unconjugated metabolites. For example, eugenol was electrolysed via a single electron transfer with the addition of a proton to the corresponding phenoxyl radical. However, the oxidation reaction of GSH to form glutathione disulfide (GSSG) prevented further stabilisation to eugenol quinone methide and subsequent GSH adduct formation, mimicking only the catalytic pathway and polymerisation process. In the case of doxorubicin, the GSH adducts were probably formed at extremely low concentrations that were below the detection limits of the mass spectrometer or the expected doxorubicin semiquinone C7 free radical was generated but its trapping was unlikely, as proposed in previous in vitro and in vivo studies, owing to its quick oxidation back to the parent drug. Also, the possibility of generating non-reactive and highly unstable electrochemical products which were not capable of forming GSH adducts was considered. Thus, dopamine and raloxifene were selected for experiments in the microfluidic device. In addition, as the behaviour of acetaminophen on SPE is well-known, it was considered suitable for investigation with the proposed chip.A polycarbonate disposable chip was developed, in which a 32 μL SPE- electrochemical cell was integrated with a serpentine channel. The chip was coupled online to an electrospray mass spectrometer for a semi-automated methodology. At an optimized flow rate of 5 μL min-1, 2.5x10-5 M solutions of dopamine and acetaminophen were allowed to electrolyse for 6.4 min in the SPE cell. The electrogenerated toxic intermediates dopaminoquinone and N-acetyl-p-benzoquinone imine reacted covalently with 5x10-5 M GSH and the resulting adducts were detected online by MS. Raloxifene failed to generate the GSH adduct in the microfluidic device owing to the requirement for lower flow rates that were incompatible with MS. In conclusion, a disposable and cost effective microfluidic device was developed for the simulation of phase II metabolism. This microdevice has the potential to reduce the expensive and time consuming use of the current in vitro and in vivo methodologies, in pharmaceutical industry and medical research

Temperature-dependent dynamical nuclear polarization bistabilities in double quantum dots in the spin-blockade regime

The interplay of dynamical nuclear polarization (DNP) and leakage current through a double quantum dot in the spin-blockade regime is analyzed. A finite DNP is built up due to a competition between hyperfine (HF) spin-flip transitions and another inelastic escape mechanism from the triplets, which block transport. We focus on the temperature dependence of the DNP for zero energy-detuning (i.e. equal electrostatic energy of one electron in each dot and a singlet in the right dot). Our main result is the existence of a transition temperature, below which the DNP is bistable, so a hysteretic leakage current versus external magnetic field B appears. This is studied in two cases: (i) Close to the crossing of the three triplet energy levels near B=0, where spin-blockade is lifted due to the inhomogeneity of the effective magnetic field from the nuclei. (ii) At higher B-fields, where the two spin-polarized triplets simultaneously cross two different singlet energy levels. We develop simplified models leading to different transition temperatures T_TT and T_ST for the crossing of the triplet levels and the singlet-triplet level crossings, respectively. We find T_TT analytically to be given solely by the HF couplings, whereas T_ST depends on various parameters and T_ST>T_TT. The key idea behind the existence of the transition temperatures at zero energy-detuning is the suppression of energy absorption compared to emission in the inelastic HF transitions. Finally, by comparing the rate equation results with Monte Carlo simulations, we discuss the importance of having both HF interaction and another escape mechanism from the triplets to induce a finite DNP.Comment: 26 pages, 17 figure

Microfluidics: The Future and Possible Practical Applications in Greece

Microfluidic engineering is a modern branch that combines science with engineering; an innovative technology with future practical applications in the Greek academy and industry. In particular, microfluidics studies the handling of fluids in small channels (micro or nano scale), thus allowing the integration of conventional biological and chemical methods. Microfluidic devices offer many advantages such as 1) low volume of reagents 2) fast chemical reactions and 3) lower cost. The application of microfluidic engineering in Greece can promote Greek research nationally and globally, offer rapid diagnosis and prognosis of diseases, higher education and ensure the quality and safety of drugs in the pharmaceutical industry

Possible mechanisms of CO₂ reduction by H₂ via prebiotic vectorial electrochemistry

Methanogens are putatively ancestral autotrophs that reduce CO2 with H2 to form biomass using a membrane-bound, proton-motive Fe(Ni)S protein called the energy-converting hydrogenase (Ech). At the origin of life, geologically sustained H+ gradients across inorganic barriers containing Fe(Ni)S minerals could theoretically have driven CO2 reduction by H2 through vectorial chemistry in a similar way to Ech. pH modulation of the redox potentials of H2, CO2 and Fe(Ni)S minerals could in principle enable an otherwise endergonic reaction. Here, we analyse whether vectorial electrochemistry can facilitate the reduction of CO2 by H2 under alkaline hydrothermal conditions using a microfluidic reactor. We present pilot data showing that steep pH gradients of approximately 5 pH units can be sustained over greater than 5 h across Fe(Ni)S barriers, with H+-flux across the barrier about two million-fold faster than OH–-flux. This high flux produces a calculated 3-pH unit-gradient (equating to 180 mV) across single approximately 25-nm Fe(Ni)S nanocrystals, which is close to that required to reduce CO2. However, the poor solubility of H2 at atmospheric pressure limits CO2 reduction by H2, explaining why organic synthesis has so far proved elusive in our reactor. Higher H2 concentration will be needed in future to facilitate CO2 reduction through prebiotic vectorial electrochemistry

Possible mechanisms of CO₂ reduction by H₂ via prebiotic vectorial electrochemistry

Methanogens are putatively ancestral autotrophs that reduce CO2 with H2 to form biomass using a membrane-bound, proton-motive Fe(Ni)S protein called the energy-converting hydrogenase (Ech). At the origin of life, geologically sustained H+ gradients across inorganic barriers containing Fe(Ni)S minerals could theoretically have driven CO2 reduction by H2 through vectorial chemistry in a similar way to Ech. pH modulation of the redox potentials of H2, CO2 and Fe(Ni)S minerals could in principle enable an otherwise endergonic reaction. Here, we analyse whether vectorial electrochemistry can facilitate the reduction of CO2 by H2 under alkaline hydrothermal conditions using a microfluidic reactor. We present pilot data showing that steep pH gradients of approximately 5 pH units can be sustained over greater than 5 h across Fe(Ni)S barriers, with H+-flux across the barrier about two million-fold faster than OH--flux. This high flux produces a calculated 3-pH unit-gradient (equating to 180 mV) across single approximately 25-nm Fe(Ni)S nanocrystals, which is close to that required to reduce CO2. However, the poor solubility of H2 at atmospheric pressure limits CO2 reduction by H2, explaining why organic synthesis has so far proved elusive in our reactor. Higher H2 concentration will be needed in future to facilitate CO2 reduction through prebiotic vectorial electrochemistry

The Combination of Electrochemistry and Microfluidic Technology in Drug Metabolism Studies

Drugs are metabolized within the liver (pH 7.4) by phase I and phase II metabolism. During the process, reactive metabolites can be formed that react covalently with biomolecules and induce toxicity. Identifying and detecting reactive metabolites is an important part of drug development. Preclinical and clinical investigations are conducted to assess the toxicity and safety of a new drug candidate. Electrochemistry coupled to mass spectrometry is an ideal complementary technique to the current preclinical studies, a pure instrumental approach without any purification steps and tedious protocols. The combination of microfluidics with electrochemistry towards the mimicry of drug metabolism offers portability, low volume of reagents and faster reaction times. This review explores the development of microfluidic electrochemical cells for mimicking drug metabolism