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Artykuły w czasopismach na temat "REDOX REACTION ANALYSIS"
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Tang, Wenxiu, Xintong Zhu i Yangyi Qian. "APPLYING FACTOR ANALYSIS FOR ASSESSING KNOWLEDGE STRUCTURE OF STUDENTS IN GRADE 10: THE SUBJECT OF REDOX REACTION". Journal of Baltic Science Education 21, nr 4 (25.08.2022): 680–93. http://dx.doi.org/10.33225/jbse/22.21.680.
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Redox reaction is an important concept in chemistry, and a well-organized knowledge structure of redox reaction is beneficial for concept learning. This study investigated the knowledge structure regarding redox reaction from 459 Grade 10 students. The pool of 15 redox reaction concepts was developed by content analysis, questionnaire survey, and interview. Six initial competing models with 15 concepts were identified via exploratory factor analysis (EFA) and paper-pencil test. Confirmatory factor analysis (CFA) was conducted to test and modify the six competing models according to the rating data of the students. As a result, six modified models fit the data well. However, the high inter-factor correlations indicate that the two- and three-factor models are the students' knowledge structures of redox reaction. The two-factor model is comprised of two distinct but correlated factors: the process of redox reaction and metrology. The three-factor model is comprised of three factors: the process of redox reaction, reaction ability, and metrology. The finding inflects the abstract relationships between the concepts related to redox reaction in students' minds. Keywords: redox reaction, chemistry education, knowledge structure, factor analysis
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Dessie, Yabibal Getahun, Qi Hong, Bachirou Guene Lougou, Juqi Zhang, Boshu Jiang, Junaid Anees i Eyale Bayable Tegegne. "Thermochemical Energy Storage Performance Analysis of (Fe,Co,Mn)Ox Mixed Metal Oxides". Catalysts 11, nr 3 (10.03.2021): 362. http://dx.doi.org/10.3390/catal11030362.
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Metal oxide materials are known for their ability to store thermochemical energy through reversible redox reactions. Metal oxides provide a new category of materials with exceptional performance in terms of thermochemical energy storage, reaction stability and oxygen-exchange and uptake capabilities. However, these characteristics are predicated on the right combination of the metal oxide candidates. In this study, metal oxide materials consisting of pure oxides, like cobalt(II) oxide, manganese(II) oxide, and iron(II, III) oxide (Fe3O4), and mixed oxides, such as (100 wt.% CoO, 100 wt.% Fe3O4, 100 wt.% CoO, 25 wt.% MnO + 75 wt.% CoO, 75 wt.% MnO + 25 wt.% CoO) and 50 wt.% MnO + 50.wt.% CoO), which was subjected to a two-cycle redox reaction, was proposed. The various mixtures of metal oxide catalysts proposed were investigated through the thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), energy dispersive X-ray (EDS), and scanning electron microscopy (SEM) analyses. The effect of argon (Ar) and oxygen (O2) at different gas flow rates (20, 30, and 50 mL/min) and temperature at thermal charging step and thermal discharging step (30–1400 °C) during the redox reaction were investigated. It was revealed that on the overall, 50 wt.% MnO + 50 wt.% CoO oxide had the most stable thermal stability and oxygen exchange to uptake ratio (0.83 and 0.99 at first and second redox reaction cycles, respectively). In addition, 30 mL/min Ar–20 mL/min O2 gas flow rate further increased the proposed (Fe,Co,Mn)Ox mixed oxide catalyst’s cyclic stability and oxygen uptake ratio. SEM revealed that the proposed (Fe,Co,Mn)Ox material had a smooth surface and consisted of polygonal-shaped structures. Thus, the proposed metallic oxide material can effectively be utilized for high-density thermochemical energy storage purposes. This study is of relevance to the power engineering industry and academia.
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Chumakov, Anton A., Valentina N. Batalova, Yuriy G. Slizhov i Tamara S. Minakova. "VERIFICATION OF NON-CATALYTIC HYDROGEN PEROXIDE DISPROPORTIONATION MECHANISM BY THERMODYNAMIC ANALYSIS OF ONE-ELECTRON REDOX REACTIONS". IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENIY KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 60, nr 6 (19.07.2017): 40. http://dx.doi.org/10.6060/tcct.2017606.5529.
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There is two-electron transfer during the process of hydrogen peroxide decomposition into water and oxygen. The detailed mechanism of non-catalytic hydrogen peroxide disproportionation is not verified until now. We assumed that any poly-electron redox process is a complex and consists of one-electron redox reactions. We have formulated equations of possible one-electron transfers during hydrogen peroxide disproportionation. Based on known laws and equations of thermochemistry we calculated standard thermodynamic functions for a total reaction and each one-elect-ron redox reaction using reference values of standard thermodynamic functions of reagents and products of reactions. Results show that the total reaction leads to significant decrease in Gibbs free energy -246.0 kJ/mol in gas phase but there is increase +39.9 kJ/mol in Gibbs free energy during the first proposed step. It is substantiation for known dependence of hydrogen peroxide dismutation kinetics at thermal, photochemical or catalytic activation. The first proposed step of non-catalytic process is one-electron plus one-proton transfer in thermally or photochemically activated dimeric hydrogen peroxide associate (H2O2)2 with simultaneous generation of hydroperoxyl HO2• and hydroxyl HO• free radicals and water molecule. There is thermodynamic argumentation for radical chain mechanism of hydrogen peroxide disproportionation after the activation. We made the graphic illustration of thermodynamically supported scheme of non-catalytic hydrogen peroxide decomposition. There is a cyclic alternation of two radical-molecular interactions during the hydrogen peroxide chain decomposition. The hydroxyl radical generates the hydroperoxyl radi-cal from a hydrogen peroxide molecule and then the hydroperoxyl radical interacts with a next hydrogen peroxide molecule followed by the hydroxyl radical generation. Interactions between the homonymic or heteronymic free radicals are the reactions of chain breaking.Forcitation:Chumakov A.A., Batalova V.N., Slizhov Yu.G., Minakova T.S. Verification of non-catalytic hydrogen peroxide disproportionation mechanism by thermodynamic analysis of one-electron redox reactions. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 6. P. 40-44.
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Palisoa, Napsin. "PERBANDINGAN HASIL BELAJAR DAN MOTIVASI BELAJAR PESERTA DIDIK PADA MATERI REAKSI REDOKS KELAS X MA AL-FATAH AMBON SEBELUM DAN SELAMA MASA PANDEMI COVID-19". Molluca Journal of Chemistry Education (MJoCE) 11, nr 2 (30.09.2021): 106–20. http://dx.doi.org/10.30598/mjocevol11iss2pp106-120.
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This study aims to determine the differences in learning outcomes and students' learning motivation on redox reaction material for class X IPA MA Al-Fatah Ambon before and during the covid-19 pandemic. The sample in this study consisted of 22 students who studied redox reaction material in class X offline and 22 students who studied redox reactions online. This study uses a quantitative experimental research method with a comparative study research design. Collecting data in this study using a questionnaire, documentation and observation. Questionnaires were used to measure students' learning motivation, documentation was used to measure learning outcomes (cognitive, affective, and psychomotor) of students in class X before the pandemic and cognitive learning outcomes in class X during the pandemic, while observation was used to measure affective and psychomotor learning outcomes. Class X students during the COVID-19 pandemic. The documentation used is the value of students in the redox reaction material for the even semester 2019/2020 and even semester 2020/2021, then observations are made by participating in live online learning. The data obtained were then analyzed using descriptive and inferential data analysis methods. Based on the results of descriptive data analysis of learning motivation and student learning outcomes on redox reaction material for class X before and during the pandemic period, it was in the moderate category, while based on the results of inferential data analysis using Mann-Whitney analysis for learning motivation, the Asymp sig value was obtained. (2-tailed) 0.646 and 0.000 learning outcomes. The results show that there are no differences in students' learning motivation before and during the COVID-19 pandemic, so H0 is accepted, and there are differences in student learning outcomes before and during the COVID-19 pandemic, so H0 is rejected.
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Hadinugrahaningsih, Tritiyatma, Yuli Rahmawati i Elma Suryani. "An analysis of preservice Chemistry teachers’ misconceptions of reduction-oxidation reaction concepts". Journal of Technology and Science Education 12, nr 2 (7.07.2022): 448. http://dx.doi.org/10.3926/jotse.1566.
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This article describes a study of 149 of preservice chemistry teachers’ misconceptions of concepts related to an reduction-oxidation reaction. A mixed-method approach was used to obtain data through the ROXCI (Redox Concept Inventory) instrument and interviews. Results indicated that the highest misconceptions were for item number 10 (4.03% or only 6 of 149 students answered correctly) and the lowest misconception occurred on item number 1 (94.63% or 141 of 149 students answered correctly). These results were supported by the analysis of the interviews where the respondents produced misconceptions when explaining the process of electron transfer in redox reactions. The highest percentage of consistent answers in the six ROXCI categories was obtained in the surface feature concept category (6.71% or 10 out of 149 respondents consistently answered correctly). This shows that preservice chemistry teachers are not able to connect the three levels of chemical representation, macroscopic, microscopic, and symbolic in studying chemistry, especially for the redox concept. Analysis of the relationships between misconceptions and average student confidence shows that every distractor chosen by the respondents at every level was followed by a degree of confidence of between 50%-70%, indicating that misconceptions became stronger because the preservice chemistry teachers did not realize that a concept believed to be true is wrong.
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Kulys, J., i Ž. Dapkūnas. "The Effectiveness of Synergistic Enzymatic Reaction with Limited Mediator". Nonlinear Analysis: Modelling and Control 12, nr 4 (25.10.2007): 495–501. http://dx.doi.org/10.15388/na.2007.12.4.14680.
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Kinetics of biocatalytical synergistic reactions has been analyzed with special emphasis on stability and reactivity of mediators. The application to the model of kinetic constants taken from the experiments showed that the quasi steady state (QSS) for reduced and oxidized enzyme was achieved in 0.001 s. However, the QSS for the mediator was not established during measurable time. For this reason the kinetics of biocatalytical synergistic reactions was modeled by solving the ordinary differential equations using software package KinFitSim©.
The calculations showed the increase of an apparent life-time of the mediator in the synergistic reaction. The apparent life-time was most affected by reactivity of mediator. The change of the mediator reactivity from 1 M−1s−1 to 105 M−1s−1 increased the apparent life-time from 19 s to 1538 s. This mediator reactivity can be achieved even for strongly endothermic reaction when difference of redox potential of substrate and mediator is 0.35 V. The increase of mediator life-time increased product yield.
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Tripathi, Anand Kumar, Miji E. Joy, Debittree Choudhury, Rubul Das i Manoj Neergat. "Kinetics of V5+/V4+ Redox Reaction—Butler-Volmer and Marcus Models". Journal of The Electrochemical Society 168, nr 11 (1.11.2021): 110548. http://dx.doi.org/10.1149/1945-7111/ac39d9.
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Kinetics of the V5+/V4+ redox reaction on Vulcan XC-72 modified glassy carbon disk electrode is investigated in a three-electrode configuration. Cyclic voltammograms of V5+/V4+ redox couple suggest that the overpotential range for the kinetic analysis is limited to ±300 mV, after excluding V4+/V3+ redox reaction at the negative overpotential and the oxygen evolution reaction at the positive overpotential. The linear sweep-voltammograms (LSVs) are corrected for potential drop due to solution resistance (iR s ), mass-transfer resistance, and most importantly, for the back reaction current. These corrections are imperative to estimate the Tafel slope in the limited range of overpotential for V5+/V4+ redox reaction. The charge-transfer coefficient (α) estimated from the Tafel slope deviates significantly from the expected value of 0.5 for the single electron-transfer reaction. Moreover, the instantaneous slope of the Tafel plot suggests that the α is overpotential dependent. Therefore, Marcus theory of electrochemical kinetics is applied to estimate the α. The reorganization energy (λ) calculated from the Arrhenius plots is in the range of values reported in the literature for the other redox couples.
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Fitriyah, Isnanik Juni, Muhammad Fajar Marsuki i Yessi Affriyenni. "Development of E-learning Based on Augmented Reality (AR) on Reduction-Oxidation Reaction Topic". International Journal of Interactive Mobile Technologies (iJIM) 16, nr 03 (10.02.2022): 151–58. http://dx.doi.org/10.3991/ijim.v16i03.28977.
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The concept of electrochemistry is based on reduction-oxidation (redox) reactions and electrolyte solutions. Where this material is difficult to understand because the aspects studied include submicroscopic aspects. It takes teaching materials that are able to display animations of redox reactions. This study aims to develop teaching materials based on Augmented Reality on Redox Reaction material. This type of research includes research and development (R&D) using the ADDIE model with the stages of analysis, design, develop and evaluation. The product will be tested for validity through expert testing and field testing. The validation test of material, media and readability experts to students resulted in a percentage of 92.5%, 94.39% and 91.6% respectively or declared very feasible and very good for use in lectures with several revisions. It can be concluded that AR-based media is stated to be very feasible and very good for use in learning. It is hoped that further testing of the effectiveness of this media will be carried out.
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Bao, Qi, Shu Fang Zhang i Dun Zhang. "Synthesis and Electrochemical Behavior of Two Microporous Polyoxomolybdates". Advanced Materials Research 79-82 (sierpień 2009): 1479–82. http://dx.doi.org/10.4028/www.scientific.net/amr.79-82.1479.
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Two new microporous polyoxomolybdates of (NH4)2[γ-Mo8O26] (Compound I) and (NH4)2[Mo4O13] (Compound II) were synthesized hydrothermally and characterized by elemental analysis, infra-red, TG analysis and single-crystal X-ray diffraction. In the synthesis process, we found that both organic template and transition metal salt play crucial roles in the formation of crystals. Cyclic voltammetry was used to study their electrochemical properties. The results reveal that the two compounds possess electrochemical activity in 0.2M H2SO4+Na2SO4 ( pH=1 ) solution and three multi-electron transferred redox reaction (I-I´, II-II´ and III-III´) processes were obtained. The first two redox reactions (I-I´, II-II´) are reversible reaction processes but another one (III-III´) is not. The electrochemical properties of the two compounds indicate their great potential applications in electroanalysis and electrocatalysis.
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Ohura, Hiroki, i Toshihiko Imato. "Rapid and Automated Analytical Methods for Redox Species Based on Potentiometric Flow Injection Analysis Using Potential Buffers". Journal of Automated Methods and Management in Chemistry 2011 (2011): 1–14. http://dx.doi.org/10.1155/2011/516165.
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Two analytical methods, which prove the utility of a potentiometric flow injection technique for determining various redox species, based on the use of some redox potential buffers, are reviewed. The first is a potentiometric flow injection method in which a redox couple such as Fe(III)-Fe(II), Fe-Fe(CN), and bromide-bromine and a redox electrode or a combined platinum-bromide ion selective electrode are used. The analytical principle and advantages of the method are discussed, and several examples of its application are reported. Another example is a highly sensitive potentiometric flow injection method, in which a large transient potential change due to bromine or chlorine as an intermediate, generated during the reaction of the oxidative species with an Fe(III)-Fe(II) potential buffer containing bromide or chloride, is utilized. The analytical principle and details of the proposed method are described, and examples of several applications are described. The determination of trace amounts of hydrazine, based on the detection of a transient change in potential caused by the reaction with a Ce(IV)-Ce(III) potential buffer, is also described.
Rozprawy doktorskie na temat "REDOX REACTION ANALYSIS"
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Lu, Shuangxing. "Electrochemical parametrization of redox potentials of metal complexes and its applications". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0019/MQ56188.pdf.
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Neuhuber, Stephanie Maria Ulrike. "In situ measurements of redox chemical species with amperometric techniques to investigate the dynamics of biogeochemical processes in aquatic systems". Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/25737.
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Inamoto, Jun-ichi, i Junichi Inamoto. "Electrochemical Characterization of Surface-State of Positive Thin-Film Electrodes in Lithium-Ion Batteries". Kyoto University, 2017. http://hdl.handle.net/2433/226784.
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DeSilva, Veronica. "Selenium redox cycling isolation and characterization of a stimulatory component from tissue of loblolly pine for multiplication of somatic embryos; development of an assay to measure l-phenylalanine concentration in blood plasma /". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/29788.
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Thesis (Ph.D)--Chemistry and Biochemistry, Georgia Institute of Technology, 2007.Committee Chair: Sheldon May; Committee Members: Nicholas Hud, Stanley Pollock, James Powers, and Gerald Pullman. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Hischier, Illias. "CO₂ splitting via a solar thermochemical cycle based on Zn/ZnO redox reactions: thermodynamic and kinetic analysis". Zürich : ETH, Swiss Federal Institute of Technology Zurich, Institute of Energy Technology, 2008. http://e-collection.ethbib.ethz.ch/show?type=dipl&nr=360.
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Iloeje, Chukwunwike Ogbonnia. "Rotary (redox) reactor-based oxy combustion chemical looping power cycles for CO₂ capture : analysis and optimization". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104249.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 224-229).
A number of CO₂ capture-enabled power generation technologies have been proposed to address the negative environmental impact of CO₂ emission. An important barrier to adopting these technologies is the associated energy and economic penalties. Chemical-looping (CLC) is an oxycombustion technology that can significantly lower such penalties, utilizing a redox process to eliminate the need for an air separation unit and enable better energy integration. Conventional CLC employs two separate reactors, with metal oxide particles circulating pneumatically in-between, leading to significant irreversibility associated with reactor temperature difference. A rotary reactor, on the other hand, maintains near-thermal equilibrium between the two stages by thermally coupling channels undergoing oxidation and reduction. In this thesis, a multiscale analysis for assessing the integration of the rotary CLC reactor technology in power generation systems is presented. This approach employs a sequence of models that successively increase the resolution of the rotary reactor representation, ranging from interacting thermal reservoirs to higher fidelity quasi-steady state models, in order to assess the efficiency potential and perform a robust optimization of the integrated system. Analytical thermodynamic availability and ideal cycles are used to demonstrate the positive impact of reactor thermal coupling on system efficiency. Next, detailed process flow-sheet models in which the rotary reactor is modeled as a set of interacting equilibrium reactors are used to validate the analytical model results, identify best cycle configurations and perform preliminary parametric analysis for between the reactor and the system while maintaining computational efficiency, an intermediate fidelity model is developed, retaining finite rate surface kinetics and internal heat transfer within the reactor. This model is integrated with a detailed system model and used for optimization, parametric analysis and characterization of the relative techno-economic performance of different oxygen carrier options for thermal plants integrated with the rotary CLC reactor. Results show that thermal coupling in the redox process increases the efficiency by up to 2% points for combined, recuperative and hybrid cycles. The studies also show that the thermal efficiency is a function of the reactor purge steam demand, which depends on the reactivity of the oxygen carrier. While purge steam constitutes a monotonic parasitic loss for the combined cycle, for recuperative and hybrid cycles, it raises the efficiency as long as the steam demand is less than a threshold value. This relationship between reactivity and system efficiency provides a useful selection criteria for the oxygen carrier material. Optimization results based on efficiency and levelized cost of electricity (LCOE) identify nickel-based oxygen carriers as the most suitable for the rotary reactor because its high reactivity ensures low steam demand and reactor cost. Compared to nickel, maximum efficiency and minimum LCOE are respectively 7% lower and 40% higher for a copper-based system; iron-based systems have 4% higher maximum efficiency and 7% higher minimum LCOE. This study also showed that optimal efficiency generally has an inverse profile to that for the optimized LCOE.
by Chukwunwike Ogbonnia Iloeje.
Ph. D.
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Hawkes, Hye-Jin. "Analysis of Redox Gene Promoters and Structural Mechanisms, Focusing on Thioredoxin and Methionine Sulfoxide Reductase A". Thesis, Griffith University, 2011. http://hdl.handle.net/10072/367671.
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When cells are exposed to oxidative stress reactive oxygen species (ROS) are formed, causing severe damage in the cell. To maintain the redox homeostasis, antioxidant systems
are switched on. Two of the major redox proteins include thioredoxin (Trx) and Methionine
Sulfoxide Reductase (MSR). Trx interacts directly and indirectly with several transcription
factors to modulate binding to gene promoters. In particular, Nrf2 is known to be an
important transcription factor in redox regulation.
To further define the mechanisms by which the Trx promoter is regulated by oxidative stress, the HEC1B endometrial cancer cell line and MDA-‐MB-‐231 breast cancer cell line were transfected with various Trx gene promoter constructs that drive expression of a luciferase reporter. When cells were transfected with constructs containing the Trx gene promoter region where the Antioxidant Responsive Element (ARE) was deleted, no induction was observed in response to tBHQ, diamide or H2O2 utilising luciferase reporter activity assays. Thus, the results confirmed the published data that the ARE is one of the most important elements in activating the Trx gene promoter during oxidative stress. Furthermore, it was established that luciferase reporter assays using the same cell line grown in media supplemented with different serum yielded significantly different results. Cells grown in medium supplemented with the serum containing the highest selenium level resulted in the lowest fold induction of the Trx gene promoter, while sera with the lowest level resulted in the highest folld inductions.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Biomolecular and Physical Sciences
Science, Environment, Engineering and Technology
Full Text
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Haussener, Sophia. "Efficiency calculations and optimization analysis of a solar reactor for the high temperature step of the zinc/zinc-oxide thermochemical redox cycle". Zürich : ETH, Eidgenössische Technische Hochschule Zürich, Departement Maschinenbau und Verfahrenstechnik, 2007. http://e-collection.ethbib.ethz.ch/show?type=dipl&nr=331.
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Baraldi, Dhãniel Dias. "Influência do sistema renina angiotensina na modulação do estado redox, no balanço autonômico e na hipertrofia cardíaca induzida pelo hipertireoidismo experimental". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2012. http://hdl.handle.net/10183/54943.
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O hipertireoidismo é uma patologia epidemiologicamente importante, que afeta o sistema cardiovascular de forma proeminente. O estado hipertireoideo pode afetar o metabolismo basal, consumo de O2 celular, sistema renina angiotensina, assim como, estimular a produção de espécies ativas de oxigênio. Estas alterações produzem consequências morfológicas, funcionais, bioquímicas e moleculares no tecido cardíaco. A hipertrofia cardíaca, decorrente do hipertireoidismo, instala-se devido a uma série de eventos que sinalizam à proliferação e sobrevivência celular, envolvendo as espécies ativas de oxigênio, a ativação do sistema renina angiotensina cardíaco e o sistema nervoso autonômico. Neste estudo, bloqueamos o receptor AT1 da angiotensina II para avaliarmos a influência do sistema renina angiotensina cardíaco sobre o desenvolvimento da hipertrofia cardíaca, a participação do balanço autonômico sobre o coração e o papel das espécies ativas de oxigênio neste processo, em modelo experimental de hipertireoidismo. Para isto, foram utilizados ratos Wistar machos, pesando cerca de 220g, divididos em 4 grupos experimentais: Controle (C), Losartan (L) (10 mg/Kg de peso corporal/dia, 28 dias, sonda intragástrica) , T4 (12mg/L água de beber, 28 dias), e T4+L. Foram avaliados a massa cardíaca, análise espectral do balanço simpato-vagal, a expressão protéica do receptor AT1 da Angiotensina II e da gp91phox, peróxido de hidrogênio (H2O2), Nrf-2 e Heme-oxigenase-1 (HO-1) no tecido cardíaco. A hipertrofia cardíaca e o desequilíbrio autonômico induzidos pelo hipertireoidismo foram atenuados no grupo T4+L. Os níveis de H2O2, Nrf-2, gp91phox e HO-1 foram elevados no grupo T4, e significativamente reduzidos no grupo T4+L, quando comparados ao grupo Controle. A expressão protéica do receptor AT1 esteve elevada nos dois grupos hipertireoideos. Os resultados obtidos sugerem que o bloqueio do receptor AT1 promove importante impacto sobre o balanço simpato-vagal e a hipertrofia cardíaca, no hipertireoidismo, sendo as espécies ativas de oxigênio e o sistema Nrf-2/HO-1 possíveis mediadores destas alterações.Hyperthyroidism is an epidemiologic relevant pathology, which substantially affects the cardiovascular system. The hyperthyroid state may affect basal metabolism, O2 cell consumption, renin-angiotensin system, and increase reactive oxygen species production. Those alterations produce morphological, biochemical, functional and molecular consequences in cardiac tissue. Hyperthyroidism induced cardiac hypertrophy develops due to a set of events, which signals cell survival and proliferation, including reactive oxygen species, cardiac rennin-angiotensin system, and autonomic nervous system. In the present study, the role of cardiac renin-angiotensin system on development of hyperthyroidism induced cardiac hypertrophy, and the involvement of autonomic nervous system and reactive oxygen species, were assessed trough blockade of angiotensin II receptor AT1. For that, were used male Wistar rats, weighting about 220g, divided in 4 experimental groups,: Control (C), Losartan (L) (10mg/Kg body weight/day, 28 days, intragastric probe), T4 (12mg/L L-thyroxin in drinking water, 28 days), and T4+L. Cardiac mass, spectral analysis (autonomic balance), hydrogen peroxide (H2O2), and myocardial protein expression of angiotensin II receptor (AT1), NADPH oxidase, Nrf-2, and heme-oxygenase-1 (HO-1), were quantified. Cardiac hypertrophy and autonomic umbalance induced by thyroid hormones were attenuated in the T4+losartan group. The H2O2, as well as Nrf-2, gp91phox, AT1 and HO-1 immunocontent were elevated in T4 group. All these effects were attenuated by losartan, except AT1 levels. The overall results suggest that blockade of AT1 receptor lead to relevant impact on autonomic balance and cardiac hypertrophy, being ROS and Nrf-2/ HO-1 system possible mediators in this alterations in experimental hyperthyroidism.
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Lemmon, Teresa L. "Development of chemostats and use of redox indicators for studying redox transformations in biogeochemical matrices". Thesis, 1995. http://hdl.handle.net/1957/35143.
Pełny tekst źródłaKsiążki na temat "REDOX REACTION ANALYSIS"
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1946-, Das Dipak Kumar, red. Methods in redox signaling. New Rochelle, NY: Mary Ann Liebert, 2009.
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1946-, Das Dipak Kumar, red. Methods in redox signaling. New Rochelle, NY: Mary Ann Liebert, 2010.
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Oxidative stress and redox regulation in plants. Amsterdam [etc.]: Elsevier/Academic Press, 2009.
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Rogers, J. E. Effects of temperature and redox conditions on degradation of chlorinated phenols in freshwater sediments: Project summary. Athens, GA: U.S. Environmental Protection Agency, Environmental Research Laboratory, 1989.
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Lemmon, Teresa L. Development of chemostats and use of redox indicators for studying redox transformations in biogeochemical matrices. 1995.
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Vulterin, J., J. Zýka, L. Gordon, R. Belcher i A. Berka. Newer Redox Titrants: International Series of Monographs in Analytical Chemistry. Elsevier Science & Technology Books, 2013.
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Jacquot, Jean-Pierre. Oxidative Stress and Redox Regulation in Plants. Elsevier Science & Technology Books, 2009.
Znajdź pełny tekst źródłaCzęści książek na temat "REDOX REACTION ANALYSIS"
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Noguchi, Takumi. "Spectroscopic Analysis of the Redox Reactions of π-Conjugated Cofactors in Photosynthetic Reaction Center". W Chemical Science of π-Electron Systems, 675–94. Tokyo: Springer Japan, 2015. http://dx.doi.org/10.1007/978-4-431-55357-1_40.
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Zhang, Wei, Juhua Zhang, Qiang Li, Yibo He, Biao Tang, Mingming Li, Zuoliang Zhang i Zongshu Zou. "Thermodynamic Analyses of Iron Oxides Redox Reactions". W PRICM, 777–89. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2013. http://dx.doi.org/10.1002/9781118792148.ch96.
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Zhang, Wei, Juhua Zhang, Qiang Li, Yibo He, Biao Tang, Mingming Li, Zuoliang Zhang i Zongshu Zou. "Thermodynamic Analyses of Iron Oxides Redox Reactions". W Proceedings of the 8th Pacific Rim International Congress on Advanced Materials and Processing, 777–89. Cham: Springer International Publishing, 2013. http://dx.doi.org/10.1007/978-3-319-48764-9_96.
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Burgot, Jean-Louis. "Some Applications of Redox Reactions in Qualitative Analysis". W Ionic Equilibria in Analytical Chemistry, 405–19. New York, NY: Springer New York, 2012. http://dx.doi.org/10.1007/978-1-4419-8382-4_21.
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Huston, David L., Robert B. Trumbull, Georges Beaudoin i Trevor Ireland. "Light Stable Isotopes (H, B, C, O and S) in Ore Studies—Methods, Theory, Applications and Uncertainties". W Isotopes in Economic Geology, Metallogenesis and Exploration, 209–44. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-27897-6_8.
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AbstractVariations in the abundances of light stable isotopes, particularly those of hydrogen, boron, carbon, oxygen and sulfur, were essential in developing mineralization models. The data provide constraints on sources of hydrothermal fluids, carbon, boron and sulfur, track interaction of these fluids with the rocks at both the deposit and district scales, and establish processes of ore deposition. In providing such constraints, isotopic data have been integral in developing genetic models for porphyry-epithermal, volcanic-hosted massive sulfide, orogenic gold, sediment-hosted base metal and banded-iron formation-hosted iron ore systems, as discussed here and in other chapters in this book. After providing conventions, definitions and standards used to present stable isotope data, this chapter summarizes analytical methods, both bulk and in situ, discusses processes that fractionate stable isotopes, documents the isotopic characteristics of major fluid and rock reservoirs, and then shows how stable isotope data have been used to better understand ore-forming processes and to provide vectors to ore. Analytical procedures, initially developed in the 1940s for carbon–oxygen analysis of bulk samples of carbonate minerals, have developed so that, for most stable isotopic systems, spots as small as a few tens of μm are routinely analyzed. This precision provides the paragenetic and spatial resolution necessary to answer previously unresolvable genetic questions (and create new questions). Stable isotope fractionation reflects geological and geochemical processes important in ore formation, including: (1) phase changes such as boiling, (2) water–rock interaction, (3) cooling, (4) fluid mixing, (5) devolatilization, and (6) redox reactions, including SO2 disproportionation caused by the cooling of magmatic-hydrothermal fluids and photolytic dissociation in the atmosphere. These processes commonly produce gradients in isotopic data, both in time and in space. These gradients, commonly mappable in space, provide not only evidence of process but also exploration vectors. Stable isotope data can be used to estimate the conditions of alteration or mineralization when data for coexisting minerals are available. These estimates use experimentally- or theoretically-determined fractionation equations to estimate temperatures of mineral formation. If the temperature is known from isotopic or other data (e.g., fluid inclusion data or chemical geothermometers), the isotopic composition of the hydrothermal fluid components can be estimated. If fluid inclusion homogenization and compositional data exist, the pressure and depth of mineralization can be estimated. One of the most common uses of stable isotope data has been to determine, or more correctly delimit, fluid and sulfur sources. Estimates of the isotopic compositions of hydrothermal fluids, in most cases, do not define unequivocal sources, but, rather, eliminate sources. As an example, the field of magmatic fluids largely overlap that of metamorphic fluids in δ18O-δD space, but are significantly different to the fields of meteoric waters and seawater. As such, a meteoric or seawater origin for a fluid source may be resolvable, but a magmatic source cannot be resolved from a metamorphic source. Similarly, although δ34S ~ 0‰ is consistent with a magmatic-hydrothermal sulfur source, the signature can also be produced by leaching of an igneous source. Recent analytical and conceptual advances have enabled gathering of new types of isotopic data and application of these data to resolve new problems in mineral deposit genesis and geosciences in general. Recent developments such as rapid isotopic analysis of geological materials or clumped isotopes will continue to increase the utility of stable isotope data in mineral deposit genesis and metallogeny, and, importantly, for mineral exploration.
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Quesnel, Benoît, Christophe Scheffer i Georges Beaudoin. "The Light Stable Isotope (Hydrogen, Boron, Carbon, Nitrogen, Oxygen, Silicon, Sulfur) Composition of Orogenic Gold Deposits". W Isotopes in Economic Geology, Metallogenesis and Exploration, 283–328. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-27897-6_10.
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AbstractOrogenic gold deposits formed in various terranes of most ages since the Paleoarchean and generally consist of quartz veins hosted in shear zones formed at the ductile brittle transition under greenschist to lower amphibolite metamorphic conditions. Vein mineralogy is dominated by quartz with various amounts of silicates, carbonates, phyllosilicates, borates, tungstates, sulfides, and oxides. The isotopic composition of these minerals and fluid inclusions has been investigated since the 1960s to constrain the characteristics of orogenic fluid systems involved in the formation of gold deposits worldwide. This review is based on 8580 stable isotope analyses, including δ18O, δD, δ13C, δ34S δ15N, δ11B, and δ30Si values, from 5478 samples from 558 orogenic gold deposits reported in the literature from 1960 to 2010. This contribution describes the variability of the light stable isotopic systems as function of the minerals, the age of the deposits, their regional setting, and their country rocks. The temperature of isotopic equilibrium of orogenic gold veins is estimated from mineral pairs for oxygen and sulfur isotopes. Based on these temperatures, and on fractionation between mineral and fluid components (H2O, CO2 and H2S), the isotopic composition of fluids is estimated to better constrain the main parameters shared by most of auriferous orogenic fluid systems. Orogenic gold deposits display similar isotopic features through time, suggesting that fluid conditions and sources leading to the formation of orogenic gold deposits did not change significantly from the Archean to the Cenozoic. No consistent secular variations of mineral isotope composition for oxygen (−8.1‰ ≤ δ18O ≤ 33‰, n = 4011), hydrogen (−187‰ ≤ δD ≤ −4‰, n = 246), carbon (−26.7‰ ≤ δ13C ≤ 12.3‰, n = 1179), boron (−21.6‰ ≤ δ11B ≤ 9‰, n = 119), and silicon (−0.5‰ ≤ δ30Si ≤ 0.8‰, n = 33) are documented. Only nitrogen (1.6‰ ≤ δ15N ≤ 23.7‰, n = 258) and sulfide sulfur from deposits hosted in sedimentary rocks (−27.2‰ ≤ δ34S ≤ 25‰, n = 717) display secular variations. For nitrogen, the change in composition is interpreted to record the variation of δ15N values of sediments devolatilized during metamorphism. For sulfur, secular variations reflect incorporation of local sedimentary sulfur of ultimate seawater origin. No significant variation of temperature of vein formation is documented for orogenic gold deposits of different ages. Quartz-silicate, quartz-carbonate and sulfide-sulfide mineral pairs display consistent temperatures of 360 ± 76 °C (1σ; n = 332), in agreement with the more common greenschist facies hostrocks and fluid inclusion microthermometry. Fluid sources for orogenic gold deposits are complex but the isotopic systems (hydrogen, boron, carbon, nitrogen, oxygen, sulfur) are most consistent with contributions from metamorphic fluids released by devolatilization of igneous, volcano-sedimentary and/or sedimentary rocks. The contribution of magmatic water exsolved from magma during crystallization is not a necessary component, even if permissible in specific cases. Isotopic data arrays can be interpreted as the result of fluid mixing between a high T (~550 °C)—high δ18O (~10‰)—low δD (~−60‰) deep-seated (metamorphic) fluid reservoir and a low T (~200 °C)—low δ18O (~2‰)—high δD (~0‰) upper crustal fluid reservoir in a number of orogenic gold deposits. The origin of the upper crustal fluid is most likely sea- or meteoric water filling the host rock porosity, with a long history of water–rock isotope exchange. Mixing of deep-seated and upper crustal fluids also explains the large variation of tourmaline δ11B values from orogenic gold veins. Regional spatial variations of oxygen and hydrogen isotope compositions of deep-seated fluid reservoirs are documented between orogenic gold districts. This is the case for the Val-d’Or (Abitibi), Coolgardie and Kalgoorlie (Yilgarn) where the oxygen isotope composition of the deep-seated fluid end-member is 4‰ lower compared to that from the Timmins, Larder Lake, and Kirkland Lake districts (Abitibi). However, both mixing trends converge towards a common, low δ18O upper crustal fluid end-member. Such variations cannot be related to fluid buffering at the site of deposition and suggest provinciality of the fluid source. The contribution of meteoric water is mainly recorded by fluid inclusions from Mesozoic and Cenozoic age deposits, but micas are not systematically in isotopic equilibrium with fluid inclusions trapped in quartz from the same vein. This suggests late involvement of meteoric water unrelated to deposit formation. Yet, a number of deposits with low δD mica may record infiltration of meteoric water in orogenic gold deposits. Isotope exchange between mineralizing fluid and country rocks is documented for oxygen, carbon, sulfur and silicon isotopes. Large variations (> 10‰) of sulfide δ34S values at the deposit scale are likely related to evolving redox conditions of the mineralizing fluid during reaction with country rocks. Deposits hosted in sedimentary rocks show a shift to higher δ18O values as a result of fluid/rock oxygen exchange with the regional sedimentary country rocks.
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Oriakhi, Christopher O. "Oxidation and Reduction Reactions". W Chemistry in Quantitative Language, 365–88. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780198867784.003.0022.
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Oxidation and Reduction Reactions deals with chemical reactions involving electron transfer. It begins with oxidation numbers and their applications in naming complex molecular or ionic compounds. Rules for assigning oxidation numbers and how to calculate the oxidation number of any atom in a compound or ion are described. Extensive coverage is given to oxidizing and reducing agents, including how to identify them in a given process. Half-cell reactions are defined. Balancing redox equations with the oxidation number method and the half-reaction method are emphasized. The chapter concludes with an overview of oxidation-reduction titration and calculations based on redox titration analysis.
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N. Pronkin, Sergey, Nina Yu. Shokina i Cuong Pham-Huu. "Redox Transitions in Pseudocapacitor Materials: Criteria and Ruling Factors". W Redox Chemistry - From Molecules to Energy Storage [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.104084.
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Pseudocapacitance is a phenomenon of charge storage involving redox transitions at the electrode/electrolyte interface. As the result of an electrode potential modulation, one or few components of the electrode and/or electrolyte change its/their oxidation states. The redox reaction may be confined to the interface or propagate into the bulk of the electrode material, thus significantly increasing the charge (and energy) capacitance of the material. The rate and the reversibility of the interfacial redox reaction are the key factors determining the efficiency of charge storage due to pseudocapacitance phenomena. The influence of the characteristics of the interfacial redox reaction on the efficiency of charge storage in pseudocapacitive materials is considered in the current chapter. In particular, the similarities and the differences between the charge storage in batteries and pseudocapacitors are discussed. The analysis of the pseudocapacitive behavior of electrode material using the impedance spectroscopy is presented.
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Povar, Igor, i Oxana Spinu. "Thermodynamics of Redox Processes in Homogeneous and Heterogeneous Multicomponent Systems". W Fundamental and Biomedical Aspects of Redox Processes, 173–97. IGI Global, 2023. http://dx.doi.org/10.4018/978-1-6684-7198-2.ch008.
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The chapter presents a thermodynamic approach for the complex chemical and redox equilibria investigation of mono- and two-phase systems containing metal ions of slightly soluble solid phases in different oxidation states. For heterogeneous systems, this approach utilizes thermodynamic relationships combined with original mass balance constraints. The forms of occurrence of metal ions are determined by the major chemical reactions in the aquatic environment such as hydrolysis, oxidation, reduction, and precipitation. On the basis of the introduced generalized equation of the overall redox reaction the physical meaning of the overall electrode potential under conditions other than standard ones, was revealed. The diagrams of complex chemical equilibria have been used for the graphical representation of complex equilibria in aqueous solutions. The developed approach can be applied to calculating potential−pH (Pourbaix) diagrams, based on the thermodynamic analysis of chemical equilibria in homogeneous and heterogeneous multicomponent systems.
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Murali Manoj, Kelath, Nikolai Bazhin, Abhinav Parashar, Afsal Manekkathodi i Yanyou Wu. "Comprehensive Analyses of the Enhancement of Oxygenesis in Photosynthesis by Bicarbonate and Effects of Diverse Additives: Z-scheme Explanation Versus Murburn Model". W Physiology. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.106996.
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The Z-scheme electron transport chain (ETC) explanation for photosynthesis starts with the serial/sequential transfer of electrons sourced from water molecules bound at Photosystem II via a deterministic array of redox centers (of various stationary/mobile proteins), before \"sinking\" via the reduction of NADP+ bound at flavin-enzyme reductase. Several research groups’ finding that additives (like bicarbonate) enhance the light reaction had divided the research community because it violated the Z-scheme. The untenable aspects of the Z-scheme perception were demonstrated earlier and a murburn bioenergetics (a stochastic/parallel paradigm of ion-radical equilibriums) model was proposed to explain photophosphorylation and Emerson effect. Herein, we further support the murburn model with accurate thermodynamic calculations, which show that the cost of one-electron abstraction from bicarbonate [491 kJ/mol] is lower than water [527 kJ/mol]. Further, copious thioredoxin enables the capture of photoactivated electrons in milieu, which aid in the reduction of nicotinamide nucleotides. The diffusible reactive species (DRS) generated in milieu sponsor phosphorylations and oxygenic reactions. With structural analysis of Photosystems and interacting molecules, we chart out the equations of reactions that explain the loss of labeled O-atom traces in delocalized oxygenesis. Thus, this essay discredits the Z-scheme and explains key outstanding observations in the field.
Streszczenia konferencji na temat "REDOX REACTION ANALYSIS"
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Karabaliev, Miroslav, Bilyana Tacheva, Boyana Paarvanova, Radostina Georgieva, Radoslav Ginin i Stefka Atanassova. "Principal component analysis of hemoglobin redox reaction in spectroelectrochemical cell". W INTERNATIONAL CONFERENCE OF COMPUTATIONAL METHODS IN SCIENCES AND ENGINEERING ICCMSE 2020. AIP Publishing, 2021. http://dx.doi.org/10.1063/5.0047853.
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Cotton, Therese M., George D. Chumanov, Jae-Ho Kim i Dale Gaul. "Surface-enhanced resonance Raman scattering studies of photosynthetic systems". W Laser Applications to Chemical Analysis. Washington, D.C.: Optica Publishing Group, 1992. http://dx.doi.org/10.1364/laca.1992.mc1.
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Surface-enhanced resonance Raman scattering (SERRS) spectroscopy is a powerful new technique for the study of membrane preparations containing chromophoric molecules. Photosynthetic reaction center and light harvesting complexes have been examined. The spatial location and redox state of the various components (chlorophylls, pheophytins, and cytochromes) can be ascertained from the spectra.
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Vahedi, Nasser, Carlos E. Romero, Mark A. Snyder i Alparslan Oztekin. "Study of Heating and Cooling Rate of Cobalt Oxide-Based TCES System Using Experimental Redox Kinetics Analysis". W ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-10734.
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Abstract Cost-effective solar power generation in CSP plants requires the challenging integration of high energy density and high-temperature thermal energy storage with the solar collection equipment and the power plant. Thermochemical energy storage (TCES) is currently a very good option for thermal energy storage, which can meet the industry requirement of large energy density and high storage temperature. TCES specifically exploits reversible chemical reactions wherein heat is absorbed during the forward endothermic reaction and released during the reverse exothermic reaction. The associated enthalpic storage of energy (i.e., the heat of reaction) offers higher density and enhanced stability compared to sensible and latent heat storage. Metal oxide redox reactions are particularly well-suited for TCES given their characteristically high enthalpy of reaction and high reaction temperature. In addition, the air is suitable as both a heat transfer fluid (HTF) and reactant; thus, simplifying process design and eliminating the need for indirect HTF storage and any intermediate heat exchanger. Among the palette of available metal oxides, cobalt oxide is one of the most promising candidates for TCES given its high enthalpy of reaction with high reaction temperature. One of the critical design parameters for TCES reactors is the optimal heating and cooling rates during respective charging and discharging modes of operation. In order to study the effect of heating/cooling rate on cobalt oxide TCES performance, a constant 10°C/min rate was selected for both storage cycle heating and cooling. Considering the intrinsic redox kinetics of cobalt oxide at considered constant heating/cooling rate, we studied milligram scale quantities of cobalt oxide (99.9% purity, 40 μm average particle size) using a dual-mode thermogravimetric (TGA)/differential scanning calorimetry (DSC) system, which simultaneously measures weight change (TGA) and differential heat flow (DSC) as a function of TCES cycling under continuous air purge. In addition, we investigated the cyclic stability of cobalt oxide in the context of the redox kinetics and particle coarsening behavior, employing scanning electron microscopy (SEM). TGA/DSC tests were conducted for 30 successive cycles using pure cobalt oxide. It was shown that pure cobalt oxide in powder form (38μ particle size) could complete both forward and reverse reaction at the selected heating rate with little degradation between cycles. In parallel, SEM was used to examine morphology and particle size changes before and after heating cycles. SEM results proved grain growth occurs even after only five initial cycles.
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Vahedi, Nasser, i Alparslan Oztekin. "Experimental Analysis of Kinetics and Cyclic Performance of Cobalt Oxide Powder As Redox Reactant Agent for High-Temperature Thermochemical Energy Storage". W ASME 2019 Heat Transfer Summer Conference collocated with the ASME 2019 13th International Conference on Energy Sustainability. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/ht2019-3681.
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Abstract For continuous operation of Concentrated Solar Power (CSP) Plants it is necessary to integrate thermal energy storage module. High-density energy storage system at a high temperature is required for the new generation of large scale CSP plants. The Thermochemical Energy Storage (TCES) systems use the enthalpy of formation of a reversible chemical reaction for energy storage and release. Gas/solid reduction-oxidation (redox) reactions of solid metal oxides using air as heat transfer fluid (HTF) can be directly integrated with air operated CSP plants, and there is no need for HTF storage and any intermediate heat exchanger. A new generation of large scale CSP plants uses high-temperature solar collectors to increase power cycle efficiency. Such operating conditions require the development of suitable high-temperature TCES systems. The selection of suitable metal oxide reactant is very critical in the design of such high-temperature storage systems and requires a detailed study of the physics of reaction within the reactor. Cobalt oxide (Co3O4/CoO) has been verified to have a high reaction temperature, high enthalpy of reaction together with reasonable cyclic and thermal stability. Unique features of cobalt oxide require more fundamental study of the physics behind the redox reaction and its cyclic performance. Study of the physics of materials during the storage/release cycle is necessary for the design and improvement of the reactor and can be used as a benchmark for comparison of any implemented changes. A high precision, true differential TGA/DSC instrument is used for simultaneous measurement of weightchange (TGA) and true differential heat flow (DSC) for pure cobalt oxide (Co3O4) powder. Storage cycle (charge/discharge) was conducted for five cycles. Complete re-oxidation was achieved within reasonable times by performing the two reactions at close temperatures and controlling heating/cooling rates. Basic performance parameters were derived as a benchmark for future references. Single-cycle controlling parameters such as heating/cooling rate, dwelling time, and purge gas rate were investigated. System response for few initial cycles was studied. It was shown that pure cobalt oxide could regain weight and complete re-oxidation with reasonable stability. A transition for heat flow was detected after a few initial cycles which reduced discharge heat and decreased overall performance.
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Krenzke, Peter, i Jane Davidson. "Thermodynamic Analysis of the Ceria Redox Cycle With Methane-Driven Reduction for Solar Fuel Production". W ASME 2014 8th International Conference on Energy Sustainability collocated with the ASME 2014 12th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/es2014-6332.
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The nonstoichiometric cerium oxide (ceria) redox cycle is an attractive pathway for storing energy from concentrated sunlight in chemical bonds by splitting water and carbon dioxide. The endothermic reduction reaction (R1)CeO2-δox→CeO2-δed+Δδ2O2 is favored thermodynamically at high temperatures and low oxygen partial pressures, while the CO2 and H2O splitting reactions (R2, R3) are exothermic and favored at lower temperatures and higher oxygen partial pressures. The produced hydrogen and carbon monoxide, referred to collectively as syngas, are important feedstocks used in the synthesis of ammonia and liquid fuels.(R2)CeO2-δed+ΔδCO2→CeO2-δox+ΔδCO (R3)CeO2-δed+ΔδH2O→CeO2-δox+ΔδH2
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Stamatiou, Anastasia, Peter G. Loutzenhiser i Aldo Steinfeld. "Solar Syngas Production From H2O and CO2 via Two Step Thermochemical Cycles Based on FeO/Fe3O4 Redox Reactions: Kinetic Analysis". W ASME 2010 4th International Conference on Energy Sustainability. ASMEDC, 2010. http://dx.doi.org/10.1115/es2010-90009.
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Syngas production via a two-step H2O/CO2-splitting thermochemical cycle based on FeO/Fe3O4 redox reactions is considered using highly concentrated solar process heat. The closed cycle consists of: 1) the solar-driven endothermic dissociation of Fe3O4 to FeO; 2) the non-solar exothermic simultaneous reduction of CO2 and H2O with FeO to CO and H2 and the initial metal oxide; the latter is recycled to the first step. The second step was experimentally investigated by thermogravimetry for reactions with FeO in the range 973–1273 K and CO2/H2O concentrations of 15–75%. The reaction mechanism was characterized by an initial fast interface-controlled regime followed by a slower diffusion-controlled regime. A rate law of Langmuir-Hinshelwood type was formulated to describe the competitiveness of the reaction based on atomic oxygen exchange on active sites, and the corresponding Arrhenius kinetic parameters were determined by applying a shrinking core model.
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Ramji, H. R., N. Glandut, J. Absi, S. F. Lim i A. A. Khan. "Comparative study of a transient redox reaction on a single electrode microdisk using finite element analysis". W II INTERNATIONAL SCIENTIFIC FORUM ON COMPUTER AND ENERGY SCIENCES (WFCES-II 2021). AIP Publishing, 2022. http://dx.doi.org/10.1063/5.0099589.
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Brendelberger, Stefan, Jan Felinks, Dominik Kolb i Christian Sattler. "Particle Conveyer for Solar Thermo-Chemical Processes and Related Solid Heat Recovery Systems". W ASME 2016 10th International Conference on Energy Sustainability collocated with the ASME 2016 Power Conference and the ASME 2016 14th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/es2016-59577.
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On the way to a de-carbonized economy by 2050 new technologies have to be developed and deployed into the market. In solar driven thermochemical processes concentrated solar radiation is used as a renewable high temperature heat source to drive a chemical reaction. These processes are promising pathways for the production of gaseous and liquid fuels and therefore they can provide sustainable chemical energy carriers with inherent long-term storage capabilities. Amongst these processes, redox cycles for the production of syngas from water and carbon dioxide received considerable interest due to their high theoretical process efficiencies. In these processes a redox material is reduced using high temperature heat which is provided by concentrated solar radiation. In a second reaction, at considerably lower temperatures, the redox material is oxidized while splitting water or carbon dioxide. One requirement for the design of efficient redox processes is a high recovery rate of the sensible heat of the solid redox material. In recent redox process concepts the use of inert heat transfer particles in combination with a particulate redox material has been proposed. Amongst other benefits this methodology allows to recover heat from the redox material. A corresponding solid-solid heat recovery system is under development. In a single stage the heat recovery unit acts as a co-current heat exchanger. By combining several units and by using a proper flow path a quasi-counter-current heat exchanger can be obtained. Such a heat recovery system requires that particles are lifted at temperatures well above 1100°C. These high temperatures require a simple design, decent thermal insulation and the thermal shielding of all moving parts and engine. The present work is dealing with the development of a respective conveying system which can be operated at the targeted temperatures, while heat losses are prevented as far as possible. A lab scale version of the conveyer is constructed and tested. A numerical model of the conveyer is developed and validated using results of an experimental campaign with particles at 1150°C. The next step in the assessment of the conveyer system is the analysis of the performance of a scale up version. A generic process analysis will be conducted to obtain operational and design requirements of the scale up conveyer. A detailed scale up version is developed accordingly and the validated numerical model is applied to this design to predict the heat losses during the particle lifting and to discuss their impact on the total process performance.
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Kodama, Tatsuya, Eiji Hiraiwa i Nobuyuki Gokon. "Reactivity of Iron-Containing YSZ for a Two-Step Thermochemical Water Splitting Using Thermal Reduction Temperatures of 1400–1500°C". W ASME 2008 2nd International Conference on Energy Sustainability collocated with the Heat Transfer, Fluids Engineering, and 3rd Energy Nanotechnology Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/es2008-54151.
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A thermochemical two-step water splitting cycle using a redox system of iron-based oxides or ferrites is one of the promising processes for converting solar energy into clean hydrogen in sunbelt regions. Fe3O4 supported on YSZ (Yttrium-Stabilized Zirconia) or Fe3O4/YSZ is a promising working material for the two-step water splitting cycle. In the water splitting cycle, an iron-containing YSZ or Fe2+-YSZ is formed by a high-temperature reaction between Fe3O4 and YSZ support at 1400°C in an inert atmosphere. The Fe2+-YSZ reacts with steam and generate hydrogen at 1000°C, to form Fe3+-YSZ that is re-activated by a thermal reduction in a separate step at 1400°C under an inert atmosphere. In the present work, the thermal reduction was performed in a higher temperature range of 1400–1500°C while the hydrolysis reaction was carried out at 1000°C. It was confirmed by XRD analysis that the cyclic redox reactions occurred based on the same reaction mechanism when using a thermal reduction temperature between 1400 and 1500°C. The conversions of Fe3O4 to Fe2+-YSZ were 20, 26 and 47% when the thermal reduction temperature were 1400, 1450, and 1500°C respectively, indicating that the x values in the formed Fe2+-YSZ or Fex2+YyZr1−yO2−y/2+x were 0.08, 0.11, and 0.19 respectively, where y = 0.15. The conversions of Fe2+-YSZ to Fe3+-YSZ in the hydrolysis reaction (at 1000°C), however, decreased from 90% to 60% when the thermal reduction temperature increased from 1400 to 1500°C. As the results, the hydrogen production reactivity of Fe3O4 supported on YSZ increased from 5.6 × 10−4 to 7.5 × 10−4 g per gram of Fe3O4/YSZ for one cycle on the cycle average by elevated thermal reduction temperature from 1400 to 1500°C.
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Vahedi, Nasser, i Alparslan Oztekin. "Parametric Study of High-Temperature Thermochemical Energy Storage Using Manganese-Iron Oxide". W ASME 2019 Heat Transfer Summer Conference collocated with the ASME 2019 13th International Conference on Energy Sustainability. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/ht2019-3682.
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Abstract Continuous power supply in Concentrated Solar Power (CSP) plants can be achieved via integration of efficient, cost-effective and reliable Thermal Energy Storage (TES) system. The new generation of CSPs operates at higher temperatures and requires thermal storage systems with higher energy density at high storage temperature. Thermochemical Energy Storage (TCES) is the available solution which can meet performance requirements of energy density, temperature, and stability. TCES systems apply reversible endothermic/exothermic chemical reaction through which energy is stored as the enthalpy of reaction and released during the reverse mode. Among several available potential reversible chemical reactions, metal oxides, with high reaction temperature and enthalpy of reaction, have remarkable advantages compared to others. They use air both as Heat Transfer Fluid (HTF) and oxidation reactant, which eliminates the need for storage and intermediate heat exchanger integration between HTF and collector working fluid. Using air as HTF has made them perfectly fitted for the new generation of air operated solar collectors. Among several screened available potential metal oxides, cobalt and manganese oxides were selected as best candidates for high-temperature storage. Pure manganese oxide does not meet the cyclic operation requirement, but the iron-doped solid solution has proven reasonable cyclic storage performance. In this study, iron-doped manganese oxide (Fe-Mn 1:3 molar ratio) has been selected as a redox agent for TCES reactor. The cylindrical packed bed configuration is considered as a reactor bed configuration. A two-dimensional axisymmetric numerical model is developed using the finite element method. Performance analysis for both charge and discharge is provided separately. The effect of inflow rate and bed porosity variations on reactor performance in complete storage cycle were studied.
Raporty organizacyjne na temat "REDOX REACTION ANALYSIS"
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Christopher, David A., i Avihai Danon. Plant Adaptation to Light Stress: Genetic Regulatory Mechanisms. United States Department of Agriculture, maj 2004. http://dx.doi.org/10.32747/2004.7586534.bard.
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Original Objectives: 1. Purify and biochemically characterize RB60 orthologs in higher plant chloroplasts; 2. Clone the gene(s) encoding plant RB60 orthologs and determine their structure and expression; 3. Manipulate the expression of RB60; 4. Assay the effects of altered RB60 expression on thylakoid biogenesis and photosynthetic function in plants exposed to different light conditions. In addition, we also examined the gene structure and expression of RB60 orthologs in the non-vascular plant, Physcomitrella patens and cloned the poly(A)-binding protein orthologue (43 kDa RB47-like protein). This protein is believed to a partner that interacts with RB60 to bind to the psbA5' UTR. Thus, to obtain a comprehensive view of RB60 function requires analysis of its biochemical partners such as RB43. Background & Achievements: High levels of sunlight reduce photosynthesis in plants by damaging the photo system II reaction center (PSII) subunits, such as D1 (encoded by the chloroplast tpsbAgene). When the rate of D1 synthesis is less than the rate of photo damage, photo inhibition occurs and plant growth is decreased. Plants use light-activated translation and enhanced psbAmRNA stability to maintain D1 synthesis and replace the photo damaged 01. Despite the importance to photosynthetic capacity, these mechanisms are poorly understood in plants. One intriguing model derived from the algal chloroplast system, Chlamydomonas, implicates the role of three proteins (RB60, RB47, RB38) that bind to the psbAmRNA 5' untranslated leader (5' UTR) in the light to activate translation or enhance mRNA stability. RB60 is the key enzyme, protein D1sulfide isomerase (Pill), that regulates the psbA-RN :Binding proteins (RB's) by way of light-mediated redox potentials generated by the photosystems. However, proteins with these functions have not been described from higher plants. We provided compelling evidence for the existence of RB60, RB47 and RB38 orthologs in the vascular plant, Arabidopsis. Using gel mobility shift, Rnase protection and UV-crosslinking assays, we have shown that a dithiol redox mechanism which resembles a Pill (RB60) activity regulates the interaction of 43- and 30-kDa proteins with a thermolabile stem-loop in the 5' UTR of the psbAmRNA from Arabidopsis. We discovered, in Arabidopsis, the PD1 gene family consists of II members that differ in polypeptide length from 361 to 566 amino acids, presence of signal peptides, KDEL motifs, and the number and positions of thioredoxin domains. PD1's catalyze the reversible formation an disomerization of disulfide bonds necessary for the proper folding, assembly, activity, and secretion of numerous enzymes and structural proteins. PD1's have also evolved novel cellular redox functions, as single enzymes and as subunits of protein complexes in organelles. We provide evidence that at least one Pill is localized to the chloroplast. We have used PDI-specific polyclonal and monoclonal antisera to characterize the PD1 (55 kDa) in the chloroplast that is unevenly distributed between the stroma and pellet (containing membranes, DNA, polysomes, starch), being three-fold more abundant in the pellet phase. PD1-55 levels increase with light intensity and it assembles into a high molecular weight complex of ~230 kDa as determined on native blue gels. In vitro translation of all 11 different Pill's followed by microsomal membrane processing reactions were used to differentiate among PD1's localized in the endoplasmic reticulum or other organelles. These results will provide.1e insights into redox regulatory mechanisms involved in adaptation of the photosynthetic apparatus to light stress. Elucidating the genetic mechanisms and factors regulating chloroplast photosynthetic genes is important for developing strategies to improve photosynthetic efficiency, crop productivity and adaptation to high light environments.
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Thompson. L52114 Efficient use of Cathodic Polarization Criteria. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), styczeń 2005. http://dx.doi.org/10.55274/r0011101.
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A series of long term polarization tests were performed to investigate efficient use of the 100mV polarization growth/decay for demonstrating CP effectiveness. Several conclusions were drawn. Absolute time limits for measuring polarization growth or decay could not be justified. Simple extrapolation of polarization growth or decay curves also could not be justified; future extrapolation needs to be mechanistically based. The application of CP can change the local environment at a steel surface including creating passivity. Redox reactions in soils complicate analysis of polarization data. For a particular system at constant applied current, formation and decay rates are similar. However, Initial polarization has less magnitude than subsequent polarizations.
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Friedman, Haya, Chris Watkins, Susan Lurie i Susheng Gan. Dark-induced Reactive Oxygen Species Accumulation and Inhibition by Gibberellins: Towards Inhibition of Postharvest Senescence. United States Department of Agriculture, grudzień 2009. http://dx.doi.org/10.32747/2009.7613883.bard.
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Dark-induced senescence could pose a major problem in export of various crops including cuttings. The assumption of this work was that ROS which is increased at a specific organelle can serve as a signal for activation of cell senescence program. Hormones which reduce senescence in several crops like gibberellic acid (GA) and possibly cytokinin (CK) may reduce senescence by inhibiting this signal. In this study we worked on Pelargonium cuttings as well as Arabidopsis rosette. In Pelargonium the increase in ROS occurred concomitantly with increase in two SAGs, and the increase persisted in isolated chloroplasts. In Arabidopsis we used two recentlydeveloped technologies to examine these hypotheses; one is a transcriptome approach which, on one hand, enabled to monitor expression of genes within the antioxidants network, and on the other hand, determine organelle-specific ROS-related transcriptome footprint. This last approach was further developed to an assay (so called ROSmeter) for determination of the ROS-footprint resulting from defined ROS stresses. The second approach involved the monitoring of changes in the redox poise in different organelles by measuring fluorescence ratio of redox-sensitive GFP (roGFP) directed to plastids, mitochondria, peroxisome and cytoplasm. By using the roGFP we determined that the mitochondria environment is oxidized as early as the first day under darkness, and this is followed by oxidation of the peroxisome on the second day and the cytoplast on the third day. The plastids became less oxidized at the first day of darkness and this was followed by a gradual increase in oxidation. The results with the ROS-related transcriptome footprint showed early changes in ROS-related transcriptome footprint emanating from mitochondria and peroxisomes. Taken together these results suggest that the first ROS-related change occurred in mitochondria and peroxisomes. The analysis of antioxidative gene’s network did not yield any clear results about the changes occurring in antioxidative status during extended darkness. Nevertheless, there is a reduction in expression of many of the plastids antioxidative related genes. This may explain a later increase in the oxidation poise of the plastids, occurring concomitantly with increase in cell death. Gibberellic acid (GA) prevented senescence in Pelargonium leaves; however, in Arabidopsis it did not prevent chlorophyll degradation, but prevented upregulation of SAGs (Apendix Fig. 1). Gibberellic acid prevented in Pelargonium the increase in ROS in chloroplast, and we suggested that this prevents the destruction of the chloroplasts and hence, the tissue remains green. In Arabidopsis, reduction in endogenous GA and BA are probably not causing dark-induced senescence, nevertheless, these materials have some effect at preventing senescence. Neither GA nor CK had any effect on transcriptome footprint related to ROS in the various organelles, however while GA reduced expression of few general ROS-related genes, BA mainly prevented the decrease in chloroplasts genes. Taken together, GA and BA act by different pathways to inhibit senescence and GA might act via ROS reduction. Therefore, application of both hormones may act synergistically to prevent darkinduced senescence of various crops.
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Delwiche, Michael, Boaz Zion, Robert BonDurant, Judith Rishpon, Ephraim Maltz i Miriam Rosenberg. Biosensors for On-Line Measurement of Reproductive Hormones and Milk Proteins to Improve Dairy Herd Management. United States Department of Agriculture, luty 2001. http://dx.doi.org/10.32747/2001.7573998.bard.
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The original objectives of this research project were to: (1) develop immunoassays, photometric sensors, and electrochemical sensors for real-time measurement of progesterone and estradiol in milk, (2) develop biosensors for measurement of caseins in milk, and (3) integrate and adapt these sensor technologies to create an automated electronic sensing system for operation in dairy parlors during milking. The overall direction of research was not changed, although the work was expanded to include other milk components such as urea and lactose. A second generation biosensor for on-line measurement of bovine progesterone was designed and tested. Anti-progesterone antibody was coated on small disks of nitrocellulose membrane, which were inserted in the reaction chamber prior to testing, and a real-time assay was developed. The biosensor was designed using micropumps and valves under computer control, and assayed fluid volumes on the order of 1 ml. An automated sampler was designed to draw a test volume of milk from the long milk tube using a 4-way pinch valve. The system could execute a measurement cycle in about 10 min. Progesterone could be measured at concentrations low enough to distinguish luteal-phase from follicular-phase cows. The potential of the sensor to detect actual ovulatory events was compared with standard methods of estrus detection, including human observation and an activity monitor. The biosensor correctly identified all ovulatory events during its testperiod, but the variability at low progesterone concentrations triggered some false positives. Direct on-line measurement and intelligent interpretation of reproductive hormone profiles offers the potential for substantial improvement in reproductive management. A simple potentiometric method for measurement of milk protein was developed and tested. The method was based on the fact that proteins bind iodine. When proteins are added to a solution of the redox couple iodine/iodide (I-I2), the concentration of free iodine is changed and, as a consequence, the potential between two electrodes immersed in the solution is changed. The method worked well with analytical casein solutions and accurately measured concentrations of analytical caseins added to fresh milk. When tested with actual milk samples, the correlation between the sensor readings and the reference lab results (of both total proteins and casein content) was inferior to that of analytical casein. A number of different technologies were explored for the analysis of milk urea, and a manometric technique was selected for the final design. In the new sensor, urea in the sample was hydrolyzed to ammonium and carbonate by the enzyme urease, and subsequent shaking of the sample with citric acid in a sealed cell allowed urea to be estimated as a change in partial pressure of carbon dioxide. The pressure change in the cell was measured with a miniature piezoresistive pressure sensor, and effects of background dissolved gases and vapor pressures were corrected for by repeating the measurement of pressure developed in the sample without the addition of urease. Results were accurate in the physiological range of milk, the assay was faster than the typical milking period, and no toxic reagents were required. A sampling device was designed and built to passively draw milk from the long milk tube in the parlor. An electrochemical sensor for lactose was developed starting with a three-cascaded-enzyme sensor, evolving into two enzymes and CO2[Fe (CN)6] as a mediator, and then into a microflow injection system using poly-osmium modified screen-printed electrodes. The sensor was designed to serve multiple milking positions, using a manifold valve, a sampling valve, and two pumps. Disposable screen-printed electrodes with enzymatic membranes were used. The sensor was optimized for electrode coating components, flow rate, pH, and sample size, and the results correlated well (r2= 0.967) with known lactose concentrations.