Récupérer l'énergie mécanique ambiante est une alternative prometteuse afin d'assurer l'autonomie énergétique d'appareils nomades. Le développement des générateurs électrostatiques souples reste toutefois à ce jour anecdotique du fait des hautes tensions de polarisation employées, de la nécessité de grandes déformations mécaniques mais aussi de l'utilisation de matériaux peu conventionnels et mal caractérisés. Le but de cette thèse est d'apporter des avancées scientifiques et des solutions aux verrous technologiques précités. Tout d'abord, une caractérisation rigoureuse des propriétés électriques et mécaniques de deux matériaux communément utilisés pour ces applications (acrylate VHB 4910 et silicone Polypower) nous a donné accès aux propriétés physiques dans un fonctionnement réel de ces polymères : influence de la précontrainte, de la nature des électrodes... Ces données ont permis d'élaborer des lois analytiques fiables que nous avons ensuite insérées dans un modèle thermodynamique permettant de définir avec précision les puissances et densités d'énergie récupérables pour ces générateurs. Des pistes d'amélioration des matériaux utilisés dans les applications générateurs peuvent être dégagées de notre modèle. Le second verrou à lever concerne la source haute tension de polarisation nécessaire à ces générateurs électrostatiques. Pour cela, nous avons proposé une solution innovante couplant l'élastomère diélectrique à un électret. Différentes configurations de générateurs hybrides dans des géométries 2D et 3D ont été évaluées. Enfin, nous avons réalisé un prototype qui a délivré une puissance de l'ordre de 35µW sachant qu'une optimisation de ce prototype est réalisable et que des puissances récupérées de plusieurs centaines de µW sont tout à fait réalistes. / Scavenging mechanical ambient energy is a promising solution to ensure the autonomy of wearable transducers. Nevertheless, the development of soft electrostatic generator (DEG) is up to now slow down due to the use of high bias voltage, high strain and innovative mischaracterized materials. The aim of this Ph-D thesis is to propose innovative solutions to these technological barriers. Firstly, a complete characterization of the electrical and mechanical properties of two commonly used dielectric polymer (acrylate VHB 4910 and silicone Polypower) has revealed the true physical properties of these polymers and especially the influence of the pre-stress and the nature of the electrode used. Thanks to these data, reliable analytic laws have been proposed and inserted into our thermodynamic model in order to predict the output power and scavenged energy density for the DEG. Moreover, our model allow us to propose improvements for the materials used in these applications. The second challenge is to propose an alternative to the high bias voltage needed for these soft generators. We have proposed an innovative solution combining an electret and a dielectric elastomer. Various configurations of hybrid generators in 2D or 3D geometry have been modelled and evaluated. Finally, a prototype has been designed allowing scavenging 35µW. With an appropriate optimization of our prototype, hundreds of µW can be scavenged.

Phosphorescent transition metal complexes make up an important group of compounds that continues to attract intense research owing to their intrinsic bioimaging applications that arise from bright emissions, relatively long excited state lifetimes, and large stokes shifts. Now for biomaging assay a model organism is required which must meet certain criteria for practical applications. The organism needs to be small, with a high turn-over of progeny (high fecundity), a short lifecycle, and low maintenance and assay costs. Our model organism C. elegans met all the criteria. The ideal phosphor has low toxicity in the model organism. In this work the strongly phosphorescent platinum (II) pyrophosphito-complex was tested for biological applications as a potential in vivo hypoxia sensor. The suitability of the phosphor was derived from its water solubility, bright phosphorescence at room temperature, and long excited state lifetime (~ 10 µs). The applications branched off to include testing of C. elegans survival when treated with the phosphor, which included lifespan and fecundity assays, toxicity assays including the determination of the LC50, and recovery after paraquat poisoning. Quenching experiments were performed using some well knows oxygen derivatives, and the quenching mechanisms were derived from Stern-Volmer plots. Reaction stoichiometries were derived from Job plots, while percent scavenging (or antioxidant) activities were determined graphically. The high photochemical reactivity of the complex was clearly manifested in these reactions.

No description available.

Improvements in embedded electronics which have effectively reduced power consumption requirements as well as advancements in IC technology allowing utilization of low power inputs have made Energy Harvesting a popular power solution for low power applications such as WSNs. In many implementation areas, we can see solar, thermal, and vibration energy harvesting techniques have taken the role of batteries as power source. Now that Energy Harvesting is a popular and considerably mature technology, with proper design and installation, any object exposing energy has the ability to be promoted as a power source. We are currently living in Internet age where we connect to the world through network packets. Ethernet, by far, is the most popular LAN technology which allows us to plug and play. Therefore, on an Ethernet link, billions of packets where our data are encapsulated in are traversing every hour. We assume each of these packets exposes some level of energy on an Ethernet link. The challenge here is harvesting the energy available from Ethernet packets and transforming it into useful energy so that it can be used to power devices such as WSNs. In this thesis work, we have revealed how much energy is available from Ethernet packets, and how much of it can be made usable. We have also designed a system where a WSN is generating all of its operating power solely from Ethernet packets and consuming this energy in communication with a base station.

No / Vitiligo is characterized by a mostly progressive loss of the inherited skin color. The cause of the disease is still unknown, despite accumulating in vivo and in vitro evidence of massive oxidative stress via hydrogen peroxide (H2O2) and peroxynitrite (ONOO−) in the skin of affected individuals. The most favored hypothesis is based on autoimmune mechanisms. Since depletion of the essential amino acid l-tryptophan (Trp) severely affects various immune responses, we here looked at Trp metabolism and signaling in these patients. Our in vivo and in vitro data revealed total absence of epidermal Trp hydroxylase activities and the presence of H2O2/ONOO− deactivated indoleamine 2,3-dioxygenase. Aryl hydrocarbon receptor signaling is severely impaired despite the ligand (Trp dimer) being formed, as shown by mass spectrometry. Loss of this signal is supported by the absence of downstream signals (COX-2 and CYP1A1) as well as regulatory T-lymphocytes and by computer modeling. In vivo Fourier transform Raman spectroscopy confirmed the presence of Trp metabolites together with H2O2 supporting deprivation of the epidermal Trp pool by Fenton chemistry. Taken together, our data support a long-expressed role for in loco redox balance and a distinct immune response. These insights could open novel treatment strategies for this disease.—Schallreuter, K. U., Salem, M. A. E. L., Gibbons, N. C. J., Maitland, D. J., Marsch, E., Elwary, S., Healey, A. R. Blunted epidermal l-tryptophan metabolism in vitiligo affects immune response and ROS scavenging by Fenton chemistry, part 2: epidermal H2O2/ONOO−-mediated stress in vitiligo hampers indoleamine 2,3-dioxygenase and aryl hydrocarbon receptor-mediated immune response signaling.

[ES] El transporte terrestre es uno de los principales contribuyentes a las emisiones y tiene un impacto en los cambios climáticos y los peligros para la salud. Para abordar estos problemas, la industria automotriz se está movien- do hacia la movilidad sostenible, donde se están evaluando nuevas tecnologías como vehículos híbridos y vehículos eléctricos. Sin embargo, dado la falta de competencia en alternativas libres de combustibles fósiles para la producción de electricidad, se está abordando la dependencia de motores de combustión interna (ICEs) para ser utilizados como extensores de autonomía y producción de electricidad. Estos extensores de autonomía son generalmente motores de dos tiempos. Debido a su diseño y rango de operación, estos ICE pueden ser compactos, tener una gran reducción de tamaño y producir menos emisiones. Por lo tanto, es esencial comprender el rendimiento de estos nuevos conceptos de ICE, mostrar beneficios potenciales y ayudar en mejoras adicionales. Con el objetivo anterior en este trabajo de tesis, se evalúa un concepto de motor de dos tiempos de barrido uniflow. Se obtienen datos experimentales de una celda de prueba de motor utilizando dos disposiciones de escape, tres velocidades de motor y dos condiciones de carga. Se desarrolla y valida un modelo gasodinámico 1D con respecto a todos los puntos probados. Se mo- dela una réplica en 3D del motor y se utiliza en una simulación CFD en 3D. Los resultados del modelo 1D validados fluidodinámicamente se utilizan como condiciones iniciales y de contorno para evaluar las métricas térmicas y de barrido de este motor en particular. Al comparar los resultados 1D y CFD, se observó que la temperatura y el cortocircuito de aire no se capturaron bien utilizando modelos de transferencia de calor y barrido de última generación durante el proceso de barrido. Esto llevó a la propuesta de un nuevo modelo de transferencia de calor y una curva sintética de barrido. La transferencia de calor en el cilindro es un fenómeno que afecta la tem- peratura de los gases quemados y el aire fresco en un motor de combustión interna. En comparación con las unidades de cuatro tiempos, esta influencia es más crítica en los motores de dos tiempos durante el proceso de barrido, ya que el campo de velocidad del gas dentro del cilindro evoluciona rápidamente en el espacio y el tiempo. Este estudio propone un nuevo modelo de coeficiente de transferencia de calor convectivo más allá de aquellos basados en el cálculo del número de Reynolds con la velocidad media del pistón. El modelo utiliza ecuaciones semiempíricas con números adimensionales ya que debe integrarse en el marco de un modelo físico de motor, donde las propiedades termo y fluidodinámicas de los gases dentro del motor se resuelven mediante enfoques 0D o 1D. En esta aplicación particular, la desviación de temperatura llevó a una predicción deficiente de la masa atrapada en el cilindro. El coeficiente propuesto se calcula utilizando una pseudo-velocidad de los gases dentro del cilindro basada en las tasas de flujo de masa en los puertos de admisión y escape durante el barrido. El barrido en un motor de dos tiempos presenta un proceso complejo, dis- tinto del ciclo de cuatro tiempos, ya que los procesos de admisión y escape ocurren simultáneamente durante una parte significativa del período de inter- cambio de gases. Debido a esta naturaleza superpuesta y a la duración más corta del intercambio de gases en comparación con un motor de cuatro tiempos, modelar con precisión la dinámica de gas dentro del cilindro se vuelve crucial. Este proceso de modelado tiene como objetivo garantizar la retención efectiva de la carga fresca suministrada y la extracción eficiente de los gases residuales del ciclo de motor anterior durante la fase de intercambio de ga- ses. Este modelado es particularmente crucial en motores avanzados de dos tiempos para obtener estimaciones confiables de la composición de la mezcla atrapada y predecir con precisi. / [CA] El transport terrestre és un dels principals contribuents a les emissions i té un impacte en els canvis climàtics i els riscos per a la salut. Per abordar aquests problemes, la indústria automobilística es mou cap a la mobilitat sos- tenible, on s'estan avaluant noves tecnologies com ara vehicles híbrids i vehicles elèctrics. No obstant això, donada la manca de competència en alternatives lliures de combustibles fòssils per a la producció d'electricitat, s'està abordant la dependència dels motors de combustió interna (ICEs) per ser utilitzats com a extensors d'autonomia i producció d'electricitat. Aquests extensors d'auto- nomia són normalment motors de dos temps. A causa del seu disseny i rang operatiu, aquests ICEs poden ser compactes, força reduïts de mida, i emetre menys. Per tant, és essencial entendre les actuacions d'aquests nous conceptes de ICE, mostrar els beneficis potencials, i ajudar en millores addicionals. Amb l'objectiu anterior en aquest treball de tesi, es valora un concepte de motor de dos temps de flux uniflow. S'obtenen dades experimentals d'una cel·la de prova de motor utilitzant dues disposicions d'escapament, tres velo- citats de motor i dues condicions de càrrega. Es desenvolupa i valida un model gasodinàmic 1D amb tots els punts provats. Es modela una rèplica en 3D del motor i s'utilitza en una simulació CFD en 3D. Els resultats del model 1D va- lidats fluidodinàmicament s'utilitzen com a condicions inicials i de contorn per avaluar les mètriques tèrmiques i de flux de gas d'aquest motor en particular. En comparar els resultats 1D i CFD, es va observar que la temperatura i el tall-circuit d'aire no es van capturar bé utilitzant models de transferència de calor i flux de gas de última generació durant el procés de flux. Això va portar a la proposta d'un nou model de transferència de calor i una corba sintètica de flux. La transferència de calor al cilindre és un fenomen que afecta la tempera- tura dels gasos cremats i l'aire fresc en un motor de combustió interna. En comparació amb les unitats de quatre temps, aquesta influència és més crítica en els motors de dos temps durant el procés de flux, ja que el camp de velocitat del gas dins del cilindre evoluciona ràpidament en l'espai i el temps. Aquest estudi proposa un nou model de coeficient de transferència de calor convectiu més enllà dels basats en el càlcul del número de Reynolds amb la velocitat mitjana del pistó. El model utilitza equacions semiempíriques amb nombres no-dimensionals ja que ha de ser integrat dins del marc d'un model físic de motor, on les propietats termo i fluidodinàmiques dels gasos dins del motores resolen mitjançant enfocaments 0D o 1D. En aquesta aplicació particular, la desviació de temperatura va portar a una predicció deficient de la massa atrapada al cilindre. El coeficient de transferència de calor convectiu proposat es calcula utilitzant una pseudo-velocitat dels gasos dins del cilindre basada en les taxes de flux de massa en els ports d'entrada i d'escapament durant el flux. El flux en un motor de dos temps presenta un procés complex, diferent del cicle de quatre temps, ja que els processos d'admissió i d'escapament ocorren simultàniament durant una part significativa del període d'intercanvi de ga- sos. A causa d'aquesta naturalesa superposada i de la durada més curta de l'intercanvi de gasos en comparació amb un motor de quatre temps, modelar amb precisió la dinàmica del gas dins del cilindre es torna crucial. Aquest procés de modelatge té com a objectiu assegurar la retenció efectiva de la càr- rega fresca lliurada i l'extracció eficient dels gasos residuals del cicle de motor anterior durant la fase d'intercanvi de gasos. Aquest modelatge és particular- ment crucial en motors avançats de dos temps per obtenir estimacions fiables de la composició de la mescla atrapada i predir amb precisió el rendiment del motor. / [EN] Transportation on land is one of the major contributors to emissions and has an impact on climatic changes and health hazards. To address these is- sues, the automotive industry is moving toward sustainable mobility, where new technologies such as hybrid vehicles and electric vehicles are being assessed. However, given the lack of competence in fossil fuel-free alternatives for electricity production, dependence on internal combustion engines (ICEs) to be used as range extenders and electricity production is being addressed. These range extenders are usually two-stroke engines. Due to their design and operating range, these ICEs can be compact, be heavily downsized, and have fewer emissions. Hence it is essential to understand the performances of these new ICE concepts, showcase potential benefits, and aid in further improvements. Aiming towards the above objective in this thesis work a two-stroke uniflow scavenged engine concept is assessed. Experimental data from an engine test cell using two exhaust layouts, three engine speeds, and two load conditions is obtained. A 1D gas dynamic model is developed and validated against all tested points. A 3D replica of the engine is modeled and used in 3D CFD simulation. Fluid dynamically validated 1D model results are used as initial and boundary conditions to assess the thermal and scavenging metrics of this particular engine. On comparing 1D and CFD results, it was observed that temperature and short-circuiting of air were not well captured using state-of- the-art heat transfer and scavenging models during the scavenging process. This led to the proposal of a new heat transfer model and a synthetic scavenging curve. In-cylinder heat transfer is a phenomenon that affects the temperature of burnt gases and fresh air in an internal combustion engine. Compared to the four-stroke units, this influence is more critical in two-stroke engines during the scavenging process since gas velocity filed inside the cylinder evolves rapidly in space and time. This study proposes a new convective heat transfer coefficient model beyond those based on Reynolds number calculation with the piston mean velocity. The model uses semi-empirical equations with non-dimensional numbers since it has to be integrated within the frame of a physical engine model, where thermo and fluid dynamic properties of the gases inside the engine are solved using 0D or 1D approaches. In this particular application, the temperature deviation led to a poor prediction of trapped mass in the cylinder. The proposed convective heat transfer coefficient is calculated using a pseudo-velocity of the gases inside the cylinder based on the mass flow rates in the intake and exhaust ports during scavenging. Scavenging in a two-stroke engine presents a complex process, distinct from the four-stroke cycle, as the intake and exhaust processes occur simultaneously for a significant portion of the gas exchange period. Due to this overlapping nature and shorter gas exchange duration compared to a four-stroke engine, accurately modeling the in-cylinder gas dynamics becomes crucial. This modeling process aims to ensure the effective retention of the fresh charge delivered and the efficient extraction of residual gases from the previous engine cycle during the gas exchange phase. Such modeling is particularly crucial in advanced two-stroke engines to obtain reliable estimations of the trapped mixture composition and predict engine performance accurately. / I would like to thank Universitat Politècnica de València for their support with FPI grant with reference FPI-2020-S2-21414 / Darbhamalla, A. (2024). Analysis of the Internal Thermofluid-Dynamics in a Uniflow Scavenged Engine [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/204641

Traumatic brain injury (TBI) represents a significant health crisis. To date there are no FDA-approved pharmacotherapies available to prevent the neurologic deficits caused by TBI. Following TBI, dysfunctional mitochondria generate reactive oxygen and nitrogen species, initiating lipid peroxidation (LP) and the formation of LP-derived neurotoxic aldehydes, which bind mitochondrial proteins, exacerbating dysfunction and opening of the mitochondrial permeability pore (mPTP), resulting in extrusion of mitochondrial sequestered calcium into the cytosol, and initiating a downstream cascade of calpain activation, spectrin degradation, neurodegeneration and neurologic impairment. As central mediators of the TBI secondary injury cascade, mitochondria and LP-derived neurotoxic aldehydes make promising therapeutic targets. In fact, Cyclosporine A (CsA), an FDA-approved immunosuppressant capable of inhibiting mPTP has been shown to be neuroprotective in experimental TBI. Additionally, phenelzine (PZ), an FDA-approved non-selective irreversible monoamine oxidase inhibitor (MAOI) class antidepressant has also been shown to be neuroprotective in experimental TBI due to the presence of a hydrazine (-NH-NH2) moiety allowing for the scavenging of LP-derived neurotoxic aldehydes. The overall goal of this dissertation is to further examine the neuroprotective effects of the mPTP inhibitor, CsA, and the LP-derived neurotoxic aldehyde scavenger, PZ, using a severe controlled cortical impact injury (CCI) model in 3-month old male Sprague-Dawley rats. First, the effects of CsA on cortical synaptic and non-synaptic mitochondria, two heterogeneous populations, are examined. Our results indicate that compared to non-synaptic mitochondria, synaptic mitochondria sustain greater damage 24h following CCI and are protected to a greater degree by CsA. Second, the neuroprotective effects of a novel 72h continuous subcutaneous infusion of CsA combined with PZ are compared to monotherapy. Following CCI, our results indicate that individually both CsA and PZ attenuate modification of mitochondrial proteins by LP-derived neurotoxic aldehydes, PZ is able to maintain mitochondrial respiratory control ratio and cytoskeletal integrity, but together, PZ and CsA, are unable to improve and in some cases negate monotherapy neuroprotective effects. Finally, the effects of PZ (MAOI, aldehyde scavenger), pargyline (PG, MAOI, non-aldehyde scavenger) and hydralazine (HZ, non-MAOI, aldehyde scavenger) are compared. Our results indicate that PZ, PG, and HZ are unable to improve CCI-induced deficits to learning and memory as measured by Morris water maze (post-CCI D3-7). Of concern, PZ animals lost a significant amount of weight compared to all other group, possibly due to MAOI effects. In fact, in uninjured cortical tissue, PZ administration leads to a significant increase in norepinephrine and serotonin. Additionally, although PZ, PG, and HZ did not lead to a statistically significant improvement in cortical tissue sparing 8 days following CCI, the HZ group saw a 10% improvement over vehicle. Overall, these results indicate that pharmacotherapies which improve mitochondrial function and decrease lipid peroxidation should continue to be pursued as neuroprotective approaches to TBI. However, further pursuit of LP-derived aldehyde scavengers for clinical use in TBI may require the development of hydrazine (-NH-NH2)-compounds which lack additional confounding mechanisms of action.

The major objectives of this study were to investigate the antioxidant properties of flaxseed lignans secoisolariciresinol (SECO 2) and secoisolariciresinol diglycoside (SDG 1) and their major oxidative compounds using 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH 47) in an in vitro model of lipid peroxidation. This investigation was facilitated by the structural elucidation of the major oxidative compounds and the ability of flaxseed lignans to delay the onset of oxidation in two model systems. <p>This study showed that SECO 2 oxidation occurs at the aromatic (4-OH) and aliphatic (9-OH) hydroxyl groups. Conversely for SDG 1, only compounds derived from the oxidation of aromatic hydroxyl groups were obtained because the 9-OH position is glucosylated. <p>SECO 2 oxidation with AAPH 47 showed that the intermediate 2a is most likely involved in the generation of early-forming (48 and 52) and 2c for the formation of late-forming (49, 50 and 51) oxidation compounds. Compound 48 is formed from dimerization of 2a that is converted to 52 and then to 51. Compound 50 was formed by the addition of a carbon-centre free radical of AAPH (AP radical) to 2c. Compounds 50 and 51 trap carbon-centered AP radicals supporting SECO 2 as a chain-breaking antioxidant and AAPH 47 as a proper model for study of SECO 2 oxidation in vitro. <p>SDG 1 oxidation with AAPH 47 indicated that intermediates 1b and 1c are most likely involved for the formation of early forming compounds (55 and 58) and 1a leads to the late forming compounds (56 and 57). Compound 55 is a result of dimerization. Compound 56 may be directly formed via intermediate radical 1a by adding AP free radicals. Compound 56 was a stable non-radical compound that could trap AP free radicals, thereby supporting SDG 1 as a chain-breaking antioxidant. Hydrogen abstraction from 4-hydroxyl yielded the radical 1a and hydroxyl radical addition to 1a yielded 57. Compound 58 formed from the addition of OH or H2O to 1c. <p>This study demonstrated that AAPH 47 produces carbon-centred AP radicals upon thermal decomposition and mimics the formation of lipid peroxyl radicals. Interaction of carbon-centred AP radicals with SECO 2 and SDG 1 provides a good model to study the antioxidant reactions of SECO 2 in vitro. p*The relative antioxidant capacity of the flaxseed lignans versus BHT 17, in two model systems, was determined. The stoichiometric ratio for SECO 2 and SDG 1 were 1.5 and 1.1-1.2, respectively, compared to BHT 17 (2.0). The induction time by Rancimat analyzer measured inhibition of autoxidation mediated by flaxseed lignans SECO, SDG and SDG polymer in comparison with BHT 17. The induction time data demonstrated that SECO 2 protected canola oil better than either SDG 1 or SDG polymer 3. <p>These results are important for better understanding about the chemistry behind flaxseed lignan antioxidant activities. This study provided useful evidence that flaxseed lignans can be used as natural antioxidants.

The major objectives of this study were to investigate the antioxidant properties of flaxseed lignans secoisolariciresinol (SECO 2) and secoisolariciresinol diglycoside (SDG 1) and their major oxidative compounds using 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH 47) in an in vitro model of lipid peroxidation. This investigation was facilitated by the structural elucidation of the major oxidative compounds and the ability of flaxseed lignans to delay the onset of oxidation in two model systems. <p>This study showed that SECO 2 oxidation occurs at the aromatic (4-OH) and aliphatic (9-OH) hydroxyl groups. Conversely for SDG 1, only compounds derived from the oxidation of aromatic hydroxyl groups were obtained because the 9-OH position is glucosylated. <p>SECO 2 oxidation with AAPH 47 showed that the intermediate 2a is most likely involved in the generation of early-forming (48 and 52) and 2c for the formation of late-forming (49, 50 and 51) oxidation compounds. Compound 48 is formed from dimerization of 2a that is converted to 52 and then to 51. Compound 50 was formed by the addition of a carbon-centre free radical of AAPH (AP radical) to 2c. Compounds 50 and 51 trap carbon-centered AP radicals supporting SECO 2 as a chain-breaking antioxidant and AAPH 47 as a proper model for study of SECO 2 oxidation in vitro. <p>SDG 1 oxidation with AAPH 47 indicated that intermediates 1b and 1c are most likely involved for the formation of early forming compounds (55 and 58) and 1a leads to the late forming compounds (56 and 57). Compound 55 is a result of dimerization. Compound 56 may be directly formed via intermediate radical 1a by adding AP free radicals. Compound 56 was a stable non-radical compound that could trap AP free radicals, thereby supporting SDG 1 as a chain-breaking antioxidant. Hydrogen abstraction from 4-hydroxyl yielded the radical 1a and hydroxyl radical addition to 1a yielded 57. Compound 58 formed from the addition of OH or H2O to 1c. <p>This study demonstrated that AAPH 47 produces carbon-centred AP radicals upon thermal decomposition and mimics the formation of lipid peroxyl radicals. Interaction of carbon-centred AP radicals with SECO 2 and SDG 1 provides a good model to study the antioxidant reactions of SECO 2 in vitro. p*The relative antioxidant capacity of the flaxseed lignans versus BHT 17, in two model systems, was determined. The stoichiometric ratio for SECO 2 and SDG 1 were 1.5 and 1.1-1.2, respectively, compared to BHT 17 (2.0). The induction time by Rancimat analyzer measured inhibition of autoxidation mediated by flaxseed lignans SECO, SDG and SDG polymer in comparison with BHT 17. The induction time data demonstrated that SECO 2 protected canola oil better than either SDG 1 or SDG polymer 3. <p>These results are important for better understanding about the chemistry behind flaxseed lignan antioxidant activities. This study provided useful evidence that flaxseed lignans can be used as natural antioxidants.

This essay attempts to propose an art practice based on an ethical and aesthetic relation of author, subject, and viewer. This relationship is productive of results that are seen as critical to a precise, useful, and ethical representation of social problems. / text