In this thesis, we investigate attack vectors against Markov decision processes anddynamical systems. This work is motivated by the recent interest in the researchcommunity towards making Machine Learning models safer to malicious attacks. Wefocus on different attack vectors: (I) attacks that alter the input/output signal of aMarkov decision process; (II) eavesdropping attacks whose aim is to detect a change ina dynamical system; (III) poisoning attacks against data-driven control methods.(I) For attacks on Markov decision processes we focus on 2 types of attacks: (1) attacksthat alter the observations of the victim, and (2) attacks that alter the control signalof the victim. Regarding (1), we investigate the problem of devising optimal attacksthat minimize the collected reward of the victim. We show that when the policy andthe system are known to the attacker, designing optimal attacks amounts to solving aMarkov decision process. We also show that, for the victim, the system uncertaintiesinduced by the attack can be modeled using a Partially Observable Markov decisionprocess (POMDP) framework. We demonstrate that using Reinforcement Learningmethods tailored to POMDP lead to more resilient policies. Regarding (2), we insteadinvestigate the problem of designing optimal stealthy poisoning attacks on the controlchannel of Markov decision processes. Previous work constrained the amplitude ofthe adversarial perturbation, with the hope that this constraint will make the attackimperceptible. However, such constraints do not grant any level of undetectabilityand do not take into account the dynamic nature of the underlying Markov process.To design an optimal stealthy attack, we investigate a new attack formulation, basedon information-theoretical quantities, that considers the objective of minimizing thedetectability of the attack as well as the performance of the controlled process.(II) In the second part of this thesis we analyse the problem where an eavesdropper triesto detect a change in a Markov decision process. These processes may be affected bychanges that need to remain private. We study the problem using theoretical tools fromoptimal detection theory to motivate a definition of online privacy based on the averageamount of information per observation of the underlying stochastic system. We provideways to derive privacy upper-bounds and compute policies that attain a higher privacylevel, concluding with examples and numerical simulations.(III) Lastly, we investigate poisoning attacks against data-driven control methods.Specifically, we analyse how a malicious adversary can slightly poison the data soas to minimize the performance of a controller trained using this data. We show thatidentifying the most impactful attack boils down to solving a bi-level non-convexoptimization problem, and provide theoretical insights on the attack. We present ageneric algorithm finding a local optimum of this problem and illustrate our analysisfor various techniques. Numerical experiments reveal that minimal but well-craftedchanges in the data-set are sufficient to deteriorate the performance of data-drivencontrol methods significantly, and even make the closed-loop system unstable. / <p>QC 20220510</p><p></p><p>Topic: Alessio Russo - LicentiateTime: May 31, 2022 04:00 PM Madrid</p><p> Zoom Meeting link https://kth-se.zoom.us/j/69452765598</p>

Clostridium perfringens is a significant human pathogen, causing 250,000 cases of food poisoning in addition to several thousand potentially lethal cases of gas gangrene each year in the United States. Historically, work in this field has centered around toxin production, as C. perfringens can produce over 13 toxins. This work expands the knowledge of the starvation-response of C. perfringens, which includes several potential virulence factors, sporulation, motility and biofilm formation. Sporulation protects cells from a variety of stresses, including starvation. Efficient sporulation requires the transcriptional regulator CcpA, mediator of catabolite repression. Sporulation is repressed by glucose, but, surprisingly, in a CcpA-independent fashion. C. perfringens cells in a biofilm are resistant to a number of environmental stresses, including oxygen and antibiotics. Biofilm formation is repressed by glucose, and other carbohydrates, independently of CcpA. Gliding motility, a type four pili (TFP)-dependent phenomenon, affords C. perfringens with a mechanism for moving across a solid surface in response to carbohydrate starvation, while carbohydrates supplementation at high levels delay the initiation of the motility response. CcpA is required for the proper initiation of motility, a ccpA^-C. perfringens strain showed a considerable increase in the time to initiation of motility on lactose and galactose, and was unable to move at all in the presence of glucose. Gliding motility represents the most significant finding of this work. TFP were previously undescribed in any Gram-positive bacterial species, and this work produced genetic evidence suggesting their presence in all members of the clostridia, and physical evidence for TFP-dependent gliding motility in a second species, C. beijerinckii. / Ph. D.

The interactions between different components of solid oxide cells (SOCs) are critical issues for achieving the tens of thousands of hour's goal for long-term performance stability and lifetime. The interactions between the ceramic electrolyte, porous ceramic air electrode, and metallic interconnect materials — including solid state interfacial reactions and vaporization/deposition of some volatile elements — have been investigated in the simulated SOC operating environment. The interactions demonstrate the material degradation mechanisms of the cell components and the effects of different factors such as chemical composition and microstructure of the materials, as well as atmosphere and current load on the air electrode side. In the aspect of materials, this work contributes to the degradation mechanism on the air electrode side and provides practical material design criteria for long-term SOC operation. In this research, an yttria-stabilized zirconia electrolyte (YSZ)/strontium-doped lanthanum manganite electrode (LSM)/AISI 441 stainless steel interconnect tri-layer structure has been fabricated in order to simulate the air electrode working environment of a real cell. The tri-layer samples have been treated in dry/moist air atmospheres at 800°C for up to 500 h. The LSM air electrode shows slight grain growth, but the growth is less in moist atmospheres. The amount of Cr deposition on the LSM surface is slightly more for the samples thermally treated in the moist atmospheres. At the YSZ/LSM interface, La enrichment is significant while Mn depletion occurs. The Cr deposition at the YSZ/LSM interface is observed. The stoichiometry of the air electrode is an important factor for the interactions. The air electrode composition has been varied by changing the x value in (La0.8Sr0.2)xMnO₃ from 0.95 to 1.05 (LSM95, LSM100, and LSM105). The enrichment of La at the YSZ/LSM interface inhibits the Cr deposition. The mechanisms of Cr poisoning and LSM elemental surface segregation are discussed. A 200 mA·cm-2 current load have been applied on the simulated cells. Mn is a key element for Cr deposition under polarization. Excessive Mn in the LSM lessens the formation of La-containing phases at the YSZ/LSM interface and accelerates Cr deposition. Deficient Mn in LSM leads to extensive interfacial reaction with YSZ forming more La-containing phase and inhibiting Cr deposition. / Ph. D.

The activity of erythrocyte amino levulenic acid dehydratase (ALA-D) and liver and bone lead concentrations were measured in 141 wild rainbow trout from two highway-influenced and two pristine streams. A significant relationship between ALA-D activity and liver lead concentrations among streams (r = 0.157) was observed. However, this relationship was opposite of expected. Trout tissue lead and stream-water lead concentrations were lower than most concentrations observed for control laboratory trout. At these low tissue and water lead concentrations observed in the present study, ALA-D activity cannot be used to document exposure of fish to environmental lead. Other significant correlations with the activity of the enzyme included: trout length (r = -0.411); trout age (r = -0.385); and sediment lead (r = 0.093). Erythrocyte ALA-D activity significantly varied due to sampling period. However, reasons for this deviation cannot be explained from the present study. Multiple regression techniques revealed little concerning trout liver lead concentrations and ALA-D activity relationships. Like ALA-D activity, liver lead concentrations were deemed a poor indicator of organisms' exposure to environmental lead. Bone lead concentrations were the best indicator of environmental contamination. However, the best regression model, which regressed water lead on bone lead, explained only 20.6% of the variation in bone lead burden. In both roadside streams, water lead was positively correlated to turbidity and area precipitation. Water lead concentrations were also positively correlated to discharge in one roadside stream. / M.S.

The purposes of this study are, first, to determine relative numbers and predominant types of bacterial organisms in the various food products studied; second, to evaluate the efficiency of the paper coverings of these foods; and third, to determine whether these products are potential sources of food poisoning.

[EN] Several major problems have to be solved before Solid Oxide Fuel Cells (SOFC) can operate continuously using hydrocarbon fuels such as natural gas. The risk of low catalytic behavior for fuel reforming, the carbon formation/deposition on the anode material at high operating temperatures and the presence of impurities in the fuel (in particular sulfides) can dramatically reduce the performance and durability of the cells. Taking all this into account, new anode materials with adequate (electro)catalytic properties are required. Recently, manganite compounds with Ruddlesden-Popper (RP) structure have been studied as potential new anode materials in INTERFASE group at Universidad Industrial de Santander (UIS). Their electrochemical performance have been described in previous works with promising results, but a fundamental knowledge was missing concerning the catalytic properties of such materials and the way to improve them by the addition of nickel metallic particles on the electrode surface. The current Ph.D. thesis was focused on the synthesis, characterization and catalytic study for steam reforming in SOFC anode conditions (low steam content) of a new RP manganite (La1.5Sr1.5Mn1.5Ni0.5O7±δ), which, in reducing atmosphere at high operating temperatures promotes via an exsolution mechanism the formation of two phases, i.e. an RP manganite of composition LaSrMnO4±δ decorated with metallic active Ni nanoparticles embedded in the surface; such strategy can be viewed as an original way to improve the (electro)catalytic properties of the anode materials and then a promising option for future SOFC systems operating with Colombian natural gas. The first chapter deals with the synthesis and characterization of the RP n= 2 phase La1.5Sr1.5Mn1.5Ni0.5O7±δ using the Pechini method. In agreement with SOFC operating temperature, Ni exsolution has been studied in diluted H2 at different temperatures (750, 800 and 850 °C) and reduction times. Ni nanoparticles decorating an RP n= 1 manganite is confirmed by XRD, TEM-EDS analysis and the size of the metallic particles on the oxide surface, below 100 nm, is characterized as a function of the exsolution conditions. The second chapter presents the catalytic behavior for the methane steam reforming reaction of the exsolved material applying the Gradual Internal Reforming concept adapted to SOFC operation (i.e. low water content, steam to carbon ratio equal to 0.15) at different reaction temperatures (750, 800 and 850 °C). The catalytic properties of Ni impregnated samples using a similar (La,Sr)2MnO4±δ ceramic support are also presented for comparison. The exsolved material exhibits better performance than the impregnated manganite for the reaction, especially at 850 °C, with higher conversion, conversion rate, and H2 production rate. Concerning the steam reforming of light alkane gas mixtures (CH4-C2H6, and CH4-C3H8), the behavior is affected due to the competition between the molecules and low available metallic active sites, but without affecting the H2 production. In addition, at long reaction times, the activity over the exsolved material is stable even with 100 h of reaction, without formation of carbonaceous species on the Ni particles, as confirmed by TEM and TGA/MS analysis. In the third and last chapter, the possible coke formation and sulfide poisoning are presented. Despite the high and stable catalytic behavior for methane steam reforming reaction with considerable carbon formation resistance, the exsolved material exhibits a high level of sensitivity to H2S poisoning, similar to the case of state-of-the-art Ni/YSZ anodic cermet and or Ni impregnated catalyst, with a drop of the activity to almost zero. Nevertheless, the exceptional overall results obtained for the exsolution-based material are promising for a possible use as SOFC anode operating with sulfur-free Colombian natural gas. / [ES] Muchos son los problemas que deben resolverse antes de que las celdas de combustible de óxido sólido (SOFC por sus siglas en inglés) puedan operar continuamente usando combustibles hidrocarbonados como por ejemplo el gas natural. El riesgo de una baja actividad catalítica para el reformado del combustible, la formación y depósito en el material de ánodo a elevadas temperaturas de operación y la presencia de impurezas en el combustible empleado (en particular de sulfuros) pueden reducir dramáticamente el desempeño y la durabilidad de las celdas. Teniendo todo esto en cuenta, nuevos materiales de ánodo con adecuadas propiedades (electro)catalíticas son necesarios. Recientemente, en el grupo INTERFASE de la Universidad Industrial de Santander (UIS), compuestos de tipo manganita con estructura Ruddlesden-Popper (RP) han sido estudiados como potenciales materiales de ánodo. Su desempeño electrocatalítico ha sido descrito en trabajos previos con promisorios resultados, pero el conocimiento fundamental sobre las propiedades catalíticas de dichos materiales y la forma de mejorarlos mediante la adición de partículas metálicas de níquel en la superficie del electrodo aún faltaba. La presente tesis doctoral se enfocó en la síntesis, caracterización y estudio catalítico en el reformado con vapor en condiciones de ánodo de celdas SOFC (bajo contenido de vapor) de una nueva manganita de tipo RP (La1.5Sr1.5Mn1.5Ni0.5O7±δ), la cual, en atmósfera reductora y a elevadas temperaturas de operación, promueven a través del mecanismo de exsolución la formación de dos fases: una manganita tipo RP de composición LaSrMnO4±δ decorada con nanopartículas metálicas y activas de Ni incrustadas en la superficie; dicha estrategia puede ser vista como una manera muy original de mejorar las propiedades (electro)catalíticas de los materiales de ánodo y por lo tanto ser consideradas como una opción prometedora para sistemas SOFC operados con gas natural colombiano. El primer capítulo trata sobre la síntesis de la fase RP n= 2 La1.5Sr1.5Mn1.5Ni0.5O7±δ usando el método de Pechini y su caracterización. De acuerdo con la temperatura de operación de las celdas SOFC, la exsolución del Ni en atmósfera de H2 diluido a diferentes temperaturas (750, 800 y 850 °C) y tiempos de reducción fue estudiada. Las nanopartículas de Ni decorando la manganita de estructura RP n= 1 es confirmada a través de análisis de DRX, MET-EDS y el tamaño de las partículas metálicas en la superficie del óxido, inferiores a 100 nm, es caracterizado en función de las condiciones de exsolución. El segundo capítulo presenta el comportamiento catalítico del material exsuelto en la reacción de reformado de metano aplicando el concepto de reformado interno gradual (GIR por sus siglas en inglés) adaptado a celdas SOFC (en otras palabras, bajo contenido de agua, relación vapor carbono igual a 0.15) a diferentes temperaturas de reacción (750, 800 y 850 °C). Las propiedades catalíticas de las muestras impregnadas con Ni utilizando como soporte un material cerámico similar (La,Sr)2MnO4±δ, son también presentados como comparación. El material exsuelto exhibe un mejor desempeño catalítico en la reacción de reformado que la manganita impregnada, especialmente a 850 °C, mostrando una más alta conversión, velocidad de conversión y de producción de H2. Con respecto al reformado de la mezcla de alcanos ligeros (CH4 -C2H6, y CH4 -C3H8), el comportamiento catalítico es afectado debido a la competición entre moléculas y la baja disponibilidad de sitios activos metálicos, sin afectar la producción de H2. Adicionalmente, a tiempos de reacción prolongados, la actividad en el material exsuelto es estable incluso con 100 h de reacción, sin formación de especies carbonáceas sobre las partículas de Ni como lo confirman las imágenes MET y el ATG/MS. En el tercer y último capítulo, la posible formación y depósito de carbón y el envenenamiento con sulfuros son presentados. Sin embargo, a pesar de la elevada y estable actividad catalítica en la reacción de reformado de metano con vapor con una considerable resistencia a la formación de carbón, el material exsuelto tiene un alto nivel de sensibilidad al envenenamiento con H2S, similar al Ni/YSZ (material de referencia de la literatura) o al material impregnado con Ni, con una disminución de la actividad catalítica a prácticamente cero No obstante, el excepcional resultado global obtenido en el material exsuelto es prometedor para un posible uso como material de ánodo en sistemas SOFC alimentados con gas natural colombiano libre de H2S. / [CA] Molts són els problemes que han de ser resolts abans que les cel·les de combustible d'òxid sòlid (SOFC per les seues sigles en anglès) puguen operar contínuament usant combustibles hidrocarbonats com per exemple el gas natural. El risc d'una baixa activitat catalítica per al reformat del combustible, la formació i depòsit en el material d'ànode a elevades temperatures d'operació i la presència d'impureses en el combustible emprat (en particular de sulfurs) poden reduir dramàticament l'acompliment i la durabilitat de les cel·les. Tenint tot això en compte, nous materials d'ànode amb propietats (electro)catalítiques adequades són necessaris. Recentment, en el grup d'investigació INTERFASE de la Universitat Industrial de Santander (UIS), compostos de tipus manganita amb estructura Ruddlesden-Popper (RP) han sigut estudiats com a potencials materials anòdics. El seu acompliment electroquímiques ha sigut tractades en treballs previs amb resultats promissoris, però el coneixement fonamental sobre les característiques catalítiques d'aquests materials i la manera de millorar-los mitjançant l'addició de partícules metàl·liques de níquel en la superfície de l'elèctrode encara faltava. La present tesi de doctorat es va enfocar en la síntesi, caracterització i estudi d'activitat catalítica en el reformat amb vapor en condicions d'ànode de cel·les SOFC (sota contingut de vapor) d'una nova manganita de d'estructura RP (La1.5Sr1.5Mn1.5Ni0.5O7±δ), la qual, en atmosfera reductora i a elevades temperatures d'operació, promouen, a través del mecanisme de exsolució; la formació de dues fases: una manganita de composició LaSrMnO4±δ decorada amb nanopartícules metàl·liques i actives de Ni incrustades en la superfície; aquesta estratègia pot ser vista com una manera molt original de millorar les propietats (electro)catalítiques dels materials d'ànode i per tant, ser considerades com una prometedora opció per a futurs usos en sistemes SOFC alimentats amb gas natural colombià. El primer capítol tracta sobre la síntesi de la fase RP n= 2 La1.5Sr1.5Mn1.5Ni0.5O7±δ usant el mètode de Pechini i la seua caracterització. D'acord amb la temperatura d'operació de les cel·les SOFC, la exsolució del Ni en atmosfera d'H2 diluït a diferents temperatures (750, 800 i 850 °C) i temps de reducció va ser estudiada. Les nanopartícules de Ni decorant la manganita d'estructura RP n= 1 és confirmada a través d'anàlisi de DRX, MET-EDS i la grandària de les partícules metàl·liques en la superfície de l'òxid, inferiors a 100 nm, és caracteritzat en funció de les condicions de exsolució. El segon capítol presenta el comportament catalític del material d’exsolució en la reacció de reformat de metà amb vapor aplicant el concepte de reformat gradual intern (GIR per les seues sigles en anglès) adaptat a cel·les SOFC (en altres paraules, sota contingut de vapor, relació vapor-carboni de 0.15) a diferents temperatures de reacció (750, 800 i 850 °C). Les propietats catalítiques de les mostres impregnades amb Ni utilitzant com a suport un material ceràmic similar (La,Sr)2MnO4±δ, són també presentats com a comparació. El material d’exsolució exhibeix un millor resultat catalític en la reacció de reformat que la manganita impregnada, especialment a 850 °C, mostrant una més alta conversió, velocitat de conversió i de producció d'H2. En el reformat de la mescla d'alcans lleugers (CH4 -C2H6, i CH4 -C3H8), el comportament catalític és afectat per la competició entre molècules i la baixa disponibilitat de llocs actius metàl·lics, sense afectar la producció d'H2. Addicionalment, a temps de reacció llargs, l'activitat en el material d’exsolució és estable fins i tot desprès de 100 h de reacció, sense formació d'espècies carbòniques sobre les partícules de Ni, com ho confirmen les imatges MET i el ATG/MS. En el tercer i últim capítol, la possible formació i depòsit de carbó i l'enverinament amb sulfurs són presentats. No obstant això, malgrat l'elevada i estable activitat catalítica en la reacció de reformat de metà amb vapor amb una considerable resistència a la formació de carbó, el material d’exsolució té un alt nivell de sensibilitat a l'enverinament amb H2S, similar al Ni/YSZ (material de referència de la literatura) o el material impregnat amb Ni, amb una disminució de l'activitat catalítica a pràcticament zero No obstant això, l'excepcional resultat global obtingut aquest nou material és prometedor per a un possible ús futur com a material d'ànode en sistemes SOFC alimentats amb gas natural colombià lliure d'H2S. / Al Departamento Administrativo de Ciencia, Tecnología e Innovación (COLCIENCIAS) por la beca de estudios de Doctorados Nacionales Conv. 647 y el proyecto # 110265842833 “Symmetrical high temperature Fuel Cell operating with Colombian natural gas”. Al Consejo Superior de Investigaciones Científicas por el apoyo con la ayuda económica para la estancia mediante la convocatoria I-coop Project # COOPA20112. / Vecino Mantilla, JS. (2020). Nickel exsolution effect on the catalytic behavior of ruddlesden-popper manganites in sofc conditions using colombian natural gas [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/149474

Solid oxide fuel cells (SOFCs) are promising devices to convert chemical energy to electrical energy due to their high efficiency, fuel flexibility, and low emissions. However, there are still some drawbacks hindering its wide application, such as high operative temperature, electrode degradation, chromium poisoning, oxidization of interconnect, and so on. Cathode plays a major role in determining the electrochemical performance of a single cell. In this dissertation, three perovskite cathode materials, La0.6Sr0.4Co0.2Fe0.8O3 (LSCF), Ba0.5Sr0.5Co0.2Fe0.8O3 (BSCF), and Sm0.5Sr0.5Co0.2Fe0.8O3 (SSCF), are comparatively studied through half-cells in the temperature range of 600-800 ºC. Sm0.2Ce0.8O1.9 (SDC) block layer on the yttria-stabilized zirconia (YSZ) electrolyte can lead to smaller polarization resistances of the three cathode materials through stopping the reaction between the cathodes and the YSZ electrolyte. SDC is also used as a catalyst to increase the oxygen reduction reaction (ORR) rate in the LSCF cathode. In addition, interconnect is protected by CoxFe1-x oxide and Co3O4/SDC/Co3O4 tri-layer coatings separately. These coatings are demonstrated to be effective in decreasing the area specific resistance (ASR) of the interconnect, inhibiting the Cr diffusion/evaporation, leading higher electrochemical performance of the SSCF-based half-cell. Only 1.54 at% of Cr is detected on the surface of the SSCF cathode with the Co0.8Fe0.2 oxide coated interconnect and no Cr is detected with the Co3O4/SDC/Co3O4 tri-layer coated interconnect. Finally, single cells with LSCF, BSCF, and SSCF as the cathodes are operated in the temperature range of 600-800 °C fueled by natural gas. BSCF has the highest power density of 39 mW cm-2 at 600 °C, 88 mW cm-2 at 650 °C, and 168 mW cm-2 at 700 °C; LSCF has the highest power density of 263 mW cm-2 at 750 °C and 456 mW cm-2 at 800 °C. Activation energies calculated from the cathode ASR are 0.44 eV, 0.38 eV, and 0.52 eV for the LSCF, BSCF, and SSCF cathodes respectively, which means the BSCF cathode is preferred. The stability test shows that the BSCF-based single cell is more stable at lower operative temperature (600 °C) while the LSCF-based single cell is more stable at higher operative temperature (800 °C). / Ph. D. / Solid oxide fuel cells (SOFCs) are promising devices to convert chemical energy to electrical energy due to their high efficiency, fuel flexibility, and low emissions. However, there are still some drawbacks hindering its wide application, such as high operative temperature, electrode degradation, chromium poisoning, oxidization of interconnect, and so on. A single cell is composed of an anode, electrolyte, and cathode. Interconnect can connect individual single cell to stack to increase voltage and current. In order to improve the electrochemical performance, such as resistance and power density, cathode materials and protective coatings to interconnect are studied. Three perovskite cathode materials, La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF), Ba_0.5Sr_0.5Co_0.2Fe_0.8O₃ (BSCF), and Sm0.5Sr0.5Co0.2Fe0.8O3 (SSCF), are comparatively studied in 600-800 ºC to obtain the optimal cathode at different operating temperatures. BSCF has the smallest resistance at 600 ºC, LSCF at 700 ºC, and SSCF at 800 ºC. A thin Sm_0.2Ce_0.8O_1.9 (SDC) block layer on the yttria-stabilized zirconia (YSZ) electrolyte can lead to smaller resistances of the three cathode materials through stopping the reaction between the cathodes and the YSZ electrolyte. SDC is also used as a catalyst by three methods to lower the resistances of the LSCF cathode. In addition, interconnect is protected by Co_xFe_1-x oxide and Co₃O₄/SDC/Co₃O₄ tri-layer coatings separately. They are demonstrated to be effective in decreasing the resistance of the interconnect, inhibiting the Cr diffusion/evaporation outward to poison cathodes. Only 1.54 at% of Cr is detected on the surface of the SSCF cathode with the Co_0.8Fe_0.2 oxide coated interconnect and no Cr with the Co₃O₄/SDC/Co₃O₄ tri-layer coated interconnect. Finally, single cells with LSCF, BSCF, and SSCF as the cathodes are operated in 600-800 °C fueled by natural gas. BSCF has the highest power densities at lower operating temperatures while LSCF has the highest power densities at higher operating temperatures. Activation energies are 0.44 eV, 0.38 eV, and 0.52 eV for the LSCF, BSCF, and SSCF cathodes respectively, which means the BSCF cathode is preferred. The stability test shows that the BSCF-based single cell is more stable at 600 °C while the LSCF-based single cell is more stable at 800 °C.

Dissertation (Ph.D.)--University of South Florida, 2008. / Title from PDF of title page. Document formatted into pages; contains 98 pages. Includes vita. Includes bibliographical references.

Selbstvergiftung in der Akutmedizin – 2005–2012 Zusammenfassung Ziel. Beschreibung des Trends der akuten Selbstvergiftung in der Notfall- und Intensivmedizin. Methode. Elektronische Akten erwachsener Patienten, die zwischen 2005 und 2012 wegen einer akuten Selbstvergiftung infolge eines Selbstmordversuches (Selbstmordgruppe), einer Berauschung (Intoxikationsgruppe) oder Medikamentenüberdosierung zwecks Schmerzlinderung (Überdosierungsgruppe) in der Notaufnahme des Universitätsklinikums Leipzig eingewiesen worden waren, wurden ausgewertet. Ergebnisse. 3533 Patienten (62,6 % männlich) wurden identifiziert, mit einem Anstieg von 305 Fällen im Jahre 2005 auf 624 in 2012. Die Aufnahmerate bezogen auf die Gesamtaufnahmen stieg von 1,2 % im Jahre 2005 auf 1,9 % im Jahre 2012 an. 31,7 % der Patienten waren < 25 Jahre alt. Die Ursachen der Selbstvergiftung waren Suizidversuch (18,1 %), Intoxikation (76,8 %) und Medikamentenüberdosierung (2,9 %). Bei 80 Fällen war eine genaue Gruppenzuordnung nicht möglich. Während psychotrope Medikamente bei 71,6 % der Suizidversuche angewandt wurden, war Alkoholintoxikation die Ursache bei 80,1 % der Fälle in der Intoxikationsgruppe. Selbstvergiftung mit mindestens zwei Substanzen lag bei 52,0 % der Suizidversuche, 10,3 % der Intoxikationsgruppe und 29,7 % der Gruppe mit Medikamentenüberdosierung vor. Während die Alkoholintoxikation nach wie vor am häufigsten vorkam, gab es eine drastische Zunahme der Intoxikationen mit Cannabinoiden, Crystal Meth und Gamma- Hydroxybuttersäure in den Jahren 2011 und 2012. Eine Aufnahme auf die Intensivstation war bei 16,6 % der Fälle erforderlich. Es gab 22 Todesfälle (0,6 % der gesamten Studienpopulation), von denen 15 aus der Suizidgruppe (2,3 %), vier aus der Intoxikationsgruppe (0,15 %), und drei aus der nicht eindeutig zugeordneten Gruppe (3.8 %) waren. Zusammenfassung. Akute Selbstvergiftung ist ein zunehmendes medizinisches Problem. Psychotrope Medikamente stellen nach wie vor die häufigsten Suizidversuchsmittel dar. Obwohl die Alkoholintoxikation weiterhin am häufigsten vorkommt, nehmen illegale Drogen als notfallmedizinischer Einweisungsgrund zu. / Self-poisoning in the acute care medicine 2005–2012 Abstract Objective. To describe the trend of acute self-poisoning in the emergency and intensive care. Methods. Electronic charts of adults who presented to the emergency department of the University Hospital Leipzig with selfpoisoning following a suicide attempt (suicide group), intoxication (intoxication group), drug overdose for relief of pain or discomfort (drug overdose group) between 2005 and 2012 were analyzed. Results. 3533 adults (62.6 % males) were identified, with the yearly admissions increasing from 305 in 2005 to 624 in 2012. The admission rate in relation to the total emergency department admissions also increased, from 1.2 % in 2005 to 1.9 % in 2012. 31.7 % of the patients were younger than 25 years. The reasons for self-poisoning were suicide attempt (18.1 %), intoxication (76.8 %) and drug overdose (2.9 %). The reason could not be clearly classified in 80 patients. Psychotropic drugs were used in 71.6 % of suicide attempts, while alcohol was the sole cause of intoxication in 80.1 % of cases in the intoxication group. Self-poisoning using at least two substances was observed in 52.0 % of the suicide attempts, 10.3 % of those with intoxication and 29.7 % of those with drug overdose. While alcohol remains the most common cause of intoxication, there was a drastic increase in the consumption of cannabinoids, Crystal Meth and gamma-hydroxybutyrate in the years 2011 and 2012. ICU admission was necessary in 16.6 % of the cases. There were 22 deaths (0.6 % of the study population), of whom 15 were in the suicide group (2.3 %), four (0.15 %) in the intoxication group, and three in the not clearly classified group (3.8 %). Conclusion. Acute self-poisoning is an increasing medical issue. Psychotropic drugs remain the most common means of suicide attempt. Although alcohol intoxication is very frequent, intake of illicit drugs as the cause of emergency admission is increasing.

Poisoning of the catalyst seems to be one of the most serious problems preventing a widespread commercialization of fuel cell technology. This thesis focuses on the effect of CO poisoning and hydrogen dilution by nitrogen on performance of fuel cells with low platinum content. Catalysts were deposited by magnetron sputtering directly on membrane etched by plasma. Alloys with different platinum-ruthenium ratio were used to mitigate the CO poisoning. We found that presence of nitrogen has almost negligible effect on the fuel cell performance. On the other hand, CO, even in small concentrations, caused a significant drop in power density. PtRu with atomic ratio 2:1 and 1:1 showed the best CO tolerance.