Dissertations / Theses on the topic 'Carlos IV'

El tema de la fiesta ha suscitado en la reciente historiografía un gran interés, con destacadas aportaciones desde diferentes campos, como la historia del arte, la historia política renovada o la historia de las mentalidades entre otras; con la ventaja para el historiador de que la fiesta es uno de aquellos fenómenos complejos que permite, a través de su estudio, una aproximación a la tan deseada historia total. La reunión de factores diversos -económicos, sociales, políticos y culturales- hacen de la fiesta una experiencia humana e histórica global que presenta, no obstante, multitud de facetas diferentes e incluso opuestas, que nos permiten distinguir, por ejemplo, entre fiesta oficial y fiesta popular, o entre fiestas profanas y fiestas religiosas. En esta vasta panorámica festiva, las fiestas reales adquieren un relieve especial, en primer término por su magnificencia y esplendor, pero también por su gran complejidad en todos los sentidos. Esta clase de eventos, típicos de la época, adquirían en el caso de Cataluña una significación política especial por todas las vicisitudes de la integración del Principado a la monarquía hispánica, encarnada y simbolizada en el rey. Sin duda, las fiestas reales más importantes y más celebradas en Cataluña eran las que se hacían por razón de la visita del rey y de la familia real. Recuperar la presencia regia representaba, especialmente después de largos períodos de distanciamiento, uno de los momentos culminantes del encuentro entre el soberano y el pueblo. La última de las visitas reales realizada en tiempos del Antiguo Régimen a Barcelona fue la de Carlos IV en otoño de 1802, cuyas circunstancias nacionales e internacionales fueron muy diferentes a las existentes en 1759, fecha de la última presencia regia: la de su padre, Carlos IIl. Así pues, a principios del s. XIX, Barcelona (como depositaria de una larga tradición mediterránea) se transformó en corte para celebrar un doble enlace: el del príncipe de Asturias, Fernando, con la princesa napolitana María Antonia; y el del heredero de Nápoles, Francisco Genaro, con la infanta española María Isabel. En la Ciudad Condal se dieron cita la familia real española en pleno -acompañada del Príncipe de la Paz, Manuel Godoy-, los príncipes napolitanos y también los soberanos del recién creado --en virtud de los manejos italianos de Napoleón- reino de Etruria: la infanta María Luisa, hija de los reyes españoles, y su esposo Luis, infante heredero de Parma. Por diversas razones históricas, faltaron al encuentro los reyes de Nápoles. Una vez confirmada la designación de la Ciudad Condal como punto de encuentro y ratificación del enlace entre las familias reales, había que analizar exhaustivamente el tema de la organización de la ciudad. A la vez que experimentaba la transformación de la guerra a la paz, de la crisis a la abundancia económica, y de la mendicidad o la ociosidad forzosa a una actividad febril de preparativos y arreglos, Barcelona se dispuso a dejar huella en la memoria histórica de la estancia regia. En los preparativos y arreglos se tuvieron en cuenta múltiples aspectos y en los que participaron de una forma u otra, según su condición, todos los estamentos de la ciudad. Nada se dejó al azar y Barcelona brilló, como ya había hecho con Carlos IlI, ante la complejidad que supuso preparar, disponer y presentar una ciudad a los ojos de la monarquía borbónica y la multitud de forasteros desplazados expresamente para el acontecimiento. A fin de afrontar con garantías de éxito este aspecto, las autoridades barcelonesas tuvieron que resolver, en primer lugar, el tema pecuniario. Al producirse el cambio de siglo, Barcelona se encontraba sumida en una grave crisis, resultado directo de las funestas consecuencias de la guerra contra Inglaterra en la economía y en la sociedad. No fue hasta 1802 que empezó a apuntar la recuperación, gracias a las perspectivas que habían de suceder a la firma en el mes de marzo de la Paz de Amiens, que abría de nuevo las grandes rutas del comercio internacional. En este prometedor marco de recuperación se inserta la visita de Carlos IV y la familia real a la Ciudad Condal, de gran significación política para la vida ciudadana. Ahora bien, las obras y los festejos que habían de realizarse en la ciudad iban a costar muchos miles de libras y, aunque a partir de mayo la coyuntura se había vuelto francamente favorable, era necesario reunir fondos para hacer frente a los cuantiosos gastos que se avecinaban y el llevarlo a cabo no fue empresa fácil. Por ello, se ideó llevar a la práctica algunas rifas, se organizaron bailes, se solicitó la pertinente contribución de los gremios y se peticionó una cooperación económica del propio Carlos IV. Una vez obtenidos algunos caudales, el Ayuntamiento pudo por fin iniciar las obras, consistentes básicamente en el arreglo de los empedrados, la renovación de las casas, la alineación de las calles, la limpieza y pintura de las fachadas, el problema del alcantarillado, la mejora de las conducciones y el abastecimiento de agua, el aseo de la ciudad y las prevenciones en caso de incendio, tareas que enlazaban en su mayor parte con la política municipal de mejora de la infraestructura surgida con el Edicto de Obrería decretado por el conde de Ricia en 1771. Una vez examinado el entramado urbano de la ciudad, necesariamente había que implicar en esta la cuestión de los alojamientos y analizar aquellos en los que residieron la familia real, la nobleza, los Guardias de Corps y, por último, la población foránea a Barcelona desplazada a la ciudad para vivir el acontecimiento de la estancia de los reyes. Ello condujo, obviamente, al análisis de los edificios susceptibles de renovación y mejora. Junto a la organización de la ciudad se trató también el otro gran problema al que hubo de enfrentarse el Ayuntamiento: solucionar la provisión de los abastecimientos y la distribución de los nuevos puntos de venta de comestibles. A la vez que se solventaban todas estas cuestiones, se tuvo que ir disponiendo y prefijando, en primer lugar, los pormenores protocolarios y de ceremonial y recepción de las familias reales y obviamente, tras solucionar esto, organizar todos aquellos actos, diversiones y obsequios susceptibles del agrado de los monarcas. Para ello, el Ayuntamiento de Barcelona, juntamente con el cuerpo de Colegios y Gremios y el de Comercio y Fábricas, y auxiliado por los diversos sectores sociales, compusieron con sus aportaciones el marco efímero de la fiesta y organizaron los obsequios considerados como más idóneos, ayudados por los mejores artistas del momento. Reproducir el viaje y la estancia de los reyes en Barcelona significó, por un lado, poner de relieve multitud de aspectos, anecdóticos si se quiere, pero sumamente interesantes a la hora de reflejar un perfil histórico y un gran número de actos llevados a cabo desde un punto de vista tradicional y, por otro, constatar como, una vez más, dentro del periplo que compone el mundo de la fiesta y los motivos de sus manifestaciones, las visitas reales se inscriben con nombre propio, constituyendo uno de los momentos mas exaltantes de la misma, sino el que mas, el momento de la entrada real. El conjunto de la tesis permite, por tanto, concluir que todas las actividades espléndidas que se desarrollaren fueron una evocación viva del despliegue económico y urbano registrado en la Ciudad Condal a las puertas del s. XIX. La iniciativa local respondió al deseo de explicitar al rey visitante los conocimientos y el excelente gusto de los catalanes en aquellos momentos (principalmente en temas artísticos), por lo que para concluir podemos decir que se le ofreció al monarca una versión integrada y asumida desde Cataluña.
At the beginning of the 19th century, Barcelona, as depository of a long Mediterranean tradition, transformed into a court to receive the kings Carlos IV and Maria Luisa of Parma. The reason for the visit was the solemn ratification of the double weddings between the Prince of Asturias, Fernando, with the Neapolitan princess Maria Antonia; and the one of the Naples inheritor, Francisco Genaro, with the Spanish infanta Maria Isabel. Carlos IV determined this double matrimonial link due to the "Adjustment of Aranjuez". The 6th of June of that year, 1802, the weddings' 'contracts' were celebrated, and Queen Maria Luisa chose Barcelona as the frame for this memorable interchange of betrotheds. City is which all the royal Spanish family met, joined by Manuel Godoy -Prince of the Peace-, the Neapolitan Princes, and also the sovereigns of the just created kingdom of Etruria: infanta Maria Luisa, daugther of the Spanish kings, married to Luis, inheritor of Parma. Because of to several motives, Fernando I and Maria Carolina, kings of Naples, didn't go to the event. The new of the visit of the royal family extended in Barcelona at the beginning of 1802, and it awoke a great expectation. The city, which the transformation that was experienced from war to peace, immersed in a frantic activity of preparations and arrangements in which multiple aspects were taken into account, and in which all the estates of the city participated. Multiple works were made and splendid feast were organized to treat the illustrious guests, who remained in the city from the 11th of September to the 8th of November. The best artists of the moment participated in these activities; then, as a result it was one of the best moments of the ephemeral Catalan art, already placed in full Neoclassicism, without forgetting the historic circumstances that framed the event.

This thesis details the development of methods for and application of the synthesis of carbon carbon bonds using organic sulfur(IV) chemistry. More specifically, the formation of C(sp2) C(sp3) and C(sp3) C(sp3) bonds is explored in detail. The necessity for this research stems from a correlation between a high proportion of sp3 centres in drug candidates, and their success in clinical trials. By facilitating the synthesis of drug candidates with higher fractions of sp3 hybridised carbon atoms, it is hoped that the rate of candidates proceeding through clinical trials may increase. The first topic addressed is the ligand coupling reactions of sulfoxides. In such reactions, the treatment of appropriately substituted sulfoxides with organometallic reagents forms C(sp2) C(sp3) coupling products via σ sulfurane intermediates. These reactions have the ability to excel where transition metal catalysed cross couplings fail; in the coupling of electron deficient (hetero)aromatic groups and alkyl groups. Very few reports have been published detailing the scope and utility of this reaction. The application of this methodology to the synthesis of diarylmethanes is explored in detail. Diarylmethanes are designated as privileged structures for the presence of these moieties in a vast array of diversely functional drug products. Investigation of the scope of the ligand coupling reaction allows for the elucidation of (hetero)aromatic moieties which can undergo this reaction. The depth of analysis in which the scope of benzylic substituents is studied allowed for the elucidation of previously unreported trends, which have been assigned to steric and electronic characteristics of the σ sulfurane intermediates. This knowledge gained is applied to the synthesis of both enantiomerically enriched diarylmethanes and well known drug products. Further exploration of the scope of ligand coupling reactions focusses on the coupling of α functionalised alkyl groups. Remarkable success is found in this completely unexplored area. Benzylic ethers, carbamates and halides are synthesised through a combination of inter molecular and intra molecular ligand coupling reactions. It is proposed that these reactions would be suitable for use in the synthesis of natural products to prove their utility. A newly-discovered sulfoxide homologation is detailed, which occurs upon reaction of sulfenate by products with the aforementioned benzylic halides, both synthesised by a ligand coupling reaction. This is particularly interesting since a similar homologated sulfoxide is found in the substructure of omeprazole, a blockbuster proton pump inhibitor. The second topic addressed is the synthesis of (±)-TAN1251A. The envisaged route proceeds through a novel palladium catalysed [3+2] cycloaddition of sulfinimines, forming methylene pyrrolidines. Previous work focussed on the use of this methodology to produce a diamine, mono-protected as a sulfonamide. A key aspect of the research presented in this thesis is the formation of the C ring of the spiro fused 1,4 diazabicyclo[3.2.1]octane moiety. Initial investigations focus on the synthesis of a pyruvic acid fragment to react with the aforementioned diamine. This concept is developed into the use of pyruvic acid synthetic equivalents: azlactones. A late stage intermediate is produced, however formation of the C ring from this intermediate is not observed. Synthesis is hampered by the deprotection of the sulfonamide, which forms several by-products under the strongly acidic conditions required. A revised retrosynthesis proposes that early deprotection of the diamine sulfonamide would prevent complications. The use of a simplified fragment to facilitate C ring formation is devised, comprising of an α-haloketone. Synthesis of the unprotected diamine is accelerated by serendipity, where a reductive amination also effects the elimination of a sulfinyl group. Formation of an α haloketone fragment is found to be troublesome, however synthesis via the natural product chavicol provides the required functionality. A wide variety of conditions are examined to effect the combination of these fragments. While coupling of the fragments is successful in providing another late-stage intermediate of (±) TAN1251A, formation of the desired C ring is not achieved. Finally, the potential to effect an enantioselective synthesis of (±)-TAN1251A is confirmed using a chiral sulfinamide to direct diastereoselective ketone reduction.

Following discoveries in our laboratory that mixed-ring uranium(III) complexes reductively couple CO to produce new C-C bonds and transform this small molecule into potentially useful small organic things, further research has taken place into the synthesis, characterisation and reactivity of the zirconium, hafnium and thorium analogues. The first part of this thesis describes the preparation of the novel zirconium(IV) and hafnium(IV) mixed-sandwich chloride complexes using sterically demanding cyclopentadienyl and cyclooctatetraenyl ligands, and their subsequent reduction into the desired low valent M(III) compounds. The second part considers the reaction between carbon oxides and three different zirconium(III) complexes in which differently substituted cyclopentadienyl ligands are employed. Reaction with CO generated two novel complexes that displayed C-C bond formation, with the products influenced by the sterics of the systems. Reaction with CO2 produced products resulting from reduction and/or reductive disproportionation of CO2, which were independent of the steric bulk of the cyclopentadienyl ligand. The third and final part of the thesis considers the synthesis of two novel mixed-ring thorium(IV) halide species, before a description of their in situ reduction in the presence of CO2 to yield products different to those previously described in this work. The reactivity illustrated here demonstrates a new approach to the reductive coupling of CO via characterised zirconium(III) complexes and provides insight into the reactivity of a transient thorium(III) sandwich complex.

A finalidade deste estudo foi verificar a resistência ao deslocamento de restaurações de Classe IV, ressaltando a sua capacidade de retenção com e sem a associação de pino(s) dentinários, bem como a comparação entre dentes humanos e bovinos, visando este último como possível substrato a dentes humanos em testes laboratoriais. Foram realizadas 60 cavidades de Classe IV com 6mm no sentido incisocervical e 3mm no sentido mesiodistal, tanto em dentes humanos como bovinos, com um bisel de 1mm de extensão, as quais foram divididas nos seguintes grupos: · G1- restaurações sem pino, sem condicionamento + adesivo (controle); · G2- restaurações com condicionamento ácido + adesivo; · G3- restaurações com um pino, sem condicionamento ácido + adesivo; · G4- restaurações com dois pinos, sem condicionamento ácido + adesivo; · G5- restaurações com um pino, com condicionamento ácido + adesivo; · G6- restaurações com dois pinos, com condicionamento ácido + adesivo. A aplicação do sistema adesivo (Single Bond) e a inserção da resina composta (Z 100) deu-se de acordo com as instruções do fabricante. Após a realização das restaurações, os corpos-de-prova foram armazenados por um período de 72 horas a 37+1oC antes de serem levados à máquina de ensaios universal para serem submetidos à carga de compressão. A análise estatística aplicada aos resultados obtidos segundo as condições experimentais em que foi realizado este trabalho permitiu as seguintes conclusões: - a presença de um ou dois pinos rosqueados em dentina apresentou tendência em aumentar a resistência ao deslocamento das restaurações de Classe IV quando associadas ao sistema adesivo; - a utilização de um pino dentinário proporcionou aumento na retenção das restaurações de Classe IV, todavia, não suficiente para suplantar estatisticamente as restaurações adesivas sem essa variável; - a utilização de dois pinos dentinários proporcionou aumento estatisticamente significante na resistência ao deslocamento das restaurações,em relação às realizadas apenas com o sistema adesivo; - não existiu diferença na resistência ao deslocamento das restaurações de Classe IV realizadas em dentes bovinos e em dentes humanos.
The goal of this study was to verify the resistance to displacement of Class IV restorations, emphasizing their retention capacity with and without the association of retentive pins (Pinlock), as well as the comparison between human and bovine teeth, aiming at the latter as a possible substrate to human teeth in laboratory tests. Sixty Class IV cavities with 6 mm in the incisal-cervical plane and 3 mm in the mesio-distal plane and with bevel 1mm were performed, both on human and bovine teeth, which were divided into the following groups: · G1 - restorations without acid conditioning and pin + adhesive (control); · G2 - restorations with acid conditioning + adhesive; · G3 - restorations without acid conditioning + one pin + adhesive; · G4 - restorations without acid conditioning + two pins + adhesive; · G5 - restorations with one pin + acid conditioning + adhesive +; · G6 - restorations with two pins + acid conditioning + adhesive. The application of the adhesive system (Single Bond) and the insertion of composite resin (Z100) were according to the manufacturer's instructions. Following restoration procedures, the specimens were stored for a period of 72 hours at 37+ oC prior to being taken to the Universal testing machine, so as to be submitted to compression load. The statistical analysis applied to the results obtained, according to the experimental conditions in which this study was performed, allowed the following conclusions:- the presence of one or two dentin-threaded pins showed a trend in increasing the displacement resistance of Class IV restorations when associated with the adhesive system; - the utilization of one dentinal pin afforded an increase in the retention of Class IV restorations, nevertheless, not sufficient to supersede the adhesive restorations statistically without this variable; - the utilization of two dentinal pins afforded a statistically significant increase in the displacement resistance of restorations, in relation to those performed only with the adhesive system; - there was no difference as to displacement resistance of Class IV restorations performed on both bovine and human teeth.

The functional group composition of acid polysaccharides was determined after isolation using cross-flow ultrafiltration, radiolabeling with 234Th(IV) and other isotopes, and separation using isoelectric focusing (IEF) and polyacrylamide gel electrophoresis (PAGE). Phosphate and sulphate concentrations were determined from cultured bacterial and phytoplankton colloid, particulate and colloidal samples collected from the Gulf of M??xico (GOM). Characterization of the 234Th(IV)-binding biomolecule was performed using ion chromatography (IC), and gas chromatography-mass spectrometry (GC-MS). Radiotracer experiments and culture experiments were conducted in determining the binding environment of the 234Th(IV)-binding ligand (i.e., sorption onto suspended particles), as well as the origin of the ligand in seawater systems. In all samples, 234Th(IV) isoelectric focusing profiles indicated that 49% to 65% of the 234Th(IV) labeled EPS from Roseobacter gallaeciensis, Sagittula stellata, Emiliania huxleyi, Synechococcus elongatus and GOM Station 4-72m was found at a pHIEF of 2 in the IEF spectrum. The carboxylic acid group appeared at the same pHIEF as 234Th(IV) for EPS from Roseobacter gallaeciensis, Emiliania huxleyi, Synechococcus elongatus and GOM colloidal organic matter sample. The phosphate group appeared at the same pHIEF as 234Th(IV) for EPS from Roseobacter gallaeciensis, and Synechococcus elongatus sample. The sulphate group was found at the same pHIEF as 234Th(IV) for EPS from S. elongatus and GOM colloidal organic matter sample. The total polysaccharide content was only 14% and 8%, uronic acids were approximately 5.4% and 87.1%, and total protein content was 2.6% and 6.2% of total carbon content of Sagittula stellata and Synechococcus elongatus, respectively. Monosaccharides identified in both Sagittula stellata and Synechococcus elongatus were galactose, glucose, and xylose in common. In addition, Sagittula stellata contained mannose and Synechococcus elongatus had galactoglucuronic acid. Thus, depending on the species, the size, structural composition, and functional groups of the 234Th(IV)-binding, acidic polysaccharides will vary. From these observations, it is concluded that the steric environment and not necessarily the exact functional group might actually be responsible for thorium-234 complexation to macromolecular organic matter. This research helped to improve our understanding of the observed variability in POC/234Th ratios in the ocean and provided insights into factors that regulate organic carbon export fluxes.

U okviru ove disertacije izvršeno je preparatvno izolovanje etarskog ulja lišća ginka (Ginkgo biloba L.) destilacijom pomoću vodene pare, u cilju određivanja pojedinih fizičko-hemijskih parametara. Oficinalnim postupkom određen je sadržaj etarskog ulja u lišću ginka i iznosi 0,0083%. Lišće ginka je ekstrahovano klasičnim rastvaračima tj. smešom alkohol-voda, pri čemu je koncentracija alkohola iznosila 40% (m/m). Primenom navedenog rastvarača, izvršena je višestupna protivstrujna ekstrakcija (u pet stupnjeva) pri čemu je dobijen tečni ekstrakt (Extracta fluida) sa relativno visokim sadržajem ekstraktivnih materija (17,06%). Tečni ekstrakt je direktno korišćen za dobijanje suvog ekstrakta lišća ginka (Extracta sicca)primenomvsušnie sa raspršivanjem (spray dryer). Kvalitativna i kvantitativna karakterzacija izvršena je primenom postupka tečne hromatografije na tankom sloju (HPTLC) i određen sadržaj ukupnih flavonoida sračunatih na rutin, a i na katehin, a određen je i sadržaj ukupnih fenola sračunatih na hlorogensku kiselinu. Glavni deo doktorske disertacije predstavlja ekstrakcija sistema lišće ginka-ugljenik (IV)-oksid pod pritiskom, pri čemu je ispitivan uticaj stepena usitnjenosti droge na prinos ekstrakcije, i korišćen koeficijent brze i spore ekstrakcije kao mera kinetičkog ponašanja ekstrakcije. Dobijeni rezultati ispitivanja su pokazali značajan uticaj stepena usitnjenosti droge na brzinu ekstrakcije, pogotovo, kod ekstrakcije natkritičnim ugljenik (IV) oksidom. Radi izbora optimalnog protoka ekstragensa ispitivani su sledeći protoci 0,095, 0,194 i 0,277 kg/h . Na osnovu prinosa ekstrakcije usvojeno je da je protok ekstragensa od 0,194 kg/h optimalan. Prinos ekstrakcije je ispitivan korišćenjem dva postupka ekstrakcije, i to: ekstrakcija tečnim ugljenik (IV) -oksidom (temperatura ispod kritične temperature Tc= 31,1^oC, a pritisak nešto ispod ili iznad kritičnog pritiska p_c=73,8 bar), i ekstrakcija natkritičnim ugljenik (IV)- oksidom (pritisak i temperatura iznad kritičnih vrednosti pritiska i temperature). U natkritičnoj oblasti promenom pritiska se značajno menjaju svojstva ekstragensa, povećava se sposobnost rastvaranja, dielektrična konstanta i dr. Ispitivan je uticaj temperature na prinos ekstrakcije (izotermni proces), pri čemu se dobijaju rezultati koji se ne mogu objasniti jednostavno, analizirajući samo uticaj gustine rastvarača na moć rastvaranja, već se za objašnjenje dobijenih rezultata uključuje i uticaj napona pare ekstrahovane komponente, tako da rastvorljivost komponente može da se poveća, smanji ili ostane ista sa povećanjem temperature na konstantnom pritisku, u zavisnosti koji uticaj je dominantniji. Kod izotermnih postupaka prinos ekstrakcije raste sa povećanjem pritiska ekstrakcije, što je u saglasnosti sa teoretskim principima. S druge strane, ekstrakti dobijeni pri višim pritiscima imaju manji sadržaj etarskog ulja što se objašnjava činjenicom da veći pritisci imaju veću moć rastvaranja glavnih komponenata kao i komponenata kao što su smole, voskovi i masna ulja. Kvalitativnom i kvantitativnom analizom selektovanih ekstrakata dobijenih tečnim (130 bar, 20^oC, 3 h) i natkritičnim (100 bar, 40^o C, 4 h) ugljenik (IV)-oksidom, kao i etarska ulja izolovana iz ovih ekstrakata nađeno je da ispitivani uzorci sadrže nalkane, račvaste alkane i jedinjenja sa kiseonikom, među kojima posebno mesto zauzimaju fenoli sa zasićenim i nezasićenim alkil ostacima.Izvršena je uporedna anliza etarskog ulja dobijenog destilacijom lišća ginka pomoću vodene pare i etarskih ulja dobijenih iz selektovanih ekstrakata. Interesantan je podatak koji se odnosi na sadržaj etarskog ulja u drogi određen direktnom destilacijom droge pomoću vodene pare i izdvajanjem etarskih ulja iz ekstrakata takođe destilacijom pomoću vodene pare. U ovom drugom slučaju dobija se, preračunavanjem, sadržaj etarskog ulja u drogi višestruko veći (4-10 puta) od sadržaja, određenog oficinalnim postupkom, u drogi. Ova pojava se objašnjava uvođenjem pojma „vezano“ etarsko ulje i „slobodno“ etarsko ulje. Ekstrakcijom ugljenik (IV)-oksidom pod pritiskom tzv. vezano etarsko ulje se oslobađa voskova i masnog ulja što se odražava na njegovu povećanu količinu u CO₂-ekstraktima. Na kraju u ovoj disertaciji izvršeno je modelovanje ekstrakcionog sistema lišće Ginkgo biloba – ugljenik (IV)-oksid pod pritiskom korišćenjem model jednačine Naika i saradnika, modifikovane model jednačine Reverchon i Sesti-Osseo kao i model, češće korišćen, koji je predložila Sovová. Korišćeni modeli mogu relativno uspešno da se koriste za opisivanje ekstrakcionog sistema lišće Ginkgo biloba – ugljenik (IV)-oksid pod pritiskom. Radi iznalaženja najpovoljnijih uslova ekstrakcije primenjen je metod odzivne površine variranjem parametra ekstrakcije (pritisak, temperatura i vreme ekstrakcije). Na osnovu eksperimentalnih rezultata dobijen je polinom drugog reda za izračunavanje optimalnog prinosa ekstrakcije i određeni su najpovoljniji uslovi ekstrakcije kao i međusobni uticaji pojedinih parametra.
Within this thesis preparative isolation of essential oil from leaves of ginkgo (Ginkgo biloba L.) by steam distillation was carried out, in order to determine some physico-chemical parameters. The essential oil content in the leaves of ginkgo wass determined by an officinal procedure and its value is 0.0083%. Ginkgo leaves were extracted with conventional solvents, i.e. alcohol-water mixture, where the alcohol concentration was 40% (w/w). The forementioned solvent was used to carry out a multistage counter-current extraction (five stages) by which the liquid extract (Extracta fluida) with a relatively high content of extracts (17.06%) was obtained. The liquid extract was directly used to obtain a dry extract of ginkgo leaves (Extracta sicca) by spay drying. The qualitative and quantitative characterisation was based on the proceedings of liquid thin layer chromatography (HPTLC), the content of total flavonoids expressed as rutin, and as catechin, and the total phenol content expressed as chlorogenic acid was determined. The main part of the doctoral thesis is the extraction system of ginkgo leaves-carbon (IV) oxide under pressure, in which the effect of the drug particle size on the extraction yield was studied, and as a measure of the kinetic behavior of extraction the coefficient of fast and slow extraction was used. The obtained results showed a significant effect of the drug particle size on the speed of extraction, particularly, the extraction with supercritical carbon (IV) oxide. For the purpose of selecting the optimal flow of the solvent several flowrates were investigated 0.095, 0.194 and 0.277 kg/h. Based on the yield of extraction the solvent flowrate of 0.194 kg/h was assumed as optimal. The extraction yield was investigated using two extraction procedures: extraction with liquid carbon (IV) oxide (temperature below the critical temperature Tc = 31.1 ⁰C and pressure slightly below or above the critical pressure p_c = 73.8 bar), and extraction with supercritical carbon (IV) oxide (pressure and temperature above the critical values of pressure and temperature). In the supercritical area the change in pressure significantly the influences the properties of the solvent, increases the ability of dissolving, dielectric constant, etc. The effect of temperature on extraction yield was examined (isothermal process), where the obtained results can not be explained simply by analyzing only the effect of solvent density on the power of dissolution, but to explain these results the effect of vapor pressure of the extracted components must be included, so that the solubility of the component may increase, decrease or remain the same with increasing temperature at constant pressure, depending on which influence is dominant. In isothermal processes the extraction yield increases with increasing pressure of extraction, which is consistent with theoretical principles. On the other hand, extracts obtained at high pressures have a lower content of essential oils which can be explained by the fact that higher pressures have a greater power of dissolution of the main components as well as components such as resins, waxes and fatty oils. The qualitative and quantitative analysis of the selected extracts obtained with liquid (130 bar, 20 ⁰C, 3 h) and supercritical (100 bar, 40 ⁰C, 4 h) carbon (IV) oxide, and essential oils isolated from these extracts showed that the studied samples contain n-alkanes, branched alkanes and compounds with oxygen, including phenols with saturated and unsaturated alkyl residues. A comparative analysis of the essential oil obtained by distillation of ginkgo leaves by steam and essential oil obtained from selected extracts was carried out. An interesting fact concerning the essential oil content in the drug determined by direct distillation of drugs by steam and separating the essential oils from extracts also produced by steam distillation. In the other case, by calculation, the obtained essential oil content in the drug is several times higher (4-10 times) of content, determined by an fficinal procedure, in the drug. This phenomenon is explained by introducing the notion of "linked" essential oil and "free" essential oil. The extraction with carbon (IV) oxide under pressure the so called linked essential oil is released from waxes and fatty oils which is reflected in its increased amount in CO₂-extracts. At the end of this dissertation the modeling of the extraction system leaves of Ginkgo biloba - carbon (IV) oxide under pressure was carried out using the model equation of Naik and associates, the modified model equation of Reverchon and Sesti Osseo and also like a frequently used model proposed Sovová. The mentioned models can be relatively used to describe the extraction system leaves of Ginkgo biloba - carbon (IV) oxide under pressure. In order to find the most favorable conditions of extraction, the response surface methodology varying extraction parameters was used (pressure, temperature and extraction time). Based on the experimental results a second order polynom for the calculation of the optimum yield of extraction was obtained and the extraction conditions and the mutual influence of some parameters were determined.

The Monte Carlo code Serpent has been used to model the material flows andisotope compositions for a lead cooled fast reactor. The demonstration sized trainingreactor ELECTRA was chosen for the investigation, and different fuel cycle scenarioswere studied. The scenarios differed in operation length (3 months, 1 year or 5years) and recycling technique (single and double PUREX or GANEX). The simulations gave detailed information on the changes of the isotope composition,activity and decay heat. The analysis of the generated waste also showed that thechoice of recycling method had great impact on the final storage time of the wastefrom the reprocessing. Performing double GANEX recycling, as compared to singlePUREX, reduced the storage time by a factor of about 3500. The results can be used for future work related to even more detailed studies ofmaterial flows and for designing an appropriate safeguards system.

Cette thèse s'est déroulée dans le cadre du projet TOLEDO (Tolérance aux dommages par impact des réservoirs hyperbares) piloté par Air Liquide en partenariat avec le CEA Le Ripault et l'institut PPRIME.L'hydrogène est stocké au sein de réservoirs de type IV à une pression de service de 700 bar.Ces structures composites présentent comme particularités d'être épaisses (> 30 mm), d'avoir une forte courbure et d'être préchargées en pression lors d'un éventuel impact.Notre travail a montré que ces particularités modifient le type, la quantité et la localisation des différents endommagements couramment observés (rupture de fibres, délaminage et fissuration matricielle).Les endommagements ont pu être quantifiés par le biais de méthodes simples et originales.L'influence des particularités sur le comportement à l'impact a pu être déterminée par l'utilisation de deux dispositifs expérimentaux conçus et réalisés au cours de cette thèse.Le premier permet de précontraindre en tension uniaxiale des plaques composites épaisses.Le second permet de précharger en état de membrane un tube composite ce qui a permis de montrer que le cas d'impact le plus critique vis-à-vis des réservoirs est lorsque ces derniers sont vides.Cette étude a permis de mettre en évidence la criticité des ruptures de fibres sur les pertes de performance au sein des réservoirs hyperbares.Un modèle numérique prenant en compte la dispersion des contraintes à rupture et des différents types d'endommagements a été développé.Il permet d'introduire un endommagement initial et a confirmé certains résultats expérimentaux
This thesis took place within the framework of the project TOLEDO (Tolerance in the damage by impact of the hyperbaric reservoirs) managed by Air Liquide in partnership with the CEA Le Ripault and PPRIME institute.The hydrogen is stored within the type IV vessel at a servive pressure of 700 bar.These composite structures present as peculiarities to be thick (> 30 mm), to have a strong curvature and to be precharged in pressure during a possible impact.Our work showed that these peculiarities modify the type, the quantity and the localization of the various usually observed damages (fiber breakage, délamination and matrix cracking).The damages were able to be quantified by means of simple and original methods.The influence of the peculiarities on the behavior in the impact was able to be determined by the use of two experimental devices designed and realized during this thesis.The first one allows to preload a thick composite plates in uniaxial tension thick composite plates.The second allows to preload in state of membrane a composite pipe and allowed to show that the most critical impact towards reservoirs is when they are empty.This study allowed to highlight the criticality of the fiber breakage on the loss of performance within the hyperbaric reservoirs.A digital model taking into account the dispersal of the failure stress and various types of damages was developed.It also allows to introduce an initial damage and confirm some experimental results

Tato práce se zabývá zpracováním snímků Slunce pořízených kosmickou sondou SDO na různých vlnových délkách a vizualizací výskytu třikrát ionizovaného uhlíku C IV jejich vhodným složením. V práci jsou uvedeny základní informace o Slunci a jeho atmosféře, dále je shrnuta potřebná teorie a možné postupy vizualizace, které jsou následně vyhodnoceny a porovnány. Součástí je i vytvořený program pro snadnou tvorbu snímků vizualizujících uhlík C IV.

Memoria para optar al Titulo Profesional de Médico Veterinario
Se realizó un estudio epidemiológico de los parásitos del sistema digestivo de los caprinos en el periodo 2002-2003 en la IV región de Chile. Para esto se hizo una cuantificación e identificación mensual de los nematodos gastrointestinales. Además mensualmente se determinó las curvas de eliminación de huevos del orden Strogyloidea y de ooquistes de cooccidias por el método de Mc. Master. Se encontraron parásitos tanto en abomaso como en intestino delgado, pero no en intestino grueso. Los parásitos encontrados fueron: Ostertagia circumcincta, Trichostrongylus axei en abomaso y Nematodirus filicollis y Cooperia cuticei en intestino delgado. Además se comparó la situación epidemiológica en animales en pastoreo y estabulados y dentro de estos grupos, animales sometidos a tratamiento antiparasitario y animales sin tratamiento. Con esto se determino que los grupos presentan diferencias en los conteos de huevos al examen de Mc. Master. Sin embargo, esta situación no se tradujo en variaciones en los pesos en los diferentes grupos

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This work refers to the development of a simple and innovative method for the synthesis of ternary composites of different proportions based on amorphous carbon, polyaniline and manganese (IV) oxide for their future use in electrochemical supercapacitors. The process presented here consists, essentially, of 3 parts: (i) at first, it has been performed the oxidative treatment of amorphous carbon and the separated synthesis of pure MnO2 and polyaniline, when all the materials involved were structurally characterized by XRD, FTIR, RAMAN, DLS and SEM, and electrochemically characterized by cyclic voltammetry measurements, in order to identify its structural, morphological and electrochemical properties and then compared with those presented by the future ternary composites; (ii) synthesis of a binary C/MnO2 composite by the anchoring of the MnO2 particles on the oxidized sites of the amorphous carbon, which represents the first stage on the formation of the ternary composites. Its purpose was to identify possible structural and electrochemical changes caused by MnO2 surface layer in the comparison of the binary composite with its individual components. Therefore, this composite was characterized by the same methods mentioned above; (iii) synthesis and characterization of ternary composites on different proportions, based on the initial formation of binary C/MnO2 followed by in situ polymerization of aniline monomers on their surface structure. The purpose of the synthesis in different proportions is to obtain a response profile when small changes in the quantity of the constituent materials are introduced in the ternary composites. The characterization of the ternary composites were carried out by XRD, FTIR, RAMAN, DLS and SEM, which allow to identify possible structural and morphological changes showed by composites compared to the individual components and, by cyclic voltammetry measurements, when it was possible to notice the electrochemical behavior of these composites and define their specific capacitance values in parallel to their processes of charge storage and ions diffusion.
Neste trabalho, buscou-se desenvolver uma metodologia simples e inovadora para a síntese de compósitos ternários de diversas proporções baseados em carbono amorfo, polianilina e óxido de manganês (IV) visando sua futura utilização em supercapacitores eletroquímicos. O trabalho consiste basicamente de 3 partes; (i) inicialmente realizou-se o tratamento oxidativo do carbono amorfo e a síntese individual dos compostos MnO2 e PAni, onde todos os materiais foram caracterizados estruturalmente por DRX, FTIR, RAMAN, DLS e MEV e eletroquimicamente por medidas de voltametria cíclica, afim identificar suas propriedades estruturais, morfológicas e eletroquímicas e compará-las com as apresentadas pelos futuros compósitos ternários; (ii) síntese de um compósito binário C/MnO2 pelo ancoramento das partículas de MnO2 sobre sítios oxidados do carbono amorfo, a qual configura a 1ª etapa da formação dos compósitos ternários. Sua finalidade foi de identificar as possíveis mudanças estruturais e eletroquímicas ocasionadas pela presença da camada superficial de MnO2 quando comparado o compósito binário aos seus componentes individuais. Para tanto, este compósito foi caracterizado pelos mesmos métodos apresentados acima; (iii) síntese e caracterização de compósitos ternários de diferentes proporções baseados na inicial formação do binário C/MnO2 seguido da polimerização in situ dos monômeros de anilina sobre sua estrutura superficial. A abordagem da síntese em diferentes proporções torna possível a obtenção de um perfil de resposta quando são introduzidas nos compósitos ternários pequenas modificações na quantidade dos materiais constituintes. A caracterização dos compósitos ternários foi realizada pelas técnicas de DRX, FTIR, RAMAN, DLS e MEV, as quais permitem identificar possíveis mudanças estruturais e morfológicas apresentadas pelos compósitos frente aos componentes individuais, e, por medidas de voltametria cíclica, onde foi possível observar o comportamento eletroquímico destes compósitos e definir seus valores de capacitância específica juntamente com seus processos de armazenamento de carga e difusão de íons.

Ce travail exploratoire porte sur l'elaboration, la caracterisation, la modelisation theorique et le potentiel industriel des composes a base de silicium, germanium, carbone. Les methodes possibles d'elaboration sont presentees. Les echantillons etudies ont ete realises par rtcvd, uhvcvd, plie, spem et mbe et caracterises par de nombreuses techniques complementaires. Un potentiel interatomique est adapte aux resultats experimentaux, afin de correler l'ordre nanoscopique aux proprietes liees a la microstructure. Cet outil, qui permet de calculer les parametres thermodynamiques a partir d'une repartition atomique, est notamment applique a l'interpretation conjointe des mesures raman, ftir, hrtem et de diffraction x. La microstructure depend de la methode d'elaboration, et un phenomene d'autoorganisation de c par rtcvd est demontre, par un faisceau convergent de caracterisations etayees par des simulations a l'echelle atomique. Les particularites liees a l'epitaxie laser (plie) sont detaillees. Une nouvelle methode de depot (spem) permet d'obtenir pour la premiere fois une couche contrainte contenant 70% de ge et 1. 6 % de c. Au niveau des proprietes thermiques, la mesure de dilatation de couches minces si#1#-#x#-#yge#xc#y constitue une nouvelle methode de dosage de ge et c. Une determination originale du pouvoir thermoelectrique par microscopie photothermique est suggeree. Pour des recuits a plus haute temperature, le carbone precipite sous forme de carbure de silicium incoherent, et l'hypothese d'un milieu devenu lacunaire s'accorde le mieux avec les resultats experimentaux. L'interdiffusion thermique de ge est etudiee quantitativement par diffraction x dans le cas de multipuits quantiques. L'etude controversee de la structure de bande des composes si#1#-#x#-#yge#xc#y est presentee. Les mesures ellipsometriques indiquent que le carbone induit un decalage de +65 mev/%c de e#1, alors que e#2 reste quasiment constant. Ce resultat est analyse dans le cadre de la theorie des potentiels de deformation. Cette etude physique eclaire l'analyse des applications industrielles de la filiere iv-iv, sous l'angle des brevets et des dispositifs, notamment en micro et opto-electronique. La comparaison avec la filiere iii-v paracheve ce memoire.

Dans le cadre des études de neutronique menées pour réacteurs de GEN-IV, les nouveaux outils de calcul des cœurs de réacteur sont implémentés dans l’ensemble du code APOLLO3® pour la partie déterministe. Ces méthodes de calculs s’appuient sur des données nucléaires discrétisée en énergie (appelées multi-groupes et généralement produites par des codes déterministes eux aussi) et doivent être validées et qualifiées par rapport à des calculs basés sur la méthode de référence Monte-Carlo. L’objectif de cette thèse est de mettre au point une technique alternative de production des propriétés nucléaires multi-groupes par un code de Monte-Carlo (TRIPOLI-4®). Dans un premier temps, après avoir réalisé des tests sur les fonctionnalités existantes de l’homogénéisation et de la condensation avec des précisions meilleures accessibles aujourd’hui, des incohérences sont mises en évidence. De nouveaux estimateurs de paramètres multi-groupes ont été développés et validés pour le code TRIPOLI-4®à l’aide de ce code lui-même, puisqu’il dispose de la possibilité d’utiliser ses propres productions de données multi-groupes dans un calcul de cœur. Ensuite, la prise en compte de l’anisotropie de la diffusion nécessaire pour un bon traitement de l’anisotropie introduite par des fuites des neutrons a été étudiée. Une technique de correction de la diagonale de la matrice de la section efficace de transfert par diffusion à l’ordre P1 (nommée technique IGSC et basée sur une évaluation du courant des neutrons par une technique introduite par Todorova) est développée. Une amélioration de la technique IGSC dans la situation où les propriétés matérielles du réacteur changent drastiquement en espace est apportée. La solution est basée sur l’utilisation d’un nouveau courant qui est projeté sur l’axe X et plus représentatif dans la nouvelle situation que celui utilisant les approximations de Todorova, mais valable seulement en géométrie 1D. A la fin, un modèle de fuite B1 homogène est implémenté dans le code TRIPOLI-4® afin de produire des sections efficaces multi-groupes avec un spectre critique calculé avec l’approximation du mode fondamental. Ce modèle de fuite est analysé et validé rigoureusement en comparant avec les autres codes : Serpent et ECCO ; ainsi qu’avec un cas analytique.L’ensemble de ces développements dans TRIPOLI-4® permet de produire des sections efficaces multi-groupes qui peuvent être utilisées dans le code de calcul de cœur SNATCH de la plateforme PARIS. Ce dernier utilise la théorie du transport qui est indispensable pour la nouvelle filière à neutrons rapides. Les principales conclusions sont : -Le code de réseau en Monte-Carlo est une voie intéressante (surtout pour éviter les difficultés de l’autoprotection, de l’anisotropie limitée à un certain ordre du développement en polynômes de Legendre, du traitement des géométries exactes 3D), pour valider les codes déterministes comme ECCO ou APOLLO3® ou pour produire des données pour les codes déterministes ou Monte-Carlo multi-groupes.-Les résultats obtenus pour le moment avec les données produites par TRIPOLI-4® sont comparables mais n’ont pas encore vraiment montré d’avantage par rapport à ceux obtenus avec des données issues de codes déterministes tel qu’ECCO
In the framework of the Generation IV reactors neutronic research, new core calculation tools are implemented in the code system APOLLO3® for the deterministic part. These calculation methods are based on the discretization concept of nuclear energy data (named multi-group and are generally produced by deterministic codes) and should be validated and qualified with respect to some Monte-Carlo reference calculations. This thesis aims to develop an alternative technique of producing multi-group nuclear properties by a Monte-Carlo code (TRIPOLI-4®).At first, after having tested the existing homogenization and condensation functionalities with better precision obtained nowadays, some inconsistencies are revealed. Several new multi-group parameters estimators are developed and validated for TRIPOLI-4® code with the aid of itself, since it has the possibility to use the multi-group constants in a core calculation.Secondly, the scattering anisotropy effect which is necessary for handling neutron leakage case is studied. A correction technique concerning the diagonal line of the first order moment of the scattering matrix is proposed. This is named the IGSC technique and is based on the usage of an approximate current which is introduced by Todorova. An improvement of this IGSC technique is then presented for the geometries which hold an important heterogeneity property. This improvement uses a more accurate current quantity which is the projection on the abscissa X. The later current can represent the real situation better but is limited to 1D geometries.Finally, a B1 leakage model is implemented in the TRIPOLI-4® code for generating multi-group cross sections with a fundamental mode based critical spectrum. This leakage model is analyzed and validated rigorously by the comparison with other codes: Serpent and ECCO, as well as an analytical case.The whole development work introduced in TRIPLI-4® code allows producing multi-group constants which can then be used in the core calculation solver SNATCH in the PARIS code platform. The latter uses the transport theory which is indispensable for the new generation fast reactors analysis. The principal conclusions are as follows:-The Monte-Carlo assembly calculation code is an interesting way (in the sense of avoiding the difficulties in the self-shielding calculation, the limited order development of anisotropy parameters, the exact 3D geometries) to validate the deterministic codes like ECCO or APOLLO3® and to produce the multi-group constants for deterministic or Monte-Carlo multi-group calculation codes. -The results obtained for the moment with the multi-group constants calculated by TRIPOLI-4 code are comparable with those produced from ECCO, but did not show remarkable advantages

Cette thèse est consacrée à l’étude de la dynamique et du transport des phonons via la résolution de l’équation de transport de Boltzmann (ETB) pour les Phonons. Un ‘solveur’ Monte Carlo dédié à la résolution de l’ETB des phonons dans l’espace réciproque, prenant en compte tous les processus d’interactions Normaux et Umklapp à trois-phonons, est proposé. Une prise en compte rigoureuse des lois de conservation de l’énergie et de la quantité de mouvement est entreprise. Des relations de dispersion réalistes, intégrant tous les modes de polarisations, sont considérées. Le calcul des taux d’interactions à trois-phonons de tous les processus Normaux et Umklapp est effectué en utilisant l’approche théorique due à Ridley qui ne nécessite qu’un unique paramètre semi-ajustable pour chaque mode de polarisation, nommément : le coefficient de couplage anharmonique représenté par les constantes de Grüneisen. Les taux d’interactions ainsi calculés ne servent pas uniquement à la résolution de l’ETB des phonons, mais ont permis aussi une analyse complète des canaux de relaxation des phonons longitudinaux optiques de centre de zone. Cette analyse a montré que le canal de Vallée-Bogani est négligeable dans le GaAs, et que vraisemblablement les temps de vie des phonons LO de centre de zone dans l’InAs et le GaSb rapportés dans la littérature sont fortement sous-estimés. Pour la première fois à notre connaissance, un couplage de deux solveurs Monte Carlo indépendants l’un dédié aux porteurs de charges (Thèse E. Tea) et l’autre dédié aux phonons, est effectué. Cela permet d’étudier l’effet des phonons chauds sur le transport des porteurs de charges. Cette étude a montré que l’approximation de temps de relaxation surestime souvent l’effet bottleneck des phonons. Le ‘solveur’ Monte Carlo est étendu pour résoudre l’ETB des phonons dans l’espace réel (en plus de l’espace réciproque), cela a permet d’étudier le transport des phonons et ainsi de la chaleur. La théorie généralisée de Ridley est toujours utilisée avec des particules de simulations qui interagissent les unes avec les autres directement. Les règles de conservation de l’énergie et de la quantité de mouvement sont rigoureusement respectées. L’effet des processus Umklapp sur la quantité de mouvement totale des phonons est fidèlement traduit; tout comme l’effet des interactions sur les directions des phonons, grâce à une procédure prenant en compte les directions vectorielles respectives lors d’une interaction, au lieu, de la distribution aléatoire usuellement utilisée. Les résultats préliminaires montrent la limite de l’équation analytique de conduction de la chaleur
This work is dedicated to the study of phonon transport and dynamics via the solution of Boltzmann Transport Equation (BTE) for phonons. The Monte Carlo stochastic method is used to solve the phonon BTE. A solution scheme taking into account all the different individual types of Normal and Umklapp processes which respect energy and momentum conservation rules is presented. The use of the common relaxation time approximation is thus avoided. A generalized Ridley theoretical scheme is used instead to calculate three-phonon scattering rates, with the Grüneisen constant as the only adjustable parameter. A method for deriving adequate adjustable anharmonic coupling coefficients is presented. Polarization branches with real nonlinear dispersion relations for transverse or longitudinal optical and acoustic phonons are considered. Zone-center longitudinal optical (LO) phonon lifetimes are extracted from the MC simulations for GaAs, InP, InAs, and GaSb. Decay channels contributions to zone-center LO phonon lifetimes are investigated using the calculated scattering rates. Vallée-Bogani’s channel is found to have a negligible contribution in all studied materials, notably GaAs. A comparison of phonons behavior between the different materials indicates that the previously reported LO phonon lifetimes in InAs and GaSb were quite underestimated in the literature. For the first time, to our knowledge, a coupling of two independent Monte Carlo solvers, one for charge carriers [PhD manuscript, E. TEA], and one for phonons, is undertaken. Hot phonon effect on charge carrier dynamics is studied. It is shown that the relaxation time approximation overestimates the phonon bottleneck effect. The phonon MC solver is extended to solve the phonon’s BTE in real space simultaneously with the reciprocal space, to study phonon and heat transport. Ridley’s generalized theoretical scheme is utilized again with simulation particles interacting directly together. Energy and momentum conservation laws are rigorously implemented. Umklapp processes effect on the total phonon momentum is thoroughly reproduced, as for the anharmonic interactions effect on resulting phonon directions. This is thanks to a procedure taking in consideration the respective vector directions during an interaction, instead of the randomization procedure usually used in literature. Our preliminary results show the limit of the analytic macroscopic heat conduction equation

This thesis employs two approaches to investigate water stress at the early and mid Epipalaeolithic site of Kharaneh IV in the Azraq Basin, Jordan. Firstly, the archaeobotanical analysis explores the local environment by using the ecology of identifiable charred seeds to indicate water availability (autoecology). Included alongside this is a seed catalogue, which presents the unique archaeobotanical assemblage recovered through sampling. Secondly, to further explore the local palaeoenvironment and due to the potential broad hydrological tolerances of some species, stable carbon isotope δ13C analysis of the archaeobotanical remains is used to track changes in water stress during the occupation of the site. These analyses provide a complementary approach to traditional archaeobotanical studies. Combined, these data offer considerable insight into questions about the local environment, particularly water stress, and the potential use of plants during the occupation of Kharaneh IV. The results presented here demonstrate that Kharaneh IV experienced variable water stress throughout its occupation, with a drying out of the site coincident with the end of occupation. This signature of drying is found within both the isotopic and autoecological analyses, providing multiple lines of evidence for this pattern. This thesis serves as a case study for the usefulness and inferential power of multi-method approaches that combine archaeobotanical and isotopic analysis.

Cette thèse est consacrée à l'étude de la dynamique et du transport des phonons via la résolution de l'équation de transport de Boltzmann (ETB) pour les Phonons. Un 'solveur' Monte Carlo dédié à la résolution de l'ETB des phonons dans l'espace réciproque, prenant en compte tous les processus d'interactions Normaux et Umklapp à trois-phonons, est proposé. Une prise en compte rigoureuse des lois de conservation de l'énergie et de la quantité de mouvement est entreprise. Des relations de dispersion réalistes, intégrant tous les modes de polarisations, sont considérées. Le calcul des taux d'interactions à trois-phonons de tous les processus Normaux et Umklapp est effectué en utilisant l'approche théorique due à Ridley qui ne nécessite qu'un unique paramètre semi-ajustable pour chaque mode de polarisation, nommément : le coefficient de couplage anharmonique représenté par les constantes de Grüneisen. Les taux d'interactions ainsi calculés ne servent pas uniquement à la résolution de l'ETB des phonons, mais ont permis aussi une analyse complète des canaux de relaxation des phonons longitudinaux optiques de centre de zone. Cette analyse a montré que le canal de Vallée-Bogani est négligeable dans le GaAs, et que vraisemblablement les temps de vie des phonons LO de centre de zone dans l'InAs et le GaSb rapportés dans la littérature sont fortement sous-estimés. Pour la première fois à notre connaissance, un couplage de deux solveurs Monte Carlo indépendants l'un dédié aux porteurs de charges (Thèse E. Tea) et l'autre dédié aux phonons, est effectué. Cela permet d'étudier l'effet des phonons chauds sur le transport des porteurs de charges. Cette étude a montré que l'approximation de temps de relaxation surestime souvent l'effet bottleneck des phonons. Le 'solveur' Monte Carlo est étendu pour résoudre l'ETB des phonons dans l'espace réel (en plus de l'espace réciproque), cela a permet d'étudier le transport des phonons et ainsi de la chaleur. La théorie généralisée de Ridley est toujours utilisée avec des particules de simulations qui interagissent les unes avec les autres directement. Les règles de conservation de l'énergie et de la quantité de mouvement sont rigoureusement respectées. L'effet des processus Umklapp sur la quantité de mouvement totale des phonons est fidèlement traduit; tout comme l'effet des interactions sur les directions des phonons, grâce à une procédure prenant en compte les directions vectorielles respectives lors d'une interaction, au lieu, de la distribution aléatoire usuellement utilisée. Les résultats préliminaires montrent la limite de l'équation analytique de conduction de la chaleur.

A breed-and-burn molten salt reactor (BBMSR) concept is proposed to address the Generation IV fuel cycle sustainability objective in a once-through cycle with low enrichment and no reprocessing. The BBMSR uses separate fuel and coolant molten salts, with the fuel contained in assemblies of individual tubes that can be shuffled and reclad periodically to enable high burnup. In this dual-salt configuration, the BBMSR may overcome several limitations of previous breed-and-burn (B$\&$B) designs to achieve high uranium utilisation with a simple, passively safe design. A central challenge in design of the BBMSR fuel is balancing the neutronic requirement of large fuel volume fraction for B$\&$B mode with the thermal-hydraulic requirements for safe and economically competitive reactor operation. Natural convection of liquid fuel within the tubes aids heat transfer to the coolant, and a systematic approach is developed to efficiently model this complex effect. Computational fluid dynamics modelling is performed to characterise the unique physics of the system and produce a new heat transfer correlation, which is used alongside established correlations in a numerical model. A design framework is built around this numerical model to iteratively search for the limiting power density of a given fuel and channel geometry, applying several defined temperature and operational constraints. It is found that the trade-offs between power density, core pressure drop, and pumping power are lessened by directing the flow of coolant downwards through the channel. Fuel configurations that satisfy both neutronic and thermal-hydraulic objectives are identified for natural, 5$\%$ enriched, and 20$\%$ enriched uranium feed fuel. B$\&$B operation is achievable in the natural and 5$\%$ enriched versions, with power densities of 73 W/cm$^3$ and 86 W/cm$^3$, and theoretical uranium utilisations of 300 $\mathrm{MWd/kgU_{NAT}}$ and 25.5 $\mathrm{MWd/kgU_{NAT}}$, respectively. Using 20$\%$ enriched feed fuel relaxes neutronic constraints so a wider range of fuel configurations can be considered, but there is a strong inverse correlation between power density and uranium utilisation. The fuel design study demonstrates the flexibility of the BBMSR concept to operate along a spectrum of modes ranging from high fuel utilisation at moderate power density using natural uranium feed fuel, to high power density and moderate utilisation using 20$\%$ uranium enrichment.

Cilj  ove  doktorske  disertacije  je  bio  razvoj  brzih  i  pouzdanih  voltametrijskih  metoda zasnovanih na primeni jednostavnih i savremenih elektroda/senzora na bazi ugljeničnih materijala (ugljenične  paste  napravljene  od  grafitnog  praha  i  parafinskog  ulja  i  štampanih  ugljeničnih elektroda)  za  određivanje  H ₂O₂ u  odabranim  složenim  model  i  realnim  uzorcima.  U  tu  svrhu, ispitana je primenljivost različitih radnih elektroda. Amperometrijska  metoda  zasnovana  na  elektrodi  od  ugljenične  paste  (CPE)  zapreminski modifikovane  sa  5%  (m:m)  MnO2 je,  pri  optimizovanim  uslovima  i  pri  radnom  potencijalu  od 0,40 V  u  odnosu  na  zasićenu  kalomelovu  elektrodu  (ZKE)  u  fosfatnom  puferu  pH  7,50  kao pomoćnom elektrolitu, omogućila kvantifikaciju H ₂O₂ u opsegu koncentracija od 1,4 do 65 µg mL -1 sa  relativnom  standardnom  devijacijom  (RSD)  manjom  od  10%.  Ova  metoda  je  primenjena  za određivanje sadržaja H ₂O₂ u uzorcima podzemne vode iz centralnog Banata (Pokrajina Vojvodina, Srbija)  tretirane  Fentonovim  (Fe ²⁺ i  H ₂O₂ )  i  Fentonu-sličnim  (Fe ³⁺ i  H ₂O₂ )  reagensima  u  cilju uklanjanja  prirodnih  organskih  materija  (POM)  pri  čemu  su  korišćene  različite  početne koncentracije  gvožđa  i  različiti  odnosi  molarnih  koncentracija  gvožđa  i  H ₂O₂ .  Utvrđeno  je  da oksidaciono  stanje  gvožđe  (Fe ²⁺ ili  Fe ³⁺)  i  molarni  odnos  jona  Fe  i  H ₂O₂ utiču  na  stepen potrošnje/razgradnje  H ₂O₂u  podzemnoj  vodi  sa  visokim  sadržajem  POM.  Takođe,  u  slučaju Fentonu-sličnog  procesa,  za  sve  početne  koncentracije  Fe ³⁺ i  H ₂O_{2 ,}  signifikantna  količina  H ₂O₂ ostaje  neiskorišćena,  što  ukazuje  na  nižu  efikasnost  ovakvog  sistema u  poređenju  sa  Fentonovim procesom.Štampana  ugljenična  elektroda  (SPCE)  zapreminski  modifikovana  sa  MnO 2 kao medijatorom  je  primenjena  za  određivanje  sadržaja  H ₂O₂ u  toku  Fentonovog  (Fe ²⁺ ,  H₂O₂ )  i vidljivom  svetlošću  potpomognutog  foto-Fentonovog  (Fe ²⁺ ,  H ₂O₂ ,  hν)  procesa  uklanjanja neonikotinoidnog  insekticida  acetamiprida  (ACT).  Pri  optimizovanim  uslovima  (radni  potencijal 0,40  V  u  odnosu  na  ZKE,  fosfatni  pufer  pH  7,50  kao  pomoćni  elektrolit)  amperometrijskog određivanja  H ₂O₂ ,  postignuta  je  linearnost  u  opsegu  koncentracija  0,01–1,24  mmol  L-1(0,34– 42,2 µg mL -1) i vrednost RSD nije prelazila 4,2%. U ispitivanimuzorcima (nakon odgovarajućegpodešavanja pH vrednosti od 2,8 do 7,5 odmah nakon  uzorkovanja radi stopiranja ili maksimalnog usporavanja  procesa  oksidacije,  filtriranja,  zamrzavanja  i  odmrzavanja  neposredno  pre  merenja) sadržaj  H ₂O₂ je  određen  metodom  standardnog  dodatka  analiziranjem  odgovarajućih amperometrijskih  krivi.  Paralelna  HPLC-DAD  merenja  su  vršena  u  cilju  praćenja koncentracije/uklanjanja ACT. U slučaju foto-Fentonovog procesa (početne koncentracije 0,31; 2,0 i 3,0 mmol L -1 (70,0; 111,7 i 102,1 µg mL -1 ) za ACT, Fe²⁺ i H ₂O₂, redom) nakon 10 min H ₂O₂ je izreagovao, a može se smatrati da je ACT uklonjen nakon 5 min. U toku Fentonovog procesa ACT je  uklonjen  nakon  20  min  tretmana  i  oko  10%  početne  koncentracije  H ₂O₂ je  ostalo  u  sistemuneiskorišćeno.CPE  je  površinski  modifikovane  kompozitom  na  bazi  nanočestica  Pt  (<  5  nm)  i grafitizovanog  ugljenika  (Pt-C,  10%  Pt  na  Vulkanu  XC72)   etodom  nanošenja  kapi. Nemodifikovana  CPE  i  modifikovana  (Pt-C/CPE)  su   okarakterisane  primenom  SEM/EDS  i  CV merenja.  Pt-C/CPE  je  pokazala  izuzetne  elektrokatalitičke  osobine  u  pogledu  elektrohemijskeredoks  reakcije  H₂O₂ u  poređenju  sa  nemodifikovanom  CPE  u  fosfatnom  puferu  (0,1 mol  L -1 ;pH 7,50),  a  takođe  i  u  acetatnom  puferu  (0,1  mol  L -1 ;  pH  4,50)  kao   pomoćnim  elektrolitima. Prilikom  amperometrijskog  određivanja  H ₂O₂ primenom  Pt-C/CPE  u  model  sistemima, zadovoljavajuća linearnost je postignuta u koncentracionom opseguH₂O₂od 0,15 do 1,45 µg mL -1 ,dok su vrednosti GO iznosile 0,06 µg mL -1 (pH 7,50, radni potencijal 0,20 V) i 0,10 µg mL -1 (pH4,50,  radni  potencijal  0,50  V).  Optimizovane  analitičke  metode  su  primenjene  za  određivanje sadržaja H ₂O₂ u komercijalno dostupnim proizvodima za ličnu negu: rastvoru za dezinfekciju (pH 7,50)  i  rastvoru  za  čišćenje  kontaktnih  sočiva  (pH  4,50).  Amperometrijski  dobijeni  rezultati  su  u dobrom  slaganju  sa  rezultatima  dobijenim  primenom  tradicionalne  spektrofotometrijske  metode bazirane  na  titanijum-sulfatu  kao  reagensu  sa  određenim  koncentracijama  2,91%  i  2,94%  zadezinfekcioni rastvor i 3,04% i 3,17% za rastvor zakontaktna sočiva, redom. RSD je bila manja od 2%.  Postignuti  rezultati  su  u  dobrom  slaganju  sa  sadržajem  H₂O₂ deklarisanim  od  strane proizvođača (3%) u oba ispitivana uzorka. Pt-C/CPE je takođe testirana za praćenje koncentracije H₂O₂ u rastvoru za kontaktna sočiva u toku procesa njegove neutralizacije/razgradnje. Nakon 6 h procesa neutralizacije, 24,68  µg mL -1 je bila određena koncentracija H ₂O_{2 ,} što je ispod dozvoljeneH₂O₂ koncentracije u rastvoru za kontaktna sočiva imajući u vidu granicu koja izaziva iritaciju oka. CPE  je  površinski  modifikovana  višezidnim  ugljeničnim  nanocevima  (MWCNT)  i kompozitima MnO 2 -MWCNT ili Pt-MWCNT metodom nanošenja kapi radi pripreme jednostavnih, osetljivih i pouzdanih voltametrijskih senzora za  određivanje H ₂O₂ u odabranom uzorku. Rezultati SEM/EDS  analize  kompozitnih  materijala  su  potvrdili da  su  medijatori,  čestice  MnO 2 i  Pt, nasumično  raspoređeni na površini MWCNT i zastupljeni sa blizu 5% (m:m) u kompozitu izraženopreko Mn i Pt. CV merenja su vršena sa pripremljenim radnim elektrodama u acetatnom (pH 4,50), fosfatnom  (pH  7,50)  i  boratnom  (pH  9,18)  puferu  kako  bi  se  okarakterisalo  osnovno elektrohemijsko  ponašanje  H ₂O₂ i  odabrali  pogodni  radni  potencijali  za  amperometrijsko određivanje ovog ciljnog analita. Pt- WCNT/CPE je primenljiva za rad kako u fosfatnom puferu pH  7,50  tako  i  u  acetatnom  puferu  pH  4,50  V  kako  pri  negativnim  tako  i  pri  pozitivnim  radnimpotencijalima, pri  čemu su vrednosti RSD uglavnom ispod 2,5%. U slučaju MnO 2-MWCNT/CPE, na  potencijalu  0,30  V  i  višim  vrednostima,  oksidacioni  signali  H₂O₂ su  signifikantni  u  blago alkalnoj sredini (pH 7,50), pri pH 4,50 ova elektroda pokazuje nezadovoljavajuće ponašanje, dok  pri pH 9,18 ima prihvatljive performanse. Granice određivanja (GO) su bile u oblasti µg mL -1 . H ₂O₂ je  određen  u  spajkovanom  uzorku  mleka  metodom  standardnog  dodatka  nakon  odgovarajuće pripreme  uzorka  (pH  podešavanje  i  centrifugiranje)  i  primenom  optimizovane  amperometrijske procedure (acetatni pufer pH 4,50, radni  potencijal-0,75 V) koristeći Pt-MWCNT/CPE kao radnu elektrodu. RSD za tri  ponovljena merenja je iznosila 2,5%, dok je prinos metode bio nešto veći od 71%.Kompozitni materijali koji se sastoje od MWCNT i  čestica na bazi Pd (Pd-MWCNT) ili Pt (Pt-MWCNT) su primenjeni za pripremu zapreminski modifikovanih SPCE (Pd-MWCNT-SPCE i Pt-MWCNT-SPCE)  i  površinski  modifikovane  SPCE  (Pd-MWCNT/SPCE).  Ove  elektrode,  kao  i nemodifikovana  SPCE  i  MWCNT-SPCE,  su  okarakterisane primenom  CV  i  amperometrije  u fosfatnom puferu pH 7,50 radi određivanja H ₂O₂ . Pd-MWCNT-SPCE i Pd-MWCNT/SPCE su se pokazale  pogodnim  za  određivanje  H ₂O₂ na  radnim  potencijalima  između  -0,50  i  0,50  V,  a  PtMWCNT-SPCE na ispitivanim radnim potencijalima od -0,80 do 0,70 V. Ove  elektrode su zatim modifikovane  enzimom  glukoza  oksidazom  (GOx)  metodom  nanošenja  kapi  rastvora  GOx  i Nafion ® -a  na  njihovu  površinu,  pri  čemu  je  optimizovana  količina  nanetog  biofilma.  GOx/PdMWCNT-SPCE  je  pokazala  bolje  analitičke  performanse  za  određivanje  glukoze  u  poređenju  sa GOx/Pd- WCNT/SPCE.  Kao  optimalan  radni  potencijal  GOx/Pd-MWCNT-SPCE  je  odabranavrednost  potencijala  -0,40  V  u  odnosu  na  ZKE,  sa  zadovoljavajućom  linearnošću  u  ispitivanom opsegu  koncentracija  glukoze  od  0,16  do  0,97  mmol  L -1 (od  29,1  do  174  µg  mL -1),  dok  je  GO iznosila 0,14 mmol L -1 (25 µg mL-1 ). Optimizovana metoda zasnovana na GOx/Pd-MWCNT-SPCE je  uspešno  primenjena  za  određivanje  glukoze  u  uzorku  livadskog  meda.  Dobijeni  rezultati  su  u dobroj  saglasnosti  sa  onima  dobijenim  primenom  komercijalno  dostupnog  aparata  za  merenje glukoze. Pogodan radni potencijal za GOx/Pt-MWCNT-SPCE je bio -0,50 V u odnosu na ZKE, pri čemu je zadovoljavajuća linearnost postignuta u ispitivanom opsegu koncentracija glukoze od 65,8 do 260,6 µg mL -1 , sa GO 35 µg mL -1 . Optimizovana metoda zasnovana na GOx/Pt-MWCNT-SPCE je  uspešno  primenjena  za  određivanje  glukoze  u  u  uzorku  belog  grožđa  i  uzorku  tableta (Traubenzucker-bonbons),  pri  čemu  su  dobijeni  rezultati  u  dobroj  saglasnosti  sa  rezultatima dobijenim primenom Accu-Chek aparata.Na  osnovu  dobijenih  rezultata  može  se  zaključiti  da  su  razvijene  analitičke  metode  pre svega jednostavne, pouzdane i pogodne za dobijanje brzih informacija o sadržaju H ₂O₂ u različitim tipovima  uzoraka.  Svakako  odabir  pogodne  radne  elektrode,  kao  i  optimizacija  eksperimentalnih uslova su ključni faktori za uspešno određivanje H ₂O₂
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The aim of this doctoral dissertation was the development of fast and reliable voltammetric methods  based  on  the  application  of  simple  and  contemporary  electrodes/sensors  based  on carbonaceous materials (carbon paste made of graphite powder and paraffin oil and screen printed carbon electrodes) for the determination of H  ₂ O₂ in the selected complex model and real samples.For this purpose, applicability of different working electrodes was investigated.The  amperometric  method  based  on  carbon  paste  electrode  (CPE)  bulk- modified     with 5% (m:m) MnO 2 , under optimized conditions, with a working potential of 0.40 V vs. the saturated calomel  elect rode  (SCE)  and  a  phosphate  buffer  solution  (pH  7.50)  as  supporting  electrolyte, enabled the quantitation of H  ₂ O₂in the concentration interval from 1.4 to 65 µg mL −1 with a relative standard deviation (RSD) of less than 10%. This meth od was applied for the determination of the H ₂ O₂ consumption  in  samples  of  groundwater  fro m  the  Central  Banat  region  (Province  of Vojvodina, Serbia) treated by the Fenton (Fe ²⁺ and H ₂O₂ ) and Fenton-  like (Fe ³⁺and H ₂O₂ ) reagents to remove natural organic matter (NOM) at  differentinitial concentrations of iron species, and of their molar ratios to the initial concentration of H₂O₂ . It was found that the form of Fe (Fe ²⁺ or Fe ³⁺ )and the molar  ratio to H ₂O₂influenced the degree of the H ₂O₂ decomposition in the groundwater with high NOM content. Besides, in the case of the Fenton-like process, for all initial doses of Fe ³⁺ and H  ₂ O₂, a sign ificant amount of H  ₂ O₂ remained unused, whi ch also indicates a lower efficiency of such system compared to the Fenton process. Screen  printed  carbon  electrode  (SPCE)  bulk-modified  with  MnO  ₂ as  a  mediator  was applied  for  amperometric  determination  of  the  H  ₂ O₂ content  during  the  Fenton  (Fe ²⁺ ,  H  ₂ O₂ )  and  visible  light-assisted ,  photo-Fenton  (Fe ²⁺  ,  H  ₂ O₂ ,  hν)   based  removal  of  neonicotinoid  insecticide acetamiprid (ACT). Under  optimized conditions (working potential of 0.40 V vs. SCE, phosphate buffer  pH  7.50  as  supporting  electrolyte)  amperometric  determination  of  H  ₂ O₂ showed  a  linear dynamic range from 0.01 to 1.24 mmol L -1 (from 0.34 to 42.2 µg mL -1) and the RSD did not exceed 4.2%. In the investigated samples (after appropriate pH adjustment from 2.8 to 7.5 instantly after the sampling  to stop or maximum decelerate the oxidation processes, filtering, and storage of the deep- frozen sample with defrosting immediately before the measurements) the H  ₂ O₂  contents were determined by the standard addition method by analyzing the corresponding amperometric curves. Parallel HPLC-DAD measurements were performed to monito r the concentration/removal of ACT. In the case of the photo- Fenton process (initial concentrations: 0.31; 2.0 and 3.0 mmol L -1 (70.0; 111.7 and 102.1 µg mL -1 ) of ACT, Fe ²⁺ and H  ₂ O₂, respec tively) after 10 min of irradiation H  ₂ O₂ was  consumed  and  it  can  be  consi dered  that  ACT  was  removed  after  5  min.  During  the  Fenton process ACT was removed after 20 min of treatment and around 10% of the initial concentration of the H 2O2 remained still unused.CPE  was  surface  modified  with  a  composite  of  Pt  nanoparticles  (<  5  nm)  on  graphitized carbon (Pt-C, 10% Pt on Vulcan XC72) by simply dropcoating method. The unmodified CPE and the  modified  one  (Pt-C/CPE)  were  characterized  by   EM/EDS  and  CV  measurements.  The  PtC/CPE showed remarkable electrocatalytic propertiestoward the electrochemical redox reaction of H ₂ O₂ compared to  modified CPE in phosphate buffer (0.1 mol L -1 ; pH 7.50), as well in acetatebuffer  (0.1 mol  L -1 ; pH .50) supporting  electrolytes. Amperometry of  H2O2 in the concentration range from 0.15 to 1.45 µg mL -1 with the Pt-C/CPE showed acceptable linearity, while the obtained values of LOQs were 0.06 µg mL -1  (pH 7.50, working potential 0.20 V) and 0.10 µg mL -1 (pH 4 .50, working potential 0.50 V). The proposed analytical  methods were applied to the determination of the H 2O2 content in commercially available personal care products; i.e., disinfection (pH 7.50) and contact lens cleaning solutions (pH 4.50). The obtained amperometric results are in good agreement with those measured by traditional titanium sulfatereagent based spectrophotometric method with determined concentrations as 2.91% and 2.94%  for the disinfection product, and 3.04% and 3.17% for the contact lens solution, respectively. RSD was lower than 2%. The obtained results are in a good agreement with the amounts of the H  ₂ O₂ declared by producers (3%) in the both investigated samples. The Pt-C/CPE was also tested for monitoring of the H  ₂ O₂ residual concentration in contact lens  solution  during  its  neutralization/decomposition  rocess.  At  6  h  of   neutralization  treatment 24.68 µg mL -1 of the H  ₂ O₂ was  determined which is almost half of the allowedH2 O2 concentration in the case of the contact lens solution concerningthe limit of eye irritation. CPE  was  surface   modified  with  multiwalled  carbon  nanotubes  (MWCNT)  and  with composites of MnO ₂ -MWCNT or Pt-MWCNT by drop coating method to prepare simply, sensitive and reliable volta mmetric sensors for the determination of H  ₂ O₂ in selected sample. The results of the  SEM/ EDS  analysis  of  composite  materials  have  confirmed  that  the  mediators,  MnO ₂ and  Pt  articles, are randomly distributed on the surface of MWCNT and represent nearly 5% (m:m) of the composite expressed as Mn and Pt. CV measurements were performed  with prepared electrodes in acetate  (pH  4.50),  phosphate  (pH  7.50)  and  borate  (pH  9.18)  buffers  to  characterize  the  basic electrochemical  behavior  of  H  ₂ O₂ and  to  select  the  working  potentials  suitable  for  amperometric determination  of  this  target  analyte.  The  Pt-MWCNT/CPE  performs  well  in  phosphate  buffer pH .50 and acetate buffer solution pH 4.50 in the  negative as well as in the positive polarization range with RSD mainly lower than 2.5%. In case of MnO ₂ -MWCNT/CPE at  0.30 V and above the H ₂ O₂ oxidation signal is rem arkable in slightly alkaline media (pH 7.50), at pH 4.50 this electrode showed poor behavior and at pH 9.18 offered acceptable performance. LOQs were in the µg mL -1 concentration  range.  H ₂ O₂ was  determined  in  a  spiked  milk  sample  by  standard addition  method after  appropriate  sample  preparation  (pH  adjustment and  centrifugation)  and  using  optimized amperometric p rocedure (acetate buffer pH 4.50, working potential -0.75 V) by Pt-MWCNT/CPE as a working electrode. RSD for three repeated measurements was 2.5%, while the recovery of the method was a bit higher than 71%. The  composite  materials  consisting  of  MWCNT  and  Pd  (Pd-MWCNT)  or  Pt  containing particles  (Pt-WCNT)  were  applied  to  the  preparation  of  bulk- modified  SPCEs  (Pd-MWCNTSPCE and Pt-MWCNT-SPCE) and surface modifiedSPCE (Pd- MWCNT/SPCE). These electrodes, as well as unmodified SPCE and MWCNT-SPCE,  were characterized by CV and  amperometry  in phosphate  buffer  solution  of  pH  7.50  for  the  H  ₂ O₂ determination.  Pd-MWCNT-SPCE  and  PdMWCNT/SPCEare convenient for the etermination of H 2O2 at working potentials from -0.50 to 0.50 V, and Pt-MWCNT-SPCE at investigated working potentials in the range from -0.80 to 0.70 V. These electrodes were then modified with glucose  oxidase (GOx) by drop coating a solution of GOxand Nafion ® on their surface, whereby the applied amount of biococktail was optimized. GOx/PdMWCNT-SPCE  showed  better  analytical  performance  for  glucose  determination  in  comparison with  GOx/Pd-MWCNT/SPCE.  The  optimal  working  potential  for  GOx/Pd-MWCNT- SPCE  was -0.40 V vs. SCE and  satisfactory linearity was obtained in the investigated glucose concentration range from 0.16 to 0.97 mmol L -1 (from 29.1 to 174  µg mL -1 ), hile the LOQ was 0.14 mmol L -1 (25 µg mL -1 ). The optimized method based on GOx/Pd-MWCNT-SPCE was successfully applied to the determination of glucose in multifloral honey sample.  The results are in a good agreement with those  obtained by commercially available equipment for determination of glucose. Optimal working potential  for  GOx/Pt-MWCNT-SPCE  was  -0.50  V  vs.  SCE,  and  the   satisfactory  linearity  was obtained in the investigated concentration range ofglucose from 65.8 to 260.6  µg mL -1 , with LOQ of 35  µg mL -1 . The optimized method based on GOx/Pt- MWCNT-SPCE was successfully applied for determination of glucose in white grape and glucose tablets (Traubenzucker-bonbons) samples, whereby  the  obtained  results  were  in  a  good  agreement  with  the  results  obtained  by  Accu-Chek device. Based on the results, the developed analytical methods are first of all simple, reliable and suitable  for  obtaining  fast  information  about  the  content  of  H ₂O₂ in  different  types  of  samples. Certainly the selection of a suitable working electrode, as well as the optimization of experimental conditions are key factors for the successful determination of H₂O₂ .

S tím, jak se neustále vyvíjejí nové technologie pro energeticky náročná průmyslová odvětví, stávající zařízení postupně zaostávají v efektivitě a produktivitě. Tvrdá konkurence na trhu a legislativa v oblasti životního prostředí nutí tato tradiční zařízení k ukončení provozu a k odstavení. Zlepšování procesu a projekty modernizace jsou zásadní v udržování provozních výkonů těchto zařízení. Současné přístupy pro zlepšování procesů jsou hlavně: integrace procesů, optimalizace procesů a intenzifikace procesů. Obecně se v těchto oblastech využívá matematické optimalizace, zkušeností řešitele a provozní heuristiky. Tyto přístupy slouží jako základ pro zlepšování procesů. Avšak, jejich výkon lze dále zlepšit pomocí moderní výpočtové inteligence. Účelem této práce je tudíž aplikace pokročilých technik umělé inteligence a strojového učení za účelem zlepšování procesů v energeticky náročných průmyslových procesech. V této práci je využit přístup, který řeší tento problém simulací průmyslových systémů a přispívá následujícím: (i)Aplikace techniky strojového učení, která zahrnuje jednorázové učení a neuro-evoluci pro modelování a optimalizaci jednotlivých jednotek na základě dat. (ii) Aplikace redukce dimenze (např. Analýza hlavních komponent, autoendkodér) pro vícekriteriální optimalizaci procesu s více jednotkami. (iii) Návrh nového nástroje pro analýzu problematických částí systému za účelem jejich odstranění (bottleneck tree analysis – BOTA). Bylo také navrženo rozšíření nástroje, které umožňuje řešit vícerozměrné problémy pomocí přístupu založeného na datech. (iv) Prokázání účinnosti simulací Monte-Carlo, neuronové sítě a rozhodovacích stromů pro rozhodování při integraci nové technologie procesu do stávajících procesů. (v) Porovnání techniky HTM (Hierarchical Temporal Memory) a duální optimalizace s několika prediktivními nástroji pro podporu managementu provozu v reálném čase. (vi) Implementace umělé neuronové sítě v rámci rozhraní pro konvenční procesní graf (P-graf). (vii) Zdůraznění budoucnosti umělé inteligence a procesního inženýrství v biosystémech prostřednictvím komerčně založeného paradigmatu multi-omics.

The role of palladium in carbon-oxygen and carbon-selenium bond forming processes has been investigated with particular emphasis on the postulated intermediacy of organopalladium(IV) species. Reactions of the diorganopalladium(II) complexes PdMeR(L\(_2\)) [R = Me, 4-tolyl (Tol); L\(_2\) = 2,2'-bipyridirle (bpy), N,N,N',N'-tetramethylethylenediamine (tmeda)] with diaroyl peroxides (ArCO\(_2\))\(_2\) [Ar = Ph, 4-CF\(_3\)C\(_6\)H\(_4\) (Ar\(_F\))] were investigated using variable temperature \(^1\)H NMR spectroscopy, revealing a complex series of reactions. The complexes Pd\(^{II}\)MeR(L\(_2\)) are predicted to undergo initial oxidative addition of (ArCO\(_2\))\(_2\) to give an unobserved Pd(IV) intermediate, Pd\(^{IV}\)(O\(_2\)CAr)\(_2\)MeR(L\(_2\))', which immediately takes part in an exchange reaction with the reagents Pd\(^{II}\)MeR(L\(_2\)) to form the observed intermediates Pd\(^{II}\)(O\(_2\)CAr)R(L\(_2\)) and Pd\(^{IV}\)(O\(_2\)2CAr)Me\(_2\)R(L\(_2\)) (except in the case of R = Tol and L\(_2\) = tmeda, where no Pd(IV) intermediate was observed). Decomposition of Pd\(^{IV}\)(O\(_2\)CAr)Me\(_2\)R(L\(_2\)) then occurred via reductive elimination of carbon-carbon bonds with absence of carbon-oxygen coupling. Carbon-oxygen coupling to form R-O\(_2\)CAr occurred from the reaction of monoorganopalladium(II) species Pd\(^{II}\)(O\(_2\)CAr)R(L\(_2\)) with (ArCO\(_2\))\(_2\), with concurrent formation of Pd\(^{II}\)(O\(_2\)CAr)\(_2\)(L\(_2\)). The exception was the reaction of Pd\(^{II}\)(O\(_2\)CAr)Tol(tmeda) with (ArCO\(_2\))\(_2\), which proceeded in a 2:1 ratio of reactants to form 4,4'-bitolyl and Pd\(^{II}\)(O\(_2\)CAr)\(_2\)(tmeda). Observed PdII and Pd(IV) intermediates and products of the reactions were also prepared by independent syntheses. Attempts to prepare Pd\(^{IV}\)(O\(_2\)CAr)\(_2\)MeR(bpy) were unsuccessful. The use of palladium and platinum complexes incorporating an intramolecularly coordinating `NCN-pincer' ligand, [C\(_6\)H\(_3\)(CH\(_2\)NMe\(_2\))\(_2\)-2,6]\(^-\), as a potential means of preparing stable models for Pd(IV) intermediates has been investigated. No reaction was observed between Pd\(^{II}\)(O\(_2\)CPh)(NCN) and (PhCO\(_2\))\(_2\), while the reaction with the platinum analogue resulted in formation and isolation of the stable complex mer-Pt\(^{IV}\)(O\(_2\)CPh)\(_3\)(NCN). The reactions of M\(^{II}\) (O\(_2\)CPh)(NCN) (M = Pd, Pt) with iodomethane resulted in formation of M\(^{II}\) I(NCN) and Me-O\(_2\)CPh in a 1:1 ratio. Low temperature \(^1\)H NMR spectroscopic studies revealed the intermediacy of a Pt(IV) species, cis-Pt\(^{IV}\)(O\(_2\)CPh)2Me(NCN), but Pd(IV) intermediates were not observed. The complex cis-Pt\(^{IV}\)(O\(_2\)CPh)\(_2\)Me(NCN) has been isolated from the reaction of Pt\(^{II}\)(O\(_2\)CPh)(NCN) with excess Ag[O\(_2\)CPh] and iodomethane, and was found to decompose via first-order kinetics to form Pt\(^{II}\)(O\(_2\)CPh)(NCN) and Me-O\(_2\)CPh. The reaction of Pt\(^{II}\)Tol(NCN) with (PhCO\(_2\))\(_2\) led to the formation of cis-Pt\(^{IV}\)(O\(_2\)CPh)\(_2\)Tol(NCN). This species has been isolated from the reaction of PtI\(_2\)Tol(NCN) with Ag[O\(_2\)CPh] and found to be resistant to decomposition. Studies of the analogous palladium chemistry were not feasible due to the instability of Pd\(^{II}\)Tol(NCN). Carbon-selenium bond-forming reactions at palladium were studied as potential models for carbon-oxygen coupling. The complexes Pd\(^{II}\)MeAr(bpy) [Ar = Tol, 4-anisyl (Anis)] were found to react with bis(4-chlorophenyl) diselenide [(CIC\(_6\)H\(_4\)Se)\(_2\)] to form trans-Pd\(^{IV}\)(SeC\(_6\)H\(_4\)Cl)\(_2\)MeAr(bpy), in a rare example of reversible oxidative addition. The Pd(IV) intermediate decomposed by both carbon-carbon and methyl-selenium coupling, with the absence of aryl-selenium coupling. Reactions of Pd\(^{II}\)MeR(tmeda) (R = Me, Tol) with (CIC\(_6\)H\(_4\)Se)\(_2\) led to the formation of products arising from both carbon-carbon and carbon-selenium coupling. Palladium(IV) species are postulated as intermediates but have not been observed. Reactions of Pd\(^{II}\)MeR(dmpe) [R = Me, Tol; dmpe = 1,2-bis(dimethylphosphino)ethane] with (CIC\(_6\)H\(_4\)Se)\(_2\) resulted in carbon=selenium coupling only. The reaction of Pd\(^{II}\)MeTol(dmpe) with one equivalent of (CIC\(_6\)H\(_4\)Se)\(_2\) gave Me-SeC\(_6\)H\(_4\)Cl and Pd\(^{II}\)(SeC\(_6\)H\(_4\)Cl)Tol(dmpe) as the major products. However, addition of a second equivalent of (CIC\(_6\)H\(_4\)Se)\(_2\) resulted in aryl-selenium coupling, from the reaction of Pd\(^{II}\)(SeC\(_6\)H\(_4\)Cl)Tol(dmpe) with (CIC\(_6\)H\(_4\)Se)\(_2\). X-ray structural studies are reported for Pd(O\(_2\)CPh\(_2\)(bpy), Pd(O\(_2\)CAr)\(_2\)(tmeda) (Ar = Ph, Ar\(_F\)), Pd(O\(_2\)CPh)Tol(bpy), M(O\(_2\)CPh)(NCN) (M = Pd, Pt), Pt(O\(_2\)CPh)\(_3\)(NCN), Pt(O\(_2\)CPh)\(_2\)R(NCN) (R = Tol, Me) and Pd(SeC\(_6\)H\(_4\)Cl)Me(dmpe). Observations of the reactivity of M(II) and M(IV) (M = Pd; Pt) complexes have led to a better understanding of the possible role of Pd(IV) in carbon-oxygen bond forming processes in reactions catalysed by palladium complexes.

碩士
國立屏東科技大學
環境工程與科學系所
99
Titanium dioxide (TiO2) is one of the most widely used catalysts. However, it requires ultraviolet light to enhance its efficiency. The recombination of electron and hole is one of the problems. Carbon nanotubes (CNT) has the mechanical properties of high strength and high chemical stability; so, the composite materials of CNT/TiO2 were common used for the photocatalysis of water and air pollutants. In this study, titanium ioxide doped with Multi-Walled Carbon Nanotubes (MWCNT) and Single-Walled Carbon Nanotubes (SWCNT) using different amounts (0.1, 0.2, 0.5 g) were prepared for the degradation of methylene blue. Different experimental factors including exposure times, light sources, batch or circulatory systems were conducted to evaluate the photocatalytic efficiency of methylene blue solutions. The best experimental parameters were applied to study the degradation of pentachlorophenol (PCP). Degradation rates, toxicity, and chloride ion concentration were also investigated. The results of X-ray diffraction (XRD) analysis confirmed that the catalyst used in this study was anatase as the major crystal. The results of scanning electron microscopy (SEM) showed the existence of MWCNT and SWCNT in various tubular structures. Different types of TiO2 surface were showed on the different amounts used. Fourier transform infrared spectroscopy (FT-IR) analysis showed that 0.2 g MWCNT will produce the most hydroxyl radicals. The highest photocatalytic efficiency (99%) was found using 0.2 g MWCNT/TiO2 under 8 hours of natural daylight exposure. With 0.2 g MWCNT/TiO2 under xenon lamp reached 85% of degradation rate in 8 hours. Using visible light and 0.2 g MWCNT/TiO2 showed 70% of degradation rate. In the circulation treatment system, only 18 % of degradation rate was reached using 0.5 g MWCNT / TiO2. The best experiment conditions with 0.2 g MWCNT/TiO2 were used, and the degradation efficiency of PCP was up to 61%.

Thesis. (M.Tech. (Chemistry)) -- Vaal University of Technology, 2011.
Bis(acetylacetonato)oxovanadium(IV), Manganese(III) acetylacetonate, Co-Zn and Co-Al were prepared as catalyst precursors for the synthesis of carbon materials in a catalytic chemical vapor deposition (CCVD) reactor. The carbon materials produced were characterized with Raman spectroscopy, Scanning electron microscope (SEM), Energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), High resolution transmission electron microscopy (TEM) and Thermogravimetric analysis, (TGA). Carbon material prepared from bis(acetylacetonato)oxovanadium(IV) catalyst precursor showed the presence of carbon spheres with average diameter of 104μm together with small traces of carbon nanotubes or amorphous carbon. Synthesis of bis(acetylacetonato)oxovanadium(IV) catalyst precursor yielded approximately 92% of carbon material. Carbon material prepared from Manganese(III) acetylacetonate catalyst precursor showed the presence of carbon spheres with diameter of 87.5μm. Synthesis of Manganese(III) acetylacetonate catalyst precursor yielded approximately 97% of carbon material. Carbon material produced from Co-Zn and Co-Al catalyst precursors showed the presence of carbon nanotubes with small amounts of amorphous carbon. The use of Co-Zn catalyst precursor yielded approximately 80% of carbon nanotubes, whereas Co-Al catalyst precursor yielded approximately 98% of carbon nanotubes.
Vaal University of Technology; NRF; SASOL

Taking into account the expected increase in global energy demands and increasing climate change issues, there is a pressing need to develop new environmentally sustainable energy systems. Nuclear energy will play a major role in being part of the energy mix since it offers a relatively clean, safe and reliable source of electrical energy. However, opportunities for building new generation nuclear systems will depend on their economic and safety attractiveness as well as their flexibility in design to adapt in different countries and situations. Keeping these objectives in mind, a framework for international cooperation was set forth in a charter of Generation IV International Forum (GIF) (GIF Charter, 2002) and six design concepts were selected for further development. To achieve high thermal efficiencies of up to 45 ??? 50%, the use of SuperCritical Fluids (SCFs) as working fluids in heat transfer cycles is proposed Generation IV designs. An important aspect towards development of SCF applications in novel Gen IV Nuclear Power Plant (NPP) designs is to understand the thermodynamic behavior and prediction of Heat Transfer Coefficients (HTCs) at supercritical (SC) conditions. In addition to the nuclear power industry applications; SCFs are also expected to play a vital role in a number of other important technologies such as refrigeration systems, and geothermal systems, to name a few. Given the potential for vast number of applications of SCFs in industry, the objective of this work was to gain an understanding on the behavior of SCFs and to develop a fundamental knowledge of the heat-transfer processes and correlations for SC Water and SC CO2 flowing in bare circular tubes. Experimental datasets for SC Water and SC CO2 were compiled and used to obtain a basic 1-D empirical correlation that can predict HTC in bare circular tubes during the transient phases. The accuracy of these correlations was also analyzed using statistical techniques. Limitations and applications for 1-D correlations are discussed as well. The new correlations showed promising results for HTC and Tw calculations for the reference dataset with uncertainty of about ??25% for HTC values and about ??10-15% for the calculated wall temperature.

Research Doctorate - Doctor of Philosophy (PhD)
Carbon dioxide (CO₂) capture from flue gas using aqueous amine solutions is considered as one of the mature and most effective techniques among other carbon capture technologies. In addition to CO₂ and depending on the sulfur content of the fossil fuels, different amounts of SO₂ are present in flue gas resulting from the combustion of fuels in thermal power plants. Sulfur dioxide is known to interfere in CO₂ capture in the amine-based post combustion capture (PCC) process from flue gas. The focus of this project is to investigate the interactions of S(IV) species with aqueous amine solutions. The results of this study have been applied to the development of an amine-based PCC technique that is capable of capturing SO₂ in a single stream normally used to capture CO₂. After a brief introduction (Chapter 1), a broad literature review is presented, which covers all of the reactions of S(IV) species in aqueous amine solution (Chapter 2). A comprehensive investigation of S(IV) speciation in aqueous solution over a wide range of pH was conducted by employing ultraviolet spectrophotometric titrations. As a result, the equilibrium constants of the reactions of S(IV) species in aqueous solutions were accurately determined. Further, an additional equilibrium in the solution, the protonation of disulfite, was identified and quantified for the first time. The molar absorption of S(IV) species have also been reported over the studied wavelength range (Chapter 3). A problem was encountered in the data analysis step of the spectrophotometric titration study of S(IV) speciation in aqueous solution. Since high concentrations of sulfite were required to achieve a measurable amount of disulfite formation, the recorded absorbances at some wavelengths exceeded the linear absorption range of the instrument. All such data points were excluded from the analysis. Therefore, an innovative adaptation of the traditional linear regression method was developed in order to use all available information in the analysis while ignoring the missing values. The algorithm is based on the insight that multivariate linear regression can be formulated as a set of individual univariate linear regressions. All available information is used and the calculations are explicit (Chapter 4). In another study the possible interaction of S(IV) species with monoethanolamine (MEA) in aqueous solutions at high temperature was investigated by following the ¹H-NMR spectrum of the solution. The ¹H-NMR spectra did not show any interaction between S(IV) species and the amine. As there is no direct interaction between SO₂ and MEA, the impact of increasing amounts of accumulated SO₂ on the cyclic capacity of the MEA solution in CO₂ capture was modelled. Moreover, the impact of similar conditions on the reaction rate of CO₂ absorption in the solution was simulated (Chapter 5). Finally, based on the understanding of the physical and chemical properties of SO₂ absorption into aqueous amine solutions, an improved CO₂ capture process has been designed that uses a single solvent and is SO₂ tolerant. SO₂ absorption is carried out in the bottom of the absorber column into a bleed stream from the bulk solvent in which a recycle flow allows the absorbent to be near saturation in SO₂. Principles underlying the concept, specifically kinetic selectivity of SO₂ absorption over CO₂ and reactivity with amines, have been studied in the laboratory. There are clear advantages to a CO₂ capture process that is able to restrict the effects of SO₂ to only a fraction of the solvent with minimum disruption to the carbon capture process. In addition, the new design will result in reduced complexity and cost compared to existing options for SO₂ treatment (Chapter 6).

Niniejsza rozprawa doktorska dotyczy optymalizacji układów fotoelektrochemicznych, zdolnych do inicjowanej światłem redukcji dwutlenku węgla do alternatywnych paliw czy związków chemicznych, w konwencjonalnych warunkach ciśnienia i temperatury. Głównym komponentem otrzymanych i scharakteryzowanych w pracy fotokatod jest półprzewodnika typu p, tlenek miedz(I) (Cu2O). Praca ma układ klasyczny, współtworzony przez część literaturową i eksperymentalną. Dwa pierwsze rozdziały stanowią wprowadzenie i uzasadnienie do podjętej w pracy tematyki badawczej. Ukazują one zarówno podejście elektrochemiczne, jak i fotoelektrochemiczne do procesu redukcji dwutlenku węgla. Kolejno, opisane zostały podstawy fizykochemiczne materiałów półprzewodnikowych w kontekście potencjalnych zastosowań (foto)elektrochemicznych. W celu uzyskania szerokiego spektrum wiedzy na temat właściwości stosowanych materiałów w procesie konwencjonalnej, elektrochemicznej oraz fotoelektrochemicznej redukcji CO2, wykonana została ich analiza w oparciu o wybraną literaturę naukową ze szczególnym uwzględnieniem miedzi, tlenku miedzi(I) oraz tlenku miedzi(II). Pozwoliło to w późniejszym toku pracy doktorskiej na opracowanie i optymalizację metodyki otrzymywania Cu2O wykazującego pożądane właściwości strukturalne czy fotoelektrochemiczne. W części literaturowej poruszona została także kwestia (foto)stabilności, oporności na korozję tlenku miedzi(I). W konsekwencji przedstawione zostały potencjalne sposoby ochrony stosowanego półprzewodnika typu p ze szczególnym uwzględnieniem zewnętrznej warstwy pokrywającej. Ponadto część teoretyczna pracy uwzględnia opis stosowanych metod/technik badawczych.

La dernière décennie a connu un intérêt croissant pour les problèmes posés par les variables instrumentales faibles dans la littérature économétrique, c’est-à-dire les situations où les variables instrumentales sont faiblement corrélées avec la variable à instrumenter. En effet, il est bien connu que lorsque les instruments sont faibles, les distributions des statistiques de Student, de Wald, du ratio de vraisemblance et du multiplicateur de Lagrange ne sont plus standard et dépendent souvent de paramètres de nuisance. Plusieurs études empiriques portant notamment sur les modèles de rendements à l’éducation [Angrist et Krueger (1991, 1995), Angrist et al. (1999), Bound et al. (1995), Dufour et Taamouti (2007)] et d’évaluation des actifs financiers (C-CAPM) [Hansen et Singleton (1982,1983), Stock et Wright (2000)], où les variables instrumentales sont faiblement corrélées avec la variable à instrumenter, ont montré que l’utilisation de ces statistiques conduit souvent à des résultats peu fiables. Un remède à ce problème est l’utilisation de tests robustes à l’identification [Anderson et Rubin (1949), Moreira (2002), Kleibergen (2003), Dufour et Taamouti (2007)]. Cependant, il n’existe aucune littérature économétrique sur la qualité des procédures robustes à l’identification lorsque les instruments disponibles sont endogènes ou à la fois endogènes et faibles. Cela soulève la question de savoir ce qui arrive aux procédures d’inférence robustes à l’identification lorsque certaines variables instrumentales supposées exogènes ne le sont pas effectivement. Plus précisément, qu’arrive-t-il si une variable instrumentale invalide est ajoutée à un ensemble d’instruments valides? Ces procédures se comportent-elles différemment? Et si l’endogénéité des variables instrumentales pose des difficultés majeures à l’inférence statistique, peut-on proposer des procédures de tests qui sélectionnent les instruments lorsqu’ils sont à la fois forts et valides? Est-il possible de proposer les proédures de sélection d’instruments qui demeurent valides même en présence d’identification faible? Cette thèse se focalise sur les modèles structurels (modèles à équations simultanées) et apporte des réponses à ces questions à travers quatre essais. Le premier essai est publié dans Journal of Statistical Planning and Inference 138 (2008) 2649 – 2661. Dans cet essai, nous analysons les effets de l’endogénéité des instruments sur deux statistiques de test robustes à l’identification: la statistique d’Anderson et Rubin (AR, 1949) et la statistique de Kleibergen (K, 2003), avec ou sans instruments faibles. D’abord, lorsque le paramètre qui contrôle l’endogénéité des instruments est fixe (ne dépend pas de la taille de l’échantillon), nous montrons que toutes ces procédures sont en général convergentes contre la présence d’instruments invalides (c’est-à-dire détectent la présence d’instruments invalides) indépendamment de leur qualité (forts ou faibles). Nous décrivons aussi des cas où cette convergence peut ne pas tenir, mais la distribution asymptotique est modifiée d’une manière qui pourrait conduire à des distorsions de niveau même pour de grands échantillons. Ceci inclut, en particulier, les cas où l’estimateur des double moindres carrés demeure convergent, mais les tests sont asymptotiquement invalides. Ensuite, lorsque les instruments sont localement exogènes (c’est-à-dire le paramètre d’endogénéité converge vers zéro lorsque la taille de l’échantillon augmente), nous montrons que ces tests convergent vers des distributions chi-carré non centrées, que les instruments soient forts ou faibles. Nous caractérisons aussi les situations où le paramètre de non centralité est nul et la distribution asymptotique des statistiques demeure la même que dans le cas des instruments valides (malgré la présence des instruments invalides). Le deuxième essai étudie l’impact des instruments faibles sur les tests de spécification du type Durbin-Wu-Hausman (DWH) ainsi que le test de Revankar et Hartley (1973). Nous proposons une analyse en petit et grand échantillon de la distribution de ces tests sous l’hypothèse nulle (niveau) et l’alternative (puissance), incluant les cas où l’identification est déficiente ou faible (instruments faibles). Notre analyse en petit échantillon founit plusieurs perspectives ainsi que des extensions des précédentes procédures. En effet, la caractérisation de la distribution de ces statistiques en petit échantillon permet la construction des tests de Monte Carlo exacts pour l’exogénéité même avec les erreurs non Gaussiens. Nous montrons que ces tests sont typiquement robustes aux intruments faibles (le niveau est contrôlé). De plus, nous fournissons une caractérisation de la puissance des tests, qui exhibe clairement les facteurs qui déterminent la puissance. Nous montrons que les tests n’ont pas de puissance lorsque tous les instruments sont faibles [similaire à Guggenberger(2008)]. Cependant, la puissance existe tant qu’au moins un seul instruments est fort. La conclusion de Guggenberger (2008) concerne le cas où tous les instruments sont faibles (un cas d’intérêt mineur en pratique). Notre théorie asymptotique sous les hypothèses affaiblies confirme la théorie en échantillon fini. Par ailleurs, nous présentons une analyse de Monte Carlo indiquant que: (1) l’estimateur des moindres carrés ordinaires est plus efficace que celui des doubles moindres carrés lorsque les instruments sont faibles et l’endogenéité modérée [conclusion similaire à celle de Kiviet and Niemczyk (2007)]; (2) les estimateurs pré-test basés sur les tests d’exogenété ont une excellente performance par rapport aux doubles moindres carrés. Ceci suggère que la méthode des variables instrumentales ne devrait être appliquée que si l’on a la certitude d’avoir des instruments forts. Donc, les conclusions de Guggenberger (2008) sont mitigées et pourraient être trompeuses. Nous illustrons nos résultats théoriques à travers des expériences de simulation et deux applications empiriques: la relation entre le taux d’ouverture et la croissance économique et le problème bien connu du rendement à l’éducation. Le troisième essai étend le test d’exogénéité du type Wald proposé par Dufour (1987) aux cas où les erreurs de la régression ont une distribution non-normale. Nous proposons une nouvelle version du précédent test qui est valide même en présence d’erreurs non-Gaussiens. Contrairement aux procédures de test d’exogénéité usuelles (tests de Durbin-Wu-Hausman et de Rvankar- Hartley), le test de Wald permet de résoudre un problème courant dans les travaux empiriques qui consiste à tester l’exogénéité partielle d’un sous ensemble de variables. Nous proposons deux nouveaux estimateurs pré-test basés sur le test de Wald qui performent mieux (en terme d’erreur quadratique moyenne) que l’estimateur IV usuel lorsque les variables instrumentales sont faibles et l’endogénéité modérée. Nous montrons également que ce test peut servir de procédure de sélection de variables instrumentales. Nous illustrons les résultats théoriques par deux applications empiriques: le modèle bien connu d’équation du salaire [Angist et Krueger (1991, 1999)] et les rendements d’échelle [Nerlove (1963)]. Nos résultats suggèrent que l’éducation de la mère expliquerait le décrochage de son fils, que l’output est une variable endogène dans l’estimation du coût de la firme et que le prix du fuel en est un instrument valide pour l’output. Le quatrième essai résout deux problèmes très importants dans la littérature économétrique. D’abord, bien que le test de Wald initial ou étendu permette de construire les régions de confiance et de tester les restrictions linéaires sur les covariances, il suppose que les paramètres du modèle sont identifiés. Lorsque l’identification est faible (instruments faiblement corrélés avec la variable à instrumenter), ce test n’est en général plus valide. Cet essai développe une procédure d’inférence robuste à l’identification (instruments faibles) qui permet de construire des régions de confiance pour la matrices de covariances entre les erreurs de la régression et les variables explicatives (possiblement endogènes). Nous fournissons les expressions analytiques des régions de confiance et caractérisons les conditions nécessaires et suffisantes sous lesquelles ils sont bornés. La procédure proposée demeure valide même pour de petits échantillons et elle est aussi asymptotiquement robuste à l’hétéroscédasticité et l’autocorrélation des erreurs. Ensuite, les résultats sont utilisés pour développer les tests d’exogénéité partielle robustes à l’identification. Les simulations Monte Carlo indiquent que ces tests contrôlent le niveau et ont de la puissance même si les instruments sont faibles. Ceci nous permet de proposer une procédure valide de sélection de variables instrumentales même s’il y a un problème d’identification. La procédure de sélection des instruments est basée sur deux nouveaux estimateurs pré-test qui combinent l’estimateur IV usuel et les estimateurs IV partiels. Nos simulations montrent que: (1) tout comme l’estimateur des moindres carrés ordinaires, les estimateurs IV partiels sont plus efficaces que l’estimateur IV usuel lorsque les instruments sont faibles et l’endogénéité modérée; (2) les estimateurs pré-test ont globalement une excellente performance comparés à l’estimateur IV usuel. Nous illustrons nos résultats théoriques par deux applications empiriques: la relation entre le taux d’ouverture et la croissance économique et le modèle de rendements à l’éducation. Dans la première application, les études antérieures ont conclu que les instruments n’étaient pas trop faibles [Dufour et Taamouti (2007)] alors qu’ils le sont fortement dans la seconde [Bound (1995), Doko et Dufour (2009)]. Conformément à nos résultats théoriques, nous trouvons les régions de confiance non bornées pour la covariance dans le cas où les instruments sont assez faibles.
The last decade shows growing interest for the so-called weak instruments problems in the econometric literature, i.e. situations where instruments are poorly correlated with endogenous explanatory variables. More generally, these can be viewed as situations where model parameters are not identified or nearly so (see Dufour and Hsiao, 2008). It is well known that when instruments are weak, the limiting distributions of standard test statistics - like Student, Wald, likelihood ratio and Lagrange multiplier criteria in structural models - have non-standard distributions and often depend heavily on nuisance parameters. Several empirical studies including the estimation of returns to education [Angrist and Krueger (1991, 1995), Angrist et al. (1999), Bound et al. (1995), Dufour and Taamouti (2007)] and asset pricing model (C-CAPM) [Hansen and Singleton (1982, 1983), Stock and Wright (2000)], have showed that the above procedures are unreliable in presence of weak identification. As a result, identification-robust tests [Anderson and Rubin (1949), Moreira (2003), Kleibergen (2002), Dufour and Taamouti (2007)] are often used to make reliable inference. However, little is known about the quality of these procedures when the instruments are invalid or both weak and invalid. This raises the following question: what happens to inference procedures when some instruments are endogenous or both weak and endogenous? In particular, what happens if an invalid instrument is added to a set of valid instruments? How robust are these inference procedures to instrument endogeneity? Do alternative inference procedures behave differently? If instrument endogeneity makes statistical inference unreliable, can we propose the procedures for selecting "good instruments" (i.e. strong and valid instruments)? Can we propose instrument selection procedure which will be valid even in presence of weak identification? This thesis focuses on structural models and answers these questions through four chapiters. The first chapter is published in Journal of Statistical Planning and Inference 138 (2008) 2649 – 2661. In this chapter, we analyze the effects of instrument endogeneity on two identificationrobust procedures: Anderson and Rubin (1949, AR) and Kleibergen (2002, K) test statistics, with or without weak instruments. First, when the level of instrument endogeneity is fixed (does not depend on the sample size), we show that all these procedures are in general consistent against the presence of invalid instruments (hence asymptotically invalid for the hypothesis of interest), whether the instruments are "strong" or "weak". We also describe situations where this consistency may not hold, but the asymptotic distribution is modified in a way that would lead to size distortions in large samples. These include, in particular, cases where 2SLS estimator remains consistent, but the tests are asymptotically invalid. Second, when the instruments are locally exogenous (the level of instrument endogeneity approaches zero as the sample size increases), we find asymptotic noncentral chi-square distributions with or without weak instruments, and describe situations where the non-centrality parameter is zero and the asymptotic distribution remains the same as in the case of valid instruments (despite the presence of invalid instruments). The second chapter analyzes the effects of weak identification on Durbin-Wu-Hausman (DWH) specification tests an Revankar-Harttley exogeneity test. We propose a finite-and large-sample analysis of the distribution of DWH tests under the null hypothesis (level) and the alternative hypothesis (power), including when identification is deficient or weak (weak instruments). Our finite-sample analysis provides several new insights and extensions of earlier procedures. The characterization of the finite-sample distribution of the test-statistics allows the construction of exact identificationrobust exogeneity tests even with non-Gaussian errors (Monte Carlos tests) and shows that such tests are typically robust to weak instruments (level is controlled). Furthermore, we provide a characterization of the power of the tests, which clearly exhibits factors which determine power. We show that DWH-tests have no power when all instruments are weak [similar to Guggenberger(2008)]. However, power does exist as soon as we have one strong instruments. The conclusions of Guggenberger (2008) focus on the case where all instruments are weak (a case of little practical interest). Our asymptotic distributional theory under weaker assumptions confirms the finite-sample theory. Moreover, we present simulation evidence indicating: (1) over a wide range cases, including weak IV and moderate endogeneity, OLS performs better than 2SLS [finding similar to Kiviet and Niemczyk (2007)]; (2) pretest-estimators based on exogeneity tests have an excellent overall performance compared with usual IV estimator. We illustrate our theoretical results through simulation experiment and two empirical applications: the relation between trade and economic growth and the widely studied problem of returns to education. In the third chapter, we extend the generalized Wald partial exogeneity test [Dufour (1987)] to non-gaussian errors. Testing whether a subset of explanatory variables is exogenous is an important challenge in econometrics. This problem occurs in many applied works. For example, in the well know wage model, one should like to assess if mother’s education is exogenous without imposing additional assumptions on ability and schooling. In the growth model, the exogeneity of the constructed instrument on the basis of geographical characteristics for the trade share is often questioned and needs to be tested without constraining trade share and the other variables. Standard exogeneity tests of the type proposed by Durbin-Wu-Hausman and Revankar-Hartley cannot solve such problems. A potential cure for dealing with partial exogeneity is the use of the generalized linear Wald (GW) method (Dufour, 1987). The GW-procedure however assumes the normality of model errors and it is not clear how robust is this test to non-gaussian errors. We develop in this chapter, a modified version of earlier procedure which is valid even when model errors are not normally distributed. We present simulation evidence indicating that when identification is strong, the standard GW-test is size distorted in presence of non-gaussian errors. Furthermore, our analysis of the performance of different pretest-estimators based on GW-tests allow us to propose two new pretest-estimators of the structural parameter. The Monte Carlo simulations indicate that these pretest-estimators have a better performance over a wide range cases compared with 2SLS. Therefore, this can be viewed as a procedure for selecting variable where a GW-test is used in the first stage to decide which variables should be instruments and which ones are valid instruments. We illustrate our theoretical results through two empirical applications: the well known wage equation and the returns to scale in electricity supply. The results show that the GW-tests cannot reject the exogeneity of mother’s education, i.e. mother’s education may constitute a valid IV for schooling. However, the output in cost equation is endogenous and the price of fuel is a valid IV for estimating the returns to scale. The fourth chapter develops identification-robust inference for the covariances between errors and regressors of an IV regression. The results are then applied to develop partial exogeneity tests and partial IV pretest-estimators which are more efficient than usual IV estimator. When more than one stochastic explanatory variables are involved in the model, it is often necessary to determine which ones are independent of the disturbances. This problem arises in many empirical applications. For example, in the New Keynesian Phillips Curve, one should like to assess whether the interest rate is exogenous without imposing additional assumptions on inflation rate and the other variables. Standard Wu-Durbin-Hausman (DWH) tests which are commonly used in applied work are inappropriate to deal with such a problem. The generalized Wald (GW) procedure (Dufour, 1987) which typically allows the construction of confidence sets as well as testing linear restrictions on covariances assumes that the available instruments are strong. When the instruments are weak, the GW-test is in general size distorted. As a result, its application in models where instruments are possibly weak–returns to education, trade and economic growth, life cycle labor supply, New Keynesian Phillips Curve, pregnancy and the demand for cigarettes–may be misleading. To answer this problem, we develop a finite-and large-sample valid procedure for building confidence sets for covariances allowing for the presence of weak instruments. We provide analytic forms of the confidence sets and characterize necessary and sufficient conditions under which they are bounded. Moreover, we propose two new pretest-estimators of structural parameters based on our above procedure. Both estimators combine 2SLS and partial IV-estimators. The Monte Carlo experiment shows that: (1) partial IV-estimators outperform 2SLS when the instruments are weak; (2) pretestestimators have an excellent overall performance–bias and MSE– compared with 2SLS. Therefore, this can be viewed as a variable selection method where the projection-based techniques is used to decide which variables should be instrumented and which ones are valid instruments. We illustrate our results through two empirical applications: the relation between trade and economic growth and the widely studied problem of returns to education. The results show unbounded confidence sets, suggesting that the IV are relatively poor in these models, as questioned in the literature [Bound (1995)].