Dissertations / Theses on the topic 'Gruppo IV'

Nel campo dei semiconduttori, lo studio delle proprietà spin dipendenti forniscono informazioni fondamentali per la realizzazione di dispositivi che uniscano spin, fotonica ed elettronica. In questi dispositivi l’informazione è codificata nel grado di libertà (DOF) dello spin, sfruttando l’accoppiamento spin-orbita (SOC) tra il momento angolare del fotone e lo spin del portatore. Ho concentrato la mia ricerca sullo studio del SOC con spettroscopia ottica in Si, Ge, Sn e loro leghe. Questi materiali possiedono proprietà promettenti per applicazioni di spintronica, tra cui lunghi tempi di vita e lunghezze di diffusione dello spin. I processi di fabbricazione aprono la strada all’ingegnerizzazione del bandgap e dello strain come DOF addizionali per sintonizzare i fenomeni spin-dipendenti. La spettroscopia ottica permette di superare i problemi delle misure elettriche, come la qualità dei contatti, che impediscono una stima corretta dei parametri cinetici. I pozzi quantici (QW), sono valide piattaforme per unire i DOF sopracitati e permettere la manipolazione dello spin con campi elettrici. Nei sistemi a QW che mancano della simmetria di inversione di punto o di quella strutturale (BIA/SIA), la degenerazione di spin è rimossa dai campi Dresselhaus o Rashba. In quanto campi magnetici, possono agire agiscono sullo spin cambiandone l’orientazione. La SIA può sorgere da un drogaggio asimmetrico. In questo caso, il dispositivo possiede anche un campo elettrico che può essere sfruttato. Infatti, con un campo elettrico esterno si può modulare il campo Rashba, manipolando lo spin. Questa possibilità è significativa per la spintronica, si pensi allo spin-FET, dove la tensione di gate seleziona l’orientazione dello spin e quindi lo stato on/off. Ho eseguito misure di fotoluminescenza (PL) su campioni costituiti da uno stack di 50 QW di Ge/Si0.15Ge0.85 cresciuto nella zona intrinseca di un diodo p-i-n. Il drogaggio asimmetrico introduce la SIA, permettendo di manipolare elettricamente lo spin. Tramite due contatti in Al, ho sintonizzato un campo elettrico esterno e studiato gli effetti sulla popolazione di spin tramite PL. Inoltre, un’analisi in funzione della potenza ha mostrato una dipendenza della polarizzazione della PL dalla pompa ottica. Ho studiato anche una singola modulation-doped QW Ge0.91Sn0.09/Ge. Il profilo di banda confina delle lacune e permette la formazione di un gas bidimensionale di lacune. La struttura asimmetrica introduce la SIA, permettendo di studiare meccanismi di conversione spin-carica. Tramite litografia ho realizzato una barra di Hall ed ho eseguito misure di effetto spin-Hall inverso, da cui ho potuto estrarre l’angolo di spin-Hall. Ho anche compiuto misure magneto-ottiche a 4K, sfruttando l’effetto Hanle, per ottenere il tempo di vita (T) del portatore, che risulta di pochi ns. L’effetto Hanle è stato applicato per la prima volta nei materiali del quarto gruppo in epistrati di Ge1-xSnx (sotto), e l’ho esteso alle QW, dimostrandosi una tecnica affidabile per determinare T. Ho studiato anche campioni di epistrato di Ge1-xSnx. Il contenuto di Sn varia da 0 a 10 %, e lo strain compressivo assicura una natura indiretta del bandgap. Ho estratto T e ho trovato un comportamento non banale al variare della percentuale di Sn, la cui origine può essere attribuita alla presenza di difetti del cristallo. Questi difetti sono dovuti possibilmente alla crescita fortemente fuori equilibrio necessaria per la realizzazione di campioni di Ge1-xSnx ricchi in Sn. Per concludere, in questa tesi mi sono occupato di misure ottiche per indagare il SOC in eterostrutture di materiali del IV gruppo. I risultati ottenuti sono un passo in avanti nell’investigazione della dinamica dello spin elettronico del gruppo IV e aprono la strada verso studi futuri sulla manipolazione elettro-ottica dello spin in tecnologie quantistiche basate sull’interazione spin-luce, come spin-FET, spin-laser
In the field of semiconductors, the study of spin-dependent properties provides fundamental information needed for the realization of devices that merge spin, photonic and electronic functionalities. In these devices the information is encoded in the spin degree of freedom (DOF), exploiting the interaction between the angular momentum of the photon and the carrier spin via the spin-orbit coupling (SOC). I focused on the study of SOC in Si, Ge, Sn and their alloys using optical spectroscopy. These materials possess promising properties for spintronics applications such as long spin lifetime, diffusion length and decoherence time. Notably, the advanced manufacture also opens the way to bandgap and strain engineering as further DOF to tune spin-dependent phenomena, whereas the application of optical spectroscopy allows to overcome typical problems of electrical measurements, e.g., the quality of contacts, that hamper the estimation of carrier kinetics parameters Quantum well (QW) systems are valid platforms to merge all the aforementioned DOF and to also introduce a way to manipulate the spin via electric fields. Indeed, in QW systems that possess bulk or structure inversion asymmetry (BIA/SIA), the spin degeneracy is removed due to the Dresselhaus or Rashba fields. As effective magnetic fields, they can act on the spin of a carrier, ultimately changing its orientation. SIA can arise from an asymmetric doping of the device. In this case, the device also possesses an intrinsic electric field, which can be of practical use for applications. Indeed, an external field can be applied to tune the Rashba field, achieving spin manipulation. This opportunity has a strong impact in spintronics devices, such as the spin-FET, where the gate voltage selects the orientation of the spin and switch between on/off states I carried out photoluminescence (PL) investigations on a stack of 50 Ge/Si0.15Ge0.85 QWs grown within the intrinsic region of a p-i-n diode. The asymmetric doping introduces the SIA, necessary for achieving electrical manipulation of the spin. Via a pair of Al contacts, I was also able to study the effect of a tunable external electric field on the spin population via continuous-wave as well as time-resolved PL. Additionally, a power dependent analysis unveiled a strong effect of the light pump on the polarization I also performed PL measurements on a single modulation-doped Ge0.91Sn0.09/Ge QW. The band edge profile confines holes in the well, resulting in the formation of a two-dimensional hole gas. The asymmetric structure introduces the SIA and allows for the observation of spin-to-charge conversion mechanisms in this 2D system. I patterned a Hall bar on the sample and performed inverse spin-Hall effect measurements, extracting the spin-Hall angle. I also performed magneto-optics measurement, namely the Hanle effect, to unveil the carrier lifetime (T) of the material, which is in the ns regime at 10 K. This optical technique was applied for the first time to group IV materials in Ge1-xSnx epilayers (below), and was extended also to the QW system, proving it to be a reliable and easy method to determine T I have also studied Ge1-xSnx epilayers. The Sn content was varied from 0 to 10 %, while the compressive strain ensured an indirect bandgap nature. I applied Hanle effect to extract T and I unveiled a non-trivial behaviour with the Sn content, whose origin is ascribed to the presence of crystal flaws possibly due to the strong out-of-equilibrium growth conditions required for the realization of Sn-rich Ge1-xSnx samples In conclusion, this thesis is devoted to an all-optical investigation of SOC in heterostructures of group IV materials. The results obtained here are a step forwards in the investigation of spin dynamics of electrons in group IV and pave the way to future exploration of electrical-optical manipulation of spins in quantum technologies based on spin-photon interaction such as spin-FETs and spin-lasers

Correlações do tipo processo-estrutura-propriedade de filmes têm sido objeto de extensos estudos já a várias décadas, tanto do ponto de vista científico como tecnológico. Mais recentemente, atenção crescente tem sido dada a filmes cada vez mais finos, principalmente para atender as necessidades de novas tecnologias. Para compreender melhor a correlação processo-estrutura, vários pesquisadores propuseram Modelos de Zonas Estruturais para filmes com espessuras, tipicamente, de algumas unidades a dezenas de micrometros. Neste trabalho, propomos Modelos de Zonas Estruturais para filmes finos de elementos do Grupo IV-B (Ti, Zr e Hf) e estudamos os mecanismos de formação da microestrutura dos filmes. Durante o desenvolvimento de nosso trabalho, curiosos aglomerados de grãos, com tamanhos de vários micrometros e com geometria fractal, foram observados nos filmes de Zr. As características geométricas dos aglomerados e os possíveis mecanismos que os originam e levam à sua evolução também são considerados aqui.
Correlations type processing-structure-property of films have been the subject of extensive studies for the last several decades, both from the point of view of science and technology. More recently, growing attention has been given to ever-thinner films, especially to satisfy the needs of newer technologies. To better understand the correlation processing-structure, many researchers have proposed Structure Zone Models for films typically a few to a few tens of micrometers thick. In this work, we propose Structure Zone Models for Group IV-B (Ti, Zr and Hf) thin films and study the microstructure forming mechanisms of the films. During the development of our work, intriguing grain aggregates several micrometers Jorge and with fractal geometry were observed in the Zr films. The geometrical characteristics of the aggregates, their possible origin and evolution mechanisms are also considered here.

Hoy en día, las organizaciones que no cuentan con información integrada, y por ende trabajan con las llamadas islas de información, no favorecen a las gerencias en la adecuada toma de decisiones, lo que genera en muchas ocasiones grandes pérdidas económicas a las compañias. El presente informe muestra cómo las necesidad intrínseca de la alta dirección de contar con información confiable, precisa e integrada ha hecho posible que la organización se integre a lo largo de las áreas. Por ende, se diferencia de la competencia mediante la implantación de un sistema de Planificación de los Recursos Empresariales (ERP), lo que permite otras ventajas, como la reducción de costos, el aumento de la productividad y la automatización de procesos, vital en una empresa que desea ser competitiva. La implementación del ERP Baan IV fuer realizada en el Grupo empresarial Vega, se llevó a cabo en respuesta a la problemática que tenía la organización con el uso de diferentes plataformas, arquitectura de red, lenguaje de programación y en resumidas cuentas: información diferente. Por lo tanto la implantación de un sistema integrado permitirá a la organización obtener una ventaja competitiva o en su defecto contribuir a alinearse comparativamente con sus competidores. De esta forma, se encontró en la organización la disponibilidad de una respuesta adecuada de información (a la medida de las necesidades), y una solución que permitiría la integración total de todas las operaciones con el fin de gestionar adecuadamente cada una de las áreas de la empresa.

Orientador: Roy E. Bruns
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica
Made available in DSpace on 2018-07-20T02:34:03Z (GMT). No. of bitstreams: 1 Oliveira_AnselmoElcanade_M.pdf: 3793179 bytes, checksum: 4423ac1d6f923cecf8f03df8273f0fd4 (MD5) Previous issue date: 1995
Mestrado

Nasza praca jest pierwszą w światowej nauce próbą odpowiedzi na pytanie o organizację grup gnostyckich, opartą na analizie wszystkich gnostyckich tekstów z Nag Hammadi, z uwzględnieniem świadectw zewnętrznych. Teksty z Nag Hammadi okazały się materiałem trudnym do jednoznacznej interpretacji, pozwoliły jednak znacznie poszerzyć dotychczasowy stan badań w interesującej nas kwestii. Stąd przytoczona we wstępie teza Julii Iwersen o ich nieprzydatności dla badań nad organizacją grupową została zupełnie sfalsyfikowana. Pierwszy wniosek, jaki płynie z naszych rozważań, jest taki, że o organizacji grup gnostyckich nie można mówić w sposób generalizujący. Rację zatem mieli w tym punkcie, niezależnie od konkluzji do których ostatecznie doszli, Adolf von Hamack i Heinz Kraft. Nie znaczy to jednak, że nie istnieje żadna wspólny fundament, na którym można by budować argumentację odnośnie do różnych grup. Ponieważ wszystkie znane nam teksty gnostyckie (to znaczy te, których myśl teologiczna może być uznana za gnostycką w świetle przyjętych przez nas kryteriów) zawierają elementy myśli chrześcijańskiej i/lub zostały nam przekazane przez chrześcijan, to - podobnie jak w wypadku apokryfów Starego Testamentu - musimy uznać je w pierwszym rzędzie właśnie za utwory chrześcijańskie. Nic nie zmusza nas do tego, aby uznawać że którykolwiek z nich, nawet jeśli nie zawiera cech ewidentnie chrześcijańskich, ma przed- czy pozachrześcijańskie pochodzenie. Jesteśmy w stanie wskazać środowisko, w którym tego typu teksty mogły powstać.

En el presente trabajo describimos el estudio de estas reacciones aplicadas a la preparación de derivados del sistema TpW (CO)z -L (L =ligando organometálico con elementos del IV grupo principal), con el objeto de comparar el componarniento del sistema del tungsteno con el del molibdeno, en parte estudiado por nosotros anteriormente.
We report the reactions of TpW(COh X (Tp = h7-C7H 7, X = Br, 1)with thc anionic species MPh3 - (Ph = C6 Hs ; M= Ge, Sn, Pb) leading to thesubstitution products TpW(C0hMPh3 (3). The compound 3d (M= Pb) couldnot be isolated due to its instability and was only detected spcctroscopically;3b (M= Ge) and 3c (M = Sn) were isolated as red crystals and caracterizedthrough elemental analysis and spectrometry (IR, 1H-NMR and MS).The reduction of TpW(COhl with Na/Hg in THF leads to the an10n[TpW (COhr (1), which also reacts with MPh3- (M = Si, Ge, Sn) forming3a (M = Si), 3b and 3c; 3a was detected only spectroscopically.

La reacción de Friedel-Crafts es un poderoso proceso de formación de enlaces carbono-carbono de gran importancia en síntesis orgánica. La aplicación de la versión asimétrica catalítica de esta reacción a la alquilación de arenos ricos en electrones, como indoles o pirroles, puede proporcionar acceso a importantes productos enantioméricamente enriquecidos alquilados y constituyen un tema de actual interés, ya que estos arenos se han identificado como estructuras "privilegiadas" o farmacóforos. Los complejos Zr(IV) y Hf(IV)-BINOL generados in situ han sido evaluados como catalizadores en la alquilación de Friedel-Crafts enantioselectiva de indoles y pirroles con diferentes cetonas α, β-insaturadas, así como en la alquilación de pirroles con diferentes tipos de los compuestos carbonilícos. Para la alquilación de Friedel-Crafts enantioselectiva de indoles con simples cetonas α,β- insaturadas no quelatantes se han utilizado como catalizadores complejos Zr(OtBu)4-(R)-3,3'-Br2-BINOL (L3) generados in situ. La reacción se lleva a cabo con muy buenos rendimientos (hasta 97%) y buena enantioselectividad (hasta 98% ee). Para hacerse una idea de la estructura del catalizador y los aspectos mecanísticos de la reacción, se investigó los espectros de RMN 1H del catalizador, así como experimentos de efectos no lineales (NLE) y estudios computacionales (DFT). La alquilación de Friedel-Crafts de pirroles con simples cetonas α,β- insaturadas no quelatantes. catalizada por Zr(OtBu)4-(R)-3,3'-Br2-5,5',6,6',7,7',8,8'-BINOL, da lugar a pirroles alquilados con buenos rendimientos y enantioselectividades de moderadas a muy buenas. También se ha desarrollado una estrategia eficaz para acceder a derivados de indol 2-sustituidos de forma enantioenriquecida. Esta estrategia se basa en una reacción catalítica asimétrica “one-pot” de Friedel-Crafts entre 4,7-dihidroindol y cetonas α,β-insaturadas, seguida de una oxidación de p-benzoquinona, utilizando el complejo Zr(OtBu)4-L5 dando lugar a buenos rendimientos y enantioselectividades moderadas. Las cetonas -trifluoro ,-insaturadas- se han utilizado como electrófilos en la alquilación de Friedel-Crafts enantioselectiva de indoles catalizada por el complejo Zr(OtBu)4-(R)-3,3'-Br2-BINOL (L3), proporcionando una variedad de indoles trifluorometilados quirales con buenos rendimientos (hasta 99%) y excelentes enantioselectividades (hasta 99% ee). (E)-1-aril-4-benciloxi-but-2-en-1-onas también pueden ser utilizadas como electrófilos en la reacción de Friedel-Crafts de indoles catalizada por el complejo Hf(OtBu)4-(R)-3,3'-Br2-BINOL (L3) para obtener indoles quirales con una cadena 1,4-funcionalizada. Los rendimientos y enantioselectividades van de buenos a excelentes para una gama de diferentes benciloximetilenonas y indoles. La alquilación de Friedel-Crafts de indoles con (E)-1,4-diaril-but-2-en-1,4-dionas catalizadas por complejos quirales de Hf(OtBu)4-(R)-6,6'-Br2-BINOL (L2) genera un centro estereogénico en  con respecto a uno de los grupos carbonilo. Esto puede considerarse como una inversión del patrón de reactividad normal o umpolung. La reacción se lleva a cabo con buenos rendimientos (hasta un 97%) y buenas enantioselectividades (hasta un 94%), independientemente de la naturaleza y la posición de los sustituyentes en las endionas o en el anillo de indol. Los (E)-4-oxo-4-fenilbutenoatos de alquilo también se han utilizado como electrófilos en la alquilación de Friedel-Crafts enantioselectiva de indoles utilizando el complejo Zr(OtBu)4-(R)-3,3'-Br2-BINOL (L3) como catalizador. En este caso, se forma el centro estereogénico en posición  al éster regioselectivamente, con buenos rendimientos y enantioselectividades. Se ha utilizado el complejos Zr(OtBu)4-(R)-3,3'-Br2-BINOL (L3) como catalizador la alquilación de Friedel-Crafts de pirroles con una variedad de diferentes 2,2,2-trifluoroacetofenonas para dar lugar a alcoholes terciarios teniendo un centro estereogénico cuaternario. La reacción tiene lugar con buenas enantioselectividades (hasta un 93% de ee) y excelentes rendimientos (hasta un 99%). También se ha descrito la alquilación de Friedel-Crafts de diferentes derivados de pirrol con una variedad de -cetoésteres catalizada por complejos Zr(OtBu)4-(L6) para dar lugar alcoholes terciarios con diferente sustituido enantioselectividades muy buena (hasta un 98% ee) y buenos rendimientos (hasta 79%). El 4,7-dihidroindol también se puede utilizar como nucleófilo en la alquilación de Friedel-Crafts con -cetoésteres, seguida de una oxidación de p-benzoquinona proporcionando derivados de indol 2-sustituidos, en un sencillo procedimiento “one-pot”.
The Friedel-Crafts (F-C) reaction is a powerful carbon-carbon bond forming process of great importance in organic synthesis. The application of the asymmetric catalytic version of this reaction to the alkylation of electron-rich arenes, such as indoles or pyrroles, can provide access to important enantiomerically enriched alkylated arene products and constitute a topic of ongoing interest, due that this arenes have identified as “privileged” structure or pharmacophore. In this Thesis Zr(IV) and Hf(IV)-BINOL complexes generated in situ have been evaluated as catalysts in enantioselective F-C alkylation of indoles and pyrroles with different α,β-unsaturated ketones, as well as in the alkylation of pyrroles with different kind of carbonyl compounds. Zr(OtBu)4-(R)-3,3'-Br2-BINOL complexes have been used as very effective catalysts for the enantioselective F-C alkylation of indoles with simple non-chelating α,β-unsaturated ketones. The reaction takes place with very good yields (up 97%) and good enantioselectivity (up 98% ee). The Friedel-Crafts alkylation of pyrroles with simple non-chelating α,β-unsaturated ketones catalyzed by Zr(OtBu)4-(R)-3,3'-Br2-5,5',6,6',7,7',8,8'-BINOL give the products with good yields and moderate to very good enantioselectivities. 2-Substituted indole derivatives were synthetized by one-pot catalytic asymmetric Friedel-Crafts reaction between 4,7-dihydroindole and α,β-unsaturated ketone, followed by a p-benzoquinone oxidation, with good yields and moderated enantioselectivities. The -unsaturated -trifluoroketones have been used as electrophiles in the enantioselective F-C alkylation of indoles catalyzed by BINOL complex, providing a variety of trifluoromethylated chiral indoles in good yields (up 99%) and excellent enantioselectivities (up 99% ee). (E)-1-aryl-4-benzyloxy-2-buten-1-ones, (E)-1,4-diaryl-2-butene-1,4-diones and (E)-4-oxo-4-phenylbutenoates can also be used as electrophiles in the F-C reactions of indoles catalyzed by the BINOL complex to obtain chiral indoles with a 1,4-difunctionalized moiety. Zr(OtBu)4-(R)-3,3'-Br2-BINOL catalyst has been used in a F-C alkylation of unprotected pyrrole with a variety of differently substituted 2,2,2-trifluoroacetophenones to give pyrroles with a trifluoromethyl substituted tertiary alcohol moiety bearing a quaternary stereogenic center. The reaction takes place with good enantioselectivities (up to 93% ee) and high isolated yields (up to 99%). Chiral complex of Zr(OtBu)4-(R)-3,3'-bis(3,5-bis(trifluoromethyl)phenyl)BINOL has been used as a catalyst in a F-C alkylation of different pyrrole and 4,7-dihidroindole derivatives with a variety of differently substituted -ketoesters to give tertiary alcohols with very good enantioselectivities (up to 98% ee) and good yields (up to 79%).

In den letzten Jahren gibt es großes Interesse am SiGeSn Materialsystem aufgrund seines Potentials für die Verwendung in der Optoelektronik, Elektronik und Photovoltaik. Während jedoch die binären Verbindungshalbleiter Si(x)Ge(1-x) und Ge(1-y)Sn(y) schon intensiv untersucht wurden, sind die Materialeigenschaften des ternären Verbindungshalbleiters Ge(1-x-y)Si(x)Sn(y) und Nanostrukturen basierend auf diesem Verbindungshalbleiter noch weitgehend unbekannt. In dieser Arbeit werden drei theoretische/theoretisch-experimentelle Studien zur Untersuchung des SiGeSn Materialsystems vorgestellt. In einer Studie wird die Abhängigkeit der Größe der direkten Bandlücke von der Zusammensetzung des Ge(1-x-y)Si(x)Sn(y) Verbindungshalbleiters untersucht. Basierend auf Messungen der Rutherford Rückstreuung, Röntgenbeugung und Photolumineszenz (PL) von Ge(1-x-y)Si(x)Sn(y) Proben mit an Ge angepassten Gitterkonstanten wird die Abhängigkeit von Größe der direkten Bandlücke und der Materialkomposition mit einer quadratischen Gleichung beschrieben. Weiterhin wird die Bandanordnung der elementaren Halbleiter Si, Ge und Sn an Grenzflächen untersucht. Anhand von Kohn-Sham basierter Density Functional Theory (DFT) in Kombination mit Local Density Approximation (LDA) berechneten Bandstrukturen von Grenzflächen zwischen Elementarhalbleitern wird der Versatz im Valenzband zwischen Si, Ge und Sn untersucht. Es wird gezeigt, dass aufgrund zu kleiner Bandlücken resultierend aus dem Kohn-Sham-Ansatz in Verbindung mit der LDA ein unphysikalischer „Broken Gap“ Versatz zwischen Ge und Sn Bändern entsteht. In einer dritten Studie werden die PL-Spektren von Ge Quantentöpfen mit Si Barrieren untersucht. Um die Abhängigkeit der PL-Spektren von Anregungsintensität und Temperatur zu verstehen, wird ein selbstkonsistentes Effektives-Massen-Model entwickelt. Mit diesem Model ist es möglich den Einfluss von Temperatur und Bandauffüllung auf das PL-Spektrum zu untersuchen.
The SiGeSn semiconductor material system has recently attracted great interest due to its prospective potential for use in optoelectronics, electronics, and photovoltaics. While the binary alloy Si(x)Ge(1-x) and Ge(1-y)Sn(y) have already been well studied, the properties of bulk and heterostructures involving the Ge(1-x-y)Si(x)Sn(y) ternary alloy are largely unknown. In this thesis, we present the results of three theoretical/experimental-theoretical investigations concerning the SiGeSn material system. First, we investigate the compositional dependence of the direct band-gap of Ge(1-x-y)Si(x)Sn(y) alloys. Based on Rutherford backscattering, x-ray diffraction, and photoluminescence (PL) measurement of Ge(1-x-y)Si(x)Sn(y) alloys lattice-matched to Ge, we describe the compositional dependence of the band gap using a quadratic equation. We predict Ge(1-x-y)Si(x)Sn(y) alloys lattice-matched to Ge to be direct-band-gap semiconductors for Sn concentrations larger than 12%. Secondly, we investigate the band alignment between the elemental semiconductors Si, Ge, and Sn. Performing bulk and interface calculations using density functional theory (DFT) in combination with the local density approximation (LDA), we attempt to calculate the valence band offset between the elemental semiconductors. We find that the Kohn-Sham based DFT-LDA calculations are flawed by the underestimation of the band-gaps of the elemental semiconductors, which leads to a false broken gap band alignment between Ge and Sn. Third, we study the PL of ultrathin Ge multiple quantum well (multiple-QW) structures grown on Si. To understand the excitation density and temperature related shifts of the PL spectra of the sample, we develop a self-consistent multivalley effective mass model. Using second-order perturbation theory, we calculate the indirect phonon-assisted radiative spontaneous recombination rate together with the no-phonon peak energy and compare our results to the experimental results.

Trabajo de Investigación Requisito para optar al Título de Cirujano Dentista
Autor no autoriza el acceso a texto completo de su tesis en el Portal de Tesis Electrónicas
INTRODUCCIÓN: Especies bacterianas anaeróbicas potencialmente patogénicas constituyen un porcentaje significativo de la microbiota normal de la cavidad bucal y hoy se sabe que su capacidad de colonizar y sobrevivir durante la niñez temprana, depende de las condiciones medioambientales que ofrezca el hospedero. Sin embargo, se desconoce la edad en que estas especies bacterianas comienzan a colonizar la cavidad bucal de los niños, como es el caso de Porphyromonas gingivalis, considerado uno de los periodontopatógenos más importantes. Esta especie posee múltiples factores de virulencia, entre los cuales se ha destacado la expresión de fimbrias, apéndices externos que juegan un rol determinante en la adhesión e invasión de los tejidos periodontales. Las fimbrias están constituidas por una subunidad proteica denominada fimbrilina (FimA), codificada por el gen fimA. Se han descrito 6 tipos de genes fimA en base a su secuencia de nucleótidos, codificando cada uno un tipo de fimbria diferente, las que se han asociado con distintos grados de salud y enfermedad periodontal. OBJETIVO: Investigar la presencia de Porphyromonas gingivalis, genotipos fimA-I, II, III y IV, en la microbiota bucal de niños de 4 a 8 años de edad. METODOLOGÍA: Se tomo muestras de hisopado de dorso lingual de 92 niños, de 4 a 8 años de edad, a quienes se les realizó un examen en búsqueda de signos clínicos de gingivitis y se distribuyeron según edad. La presencia de Porphyromonas gingivalis se investigó mediante cultivo microbiológico, pruebas bioquímicas y Reacción en Cadena de la Polimerasa (PCR). La detección de los genotipos fimA se llevó a cabo mediante PCR. RESULTADOS: Se detectó Porphyromonas gingivalis en el 11,95% de los niños (n=11), mediante cultivo y PCR, y 3 sujetos resultaron positivos a la presencia del genotipo fimA-IV de esta especie. Los 8 sujetos restantes no presentaron ninguno de los otros genotipos analizados en este estudio. CONCLUSIONES: Porphyromonas gingivalis puede ser miembro de la microbiota comensal de niños de 4 a 8 años de edad. La detección del genotipo fimA-IV podría indicar una colonización preferencial a edades tempranas por parte de este genotipo, lo que ameritaría una revisión en el tiempo, para evaluar su permanencia, reemplazo o asociación con la aparición de patologías periodontales

Dissertação (Mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas. Curso de Pós-Graduação em Química
Made available in DSpace on 2012-10-18T23:07:01Z (GMT). No. of bitstreams: 0Bitstream added on 2016-01-09T02:59:49Z : No. of bitstreams: 1 182700.pdf: 12886246 bytes, checksum: d9173f6997a07995d2baf4a087cf297a (MD5)
O vanádio é um elemento essencial em muitos processos biológicos, podendo ser encontrado nas haloperoxidases de algas marinhas e líquens, e em algumas nitrogenases. Em organismos superiores, o vanádio encontra-se ligado as transferrinas, formando as vanádio-transferrinas, as quais são a provável forma de transporte do vanádio nesses organismos. Buscando uma melhor compreensão a respeito do sítio de coordenação das vanádio-transferrinas, tem-se utilizado o estudo de compostos modelo cujas propriedades espectroscópicas sejam comparáveis às apresentadas pela proteína. Neste trabalho são apresentas a síntese e caracterização de dois novos ligantes contendo grupos retiradores de elétrons e de seus complexos de vanádio(III) e oxovanádio(IV), propostos como modelos para as vanádio-transferrinas. Através da resolução das estruturas por raios-X, observou-se uma influência dos grupos Br e NO2 nos comprimentos de ligação V-O e V-N em relação aos complexos com H. A influência desses grupos também foi observada nos estudos de EPR e UV-Vis. Os estudos espectroscópicos permitiram, pela primeira vez, a atribuição da banda de transferência de carga observada nos espectros eletrônicos dos complexos de oxovanádio(IV), como sendo um processo TCLM do tipo Ofenolato®VIV. Através da análise do comportamento redox dos complexos de vanádio(III) e (IV), encontrou-se uma correlação linear entre E1/2 e sp. A estabilidade dos complexos de vanádio(III) frente a oxidação por O2 atmosférico, bem como as propriedades espectroscópicas apresentadas pelos complexos de vanádio(III) e (IV) elegem estes compostos como modelos para as transferrinas de vanádio(III) e (IV).

A necessidade de investimento em saneamento no Brasil é essencial, pois está vinculada à melhoria da qualidade de vida da sociedade. Os projetos de saneamento exigem altos investimentos e, para garantir a prestação dos serviços, é necessário um sistema complexo de infraestrutura. Os elevados custos envolvidos e a limitação de recursos financeiros fazem com que seja preciso estabelecer prioridades para execução de projetos de saneamento. Com efeito, o objetivo desta pesquisa é propor um modelo multicritério de decisão para apoiar decisões de hierarquia de projetos de abastecimento de água e esgotamento sanitário. A pesquisa abordada tem enfoque qualitativo, sendo também vista como metodológica, pois sua finalidade é envolver métodos e procedimentos adotados como científicos. Assim, traz como escopo apoiar e estruturar o processo de decisão em que são definidos: os elementos (intervenientes, alternativas potenciais, critérios, problemática); tipos de decisão em grupo; escolha dos métodos multicritérios (PROMETHEE II & GAIA e ELECTRE IV); modelagem de preferência; sistemas de apoio à decisão (D-SIGHT e ELECTRE III-IV); avaliação de resultados e análise de sensibilidade. Procura-se garantir que a pesquisa tenha caráter prático, razão por que foi realizada a aplicação numérica do modelo no contexto da bacia dos rios Piracicaba, Capivari e Jundiaí, região sudeste do Brasil.
The need of investment in water supply and sewage projects in Brazil is substantial to improve the quality of life. These projects require high investments and, mostly, to ensure the provision of these services it is necessary a complex infrastructure. Due to the high costs associated with the lack of resources, it is relevant to prioritize projects. Thus, the purpose of this research is to propose a multicriteria decision model to support decisions hierarchy of water supply and sewage projects. This work has a qualitative and methodological approach; the goal is to inquire a scientific procedure. The object is to structure the decision-making process defined by its main concepts (actors, potential alternatives, criteria, problems), group decision making; selection of multiple criteria methods (PROMETHEE II & GAIA, ELECTRE IV); preference modeling, decision support systems (D-SIGHT and ELECTRE III-IV), evaluation and sensitivity analysis. This study seeks a practical purpose, so the proposed model, is applied in the basin of Piracicaba, Capivari e Jundiaí. The contribution here to aid similar situations where is necessary to establish priorities of sanitation projects.

A presente dissertação tem como tema a criação de visibilidade de grupos marginalizados, e o fomento da produção gráfica independente que age a esse favor no Brasil. Utilizando-se dos conhecimentos prévios da autora no campo do design, e das competências adquiridas neste mestrado no campo da gestão cultural, apresenta o processo de conhecimento e decisão para planear a criação de uma plataforma online expositiva, com o nome Curadoria Marginal, que utiliza-se de uma prática curatorial para selecionar e expor tais peças e seus autores, e de uma prática programática para criação de público e engajamento com o material exposto e o que aquilo que ele discute, visando, dessa maneira, ir contra o crescente movimento de discriminação e intolerância à pluralidade, que esses grupos sofrem atualmente em ambientes online e offline na sociedade brasileira.

Od okresu przedrzymskiego po okres wczesnego średniowiecza fibule – ozdoby służące spinaniu szat – stanowiły integralną część stroju. Na przestrzeni dziejów zmieniały się technika ich wykonania, konstrukcja i ornamentyka. Dla archeologów zabytki te stanowią jeden z najbardziej precyzyjnych wskaźników datujących. W tym samym okresie na terytoriach różnych kultur występowały odmienne formy zapinek, stąd też w pracy postawiono hipotezę, że ozdoby te stanowią wyznacznik nie tylko chronologiczny, lecz także kulturowy i etniczny. Celem pracy jest analiza fibul datowanych na wczesny okres wpływów rzymskich (I-II w. n.e.) znalezionych na obszarze kultury Dollkeim-Kovrovo, a więc na terenie dzisiejszego Obwodu Kaliningradzkiego Federacji Rosyjskiej i w północno-wschodniej Polsce. From the Pre-Roman Period up to the Early Middle Ages brooches – ornaments fastening clothes – were an integral part of a dress. During those times their workmanship, construction or ornamentation were changing. For archaeologists those finds are one of the most precise chronological factors. In the same period at territories of different cultures different fibulas were worn. That is the reason why the following hypothesis was accepted – brooches could have been not only the chronological factor, but also cultural and ethnic factors. The aim of the thesis is the analysis of brooches dated to the Early Roman Period (1st-2nd cc. AD) found at the area of the Dollkeim/Kovrovo Culture, so at the present Kaliningrad Oblast of the Russian Federation and in the north-eastern Poland.

Tese de doutoramento em Ciências Farmacêuticas, na especialidade de Farmacognosia e Fitoquímica, apresentada à Faculdade de Farmácia da Universidade de Coimbra
Cymbopogon citratus (DC). Stapf (Poaceae), commonly known as lemongrass, is a tropical perennial shrub originated from the Southeast Asia. This plant is reported to possess antifungal, insecticidal, anti-diabetic, anti-septic, anti-mutagenic, anti-carcinogenic activities as well as anti-inflammatory. In fact, aqueous extracts of dried leaves are used all over the year in folk medicine for the treatment of peptic ulcers and inflammatory conditions. Recently, some phenolic compounds, such as luteolin and apigenin glycosides and condensed tannins, were identified and related to both antioxidant and anti-inflammatory properties. The purposes of this work were to i) validate an analytical method for quantification of phenolic compounds of C. citratus; ii) study the influence of harvest time and plant quality on the phenolic composition and antioxidant activity; iii) characterize the tannins; iv) validate the traditional uses of lemongrass infusion as anti-inflammatory in vivo; v) obtain a topical formulation to evaluate the phenolic compounds permeation and their anti-inflammatory activity; vi) trace the pharmacokinetic profile of the main phenolic compounds in rats. Three different extracts: infusion (CcI), 50% aqueous ethanol (CcM50%) and ethanol (CcM100%) extracts were prepared and a simple and efficient RP-HPLC-PDA method was successfully validated for simultaneous identification and quantification of phenolic acids and flavonoids. Infusions were also obtained from different harvest dates (April, June, July, August and September) and quality grades (High, Medium and Low). It was verified that the content on polyphenols and the antioxidant capacity of CcI is strongly related with the quality of the plant. The total phenols assay showed a substantial loss from August to September. It was possible to find out the best month to harvest the plant to get the most of each phenolic group: April and June for hydroxycinnamic acids; June and September for flavonoids; June, July and August for tannins. Regardless the group of phenolic compound addressed, its content was always inversely proportional to the degree of leaves ageing. For all tested oxidant species, the high-quality samples exhibited the best antioxidant results. CcI was fractionated by column chromatography and polyphenol-rich fractions, namely phenolic acids (CcPA), flavonoids (CcF) and tannins (CcT) were obtained. CcT was characterized by HPLC-PDA-ESI/MSn, revealing the presence of proanthocyanidin hetero-dimers, along with some common procyanidin dimers. These hetero-dimeric flavan structures have been described for the first time in lemongrass and consist of apigeniflavan or luteoliflavan units linked to a flavanone, either naringenin or eriodictyol, and may occur as aglycone or glycosylated forms. For the in vivo assays, CcI, CcF and CcT were tested. CcI administered before and after ethanol stimulus, significantly reduced the incidence and severity of gastric lesions and, consequently, the ulcer index, corroborating the traditional medicinal use of this plant to ameliorate gastritis and/or peptic ulcers symptoms. On the other hand, CcI, CcF and CcT were orally administered to rats, in order to evaluate the anti-inflammatory effect at the carrageenan-induced paw edema assay. The observed effect by CcI (68.24 mg/kg), 82.30% of edema inhibition, was very similar to that obtained by the reference NSAID used (diclofenac, 10 mg/kg), 84.00%. On the other hand, flavonoid (7.42 mg/kg) and the tannin-rich (5.96 mg/kg) fractions significantly contributed for the anti-inflammatory activity on the edema volume (59 and 61%, respectively). The topical anti-inflammatory activity of CcI was also addressed. The results suggest that flavonoids, mainly, luteolin 7-O-neohesperidoside, cassiaoccidentalin B, carlinoside and cynaroside, may contribute to the topical anti-inflammatory effect. CcF (0.6%), CcT (0.3%) and CcF+CcT (0.66%+0.34%) topical formulations were also tested, and the results obtained suggest that tannins and flavonoids also possess a significant activity and that a synergistic mechanism of action may occur. In fact, edema inhibitions of 43%, 47% and 59% were respectively verified, being CcF+CcT effect very close to that of 1% diclofenac (65.9%). Pharmacokinetic analysis was performed in plasma, liver and kidney and showed that the compounds present in CcI are not detected in vivo after a single-dose oral administration. In contrary, the metabolites, luteolin 7-O-glucuronide and luteolin 3’-O-sulfate, present at the highest bioavailability, are probably the main responsible for the anti-inflammatory activity previously reported. In conclusion, this work has developed a method to quantify the phenolic compounds contained in C. citratus; pointed the importance of harvesting and storing the plant material, in order to take the maximum advantages from the phenolic compounds use; and demonstrated, in safe doses, its anti-inflammatory activity, using an in vivo approach, which supports the traditional use of lemongrass infusion. Furthermore, C. citratus leaves flavonoids and tannins were highlighted as bioactive compounds, encouraging the development of new anti-inflammatory drugs or nutraceuticals.