Viver no campo ou na cidade? resposta dos morcegos (Mammalia, Chiroptera) à antropização da paisagem

Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Biológicas, Departamento de Ecologia, Programa de Pós-Graduação em Ecologia, 2015.

Materials design for ambipolar devices: tuning orbital energetics in oligothiophene-naphthalimides semiconductors

Ambipolar organic field-effect transistors (OFETs), which can efficiently transport both holes and electrons, using a single type of electrode, are currently of great interest due to their possible applications in complementary metal oxide semiconductor (CMOS)-like circuits, sensors, and in light-emitting transistors. Several theoretical and experimental studies have argued that most organic semiconductors should be able to transport both types of carrier, although typically unipolar behavior is observed. One factor that can compromise ambipolar transport in organic semiconductors is poor solid state overlap between the HOMO (p-type) or LUMO (n-type) orbitals of neighboring molecules in the semiconductor thin film. In the search of low-bandgap ambipolar materials, where the absence of skeletal distortions allows closer intermolecular π-π stacking and enhanced intramolecular π-conjugation, a new family of oligothiophene-naphthalimide assemblies have been synthesized and characterized, in which both donor and acceptor moieties are directly conjugated through rigid linkers. In previous works we found that oligothiophene-napthalimide assemblies connected through amidine linkers (NDI derivates) exhibit skeletal distortions (50-60º) arising from steric hindrance between the carbonyl group of the arylene core and the sulphur atom of the neighbored thiophene ring (see Figure 1). In the present work we report novel oligo- and polythiophene–naphthalimide analogues NAI-3T, NAI-5T and poly-NAI-8C-3T, in which the connections of the amidine linkage have been inverted in order to prevent steric interactions. Thus, the nitrogen atoms are directly connected to the naphthalene moiety in NAI derivatives while they were attached directly to the thiophene moiety in the previously investigated NDI-3T and NDI-5T. In Figure 1 is depicted the calculated molecular structure of NAI-3T together with that of NDI-3T showing how the steric interactions are not present in the novel NAI derivative. The planar skeletons in these new family induce higher degree of crystallinity and the carrier charge transport can be switched from n-type to ambipolar behaviour. The highest FET performance is achieved for vapor-deposited films of NAI-3T with mobilities of 1.95x10-4cm2V-1s-1 and 2.00x10-4cm2V-1s-1 for electrons and holes, respectively. Finally, these planar semiconductors are compared with their NDI derivates analogues, which exhibit only n-type mobility, in order to understand the origin of the ambipolarity in this new series of molecular semiconductors.

Functional, clustered, feedforward, and mesoscale brain networks

The brain is a network spanning multiple scales from subcellular to macroscopic. In this thesis I present four projects studying brain networks at different levels of abstraction. The first involves determining a functional connectivity network based on neural spike trains and using a graph theoretical method to cluster groups of neurons into putative cell assemblies. In the second project I model neural networks at a microscopic level. Using diferent clustered wiring schemes, I show that almost identical spatiotemporal activity patterns can be observed, demonstrating that there is a broad neuro-architectural basis to attain structured spatiotemporal dynamics. Remarkably, irrespective of the precise topological mechanism, this behavior can be predicted by examining the spectral properties of the synaptic weight matrix. The third project introduces, via two circuit architectures, a new paradigm for feedforward processing in which inhibitory neurons have the complex and pivotal role in governing information flow in cortical network models. Finally, I analyze axonal projections in sleep deprived mice using data collected as part of the Allen Institute's Mesoscopic Connectivity Atlas. After normalizing for experimental variability, the results indicate there is no single explanatory difference in the mesoscale network between control and sleep deprived mice. Using machine learning techniques, however, animal classification could be done at levels significantly above chance. This reveals that intricate changes in connectivity do occur due to chronic sleep deprivation.

Trichodina colisae (Ciliophora: Trichodinidae): new parasite records for two freshwater fish species farmed in Brazil

Tricodinídeos são protozoários ciliados móveis com ampla distribuição mundial; são considerados um dos agentes parasitários que mais acometem peixes cultivados. No Brasil, a maioria dos tricodinídeos que parasitam importantes espécies de peixes cultivados são desconhecidos, o que requer mais estudos taxonômicos com esse grupo de parasitos. Este estudo caracteriza morfologicamente Trichodina colisae Asmat & Sultana, 2005 de pacu (Piaractus mesopotamicus) e do híbrido patinga (P. mesopotamicus × P. brachypomus) cultivados, respectivamente, no Centro-Oeste e Sudeste do Brasil. Foram feitas montagens a fresco do raspado de muco da pele, nadadeiras e brânquias, fixados com metanol e, posteriormente, impregnados com nitrato de prata e coradas com Giemsa para avaliação em microscopia óptica. O presente estudo relata não só a segunda ocorrência de T. colisae no mundo, mas também a primeira ocorrência na América do Sul.

A BACKING DEVICE BASED ON AN EMBEDDED STIFFENER AND RETRACTABLE INSERTION TOOL FOR THIN-FILM COCHLEAR ARRAYS

Intracochlear trauma from surgical insertion of bulky electrode arrays and inadequate pitch perception are areas of concern with current hand-assembled commercial cochlear implants. Parylene thin-film arrays with higher electrode densities and lower profiles are a potential solution, but lack rigidity and hence depend on manually fabricated permanently attached polyethylene terephthalate (PET) tubing based bulky backing devices. As a solution, we investigated a new backing device with two sub-systems. The first sub-system is a thin poly(lactic acid) (PLA) stiffener that will be embedded in the parylene array. The second sub-system is an attaching and detaching mechanism, utilizing a poly(N-vinylpyrrolidone)-block-poly(d,l-lactide) (PVP-b-PDLLA) copolymer-based biodegradable and water soluble adhesive, that will help to retract the PET insertion tool after implantation. As a proof-of-concept of sub-system one, a microfabrication process for patterning PLA stiffeners embedded in parylene has been developed. Conventional hotembossing, mechanical micromachining, and standard cleanroom processes were integrated for patterning fully released and discrete stiffeners coated with parylene. The released embedded stiffeners were thermoformed to demonstrate that imparting perimodiolar shapes to stiffener-embedded arrays will be possible. The developed process when integrated with the array fabrication process will allow fabrication of stiffener-embedded arrays in a single process. As a proof-of-concept of sub-system two, the feasibility of the attaching and detaching mechanism was demonstrated by adhering 1x and 1.5x scale PET tube-based insertion tools and PLA stiffeners embedded in parylene using the copolymer adhesive. The attached devices survived qualitative adhesion tests, thermoforming, and flexing. The viability of the detaching mechanism was tested by aging the assemblies in-vitro in phosphate buffer solution. The average detachment times, 2.6 minutes and 10 minutes for 1x and 1.5x scale devices respectively, were found to be clinically relevant with respect to the reported array insertion times during surgical implantation. Eventually, the stiffener-embedded arrays would not need to be permanently attached to current insertion tools which are left behind after implantation and congest the cochlear scala tympani chamber. Finally, a simulation-based approach for accelerated failure analysis of PLA stiffeners and characterization of PVP-b-PDLLA copolymer adhesive has been explored. The residual functional life of embedded PLA stiffeners exposed to body-fluid and thereby subjected to degradation and erosion has been estimated by simulating PLA stiffeners with different parylene coating failure types and different PLA types for a given parylene coating failure type. For characterizing the PVP-b-PDLLA copolymer adhesive, several formulations of the copolymer adhesive were simulated and compared based on the insertion tool detachment times that were predicted from the dissolution, degradation, and erosion behavior of the simulated adhesive formulations. Results indicate that the simulation-based approaches could be used to reduce the total number of time consuming and expensive in-vitro tests that must be conducted.

Documentary sources to investigate multidecadal variability of droughts

Droughts are probably the natural hazard with the highest socioeconomic impact. Simultaneously, they are a very complex phenomenon; they are triggered by a diversity of physical factors and occur at a variety of time scales. Consequently, the instrumental record currently available is too short and the characterization of its multidecadal variability requires the use of natural proxies (tree rings, sedimentary records) or documentary sources. In this paper we analyse three documentary sources with potential to analyse the long-term variability of droughts: chapter acts, logbooks and chronicles. The chapter acts recorded discussions and decisions made during the assemblies of the local authorities and provide continuous and direct evidence on drought impacts. They are especially useful to study droughts between the 15th and the 19th centuries in Europe and the 17th to 18th in the former colonies. Logbooks recorded the meteorological conditions and the incidents occurred during navigation. They provide indirect information through the circulation indices that can be very helpful to understand the mechanisms and teleconnections associated to droughts. Finally, the chronicles are historiographical documents describing political and social events. They are secondary sources and the references to climatic events are discontinuous, thus their analysis must be extremely careful, but they are especially useful to study specific drought events especially prior to 15th century when no other sources are available.

Self-assembly of gold nanocrystals into discrete coupled plasmonic structures

Development of methodologies for the controlled chemical assembly of nanoparticles into plasmonic molecules of predictable spatial geometry is vital in order to harness novel properties arising from the combination of the individual components constituting the resulting superstructures. This paper presents a route for fabrication of gold plasmonic structures of controlled stoichiometry obtained by the use of a di-rhenium thio-isocyanide complex as linker molecule for gold nanocrystals. Correlated scanning electron microscopy (SEM)—dark-field spectroscopy was used to characterize obtained discrete monomer, dimer and trimer plasmonic molecules. Polarization-dependent scattering spectra of dimer structures showed highly polarized scattering response, due to their highly asymmetric D∞h geometry. In contrast, some trimer structures displayed symmetric geometry (D3h), which showed small polarization dependent response. Theoretical calculations were used to further understand and attribute the origin of plasmonic bands arising during linker-induced formation of plasmonic molecules. Theoretical data matched well with experimentally calculated data. These results confirm that obtained gold superstructures possess properties which are a combination of the properties arising from single components and can, therefore, be classified as plasmonic molecules

Transfert ultrarapide d’électron et transfert modéré d’énergie au sein d’assemblages supramoléculaires de colorants et d’un cluster de palladium

Résumé : Les transferts d’électrons photo-induits et d’énergie jouent un rôle primordial dans un grand nombre de processus photochimiques et photobiologiques, comme la respiration ou la photosynthèse. Une très grande quantité de systèmes à liaisons covalentes ont été conçus pour copier ces processus de transferts. Cependant, les progrès sont, en grande partie, limités par les difficultés rencontrées dans la synthèse de nouveaux couples de types donneurs-accepteurs. Récemment, des espèces utilisant des liaisons non-covalentes, comme les liaisons hydrogènes, les interactions [pi]-[pi], les liaisons de coordination métal-ligands ou encore les interactions électrostatiques sont le centre d’un nouvel intérêt du fait qu’ils soient plus faciles à synthétiser et à gérer pour obtenir des comportements de transferts d’électrons ou d’énergie plus flexibles et sélectifs. C’est dans cette optique que le travail de cette thèse a été mené, i.e. de concevoir des composés auto-assemblés avec des porphyrines et un cluster de palladium pour l’étude des transferts d’électrons photo-induits et d’énergie. Cette thèse se divise en quatre parties principales. Dans la première section, le chapitre 3, deux colorants porphyriniques, soit le 5-(4-carboxylphényl)-10, 15, 20-tristolyl(porphyrinato)zinc(II) (MCP, avec Na+ comme contre-ion) et 5, 15-bis(4-carboxylphényl)-15, 20-bistolyl(porphyrinato)zinc(II) (DCP, avec Na+ comme contre-ion) ont été utilisés comme donneurs d’électrons, et le [Pd3(dppm)3(CO)]2+ ([Pd32+], dppm = (Ph2P)2CH2, PF6‾ est le contre-ion) a été choisi comme accepteur d’électrons. La structure de l’assemblage [Pd32+]•••porphyrine a été élucidée par l’optimisation des géométries à l’aide de calculs DFT. La spectroscopie d’absorption transitoire (TAS) montre la vitesse de transferts d’électrons la plus rapide (< 85 fs, temps inférieurs à la limite de détection) jamais enregistrée pour ce type de système (porphyrine-accepteur auto-assemblés). Généralement, ces processus sont de l’ordre de l’échelle de la ps-ns. Cette vitesse est comparable aux plus rapides transferts d’électrons rapportés dans le cas de systèmes covalents de type porphyrine-accepteur rapide (< 85 fs, temps inférieurs à la limite de détection). Ce transfert d’électrons ultra-rapide (ket > 1.2 × 1013 s-1) se produit à l’état énergétique S1 des colorants dans une structure liée directement par des interactions ioniques, ce qui indique qu’il n’est pas nécessaire d’avoir de forts liens ou une géométrie courbée entre le donneur et l’accepteur. Dans une deuxième section, au chapitre 4, nous avons étudié en profondeur l’effet de l’utilisation de porphyrines à systèmes π-étendus sur le comportement des transferts d’électrons. Le colorant 9, 18, 27, 36-tétrakis-meso-(4-carboxyphényl)tétrabenzoporphyrinatozinc(II) (TCPBP, avec Na+ comme contre-ion) a été sélectionné comme candidat, et le 5, 10, 15, 20-tétrakis-meso-(4-carboxyphényl)porphyrineatozinc(II) (TCPP, avec Na+ comme contre-ion) a aussi été utilisé à des fins de comparaisons. TCPBP et TCPP ont, tous deux, été utilisés comme donneurs d’électrons pour fabriquer des assemblages supramoléculaires avec le cluster [Pd32+] comme accepteur d’électrons. Les calculs DFT ont été réalisés pour expliquer les structures de ces assemblages. Dans les conditions expérimentales, ces assemblages sont composés principalement d’une porphyrine avec 4 équivalents de clusters. Ces systèmes ont aussi été investigués par des mesures de quenching (perte de luminescence), par électrochimie et par d’autres techniques. Les transferts d’électrons (< 85 fs; temps inférieurs à la limite de détection) étaient aussi observés, de façon similaire aux assemblages MCP•••[Pd32+] et [Pd32+]•••DCP•••[Pd32+]. Les résultats nous indiquent que la modification de la structure de la porphyrine vers la tétrabenzoporphyrine ne semble pas influencer le comportement des cinétiques de transferts d’électrons (aller ou retour). Dans la troisième section, le chapitre 5, nous avons synthétisé la porphyrine hautement [pi]-conjuguée: 9, 18, 27, 36-tétra-(4-carboxyphényléthynyl)tétrabenzoporphyrinatozinc(II) (TCPEBP, avec Na+ comme contre-ion) par des fonctionnalisations en positions meso- et β, β-, qui présente un déplacement vers le rouge de la bande de Soret et des bandes Q. TCPEBP était utilisé comme donneur d’électrons pour fabriquer des motifs supramoléculaires avec le [Pd32+] comme accepteur d’électrons. Des expériences en parallèle ont été menées en utilisant la 5, 10, 15, 20-tétra-(4-carboxyphényl)éthynylporphyrinatozinc(II) (TCPEP, avec Na+ comme contre-ion). Des calculs DFT et TDDFT ont été réalisés pour de nouveau déterminer de façon théorique les structures de ces systèmes. Les constantes d’association pour les assemblages TCPEBP•••[Pd32+]x sont les plus élevées parmi tous les assemblages entre des porphyrines et le cluster de palladium rencontrés dans la littérature. La TAS a montré, encore une fois, des processus de transferts d’électrons dans des échelles de l’ordre de 75-110 fs. Cependant, les transferts de retour d’électrons sont aussi très rapides (< 1 ps), ce qui est un obstacle potentiel pour des applications en cellules solaires à pigment photosensible (DSSCs). Dans la quatrième section, le chapitre 6, les transferts d’énergie triplets (TET) ont été étudiés pour les assemblages MCP•••[Pd32+] et [Pd32+]•••DCP•••[Pd32+]. Les analyses spectrales des états transitoires dans l’échelle de temps de la ns-[mu]s démontrent de façon évidente les TETs; ceux-ci présentent des transferts d’énergie lents et/ou des vitesses moyennes pour des transferts d’énergie T1-T1 (3dye*•••[Pd32+] → dye•••3[Pd32+]*) opérant à travers exclusivement le mécanisme de Förster avec des valeurs de kET autour de ~ 1 × 105 s-1 selon les mesures d’absorption transitoires à 298 K. Des forces motrices non-favorables rendent ces types de processus non-opérants ou très lents dans les états T1. L’état T1 de [Pd32+] (~8190 cm-1) a été qualitativement déterminé par DFT et par la mise en évidence de l’émission S0 ← Tn retardée à 680-700 nm provenant de l’annihilation T1-T1, ce qui fait que ce cluster peut potentiellement agir comme un donneur à partir de ses états Tn, et accepteur à partir de T1 à l’intérieur de ces assemblages. Des pertes d’intensités de types statiques pour la phosphorescence dans le proche-IR sont observées à 785 nm. Ce travail démontre une efficacité modérée des colorants à base de porphyrines pour être impliquée dans des TETs avec des fragments organométalliques, et ce, même attachées grâce à des interactions ioniques. En conclusion, les assemblages ioniques à base de porphyrines et de clusters de palladium présentent des propriétés de transferts d’électrons S1 ultra-rapides, et des transferts d’énergie T1 de vitesses modérées, ce qui est utile pour de possibles applications comme outils optoélectroniques. D’autres études, plus en profondeur, sont présentement en progrès.

Physicochemical complexity in complex chemical systems

Self-replication and compartmentalization are two central properties thought to be essential for minimal life, and understanding how such processes interact in the emergence of complex reaction networks is crucial to exploring the development of complexity in chemistry and biology. Autocatalysis can emerge from multiple different mechanisms such as formation of an initiator, template self-replication and physical autocatalysis (where micelles formed from the reaction product solubilize the reactants, leading to higher local concentrations and therefore higher rates). Amphiphiles are also used in artificial life studies to create protocell models such as micelles, vesicles and oil-in-water droplets, and can increase reaction rates by encapsulation of reactants. So far, no template self-replicator exists which is capable of compartmentalization, or transferring this molecular scale phenomenon to micro or macro-scale assemblies. Here a system is demonstrated where an amphiphilic imine catalyses its own formation by joining a non-polar alkyl tail group with a polar carboxylic acid head group to form a template, which was shown to form reverse micelles by Dynamic Light Scattering (DLS). The kinetics of this system were investigated by 1H NMR spectroscopy, showing clearly that a template self-replication mechanism operates, though there was no evidence that the reverse micelles participated in physical autocatalysis. Active oil droplets, composed from a mixture of insoluble organic compounds in an aqueous sub-phase, can undergo processes such as division, self-propulsion and chemotaxis, and are studied as models for minimal cells, or protocells. Although in most cases the Marangoni effect is responsible for the forces on the droplet, the behaviour of the droplet depends heavily on the exact composition. Though theoretical models are able to calculate the forces on a droplet, to model a mixture of oils on an aqueous surface where compounds from the oil phase are dissolving and diffusing through the aqueous phase is beyond current computational capability. The behaviour of a droplet in an aqueous phase can only be discovered through experiment, though it is determined by the droplet's composition. By using an evolutionary algorithm and a liquid handling robot to conduct droplet experiments and decide which compositions to test next, entirely autonomously, the composition of the droplet becomes a chemical genome capable of evolution. The selection is carried out according to a fitness function, which ranks the formulation based on how well it conforms to the chosen fitness criteria (e.g. movement or division). Over successive generations, significant increases in fitness are achieved, and this increase is higher with more components (i.e. greater complexity). Other chemical processes such as chemiluminescence and gelation were investigated in active oil droplets, demonstrating the possibility of controlling chemical reactions by selective droplet fusion. Potential future applications for this might include combinatorial chemistry, or additional fitness goals for the genetic algorithm. Combining the self-replication and the droplet protocells research, it was demonstrated that the presence of the amphiphilic replicator lowers the interfacial tension between droplets of a reaction mixture in organic solution and the alkaline aqueous phase, causing them to divide. Periodic sampling by a liquid handling robot revealed that the extent of droplet fission increased as the reaction progressed, producing more individual protocells with increased self-replication. This demonstrates coupling of the molecular scale phenomenon of template self-replication to a macroscale physicochemical effect.

Evaluación de la exposición laboral a sílice en empresas de diferentes sectores económicos en Colombia

Introducción: La sílice es un elemento de fácil aprovechamiento y por sus características fisicoquímicas ha sido ampliamente empleado en la industria como objetivo, materia prima o subproducto que genera silicosis en los trabajadores que han estado expuestos a polvo de sílice a través de los años y es una enfermedad que progresa incluso cuando la exposición cesa. La silicosis es conocida como una enfermedad de alta e histórica incidencia y prevalencia a nivel mundial, por lo que es necesario evaluar la exposición laboral a sílice (fracción respirable) en empresas pertenecientes a diferentes sectores económicos que están afiliadas una ARL en Colombia, para contribuir con información diagnóstica actualizada en diferentes regiones y en variadas actividades económicas. Objetivos: Evaluar la exposición laboral a sílice y el nivel de riesgo en empresas afiliadas a una ARL de acuerdo con su ubicación geográfica, actividad económica, área de trabajo, cargo y relacionar las medidas de control empleadas en cada empresa. Materiales y métodos: Se llevó a cabo un estudio de corte transversal sobre 239 mediciones de higiene industrial de 159 empresas de diferentes actividades través de la asociación de variables ocupacionales con las características de la exposición a sílice. Las variables cuantitativas fueron calculadas empleando medidas de tendencia central como media y mediana y medidas de dispersión como rango y desviación estándar con sus correspondientes coeficientes de variación. El nivel máximo permisible o TLV establecido de acuerdo con los parámetros señalados por la Conferencia Americana de Higienistas Industriales Gubernamentales (ACGIH en inglés) y empleado en este estudio para sílice cristalina, fue de 0,025 mg/m3. Resultados: Las actividades económicas que reportaron las mayores concentraciones corregidas a condiciones estándar de polvo de sílice fueron: la minería y actividades Extractivas con 6,340 mg/m3, el mantenimiento industrial, montajes electromecánicos y civiles con 1,312 mg/m3, la maquinaria, metalmecánica, electrodomésticos y equipos con 0,096 mg/m3 y la construcción con 0,702 mg/m3; Discusión: Se realizó un análisis segmentado en dos grupos A y B de acuerdo con el tiempo de medición, se encontró que para el índice de riesgo en ambos grupos indican una sobre-exposición de los trabajadores a niveles críticos, razón por la cual es necesario generar una estrategia de intervención que permita disminuir a tiempo las concentraciones de sílice en las áreas de trabajo y así reducir la exposición de los trabajadores.

El clientelismo y los resultados electorales de la Alcaldía Mayor de Bogotá y el Concejo de Bogotá: un análisis comparado de 2007, 2011 y 2015

La presente investigación tiene como objetivo principal identificar los acuerdos de apoyo político mutuo entre los candidatos al Concejo y los candidatos a la Alcaldía que influyeron en la captación de votos durante los comicios para la Alcaldía Mayor de Bogotá y el Concejo de Bogotá durante 2007, 2011 y 2015. De esta manera, sostiene que los resultados electorales de estos comicios se relacionan de una manera imperfecta. Por ello, se examinará la relación entre los resultados electorales de la Alcaldía y el Concejo de Bogotá con el fin de hallar correlaciones, transferencias de votos y patrones de comportamiento espaciales. Finalmente, esta investigación establecerá relaciones entre los índices de participación y la presencia de redes clientelistas en las UPZ de Bogotá. Se utilizará el método de investigación cualitativo, mediante trabajo de archivo y cartografía electoral, utilizando principalmente fuentes primarias.

El videojuego League of legends y su efecto en memoria de trabajo visual y solución de problemas

El propósito de este estudio es medir los efectos que tiene el videojuego League of Legends en los procesos cognitivos de memoria de trabajo visual (MVT) y solución de problemas (SP). Para medir dichos efectos se implementó un diseño pre test-post con un grupo experimental y uno control, compuestos cada uno por siete participantes, en donde se evaluaron los procesos previamente mencionados utilizando los cubos de Corsi para MVT y las matrices del WAIS III para SP. Después de realizar los respectivos entrenamientos se encontraron resultados significativos en los diferentes momentos de aplicación. En el grupo experimental se encontraron diferencias en la variable dependiente SP, mientras que en el grupo control en MVT, pero no en la interacción entre grupos ni diferencias entre grupos, lo que sugiere un efecto de familiarización a la prueba.

Cadmium Telluride Magic-Sized Clusters and Superstructures

The aim of the present work is to gain new insights into the formation mechanism of CdTe magic-sized clusters (MSCs) at low temperatures, as well as on their evolution towards 1D and 2D nanostructures and assemblies thereof, under mild reaction conditions. The reaction system included toluene as solvent, octylamine as primary alkylamine, trioctylphosphine-Te as chalcogenide precursor and Cd(oleate)2 as metal precursor. UV-Vis absorption spectroscopy and transmission electron microscopy (TEM) were used to analyze samples containing concentrations of octylamine of 0.2, 0.8 and 2 M: well-defined, sharp absorption peaks were observed, with peaks maxima at 449, 417 and 373 nm respectively, and 1D structures with a string-like appearance were displayed in the TEM images. Investigating peaks growth, step-wise peaks shift to lower energies and reverse, step-wise peak shift to higher energies allowed to propose a model to describe the system, based on interconnected [CdTe]x cluster units originating an amine-capped, 1-dimensional, polymer-like structure, in which different degrees of electronic coupling between the clusters are held responsible for the different absorption transitions. The many parameters involved in the synthesis procedure were then investigated, starting from the Cd:Te ratio, the role of the amine, the use of different phosphine-Te and Cd precursors. The results allowed to gain important information of the reaction mechanism, as well as on the different behavior of the species featuring the sharp absorption peaks in each case. Using Cd(acetate)2 as metal precursor, 2D structures were found to evolve from the MSCs solutions over time, and their tendency to self-assemble was then analyzed employing two amines of different alkyl chain length, octylamine (C-8) and oleylamine (C-18). Their co-presence led to the formation of free-floating triangular nanosheets, which tend to readily aggregate if only octylamine is present in solution.

Photoactive (supra)molecular devices in double layer membranes

Biological systems are complex and highly organized architectures governed by non-covalent interactions responsible for the regulation of essential tasks in all living organisms. These systems are a constant source of inspiration for supramolecular chemists aiming to design multicomponent molecular assemblies able to perform elaborated tasks, thanks to the role and action of the components that constitute them. Artificial supramolecular systems exploit non-covalent interactions to mimic naturally occurring events. In this context, stimuli-responsive supramolecular systems have attracted attention due to the possibility to control macroscopic effects through modifications at the nanoscale. This thesis is divided in three experimental chapters, characterized by a progressive increase in molecular complexity. Initially, the preparation and studies of liposomes functionalized with a photoactive guest such as azobenzene in the bilayer were tackled, in order to evaluate the effect of such photochrome on the vesicle properties. Subsequently, the synthesis and studies of thread-like molecules comprising an azobenzene functionality was reported. Such molecules were conceived to be intercalated in the bilayer membrane of liposomes with the aim to be used as components for photoresponsive transmembrane molecular pumps. Finally, a [3]rotaxane was developed and studied in solution. This system is composed of two crown ether rings interlocked with an axle containing three recognition sites for the macrocycles, i.e. two pH-switchable ammonium stations and a permanent triazolium station. Such molecule was designed to achieve a change in the ratio between the recognition sites and the crown ethers as a consequence of acid-base inputs. This leads to the formation of rotaxanes containing a number of recognition sites respectively larger, equal or lower than the number of interlocked rings and connected by a network of acid-base reactions.

Mitochondrial Inheritance, Mito-nuclear Coevolution, and Sex-associated Genes in Bivalve Molluscs: Transcriptomics and Molecular Evolution

Bivalvia represents an ancient taxon including around 25,000 living species that have adapted to a wide range of environmental conditions, and show a great diversity in body size, shell shapes, and anatomic structure. Bivalves are characterized by highly variable genome sizes and extremely high levels of heterozygosity, which obstacle complete and accurate genome assemblies and hinder further genomic studies. Moreover, some bivalve species presented a stable evolutionary exception to the strictly maternal inheritance of mitochondria, namely doubly uniparental inheritance (DUI), making these species a precious model to study mitochondrial biology. During my PhD, I focused on a DUI species, the Manila clam Ruditapes philippinarum, and my work was two-folded. First, taking advantage of a newly assembled draft genome and a large RNA-seq dataset from different tissues of both sexes, I investigated 1) the role of gene expression and alternative splicing in tissue differentiation; 2) the relationship across tissue specificity, regulatory network connectivity, and sequence evolution; 3) sexual contrasting genetic markers potentially associated with sexual differentiation. The detailed information for this part is in Chapter 2. Second, using the same RNA-seq data, I investigated how nuclear oxidative phosphorylation (OXPHOS) genes coordinate with two divergent mitochondrial genomes in DUI species (mito-nuclear coordination and coevolution). To address this question, I compared transcription, polymorphism, and synonymous codon usage in the mitochondrial and nuclear OXPHOS genes of R. philippinarum in Chapter 3. To my knowledge, this thesis represents the first study exploring the role of alternative splicing in tissue differentiation, and the first study analyzing both transcriptional regulation and sequence evolution to investigate the coordination of OXPHOS genes in bivalves.