Marine ecosystems can be a promising reservoir of various kinds of chemical components, applicable as pharmaceutical materials, food, cosmetics, nutraceuticals, and others for different industry. As an example, Tunicates, a group of marine animals, have been attracted a lot of attention in medical application, food market, water pollution issues, and Cellulose nanomaterial production due to their consisting of chemical compounds such as cellulose, amino-sugars, and proteins or protein-polysaccharide complexes e.g. collagen, glycosaminoglycan, chitin, scleroprotein, iodine-binding proteins, and elastin. In this project,  two dominant species of Scandinavian Tunicates, i.e. Ciona intestinalis and Clavelina lepadiformis, harvested from Norwegian ocean have been classified according to body sizes, depths from the ocean surface, ages and species, and separated physically into outer layer and internal organs, followed by measurements of sugar composition, oil content, and  protein content. Application potentials have been investigated by trials for production of pure crystalline cellulose, bioethanol, and biodiesel, and by analysis of amino acid composition of the samples. The cellulose percentage and cellulose yield for the chemically pure cellulose obtained, is around 96% and 54% respectively, and the protein content is decreased step by step by the acid, alkali, and bleaching process applied. Bioethanol can be obtained by fermentation of tunicate hydrolysate with strains A and C which are derived from Saccharomyces cerevisiae. The biodiesel yield of tunicate samples is around 4-6% as an average. The amino acid compositions in our tunicate samples are similar to egg albumin, implying tunicate being an alternative material for animal feed production. Several processing treatments have been conducted with the aims to fractionate tunicate biomass components or enhance the cellulose accessibility and reactivity. After a single processing step, Ba(OH)2 treated samples seemed to be the best in terms of both cellulose preservation (66.5% cellulose) and protein removal (6% protein in the treated residue). Results from the physical separation plus washing reveal that the highest amount of cellulose and protein presents is found in the outer (Tunic) part and internal organs of Tunicate samples respectively. Data obtained from FTIR(Fourier Transform Infrared Spectroscopy) and SEM(Scanning Electron Microscope) indicate that among all processing trials, H3PO4 is the most effective in decreasing the cellulose crystallinity, which renders a higher accessibility for acidic or enzymatic reaction during bioethanol production due to a higher amount of amorphous structure of cellulose. From the analysis results of component contents and structures, it could be concluded that increase of deepness results in a decrease of sugar content of the Tunicate samples while there are no differences in protein and carbohydrate content in different tunicate species. The body size has a positive influence on the protein content and the sample age alters the contents of both sugar and protein. In addition, Tunicate oil has high phospholipid content instead of glycerol ester, the latter being the common oil from vegetable origins. Moreover, lots of free fatty acid is present, and the composition profile of Tunicate fatty acids seems to be similar to fish oil, as revealed by NMR (Nuclear Magnetic Resonance Spectroscopy), FTIR, and GC-MS (Gas Chromatography-Mass Spectrometry).

Marine ecosystems can be a promising reservoir of various kinds of chemical components, applicable as pharmaceutical materials, food, cosmetics, nutraceuticals, and others for different industry. As an example, Tunicates, a group of marine animals, have been attracted a lot of attention in medical application, food market, water pollution issues, and Cellulose nanomaterial production due to their consisting of chemical compounds such as cellulose, amino-sugars, and proteins or protein-polysaccharide complexes e.g. collagen, glycosaminoglycan, chitin, scleroprotein, iodine-binding proteins, and elastin. In this project,  two dominant species of Scandinavian Tunicates, i.e. Ciona intestinalis and Clavelina lepadiformis, harvested from Norwegian ocean have been classified according to body sizes, depths from the ocean surface, ages and species, and separated physically into outer layer and internal organs, followed by measurements of sugar composition, oil content, and  protein content. Application potentials have been investigated by trials for production of pure crystalline cellulose, bioethanol, and biodiesel, and by analysis of amino acid composition of the samples. The cellulose percentage and cellulose yield for the chemically pure cellulose obtained, is around 96% and 54% respectively, and the protein content is decreased step by step by the acid, alkali, and bleaching process applied. Bioethanol can be obtained by fermentation of tunicate hydrolysate with strains A and C which are derived from Saccharomyces cerevisiae. The biodiesel yield of tunicate samples is around 4-6% as an average. The amino acid compositions in our tunicate samples are similar to egg albumin, implying tunicate being an alternative material for animal feed production. Several processing treatments have been conducted with the aims to fractionate tunicate biomass components or enhance the cellulose accessibility and reactivity. After a single processing step, Ba(OH)2 treated samples seemed to be the best in terms of both cellulose preservation (66.5% cellulose) and protein removal (6% protein in the treated residue). Results from the physical separation plus washing reveal that the highest amount of cellulose and protein presents is found in the outer (Tunic) part and internal organs of Tunicate samples respectively. Data obtained from FTIR(Fourier Transform Infrared Spectroscopy) and SEM(Scanning Electron Microscope) indicate that among all processing trials, H3PO4 is the most effective in decreasing the cellulose crystallinity, which renders a higher accessibility for acidic or enzymatic reaction during bioethanol production due to a higher amount of amorphous structure of cellulose. From the analysis results of component contents and structures, it could be concluded that increase of deepness results in a decrease of sugar content of the Tunicate samples while there are no differences in protein and carbohydrate content in different tunicate species. The body size has a positive influence on the protein content and the sample age alters the contents of both sugar and protein. In addition, Tunicate oil has high phospholipid content instead of glycerol ester, the latter being the common oil from vegetable origins. Moreover, lots of free fatty acid is present, and the composition profile of Tunicate fatty acids seems to be similar to fish oil, as revealed by NMR (Nuclear Magnetic Resonance Spectroscopy), FTIR, and GC-MS (Gas Chromatography-Mass Spectrometry).

This thesis documents three main projects performed during my PhD. Chapter 3 describes a published project in which detailed behavioral analysis based on machine learning approaches for pose-estimation were used to characterize a novel sensorimotor transformation in which mice use whisker information to rapidly modify their gait in order to rapidly avoid an obstacle in their path (Warren et al., 2021). I contributed to designing experiments, data collection and analysis related to this project spanning roughly from Aug. 2018 to Aug. 2019. Appendix 1 describes a follow-up study in which I performed multi-site silicon probe recordings and anatomical reconstruction of recording sites across the deep cerebellar nuclei in head-fixed mice performing the same obstacle avoidance behavior mentioned above. Data collection for this project spanned roughly from May 2019 to Jan. 2021. This data was initially analyzed in collaboration with Richard Warren and is currently being analyzed in collaboration with Ramin Kajeh in Dr. Larry Abbott’s group. Finally, Chapter 2 reports on the major independent work undertaken as part of my thesis, spanning from Sept. 2021 to present. As such, the Introduction relates solely to Chapter 2. The goal of this ongoing project is to extend the Sawtell laboratory studies of the mechanisms for sensory prediction and cancellation in the cerebellum-like circuitry of the electrosensory lobe (ELL) of electric fish to a cerebellum-like circuit in mammals, the dorsal cochlear nucleus (DCN) in the auditory brainstem. In particular, my work provides initial insights into the function of the cartwheel cell (CWC), a previously enigmatic cell type that occupies a similar place in the circuitry of the dorsal cochlear nucleus as the Purkinje cell of the cerebellum and the medium ganglion (MG) cell of the ELL. We have demonstrated that CWCs convey tonotopically-specific signals that are well-suited for canceling self-generated auditory responses in fusiform cells (FCs), the principal output cells in the DCN. Additionally, our findings reveal that the two characteristic types of spikes observed in CWCs—the axonal simple spikes (comparable to simple spikes in Purkinje cells and narrow spikes in MG cells) and dendritic complex spikes (similar to complex spikes in Purkinje cells and broad spikes in MG cells)—are distinctly modulated by both self-generated behavior and external acoustic stimuli, suggesting that these two types of spikes serve separate functional roles in the processing of the cancellation signal, as well as auditory information, within the DCN circuitry. This finding is consistent with the reported distinct functions of narrow and broad spikes in MG cells within the circuitry of the ELL, suggesting an evolutionarily conserved role of Purkinje-like cells in cerebellum-like circuits.

L'estérification est une méthode connue pour contourner les difficultés liées à la mise en œuvre de la cellulose (faible compatibilité avec les matériaux apolaires, agrégation, hydrophilie). Notre étude a ainsi porté sur le développement d'un procédé en phase gazeuse (sans solvant) permettant le greffage de chlorure d'acide gras sur les hydroxyles de la cellulose. L'étude de cette réaction s'est faite à différentes échelles: de la fibre aux whiskers de cellulose. En premier lieu, le procédé a été étudié pour l'hydrophobisation du papier. Le développement d'une modélisation en parallèle des résultats expérimentaux a permis d'appréhender les cinétiques de diffusion et de greffage impliquées. L'estérification a ensuite été élargie à des substrats possédant de plus grandes surfaces spécifiques : les microfibrilles issues de pâte de bois, les whiskers (coton, tunicier) et la cellulose bactérienne. Les mesures du degré d'avancement de la réaction par RMN du solide et par gravimétrie ont montré que la densité de greffage était influencée non seulement par les conditions expérimentales mais également par la nature des substrats. Sous certaines conditions, une substitution pratiquement complète est possible. Les changements de morphologie et de structure induits par la réaction ont été étudiés par diffraction des rayons X, microscopie électronique à transmission et calorimétrie différentielle à balayage. Des caractérisations par analyse mécanique dynamique (DMTA) et par des tests de traction ont montré que l'incorporation de microfibrilles dérivatisées permet une amélioration significative des propriétés mécaniques d'un polyéthylène sans diminution majeure de sa résilience.

In the first part of this diploma thesis there are discribed basic findings about cutting ceramics (sorts, notation, structure, physical-mechanical properties, using, production) and it evaluates this tool material from the aspect of cutting power. The second part focuses on complex data processing about assortment of ceramics cutting materials of significant tool materials producers and comparison of service conditions (kind of mechanided materials, cutting conditions), which are recommend for effective turning by producers.

Environmental concerns arising from the use of non-degradable plastics have resulted in search for suitable substitutes. The thesis deals with new nanostructured composites based on reinforcement of nanocellulose whiskers in "green" polymers such as xylan. Since the reinforcement filler and the matrix are both biobased and are thereby environmental friendly. Xylan incorporated with cellulose whiskers films provided with improved water and oxygen barrier properties. It appears that the high degree of crystallinity of cellulose whiskers, dense composite structure formed by the whiskers and rigidly hydrogen-bonded cellulose whiskers can cause cellulose whiskers to form integrated matrix which contribute to substantial benefit in the overall reduction of transmission rate. The spectral data obtained for the NCW/xylan nanocomposite films showed that the amount of xylan adsorbed to cellulose increases with the addition of NCW in the matrix. In addition, NMR T2 relaxation experiments studies were conducted to investigate the change in the nature of carbohydrate-water interactions as a result of NCW incorporation. These results facilitated an improved understanding of the mechanisms involved in the superior barrier and mechanical properties of xylan-whisker nanocomposite films. XRD studies show that when a xylan-whisker nanocomposite films is formed the mixing occurs on the atomic scale and NCW loading increases the matrix crystallinity.

The impedance response of silicon carbide whisker-alumina composites is investigated utilizing novel stereological techniques along with a microstructural simulation. The stereological techniques developed allow for a measurement of the trivariate length, radius and orientation distribution of whiskers in the composite from measurements made on two-dimensional sectioning planes. The measured distributions are then utilized in a Monte Carlo simulation that predicts connectivity in the composite for a given volume fraction. It is assumed in the simulation that connectivity factors dominate the electrical response, not interfacial phenomena. The results of the simulation are compared with impedance spectra taken from real samples, and conclusions are drawn regarding the nature of the impedance response.

Ceramic-matrix composites of alumina and silicon carbide whiskers have recently found novel commercial application as electromagnetic absorbers. However, a detailed understanding of how materials issues influence the composite electrical response, which underpins this application, has been absent until now. In this project, such composites were electrically measured over a wide range of conditions and modeled in terms of various aspects of the microstructure in order to understand how they work. For this purpose, three types of composites were made by different methods from the same set of ceramic powder blends loaded with different volume fractions of whiskers. In doing so, the interfaces between whiskers, the preferred orientations of whiskers, and the structure of electrically-connected whisker clusters were varied; the whisker aspect-ratio distributions were the same for all methods. At the electrode interfaces, Schottky barriers at the junctions of the electrically-percolating wide-bandgap semiconductor whiskers on the surface were responsible for a significant portion of the total measured impedance. The associated electrical response was studied on the microscopic and macroscopic level, and the gap between these different scales was bridged. Also, a modeling approach was developed for the non-linear behavior of the composite which results from these barriers. In regards to the whiskers within the composite bulk, the effects of various factors on the wide-band frequency dependence of the dielectric response and dc conductivity were explained and contextualized for the electromagnetic absorber application. Such factors include whisker preferred orientation, electrical percolation and cluster structure, the interfaces between electrically-connected SiC whiskers, and porosity. A quantitative correlation between the anisotropy of the microstructure and that of the conductivity was found, and was understood in terms of the interfacial SiC-Al2O3-SiC conduction mechanism. This behavior was shown to differ from the behavior commonly observed for other disordered mixtures of relatively conductive particles dispersed inside insulating polymer hosts. A description of this new mechanism was developed based on an observed correlation between the temperature dependencies of the static and radio-frequency electrical responses. Also, the aforementioned non-linear response model was expanded upon to describe conduction through and across electrically-percolated clusters. The model demonstrates how loading and interface behavior influence the topology and the strength of the non-linear response of the clusters.

Made available in DSpace on 2014-10-09T12:45:01Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:20Z (GMT). No. of bitstreams: 1 07007.pdf: 10191940 bytes, checksum: 90f949a8767cea7a6c8e8cc3d2aee4ee (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:45:01Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:20Z (GMT). No. of bitstreams: 1 07007.pdf: 10191940 bytes, checksum: 90f949a8767cea7a6c8e8cc3d2aee4ee (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP