Fatigue crack growth in ±-Zirconium phosphate/epoxy nanocomposites was investigated. A new fatigue testing technique was implemented for miniature samples. Two different methods “strength of materials and Rayleigh-Ritz - were used in determining the bending stress. The fatigue stress and fatigue life of different nanocomposite specimens were plotted in a traditional stress-life (S-N) curve. It was inferred from the S-N plot that the values obtained from both the methods compare well. The experimental results showed that fatigue life of filled epoxy nanocomposite is more than that of the unfilled epoxy composite. A model for bending stresses, ultimate strength and the number of cycles to failure was obtained to predict a component service life without conducting elaborate tests. Scanning electron examination of the fractured surfaces revealed that the crack takes a tortuous path during its propagation course, indicating crack blunting and crack deflection roles of ZrP and CSR nanofillers, which consequently improve the fracture resistance. In case of the M-ZrP-epoxy systems, delamination of ZrP platelets from surrounding epoxy matrix was proposed as the reason behind crack growth. The improved fracture resistance of these nanocomposites was attributed to the delamination of ZrP platelets and deflection of crack direction. The superior behavior of CSR-ZrP-epoxy composites was attributed to the cavitation process and void coalescence due to CSR particles delamination.

Electron crystallography is an important technique for studying micro- and nano-sized materials. It has two important advantages over X-ray crystallography for structural studies: 1) crystals millions of times smaller than those needed for X-ray diffraction can be studied; 2) it is possible to; focus the electrons to form an image. The local atomic arrangement can be seen directly by high-resolution transmission electron microscopy (HRTEM). The crystallographic structure factor phases, which are lost in recording diffraction patterns, are present in HRTEM images and can be determined experimentally. The main disadvantages of electron crystallography compared to X-ray diffraction are that the data are difficult to collect, often incomplete and suffer from dynamic scattering. New methods need to be developed to overcome these problems. In this work, structure determination of several unique and complex porous materials including zeolites and mesoporous silica is demonstrated. None of the structures of these materials could be solved by X-ray crystallography. New techniques are also developed in order to overcome the disadvantages of electron crystallography. The new techniques include a digital sampling method for collecting precession electron diffraction data and a rotation method for automatic collection of complete 3D electron diffraction data. A number of practical issues concerning data collection and data processing are described and the data quality is analysed. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Submitted.

Neutrophils are implicated in many inflammatory lung disorders. However, the mechanisms regulating neutrophil migration in acute lung inflammation are incompletely understood. Although, integrin β2 mediates neutrophil migration in lungs in response to many stimuli such as E. coli, integrin involved in <i>S. pneumoniae</i> induced neutrophil migration is not known. Therefore, the role of integrin αvβ3 in neutrophil recruitment was tested. First, it was found that the number of neutrophils expressing the integrin subunits αv and β3 is reduced or remains in lung inflammation induced by E. coli or <i>S. pneumoniae</i>, respectively. Next, the role of integrin αvβ3 using β3 knockout mice (β3-/-) and function blocking antibodies was addressed. Neutrophil recruitment did not vary between wild type and β3-/- mice. Although β3 antibodies reduced neutrophil recruitment, similar effect was observed with isotype antibodies. Therefore, one can conclude that integrin αvβ3 is not critical for neutrophil recruitment in <i>S. pneumoniae</i> induced pneumonia. <p>Apart from integrins, TLR4 also regulate neutrophil migration. Because, the pattern of TLR4 expression at various times of lung inflammation is not known, TLR4 expression during different phases of lung inflammation in a rat model of LPS-induced inflammation was studied. TLR4 expression in the septum increased and decreased at 6h and 12-36h of inflammation, respectively. Since these correlate with the time of increase and decline of neutrophil recruitment, the findings support previously observed requirement for TLR4 in neutrophil recruitment. <p>Neutrophils recruited into the lungs regulate the inflammatory process by controlling subsequent monocyte/macrophage recruitment. The mechanisms involved and the pattern of monocyte/macrophage recruitment in lungs are not completely understood. Therefore, the possible involvement of monocyte chemoattractant protein (MCP)-1, which is a premier chemokine in monocyte/macrophage migration and produced by neutrophils and other cells was tested. This was addressed by quantification of monocytes/macrophages at various times and using neutrophil depletion experiments in LPS-induced lung inflammation in rats. It was found that monocytes/macrophages migrate very early and before neutrophils in addition to their migration in the late phase of acute lung inflammation. Neutrophil depletion abrogated both early as well as the late monocyte/macrophage recruitment without altering the expression of MCP-1. Therefore, possibly other chemokines and not MCP-1 are involved in neutrophil dependent monocyte/macrophage recruitment. <p>To conclude, the experiments further the understanding on acute lung inflammation by ruling-out the involvement of integrin αvβ3 and MCP-1 in β2-independent neutrophil migration and neutrophil dependent monocyte/macrophage recruitment, respectively. Further studies are essential to find the integrins and chemokines operating in the above situations. Equally important will be to understand the functional significance of early recruited monocytes/macrophages in the lung.

Application of carbon nanotubes (CNTs) in various fields demands a thorough investigation of their stability under irradiation. Open structure, ability to reorganize and heal defects, and large surface-to-volume ratio of carbon nanotubes affect materials' radiation response so that it differs from their bulk counterparts. Despite the work conducted to this date, radiation damage and mechanisms governing the evolution of CNTs under irradiation are still deficient in fundamental understanding. This dissertation is aimed to comprehend and characterize radiation response and crystalline-to-amorphous transition in ion and electron irradiated carbon nanotubes using various techniques, including but not limited to, transmission electron microscopy (TEM) and Raman spectroscopy. It shows that ion irradiation can be used to engineer properties of nanotubes in a controllable manner and significantly improve thermal diffusivity and conductivity of the material. This work also establishes the role of nuclear and electronic stopping powers in thermal diffusivity enhancement: thermal properties of irradiated CNTs are governed by nuclear stopping power of bombarding species. The change of thermal properties with irradiation is driven by two competing mechanisms: inter-tube displacement-mediated phonon transport and defect-induced phonon scattering. In addition to experiments, molecular dynamic simulations are used to confirm validity of the obtained results. Radiation damage in CNTs at various temperatures as a function of ion energy, flux and fluence is examined. Mechanisms governing crystalline-to-amorphous transition under electron and ion irradiations are explored, applicability of previously suggested models discussed, and new models introduced. The results show enhanced defect annealing at elevated irradiation temperatures, which delays the formation of amorphous regions. Investigation of nanotube stability after various processing techniques and irradiation indicated that radiation response of CNTs in a composite is similar to that of individual nanotubes.

En aquest treball s'ha determinat l'efecte i la capacitat de captació dels metalls pesants (Pb i Cu) per part de diferents microorganismes fotòtrofs i heteròtrofs, mitjançant tècniques microscòpiques d'alta resolució per tal de seleccionar microorganismes com a indicadors de contaminació per metalls. Per a aquest objectiu, han estat seleccionats diferents microorganismes fotòtrofs aïllats dels tapets microbians del delta de l'Ebre (un ecosistema declarat Parc Natural al 1983) i cianobacteris de la col.lecció de cultius Pasteur (PCC). Aquests tapets on dominen els microorganismes fotosintètics com els cianobacteris i les algues (productors primaris en aquests ecosistemes) poden patir contaminació per compostos tòxics com ara el petroli o els metalls pesants. En aquest treball, els metalls assajats per a la selecció de bioindicadors, han estat el plom (Pb) i el coure (Cu) donat que tots dos s'han detectat en el riu Ebre, i també perquè el primer és molt tòxic i no presenta cap funció biològica i el segon és en canvi un element essencial a baixes dosis i tòxic a elevades dosis. Per determinar la sensibilitat a un metall (tolerància-resistència), s'ha utilitzat la microscopia làser confocal acoblada a un detector espectrofluoromètric (CLSM-λscan). Els resultats demostren que Chroococcus sp. PCC 9106 i la microalga DE2009 presenten una major tolerància a Pb (0.5 mM) que Oscillatoria sp. PCC 7515 i Spirulina sp. 6313 (0,1 mM). Per determinar la biocaptació externa i interna del metall, s'ha utilitzat la microscòpia electrònica de rastreig (SEM), la microscòpia electrònica de transmissió (TEM) i el microanàlisi d'energia dispersiva per raigs X (EDX) acoblada a aquests dos microscopis. Els resultats indiquen que, tots els microorganismes utilitzats (tant els fotòtrofs com els heteròtrofs) tenen la capacitat d'acumular Pb i Cu externament en el seu EPS. Finalment, l'anàlisi de les seccions ultrafines (TEM-EDX) mostra que tots els microorganismes fotòtrofs estudiats acumulen Pb en les inclusions de polifosfat (PP). Per contra, els bacteris heteròtrofs tot i presentar aquestes inclusions, no acumulen cap dels dos metalls, ni en el citoplasma ni en les inclusions intracel·lulars. Una vegada provada l'eficàcia d'aquestes tècniques microscòpiques tant en els microorganismes aïllats de l'ambient natural com en els de col.lecció, s'ha realitzat el mateix tipus d'assajos en microcosmos, amb l'objectiu d'obtenir bons bioindicadors de contaminació per metalls, tenint com a objectiu final la seva aplicació en l'ambient natural. En aquests experiments s'ha assajat únicament el Pb, i s'ha comprovat que igual que en els cultius, els microorganismes més abundants seleccionats en aquest sistema artificial, Lyngbya-like i Phormidium-like (cianobacteris) tenen la capacitat d'acumular aquest metall tant externa com internament i sempre en inclusions de PP. Considerant tots els resultats obtinguts es podria concloure que tots els cianobacteris i la microalga DE2009 analitzats podrien ser considerats bons indicadors de contaminació per metalls. No obstant això, Oscillatoria sp. i Microcoleus sp. han estat seleccionats per ser: els més abundants en l'ambient natural, de major grandària, tolerants a elevades concentracions de metalls i finalment per la seva capacitat d'acumular-los extra i intracel·lularment. / In this work, the effect and capacity to capture heavy metals (Pb and Cu) of different phototrophic and heterotrophic microorganisms have been studied through high-resolution microscopy techniques in order to select microorganisms as metal pollution indicators. For this purpose, different phototrophic microorganisms isolated from Ebro Delta microbial mats (an ecosystem declared as Natural Park in 1983) and cyanobacteria from the Pasteur culture collection (PCC) have been selected. These mats, dominated by photosynthetic microorganisms like cyanobacteria and algae (primary producers in these habitats) can suffer pollution by toxic compounds such as oil or heavy metals. In this study, metals tested to select the bioindicators were lead (Pb) and copper (Cu), as both have been detected in the Ebro River, and also because the former is very toxic, showing no biological function, while the latter, by contrast, is an essential element at low doses, while at high doses it is toxic. To determine the sensitivity to a metal (tolerance-resistance), confocal laser microscopy coupled to a spectrofluorometric detector (CLSM-λscan) has been used. The results show that Chroococcus sp. PCC 9106 and DE2009 microalgae show greater tolerance to lead Pb (0.5 mM) than Oscillatoria sp. PCC 7515 and Spirulina sp. 6313 (0.1 mM). To determine the external and intracellular metal biocapture, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive Xray microanalysis (EDX) coupled with these microscopes have been used, respectively. The results indicated that, all the microorganisms tested (both phototrophic and heterotrophic) have capacity to accumulate Pb and Cu externally in the EPS. Finally, the analysis of ultrathin sections (TEM-EDX) shows that all the phototrophic microorganisms studied accumulate Pb in the polyphosphate inclusions (PP). By contrast, although the heterotrophic bacteria show these inclusions, they do not accumulate either of the two metals either in cytoplasm or in intracellular inclusions. Once the effectiveness of these microscopy techniques has been shown both in microorganisms isolated from the natural environment and in those from the culture collection, the same tests have been carried out in microcosms in order to obtain good bioindicators of metal pollution, with the ultimate aim of applying them in the natural environment. In these experiments it has been shown that, as in cultures, the most abundant microorganisms selected in this artificial ecosystem, Lyngbya-like and Phormidium-like (cyanobacteria), have the capacity to accumulate this metal both externally and internally, always in PP inclusions. Considering all the results obtained it can be concluded that all cyanobacteria and DE2009 microalga analysed could be considered good metal pollution indicators. However, Oscillatoria sp. and Microcoleus sp. have been selected as the best indicators of metal pollution in the natural environment because: they are the most abundant, largest in size, tolerant to high concentrations of metals and, finally, capable of accumulating metal extra- and intracellularly.

No description available.

Neutrophils are implicated in many inflammatory lung disorders. However, the mechanisms regulating neutrophil migration in acute lung inflammation are incompletely understood. Although, integrin β2 mediates neutrophil migration in lungs in response to many stimuli such as E. coli, integrin involved in <i>S. pneumoniae</i> induced neutrophil migration is not known. Therefore, the role of integrin αvβ3 in neutrophil recruitment was tested. First, it was found that the number of neutrophils expressing the integrin subunits αv and β3 is reduced or remains in lung inflammation induced by E. coli or <i>S. pneumoniae</i>, respectively. Next, the role of integrin αvβ3 using β3 knockout mice (β3-/-) and function blocking antibodies was addressed. Neutrophil recruitment did not vary between wild type and β3-/- mice. Although β3 antibodies reduced neutrophil recruitment, similar effect was observed with isotype antibodies. Therefore, one can conclude that integrin αvβ3 is not critical for neutrophil recruitment in <i>S. pneumoniae</i> induced pneumonia. <p>Apart from integrins, TLR4 also regulate neutrophil migration. Because, the pattern of TLR4 expression at various times of lung inflammation is not known, TLR4 expression during different phases of lung inflammation in a rat model of LPS-induced inflammation was studied. TLR4 expression in the septum increased and decreased at 6h and 12-36h of inflammation, respectively. Since these correlate with the time of increase and decline of neutrophil recruitment, the findings support previously observed requirement for TLR4 in neutrophil recruitment. <p>Neutrophils recruited into the lungs regulate the inflammatory process by controlling subsequent monocyte/macrophage recruitment. The mechanisms involved and the pattern of monocyte/macrophage recruitment in lungs are not completely understood. Therefore, the possible involvement of monocyte chemoattractant protein (MCP)-1, which is a premier chemokine in monocyte/macrophage migration and produced by neutrophils and other cells was tested. This was addressed by quantification of monocytes/macrophages at various times and using neutrophil depletion experiments in LPS-induced lung inflammation in rats. It was found that monocytes/macrophages migrate very early and before neutrophils in addition to their migration in the late phase of acute lung inflammation. Neutrophil depletion abrogated both early as well as the late monocyte/macrophage recruitment without altering the expression of MCP-1. Therefore, possibly other chemokines and not MCP-1 are involved in neutrophil dependent monocyte/macrophage recruitment. <p>To conclude, the experiments further the understanding on acute lung inflammation by ruling-out the involvement of integrin αvβ3 and MCP-1 in β2-independent neutrophil migration and neutrophil dependent monocyte/macrophage recruitment, respectively. Further studies are essential to find the integrins and chemokines operating in the above situations. Equally important will be to understand the functional significance of early recruited monocytes/macrophages in the lung.

<p>Melanin is a biological pigment that is ubiquitous in nature and generally produced within melanosomes, specialized organelles. Typically, melanin is categorized into two distinct classes, based on color and molecular precursor: eumelanin (brown-black) and pheomelanin (yellow-red). Whereas much is known regarding the molecular precursors to the two pigments, an understanding of their resulting molecular structure remains elusive. Despite this lack of knowledge, several functions are attributed to the pigments, including photoprotection and photosensitization. Epidemiological data for skin and ocular cancers have observed an increased incidence for increased relative concentrations of pheomelanin. Furthermore, eumelanin is generally identified as photoprotective and antioxidant, whereas pheomelanin is generally identified as photoreactive and pro-oxidant. This thesis describes the photophysical properties of the naturally-occuring melanin pigments and presents new insights into their roles within the context of skin and ocular cancers.</p><p> Photoemission electron microscopy provides a unique opportunity to probe the complex photoproperties of melanins contained within intact melanosomes isolated from tissues of bovine and human eyes. Photoionization threshold potentials characteristic of eumelanin and pheomelanin have been determined and are used to investigate the molecular architecture of the pigments within the melanosome. Furthermore, a novel approach to photoemission electron microscopy is used to obtain the first direct measurements of the absorption coefficients from intact melanosomes. </p><p> Human iridal stroma melanosomes are comprised of both eumelanin and pheomelanin in various ratios according to iris color; dark brown and blue-green iris melanosomes are characterized by a eumelanin:pheomelanin ratio of 14.8 and 1.3, respectively. Despite the significant difference in the overall pigment composition, a common eumelanin surface photoionization threshold is obtained for both melanosomes. This data indicates that within the melanosome, the phototoxic pheomelanin pigment is encased by eumelanin. This structure mitigates the adverse photochemical properties of pheomelanin. However, damage to the eumelanic exterior and or significant reduction in the amount of eumelanin present could compromise the protective ability of eumelanin, providing mechanisms for exposure of pheomelanin and consequently contributing to oxidative stress.</p><p> The absorption spectra of intact melanosomes of varying melanin compositions were determined over the spectral range from 244 to 310 nm. The absorption spectra of eumelanic melanosomes are similar regardless of monomer composition or embryonic origin. Furthermore, the absorption spectra of melanosomes containing a mixture of pigments were similar to those containing pure eumelanin, arguing that the absorption properties of the melanosome are maintained regardless of increased pheomelanin composition. Therefore, the correlation between epidemiological data and the eumelanin:pheomelanin ratio is not predicted to be a reflection of the melanosome's decreased ability to attenuate biologically relevant wavelengths, but instead is predicted to be a reflection of the different photoreactivities of the melanin pigments contained within.</p> / Dissertation

The stable interfaces between NiO and ZrO2 reached by nanofilms interface rotation method are reported in this study. Epitaxial nanofilms of NiO and ZrO2 were synthesized on single crystal NaCl (001), (011), (111) surfaces. All nanofilms are investigated by transmission electron microscopy and selected-area diffraction (SAD) patterns. Composite nanofilms were formed by overlapping nanofilms of NiO and ZrO2 at difference angles and thermally treated. The rotation process and final stable interfaces in the overlapped nanofilms are analyzed by SAD patterns. Orientation relationships and interface rotation are analyzed. This study found five new interfaces. (1) (001)N/ Z¡A[110]N//[110]Z (2) (001)N/ Z¡A[100]N//[110]Z (3) N/ Z¡A[110]N//[110]Z (4) N/ Z¡A[111]N//[110]Z (5) N/ Z¡A[001]N//[110]Z

The present study aims at clarifying the effects of processing parameters and substrate orientation on the epitaxial growth of Ni on polycrystalline Cu by electrodeposition from a sulfamate solution. The deposits were analyzed by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), auger electron spectroscopy (AES) and transmission electron microscopy (TEM). Two morphologies: rough and smooth, of the substrate surface were introduced by electropolishing. Auger electron spectroscopy showed that Ni was deposited on both areas without preference. However, the deposition rate for the rough area was slightly higher at a low current density of 0.01 A/dm2. At higher current densities, both areas possessed the same rate of deposition. In-plane TEM results demonstrated that Ni deposited on Cu epitaxially regardless the orientation of the Cu grains, electrolyte temperature and current density. EBSD analysis indicated that the Ni epilayer with an orientation of <001>//ND grew epitaxially to as thick as 12 £gm, whereas randomly oriented Ni nucleated on the epilayer having orientations of <011>//ND or <-111>//ND on prolonging deposition at current of 10 A/dm2. In other words, the epitaxial growth of Ni on Cu cannot be sustained to a thickness of hundreds of micrometers without a <001>//ND orientation.