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The gear noise problem that widely occurs in power transmission systems is typically characterised by one or more high amplitude acoustic signals. The noise originates from the vibration of the gear pair system caused by transmission error excitation that arises from tooth profile errors, misalignment and tooth deflections. This work aims to further research the effect of tooth profile modifications on the transmission error of gear pairs. A spur gear pair was modelled using finite elements, and the gear mesh was simulated and analysed under static conditions. The results obtained were used to study the effect of intentional tooth profile modifications on the transmission error of the gear pair. A detailed parametric study, involving development of an optimisation algorithm to design the tooth modifications, was performed to quantify the changes in the transmission error as a function of tooth profile modification parameters as compared to an unmodified gear pair baseline. The work also investigates the main differences between the static and dynamic transmission error generated during the meshing of a spur gear pair model. A combination of Finite-Element Analysis, hybrid numerical/analytical methodology and optimisation algorithms were used to scrutinise the dynamic behaviour of the gear pairs under various operating conditions.

We evaluate the changes in fluorescence from endogenous fluorophores such as amino acids, structural proteins and enzymatic co-factors to predict malignancy and risk of developing ovarian cancer. 249 ovarian biopsies of the surface epithelium were interrogated in vitro, over 270-550 nm excitation, and fluorescence was collected from 290-700nm. Spectroscopic data was analyzed using parallel factor analysis (PARAFAC) to determine excitation and emission spectra of the underlying fluorophores that contribute to the total detected fluorescence intensity. Using multivariate normal distribution fits and cross-validation techniques, sensitivity (SN) and specificity (SP) of 88 and 93 percent, respectively, were achieved when classifying malignant samples versus others, while 88 and 80 percent, respectively, were achieved when classifying normal post menopausal patients as being either at low- or high-risk of developing ovarian cancer based on their personal and family history of cancer. Also, the performance of classifying cancer increases when the normal group excludes benign neoplasm and endometriosis samples, while the performance of low- v. high-risk decreases when both pre- and post-menopausal samples are included. These results could potentially be useful in screening women at increased risk of developing ovarian cancer. This motivated our study to investigate similar changes in ovarian autofluorescence in vivo. 40 patients were recruited and a total of 189 samples were imaged using a fiber optic bundle and biopsied. Using PARAFAC, the factors computed from in vitro data analysis and in vitro data as a training set; pathology from each in vivo site biopsied was compared to calibrated tissue-fluorescence. It resulted in a SN and SP of 100 and 94 percent, respectively, for classifying normal versus malignant. In the case of risk assessment, cross validated in vivo data gave a SN and SP of 68 and 93%. Results obtained were consistent with those obtained in vitro, except for the presence of blood absorption peaks which affected risk assessment. Assessing endogenous fluorescence has diagnostic potential and if adapted to trans-vaginal access, would make the screening procedure less costly and less invasive, and would be most useful and economical in women at increased risk of developing ovarian cancer and might determine the ideal time to undergo an oophorectomy.

The overall goal of the thesis is to establish detailed comparisons among different well-known models of excitations in their application on Microstrip-like Monopoles. Comparisons are made over the input impedances predicted by these excitations. In this way, the Galerkin’s version of the Method of Moment is applied and rooftops functions are chosen as our basis/weighting functions. Different excitation models have their influence over the excitation vector and a unique MoM matrix is used to give input impedances. We shall elicit the effects of several parameters over relative input self/mutual impedances derived from these excitation models and finally make conclusions about their differences in anticipating the input Resistance, input Reactance and also resonance frequencies.

During photosynthesis sunlight is absorbed by photosynthetic pigments and converted into organic compounds, such as carbohydrates. Photosynthesis needs to be highly regulated, since both too much and too little light are harmful to plant. If too little light is absorbed, a plant cannot store enough energy, which will have effects on growth and fitness of the plant. With too much light absorbed, a dangerous side reaction of photosynthesis, the production of reactive oxygen species can happen. These reactive oxygen species can damage the proteins in the chloroplast and the lipids of the chloroplast. To avoid the production of reactive oxygen species, plants have evolved many mechanisms, which act on different time-scales and different levels of organization. As a first measure, when the absorbed light is exceeding the capacity for its utilization, is to switch the light-harvesting antenna from efficient light harvesting to energy dissipation. This process is called feedback de-excitation (FDE). The protein PsbS is essential for this process as well as a functioning xanthophylls cycle with the enzyme violaxanthin de-epoxidase (VDE). I have investigated the effects of plants with changes in their ability to dissipate excess excitation energy in the model plants species Arabidopsis thaliana. Three genotypes with either increased or decreased capacity for FDE were used during my experiments. The first genotype over-expresses the PsbS gene, having approximately two-fold increased amounts of PsbS and FDE. The second is a PsbS deletion mutant with no PsbS protein and no FDE. The third genotype cannot perform the conversion of violaxanthin to zeaxanthin, because the enzyme VDE is missing. This mutant has some FDE left. Arabidopsis thaliana is an annual plant, which flowers only once in its lifetime. Therefore, when counting the seeds produced an estimation of fitness can be made from the amount of seeds produced. This was done during my experiments and shown that FDE is a trait and that plants with increased FDE have a higher fitness and vice versa. This was also the case for a collection of plants lacking a single protein from the light harvesting antenna. All of these genotypes had a fitness reduction, proving that their function is not redundant. In an attempt to explain why the fitness is reduced in plants with altered FDE, photosynthetic measurements, as well as a determination of the transcriptome and the metabolome was performed. Plants lacking FDE had higher levels of photoinhibition, leading both to lower rates of photosynthesis and to higher repair cost. This could in part explain the reduction in fitness. These plants also had major changes in their transcriptome and their metabolome. Primary metabolism was most effected, for example carbohydrate and amino acid metabolism. But there were also changes in secondary metabolism such as an up regulation of the biosynthesis of anthocyanins.

It is considered that coincident inputs from multiple presynaptic axons are required to achieve both the suprathreshold level of excitation for the central neurons and the activation of NMDA receptors. The aim of the present study was to determine, whether a discharge of single retinal ganglion cell, which axon terminates in the tectum layer F, can evoke a suprathreshold excitation of frog tectum neurons and activate the NMDA receptors. Extracellular recordings of the neuronal activity elicited by the electrical stimulation of single optic fiber were made in frog tectum. We conclude, that: (1) a train of action potentials of single optic fiber, which terminates in the frog tectum layer F, surely elicits a suprathreshold excitation of tectal neurons at physiological conditions. The suprathreshold level is achieved due to the frequency facilitation of the fast non-NMDA retinotectal synaptic potentials. (2) The train of action potentials of higher frequency activates the NMDA receptors of the tectal neurons at physiological conditions. The activation of NMDA receptors is achieved due to the temporal summation and frequency facilitation of the fast synaptic potentials. (3) Two different kinds of optic fibers (likely darkness and moving edge detectors) exhibit different efficiency to achieve both the suprathreshold excitation of the tectal neurons and the activation of NMDA receptors. Findings of the present study improve the understanding of how the local neural network operates... [to full text]

Fluorescence-based techniques are widely used in bioscience, offering a high sensitivity and versatility. In this work, fluorescence electronic energy migration/ transfer is applied to measure intramolecular distances in two types of systems and under various conditions. The main part of the thesis utilizes the process of donor-acceptor energy transfer to probe distances within the ribosomal protein S16. Proteins are essential to all organisms. Therefore, it is of great interest to study protein structure and function in order to understand and prevent protein malfunction. Moreover, it is also important to try to study the proteins in an environment which resembles its natural habitat. Here two protein homologs were investigated; S16Thermo and S16Meso, isolated from a hyperthemophilic bacterium and a mesophilic bacterium, respectively. It was concluded that the chemically induced unfolded state ensemble of S16Thermo is more compact than the corresponding ensemble of S16Meso. This unfolded state compaction may be one reason for the increased thermal stability of S16Thermo as compared to S16Meso. The unfolded state of S16 was also studied under highly crowded conditions, mimicking the environment found in cells. It appears that a high degree of crowding, induced by 200 mg/mL dextran 20, forces the unfolded state ensemble of S16Thermo to become even more compact. Further, intramolecular distances in the folded state of five S16 mutants were investigated upon increasing amounts of dextran 20. We found that the probed distances in S16Thermo are unaffected by increasing degree of crowding. However, S16Meso shows decreasing intramolecular distances for all three studied variants, up to 100 mg/mL dextran. At higher concentrations, the change in distance becomes anisotropic. This suggests that marginally stable proteins like s16Meso may respond to macromolecular crowding by fine-tuning its structure. More stable proteins like S16Thermo however, show no structural change upon increasing degree of crowding. We also investigated the possibility of local specific interactions between the protein and crowding agent, by means of fluorescence quenching experiments. Upon increasing amounts of a tyrosine labelled dextran, a diverse pattern of fluorescence quantum yield and lifetime suggests that specific, local protein-crowder interactions may occur. In a second studied system, electronic energy migration between two donor-groups, separated by a rigid steroid, was studied by two-photon excitation depolarization experiments. Data were analysed by using recent advances, based on the extended Förster theory, which yield a reasonable value of the distance between the two interacting donor-groups. To the best of our knowledge, this is the first quantitative analysis of energy migration data, obtained from two-photon excited fluorescence.

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Introduction We measured the excitation functions of natZn (p,x) reactions up to 17.6 MeV using the stacked-foils activation technique. High-purity natural zinc (and copper) foils were irradiated with proton beams from an 18MeV medical cyclotron, the predominant purpose of which is to provide a routine regional service for clinical PET radiopharmaceuticals. Thick-target integral yields were also deduced from the measured excitation functions of the produced radioisotopes. These results were compared with the literature and were found to be in good agreement with most but not all published reports. Material and Methods The excitation functions of the natZn(p,x) reactions were measured by the well-known stacked foil technique (1). High purity zinc foils (99.99%; Goodfellow Metals Ltd., UK) each thickness 0.025 ± 0.003 mm with isotopic composition 64Zn (48.6 %), 66Zn (27.9 %), 67Zn (4.1 %), 68Zn (18.8 %) and 70Zn (0.6 %) were loaded into a solid targetry system on a 300-mm external beam line utilising helium-gas and chilled water to cool the target body (2). A typical foils stack consisted of repeated units of four Zn foils interleaved with a high purity copper foil (0.025 ± 0.004 mm); the latter for monitoring beam flux using the well documented 63,65Cu(p,n)63,65Zn reactions. Foil stacks were irradiated with a primary beam of energy 17.6 MeV, accounting for beam degradation by an obligatory 0.0250 ± 0.0005 mm-thick Havar® foil beam-line vacuum window. Irradiation was for 3 min at a beam current of 5 µA. Activated foils were measured using cryo high-purity Ge γ-spectroscopy to quantify the product radionuclides 61Cu, 66Ga, 67Ga and 65Zn. Radioactivity of each isotope was corrected to end of bombardment (EOB). Results and Conclusion New cross-sectional data for natZn(p,x) reactions up to 17.6 MeV yielding 61Cu, 66Ga, 67Ga and 65Zn isotopes were measured in independent replicated (N = 3) experiments. Results were generally in good agreement with published data. These isotopes can potentially be used in clinical or preclinical studies, following appropriate chemical separations of the zinc, gallium and copper (3). The FIG. 1 shows thick-target integral yields calculated from excitation functions measured in this study. It can be calculated (for example) that useful activities of 61Cu can be produced using a 100 µm thick natZn target in a beam provided by a standard medium-energy medical cyclotron. For example, an irradiation at 40 µA for 2 hr at 17.6 MeV would produce approximately 1.7 GBq of 61Cu at EOB. Such currents are readily achievable using solid targetry in our laboratory (2).

Fluorescence techniques are being considered for the detection and identification of bacterial spores. This thesis sets out to empirically characterize the detailed autofluorescence spectroscopic properties of spores and their target molecules. The multiwavelength fluorescence studies from a unique endogenous biomarker, dipicolinic acid (DPA) and its calcium salt (CaDPA) in bacterial spores are found to be useful for fluorescence characterization of spores. A systematic determination of the fluorescence profile of the major chemical components of Bacillus spores and the effect of UV irradiation on them has been performed in dry samples, wet paste and in aqueous solution. The thesis applies reliable tools for accurately describing complex nature of spectral profile from bacterial spores, and for interpreting and identifying their spectral properties. We show that multiwavelength fluorescence technique combined with Principal Component Analysis (PCA) clearly indicates identifiable grouping among dry and wet Bacillus spore species. Differences are also observed between dried, wet and redried spores, indicating the stark effect of hydration on fluorescence fingerprints. The study revealed that changes in fluorescence of spores due to hydration/drying were reversible and supports a recent model of a dynamic and dormant spore structure. The spectra were analysed with PCA, revealing several spectroscopically characteristic features enabling spore species separation. The identified spectral features could be attributed to specific spore chemical components by comparing the spore sample signals with spectra obtained from the target molecules. PCA indicated underlying spectral patterns strongly related to species and the derived components were correlated with the chemical composition of the spore samples. More importantly, we examined and compared the fluorescence of normal spores with a mutant of the same strain whose spores lack DPA. We discovered that the dramatic fluorescence enhancement of Bacillus spores can be caused by UV irradiation in the spectral region of this unique biomarker without any pre treatment. Differences between spectra of spores, spore strains and other biological samples are very marked and are due to the dominance of the dipicolinate features in the spore spectra. This could lead to a cheap, more sensitive, faster and reagentless bacterial spore detector.