Accelerated study on lysozyme deposition on poly(HEMA) contact lenses

A technique was developed to accelerate lysozyme deposition on poly(HEMA) contact lenses and measure the amounts of the deposited lysozyme. This technique was for evaluation of bendazac lysine solution, a contact lens cleaning and wetting solution. Effect of temperature on lysozyme deposition on poly(HEMA) contact lenses was examined. Five temperatures ranging from 25 degrees C to 90 degrees C were chosen to examine the temperature effect. The amounts of lysozyme deposited on poly(HEMA) contact lenses at 25 C and 60 C were 0.27 microg/lens and 0.61 microg/lens, respectively. The amount increased sharply to 23 microg/lens at 70 degrees C with the maximum of 31 microg/lens at 90 degrees C. Kinetics of lysozyme deposition on poly(HEMA) contact lenses was examined at 80 degrees C. Lysozyme deposition increased sharply during the first 2 h and reached a plateau after 2 h. Effectiveness of various cleaning procedures was examined using bendazac lysine solution. When the contact lenses were washed without rubbing with fingers, the bendazac lysine reduced the amount of deposited lysozyme by more than 40% from 18.3 microg/lens to 10.6 microg/lens. The effect of bendazac lysine was most prominent when the contact lenses were shaken during storage in the presence of lysozyme in solution. If the contact lenses were cleaned by rubbing with fingers, the effect of bendazac lysine solution on the prevention of lysozyme deposition was negligible.     

Scale-up unit of a unique moderately high pressure unit to enhance microbial inactivation

The efficacy of a scale-up of a moderately high pressure unit built in this work was investigated with regards to inactivation of Geobacillus stearothermophilus spores suspended in pumpkin soup, and effect of the process on l-ascorbic acid. In this design saturated steam was used as a heating medium. The treatment unit is a double pipe heat exchanger in which the food is pumped in its inner tube, while steam is passed in the annular region to heat the sample. This technology comprises a unique approach of generating a mild pressure (80-100 MPa) utilizing thermal expansion of the liquid being treated. The results show that this unique application decreased the D-values of Geobacillus stearothermophilus ATCC 7953 spores suspended in soup samples in comparison to thermal treatment alone. The improvement was more significant at lower treatment temperatures. The D-values obtained were in a good agreement with that of the small unit built earlier in which oil was used as a heating medium. The effect of treatment on l-ascorbic acid was similar to that of thermal treatment. The treated samples were subjected to shelf life study by storing them at two different temperatures. No evidence of spore recovery was noted during the post-treatment storage period.     

Experimental characterization of meso‐scale deformation mechanisms and the RVE size in plastically deformed carbon steel

The local deformation response of low carbon steel subjected to uniaxial tensile loading is investigated, and the local strain field at sub‐grain scale is obtained using high‐spatial‐resolution digital image correlation. The implemented digital image correlation method enables the observation and study of inhomogeneous deformation response at microstructural levels. Detailed local deformation mechanisms including mesoscopic slip bands are captured. Furthermore, the local information is used for the determination of representative volume element size in polycrystalline low carbon steel. To obtain the representative volume element size, we proposed and successfully implemented a strain variation method. Further, the influence of global strain on the local deformation mechanisms and representative volume element size is discussed. The challenges associated with the local strain measurement using digital image correlation are also discussed.     

Mixed-mode dynamic crack propagation in graded materials under thermo-mechanical loading

Mixed-mode dynamic crack growth behavior in functionally graded materials (FGMs) under thermo-mechanical loading is studied. Asymptotic analysis in conjunction with displacement potentials has been used to develop thermo-mechanical stress fields for a mixed mode propagating crack in a FGM. The shear modulus, mass density, thermal conductivity and coefficient of thermal expansion of the FGM are assumed to vary exponentially along the gradation direction. First, asymptotic temperature fields are derived for an exponential variation of thermal conductivity and later these temperature fields are used in deriving stress fields. Using asymptotic thermo-mechanical stress fields the variation of maximum shear stress, circumferential stress and strain-energy density as a function of temperature around the crack tip are generated. Finally, utilizing the minimum strain-energy density criterion and the maximum circumferential stress criterion, the crack growth direction for various crack-tip speeds, non-homogeneity coefficients and temperature fields are determined.     

Photodynamic Therapy in Non-Gastrointestinal Thoracic Malignancies

Photodynamic therapy has a role in the management of early and late thoracic malignancies. It can be used to facilitate minimally-invasive treatment of early endobronchial tumours and also to palliate obstructive and bleeding effects of advanced endobronchial tumours. Photodynamic therapy has been used as a means of downsizing tumours to allow for resection, as well as reducing the extent of resection necessary. It has also been used successfully for minimally-invasive management of local recurrences, which is especially valuable for patients who are not eligible for radiation therapy. Photodynamic therapy has also shown promising results in mesothelioma and pleural-based metastatic disease. As new generation photosensitizers are being developed and tested and methodological issues continue to be addressed, the role of photodynamic therapy in thoracic malignancies continues to evolve.     

A degeneracy study in the circulant and bordered-circulant approach to birdcage and planar coils

A method for finding closed-form solutions for the normal mode frequencies of systems with circulant symmetry was investigated. This method is particularly useful for questions of degeneracy that arise when one considers parallel imaging techniques like SENSE and SMASH in MRI. It is applicable to systems that include birdcage coils as well as planar coils with the appropriate rotational symmetry. A proof is given that complete degeneracy of all normal mode frequencies is impossible when all mutual inductive couplings are included. We tested the method against measurements made on a planar coil array and on an 8-element birdcage coil. The inclusion of the co-rotating end-ring mode changes the fundamental symmetry of the system from circulant to 'bordered circulant.' Closed-form solutions for the normal mode frequencies of a bordered circulant system are also given.     

Investigation of constantly and transiently propagating cracks in functionally graded materials by dynamic photoelasticity

In this study, the stress intensity factors (SIFs) for steady and transient propagation of cracks in transparent homogeneous functionally graded materials were analyzed by using the photoelasticity technique. The fracture analysis was carried out for the cracks propagating from a region with high elasticity towards low elasticity, as well as the cracks propagating from a region with low elasticity towards high elasticity. The analysis includes cracks propagating (1) at an almost steady speed, and (2) with the rapid increase, followed by a decrease in speed. For cracks with almost constant velocity, the SIFs were greater when a crack started from a high elasticity region, as compared to the cracks which initiated from a low elasticity region. For cracks propagating with rapid acceleration and deceleration, when the strain energy accumulated in the material due to an increase in load or stress was released at the moment of crack propagation, the SIF was momentarily lowered by approximately 45 %–50 % of the static SIF(before crack initiation), which subsequently increases by approximately 30 % eventually, the crack acceleration approaches nearly zero; the SIF decreases and increases respectively as the crack propagates in a material with decreasing and increasing modulus of elasticity.

     

Quasi-static and dynamic fracture initiation toughness of Ti/TiB layered functionally graded material under thermo-mechanical loading

Quasi-static and dynamic fracture initiation toughness of Ti/TiB layered functionally graded material (FGM) is investigated using a three point bend specimen. The modified split Hopkinson pressure bar (SHPB) apparatus in conjunction with induction coil heating system is used during elevated temperature dynamic loading experiments. A simple and accurate technique has been developed to identify the time corresponding to the load at which the fracture initiates. A series of experiments are conducted at different temperatures ranging from room temperature to 800 °C, and the effect of temperature and loading rate on the fracture initiation toughness is investigated. The material fracture toughness is found to be sensitive to temperature and the fracture initiation toughness increases as the temperature increases. Furthermore, the fracture initiation toughness is strain rate sensitive and is higher for dynamic loading as compared to quasi-static loading.     

Toward shielding improvements in MRI gradients and other systems.

A new method is described for reducing the shielding-error function in the 'supershielding' approach to designing MRI systems. The method is thus shown to lead to significantly better shielding and better control of eddy current effects associated with gradient coils. To illustrate this technique, a set of results for a z-gradient coil is presented. A generalization to non-standard geometries can be made in a straightforward manner with the new method. The usefulness of the relationship of all fringe-field quantities to the shielding-error function is emphasized. The formal limit of perfect shielding in a 'least-squares' sense is shown for a simple strip-shield model along with a numerical eigenvalue study for comparison with the theoretical limit.