Search

A durability testing method under thermo-mechanical stress for thermal barrier coatings (TBC) specimens was designed by a combination of an electric furnace and a tensile testing machine, which was done on TBCs on NIMONIC 263 substrates by an atmospheric plasma spraying (APS) deposition method. The testing conditions were chosen according to a preliminary experiment that identified the elastic deformation region of the top coating and the substrate during mechanical loading. Surface cracking and a decrease in the thickness of the top coating, which are typical degradation behaviors under conventional thermal shock testing, were observed after the designed thermal fatigue test, and delamination at the top coating-bond coating interface occurred by the mechanical load. Lifetime assessment was conducted by statistical software using lifecycle data which were obtained after the thermal fatigue test.

The degradation behavior of TiN coatings with different thicknesses deposited on Inconel 617 substrates was investigated in terms of surface and interface microstructures after pulsed laser thermal shock. The specimens with coating thicknesses of 1.0 and 4.5 ?m were exposed to repetitive laser shock using a pulsed laser ablation system (LSX-213). The TiN coating with a 1.0 ?m thickness contained cracks along the columnar grains in the coating layer, and spalling and delamination with interface cracks appeared with an increase in the number of ablations. In contrast, the 4.5 ?m thick TiN coating still maintained adhesion to the substrate until the substrate elements dissolved out to the surface. Surface and cross-sectional observation showed that the pulsed laser seems to simultaneously induce normal and shear stress to the surface at the ablated spots with high thermal stress. (Received March 18, 2013)

Upon nutrient depletion during recombinant Chinese hamster ovary (rCHO) cell batch culture, cells are subjected to apoptosis, type I programmed cell death (PCD), and autophagy which can be type II PCD or a cell survival mechanism. To investigate the effect of nutrient supplementation on the two PCDs and protein production in rCHO cells, an antibody-producing rCHO cell line was cultivated in batch and fed-batch modes. The feed medium containing glucose, amino acids, and vitamins was determined through flask culture tests and used in bioreactor cultures. In the bioreactor cultures, the nutrient feedings extended the culture longevity and enhanced antibody production. In addition, cells in the fed-batch culture showed delayed onset of both apoptosis and autophagy, compared with those in the batch culture. The inhibition of apoptosis was demonstrated by a decreased amount of cleaved caspase-7 protein and less fragmentation of chromosomal DNA. Concurrently, reduced LC3 conversion, from LC3-I to LC3-II, was observed in cells that received the feeds. Cultivation with pharmacological autophagy inducer (rapamycin) or inhibitor (bafilomycin A1) indicated that autophagy is necessary for the cells to survive under nutrient depletion. Taken together, the delayed and relieved cell death by nutrient supplementation could improve antibody production.

Constitutively active Ras (CA-Ras) is known to enhance cell growth through the induction of various signaling cascades including the phosphoinositide 3-kinase (PI3K)/Akt and mitogen-activated protein kinase (MAPK)/ERK signaling pathways, although the cellular response is highly dependent on the cell type. To evaluate the effect of CA-Ras overexpression on cell growth in recombinant Chinese hamster ovary (rCHO) cells, an erythropoietin (EPO)-producing rCHO cell line with regulated CA-Ras overexpression (EPO-off-CA-Ras) was established using the Tet-off system. The CA-Ras expression level in EPO-off-CA-Ras cells was tightly regulated by doxycycline addition. Although CA-Ras overexpression slightly increased the viable cell concentration during the late exponential phase, it did not increase the maximum viable cell concentration or specific growth rate to a significant degree. Unexpectedly, CA-Ras overexpression in rCHO cells led only to the enhancement in the activation of the MAPK/ERK signaling pathway and not the PI3K/Akt signaling pathway. Taken together, CA-Ras overexpression in rCHO cells did not significantly affect cell growth; it also had no critical impact on viable cell concentration or EPO production, possibly due to a failure to activate the PI3K/Akt signaling pathway.

The Camellia japonica vegetation in the Korean Peninsula was investigated by the methology of the Z-M school. The synthesis table of Camellion japonicae were arranged for association classification from 263 quadrats. The vegetation of Camellia japonica forest, classfied as an alliance includes nine new associations : Camellietum japonicae typicum Jin et Kim 2005, Machilo thunbergii-Camellietum japonicae Jin et Kim 2005, Pino thunbergii-Camellietum japonicae Jin et Kim 2005, Castanopo cuspidatae var. sieboldii-Camellietum japonicae Jin et Kim 2005, Lito japonicae-Camellietum japonicae Jin et Kim 2005, Castnnopo cuspidatae var. thunbergii-Camellietum japonicae Jin et Kim 2005, Querco acutae-Camellietum japonicae Jin et Kim 2005, Neolito sericae-Camellietum japonicae Jin et Kim 2005, Cinnamomo japonicae-Camellietum Japonirae Jin et Kim 2005.

The effects of growth parameters on growth behavior of Pendeo-epitaxial GaN layers in (1100) patterned GaN seed stripes on sapphire were systematically investigated to improve the structural properties of the overgrown layers. It was found that the ratio of lateral to vertical growth rate (y) is strongly affected by changes in growth temperature, reactor pressure, and V/III ratio, which have an effect on the distribution of crystallographic tilt among the wing regions. Also, the crystallographic anisotropy, which was determined from the results of (0002) X-ray diffraction rocking curves taken perpendicular and parallel to the seed stripe direction, can be improved with relatively high V/III ratio.

We have investigated the effect of isoelectronic In doping on deep levels in GaN films grown by metalorganic chemical vapor deposition via deep level transient spectroscopy. Deep level E2 0.5 eV below the conduction band was observed in both undoped GaN and In-doped GaN. However, with increasing In mole flow rate, the trap concentration of E2 decreases sharply from 2.3 × 10 14 to 2.27 × 10 13 cm -3 , nearly an order of magnitude in reduction, comparing to undoped GaN. This might be due to the dislocation pinning and/or bending effect. Therefore, In doping in GaN growth can effectively decrease the dislocation density and suppress the formation of deep levels E2.

We have studied the effect of isoelectronic In-doping on the structural properties of GaN grown by pendeo-epitaxy. From an analysis of cross-sectional transmission electron microscopy (TEM) images, the threading dislocation originating from the (0001) facet of GaN seed layer, thereafter propagating onto the top surface of regrown GaN layer, were reduced due to isoelectronic In-doping, which could enhance vacancy trapping. In addition, threading dislocations in the coalescence region were not observable. These results indicate that these dislocations are bent or terminated in the boundary of coalesced region. Also, the crystalline quality was improved from the results of high resolution X-ray diffraction and TEM measurements.

Hyperosmolality in recombinant Chinese hamster ovary (rCHO) cell cultures induces autophagy and apoptosis. To investigate the effect of Bcl-x(L) overexpression on autophagy and apoptosis in hyperosmotic rCHO cell cultures, an erythropoietin (EPO)-producing rCHO cell line with regulated Bcl-x(L) overexpression was subjected to hyperosmolality resulting from NaCl addition in a batch culture and nutrient supplementation in a fed-batch culture. In the batch culture, Bcl-x(L) overexpression suppressed apoptosis, as evidenced by a decreased amount of cleaved caspase-7 and PARP. Concurrently, Bcl-x(L) overexpression also delayed autophagy, as indicated by reduced LC3 conversion, from LC3-I to LC3-II. As a result, the cell viability and EPO production were improved by Bcl-x(L) overexpression. In the fed-batch culture, the simultaneous application of Bcl-x(L) overexpression and nutrient feeding increased the culture longevity and maximum EPO concentration. Taken together, Bcl-x(L) overexpression delayed autophagy and apoptosis in hyperosmotic rCHO cell cultures, resulting in increased EPO production.

In order to understand the intracellular responses in recombinant CHO (rCHO) cells producing antibody in serum-free medium (SFM) supplemented with optimized hydrolysates mixtures, yielding the highest specific growth rate (μ, SFM#S1) or the highest specific antibody productivity (q Ab, SFM#S2), differentially expressed proteins in rCHO cells are measured by two-dimensional gel electrophoresis combined with nano-LC-ESI-Q-TOF tandem MS. The comparative proteomic analysis with basal SFM without hydrolysates revealed that the addition of hydrolysate mixtures significantly altered the profiles of CHO proteome. In SFM#S1, the expression of metabolism-related proteins, cytoskeleton-associated proteins, and proliferation-related proteins was up-regulated. On the other hand, the expression of anti-proliferative proteins and pro-apoptotic protein was down-regulated. In SFM#S2, the expression of various chaperone proteins and proliferation-linked proteins was altered. 2D-Western blot analysis of differentially expressed proteins confirmed the proteomic results. Taken together, identification of differentially expressed proteins in CHO cells by a proteomic approach can provide insights into understanding the effect of hydrolysates on intracellular events and clues to find candidate genes for cell engineering to maximize the protein production in rCHO cells.

During recombinant Chinese hamster ovary (rCHO) cell culture, various events, such as feeding with concentrated nutrient solutions or the addition of base to maintain an optimal pH, increase the osmolality of the medium. To determine the effect of hyperosmotic stress on two types of programmed cell death (PCD), apoptosis and autophagy, of rCHO cells, two rCHO cell lines, producing antibody and erythropoietin, were subjected to hyperosmotic stress resulting from NaCl addition (310― 610 mOsm/kg). For both rCHO cell lines, hyperosmolality up to 610 mOsm/kg increased cleaved forms of PARP, caspase-3, caspase-7, and fragmentation of chromosomal DNA, confirming the previous observation that apoptosis was induced by hyperosmotic stress. Concurrently, hyperosmolality increased the level of accumulation of LC3-II, a widely used autophagic marker, which was determined by Western blot analysis and confocal microscopy. When glucose and glutamine concentrations were measured during the cultures, glucose and glutamine concentrations in the culture medium at various osmolalities (310―610 mOsm/kg) showed no significant differences. This result suggests that induction of PCD by hyperosmotic stress occurred independently of nutrient depletion. Taken together, autophagy as well as apoptosis was observed in rCHO cells subjected to hyperosmolality.

I was given this book to review recently while visiting Oulu, and have read it cover to cover by the time I landed at Toronto. This indicates what a great storyteller Robert Fortuine is, and the story of the rise and not quite fall of tuberculosis in Alaska is a great story indeed.(Int J Circumpolar Health 2005; 64(5):536-537)

Langerhans cell histiocytosis can cause central diabetes insipidus. Here, a case of Langerhans cell histiocytosis invading the pituitary stalk was experienced. The patient was 15 years old boy, with complaint of polydipsia and polyuria. A water deprivation test was carried out, and the urine osmolarity was increased from 165 to 469 mosm/kg following an injection of AVP to confirm the diagnosis of central diabetes insipidus. A pituitary function stimulation test gave a normal response. A sellar MRI was performed, which showed a thickened pituitary stalk mass (about 5.7 mm), with an increased size, 6.9 mm, on a second MRI 2 month later. A tissue biopsy was performed, which showed aggregates of histiocytes and inflammatory cells, with prominent eosinophils (H&E), and also revealed strong reactivity to anti-CD1a antibody on the immunohistochemistry. After confirmative tissue diagnosis, the patient received radiotherapy (900 cGy). The thickened mass of the pituitary stalk disappeared on the MRI following the radiotherapy. The patient was managed with DDAVP nasal spray, after which the polyuric symptoms were completely relieved (J Kor Soc Endocrinol 20:513～518, 2005).

Helicobacter pylori is a bacterial infection of the stomach lining known to cause ulcers and stomach cancer This infection has become a major concern of Indigenous peoples living in the Northwest Territories, where H. pylori infection and stomach cancer are more prevalent relative to much of southern Canada and the United States. I joined the Canadian North Helicobacter pylori (CANHelp) Working Group in 2010 to conduct participant observation in the Aklavik H. pylori Project (AHPP) and identify ways that ethnography can be integrated into the ongoing multi-pronged research that incorporates epidemiology, microbiology, gastroenterology, knowledge translation, and the development of public health policy. Between September, 2011 and June, 2012, I lived as a participant observer in Aklavik. I led an epidemiological study of the incidence and re-infection of H. pylori infection. I examined how different risk perceptions emerge from processes of “making sense” of H. pylori as a “pathogen” or as a “contaminant” and described how these different constructions influence people’s behaviours. Ethnography, in this way, can make visible the lenses through which different groups of actors perceive, experience, and react to H. pylori infection. The recognition that the social inequities most strongly associated with H. pylori infection and re-infection that exist today are the result of Aklavik’s colonial history is one example of a space in which different lenses can be brought into a shared focus. From such shared understandings, consensus knowledge can be built collaboratively between outside researchers and Indigenous Arctic communities in an ongoing, and community-driven, research project. Furthermore, I critically examined the definition and use of the “household” as a level-unit of risk assessment and have outlined steps for assessing possible risk factors as these are distributed across multi-household extended kin groups that can be identified and followed in long-term research. Doctor of Social Science