Dissertations / Theses on the topic 'Active screen'

Nitriding is a plasma based processing technique that is used to improve the surface properties of components and products in many areas including the aerospace, automotive and biomedical industries to name a few. Active Screen Plasma Nitriding (ASPN) is a relatively new nitriding technique which has potential advantages over the more traditional nitriding techniques such as Direct Current (DC) plasma nitriding where high substrate biases can be problematic. However, there is considerable debate as to the mechanism for nitriding in ASPN. This thesis focuses on investigating the mechanism for nitriding in a commercial ASPN system. Commercial ASPN treatments of nitrideable alloy steels were found to be unsatisfactory unless a sufficient bias was applied. The level of bias required to produce a satisfactory nitriding response, in terms of the cross sectional hardness, was found to depend on the concentration of strong alloy nitride forming elements present in the steel. Although active screen material was found to be transferred to the workload, no evidence was found that this process played a significant role in enhancing the nitriding response. The primary mechanism for nitrogen mass transfer in ASPN was found to be dependent on the active screen/workload separation distance. When this separation is small (less than approximately 10cm for the conditions used in this study) then nitrogen mass transfer in the form of energetic ions or neutrals can occur between the active screen and the workload. This allows samples to be treated without a substrate bias. On the other hand, when the active screen/workload separation distance is large (greater than approximately 10cm) as is normally the case in a commercial environment, this mechanism for nitrogen mass transfer breaks down and a substrate bias is essential. In this latter case, nitrogen ions attracted to the workload using a bias is the primary nitrogen mass transfer mechanism and the role of the active screen is primar ily to uniformly heat the workload.

Surface modification of polymers has long been known in polymer chemistry but has not yet been widely applied to biomaterials. A newly developed active screen plasma technology has a potential to treat such non-conductive materials as polymers to improve their surface properties since this is a low-temparature, low cost and environmentally friendly plasma process. in this project, three kind of polymeric materials, ultra high molecular weight polyethylene, polyurethane and polycaprolacton, were surface modified using active screen plasma nitriding technology. The results demonstrated that it is feasible to conduct plasma surfae modification of polymeric materials using the newly developed active-screen plasma technology without causing any etching, significant sputtering or other surface damage. Changes in chemical composition and structure have been found an all three polymeric materials' surface following active screen plasma surface treatments. Crosslinking or/and new functional groups are formed on the topmost surface layer after the treatment. Along with changes in surface morphologies and structural, the wettability of the surface of all three polymeric materials can also be effectively improved by the active screen plasma nitriding treatments. Active-screen plasma nitriding technique is an effective and practical method to improve osteoblast cell adhesion and spreading on all three polymeric materials' surface.

Active Screen Plasma Nitriding (ASPN) is a novel surface engineering technique, the main advantage of which is the capacity to treat homogeneously all kind of materials surfaces of any shape. Here, ASPN is used to modify the surface properties of ionomer glasses and polymers in order to improve the surface cellular compatibility of these materials. A conventional DC nitriding unit has been used together with an AS experimental arrangement. The materials that were treated were an ionomer glass composition and UHMWPE. All treated/untreated samples were seeded with the 3T3 fibroblasts. In order to identify the effect of the plasma treatment, chemical and mechanical properties characterization was conducted. For the cellular samples, SEM, Interferometry, AFM and MTT assay were conducted in order to observe cells’ behavior on the untreated and treated materials. The inert surface of the untreated glass showed good interaction with fibroblasts only after the ASPN treatment which resulted in enhanced fibroblasts attachment and proliferation. The treatment temperature, the length of treatment and the presence of nitrogen had an influence on the surface properties of glass. UHMWPE treated samples chemical characterization showed the formation of C-N and N-H groups resulting in an increase of the functionality of treated surfaces. 3T3 fibroblasts cell culture studies showed that the ASPN treatment had a positive effect on the adhesion and proliferation of cells according to the time of treatment and the increase of the nitrogen concentration in the gas mixture. As a conclusion ASPN treatment can be a very effective method to modify inorganic and organic polymeric surfaces in order to improve cellular compatibility.

Thesis advisor: Charles S. Hoffman
The biological roles of the most recently discovered mammalian cyclic nucleotide phosphodiesterase (PDE) family, PDE11, are poorly understood, in part due to the lack of selective inhibitors. To address this need for such compounds I completed a ~200,000 compound high throughput screen (HTS) for PDE11 inhibitors using a yeast-based growth assay. Further characterization of lead candidates using both growth-based assays in the fission yeast Schizosaccharomyces pombe and in vitro enzyme assays identified four potent and selective PDE11 inhibitors. I examined the effect of these compounds on human adrenocortical cells, where PDE11 is believed to regulate cortisol levels. One compound, along with two structural analogs, elevates cAMP levels and cortisol production through PDE11 inhibition, thus phenocopying the behavior of adrenocortical tumors associated with Cushing syndrome. These compounds can be used as research tools to study the biological function of PDE11, and can also serve as leads to develop therapeutic compounds for the treatment of adrenal insufficiencies. This study further validates the yeast-based HTS platform as a powerful tool for the discovery of potent, selective and biologically-active PDE inhibitors
Thesis (PhD) — Boston College, 2012
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Biology

Low temperature plasma surface engineering has been a useful method for increasing the hardness and wear resistance of austenitic stainless steel without reducing the corrosion resistance of this alloy. Plasma carburising is of particular interest as it produces thicker hardened layers than plasma nitriding, and an equivalent improvement in the tribological and corrosion performance of the base material. In this project, the active screen (AS) plasma technique was used to carburise austenitic stainless steel AISI 316 and the obtained layer of carbon expanded austenite was compared with the one produced by conventional DC plasma treatments. The hardening and wear resistance produced by AS and DC plasma carburising were equivalent. With regard to corrosion, the AS treated material performed better than its DC counterpart as a consequence of the improved surface quality of the former. The mechanism of AS carburising was comparatively studied with its AS nitriding counterpart. Different experimental arrangements and two plasma diagnostic techniques were used for this purpose: optical emission spectroscopy and electrostatic probes. The evidence shows that AS nitriding relies on the deposition of iron nitrides and the active species in the plasma to produce hardening, whilst AS carburising requires the plasma activation and moderate ion bombardment.

It is well accepted that the absorption bandwidth of a metal back-plane absorber, built with either dielectric or magnetic materials, is inherently narrow. It is also well known that in order to increase the absorption bandwidth, the absorber thickness must be increased through decreasing the permittivity or permeability of its spacer. This improved performance, however, comes at a cost. The absorption bandwidth is increased at the expense of not only an increase of absorber thickness, specially at lower frequencies, but also the yielding of a mechanically weaker structure. The most important implication of the former is that there is a tradeoff between absorber thickness and absorption bandwidth. These two conflicting absorber properties are, however, of equal importance since the optimum absorber is one which has a small thickness as well as a wideband absorption response. This inherent trade-off is due to the fundamental frequency limitations imposed by the constitutive parameters of materials and is more detrimental at microwave frequencies. The aim of the research programme described in this thesis was thus to investigate the use of adaptive complex impedance structures, in the form of active frequency selective surfaces (AFSSs), to extend the absorption bandwidth of a small thickness Salisbury screen absorber, thus addressing directly the aforementioned by minimizing the trade-off that exists between absorber thickness and absorption bandwidth.

No presente trabalho foi investigada a nitretação a plasma do aço rápido ASTM M2 utilizando diferentes configurações, envolvendo as técnicas convencional e com tela ativa. Na técnica convencional, o material a ser nitretado atua como o cátodo do sistema, sendo coberto diretamente pela bainha da descarga luminescente. Nos tratamentos conduzidos com a técnica de tela ativa, uma estrutura de tela em formato cilíndrico atua como cátodo e o material a ser nitretado é posicionado no seu interior. Neste novo processo, como não há potencial elétrico externo aplicado aos substratos, a descarga luminescente se desenvolve apenas na estrutura da tela, evitando problemas intrínsecos do método convencional de nitretação a plasma. Todos os tratamentos investigados foram executados com os seguintes parâmetros: Temperatura de 500 °C, mistura gasosa composta 76% de volume de gás nitrogênio e 24% de volume de gás hidrogênio e pressão de 3 milibar. Para os tratamentos com tela ativa, os substratos foram mantidos eletricamente isolados. Os resultados foram comparados observando a diferença de método de nitretação (com e sem o uso de tela ativa) e a influência do tempo de tratamento (variando sua duração em 1, 4 e 8 horas) Todos os experimentos foram realizados utilizando uma fonte de potência de tensão retificada aplicada na tela ou nas amostras, dependendo da configuração. Adicionalmente, para o tempo de nitretação de 4 horas uma fonte de potência com tensão pulsada também foi aplicada. As amostras nitretadas foram caracterizadas por ensaios de rugosidade, ensaios de dureza e microdureza, microscopia ótica, microscopia eletrônica de varredura e difração de raios-X. Ensaios tribológicos para avaliação da resistência ao desgaste das diferentes condições de tratamento foram conduzidos. Dentre os principais resultados foi observada uma clara diferença na profundidade de camada nitretada, que foi sempre mais profunda nos tratamentos convencionais. Apesar de formadas camadas menos profundas, as amostras nitretadas oriundas dos tratamentos com tela ativa demonstraram melhor desempenho nos ensaios tribológicos, resultando em taxas de desgaste até sete vezes inferior do que as amostras do nitretadas convencionalmente, este resultado foi atribuído a não formação da zona de compostos nas amostras nitretadas com tela ativa.
In the present work an investigation on the plasma nitriding of ASTM M2 High-Speed Steel using different configurations was carried out, involving traditional and active screen techniques. In the traditional technique, the material to be nitrided act as the system cathode, being directly covered by the glow discharge sheath. In the active screen treatments, a cylindrical mesh structure (screen) plays the role of the cathode and the material to be nitrided is positioned in its interior. In this new process, as there is no external electric potential applied to the specimens, the glow discharge develops only in the screen structure, avoiding intrinsic problems from the conventional plasma nitriding method. All the studied treatments were carried out with the following parameters: temperature of 500 °C, gas mixture of 76 vol.-% N2 and 24 vol.-% H2 and pressure of 3 millibar. For the active screen treatments, the samples were kept electrically insulated. The results were compared observing the differences in the nitriding method (with and without the use of active screen) and the nitriding time influence (varying its duration in 1, 4 and 8 hours) All experiments were carried using a rectified voltage power supply applied to the screen or to the samples, depending on the configuration. Additionally, for the nitriding time of 4 hours a pulsed voltage power supply was also employed. The nitrided samples were characterized by roughness tests, hardness and microhardness tests, optical microscopy and scanning electron microscopy, X-ray diffraction. Tribological tests to evaluate the wear resistance of the different treatment conditions were also carried out. Among the main results a clear difference in the case layer depth was noticed, which was always deeper in the conventional treatments. Although forming shallower case depths, the active screen nitrided specimens presented better performance in the tribological tests, resulting in wear rates up to seven times lower than the wear rate for conventionally plasma nitrided samples, this result was assigned due to the non-formation of compound layer in the active screen plasma nitrided samples.

This work investigates the functional heterogeneity of influenza virus quasispecies through quantitative analysis of cellular responses to the entry of noninfectious biologically active particles, the effect of reassortment of gene segments on the generation and function of these particle subpopulations, and the potential of these subpopulations as in vitro correlates of in vivo effectiveness of live-attenuated influenza vaccines (LAIVs).

For the first time, the clonogenic assay was used to show that populations of most influenza A viruses contained cell-killing particles in excess of infectious particles when tested in the same host cell. Thus, a new class of influenza virus particles was revealed – noninfectious cell-killing particles which required the synthesis of a specific viral polymerase subunit to kill cells and the expression of NS1 protein to temporally delay apoptosis/cell-killing.

The noninfectious cell-killing particles were clearly distinguished from the well known defective-interfering particles by differences in their numbers in standard influenza virus populations, their temporal appearance and quantity during serial high multiplicity propagation in mammalian and chicken cells, an inability of defective-interfering particles to kill cells or interfere with the cell-killing capacity of noninfectious cell-killing particles, genetic requirements (a small DI RNA ∼350 nt and a large RNA ∼2,300 nt for defective-interfering and noninfectious cell-killing particle activities, respectively), and the extracellular T½ at 40.5 °C (∼40h and ∼85h for noninfectious cell-killing particles and defective-interfering particles, respectively).

Specific exchange of the NS gene segment from lethal A/HK/156/97 (H5N1) (NS1: E92, or E92D) virus for the cognate NS gene segment of A/PR/834 (H1N1) (NS1: D92) virus caused de novo generation of large defective-interfering particle subpopulations and >10-fold enhancement of interferon-inducing particle efficiency. These changes were attributed to dysfunction of the H5N1 virus NS1 gene.

Populations of two effective LAIVs (Vac⁺) in chickens were characterized by high defective-interfering to interferon-inducing particle ratios and induction of large amounts of interferon in chicken cells. Interferon is an antiviral cytokine that acts as a potent natural adjuvant of adaptive immune responses in chickens. Populations of two ineffective LAIVs (Vac ^-) in chickens had lower defective-interfering to interferon-inducing particle ratios and induced less interferon. Unexpectedly, these phenotypes were reversed in mammalian cells. Populations of Vac^- (in chickens) LAIV candidates were excellent interferon inducers with high defective-interfering to interferon-inducing particle ratios in mammalian cells. In contrast, populations of Vac⁺ (in chickens) LAIV candidates were poor interferon inducers with low defective-interfering to interferon-inducing particle ratios in mammalian cells. As predicted by the in vitro screen, the Vac phenotypes were reversed in vivo (in mice) relative to chickens.

Overall, this study shows that the majority of noninfectious particles of influenza virus are biologically active, reassortment can change the subpopulation make of influenza virus, and a high defective-interfering to interferon-inducing particle ratio is a strong in vitro correlate of the effectiveness of self-adjuvanting LAIVs. Taken together, these attributes of an influenza virus population represent a novel ensemble of in vitro parameters that may be used to distinguish between Vac⁺ and Vac ^- LAIV candidates.

 

Aspalathus linearis (A. linearis), commonly known as Rooibos tea or Red bush tea and amellia sinensis (C. sinensis) or Black tea are beverages that are consumed throughout theworld. These teas possess antioxidant, immunomodulating and anti-cancer actions. The aim of this study was to use in vitro assays to screen Rooibos and Black tea for endocrine modulation. The immune modulating effects of Rooibos and Black tea were investigated using an in vitro whole blood culture (WBC) assay. Unstimulated WBCs treated with Rooibos tea secreted higher levels of IL-6, IL-10 and IFN&gamma
than cultures treated with DMSO control. Rooibos treatment of stimulated WBCs resulted in higher IL-6, lower IL-10 and no effect on IFN&gamma
secretion compared to DMSO treated stimulated WBC. Black tea treatment of stimulated WBC resulted in decreased IL-6, IL-10 and IFN&gamma
secretion compared to the DMSO treated stimulated WBC. Extracts of Rooibos and Black tea were assessed for phytoestrogens using quantitative estrogen ELISAs. Both teas contain phytoestrogens. The quantitative ELISAs showed that Rooibos tea contained significantly lower estrone (E1), estradiol (E2) and estriol (E3) levels than Black tea. The effects of Rooibos and Black tea on proliferation of the estrogen dependant MCF-7 cell line was determined to further characterise the phytoestrogenic properties of the teas. Both Rooibos and Black tea extracts caused a significant inhibition of MCF-7 proliferation. This study shows that Rooibos tea and Black tea are beverages that can either stimulate or suppress the immune system. Also, both teas contain significant levels of phytoestrogens as determined by quantitative ELISAs. The current study confirms previous reports showing inhibition of growth in breast cancer cell lines by phytoestrogens. The findings extend related observations on the anti-carcinogenic potential of the two teas.

Working from a child participatory perspective, the study aimed to explore children's perceptions and experiences of screen violence. Within this process there is an attempt to understand how children assign meaning to these violent screen images at an interpersonal and broader social level.

Cancer is a common disease and due to problems with resistance against cancer drugs and the limited benefit from chemotherapy in many diagnoses, there is a need to develop new cancer drugs. In this thesis new methods to screen for cancer drugs and to evaluate their mechanism of action are discussed.

In Paper I, it was found that by studying the gene expression of a cell line panel and combining the data with sensitivity data of a number of cytotoxic drugs, it was possible to cluster compounds according to mechanism of action as well as identifying genes associated with chemosensitivity.

In Paper II, studies of compounds with selective activity in drug-resistant cell lines revealed the glucocorticoids as a group of interesting compounds. The glucocorticoid receptor was overexpressed in 8226/Dox40 and the difference in sensitivity was abolished when the cells were treated with a glucocorticoid receptor antagonist.

In Paper III, an image-based screening method for new proteasome inhibitors was successfully developed and the compounds disulfiram, PDTC and NSC 95397 were identified as inhibitors of the proteasome.

In Paper IV, disulfiram and PDTC were shown to induce cytotoxic activity, to inhibit the activation of the transcription factor NFkappaB and to inhibit the degradation of proteins normally degraded by the proteasome.

In Paper V, NSC 95397 was shown to be cytotoxic to all cells in the resistance-based cell line panel as well as to patient samples from a variety of cancer diagnoses. Connectivity Map was successfully used as a tool to propose a new mechanism of action of NSC 95397. The gene expression induced by NSC 95397-treatment was similar to that induced by several proteasome inhibitors not present in the Connectivity Map.

Endocrine&ndash
disrupting compounds (EDCs) are exogenous compounds/chemicals which interfere with, or have adverse effects on the production, distribution and function of natural hormones, thereby affecting normal endocrine activity, health and quality of life of both humans and wildlife. The reproductive system is highly susceptible to EDCs due to it being controlled by an array of hormonal signals. The effects of EDCs on the male reproductive system include infertility, decreased sperm count, function and morphology, abnormal development of secondary sex characteristics, reproductive function and sexual behaviour as well as decreased libido. There are various sources by which EDCs enter the environment which include effluents from several industries (mining, agriculture, smelting, hazardous waste sites, manufacturing industries, etc.), sewage treatment effluents, urban and agricultural runoff and effluents which include natural and pharmaceutical chemicals excreted in the urine of humans and domestic livestock, pesticides, polychlorinated biphenyls, dioxins, plasticizers, surfactants, etc. Humans and animals can also be affected by EDCs by consuming food containing endocrine active substances. The growing concern regarding adverse effects due to EDC exposure of humans and wildlife, as well as the increased incidence of EDC contamination has prompted extensive research into the development and validation of screening tests to detect and monitor known EDCs and new substances with endocrine-disrupting capability. These screening tests involve assessing the effect of known and potential EDCs on reproductive function and development as well as 
hormone production. To assess the effect of EDCs on the reproductive system different methods are employed which include in vitro, in vivo and ex vivo methods. In vitro methods have been suggested as a suitable screening tool for EDC monitoring due to low costs, reduced animal usage, the use of standard and basic equipment as well as the ability to screen a large number of samples with multiple endpoints. Of the available in vitro methods, the minced testes method has been suggested as the most suitable method for screening EDCs and for this reason has been employed in this study. The aim of this study was thus to employ a minced testes method to screen samples for male reproductive toxicity using cell viability and hormone production (testosterone and estradiol) as endpoints.The first objective of this study was to optimize an in vitro testicular cell culture assay by determining both optimal luteinizing hormone (LH) 
concentration and incubation time needed for testosterone production. Testicular cell cultures were prepared and cells were treated with varying concentrations of LH (10, 1, 0.1, 0.01 and 0 mu/ml) and incubated for 4 hours and 20 hours. Testosterone production was evaluated for each incubation period. Testosterone production was significantly increased for both incubation periods at all LH concentrations tested as compared to the control. For both incubation periods, there was no significant difference in testosterone production between the different LH concentrations tested. From the data obtained, the 4 hour incubation period as well as the LH concentration of 10 mu/ml were selected as optimal for the testicular cell culture assay. The second objective of this study was to determine the effect of Tulbaghia violacea Harv. on the male reproductive system. T. violacea is a plant species indigenous to southern Africa and is used locally as a herbal remedy/medicine to treat several ailments. Cells were treated with varying concentrations of the T. violacea ethanol extract (with/without LH-treatment) and incubated for 4 hours. Hormone production and cell viability were evaluated. The results obtained from this pilot in vitro study demonstrated that the ethanol extract of T.violacea has androgenic properties by significantly increasing LH-induced testosterone production in mouse testes with no significant change in cell viability. The third objective of this study was to assess the effect of Sutherlandia frutescens(L.) R.Br and Artemisia afra Jacq. Ex Willd. on the male reproductive system. S. frutescens and A. afra are also plant species indigenous to southern Africa and used locally as a herbal remedy/medicine to treat several ailments. Ethanol extracts of each plant was prepared and cells were treated with varying concentrations of each extract (0, 156.25, 312.5, 625, 1250,2500 and 5000 &mu
g/ml) with or without LH-treatment and incubated for 4 hours. Cytotoxicity by LDH measurement and hormone production (testosterone and estradiol) were endpoints that were evaluated. The results obtained showed that the ethanol extracts of both plants are not cytotoxic to testicular cells and that A. afra decreases testosterone production at high concentrations. The fourth and final objective of this study was to assess the acute effect of four heavy metals, namely manganese, copper, cadmium and magnesium on the male reproductive system. These heavy metals are used extensively in manufacturing and mining industries. Cells were treated with varying concentrations of each metal salt (200, 100, 50, 25, 12.5, and 6.25 
&mu
M) with or without LH-treatment and incubated for 4 hours. Endpoints evaluated included cell viability, testosterone and estradiol production. The results obtained showed that manganese, cadmium and copper are highly toxic to testicular cells in vitro and therefore may potentially cause reproductive toxicity.

The budding yeast S. cerevisiae is widely used as a model organism to study biological processes that are conserved among eukaryotes. Di fferent genomic approaches have been applied successfully to interrogate the mode of action of small molecules and their combinations. In this thesis, these technologies were applied to di fferent sets of chemical compounds in the context of two collaborative projects. In addition to insight into the mode of action of these molecules, novel approaches for analysis of chemical-genetic pro files to integrate GO annotation, genetic interactions and protein complex data have been developed. The fi rst project was motivated by a pressing need to design novel therapeutic strategies to combat infections caused by opportunistic fungal pathogens. Systematic screens of 1180 FDA approved drugs identifi ed 148 small molecules that exhibit synergy in combination with uconcazole, a widely used anti-fungal drug (Wright lab, McMaster University, Canada). Genome-wide chemical-genetic profiles for 6 of these drugs revealed two di fferent modes of action of synergy. Five of the compounds a ffected membrane integrity; these chemical-genetic interactions were supported by microscopy analysis and sorbitol rescue assays. The sixth compound targets a distinct membrane-associated pathway, sphingolipid biosynthesis. These results not only give insight into the mechanism of the synergistic interactions, they also provide starting points for the prediction of synergistic anti-fungal combinations with potential clinical applications. The second project characterised compounds that aff ected melanocytes in a chemical screen in zebra fish (Patton lab, Edinburgh). Chemical-genetic screens in S.cerevisiae enabled us to show that melanocyte pigmentation reducing compounds do so by interfering with copper metabolism. Further, we found that defects in intracellular AP1 and AP3 trafficking pathways cause sensitivity to low copper conditions. Surprisingly, we observed that the widely-used MAP-kinase inhibitor U0126 a ffects copper metabolism. A nitrofuran compound was found to speci fically promote melanocyte cell death in zebrafi sh. This enabled us to study off -target eff ects of these compounds that are used to treat trypanosome infections. Nifurtimox is a nitrofuran prodrug that is activated by pathogen-specifi c nitroreductases. Using yeast and zebra fish we were able to show that nitrofurans are also bioactivated by host-specifi c aldehyde dehydrogenases suggesting that a combination therapy with an aldehyde dehydrogenase inhibitor might reduce side e ffects associated with nifurtimox.

Target-based screening projects for bioactive (orphan) compounds have been shown in many cases to be insufficiently predictive for in vivo efficacy, leading to attrition in clinical trials. Phenotypic screening has hence undergone a renaissance in both academia and in the pharmaceutical industry, partly due to this reason. One key shortcoming of this paradigm shift is that the protein targets modulated need to be elucidated subsequently, which is often a costly and time-consuming procedure. In this work, we have explored both improved methods and real-world case studies of how computational methods can help in target elucidation of phenotypic screens. One limitation of previous methods has been the ability to assess the applicability domain of the models, that is, when the assumptions made by a model are fulfilled and which input chemicals are reliably appropriate for the models. Hence, a major focus of this work was to explore methods for calibration of machine learning algorithms using Platt Scaling, Isotonic Regression Scaling and Venn-Abers Predictors, since the probabilities from well calibrated classifiers can be interpreted at a confidence level and predictions specified at an acceptable error rate. Additionally, many current protocols only offer probabilities for affinity, thus another key area for development was to expand the target prediction models with functional prediction (activation or inhibition). This extra level of annotation is important since the activation or inhibition of a target may positively or negatively impact the phenotypic response in a biological system. Furthermore, many existing methods do not utilize the wealth of bioactivity information held for orthologue species. We therefore also focused on an in-depth analysis of orthologue bioactivity data and its relevance and applicability towards expanding compound and target bioactivity space for predictive studies. The realized protocol was trained with 13,918,879 compound-target pairs and comprises 1,651 targets, which has been made available for public use at GitHub. Consequently, the methodology was applied to aid with the target deconvolution of AstraZeneca phenotypic readouts, in particular for the rationalization of cytotoxicity and cytostaticity in the High-Throughput Screening (HTS) collection. Results from this work highlighted which targets are frequently linked to the cytotoxicity and cytostaticity of chemical structures, and provided insight into which compounds to select or remove from the collection for future screening projects. Overall, this project has furthered the field of in silico target deconvolution, by improving the performance and applicability of current protocols and by rationalizing cytotoxicity, which has been shown to influence attrition in clinical trials.

Background and objectives: Apoptosis is a process in which a cell programmes its own death. It is a highly organized physiological mechanism in which injured or damaged cells are destroyed. Apart from physiological stimuli however, exogenous factors can induce apoptosis. Many anti-cancer drugs work by activating apoptosis in cancer cells. Natural substances have been found to have the ability to induce apoptosis in various tumour cells and these substances have been used as templates for the construction of 
novel lead compounds in anticancer treatment. On the other hand, alkylating agents such as cisplatin, cis- [PtCl2 (NH3) 2] have been widely used as antineoplastic agents for a 
wide variety of cancers including testicular, ovarian, neck and head cancers, amongst others. However, the use of cisplatin as an anticancer agent is limited due to toxicity and resistance problems. The aim of this present study was to screen the leaves of Rhus laevigata, a South African indigenous plant, for the presence of pro-apoptotic and 
anti-proliferative natural compounds and also to screen newly synthesised palladium based complexes (15 and 57) and a platinum based complex (58) for their antineoplastic 
activities tested against a panel of cell lines. Results. The results showed that crude methanol extracts from Rhus laevigata as well as the newly synthesised palladium based complexes (15 and 57) and a platinum based complex (58) induced apoptosis in the cell lines tested, as demonstrated by the externalization of phosphatidylserine, mitochondrial membrane permeabilization,caspase-3 activation, and DNA fragmentation. Caski (cervical cancer) and H157 (non small cell lung carcinoma) cell lines treated with the methanol extract from Rhus laevigata however, were more resistant to apoptosis induction. Among the metallocomplexes, complexes 15 and 57, palladium based complexes, were the most active. Conclusion: The methanol extract from the leaves of Rhus laevigata contain pro-apoptotic and antiproliferative natural compound(s), which need to be characterised and elucidated as they could provide the much-needed lead compounds in the fight against cancer. On the other hand the newly synthesized palladium complexes also need further evaluation to 
see if they can be used as anticancer agents that can overcome the problems associated with cisplatin.

Laura Linney has an extensive education and experience in performance, which has influenced her to create a well-defined methodology when she approaches new roles. She uses a dialectical approach to performance. This approach has two parts as she outlined in a personal interview: phase one is her research, education, understanding of the script, and previous experiences working together to create a character, while phase two is her release of control over the character and the opportunity for the text (film or otherwise) and role to take on their own distinct personalities. This means that Linney eventually gives up agency over her characters in order for them to be effective and successful in the whole of a film. In effect, her characters are created by numerous influences within and outside her range of control. My intentions in this article are to prove that this dialectical methodology is prominent within all aspects of Laura Linney?s performances. In fact, I suggest that her utilization of this technique is what makes her a dynamic, effective, and unique actress. The dialectical nature of her performance techniques can be observed most effectively in specific breakthrough moments within her films. These moments exist most prominently in Linney?s films that are rooted in close character analysis like You Can Count On Me, The Savages, and the HBO mini-series John Adams. Close textual analyses of these scenes show a dramatic hiatus from the standard performance that she has used to help build a character. They show distinct differences between characters, which reinforces my point that each role is not only mandated by Linney?s creative power over her acting, but also a complete release of this control. They highlight how Linney allows herself to be directed and molded to develop deep, complex characters that work organically within the greater text of the film.

The recent leaps in virtual reality (VR) technology have unleashed revolutionary potential for applications in a wide variety of areas, including education, training, psychological-therapy, etc. As part of the effort on understanding how users interact with VR, I focused on studying full-body joint action using a road crossing task which involves perception, decision-making, action, and joint action. I have been heavily involved in the design, implementation, and construction of two large-screen, room-like stereoscopic virtual environment (VE) simulators. Using this system, I developed a three-part research plan with a series of studies to examine how people engage in full-body joint-action with a partner under three scenarios: 1. two people who are physically present in a co-occupied virtual environment; 2. one person who shares a virtual environment with a computer-generated agent (CG agent); 3. two people who share the same virtual environment remotely in physically separate places where each person is motion tracked and presented in the environment as a graphic avatar. The behaviors of participants were recorded and processed through a customized pipeline that captures important performance metrics, such as how participants pick crossable gaps and time their movements. The VE system, user study designs, and findings are introduced in this dissertation.

Phosphoinositides (PIs) are pivotal lipid molecules with both scaffolding and signalling functions regulating key aspects of cellular physiology. For example, phosphatidylinositol (3,4,5)-trisphosphate, generated by phosphoinositide 3-kinase (PI3K), is an essential mediator of the PI3K/AKT signalling pathway, which is crucial for cell proliferation, survival and apoptosis. Constitutive activation of this signalling cascade has been identified in acute myeloid leukaemia (AML), the most common haematopoietic malignancy in adults, and experimental deletion of the PI3K antagonists PTEN and SHIP cause leukaemia in mice. However, little is known regarding the role of other PI modulator proteins in AML. Thus, in this thesis, a lentivirally delivered small hairpin RNA (shRNA) library targeting 103 genes (345 pLKO knockdown constructs) with presumed or established roles in PI metabolism was utilised to screen for genes required for AML blast cell viability/proliferation and differentiation. First, knockdown constructs were tested for their impact on proliferation/viability in seven human AML cell lines by measuring fold change in fluorescence of the cell viability dye alamarBlue relative to controls (cells transduced with a non-targeting control hairpin) over three days. This identified 13 candidate genes selected with the criterion that two or more knockdown constructs per gene reduce cell viability/proliferation relative to control by greater than or equal to50 % across all cell lines. From these candidate genes, PIP4K2A, INPP5B and IMPAD1 were selected for downstream validation experiments, which reproduced the observation from the primary screen. For INPP5B and IMPAD1, knockdown constructs also reduced clonogenic potential of primary human AML samples but only showed a modest effect on normal CD34+ haematopoietic stem or progenitor cells (HSPCs) in a methylcellulose based assay. This could be recapitulated in a murine setting where knockdown constructs targeting both genes reduced clonogenic potential of murine MLL- AF9 AML cells with little effect on normal KIT+ HSPCs. In line with this, Inpp5b knockout KIT+ BM cells either failed to immortalise or weakly immortalised, following forced expression of the powerful MLL-AF9 oncogene. A further screen was performed to identify regulators of THP-1 blast cell differentiation, by seeding knockdown construct transduced cells into methylcellulose based semisolid media. After ten days of incubation the degree of macrophage differentiation was evaluated by light microscopy and an arbitrary differentiation score was given. With the criterion that greater than or equal to2 knockdown constructs per gene received the highest differentiation score, reflecting terminal macrophage differentiation of all seeded cells, SBF2 was identified as the top-scoring hit. Validation experiments have confirmed macrophage differentiation based on cytospin preparations of SBF2 knockdown THP-1 cells. Moreover, xenograft assays have shown that knockdown constructs targeting PIP4K2A and SBF2 delayed or abrogated in vivo leukaemogenesis. Thus this work has identified novel roles for PI modulator genes in human AML with possible therapeutic potential.

Nowadays, scientific and political communities are focused on ways to better preserve and manage the natural resources of our planet. In order to reduce consumption of fossil resources, and to develop more environmentally friendly industrial processes, the industry of flavors and fragrances became interested in developing new bio-based encapsulating materials. In the present work, maltodextrins have been chosen as main component of the matrix, and pea protein isolate and a modified starch were selected as compatibilizing additives. The incorporation of volatile odorant compounds and the elaboration of the new bio-based delivery systems were performed, all in one single step, by low temperature twin-screw extrusion. The physicochemical, thermal and morphological properties of these matrices were studied, as well as the encapsulation efficiency and the release profile of the active compounds. These investigations have led to a better understanding of the impact of the formulations and of the incorporation of the active compound on the process parameters. The interactions between the wall and the encapsulated materials were also analyzed. The characteristics of the new bio-based delivery systems and the established extrusion process conditions were found to be very promising to be employed in the field of perfumery.

碩士
大同大學
材料工程學系(所)
95
Active screen plasma nitriding (ASPN) on the corrosion properties of UNS S31803 duplex stainless steel with different temperature and times has been studied. The surface hardness of ASPN DSS specimen was raised to 1000~1200HK. From the experimental results, the S-phase (γN) and αN phase were observed in the surface of ASPN DSS specimens conducted under 400 to 450℃, and increasing corrosion resistance at 420℃ with 10-20 hours after plasma nitriding. When working time increase to 25 hours will lose the property of corrosion resistance, and working temperature above 435℃ will also lose the property of corrosion resistance due to chromium nitride formation. The hardness of nitrided layer reach to 900HV above and increasing wear resistance obviously after plasma nitriding. Working temperature and time below 420℃ and 20 hours are the optimum treatment condition of duplex stainless steel by active screen plasma nitriding.

M.Tech.
This study is based on the premise that awareness of active citizenship among South African citizens should be encouraged and can be developed through specific educational and skills interventions embedded in Visual Art learning programmes. South Africa‟s developing democracy requires active citizens with the capacity to disseminate values of equality, dignity, liberty and social justice, amongst other constitutional rights. Our country‟s history in the struggle for liberation encompasses a legacy of resistance, and screen-printed protest posters played an important role in communicating dissent towards the apartheid state (Seidmann 2009, Peffer 2009). My research examines the role of screen-printing as a particular graphic medium which is an organising tool to create awareness and communication. The project uses co-operative enquiry as a participatory action research method to facilitate the application of hand-made fine art screen-printed artworks and posters that support skills development, an understanding of self-identity and a sharing of skills that contribute to active citizenship. I present three visual art screen-printing projects that I facilitated from 2010 to 2011 at Artist Proof Studio (APS), an art centre in Johannesburg, whose mission is to inculcate aspects of active citizenship among the participating learners. I contend that the combination of all three screen-print projects presented to the group of students, leads to skills-development, awareness of personal identity and participation in community engagement projects which may enhance their ability to participate as active citizens and which in turn supports the mission statement of the education unit at APS. Such an intervention serves as a learning model that can further contribute to social, educational and economic redress among the participants at APS.

En raison des progrès technologiques, les comportements sédentaires (souvent devant un écran) sont devenus les activités de loisir préférées pour beaucoup d’enfants, au lieu de s’engager dans le jeu actif, des sports ou d’autres activités requérant de l’effort physique. L’utilisation de transport actif est aussi en déclin, la majorité des enfants se rendant à l’école en voiture ou dans d’autres moyens de transport passifs. Pourtant, l’inactivité et la sédentarité constituent des facteurs de risque pour de multiples problèmes de santé physique et mentale. Tel que décrit dans le premier chapitre, les bienfaits de l’activité physique sur le bien-être sont bien documentés et les risques associés aux comportements sédentaires sont de plus en plus étudiés. Néanmoins, la plupart des études ne regardent ces deux aspects que séparément et ne s’intéressent qu’à l’impact immédiat sur une dimension spécifique du bien-être. Le but de cette thèse doctorale était donc d’étudier le rôle que l’activité physique et les comportements sédentaires, à la fin de la maternelle, jouent sur le bien-être physique, cognitif et psychosocial au début de l’adolescence (deux périodes de transition importantes pour les enfants). Le premier article (Chapitre II) a examiné les associations prospectives entre la participation aux activités physiques pendant les loisirs, à l’âge de 6 ans, et le rendement scolaire à l’âge de 12 ans. Les résultats montrent que les enfants qui participent davantage aux sports et à d’autres activités physiques structurées et non structurées présentent de meilleurs résultats scolaires et un engagement en classe plus élevé six ans plus tard que les enfants qui s’adonnent moins à ces activités. Le deuxième article (Chapitre III) a examiné les liens prospectifs entre un mode de vie qui tient compte, simultanément, de la participation à des activités physiques pendant les loisirs, de l’utilisation de transport actif et du temps consacré aux comportements sédentaires (ordinateur, télévision et jeux vidéo), à l’âge de 6 ans, et des indicateurs reliés au rendement scolaire et au bien-être physique et psychosocial, à l’âge de 12 ans. Les résultats montrent que les enfants qui mènent un mode de vie plus actif/moins sédentaire avant de commencer la scolarité présentent, ultérieurement, des habitudes de vie plus saines (plus d’activité physique et moins de temps d’écran) et moins de troubles émotifs et de victimisation, comparativement aux enfants menant un mode de vie moins actif/plus sédentaire. Dans les deux articles, les associations spécifiques pour chaque genre ont également été explorées. Les résultats des analyses fondées sur le genre montrent que même si tant les filles que les garçons bénéficient d’être plus actifs/moins sédentaires, chaque sous-groupe éprouve les bienfaits différemment. Une discussion des principaux résultats et des implications est présentée dans le dernier chapitre. En somme, cette thèse souligne l’importance de promouvoir un mode de vie actif dès un âge précoce et de développer des communautés qui offrent aux enfants de multiples occasions de se maintenir actifs. Ceci permettra de prévenir les nombreux risques associés à l’inactivité et la sédentarité et de contribuer au bien-être des jeunes, à court et à long terme.
Due to advances in technology, sedentary behaviors (which typically involve screens) have become the preferred leisure activity for many children, instead of engaging in active play, sports, or other activities requiring physical effort. Due to urban sprawl, the use of active transportation is also in decline and most children travel to school by car or other passive means of transportation. However, physical inactivity and sedentariness are both risk factors for multiple physical and mental health problems. As described in the first chapter, the protective benefits of physical activity on well-being are well documented and the risks associated with sedentary behaviors are increasingly being studied. Nevertheless, most studies look at these two aspects separately and focus solely on the immediate impact on a specific sphere of well-being. The aim of this doctoral thesis was therefore to study, during two important transition periods in development, the links between physical activity and sedentary behavior in kindergarten and physical, cognitive, and psychosocial well-being while children transition out of elementary school. The first article (Chapter II) examined the prospective associations between participation in leisure-time physical activity at age 6 and academic performance at age 12. The results suggest that children who participate more in sports and other structured and unstructured physical activities perform better in school and present a higher classroom engagement six years later, than children who are less involved in these activities. The second article (Chapter III) examined the prospective links between a lifestyle that takes into account, at the same time, participation in leisure-time physical activity, use of active transportation, and time spent on sedentary behaviors (computer, television, and video games) at age 6, and several indicators related to academic performance and physical and psychosocial well-being at age 12. The results reveal that children who lead a more active/less sedentary lifestyle before starting school present healthier lifestyles (more physical activity and less screen time), fewer emotional disorders and less victimization later in life, compared to children leading a less active/more sedentary lifestyle. In both articles, gender-specific associations were also explored. The results of the gender-based analyses suggest that even if both girls and boys benefit from being more active/less sedentary, each gender experiences these benefits differently. A discussion of the main findings and implications is presented in the last chapter. In summary, this thesis highlights the importance of promoting an active lifestyle from an early age and the need of developing communities that provide children with multiple opportunities to stay physically active. This will help prevent the many risks associated with inactivity and sedentariness among youth and thus contribute to their well-being, both in the short and long term.

When portraying a character in a fictional world the actor is faced with many challenges. To circumvent these challenges, he must become congruent with the reality of the fictional world. In order to do so, the actor has to ‘believe’ in the circumstances of the unfolding scene and live ‘in the moment’. These external circumstances act as stimuli which the actor uses to create and consequently ‘believe’ in the environment that the character inhabits. However, the use of green screen technology in special effects limits or eliminates these stimuli and the external circumstances. Green screen is a technique used in film and television that allows the filmmaker to film an actor in combination with a green screen and then replace the ‘green’ with anything the filmmaker requires. This allows for compositing to occur and the filmed reality to be manipulated. However, this technology challenges the actor’s ‘belief’ and behaviour, thus affecting congruence with and the (photo)realism of the created fictional world. In a green screen environment the actor is challenged to imagine, experience and act in line with the circumstances of the fictional world that will replace the green screen, instead of the green environment in which he finds himself. One acting strategy that elicits imagination, action and feeling is Stanislavsky’s notion of the magic if. Accordingly, this dissertation proposes that this strategy can assist the actor in circumventing the challenges that arise when working with green screen technology. Stanislavsky developed his acting principles by observing human behaviour in an attempt to use the mind–body paradigm in circumnavigating the acting moment. The field of cognitive neuroscience has also investigated human behaviour and the mind–body paradigm and recent discoveries have increased understanding of the fields. These discoveries have validated the notion of the magic if and the components it incorporates. Yet, the discoveries surrounding the notion of the magic if and, subsequently, the increased understanding of the concept have not to date been applied to acting with green screen technology. It is therefore hypothesised that, by triangulating the challenges of ‘green screen acting’, the principles of the magic if and the knowledge gained from cognitive neuroscience, an acting strategy can be developed that will assist the actor in the green screen environment and thus create verisimilitude with the fictional world. This hypothesis has led to the theoretical development of explorations that will strengthen the skills the actor needs in order to apply the notion of the magic if; as well as an acting strategy to assist the actor when entering the green screen environment.
Dissertation (MA)--University of Pretoria, 2013.
gm2014
Drama
Unrestricted

no
Introduction: Potential-sensitive dyes have primarily been used to optically record action potentials (APs) in whole heart tissue. Using these dyes to record drug-induced changes in AP morphology of isolated cardiac myocytes could provide an opportunity to develop medium throughout assays for the pharmaceutical industry. Ideally, this requires that the dye has a consistent and rapid response to membrane potential, is insensitive to movement, and does not itself affect AP morphology. Materials and methods: We recorded the AP from isolated adult guinea-pig ventricular myocytes optically using di-8-ANEPPS in a single-excitation dual-emission ratiometric system, either separately in electrically field stimulated myocytes, or simultaneously with an electrical AP recorded with a patch electrode in the whole-cell bridge mode. The ratio of di-8-ANEPPS fluorescence signal was calibrated against membrane potential using a switch-clamp to voltage clamp the myocyte. Results: Our data show that the ratio of the optical signals emitted at 560/620 nm is linearly related to voltage over the voltage range of an AP, producing a change in ratio of 7.5% per 100mV, is unaffected by cell movement and is identical to the AP recorded simultaneously with a patch electrode. However, the APD90 recorded optically in myocytes loaded with di-8-ANEPPS was significantly longer than in unloaded myocytes recorded with a patch electrode (355.6 ± 13.5 vs. 296.2 ± 16.2ms; p< 0.01). Despite this effect, the apparent IC50 for cisapride, which prolongs the AP by blocking IKr, was not significantly different whether determined optically or with a patch electrode (91 ± 46 vs. 81 ± 20 nM). Discussion: These data show that the optical AP recorded ratiometrically using di-8- ANEPPS from a single ventricular myocyte accurately follows the action potential morphology. This technique can be used to estimate the AP prolonging effects of a compound, although di-8-ANEPPS itself prolongs APD90. Optical dyes require less technical skills and are less invasive than conventional electrophysiological techniques and, when coupled to ventricular myocytes, decreases animal usage and facilitates higher throughput assays.

碩士
國立中正大學
機械系
88
The design of tooth profiles of twin-screw compressor plays an important role to avoid the problem of leakage. In the process of design of the tooth profile, it is known that the line of action (i.e., the summation of instant contact points in the fixed coordinate system) causes great effects on the performance of the screw compressor. It is very important to have shorter length of line of action, the closing and continuous line of action and the shorter distance between the end of line of action and the housing cusp for designing good performance rotors. Therefore, the significance of line of action is apparently. This study proposes a mathematical model for the tooth profiles of twin-screw compressor by using the given line of action. This mathematical model can be applied to any kind of line of action. The relative curvature, sliding velocity, contact ratio, limitation of undercutting and the mating tooth profiles are derived directly from the line of action. Utilizing the mathematical model, it can directly design the line of action that satisfies the requirement of lower leakage and then derive the new profiles which needs for the rotor of twin-screw compressor.

碩士
國立中正大學
機械系
93
The leakage of rotors could be observed from the sealing line. The leakage is an important factor that influences the efficiency. Conventionally, the development of a twin screw rotor with high efficiency is started from designing a tooth profile. It is logical to observe the sealing line of the rotor to judge that the leakage is decreased or not. If the leakage is not decreased, modify the tooth profile till you obtain a good sealing line. Therefore, we try to develop a design process starts from the shape of the sealing line. Several segmented cubic splines are used to describe the sealing line. We develop a sealing line with little leakage and then use the sealing line to derive the equations of tooth profile. Control points on the sealing line are used as design variables. We can move the control points to change the shape of the sealing line and then derive the corresponding tooth profile of screw rotors. Using software to calculate the volumetric efficiency, isentropic indicated efficiency and average torque on male and female rotors. The tooth profiles are optimized by the isentropic indicated efficiency with the constraints of the transmitted torque, the minimum curvature of the tooth profile, etc. The design variables include the shape of the sealing line, tip radius, addendum, the ratio between rotor length and the outer diameter, and the wrap angle. A numerical example is presented to show the validation of the purposed design process.

碩士
國立中正大學
機械系
90
The efficiency of the twin-screw compressor depends mainly on the leakage. Smaller leakage leads to higher efficiency. The conventional design process for the tooth profile of the twin-screw rotor is started from a pre-determined rotor addendum curve. According to the addendum curve, the conjugate dedendum are derive. Then, the length of the sealing line, the size of blow hole and volume efficiency are calculated. However, the conventional design process is very difficult to improve the tooth profile design because the performance of twin-screw rotor can not be observed directly on the addendum curve. In this thesis, a design process of the tooth profile of rotor is proposed to lower the leakage and improve the volume efficiency. Since the leakage can be observed directly form the sealing line (instantaneous contact line between rotors, i.e. line of action ), we propose a design procedure started from the line of action. The line of action can be composed from arc, involute curve, straight line, cycloidal curve, or cubic spline. The tooth profile and the conditions of undercut are derived based on the shape of the line of action. Differential geometry and theory of gearing are utilized to guarantee the smooth tooth profile and the smooth running between rotors. Numerical examples are presented to explore the design guide lines. Three improved rotor tooth profiles are proposed to show the capability of the proposed design procedures. According to the numerical examples, the proposed tooth profile have higher volume efficiency, shorter sealing line and smaller blow hole than SRM tooth profile which is the major commercial products available on the market.