To see the other types of publications on this topic, follow the link: Epithelial cells – Electric properties.
Dissertations / Theses on the topic 'Epithelial cells – Electric properties'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Epithelial cells – Electric properties.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Thomson, Susmita. "Local feedback regulation of salt & water transport across pumping epithelia : experimental & mathematical investigations in the isolated abdominal skin of Bufo marinus." University of Western Australia. Dept. of Physiology, 2003. http://theses.library.uwa.edu.au/adt-WU2003.0022.
Full textAbstract:
[Truncated abstract] This study describes the results of a four and a half year investigation examining local regulation of ion transport through pumping epithelial cells. The study focussed on the standard isolated toad skin preparation, made famous by Hans Ussing. Originally, the objective was to perform some simple manipulations on the isolated toad skin, a standard and well-tested epithelial layer, which, according to the literature, was a well-behaved and stable preparation. The purpose of doing these toad skin experiments was to gain familiarity with the experimental techniques, such as measuring the open-circuit voltage (Voc) and the short-circuit current (Isc) across an epithelium. In the process, the experimental information that was obtained was to assist in the development and refinement of a mathematical model of a single pumping epithelial cell . . . Finally, it should be emphasised the toad skin was a convenient tissue model for exploring more general issues such as: (i) how pumping epithelial cells may adjust to changes in the extracellular environment by locally regulating their membrane conductances; (2) how the topology of a cell can influence its function (i.e. the topology can determine whether a cell is optimised for salt transport or water transport). (3) how different cells, with different functions, may be positioned in apposition in a pumping epithelial tissue so that gradients generated by one cell type can be utilised by another. From a broader perspective, it is likely that such issues are also applicable to other pumping epithelia, and ultimately, may assist in understanding how these epithelia function.
2
Francou, Alexandre. "Epithelial properties of Second Heart Field cardiac progenitor cells." Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4062.
Full textAbstract:
Une partie du cœur est formée à partir des cellules progénitrices du second champ cardiaque, qui permettent une élongation rapide du tube cardiaque. Des défauts dans le développement de ces cellules entrainent des malformations cardiaques congénitales. Ces cellules sont localisées dans le péricarde dorsal au sein du mésoderme pharyngé. Mon travail de thèse a permis de démontrer pour la première fois que ces cellules sont épithéliales et polarisées, et qu’elles forment des filopodes dynamiques du côté basal. La délétion du facteur de transcription Tbx1 perturbe la polarité des cellules et la formation des filopodes, et augmente le niveau de la protéine apicale aPKCζ. Le traitement avec un activateur de aPKCζ montre le lien entre l’intégrité épithéliale, la polarité et la formation des filopodes, et l’état progéniteur des cellules. J’ai également analysé la polarité planaire dans l’épithélium, et montrais que les cellules sont anisotropiques, étirées et allongées en direction du pole artériel. Cet étirement crée une tension orientée, révélée par une accumulation polarisée d’actomyosine, jouant le rôle de rétrocontrôle négatif. En absence d‘élongation du tube cardiaque cette tension orientée est absente. Nous avons identifié une région postérieure de l’épithélium où se trouvent une tension et une prolifération élevées, ainsi qu’une forte activité YAP/TAZ qui jouerait le rôle de relai entre tension et prolifération. La tension orientée oriente les divisions cellulaires et oriente ainsi la croissance du tissu, promouvant l’addition des cellules au pole artériel. La biomécanique des cellules du second champ cardiaque semble ainsi un moteur important pour l’élongation du cœurA major part of the heart is formed by progenitor cells called the second heart field, that contribute to rapid elongation of the heart tube. Defects in second heart field development leads to congenital heart malformations. Second heart field cells are localised in pharyngeal mesoderm in the dorsal pericardial wall. This study focuses on the epithelial properties of second heart field cells and first shows that these progenitors in the dorsal pericardial wall are epithelial and polarised, and form dynamic basal filopodia. Deletion of the transcription factor Tbx1 perturbs epithelial polarity and filopodia formation and upregulates the apical determinant aPKCζ. Treatment with an activator of aPKCζ reveals that epithelial integrity, polarity and basal filopodia are coupled to the progenitor status of second heart field cells. Next we evaluated planar polarity of second heart field cells in the dorsal pericardial wall. Cells are anisotropic, being stretched and elongated on an axis directed towards the arterial pole. This stretch results in oriented epithelial tension revealed by polarised actomyosin accumulation through a negative feedback loop. In the absence of cell addition to the cardiac poles oriented tension is absent. We identified a posterior region in the epithelium with high tension, elevated proliferation and a high level of active YAP/TAZ that may act as relay between tension and proliferation. Oriented tension orients the axis of cell division and the growth of the tissue on an axis toward the arterial pole, further promoting addition of the tissue to the pole. Biomechanical feedback may thus be an important driver of heart tube elongation
3
Wang, Entong. "Directed migration, re-orientation and inhibited proliferation of lens epithelial cells in applied electric fields." Thesis, University of Aberdeen, 2001. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU485602.
Full textAbstract:
Physiological electric fields (EFs) exist in the vertebrate lens, but the importance of the endogenous EF is not well understood yet. In the present study, an applied EF to mimic endogenous EFs was applied to cultured lens epithelial cells (LECs) to investigate the effects of EFs on the behaviours of LECs and the underlying mechanisms. It was showed that LEG migration was directed and migration rate was increased in applied EFs, and serum or growth factors were required for these EF-induced cell responses. LECs elongated and re-oriented to lie perpendicular to field vector. Healing of LEG monolayer wounds was also influenced by EF polarity. EF exposure enhanced the activation of extracellular signal-regulated kinase (ERK) ½ and induced an asymmetric distribution of active ERK ½ in monolayer wounds. Mitogen-activated protein (MAP) kinase inhibitor U0126 inhibited the directed migration and reorientation of LECs in EFs and the healing of LEG monolayer wound, and U0126 also completely prevented activation of ERK ½ in LECs. It is suggested that MAP kinase signaling pathways were involved in the responses of LECs to EF stimulation. EF exposure also inhibited the proliferation of the LECs. Cell cycle analysis showed that EF exposure inhibited the Gl/S transition of the cell cycle progression in LECs, resulting in a Gl-block. The EF-induced down-regulated expression of Gl-specific cell cycle protein cyclin E and the up-regulated expression of cyclin-Cdk (cycle dependent kinase) complex inhibitor p27 kipl were accounted for the cell cycle arrest of LECs in EFs. This study implies that a physiological EF may be one of the guidance cues regulating LEG behaviours in vivo and applying EFs may be one way of controlling aberrant LEG behaviours in vitro and in vivo.
4
Charles, Amelia Kate. "The oestrogenic and genotoxic properties of cosmetic chemicals in human breast epithelial cells." Thesis, University of Reading, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.542056.
Full text
5
Liu, Yu, and 劉鈺. "Biological properties of EBV-encoded latent membrane protein 1 in nasopharyngeal epithelial cells." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31242078.
Full text
6
Dodd, Sara. "Hydrodynamic and hydrogel properties of mucins from cultured guinea-pig tracheal epithelial cells." Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287166.
Full text
7
Liu, Yu. "Biological properties of EBV-encoded latent membrane protein 1 in nasopharyngeal epithelial cells /." Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk/hkuto/record.jsp?B23001008.
Full text
8
Bentivegna, Valerie. "The biomechanical properties of epithelial cells and tissue in two and three dimensions." Thesis, University of Dundee, 2019. https://discovery.dundee.ac.uk/en/studentTheses/0e957e85-9e8d-46f7-b6f0-9ab3307c43bc.
Full textAbstract:
During development and disease progression, cells and tissue undergo mechanical changes and alter their response to external physical cues. This is also true during the onset of colorectal cancer, the second most common cause of cancer deaths in the Western world. Before the changes that occur during cancer onset can be understood, a better appreciation is needed of the mechanical forces and properties involved. Therefore, there is a drive to develop novel tools to accurately measure biomechanical properties at different spatial scales. 3D cell models are a useful method to understand the mechanical properties at cell and tissue scale, as they provide a more physiologically relevant environment for cells than 2D cell culture. Additional insight may be achieved by complementing experimental approaches with computational models to reveal how the properties of individual cells work as a system to generate the mechanical properties of 3D tissue structures. In this work, Madine-Darby Canine Kidney (MDCK) cells and cysts were used as a model for epithelial tissue. These cells can be genetically modified to mimic the onset of colorectal cancer, by the expression of a truncated Adenomatous polyposis coli (APC) protein: N-APC. N-APC is present in most cases of colorectal cancer and provides a useful tool to study the early changes in colorectal cancer. MDCK cells form spherical cysts up to 100 μm in diameter with a hollow lumen when cultured in an extracellular matrix (ECM) gel. Atomic Force Microscopy (AFM) experiments have revealed that MDCK cells expressing N-APC grown at continued confluency were significantly stiffer than cells expressing only WT-APC. Cells expressing N-APC had an average stiffness of 4.59 ± 1.30 kPa in the nuclear region, while the average stiffness of WT cells was 2.90 ± 0.59 kPa. This is the first time a mechanical effect of N-APC expression has been observed. Adapting AFM for use on 3D tissue models is challenging, as these structures are grown embedded in an ECM gel and cannot be probed directly. This work describes a novel protocol that allowed the AFM cantilever to come in contact with a MDCK cyst surface. These experiments have been used to validate a Finite Ele- ment (FE) model of the mechanical behaviour of an MDCK cyst, that predicted the deformation behaviour of a cyst being compressed by an AFM cantilever. Alternatively, microultrasound (μUS) imaging was evaluated as an approach to provide additional useful information about 3D tissue models, with the benefit that direct contact with the sample is not required. Quantitative analysis of the μUS signal allowed the calculation of the apparent speed of sound through an MDCK cysts, which was on average 1112.96 ± 383.87 m/s. This was significantly lower than the apparent speed of sound through a spheroid (a 3D structure that does not contain a lumen) such as HCT-116 spheroids, which had an average apparent speed of sound of 1494.68 ± 951.82 m/s. This suggests that the speed of sound depends on the geometrical features of a spherical structure. Indeed, FE modelling has confirmed that stronger interference effects occur for a sound wave interacting with a cyst compared to a spheroid due to surface and Lamb waves. In addition, cellular and molecular markers for mechanical stress were identified to determine the effect of static compression applied with a weighted coverslip: compressed cells had nuclei with smoother nuclear envelopes (decrease in amount of folded nuclear envelopes of 32 % ± 41 % for WT-MDCK cells) and an increased vinculin signal (increase of signal intensity of 22 % ± 10 % for WT-MDCK cells) at the junctional membrane. Finally, the use of acoustic radiation force (ARF) was explored as a means of applying compression to cells. While preliminary experiments that exposed the apical surface of samples to continuous acoustic radiation did not reveal an ob- servable effect on the cells, a FE model has been developed to aid further design of ARF experiments. This project explored a range of different tools for studying the mechanical properties of cells and tissue, specifically in the context of 3D models. Experimental approaches have been complemented with FE models to increase understanding of how mechanical properties relate over different length scales, from cells to tissue structures, and how acoustic waves interact with cells and tissue structures. In the future, these approaches could permit further investigation of how the mechanical properties of cells and tissues change during the onset of colorectal cancer.
9
Weaver, Jennifer. "Development of an in vitro model for investigating the properties of human prostate epithelial cells and prostatic carcinoma cells /." St Andrews, 2008. http://hdl.handle.net/10023/755.
Full text
10
Nauseef, Jones Trevor. "An investigation of the molecular and biophysical properties of metastatic cells." Diss., University of Iowa, 2015. https://ir.uiowa.edu/etd/3150.
Full textAbstract:
Prostate cancer presents a significant paradox: it is very common, yet rarely fatal. To wit, the prostate is the most common non-skin tissue for cancer diagnosis in men in the United States. Despite its high incidence, fatal malignancy occurs in only a small fraction of diagnosed men. The fatal cases are characteristically defined by distant spread in the body, also known as metastasis. In order to metastasize a cancer cell must complete several sequential steps. These include degradation of and invasion through the epithelial basement membrane, typically through the loss of static intracellular adhesions with fellow epithelial cells; entrance into the blood stream (intravasation); survival within circulation; exit from the blood stream upon arrival at a new tissue (extravasation); and survival and colonization at the secondary site.
At the time of diagnosis, it is not currently possible to accurately predict future metastasis and thereby clinicians cannot delineate those men at high risk for fatal disease from the vast majority of men who are likely to experience an indolent disease course. Consequently, we examined the behavior of cancer cells in several steps of the metastatic cascade. In doing so, we uncovered both molecular and biophysical characteristics of cancer cells that may facilitate successful metastatic dissemination and tumor outgrowth.
Epithelial-to-mesenchymal transition (EMT) is physiological process of transdifferentiation that is normally initiated during vertebrate development, but has recently been implicated in tumor development, progression, and metastases. The EMT program results in dramatic changes, including the exchange of epithelial for mesenchymal markers, altered cellular morphology, and gain of motility. EMT-like cellular alterations have been implicated most strongly in the metastasis steps of invasion and survival of cells at primary tumors sites. How EMT-like changes may facilitate survival and growth in the microenvironment of a micrometastatic niche has been less clearly elucidated. Consequently, we evaluated how EMT-like changes may affect the survival and subsequent outgrowth of prostate cancer cell lines following restrictive growth conditions. We observed that EMT-like cells as compared to their more epithelial counterparts displayed enhanced maintenance of their proliferative potential following extended culture in nutrient restriction. This phenotype depended on an EMT-associated increase in autophagy. Notably, the post-stress outgrowth phenotype could be conferred through a paracrine signaling mechanism that may involve autophagy-derived exosome-like extracellular vesicles. These studies demonstrated that EMT-like cells have a resistance to nutrient restriction through enhanced autophagy and may have uncovered a novel autophagy-dependent exosomal secretion pathway.
Metastatic efficiency is thought to be strongly limited by the destruction of circulating tumor cells by the hemodynamic shear forces within the vasculature. However, such a persistent belief has little appropriate published experimental evidence. We developed an in vitro assay to expose cells to fluid shear stress (FSS). By monitoring the viability of the cells, we determined that transformed cells had a highly conserved ability to resist even very high FSS. The mechanism depended on the capacity to patch membrane defects, extracellular calcium, and a dynamic cytoskeleton. We also observed a stiffening of cancer cell membranes after exposure to FSS. Taken together, these studies expand the understanding of how cancer cells survive in circulation and indicate that metastatic efficiency is less limited by hemodynamic forces than previously thought.
The steps of hematogenous metastasis between intravasation and extravasation necessitate the existence of circulating tumor cells (CTCs). Collection, enumeration, and study of CTCs have the potential to serve as a "liquid biopsy" of the metastatic cascade. In prostate cancer, the enumeration of CTCs by detection of the expression of epithelial markers has displayed limited clinical utility. We hypothesized that the prognostic value of CTC number may be enhanced by detection of cells which have undergone the pro-metastatic EMT-like program. We developed a flow cytometry-based experimental assay for enumeration of CTCs using epithelial (EpCAM) and mesenchymal-like (N-cadherin) surface proteins. We detected from prostatectomy patients before and after surgery events expressing EpCAM, N-cadherin, and both. However, the detection of background events from healthy control subjects was unacceptably high. These studies support the idea of mesenchymal-like tumor cells in circulation, but will require further assay development for reliable conclusions to be drawn.
In sum, the work described above has provided descriptive and mechanistic insight to molecular and biophysical properties that may facilitate prostate cancer metastasis. It is our hope that these data will result in the development of relevant preventative, diagnostic, and therapeutic clinical strategies for prostate cancer.
11
Weaver, Jennifer. "Development of an in vitro model for investigating the properties of human prostate epithelial cells and prostatic carcinoma cells." Thesis, University of St Andrews, 2009. http://hdl.handle.net/10023/755.
Full textAbstract:
Prostate cell lines were derived from two regions of prostate tissue from the same patient. The objective was to produce cell lines (as a useful in vitro model) from these two different regions which exhibit different properties for carcinoma development. The tissue was obtained from patients suffering from benign prostate hyperplasia undergoing trans-urethral resection. Tissue was taken from the deep (peripheral) and superficial (peri-urethral) areas. The cells were immortalised by transduction with constructs over expressing the cdk4 and hTERT genes. These cell lines were then characterised for their cellular phenotypes utilized for radiation transformation studies and utilized to investigate the role of plant derived polyphenols on normal and tumour cells. The cell line from the superficial region (P21s) was treated to fractionated doses of gamma radiation and a transformed cloned cell line was derived (P21s 40Gy (clone-a)). The cell line from the deep region (P21d) was found to consist of a mixed population of abnormal cells and a transformed cloned cell line was derived from it (P21d 0Gy (clone-a). In an attempt to obtain a normal P21d cell line cloned cell lines from early passage P21d cells were established. All seven cloned lines were abnormal with an average of 80 chromosomes per cell, invasive using a Matrigel assay and produced anchorage independent colonies. All cell lines were fully characterised with immunocytochemistry, chromosome analysis, invasion assays, and anchorage independent colony formation. P21s expressed basal cell markers (cytokeratin 5 (CK5) and 14), were positive for stem cell markers (prostate specific stem cell antigen PSCA, CK6), positive for p16, p63 and telomerase expression and negative for c-Myc expression. P21s was not invasive in a Matrigel assay and did not produce anchorage independent colony formation. P21d and P21d 0Gy (clone-a) also expressed CK5, CK14, PSCA, CK6, and telomerase but not p16 or p63 and showed an increase in expression of nuclear c-Myc, highly invasive and produced anchorage independent colonies. P21s 40Gy (clone-a) expressed CK5, CK14, PSCA, CK6, telomerase and p63, produced anchorage independent colonies, and was weakly positive for c-Myc expression. Spectral karyotyping analysis (SKY) showed P21s had a normal chromosome complement except an additional chromosome 20 whereas the P21s 40Gy (clone-a), P21d and P21d 0Gy (clone-a) cell lines had an abnormal chromosome complement with P21d and P21d 0Gy (clone-a) cell lines expressing multiple copies of every chromosome including loss of the Y chromosome. These results were echoed in the single nucleotide polymorphism chip (SNP) results which showed P21s as normal but P21d and P21d 0Gy (clone-a) to have large deletion and amplification regions that correlated with the SKY analysis. No differential cytotoxic response was noted between normal and abnormal cell lines including prostatic carcinoma cell lines LNCaP and PC-3 following treatment with strawberry polyphenol compounds. Most reports of a cytotoxic response to tumour cells in the literature did not compare the response to normal cells and used established cell lines. Human lymphocytes were also tested and all compounds were toxic in high doses. Polyphenol and ellagitannin rich polyphenol fractions were very cytotoxic and the anthocyanin rich fraction less toxic. In contrast to the lack of a direct differential cytotoxic effect, plant polyphenols did produce a protective effect to a carcinogenic insult. However a protective effect was noted via micronucleus assay with 3 hour incubation with the polyphenol rich fraction prior to radiation treatment. Finally, the expression and association of metabolic enzymes within the cells cytosol were investigated. The P21s cells were found to express both isoforms of LDH and so thought to be able to metabolise anaerobically and aerobically. P21d and P21d 0Gy (clone-a) cells were found to only express one isoform in the complex and so it was assumed that these cells favoured anaerobic metabolism of ATP in correlation to the Warburg effect. c-Myc association with compounds in the cell cytosol of P21s cells existed whereas, abnormal cells lost this association along with up-regulation of c-Myc expression and down stream targets of c-Myc in the nuclei. Thus these newly established human prostate cell lines provide a useful model system for investigating the biology of the prostate and prostate cancer.
12
Yu, Shuqing [Verfasser]. "Computational Modelling of Opto-electric Properties of Nanowire Array Solar Cells / Shuqing Yu." Kassel : Kassel University Press, 2014. http://d-nb.info/1065322658/34.
Full text
13
Mießler, Katharina Sophie [Verfasser]. "Analysis of hydrostatic pressure effects on the barrier properties of mammary epithelial cells / Katharina Sophie Mießler." Berlin : Freie Universität Berlin, 2018. http://d-nb.info/1196804028/34.
Full text
14
Dunning-Foreman, N. L. "Investigating the properties of cancer stem cells and epithelial to mesenchymal transition in human prostate cancer." Thesis, Nottingham Trent University, 2012. http://irep.ntu.ac.uk/id/eprint/67/.
Full textAbstract:
In recent years, the cancer stem cell hypothesis has emerged as a compelling but controversial model of cancer progression. Contrary to the clonal evolution model, the cancer stem cell hypothesis postulates that, akin to normal tissues, tumours are hierarchical and only a rare subpopulation of cells, so-called “cancer stem cells” (CSCs), possess the unique biological properties required for tumourigenesis. In addition to tumour initiation, cancer stem cells are held solely accountable for tumour differentiation, tumour maintenance, tumour spread and tumour relapse following therapy. Of late, there has been much evidence to suggest that cancer cells reactivate the latent embryonic programme, epithelial to mesenchymal transition (EMT), in order to acquire the invasive and migratory properties necessary for the successful completion of the invasion-metastasis cascade. Intriguingly, the EMT programme was recently implicated in the generation of cells with the properties of stem cells in a breast cancer model, therefore, it is evident that multiple populations of CSCs may exist within a given tumour. Since metastasis is accountable for the vast majority of cancer-associated mortalities and CSCs are implicated in therapy failure and subsequent cancer relapse, it is apparent that epithelial to mesenchymal transition and cancer stem cells are of utmost clinical relevance. Consequently, this study sought to investigate the properties of CSCs and EMT in human prostate cancer. Using the method previously reported in the literature, this work failed to identify and isolate putative prostate CSCs. However, this study successfully identified the OPCT-1 cell line as a suitable model for the investigation of EMT and subsequently derived and selected five phenotypically distinct clones that provided a model to determine a possible correlation between EMT and the generation of CSCs in human prostate cancer. The present work revealed that EMT of prostate cancer cells does not always generate cells with the properties of stem cells. Furthermore, this study demonstrated evidence for the existence of multiple cancer stem cell-like populations in human prostate cancer. In addition, evidence of EMT in primary cultures and clinical specimens from prostate cancer patients was shown and evidence to suggest that tumours contribute to their own stromal microenvironment via EMT was also provided. The foundations laid by the completion of this project provide considerable scope for future studies which may reveal valuable insights into the fundamental mechanisms involved in prostate cancer progression.
15
Nightingale, Wendy Denise. "Electrical characteristics of an identified insect motoneurone cell body : a current- and voltage-clamp study." Thesis, University of St Andrews, 1989. http://hdl.handle.net/10023/14077.
Full textAbstract:
1. The electrical characteristics of the cell body of an identified excitatory motoneurone (cell 3) from the cockroach (Periplaneta americana) have been studied under current- and voltage-clamp. 2. Under voltage-clamp depolarising command pulses evoked an outward current which increased with the magnitude of the command step up to approximately +100mV, a component of the current developed more slowly and took longer to reach a maximum. With increasing depolarisation the outward current response fell to a lower level before further increasing. This current response gave rise to a characteristic N-shape I-V relationship. The position of the negative conductance region depends on the time current measurements are taken after the onset of the command pulse. 3. Externally applied cadmium (1mM) or manganese ions (5mM) abolished the slowly developing current responsible for the hump in the I-V relationship. These results indicate that calcium ions are required for the activation of this component of the outward current. Verapamil (50?M) also reduced this current component and appeared to be non-specific in reducing another current component. Furthermore, verapamil caused inactivation of the remaining current which was more marked for long duration (500ms) command pulses. 4. Externally applied TEA+ (at concentrations greater than 25mM) blocked the calcium-dependent current and a calcium-independent component. Under current-clamp TEA+ (50mM) unmasked a broad action potential. 5. Externally applied aminopyridines did not enhance excitability under current-clamp. Under voltage-clamp aminopyridines had significant effect in shifting the voltage dependence of the hump in the I-V relationship toward more negative potentials. 6. When holding at -90mV and stepping to more positive potentials there was no indication of an early, fast, transient component similar to IA. If present at all, IA made only a minor contribution to the total outward currents. 7. A double command pulse regime was used to study tail currents whereby a standard pre-pulse (pulse (I)) was immediately followed by a test pulse (pulse (II)) to various command potentials. Tail current measurements were taken during pulse (II). The tail currents showed strong outward rectification and were severely reduced in saline containing cadmium ions (ImM). 8. The tail-current reversal potential was dependent on the pulse (I) magnitude and duration. Preliminary results indicated that increasing the pulse (I) magnitude caused a negative shift in reversal potential. Increasing the pulse (I) duration from 10ms to 50ms caused a positive shift in the reversal potential equivalent to a two-fold increase in extracellular cation concentration. 9. A five-fold increase (from 3.1 to 15mM) in external potassium ion concentration produced a small and variable shift in reversal potential, which did not conform to that predicted by the Nernst equation. A five-fold decrease (from 235 to 47mM) in external chloride ion concentration had little effect on the tail current reversal potential but did cause a slight reduction in the outward currents. Furthermore, the voltage dependency of the hump in the I-V relationship was shifted toward more negative potentials. 10. Action potentials induced by intracellular citrate injection were only slightly enhanced by a four-fold increase (from 9 to 36mM) in external calcium ion concentration. They were reversibly reduced to a graded spike in saline containing verapamil (10?M) and reversibly abolished by manganese ions (40mM), but were relatively unaffected by sodium-free saline. These observations suggest that calcium ions were the major ion carrying the inward current under these conditions. 11. Carbon dioxide-induced action potentials were reversibly reduced to a graded spike in sodium-free or manganese saline (40mM) whereas tetrodotoxin (50nM) irreversibly abolished action potentials for wash period up to 20mins. These observations suggest that both calcium and sodium ions were responsible for the inward current under these conditions. 12. The regenerative component of the axotomy-induced action- potentials was reversibly reduced in sodium-free saline and only partially reduced with some broadening in calcium-free or manganese saline (40mM). Either treatment alone was insufficient to completely abolish or reduce the action potential to a graded spike. A combination of Na-free saline with manganese ions (40mM) caused a more complete block by reducing the regenerative component to a graded spike. These results suggest that sodium ions, and to a lesser extent, calcium ions were responsible for the inward current under these conditions.
16
Karlsson, Markus. "Oxidative stress-related damage of retinal pigment epithelial cells : possible protective properties of autophagocytosed iron-binding proteins." Doctoral thesis, Linköpings universitet, Avdelningen för neurovetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-111558.
Full textAbstract:
Oxidative stress is a major pathogenic factor in the development of age-related macular degeneration (AMD), which is the most common cause of severe central visual impairment in the elderly population in the western world. It is believed that the degenerative process starts in the retinal pigment epithelium (RPE). The post-mitotic RPE is a single layer of pigmented cells located behind the photoreceptors – rods and cones – of the retina. Daily, the RPE cells phagocytose and recycle the expended tips of the photoreceptor outer segments. This heavy phagocytic burden leads to substantial oxidative stress in the cells, which is further enhanced by intense illumination and a high oxygen tension. A hallmark of early AMD is a progressive build-up of the non-degradable age pigment lipofuscin (LF) in lysosomes of the RPE. LF accumulation hampers phagocytosis and autophagy in the RPE, resulting in increased amounts of cellular debris in and around the cells. This decreases the function and viability of both RPE cells and photoreceptors. Iron is known to accumulate in the retina with increasing age, particularly in AMDaffected eyes, and amplifies oxidative stress by acting as a potent catalyst in the generation of hydroxyl radicals. These highly reactive radicals contribute to LF formation and may, if abundantly present, also directly damage lysosomal membranes. The subsequent leakage of degrading enzymes to the cytosol initiates cell death via apoptosis or necrosis. In this thesis, we have investigated the oxidative stress response of human RPE (ARPE-19) cells compared to murine J774 cells, another type of lysosome-rich cells with a high phagocytic capacity. The ARPE-19 cells were found to be extremely resistant to oxidative stress and tolerated exposure to single doses of H2O2 in concentrations up to 150 times higher than the J774 cells before lysosomal rupture and ensuing cell death occurred. This resistance was increased even further when the cells were protected with a potent iron chelator that prevents redox-active iron to participate in hydroxyl radical generation. Both cell lines were shown to be equally effective in degrading H2O2 and seem to contain comparable amounts of total as well as intralysosomal iron. Therefore, we reasoned that the insensitivity of ARPE-19 cells to H2O2 exposure might be related to a mechanism which keeps their intralysosomal iron bound in a non redox-active form. This theory was supported by our finding of very high basal expression levels of metallothionein (MT), heat shock-protein 70 (HSP70) and ferritin (FT) in ARPE-19 cells compared to J774 cells. All of these proteins have previously been shown to possess potent iron-binding properties. The ARPE-19 cells were also shown to have a higher basal rate of autophagy. SiRNA-mediated attenuation of MT, HSP70 and FT levels in the ARPE-19 cells resulted, to some degree, in an increased sensitivity to H2O2 treatment. Furthermore, a human cell stress array showed several other stress-related proteins to be up-regulated in ARPE-19 cells. Additionally, we evaluated the commonly used, but frequently misinterpreted, H2DCF test for oxidative stress. It was demonstrated that oxidation of H2DCF into fluorescent DCF mainly reflects relocation to the cytosol of lysosomal iron and mitochondrial cytochrome c, rather than being the result of some poorly defined “general” oxidative stress. In conclusion, our results indicate that the extreme resistance to oxidative stress exhibited by the ARPE-19 cells might be related to a high continuous autophagic influx of iron-binding proteins into the lysosomal compartment. Before being degraded, such proteins will temporarily keep intralysosomal iron bound in a non redox-active form, thereby inhibiting hydroxyl radical formation. This may partly explain why RPE cells, in spite of their exposed location and heavy burden of phagocytosis, usually manage to survive and evade significant LF accumulation until late in life.
17
Subisak, Angel Dharshini. "Role of Substrate Stiffness on Migratory Properties and Epithelial to Mesenchymal Transition in Human Lung Cancer Cells." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1356943256.
Full text
18
Chan, Yau-chi, and 鄭有志. "Cellular electrophysiology of cardiac pacemaker channel-implications on novel drug and gene therapies development." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B41290458.
Full text
19
Magalhães, Ana Carolina de. "Investigation of the influence of red and infrared illumination on mechanical properties of cells: Photobiomodulation." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-05012017-145626/.
Full textAbstract:
The photobiomodulation therapy (PBMT) has many demonstrated applications in the health area including anti-inflammatory and wound healing effects. The main objective of this work is to verify if the PBMT causes measurable changes in the mechanical properties of cells, specifically in red blood cells, epithelial cells and fibroblasts. In addition, to contribute to the knowledge of the action mechanisms of the PBMT, this study intends to support applications of the PBMT during invasive procedures, such as the direct photo-treatment of the blood in surgical procedures with cardiopulmonary bypass, regarding security of the cellular integrity. For this analysis, three experimental techniques were used: optical magnetic twisting cytometry (OMTC), defocusing microscopy and confocal laser-scanning microscopy. Human bronchial epithelial cells were evaluated with OMTC. The epithelial cell culture was either photo-treated or not, with red laser (lambda=660 nm), and fixed power and time (power density of 153 mW/cm2, time 300 s). It was not possible to observe significant differences between photo-treated and control epithelial cells, for the hysteresivity (ratio between the cell loss and elastic shear moduli). The defocusing microscopy, similar to a phase contrast microscopy, was used to study human red blood cells from fresh blood. The red blood cells were either photo-treated or not, with red laser (lambda=660 nm), and different powers and times (power densities from 0 to 510 mW/cm2, times from 0 to 180 s). Some morphological and mechanical characteristics of individual red blood cells were evaluated, such as volume, radial profile of cell thickness, lateral and vertical membrane fluctuations, for the photo-treated and control red blood cells. It was not possible to detect differences between the two groups, for any of the parameters analyzed. For both techniques, the absence of detectable differences might be due to several factors, such as the non-action of the PBMT, with the parameters used, in the epithelial cells and red blood cells or to the small sensitivity of each technique. Confocal laser-scanning microscopy was used to evaluate the actin filaments of mouse fibroblasts. The fibroblast cell culture was either photo-treated or not, with red (lambda=625 nm) or infrared (lambda=808 nm) light and fixed power and time (power density from 113 to 158 mW/cm2, time 300 s). The nucleus and cell areas increased slightly when comparing photo-treated and control cells. On the other hand, the total actin, total actin density and the number of filaments decreased. These changes were detected for a short time after treatment, however, after 24 h they are not anymore detectable. The total branch length does not seem to suffer any modifications. In summary, with the data acquired with the three techniques, it was found that the PBMT, in the red range, with the parameters used, could not cause noticeable changes in red blood cells and epithelial cells, in vitro. On the other hand, the PBMT in the red and near-infrared range, with the power and times used, cause changes in actin filaments of fibroblasts, in vitro, in particular the decrease of the total actin density.A terapia por fotobiomodulação tem muitas aplicações na área de Saúde devido a sua ação anti-inflamatória e de reparação tecidual. O objetivo geral desse trabalho é verificar se a terapia por fotobiomodulação provoca mudanças nas propriedades mecânicas de células, em particular em hemácias, células epiteliais e fibroblastos. Além de contribuir com o conhecimento dos mecanismos de ação da terapia por fotobiomodulação, este estudo pretende subsidiar aplicações da terapia por fotobiomodulação durante procedimentos mais invasivos, como a iluminação direta do sangue em procedimentos cirúrgicos com circulação extracorpórea, sob o ponto de vista da segurança quanto à integridade celular. Para essa análise foram utilizadas três técnicas experimentais: citometria óptica magnética de oscilação (OMTC), microscopia de desfocalização e microscopia confocal. Com a técnica de OMTC foram avaliadas células epiteliais brônquicas humanas em cultura, foto-tratadas com laser vermelho (lambda=660 nm), com potência e tempo fixos (densidade de potência de 153 mW/cm2, tempo 300 s). Não foi possível constatar diferenças significativas entre as células epiteliais foto-tratadas e as células controle, para a histerisividade (razão entre os módulos viscoso e elástico das células). Com a técnica de microscopia de desfocalização, semelhante a uma microscopia de contraste de fase, foram estudadas hemácias humanas de sangue recém coletado. As hemácias foram tratadas com laser vermelho (lambda=660 nm), com potências e tempos variados (densidade de potência de 0 a 510 mW/cm2, tempo de 0 a 180 s). Foram avaliadas algumas características morfológicas e mecânicas das hemácias individualmente, como o volume, perfil radial de espessura, flutuações lateral e vertical da membrana, tanto para hemácias foto-tratadas quanto para hemácias controle. Não foi possível detectar diferenças entre as hemácias foto-tratadas e controle para nenhum dos parâmetros avaliados. Para ambas as técnicas, a falta de mudanças observáveis poderia ser devida a diversos fatores, como a não ação da terapia por fotobiomodulação nas células epiteliais e nas hemácias, com os parâmetros aqui empregados, ou à falta de sensibilidade de cada uma das técnicas usadas. A microscopia confocal foi utilizada para avaliar os filamentos de actina de fibroblastos de camundongo em cultura, os quais foram foto-tratados com luz vermelha (lambda=625 nm) ou infravermelha (lambda=808 nm) e potência e tempo fixos (densidade de potência de 113 a 158 mW/cm2, tempo 300 s). Foi possível constatar ligeiro aumento nas áreas nuclear e celular das células foto-tratadas em relação aos fibroblastos controle. Também foi possível verificar a diminuição da quantidade total de actina, densidade de actina e do número de filamentos de actina nos fibroblastos foto-tratados. Essas mudanças são detectadas para tempos curtos após o tratamento, sendo que depois de 24 h elas desaparecem. O tamanho total dos filamentos parece não sofrer alterações. A partir dos dados coletados com as três técnicas, foi possível constatar que a terapia por fotobiomodulação, com os parâmetros utilizados, não consegue provocar mudanças perceptíveis em hemácias e em células epiteliais, in vitro. Porém, causa mudanças nos filamentos de actina de fibroblastos, in vitro, em particular a diminuição da densidade de actina total.
20
Salimi, Elham. "Dielectrophoresis study of electroporation effects on dielectric properties of biological cells." American Institute of Physics, 2016. http://hdl.handle.net/1993/31945.
Full textAbstract:
Electroporation affects the dielectric properties of cells. Dielectric measurement techniques can provide a label-free and non-invasive modality to study this phenomenon. In this thesis we introduce a dielectrophoresis (DEP) based technique to study changes in the cytoplasm conductivity of single Chinese hamster ovary (CHO) cells immediately after electroporation. Using a microfluidic chip, we study changes in the DEP response of single CHO cells a few seconds after electroporation. First, in order to quantify our DEP measurement results and relate them to the cells internal conductivity, we introduce a dielectric model for CHO cells. This is achieved by measuring the DEP response of many individual cells in the β-dispersion frequency region and curve fitting to the measured data. Second, we present quantitative results for changes in the cytoplasm conductivity of single cells subjected to pulsed electric fields with various intensities. We observe that when electroporation is performed in media with lower ionic concentration than cells cytoplasm, their internal conductivity decreases after electroporation depending on the intensity of applied pulses. We also observe that with reversible electroporation there is a limit on the decrease in the cells’ internal conductivity. We hypothesize the reason is the presence of large and relatively immobile negative ions inside the cell which attract mobile positive ions (mainly sodium and potassium) to maintain cell electrical neutrality. We monitor the temporal response of cells after electroporation to measure the time constant of changes due to ion transport and observe this ranges from seconds to tens of seconds depending on the applied pulse intensity. This result can be used to infer information about the density and resealing time of very small pores (not measurable with conventional marker molecules). Lastly, we measure the electroporation of cells in media with different conductivities. Our results show that electroporation in very low conductivity media requires stronger pulses to achieve a similar poration extent as in high conductivity media. The outcome of this thesis can be used to improve our understanding of the dynamics of electroporation as well as its modelling in order to make more accurate predictions or optimize the process for specific applications.February 2017
21
Lo, Kwok-fung Angela, and 勞幗鳳. "Alterations of gene expression and biological properties in nasopharyngeal epithelial cells by the Epstein-barr virus encodedlatent membrane protein 1." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B31243423.
Full text
22
Paye, Julie Melissa Davis. "Effect of the Insulin-like Growth Factor (IGF) Axis on the Transport Properties of Endothelial and Epithelial Cells In Vitro." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/29071.
Full textAbstract:
The overall objective of this research consists of two main parts: (1) provide evidence that autocrine production of IGF-I modulates tight junction permeability and (2) demonstrate the ability of IGFBPs to regulate IGF-I delivery across cell layers. To meet the first objective, parental and IGF-I secreting bovine mammary epithelial cells were tested for cell layer permeability, tight and adherens junction proteins, IGF-IR, and a downstream signaling components of IGF-IR. In comparison with parental cells, IGF-I secreting cells had high levels of IGF-IRs, but low levels of the junction components E-cadherin, b-catenin, and occludin. The differences in parental and IGF-I secreting cells was not due to extracellular stimuli since inclusion of IGF-I, IGFBP-3, or co-culture with SV40-IGF-I cells did not alter the barrier properties of parental cells, suggesting that intracrine signaling may alter cell connectivity. The second objective focused on exogenous rather than endogenous IGF-I and the role of IGFBPs and IGF-IRs in ligand transcytosis. Bovine aortic endothelial cells (BAECs) cultured on surfaces optimized to minimize paracellular transport were utilized to investigate the kinetics involved in the transport of insulin-like growth factor-I from the apical side of confluent monolayers to the basolateral side. Binding competitors were used to determine the role of the cell surface insulin-like growth factor-I receptor (IGF-IR) and cell surface insulin-like growth factor binding proteins (IGFBPs) in this transport process. Although IGFBPs initially retard delivery of IGF-I, using a computation model, this report shows that pulse durations of less than 6 hrs resulted in enhanced delivery of IGF-I in the presence of IGFBPs, above that for delivery in the absence of IGFBPs. In addition, the model was utilized to identify key parameters to target when developing engineered growth factors for the treatment of diseases. It is shown that the sorting factions and internalization rates are reasonable targets for the design of engineered growth factors. Since the sorting fractions are dictated by binding affinities in the acidic environment of the endosomes, it may be beneficial to design and analog of IGF-I that is more resistant to changes in pH, similar to those develop from epidermal growth factor.Ph. D.
23
Krygowski, Thomas Wendell. "A novel simultaneous diffusion technology for low-cost, high-efficiency silicon solar cells." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/22973.
Full text
24
Moritz, Joseph M. (Joseph Michael). "Increased differentiation properties in two- and three-dimensional coculture of hepatocytes and liver epithelial cells by a novel quantitative functional liver assay." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/39352.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2007.Includes bibliographical references (leaves 100-121).
Hepatic stem cells in adult rats are activated by chemical injury to the liver, causing hepatic progenitor cells to proliferate, integrate into the hepatic plates, and differentiate into hepatocytes. In an attempt to model this process in vitro, we established and quantitatively assayed the differentiation properties of a strain of rat liver epithelial cells (LEC), lig8, grown in coculture with mature liver cells in a three dimensional, perfused microreactor optimized for hepatocyte culture. Lig8 was derived by suppression of the asymmetric growth kinetics that may be indicative of stem cells, and Lig8 progeny can be induced to exhibit several hepatocyte-specific differentiation properties in vitro; however, Lig8 full hepatocyte functional differentiation in culture has not yet been achieved. We hypothesized that more extensive differentiation properties may be observed in vitro if the Lig8 cells are cultured in an engineered analog of the 3D tissue environment that influences progenitor cell differentiation in vivo. We also assayed the differentiation properties of the hepatocytes in coculture. Previous studies have shown an increase in the differentiation of hepatocytes in 2D hepatocyte-LEC cocultures; we wished to determine if the benefit of coculture also occurs in the 3D microreactor.
(cont.) We therefore compared the differentiation properties of both cell types in 3D microreactor cocultures to three more traditional culture formats: 2D rigid collagen monolayer, 2D collagen gel sandwich, and 3D spheroids. To assess the functional differentiation state of both cell types in these cocultures, we implemented a cell-localizable quantitative assay for endocytotic uptake of fluorescent ligands of the hepatocyte asialoglycoprotein receptor (ASGPR). T'o additionally assay overall differentiation of the cultures, we examined the level of expression compared to in vivo of three hepatocyte-specific transcripts: ASGPR, and two highly abundant drug-metabolic enzymes CYP3A1 and CYP2E1. Of all the culture modes tested, three-dimensional microreactor coculture was shown to be the most highly differentiated by the fluorescent ligand uptake assay for ASGPR and CYP3A1, with near in vivo expression of CYP3A1. However, coculture only improved the expression of the transcripts for ASGPR and CYP2E1 in 2D rigid collagen monolayer cocultures. lig8 exhibited no uptake of the ASGPR-ligand in monoculture, but in all cocultures tested, rare cells were found positive, with a higher percentage of lig8 taking up the ligand in 31) than in 2D (although cell fusion was not ruled out).
(cont.) We conclude that this three-dimensional coculture system may be more physiological in vitro model for the study of LEC-mature cell interactions and liver response to carcinogens.
by Joseph M. Moritz.
Ph.D.
25
Harrop, Ceri. "Biochemical, biophysical and network properties of mucins and mucus gels produced by human bronchial epithelial cells in response to disease-relevant mediators." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.532253.
Full text
26
Thomsen, Elizabeth Alice. "Characterisation of materials for organic photovoltaics." Thesis, St Andrews, 2008. http://hdl.handle.net/10023/462.
Full text
27
Lagerquist, Hägglund Christine. "Affinity-, partition- and permeability properties of the human red blood cell membrane and biomembrane models, with emphasis on the GLUT1 glucose transporter /." Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3525.
Full text
28
Ivey, Jill Winters. "Investigating the Applications of Electroporation Therapy for Targeted Treatment of Glioblastoma Multiforme Based on Malignant Properties of Cells." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/78806.
Full textAbstract:
Glioblastoma multiforme (GBM) is the most common and lethal primary brain cancer with an average survival time of 15 months. GBM is considered incurable with even the most aggressive multimodal therapies and is characterized by near universal recurrence. Irreversible electroporation (IRE) is a cellular ablation method currently being investigated as a therapy for a variety of cancers. Application of IRE involves insertion of electrodes into tissue to deliver pulsed electric fields (PEFs), which destabilize the cell membrane past the point of recovery, thereby inducing cell death. While this treatment modality has numerous advantages, the lack of selectivity for malignant cells limits its application in the brain where damage to healthy tissue is especially deleterious. In this dissertation we hypothesize that a form of IRE therapy, high-frequency IRE (H-FIRE), may be able to act as a selective targeted therapy for GBM due to its ability to create an electric field inside a cell to interact with altered inner organelles. Through a comprehensive investigation involving experimental testing combined with numerical modeling, we have attained results in strong support of this hypothesis. Using tissue engineered hydrogels as our platform for therapy testing, we demonstrate selective ablation of GBM cells. We develop mathematical models that predict the majority of the electric field produced by H-FIRE pulses reach the inside of the cell. We demonstrate that the increased nuclear to cytoplasm ratio (NCR) of malignant GBM cells compared to healthy brain—evidenced in vivo and in in vitro tissue mimics—is correlated with greater ablation volumes and thus lower electric field thresholds for cell death when treated with H-FIRE. We enhance the selectivity achieved with H-FIRE using a molecularly targeted drug that induces an increase in NCR. We tune the treatment pulse parameters to increase selective malignant cell killing. Finally, we demonstrate the ability of H-FIRE to ablate therapy-resistant GBM cells which are a focus of many next-generation GBM therapies. We believe the evidence presented in this dissertation represents the beginning stages in the development of H-FIRE as a selective therapy to be used for treatment of human brain cancer.Ph. D.
29
Lewis, Andrew J. "Characterisation of organic materials for photovoltaic devices." Thesis, St Andrews, 2006. http://hdl.handle.net/10023/144.
Full text
30
Qiu, C. X. (Xing Xing). "Characteristics of ZnOCuInSe2 heterojunctions and CuInSe2 homojunctions." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65991.
Full text
31
Bergmann, Annabel Elisabeth [Verfasser], Christoph [Akademischer Betreuer] Knorr, Detlef [Gutachter] Rath, and Wolfgang [Gutachter] Holtz. "Sperm binding properties to uterine epithelial cells in vitro employing a primary porcine endometrium culture system / Annabel Elisabeth Bergmann. Betreuer: Christoph Knorr. Gutachter: Detlef Rath ; Wolfgang Holtz." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2016. http://d-nb.info/1102535877/34.
Full text
32
Ross, Iona Catherine. "Investigation and development of cuprous delafossites for solid oxide fuel cell cathodes." Thesis, University of St Andrews, 2017. http://hdl.handle.net/10023/16726.
Full textAbstract:
The research into materials for use as cathode materials for solid oxide fuel cells (SOFC) is ongoing, with many different avenues being investigated. Copper based delafossites were studied for cathode side applications in SOFCs, as a novel and comparatively cheap material. The aim was to identify suitable materials with appropriate electrical conductivity, thermal, chemical and mechanical stability in air. Furthermore, understanding the behaviour of the delafossites during the thermal oxidation to spinel and copper oxide would be beneficial to further development of the materials. The structure and properties of the copper based delafossites CuFeO₂, CuAlO₂ and CuCrO₂ were studied, alongside several doped compositions for each parent composition. The electronic conductivity of the CuFeO₂ family was improved by doping fluorine into the structure, with 1 atomic % doping producing ~3.8 S cm⁻¹ at 800 °C. However, as reported in literature the structure is vulnerable to oxidation at higher temperatures. In contrast, CuAlO₂ was stable over the SOFC temperature range, and therefore had appropriate thermal expansion coefficients (TEC) of ~11 x 10⁻⁶ K⁻¹, but relatively low electronic conductivity. CuCrO₂ compositions had good overall TECs, but aliovalent doping of Mg²⁺ improved the conductivity to ~17.1 S cm⁻¹ at 800°C for 2.5 atomic % doped CuCrO₂. Neutron diffraction was utilised to study members of the solid solution CuFe₁₋ₓCrₓO₂ (x = 0, 0.25 and 0.5) during in-situ oxidation at high temperature. Points of positive scattering density were identified within the CuFeO₂ structure, which were attributed to the location of the intercalated oxygen ions before the transformation proceeded. Additionally, the cation distribution between the tetrahedral and octahedral sites within the developing spinel were characterised for x = 0, and partially for the x = 0.25 and 0.5 compositions using complimentary XRD patterns. Finally, magnesium doped CuCrO₂ delafossites were used in several different preliminary symmetrical cells for study using electrochemical impedance spectroscopy (EIS). Pure delafossite inks gave relatively large area specific resistance (ASR) values, 1.29 - 2.69 Ω cm² at 800 °C. It was attempted to improve upon these values through infiltration of CeO₂ and through change in microstructure using composite type inks, without much success. Inks using CuCr₀.₈Fe₀.₂O₂ were also tested as both a single phase electrode and as a composite type electrode. The pure delafossite electrode still had a large ASR value, (~33.4 Ω cm² at 800 °C) while composite electrodes obtained much more respectable ASR values ~0.75 Ω cm² at 800 °C.
33
Stefan, Elena. "Development of spinel-based electrode supports for solid oxide fuel cells." Thesis, University of St Andrews, 2013. http://hdl.handle.net/10023/3605.
Full textAbstract:
The high temperature oxidation of ferritic stainless steel interconnects results in chromium poisoning of the solid oxide fuel cell (SOFC) electrodes, which is a limiting factor for their utilisation as SOFC interconnects. Chromium-rich spinel materials were studied as electrode supports that would be situated at the interface between interconnect and electrode, in order to reduce the effect of chromium poisoning of the electrodes. The main goal of this thesis was to find chromium-rich spinel materials with good electrical conductivity (σ ≥ 0.1 S∙cm⁻¹) in air and reducing atmosphere, chemically and mechanically stable in SOFC testing conditions. The structure and properties of newly formulated chromium-rich spinels, such as Mn₁₊ₓCr₂₋ₓO₄ (x = 0, 0.5), MnFeₓCr₂₋ₓO₄ (x = 0.1, 1), MgMnCrO₄, MnLiₓCr₂₋ₓO₄ (x = 0.1) and MgMₓCr₂₋ₓO₄, (M = Li, Mg, Ti, Fe, Cu, Ga) were studied aiming at their application as electrode support material for solid oxide fuel cells. Cation distributions were determined by Rietveld refinement from X-ray diffraction (XRD), within the limits of XRD precision and correlated with electrical properties determined experimentally. The chemical stability in reducing conditions was studied and the reduction effects upon materials were evaluated by XRD phase analysis and microstructure analysis. It was found that MnMₓCr₂₋ₓO₄ materials have a limited stability to reduction, only MnCr₂O₄ proved to have good stability when reduced, with negative influence for its p-type semiconductor conductivity. Even though MnFeCrO₄ had limited stability to reduction, in reducing conditions the conductivity changed from p-type to n-type semiconductor. A similar behaviour to reduction was observed for MgFeCrO₄. Also the mechanical and chemical compatibility of some spinels with YSZ was studied in terms of thermal expansion coefficient (TEC/K⁻¹), sintering step and possible chemical reactions. Lithium titanate spinels, starting with LiCrTiO₄, were investigated in terms of structure, properties and spinel - ramsdellite phase transition temperature also with the purpose of new material development. For these materials positive results were obtained in conductivity and chemical stability in reducing conditions. The performance of MnFeCrO₄ and MgFeCrO₄ as electrode support materials was investigated when used alone or impregnated with (La₀.₇₅Sr₀.₂₅)₀.₉₇Cr₀.₅Mn₀.₅O₃, La₀.₈Sr₀.₂FeO₃, Ce₀.₉Gd₀.₁O₂, CeO₂ or Pd. Composite anodes for SOFC were prepared by aqueous infiltration of nitrate salts into porous MnFeCrO₄ and MgFeCrO₄ scaffolds and studied by electrochemical impedance spectroscopy (EIS) in symmetrical cell configuration. The performance of the composite anodes was evaluated in humidified 5%H₂/Ar in order to understand their stability and performance at 850 °C or lower temperature with respect to the porous substrates. It was found that all the impregnated phases adhere very well to the spinel and considerably enhance performance and stability to a level required for SOFC applications. An interesting next step in this work would be to apply such spinel materials on steel interconnects, integrate them into testing SOFC devices and evaluate their effect upon chromium poisoning of the electrodes.
34
Kosinski, Marcin Robert. "Nanomaterials for solid oxide fuel cell electrolytes and reforming catalysts." Thesis, University of St Andrews, 2011. http://hdl.handle.net/10023/2588.
Full textAbstract:
In this work, a broad range of analytical methods was applied to the study of the following three materials systems: yttria-stabilised zirconia (YSZ), samarium-doped ceria (SDC) and SDC-supported metal catalysts. YSZ and SDC were studied in the light of their application as solid electrolytes in Solid Oxide Fuel Cells. The SDC-supported metal catalysts were evaluated for application in the reforming of methanol. The conductive properties of YSZ pellets derived from powders of different Y contents and particle size ranges were investigated using Impedance Spectroscopy (IS). Comparative studies of the crystallography (by X-ray Powder Diffraction (XRD)), morphology (by Scanning and Transmission Electron Microscopy (SEM, TEM)), chemical composition (by Energy Dispersive X-ray Spectroscopy (EDX) and Inductively Coupled Plasma Mass Spectroscopy (ICP-MS)) and sintering behaviour (dilatometry) were employed in the overall assessment of the conductivity results collected. Detailed studies of three SDC compositions were performed on nanopowders prepared by a low temperature method developed in the Baker group. Modifications led to a simple and reliable method for producing high quality materials with crystallites of ~10 nm diameter. The products were confirmed by XRD and TEM to be single-phase materials. Thermogravimetric analysis, dilatometry, specific surface area determination, elemental analysis and IS were carried out on these SDC powders. The relationships between particle size, chemical composition, sintering conditions and conductivity were studied in detail allowing optimum sintering conditions to be identified and ionic migration and defect association enthalpies to be calculated. Finally, the interesting results obtained for the SDC nanopowders were a driving force for the preparation of SDC-supported metal catalysts. These were prepared by three different methods and characterised in terms of crystallographic phase, specific surface area and bulk and surface chemical composition. Isothermal catalytic tests showed that all catalysts had some activity for the reforming of methanol and that some compositions showed both very high conversions and high selectivities to hydrogen. These catalysts are of interest for further study and possibly for commercial application.
35
Lambert, Darcy Erin. "Nanostructured Extremely Thin Absorber (ETA) Hybrid Solar Cell Fabrication, Optimization, and Characterization." PDXScholar, 2011. https://pdxscholar.library.pdx.edu/open_access_etds/637.
Full textAbstract:
Traditional sources of electrical energy are finite and can produce significant pollution. Solar cells produce clean energy from incident sunlight, and will be an important part of our energy future. A new nanostructured extremely thin absorber solar cell with 0.98% power conversion efficiency and maximum external quantum efficiency of 61% at 650 nm has been fabricated and characterized. This solar cell is composed of a fluorine-doped tin oxide base layer, n-type aluminum doped zinc oxide nanowires, a cadmium selenide absorber layer, poly(3-hexylthiophene) as a p-type layer, and thermally evaporated gold as a back contact. Zinc oxide nanowire electrodeposition has been investigated for different electrical environments, and the role of a zinc oxide thin film layer has been established. Cadmium selenide nanoparticles have been produced and optimized in-house and compared to commercially produced nanoparticles. Argon plasma cleaning has been investigated as a method to improve electronic behavior at cadmium selenide interfaces. The thermal anneal process for cadmium selenide nanoparticles has been studied, and a laser anneal process has been investigated. It has been found that the most efficient solar cells in this study are produced with a zinc oxide thin film, zinc oxide nanowires grown under constant -1V bias between the substrate material and the anode, cadmium selenide nanoparticles purchased commercially and annealed for 24 hours in the presence of cadmium chloride, and high molecular weight poly(3-hexylthiophene) spin-coated in a nitrogen environment.
36
Zhang, Yaoqing. "Exploring novel functionalities in oxide ion conductors with excess oxygen." Thesis, University of St Andrews, 2011. http://hdl.handle.net/10023/2576.
Full textAbstract:
Functional materials, particularly metal oxides, have been the focus of much attention in solid state chemistry for many years and impact every aspect of modern life. The approach adopted in this thesis to access desirable functionality for enhanced fundamental understanding is via modifying existing materials by deploying reducing synthetic procedures. This work spans several groups of inorganic crystalline materials, but is unified by the development of new properties within host compounds of particular relevance to solid oxide fuel cell technology, which allow interstitial oxide ion conduction at elevated temperatures. The Ca₁₂Al₁₄O₃₂e₂ electride was successfully synthesized by replacing the mobile extra-framework oxygen ions with electrons acting as anions. The high concentration of electrons in the C12A7 electride gives rise to an exceptionally high electronic conductivity of up to 245 S cm⁻¹ at room temperature. Making use of the high density of electrons in Ca₁₂Al₁₄O₃₂e₂ electride, the strong N-N bonds in N₂ was found to be broken when heating Ca₁₂Al₁₄O₃₂e₂ in a N₂ atmosphere. A reaction between silicate apatites and the titanium metal yielded another completely new electride material La₉.₀Sr₁.₀(SiO₄)₆O₂.₄e₀.₂ which was found to be a semiconductor. To fully understand the role of oxygen interstitials in silicate apatites, high-resolution transmission electron microscopy (HRTEM) was employed as the main technique in probing how the oxygen nonstoichiometry is accommodated at the atomic level. Atomic-resolution imaging of interstitial oxygen in La₉.₀Sr₁.₀(SiO₄)₆O₂.₅ proved to be a success in this thesis. Substitution of oxygen in 2a and interstitial sites with fluoride ions in La[subscript(8+y)]Sr[subscript(2- z)](SiO₄)₆O[subscript(2+(3y-2z)/2)] (0
37
O'Beirne, Greg A. "Mathematical modelling and electrophysiological monitoring of the regulation of cochlear amplification." University of Western Australia. School of Biomedical and Chemical Sciences, 2005. http://theses.library.uwa.edu.au/adt-WU2006.0115.
Full textAbstract:
[Truncated abstract] The cochlea presumably possesses a number of regulatory mechanisms to maintain cochlear sensitivity in the face of disturbances to its function. Evidence for such mechanisms can be found in the time-course of the recovery of CAP thresholds during experimental manipulations, and in observations of slow oscillations in cochlear micromechanics following exposure to low-frequency tones (the “bounce phenomenon”) and other perturbations. To increase our understanding of these oscillatory processes within the cochlea, and OHCs in particular, investigations into cochlear regulation were carried out using a combination of mathematical modelling of the ionic and mechanical interactions likely to exist within the OHCs, and electrophysiological experiments conducted in guinea pigs. The electrophysiological experiments consisted of electrocochleographic recordings and, in some cases, measurement of otoacoustic emissions, during a variety of experimental perturbations, including the application of force to the cochlear wall, exposure to very-low-frequency tones, injection of direct current into scala tympani, and intracochlear perfusions of artificial perilymph containing altered concentrations of potassium, sodium, and sucrose. To obtain a panoramic view of cochlear regulation under these conditions, software was written to enable the interleaved and near-simultaneous measurement of multiple indicators of cochlear function, including the compound action potential (CAP) threshold, amplitude and waveshape at multiple frequencies, the OHC transfer curves derived from low-frequency cochlear microphonic (CM) waveforms, distortion-product otoacoustic emissions (DPOAEs), the spectrum of the round-window neural noise (SNN), and the endocochlear potential (EP). ... The mathematical model we have developed provided a physiologically-plausible and internally-consistent explanation for the time-courses of the cochlear changes observed during a number of different perturbations. We show that much of the oscillatory behaviour within the cochlea is consistent with underlying oscillations in cytosolic calcium concentration. We conclude that a number of the discrepancies between the simulation results and the experimental data can be resolved if the cytosolic calcium functions as two distinct pools: one which controls basolateral permeability and one which controls slow motility. This two-calcium-pool model is discussed.
38
Chu, Yen-Chang, and 褚晏彰. "Stiffness of Substrate Affects Corneal Epithelial Cells Migration in Electric Fields." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/57122345459068739762.
Full textAbstract:
碩士國立臺灣大學
醫學工程學研究所
98
Cell migration involves in many fields, such as wound healing, tumor metastasis, organ development, immune response and morphological change. Cell migration is affected by many factors, such as electric field, rigidity of the substrate, and chemical gradient. Amniotic membrane (AM) is commonly used to treat persistent corneal injuries. In an attempt to understand mechanisms behind this enhancement of the healing process, bovine corneal epithelial cells were used to examine cell migration on the various substrates. External electric field was applied to simulate the intrinsic current generated at corneal wound edges. Higher migration speed and directional velocity were found on the basement membrane side of AM, cornea section and on lower collagen concentrations. Collagen type I and type IV both benefit cell migration rather than fibronectin and laminin. At the same time, most cells assume a spindle shape and form more lamellipodia in these conditions that may correspond with the migration result. The studies on calcium alginate with varied stiffness prove that cell responses to differential mechanical forces between cell and substrate, and cells prefer to migrate on maximal mechanical input. When enhancing wound healing with any substrate, the physical properties of surface is always something to be considered. Result from this study may benefit our understanding of the cornea wound healing mechanism and provide further treatment options.
39
Ye, Jia Kai, and 葉家凱. "Study of electric and magnetic properties on magnetic tunnel junction cells." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/70138415554873060461.
Full textAbstract:
碩士國立彰化師範大學
物理學系
94
A new breed of magnetic random access memory (MRAM) based on a magnetic tunnel junction (MTJ) storage element has emerged as a promising candidate for nonvolatile memory application. The objective of this thesis is mainly to investigate the electric and magnetic properties of magnetic tunnel junction cells. Firstly, we get to know the magnetic property changes of multilayer under different temperatures. Though top-down processes, including electron beam lithography, photolithography, ECR ion-milling, reactive ion etching, sputtering and thermal evaporation, micron-patterned magnetic tunnel junction devices have been fabricated. We also investigated the influences on electric and magnetic properties of magnetic tunnel junction cells with different anneal temperature. Through AFM&SEM observe the surface texture of MTJ devices and try to resolve the re-deposition what is caused by etching process. By measuring the MR loop characteristic and magnetoresistance, factors which cause device damages in the fabrication process can be found. In the fabrication process, shorting is caused by re-deposition. Then the tunneling effect disappeared. So we etching the cells by tilting an angle to clean the re-deposition. When devices were fabricated, the contact between top electrode and cells become more inseparably by annealing without applied magnetic field. And the TMR ratio was also increasing. We have a long-ranged nice view when MRAM enter to the market.
40
Kuang-TengHung and 洪廣騰. "Studies of Synthesis and Opto-Electric Properties of Organic Solar Cells." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/17328066600720076568.
Full text
41
"Human umbilical cord lining epithelial cells with stem cell-like properties: an adjunct to skin regeneration." 2013. http://library.cuhk.edu.hk/record=b5549751.
Full textAbstract:
皮膚是人體最大的器官，具有多種功能，其中最重要的功能之一就是作為身體內部和外界環境之間的的保護屏障。完整地修復這一保護屏障是創傷癒合和組織再生領域的一個重要內容。本論文探討了人類臍帶被覆上皮細胞 (cord lining epithelial cells, CLECs)作為一種幹細胞來源，可用于表皮重建的潛能.本論文的第二章對CLECs的體外分離和增殖進行了詳細地描述。這一類細胞具有較長的染色體端粒，較高的增殖潛能和傳代能力。同時，它們表達上皮幹細胞和多能性幹細胞的標誌性表面抗原。它們還具有多種分化潛能，包括成脂、成骨和成軟骨。然而當皮下異種移植後，它們並不會形成畸胎瘤。
本論文的第三章對CLECs的免疫特性進行了評估。結果顯示CLECs不但具有低免疫原性，還具有免疫調節功能。它們表達典型性的一型主要組織相容性複合體(MHC class I)，即人白細胞ABC抗原(HLA-ABC)，但不表達典型性的二型主要組織相容性複合體(MHC class II)，即人白細胞DR抗原(HLA-DR)。它們同時還表達非典型性的MHC class I, 包括人白細胞G抗原和人白細胞E 抗原(HLA-G和HLA-E), 但不表達共激分子(CD40, CD80和CD86)。此外，體外檢測還發現它們表達適度的促炎/抗炎細胞因子和大量的生長因子.
本論文的第四章對CLECs在表皮重建應用中的潛能進行了考察。結果顯示無論在體外器官培養還是異種移植動物模型中，CLECs都能形成分層的上皮結構，與用表皮細胞構建的分層上皮結構相類似。而且在CLECs構建的皮膚替代物中證實了有表皮分化標誌性抗原的表達。
結論：本論文證明了CLECs具有幹細胞樣特性但無致瘤性，具有低免疫原性和表皮分化的可塑性。研究結果支持CLECs在創傷癒合和皮膚再生領域的臨床應用可行性.
The skin is the largest organ in the body and has multiple functions. One of the most important functions is to serve as a protective barrier between the internal and external environments of the body. Restoration of the integrity of this protective barrier is an essential aspect of wound healing and tissue regeneration. In this thesis, the potential of human umbilical cord lining epithelial cells (CLECs) as a source of stem cells with appropriate differentiation capacity for epidermal reconstitution has been explored.
The isolation and propagation of CLECs from human umbilical cord lining epithelium were described in Chapter II. The cells presented a long telomere length and had high proliferative potential and passaging capability. They were also shown to display both epithelial and pluripotent stem cell markers. They were capable of multipotent differentiation, including adipogenesis, osteogenesis and chondrogenesis. However, they didn’t form teratoma after subcutaneous xenotransplantation until 12 weeks.
The immune properties of CLECs in vitro were assessed in Chapter III. The cells were shown to have low immunogenicity but high immunosuppressive function. They expressed classical major histocompatibility complex (MHC) class I antigens (HLA-ABC), but not MHC class II antigen (HLA-DR). They also expressed non-classical MHC class I antigens (HLA-G and HLA-E), but lacked the expression of the co-stimulatory molecules (CD40, CD80 and CD86). Moreover, they expressed moderate pro/anti-inflammatory cytokines and multiple growth factors both in cell supernatants and cell lysates.
The potential of CLECs for epidermal reconstitution was investigated in Chapter IV. In both organotypic culture and xenotransplantation model, CLECs were capable of generating a stratified epithelial structure, which is similar to that constructed by using keratinocytes. Furthermore, the expression of epidermal differentiation markers was verified in CLEC-constructed skin substitutes.
In conclusion, the stem cell-like properties of CLECs have been demonstrated in the present study. In addition to the lack of tumorigenicity, CLECs also have low immunogenicity and significant plasticity in epidermal differentiation. The findings support the potential clinical application of CLECs in wound healing and skin regeneration.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Cai, Yijun.
"October 2012."
Thesis (Ph.D.)--Chinese University of Hong Kong, 2013.
Includes bibliographical references (leaves 114-129).
Abstract also in Chinese.
Abstrac --- p.i
Table of Contents --- p.v
Abbreviations --- p.vii
List of Figures --- p.viii
List of Tables --- p.x
Chapter Chapter I --- Introduction --- p.1
Skin --- p.3
Wound healing --- p.6
Wound regeneration and repair --- p.6
Recent history of wound treatment --- p.9
Skin substitutes --- p.11
Stem cells for wound treatment --- p.14
Stem cells overview --- p.15
Adult stem cells --- p.16
Fetal stem cells --- p.18
Amniotic membrane derived stem cells --- p.19
Umbilical cord stem cells --- p.22
Hypothesis and Specific aims --- p.24
Chapter Chapter II --- The Isolation and Characterization of the Stem Cell-like Properties of Human Umbilical Cord Lining Epithelial Cells --- p.28
Introduction --- p.28
Materials and methods --- p.30
Results --- p.47
Discussion --- p.62
Conclusion --- p.67
Chapter Chapter III --- The assessment of the Immune Properties of Human Umbilical Cord Lining Epithelial Cells --- p.69
Introduction --- p.69
Materials and methods --- p.72
Results --- p.75
Discussion --- p.83
Conclusion --- p.88
Chapter Chapter IV --- The Investigation of the Potential of Human Umbilical Cord Lining Epithelial Cells for the Epidermal Reconstitution --- p.89
Introduction --- p.89
Materials and methods --- p.91
Results --- p.94
Discussion --- p.101
Conclusion --- p.104
Chapter Chapter V --- Summary and Future Plan --- p.105
Summary --- p.105
Future plan --- p.108
Acknowledgements --- p.113
References --- p.114
Appendix --- p.130
42
Pedrigi, Ryan M. "Biomechanics of the Lens Capsule from Native to After Cataract Surgery." 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2008-08-40.
Full textAbstract:
The primary function of the lens capsule of the eye unfolds during the process of
accommodation; wherein, tension imposed onto its equator is released, allowing the
elastic capsule to mold the underlying lens nucleus and cortex into a more quasispherical
morphology to change focus from distant to near objects. Given its highly
mechanical nature, it is prudent to study the native lens capsule from the perspective of
biomechanics for such applications as understanding the mechanism of accommodation.
Further, cataract surgery introduces alterations to the geometry of the lens capsule that
lead to changes in resident cell behavior from quiescent to contractile and synthetic.
Though resultant changes in capsule histology are well documented little has been done
to quantify the corresponding altered mechanics, which is important for elucidating
related post-surgical pathologies and improving prosthetic lens design.
In this study we present the first data on the in situ multiaxial mechanical
behavior of the native and hyperglycemic anterior lens capsule in both the porcine and
human models. From these data, native stresses in the lens capsule are calculated using a
finite element analysis, and alterations in the corresponding strain field are calculated after the introduction of a continuous circular capsulorhexis, which is imposed during
cataract surgery. Finally, we quantify both the altered mechanical behavior and
contractile loads imposed onto the lens capsule after cataract surgery.
43
Bergmann, Annabel Elisabeth. "Sperm binding properties to uterine epithelial cells in vitro employing a primary porcine endometrium culture system." Doctoral thesis, 2015. http://hdl.handle.net/11858/00-1735-0000-0028-875C-6.
Full textAbstract:
In der Schweinezucht werden konventionell 1-3 x109 Spermien als Frischsamen in einem Volumen von 80-100 ml intrauterin versamt. Im Vergleich zur Rinderbesamung, bei der mitunter 2 x106 Spermien zu Trächtigkeiten führen, sind Ejakulate von Ebern ineffizient. Die einzige Möglichkeit geringe Spermienzahlen erfolgreich zu versamen besteht darin die Spermienablage nahe dem Ort der Befruchtung im distalen Isthmus des Eileiters durchzuführen. Die spezies-spezifische Bindung von Säugerspermien an diverse Oberflächenzellen des weiblichen Traktes, die der Kapazitation und Hyperaktivierung vorangehen, setzt die Erkennung von Kohlenhydraten durch lektin-ähnliche Proteine der Spermienplasmamembran voraus Daher wurde vermutet, dass eine mutmaßliche Bindung porziner Spermien an das Uterusepithel ebenfalls Protein-Kohlenhydrat vermittelt ist. Ziel der vorliegenden Arbeit war die Etablierung eines Zellkulturmodells aus primären Uterusepithelien der Sau (Sus scrofa), um mögliche Gründe für die hohen Spermienzahlen in der Schweinbesamung zu untersuchen und zu identifizieren.
Porzine uterine Epithelien wurden mittels Verdau mit Trypsin/EDTA (1x) gewonnen. Zellen wurden auf Collagen (rat tail, type I) auf Kollagen-beschichteten Deckgläschen aus Glas in 6-Well Kulturschalen ausgesät. Die Anheftung der Zellen an die Kollagen-Matrix wurde nach 12-36 Stunden beobachtet. Erste Kolonien bildeten sich nach fünf bis sieben Tagen und Konfluenz wurde nach zehn bis fünfzehn Tagen erreicht. Der Nachweis der Zellart erfolgte mittels Immunfluoreszenz-Färbung mit einem Epithelien-spezifischen Antikörper (anti-Cytokeratin-19). Eberspermien banden innerhalb weniger Minuten an die UEC und verblieben währenddessen motil. Eine verringerte Spermienbindung wurde sowohl auf Aortenendothelien als auch fötalen Fibroblasten des Schweins beobachtet. Dies weist auf das Vorhandensein spermienspezifischer Liganden auf den UEC hin. Spermien, wie auch UEC wiesen hohe Bindungsintensitäten für Lektine die an Glc-NAc, (WGA) sowie Gal-NAc (sWGA) binden. Die Sättigung von Sialinsäure führte zu einer stark verminderten Spermienbindung auf den UEC. Bei einer Sättigung von Glc-NAC wurde kein Unterschied beobachtet. Dies kennzeichnet Sialinsäure als den vermutlich wichtigsten Kohlenhydratrest in der Spermien-Epithelzellbindung.
44
Lu, Shao-Ming, and 呂紹銘. "The study on electro-optical properties of cholesteric liquid crystal cells driven by in-plane electric fields." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/5h635b.
Full textAbstract:
碩士國立臺北科技大學
光電工程系研究所
105
In this study, the electro-optical properties of a bistable cholesteric liquid crystal composed of chiral dopant and nematic liquid crystal with negative dielectric anisotropy is investigated. The cholesteric liquid crystal has periodic helical structure that results in Bragg reflection. We drive the cholesteric liquid crystal using in-plane finger electrodes. The cell can operated from the planar state to lying-helix configuration by in-plane electric field switching at low voltage. At large voltage, the cell does not have helical structure. Different width and spacing of in-plane finger electrodes will affect the structure of cholesteric liquid crystal. The electrohydrodynamical effect of liquid crystal at high voltage before racemic state is observed. The various states at the different voltage of cholesteric liquid crystal are observed and transmittance and phase retardation are measured.
45
Jamil, M. Mahadi Abdul, M. A. M. Zaltum, N. A. A. Rahman, R. Ambar, Morgan C. T. Denyer, F. Javed, Farshid Sefat, M. Mozafari, and Mansour Youseffi. "Investigation of Pulse electric field effect on HeLa cells alignment properties on extracellular matrix protein patterned surface." 2018. http://hdl.handle.net/10454/16996.
Full textAbstract:
YesCell behavior in terms of adhesion, orientation and guidance, on extracellular matrix (ECM) molecules including collagen, fibronectin and laminin can be examined using micro contact printing (MCP). These cell adhesion proteins can direct cellular adhesion, migration, differentiation and network formation in-vitro. This study investigates the effect of microcontact printed ECM protein, namely fibronectin, on alignment and morphology of HeLa cells cultured in-vitro. Fibronectin was stamped on plain glass cover slips to create patterns of 25μm, 50μm and 100μm width. However, HeLa cells seeded on 50μm induced the best alignment on fibronectin pattern (7.66° ±1.55SD). As a consequence of this, 50μm wide fibronectin pattern was used to see how fibronectin induced cell guidance of HeLa cells was influenced by 100μs and single pulse electric fields (PEF) of 1kV/cm. The results indicates that cells aligned more under pulse electric field exposure (2.33° ±1.52SD) on fibronectin pattern substrate. Thus, PEF usage on biological cells would appear to enhance cell surface attachment and cell guidance. Understanding this further may have applications in enhancing tissue graft generation and potentially wound repair.
Ministry of Higher Education Malaysia and UTHM Tier 1 Research Grant (U865)
46
van, Heerden Johannes Lodewikus. "Material properties of ZnO thin films prepared by spray pyrolysis." Thesis, 2012. http://hdl.handle.net/10210/6033.
Full textAbstract:
Ph.D.In the search to improve the conversion efficiency of solar cells such as α-Si and CuInSe2 cells, attention have recently been focused on the use of transparent conducting oxides (TCO's) as window layers and top electrodes in these cells. Materials such as indium tin oxide (ITO) and fluorine-doped tin oxide (FTO) thin films were used due to their excellent electro-optical properties, but it was found that they were unstable when subjected to a hydrogen plasma (during the a-Si deposition) and that the materials reduced to their metallic forms, degrading their electrical and optical properties. Zinc oxide (ZnO), however, possess electrical and optical properties equal to ITO and FTO, but is stable in the presence of a hydrogen plasma. In this study a system for the deposition of ZnO thin films by spray pyrolysis was developed and the films successfully deposited. The films were also doped with A1C1 3 in an attempt to further improve the films' conductivities. The films were then characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), electrical measurements (Hall and four-point probe measurements) and optical analyses of the films. The films were compared with films deposited by atomic layer epitaxy (ALE) and DC sputtering. It was found that the films were crystalline with a predominantly (002) preferred orientation. The addition of Al as dopant, however, resulted in the film structure deteriorating. The SEM micrographs obtained of the films indicated films with a close-packed structure, existing of small grains and the film surface having a textured appearance. It was further found that the deposition parameters of the films influenced both the structures of the films and the morphologies and the micrographs indicated that the addition of Al as dopant resulted in the film formation being inhibited and even resulting in no proper film being deposited. It was found that the as-deposited ZnO films were resistive and that the films had to be subjected to a post-deposition annealing to decrease the film resistivity. The annealing conditions were investigated and it was found that annealing the films in hydrogen at their deposition temperature for an hour resulted in the largest decrease in the films' resistivities, typically two orders of magnitude. Studies of the substrate temperature indicated that the films had to be deposited at between 350 and 420°C and that a reduction in the substrate temperature resulted in the film resistivity increasing. Contrary to literature, it was found that the addition of Al as dopant had no beneficial influence on the electrical properties of the films and that dopant concentrations exceeding 1.0 at.% resulted in the film resistivity increasing. The films were characterized optically by analysing the transmission spectra obtained of the films, using the envelope technique. It was found that the films had transmissions exceeding 95% and that the refractive indices and optical gaps centred around 1.99 and 3.3 eV respectively. Both properties were affected by the deposition parameters. The ZnO films deposited by spray pyrolysis compared excellently with the films prepared by ALE and DC sputtering in all aspects. It is hence clear that ZnO films, with characteristics suitable for solar cell application, can be deposited by the simple and inexpensive technique of spray pyrolysis.
47
Lin, Yu-Ting, and 林鈺庭. "Study on Electro-optical Properties of Cholesteric Liquid Crystal Cells Driven by In-plane and Vertical Electric Fields." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/dpad3p.
Full textAbstract:
碩士國立臺北科技大學
光電工程系研究所
102
In this thesis, the electro-optical properties of a cholesteric liquid crystal cell, composed of chiral dopant and nematic liquid crystal with negative dielectric anisotropy, are investigated. The chiral dopant gives rise to a helical structure of the nematic LC. The cell has Bragg reflection as a result of the helical pitch of the liquid crystals molecules. We drive the chiral nematic liquid crystal cell using three-terminal electrodes. Bragg reflection and threshold voltage of the cell are significantly related with the chiral dopant concentration. Wavelength shifts are observed by in-plane electric field drving and temperature change. Bistable switching between the standing-helix and lying-helix states is achieved by in-plane and vertical electrical field. Compared to conventional cholesteric cells switching between the focal conic and homeotropic states, the proposed cell has fast bistable switching. We realize a fast-swtiching memory mode in a cholesteric cell utilizing three-terminal electrodes.
48
"Phosphorous diffusion and hydrogen passivation of polycrystalline silicon for photovoltaic cells." Thesis, 2012. http://hdl.handle.net/10210/5415.
Full textAbstract:
M.Sc.Techniques for the fabrication of polycrystalline silicon solar cells have advanced in recent years with efficiencies exceeding 17%. The major advantage of polycrystalline silicon is its low cost relative to single-crystalline silicon. The disadvantage is the significantly smaller minoritycarrier bulk diffusion length and inhomogeneous nature of the material. These two drawbacks are due to the presence of grain boundaries as well as high concentrations of dislocations and other physical and chemical defects. In this study the experimental conditions were determined to fabricate solar cells on polycrystalline silicon substrates. The controlled diffusion of phosphorous into silicon and subsequent evaluation of the doped layers (by spreading resistance profiling and chemical staining) were important aspects of this study. From these results the diffusion parameters (i.e. temperature and reaction times) could be optimized in order to improve the solar cell output parameters. Additional material improvement (increase in surface- and bulk minority carrier lifetimes) was demonstrated by the hydrogen passivation of electrically active defects in polycrystalline silicon. However. measurements on hydrogenated silicon samples also indicated that excess passivation can result in surface damage and subsequent reduction in the minority carrier lifetimes. Preliminary solar cells were fabricated on polycrystalline silicon with efficiencies ranging between 0.5 and 6% (total area = 16 cm2).
49
Greer, Michael R. "A 6% efficient MIS particulate silicon solar cell." Thesis, 1998. http://hdl.handle.net/1957/34037.
Full text
50
Van, der Merwe Johan Petrus. "Elektriese eienskappe van aluminium kontakte op polikristallyne silikon." Thesis, 2012. http://hdl.handle.net/10210/6737.
Full textAbstract:
M.Sc.The efficiency of commercial polycrystalline silicon solar cells is currently 12% and 15% in the case of single crystalline cells. It is possible to lose about half of the open circuit voltage due to inferior contacts on the cell. It is thus clear that inferior contacts can seriously impede the relative low efficiency and care should be taken to make good ohmic contacts. Experiments were done to evaluate the influence of several factors on the quality and stability of the contacts. 1 C2•cm p-type polycrystalline silicon and 3 52.cm n-type single crystalline silicon were primarily used for these experiments. Results of molybdenum contacts on n-type silicon are also presented and the problems with silver epoxy contacts are discussed. It was found that aluminium contacts on p-type polycrystaline silicon improve with temperature and time, while those on single crystaline n-type degrade with temperature and time. These changes are already present at room temperature and are attributed to solid state diffusion of the aluminium into the silicon. This results in a p + layer. In the case of contacts on p-type, the behaviour is that of a Schottky diode. After the solid state diffusion, it becomes possible for the charges to quantum mechanically tunnel through the p+ layer. This results in an improvement of the contact. The contacts on n-type however, are ohmic just after evaporation. Similar to the p-material, the p+ layer causes a p+-n-junction with the depletion layer primarily in the n-type material. This causes a degradation in the contact quality. It is possible to achieve good quality contacts on polycrystaline p-type material, by annealing the contacts above 500°C for one minute. These contacts however, are non-ideal. SEM photographs show that the silicon surface is crated by pits due to solid state diffusion. It is only at these pits that conduction through the Schottkybarrier is possible. Since the area of the pits constitutes only a portion of the total area, only a portion of the surface will partake in conduction. Contact resistance is always present. For pm sized contacts on integrated circuits, the spesific resistance is of the order of 10 -6 Q.cm2. Contacts on solar cells, however, are of millimetre dimensions and the spesific resistance can be four orders of magnitude larger. The conduction through the surface can be modelled as conduction through a surface that is constituted of a mixture of minute ohmic and diode surfaces.