• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 400
  • 79
  • 38
  • 32
  • 21
  • 19
  • 12
  • 7
  • 6
  • 5
  • 5
  • 4
  • 4
  • 3
  • 3
  • Tagged with
  • 752
  • 87
  • 80
  • 78
  • 77
  • 72
  • 65
  • 58
  • 50
  • 47
  • 46
  • 45
  • 40
  • 39
  • 39
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
181

Protein Deposition and Bacterial Adhesion to Conventional and Silicone Hydrogel Contact Lens Materials

Nagapatnam Subbaraman, Lakshman January 2009 (has links)
Introduction Contact lenses suffer from the same problems of deposition that other biomaterials exhibit, being rapidly coated with a variety of proteins, lipids and mucins. The first event observed at the interface between a contact lens and tear fluid is protein adsorption. Protein deposits on contact lenses are associated with diminished visual acuity, dryness and discomfort and lid-related inflammatory changes. The aim of this thesis was to determine the quantity and the conformational state of lysozyme deposited on contact lens materials over various time periods and also to determine the clinical relevance of protein deposits on contact lenses. The specific aims of each chapter of this thesis were as follows: • Chapter 4: To determine the total lysozyme deposition on conventional and silicone hydrogel contact lens materials as a function of time by artificially doping lenses with 125I-labeled lysozyme. • Chapter 5: To determine the conformational state of lysozyme deposited on conventional and silicone hydrogel contact lens materials as a function of time using an in vitro model. • Chapter 6: To quantify the total protein, total lysozyme and the conformational state of lysozyme deposited on a novel, lathe-cut silicone hydrogel contact lens material after three-months of wear. • Chapter 7: To determine the relationship between protein deposition and clinical signs & symptoms after one-day wear of etafilcon lenses in a group of symptomatic and asymptomatic lens wearers. • Chapter 8: To determine the influence of individual tear proteins (lysozyme, lactoferrin and albumin) on the adhesion of Gram positive and Gram negative bacteria to conventional and silicone hydrogel contact lens materials. Methods • Chapter 4: Conventional hydrogel FDA group I (polymacon), group II (alphafilcon A and omafilcon A), group IV (etafilcon A and vifilcon A), polymethyl methacrylate and silicone hydrogel lens materials (lotrafilcon A, lotrafilcon B, balafilcon A, galyfilcon A and senofilcon A) were incubated in a lysozyme solution containing 125I-labeled lysozyme for time periods ranging from 1 hour to 28 days. After each time period, lysozyme deposited on contact lens materials was determined using a Gamma Counter. • Chapter 5: Conventional hydrogel FDA groups I, II, IV and silicone hydrogel lens materials were incubated in lysozyme solution for time periods ranging from 1 hour to 28 days. After each time period, the lysozyme deposited on the lenses was extracted and the sample extracts were assessed for lysozyme activity and total lysozyme. • Chapter 6: 24 subjects completed a prospective, bilateral, daily-wear, nine month clinical evaluation in which the subjects were fitted with a novel, custom-made, lathe-cut silicone hydrogel lens material (sifilcon A). After 3 months of wear, the lenses were collected and total protein, total lysozyme and active lysozyme deposition were assessed. • Chapter 7: 30 adapted soft contact lens wearers (16 symptomatic and 14 asymptomatic) were fitted with etafilcon lenses. Objective measures and subjective symptoms were assessed at baseline and after hours 2, 4, 6 and 8. After 2, 4, 6 and 8 hour time points, lenses were collected and total protein, total lysozyme and active lysozyme deposition were assessed. • Chapter 8: Three silicone hydrogel (balafilcon A, lotrafilcon B & senofilcon A) and one conventional hydrogel (etafilcon A) lens materials were coated with lysozyme, lactoferrin and albumin. Uncoated and protein-coated contact lens samples were incubated in a bacterial suspension of Staphylococcus aureus 31 and two strains of Pseudomonas aeruginosa (6294 & 6206). The total counts and the viable counts of the adhered bacteria were assayed. Results • Chapter 4: Lysozyme accumulated rapidly on conventional hydrogel FDA group IV lenses, reached a maximum on day 7 and then plateaued with no further increase. PMMA showed a deposition pattern similar to that seen on lotrafilcon A and lotrafilcon B silicone hydrogel lenses. After 28 days, conventional hydrogel FDA group IV lenses deposited the most lysozyme. • Chapter 5: After 28 days, lysozyme deposited on group IV lenses exhibited the greatest activity. Lysozyme deposited on polymacon, lotrafilcon A and lotrafilcon B exhibited the lowest activity. Lysozyme deposited on omafilcon, galyfilcon, senofilcon, and balafilcon exhibited intermediate activity. • Chapter 6: The total protein recovered from the custom-made lenses was 5.3±2.3 µg/lens and the total lysozyme was 2.4±1.2 µg/lens. The denatured lysozyme found on the lenses was 1.9±1.0 µg/lens and the percentage of lysozyme denatured was 80±10%. • Chapter 7: Correlations between subjective symptoms and protein deposition showed poor correlations for total protein/ lysozyme and any subjective factor, and only weak correlations between dryness and active lysozyme. However, stronger correlations were found between active lysozyme and subjective comfort. • Chapter 8: Different tear proteins had varying effects on the adhesion of bacteria to contact lens materials. Lysozyme deposits on contact lenses increased the adhesion of Gram positive Staphyloccocus aureus 31 strain, while albumin deposits increased the adhesion of both the Gram positive Staphyloccocus aureus and Gram negative Pseudomonas aeruginosa 6206 & 6294 strains. Lactoferrin deposits increased the total counts of both the Gram positive and Gram negative strains, while they reduce the viable counts of the Gram negative strains. Conclusions • Chapter 4: Lysozyme deposition is driven by both the bulk chemistry and also the surface properties of conventional and silicone hydrogel contact lens materials. The surface modification processes or surface-active monomers on silicone hydrogel lens materials also play a significant role in lysozyme deposition. • Chapter 5: The reduction in the activity of lysozyme deposited on contact lens materials is time dependent and the rate of reduction varies between lens materials. This variation in activity recovered from lenses could be due to the differences in surface/ bulk material properties or the location of lysozyme on these lenses. • Chapter 6: Even after three-months of wear, the quantity of protein and the conformational state of lysozyme deposited on these novel lens materials was very similar to that found on similar surface-coated silicone hydrogel lenses after two to four weeks of wear. These results indicate that extended use of the sifilcon A material is not deleterious in terms of the quantity and quality of protein deposited on the lens. • Chapter 7: In addition to investigating the total protein deposited on contact lenses, it is of significant clinical relevance to determine the conformational state of the deposited protein. • Chapter 8: Uncoated silicone hydrogel lens materials bind more Gram positive and Gram negative bacteria than uncoated conventional hydrogel lens materials. Lysozyme deposited on contact lens materials does not possess antibacterial activity against all bacterial strains tested, while lactoferrin possess an antibacterial effect against certain Gram negative strains tested in this study. This thesis has provided hitherto unavailable information on contact lens deposition and its influence on subjective symptoms and bacterial binding. These results suggest that protein deposition has a significant potential to cause problems. Therefore, it is important that practitioners advise their patients regarding the importance of lens disinfection and cleaning and appropriate lens replacement schedules. These results will also be useful for the contact lens industry and the general field of biomaterials research.
182

Paralinguistic and Nonverbal Behaviour in Social Interactions: A Lens Model Perspective

Ethier, Nicole Ann January 2010 (has links)
It is widely accepted in our society that people’s paralinguistic (i.e., non-semantic characteristics of the voice) and nonverbal (i.e., posture, gestures, and facial expressions) behaviours play an important role in conveying information about their personality traits. Two particularly relevant traits include one’s preferred levels of dominance and affiliation, which are the two major axes of the interpersonal circumplex. The current study investigates how dominance and affiliation are conveyed through paralinguistic and nonverbal behaviour using a lens model framework. Two major issues addressed by this framework include: 1) How do observers make inferences about people’s dominance and affiliation using paralinguistic and nonverbal behaviours and 2) How do people’s trait dominance and affiliation relate to these behavioural cues? To examine these two questions, we collected data from 114 opposite-sex dyads who worked together to complete a relatively unstructured collaborative task. The videotaped interactions were coded for specific paralinguistic (e.g., pitch, volume, resonance) and nonverbal (e.g., hand gestures, trunk posture, facial expressions) behaviours, in addition to coding more global displays of dominance and affiliation. Participants also completed several measures of trait dominance and affiliation, which tapped both their relatively conscious (i.e., explicit) and their relatively unconscious (i.e., implicit) levels of these traits. Our findings suggest that observers used mainly paralinguistic behaviour to infer dominance and mainly nonverbal behaviour to infer affiliation. In comparison to observers’ perceptions, there were fewer significant relations between individuals’ self-reported trait dominance and affiliation and the nonverbal and paralinguistic behaviours they expressed during the interaction, suggesting that people may have limited conscious awareness of how these behaviours convey information about their trait dominance and affiliation. In line with this idea, several behaviours showed relations to implicit measures of trait dominance and affiliation. We also conducted factor analyses of the measured paralinguistic and nonverbal behaviours, to examine whether or not these behaviours might co-occur as subsets or factors. We found that paralinguistic and nonverbal behaviours can be captured by overarching factors which relate meaningfully to measures of dominance and affiliation. Finally, we demonstrated that dyad members’ paralinguistic and nonverbal behaviours become interdependent as they interact with one another.
183

RAPD markers for ascochyta resistance, phylogenetic studies and cultivar identification In lentil

Andrahennadi, Chandra Pemajayantha 01 January 1997 (has links)
Random amplified polymorphic DNA (RAPD) markers were used in three genetic studies in lentil (<i>Lens culinaris</i> Medikus). The first study involved development of RAPD markers linked with genes for resistance to ascochyta blight, caused by <i>Ascochyta fabae</i> f. sp. lentis Gossen et al. Seventy F<sub>2</sub>-derived F<sub>3</sub> (F<sub>2:3</sub>) lines were field screened for ascochyta blight reaction in each of two hybrid populations, Indianhead x Eston and ILL 5588 x Eston, that were segregating for resistance to ascochyta blight. Resistance to ascochyta blight in ILL 5588 lentil was conferred by a single dominant gene (<i>Ral<sub>1</sub></i>), whereas resistance in Indianhead lentil was conferred by a single recessive gene (<i>ral<sub>2</sub></i>). An efficient DNA extraction procedure and a PCR protocol that yielded RAPD markers with high resolution were developed for lentil. Bulked segregant analysis was used to produce four bulks of DNA from resistant vs. susceptible F<sub>2</sub> plants in each of these two populations which were then screened for RAPD markers using 400 random oligonucleotide primers. One RAPD marker, UBC227<sub>1290</sub>, was linked to the recessive gene, <i>ral<sub>2</sub></i>, in Indianhead lentil in repulsion phase with a map distance of 14.1 ± 4.5 cM. No RAPD marker was linked with the <i>Ral<sub>1</sub></i> gene in ILL 5588 lentil. In the second study, RAPD markers were used to study phylogeny of the genus Lens. DNA, extracted from 23 accessions of all five taxa of the genus Lens (culinaris, orientalis, nigricans, odemensis and ervoides), was screened for RAPD polymorphisms, using 11 random oligonucleotide primers. Two accessions of the differentiated cytotype of L. nigricans were also included. One hundred and forty eight polymorphic RAPD markers were resolved. A dendrogram for these RAPD markers, using the unweighted pair group method, clearly separated all accessions into their supposedly related taxa. Lens orientalis was the undisputed progenitor of the cultivated lentil, <i>Lens culinaris</i>. A low level of RAPD polymorphism was observed in <i>Lens culinaris</i> and L. ervoides. The differentiated cytotype of L. nigricans was well separated from the normal cytotype of L. nigricans and was closely associated with the L. odemensis accessions, indicating its close genetic similarity to L. odemensis. Principal component analysis (PCA) also indicated a similar relationship among these accessions, but resulted in a better resolution of the groupings. In the third study, the genetic polymorphism of seven Canadian lentil cultivars were studied using RAPD markers. Four lentil cultivars, CDC Gold, CDC Matador, Eston and Indianhead each had a unique, cultivar-specific RAPD marker, allowing their identification.
184

none

Lin, Hsiang-jyi 30 June 2010 (has links)
none
185

Studies of the electro-optical properties of liquid-crystal Fresnel lens based on cholesteric blue phase

Wang, Yu-yin 02 August 2010 (has links)
In this study, a liquid crystal Fresnel lens based on the cholesteric blue phase liquid crystals is proposed. Blue phases are liquid-crystalline phases that appear in a very small temperature range between a cholesteric phase and an isotropic phase. There are three types of blue phases; BP¢¹,BP¢º and BP¢». The BP¢¹ and BP¢º are characterized by a spatially periodic director field with lattice constants comparable to the wavelength of visible light. Because of the structural symmetry, blue phases are optically isotropic. In this study, the electro-optical properties of the BP¢º under different applied voltages are investigated. The results reveal that the Bragg reflection of the BPII has a red shift by increasing the applied voltage and a phase transition from BPII to cholesteric phase occurs at the high voltage regime (>100V). Based on the results, an electrically controlled blue phase Fresnel lens with polarization independence and high diffraction efficiency is demonstrated.
186

Bidirectional Transceiver Modules on the Silicon Bench using Ultra-thin Thin-film Filter and Optical Fibers

Yang, Chia-chin 13 June 2005 (has links)
The primary target of this paper is to fabricate bidirectional transceiver modules based on single mode fiber (SMF) and ultra-thin thin-film filter (TFF). Two major components, namely, SMF and ultra-thin TFF are hybrid integrated on the silicon bench using V-groove and U-groove techniques. A 1310 nm wavelength light was launched into the input SMF of the module. After passing through the filter, the light was received by the output SMF of the module. On the other hand, a 1550 nm wavelength light input to the SMF is reflected by the filter and collected by the output multimode fiber (MMF). Transceiver modules using two different fiber structures were fabricated. The first kind of the module uses standard SMF for 1310 nm light transmission. The insertion loss of the module for the 1310 nm wavelength light was 5.66 dB. In the second kind of the module lens fibers were used to replace the standard SMF. The insertion loss for the 1310 nm wavelength light was reduced to 0.98 dB. A reduction of 4.6 dB was achieved. For both modules, the insertion loss for the 1550 nm wavelength light reflected from the filter was around 0.5 dB.
187

Integral Equation Analysis of a Multi-Layered Dielectric Sphere with a Metallic Cap

Tsai, Ang-hsun 11 July 2005 (has links)
The problems of the scattering off the perfect conductor sphere and the dielectric sphere have the exact solutions. But there are no exact solutions for the scattering off a multi-layered dielectric sphere with a metallic cap like the Lunberg lens reflectors which is used as a strong omni-directional reflector found in many microwave applications. Haruo Sakurai applied the modal expansion technique and point-matching method (PMM) to study the scattering of the Lunberg lens reflectors. The problem is eventually formulated as 2MN by 2MN simultaneous matrix equation with M regions each having 2N unknowns due to two set of coupled polarization vectors. Strictly speaking, the formulae of the mode matching method for the problem of the scattering of the dielectric sphere are not exact. Furthermore, the size of the simultaneous matrix equation is also unnecessarily too larger. In this thesis, we employ an integral equation formulation in the Frequency-domain together with the modified impedance transformation technique for the spherically layers to study the scattering of the Lunberg lens reflectors. We show that the formulae of the integral equation are exact and using an equivalent matrix equation, that the entire problem can be reduced to a N by N matrix equation where N is the number of terms of the expansion of the unknown field in the opening. To verify our formulation we compute the total field of the plane wave incident upon the multi-layered micro lenses and compared the results with those from the geometric optics. We get good agreement for the regions that both theories apply. Small discrepancy is also observed and is consistent with the theoretical prediction.
188

Fabrication of Micro-ball Lenses Array and its Optical Performance Analysis

Hsieh, Chi-Chang 28 July 2005 (has links)
Along with the rising and flourishing development of the modern technology and human knowledge, the demands for optical-electric products and communication systems are getting more and more. By combining the semi-conductor technology process with micro optical elements, a complete micro optical system can be integrated. The functions of a micro optical system include beam-splitting, beam-light offsetting, focusing, and switching, etc. Letting micro optical elements be integrated on a substrate, the fix and alignment problems, which are caused by the relative displacements between the elements, can be improved. Also, the production rate can be increased and cost can be reduced if the products are made by micro mold and array fabricated process. Thus, the technology of the Micro Optical Electro Mechanical System is widely applied to manufacture the products of optical-electric and communication, such as the backlight module of a LCD, projector, and optical fiber communication system, etc. The main purpose of this study is to design and fabricate a microball-lens array, and to apply it to couple optical fibers. The proposed product is a 3D micro-ball-lens array with vertical and non-vertical focus directions and better coupling efficiency. A v-groove is fabricated by using semi-conductor technology in order to fix the micro-ball-lens array and optical fiber such that an optical fiber switch coupling system can be obtained. The packaging of the optical fiber switch coupling system is formed by UV-cure and a microcap which is fabricated by MEMS. It can provide the protection to the system. Also, the completed system can achieve the demands of the industry fields such as precise localization, cost reduction and so on.
189

Genetic Transformation Of Lentil ( Lens Culinaris M. Cv.sultan.1) With A Transcription Factor Regulator (mbf1c) And Analysis Of Transgenic Plants

Kamci, Hamdi 01 September 2011 (has links) (PDF)
iv ABSTRACT GENETIC TRANSFORMATION OF LENTIL ( Lens culinaris M. cv.Sultan.1) WITH A TRANSCRIPTION FACTOR REGULATOR (MBF1c) AND ANALYSIS OF TRANSGENIC PLANTS KAM&Ccedil / I, Hamdi Ph.D., Biotechnology, Institute of Natural ad Applied Sciences Supervisor Prof. Dr. Meral Y&Uuml / CEL Co-Supervisor: Dr. Ufuk &Ccedil / elikkol AK&Ccedil / AY September 2011, 252 pages In this study, Agrobacterium mediated genetic transformation of lentil Sultan 1 cultivar with MBF1c and evaluation of transgenic plants was aimed. The study was initially based on optimized protocol with Agrobacterium tumefaciens KYRT1 strain and pTJK136 binary plasmid. Based on this protocol and transient marker gene expression in embryo apex, 15% stable transformation efficiency was aimed. However limited knowledge about pTJK136 and problem with curing KYRT1 leaded us to use Agrobacterium tumefaciens C58C1 strain and also to engineer an alternative binary plasmid / pPZP101. Hence, scope of this study became construction of a plant binary transformation vector and lentil transformation optimization with C58C1 strain.First plant transformation vector designed in this study was pPZP101ManA-MBF1c. Transformations with C58C1::pPZP101ManA-MBF1c were carried out with a reformulated co-cultivation media. Cotyledonary nodes were isolated from three days old lentil seedlings germinated with phytormone (BAP/TDZ) induction. Isolated nodes were either injured and pre-incubated in co-cultivation media or pre- incubated and then injured prior to transformation. Regeneration and necrosis behaviors of the transformed explants leaded us to the conclusion that explant preparation is the critical step of transformation. And data suggest that explants isolated from 2mg/l BAP, pre-incubated two days in co-cultivation media, injured and transformed performed significantly better scores for necrosis shoot regeneration and callus formation parameters. Transformed explants that survived in subsequent sub-cultures in mannose selection raised shoots. These shoots were grafted and regenerated into plantlets. The putative transgenic plantlets were screened for transgene with PCR. Initial amplification signals fainted and lost as grafts grew. In order to make a diagnosis of this fainting behavior the second plant transformation vector pPZP101ManA- GUSint-MBF1c was constructed and transient GUS expression analysis were made.
190

Genetic Transformation Of Lentil (lens Culinaris M. Cv.sultan.1) With A Transcription Factor Regulator (mbf1c) And Analysis Of Transgenic Plants

Kamci, Hamdi 01 October 2011 (has links) (PDF)
ABSTRACT GENETIC TRANSFORMATION OF LENTIL ( Lens culinaris M. cv.Sultan.1) WITH A TRANSCRIPTION FACTOR REGULATOR (MBF1c) AND ANALYSIS OF TRANSGENIC PLANTS KAM&Ccedil / I, Hamdi Ph.D., Biotechnology, Institute of Natural ad Applied Sciences Supervisor Prof. Dr. Meral Y&Uuml / CEL Co-Supervisor : Dr. Ufuk &Ccedil / elikkol AK&Ccedil / AY September 2011, 252 pages In this study, Agrobacterium mediated genetic transformation of lentil Sultan 1 cultivar with MBF1c and evaluation of transgenic plants was aimed. The study was initially based on optimized protocol with Agrobacterium tumefaciens KYRT1 strain and pTJK136 binary plasmid. Based on this protocol and transient marker gene expression in embryo apex, 15% stable transformation efficiency was aimed. However limited knowledge about pTJK136 and problem with curing KYRT1 leaded us to use Agrobacterium tumefaciens C58C1 strain and also to engineer an alternative binary plasmid / pPZP101. Hence, scope of this study became construction of a plant binary transformation vector and lentil transformation optimization with C58C1 strain. First plant transformation vector designed in this study was pPZP101ManA-MBF1c. Transformations with C58C1::pPZP101ManA-MBF1c were carried out with a reformulated co-cultivation media. Cotyledonary nodes were isolated from three days old lentil seedlings germinated with phytormone (BAP/TDZ) induction. Isolated nodes were either injured and pre-incubated in co-cultivation media or pre-incubated and then injured prior to transformation. Regeneration and necrosis behaviors of the transformed explants leaded us to the conclusion that explant preparation is the critical step of transformation. And data suggest that explants isolated from 2mg/l BAP, pre-incubated two days in co-cultivation media, injured and transformed performed significantly better scores for necrosis shoot regeneration and callus formation parameters. Transformed explants that survived in subsequent sub-cultures in mannose selection raised shoots. These shoots were grafted and regenerated into plantlets. The putative transgenic plantlets were screened for transgene with PCR. Initial amplification signals fainted and lost as grafts grew. In order to make a diagnosis of this fainting behavior the second plant transformation vector pPZP101ManA-GUSint-MBF1c was constructed and transient GUS expression analysis were made.

Page generated in 0.0273 seconds