by Ng Chiu-king. / Chinese title: / Bibliography: leaves 68-69 / Thesis (M.Phil.)--Chinese University of Hong Kong, 1983

Plants rely on light to supply photosynthetic energy and to provide information of the surrounding environment. Phytochromes are photoreceptors that sense external light quality and quantity, which in turn guide the strategy of plant growth. A large body of research has focused on Arabidopsis thaliana seedlings, where phytochrome control of responses such as hypocotyl elongation, hook opening and cotyledon greening, has been intensively explored. Mathematical models have also helped elucidate the molecular mechanism of phytochrome signalling. A smaller proportion of studies have investigated the role of phytochrome in controlling plant plasticity in adult plants. This work has shown that phytochrome depletion enhances leaf petiole elongation and slows growth, but there is a lack of information on how these marked changes alter metabolism. In this thesis, I use phytochrome multiple mutants of to explore how phytochromes interact with metabolism to affect plant growth. My analysis revealed that phytochrome loss results in dramatically reduced biomass production, especially in high order phyABDE mutant that lacks four out of five phytochromes. This is caused, at least partly, by impaired photosynthesis in phytochrome mutants, including reduced chlorophyll level and less CO2 uptake. Furthermore, cell wall synthesis and protein levels, major dry biomass constituents, are also repressed in phytochrome-depleted plants. Interestingly, these mutants accumulate more daytime sucrose and starch than wild type does, possibly due to their retarded growth in light. Further metabolic profiling reveals that these phytochrome mutants over-accumulate sugars, organic acids and amino acids. The sizable increase in raffinose and proline suggests a possible link to stress tolerance. Indeed, ABA and salt responses are significantly reduced in phytochrome mutants at both seedling and adult stages. These mutants are also more resistant to prolonged darkness, with less chlorophyll degradation in dark and higher survival rates. Collectively, this thesis shows that phytochromes have a novel role in plant resource management, controlling the allocation of resources for growth, switching the metabolism between growth and stress-coping states based on the availability of light from the environment. It brings new interest into phytochrome research in Arabidopsis, suggesting possible application of such knowledge to crop studies in the future.

Thesis. 1979. M.Arch--Massachusetts Institute of Technology. Dept. of Architecture. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ROTCH. / Bibliography: p. 71-73. / M.Arch

by Chan Lai Yin, Simon. / "December 1998." / Thesis (Ph.D.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

In the past decades, polymeric light-emitting diode (PLED) have been a focus of research interest to scientists all over the world due to its potential application in flat panel displays. In previous studies, tremendous progresses in material developments, device engineering and theoretical modeling for PLEDs have been achieved. However, there are still a number of crucial problems to be solved in order for PLEDs to be widely employed in commercial flat panel displays. In this thesis, we present studies of PLEDs that used a high work-function metal aluminum as the cathode. The device exhibits a highly enhanced efficiency by modifying the cathode using certain non-ionic surfactant polymers. Based on this finding, we further demonstrated top-emitting PLEDs with environmentally stable cathodes. In another development, we show that a three-coloremitting device with a bilayer emitting polymer structure can be achieved by a dry photo-patterning process. Each of the red, green and blue emission in the device has a comparable emitting efficiency to the traditional standard red, green or blue device with single color emission. These results are believed to be important and beneficial for obtaining low-cost, large-scale and long life-time flat panel displays based on PLEDs. / by Deng Xianyu. / "September 2006." / Adviser: King Young Wong. / Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1871. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 92-101). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

No description available.

No description available.

The ability to withstand environmental temperature variation is essential for plant survival. Formative studies in Arabidopsis have revealed that light signalling pathways has a potentially unique role in shielding plant growth and development from seasonal and daily fluctuations in temperature. In this thesis we further investigate the integration of the light signalling networks and temperature signalling on the molecular level in Arabidopsis. First, we identified the transcript of the bHLH transcription factor LONG HYPOCOTYL IN FAR-RED 1 (HFR1) to be highly dependent on the ambient temperature and under strong control of the red light photoreceptor PHYTOCHROME B (phyB). We found that the long hypocotyl phenotype of the hfr1 mutant was exaggerated in warm conditions, specifically in blue light, downstream of cryptochrome 1. We further show that HFR1 acts in the warm by suppressing the function of PHYTOCHROME INTERACTING FACTOR 4 and 5 (PIF4, PIF5). PIF4 appears to act as a master regulator of several temperature responses and is directly regulated by the phytochromes. Thus, we define a molecular network where red light and blue light signals together with temperature merge on the regulation of PIF4. In the second part of this thesis, we investigate the relationship between temperature and the fluence rate of light on the inhibition of hypocotyl elongation in Arabidopsis. We find that the response to increasing fluence rates of light is highly dependent on the ambient temperature and that PIF4 and PIF5 acting downstream of the major red light photoreceptor, phyB, are essential for this response. In addition, we provide evidence that in cool conditions, PIF activity is under strong suppression by the gibberellin and HY5 pathways specifically at high fluence rates of red light. The collected work of this thesis highlights the importance of the PIF proteins as integrators of temperature and light signals and furthermore, demonstrates that the response to temperature is highly dependent on both the quality and quantity of light.

No description available.

Organic light emitting diodes (OLEDs) are an emerging display technology with the advantages of being efficient, bright, portable and flexible. In this work, a number of novel compounds have been developed for incorporation into OLEDs as emitting dopants. A series of ligands containing dipyrido[3,2-a:2�,3�-c]phenazine substituted at the 11-position with ethyl ester, bromo-, nitrile and 5-phenyl-1,3,4-oxadiazole moieties have been synthesised. Each of the ligands were coordinated to Re(I), Cu(I), Ru(II) and Ir(III) metal centres. Ligands and complexes were characterised by �H NMR and IR spectroscopy, mass spectrometry and microanalysis. Single crystal X-ray analyses were performed on fac-chlorotricarbonyl(dipyrido[3,2-a:2�,3�-c]phenazine-11-carboxylic ethyl ester)rhenium (triclinic, P-1, a = 6.403(5) Å, b = 10.388(5) Å, c = 16.976(5) Å, α = 84.087(5)�, β = 84.161(5)�, γ = 79.369(5)�, Z = 2, R1 = 0.0536, wR2 = 0.0978), fac-chlorotricarbonyl(11-bromodipyrido[3,2-a:2�,3�-c]phenazine)rhenium.CH₃OH (monoclinic, C2/c, a = 19.506(5) Å, b = 18.043(5) Å, c = 13.320(5) Å, α = γ = 90�, β = 114.936(5)�, Z = 4, R1 = 0.0345, wR2 = 0.0827), fac-chlorotricarbonyl(11-cyanodipyrido[3,2-a:2�,3�-c]phenazine)rhenium (triclinic, P-1, a = 6.509(5) Å, b = 12.403(5) Å, c = 13.907(5) Å, α = 96.88(5)�, β = 92.41(5)�, γ = 92.13(5)�, Z = 2, R1 = 0.0329, wR2 = 0.0701), bis-2,2�-bipyridyl(2-(11-dipyrido[3,2-a:2�,3�-c]phenazine)-5-phenyl-1,3,4-oxadiazole)ruthenium triflate.2CH₃CN (triclinic, P-1, a = 10.601(5) Å, b = 12.420(5) Å, c = 20.066(5) Å, α = 92.846(5)�, β = 96.493(5)�, γ = 103.720(5)�, Z = 2, R1 = 0.0650, wR2 = 0.1458) and bis-(2-phenylpyridine-C�,N�)(dipyrido[3,2-a:2�,3�-c]phenazine)iridium(III) hexafluorophosphate.(CH₃)₂CO (triclinic, P-1, a = 13.505(5) Å, b = 16.193(5) Å, c = 19.788(5) Å, α = 92.857(5)�, β = 98.710(5)�, γ = 93.432(5)�, Z = 2, R1 = 0.0494, wR2 = 0.1097). The ground and excited state properties of the ligands and complexes were investigated by a range of techniques, including electrochemistry, absorption and emission spectroscopy, spectroelectrochemistry and excited state lifetime studies. Complexes of dppz-based ligands typically show MOs which are segregated over either the bpy or phz region of the dppz backbone. The properties of the Ru(II) and Ir(III) complexes of the ligand series investigated in this work were consistent with this model, and the LUMOs of these complexes were assigned as the b₁(phz) phz-localised MO. The Re(I) and Cu(I) complexes of the ligand series appeared to show MOs which were delocalised over the entire dppz ligand. A modular complex containing an electron transport group, hole transport group and emitting centre was synthesised. The complex fac-tricarbonyl(trans-(E)-1-((2,2�:5�,2��-terthiophen)-3�-yl)-2-(4�-pyridyl)-ethane)(2-(11-dipyrido[3,2-a:2�,3�-c]phenazine)-5-phenyl-1,3,4-oxadiazole)rhenium(I) hexafluorophosphate was oxidised and reduced readily, encouraging efficient transport of both holes and electrons. However, this resulted in the complex having a small band gap and hence a low quantum yield of emission. Emission from this complex appeared to be from more than one state. The complexes containing the dppz-based ligand series show complicated excited state behaviour. Emission behaviour is consistent with input from more than one state for many of the Re(I), Cu(I) and Ir(III) complexes. The Ru(II) complexes of the ligand series emit from a �MLCT state between metal-based and bpy-based MOs located on the dppz ligands, as is usual for complexes of this type. All complexes containing 11-cyanodipyrido[3,2-a:2�,3�-c]phenazine showed extremely short excited state lifetimes consistent with extremely efficient non-radiative deactivation of the excited state. Ligands and complexes were incorporated into OLEDs with the structure [ITO/PEDOT:PSS/PVK:BuPBD:dopant/BCP/Alq₃/LiF/Al] to test their ability to behave as emissive dyes. Many of the compounds behaved poorly as dopants due to their low emission quantum yields, and poor alignment of HOMO and LUMO energy levels with those of the other compounds within the device. �MLCT-based emission was achieved through energy transfer from the PVK host for the devices containing chlorotricarbonylrhenium(I) complexes of the ligand series. The OLEDs containing Ru(II) and Ir(III) complexes also emitted from dopant-centred �MLCT states. In these devices, dopant excitation appeared to occur through direct charge trapping from the adjacent hole transport and electron transport layers.