No description available.

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Security hardware based on asymmetric algorithm is the key component of Public Key Infrastructure (PKI), which decides the safety and performance of system. Security device in server or client have some common functions. We designed the client token and cryptographic server to improve the performance of PKI, and got obvious effect.

Many animals on earth need to navigate in their own environments for breeding and foraging. The ability to determine a correct heading and the current location for a migratory bird is critical for its survival. Animals that are sensitive to the Earth’s magnetic field can use it to obtain their direction of travel. In 2000, a paper suggested that radical pair reaction could form the basis for magnetoreception in migratory birds and a flavoprotein, cryptochrome, was proposed as the candidate for the radical pair precursor. Recent in vivo experimental results strongly support the hypothesis that radical pairs formed in the eyes of migratory birds are responsible for their magnetic compass sense. Cryptochrome has also been located in the UV-cones in the retinas of two different species of bird. Radical pairs in living cells are influenced mainly by Zeeman interaction, hyperfine interaction, rotational modulation, etc., and together they influence the recombination reactions of the radical pairs. This thesis considers the possible role of radical pairs in avian magnetoreception, using computer simulations of the quantum mechanical evolution of a radical pair under a variety of conditions. Chapter 1 contains the introductions to spin chemistry, avian magnetoreception, and the mathematical description of the quantum evolution of a radical pair. Chapter 2 describes the four different theoretical models for a general non-diffusion-controlled radical pair reaction and the product yields of a radical pair reaction predicted by these four models are analysed and compared. Chapter 3 introduces a model for avian magnetoreception that integrates photoselection with the radical pair reaction and the model is used to predict the retinal patterns that a bird may be able to use for magnetoreception. The anisotropic singlet product yields of a radical pair comprises the flavin chromophore and the tryptophan of a cryptochrome are also presented in this chapter. A paper based on some parts of this chapter is published [1] in the Journal of The Royal Society Interface. Chapter 4 describes a modified version of an algorithm that is used to calculate the product yields detected in a reaction yield detected magnetic resonance (RYDMR) experiment. The new algorithm is used to analyse the results of two sets of RYDMR experiments in which two radical pair systems, pyrene/1,3-dicyanobenzene and chrysene/1,4-dicyanobenzene, were used. The modulated detection technique used in the RYDMR experiments is also discussed in this chapter.

Materials with potential for high temperature inorganic pigment applications (e.g. ceramics) have been synthesised using solid state methods and characterised using powder X-ray and neutron diffraction, magic angle spinning NMR, Mossbauer spectroscopy, UVNis spectroscopy and colour measurement techniques. A number of compounds containing tin (H) and niobium (V) have been modified and doped with various constituents to tailor and widen the colour properties of the bright yellow parent phases. The dark yellow (L*(91.28), a*(13.74), b*(54.76)) tin niobium oxide pyrochlores have been re-characterised using neutron diffraction techniques. These materials exhibit both cation and anion disorder caused by a stereoactive lone pair on the tin (H) metal centres. Solid state NMR and Mossbauer studies have shown the presence of tin (IV) on a symmetric site within the primary phase of the pure oxide pyrochlore and methods have been investigated to minimise the tin (H) disproportion method from where the tin (IV) is derived.

It has been shown that pair-matching on an ordered baseline with normally distributed measures reduces the variance of the estimated treatment effect (Park and Johnson, 2006). The main objective of this study is to examine if pair-matching improves the power when the distribution is a mixture of two normal distributions. Multiple scenarios with a combination of different sample sizes and parameters are simulated. The power curves are provided for three cases, with and without matching, as follows: analysis of post-intervention data only, adding baseline as a covariate, and classic pre-post comparison. The study shows that the additional variance reduction provided by pair-matching in the pre-post design is limited for high correlation. When correlation is low, there is a significant power increase. It is shown that the baseline pair-matching improves the power when the two means of a mixture normal distribution are widely spread. The pattern becomes clear for low correlation.

The oxygen evolution reaction (OER) is kinetically slow and hence a significant efficiency loss in electricity-driven water electrolysis. Understanding the relationships between architecture, composition, and activity in high-performing catalyst systems are critical for the development of better catalysts. This dissertation discusses areas both fundamental and applied that seek to better understand how to accurately measure catalyst activity as well as ways to design higher performing catalysts. Chapter I introduces the work that has been done in the field to date. Chapter II compares various methods of determining the electrochemically active surface area of a film. It further discusses how pulsed and continuous electrodepostition techniques effect film morphology and behavior, and shows that using a simple electrodeposition can create high loading films with architectures that outperform those deposited onto inert substrates. The reversibility of the films, a measure of the films transport efficiency, is introduced and shown to correlate strongly with performance. Chapter III uses high energy x-ray scattering to probe the nanocrystalline domains of the largely amorphous NiFe oxyhydroxide catalysts, and shows that significant similarities in the local structure are not responsible for the change in performance for the films synthesized under different conditions. Bond lengths for oxidized and reduced catalysts are determined, and show no significant phase segregation occurs. Chapter IV seeks to optimize the deposition conditions introduced in Chapter II and to provide a physical representation of how tuning each of the parameters affects film morphology. The deposition current density is shown to be the most important factor affecting film performance at a given loading. Chapter V highlights the different design considerations for films being used in a photoelectrochemical cell, and how in situ techniques can provide information that may otherwise be unobtainable. Chapter VI serves as a summary and provides future directions. This dissertation contains previously published coauthored material.

No description available.

This dissertation describes our study of a photophysical process that leads to ultrafast generation of triplet excitons following photoexcitation, singlet exciton fission, in three different acene dimers and diradicaloids. In pentacene and tetracene dimers, we investigate their mechanism of singlet fission. In a series of diradicaloids, we study the relation between molecular structure, diradical character and the suitability for singlet fission. In the first two chapters we explore singlet fission in pentacene dimer. We demonstrate fast and highly efficient intramolecular singlet fission, consisting of two covalently attached pentacene units. The singlet fission pathway is governed by the energy gap between singlet and charge-transfer states, which change dynamically with molecular geometry but are primarily set by the side group. The process exhibits a sensitivity to solvent polarity and competes with geometric relaxation in the singlet state, while subsequent triplet decay is strongly dependent on conformational freedom. The near orthogonal arrangement of the pentacene units is unlike any structure currently proposed for efficient singlet fission and points toward new molecular design rules. Furthermore, these results are the first to demonstrate the role of charge-transfer states in singlet fission and highlight the importance of solubilising groups to optimise excited-state photophysics. In the next chapter, we examine singlet fission in tetracene dimer, where singlet fission is energetically unfavourable. We demonstrate triplet yield as high as 190% can be achieved via fission from higher singlet excited states mediated by charge-transfer states. The outcomes of this study provide deeper insight into the role of hot singlet states in singlet fission and point toward less stringent molecular design rules. In the last chapter, we shift our focus on a new class of molecules, diradicaloid molecules. We explore a family of zethrene molecules, with tuneable diradical character, and demonstrate their general ability to undergo rapid singlet fission via spin-entangled and emissive triplet-pair state TT. A wide range of zethrene molecules are found to be suitable for singlet fission, with additional benefits of high absorption coefficients and photo-/chemical stability.

Thesis. 1976. Ph.D. cn--Massachusetts Institute of Technology. Dept of Physics. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. Vita. / Includes bibliographical references. / Ph.D.cn

Chan Ching Yin. / Thesis submitted in: October 2003. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 197-221). / Abstracts in English and Chinese. / Acknowledgement --- p.i / Abstract --- p.iii / Abstract in Chinese --- p.vi / List of abbreviations --- p.ix / List of tables --- p.xv / List of figures --- p.xvi / Contents --- p.xviii / Chapter 1. --- Introduction --- p.1 / Chapter 1.1. --- What are astrocytic tumors? --- p.1 / Chapter 1.1.1. --- Histological characteristics and classification --- p.2 / Chapter 1.1.2. --- Epidemiology --- p.2 / Chapter 1.1.3. --- Treatment and patient survival --- p.4 / Chapter 1.2. --- "Cytogenetics, molecular genetics and epigenetics of astrocytic tumors" --- p.6 / Chapter 1.2.1. --- Cytogenetics --- p.6 / Chapter 1.2.2. --- Genetic imbalances --- p.7 / Chapter 1.2.3. --- Tumor suppressor genes --- p.13 / Chapter 1.2.4. --- Oncogenes --- p.22 / Chapter 1.2.5. --- Primary and secondary GBMs --- p.26 / Chapter 1.3. --- Major pathways involved in astrocytic tumorigenesis --- p.30 / Chapter 1.3.1. --- Cell cycle dysregulation and suppression of apoptosis --- p.30 / Chapter 1.3.2. --- Promotion of proliferation and survival --- p.33 / Chapter 1.4. --- BRAF mutation in human cancers --- p.38 / Chapter 1.5. --- Other CNS tumors included in the current study --- p.52 / Chapter 2. --- Aims of study --- p.61 / Chapter 3. --- Materials and methods --- p.64 / Chapter 3.1. --- Clinical materials --- p.64 / Chapter 3.2. --- Cell lines --- p.75 / Chapter 3.3. --- Cell culture --- p.77 / Chapter 3.4. --- DNA extraction --- p.78 / Chapter 3.4.1. --- Pre-treatment of samples --- p.78 / Chapter 3.4.2. --- Cell lysis and protein removal --- p.80 / Chapter 3.4.3. --- Precipitation of DNA --- p.81 / Chapter 3.4.4. --- Determination of DNA concentration --- p.81 / Chapter 3.5. --- Mutation analysis of BRAF by cycle sequencing --- p.83 / Chapter 3.5.1. --- Amplification of BRAF exons --- p.83 / Chapter 3.5.2. --- Cycle sequencing and automated gel electrophoresis --- p.84 / Chapter 3.6. --- Immunohistochemistry of B-Raf and GFAP --- p.87 / Chapter 3.6.1. --- Pre-treatment of samples --- p.87 / Chapter 3.6.2. --- Detection of B-Raf and GFAP antigens by ABC method --- p.88 / Chapter 3.6.3. --- Controls --- p.90 / Chapter 3.7. --- Quantification of EGFR gene dosage by TaqMan based real-time PCR --- p.91 / Chapter 3.7.1. --- Preparation of gene constructs --- p.92 / Chapter 3.7.2. --- Primers and TaqMan probes --- p.93 / Chapter 3.7.3. --- Experimental condition and PCR program --- p.95 / Chapter 3.7.4. --- DNA standards --- p.95 / Chapter 3.7.5. --- Controls --- p.96 / Chapter 3.7.6. --- Experimental layout --- p.96 / Chapter 3.8. --- Microsatellite analysis of chromosome 14q in astrocytic tumors --- p.97 / Chapter 4. --- Results --- p.101 / Chapter 4.1. --- Mutation analysis of BRAF --- p.101 / Chapter 4.2. --- Immunohistochemistry of B-Raf protein --- p.107 / Chapter 4.3. --- Quantification of EGFR gene dosage --- p.117 / Chapter 4.4. --- Correlation between EGFR dosage and BRAF mutation --- p.128 / Chapter 4.5. --- Correlation between EGFR dosage and B-Raf expression --- p.129 / Chapter 4.6. --- Microsatellite analysis of chromosome 14q in astrocytic tumors --- p.131 / Chapter 5. --- Discussions --- p.149 / Chapter 5.1. --- BRAF mutations as common events in human cancers --- p.149 / Chapter 5.2. --- BRAF mutation in CNS tumor specimens --- p.150 / Chapter 5.2.1. --- Tumorigenic effect of the V599E substitution --- p.153 / Chapter 5.2.2. --- V599E B-Raf mutant activation independent of Ras activation --- p.155 / Chapter 5.2.3. --- Autocrine stimulation of Ras signaling in V599E B-Raf mutant --- p.156 / Chapter 5.3. --- BRAF expression in astrocytic tumors --- p.159 / Chapter 5.4. --- Mutually exclusive pattern between EGFR amplification and BRAF expression --- p.161 / Chapter 5.4.1. --- Similar effect of EGFR activation and B-Raf activation --- p.163 / Chapter 5.4.2. --- Mutual effects between Ras/Raf/Mek/Erk and Akt signaling --- p.164 / Chapter 5.5. --- Microsatellite analysis of chromosome 14q in human cancers --- p.167 / Chapter 5.6. --- Microsatellite analysis of chromosome 14q in astrocytic tumors --- p.170 / Chapter 5.6.1. --- Finer mapping of common regions of deletion --- p.170 / Chapter 5.6.2. --- Genes within the common regions of deletion --- p.173 / Chapter 5.6.3. --- Overlapping deletion regions in astrocytic and non-CNS tumors --- p.186 / Chapter 6. --- Further studies --- p.190 / Chapter 6.1. --- Role of BRAF alterations in astrocytic tumors --- p.190 / Chapter 6.2. --- B-Raf expression in astrocytic tumors and correlation with EGFR overexpression --- p.193 / Chapter 6.3. --- Microsatellite analysis of 14q in astrocytic tumors --- p.194 / Chapter 7. --- Conclusions --- p.195 / Chapter 8. --- References --- p.198