Reflective dot arrays represent a promising innovation in the field of surface acoustic wave devices. This work has investigated a simple model for uniform rectangular dot arrays. Prom this model the reflection coefficents of the dots and the correct angle for the array's reflectors can be deduced. Experimental results for these parameters are reported for some specific types of metal dot array using aluminium dots on Y-cut lithium niobate. Several different arrangements of dots within the arrays have been investigated, and their different advantages and disadvantages are contrasted. The use of specific array patterns to suppress undesired reflection modes has been investigated, and it has been shown that such suppresion can be achieved by this means. Some information has been gathered on the reflection properties of different shapes of metal dots and with different thicknesses of metal. The properties of these different dot types have been compared and their implications on a theory for the behaviour of reflective metal dots have been discussed. Experimental results have been obtained for the reflection of surface waves on YZ lithium niobate by thin metal strips at normal incidence. These results have been shown to agree with the available theoretical models for the problem. The effect of the mutual capacity of the strips on their behaviour has been shown to be important if several of them are grouped together. This part of the work is seen as a preliminary to the possible development of a model for the reflection properties of metal dots. Two inline reflective dot array devices have been made. The results reported show that the principle of these devices has been sucessful, but that more work is still needed if they are to fulfil their full promise.

One bond coupling constants were measured as a function of temperature for bonds between carbon and carbon (^lJ_CC) and, less commonly, hydrogen (^lJ_CH) or fluorine (^lJ_CF). Precisions of ^±0.01 Hz were achieved using double isotopic substitution (for ^lJ_CC) and least squares curve fitting. Temperatures were measured to ^±0.5 K using carbon chemical shift thermometers. Molecules having no conformational equilibria showed substituent, temperature and solvent effects on the couplings, throwing doubt on some conformational uses of higher order couplings. Comparison of ^lJ_CC values and their temperature dependences (ΔJ/ΔT) for some amines and appropriate models allowed determination of conformational free energies (ΔG°) . ΔG° was estimated for some ethylamines (trans and gauche conformers) and for piperidine (axial and equatorial N-H) . The method depends on the differences in ^lJ_CC for a bond in an ethyl group (ethylamines) or ring (piperidines) according to whether it is cis, gauche, or trans to a nitrogen lone pair. Conformational information was generally obtained from comparison of absolute ^lJ_CC , values, not from ΔJ/ΔT. A hindered internal rotation of the ethyl in r-2,c-4,c-6-trimethyl-N-ethylpiperidine was discovered; ^lJ_CC was observed for separate conformers at low temperature and ΔG° was estimated at room temperature. The result was compared with ΔG°s obtained using other carbon n.m.r. methods, i.e., measurement of line broadening, integrated resonances at low temperature and averaged chemical shifts. Axial /equatorial equilibr were studied by known n.m.r. methods for N-ethyl- and analogous N-methyl-piperidines . ^lJ_CC is dependent on conformation in [(^l3C₂)ethyl] benzene and its mesityl analogue; mathematical treatment should provide an estimate of the barrier to rotation in ethylbenzene. ^lJ_CC is dependent on conformation in ketones (e.g. diethylketone) and on the configuration (syn/anti) of their derivatives. Hyperconjugation with unsaturated centres explains the conformational dependences of ^lJ_CC , analogous to those known for ^lJ_CH.

No description available.

Data for pool boiling heat transfer from a 0.0376 cm diameter Nickel-Aluminium wire 14.65 cm long to six binary mixtures of water/ethylene glycol and five of isopropyl alcohol/water plus the pure components are reported. Experiments were carried out in the pressure range 10.1–101.3 KN/m2 (0.1–1.0 atmosphere) to investigate the effect of pressure on boiling heat transfer to pure and binary liquid mixtures.

No description available.

Nitrogen glasses are prepared in various M-Si-O-N and M-Si-Al-O-N systems (M - Mg, Y, Ca & Nd) by fusing the appropriate metal oxide powders with Si0₂,A1₂0₃• Si₃N₄and AlN at 1600°-1700°C under a nitrogen atmosphere. The limits of glass formation in some of the nitrogen-containing systems are investigated and properties of the glasses are evaluated. Nitrogen is incorporated in M-Si-Al-0-N glasses up to 10-12.5 a/o, the highest being in the Y-Si-Al-0-N system. The nitrogen glass-forming regions are extensions of their appropriate M-Si-Al-O-N vitreous regions. Small homogeneous glass regions also form in some M-Si-O-N systems. Property measurements on both oxide and nitrogen glasses of the same cation composition show that viscosity, refractive index, dielectric constant, and a.c. conduotivity all increase with nitrogen incorporation these ohanges being due to the increased strength, directional charaoter and polarisabi1ity of the nitrogen bond compared with oxygen in the glass network. Grain-boundary vitreous phases, previously considered to b,e oxides, occurring in densified silicon nitride and β'-sialons have compositions within the nitrogen glass regions of their appropriate M-Si-O-N or M-Si-Al-O-N systems (where M - Mg or Y), and are therefore shown to be oxynitrides. A new Mg-Si-Al-O-N phase β" -magnesium sialon, isostructural with β-Si₃N₄and with a range of compositions near Mg₂₁Si₁₈Al₃0₄₈N₁₀, is obtained by devitrification of Mg-Si-Al-O-N glasses with a metal:non-metal atom ratio 3M:4X in the presence of undissolved β-Si₃N₄.

The structural response of a subsonic turbulent jet to controlled forcing has been investigated both theoretically and experimentally. An experimental study has been carried out in which a model jet was subjected to acoustic excitation in the form of circumferential modes of azimuthal wavenumber m=0,1 and 2. Detailed aerodynamic measurements on the initial region of the jet indicate that the m=0 and m=1 modes have comparable axial growth rates. Further, when forcing was applied in a combination of first (m = ±1) or second (m = ±2) order modes, substantial changes in the mean flow were evident over the first twelve diameters of the jet. A linear stability analysis of higher order azimuthally coherent wave-like disturbances on a slowly diverging mean flow has been used to predict the axial-growth rates, phase speeds and radial distributions of the flow characteristics in the forced turbulent jet. Similar axial growth rates result for the m=0 and m=1 modes but, in both these cases, they compare unfavourably with the measured rates which reflect the highly non-linear response of the instability wave to the strong forcing level used. The phase speeds are well predicted, as are the measured radial structures of the instability wave velocity components. The latter agree surprisingly well in view of the highly non-linear axial development of these quantities and this interesting result lends support to the previously unwarranted use of "shape functions" in non-linear stability calculations. Finally the effects of an external flow on a forced jet have been considered. Linear stability theory has been used to examine the axial development of a plane wave disturbance on a slowly diverging jet embedded in an infinite co-flowing stream. The results indicate that at a diameter-based Strouhal number of 0.5 the disturbance suffers very little downstream amplification in the presence of a significant external flow. This is in agreement with increasing experimental evidence which casts doubt on the significance of jet forcing when the device producing the jet is in flight relative to the ambient medium.

Scattering problem is one of the most fundamental problems in physics, spanning almost all areas of physics. In this dissertation, we focus on scattering theory in two types of systems: two dimensional electron scattering in the presence of a random potential and light scattering by metallic nanoparticles. The first scattering problem we study is electron branched flow. In this system, electrons are confined to move in two dimensions while a smoothly changing weak random potential deflects their trajectories, resulting in the so-called branched flow. A semiclassical theory based on ray tracing was developed to explain all the observed features of branched flow. However, this semiclassical theory was challenged by the result of a more recent experiment, which claims to have uncovered "unexpected features of branched flow". We show how these features can actually be explained by the semiclassical theory. Besides electron scattering, we also investigate light scattering by metallic nanoparticles. In this case, we study the multiple scattering effect in the plasmon dimer system and show that one can use these metallic nanoparticles to put the incoming electromagnetic fields into different shapes by solving an inverse scattering problem.

Adoptive Immunotherapy has long been explored as a possible cure for challenging diseases including cancer and HIV infection. The key step in such therapies is to identify and select disease-specific effector cells, which in the past have relied on well-plate based bulk manipulations. But as effector cells against a specific disease are often scarce, bulk studies are ineffective at identifying and selecting the rare effector cells with accuracy. It also takes weeks to prepare a desired population. Though recent advances such as genetically engineered T cell technology and the mutation selection technology have shown great promises, the former is limited by the difficulty in identifying the receptor and antigen, the latter is limited by the direct cell surface fluorescent tagging which could impairs the functional epitomes of surface activation marker and the ineffectiveness of the surface activation marker based selection. Thus I developed a microfluidic system to identify and select effector cells with unprecedented accuracy and speed, by probing the dynamic single cell immune response through co assessing single cell cytokine secretion and cytolysis in picoliter droplets. / Engineering and Applied Sciences - Applied Physics

The field of nanopore research has been driven by the need to inexpensively and rapidly sequence DNA. In order to help realize this goal, this thesis describes the PoreSeq algorithm that identifies and corrects errors in real-world nanopore sequencing data and improves the accuracy of \textit{de novo} genome assembly with increasing coverage depth. The approach relies on modeling the possible sources of uncertainty that occur as DNA advances through the nanopore and then using this model to find the sequence that best explains multiple reads of the same region of DNA. PoreSeq increases nanopore sequencing read accuracy of M13 bacteriophage DNA from 85\% to 99\% at 100X coverage. We also use the algorithm to assemble \textit{E. coli} with 30X coverage and the $\lambda$ genome at a range of coverages from 3X to 50X. Additionally, we classify sequence variants at an order of magnitude lower coverage than is possible with existing methods. This thesis also reports preliminary progress towards controlling the motion of DNA using two nanopores instead of one. The speed at which the DNA travels through the nanopore needs to be carefully controlled to facilitate the detection of individual bases. A second nanopore in close proximity to the first could be used to slow or stop the motion of the DNA in order to enable a more accurate readout. The fabrication process for a new pyramidal nanopore geometry was developed in order to facilitate the positioning of the nanopores. This thesis demonstrates that two of them can be placed close enough to interact with a single molecule of DNA, which is a prerequisite for being able to use the driving force of the pores to exert fine control over the motion of the DNA. Another strategy for reading the DNA is to trap it completely with one pore and to move the second nanopore instead. To that end, this thesis also shows that a single strand of immobilized DNA can be captured in a scanning nanopore and examined for a full hour, with data from many scans at many different voltages obtained in order to detect a bound protein placed partway along the molecule. / Engineering and Applied Sciences - Applied Physics