The period of transition from high school is challenging for most adolescents. There are a substantial number of life-changing decisions that transpire during this time. Choices must be made regarding career paths, continued education, future residence, and avenues for social activities and general integration in the community. Person-centered planning provides a structure for addressing these questions, with the interests and aspirations of the individual at the forefront. While much has been written about person-centered planning, there is still a sparse evidence base to support its use and no formal examination of the fidelity of implementation of these programs. This study utilized a multiple-baseline single subject design to assess the effects of structured meetings with performance feedback on fidelity of implementation of participants' action plan steps in their person-centered plan. Analysis of the results suggests a strong functional relation between the use of structured follow-up with performance feedback and activity related to the person-centered plan action plan. Quality of life data were also gathered prior to planning and prior to and following the performance feedback intervention, with little change in the scores across the three points in time. Social validity was also assessed. The implications of these findings are discussed.

For some time it was believed that simple, single - component, fluid phase behaviour was limited to a homogeneous gas and homogeneous liquid phase separated by a line of first order phase transitions. However, recent studies have demonstrated that simple fluid behaviour can be extended to richer phase diagrams through tuning of the effective potential. Fluids whose constituent particles feel a strong attraction at close range and weak repulsion at longer ranges have been shown, under certain conditions, to assemble into heterogeneous structures such as spherical and cylindrical clusters, lamellae and spherical and cylindrical voids. Lattice Monte Carlo simulations are used to explore the phase diagram of a single - component fluid following a hard - core effective potential with an attractive and a repulsive Yukawa tail. The relative strngths of attractive and repulsive potentials are found for which heterogeneous structures become stable. Then the region of stability of heterogeneous structures is delimited through the use of histogram reweighting to map out the locus of points at which the homogeneous and heterogeneous states have equal free energy. A transition matrix Monte Carlo biasing technique is used to reveal the system behaviour inside the free energy barrier at low temperatures, when the gas - liquid phase transition appears to have re-asserted itself. Finally, a discussion as to the mechanism for assembly of the heterogeneous structures is offered.

We study dynamic phase transitions in the constant-volume and constant- pressure ensembles of two different systems: a one-dimensional system of diffusive hard particles and a three-dimensional glass-former of nearly-hard repulsive particles. The dynamic transitions are observed using ensembles of trajectories biased with respect to their dynamic activity, biasing to greater or lower activities than equilibrium allows us to sample different dynamic phases. We perform finite-size scaling of the transitions with respect to sys- tem size and observation time, and compare them to first-order phase tran- sitions. The two ensembles are not equivalent in the one-dimensional model. We compare our results to analytic predictions for diffusive systems in both the active and inactive phases, there are structural signatures for both dy- namic regimes. The active phases show hyperuniform ordering and the inac- tive regimes show jamming behaviour, local jamming in the constant-volume ensemble is achieved through phase separation. In the three-dimensional sys- tem we observe a dynamic transition to a glassy inactive phase, there is no obvious structural change and the structural relaxation time increases sig- nificantly. We take configurations from the active and inactive phases and subject them to a jamming protocol in order to compare the final density of the jammed packings. Previous work shows that the inactive phase of glass-forming systems have a different distribution of vibrational modes and a higher compressibility, this suggests that the jamming behaviour should differ between the two phases. We show that jammed packings generated from inactive configurations are denser than those generated from active configurations.

Background. Recently, 'mental defeat' (MD) has been explored amongst the chronic pain population and considered as a sort of 'self-processing'. Initial research has linked it to anxiety, pain interference and functional disability. Research has recommended that we explore the relationship between MD and other cognitive constructs, such as hopelessness and depression. The present study firstly considers MD as a predictor for pain symptomology and self-efficacy when related cognitive constructs are examined. Secondly, although chronic pain and MD commonly co-occur, causal relationships have yet to be established1. Method. For the cross-sectional analysis, 59 participants from three pain services completed a questionnaire pack assessing five cognitive constructs; anxiety, depression, hopelessness, pain catastrophizing, and mental defeat. Participants also answered questions about their demographics, pain symptomology and self-efficacy. Results. Linear regression analyses revealed that anxiety was most strongly associated with pain symptomology, accounting for 26% of the variance. When breaking down pain symptomology, catastrophizing showed the strongest association with sensory pain, and mental defeat the strongest association with affective pain. Finally, mental defeat was the most strongly associated variable with self-efficacy, accounting for 47% of the variance. Implications. This research has demonstrated the potential importance of assessing mental defeat in chronic pain patients and, where suitable, targeting these feelings during interventions and therapy. This may have an impact on how well people feel able to cope with their pain. Further, the study indicates mental defeat is different to related cognitive constructs involved in pain, such as depression, hopelessness and catastrophizing.

Guo-cong Guo. / "June 1999." / Thesis (Ph.D.)--Chinese University of Hong Kong, 1999. / 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.

Chapter 1 focuses on the computational study of Zr(CH2Ph)4 and chapter 2 discusses synthesis, characterization and density functional study of 2-imidazolethione. Chapters 3 - 6 describe the synthesis, structural characterization several multidentate tripodal ligands, namely tris(mercaptoimidazolyl)-hydroborato ligand, [TmR], tris(2-pyridylseleno)methyl ligand, [Tpsem], bis(2-pyridonyl)(pyridine-2-yloxy)methyl ligand, [O-poBpom] and allyl-tris(3-t-butylpyrazolyl)borato ligand, [allylTpBut], and their application to main group and transition metals. Chapter 1 describes the analysis of a monoclinic modification of Zr(CH2Ph)4 by single crystal X-ray diffraction, which reveals that the Zr-CH2-Ph bond angles in this compound span a range of 25.1°; that is much larger than previously observed for the orthorhombic form (12.1°;). In accord with this large range, density functional theory calculations demonstrate that little energy is required to perturb the Zr-CH2-Ph bond angles in this compound. Furthermore, density functional theory calculations on Me3ZrCH2Ph indicate that bending of the Zr-CH2-Ph moiety in the monobenzyl compound is also facile, thereby demonstrating that a benzyl ligand attached to zirconium is intrinsically flexible, such that its bending does not require a buffering effect involving another benzyl ligand. Chapter 2 describes the structure of 1-t-butyl-1,3-dihydro-2H-benzimidazole-2-thione which has been determined by X-ray diffraction. The compound exists in the chalcogenone form instead of chalcogenol form, which is similar to its oxo and selone counterparts. Comparison of 2-imidazolone, 2-imidazolethione and 2-imidazoleselone compounds shows that two N-C-E bond angles in the chalcogenone forms are not symmetric. This trend can be reproduced by density functional theory calculations. Additionally, H(mbenzimBut) has intermolecular hydrogen bonding interactions, whereas its selenium counterpart does not. The C-E bond lengths of 2-imidazolone, 2-imidazolethione and 2-imidazoleselone compounds are intermediate between those of formal C-E single and double bonds, which is in accord with the notion that zwitterionic structures that feature single C+-E- dative covalent bonds provide an important contribution in such molecules. Furthermore, NBO analysis of the bonding in H(ximBut) derivatives demonstrates that the doubly bonded C=E resonance structure is most significant for the oxygen derivative, whereas singly bonded C+-E- resonance structures dominate for the tellurium derivative. This result appears to be counterintuitive, based on the fact that it opposes the trend that one would expect on the basis of electronegativity difference, however, studies on XC(E)NH2 derivatives provide solid support for it. In this regard, the C~E bonding in these compounds is significantly different to that in chalcogenoformaldehyde derivatives for which the bonding is well represented by a H2C=E double bonded resonance structure. Chapter 3 describes the computational study on [TmMeBenz] anion and the synthesis and characterization of [TmButBenz]Na, [TmButBenz]Tl and [TmButBenz]Tl. It is worth noting that the two thallium compounds are the first structurally characterized monovalent monomeric [TmR]Tl complexes. Chapter 4 describes the synthesis and characterization of a few [TmR]M (M = Ti, Zr, Hf) complexes, including (i) Cp[TmBut]TiCl2 and Cp[TmBut]ZrCl2, which are analogues of Cp2TiCl2 and Cp2ZrCl2; (ii) [TmBut]Zr(CH2Ph)3 and (iii) [TmBut]Hf(CH2Ph)3 and [TmAd]Hf(CH2Ph)3, which are the first structurally characterized [TmR]Hf complexes. Chapter 5 describes two multidentate, L3X type ligands, which feature [CN3] and [CNO2] donors, namely tris(2 pyridylseleno)methane, [Tpsem]H, and bis(2-pyridonyl)(pyridin-2-yloxy)methane, [O-poBpom]H. They have been synthesized, characterized, and employed in the synthesis of zinc and cadmium complexes. Chapter 6 describes the synthesis and structural characterization of a new [Tp] ligand featuring an allyl substituent on the central boron atom, namely [allylTpBut]Li is reported. The compound reacts steadily with CH3CH2SH under 350 nm UV light via a thiol-ene click reaction. The resulting [CH3CH2S(CH2)3TpBut]Li complex can further react with metal halide. For example, the reaction of [CH3CH2S(CH2)3TpBut]Li with ZnI2 produced [CH3CH2S(CH2)3TpBut]ZnI at room temperature. This study provides a simple model on the immobilization of [Tp] metal complexes to the polymer chains with -SH terminals.

New chiral half-sandwich Ru hydride enantiomers with asymmetric disubstitution on the Cp ligand have been successfully synthesized and resolved. An enantiopure thiolate ligand was installed on the Ru center to form a pair of diastereomers, which were separated by crystallization via vapor diffusion of pentane into their saturated Et2O solution. Racemization occurred at elevated temperatures, but a room temperature conversion pathway was developed to remove the chiral thiolate ligand and generate the enantiopure hydride complex. Two new Rh(III) hydride complexes and their Ir analogues have been synthesized and characterized. The hydride complexes readily transfer H– to the N-carbophenoxypyridinium cation at room temperature, giving mixtures of 1,2- and 1,4-dihydropyridine products. In CD3CN, all four hydrides give nearly the same product ratio, demonstrating that the hydride transfer mechanism is outer sphere. In weak or non-coordinating solvents, the resulting 16-electron cations catalyze the isomerization of 1,2- to 1,4-dihydropyridine at rates that depend upon the cation and the solvent. The fastest isomerization was observed with the Rh(III) cation [Cp*Rh(2-(2-pyridyl)phenyl)]+, Acetonitrile can trap the 16-electron cations resulting from hydride transfer, dramatically slowing the isomerization process. The thermodynamics and kinetics of hydride, hydrogen atom and proton transfer reactions of the Rh(III) hydride, Cp*Rh(2-(2-pyridyl)phenyl)H, were studied both thermodynamically and kinetically. This hydride is both a good hydride and hydrogen atom donor, but a poor proton donor. This previously unobserved combination of properties is due to the high energy of the hydride’s conjugate base, [Cp*Rh(2-(2-pyridyl)phenyl)]−. Its exceptional hydride donor ability makes Cp*Rh(2-(2-pyridyl)phenyl)H a very efficient catalyst for the ionic hydrogenation of iminium cations.

Proton exchange membrane or anion exchange membrane water electrolyzers and fuel cells are still expensive for large-scale commercialization. It requires more investigation and research on finding more economical and efficient electrocatalysts for reactions in these devices. This thesis investigates the performance of metal-modified transition metal carbides on hydrogen evolution reaction (HER) and ethanol oxidation reaction (EOR). The catalysts screening principles for HER and EOR in acid and alkaline are examined and developed by correlating density functional theory (DFT) calculations with experimental results. Metal-modified transition metal carbides can reduce the amount of platinum group metals required for HER, but it is unclear what descriptors are relevant for these materials for the HER under alkaline conditions. Several transition metal carbides (Mo2C, NbC, TaC, WC, VC) thin films were synthesized and modified with monolayers of platinum or gold. The experimentally measured HER exchange current densities were compared with DFT calculations of adsorbed hydrogen and hydroxyl binding energies. The plot of HER activity versus hydrogen binding energy showed a volcano shape for catalysts in both acid and alkaline electrolytes, but the hydroxyl binding energy did not form a strong correlation with alkaline HER activity. Relatively high surface area molybdenum carbide (Mo2C) particles was modified with 5 wt % silver, copper, nickel, platinum, and palladium and subsequently assessed for their HER activity in alkaline and acid electrolytes. DFT‐calculated hydrogen binding energies predicted that Pt–Mo2C and Pd–Mo2C should be most active, which was confirmed with experimental results. Similar activity trends were observed at both high and low pH values, with Cu/Mo2C being the least active. X‐ray photoelectron spectroscopy (XPS) confirmed that metal particles remained on the sample before and after HER testing. Pt‐modified nanocrystalline Mo2C showed superior HER activity compared with Pt‐modified commercial Mo2C, making it a potential replacement for bulk Pt in alkaline membrane electrolyzers. The positive effect on the HER activity of the metal contact with non‐passivated Mo2C surfaces was also demonstrated. Ethanol is an ideal fuel in low-temperature fuel cells. The EOR on platinum-modified tantalum carbide (TaC) was investigated using both model thin films and powder catalysts. The results demonstrated that the 1.5 wt% Pt-modified TaC catalyst obtained enhanced EOR activity compared to Pt. In-situ infrared reflection absorption spectroscopy (IRRAS) study revealed that the Pt surface was less poisoned by EOR intermediates and a higher CO2 selectivity (7~9%) was achieved on the 1.5 wt% Pt/TaC catalyst, compared to the 40 wt% Pt/C. DFT calculations revealed that the binding energies of EOR intermediates on the Pt/TaC(111) surface a weaker than on Pt(111), suggesting an enhanced poison-tolerance from the adsorption of these intermediates. The combined experimental and theoretical investigations strongly suggested that Pt/TaC should be a promising electrocatalyst for EOR. Palladium-modified tungsten carbide (Pd/WC) as an efficient catalyst was investigated for EOR through combined DFT, surface science and electrochemical measurements. Compared to the Pd(111) surface, DFT calculations suggested that the Pd/WC(0001) surface should be less poisoned by the ethanol decomposition intermediates, consistent with surface science results that desorption temperatures of the detected intermediates were lower on the Pd/WC surface. Electrochemical evaluation coupled with in-situ IRRAS measurements of 5 wt% Pd/WC/C powder catalysts were then conducted. The EOR activity of the 5 wt% Pd/WC/C-op catalyst synthesized by the one-pot (op) method was noticeably enhanced, compared to the benchmark 40 wt% Pd/C and 5 wt% Pd/WC/C-iwi that was synthesized using a conventional incipient wetness impregnation (iwi) method. The IRRAS results showed that the EOR products were detected at a lower onset potential on 5 wt% Pd-WC/C-op than on 40 wt% Pd/C. Overall, results from the current thesis demonstrated the feasibility of using metal-modified transition metal carbides as lower-cost and more efficient electrocatalysts for HER and EOR. These results identified descriptors that can be potentially used to design more cost-effective catalysts. Furthermore, results from this thesis also revealed the general similarities and differences of the activity and stability of carbide-based catalysts in acid and alkaline electrolytes.

Two dimensional transition metal dichalcogenides provide a host of unique optoelectronic properties, attributed to their two dimensional nature and unique band structure, making them promising for future optoelectronics device applications. In the work presented in this thesis, we focus on the theoretical understanding and modelling of the optoelectronic properties of monolayer transition metal dichalcogenides, their heterostructures and multilayers. We studied the relaxation rates of photo-excited carriers leading to the formation of electron-hole pairs and their subsequent radiative recombination, resulting in emission of light. We find sub-ps relaxation times, attributed to the strong coupling of carriers with optical phonons, allowing the efficient formation of strongly bound multi-particle complexes such as excitons, trions and biexcitons, which can recombine radiatively if allowed by selection rules. We classify the various complexes according to their optical activity, and predict using diffusion quantum Monte Carlo calculations the resulting photoluminescence spectra in these materials. We proposed a novel, material specific, Auger process in WS2 and WSe2 involving dark excitons, which dominates over radiative processes for relatively low carrier densities, providing an explanation to the observed low quantum efficiencies in these materials. In the same pair of materials, we have shown how the ground state dark trions and biexcitons can become bright and recombine radiatively through an electron-electron intervalley scattering process, resulting in new observable lines in the photoluminescence spectra of these materials. The ability to form van der Waals heterostructures of two or more layers of these materials, allows for new degrees of freedom to be explored and utilised. The heterobilayer system made of MoSe2/WSe2 has a type-II band alignment, allowing for the formation of interlayer bound complexes with carriers localized on opposite layers. We studied the bound complexes formed in this bilayer system, localized on donor impurities. We used quantum Monte Carlo methods to obtain binding energies and wave functions, and calculated the radiative rates and doping dependent photoluminescence spectra of these complexes for closely aligned layers, and asymptotic behaviour for strongly misaligned layers. Finally, we studied few-layers of 2H-stacked transition metal dichalcogenides. The van der Waals quantum well structure results in the splitting of the conduction and valence bands into multiple subbands with energy spacings covering densely the infrared to far-infrared spectral range. We developed a hybrid k.p-tight binding model parameterised by DFT calculations of monolayer and bulk crystals of the studied materials. We used the model to describe the subband dispersions, transition energies, phonon induced broadening and resulting absorption lineshapes for both p-doped and n-doped few-layer films.

The aim of this thesis is to investigate the environmental changes across the Mesolithic-Neolithic transition (c.7000-5000 cal BP) at two sites in north-west Europe. Specific research questions focus on the role of fire, the interaction of climate and environmental change and human impacts, and the degree of continuity across the transition. Previous work has led to hypotheses of human impacts in the late Mesolithic, usually through the use of fire, increasing the abundance of food. Detection of these practices and the change to farming in the Neolithic has long been the study of pollen analysts, but in this project additional techniques of NPPs, size-class differentiated charcoal, and silicon and titanium were added at high resolution in order to determine the relationships between the different forcing factors on mid-Holocene environments. Sites were selected close to locations where known later Mesolithic artefacts have been found, with dated archaeological excavations. An upland UK bog site (Dan Clough Moss, near March Hill, West Yorkshire) and a lowland Swedish lake (Bökeberg, Skåne) provided contrasting environments, and enabled a range of proxies to be used from terrestrial peat and limnic sediments. 14C dates from selected macrofossils enabled an age-depth curve to be produced from each profile, with a Bayesian model applied to estimate the age of each sample. Results show a detailed record of woodland change from both areas. At Dan Clough Moss, disturbance phases with evidence of local fires occur frequently (typically every 20-30 years) in the late Mesolithic, and have low magnitude but consistent records of coprophilous fungi. Some phases of disturbance are different however, without the fungal spore evidence, and with heath plants increasing in representation. Drier phases appear to correlate with more local fire, and increased hazel. The transition is marked by a change to longer duration but distant fires, and longer periods of woodland disturbance, increased ruderal species and more heathland. The dates of occupation phases show a late survival of Mesolithic practices, overlapping with the Neolithic by around 300 years. At Bökeberg, a contrasting pattern is shown, with longer-duration phases of inferred human impact being replaced by shorter episodes of fire-associated disturbance after the date of the transition. Pollen and spore zones of disturbance concur with the dated occupation of late Mesolithic sites at the former lake edge. There is some evidence for markedly wetter, and then significantly drier, climate through the transition, and it could be inferred that this influenced the change in food production economies. However, the overall landscape changed only subtly, with more evidence of potential weeds of cultivation. At Bökeberg, there was no overlap- both radiocarbon and palynology suggest an abrupt transition from Mesolithic to Neolithic. The landscape impact of the transition from Mesolithic to Neolithic at both sites was not a clear and consistent one. While Ulmus decline levels and thereafter had increases in weed species and other herbs the overall balance of trees and shrubs changed less than 20%. At both sites, climate may have been influential, although the evidence is inconclusive. Fires were important at both sites and in both periods, but at different scales and duration. Disturbance phases varied within the Mesolithic as well as between the Mesolithic and the Neolithic.