Ferromagnetically ordered states in the Hubbard model on the H00H_{00} hexagonal golden-mean tiling

We study magnetic properties of the half-filled Hubbard model on the two-dimensional $H_{00}$ hexagonal golden-mean quasiperiodic tiling. The tiling is composed of large and small hexagons, and parallelograms, and its vertex model is bipartite with a sublattice imbalance. The tight-binding model on the tiling has macroscopically degenerate states at $E = 0$. We find the existence of two extended states in one of the sublattices, in addition to confined states in the other. This property is distinct from that of the well-known two-dimensional quasiperiodic tilings such as the Penrose and Ammann-Beenker tilings. Applying the Lieb theorem to the Hubbard model on the tiling, we obtain the exact fraction of the confined states as $1/2\tau^2$, where $\tau$ is the golden mean. This leads to a ferromagnetically ordered state in the weak coupling limit. Increasing the Coulomb interaction, the staggered magnetic moments are induced and gradually increase. Crossover behaviour in the magnetically ordered states is also addressed in terms of perpendicular space analysis.Comment: 11 pages, 14 figure

Confined states in the tight-binding model on the hexagonal golden-mean tiling

We study the tight-binding model with two distinct hoppings $(t_L, t_S)$ on the two-dimensional hexagonal golden-mean tiling and examine the confined states with $E=0$, where $E$ is the eigenenergy. Some confined states found in the case $t_L=t_S$ are exact eigenstates even for the system with $t_L \neq t_S$, where their amplitudes are smoothly changed. By contrast, the other states are no longer eigenstates of the system with $t_L \neq t_S$. This may imply the existence of macroscopically degenerate states which are characteristic of the system with $t_L=t_S$, and that a discontinuity appears in the number of the confined states in the thermodynamic limit.Comment: 7 pages, 5 figure

C₆₀ on impurity phases of the 2–fold surface of the Al–Pd–Mn quasicrystal

Abstract Using STM, we show several off-stoichiometric impurity phases detected at the 2-fold Al–Pd–Mn quasicrystal surface. By comparing the observed surface structure to planes from similar bulk phases in the Al–Pd system, we identify these phases as β–Al–Pd and Pd5Mn3. C 60 is adsorbed at these domains, forming simple hexagonal close packed (hcp) structures. We identify potential adsorption schemes, and compare the adsorption behaviour to C60 on the quasicrystalline phase.</jats:p

Training for real: matching employer needs to training supply

For 40 years, the Water, Engineering and Development Centre of Loughborough University has trained engineers in the practical requirements for infrastructure services in low- and middle-income countries. This was started to rectify a mismatch between what was being taught in universities and what was being done in practice. Often this gap was addressed by ad hoc, uncoordinated, costly and often ineffective training courses. This mismatch is still apparent and so researchers explored why training providers are not meeting employers' needs. The action research went behind training needs analysis to examine the dialogue between the 'suppliers' (universities) and the 'demands' of the employers (local authorities and water utilities), across the water and sanitation sector in Uganda, through a series of forums, interviews, workshop appraisals and case studies, as well as trialling innovative training techniques. The research identified areas for improvement, especially in the area of employer engagement, skill needs and the management of human resource development

Influence of differences in orientational planar density on the growth of Pb on the i-Ag-In-Yb quasicrystal

Metal adsorption upon the 3-fold and 5-fold symmetric surfaces of the i-Ag–In–Yb quasicrystal has led to the observation of unique growth modes. Here, we present a study of the growth of Pb upon the 2-fold i-Ag–In–Yb surface, where the growth mechanism is found to be different from those observed on the other, higher symmetry surfaces of the same system. Initial Pb atoms occupy non-chemically-specific surface sites before forming a row structure. At higher coverages, the Pb atoms form a dense wetting layer before 1D Pb chains of limited size are self-assembled as a second layer. We therefore consider the Pb atoms to exhibit a type of Stranski–Krastanov growth mode. Substrate–adsorbate interaction is favoured in the wetting layer, before adsorbate–adsorbate interaction promotes chain growth. The difference in growth modes upon the three high symmetry surfaces is discussed with respect to their respective atomic densities

A survey of environmental performance enhancement strategies and building data capturing techniques in the Nigerian context

Abstract: The need to improve the performance of Nigeria’s office buildings is due to, energy challenges, increasing population, changing user needs, and climate change. With the expansion of several Nigerian cities, existing buildings constitute a significant portion of the building stock, and improving their environmental performance could be more cost-effective than reconstruction. The use of simulation packages to assess alternative retrofitting enhancement scenarios is a straightforward approach. However, in Nigeria it is often challenging to get appropriate information to facilitate this type of evaluation; many buildings were not built to their original specifications, and when available, the records are often in a poor state due to deterioration. Studies that aimed at enhancing a building’s performance hardly stated the acquisition of the required building information. This paper investigates current practices and future possibilities of improvement measures and data capturing of existing buildings using a questionnaire survey of 133 building professionals in Benin City. The inter-relationship between energy efficiency, the environment, and building design with a high potential for meaningful retrofit to mitigate energy inefficiencies is known but not fully utilized. The collected thought on current practices signifies the need for developing a more economical and reliable methodology for data capturing and evaluation