Vertically coupled double quantum rings at zero magnetic field

Within local-spin-density functional theory, we have investigated the `dissociation' of few-electron circular vertical semiconductor double quantum ring artificial molecules at zero magnetic field as a function of inter-ring distance. In a first step, the molecules are constituted by two identical quantum rings. When the rings are quantum mechanically strongly coupled, the electronic states are substantially delocalized, and the addition energy spectra of the artificial molecule resemble those of a single quantum ring in the few-electron limit. When the rings are quantum mechanically weakly coupled, the electronic states in the molecule are substantially localized in one ring or the other, although the rings can be electrostatically coupled. The effect of a slight mismatch introduced in the molecules from nominally identical quantum wells, or from changes in the inner radius of the constituent rings, induces localization by offsetting the energy levels in the quantum rings. This plays a crucial role in the appearance of the addition spectra as a function of coupling strength particularly in the weak coupling limit.Comment: 18 pages, 8 figures, submitted to Physical Review

Alkali Atoms Attached to 3^3He Nanodroplets

We have experimentally studied the electronic $3p-> 3s$ excitation of Na atoms attached to $^3$He droplets by means of laser-induced fluorescence as well as beam depletion spectroscopy. From the similarities of the spectra (width/shift of absorption lines) with these of Na on $^4$He droplets, we conclude that sodium atoms reside in a ``dimple'' on the droplet surface and that superfluid-related effects are negligible. The experimental results are supported by Density Functional calculations at zero temperature, which confirm the surface location of Na, K and Rb atoms on $^3$He droplets. In the case of Na, the calculated shift of the excitation spectra for the two isotopes is in good agreement with the experimental data.Comment: 6 pages, 3 figures, sent to JLT

The oral hygiene status of institution dwelling orphans in Benin City, Nigeria

Introduction: Orphans like other vulnerable children face a number of challenges including limited or no access to basic health care including oral health care, which is one of their unmet health care needs. Neglected oral health care is associated with the development and progression of periodontal diseases among others.Objective: To determine the oral hygiene status of institution dwelling orphans.Materials and Methods: Thirty eight orphans from four orphanages in Benin City, Edo State of Nigeria were clinically examined and their oral hygiene status determined using the simplified oral hygiene index of Greene and Vermillion (OHI-S).Results: Seventy-three percent of the orphans were found to have fair oral hygiene comprising mostly of those aged 6-13 years. More females were in this category while more males presented with poor oral hygiene status.Conclusion: More orphans presented with fair oral hygiene that indicated inadequate oral care. There was poor oral health education and limited access to services. There is need for these to be improved as a solution to poor oral health status of these vulnerable children.Key words: Institution dwelling, oral hygiene, orphans, statu

Nutrition And Oral Health

There is an interdependent relationship between nutrition and health of oral tissues. The well-being of the oral tissues, the quantity and quality of saliva and the dimension of taste depend on the intake of nutrients. Oral health determines the type of food consumed and ultimately the nutritional level. A review of literature was to outline this interdependent relationship

Optimization of community based virtual power plant with embedded storage and renewable generation

© ICST Institute for Computer Sciences, Social Informatics and Telecommunications Engineering 2017. The current global challenge of climate change has made renewable energy usage very important. There is an ongoing drive for the deployment of renewable energy resource at the domestic level through feed-in tariff, etc. However, the intermittent nature of renewable energy has made storage a key priority. In this work, a community having a solar farm with energy storage embedded in the house of the energy consumers is considered. Consumers within the community are aggregated in to a local virtual power plant. Genetic algorithm was used to develop an optimized energy transaction for the virtual power plant with respect to differential pricing and renewable generation. The results show that it is feasible to have a virtual power plant setup in a local community that involve the use of renewable generation and embedded storage. The results show that both pricing and renewable generation window should be considered as a factor when setting up a virtual power plant that involve the use of storage and renewable generation at the community level. Also, when maximization of battery state of charge is considered as part of an optimization problem in a day ahead market, certain trade-off would have to be made on the profit of the virtual power plant, the incentive of the prosumer, as well as the provision of peak service to the grid.Published versio

Geological and Electrical Resistivity Sounding of Olokonla Area in North-Central Nigeria

Geological mapping and Electrical resistivity sounding were carried out in Olokonla area in Moro Local Government of Kwara State in order to determine the apparent resistivities of the subsurface lithologies and correlate them with the exposed rocks observed during the geological mapping. The studies also delineate the pattern of fractures in the area which form prefential pathways for ground water. Three vertical electrical soundings (VES) were performed radially adopting the Schlumberger electrode configuration, with half-current electrode separation (AB/2) varying from 1m to 100m. Anisotropy polygon was also constructed based on the radial electrical sounding. The geoelectric parameters revealed five subsurface layers which were interpreted as topsoil, lateritic soil, dry sand soil, weathered granite and granite respectively. The geological mapping showed that the area is underlain by crystalline rocks comprising biotite granite, granite-gneiss and migmatite. The anisotropy polygon showed that a major fracture direction along 600 (northeast to southwest) and the coefficient of anisotropy is 0.79. Based on the apparent resistivities and the structural disposition, a potential aquifer was inferred at a depth of 45m. The fracture pattern in the area was constrained to northeast to southwest direction. The data obtained would be useful in borehole drilling for water within the study area.KEYWORDS: Vertical electrical sounding, aquifer, electrical resistivity, anisotropy polygon, geological mapping, fracture patter

Surface location of sodium atoms attached to He-3 nanodroplets

We have experimentally studied the electronic $3p\leftarrow 3s$ excitation of Na atoms attached to $^3$He droplets by means of laser-induced fluorescence as well as beam depletion spectroscopy. From the similarities of the spectra (width/shift of absorption lines) with these of Na on $^4$He droplets, we conclude that sodium atoms reside in a ``dimple'' on the droplet surface. The experimental results are supported by Density Functional calculations at zero temperature, which confirm the surface location of sodium on $^3$He droplets, and provide a microscopic description of the ``dimple'' structure.Comment: 4 pages, 5 figure

Freezing of He-4 and its liquid-solid interface from Density Functional Theory

We show that, at high densities, fully variational solutions of solid-like type can be obtained from a density functional formalism originally designed for liquid 4He. Motivated by this finding, we propose an extension of the method that accurately describes the solid phase and the freezing transition of liquid 4He at zero temperature. The density profile of the interface between liquid and the (0001) surface of the 4He crystal is also investigated, and its surface energy evaluated. The interfacial tension is found to be in semiquantitative agreement with experiments and with other microscopic calculations. This opens the possibility to use unbiased DF methods to study highly non-homogeneous systems, like 4He interacting with strongly attractive impurities/substrates, or the nucleation of the solid phase in the metastable liquid.Comment: 5 pages, 4 figures, submitted to Phys. Rev.