Solid Wastes Generation in Covenant University, Ota, Nigeria: Characterisation and Implication for Sustainable Waste Management

Adequate waste characterisation is a requirement for effective waste management and environmental benign waste disposal system. The objectives of this paper were to estimate the percentage of various components in characterised solid waste materials generated in selected sites in Covenant University, Ota, Nigeria. The study was undertaken for 10 weeks through the weighing of solid waste generated in the institution before their delivery to landfills. The study shows that of the average waste generated per day in the institution, food waste exhibited the highest percentage generation at 26.29%, followed by polythene bag at 19.37% then 13.64% plastic bottles, 11.59% metal cans, 10.52% paper, 7.24% plastic food pack, 5.69% other combustible wastes and 5.67% polystyrene food pack. The high composition of non biodegradable wastes from this results bears implication of the requirement of alternative waste management solutions for attaining sustainable and environmental friendly waste management system in the university community

Sealing is at the Origin of Rubber Slipping on Wet Roads

Loss of braking power and rubber skidding on a wet road is still an open physics problem, since neither the hydrodynamical effects nor the loss of surface adhesion that are sometimes blamed really manage to explain the 20-30% observed loss of low speed tire-road friction. Here we advance a novel mechanism based on sealing of water-filled substrate pools by the rubber. The sealed-in water effectively smoothens the substrate, thus reducing the viscoelastic dissipation in bulk rubber induced by surface asperities, well established as a major friction contribution. Starting with the measured spectrum of asperities one can calculate the water-smoothened spectrum and from that the predicted friction reduction, which is of the right magnitude. The theory is directly supported by fresh tire-asphalt friction data.Comment: 5 pages, 4 figures. Published on Nature Materials (November 7th 2004

Statistics of the electromagnetic response of a chaotic reverberation chamber

This article presents a study of the electromagnetic response of a chaotic reverberation chamber (RC) in the presence of losses. By means of simulations and of experiments, the fluctuations in the maxima of the field obtained in a conventional mode-stirred RC are compared with those in a chaotic RC in the neighborhood of the Lowest Useable Frequency (LUF). The present work illustrates that the universal spectral and spatial statistical properties of chaotic RCs allow to meet more adequately the criteria required by the Standard IEC 61000-4-21 to perform tests of electromagnetic compatibility.Comment: 6 pages, 9 figure

Utilization of insecticide treated nets against malaria among pregnant women in Southern Nigeria

Malaria remains one of the most important causes of maternal and child morbidity and mortality in sub-Saharan African, despite the availability of effective intervention. Pregnant women are susceptible to symptomatic malaria due to the invasion of the placenta by Plasmodium. There are public health endeavours in promoting use of insecticide treated nets (ITNS), but there is dearth of data on effectiveness of such endeavour. This narrative review looks briefly at the historical background of use of ITNS against malaria, Government policy and program evaluation process on free ITNS for vulnerable groups, relevance of knowledge in use of insecticide treated nets among pregnant mothers, and the role of attitude and practice on effective use of ITNS in prevention of malaria. There is evidence that relatively few people in high-risk regions access and use ITNS. The low utilization of ITNs attributable to perceived cost, inability to adjust to size of the beds, and side-effects heat and ventilation when slept under it

Convective intensification of magnetic fields in the quiet Sun

Kilogauss-strength magnetic fields are often observed in intergranular lanes at the photosphere in the quiet Sun. Such fields are stronger than the equipartition field B_e, corresponding to a magnetic energy density that matches the kinetic energy density of photospheric convection, and comparable with the field B_p that exerts a magnetic pressure equal to the ambient gas pressure. We present an idealised numerical model of three-dimensional compressible magnetoconvection at the photosphere, for a range of values of the magnetic Reynolds number. In the absence of a magnetic field, the convection is highly supercritical and is characterised by a pattern of vigorous, time-dependent, “granular” motions. When a weak magnetic field is imposed upon the convection, magnetic flux is swept into the convective downflows where it forms localised concentrations. Unless this process is significantly inhibited by magnetic diffusion, the resulting fields are often much greater than B_e, and the high magnetic pressure in these flux elements leads to their being partially evacuated. Some of these flux elements contain ultra-intense magnetic fields that are significantly greater than B_p. Such fields are contained by a combination of the thermal pressure of the gas and the dynamic pressure of the convective motion, and they are constantly evolving. These ultra-intense fields develop owing to nonlinear interactions between magnetic fields and convection; they cannot be explained in terms of “convective collapse” within a thin flux tube that remains in overall pressure equilibrium with its surroundings

Center of mass and relative motion in time dependent density functional theory

It is shown that the exchange-correlation part of the action functional $A_{xc}[\rho (\vec r,t)]$ in time-dependent density functional theory , where $\rho (\vec r,t)$ is the time-dependent density, is invariant under the transformation to an accelerated frame of reference $\rho (\vec r,t) \to \rho ' (\vec r,t) = \rho (\vec r + \vec x (t),t)$, where $\vec x (t)$ is an arbitrary function of time. This invariance implies that the exchange-correlation potential in the Kohn-Sham equation transforms in the following manner: $V_{xc}[\rho '; \vec r, t] = V_{xc}[\rho; \vec r + \vec x (t),t]$. Some of the approximate formulas that have been proposed for $V_{xc}$ satisfy this exact transformation property, others do not. Those which transform in the correct manner automatically satisfy the ``harmonic potential theorem", i.e. the separation of the center of mass motion for a system of interacting particles in the presence of a harmonic external potential. A general method to generate functionals which possess the correct symmetry is proposed

Computer Aided Design for Soil Classification Relational Database and Retrieval Techniques

The paper focuses on the problems associated with classification, storage and retrieval of information on soil data, such as the incompatibility of soil data semantics; inadequate documentation, and lack of indexing; hence it is pretty difficult to efficiently access large database. Consequently, information on soil is very difficult to retrieve hence, modification and update of soil data become very difficult. The relations supported by the system for the purpose of storage and retrieval of soil classification are outlined and translated into graphical presentation. The paper also presents algorithms showing the procedure for generating various soil classifications, retrieval techniques for efficient and quick retrieval of information on soil data. African Research Review Vol. 1 (2) 2007: pp. 141-15

Bifurcation and Chaos in Coupled Ratchets exhibiting Synchronized Dynamics

The bifurcation and chaotic behaviour of unidirectionally coupled deterministic ratchets is studied as a function of the driving force amplitude ($a$) and frequency ($\omega$). A classification of the various types of bifurcations likely to be encountered in this system was done by examining the stability of the steady state in linear response as well as constructing a two-parameter phase diagram in the ($a -\omega$) plane. Numerical explorations revealed varieties of bifurcation sequences including quasiperiodic route to chaos. Besides, the familiar period-doubling and crises route to chaos exhibited by the one-dimensional ratchet were also found. In addition, the coupled ratchets display symmetry-breaking, saddle-nodes and bubbles of bifurcations. Chaotic behaviour is characterized by using the sensitivity to initial condition as well as the Lyapunov exponent spectrum; while a perusal of the phase space projected in the Poincar$\acute{e}$ cross-section confirms some of the striking features.Comment: 7 pages; 8 figure

Timelike self-similar spherically symmetric perfect-fluid models

Einstein's field equations for timelike self-similar spherically symmetric perfect-fluid models are investigated. The field equations are rewritten as a first-order system of autonomous differential equations. Dimensionless variables are chosen in such a way that the number of equations in the coupled system is reduced as far as possible and so that the reduced phase space becomes compact and regular. The system is subsequently analysed qualitatively using the theory of dynamical systems.Comment: 23 pages, 6 eps-figure