Abstract:
This paper examines the effect of treatment of Dengue fever disease. A
non linear mathematical model for the problem is proposed and analysed
quantitatively using the stability theory of the differential equations. The
results show that the disease-free equilibrium point is locally andglobally
asymptotically stable if the reproduction number (R_{0}) is less than unity. The
additive compound matrices approach is used to show that the dengue fever
model’s endemic equilibrium point is locally asymptotically stable when trace, determinant
and determinant of second additive compound matrix of the Jacobian matrix are
all negative. However, treatment will have a control of dengue fever disease.
Numerical simulation of the model is implemented to investigate the sensitivity
of certain key parameters on the dengue fever disease with treatment.

Abstract:
Incinerator ash was investigated for its potential use as a replacement for sand and cement in
concrete interlocking bricks. The physical characteristics of the raw materials were
examined. Two sets of mixes were prepared. For the first set, sand and water quantities were
fixed while incinerator ash was used at 0% to 100% replacement by weight for cement in
steps of 10%. In the second set, incinerator ash was used at 0% to 100% replacement by
weight for sand while cement and water quantities was fixed. The mixing proportions for
cement, sand and water were 1:3:0.7, respectively. Compressive strength and leachability
tests were performed on the specimens.
Results showed that the replacement of sand by incinerator ash up to 40% exhibited higher
compressive strength than the control mix (0% incinerator ash) after 28 days curing.
Maximum compressive strength of 33.33N/mm^{2} was obtained after 28 days curing using using 20% incinerator ash substitution for sand. Replacement of cement by incinerator ash
up to 20% exhibited higher compressive strength than the control mix. Compressive strength
of 28.2 N/mm^{2} was achieved after 28 days curing period using a 20% ash substitution for cement. Leaching of heavy metals (Pb and Cd ) present in the ash was observed in
concentrated nitric acid.

Abstract:
A 76-year-old man was admitted with a suspicion of small bowel obstruction. His symptoms subsequently resolved without any operative intervention. However, a computed tomographic scan showed evidence of an enlarged "porcelain" gallbladder. A decision was made to electively perform a cholecystectomy, which was accomplished laparoscopically. His postoperative course was uneventful.Tissue sections were fixed in 10% neutral buffered formalin, processed, embedded in paraffin, further processed and stained with hematoxylin and eosin. For immunohistochemistry, selected 4-micron thick, formalin-fixed, deparaffinized and rehydrated sections were stained with antibodies to ki-67 (clone MIB-1, dilution 1:100, heat-induced epitope retrieval [HIER], DakoCytomation, Carpinteria, CA], carcinoembyronic antigen (CEA) (polyclonal, 1:200, Proteolytic epitope retrieval), cytokeratin 7 (OV-TL 12/30, 1:100, HIER, DakoCytomation), p53 (D07, 1:50, HIER, DakoCytomation), and chromogranin A (DAK-A3, 1:100, HIER, DakoCytomation). Assays were performed on a DAKO autostainer (DakoCytomation) based on the avidin-biotin complex method.Macroscopic evaluation of the gallbladder showed it to measure 11.0 × 3.5 × 3.5 cm, and with a white-tan irregular serosal surface. The gallbladder wall was diffusely thickened, measuring up to 0.5 cm in thickness and displaying several areas of gross calcification. The mucosal surface of the gallbladder was tan-yellow. Although several nonspecific irregularities were noted on the mucosal surface, there was no distinct mass lesion. No choleliths were present. Seventy-four tissue sections, which represented approximately 80% of the entire gallbladder, were routinely processed for microscopic examination.The gallbladder showed diffuse mural fibrosis and dystrophic calcification (porcelain gallbladder). In approximately 50% of the sections examined, the mucosa was denuded. Where present, it was largely unremarkable. There were scattered foci of mucosal hyperplasia, as

Abstract:
Engineering research is a sine-qua-non for development of new products, new production processes, hence production lines in the quest for self reliance in any economy. Modeling and simulation is a veritable tool for such research and development. This paper presents the multifaceted use of modeling and simulation as decision tools for engineering facet of an economy drawing examples from two different engineering disciplines- Metallurgical and Civil.

Abstract:
WHO African region has got the highest maternal mortality rate compared to the other five regions. Maternal mortality is hypothesized to have significantly negative effect on the gross domestic product (GDP). The objective of the current study was to estimate the loss in GDP attributable to maternal mortality in the WHO African Region. The burden of maternal mortality on GDP was estimated using a doublelog econometric model. The analysis is based on cross-sectional data for 45 of the 46 Member States in the WHO African Region. Data were obtained from UNDP and the World Bank publications. All the explanatory variables included in the doublelog model were found to have statistically significant effect on per capita gross domestic product (GDP) at 5% level in a t-distribution test. The coefficients for land (D), capital (K), educational enrolment (EN) and exports (X) had a positive sign; while labor (L), imports (M) and maternal mortality rate (MMR) were found to impact negatively on GDP. Maternal mortality of a single person was found to reduce per capita GDP by US$ 0.36 per year. The study has demonstrated that maternal mortality has a statistically significant negative effect on GDP. Thus, as policy-makers strive to increase GDP through land reform programs, capital investments, export promotion and increase in educational enrolment, they should always remember that investments in maternal mortalityreducing interventions promises significant economic returns. African Journal of Health Sciences Vol. 13 (1-2) 2008: pp. 86-95

Abstract:
This study investigates various insulation thicknesses requirements for double-walled spherical pressure vessels for the storage of cryogenic liquids. The inner tank is suspended from the outer tank by straps or cables and the annular space between the tanks is filled with insulation. The outer tank is not subjected to the freezing temperatures and is thus assumed to be a standard carbon steel sphere. In the Finite Element Analysis model of the system, one dimensional analysis was employed. This is due to the assumption that temperature gradient does only exist along the spherical radial direction. In the developed model, once the thickness of the inner shell has been determined based on relevant standards and codes—ASME Sec VIII Div 1 or 2, BS 5500 etc and the thickness of the outer shell is known; the required insulation material thicknesses were calculated for different insulating materials. Set of equations resulting from Finite Element Analysis were solved with computer programme code which was written in FORTRAN 90 programming language. The results obtained are validated by analytical method. The results showed no significant difference (P > 0.05) with values obtained through analytical method. The thicknesses for different insulating materials in-between inner and outer tank shells were compared. The results showed that as the insulating material thickness was increased, the heat flux into the stored product was decreasing and at a certain thickness; it started increasing. The insulating thickness at which this happens is termed as critical thickness of insulating material—the thickness of insulation at which the heat influx to the stored products is minimal; this would therefore reduce boil-off of the stored cryogenic product. High thermal conductivity insulating materials need to be thicker than lower thermal conductivity insulating materials if the system is conditioned to have the same heat flux into the stored product for all insulating materials. In the simulation, different insulating material gives different minimal heat influx into the stored products.

Abstract:
Road tankers are the most used means of transporting petroleum product to end users due to its cost effectiveness and energy-efficiency. The cylindrical tank has been well designed for by ASME VIII divisions 1 and 2 using analytical equations. Petrol tankers are not circular but elliptical probably for stability during transportation. This paper has used the finite element method to investigate in-plane displacements and Von-Mises stresses in both circular and elliptical cylindrical tanks under full loading. An elliptical OANDO^{?} tanker of 66.78 m^{3}volume and shell thickness of0.2 mmand an equivalent volume circular cylindrical tank was used for the simulation. MATLAB^{?} was used to generate geometrical mesh model of the petroleum tankers, extract element coordinates and conduct the finite element analysis. Plane strain condition was used in analyzing a section of the petroleum tanker. It was observed that an equivalent volume circular cylindrical tank was under a higher internal pressure (16,858 N/m^{2}) compared to the elliptical cylinder (14,480 N/m^{2}). Von-Mises stress and in-plane displacements showed direct linear relationships with internal fluid pressure. Von-Mises stress in the elliptical tank was found to be lower (5.7 × 10^{6} N/m^{2}) than for the circular tank (8 × 10^{6} N/m^{2}). In plane displacements was zero in the longitudinal direction for both tanks and of the order of 10^{-4} mm in the y-direction for both tanks with the circular larger by about 2.5 ×^{ }10^{-3 }cm. So in addition to tank stability on the lorry, the Von-Mises stresses were lower as well for the elliptical tank. It was also observed that Von-Mises stresses were far below the yield stress of the steel plate. However, the effect of weldment area on lowering of yield stress was not studied. Stress values were validated using analytical method and found to be insignificantly different (P > 0.05).

Abstract:
All real physical structures behave dynamically when subjected to loads or displacements. This research paper, therefore, presents seismic response of field fabricated liquefied natural gas spherical storage vessels using finite element analysis. The seismic analysis procedure used represents a practical approach in quantifying the response of spherical storage vessel with its content when it is subjected to seismic loading. In the finite element method approach, six degrees of freedom per node is used for legs/column of the spherical storage tanks. Lumped mass procedure is employed to determine system mass matrix of the structure. Computer programme code is developed for the resulting matrix equation form finite element analysis of the structure using FORTRAN 90 programming language. The modeling of the seismic load utilizes the ground acceleration curve of a site. From the results of the modal analysis, the system is uncoupled thereby gives way to the application of Newmark’s method. Newmark’s method as one of the widely used time-step approach for the seismic response is applied. The developed programme coding is validated with analytical results (P > 0.5). It shows that the approach in this research work can be successfully used in determine the stability of large spherical storage vessels against seismic loadings when base acceleration spectral of the site are known. This approach gives better results than the static-force approach which gives conservative results. While the approach used in this research treats seismic loads as time event, static-force approach assumed that the full ground force due to seismic motion is applied instantaneously.

Abstract:
This work builds on an earlier work done which used global coordinates where a large number of elements were needed to form a convergence of results for shop built spherical pressure vessels. In this work area coordinates were used. Any action that leads to an inability on the part of a structure to function as intended is known as failure. This research, therefore, investigates stresses developed in a shop built carbon steel spherical storage vessels using finite element approach as the analytical tool. 3-D finite element modeling using 3-node shallow triangular element with five degrees of freedom at each node is employed. These five degrees of freedom are the essential nodal degrees of freedom without the sixth in-plane rotation. The resulting equations from finite element analysis are coded using FORTRAN 90 computer programme. Spherical storage vessels are subjected to various internal loading pressures while nodal displacements, strains and the corresponding maximum Von-mises stresses are determined. The calculated maximum Vonmises stresses are compared with the yield strength of the shell plate material. Using specified safety factor, safety internal pressures with the corresponding shell thicknesses for shop built spherical pressure vessels are determined. The finite element modeling carried out in this research can be used to predict in-service stresses, strains, and deformations of shop built spherical pressure vessels using Von-mises yield stress as the failure criteria. The results obtained were validated by analytical method and it showed there was no significant difference (P > 0.05) with values obtained through analytical method.

Abstract:
This study investigated thickness requirements for field fabricated (large) spherical liquefied natural gas (LNG) pressure vessels using the finite element method. In the FEM modeling, 3-dimenisonal analysis was used to determine thickness requirements at different sections of a 5-m radius spherical vessels based on the allowable stress of the material as given in ASME Section II Part D. Shallow triangular element based on shallow shell formation was employed using area coordinate system which had been proved better than the global coordinate system in an earlier work of the authors applied to shop built vessels. This element has five degrees of freedom at each corner node-five of which are the essential external degrees of freedom excluding nodal degree of freedom associated with in plane shell rotation. Set of equations resulting from Finite Element Analysis were solved with computer programme code written in FORTRAN 90 while the thickness requirements of each section of spherical pressure vessels subjected to different loading conditions were determined. The results showed membrane thickness decreasing from the base upwards for LNG vessels but constant thickness for compressed gas vessels. The obtained results were validated using values obtained from ASME Section VIII Part UG. The results showed no significant difference (P > 0.05) with values obtained through ASME Section VIII Part UG.