Browsing by Author "Asare, K."
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Item Antibody responses to two new Lactococcus lactis-produced recombinant Pfs48/45 and Pfs230 proteins increase with age in malaria patients living in the Central Region of Ghana(Malaria Journal, 2017) Acquah, F.K.; Obboh, F.K.; Asare, K.; Boampong, J.N.; Nuvor, S.V.; Singh, S.K.; Theisen, M.; Williamson, K.C.; Amoah, L.E.Background: Recent advances in malaria control efforts have led to an increased number of national malaria control programmes implementing pre-elimination measures and demonstrated the need to develop new tools to track and control malaria transmission. Key to understanding transmission is monitoring the prevalence and immune response against the sexual stages of the parasite, known as gametocytes, which are responsible for transmission. Sexual-stage specific antigens, Pfs230 and Pfs48/45, have been identified and shown to be targets for transmission blocking antibodies, but they have been difficult to produce recombinantly in the absence of a fusion partner. Methods: Regions of Pfs48/45 and Pfs230 known to contain transmission blocking epitopes, 6C and C0, respectively, were produced in a Lactococcus lactis expression system and used in enzyme linked immunosorbent assays to determine the seroreactivity of 95 malaria patients living in the Central Region of Ghana. Results: Pfs48/45.6C and Pfs230.C0 were successfully produced in L. lactis in the absence of a fusion partner using a simplified purification scheme. Seroprevalence for L. lactis-produced Pfs48/45.6C and Pfs230.C0 in the study population was 74.7 and 72.8%, respectively. Conclusions: A significant age-dependent increase in antibody titers was observed, which suggests a vaccine targeting these antigens could be boosted during a natural infection in the field. © 2017 The Author(s).Item Characterization and Evaluation of Zeolite A/Fe3O4 Nanocomposite as a Potential Adsorbent for Removal of Organic Molecules from Wastewater(Journal of Chemistry, 2019-07-28) Nyankson, E.; Adjasoo, J.; Efavi, J.K.; Amedalor, R.; Yaya, A.; Manu, G.P.; Asare, K.; Amartey, N.A.In this work, zeolite (Z) and Z-Fe3O4 nanocomposite (Z-Fe3O4 NC) have been synthesized. The Fe3O4 nanoparticles were synthesized using the extract from maize leaves and ferric and ferrous chloride salts and encapsulated into the zeolite framework. The nanocomposite (Z-Fe3O4 NC) was characterized using X-ray diffractometer (XRD), Fourier-transform infrared (FT-IR) spectroscopy, energy-dispersive X-ray (EDX) spectroscopy, and scanning electron microscopy (SEM). The potential of Z-Fe3O4 NC as an adsorbent for removing methylene blue molecules (MB) from solution was examined using UV-Vis and kinetic and equilibrium isotherm models. The adsorption data fitted best with the pseudo-second-order model and Weber and Morris model, indicating that the adsorption process was chemisorption, while the Weber and Morris described the rate-controlling steps. The intraparticle diffusion model suggests that the adsorption processes were pore and surface diffusion controlled. The Langmuir isotherm model best describes the adsorption process indicating homogeneous monolayer coverage of MB molecules onto the surface of the Z-Fe3O4 NC. The maximum Langmuir adsorption capacity was 2.57 mg/g at 25°C. The maximum adsorption efficiency was 97.5%. After regeneration, the maximum adsorption efficiency achieved at a pH of 7 was 82.6%.Item Extreme value modelling of Ghana stock exchange index(Springerplus, 2015-11) Nortey, E.N.N.; Asare, K.; Mettle, F.O.Modelling of extreme events has always been of interest in fields such as hydrology and meteorology. However, after the recent global financial crises, appropriate models for modelling of such rare events leading to these crises have become quite essential in the finance and risk management fields. This paper models the extreme values of the Ghana stock exchange all-shares index (2000–2010) by applying the extreme value theory (EVT) to fit a model to the tails of the daily stock returns data. A conditional approach of the EVT was preferred and hence an ARMA-GARCH model was fitted to the data to correct for the effects of autocorrelation and conditional heteroscedastic terms present in the returns series, before the EVT method was applied. The Peak Over Threshold approach of the EVT, which fits a Generalized Pareto Distribution (GPD) model to excesses above a certain selected threshold, was employed. Maximum likelihood estimates of the model parameters were obtained and the model’s goodness of fit was assessed graphically using Q–Q, P–P and density plots. The findings indicate that the GPD provides an adequate fit to the data of excesses. The size of the extreme daily Ghanaian stock market movements were then computed using the value at risk and expected shortfall risk measures at some high quantiles, based on the fitted GPD model.Item Inventorizing Selected Archaeological and Cultural Heritage Sites of Ghana(University of Ghana, 2021-12) Asare, K.Ghana has many archaeological and cultural heritage sites. However, the country lacks a comprehensive inventory of these assets. This makes it impracticable to effectively manage Ghana’s archaeological and cultural heritage resources, and put the resources at risk of destruction. Archaeological, historic, and cultural heritage sites are, for example destroyed indiscriminately by large-scale earth-moving construction and other infrastructural development activities. This pilot digital heritage inventory project uses computer software programmes, such as ArcGIS, Microsoft Excel and Word to document, annotate, profile, graphically represent and develop an inventory of nine selected archaeological and cultural heritage sites in Ghana. The study also uses desk research (literature search and review), collection of oral narratives, site visits, photography to gather complementary research data. This work is expected to create awareness, enhance the conservation, safeguarding and overall management of the selected sites and other heritage sites in the country. It is recommended that this inventory compilation be continued and more sites should be added to this inventory.Item Location, biophysical and agronomic parameters for croplands in northern Ghana(Copernicus Publications, 2022) Gómez-Dan, J.L.; Lewis, P.E.; Yin, F.; Asare, K.; Lamptey, P.; Aidoo, K.K.Y.; MacCarth, D.S.; Ma, H.; et al.Smallholder agriculture is the bedrock of the food production system in sub-Saharan Africa. Yields in Africa are significantly below potentially attainable yields for a number of reasons, and they are particularly vulnerable to climate change impacts. Monitoring of these highly heterogeneous landscapes is needed to respond to farmer needs, develop an appropriate policy and ensure food security, and Earth observation (EO) must be part of these efforts, but there is a lack of ground data for developing and testing EO methods in western Africa, and in this paper, we present data on (i) crop locations, (ii) biophysical parameters and (iii) crop yield, and biomass was collected in 2020 and 2021 in Ghana and is reported in this paper. In 2020, crop type was surveyed in more than 1800 fields in three different agroecological zones across Ghana (the Guinea Savannah, Transition and Deciduous zones). In 2021, a smaller number of fields were surveyed in the Guinea Savannah zone, and additionally, repeated measurements of leaf area index (LAI) and leaf chlorophyll concentration were made on a set of 56 maize fields. Yield and biomass were also sampled at harvesting. LAI in the sampled fields ranged from 0.1 to 5.24 m2 m−2 , whereas leaf chlorophyll concentration varied between 6.1 and 60.3 µg cm−2 . Yield varied between 190 and 4580 kg ha−1 , with an important within-field variability (average per-field standard deviation 381 kg ha−1 ). The data are used in this paper to (i) evaluate the Digital Earth Africa 2019 cropland masks, where 61 % of sampled 2020/21 cropland is flagged as cropland by the data set, (ii) develop and test an LAI retrieval method from Earth observation Planet surface reflectance data (validation correlation coefficient R = 0.49, root mean square error (RMSE) 0.44 m2 m−2 ), (iii) create a maize classification data set for Ghana for 2021 (overall accuracy within the region tested: 0.84), and (iv) explore the relationship between maximum LAI and crop yield using a linear model (correlation coefficient R = 0.66 and R = 0.53 for in situ and Planet-derived LAI, respectively). The data set, made available here within the context of the Group on Earth Observations Global Agricultural Monitoring (GEOGLAM) initiative, is an important contribution to understanding crop evolution and distribution in smallholder farming systems and will be useful for researchers developing/validating methods to monitor these systems using Earth observation data. The data described in this paper are available from https://doi.org/10.5281/zenodo.6632083 (Gomez-Dans et al., 2022).Item Mapping Evapotranspiration of Agricultural Areas in Ghana(The Scientific World Journal, 2021) Aidoo, K.; Klutse, N.A.B.; Asare, K.; Botchway, C.G.; Fosuhene, S.Climate change is having an adverse effect on the environment especially in sub-Sahara Africa, where capacity for natural resource management such as water is very low. 'e scope of the effect on land use types have to be estimated to inform proper remedy. A combined estimation of transpiration and evaporation from plants and soil is critical to determine annual water requirement for different land use. Evapotranspiration (ET) is a major component in the world hydrological cycle, and understanding its spatial dimensions is critical in evaluating the effects it has on regional land use. A measure of this component is challenging due to variation in rainfall and environmental changes. 'e mapping evapotranspiration with high resolution and internalized calibration (METRIC) method is employed to create evapotranspiration map for land use, using remotely sensed data by satellite, processed, and analyzed in ArcGIS. Normalized difference vegetation index (NDVI) was related to the availability of water for vegetation on different land use, and the results indicate a high evapotranspiration for vegetated land use with high NDVI than land use with low NDVI.Item Mapping Evapotranspiration of Agricultural Areas in Ghana(Hindawi, 2021) Aidoo, K.; Klutse, N.A.B.; Asare, K.; Botchway, C.G.; Fosuhene, S.Climate change is having an adverse effect on the environment especially in sub-Sahara Africa, where capacity for natural resource management such as water is very low. 'e scope of the effect on land use types have to be estimated to inform proper remedy. A combined estimation of transpiration and evaporation from plants and soil is critical to determine annual water requirement for different land use. Evapotranspiration (ET) is a major component in the world hydrological cycle, and understanding its spatial dimensions is critical in evaluating the effects it has on regional land use. A measure of this component is challenging due to variation in rainfall and environmental changes. 'e mapping evapotranspiration with high resolution and internalized cali bration (METRIC) method is employed to create evapotranspiration map for land use, using remotely sensed data by satellite, processed, and analyzed in ArcGIS. Normalized difference vegetation index (NDVI) was related to the availability of water for vegetation on different land use, and the results indicate a high evapotranspiration for vegetated land use with high NDVI than land use with low NDVI.Item Monodispersed AgNPs Synthesized from the Nanofactories of Theobroma cacao (Cocoa) Leaves and Pod Husk and Their Antimicrobial Activity(Hindawi, 2022) Efavi, J.K.; Nyankson, E.; Kyeremeh, K.; Manu, G.P.; Asare, K.; Yeboah, N.Silver nanoparticles (AgNPs) have been synthesized from the more chemically rich and diverse cocoa pod; the synthesis of silver nanoparticles from cocoa leaves, which are less rich and have low diversity in bioactive molecules, is yet to be achieved. In this work, AgNPs produced using the extracts of the cocoa leaf (CL) and cocoa pods (CP) have been investigated and their antimicrobialnactivity against E. coli was evaluated. UV-visible absorption spectroscopy was used to examine the reduction of silverions in solution and the surface plasmon resonance of AgNPs. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), dynamic light scattering (DLS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) were used to further characterize the nanoparticles. -e crystalline nature of AgNPs was confirmed by XRD, and the purity and presence of elemental silver were determined by EDX. CL-AgNPs were observed to have a surface plasmon resonance of 425 nm, while CP-AgNPs had a surface plasmon resonance of 440 nm. CL-AgNPs had a significantly higher purity than CPAgNPs. With a shorter nucleation time, the intensity of the UV-Vis spectrum was always higher in the case of CL-AgNPs, indicating a larger population of bioactive molecules available for CL-AgNPs synthesis. FTIR confirmed the presence of phenolic compounds in the leaf and pod extract, implying that water-soluble polyphenolic and flavonoid chemicals are responsible for nanoparticle reduction, capping, and stability. AgNPs generated from CL and CP extracts are polydispersed, with particle sizes of 10–110nm and 20–680 nm, respectively, according to DLS. The corresponding zeta potentials measured are −2.7mV for CLAgNPs and −0.93mV for CP-AgNPs. The zeta potential values suggest that the particles have long-term stability. Furthermore, CLAgNPs outperformed CP-AgNPs in terms of antibacterial activity against Escherichia coli. CL-AgNPs were found to have amaximal inhibitory zone of 21 mm.Item Natural antibody responses to Plasmodium falciparum MSP3 and GLURP(R0) antigens are associated with low parasite densities in malaria patients living in the Central Region of Ghana(Parasites and Vectors, 2017) Amoah, L.E.; Nuvor, S.V.; Obboh, E.K.; Acquah, F.K.; Asare, K.; Singh, S.K.; Boampong, J.N.; Theisen, M.; Williamson, K.C.Background: Plasmodium falciparum genetic diversity and multiplicity of infection (MOI) are parasite features that have been suggested to influence the acquisition of protective immunity against malaria. This study sought to assess the relationship between MOI and parasite density (PD) in malaria patients living in the Central Region of Ghana and to determine whether naturally occurring antibody levels against P. falciparum GLURP (PF3D7-1035300) and MSP3 (PF3D7-1035400) antigens are associated with decreased parasite load. Methods: Dried filter paper blood blots were obtained from children and adults diagnosed with uncomplicated P. falciparum malaria. Microscopy was used to estimate P. falciparum parasite density and polymerase chain reaction (PCR) amplification of the polymorphic regions of msp1 (PF3D7-0930300) and msp2 (PF3D7-0206800) was used for parasite genotyping and MOI determination. ELISA was used to measure the serum IgG concentration of R0 fragment of GLURP (GLURP(R0)) and MSP3 antibodies. Results: All 115 samples were positive for P. falciparum by PCR using either the msp1 or msp2 genotyping primer sets. The most prevalent msp1 and msp2 alleles were KI and 3D7, respectively. The geometric mean (GM) for MOI determined by both msp1 and msp2 genotyping was 1.3 for the entire population and was generally higher in children than in adults. Seropositivity was estimated at 67 and 63% for GLURP(R0) and MSP3 antibodies, respectively, and antibody titers were negatively correlated with parasite density. Conclusions: The negative correlation between naturally occurring GLURP(R0) and MSP3 antibody levels and parasite density observed in this study suggest that augmenting the antibody response with the GMZ2 vaccine could enhance protection in the Central Region of Ghana. © 2017 The Author(s).Item Synthesis and characterisation of zeolite-A and Zn-exchanged zeolite-A based on natural aluminosilicates and their potential applications(Cogent Engineering, 2018-03) Nyankson, E.; Efavi, J.K.; Yaya, A.; Manu, G.; Asare, K.; Daafuor, J.; Abrokwah, R.Y.Zeolites have been hydrothermally synthesized using alumina and silica based deposits (kaolin, bauxite, silica and feldspar) sampled from three regions in Ghana and the chemical compositions of the zeolites varied by batch formulations. The as-synthesized zeolites were characterized using X-ray Diffraction, Fourier Transform Infra-Red and Porosimetry techniques. The morphology and elemental compositions were examined using Scanning Electron Microscopy and energy dispersive X-ray spectroscopy (EDX). The results indicate that zeolite A was formed with a cubic structure and structural variations depending on the batch formulations. By increasing the silica content (Si/Al ratio) through batch formulations, the crystallite sizes of zeolites increased forming Zeolite A with LTA structure and Zeolite A (K-exchanged dehydrated). Samples with higher alumina content produced Zeolite A (Hydrated), Zeolite-Na and Zeolite A (Na, Dehydrated) with lower crystallite sizes. The zeolite synthesized was then used in the synthesis of zinc exchanged Zeolite A (Zn-zeolite A). EDX analysis confirmed a complete exchange of Na in the Zeolite framework with Zn and the feasibility as an adsorbent for methylene blue tested. The synthesized Zn-exchanged Zeolite A showed strong adsorption for methylene blue dye. The adsorption kinetics of the MB onto Zn-exchanged Zeolite A was observed to follow pseudo-second-order model. Freundlich model better described the interaction among adsorbate molecules onto the Zn-exchanged Zeolite A adsorbent, suggesting a multilayer distribution of adsorbate molecules with some level of interaction between adsorbed molecules. The regeneration capacity of the adsorbent was low and calculated to be about 48% at pH of 12. © 2018 The Author(s). This open access article is distributed under a Creative Commons Attribution (CC-BY) 4.0 license.