School of Physical and Mathematical Sciences

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A methodology for stochastic analysis of share prices as Markov chains with finite states
(2014-11-06) Mettle, F.O.; Quaye, E.N.B.; Laryea, R.A.
Abstract Price volatilities make stock investments risky, leaving investors in critical position when uncertain decision is made. To improve investor evaluation confidence on exchange markets, while not using time series methodology, we specify equity price change as a stochastic process assumed to possess Markov dependency with respective state transition probabilities matrices following the identified state pace (i.e. decrease, stable or increase). We established that identified states communicate, and that the chains are aperiodic and ergodic thus possessing limiting distributions. We developed a methodology for determining expected mean return time for stock price increases and also establish criteria for improving investment decision based on highest transition probabilities, lowest mean return time and highest limiting distributions. We further developed an R algorithm for running the methodology introduced. The established methodology is applied to selected equities from Ghana Stock Exchange weekly trading data.
Acceptance of biotechnology and social-cultural implications in Ghana
(African Journal of Biotechnology, 2009-05) Quaye, W.; Yawson, I.; Yawson, R.M.; Williams, I.E.
Despite major scientific progress in the application of biotechnology in agriculture, public attitudes towards biotechnology in general and genetically modified food (GM food) products in particular remain mixed in Africa. Examining responses on acceptance of GM food through a stakeholder survey in Ghana, it was established that half of the 100 people sample interviewed were not in favor of GM foods. To this group acceptance of GM foods would make farmers loose focus on the traditional ways of cultivation, putting the whole nation at the mercy of profit driven foreign companies who produce GM foods. In order to have clear and unbiased attitudes towards agricultural biotechnology in Africa, there is the need to substitute dominant ideologies in the way biotechnology research and dissemination are conducted in developed countries with tailor-made methodologies in developing countries. This paper emphasizes the social dynamic force of food focusing on the need for social shaping of biotechnologies to reflect local and regional needs. Respondents' perceptions of GM foods suggest that food is seen as not just a commodity to be consumed but food has both cultural and national identities. Generally, people are identified by their consumption and nutrition lifestyles and therefore take pride in what they eat. A proposal is made to set biotechnology research agenda in the context of social choices; social scientific coalition of biotechnology with endogenous development pathways' as opposed to 'exogenous biotechnology research'. Also there is the need for adequate capacity building of the existing regulatory institutions to handle ethical and moral issues associated with biotechnology research since survey findings showed lacked of public confidence in them. © 2009 Academic Journals.
Acceptor-donor-acceptor small molecules based on derivatives of 3,4-ethylenedioxythiophene for solution processed organic solar cells
(Royal Society of Chemistry, 2016) Antwi, B.Y.; Taylor, R.G.D.; Cameron, J.; Owoare, R.B.; Kingsford-Adaboh, R.; Skabara, P.J.
Three simple semiconducting acceptor-donor-acceptor (A-D-A) small molecules based on an electron-rich (3,4-ethylenedioxythiophene) EDOT central core have been synthesised (DIN-2TE, DRH-2TE, DECA-2TE) and characterised. Organic photovoltaic (OPV) devices incorporating these materials have been prepared and evaluated. The physical properties of the molecules were characterised by TGA, DSC, UV/vis spectroscopy and cyclic voltammetry. The optical HOMO-LUMO energy gaps of the molecules in the solid state were in the range 1.57-1.82 eV, and in solution 1.88-2.04 eV. Electrochemical HOMO-LUMO energy gaps determined by cyclic voltammetry were found to be in the range 1.97-2.31 eV. The addition of 1% 1,8-diiodooctane (DIO) to photoactive blends of the A-D-A molecules and PC71BM more than doubled the power conversion efficiency (PCE) in the case of DRH-2TE:PC71BM devices to 1.36%. © 2016 The Royal Society of Chemistry.
Accramycin A, A New Aromatic Polyketide, from the Soil Bacterium, Streptomyces sp. MA37
(molecules, 2019-09-12) Kyeremeh, K.; Maglangit, F.; Fang, Q.; Leman, V.; Soldatou, S.; Ebel, R.; Deng, H.
Abstract: Drug-like molecules are known to contain many di erent building blocks with great potential as pharmacophores for drug discovery. The continued search for unique sca olds in our laboratory led to the isolation of a novel Ghanaian soil bacterium, Streptomyces sp. MA37. This strain produces many bioactive molecules, most of which belong to carbazoles, pyrrolizidines, and fluorinated metabolites. Further probing of the metabolites of MA37 has led to the discovery of a new naphthacene-type aromatic natural product, which wehave named accramycinA1. This molecule was isolated using an HPLC-photodiode array (PDA) guided isolation process and MS/MS molecular networking. The structure of 1 was characterized by detailed analysis of LC-MS, UV, 1D, and 2D NMR data. Preliminary studies on the antibacterial properties of 1 using Group B Streptococcus (GBS) produced a minimum inhibitory concentration (MIC) of 27 g/mL. This represents the first report of such bioactivity amongst the naphthacene-type aromatic polyketides, and also suggests the possibility for the further development of potent molecules against GBS based on the accramycin sca old. A putative acc biosynthetic pathway for accramycin, featuring a tridecaketide-specific type II polyketide synthase, was proposed.
Acid mine drainage - Effect on creeks or streams in a mining community in Ghana and treatment options
( International Journal of Environmental Science and Development, 2010-09) Afriyie-Debrah, C.; Obiri-Danso, K.; Ephraim, J.H.
Heavy metals contamination and other physicochemical changes in underground and surface water by acid mine drainage (AMD) were determined on the impact on creeks or streams. High levels of these metals have been reported in mining areas over the years; however, investigations indicates that less monitoring has been done on water discharged as effluent for effective maintenance mechanisms to be effected. Field and laboratory studies were carried out within the mining community on Latitude S 2° 35 W and Longitude N 5° 31W to investigate the levels of heavy metals (As, Fe, Cu, Zn, Mn and Cd) and physico-chemical changes (pH, temperature, E.C, D.O, alkalinity, S042-, free CN) in both underground and surface water for seven sampling sites. Results from atomic absorption spectrometry (AAS) determination indicated an average concentrations of iron (6.185 mg/l) and manganese (2.271 mg/l) in both surface and underground waters which are higher than threshold limits for mmmg effluent. The physico-chemical changes were determined using standard methods. Results also indicated higher levels of electric conductivity (1435.0μs/cm) and sulphate (344.0 mg/l). Differences in pH, temperature, E.C, alkalinity, S042-, Fe, Cu, Zn and Mn levels in the seven water samples were statistically significant (p ≤ 0.05). This may be attributed to the higher release of metals, relative to H+. Result also showed significant impact of AMD on water quality in the mining area. This effect could be attributed to the release of metals as a result of oxidation of metal-bearing sulphides in the mine dumps and pits at the selected sampling sites. The study showed that addition of lime as a treatment option has not been effective. Hence new conventional methods such as Aerobic wetland, Compost or Anaerobic Wetland, Open Limestone Channels, Diversion wells, Anoxic Limestone Drains (ALD) etc. should be considered in the treatment of acidic water (AMD) in the mining area. © 2010 IEEE.
Acoustoelectric direct current density in fluorine doped single-walled carbon nanotubes due to harmonic mixing of bichromatic fields with commensurate frequencies
(Diamond & Related Materials, 2023) Sekyi-Arthur, D.; Mensah, S.Y.; Amewode, E.K.; Arthur, R.; Adams, R.R.
Herein, we theoretically report on the acoustoelectric direct current (ADC) generation in a non-degenerate fluorine doped single-walled carbon nanotubes (FSWCNTs), due to mixing of waves with commensurate harmonics in the hypersound regime, qℓ≫1 (where q is the acoustic wavenumber and ℓ is the carrier mean free path). The only restriction of the theory on the sound intensity was that, the interaction energy between the carrier and the acoustic phonons must be small in comparison with the characteristic carrier energy. It was observed that in this situation, the higher harmonics of the effective field of the acoustic wave can be neglected; the origin of the nonlinearity was due to the distortion of the distribution function for carriers moving in phase with the phonons, as a result of interaction with the acoustic wave; the nonlinear effects can then be very important. The ADC generated was highly nonlinear and non-ohmic and depended on the amplitude of the bichromatic fields (i.e., pump and probe field), overlapping integral for jumps (Δs and Δz), carrier concentration (no), Bloch frequency (Ω), photon frequency (ω) and acoustic phonon frequency (ωq). The strong nonlinearity and non-ohmicity of the I-V characteristic of the FSWCNTs may be associated with a number of nonlinear phenomena including the non-parabolic band relation, carrier heating due to distortion in carrier distribution function, Stark component, and Bloch oscillations of intraminiband carriers. It was possible to alter the magnitude and direction of the rectified ADC by adjusting the phase of the fields, and the generation of ADC corresponded to even instability zones in the FSWCNTs. Thus, based on the high ADC obtained, we propose FSWCNTs for ADC generation under bichromatic fields with commensurate harmonics.
Adapting to Changing Climate: Understanding Coastal Rural Residents’ Relocation Intention in Response to Sea Level Rise
(MDPI, 2023-05) Klutse, A. B.; Adade, R.; Jaiye, D.; et al
Ex situ adaptation in the form of relocation has become inevitable in some low-lying coastal zones where other adaptation strategies become impractical or uneconomical. Although relocation of coastal low-lying communities is anticipated globally, little is still known about the factors that influence household-level adoption. This study draws on an extended version of Protection Motivation Theory (PMT) to assess the factors influencing the relocation intention of three highly vulnerable coastal rural communities in Ghana. A total of 359 household heads were randomly selected for a questionnaire survey. The study employed binary logistic regression to identify key factors that influence residents’ readiness to relocate. The results indicated that cognitive and compositional factors were more important than contextual factors in explaining the intention to relocate among coastal rural communities in Ghana. However, contextual factors mediated or attenuated the influence of cognitive and compositional factors on relocation intention. Based on the findings, this study advocates for intensive education on the effects of future sea-level rise impacts on communities as well as structural and non-structural measures to improve the socio-economic capacity of rural communities.
An advance ensemble classification for object recognition
(Neural Computing and Applications, 2021) Owusu, E.; Wiafe, I.
The quest to improve performance accuracy and prediction speed in machine learning algorithms cannot be overemphasized, as the need for machines to outperform humans continue to grow. Accordingly, several studies have proposed methods to improve prediction performance and speed particularly for spatio-temporal analysis. This study proposes a novel classifier that leverages ensemble techniques to improve prediction performance and speed. The proposed classifier, Ada-AdaSVM uses an AdaBoost feature selection algorithm to select small features of input datasets for a joint support vector machine (SVM)–AdaBoost classifier. The proposition is evaluated against a selection of existing classifiers (SVM, AdaSVM and AdaBoost) using the Jaffe, Yale, Taiwanese facial expression database (TFEID) and CK + 48 datasets with Haar features as the preferred method for feature extraction. The findings indicated that Ada-AdaSVM outperforms SVM, AdaSVM and AdaBoost classifiers in terms of speed and accuracy.
An advance ensemble classification for object recognition
(Neural Computing and Applications, 2021) Owusu, E.; Wiafe, I.
The quest to improve performance accuracy and prediction speed in machine learning algorithms cannot be overemphasized, as the need for machines to outperform humans continue to grow. Accordingly, several studies have proposed methods to improve prediction performance and speed particularly for spatio-temporal analysis. This study proposes a novel classifier that leverages ensemble techniques to improve prediction performance and speed. The proposed classifier, Ada-AdaSVM uses an AdaBoost feature selection algorithm to select small features of input datasets for a joint support vector machine (SVM)–AdaBoost classifier. The proposition is evaluated against a selection of existing classifiers (SVM, AdaSVM and AdaBoost) using the Jaffe, Yale, Taiwanese facial expression database (TFEID) and CK ? 48 datasets with Haar features as the preferred method for feature extraction. The findings indicated that Ada-AdaSVM outperforms SVM, AdaSVM and AdaBoost classifiers in terms of speed and accuracy.
Ages and tectonic implications of the mafic–ultramafic-carbonatite intrusive rocks and associated Cu-Ni, Fe-P and apatite-vermiculite deposits from the Quruqtagh district, NW China
(Elsevier B.V., 2016) Han, C.; Xiao, W.; Su, B.; Ao, S.; Zhang, J.; Wan, B.; Song, D.; Wang, Z.; Sakyi, P.A.
The Tarim Craton is an important tectonic unit and a suitable target to investigate and understand the Proterozoic tectonic framework of the Central Asian Orogenic Belt and supercontinent Rodinia. Precambrian ultramafic–mafic-carbonatite rocks are widely distributed in the Quruqtagh domain of NE-Tarim. In the Quruqtagh, Cu-Ni, Fe-P and apatite-vermiculite deposits hosted in the ultramafic-mafic-carbonatite rocks occur in the Xingdi, Qieganbulake, Daxigou, and Kawuliuke. These deposits associated with the ultramafic-mafic-carbonatite rocks in Quruqtagh formed in a period between the Paleoproterozoic and Neoproterozoic. The Paleoproterozoic Fe-P deposit is represented by the Daxigou deposit that yielded a SIMS U-Pb zircon age of 2452 ± 10 Ma. The other Cu-Ni, Fe-P and apatite-vermiculite deposits, hosted in the ultramafic–mafic rocks, formed in the Neoproterozoic, represented by the Xingdi, Kawuliuke, and Qieganbulake deposits that formed between 812 Ma and 707 Ma. The Paleoproterozoic mineralization event was coincident with the global collisional events that led to the assembly of the Paleo-Mesoproterozoic Columbia (Nuna) supercontinent. And the emplacement of these Neoproterozoic ultramafic-mafic-carbonatite rocks was related to a mantle plume event that led to the breakup of the Tarim Craton from the Rodinia supercontinent. © 2016 Elsevier B.V.
Alaskan-type nature and PGE mineralization of the Wuxing mafic–ultramafic complex in eastern part of the Central Asian Orogenic belt
(Ore Geology Reviews, 2020-05-04) Anani, C.Y.; Cui, M-M.; Su, B-X.; Wang, J.; Chen, K-Y.; Sakyi, P.A.; Tang, D-M.; He, Y-P.; Sun, J-G.; Cui, J.; Gao, D-L.
The Wuxing mafic–ultramafic complex is located in the eastern part of the Central Asian Orogenic Belt (CAOB). It consists of hornblende-olivine clinopyroxenite, hornblende clinopyroxenite, clinopyroxenite, gabbro and diorite. Hornblende occurs in all the rock types of the complex and is pargasite in composition. Clinopyroxene is diopsidic in composition with high CaO and low TiO2 contents. The flat REE and sub-parallel trace element patterns of both clinopyroxene and hornblende suggest that these rocks were formed by fractional crystallization from common magma with no significant crustal contamination. Enrichment in large ion lithophile elements relative to high field strength elements of the silicate minerals, together with the variable sulfur isotope compositions (δ34S = -2.55 ~ 11.01‰) of the sulfides, indicate the involvement of subducted oceanic materials into the mantle source. These petrological, mineralogical and geochemical features strongly suggest the Alaskan-type nature of the Wuxing complex. The hydrous parental magma of the Wuxing complex was derived from partial melting of the mantle wedge, which had been metasomatized by subducted melts/fluids. The Wuxing complex is a unique Pt-Pd-rich Ni-Cu sulfide deposit in the CAOB. The ore minerals, which are dominated by pyrite, pyrrhotite, pentlandite, chalcopyrite and platinum-group mineral (PGM), mainly occur in clinopyroxenite and hornblende clinopyroxenite. The sulfide ores are predominantly present as net-textured and disseminated textures. Pentlandite and chalcopyrite associated with pyrrhotite commonly occur in the marginal zone of the pyrrhotite grains. The PGMs occur as interstitial grains at the contact between base-metal sulfides and silicate minerals or along the crack of pyrrhotite or clinopyroxene, or as inclusions in pyrrhotite. The occurrences of sulfides and PGMs in the Wuxing complex, together with sulfur isotope compositions and PGE patterns, reveal that the PGE enrichment of the Alaskan-type complexes can be attributed to the high-degree partial melting of the mantle source, sulfur involvement in the source, and PGE transportation of hydrous melts.
Alpinumisoflavone
(Acta Crystallographica, 2008-03) Harrison, K.E.J.J.; Tabuchi, Y.; Ishida, H.; Kingsford-Adaboh, R.
Alpinumisoflavones
(Acta Crystaltographics E Section E 4(64): 07-13, 2008) Kingsford-Adaboh, R.; Harrison, J. J. E. K.
The title compound, C20H16O5, [systematic name: 5-hydroxy-7-(4-hydroxyphenyl)-2,2-dymethuyly-2H, 6H=benzol (1, 2-b:5, 4-b)] – dipyran-6-one], was obtained by demethylation of the biologically active related compound, 4-O methylaphinumiso-flavone. The molecular structure of the title compound is characterized by a fused tricyclic system that contains an approximately planar benzopyrone ring fragment. The six membered pyran ring adopts a half-chair conformation. Both ring systems show an out-of-plane twist. The dihedral angle between the mean plane of the benzopyrone system and the benzene ring is 54.29(3)o. The molecules are linked by O-H … hydrogen bonds, forming a molecular tape running along the b axis.
Alternative boronic acids in the detection of Mycolactone A/B using the thin layer chromatography (f-TLC) method for diagnosis of Buruli ulcer
(BMC Infectious Diseases, 2023) Akolgo, G.A.; Partridge, B.M.; Craggs, T.D.; Amewu, R.K
Background Mycobacterium ulcerans is the causative agent of Buruli ulcer. The pathology of M. ulcerans disease has been attributed to the secretion of a potent macrolide cytotoxin known as mycolactone which plays an important role in the virulence of the disease. Mycolactone is a biomarker for the diagnosis of BU that can be detected using the fuorescent-thin layer chromatography (f-TLC) technique. The technique relies on the chemical derivatization of mycolactone A/B with 2-naphthylboronic acid (BA) which acts as a fuorogenic chemosensor. However, back ground interferences due to co-extracted human tissue lipids, especially with clinical samples coupled with the subjectivity of the method call for an investigation to fnd an alternative to BA. Methods Twenty-six commercially available arylboronic acids were initially screened as alternatives to BA using the f-TLC experiment. UV–vis measurements were also conducted to determine the absorption maximum spectra of mycolactone A/B and myco-boronic acid adducts followed by an investigation of the fuorescence-enhancing ability of the boronate ester formation between mycolactone A/B and our three most promising boronic acids (BA15, BA18, and BA21). LC–MS technique was employed to confrm the adduct formation between mycolactone and boronic acids. Furthermore, a comparative study was conducted between BA18 and BA using 6 Polymerase Chain Reaction (PCR) confrmed BU patient samples. Results Three of the boronic acids (BA15, BA18, and BA21) produced fuorescent band intensities superior to BA. Complexation studies conducted on thin layer chromatography (TLC) using 0.1 M solution of the three boronic acids and various volumes of 10 ng/µL of synthetic mycolactone ranging from 1 µL – 9 µL corresponding to 10 ng – 90 ng gave similar results with myco-BA18 adduct emerging with the most visibly intense fuorescence bands. UV–vis absorption maxima (λmax) for the free mycolactone A/B was observed at 362 nm, and the values for the adducts myco-BA15, myco-BA18, and myco-BA21 were at 272 nm, 270 nm, and 286 nm respectively. The comparable experi mental λmax of 362 nm for mycolactone A/B to the calculated Woodward-Fieser value of 367 nm for the fatty acid side chain of mycolactone A/B demonstrate that even though 2 cyclic boronates were formed, only the boronate of the southern side chain with the chromophore was excited by irradiation at 365 nm. Fluorescence experiments have demonstrated that coupling BA18 to mycolactone A/B along the 1,3-diols remarkably enhanced the fuores cence intensity at 537 nm. High-Resolution Mass Spectrometer (HR-MS) was used to confrm the formation of the myco-BA15 adduct. Finally, f-TLC analysis of patient samples with BA18 gave improved BA18-adduct intensities compared to the original BA-adduct. Conclusion Twenty-six commercially available boronic acids were investigated as alternatives to BA, used in the f-TLC analysis for the diagnosis of BU. Three (3) of them BA15, BA18, and BA21 gave superior fuorescence band intensity profles. They gave profles that were easier to interpret after the myco-boronic acid adduct formation and in experi ments with clinical samples from patients with BA18 the best. BA18, therefore, has been identifed as a potential alternative to BA and could provide a solution to the challenge of background interference of co-extracted human tissue lipids from clinical samples currently associated with the use of BA.
Aminoacyl chain translocation catalysed by a type II thioesterase domain in an unusual non-ribosomal peptide synthetase
(NATURE COMMUNICATIONS, 2022) Wang, S.; Brittain, W.D.G.; Zhang, Q.; Lu, Z.; Tong, M.H.; Wu, K.; Kyeremeh, K.; Jenner, M.; Yu, Y.; Cobb, S.L.; Deng, H.
Non-Ribosomal Peptide Synthetases (NRPSs) assemble a diverse range of natural products with important applications in both medicine and agriculture. They consist of several multienzyme subunits that must interact with each other in a highly controlled manner to facilitate efficient chain transfer, thus ensuring biosynthetic fidelity. Several mechanisms for chain transfer are known for NRPSs, promoting structural diversity. Herein, we report the first biochemically characterized example of a type II thioesterase (TEII) domain capable of catalysing aminoacyl chain transfer between thiolation (T) domains on two separate NRPS subunits responsible for installation of a dehydrobutyrine moiety. Biochemical dissection of this process reveals the central role of the TEII-catalysed chain translocation event and expands the enzymatic scope of TEII domains beyond canonical (amino)acyl chain hydrolysis. The apparent co-evolution of the TEII domain with the NRPS subunits highlights a unique feature of this enzymatic cassette, which will undoubtedly find utility in biosynthetic engineering efforts.
Amphibole as a witness of chromitite formation and fluid metasomatism in ophiolites
(2022) Pan, Q.; Xiao, Y.; Su, B.; Liu, X.; Robinson, P.T.; Uysal, I.
Here we present new occurrences of amphibole in a suite of chromitites, dunites, and harzburgites from the mantle sequence of the Lycian ophiolite in the Tauride Belt, southwest Turkey. The amphibole occurs both as interstitial grains among the major constituent minerals and as inclusions in chromite grains. The interstitial amphibole shows generally decreasing trends in Na2O and Al2O3 contents from the chromitites (0.14–1.54 wt% and 0.04–6.67 wt%, respectively) and the dunites (0.09–2.37 wt%; 0.12–11.9 wt%) to the host harzburgites (<0.61 wt%; 0.02–5.41 wt%). Amphibole inclusions in chromite of the amphibole-bearing harzburgites are poorer in Al2O3 (1.12–8.86 wt%), CaO (8.47–13.2 wt%), and Na2O (b.d.l.–1.38 wt%) than their counterparts in the amphibole-bearing chromitites (Al2O3 = 6.13–10.0 wt%; CaO = 12.1–12.9 wt%; Na2O = 1.11–1.91 wt%). Estimated crystallization temperatures for the interstitial amphibole grains and amphibole inclusions range from 706 to 974 °C, with the higher values in the latter. A comparison of amphibole inclusions in chromite with interstitial grains provides direct evidence for the involvement of water in chromitite formation and the presence of hydrous melt/fluid metasomatism in the peridotites during initial subduction of Neo-Tethyan oceanic lithosphere. The hydrous melts/fluids were released from the chromitites after being collected on chromite surfaces during crystallization. Different fluid/wall rock ratios are thought to have controlled the crystallization and composition of the Lycian amphibole and the extent of modification of the chromite and pyroxene grains in the peridotites. Considering the wide distribution of podiform chromitites in this ophiolite, the link between chromitite formation and melt/fluid metasomatism defined in our study may be applicable to other ophiolites worldwide.
Analysis and Implementation of Optimization Techniques for Facial Recognition
(Hindawi, 2021) Appati, J.K.; Abu, H.; Owusu, E.; Darkwah, K.
Amidst the wide spectrum of recognition methods proposed, there is still the challenge of these algorithms not yielding optimal accuracy against illumination, pose, and facial expression. In recent years, considerable attention has been on the use of swarm intelligence methods to help resolve some of these persistent issues. In this study, the principal component analysis (PCA) method with the inherent property of dimensionality reduction was adopted for feature selection. +e resultant features were optimized using the particle swarm optimization (PSO) algorithm. For the purpose of performance comparison, the resultant features were also optimized with the genetic algorithm (GA) and the artificial bee colony (ABC). +e optimized features were used for the recognition using Euclidean distance (EUD), K-nearest neighbor (KNN), and the support vector machine (SVM) as classifiers. Experimental results of these hybrid models on the ORL dataset reveal an accuracy of 99.25% for PSO and KNN, followed by ABC with 93.72% and GA with 87.50%. On the central, an experimentation of the PSO, GA, and ABC on the YaleB dataset results in 100% accuracy demonstrating their efficiencies over the state-of-the art methods.
Analysis of Exchange Rates as Time-Inhomogeneous Markov Chain with Finite States
(Journal of Applied Mathematics, 2022) Mettle, F.O.; Boateng, L.P.; Quaye, E.N.B.; Aidoo, E.K.; Seidu, I.
Irrespective of whether the test for homogeneity is significant or not, most researchers assume time-homogeneity in analysing Markov chains due to scanty literature on the analysis of time-inhomogeneous Markov chains. Based on the assumption that, for each point in time in the future, a stochastic process will be subjected to a randomly selected transition matrix from an ergodic set of transition matrices the process was subjected to in the recent past, a methodology was proposed for analysing the long-run behaviours of time-inhomogeneous Markov chains. The proposed model was implemented to historical data consisting of the exchange rate of cedi-dollar, cedi-pound, and cedi-euro spanning over 6 years (January 2012 to December 2017). The results show that under certain “closeness” conditions, the long-run behaviours of the time-inhomogeneous case are almost identical to those of the time-homogeneous case. The paper asserted that even if the Markov chain exhibit time-inhomogeneity, analysing the Markov chain under the assumption of time-homogeneity is a step in the right direction under certain “closeness” conditions; otherwise, the proposed method is recommended. It was also found that investing in dollars yields better returns than the other currencies in Ghana.
Analysis of groundwater quality using multivariate and spatial analyses in the Keta basin, Ghana
(Journal of African Earth Sciences, 2010-09) Yidana, S.M.; Banoeng-Yakubo, B.; Akabzaa, T.M.
A holistic assessment of the quality of groundwater from the shallow unconfined aquifers of the Keta strip of the Keta basin has been conducted using multivariate statistical and spatial analyses. A groundwater classification scheme has been developed for groundwater in the area using a robust water quality index (WQI) modified for the case of the Keta basin. On the basis of the WQI so computed, groundwater in the area has been spatially classified into 'good', 'fair', and 'marginal' water types using ordinary kriging developed from a well fitted linear semivariogram function. This study finds that the salinity of groundwater in the basin is largely attributed to mineral weathering and seawater intrusion. Groundwater is stable within kaolinite and Na-smectite field, suggesting the predominance of Na-rich silicate minerals over the high temperature Ca-rich minerals. There are localized influences of domestic waste discharge and agricultural activities on the hydrochemistry of groundwater in the area. Where these effects are high, high nitrate and fluoride concentrations have been noted. Four groundwater clusters have also been distinguished: clusters 1 and 4 are low salinity Ca-HCO3 waters distinguished by differences in pH, whereas clusters 2 and 3 represent high and intermediate salinity Na-Cl waters respectively. This study further finds that clusters 1 and 4 present the best water types for irrigation purposes in the Keta basin. On account of high salinity, cluster 2 members are not suitable for irrigation of any crop in the basin. Sodium adsorption ratio (SAR) appears to display weak seasonal variations due to the influence of seawater intrusion, whose effects vary with the level of the water table relative to sea level. During dry seasons when the water table is low, saline water intrusion elevates the content of sodium in groundwater. This is reflected in the SAR values in some of the wells sampled. © 2010 Elsevier Ltd.
Analysis of groundwater quality using water quality index and conventional graphical methods: The Volta region, Ghana
(Environmental Earth Sciences, 2009-12) Banoeng-Yakubo, B.; Yidana, S.M.; Emmanuel, N.; Akabzaa, T.; Asiedu, D.
Conventional graphical and statistical methods were used with water quality indices to characterize the hydrochemistry of groundwater from the northern part of the Volta region of Ghana. The objective was to determine the processes that affect the hydrochemistry and the variation of these processes in space among the three main geological terrains: the Buem formation, Voltaian System and the Togo series that underlie the area, and to determine the suitability of groundwater from the area for drinking purposes. The Q-mode cluster analysis reveals three main water groups. The groups established from the Q-mode HCA appear to indicate different degrees of weathering which could further indicate varying levels of fracturing aquifer hydraulic properties. R-mode HCA and factor analysis (using varimax rotation and Kaiser Criterion) were then applied to determine the significant sources of variation in the hydrochemistry. This study finds that groundwater hydrochemistry in the area is controlled by the weathering of silicate and carbonate minerals, as well as the chemistry of infiltrating precipitation. Mineral activity diagrams for the CaO-Na2O-Al2O3-SiO2-H2O and CaO-MgO-Al2O3-SiO2-H2O systems plotted for the area indicate stability in the smectite field and attribute hydrochemistry to the weathering of silicate minerals. Silicate mineral weathering and the effects of precipitation appear to be pervasive among all the three main geological terrains, whereas carbonate weathering is localized among the Voltaian aquifers. Cation exchange does not appear to play a significant role in the hydrochemistry but mild Water quality indices (WQI) were calculated for the samples using the concentrations of Na+, Ca2+, Mg2+, Cl-, NO3 -, F-, and EC at the various sample locations. The WQI values indicate that groundwater from the study area is of excellent quality for drinking purposes. WQI values from groundwater samples are averagely higher than samples taken from surface water sources in the area. This implies that geology has had an impact on the WQI of groundwater in the area. © Springer-Verlag 2009.

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