ghanaopendata/ghanaian-research-english huggingface dataset:
Matrix effects on flavour volatiles release in dark chocolates varying in particle size distribution and fat content using GC–mass spectrometry and GC–olfactometry

Influences of matrix particle size distribution (PSD) (18, 25, 35 and 50 μm) and fat content (25%, 30% and 35%) on flavour release of dark chocolate volatiles were quantified by static headspace gas chromatography using GC–MS. Sixty-eight (68) flavour compounds were identified, comprising alcohols, aldehydes, esters, ketones, furans, pyrans, pyrazines, pyridines, pyroles, phenols, pyrones and thiozoles. From GC–olfactometry, 2-methylpropanal, 2-methylbutanal and 3-methylbutanal had chocolate notes. With cocoa/roasted/nutty notes were trimethyl-, tetramethyl-, 2,3-dimethyl-, 2,5-dimethyl-, 3(or 2),5- dimethyl-2(or 3)-ethyl- and 3,5(or 6)-diethyl-2-methylpyrazine and furfuralpyrrole. Compounds with fruity/floral notes included 3,7-dimethyl-1,6-octadien-3-ol and 5-ethenyltetrahydro-R,R,5-trimethyl- cis-2-furanmethanol. Caramel-like, sweet and honey notes were conferred by 2-phenylethanol, phenyl- acetaldehyde, 2-phenylethylacetate, 2,3,5-trimethyl-6-ethylpyrazine, 2-carboxaldehyde-1H-pyrrole, furancarboxaldehyde, furfuryl alcohol and 2,5-dimethyl-4-hydroxy-3(2H)furanone. There were direct relationships of fat content with 3-methylbutanal and branched pyrazines but inverse ones with 2-phen- ylethanol, furfuryl alcohol, methylpyrazine, phenylacetaldehyde, 2, 3, 5-trimethyl-6-ethylpyrazine and 2- carboxaldehyde-1-H-pyrrole. Particle size influenced higher alcohol, aldehyde, ester, ketone and pyrazine concentrations at all fat contents. A multivariate product space suggested flavour effects of the interacting factors.

Source: UG
Mature liver stages of cloned plasmodium falciparum share epitopes with proteins from sporozoites and asexual blood stages

The liver merozoites of malaria parasites are of paramount importance, as they initiate the parasite invasion of red blood cells and start the cycle associated with the clinical features of malaria. Investigating liver merozoite antigen is difficult because of the lack of a rodent model of human malaria. In addition, only a low proportion of cells are obtained in vivo, the parasites from Cebus and Aotus monkeys are immature, and in-vitro experiments with liver cells are often confounded by contamination with the natural mosquito flora copurified with the sporozoites used for seeding the liver cultures. In our study, mature liver schizonts were shown to possess many of the antigenic determinants recognized by MoAbs and sera specific for defined sporozoite and blood-stage antigens. We employed an immunofluorescence procedure based on evaluating parasites in cryosections prepared from infected chimpanzee liver. Sufficient numbers of sectioned parasites were evaluated with each antibody, to assure the reproducibility of the results, and the fixation procedure used was sufficiently non-destructive to parasite antigens so that clear differences between reactions of specific antibodies and negative controls were observed. Our evidence for sharing of epitopes by liver merozoites and sporozoites or by liver merozoites and asexual blood-stage parasites raises the possibility that immune responses elicited against sporozoites or asexual stage antigens being considered as vaccine candidates may also act against this important, little-studied stage of the parasite.

Source: UG
Maxillofacial and concomitant injuries in multiple injured patients at Korle Bu Teaching Hospital, Ghana

BACKGROUND: Patients with maxillofacial injuries may sustain concomitant injuries. The presentation of other injuries may be the initial focus of attention of the primary attending surgeon who may miss the maxillofacial injuries to the detriment of the patient.OBJECTIVE: To determine the incidence of injuries associated with maxillofacial injuries at Korle Bu Teaching Hospital (KBTH) from January 2009 to December 2010.METHODS: A prospective study was carried out on patients who were referred to the Maxillofacial Unit of the University of Ghana Dental School and KBTH over the two years with maxillofacial injuries. Their age, sex, type of injury in the maxillofacial region, its aetiology and concomitant injuries were charted. The data was analysed using SPSS 16.0 software.RESULTS: Two hundred and fifty eight (258) patients were seen of which 67 (26.0%) had concomitant injuries. The average age was 29.1 years. The peak incidence was in the age group 21-30 (N=73, 28.3%). 74% were male and 26.0% female. The commonest cause of injury was road traffic accident (RTA) (N=142;55.0%). 52.7% (N=136) of the patients had injuries of the maxillofacial region. 26.7% (N=69) had mandibular fractures, 19.4% (N=50) had middle third fractures and 8.1% (N=21) had fractures of both. Concomitant injuries were mainly orthopaedic (N=31;12%) and the head and spinal region (N=29;11.2%).CONCLUSION: A significant number of patients who suffer maxillofacial injuries also sustain injuries of other parts of the body at KBTH. Prompt multidisciplinary management may contribute to improved outcomes.

Source: UG
Maximal function and carleson measures in the theory of Békollé–Bonami weights

Let ω be a Békollé–Bonami weight. We give a complete characterization of the positive measures µ such that (Equation presented) where Mω is the weighted Hardy–Littlewood maximal function on the upper half-plane H and 1 ≤ p, q < ∞. © Instytut Matematyczny PAN, 2016.

Source: UG
Maximizing efficiency of genomic selection in CIMMYT’s tropical maize breeding program

The current strategy for large-scale implementation of genomic selection (GS) at the International Maize and Wheat Improvement Center (CIMMYT) global maize breeding program has been to train models using information from full-sibs in a “test-half-predict-half approach.” Although effective, this approach has limitations, as it requires large full-sib populations and limits the ability to shorten variety testing and breeding cycle times. The primary objective of this study was to identify optimal experimental and training set designs to maximize prediction accuracy of GS in CIMMYT’s maize breeding programs. Training set (TS) design strategies were evaluated to determine the most efficient use of phenotypic data collected on relatives for genomic prediction (GP) using datasets containing 849 (DS1) and 1389 (DS2) DH-lines evaluated as testcrosses in 2017 and 2018, respectively. Our results show there is merit in the use of multiple bi-parental populations as TS when selected using algorithms to maximize relatedness between the training and prediction sets. In a breeding program where relevant past breeding information is not readily available, the phenotyping expenditure can be spread across connected bi-parental populations by phenotyping only a small number of lines from each population. This significantly improves prediction accuracy compared to within-population prediction, especially when the TS for within full-sib prediction is small. Finally, we demonstrate that prediction accuracy in either sparse testing or “test-half-predict-half” can further be improved by optimizing which lines are planted for phenotyping and which lines are to be only genotyped for advancement based on GP

Source: UG
Maximizing microscopy as a diagnostic tool in peripheral health centres of BU endemic areas in Ghana

Background: Buruli ulcer (BU) disease, a skin condition caused by Mycobacterium ulcerans (M. ulcerans) is endemic in remote rural areas. Disease diagnosis on clinical basis alone can be misleading, requiring definitive diagnosis based on laboratory tests. Resource constraints in BU endemic areas make microscopy for the detection of acid fast bacilli (AFB) an important and useful method. It is rapid, user-friendly, convenient and cheap. Despite its usefulness, its performance is relatively low. This study investigated modifications of the current method aimed at improving its performance. Forty (IS) 2404 polymerase chain reactions (PCR) positive BU samples were processed by eight physical (centrifugation and overnight sedimentation) and chemical (phenol ammonium sulphate and sodium hypochlorite) modifications of the current direct method. Assessments were based on standard AFB evaluation coupled with in house criteria; positivity (P), clarity and contrast (C) release of bacilli from specimen (R). Overall AFB positivity rate was 64% (409/640). Each protocol had 80 smears. The percentage positivity (P) for the conventional method was 58% (46/80) smears. The highest positivity rate of 57/80 (%) was by protocol 7 (5% phenol in 4% ammonium sulphate (PhAS) and concentrated by overnight gravitational sedimentation). The least positivity rate at 35% (28/80) was by protocol 1 (smears from direct application of swab tips). The differences in performance between the two chemical tested; 5% phenol in 4% ammonium sulphate (PhAS) and 3.5% NaHOCl was significant (p<. 0.05). The differences between the two physical methods were however not significant (p>. 0.05). This study concluded that BU samples treated with a solution of 5% phenol in 4% ammonium sulphate and concentrated by either centrifugation or overnight sedimentation is useful for maximizing AFB detection by bright field microscopy. This can be useful in rural health facilities with resource constraints. © 2015 Asian-African Society for Mycobacteriology.

Source: UG
Maximizing the Benefits and Minimizing the Risks from the Contribution of “Outsiders” to the Development of Services for Persons with Communication Disability in Sub-Saharan Africa

Abstract Background: Services for persons with communication disability are scarce in many low- and middle-income countries, including most countries in sub-Saharan Africa (SSA). Speech–language therapists (SLTs) from high-income countries have long been involved in supporting service developments in SSA. This has often been through short-, medium-, or long-term posts (e.g., through individuals being employed by nongovernmental organizations, working as volunteer expatriates, or being locally employed), delivering direct services to clients and their families, training other professionals, and/or educating SLTs. Consultants working on a short-term basis advise universities and government ministries on the establishment of speech–language therapy (SLT) services and educational programs. There is some professional literature guiding SLTs from high-income countries on how to prepare for such work, but little has been written about what low- and middle-income country-based professionals, clients, or their families think about or would like from outsider SLTs. Furthermore, there is little or no evidence indicating what makes outsider support successful. Methodology: Two SLTs, with a combined experience of over 40 years (a Ghanaian SLT and an SLT based in the UK with considerable experience working in low- and middle-income countries), present a written dialogue about insiders and outsiders working together in low- and middle-income country contexts. Four fictitious case examples of outsider-insider experiences of collaboration are then given, illustrating points made in the dialogue. The third author then reports on part of her PhD study of an SLT insider-outsider collaboration in Uganda. Results/Discussion: Learning from all three sections and the previously published literature is then used to generate recommendations for maximizing the benefits of insider-outsider SLT collaborations in low- and middle-income countries.

Source: UG
Maximum efforts in contests with asymmetric valuations

Efforts may be reduced when players with different valuations participate in a contest. This paper considers the problem of designing a contest to elicit maximum aggregate effort from players with asymmetric valuations. Optimal designs for different classes of contest technologies are computed and characterized. A value weighted contest is optimal in the concave case. In the unconstrained case, the optimal contest is equivalent to a first price all-pay auction with a reserve price. The optimal design discounts the effort of the high valuation player in order to induce him to compete vigorously. © 2004 Elsevier B.V. All rights reserved.

Source: UG
“Maximum Penalized Likelihood Approach for Current Status Data with Informative Censoring Based on Frailties”

Current status data arise in many fields including epidemiological surveys and animal carcinogenicity experiments. By current status data we mean each subject in a study is observed only once at a certain time to ascertain whether or not the event of interest has occurred. This means that for current status data, the event (failure) time is not exactly observed but only known to be smaller or greater than the observation (censoring) time. The standard assumption in survival data analysis is that the observation time is non-informative, that is, the observation time is unrelated to the failure time. However, this assumption may not be valid in some circumstances, especially if the subject is lost-to-follow-up before the study ends. The examination time for such a subject can potentially be linked to the failure time and hence the examination time will be said to be informatively censored. To avoid severely misleading inferences that can result from failing to account for informative censoring, shared frailty models have been proposed in literature to account for informative censoring with current status data. The most commonly used estimation procedure is the Expectation-Maximization (EM) algorithm, but this approach yield discrete estimation of the distribution and possibly a negative hazard estimate. Thus the EM algorithm might not only be able to provide an accurate trend of how the baseline hazard estimates are changing over time, but also affect the accuracy of the estimated parameters. The goal of this thesis therefore, is to develop Maximum Penalized Likelihood (MPL) methods for current status data with informative censoring based on gamma-shared frailty assumption. We intend to show how the MPL procedure can be employed to simultaneously estimate the regression parameters and the smooth baseline continuous hazard functions for Proportional Hazards Model, Semiparametric transformation Model and Clustered data under the proportional hazards model. The variances and the asymptotic properties of these MPL estimators will be studied. Simulations studies will also be conducted to ascertain the performance of our proposed MPL methods. Comparisons will also be made with some of the existing EM methods. For illustrative purposes, we will apply our methods to the data set on rodent tumorigenicity experiment example provided by National Toxicology Program (1998)

Source: UG
Maximum Power Point Tracking in Power System Control Using Reservoir Computing

This article deals with an innovative approach to maximum power point tracking (MPPT) in power systems using the reservoir computing (RC) technique. Even though extensive studies have been conducted on MPPT to improve solar PV systems efficiency, there is still considerable room for improvement. The methodology consisted in modeling and programming with MATLAB software, the reservoir computing paradigm, which is a form of recurrent neural network. The performances of the RC algorithm was compared to two well-known methods of maximum power point tracking: perturbed and observed (P&O) and artificial neural networks (ANN). Power, voltage, current, and temperature characteristics were assessed, plotted, and compared. It was established that the RC-MPPT provided better performances than P&O-MPPT and ANN-MPPT from the perspective of training and testing MSE, rapid convergence, and accuracy of tracking. These findings suggest the need for rapid implementation of the proposed RC-MPPT algorithm on microcontroller chips for their widespread use and adoption globally

Source: UG
A maximum principle for controlled stochastic factor model

In the present work, we consider an optimal control for a three-factor stochastic factor model. We assume that one of the factors is not observed and use classical filtering technique to transform the partial observation control problem for stochastic differential equation (SDE) to a full observation control problem for stochastic partial differential equation (SPDE). We then give a sufficient maximum principle for a system of controlled SDEs and degenerate SPDE. We also derive an equivalent stochastic maximum principle. We apply the obtained results to study a pricing and hedging problem of a commodity derivative at a given location, when the convenience yield is not observable.

Source: UG
The maximum principles for partially observed risk-sensitive optimal controls of Markov regime-switching jump-diffusion system

This paper studies partially observed risk-sensitive optimal control problems with correlated noises between the system and the observation. It is assumed that the state process is governed by a continuous-time Markov regime-switching jump-diffusion process and the cost functional is of an exponential-of-integral type. By virtue of a classical spike variational approach, we obtain two general maximum principles for the aforementioned problems. Moreover, under certain convexity assumptions on both the control domain and the Hamiltonian, we give a sufficient condition for the optimality. For illustration, a linear-quadratic risk-sensitive control problem is proposed and solved using the main results. As a natural deduction, a fully observed risk-sensitive maximum principle is also obtained and applied to study a risk-sensitive portfolio optimization problem. Closed-form expressions for both the optimal portfolio and the corresponding optimal cost functional are obtained. © 2018 Taylor & Francis Group, LLC

Source: UG
Maximum Principles of Markov Regime-Switching Forward–Backward Stochastic Differential Equations with Jumps and Partial Information

This paper presents three versions of maximum principle for a stochastic optimal control problem of Markov regime-switching forward–backward stochastic differential equations with jumps. First, a general sufficient maximum principle for optimal control for a system, driven by a Markov regime-switching forward–backward jump–diffusion model, is developed. In the regime-switching case, it might happen that the associated Hamiltonian is not concave and hence the classical maximum principle cannot be applied. Hence, an equivalent type maximum principle is introduced and proved. In view of solving an optimal control problem when the Hamiltonian is not concave, we use a third approach based on Malliavin calculus to derive a general stochastic maximum principle. This approach also enables us to derive an explicit solution of a control problem when the concavity assumption is not satisfied. In addition, the framework we propose allows us to apply our results to solve a recursive utility maximization problem. © 2017, The Author(s).

Source: UG
McClusky’s Theory of Margin and its implications on adult learners in higher education institutions

This paper draws on McClusky’s Theory of Margin which contains elements of life transitions. Adulthood period is one of growth, change and integration of balance between energy needed to engage in learning. There is an increasing participation of adult learners in higher education institutions. This paper finds out whether learners complete degree programmes on time, or otherwise by examining responsibilities, resources required for learning, challenges faced and margin available to learners. This qualitative case study used Accra Learning Centre and adopted homogenous, random and sequential purposive sampling procedures. Fifteen participants participated in the in-depth interview conducted. Thematic, narrative and interpretivist approaches were adapted in analysing data collected. It emerged that adult learners have limitless potentials to learn, yet poor time management, work commitments and financial challenges made it difficult to complete programmes on time. Engagement in multiplicities of responsibilities consumed adult learners’ time and energy to learn. The findings made are discussed and recommendations are made.

Source: UG
MCP1 haplotypes associated with protection from pulmonary tuberculosis

Abstract Background The monocyte chemoattractant protein 1 (MCP-1) is involved in the recruitment of lymphocytes and monocytes and their migration to sites of injury and cellular immune reactions. In a Ghanaian tuberculosis (TB) case-control study group, associations of the MCP1 -362C and the MCP1 -2581G alleles with resistance to TB were recently described. The latter association was in contrast to genetic effects previously described in study groups originating from Mexico, Korea, Peru and Zambia. This inconsistency prompted us to further investigate the MCP1 gene in order to determine causal variants or haplotypes genetically and functionally. Results A 14 base-pair deletion in the first MCP1 intron, int1del554-567, was strongly associated with protection against pulmonary TB (OR = 0.84, CI 0.77-0.92, Pcorrected = 0.00098). Compared to the wildtype combination, a haplotype comprising the -2581G and -362C promoter variants and the intronic deletion conferred an even stronger protection than did the -362C variant alone (OR = 0.78, CI 0.69-0.87, Pnominal = 0.00002; adjusted Pglobal = 0.0028). In a luciferase reporter gene assay, a significant reduction of luciferase gene expression was observed in the two constructs carrying the MCP1 mutations -2581 A or G plus the combination -362C and int1del554-567 compared to the wildtype haplotype (P = 0.02 and P = 0.006). The associated variants, in particular the haplotypes composed of these latter variants, result in decreased MCP-1 expression and a decreased risk of pulmonary TB. Conclusions In addition to the results of the previous study of the Ghanaian TB case-control sample, we have now identified the haplotype combination -2581G/-362C/int1del554-567 that mediates considerably stronger protection than does the MCP1 -362C allele alone (OR = 0.78, CI 0.69-0.87 vs OR = 0.83, CI 0.76-0.91). Our findings in both the genetic analysis and the reporter gene study further indicate a largely negligible role of the variant at position -2581 in the Ghanaian population studied.

Source: UG