Federal University of Technology

On the Internet, where the number of choices is overwhelming, there is need to filter, prioritize and efficiently deliver relevant information in order to alleviate the problem of information overload, which has created a potential problem to many Internet users. Recommender systems solve this problem by searching through large volume of dynamically generated information to provide users with personalized content and services. This paper explores the different characteristics and potentials of different prediction techniques in recommendation systems in order to serve as a compass for research and practice in the field of recommendation systems.

Essential oils are complex mixtures of hydrocarbons and their oxygenated derivatives arising from two different isoprenoid pathways. Essential oils are produced by glandular trichomes and other secretory structures, specialized secretory tissues mainly diffused onto the surface of plant organs, particularly flowers and leaves, thus exerting a pivotal ecological role in plant. In addition, essential oils have been used, since ancient times, in many different traditional healing systems all over the world, because of their biological activities. Many preclinical studies have documented antimicrobial, antioxidant, anti-inflammatory and anticancer activities of essential oils in a number of cell and animal models, also elucidating their mechanism of action and pharmacological targets, though the paucity of in human studies limits the potential of essential oils as effective and safe phytotherapeutic agents. More well-designed clinical trials are needed in order to ascertain the real efficacy and safety of these plant products.

Aluminium hybrid composites are a new generation of metal matrix composites that have the potentials of satisfying the recent demands of advanced engineering applications. These demands are met due to improved mechanical properties, amenability to conventional processing technique and possibility of reducing production cost of aluminium hybrid composites. The performance of these materials is mostly dependent on selecting the right combination of reinforcing materials since some of the processing parameters are associated with the reinforcing particulates. A few combinations of reinforcing particulates have been conceptualized in the design of aluminium hybrid composites. This paper attempts to review the different combination of reinforcing materials used in the processing of hybrid aluminium matrix composites and how it affects the mechanical, corrosion and wear performance of the materials. The major techniques for fabricating these materials are briefly discussed and research areas for further improvement on aluminium hybrid composites are suggested.

Since 1950 to 2018, about 6.3 billion tonnes of plastics have been produced worldwide, 9% and 12% of which have been recycled and incinerated, respectively. Human population increase and consistent demand for plastics and plastic products are responsible for continuous increase in the production of plastics, generation of plastic waste and its accompanied environmental pollution. We have reviewed in this paper, the most relevant literatures on the different types of plastics in production, the hazardous chemical constituents, prevailing disposal methods and the detrimental effects of these constituents to air, water, soil, organisms and human health viz-a-viz the different disposal methods. Papers that reported environmental and public health effects of plastic constituents but not plastics directly were also reviewed. Varieties of plastics used in the production of many consumable products including medical devices, food packaging and water bottles contain toxic chemicals like phthalates, heavy metals, bisphenol A. brominated flame retardants, nonylphenol, polychlorinated biphenylethers, dichlorodiphenyldichloroethylene, phenanthrene etc.

Financial fraud is an ever growing menace with far consequences in the financial industry. Data mining had played an imperative role in the detection of credit card fraud in online transactions. Credit card fraud detection, which is a data mining problem, becomes challenging due to two major reasons - first, the profiles of normal and fraudulent behaviours change constantly and secondly, credit card fraud data sets are highly skewed. The performance of fraud detection in credit card transactions is greatly affected by the sampling approach on dataset, selection of variables and detection technique(s) used. This paper investigates the performance of naïve bayes, k-nearest neighbor and logistic regression on highly skewed credit card fraud data. Dataset of credit card transactions is sourced from European cardholders containing 284,807 transactions. A hybrid technique of under-sampling and oversampling is carried out on the skewed data. The three techniques are applied on the raw and preprocessed data. The work is implemented in Python. The performance of the techniques is evaluated based on accuracy, sensitivity, specificity, precision, Matthews correlation coefficient and balanced classification rate. The results shows of optimal accuracy for naïve bayes, k-nearest neighbor and logistic regression classifiers are 97.92%, 97.69% and 54.86% respectively. The comparative results show that k-nearest neighbour performs better than naïve bayes and logistic regression techniques.

The upsurge in the volume of unwanted emails called spam has created an intense need for the development of more dependable and robust antispam filters. Machine learning methods of recent are being used to successfully detect and filter spam emails. We present a systematic review of some of the popular machine learning based email spam filtering approaches. Our review covers survey of the important concepts, attempts, efficiency, and the research trend in spam filtering. The preliminary discussion in the study background examines the applications of machine learning techniques to the email spam filtering process of the leading internet service providers (ISPs) like Gmail, Yahoo and Outlook emails spam filters. Discussion on general email spam filtering process, and the various efforts by different researchers in combating spam through the use machine learning techniques was done. Our review compares the strengths and drawbacks of existing machine learning approaches and the open research problems in spam filtering. We recommended deep leaning and deep adversarial learning as the future techniques that can effectively handle the menace of spam emails.

The high species richness of tropical forests has long been recognized, yet there remains substantial uncertainty regarding the actual number of tropical tree species. Using a pantropical tree inventory database from closed canopy forests, consisting of 657,630 trees belonging to 11,371 species, we use a fitted value of Fisher's alpha and an approximate pantropical stem total to estimate the minimum number of tropical forest tree species to fall between ∼ 40,000 and ∼ 53,000, i.e., at the high end of previous estimates. Contrary to common assumption, the Indo-Pacific region was found to be as species-rich as the Neotropics, with both regions having a minimum of ∼ 19,000-25,000 tree species. Continental Africa is relatively depauperate with a minimum of ∼ 4,500-6,000 tree species. Very few species are shared among the African, American, and the Indo-Pacific regions. We provide a methodological framework for estimating species richness in trees that may help refine species richness estimates of tree-dependent taxa.

The simplicity, transparency, reliability, high efficiency and robust nature of PID controllers are some of the reasons for their high popularity and acceptance for control in process industries around the world today. Tuning of PID control parameters has been a field of active research and still is. The primary objectives of PID control parameters are to achieve minimal overshoot in steady state response and lesser settling time. With exception of two popular conventional tuning strategies (Ziegler Nichols closed loop oscillation and Cohen-Coon's process reaction curve) several other methods have been employed for tuning. This work accords a thorough review of state-of-the-art and classical strategies for PID controller parameters tuning using metaheuristic algorithms. Methods appraised are categorized into classical and metaheuristic optimization methods for PID parameters tuning purposes. Details of some metaheuristic algorithms, methods of application, equations and implementation flowcharts/algorithms are presented. Some open problems for future research are also presented. The major goal of this work is to proffer a comprehensive reference source for researchers and scholars working on PID controllers.

BACKGROUND: Chlorogenic acid is a major phenolic compound that forms a substantial part of plant foods and is an ester of caffeic acid and quinic acid. However, the effect of the structures of both chlorogenic and caffeic acids on their antioxidant and antidiabetic potentials have not been fully understood. Thus, this study sought to investigate and compare the interaction of caffeic acid and chlorogenic acid with α-amylase and α-glucosidase (key enzymes linked to type 2 diabetes) activities in vitro. METHODS: The inhibitory effect of the phenolic acids on α-amylase and α-glucosidase activities was evaluated. Thereafter, their antioxidant activities as typified by their 1,1-diphenyl-2 picrylhydrazyl radical scavenging ability and ferric reducing antioxidant properties were determined. RESULTS: The results revealed that both phenolic acids inhibited α-amylase and α-glucosidase activities in a dose-dependent manner (2-8 μg/mL). However, caffeic acid had a significantly (p<0.05) higher inhibitory effect on α-amylase [IC50 (concentration of sample causing 50% enzyme inhibition)=3.68 μg/mL] and α-glucosidase (IC50=4.98 μg/mL) activities than chlorogenic acid (α-amylase IC50=9.10 μg/mL and α-glucosidase IC50=9.24 μg/mL). Furthermore, both phenolic acids exhibited high antioxidant properties, with caffeic acid showing higher effects. CONCLUSIONS: The esterification of caffeic acid with quinic acid, producing chlorogenic acid, reduces their ability to inhibit α-amylase and α-glucosidase activities. Thus, the inhibition of α-amylase and α-glucosidase activities by the phenolic acids could be part of the possible mechanism by which the phenolic acids exert their antidiabetic effects.

Right from the early days, polymer materials have been discovered as being beneficial for various applications but a poor understanding of these materials greatly handicapped their usage. However, with a change in this trend, polymer materials have gradually displaced other materials in most applications. In recent times, due to improved research and knowledge, polymer-based materials are the first choice materials for several applications and are now replacing other materials rapidly. More advanced materials from polymers are being developed daily as a substitute for other materials even in areas where polymers are considered not to be suitable in the time past. More recently, polymers have replaced metals and ceramics in applications like constructions, aerospace, automobiles, and medical. It is no doubt that this trend will continue due to the inherent properties of polymers and sustainability potential. Today, most of the limitations of polymers are being taken care of in the formulation of composite materials. Besides, the adaptation to positive environmental influence is being handled by scientists and researchers. Hence, this review reveals core areas of application of polymer-based composites and the significance of these materials to the advancement of humanity.

Enzymatic hydrolysate of African yam bean seed protein isolate was prepared by treatment with alcalase. The hydrolysate was further fractionated into peptide sizes of <1, 1-3, 3-5 and 5-10 kDa using membrane ultrafiltration. The protein hydrolysate (APH) and its membrane ultrafiltration fractions were assayed for in vitro antioxidant activities. The <1 kDa peptides exhibited significantly better (p < 0.05) ferric reducing power, diphenyl-1-picryhydradzyl (DPPH) and hydroxyl radical scavenging activities when compared to peptide fractions of higher molecular weights. The high activity of <1 kDa peptides in these antioxidant assay systems may be related to the high levels of total hydrophobic and aromatic amino acids. In comparison to glutathione (GSH), the APH and its membrane fractions had significantly higher (p < 0.05) ability to chelate metal ions. In contrast, GSH had significantly greater (p < 0.05) ferric reducing power and free radical scavenging activities than APH and its membrane fractions. The APH and its membrane fractions effectively inhibited lipid peroxidation, results that were concentration dependent. The activity of APH and its membrane fractions against linoleic acid oxidation was higher when compared to that of GSH but lower than that of butylated hydroxyl toluene (BHT). The results show potential use of APH and its membrane fractions as antioxidants in the management of oxidative stress-related metabolic disorders and in the prevention of lipid oxidation in food products.

Caffeic acid (CAA) and chlorogenic acid (CHA) are important members of hydroxycinnamic acid with natural antioxidant and cardio-protective properties. The present study aimed to determine the effect of CAA and CHA on systolic blood pressure, heart rates (HR) as well as on the activity of the angiotensin-1-converting enzyme (ACE), acetylcholinesterase (AChE), butrylcholinesterase (BChE) and arginase in cyclosporine-induced hypertensive rats. Experimental rats were distributed into 7 groups (n = 6): normotensive control rats; hypertensive rats (induced rats) as well as hypertensive- treated groups with captopril (10 mg/kg/day), CAA (10 and 15 mg/kg/day) and CHA (10 and 15 mg/kg/day), respectively. The experiment lasted for 7 days and the systolic blood pressure (SBP) and heart rates were recorded using tail-cuff method. Oral administration of captopril, caffeic acid and chlorogenic acid normalized hypertensive effect caused by cyclosporine administration. CAA and CHA significantly (P < 0.05) reduced SBP and HR, activity of ACE, AChE, BChE and arginase in the treated hypertensive rats compared with cyclosporine induced-hypertensive rats. Likewise, CAA and CHA improved nitric oxide (NO) bioavailability, increased catalase activity and reduced glutathione content while malondialdehyde (MDA) level was reduced compared with cyclosporine hypertensive rats. Findings from this study shows that CAA and CHA exhibited blood pressure lowering properties and reduced activities of key enzymes linked to the pathogenesis of hypertension in cyclosporine-induced rats. These might be some of the possible mechanisms of action by which their cardio-protective properties are exhibited.

Abstract Charcoal production, widespread in Ghana like in other W African countries, is a major driver of land‐cover change. Effects of charcoal production on soil physical, including hydrological, properties, were studied in the forest–savannah transition zone of Ghana. Core and composite samples from 12 randomly selected sites across the width of Kotokosu watershed were taken from 0–10 cm layer at charcoal‐site soils and adjacent field soils (control). These were used to determine saturated hydraulic conductivity ( K sat ), bulk density, total porosity, soil texture, and color. Infiltration rates, surface albedo, and soil‐surface temperature were also measured on both sites. The results showed that the saturated hydraulic conductivity of soils under charcoal kilns increased significantly ( p &lt; 0.01) from 6.1 ± 2.0 cm h –1 to 11.4 ± 5.0 cm h –1 , resulting to a relative increase of 88%. Soil color became darkened under charcoal kilns with hue, value, and chroma decreasing by 8%, 20%, and 20%, respectively. Bulk density on charcoal‐site soils reduced by 9% compared to adjacent field soils. Total porosity increased from 45.7% on adjacent field soils to 50.6% on earth kilns. Surface albedo reduced by 37% on charcoal‐site soils while soil‐surface temperature increased up to 4°C on average. Higher infiltration rates were measured on charcoal‐site soils, which suggest a possible decrease in overland flow and less erosion on those kiln sites.

Cellulose nanomaterials from plant fibre provide various potential applications (i.e., biomedical, automotive, packaging, etc.). The biomedical application of nanocellulose isolated from plant fibre, which is a carbohydrate-based source, is very viable in the 21st century. The essential characteristics of plant fibre-based nanocellulose, which include its molecular, tensile and mechanical properties, as well as its biodegradability potential, have been widely explored for functional materials in the preparation of aerogel. Plant cellulose nano fibre (CNF)-based aerogels are novel functional materials that have attracted remarkable interest. In recent years, CNF aerogel has been extensively used in the biomedical field due to its biocompatibility, renewability and biodegradability. The effective surface area of CNFs influences broad applications in biological and medical studies such as sustainable antibiotic delivery for wound healing, the preparation of scaffolds for tissue cultures, the development of drug delivery systems, biosensing and an antimicrobial film for wound healing. Many researchers have a growing interest in using CNF-based aerogels in the mentioned applications. The application of cellulose-based materials is widely reported in the literature. However, only a few studies discuss the potential of cellulose nanofibre aerogel in detail. The potential applications of CNF aerogel include composites, organic-inorganic hybrids, gels, foams, aerogels/xerogels, coatings and nano-paper, bioactive and wound dressing materials and bioconversion. The potential applications of CNF have rarely been a subject of extensive review. Thus, extensive studies to develop materials with cheaper and better properties, high prospects and effectiveness for many applications are the focus of the present work. The present review focuses on the evolution of aerogels via characterisation studies on the isolation of CNF-based aerogels. The study concludes with a description of the potential and challenges of developing sustainable materials for biomedical applications.

Mg and its alloys have continued to attract interest for several structural and super-sensitive applications because of their light weight and good combination of engineering properties. However for some of these applications, high plastic deformability is required to achieve desired component shapes and configurations; unfortunately, Mg and its alloys have low formability. Scientifically, the plastic behaviour of Mg and its alloys ranks among the most complex and difficult to reconcile in metallic material systems. But basically, the HCP crystal structure coupled with low stacking fault energies (SFE) are largely linked to the poor ductility exhibited by Mg alloys. These innate material characteristics have regrettably limited wide spread applicability of Mg and its alloys. Several research efforts aimed at exploring processing strategies to make these alloys more amenable for high formability – mediated engineering use have been reported and still ongoing. This paper reviews the structural metallurgy of Mg alloys and its influence on mechanical behaviour, specifically, plasticity characteristics. It also concisely presents various processing routes (Alloying, Traditional Forming and Severe Plastic Deformation (SPD)) which have been explored to enhance plastic deformability in Mg and its alloys. Grain refinement and homogenising of phases, reducing CRSS between slip modes, twinning suppression to activate non-basal slip, and weakening and randomisation of the basal texture were observed as the formability enhancing strategies explored in the reviewed processes. While identifying the limitations of these strategies, further areas to be explored for enhancing plasticity of Mg alloys are highlighted. Keywords: Mg alloys, HCP crystal structure, Basal texture, Severe plastic deformation, Formability

Abstract Climate change and anthropogenic pressures are widely expected to exacerbate coastal hazards such as episodic coastal flooding. This study presents global-scale potential coastal overtopping estimates, which account for not only the effects of sea level rise and storm surge, but also for wave runup at exposed open coasts. Here we find that the globally aggregated annual overtopping hours have increased by almost 50% over the last two decades. A first-pass future assessment indicates that globally aggregated annual overtopping hours will accelerate faster than the global mean sea-level rise itself, with a clearly discernible increase occurring around mid-century regardless of climate scenario. Under RCP 8.5, the globally aggregated annual overtopping hours by the end of the 21 st -century is projected to be up to 50 times larger compared to present-day. As sea level continues to rise, more regions around the world are projected to become exposed to coastal overtopping.

This review is devoted to the understanding of the recrystallization mechanisms and its role in the control of the microstructure in emerging metallic materials. Recrystallization is a very pervasive transformation phenomenon that is considered to be very important in efficient microstructure designs. Currently, there is hardly any work which has attempted to present a concise and systematic review of the recrystallization in emerging materials with a view to reconcile its manifestations with trends established from recrystallization studies in traditional alloys. This review aims to address this by first reviewing the fundamental and nascent recrystallization mechanism concepts and then analyzing their forms in emerging metallic materials, such as high strength steels, Ti- and Mg-based alloys, as well as high-entropy and shape-memory alloys. The reviews on these systems show that the classic recrystallization concepts are still relevant for explaining the recrystallization behavior and by extension to the microstructure development in the materials. However, in some instances, structural factors exclusive to these materials influenced the driving force and recrystallization behavior yielding outcomes sufficiently distinct from that observed in traditional alloys. Basically, deformation processing and material factors such as stress accumulation, inhomogeneous strain distribution, stored energy, available slip systems, phase composition, microstructural variability, initial grain size, texture, stacking fault and lattice distortion energies, strain path, deformation temperature, and solute clustering and diffusion rates were at play in determining the recrystallization mechanisms and kinetics in these emerging metallic materials. Keywords: Recrystallization mechanisms, Microstructure, Deformation processing, Stored energy, Emerging metallic materials

The fabrication characteristics and mechanical behaviour of Al-Mg-Si alloy matrix composites reinforced with alumina (Al2O3) and rice husk ash (RHA, an agro-waste) was investigated. This was aimed at assessing the viability of developing high performance Al matrix composites at reduced cost. Al2O3 particulates added with 0, 2, 3, and 4 wt% RHA were utilized to prepare 10 wt% of the reinforcing phase with Al-Mg-Si alloy as matrix using two-step stir casting method. Density measurement, estimated percent porosity, tensile testing, micro-hardness measurement, optical microscopy, and SEM examination were used to characterize the composites produced. The results show that the less dense Al-Mg-Si/RHA/Al2O3 hybrid composites have estimated percent porosity levels as low as the single Al2O3 reinforced grade (< 2.3% porosity). The hardness of the hybrid composites decreases slightly with increase in RHA content with a maximum reduction of less than 11% observed for the Al-4 wt% RHA-6wt% Al2O3 composition (in comparison with the Al-10 wt% Al2O3 single reinforced composition). Tensile strength reductions of 8% and 13%, and specific strengths which were 3.56% and 7.7% lower were respectively observed for the 3 wt% and 4 wt% RHA containing hybrid composites. The specific strength, percent elongation and fracture toughness of the 2 wt% RHA containing hybrid composite was however, higher than that of the single Al2O3 reinforced and other hybrid composite compositions worked on. RHA thus has great promise to serve as a complementing reinforcement for the development of low cost-high performance aluminum hybrid composites.

In this narrative review, we have comprehensively reviewed the plant sources used as antiulcer agents. From traditional uses as herbal remedies, we have moved on to preclinical evidence, critically discussing the in vitro and in vivo studies focusing on plant extracts and even isolated phytochemicals with antiulcerogenic potential. A particular emphasis was also paid to Helicobacter pylori activity, with emphasis on involved mechanisms of action. Lastly, the issue of safety profile of these plant products has also been addressed.

Abstract Increase in industrial and anthropogenic activities leads to a decline in water quality. This necessitates the need for the removal of contaminants from industrial and domestic wastewater. Clay minerals are naturally abundant and non-toxic materials that found to be useful for remediation of emerging contaminants from wastewater. This review paper presents an insight into clay, the simplest material (in solgel techniques) for the synthesis of TiO 2 and ZnO, mechanisms of their reactions, analytical techniques used for characterizations, and their nanocomposites for wastewater treatment. Nanomaterials, such as nanoclay, titanium, and zinc oxide, have offered the opportunities of sequestering variety of pollutants in wastewater. TiO 2 and ZnO anchored on clay have been found to be good promising sequesters and have been explored for wastewater remediation via nanotechnology. This water treatment method includes adsorption/absorption, photocatalysis, and microbial disinfection. These nanocomposites provide more active surface sites and reduce the agglomeration of the nanoparticles, but leaching has been their shortcomings. To overcome this, the filtration technique may become significant for the removal and avoidance of fouling of wastewater. This can be achieved through the fabrication of nano-based filters using the nanocomposites.