Showing papers by "National University of Malaysia published in 2016"

A century of trends in adult human height

Abstract: Being taller is associated with enhanced longevity, and higher education and earnings. We reanalysed 1472 population-based studies, with measurement of height on more than 18.6 million participants to estimate mean height for people born between 1896 and 1996 in 200 countries. The largest gain in adult height over the past century has occurred in South Korean women and Iranian men, who became 20.2 cm (95% credible interval 17.5–22.7) and 16.5 cm (13.3–19.7) taller, respectively. In contrast, there was little change in adult height in some sub-Saharan African countries and in South Asia over the century of analysis. The tallest people over these 100 years are men born in the Netherlands in the last quarter of 20th century, whose average heights surpassed 182.5 cm, and the shortest were women born in Guatemala in 1896 (140.3 cm; 135.8–144.8). The height differential between the tallest and shortest populations was 19-20 cm a century ago, and has remained the same for women and increased for men a century later despite substantial changes in the ranking of countries.

Cross-Comparison of Exome Analysis, Next-Generation Sequencing of Amplicons, and the iPLEX® ADME PGx Panel for Pharmacogenomic Profiling

Abstract: Whole-exome sequencing (WES) has been widely used for analysis of human genetic diseases, but its value for the pharmacogenomic profiling of individuals is not well studied. Initially, we performed an in-depth evaluation of the accuracy of WES variant calling in the pharmacogenes CYP2D6 and CYP2C19 by comparison with MiSeq(®) amplicon sequencing data (n = 36). This analysis revealed that the concordance rate between WES and MiSeq(®) was high, achieving 99.60% for variants that were called without exceeding the truth-sensitivity threshold (99%), defined during variant quality score recalibration (VQSR). Beyond this threshold, the proportion of discordant calls increased markedly. Subsequently, we expanded our findings beyond CYP2D6 and CYP2C19 to include more genes genotyped by the iPLEX(®) ADME PGx Panel in the subset of twelve samples. WES performed well, agreeing with the genotyping panel in approximately 99% of the selected pass-filter variant calls. Overall, our results have demonstrated WES to be a promising approach for pharmacogenomic profiling, with an estimated error rate of lower than 1%. Quality filters, particularly VQSR, are important for reducing the number of false variants. Future studies may benefit from examining the role of WES in the clinical setting for guiding drug therapy.

A novel SVM-kNN-PSO ensemble method for intrusion detection system

Abstract: Graphical abstractThe objective of this paper is to develop ensemble based classifiers that will improve the accuracy of Intrusion Detection. For this purpose, we trained and tested 12 experts and then combined them into an ensemble. We used the PSO algorithm to weight the opinion of each expert. Because the quality of the behavioral parameters inserted by the user into PSO strongly affects its effectiveness, we have used the LUS method as a meta-optimizer for finding high-quality parameters. We then used the improved PSO to create new weights for each expert. For comparison, we also developed an ensemble classifier with weights generated using WMA 12. Fig. 1 depicts the entire process. For simplicity, the system framework was divided into the following seven stages:1.Kdd99 data pre-processing.2.Data classification with six different SVM experts.3.Data classification with six different k-NN experts.4.Data classification with ensemble classifier based on PSO.5.Data classification with ensemble classifier based on LUS improvement of PSO.6.Data classification with ensemble classifier based on WMA.7.Comparison of results for each approach.Display Omitted HighlightsIDS implemented using ensemble of a six SVM and a six k-NN classifier.Ensembles are created with weight generated by PSO and meta-PSO algorithms.These two ensembles outperform third ensemble system that is created with WMA. In machine learning, a combination of classifiers, known as an ensemble classifier, often outperforms individual ones. While many ensemble approaches exist, it remains, however, a difficult task to find a suitable ensemble configuration for a particular dataset. This paper proposes a novel ensemble construction method that uses PSO generated weights to create ensemble of classifiers with better accuracy for intrusion detection. Local unimodal sampling (LUS) method is used as a meta-optimizer to find better behavioral parameters for PSO. For our empirical study, we took five random subsets from the well-known KDD99 dataset. Ensemble classifiers are created using the new approaches as well as the weighted majority algorithm (WMA) approach. Our experimental results suggest that the new approach can generate ensembles that outperform WMA in terms of classification accuracy.

A comprehensive review of microbial electrolysis cells (MEC) reactor designs and configurations for sustainable hydrogen gas production

Abstract: Hydrogen gas has tremendous potential as an environmentally acceptable energy carrier for vehicles. A cutting edge technology called a microbial electrolysis cell (MEC) can achieve sustainable and clean hydrogen production from a wide range of renewable biomass and wastewaters. Enhancing the hydrogen production rate and lowering the energy input are the main challenges of MEC technology. MEC reactor design is one of the crucial factors which directly influence on hydrogen and current production rate in MECs. The rector design is also a key factor to up-scaling. Traditional MEC designs incorporated membranes, but it was recently shown that membrane-free designs can lead to both high hydrogen recoveries and production rates. Since then multiple studies have developed reactors that operate without membranes. This review provides a brief overview of recent advances in research on scalable MEC reactor design and configurations.

A review of the stage-of-the-art charging technologies, placement methodologies, and impacts of electric vehicles

Abstract: The world population depends highly on fossil fuels, particularly for transportation and power generation. This dependency leads to oil price increases because of the depletion of fossil fuels. Burning of fossil fuels also increases greenhouse gas emissions that are greatly responsible for global warming. Thus, electric vehicles (EVs) are considered one of the premium solutions in the land transportation system because they can significantly reduce the dependency on crude oil and minimize transportation-related carbon dioxide emissions along with other pollutants. This study presents an extensive review of the three key areas of EV research, namely, EV charging technologies, the various impacts of EVs, and optimal EV charging station (CS) placement and sizing. Several technical publications related to EV charging technologies are highlighted, and the performance comparison of different EV technologies is discussed. A review of literature on these key areas reveals an increasing interest in these topics in the last decade, with the impacts of EV on the electric power system and the optimal placement and sizing of CS issues widely investigated. By providing an overview of these areas, this study demonstrates the current issues and challenges of widespread deployment of EVs in the market as well as the future research direction in this field. A total of 185 publications are arranged and appended for quick referencing.

Animal models of metabolic syndrome: a review

Abstract: Metabolic syndrome (MetS) consists of several medical conditions that collectively predict the risk for cardiovascular disease better than the sum of individual conditions. The risk of developing MetS in human depends on synergy of both genetic and environmental factors. Being a multifactorial condition with alarming rate of prevalence nowadays, establishment of appropriate experimental animal models mimicking the disease state in humans is crucial in order to solve the difficulties in evaluating the pathophysiology of MetS in human. This review aims to summarize the underlying mechanisms involved in the pathophysiology of dietary, genetic, and pharmacological models of MetS. Furthermore, we will discuss the usefulness, suitability, pros and cons of these animal models. Even though numerous animal models of MetS have been established, further investigations on the invention of new animal model and clarification of plausible mechanisms are still necessary to confer a better understanding to researchers on the selection of animal models for their studies.

Recent advances and emerging challenges in microbial electrolysis cells (MECs) for microbial production of hydrogen and value-added chemicals

Abstract: Microbial electrolysis cell (MEC) is a potentially attractive green technology to tackle the global warming and energy crisis, which employs electrochemically active bacteria to convert organic matter into hydrogen or a wide range of chemicals, such as methane, acetate, hydrogen peroxide, ethanol, and formic acid, without causing environmental pollution. Until now, probably the cleanest and the most efficient method of producing hydrogen has been MEC. However, this technology is still in its infancy period and poses various challenges towards up-scaling and widespread applications, such as such as lower hydrogen production rate (HPR), high internal resistance, complicated architecture, and expensive materials. New advances are needed in biofilm engineering, materials for electrodes and reactor configuration for successful real-world application of this technology. Thus, the present review deals with development of practical MEC technology and includes the following sections: firstly a general introduction to MECs; their operating principles, thermodynamics of MEC, and energy or voltage losses in the MEC system were provided. Followed by a section on the critical factors affecting MEC performance; microorganisms, anode, cathode, membrane or separator, fuel sources, the state-of-art MECs designs, other key operational factors, and its potential application in microbial production of value added products are discussed in detail. Afterwards, current challenges involved in developing practical MEC systems are highlighted, and outlooks for future development are also suggested. The review aims to assist researcher and engineers to gain fundamental understandings of MEC, and it also provides several future research directions and a road map on how to overcome the barriers, so the MEC technology can be further advanced and applied in larger scale.

WCRP COordinated Regional Downscaling EXperiment (CORDEX): A diagnostic MIP for CMIP6

Abstract: . The COordinated Regional Downscaling EXperiment (CORDEX) is a diagnostic model intercomparison project (MIP) in CMIP6. CORDEX builds on a foundation of previous downscaling intercomparison projects to provide a common framework for downscaling activities around the world. The CORDEX Regional Challenges provide a focus for downscaling research and a basis for making use of CMIP6 global climate model (GCM) output to produce downscaled projected changes in regional climates and assess sources of uncertainties in the projections, all of which can potentially be distilled into climate change information for vulnerability, impacts and adaptation studies. CORDEX Flagship Pilot Studies advance regional downscaling by targeting one or more of the CORDEX Regional Challenges. A CORDEX-CORE framework is planned that will produce a baseline set of homogeneous high-resolution, downscaled projections for regions worldwide. In CMIP6, CORDEX coordinates with ScenarioMIP and is structured to allow cross comparisons with HighResMIP and interaction with the CMIP6 VIACS Advisory Board.

Typical conversion of lignocellulosic biomass into reducing sugars using dilute acid hydrolysis and alkaline pretreatment

Abstract: The development and production of fossil fuel alternatives have become one of the main focal points in recent investigations. Lignocellulosic biomass is a renewable source of fermentable sugars for second-generation biofuels and chemicals via biotechnological pathways. However, the presence of lignin and hemicellulose in lignocellulosic biomass makes it difficult for the biomass to be hydrolyzed or digested during fermentation. Thus, effective biomass pretreatment is vital. The present review shows that chemical pretreatment is the current preferred method to obtain high sugar yields at low cost, with dilute acid and alkaline hydrolysis as the two most reported technologies. Dilute acid favours hydrolysis of the hemicelluloses whereas alkaline hydrolysis targets the lignin fraction. Both methods have merits and demerits, and have been combined with other treatments such as hydrothermal and enzymatic hydrolysis. Further investigation is required to improve the pretreatment processes and to ensure the economic viability of bioconversion.

The effect of building envelope on the thermal comfort and energy saving for high-rise buildings in hot–humid climate

Abstract: This paper is about the research into the effect of building envelopes on energy consumption and thermal performance of high-rise buildings in the Malaysian Tropical climate. A suitable indoor thermal condition in buildings is important because of the building occupants comfort. In addition, it is indicating building energy consumption, staff productivity, less absenteeism, health and well-being effects. Energy consumption can be significantly reduced by adopting energy efficiency strategies in such buildings. Due to environmental concerns and expensive energy costs in recent years, energy efficiency in buildings has garnered renewed interests. A research recently conducted in Malaysia specifies that residential buildings do about 19% of the overall energy consumed in Malaysian sectors. One of the most potential strategies applied on building envelope in hot–humid tropical regions is the passive design method and is done to the building envelope in hot–humid tropical regions. This paper reviews the results of the other studies that establish to the selecting of proper parameters of building envelope to the high-rise residential. The building design criteria has been scrutinized through a set of defined parameters such as climatic conditions, form, width, length and height, external walls, roofs, glazing area, natural ventilation and occupants thermal comfort, as well as external shading devices on energy consumption of high-rise buildings in Malaysia. The thermal comfort zone was investigated by researchers for Malaysian residential buildings, discovering that the comfort ranged between 25 °C and 31 °C. Recommendations are given based on the significant findings as resources to help designers in laying out the design plan for high-rise buildings in hot and humid climate.

Targeting Staphylococcus aureus Toxins: A Potential form of Anti-Virulence Therapy.

Abstract: Staphylococcus aureus is an opportunistic pathogen and the leading cause of a wide range of severe clinical infections. The range of diseases reflects the diversity of virulence factors produced by this pathogen. To establish an infection in the host, S. aureus expresses an inclusive set of virulence factors such as toxins, enzymes, adhesins, and other surface proteins that allow the pathogen to survive under extreme conditions and are essential for the bacteria’s ability to spread through tissues. Expression and secretion of this array of toxins and enzymes are tightly controlled by a number of regulatory systems. S. aureus is also notorious for its ability to resist the arsenal of currently available antibiotics and dissemination of various multidrug-resistant S. aureus clones limits therapeutic options for a S. aureus infection. Recently, the development of anti-virulence therapeutics that neutralize S. aureus toxins or block the pathways that regulate toxin production has shown potential in thwarting the bacteria’s acquisition of antibiotic resistance. In this review, we provide insights into the regulation of S. aureus toxin production and potential anti-virulence strategies that target S. aureus toxins.

Reference ranges of handgrip strength from 125,462 healthy adults in 21 countries: a prospective urban rural epidemiologic (PURE) study.

Abstract: Background The measurement of handgrip strength (HGS) has prognostic value with respect to all-cause mortality, cardiovascular mortality and cardiovascular disease, and is an important part of the evaluation of frailty. Published reference ranges for HGS are mostly derived from Caucasian populations in high-income countries. There is a paucity of information on normative HGS values in non-Caucasian populations from low- or middle-income countries. The objective of this study was to develop reference HGS ranges for healthy adults from a broad range of ethnicities and socioeconomically diverse geographic regions. Methods HGS was measured using a Jamar dynamometer in 125,462 healthy adults aged 35-70 years from 21 countries in the Prospective Urban Rural Epidemiology (PURE) study. Results HGS values differed among individuals from different geographic regions. HGS values were highest among those from Europe/North America, lowest among those from South Asia, South East Asia and Africa, and intermediate among those from China, South America, and the Middle East. Reference ranges stratified by geographic region, age, and sex are presented. These ranges varied from a median (25th–75th percentile) 50 kg (43–56 kg) in men 60 years from South East Asia. Reference ranges by ethnicity and body-mass index are also reported. Conclusions Individual HGS measurements should be interpreted using region/ethnic-specific reference ranges.

Hybrid feature selection based on enhanced genetic algorithm for text categorization

Abstract: An enhanced genetic algorithm (EGA) is proposed to reduce text dimensionality.The proposed EGA outperformed the traditional genetic algorithm.The EGA is incorporated with six filter feature selection methods to create hybrid feature selection approaches.The proposed hybrid approaches outperformed the single filtering methods. This paper proposes hybrid feature selection approaches based on the Genetic Algorithm (GA). This approach uses a hybrid search technique that combines the advantages of filter feature selection methods with an enhanced GA (EGA) in a wrapper approach to handle the high dimensionality of the feature space and improve categorization performance simultaneously. First, we propose EGA by improving the crossover and mutation operators. The crossover operation is performed based on chromosome (feature subset) partitioning with term and document frequencies of chromosome entries (features), while the mutation is performed based on the classifier performance of the original parents and feature importance. Thus, the crossover and mutation operations are performed based on useful information instead of using probability and random selection. Second, we incorporate six well-known filter feature selection methods with the EGA to create hybrid feature selection approaches. In the hybrid approach, the EGA is applied to several feature subsets of different sizes, which are ranked in decreasing order based on their importance, and dimension reduction is carried out. The EGA operations are applied to the most important features that had the higher ranks. The effectiveness of the proposed approach is evaluated by using naive Bayes and associative classification on three different collections of Arabic text datasets. The experimental results show the superiority of EGA over GA, comparisons of GA with EGA showed that the latter achieved better results in terms of dimensionality reduction, time and categorization performance. Furthermore, six proposed hybrid FS approaches consisting of a filter method and the EGA are applied to various feature subsets. The results showed that these hybrid approaches are more effective than single filter methods for dimensionality reduction because they were able to produce a higher reduction rate without loss of categorization precision in most situations.

Direct conversion technologies of methane to methanol: An overview

Abstract: The emission of greenhouse gases (GHGs) is a major air pollution issue that affects climate change across the globe. Methane (CH 4 ), behind carbon dioxide (CO 2 ), is the second most abundant GHGs that negatively impact the atmosphere layer. Many studies have been conducted to identify a method for reducing the concentration of methane in the atmosphere. Converting methane to alternative forms source of energy, such as methanol, is a preferred method for methane reduction. This review aims to present an overview of recent literature that focuses on conversion of methane to methanol, with a focus primarily on the manufacturing systems and processes used in this conversion. Basic descriptions are given of several relevant technologies for converting methane to methanol and their characteristics, including conventional catalytic processes, plasma technology, photo-catalysts, supercritical water processes, biological processes and other processes. All of these options are feasible for use in the conversion process of methane to methanol.

A concise review of testosterone and bone health.

Abstract: Osteoporosis is a condition causing significant morbidity and mortality in the elderly population worldwide. Age-related testosterone deficiency is the most important factor of bone loss in elderly men. Androgen can influence bone health by binding to androgen receptors directly or to estrogen receptors (ERs) indirectly via aromatization to estrogen. This review summarized the direct and indirect effects of androgens on bone derived from in vitro, in vivo, and human studies. Cellular studies showed that androgen stimulated the proliferation of preosteoblasts and differentiation of osteoblasts. The converted estrogen suppressed osteoclast formation and resorption activity by blocking the receptor activator of nuclear factor k-B ligand pathway. In animal studies, activation of androgen and ERα, but not ERβ, was shown to be important in acquisition and maintenance of bone mass. Human epidemiological studies demonstrated a significant relationship between estrogen and testosterone in bone mineral density and fracture risk, but the relative significance between the two remained debatable. Human experimental studies showed that estrogen was needed in suppressing bone resorption, but both androgen and estrogen were indispensable for bone formation. As a conclusion, maintaining optimal level of androgen is essential in preventing osteoporosis and its complications in elderly men.

Biomass energy, technological progress and the environmental Kuznets curve: Evidence from selected European countries

Abstract: We examine the causal relationship between economic growth and CO2 emissions in a panel of 24 European countries from 1980 to 2010. Using an analytical framework that considers pooled mean group estimations in a dynamic heterogeneous panel setting, we show that there is an inverted U-shaped relationship between CO2 emissions and economic growth in the long run and that there is no such relationship in the short run. In particular, we find that biomass energy is insignificantly linked to CO2 emission. However, technological innovation significantly facilitates reduction of CO2 emissions in the investigated countries. Altogether, our study implies that economic growth and environmental quality can be achieved simultaneously, which opens up new insights for policy-makers for sustainable economic development via implementation of renewable energy consumption through technological innovation.

Modified Nafion membranes for direct alcohol fuel cells: An overview

Abstract: Direct alcohol fuel cells (DAFCs) have attracted considerable attention recently as alternative energy resources due to their high efficiency compared with other types of fuel cells. Currently, the two most common types of DAFCs are direct methanol fuel cells (DMFCs) and direct ethanol fuel cells (DEFCs), which use methanol and ethanol solutions as fuel, respectively. The most widely used polymer membrane for DAFCs is Nafion because it exhibits superior proton conductivity and excellent mechanical properties and chemical stability. However, Nafion membranes for DAFCs are expensive, have limited device lifetimes due to chemical and mechanical degradation, and have higher fuel crossovers through the membrane. Typically, to improve Nafion membranes, many researchers have modified Nafion membranes by modifying the Nafion matrix with organic or inorganic materials with different structures, sizes and compositions, modification techniques, or multilayered systems in order to improve the physical properties of Nafion. The characterization, properties, and performance of DAFCs from various types of modified Nafion membranes are critically reviewed by giving detailed examples. The challenges and future prospects for the modification of Nafion membranes for DAFC applications are also discussed.