Displaying publications 1 - 20 of 68 in total

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  1. Javed S, Ahmad NA
    ScientificWorldJournal, 2014;2014:625280.
    PMID: 24688412 DOI: 10.1155/2014/625280
    An efficient and computationally linear algorithm is derived for total least squares solution of adaptive filtering problem, when both input and output signals are contaminated by noise. The proposed total least mean squares (TLMS) algorithm is designed by recursively computing an optimal solution of adaptive TLS problem by minimizing instantaneous value of weighted cost function. Convergence analysis of the algorithm is given to show the global convergence of the proposed algorithm, provided that the stepsize parameter is appropriately chosen. The TLMS algorithm is computationally simpler than the other TLS algorithms and demonstrates a better performance as compared with the least mean square (LMS) and normalized least mean square (NLMS) algorithms. It provides minimum mean square deviation by exhibiting better convergence in misalignment for unknown system identification under noisy inputs.
  2. Aminu M, Ahmad NA
    ACS Omega, 2020 Oct 20;5(41):26601-26610.
    PMID: 33110988 DOI: 10.1021/acsomega.0c03362
    Partial least squares discriminant analysis (PLS-DA) is a well-known technique for feature extraction and discriminant analysis in chemometrics. Despite its popularity, it has been observed that PLS-DA does not automatically lead to extraction of relevant features. Feature learning and extraction depends on how well the discriminant subspace is captured. In this paper, discriminant subspace learning of chemical data is discussed from the perspective of PLS-DA and a recent extension of PLS-DA, which is known as the locality preserving partial least squares discriminant analysis (LPPLS-DA). The objective is twofold: (a) to introduce the LPPLS-DA algorithm to the chemometrics community and (b) to demonstrate the superior discrimination capabilities of LPPLS-DA and how it can be a powerful alternative to PLS-DA. Four chemical data sets are used: three spectroscopic data sets and one that contains compositional data. Comparative performances are measured based on discrimination and classification of these data sets. To compare the classification performances, the data samples are projected onto the PLS-DA and LPPLS-DA subspaces, and classification of the projected samples into one of the different groups (classes) is done using the nearest-neighbor classifier. We also compare the two techniques in data visualization (discrimination) task. The ability of LPPLS-DA to group samples from the same class while at the same time maximizing the between-class separation is clearly shown in our results. In comparison with PLS-DA, separation of data in the projected LPPLS-DA subspace is more well defined.
  3. Firdaus F, Ahmad NA, Sahibuddin S
    Sensors (Basel), 2019 Dec 15;19(24).
    PMID: 31847488 DOI: 10.3390/s19245546
    Wireless local area networks (WLAN)-fingerprinting has been highlighted as the preferred technology for indoor positioning due to its accurate positioning and minimal infrastructure cost. However, its accuracy is highly influenced by obstacles that cause fluctuation in the signal strength. Many researchers have modeled static obstacles such as walls and ceilings, but few studies have modeled the people's presence effect (PPE), although the human body has a great impact on signal strength. Therefore, PPE must be addressed to obtain accurate positioning results. Previous research has proposed a model to address this issue, but these studies only considered the direct path signal between the transmitter and the receiver whereas multipath effects such as reflection also have a significant influence on indoor signal propagation. This research proposes an accurate indoor-positioning model by considering people's presence and multipath using ray-tracing, we call it (AIRY). This study proposed two solutions to construct AIRY: an automatic radio map using ray tracing and a constant of people's effect for the received signal strength indicator (RSSI) adaptation. The proposed model was simulated using MATLAB software and tested at Level 3, Menara Razak, Universiti Teknologi Malaysia. A K-nearest-neighbor (KNN) algorithm was used to define a position. The initial accuracy was 2.04 m, which then reduced to 0.57 m after people's presence and multipath effects were considered.
  4. Mishra RK, Ramasamy K, Ahmad NA, Eshak Z, Majeed AB
    J Mater Sci Mater Med, 2014 Apr;25(4):999-1012.
    PMID: 24398912 DOI: 10.1007/s10856-013-5132-x
    Stimuli responsive hydrogels have shown enormous potential as a carrier for targeted drug delivery. In this study we have developed novel pH responsive hydrogels for the delivery of 5-fluorouracil (5-FU) in order to alleviate its antitumor activity while reducing its toxicity. We used 2-(methacryloyloxyethyl) trimetylammonium chloride a positively charged monomer and methacrylic acid for fabricating the pH responsive hydrogels. The released 5-FU from all except hydrogel (GEL-5) remained biologically active against human colon cancer cell lines [HT29 (IC50 = 110-190 μg ml(-1)) and HCT116 (IC50 = 210-390 μg ml(-1))] but not human skin fibroblast cells [BJ (CRL2522); IC50 ≥ 1000 μg ml(-1)]. This implies that the copolymer hydrogels (1-4) were able to release 5-FU effectively to colon cancer cells but not normal human skin fibroblast cells. This is probably due to the shorter doubling time that results in reduced pH in colon cancer cells when compared to fibroblast cells. These pH sensitive hydrogels showed well defined cell apoptosis in HCT116 cells through series of events such as chromatin condensation, membrane blebbing, and formation of apoptotic bodies. No cell killing was observed in the case of blank hydrogels. The results showed the potential of these stimuli responsive polymer hydrogels as a carrier for colon cancer delivery.
  5. Jeyaprakasam NK, Razak MF, Ahmad NA, Santhanam J
    Mycopathologia, 2016 Jun;181(5-6):397-403.
    PMID: 26847667 DOI: 10.1007/s11046-016-9984-8
    Although non-sporulating molds (NSM) are frequently isolated from patients and have been recognized as agents of pulmonary disease, their clinical significance in cutaneous specimens is relatively unknown. Therefore, this study aimed to identify NSM and to determine the keratinolytic activity of isolates from cutaneous sites. NSM isolates from clinical specimens such as skin, nail, and body fluids were identified based on their ribosomal DNA sequences. Of 17 NSM isolates (7 Ascomycota, 10 Basidiomycota), eleven were identified to species level while five were identified to the genus level. These include Schizophyllum commune, a known human pathogen, Phoma multirostrata, a plant pathogen, and Perenniporia tephropora, a saprophyte. To determine fungal pathogenicity, keratinolytic activity, a major virulence factor, was evaluated ex vivo using human nail samples by measuring dye release from keratin azure, for NSM along with pathogens (Trichophyton mentagrophytes, Trichophyton rubrum, Microsporum canis and Fusarium spp.) and nonpathogenic (endophyte) fungi for comparison. This study showed that pathogenic fungi had the highest keratinolytic activity (7.13 ± 0.552 keratinase units) while the nonpathogenic endophytes had the lowest activity (2.37 ± 0.262 keratinase units). Keratinolytic activity of two Ascomycota NSM (Guignardia mangiferae and Hypoxylon sp.) and one Basidiomycota NSM (Fomitopsis cf. meliae) was equivalent to that of pathogenic fungi, while Xylaria feejeensis showed significantly higher activity (p 
  6. Alshami IH, Ahmad NA, Sahibuddin S, Firdaus F
    Sensors (Basel), 2017 Aug 05;17(8).
    PMID: 28783047 DOI: 10.3390/s17081789
    The Global Positioning System demonstrates the significance of Location Based Services but it cannot be used indoors due to the lack of line of sight between satellites and receivers. Indoor Positioning Systems are needed to provide indoor Location Based Services. Wireless LAN fingerprints are one of the best choices for Indoor Positioning Systems because of their low cost, and high accuracy, however they have many drawbacks: creating radio maps is time consuming, the radio maps will become outdated with any environmental change, different mobile devices read the received signal strength (RSS) differently, and peoples' presence in LOS between access points and mobile device affects the RSS. This research proposes a new Adaptive Indoor Positioning System model (called DIPS) based on: a dynamic radio map generator, RSS certainty technique and peoples' presence effect integration for dynamic and multi-floor environments. Dynamic in our context refers to the effects of people and device heterogeneity. DIPS can achieve 98% and 92% positioning accuracy for floor and room positioning, and it achieves 1.2 m for point positioning error. RSS certainty enhanced the positioning accuracy for floor and room for different mobile devices by 11% and 9%. Then by considering the peoples' presence effect, the error is reduced by 0.2 m. In comparison with other works, DIPS achieves better positioning without extra devices.
  7. Ahmad NA, Ismail NW, Ahmad Sidique SF, Mazlan NS
    Environ Sci Pollut Res Int, 2021 Feb;28(7):8709-8721.
    PMID: 33068244 DOI: 10.1007/s11356-020-11191-3
    Although industrialisation is a crucial aspect of economic growth across developing nations, through the release of air contaminants, industrial activities may also create adverse environmental health consequences. Noting that continuous production and other economic activities are crucial for continued survival, this study explores this issue by including the role of governance that is deemed essential but the literature is relatively sparse particularly in the context of developing countries. This research empirically analyses the relationship between air pollution and adult mortality rates from 72 developing countries from the period of 2010 until 2017. Particulate matter (PM2.5) and carbon dioxide (CO2) are used as indicators of air pollution. From the generalized method of moments (GMM) estimations, the results reveal that air pollution negatively affects adult mortality rate. The result reveals that a 10% increase in the PM2.5 level induces the adult mortality rates to increase between 0.04% and 0.06%. In addition, the government significantly moderates the negative effect of air pollution on adult mortality, whereby a one-unit enhancement in governance quality index reduces mortality among the adults in the developing countries by 0.01%. On the other hand, CO2 emission also appears to be positive, but not statistically significant. The results suggest that governance and public health interplay in the sense of a transition towards economic development for improved living and health states can be achievable with improved governance quality.
  8. Ahmad NA, Mohamed Zulkifli R, Hussin H, Nadri MH
    J Mol Graph Model, 2021 06;105:107872.
    PMID: 33765525 DOI: 10.1016/j.jmgm.2021.107872
    Aptamers are short oligonucleotides that possess high specificity and affinity against their target. Generated via Systematic Evolution of Ligands by Exponential Enrichment, (SELEX) in vitro, they were screened and enriched. This review covering the study utilizing bioinformatics tools to analyze primary sequence, secondary and tertiary structure prediction, as well as docking simulation for various aptamers and their ligand interaction. Literature was pooled from Web of Science (WoS) and Scopus databases until December 18, 2020 using specific search string related to DNA aptamers, in silico, structure prediction, and docking simulation. Out of 330 published articles, 38 articles were assessed in the analysis based on the predefined inclusion and exclusion criteria. It was found that Mfold and RNA Composer web server is the most popular tool in secondary and tertiary structure prediction of DNA aptamers, respectively. Meanwhile, in docking simulation, ZDOCK and AutoDock are preferred to analyze binding interaction in the aptamer-ligand complex. This review reports a brief framework of recent developments of in silico approaches that provide predictive structural information of ssDNA aptamer.
  9. Abd Rahim SNH, Ahmad NA, Mohamed-Yassin MS
    Am J Case Rep, 2021 Jun 25;22:e932320.
    PMID: 34170887 DOI: 10.12659/AJCR.932320
    BACKGROUND Trichoblastoma is a rare, benign, cutaneous adnexal neoplasm arising from rudimentary hair follicles. The incidence and prevalence in the general population is unknown. However, most cases occur in adults aged 40 years and older. CASE REPORT A 62-year-old woman presented to our primary care clinic for a hypertension and diabetes followup visit. The doctor, who had never seen the patient before, noticed several small lumps over the patient's eyebrows. After she removed her headscarf and face mask for a thorough examination, numerous skin-colored papules and nodules were seen on her nose, nasal bridge, forehead, and around her eyebrows. She was referred to a dermatologist, and a skin biopsy showed well-circumscribed dermal nests of basaloid cells, with peripheral palisading, and keratin horn cysts surrounded by dense fibrous stroma. These features were consistent with trichoblastoma. She was then referred to a plastic surgeon to discuss further management options. The patient finally chose laser ablation as she was fearful of the other more invasive surgical options. CONCLUSIONS This is a very rare case of extensive facial trichoblastoma. It highlights the need for clinicians to ensure optimal exposure when examining patients. It also highlights the role of biopsies for skin lesions of uncertain etiology. In this case, it helped to rule out basal cell carcinoma, which can be a more locally destructive condition than trichoblastoma. This case also serves as a reminder about the need for ongoing review and referral for further management for conditions for which previous treatment was unsuccessful.
  10. Yusoff F, Saari R, Naidu BM, Ahmad NA, Omar A, Aris T
    Asia Pac J Public Health, 2014 Sep;26(5 Suppl):9S-17S.
    PMID: 25038193 DOI: 10.1177/1010539514542424
    The National School-Based Health Survey 2012 was a nationwide school health survey of students in Standard 4 to Form 5 (10-17 years of age), who were schooling in government schools in Malaysia during the period of data collection. The survey comprised 3 subsurveys: the Global School Health Survey (GSHS), the Mental Health Survey, and the National School-Based Nutrition Survey. The aim of the survey was to provide data on the health status of adolescents in Malaysia toward strengthening the adolescent health program in the country. The design of the survey was created to fulfill the requirements of the 3 subsurveys. A 2-stage stratified sampling method was adopted in the sampling. The methods for data collection were via questionnaire and physical examination. The National School-Based Health Survey 2012 adopted an appropriate methodology for a school-based survey to ensure valid and reliable findings.
    Study name: Global School-Based Student Health Survey (GSHS)
  11. Abdul Wahab RM, Zainal Ariffin SH, Yeen WW, Ahmad NA, Senafi S
    ScientificWorldJournal, 2012;2012:236427.
    PMID: 22629122 DOI: 10.1100/2012/236427
    Three specific orthodontic tooth movement genes, that is, FCRL1, HSPG2, and LAMB2 were detected at upper first premolar (with appliance) dental pulp tissue by using GeneFishing technique as compared to lower first premolar (without appliance). These three differentially expressed genes have the potential as molecular markers during orthodontic tooth movement by looking at molecular changes of pulp tissue.
  12. Mohd Tap R, Sabaratnam P, Ahmad NA, Abd Razak MF, Hashim R, Ahmad N
    Mycopathologia, 2015 Aug;180(1-2):137-41.
    PMID: 25894509 DOI: 10.1007/s11046-015-9890-5
    An 11-year-old girl presented with multiple blisters on her the right foot complicated with cellulitis. The conventional and molecular identification were performed on the culture. The internal transcribed spacer (ITS) region in rRNA gene of the isolate was amplified by PCR. The sequence of the amplified ITS region matched 99 % with that of Chaetomium globosum in the GenBank. This is the first report describing C. globosum causing cutaneous infection in Malaysia.
  13. Ahmad NA, Vythilingam I, Lim YAL, Zabari NZAM, Lee HL
    Am J Trop Med Hyg, 2017 Jan 11;96(1):148-156.
    PMID: 27920393 DOI: 10.4269/ajtmh.16-0516
    Wolbachia-based vector control strategies have been proposed as a means to augment the currently existing measures for controlling dengue and chikungunya vectors. Prior to utilizing Wolbachia as a novel vector control strategy, it is crucial to understand the Wolbachia-mosquito interactions. In this study, field surveys were conducted to screen for the infection status of Wolbachia in field-collected Aedes albopictus The effects of Wolbachia in its native host toward the replication and dissemination of chikungunya virus (CHIKV) was also studied. The prevalence of Wolbachia-infected field-collected Ae. albopictus was estimated to be 98.6% (N = 142) for females and 95.1% (N = 102) for males in the population studied. The Ae. albopictus were naturally infected with both wAlbA and wAlbB strains. We also found that the native Wolbachia has no impact on CHIKV infection and minimal effect on CHIKV dissemination to secondary organs.
  14. Aslam TM, Zaki HR, Mahmood S, Ali ZC, Ahmad NA, Thorell MR, et al.
    Am J Ophthalmol, 2018 Jan;185:94-100.
    PMID: 29101008 DOI: 10.1016/j.ajo.2017.10.015
    PURPOSE: To develop a neural network for the estimation of visual acuity from optical coherence tomography (OCT) images of patients with neovascular age-related macular degeneration (AMD) and to demonstrate its use to model the impact of specific controlled OCT changes on vision.

    DESIGN: Artificial intelligence (neural network) study.

    METHODS: We assessed 1400 OCT scans of patients with neovascular AMD. Fifteen physical features for each eligible OCT, as well as patient age, were used as input data and corresponding recorded visual acuity as the target data to train, validate, and test a supervised neural network. We then applied this network to model the impact on acuity of defined OCT changes in subretinal fluid, subretinal hyperreflective material, and loss of external limiting membrane (ELM) integrity.

    RESULTS: A total of 1210 eligible OCT scans were analyzed, resulting in 1210 data points, which were each 16-dimensional. A 10-layer feed-forward neural network with 1 hidden layer of 10 neurons was trained to predict acuity and demonstrated a root mean square error of 8.2 letters for predicted compared to actual visual acuity and a mean regression coefficient of 0.85. A virtual model using this network demonstrated the relationship of visual acuity to specific, programmed changes in OCT characteristics. When ELM is intact, there is a shallow decline in acuity with increasing subretinal fluid but a much steeper decline with equivalent increasing subretinal hyperreflective material. When ELM is not intact, all visual acuities are reduced. Increasing subretinal hyperreflective material or subretinal fluid in this circumstance reduces vision further still, but with a smaller gradient than when ELM is intact.

    CONCLUSIONS: The supervised machine learning neural network developed is able to generate an estimated visual acuity value from OCT images in a population of patients with AMD. These findings should be of clinical and research interest in macular degeneration, for example in estimating visual prognosis or highlighting the importance of developing treatments targeting more visually destructive pathologies.

  15. Shoaib LA, Safii SH, Naimie Z, Ahmad NA, Sukumaran P, Yunus RM
    Eur J Dent Educ, 2018 Feb;22(1):e26-e34.
    PMID: 27995730 DOI: 10.1111/eje.12252
    OBJECTIVES: This study was conducted in University of Malaya to evaluate student perceptions on the contribution and role of an effective clinical teacher based on the cognitive apprenticeship model in clinical practice.

    METHODS: Self-administered questionnaires were distributed to 233 undergraduate dental students involved with clinical teaching. This modified and validated questionnaire focusing on students' learning environment was used in order to gain relevant information related to dental clinical teaching. Six domains with different criteria applicable to clinical teaching in dentistry were selected consisting of modelling (four criteria), coaching (four criteria), scaffolding (four criteria), articulation (four criteria), reflection (two criteria) and general learning environment (six criteria). Data analyses were performed using IBM SPSS Statistics 20.

    RESULTS: Majority of the students expressed positive perceptions on their clinical learning experience towards the clinical teachers in the Faculty of Dentistry, University of Malaya, in all criteria of the domains. Few negative feedbacks concerning the general learning environment were reported.

    CONCLUSION: Further improvement in the delivery of clinical teaching preferably by using wide variety of teaching-learning activities can be taken into account through students' feedback on their learning experience.

  16. Naderipour A, Abdul-Malek Z, Ahmad NA, Kamyab H, Ashokkumar V, Ngamcharussrivichai C, et al.
    Environ Technol Innov, 2020 Nov;20:101151.
    PMID: 32923529 DOI: 10.1016/j.eti.2020.101151
    Coronavirus 2019 (COVID-19) has globally affected the human mortality rate and economic history of the modern world. According to the World Health Organization, COVID-19 has caused a severe threat to the health of the vulnerable groups, notably the elderly. There is still some disagreements regarding the source of the virus and its intermediate host. However, the spread of this disease has caused most countries to enforce strict curfew laws and close most industrial and recreational centres. This study aims to show the potential positive effects of COVID-19 on the environment and the increase of renewable energy generation in Malaysia. To prevent the spread of this disease, Malaysia enacted the Movement Control Order (MCO) law in March 2020. Implementation of this law led to a reduction in environmental pollution, especially air pollution, in this country. The greenhouse gases (GHG) emission , which was 8 Mt CO2 eq. from January 2020 to March 2020, reduced to <1 Mt CO2 eq. for April and May. The reduction of GHG emission and pollutant gases allowed more sunlight to reach photovoltaic panels, hence increasing the renewable energy generation.
  17. Ahmad NA, Jumbri K, Ramli A, Abd Ghani N, Ahmad H, Lim JW
    Molecules, 2018 Dec 05;23(12).
    PMID: 30563037 DOI: 10.3390/molecules23123201
    The antiradical efficiency (AE) and kinetic behavior of a new ferulate-based protic ionic liquids (PILs) were described using 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical assay. The reduction of the DPPH free radical (DPPH•) was investigated by measuring the decrease in absorbance at 517 nm. The time to reach steady state for the reaction of parent acid (ferulic acid) and synthesized PILs with DPPH• was continuously recorded for 1 h. Results revealed that the AE of 2-butylaminoethanol ferulate (2BAEF), 3-dimethylaminopropanol ferulate (3DMAPF) and 3-diethylaminopropanol ferulate (3DEAPF) PILs have improved compared to ferulic acid (FA) as the reaction class changes from low to medium. This attributed to the strong hydrogen abstraction occurred in the PILs. Furthermore, these PILs were found to have a good kinetic behavior compared to FA due to the high rate constant (k₂) (164.17, 242.84 and 244.73 M-1 s-1, respectively). The alkyl chain length and more alkyl substituents on the nitrogen atom of cation were believed to reduce the cation-anion interaction and speed up the hydrogen atom transfer (HAT) and electron transfer (ET) mechanisms; hence, increased rate constant was observed leading to a strong antioxidant activity of the synthesized PILs.
  18. Sahril N, Ahmad NA, Idris IB, Sooryanarayana R, Abd Razak MA
    Children (Basel), 2021 Feb 07;8(2).
    PMID: 33562212 DOI: 10.3390/children8020119
    Mental health problems are a major public health issue, particularly among children. They impair children's development, academic achievement, and ability to live a productive life. The present study aimed to determine the prevalence and factors associated with mental health problems among children aged 5 to 15 years old in Malaysia. Data from the National Health and Morbidity Survey (NHMS) 2015 were analyzed. A validated Strengths and Difficulties Questionnaire (SDQ) was used. The overall prevalence of mental health problems among children in Malaysia was 11.1%. Multiple logistic regression analysis revealed that for every year increment in age, mental health problems decreased by 5%. Further analysis found that children who had fathers with a non-formal education and worked in the private sector, had parents who were widowed or divorced, and had either parent with mental health problems were more likely to have mental health problems themselves. Children from the lower socioeconomic group and who had either parent with mental health problems had higher odds of having mental health problems in Malaysia.
    Study name: National Health and Morbidity Survey (NHMS-2015)
  19. Prabu S, Samad NA, Ahmad NA, Jumbri K, Raoov M, Rahim NY, et al.
    Carbohydr Res, 2020 Nov;497:108138.
    PMID: 32911205 DOI: 10.1016/j.carres.2020.108138
    The behavior of the inclusion behavior of guanosine (GU) with beta-cyclodextrin (β-CD) in the liquid, solid and virtual state were investigated. The absorption and fluorescence spectral were used to determine the inclusion behavior in liquid state. FT-IR, NMR, TGA, DSC, PXRD and FESEM techniques were used to investigate the inclusion behavior in solid-state, meanwhile the virtual state studies are done by molecular docking. The solid inclusion complex (GU: β-CD) was prepared by using the co-precipitation method. The binding constant (K) of (GU: β-CD) was calculated by using Benesi-Hildebrand. Besides that, the 1:1 stoichiometric ratio of inclusion complex was confirmed by using the Benesi-Hildebrand plot and Job's plot of continuous variation method. The most preferable model of GU: β-CD that suggested via molecular docking studies was in good agreement with experimental results. The inclusion complex of GU: β-CD exerted its toxicity effects towards HepG2 cell lines based on the reduced number of cell viability and lowest IC50 value compared to the GU and β-CD viability.
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