Displaying publications 1 - 20 of 157 in total

  1. Idris SS, Rahman NA, Ismail K
    Bioresour Technol, 2012 Nov;123:581-91.
    PMID: 22944493 DOI: 10.1016/j.biortech.2012.07.065
    The combustion characteristics of Malaysia oil palm biomass (palm kernel shell (PKS), palm mesocarp fibre (PMF) and empty fruit bunches (EFB)), sub-bituminous coal (Mukah Balingian) and coal/biomass blends via thermogravimetric analysis (TGA) were investigated. Six weight ratios of coal/biomass blends were prepared and oxidised under dynamic conditions from temperature 25 to 1100°C at four heating rates. The thermogravimetric analysis demonstrated that the EFB and PKS evolved additional peak besides drying, devolatilisation and char oxidation steps during combustion. Ignition and burn out temperatures of blends were improved in comparison to coal. No interactions were observed between the coal and biomass during combustion. The apparent activation energy during this process was evaluated using iso-conversional model free kinetics which resulted in highest activation energy during combustion of PKS followed by PMF, EFB and MB coal. Blending oil palm biomass with coal reduces the apparent activation energy value.
  2. Kheng TY, Ding P, Abdul Rahman NA
    J Sci Food Agric, 2012 Jan 15;92(1):171-6.
    PMID: 21780132 DOI: 10.1002/jsfa.4559
    A series of physico-chemical quality (peel and pulp colours, pulp firmness, fruit pH, sugars and acids content, respiration rate and ethylene production) were conducted to study the optimum harvest periods (either week 11 or week 12 after emergence of the first hand) of Rastali banana (Musa AAB Rastali) based on the fruit quality during ripening.
  3. Othman S, Rahman NA, Yusof R
    Trans R Soc Trop Med Hyg, 2010 Dec;104(12):806-8.
    PMID: 20800252 DOI: 10.1016/j.trstmh.2010.07.004
    In contrast to many viruses that escape the host's immune responses by suppressing the major histocompatibility complex (MHC) class I pathway, flaviviruses have been shown to up-regulate the cell surface expression of MHC class I complex. The mechanism by which dengue virus (DV) achieves this up-regulation remains unclear. Our investigation on the HLA-A2 gene in human liver cells demonstrated that all four serotypes of dengue virus, DV1 to DV4, resulted in variable degrees of promoter induction. This illustrates the importance of MHC class I transcription regulation in primary infections by different DV serotypes that may have even greater impact in secondary infections, associated with increased disease severity.
  4. Yaeghoobi M, Rahman NA, Ng SW
    PMID: 21583886 DOI: 10.1107/S1600536809013348
    In the title Schiff base, C(16)H(16)ClNO(2), the 2-(4-methoxy-phen-yl)ethyl (CH(3)OC(6)H(4)CH(2)CH(2)-; r.m.s. deviation = 0.10 Å) and 4-chloro-2-(imino-meth-yl)phenol (N=CHC(6)H(3)ClOH; r.m.s. deviation = 0.01 Å) portions are both essentially planar, the two parts being inclined at an angle of 61.8 (1)°. The hydroxy group forms a hydrogen bond to the imino N atom.
  5. Ramanathan Y, Rajagopalan R, Rahman NA
    Ear Nose Throat J, 2007 Nov;86(11):685-6.
    PMID: 18225631
    Metastases to the larynx from distant primaries are rare. We report a case of a laryngeal metastasis from a rectal carcinoma.
  6. Yusof AM, Rahman NA, Wood AK
    Biol Trace Elem Res, 1994;43-45:239-49.
    PMID: 7710833
    Trace elements, such as As, Co, Cr, Hg, Sb, and Zn, were determined by neutron activation analysis (NAA), whereas Cd, Cu, and Pb were determined by graphite furnace atomic absorption spectroscopy (GFAAS) in clam, crab, prawn, swamp cerith, and mussel samples after digestion by microwave heating under controlled conditions before eluting the solutions through a column of a chelating resin, Chelex-100. The standard used in the determination of percentage volatile elements retained by microwave digestion and also in the activation process was Lobster Hepatopancreas TORT-1, whereas known mixed standards were prepared from nitrate salts to determine the efficiency of the separation procedure at a controlled pH. Mercury and lead detected in crabs exceeded the maximum permissible level. Some species also showed a high affinity toward certain elements, and their levels of accumulation in the tissues of these species corresponded with the concentration of these elements in sediments, especially at sites in the vicinity of an industrial zone.
  7. Ahmed T, Rahman NA, Alam MK
    Prog Orthod, 2019 Jul 08;20(1):26.
    PMID: 31281954 DOI: 10.1186/s40510-019-0277-x
    BACKGROUND: To introduce an orthodontic bracket debonding device capable of measuring debonding force clinically by a novel sensor mechanism MATERIALS AND METHOD: A prototype orthodontic debonding device was constructed utilizing a lift-off debonding instrument (LODI) and force-sensitive resistor (FSR). For data interpretation, the force sensor was equipped with a microcontroller and C++ programming software running on a computer. Ninety-nine (99) 0.022-in. conventional metallic brackets were bonded to premolar teeth in vitro by a single clinician applying the same adhesive and bonding technique. For validation, the mean debonding force measured by the prototype debonding device (n = 30) and the universal testing machine (n = 30) was compared. Both intra- and inter-examiner reliability tests were done by holding and operating the device in a standardized manner. Following debonding by the prototype device, the bracket failure pattern was evaluated (n = 30) by adhesive remnant index (ARI) under the stereomicroscope at × 30 magnification. Statistical analysis included independent samples t test for validation and intraclass correlation coefficient (ICC) with a 95% confidence interval for both intra- and inter-examiner reliability.

    RESULTS: Mean orthodontic bracket debonding force measured by the prototype device (9.36 ± 1.65 N) and the universal testing machine (10.43 ± 2.71 N) was not significantly different (p 

  8. Othman S, Rahman NA, Yusof R
    Virus Res, 2012 Jan;163(1):238-45.
    PMID: 22001567 DOI: 10.1016/j.virusres.2011.09.040
    Despite aggressive efforts in dengue research, the control of dengue diseases and discovery of therapeutics against them await complete elucidation of its complex immune-pathogenesis. Unlike many viruses that escape the host's immune responses by suppressing the major histocompatibility complex (MHC) Class I pathway, many Flaviviruses up-regulate the cell surface expression of MHC Class I complex. We recently reported MHC Class I HLA-A2 promoter activation by all serotypes of dengue virus (DV). The mechanism by which DV regulates this is further explored here in HepG2 human liver cell line. Using real-time PCR, evidence that, similar to infections by other Flaviviruses, DV infection has the ability to up-regulate the MHC Class I transcription and mRNA synthesis, is presented. The region responsive towards DV infection of all serotypes was mapped to the Class I Regulatory Complex (CRC) of the HLA-A2 promoter. Competition electrophoretic mobility shift assay (EMSA) with NFκB probe established the presence of specific DNA-protein complex in DV-infected nuclear extracts. Antibody-supershift assays identified the MHC Class I promoter activation by DV to occur through binding of p65/p50 heterodimers and p65 homodimers to κB1 and κB2 cis-acting elements, respectively, within the CRC, and not with the interferon consensus sequence (ICS). This study presents evidence of MHC Class I gene modulation by DV, hence providing a better understanding of dengue immune-pathogenesis that would consequently facilitate the discovery of antiviral therapeutics against dengue.
  9. Asi AM, Rahman NA, Merican AF
    J Mol Graph Model, 2004 Mar;22(4):249-62.
    PMID: 15177077
    Protein-ligand binding free energy values of wild-type and mutant C-terminal domain of Escherichia coli arginine repressor (ArgRc) protein systems bound to L-arginine or L-citrulline molecules were calculated using the linear interaction energy (LIE) method by molecular dynamics (MD) simulation. The binding behaviour predicted by the dissociation constant (K(d)) calculations from the binding free energy values showed preferences for binding of L-arginine to the wild-type ArgRc but not to the mutant ArgRc(D128N). On the other hand, L-citrulline do not favour binding to wild-type ArgRc but prefer binding to mutant ArgRc(D128N). The dissociation constant for the wild-type ArgRc-L-arginine complex obtained in this study is in agreement with reported experimental results. Our results also support the experimental data for the binding of L-citrulline to the mutant ArgRc(D128N). These showed that LIE method for protein-ligand binding free energy calculation could be applied to the wild-type and the mutant E. coli ArgRc-L-arginine and ArgRc-L-citrulline protein-ligand complexes and possibly to other transcriptional repressor-co-repressor systems as well.
  10. Ahmed T, Rahman NA, Alam MK
    Biomed Res Int, 2021;2021:6663683.
    PMID: 33959664 DOI: 10.1155/2021/6663683
    Objective: To compare the orthodontic bracket debonding force and assess the bracket failure pattern clinically between different teeth by a validated prototype debonding device. Materials and Method. Thirteen (13) patients at the end of comprehensive fixed orthodontic treatment, awaiting for bracket removal, were selected from the list. A total of 260 brackets from the central incisor to the second premolar in both jaws were debonded by a single clinician using a validated prototype debonding device equipped with a force sensitive resistor (FSR). Mean bracket debonding forces were specified to ten (10) groups of teeth. Following debonding, Intraoral microphotographs of the teeth were taken by the same clinician to assess the bracket failure pattern using a 4-point scale of adhesive remnant index (ARI). Statistical analysis included one-way ANOVA with post hoc Tukey HSD and independent sample t-test to compare in vivo bracket debonding force, Cohen's kappa (κ), and a nonparametric Kruskal-Wallis test for the reliability and the assessment of ARI scoring.

    Results: A significant difference (p < 0.001) of mean debonding force was found between different types of teeth in vivo. Clinically, ARI scores were not significantly different (p = 0.921) between different groups, but overall higher scores were predominant.

    Conclusion: Bracket debonding force should be measured on the same tooth from the same arch as the significant difference of mean debonding force exists between similar teeth of the upper and lower arches. The insignificant bracket failure pattern with higher ARI scores confirms less enamel damage irrespective of tooth types.

  11. Shamsul NS, Kamarudin SK, Rahman NA
    Bioresour Technol, 2018 Jan;247:821-828.
    PMID: 30060418 DOI: 10.1016/j.biortech.2017.09.140
    Treated sludge, goat manure, sugarcane bagasse, empty fruit bunches of oil palm (EFBP) and dry leaves are agro wastes that have high potential for use as feedstocks for the production of 5-hydroxymethylfurfural (5-HMF). The focus of this study is to investigate the production of 5-HMF from agro wastes via co-hydrothermal (CHT) treatment and extraction. Present study include examine on agro waste's physical and chemical properties and also their thermal degradation behaviour. The analysis of the bio-oil products is conducted by FTIR and GC-MS. Co-hydrothermal experiments were conducted at a temperature of 300°C with an experimental time of 15min, followed by alcohol extraction. Highest carbon and hydrogen content are 45.94% and 6.49% (dry leaves) with maximum high heating value 18.39MJ/kg (dry leaves) and fix carbon value 6.60 (goat manure). Through CHT about 39% 5-HMF, 22.97% carboxylic acids, 0.97% of aromatic and 0.73% aldehyde obtained.
  12. Roslan AA, Rahman NA, Alam MK
    J Orthod Sci, 2018;7:16.
    PMID: 30271761 DOI: 10.4103/jos.JOS_37_18
    OBJECTIVE: This study was carried to study the prevalence of dental anomalies and treatment modalities/planning among the orthodontic patients.

    MATERIALS AND METHODS: A total of 370 orthodontic records including their pre-treatment orthopantomographs (OPG) and study models of orthodontic patients in permanent dentition who attended dental clinic were assessed for impaction, hypodontia, supernumerary, supraocclusion, infraocclusion, and any other anomalies excluding the third molars. The association of anomalies with gender status and racial status was analyzed using Pearson's Chi-square test. A P value of <0.05 is considered as significant. The confidence interval at 95% (CI) was set.

    RESULTS: Among the 370 subjects, 105 (28.4%) presented with at least one anomaly. Eighty-five (23%) demonstrated a single anomaly and 20 (5.4%) with more than one anomaly. The most prevalent anomaly was impaction (14.32%), followed by hypodontia (7.03%). The less common anomalies were microdontia (1.08%), dilacerations (0.27%), and generalised enamel hypoplasia (0.27%). Maxillary right lateral incisors and canines were the most common affected teeth and these are located on the maxillary right quadrant. It was evident that dental anomalies were statistically dependant on race (P = 0.025), but independent of gender. The most common treatment planned for these patients was fixed appliance.

    CONCLUSIONS: Impaction was predominant among 28.4% subjects observed with anomaly and most patients with anomaly are treated with fixed appliances (49%).

    CLINICAL RELEVANCE: These anomalies play a great role in occlusion and alignment in treatment planning and relapse for orthodontic treatment.

  13. Ahmed T, Rahman NA, Alam MK
    Eur J Dent, 2018 10 30;12(4):602-609.
    PMID: 30369810 DOI: 10.4103/ejd.ejd_22_18
    The aim of this study was to systematically review the available studies measuring the bond strength of orthodontic bracket-adhesive system under different experimental conditions in vivo. Literature search was performed in four different databases: PubMed, Web of Science, Cochrane, and Scopus using the keywords - bond strength, orthodontic brackets, bracket-adhesive, and in vivo. A total of six full-text articles were selected based on the inclusion and exclusion criteria of our study after a careful assessment by the two independent reviewers. Data selection was performed by following PRISMA 2009 guidelines. Five of the selected studies were clinical trials; one study was a randomized clinical trial. From each of the selected articles, the following data were extracted - number of samples, with the type of tooth involved materials under experiment methods of measurement, the time interval between bonding and debonding orthodontic brackets, mode of force application, and the bond strength results with the overall outcome. The methodological quality assessment of each article was done by the modified Downs and Black checklist method. The qualitative analyses were done by two independent reviewers. Conflicting issues were resolved in a consensus meeting by consulting the third reviewer (MKA). Meta-analysis could not be performed due to the lack of homogenous study results. The review reached no real conclusion apart from the lack of efforts to clinically evaluate the bonding efficiency of a wide range of orthodontic bracket-adhesive systems in terms of debonding force compared to laboratory-based in vitro and ex vivo studies.
  14. Kueh R, Rahman NA, Merican AF
    J Mol Model, 2003 Apr;9(2):88-98.
    PMID: 12707802
    The arginine repressor (ArgR) of Escherichia coli binds to six L-arginine molecules that act as its co-repressor in order to bind to DNA. The binding of L-arginine molecules as well as its structural analogues is compared by means of computational docking. A grid-based energy evaluation method combined with a Monte Carlo simulated annealing process was used in the automated docking. For all ligands, the docking procedure proposed more than one binding site in the C-terminal domain of ArgR (ArgRc). Interaction patterns of ArgRc with L-arginine were also observed for L-canavanine and L-citrulline. L-lysine and L-homoarginine, on the other hand, were shown to bind poorly at the binding site. Figure A general overview of the sites found from docking the various ligands into ArgRc ( grey ribbons). Red coloured sticks: residues in binding site H that was selected for docking
  15. Airak S, Sukor NSA, Rahman NA
    Transp Res Interdiscip Perspect, 2023 Mar;18:100784.
    PMID: 36844954 DOI: 10.1016/j.trip.2023.100784
    The COVID-19 pandemic has disrupted travel behaviours due to the need for movement restrictions. The restrictions adversely affected various aspects of health and the economy. This study aimed to investigate factors affecting trip frequency during the recovery period of the COVID-19 pandemic in Malaysia. An online national cross-sectional survey was conducted to collect data in conjunction with different movement restriction policies. The questionnaire includes socio-demographics, experience with COVID-19, risk perception of COVID-19, and trip frequency on several activities during the pandemic. Mann Whitney U was conducted to determine whether there were statistically significant differences between the socio-demographic factors for the respondents in the first and second surveys. Results show no significant difference in socio-demographic factors except for the level of education. The results indicate that the respondents from both surveys were comparable. Next, Spearman correlation analyses were conducted to find significant correlations between trip frequencies toward socio-demographics, experience with COVID-19 and risk perception. There was a correlation between the frequency of travel and risk perception for both surveys. Regression analyses were performed based on the findings to investigate trip frequency determinants during the pandemic. Perceived risk, gender, and occupation influenced the trip frequencies for both surveys. By understanding the influence of risk perception on the frequency of travel, the government can identify the appropriate policy during a pandemic or health emergency to avoid impeding normal travel behaviour. Thus, people's mental and psychological well-being are not negatively affected.
  16. Rothan HA, Mohamed Z, Paydar M, Rahman NA, Yusof R
    Arch Virol, 2014 Apr;159(4):711-8.
    PMID: 24142271 DOI: 10.1007/s00705-013-1880-7
    Doxycycline is an antibiotic derived from tetracycline that possesses antimicrobial and anti-inflammatory activities. Antiviral activity of doxycycline against dengue virus has been reported previously; however, its anti-dengue properties need further investigation. This study was conducted to determine the potential activity of doxycycline against dengue virus replication in vitro. Doxycycline inhibited the dengue virus serine protease (DENV2 NS2B-NS3pro) with an IC50 value of 52.3 ± 6.2 μM at 37 °C (normal human temperature) and 26.7 ± 5.3 μM at 40 °C (high fever temperature). The antiviral activity of doxycycline was first tested at different concentrations against DENV2 using a plaque-formation assay. The virus titter decreased significantly after applying doxycycline at levels lower than its 50 % cytotoxic concentration (CC50, 100 μM), showing concentration-dependent inhibition with a 50 % effective concentration (EC50) of approximately 50 μM. Doxycycline significantly inhibited viral entry and post-infection replication of the four dengue serotypes, with serotype-specific inhibition (high activity against DENV2 and DENV4 compared to DENV1 and DENV3). Collectively, these findings underline the need for further experimental and clinical studies on doxycycline, utilizing its anti-dengue and anti-inflammatory activities to attenuate the clinical symptoms of dengue virus infection.
  17. Frimayanti N, Chee CF, Zain SM, Rahman NA
    Int J Mol Sci, 2011;12(2):1089-100.
    PMID: 21541045 DOI: 10.3390/ijms12021089
    Dengue is a serious disease which has become a global health burden in the last decade. Currently, there are no approved vaccines or antiviral therapies to combat the disease. The increasing spread and severity of the dengue virus infection emphasizes the importance of drug discovery strategies that could efficiently and cost-effectively identify antiviral drug leads for development into potent drugs. To this effect, several computational approaches were applied in this work. Initially molecular docking studies of reference ligands to the DEN2 NS2B/NS3 serine protease were carried out. These reference ligands consist of reported competitive inhibitors extracted from Boesenbergia rotunda (i.e., 4-hydroxypanduratin A and panduratin A) and three other synthesized panduratin A derivative compounds (i.e., 246DA, 2446DA and 20H46DA). The design of new lead inhibitors was carried out in two stages. In the first stage, the enzyme complexed to the reference ligands was minimized and their complexation energies (i.e., sum of interaction energy and binding energy) were computed. New compounds as potential dengue inhibitors were then designed by putting various substituents successively on the benzyl ring A of the reference molecule. These substituted benzyl compounds were then computed for their enzyme-ligand complexation energies. New enzyme-ligand complexes, exhibiting the lowest complexation energies and closest to the computed energy for the reference compounds, were then chosen for the next stage manipulation and design, which involved substituting positions 4 and 5 of the benzyl ring A (positions 3 and 4 for 2446DA) with various substituents.
  18. Rahman NA, Olutoye MA, Hameed BH
    Bioresour Technol, 2011 Oct;102(20):9749-54.
    PMID: 21855332 DOI: 10.1016/j.biortech.2011.07.023
    The potential of Mg(x)Co(2-)(x)O(2) as heterogeneous reusable catalyst in transesterification of palm oil to methyl ester was investigated. The catalyst was prepared via co-precipitation of the metal hydroxides at different Mg-Co ratios. Mg(1.7)Co(0.3)O(2) catalyst was more active than Mg(0.3)Co(1.7)O(2) in the transesterification of palm oil with methanol. The catalysts calcined at temperature 300 °C for 4 h resulted in highly active oxides and the highest transesterification of 90% was achieved at methanol/oil molar ratio of 9:1, catalyst loading of 5.00 wt.%, reaction temperature of 150 °C and reaction time of 2 h. The catalyst could easily be removed from reaction mixture, but showed 50% decrease in activity when reused due to leaching of active sites.
  19. Tay KS, Rahman NA, Abas MR
    Water Environ Res, 2011 Aug;83(8):684-91.
    PMID: 21905405
    This study investigated the removal of parabens, N,N-diethyl-m-toluamide (DEET), and phthalates by ozonation. The second-order rate constants for the reaction between selected compounds with ozone at pH 7 were of (2.2 +/-0.2) X 10(6) to (2.9 +/-0.3) X 10(6) M 1/s for parabens, (2.1+/- 0.3) to (3.9 +/-0.5) M-1/s for phthalates, and (5.2 +/-0.3) M-1/s for DEET. The rate constants for the reaction between selected compounds with hydroxyl radical ranged from (2.49 +/-0.06) x 10(9) to (8.5 +/-0.2) x 10(9) M-1/s. Ozonation of selected compounds in secondary wastewater and surface waters revealed that ozone dose of 1 and 3 mg/L yielded greater than 99% depletion of parabens and greater than 92% DEET and phthalates, respectively. In addition, parabens were found to transform almost exclusively through the reaction with ozone, while DEET and phthalates were transformed almost entirely by hydroxyl radicals (.OH).
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