Displaying publications 41 - 60 of 640 in total

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  1. Ahmad A, Rafatullah M, Sulaiman O, Ibrahim MH, Hashim R
    J Hazard Mater, 2009 Oct 15;170(1):357-65.
    PMID: 19464117 DOI: 10.1016/j.jhazmat.2009.04.087
    Meranti (Philippine mahogany) sawdust, an inexpensive material, showed strong scavenging behaviour through adsorption for the removal of methylene blue (MB) from aqueous solution. Batch studies were performed to evaluate and optimize the effects of various parameters such as contact time, pH, initial dye concentrations and adsorbent dosage. Langmuir, Freundlich and Temkin isotherms were used to analyze the equilibrium data at different temperatures. The experimental data fitted well with the Langmuir adsorption isotherm, indicating thereby the mono layer adsorption of the dye. The monolayer sorption capacity of meranti sawdust for MB was found to be 120.48, 117.64, 149.25 and 158.73 mg/g at 30, 40, 50 and 60 degrees C, respectively. Thermodynamic calculations showed that the MB adsorption process is endothermic and spontaneous in nature. Kinetic studies showed that the adsorption followed a pseudo-second-order kinetic model. The results indicated that the meranti sawdust could be an alternative material in place of more costly adsorbents used for dye removal.
  2. Ahmad AL, Chong MF, Bhatia S
    J Hazard Mater, 2009 Nov 15;171(1-3):166-74.
    PMID: 19573986 DOI: 10.1016/j.jhazmat.2009.05.114
    The discharge of palm oil mill effluent (POME) causes serious pollution problems and the membrane based POME treatment is suggested as a solution. Three different designs, namely Design A, B and C distinguished by their different types and orientations of membrane system are proposed. The results at optimum condition proved that the quality of the recovered water for all the designs met the effluent discharge standards imposed by the Department of Environment (DOE). The economic analysis at the optimum condition shows that the total treatment cost for Design A was the highest (RM 115.11/m(3)), followed by Design B (RM 23.64/m(3)) and Design C (RM 7.03/m(3)). In this study, the membrane system operated at high operating pressure with low membrane unit cost is preferable. Design C is chosen as the optimal design for the membrane based POME treatment system based on the lowest total treatment cost.
  3. Lee YK, Za'aba A, Madzhi NK, Ahmad A
    PMID: 19964239 DOI: 10.1109/IEMBS.2009.5333674
    Previous works on the effects of salivary alpha amylase in respond to various stressors report encouraging findings on it being a good indicator of stress. Ellestad protocol is a clinical procedure to screen for coronary artery disease by introducing exercise induced physical stress. If a salivary based biomarker profile in accordance to a stress test protocol could be established, the critical stress state which disable rational decision making could be ascertained in a standardized procedure. This technique would serve to aid human resource management in times of critical events such as rescue, firefighting or even military, that would potentially prevent unnecessary sacrifice of human lives. In this pilot study with five healthy volunteers performing the Ellestad protocol treadmill, a measurement profile with physiologic and salivary based biomarker is obtained. It is found that the alpha amylase levels or the changes in it as workload changes from resting-walking-running at ease-exhaustive running, is relatively more significant in reflecting the stress state than heart rate and blood pressure. Moreover, it is strongly associated with mood state with correlation coefficient of 0.8 and significance of 0.01.
  4. Rafatullah M, Sulaiman O, Hashim R, Ahmad A
    J Hazard Mater, 2010 May 15;177(1-3):70-80.
    PMID: 20044207 DOI: 10.1016/j.jhazmat.2009.12.047
    In this article, the use of low-cost adsorbents for the removal of methylene blue (MB) from solution has been reviewed. Adsorption techniques are widely used to remove certain classes of pollutants from waters, especially those which are not easily biodegradable. The removal of MB, as a pollutant, from waste waters of textile, paper, printing and other industries has been addressed by the researchers. Currently, a combination of biological treatment and adsorption on activated carbon is becoming more common for removal of dyes from wastewater. Although commercial activated carbon is a preferred adsorbent for color removal, its widespread use is restricted due to its relatively high cost which led to the researches on alternative non-conventional and low-cost adsorbents. The purpose of this review article is to organize the scattered available information on various aspects on a wide range of potentially low-cost adsorbents for MB removal. These include agricultural wastes, industrial solid wastes, biomass, clays minerals and zeolites. Agricultural waste materials being highly efficient, low cost and renewable source of biomass can be exploited for MB remediation. It is evident from a literature survey of about 185 recently published papers that low-cost adsorbents have demonstrated outstanding removal capabilities for MB.
  5. Hameed BH, Salman JM, Ahmad AL
    J Hazard Mater, 2009 Apr 15;163(1):121-6.
    PMID: 18667269 DOI: 10.1016/j.jhazmat.2008.06.069
    In this work, the adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) on activated carbon derived from date stones (DSAC) was studied with respect to pH and initial 2,4-D concentration. The experimental data were analyzed by the Freundlich isotherm, the Langmuir isotherm, and the Temkin isotherm. Equilibrium data fitted well with the Langmuir model with maximum adsorption capacity of 238.10 mg/g. Pseudo-first and pseudo-second-order kinetics models were tested with the experimental data, and pseudo-first-order kinetics was the best for the adsorption of 2,4-D by DSAC with coefficients of correlation R(2)>or=0.986 for all initial 2,4-D concentrations studied. The results indicated that the DSAC is very effective for the adsorption of 2,4-D from aqueous solutions.
  6. Hameed BH, Mahmoud DK, Ahmad AL
    J Hazard Mater, 2008 Oct 30;158(2-3):499-506.
    PMID: 18353547 DOI: 10.1016/j.jhazmat.2008.01.098
    The sorption of basic dye from aqueous solutions by banana stalk waste (BSW), an abundant agricultural waste in Malaysia, was studied in a batch system with respect to pH and initial dye concentration. Sorption isotherm of methylene blue (MB) onto the BSW was determined at 30 degrees C with the initial concentrations of MB in the range of 50-500 mg/L. At pH 2.0, the sorption of dye was not favorable, while the sorption at other pHs (4.0-12.0) was remarkable. Equilibrium data were fitted to the Langmuir, Freundlich and Temkin isotherm models. The equilibrium data were best represented by the Langmuir isotherm model, with maximum monolayer adsorption capacity of 243.90 mg/g. The sorption kinetic data were analyzed using pseudo-first-order, pseudo-second-order and intraparticle diffusion models. It was found that the pseudo-second-order kinetic model was the best applicable model to describe the sorption kinetics. The results showed that BSW sorbent was a promising for the removal of MB from aqueous solutions.
  7. Hameed BH, Mahmoud DK, Ahmad AL
    J Hazard Mater, 2008 Oct 1;158(1):65-72.
    PMID: 18308467 DOI: 10.1016/j.jhazmat.2008.01.034
    In this paper, the ability of coconut bunch waste (CBW), an agricultural waste available in large quantity in Malaysia, to remove basic dye (methylene blue) from aqueous solution by adsorption was studied. Batch mode experiments were conducted at 30 degrees C to study the effects of pH and initial concentration of methylene blue (MB). Equilibrium adsorption isotherms and kinetics were investigated. The experimental data were analyzed by the Langmuir, Freundlich and Temkin models of adsorption. The adsorption isotherm data were fitted well to Langmuir isotherm and the monolayer adsorption capacity was found to be 70.92 mg/g at 30 degrees C. The kinetic data obtained at different concentrations have been analyzed using a pseudo-first-order, pseudo-second-order equation and intraparticle diffusion equation. The experimental data fitted very well the pseudo-second-order kinetic model.
  8. Shuhaimi-Othman M, Mushrifah I, Lim EC, Ahmad A
    Environ Monit Assess, 2008 Aug;143(1-3):345-54.
    PMID: 17987397
    Water from 15 sampling stations in Tasik Chini (Chini Lake), Peninsular Malaysia were sampled for 12 months from September 2004 until August 2005 and analyzed for 11 metals including iron (Fe), aluminum (Al), manganese (Mn), barium (Ba), zinc (Zn), lead (Pb), copper (Cu), cadmium (Cd), nickel (Ni), chromium (Cr) and cobalt (Co). Results showed that the mean (min-max) metal concentrations (in micrograms per liter) in Tasik Chini waters for the 12 months sampling based on 15 sampling stations (in descending order) for Fe, Al, Mn, Ba, Zn, Pb, Cu and Cd were 794.84 (309.33-1609.07), 194.53 (62.37-665.93), 29.16 (16.68-79.85), 22.07 (15.64-29.71), 5.12 (2.224-6.553), 2.36 (1.165-4.240), 0.832 (0.362-1.443) and 0.421 (0.254-0.696) respectively. Concentration for three metals i.e. Ni, Cr and Co were too low and not detected by the graphite furnace Atomic Absorption Spectrophotometry (AAS). Comparison with various water quality standards showed that the mean metals concentration in surface water of Tasik Chini were low and within the range of natural background except for Fe and Al. In general, metal concentrations in Tasik Chini water varied temporally and spatially. The main factors influencing these metal concentrations in the water were the raining season and mining activities. Stations located at Tanjung Jerangking and Melai areas were the most effected due to those factors.
  9. Ahmad AA, Hameed BH, Aziz N
    J Hazard Mater, 2007 Mar 6;141(1):70-6.
    PMID: 16887263
    Palm ash, an agriculture waste residue from palm-oil industry in Malaysia, was investigated as a replacement for the current expensive methods of removing direct blue 71 dye from an aqueous solution. The experimental data were analyzed by the Langmuir and Freundlich models of adsorption. Equilibrium data fitted well with Freundlich model in the range of 50-600mg/L. The equilibrium adsorption capacity of the palm ash was determined with the Langmuir equation and found to be 400.01mg dye per gram adsorbent at 30 degrees C. The rates of adsorption were found to conform to the pseudo-second-order kinetics with good correlation. The results indicate that the palm ash could be employed as a low-cost alternative to commercial activated carbon.
  10. Bloh AH, Usup G, Ahmad A
    Vet World, 2016 Feb;9(2):142-6.
    PMID: 27051199 DOI: 10.14202/vetworld.2016.142-146
    AIM: Bacteria associated with harmful algal blooms can play a crucial role in regulating algal blooms in the environment. This study aimed at isolating and identifying algicidal bacteria in Dinoflagellate culture and to determine the optimum growth requirement of the algicidal bacteria, Loktanella sp. Gb-03.

    MATERIALS AND METHODS: The Dinoflagellate culture used in this study was supplied by Professor Gires Usup's Laboratory, School of Environmental and Natural Resources Sciences, Faculty of Science and Technology, University Kebangsaan Malaysia, Malaysia. The culture was used for the isolation of Loktanella sp., using biochemical tests, API 20 ONE kits. The fatty acid content of the isolates and the algicidal activity were further evaluated, and the phenotype was determined through the phylogenetic tree.

    RESULTS: Gram-negative, non-motile, non-spore-forming, short rod-shaped, aerobic bacteria (Gb01, Gb02, Gb03, Gb04, Gb05, and Gb06) were isolated from the Dinoflagellate culture. The colonies were pink in color, convex with a smooth surface and entire edge. The optimum growth temperature for the Loktanella sp. Gb03 isolate was determined to be 30°C, in 1% of NaCl and pH7. Phylogenetic analysis based on 16S rRNA gene sequences showed that the bacterium belonged to the genus Loktanella of the class Alphaproteobacteria and formed a tight cluster with the type strain of Loktanella pyoseonensis (97.0% sequence similarity).

    CONCLUSION: On the basis of phenotypic, phylogenetic data and genetic distinctiveness, strain Gb-03, were placed in the genus Loktanella as the type strain of species. Moreover, it has algicidal activity against seven toxic Dinoflagellate. The algicidal property of the isolated Loktanella is vital, especially where biological control is needed to mitigate algal bloom or targeted Dinoflagellates.

  11. Rahman WA, Che'Rus A, Ahmad AH
    PMID: 9561615
    Until today, malaria is still one of the most important diseases in Malaysia. This is because Malaysia is located within the equatorial zone with high temperatures and humidities, usually important for the transmission of malaria. The number of malaria cases were estimated to be around 300,000 before the launching of the Malaria Eradication Program (MEP). The program was successful in reducing the numbers progressively during the 1967-1982 period. During the period 1980-1991, the highest number of malaria cases recorded for the country was 65,283 in 1989 (16,902 in Peninsular Malaysia, 47,545 in Sabah and 836 in Sarawak) whilst the lowest was 22,218 (10,069 in Peninsular Malaysia, 11,290 in Sabah and 859 in Sarawak) in 1983. In Malaysia, there are 434 species of mosquitos, representing 20 genera. Of these, 75 species are Anopheles that comprise of 2 subgenus, i.e. Anopheles and Cellia. Of the 75 species, only 9 have been reported as vectors: An. maculatus, An balabacensis, An. dirus, An. letifer An. campestris, An. sundaicus, An. donaldi, An. leucophyrus and An. flavirostris. The behavior, seasonal abundance, biting activities and breeding sites of these species are discussed.
  12. Ahmad A, Ghufran R, Al-Hosni TK
    J Environ Health Sci Eng, 2019 Dec;17(2):1195-1203.
    PMID: 32030185 DOI: 10.1007/s40201-019-00434-2
    To investigate the interaction of zinc oxide nanoparticles (ZnO NPs) with fly ash soil (FAS) for the reduction of metals from FAS by Parthenium hysterophorus were studied. The average accumulation of metals by P. hysterophorus stem were Fe 79.6%; Zn 88.5%; Cu 67.5%; Pb 93.6%; Ni 43.5% and Hg 39.4% at 5.5 g ZnO NP. The concentration of ZnO NP at 1.5 g did not affect the metals accumulation, however at 5.5 g ZnO NP showed highest metal reduction was 96.7% and at 10.5-15.5 g ZnO NP of 19.8%. The metal reduction rate was R
    max
    for Fe 16.4; Zn 21.1; Pb 41.9; Hg 19.1 was higher than Ni 6.4 and Cu 11.3 from the FAS at 5.5 g ZnO NP whereas, the reduction rate of Pb showed highest. With doses of 5.5 g ZnO NP the biomass increased upto 78%; the metal reduced upto 98.7% with the share of 100% ZnO NP from FAS. Further investigation with phytotoxicity the plant reactive oxygen species (ROS) production were affected due was mainly due to the recovery of metals from FAS (R2 = 0.99).
  13. Rushdi I, Che-Ahmad A, Abdul-Ghani K, Mohd-Rus R
    Malays Orthop J, 2020 Nov;14(3):57-65.
    PMID: 33403063 DOI: 10.5704/MOJ.2011.010
    Introduction: Distal tibia fractures are frequently associated with an extensive soft tissue injury which then leads to a higher risk of complications such as infection, non-union and eventually poor overall outcome. The purpose of this study is to measure the outcome of distal tibia fractures treated with internal fixation, external fixator or Ilizarov external fixator(IEF). We aim to propose an algorithm for management of distal tibia fractures by evaluating the treatment options, outcomes and risk factors present.

    Material and Methods: This study is a cross-sectional study of all distal tibia fractures treated surgically in Tengku Ampuan Rahimah Hospital, Klang from 1st January 2016 till 30th June 2018. Patient records were reviewed to analyse the outcomes of surgical treatment and risk factors associated with it.

    Results: Ninety-one patients were included with a mean age of 41.5 years (SD = 16.4). Thirty-nine cases (42.9%) were open fractures. Thirty-eight patients (41.8%) were treated with internal fixation, 27 patients (29.7%) were treated with IEF and 26 patients (28.6%) were treated with an external fixator. Among open fractures cases, no significant finding can be concluded when comparing each surgical option and its outcome, although one option was seen better than the other in a particular outcome. Initial skeletal traction or temporary spanning external fixator in close fractures reduced the risk of mal-alignment (p value=0.001). Internal fixation is seen superior to IEF and external fixator in close fractures in term of articular surface reduction (p value = 0.043) and risk of mal-alignment (p value = 0.007).

    Conclusion: There is no single method of fixation that is ideal for all pilon fractures and suitable for all patients. This proposed algorithm can help surgeons in deciding treatment strategies in the challenging management of distal tibia fractures to reduce associated complications.

  14. Ahmad A, Sreedhar Reddy S, Rumana G
    Int J Phytoremediation, 2019;21(5):471-478.
    PMID: 30648407 DOI: 10.1080/15226514.2018.1537243
    To assess the tolerance, the rye-grass L. grown on soil amended with petroleum wastewater (PWW) containing four metals lead, zinc, nickel and mercury. The PWW (25 to 50%) showed remarkable increase in length and biomass. Chlorophyll 'a and b' increased with an increase of PWW from 25-50% while such contents decreased on increasing the 75-100% compared to control. The mass balance performed on the system showed the removal of 90-97.6% lead, 85.5-92.9% zinc, 78.9-85.5% nickle and 47.6-27.5% mercury. The model for the maximum metal reduction rate (Rmax) was much better for Pb (89.5) and Zn (72.1) with respect to Ni (57.3) and Hg (32.4). Survival of rye-grass (30-days, statics, and renewal exposures) was increased by 50% as compared to control. The toxicity index Y of PWW showed 0-25% deficiency level, 25-50% tolerance level, 50-90% toxic level and 90-100% lethal level. The experimental data showing high correlation coefficient (R2 = 0.98).
  15. Ahmad A, Nazar Z, Swaminathan D
    Oral Health Prev Dent, 2018 7 22;16(3):281-289.
    PMID: 30027167 DOI: 10.3290/j.ohpd.a40759
    PURPOSE: To investigate the association between plasma CRP levels and periodontal disease during pregnancy.

    MATERIALS AND METHODS: Fifty-six pregnant women attending the Antenatal Clinic, UMMC for their first antenatal check-up consented and were recruited for this study: 28 subjects with diseased periodontium (test group) and 28 subjects with healthy periodontium (control). The test group underwent nonsurgical periodontal therapy and the control group was given oral hygiene education. Periodontal parameters and CRP levels were evaluated at baseline and 6 weeks. Pregnancy outcome data were recorded from the Antenatal Clinic, UMMC.

    RESULTS: Plasma CRP levels in the test group were statistically significantly elevated compared to the control group (8.55 ± 5.28 mg/l vs 5.66 ± 2.91 mg/l). After nonsurgical periodontal therapy, a statistically significant reduction in the CRP level in the test group (2.06 mg/l) along with statistically significant improvement in periodontal status in both groups was observed. The mean birth weight for infants of both groups showed no statistically significant difference.

    CONCLUSIONS: Plasma CRP levels in pregnant women with diseased periodontium were statistically significantly reduced after nonsurgical periodontal therapy. However, no association between CRP levels and adverse pregnancy outcome was observed.

  16. Ng JW, Ahmad AR, Solayar GN
    Malays Orthop J, 2020 Jul;14(2):90-93.
    PMID: 32983382 DOI: 10.5704/MOJ.2007.017
    Introduction: This study was conducted to evaluate the demographics, causes and outcomes of patients who underwent Posterior Cruciate Ligament (PCL) reconstruction and/or Posterolateral Corner (PLC) reconstruction performed at our institution over the last three years. Sub-analysis was performed to assess the impact of delay from injury to surgery and how this affected outcomes.

    Material and Methods: From an initial number of 10 patients, seven were contactable and available for analysis. All patients underwent PCL and/or PLC reconstruction (modified Larson's procedure) between 2017 and 2019. The mean age of our cohort was 31.4±9.6 years (range, 21 to 46). Assessment of functional outcomes pre- and post-operatively were done using the Lysholm knee scoring scale, the Knee injury and Osteoarthritis Outcome Score (KOOS) and visual analogue scale (VAS). The mean follow-up from operation at time of reporting was seven months (range, 2 to 12 months).

    Results: There were four combined PCL and PLCs, two isolated PLCs and one patient who underwent an isolated PCL reconstruction. There were significant improvements between pre-operative and post-operative in all functional outcome scores utilised following PCL reconstruction and/or modified Larson's reconstruction. Lysholm knee scoring scale improved from pre-operative to post-operative at 41.14±12.32 to 74.86±13.52 (p=0.0001), KOOS from 49.71±11.19 to 71.43±13.84 (p=0.001), and VAS from 5.71±2.06 to 2.86±2.48 (p=0.001). Our sub-analysis showed that higher functional outcomes were present when surgery was done less than six months from the time of index injury. There were no complications (eg. Infections, revisions) in this cohort at the time of reporting.

    Conclusion: Reconstructive surgery for PCL and/or PLC injury is successful in increasing the functional outcomes of patients post-operatively. Delays from injury to surgery remains a problem in the public setting as patients may need to await appropriate imaging and approval of funding. Increased awareness for early surgical intervention may improve overall outcomes of PCL and/or PLC reconstruction in Malaysia.

  17. Clink DJ, Hamid Ahmad A, Klinck H
    Sci Rep, 2020 Jan 28;10(1):1282.
    PMID: 31992788 DOI: 10.1038/s41598-020-57976-x
    Early morning calling occurs across diverse taxa, which may be related to optimal conditions for sound transmission. There exists substantial inter- and intra-specific variation in calling time which is influenced by intrinsic, social and/or environmental factors. Here, we investigate environmental predictors of calling in gibbons. We hypothesized that male solos- which occur earlier and tend to be longer than duets-would be more influenced by environmental variables, if earlier, longer calling bouts are energetically costly, and therefore limited by overnight energy expenditure. Our top model for male solo events included amount of rain in the previous 24 hours, and explained 30% of the variance, whereas the top model for duet events (which included presence and amount of rainfall) explained only 5% of the variance. Rain the previous night led to a later start time of male solos (~30 minutes), but our top model for duet start time did not include any reliable predictors. Male solo events appear to be more influenced by environmental factors, and duets may be influenced more by social factors. Our results are in line with previous studies that show that changes in overnight conditions -which may alter energy expenditure -can influence early morning calling behavior.
  18. Pin LC, Teen LP, Ahmad A, Usup G
    Mar Biotechnol (NY), 2001 May;3(3):246-55.
    PMID: 14961362
    The genus Ostreopsis is an important component of benthic and epiphytic dinoflagellate assemblages in coral reefs and seaweed beds of Malaysia. Members of the species may produce toxins that contribute to ciguatera fish poisoning. In this study, two species have been isolated and cultured, Ostreopsis ovata and Ostreopsis lenticularis. Analyses of the 5.8S subunit and internal transcribed spacer regions ITS1 and ITS2 of the ribosomal RNA gene sequences of these two species showed that they are separate species, consistent with morphological designations. The nucleotide sequences of the 5.8S subunit and ITS1 and ITS2 regions of the rRNA gene were also used to evaluate the interpopulation and intrapopulation genetic diversity of O. ovata found in Malaysian waters. Results showed a low level of sequence divergence within populations. At the interpopulation level, the rRNA gene sequence distinguished two groups of genetically distinct strains, representative of a Malacca Straits group (isolates from Port Dickson) and a South China Sea group (isolates from Pulau Redang and Kota Kinabalu). Part of the sequences in the ITS regions may be useful in the design of oligonucleotide probes specific for each group. Results from this study show that the ITS regions can be used as genetic markers for taxonomic, biogeographic, and fine-scale population studies of this species.
  19. Singh S, Tan CL, Ahmad AR
    Malays Orthop J, 2021 Jul;15(2):1-8.
    PMID: 34429815 DOI: 10.5704/MOJ.2107.001
    Osteomyelitis is a chronic infection of bones. Eradication of bone infection is usually with antibiotics and debridement, but it is slow and the infection can recur even after many years. It is now established that osteomyelitis is due to biofilm and a better understanding of the process is required. We review the development of biofilm and apply it to osteomyelitis management. The planktonic microbes' response to adverse conditions is the formation of biofilm. Bacterial infections in planktonic forms cause infections that can be controlled with antibiotics and immunisation, however the same microbe when its phenotype becomes biofilm is more resilient. The understanding of how planktonic bacteria convert to biofilm is one of the aims set out for this article.
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