Displaying publications 21 - 40 of 640 in total

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  1. Odeyemi OA, Ahmad A
    Saudi J Biol Sci, 2017 Jan;24(1):65-70.
    PMID: 28053573 DOI: 10.1016/j.sjbs.2015.09.016
    This study aimed to investigate antibiotics resistance pattern and phenotyping of Aeromonas species isolated from different aquatic sources in Melaka, Malaysia. A total of 53 Aeromonas species were isolated from the following sources: sediment (n = 13), bivalve (n = 10), sea cucumber (n = 16) and sea water (n = 14) and resistance to 12 antibiotics - Tetracycline (30 μg), Kanamycin (30 μg), Oxytetracycline (30 μg), Ampicillin (10 μg), Streptomycin (10 μg), Gentamicin (10 μg), Sulphamethoxazole (25 μg), Nalixidic acid (30 μg), Trimethoprim (1.25 μg), Novobiocin (5 μg), Penicilin (10 μg) and Chloramphenicol (10 μg) was tested. The results obtained from this study reveal multi drug resistance pattern among the isolates. All the isolates were completely resistant to Ampicillin, Novobiocin, Sulphamethoxazole and Trimethoprim, respectively but susceptible to Tetracycline (100%), Kanamycin (5.7%), Gentamicin (5.7%) and Oxytetracycline (24.5%). Antibiotics phenotyping of the bacteria revealed 21 different phenotypes among the isolates.
  2. Ahmad A, Ghufran R
    Crit Rev Biotechnol, 2023 Dec;43(8):1236-1256.
    PMID: 36130802 DOI: 10.1080/07388551.2022.2103641
    This critical review for anaerobic degradation of complex organic compounds like butyrate using reactors has been enormously applied for biogas production. Biogas production rate has a great impact on: reactor granulation methanogenesis, nutrient content, shear velocity, organic loading and loss of nutrients taking place in the reactor continuously. Various technologies have been applied to closed anaerobic reactors to improve biogas production and treatment efficiency. Recent reviews showed that the application of closed anaerobic reactors can accelerate the degradation of organics like volatile fatty acid-butyrate and affect microbial biofilm formation by increasing the number of methanogens and increase methane production 16.5 L-1 CH4 L-1 POME-1. The closed anaerobic reactors with stable microbial biofilm and established organic load were responsible for the improvement of the reactor and methane production. The technology mentioned in this review can be used to monitor biogas concentration, which directly correlates to organic concentrations. This review attempts to evaluate interactions among the: degradation of organics, closed anaerobic reactors system, and microbial granules. This article provides a useful picture for the improvement of the degradation of organic butyrate for COD removal, biogas and methane production in an anaerobic closed reactor.
  3. Dzulkarnain AAA, Azizi AK, Sulaiman NH
    J Taibah Univ Med Sci, 2020 Dec;15(6):495-501.
    PMID: 33318741 DOI: 10.1016/j.jtumed.2020.08.007
    Objective: This study aims to investigate the auditory sensory gating capacity in Huffaz using an auditory brainstem response (ABR) test with and without psychological tasks.

    Methods: Twenty-three participants were recruited for this study. The participants were comprised of 11 Huffaz who memorized 30 chapters of the Islamic Scripture (from the Quran) and 12 non-Huffaz as the control group. All participants had normal hearing perception and underwent an ABR test with and without psychological tasks. The ABR was elicited at 70 dB nHL using a 3000 Hz tone burst stimulus with a 2-0-2 cycle at a stimulus repetition rate of 40 Hz. The ABR wave V amplitude and latencies were measured and statistically compared. A forward digit span test was also conducted to determine participants' working memory capacity.

    Results: There were no significant differences in the ABR wave V amplitudes and latencies between Huffaz and non-Huffaz in ABR with and without psychological tasks. There were also no significant differences in the ABR wave V amplitudes and latencies in both groups of ABR with and without psychological tasks. In addition, no significant differences were identified in the digit span working memory score between both groups.

    Conclusions: In this study, based on the ABR findings, Huffaz showed the same auditory sensory gating capacity as the non-Huffaz group. The ABR result was consistent with the digit span working memory test score. This finding implies that both groups have similar working memory performance. However, the conclusion is limited to the specific assessment method that we used in this study.

  4. Majid AAA, Wu DT, Koh CA
    Langmuir, 2017 10 24;33(42):11436-11445.
    PMID: 28926254 DOI: 10.1021/acs.langmuir.7b02642
    In situ rheological measurements for clathrate hydrate slurries were performed using a high pressure rheometer to determine the effect of hydrate particles on the viscosity and transportability of these slurries. These measurements were conducted using a well-characterized model water-in-oil emulsion ( Delgado-Linares et al. Model Water in-Oil Emulsions for Gas Hydrate Studies in Oil Continuous Systems . Energy Fuels 2013 , 27 , 4564 - 4573 ). The emulsion consists of a model liquid hydrocarbon, water, and a surfactant mixture of sorbitane monooleate 80 (Span 80) and sodium di-2-ethylhexylsulfosuccinate (Aerosol OT, AOT). This emulsion was used as an analog to water-in-crude oil (w/o) emulsions and provides reproducible results. The flow properties of the model w/o emulsion prior to hydrate formation were investigated in terms of several parameters including water percentage, temperature and pressure. A general equation that describes the viscosity of the emulsion as a function of the aforementioned parameters was developed. This general equation was able to predict the viscosity of a saturated emulsion at various temperatures and water percentages to within ±13% error. The general equation was then used to analyze the effect of hydrate formation on the transportability of gas hydrate slurries. As for hydrate slurries investigation, measurements were performed using methane gas as the hydrate former and a straight vane impeller as a stirring system. Tests were conducted at constant temperature and pressure (1 °C and 1500 psig of methane) and water percentages ranging from 5 to 30 vol %. Results of this work were analyzed and presented in terms of relative values, i.e., viscosities of the slurries relative to the viscosities of the continuous phase at similar temperature and pressure. In this work, a correlation to predict the relative viscosity of a hydrate slurry at various hydrate volume fractions was developed. Analysis of the developed correlation showed that the model was able to predict the relative viscosity of a hydrate slurry to within ±17% error.
  5. Idriss AA, Ahmad AK
    Bull Environ Contam Toxicol, 2015 Feb;94(2):204-8.
    PMID: 25564001 DOI: 10.1007/s00128-014-1452-x
    This study examined the concentration of heavy metals in 13 fish species. The results indicated that shellfish species (clams) have the highest metal concentrations, followed by demersal and pelagic fishes. The mean concentration of metals in clams are Zn 88.74 ± 11.98 µg/g, Cu 4.96 ± 1.06 µg/g, Pb 1.22 ± 0.19 µg/g, Cd 0.34 ± 0.04 µg/g dry wt. basis, whereas the same measure in fish tissues was 58.04 ± 18.51, 2.47 ± 1.21, 0.58 ± 0.27 and 0.17 ± 0.08 µg/g dry wt. basis. The concentrations of heavy metals in clams and fish tissues were still lower than the maximum allowable concentrations as suggested by the Malaysian Food Act (1983) and are considered safe for local human consumption.
  6. Ahmad AA, Hameed BH
    J Hazard Mater, 2010 Mar 15;175(1-3):298-303.
    PMID: 19883979 DOI: 10.1016/j.jhazmat.2009.10.003
    In this work, the adsorption potential of bamboo waste based granular activated carbon (BGAC) to remove C.I. Reactive Black (RB5) from aqueous solution was investigated using fixed-bed adsorption column. The effects of inlet RB5 concentration (50-200mg/L), feed flow rate (10-30 mL/min) and activated carbon bed height (40-80 mm) on the breakthrough characteristics of the adsorption system were determined. The highest bed capacity of 39.02 mg/g was obtained using 100mg/L inlet dye concentration, 80 mm bed height and 10 mL/min flow rate. The adsorption data were fitted to three well-established fixed-bed adsorption models namely, Adam's-Bohart, Thomas and Yoon-Nelson models. The results fitted well to the Thomas and Yoon-Nelson models with coefficients of correlation R(2)>or=0.93 at different conditions. The BGAC was shown to be suitable adsorbent for adsorption of RB5 using fixed-bed adsorption column.
  7. Ahmad AA, Hameed BH
    J Hazard Mater, 2010 Jan 15;173(1-3):487-93.
    PMID: 19765899 DOI: 10.1016/j.jhazmat.2009.08.111
    This study deals with the use of activated carbon prepared from bamboo waste (BMAC), as an adsorbent for the removal of chemical oxygen demand (COD) and color of cotton textile mill wastewater. Bamboo waste was used to prepare activated carbon by chemical activation using phosphoric acid (H(3)PO(4)) as chemical agent. The effects of three preparation variables activation temperature, activation time and H(3)PO(4):precursor (wt%) impregnation ratio on the color and COD removal were investigated. Based on the central composite design (CCD) and quadratic models were developed to correlate the preparation variables to the color and COD. From the analysis of variance (ANOVA), the most influential factor on each experimental design response was identified. The optimum condition was obtained by using temperature of 556 degrees C, activation time of 2.33 h and chemical impregnation ratio of 5.24, which resulted in 93.08% of color and 73.98% of COD.
  8. Ahmad AA, Hameed BH
    J Hazard Mater, 2009 Dec 30;172(2-3):1538-43.
    PMID: 19740605 DOI: 10.1016/j.jhazmat.2009.08.025
    In this work, activated carbon was prepared from bamboo waste by chemical activation method using phosphoric acid as activating agent. The activated carbon was evaluated for chemical oxygen demand (COD) and color reduction of a real textile mill effluent. A maximum reduction in color and COD of 91.84% and 75.21%, respectively was achieved. As a result, the standard B discharge limit of color and COD under the Malaysian Environmental Quality act 1974 was met. The Freundlich isotherm model was found best to describe the obtained equilibrium adsorption data at 30 degrees C. The Brunauer-Emmett-Teller (BET) surface area, total pore volume and the average pore diameter were 988.23 m(2)/g, 0.69 cm(3)/g and 2.82 nm, respectively. Various functional groups on the prepared bamboo activated carbon (BAC) were determined from the FTIR results.
  9. Hameed BH, Ahmad AA
    J Hazard Mater, 2009 May 30;164(2-3):870-5.
    PMID: 18838221 DOI: 10.1016/j.jhazmat.2008.08.084
    The potential of garlic peel (GP), agricultural waste, to remove methylene blue (MB) from aqueous solution was evaluated in a batch process. Experiments were carried out as function of contact time, initial concentration (25-200mg/L), pH (4-12) and temperature (303, 313 and 323 K). Adsorption isotherms were modeled with the Langmuir, Freundlich, and Temkin isotherms. The data fitted well with the Freundlich isotherm. The maximum monolayer adsorption capacities were found to be 82.64, 123.45, and 142.86 mg/g at 303, 313, and 323 K, respectively. The kinetic data were analyzed using pseudo-first-order and pseudo-second-order models. The results indicated that the garlic peel could be an alternative for more costly adsorbents used for dye removal.
  10. Ahmad AL, Mustafa NN
    J Colloid Interface Sci, 2006 Sep 15;301(2):575-84.
    PMID: 16797579
    The alumina ceramic membrane has been modified by the addition of palladium in order to improve the H(2) permeability and selectivity. Palladium-alumina ceramic membrane was prepared via a sol-gel method and subjected to thermal treatment in the temperature range 500-1100 degrees C. Fractal analysis from nitrogen adsorption isotherm is used to study the pore surface roughness of palladium-alumina ceramic membrane with different chemical composition (nitric acid, PVA and palladium) and calcinations process in terms of surface fractal dimension, D. Frenkel-Halsey-Hill (FHH) model was used to determine the D value of palladium-alumina membrane. Following FHH model, the D value of palladium-alumina membrane increased as the calcinations temperature increased from 500 to 700 degrees C but decreased after calcined at 900 and 1100 degrees C. With increasing palladium concentration from 0.5 g Pd/100 ml H(2)O to 2 g Pd/100 ml H(2)O, D value of membrane decreased, indicating to the smoother surface. Addition of higher amount of PVA and palladium reduced the surface fractal of the membrane due to the heterogeneous distribution of pores. However, the D value increased when nitric acid concentration was increased from 1 to 15 M. The effect of calcinations temperature, PVA ratio, palladium and acid concentration on membrane surface area, pore size and pore distribution also studied.
  11. Zakaria R, Ahmad AH, Othman Z
    Folia Biol. (Praha), 2016;62(5):181-187.
    PMID: 27978412
    Pineal melatonin biosynthesis is regulated by the circadian clock located in the suprachiasmatic nucleus of the hypothalamus. Melatonin has been found to modulate the learning and memory process in human as well as in animals. Endogenous melatonin modulates the process of newly acquired information into long-term memory, while melatonin treatment has been found to reduce memory deficits in elderly people and in various animal models. However, the mechanisms mediating the enhancing effect of melatonin on memory remain elusive. This review intends to explore the possible mechanisms by looking at previous data on the effects of melatonin treatment on memory performance in rodents.
  12. Ahmad A, Dada AC, Usup G
    PMID: 24974655
    Partial gene sequences of phenylalanyl-tRNA synthase alpha subunit (pheS) and RNA polymerase alpha subunit (rpoA) were evaluated for species delineation and detection of recombination among enterococci populations recovered from a bathing beach impacted by low tide river flow. At inter-species level, a maximum similarity of 86.5% and 94.8% was observed among the enterococci pheS and rpoA sequence, respectively. A superimposed plot of delimited pairwise similarity values obtained for 266 pair-wise observations revealed that while there was a harmony between species identity obtained from both genes, pheS was more discriminatory than rpoA. The difference was more pronounced for inter-species comparison. A number of putative recombination events between indigenous and non-indigenous strains was detected based on a library of aligned sequences. Virulence genes cyl, esp, gelE and asa were detected in 7, 22, 100 and 63%, respectively among river isolates but at lower proportion of 0, 20, 67 and 42%, respectively among beach water isolates. Random amplified polymorphic DNA profiling presented evidence suggesting low tide river as a source of fecal enterococci entering the recreation beach water. Multilocus sequence typing analysis of a number of Enterococcus faecalis isolates presented four sequence types, ST59, 117, 181 and 474. The presence of genetically diverse fecal enterococci with associated virulence traits and a background of recombination events in surface recreational water could present a potential public health risk.
  13. Taweel A, Shuhaimi-Othman M, Ahmad AK
    Ecotoxicol Environ Saf, 2013 Jul;93:45-51.
    PMID: 23642778 DOI: 10.1016/j.ecoenv.2013.03.031
    Concentrations of the heavy metals copper (Cu), cadmium (Cd), zinc (Zn), lead (Pb) and nickel (Ni) were determined in the liver, gills and muscles of tilapia fish from the Langat River and Engineering Lake, Bangi, Selangor, Malaysia. There were differences in the concentrations of the studied heavy metals between different organs and between sites. In the liver samples, Cu>Zn>Ni>Pb>Cd, and in the gills and muscle, Zn>Ni>Cu>Pb>Cd. Levels of Cu, Cd, Zn and Pb in the liver samples from Engineering Lake were higher than in those from the Langat River, whereas the Ni levels in the liver samples from the Langat River were greater than in those from Engineering Lake. Cd levels in the fish muscle from Engineering Lake were lower than in that from the Langat River. Meanwhile, the Cd, Zn and Pb levels in the fish muscle from the Langat River were lower than in that from Engineering Lake, and the Ni levels were almost the same in the fish muscle samples from the two sites. The health risks associated with Cu, Cd, Zn, Pb and Ni were assessed based on the target hazard quotients. In the Langat River, the risk from Cu is minimal compared to the other studied elements, and the concentrations of Pb and Ni were determined to pose the greatest risk. The maximum allowable fish consumption rates (kg/d) based on Cu in Engineering Lake and the Langat River were 2.27 and 1.51 in December and 2.53 and 1.75 in February, respectively. The Cu concentrations resulted in the highest maximum allowable fish consumption rates compared with the other studied heavy metals, whereas those based on Pb were the lowest. A health risk analysis of the heavy metals measured in the fish muscle samples indicated that the fish can be classified at one of the safest levels for the general population and that there are no possible risks pertaining to tilapia fish consumption.
  14. Yusoff N, Taib NA, Ahmad A
    Asian Pac J Cancer Prev, 2011;12(10):2563-70.
    PMID: 22320956
    The aim of this study was to assess why women delay in getting treatment (i.e. surgery) for breast cancer, as well as to explore on what type of issues are involved in such delay cases. Basic interpretative of qualitative methodology was applied to construct the reality of delay phenomena, and its interaction with social worlds. Six themes were identified: new conception of breast cancer treatment, psychological defenses, health support system, symtomatology experience, model and barriers. The delay issue in breast cancer requires attention as a multidimensional problem as this will facilitate more comprehensive and effective intervention to reduce delay.
  15. Magurran AE, Khachonpisitsak S, Ahmad AB
    J Fish Biol, 2011 Dec;79(6):1393-412.
    PMID: 22136233 DOI: 10.1111/j.1095-8649.2011.03091.x
    For over 150 years, ecologists have been striving to explain fundamental patterns of biological diversity, such as the observation that communities invariably consist of common and rare species, and to unravel the processes that underpin these patterns. This task is increasingly urgent given the accelerating loss of biological diversity. Although fishes are the most diverse vertebrate taxon and fish communities occur in a wide range of habitats, they have been relatively little studied in the quest to elucidate the processes that shape patterns of biological diversity. Here, some of the topics that investigations of fish assemblages can illuminate are highlighted. These include the characteristics of ecological communities and the role that dispersal limitation plays in structuring them, the distinction between core and occasional species, the insights that evaluating abundance in different currencies can bring and the assessment of community capacity. Questions are identified that future investigations of fish communities might tackle and a case study of a biodiverse ecoregion (Thailand and Peninsula Malaysia) is used to illustrate the need for better links between these ecological questions and effective conservation practice.
  16. Ahmad A, Ghufran R, Abd Wahid Z
    J Hazard Mater, 2011 Dec 30;198:40-8.
    PMID: 22047724 DOI: 10.1016/j.jhazmat.2011.10.008
    The granulation process in palm oil mill effluent using calcium oxide-cement kiln dust (CaO-CKD) provides an attractive and cost effective treatment option. In this study the efficiency of CaO-CKD at doses of 1.5-20 g/l was tested in batch experiments and found that 10 g of CaO/l caused the greatest degradation of VFA, butyrate and acetate. An upflow anaerobic sludge blanket (UASB) reactor was operated continuously at 35°C for 150 days to investigate the effect of CaO-CKD on sludge granulation and methanogenesis during start-up. The treatment of POME emphasized the influence of varying organic loading rates (OLR). Up to 94.9% of COD was removed when the reactor was fed with the 15.5-65.5 g-CODg/l at an OLR of 4.5-12.5 kg-COD/m(3)d, suggesting the feasibility of using CaO in an UASB process to treat POME. The ratio of volatile solids/total solids (VS/TS) and volatile fatty acids in the anaerobic sludge in the UASB reactor decreased significantly after long-term operation due to the precipitation of calcium carbonate in the granules. Granulation and methanogenesis decreased with an increase in the influent CaO-CKD concentration.
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