Displaying publications 101 - 120 of 292 in total

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  1. Ultrasound and enzyme assisted preparation of novel lactoferrin-cereal phenolic acid conjugates: structural, physicochemical and functional properties
    Li Y, Dong L, Liu Y, Chen Q, Wu Z, Liu L, et al.
    Food Chem, 2024 Mar 01;435:137572.
    PMID: 37778268 DOI: 10.1016/j.foodchem.2023.137572
    The effects of covalent binding of protocatechuic acid (PA) and gallic acid (GA) to lactoferrin (LF) on the structure, functional, and antioxidant properties of the protein conjugate were investigated. These protein-phenolic conjugates were produced by laccase cross-linking and ultrasound-assisted free radical grafting, which were characterized using turbidity, particle size, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analyses. Structural changes in conjugates were monitored by endogenous fluorescence spectroscopy, fourier transform infrared spectroscopy (FTIR), and circular dichroism (CD). The antioxidant capacities and pH stability were determined using DPPH, ABTS, FRAP, and potentiometric analysis. The enzymatic cross-linking and free radical grafting yielded LF-PA/GA conjugates with altered hydrodynamic diameter and zeta-potential. Spectroscopic and chromatographic analyses revealed that binding to PA/GA altered the molecular structure of LF, with a decrease in LF isoelectric point post binding to PA/GA, without affecting antioxidant activities. In conclusion, LF-PA/GA conjugates present potential applications in the food industry.
  2. Fulltext Role of diabetes in the prognosis and therapeutic outcome of tuberculosis
    Syed Suleiman SA, Ishaq Aweis DM, Mohamed AJ, Razakmuttalif A, Moussa MA
    Int J Endocrinol, 2012;2012:645362.
    PMID: 22570649 DOI: 10.1155/2012/645362
    Background. Increased susceptibility of diabetic mellitus (DM) patients to infection, including tuberculosis (TB), is well documented. The prevalence of DM in Malaysia is reaching epidemic proportions. In this study, we sought to assess risk factors for TB and the impact of DM on the outcome of TB treatment. Methods. TB patients, diabetic patients, and diabetic patients with TB were divided into three groups of 200 subjects each. Data were obtained from patients' medical files at the beginning and end of the study period. Prevalence rates of DM and HIV among TB patients were assessed. Prognosis, TB-related complications, anatomical site of infection, and duration of infection and diabetes were also examined. Results. The prevalence rates of HIV and DM amongst TB patients were 7.7 and 30%, respectively. The diabetic TB patient group contained more males (72%) and smokers (45.5%) compared to the nondiabetic group (58.3% and 33.5%, resp.). Approximately 74% of diabetic patients were Mycobacterium sputum positive compared to only 51% of nondiabetic patients. Diabetic patients were also more likely to develop pulmonary TB (87%) compared to nondiabetic TB patients (59%). Diabetic TB patients had a higher mortality rate (7.5%) compared to the TB only and DM only groups (1 and 2%, resp.). The duration of TB symptoms was longer in nondiabetic TB patients compared to diabetic TB patients (4.5 versus 2.6 months, resp.). Diabetes antedated TB by a mean time of 4 years. Conclusions. We found a higher number of sputum-smear-positive cases and pulmonary TB cases as well as a greater number of males and higher mortality rate in diabetic patients compared to nondiabetic patients.
  3. Demystifying uncertainty in PM10 susceptibility mapping using variable drop-off in extreme-gradient boosting (XGB) and random forest (RF) algorithms
    AlThuwaynee OF, Kim SW, Najemaden MA, Aydda A, Balogun AL, Fayyadh MM, et al.
    Environ Sci Pollut Res Int, 2021 Aug;28(32):43544-43566.
    PMID: 33834339 DOI: 10.1007/s11356-021-13255-4
    This study investigates uncertainty in machine learning that can occur when there is significant variance in the prediction importance level of the independent variables, especially when the ROC fails to reflect the unbalanced effect of prediction variables. A variable drop-off loop function, based on the concept of early termination for reduction of model capacity, regularization, and generalization control, was tested. A susceptibility index for airborne particulate matter of less than 10 μm diameter (PM10) was modeled using monthly maximum values and spectral bands and indices from Landsat 8 imagery, and Open Street Maps were used to prepare a range of independent variables. Probability and classification index maps were prepared using extreme-gradient boosting (XGBOOST) and random forest (RF) algorithms. These were assessed against utility criteria such as a confusion matrix of overall accuracy, quantity of variables, processing delay, degree of overfitting, importance distribution, and area under the receiver operating characteristic curve (ROC).
  4. Case management of malaria fever at community pharmacies in Pakistan: a threat to rational drug use
    Malik M, Hassali MA, Shafie AA, Hussain A, Aljadhey H, Saleem F
    Pharm Pract (Granada), 2013 Jan;11(1):8-16.
    PMID: 24155844
    OBJECTIVE: To document the case management of uncomplicated malaria fever at community pharmacies located in the two major cities of Pakistan; Islamabad (national capital) and Rawalpindi (twin city).

    METHODS: A comparative, cross-sectional study was designed to document the management of uncomplicated malaria fever at community pharmacies in twin cities of Pakistan through simulated patient visits. Visits were conducted in 238 randomly selected pharmacies to request advice for a simulated patient case of malaria. The pharmacy's management was scored on a checklist including history taking and provision of advice and information. Kruskal-Wallis test and Mann-Whitney U test were used to compare management of uncomplicated malaria fever by different types of dispensers working at community pharmacies situated at different locations in the twin cities.

    RESULTS: The simulated patients were handled by salesmen (74.8%, n=178), pharmacist (5.4%, n=13) and diploma holders (19.8 %, n=47). Medication was dispensed in 83.1 % (n=198) of the visits, but only few of the treated cases were in accordance to standard treatment guidelines for malaria. However, in 14.8% (n=35) of the cases the simulated patients were directly referred to a physician. There was a significant difference observed in the process of history taking performed by different dispensers (e.g. pharmacist, pharmacy assistant, pharmacy diploma holders and salesman) while no significant differences in the provision of advice by these dispensers was observed. Pharmacists were seen more frequently involved in the process of history taking if available at the community pharmacies. On the other hand, no significant differences were observed in the case management (history taking and provision of advice) for the treatment of malaria fever among community pharmacies situated at different locations (e.g. near hospital/super market/small market) in the twin cities.

    CONCLUSIONS: The results of the study revealed that the overall process of disease management of uncomplicated malaria fever at community pharmacies was not in accordance with the national standard treatment guidelines for malaria. Patients were being treated by untrained personnel's at community pharmacies without any understanding of referral. However, pharmacists were more frequently involved in history taking, though their availability was low at community pharmacies.

  5. Fulltext Patients' beliefs about generic medicines in Malaysia
    Wong ZY, Hassali MA, Alrasheedy AA, Saleem F, Yahaya AH, Aljadhey H
    Pharm Pract (Granada), 2014 Oct;12(4):474.
    PMID: 25580171
    BACKGROUND: Acceptance of generic medicines by patients is an essential factor given that they are the end users of these medicines. In fact, adequate knowledge and positive perceptions are prerequisite to patients' acceptance and use of generic medicines.
    OBJECTIVE: To assess the current belief and views of patients about generic medicines in Malaysia.
    METHOD: This was a self-administered questionnaire-based study. The study was conducted with patients visiting outpatient pharmacy department at a tertiary care hospital in Malaysia. The Malaysian version of Generic Medicines Scale (GMS) was used. The GMS consists of two subscales: efficacy and similarity of generic medicines to original brand medicines. The efficacy subscale consists of 10 items while the similarity subscale consists of 6 items. The responses to the items were framed as a five-point Likert scale (1=strongly disagree to 5=strongly agree).
    RESULTS: A total of 202 out of 300 patients participated in the study, giving a response rate of 67.3%. In this study, only 49% of them (n=99) knew the term 'generic medicine'. Moreover, only 53.5% of the respondents (n=108) believed that the efficacy of generic medicines was the same as original brand medicines. In terms of quality, only 44% of the respondents (n=89) disagreed that generic medicines were of a lower quality. About one third (n=65, 32.2%) believed that generic medicines were cheaper because they were less efficacious. In terms of side effects, 44.5% of the respondents (n=90) believed that generic medicines had the same side effect profile as original brand medicines.
    CONCLUSIONS: The study finding showed that almost half of the respondents had negative belief in generic medicines. Similarly, many patients were not aware of the similarities and differences between generic and original brand medicines. Therefore, there is a need to provide patients with adequate information about generic medicines.

    Study site: outpatient pharmacy department at a tertiary care hospital in Malaysia
  6. Investigating the crude oil biodegradation performance in bioreactor by using a consortium of symbiotic bacteria
    Chuah LF, Nawaz A, Dailin DJ, Oloruntobi O, Habila MA, Tong WY, et al.
    Chemosphere, 2023 Oct;337:139293.
    PMID: 37369285 DOI: 10.1016/j.chemosphere.2023.139293
    Crude oil pollution is one of the most serious environmental issues today, and the clean-up procedure is perhaps the most difficult. Within one to three weeks, the vast majority of oil bacteria may degrade approximately 60% of the crude oil, leaving approximately 40% intact. The by-product metabolites produced during the breakdown of oil are essentially organic molecules in nature. These metabolites inhibit its enzymes, preventing the oil bacteria from further degrading the oil. By combining a variety of different oils with heterotrophic bacteria in a bioreactor, the rate of crude oil biodegradation was accelerated. In this study, two strains of oil-resistant, heterotrophic bacteria (OG1 and OG2-Erythrobacter citreus) and a bacterium that uses hydrocarbons (AR3-Pseudomonas pseudoalcaligenes) were used. Gas chromatography-mass spectroscopy was used to investigate the effectiveness of this consortium of symbiotic bacteria in the biodegradation of crude oil. According to gravimetric and gas chromatography analyses, the consortium bacteria digested 69.6% of the crude oil in the bioreactor, while the AR3 single strain was only able to destroy 61.9% of it. Under the same experimental conditions, consortium bacteria degraded approximately 84550.851 ppb (96.3%) of 16 aliphatic hydrocarbons and 9333.178 ppb (70.5%) of 16 aromatic hydrocarbons in the bioreactor. It may be inferred that the novel consortium of symbiotic bacteria accelerated the biodegradation process and had great potential for use in increasing the bioremediation of hydrocarbon-contaminated locations.
  7. Fatty Acid Conjugated Chalcones as Tubulin Polymerization Inhibitors: Design, Synthesis, QSAR, and Apoptotic and Antiproliferative Activity
    Mohamed SM, Abou-Ghadir OMF, El-Mokhtar MA, Aboraia AS, Abdel Aal AM
    J Nat Prod, 2023 May 26;86(5):1150-1158.
    PMID: 37098901 DOI: 10.1021/acs.jnatprod.2c00793
    Cancer is often associated with an aberrant increase in tubulin and microtubule activity required for cell migration, invasion, and metastasis. A new series of fatty acid conjugated chalcones have been designed as tubulin polymerization inhibitors and anticancer candidates. These conjugates were designed to harness the beneficial physicochemical properties, ease of synthesis, and tubulin inhibitory activity of two classes of natural components. New lipidated chalcones were synthesized from 4-aminoacetophenone via N-acylation followed by condensation with different aromatic aldehydes. All new compounds showed strong inhibition of tubulin polymerization and antiproliferative activity against breast and lung cancer cell lines (MCF-7 and A549) at low or sub-micromolar concentrations. A significant apoptotic effect was shown using a flow cytometry assay that corresponded to cytotoxicity against cancer cell lines, as indicated by a 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide assay. Decanoic acid conjugates were more potent than longer lipid analogues, with the most active being more potent than the reference tubulin inhibitor, combretastatin-A4 and the anticancer drug, doxorubicin. None of the newly synthesized compounds caused any detectable cytotoxicity against the normal cell line (Wi-38) or hemolysis of red blood cells below 100 μM. It is unlikely that the new conjugates described would affect normal cells or interrupt with cell membranes due to their lipidic nature. A quantitative structure-activity relationship analysis was performed to determine the influence of 315 descriptors of the physicochemical properties of the new conjugates on their tubulin inhibitory activity. The obtained model revealed a strong correlation between the tubulin inhibitory activity of the investigated compounds and their dipole moment and degree of reactivity.
  8. Dissecting Maillard reaction production in fried foods: Formation mechanisms, sensory characteristic attribution, control strategy, and gut homeostasis regulation
    Shi B, Guo X, Liu H, Jiang K, Liu L, Yan N, et al.
    Food Chem, 2024 Apr 16;438:137994.
    PMID: 37984001 DOI: 10.1016/j.foodchem.2023.137994
    Foods rich in carbohydrates or fats undergo the Maillard reaction during frying, which promotes the color, flavor and sensory characteristics formation. In the meanwhile, Maillard reaction intermediates and advanced glycation end products (AGEs) have a negative impact on food sensory quality and gut homeostasis. This negative effect can be influenced by food composition and other processing factors. Whole grain products are rich in polyphenols, which can capture carbonyl compounds in Maillard reaction, and reduce the production of AGEs during frying. This review summarizes the Maillard reaction production intermediates and AGEs formation mechanism in fried food and analyzes the factors affecting the sensory formation of food. In the meanwhile, the effects of Maillard reaction intermediates and AGEs on gut homeostasis were summarized. Overall, the innovative processing methods about the Maillard reaction are summarized to optimize the sensory properties of fried foods while minimizing the formation of AGEs.
  9. Effect of steam sterilisation on lipophilic nutrient stability in a chloroplast-rich fraction (CRF) recovered from postharvest, pea vine field residue (haulm)
    Wattanakul J, Syamila M, Briars R, Ayed C, Price R, Darwish R, et al.
    Food Chem, 2021 Jan 01;334:127589.
    PMID: 32707366 DOI: 10.1016/j.foodchem.2020.127589
    Postharvest, pea vine field residue (haulm) was steam-sterilised and then juiced; a chloroplast-rich fraction (CRF) was recovered from the juice by centrifugation. The stability of selected nutrients (β-carotene, lutein, and α-tocopherol) in the freeze-dried CRF material was measured over 84 days; the impact of temperature (-20 °C, 4 °C, 25 °C and 40 °C), light and air on nutrient stability was established. All three nutrients were stable at -20 °C and 4 °C in the presence or absence of air; this stability was lost at higher temperatures in the presence of air. The extent and rate of nutrient breakdown significantly increased when the CRF samples were exposed to light. β-Carotene appeared to be more susceptible to degradation than lutein and α-tocopherol at 40 °C in the presence of air, but when CRF was exposed to light all three nutrients measured were significantly broken down during storage at 25 °C or 40 °C, whether exposed to air or not.
  10. Fulltext Defining habitat covariates in camera-trap based occupancy studies
    Niedballa J, Sollmann R, bin Mohamed A, Bender J, Wilting A
    Sci Rep, 2015;5:17041.
    PMID: 26596779 DOI: 10.1038/srep17041
    In species-habitat association studies, both the type and spatial scale of habitat covariates need to match the ecology of the focal species. We assessed the potential of high-resolution satellite imagery for generating habitat covariates using camera-trapping data from Sabah, Malaysian Borneo, within an occupancy framework. We tested the predictive power of covariates generated from satellite imagery at different resolutions and extents (focal patch sizes, 10-500 m around sample points) on estimates of occupancy patterns of six small to medium sized mammal species/species groups. High-resolution land cover information had considerably more model support for small, patchily distributed habitat features, whereas it had no advantage for large, homogeneous habitat features. A comparison of different focal patch sizes including remote sensing data and an in-situ measure showed that patches with a 50-m radius had most support for the target species. Thus, high-resolution satellite imagery proved to be particularly useful in heterogeneous landscapes, and can be used as a surrogate for certain in-situ measures, reducing field effort in logistically challenging environments. Additionally, remote sensed data provide more flexibility in defining appropriate spatial scales, which we show to impact estimates of wildlife-habitat associations.
  11. Fulltext Optimal battery sizing in photovoltaic based distributed generation using enhanced opposition-based firefly algorithm for voltage rise mitigation
    Wong LA, Shareef H, Mohamed A, Ibrahim AA
    ScientificWorldJournal, 2014;2014:752096.
    PMID: 25054184 DOI: 10.1155/2014/752096
    This paper presents the application of enhanced opposition-based firefly algorithm in obtaining the optimal battery energy storage systems (BESS) sizing in photovoltaic generation integrated radial distribution network in order to mitigate the voltage rise problem. Initially, the performance of the original firefly algorithm is enhanced by utilizing the opposition-based learning and introducing inertia weight. After evaluating the performance of the enhanced opposition-based firefly algorithm (EOFA) with fifteen benchmark functions, it is then adopted to determine the optimal size for BESS. Two optimization processes are conducted where the first optimization aims to obtain the optimal battery output power on hourly basis and the second optimization aims to obtain the optimal BESS capacity by considering the state of charge constraint of BESS. The effectiveness of the proposed method is validated by applying the algorithm to the 69-bus distribution system and by comparing the performance of EOFA with conventional firefly algorithm and gravitational search algorithm. Results show that EOFA has the best performance comparatively in terms of mitigating the voltage rise problem.
  12. Fulltext Comparative study of popular objective functions for damping power system oscillations in multimachine system
    Islam NN, Hannan MA, Shareef H, Mohamed A, Salam MA
    ScientificWorldJournal, 2014;2014:549094.
    PMID: 24977210 DOI: 10.1155/2014/549094
    Power oscillation damping controller is designed in linearized model with heuristic optimization techniques. Selection of the objective function is very crucial for damping controller design by optimization algorithms. In this research, comparative analysis has been carried out to evaluate the effectiveness of popular objective functions used in power system oscillation damping. Two-stage lead-lag damping controller by means of power system stabilizers is optimized using differential search algorithm for different objective functions. Linearized model simulations are performed to compare the dominant mode's performance and then the nonlinear model is continued to evaluate the damping performance over power system oscillations. All the simulations are conducted in two-area four-machine power system to bring a detailed analysis. Investigated results proved that multiobjective D-shaped function is an effective objective function in terms of moving unstable and lightly damped electromechanical modes into stable region. Thus, D-shape function ultimately improves overall system damping and concurrently enhances power system reliability.
  13. In vivo anti-hyperglycemic activity of saliva extract from the tropical leech Hirudinaria manillensis
    Mohammed AA, Mohammad GA, Mohamed A, Mohamed A, Ahmed M
    Chin J Nat Med, 2013 Sep;11(5):488-93.
    PMID: 24359772 DOI: 10.1016/S1875-5364(13)60089-8
    The anticoagulant effect of leech saliva was traditionally employed in the treatment of diabetes mellitus complications such as peripheral vascular complications. This study was carried out to examine the effect of leech saliva extract (LSE) on blood glucose levels in alloxan-induced diabetic rats. First, LSE was collected from leeches which were fed on a phagostimulatory solution. Second, total protein concentration was estimated using the Bradford assay. Third, diabetic rats were injected subcutaneously (sc) with LSE at doses of 500 and 1 000 μg·kg(-1) body weight (bw). Other diabetic rats were injected sc with insulin at doses of 10 and 20 U·kg(-1) bw. Another group was injected simultaneously with LSE (250 μg·kg(-1) bw) and insulin (10 U·kg(-1) bw). Fasting blood glucose (FBG) concentrations were monitored during a study period of eight hours at regular intervals. Findings showed that both doses of LSE resulted in a significant and gradual decrease in FBG starting from 10%-18% downfall after two hours of injection reaching the maximal reduction activity of 58% after eight hours. Remarkably, LSE was sufficient to bring the rats to a near norm-glycemic state. The high dose of insulin induced a severe hypoglycemic condition after 2-4 h of injection. The lower dose was able to decline FBG for 2-6 h in rats which became diabetic again after 8 h. On the other hand, the concurrent injection of low doses of LSE and insulin produced a hypoglycemic effect with all rats showing normal FBG levels. Taken together, these findings indicated that the subcutaneous injection of LSE of the medicinal Malaysian leech was able to provide better glycemic control compared with insulin. Moreover, the synergism between LSE and insulin suggests that LSE could be utilized as an adjuvant medication in order to reduce insulin dosage or to achieve better control of blood glucose.
  14. An intelligent load shedding scheme using neural networks and neuro-fuzzy
    Haidar AM, Mohamed A, Al-Dabbagh M, Hussain A, Masoum M
    Int J Neural Syst, 2009 Dec;19(6):473-9.
    PMID: 20039470
    Load shedding is some of the essential requirement for maintaining security of modern power systems, particularly in competitive energy markets. This paper proposes an intelligent scheme for fast and accurate load shedding using neural networks for predicting the possible loss of load at the early stage and neuro-fuzzy for determining the amount of load shed in order to avoid a cascading outage. A large scale electrical power system has been considered to validate the performance of the proposed technique in determining the amount of load shed. The proposed techniques can provide tools for improving the reliability and continuity of power supply. This was confirmed by the results obtained in this research of which sample results are given in this paper.
  15. Evaluation of shear strength of oil treated laminated bamboo
    Sulaiman O, Hashim R, Wahab R, Ismail ZA, Samsi HW, Mohamed A
    Bioresour Technol, 2006 Dec;97(18):2466-9.
    PMID: 16524726
    Studies were carried out on heat treatment of bamboo species Gigantochloa scortechinii Gamble using palm oil. The samples were laminated and glued. The adhesion results showed that the delamination of glue line increased as the temperature and duration of oil heat treatment increased. Maximum load and shear strength of the glue line reduced as the heat treatment become more severe. It was found that the palm oil used as the heating medium penetrated in some parts of the cell wall as well as in the cell lumen of the bamboo.
  16. Neural network modeling of the kinetics of SO2 removal by fly ash-based sorbent
    Raymond-Ooi EH, Lee KT, Mohamed AR, Chu KH
    J Environ Sci Health A Tox Hazard Subst Environ Eng, 2006;41(2):195-210.
    PMID: 16423725
    The mechanistic modeling of the sulfation reaction between fly ash-based sorbent and SO2 is a challenging task due to a variety reasons including the complexity of the reaction itself and the inability to measure some of the key parameters of the reaction. In this work, the possibility of modeling the sulfation reaction kinetics using a purely data-driven neural network was investigated. Experiments on SO2 removal by a sorbent prepared from coal fly ash/CaO/CaSO4 were conducted using a fixed bed reactor to generate a database to train and validate the neural network model. Extensive SO2 removal data points were obtained by varying three process variables, namely, SO2 inlet concentration (500-2000 mg/L), reaction temperature (60-80 degreesC), and relative humidity (50-70%), as a function of reaction time (0-60 min). Modeling results show that the neural network can provide excellent fits to the SO2 removal data after considerable training and can be successfully used to predict the extent of SO2 removal as a function of time even when the process variables are outside the training domain. From a modeling standpoint, the suitably trained and validated neural network with excellent interpolation and extrapolation properties could have immediate practical benefits in the absence of a theoretical model.
  17. Optimizing the specific surface area of fly ash-based sorbents for flue gas desulfurization
    Lee KT, Bhatia S, Mohamed AR, Chu KH
    Chemosphere, 2006 Jan;62(1):89-96.
    PMID: 15996711
    High performance sorbents for flue gas desulfurization can be synthesized by hydration of coal fly ash, calcium sulfate, and calcium oxide. In general, higher desulfurization activity correlates with higher sorbent surface area. Consequently, a major aim in sorbent synthesis is to maximize the sorbent surface area by optimizing the hydration conditions. This work presents an integrated modeling and optimization approach to sorbent synthesis based on statistical experimental design and two artificial intelligence techniques: neural network and genetic algorithm. In the first step of the approach, the main and interactive effects of three hydration variables on sorbent surface area were evaluated using a full factorial design. The hydration variables of interest to this study were hydration time, amount of coal fly ash, and amount of calcium sulfate and the levels investigated were 4-32 h, 5-15 g, and 0-12 g, respectively. In the second step, a neural network was used to model the relationship between the three hydration variables and the sorbent surface area. A genetic algorithm was used in the last step to optimize the input space of the resulting neural network model. According to this integrated modeling and optimization approach, an optimum sorbent surface area of 62.2m(2)g(-1) could be obtained by mixing 13.1g of coal fly ash and 5.5 g of calcium sulfate in a hydration process containing 100ml of water and 5 g of calcium oxide for a fixed hydration time of 10 h.
  18. Fulltext Improved Power System Stability Using Backtracking Search Algorithm for Coordination Design of PSS and TCSC Damping Controller
    Niamul Islam N, Hannan MA, Mohamed A, Shareef H
    PLoS One, 2016;11(1):e0146277.
    PMID: 26745265 DOI: 10.1371/journal.pone.0146277
    Power system oscillation is a serious threat to the stability of multimachine power systems. The coordinated control of power system stabilizers (PSS) and thyristor-controlled series compensation (TCSC) damping controllers is a commonly used technique to provide the required damping over different modes of growing oscillations. However, their coordinated design is a complex multimodal optimization problem that is very hard to solve using traditional tuning techniques. In addition, several limitations of traditionally used techniques prevent the optimum design of coordinated controllers. In this paper, an alternate technique for robust damping over oscillation is presented using backtracking search algorithm (BSA). A 5-area 16-machine benchmark power system is considered to evaluate the design efficiency. The complete design process is conducted in a linear time-invariant (LTI) model of a power system. It includes the design formulation into a multi-objective function from the system eigenvalues. Later on, nonlinear time-domain simulations are used to compare the damping performances for different local and inter-area modes of power system oscillations. The performance of the BSA technique is compared against that of the popular particle swarm optimization (PSO) for coordinated design efficiency. Damping performances using different design techniques are compared in term of settling time and overshoot of oscillations. The results obtained verify that the BSA-based design improves the system stability significantly. The stability of the multimachine power system is improved by up to 74.47% and 79.93% for an inter-area mode and a local mode of oscillation, respectively. Thus, the proposed technique for coordinated design has great potential to improve power system stability and to maintain its secure operation.
  19. Fulltext Markers of ventricular tachyarrythmias in patients with acromegaly
    Mohamed AL, Yusoff K, Muttalif AR, Khalid BAk
    Med J Malaysia, 1999 Sep;54(3):338-45.
    PMID: 11045060
    Sudden cardiac death is a known complication of acromegaly. Little is known of the exact mechanism leading to sudden cardiac death in these patients. Ventricular tachyarrhythmias may be an important cause. If this is so, clinical markers of ventricular tachyarrhythmias may be more common in this group of patients. The presence of these markers allow better risk stratification among acromegalic patients.
  20. Fulltext Parents' awareness and knowledge of the special needs of their hearing-impaired child
    Mukari SZ, Vandort S, Ahmad K, Saim L, Mohamed AS
    Med J Malaysia, 1999 Mar;54(1):87-95.
    PMID: 10972010
    We surveyed parents of school-aged hearing impaired children to investigate their awareness and knowledge of the special needs of their child, especially in the area of the usage of hearing aids and methods of communication. Questionnaires were distributed to parents of hearing impaired children at 13 special schools for the deaf in Malaysia. Out of 1,267 questionnaires given out, 787 (62.1%) were completed and returned. Results of the survey indicated the majority of parents (68.6%) suspected hearing loss late, that is after their child's first birthday, and there was a significant time lag before the suspicion was confirmed. Over 82.8% of the children were diagnosed only after 1 year of age, with 41.3% being diagnosed after 3 years of age. Hearing aids were fitted late (mean = 5.32 years; SD = 2.66). Hearing aid ownership was influenced by the factors of socio-economic level and ethnic group (p < 0.01) whereas knowledge of use and proper care of the aids was influenced by socio-economic level (p < 0.01). Communication methods were generally inappropriate with 41.3% of the mothers and 48.5% of the fathers reporting ignorance of Bahasa Malaysia Kod Tangan, the sign language that is commonly used by their children. The parents' choice of communication method was not significantly influenced by socio-economic level or ethnic group. The study revealed the present inadequate state of services available for the rehabilitation of children with congenital hearing impairment.
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