Displaying publications 1 - 20 of 89 in total

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  1. Fulltext Communication systems melioration by employing fast frequency hopping spread spectrum with low-density parity-check codes
    Yahya, A., Sidek, O., Salleh, M.F.M.
    ASM Science Journal, 2010;4(1):48-54.
    MyJurnal
    Frequency hopping spread spectrum (FHSS) systems with partial band interference require appropriate compounding of spread spectrum modulation, error correcting code, diversity and decoding method to receive improved transmission signal. In this paper, a fast FHSS system with regular low-density parity-check codes was employed to cater some anti-jamming competence by using good waterfall and error floor performance. The performance evalution of the previously mentioned system was conducted in the presence of partial band noise jamming. The best possible design of the system was achieved with the combination of diversity level L=2 with a probability rate of at 0.7 dB which showed the robustness of the system.
  2. Fulltext Effects of saline irrigation water on morphological characteristics of banana (Musa spp.)
    Al Harthy, K. M., Siti Aishah, H., Yahya, A., Roslan, I., Al Yahyai, R.
    International Food Research Journal, 2018;25(102):195-200.
    MyJurnal
    Banana is one of the most important food crops after rice, wheat and corn around the world. It is susceptible to a wide spectrum of non-infectious problems such as abiotic stresses resulting in restricting growth and production. Studies were conducted to determine the effects of four salinity levels (0.17 (control), 3.0, 6.0, and 9.0 dS m-1) on morphological characteristics of four banana cultivars at vegetative growth stage. Banana cultivars from the Cavendish group (Williams, Malindi) and plantains group (FHIA18 and Diwan) were grown in 61 x 76 cm polyethylene bags filled with soil mixture comprising of top soil, sand and peat moss (3:1:2 v/v), with pH ranging from 6 - 6.5 and EC 0.02 mScm-1. The experiment was carried out under a rain-shelter in split-plot design with three replicates. Plants were irrigated manually. Data were collected at 3, 6 and 9 months after transplanting. The results revealed that, the number of leaves, stem height, stem girth and total leaf area were significantly affected by salinity, variety and plant age. Significant interaction was also found between salinity and variety, salinity and plant age, as well as variety and plant age. The morphological characteristics of banana were negatively affected by higher salinity levels (6.0 and 9.0 dS m-1). Under similar salinity level, cultivar Malindi had higher number of leaves, stem height, stem girth and total leaf area as compared to cultivar Williams. Among plantains banana, cultivar FHIA18 was more tolerance to high salinity levels than Diwan cultivar, while Malindi from Cavendish group shows high salt tolerant than Williams. Therefore cultivars Malindi and FHIA18 could be grown in arid and semiarid environment depend on their tolerance to high salinity level above 1.0 dS m-1.
  3. Fulltext Food waste handling in Malaysia and comparison with other Asian countries
    Lim, W. J., Chin, N. L., Yusof, A. Y., Yahya, A., Tee, T. P.
    International Food Research Journal, 2016;23(101):1-6.
    MyJurnal
    The increasing amount of food waste in Malaysia in recent years has brought many environmental
    issues in the country where it affects the nation’s solid waste management framework. At the
    moment, the government is limited to other alternatives of food waste disposal besides the
    conventional landfill and incineration methods. This paper provides information on the current
    status of food waste handling, management, regulations, and policies in Malaysia. It helps
    to draw the problem and challenge to a clearer view in efforts of achieving sustainable and
    integrative food waste handling in the country.
  4. Fulltext Myocardial infarction induced by appetite suppressants in Malaysia
    Azarisman SM, Magdi YA, Noorfaizan S, Oteh M
    N Engl J Med, 2007 Nov 1;357(18):1873-4.
    PMID: 17978302 DOI: 10.1056/NEJMc070990
  5. Sociobiological risk factors for spontaneous abortion in Malaysia
    Tan NH, Yahya A, Adeeb N
    J Obstet Gynaecol (Tokyo 1995), 1995 Aug;21(4):313-8.
    PMID: 8775898
    OBJECTIVE: To evaluate the risk factors of spontaneous abortion.

    METHODS: A case-control study was conducted by interviewing 350 women who were admitted to the university gynaecological unit for spontaneous abortion and 350 women who delivered normally at the university obstetric unit. Odds ratios, as the estimators of relative risks, were calculated.

    RESULTS: The relative risk for spontaneous abortion among women in the age-group 30 to 39 years was 1.61 and among women above 40 years of age was 3.68 when compared to those below 30 years of age. In relation to career women, the relative risk of spontaneous abortion for housewives was 0.45. Ethnic group, parity, subfertility, previous induced abortion, ectopic pregnancy, contraception and menarcheal age did not influence the risk of spontaneous abortion.

    CONCLUSION: Increasing age and a woman's career are significant risk factors of spontaneous abortion.

  6. Bioremediation of palm oil mill effluent (POME) using indigenous Meyerozyma guilliermondii
    Ganapathy B, Yahya A, Ibrahim N
    Environ Sci Pollut Res Int, 2019 Apr;26(11):11113-11125.
    PMID: 30788704 DOI: 10.1007/s11356-019-04334-8
    Despite being a key Malaysian economic contributor, the oil palm industry generates a large quantity of environmental pollutant known as palm oil mill effluent (POME). Therefore, the need to remediate POME has drawn a mounting interest among environmental scientists. This study has pioneered the application of Meyerozyma guilliermondii with accession number (MH 374161) that was isolated indigenously in accessing its potential to degrade POME. This strain was able to treat POME in shake flask experiments under aerobic condition by utilising POME as a sole source of carbon. However, it has also been shown that the addition of suitable carbon and nitrogen sources has significantly improved the degradation potential of M. guilliermondii. The remediation of POME using this strain resulted in a substantial reduction of chemical oxygen demand (COD) of 72%, total nitrogen of 49.2% removal, ammonical nitrogen of 45.1% removal, total organic carbon of 46.6% removal, phosphate of 60.6% removal, and 92.4% removal of oil and grease after 7 days of treatment period. The strain also exhibited an extracellular lipase activity which promotes better wastewater treatment. Additionally, Fourier transform infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC-MS) analyses have specifically shown that M. guilliermondii strain can degrade hydrocarbons, fatty acids, and phenolic compounds present in the POME. Ultimately, this study has demonstrated that M. guilliermondii which was isolated indigenously exhibits an excellent degrading ability. Therefore, this strain is suitable to be employed in the remediation of POME, contributing to a safe discharge of the effluent into the environment.
  7. Comparative study of cytologic and colposcopic findings in preclinical cervical cancer
    Maziah AM, Sharifah NA, Yahya A
    Malays J Pathol, 1991 Dec;13(2):105-8.
    PMID: 1823091
    Seventy-seven patients who had PAP smear cytology and colposcopic examination in a 2-year period between 1988 and 1989 were reviewed. Those with findings indicative or suspicious of malignancy were subjected to biopsy. All 50 patients thus biopsied were confirmed to have preclinical cancer on histological examination. Compared against histology, PAP smear cytology gave an accuracy rate of 90% (5 false negatives) and colposcopy gave an accuracy rate of 94% (3 false negatives). These results demonstrate that the two techniques are useful as screening tests for preclinical cervical cancer. The results are improved if they are used complementarily. However, there was poor specificity in the categorisation of cervical cancer by both methods. This was probably due to the subjectiveness of the two procedures. The study also raised the possibility of a higher incidence of preclinical cervical cancer in the Chinese ethnic group.
  8. Analysis and outcome of 502 cases of laser excision cone (LEC) at the Samaritan Hospital for Women, London
    Yahya AA, McIndoe GA, Mason WP
    Asia Oceania J Obstet Gynaecol, 1992 Dec;18(4):315-8.
    PMID: 1492803
    When performed based on cytology, histological accuracy of the laser cone specimen improved with the more severe cytology. The incidence of adenocarcinoma in situ is 1.0%. With and without residual disease, the rate of abnormal cytology after laser excision cone are 0.6% and 1.6% respectively. There is good correlation between colposcopic biopsy and cone specimen in the more severe lesions. Out of 139 cases of incomplete excision, only 3 cases had abnormal cytology at follow-up. The complication rates are very low.
  9. Fulltext Understanding the structural, optical, and dielectric characteristics of SrLaLiTe1-xMnxO6 perovskites
    Halizan MZM, Mohamed Z, Yahya AK
    Sci Rep, 2021 May 07;11(1):9744.
    PMID: 33963258 DOI: 10.1038/s41598-021-89132-4
    In electronic applications, good dielectric permittivity material has huge potential in the capacitive energy storage devices. Herein, in the present work the dielectric study of SrLaLiTe1-xMnxO6 (x = 0.02, 0.04, 0.06, 0.08, and 0.10) double perovskites has been studied and discussed. These compounds were prepared through solid-state reaction method. All of the prepared compounds were confirmed to crystallized in monoclinic structure of P21/n space symmetry with better crystallization when dopant concentrations increased until x = 0.08. The formation of Li-O-Te/Mn bonds in octahedral structures in all compounds were confirmed in this study. The existence of peaks at specific wavenumbers indicated vibrations of B-site cations' bonds. When dopant amounts were increased from x = 0.02 to x = 0.08, there was an increasing trend of grains sizes formation in the compounds. The discussions on effects of grain sizes towards dielectric properties were included in this paper. Other important results and discussions comprised of the significant effects of dopant on the optical band gap (Eopt) and absorption frequencies of the compounds. The decreasing trend of Eopt towards semiconductor range indicated the compounds' promising potentials for optoelectronic device application.
  10. Cloning and functional analysis of the genes coding for 4-aminobenzenesulfonate 3,4-dioxygenase from Hydrogenophaga sp. PBC
    Gan HM, Shahir S, Yahya A
    Microbiology (Reading), 2012 Aug;158(Pt 8):1933-1941.
    PMID: 22609751 DOI: 10.1099/mic.0.059550-0
    The gene coding for the oxygenase component, sadA, of 4-aminobenzenesulfonate (4-ABS) 3,4-dioxygenase in Hydrogenophaga sp. PBC was previously identified via transposon mutagenesis. Expression of wild-type sadA in trans restored the ability of the sadA mutant to grow on 4-ABS. The inclusion of sadB and sadD, coding for a putative glutamine-synthetase-like protein and a plant-type ferredoxin, respectively, further improved the efficiency of 4-ABS degradation. Transcription analysis using the gfp promoter probe plasmid showed that sadABD was expressed during growth on 4-ABS and 4-sulfocatechol. Heterologous expression of sadABD in Escherichia coli led to the biotransformation of 4-ABS to a metabolite which shared a similar retention time and UV/vis profile with 4-sulfocatechol. The putative reductase gene sadC was isolated via degenerate PCR and expression of sadC and sadABD in E. coli led to maximal 4-ABS biotransformation. In E. coli, the deletion of sadB completely eliminated dioxygenase activity while the deletion of sadC or sadD led to a decrease in dioxygenase activity. Phylogenetic analysis of SadB showed that it is closely related to the glutamine-synthetase-like proteins involved in the aniline degradation pathway. This is the first discovery, to our knowledge, of the functional genetic components for 4-ABS aromatic ring hydroxylation in the bacterial domain.
  11. Fulltext Coverage extension and balancing the transmitted power of the moving relay node at LTE-A cellular network
    Aldhaibani JA, Yahya A, Ahmad RB
    ScientificWorldJournal, 2014;2014:815720.
    PMID: 24672378 DOI: 10.1155/2014/815720
    The poor capacity at cell boundaries is not enough to meet the growing demand and stringent design which required high capacity and throughput irrespective of user's location in the cellular network. In this paper, we propose new schemes for an optimum fixed relay node (RN) placement in LTE-A cellular network to enhance throughput and coverage extension at cell edge region. The proposed approach mitigates interferences between all nodes and ensures optimum utilization with the optimization of transmitted power. Moreover, we proposed a new algorithm to balance the transmitted power of moving relay node (MR) over cell size and providing required SNR and throughput at the users inside vehicle along with reducing the transmitted power consumption by MR. The numerical analysis along with the simulation results indicates that an improvement in capacity for users is 40% increment at downlink transmission from cell capacity. Furthermore, the results revealed that there is saving nearly 75% from transmitted power in MR after using proposed balancing algorithm. ATDI simulator was used to verify the numerical results, which deals with real digital cartographic and standard formats for terrain.
  12. Effect of Er substitution on ultrasonic anomaly in Dy(0.5-x)Er(x)Ba(0.5)CoO3 cobaltates
    Shamsuddin S, Ibrahim AB, Yahya AK
    Ultrasonics, 2013 Aug;53(6):1084-8.
    PMID: 23497912 DOI: 10.1016/j.ultras.2013.02.002
    Rare-earth cobaltates Dy0.5-xErxBa0.5CoO3 (x=0, 0.03 and 0.05) have been systematically investigated to elucidate the effect of Er substitution on elastic as well as magnetic and transport properties. DC electrical resistance and AC susceptibility measurements showed that the x=0 sample exhibited an insulating behavior and an anti-ferromagnetic (AFM) transition, TN at 198 K as well as ferromagnetic (FM) transition, TC at 260 K. Increasing of Er content suppressed the FM and AFM state suggestively due to the increase in size disorder arising from the size mismatch between A-site cations as shown from our calculation of variance σ(2). On the other hand, both absolute longitudinal and shear velocities and related elastic moduli measured at 210 K decreased with Er content in conjunction with the declining in the FM domain indicating a weakening in elastic properties. A longitudinal velocity anomaly characterized by a drop in velocity upon cooling before hardening with further cooling was observed for all samples. This abnormal elastic anomaly can be attributed due to the Jahn-Teller (JT) distortion of intermediate-spin Co(3+) ions. Analysis of the elastic anomaly using the mean-field theory suggested that it is related to the JT effect which transformed from dynamic to static type with decreasing temperature. The elastic anomaly shifted to lower temperature from 129 K (x=0) to 124 K (x=0.05) with Er substitution indicating a weakening of the static JT effect.
  13. Characteristics of developed granules containing selected decolourising bacteria for the degradation of textile wastewater
    Ibrahim Z, Amin MF, Yahya A, Aris A, Muda K
    Water Sci Technol, 2010;61(5):1279-88.
    PMID: 20220250 DOI: 10.2166/wst.2010.021
    Textile wastewater, one of the most polluted industrial effluents, generally contains substantial amount of dyes and chemicals that will cause increase in the COD, colour and toxicity of receiving water bodies if not properly treated. Current treatment methods include chemical and biological processes; the efficiency of the biological treatment method however, remains uncertain since the discharged effluent is still highly coloured. In this study, granules consisting mixed culture of decolourising bacteria were developed and the physical and morphological characteristics were determined. After the sixth week of development, the granules were 3-10 mm in diameter, having good settling property with settling velocity of 70 m/h, sludge volume index (SVI) of 90 to 130 mL/g, integrity coefficient of 3.7, and density of 66 g/l. Their abilities to treat sterilised raw textile wastewater were evaluated based on the removal efficiencies of COD (initial ranging from 200 to 3,000 mg/L), colour (initial ranging from 450 to 2000 ADMI) of sterilised raw textile wastewater with pH from 6.8 to 9.4. Using a sequential anaerobic-aerobic treatment cycle with hydraulic retention time (HRT) of 24 h, maximum removal of colour and COD achieved was 90% and 80%, respectively.
  14. Aerobic granular sludge formation for high strength agro-based wastewater treatment
    Abdullah N, Ujang Z, Yahya A
    Bioresour Technol, 2011 Jun;102(12):6778-81.
    PMID: 21524907 DOI: 10.1016/j.biortech.2011.04.009
    The present study investigates the formation of aerobic granular sludge in sequencing batch reactor (SBR) fed with palm oil mill effluent (POME). Stable granules were observed in the reactor with diameters between 2.0 and 4.0mm at a chemical oxygen demand (COD) loading rate of 2.5 kg COD m(-3) d(-1). The biomass concentration was 7600 mg L(-1) while the sludge volume index (SVI) was 31.3 mL g SS(-1) indicating good biomass accumulation in the reactor and good settling properties of granular sludge, respectively. COD and ammonia removals were achieved at a maximum of 91.1% and 97.6%, respectively while color removal averaged at only 38%. This study provides insights on the development and the capabilities of aerobic granular sludge in POME treatment.
  15. A case of an undifferentiated embryonal sarcoma of the liver mimicking a liver abscess
    Hanafiah M, Yahya A, Zuhdi Z, Yaacob Y
    Sultan Qaboos Univ Med J, 2014 Nov;14(4):e578-81.
    PMID: 25364566
    An undifferentiated embryonal sarcoma of the liver is a rare malignant tumour. We highlight the diagnostic dilemma and differential diagnosis of a case involving a large cystic liver lesion in a young adult. A 20-year-old man presented with a large liver lesion to the Universiti Kebangsaan Malaysia Medical Center, Kuala Lumpur, Malaysia, in February 2012. The initial clinico-radiological presentations were suggestive of a liver abscess. A total tumour resection was performed and the final histopathological results of the resected specimen indicated an undifferentiated embryonal sarcoma of the liver. The ultrasound and computed tomographic images of the tumour were reviewed and found to be contradictory in appearance, as the tumour seemed predominantly solid in the ultrasound image and predominantly cystic in the computed tomographic image. Familiarisation with the imaging appearance of this tumour and a high index of suspicion is therefore crucial in making a successful diagnosis.
  16. Influence of Feeding and Controlled Dissolved Oxygen Level on the Production of Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate) Copolymer by Cupriavidus sp. USMAA2-4 and Its Characterization
    Shantini K, Yahya AR, Amirul AA
    Appl Biochem Biotechnol, 2015 Jul;176(5):1315-34.
    PMID: 25951779 DOI: 10.1007/s12010-015-1648-5
    Copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] has been the center of attention in the bio-industrial fields, as it possesses superior mechanical properties compared to poly(3-hydroxybutyrate) [P(3HB)]. The usage of oleic acid and 1-pentanol was exploited as the carbon source for the production of P(3HB-co-3HV) copolymer by using a locally isolated strain Cupriavidus sp. USMAA2-4. In this study, the productivity of polyhydroxyalkanoate (PHA) was improved by varying the frequency of feeding in fed-batch culture. The highest productivity (0.48 g/L/h) that represents 200 % increment was obtained by feeding the carbon source and nitrogen source three times and also by considering the oxygen uptake rate (OUR) and oxygen transfer rate (OTR). A significantly higher P(3HB-co-3HV) concentration of 25.7 g/L and PHA content of 66 wt% were obtained. The 3-hydroxyvalerate (3HV) monomer composition obtained was 24 mol% with the growth of 13.3 g/L. The different frequency of feeding carried out has produced a blend copolymer and has broadened the monomer distribution. In addition, increase in number of granules was also observed as the frequency of feeding increases. In general, the most glaring increment in productivity offer advantage for industrial P(3HB-co-3HV) production, and it is crucial in developing cost-effective processes for commercialization.
  17. Sterilizing orthodontic appliances: A systematic review and meta-analysis on the available methods
    Abutayyem H, Alam MK, Kanwal B, Alswairki HJ, Alogaibi YA
    J Orthod Sci, 2023;12:51.
    PMID: 37881658 DOI: 10.4103/jos.jos_53_23
    Infection control is essential to protect both the doctor and the patient by preventing the spread of infectious diseases. There is no exception in the field of dentistry, particularly in orthodontics, where numerous appliances are used for a variety of functions and also because the mouth cavity has the highest concentration of bacteria of any body part. Through this systematic review, we aimed to assess the various methods of sterilization employed in an orthodontic setting. Using relevant keywords, reference searches, and citation searches, the databases such as PubMed, MEDLINE, Web of Science, Cochrane, and Scopus were all searched; a total of 206 documents were found, of which 113 were initially selected. The remaining 23 distinct papers were initially made available after 90 publications that were identical to or similar to one another were eliminated. The final selection was made from eight documents that met all inclusion and exclusion requirements. The existing methods of sterilization were found to be competent in dealing with the microorganisms found in a typical orthodontic setting. The chemical method of sterilization was the norm in most of the studies that we assessed, with glutaraldehyde and peracetic acid (PAA) being the most commonly employed compounds for disinfection. PROSPERO Registration Number: CRD42022380831.
  18. Catastrophic Health Expenditure Among Colorectal Cancer Patients and Families: A Case of Malaysia
    Azzani M, Yahya A, Roslani AC, Su TT
    Asia Pac J Public Health, 2017 Sep;29(6):485-494.
    PMID: 29019257 DOI: 10.1177/1010539517732224
    This study aimed to estimate the cost of colorectal cancer (CRC) management and to explore the prevalence and determinants of catastrophic health expenditure (CHE) among CRC patients and their families arising from the costs of CRC management. Data were collected prospectively from 138 CRC patients. Patients were interviewed by using a structured questionnaire at the time of the diagnosis, then at 6 months and 12 months following diagnosis. Simple descriptive methods and multivariate binary logistic regression were used in the analysis. The mean cost of managing CRC was RM8306.9 (US$2595.9), and 47.8% of patients' families experienced CHE. The main determinants of CHE were the economic status of the family and the likelihood of the patient undergoing surgery. The results of this study strongly suggest that stakeholders and policy makers should provide individuals with financial protection against the consequences of cancer, a costly illness that often requires prolonged treatment.
  19. Fulltext Solid-state fermentation of oil palm frond petiole for lignin peroxidase and xylanase-rich cocktail production
    Mohamad Ikubar MR, Abdul Manan M, Md Salleh M, Yahya A
    3 Biotech, 2018 May;8(5):259.
    PMID: 29765817 DOI: 10.1007/s13205-018-1268-1
    In current practice, oil palm frond leaflets and stems are re-used for soil nutrient recycling, while the petioles are typically burned. Frond petioles have high commercialization value, attributed to high lignocellulose fiber content and abundant of juice containing free reducing sugars. Pressed petiole fiber is the subject of interest in this study for the production of lignocellulolytic enzyme. The initial characterization showed the combination of 0.125 mm frond particle size and 60% moisture content provided a surface area of 42.3 m2/g, porosity of 12.8%, and density of 1.2 g/cm3, which facilitated fungal solid-state fermentation. Among the several species of Aspergillus and Trichoderma tested, Aspergillus awamori MMS4 yielded the highest xylanase (109 IU/g) and cellulase (12 IU/g), while Trichoderma virens UKM1 yielded the highest lignin peroxidase (222 IU/g). Crude enzyme cocktail also contained various sugar residues, mainly glucose and xylose (0.1-0.4 g/L), from the hydrolysis of cellulose and hemicellulose. FT-IR analysis of the fermented petioles observed reduction in cellulose crystallinity (I900/1098), cellulose-lignin (I900/1511), and lignin-hemicellulose (I1511/1738) linkages. The study demonstrated successful bioconversion of chemically untreated frond petioles into lignin peroxidase and xylanase-rich enzyme cocktail under SSF condition.
  20. Fulltext Correlation analysis of air pollutant index levels and dengue cases across five different zones in Selangor, Malaysia
    Thiruchelvam L, Dass SC, Zaki R, Yahya A, Asirvadam VS
    Geospat Health, 2018 05 07;13(1):613.
    PMID: 29772882 DOI: 10.4081/gh.2018.613
    This study investigated the potential relationship between dengue cases and air quality - as measured by the Air Pollution Index (API) for five zones in the state of Selangor, Malaysia. Dengue case patterns can be learned using prediction models based on feedback (lagged terms). However, the question whether air quality affects dengue cases is still not thoroughly investigated based on such feedback models. This work developed dengue prediction models using the autoregressive integrated moving average (ARIMA) and ARIMA with an exogeneous variable (ARIMAX) time series methodologies with API as the exogeneous variable. The Box Jenkins approach based on maximum likelihood was used for analysis as it gives effective model estimates and prediction. Three stages of model comparison were carried out for each zone: first with ARIMA models without API, then ARIMAX models with API data from the API station for that zone and finally, ARIMAX models with API data from the zone and spatially neighbouring zones. Bayesian Information Criterion (BIC) gives goodness-of-fit versus parsimony comparisons between all elicited models. Our study found that ARIMA models, with the lowest BIC value, outperformed the rest in all five zones. The BIC values for the zone of Kuala Selangor were -800.66, -796.22, and -790.5229, respectively, for ARIMA only, ARIMAX with single API component and ARIMAX with API components from its zone and spatially neighbouring zones. Therefore, we concluded that API levels, either temporally for each zone or spatio- temporally based on neighbouring zones, do not have a significant effect on dengue cases.
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