Displaying publications 1 - 20 of 98 in total

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  1. Enhanced photodegradation of o-cresol in aqueous Mn(1%)-doped ZnO suspensions
    Abdollahi Y, Abdullah AH, Gaya UI, Zainal Z, Yusof NA
    Environ Technol, 2012 Jun;33(10-12):1183-9.
    PMID: 22856288
    The effective removal of o-cresol is currently both an environmental and economic challenge. ZnO is not only an efficient photocatalyst but is also cost effective, as its photoabsorption can extend from the ultraviolet (UV) to the visible range thereby allowing the use of inexpensive visible light sources, such as sunlight. The principal objective of the present work is to investigate the visible light-driven removal of o-cresol from aqueous solution in the presence of 1.0 wt% Mn-doped ZnO. To measure the efficiency ofphotodegradation, the variables studied included the amount ofphotocatalyst, concentration of o-cresol, pH and irradiation time. The concentration ofo-cresol and residual organic carbon was monitored using a UV-visible spectrophotometer, ultra high-pressure liquid chromatography and a total organic carbon analyser. The optimum conditions under which the photodegradation of o-cresol was most favourable corresponded to 1.5 g/l ZnO, 35 ppm o-cresol and pH 9. The ZnO-1 wt% Mn photoprocess has demonstrated reusability for more than three times, which warrants its scale-up from laboratory- to in industrial-scale application.
  2. Effects of different doses of gamma irradiation on oxygen and water vapour transmission rate of preserved human amniotic membrane
    Zahari NK, Sheikh Ab Hamid S, Yusof N
    Cell Tissue Bank, 2015 Mar;16(1):55-63.
    PMID: 24647964 DOI: 10.1007/s10561-014-9438-9
    Preserved human amniotic membrane either air dried or glycerol preserved has been used effectively to treat superficial and partial thickness wounds without leaving any obvious hypertrophic scar. The preserved amnion, sterilised by ionising radiation, is known as an effective barrier for heat, fluid and protein loss while adheres nicely on wound. Air drying slightly reduced the oxygen transmission rate (OTR) of the amnion and the value significantly dropped after 15 kGy (p < 0.05). Glycerol preservation significantly reduced (p < 0.05) the OTR indicating less oxygen transmitted through the well structured cells of the amnion. Increase in the OTR with the increasing radiation doses up to 35 kGy possibly due to direct effects of radiation that resulted in large intercellular gaps. Both preservation methods significantly increased (p < 0.05) the water vapour transmission rate (WVTR). However, the low WVTR in the air dried amnion at 15 and 25 kGy was postulated due to cross-linking of collagen. Changes in the biophysical properties can be linked to direct and indirect effects of radiation on collagen bundles. The radiation dose of 25 kGy caused no adverse effect on biophysical properties hence it is still acceptable to sterilize both the air dried and the glycerol preserved amnions.
  3. Does bone marrow aspirate help enhance the integration of gamma irradiated allograft bone?
    Thong FY, Mansor A, Ramalingam S, Yusof N
    Cell Tissue Bank, 2020 Mar;21(1):107-117.
    PMID: 31894432 DOI: 10.1007/s10561-019-09804-4
    Bone allografts donated by other individuals offer a viable alternative to autograft. Risks of disease transmission are overcome by sterilizing the bone; unfortunately sterilization methods generally affect bone functional properties including osteogenic potential and biomechanical integrity. This study aimed to determine any enhancement effect when gamma sterilised allografts was impregnated with autologous bone marrow in improving the rate and quality of integration in metaphyseal-tibial defects of rabbits. Almost all subjects showed 50% of the defect being covered by new bones by the third week and smaller residual defect size in the treated group at the fifth week. Hounsfield units at the defect site showed increasing healing in all samples, with the treated group having an apparent advantage although insignificant (p > 0.05). In the histopathological score evaluating healing over cortical and cancellous bone at the fracture site showed only slight variations between the groups (p > 0.05). Therefore no enhanced healing by the autologous bone marrow was observed when added to the bone allografts in treating the unicortical defects.
  4. Fulltext Online News Coverage of the Sugar-Sweetened Beverages Tax in Malaysia: Content Analysis
    Mohd Hanim MF, Md Sabri BA, Yusof N
    JMIR Public Health Surveill, 2021 08 18;7(8):e24523.
    PMID: 34406125 DOI: 10.2196/24523
    BACKGROUND: In Malaysia, the Sugar-Sweetened Beverages (SSBs) tax was announced during the parliament's 2019 Budget Speech. The tax was slated to be enforced by April 2019 but was later postponed to July 2019. The announcement has since generated significant media coverage and public feedback.

    OBJECTIVE: This study presents a qualitative and quantitative cross-sectional study using netnography to examine how Malaysian online news articles responded to the SSBs tax after the announcement and postimplementation.

    METHODS: Online news articles published on popular online news platforms from November 2018 to August 2019 were downloaded using NCapture and imported into NVivo for analysis using the inductive approach and thematic content analysis following the initial SSBs implementation announcement.

    RESULTS: A total of 62 news articles were analyzed. Most of the articles positively portrayed the SSBs tax (46.8%) and highlighted its health impacts (76%). There were 7 key framing arguments identified in the articles. The positive arguments revolved around incentivizing manufacturers to introduce healthier products voluntarily, positive health consequences, the tax's impact on government revenue, and the use of the generated revenue toward beneficial social programs. The opposing arguments included increased operating costs to the manufacturer, the increased retail price of drinks, and how the SSBs tax is not a robust solution to obesity. The top priority sector considered in introducing the tax was the health perspective, followed by economic purposes and creating policies such as regulating the food and drinks industry.

    CONCLUSIONS: The majority of online news articles positively reported the implementation of the SSBs tax in Malaysia. This suggests media played a role in garnering support for the health policy. As such, relevant bodies can use negative findings to anticipate and reframe counteracting arguments opposing the SSBs tax.

  5. Fulltext Cadaveric Bone Donation amid COVID-19 Pandemic: An Unstoppable Chronicle in Uncharted Waters
    Mansor A, Ramalingam S, Yusof N
    Malays Orthop J, 2021 Nov;15(3):155-156.
    PMID: 34966515 DOI: 10.5704/MOJ.2111.028
  6. Advances of radiation sterilisation in tissue banking
    Yusof N
    Cell Tissue Bank, 2018 Jun;19(2):175-186.
    PMID: 29022196 DOI: 10.1007/s10561-017-9651-4
    Under the auspices of the IAEA tissue banking programme on "Radiation Sterilisation of Tissue Graft" conducted from 1985 to 2004, many scientists and surgeons were involved in various regional research and development (R&D) projects mainly in dealing with radiation dose selection, radiation effects on human tissues and quality system in radiation sterilisation. New findings on radiation effects, tissue processing and preservation were shared during the regional and interregional meetings and workshops. Many tissue banks started to use radiation (25 kGy) to sterilize tissue grafts for tissue safety and efficacy and still continue to use it. The IAEA Code of Practice for Radiation Sterilization of Tissues Allografts developed in 2007 offered simpler methods to conduct radiation dose setting and dose validation experiments for tissue grafts. Advances in dose selection and dose mapping are continued under the quality management system when banks need to be certified to continue their operation. The combination of good tissue processing and preservation as well as good radiation practice will ensure the tissue products are properly sterilised thus safe and of high quality. Experience in meeting challenges in using radiation sterilisation and achievements reported by the tissue bankers are shared here.
  7. Fulltext Recent Development of Nanocomposite Membranes for Water and Wastewater Treatment
    Ismail AF, Goh PS, Yusof N
    Nanomaterials (Basel), 2023 May 20;13(10).
    PMID: 37242102 DOI: 10.3390/nano13101686
    The field of membrane technology has experienced significant growth in recent years, especially in the areas of wastewater treatment and desalination [...].
  8. Online commentaries of the sugar-sweetened beverages tax in Malaysia: Content analysis
    Mohd Hanim MFB, Md Sabri BA, Yusof N
    Public Health Nurs, 2024;41(1):139-150.
    PMID: 37953703 DOI: 10.1111/phn.13262
    INTRODUCTION: Implementing taxes on sugary drinks, or SSBs, has been a controversial topic in many countries, including Malaysia. This study aimed to examine how Malaysian Facebook users responded to the announcement and implementation of the SSBs tax through netnography.

    METHODS: This cross-sectional study employed qualitative and quantitative methods and used an inductive approach and thematic content analysis to analyze online commentaries on news articles published on popular online news portals from November 2018 to August 2019. Data was collected by downloading the commentaries onto Microsoft Word and importing them into NVivo.

    RESULTS: Of the commentaries analyzed, 60.9% rejected the SSBs tax, and 39.1% favored it. No association was found between the online news articles and the slants of the commentaries.

    CONCLUSION: The results of this study demonstrate a clear divide in public opinion regarding the SSBs tax in Malaysia, with many online readers expressing opposition to the tax despite evidence of the harmful effects of sugar presented in the articles they are commenting on. These findings have implications for policymakers and public health advocates seeking to implement similar taxes in the future.

  9. Components in downstream health promotions to reduce sugar intake among adults: a systematic review
    Azhar Hilmy SH, Nordin N, Yusof MYPM, Soh TYT, Yusof N
    Nutr J, 2024 Jan 17;23(1):11.
    PMID: 38233923 DOI: 10.1186/s12937-023-00884-3
    Excessive sugar consumption is well documented as a common risk factor for many Non-Communicable Diseases (NCDs). Thus, an adequate intervention description is important to minimise research waste and improve research usability and reproducibility. A systematic review was conducted to identify components in published evidence interventions pertaining to the health promotions on reducing sugar intake among adults. The review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement and used the Mixed Methods Appraisal Tool (MMAT) for quality appraisal. The period for the selected study was from 2000 to 2022, and articles were retrieved from Web of Science (WOS), Medline, Scopus, and PubMed. The target population was adults aged 18 years old and above who underwent intervention to assess the changes in their sugar intake. Data sources and all human epidemiologic studies were included. Out of the 9,333 papers identified, 25 were included. The overall quality of evidence of the studies was considered moderate. Apart from the characteristics of the reviewed studies, components of interventions are including the basis of theoretical or model for the intervention, which majority use Social Cognitive Theory, followed by PRECEDE-PROCEED model, socio-ecological and process-improvement theories and Transtheoretical Model; providers, who are commercial provider, qualified nutritionist, professor of nutrigenomics and nutrigenetics, doctor, dietitian nutritionist, lifestyle coaches, and junior public health nurses; duration of the intervention and follow-up time, varies from as short as one month to as long as 24 months; material provided either softcopy or hardcopy; tailoring approach, based on the individual goals, the process of change, genotype analysis, beliefs, barriers, and sociocultural norms; delivery mechanism either face-to-face or technology-mediated; and tools to measure the sugar consumption outcome mostly used Food Frequency Questionnaire (FFQ), besides 24-h dietary recalls, and food diaries. There are various components in downstream health promotion to reduce sugar intake among adults that can be adapted according to the local health promotion and intervention context. More well-designed interventions using integration components are encouraged in further studies.
  10. Fulltext Bilateral persistent sciatic arteries with unilateral complicating aneurysm
    Aziz ME, Yusof NR, Abdullah MS, Yusof AH, Yusof MI
    Singapore Med J, 2005 Aug;46(8):426-8.
    PMID: 16049615
    Persistent sciatic artery is a very uncommon embryological vascular variant. This case report highlights this rare vascular anomaly, diagnostic difficulty, complication and subsequent treatment in a 43-year-old man who presented with sudden onset of right leg pain for a few hours. He was unable to walk because of pain and numbness. Emergency right lower limb angiogram showed a large aneurysm that was initially thought to arise from the right common femoral artery, associated with thrombus formation within the right popliteal artery. A below knee amputation was performed due to worsening ischaemia of the right leg. The persistent right sciatic artery was later obliterated using percutaneous stenting and endovascular grafting, with deployment of two wallstents.
  11. Fulltext Antimicrobial resistance in methicillin-resistant staphylococcus aureus
    Ali Alghamdi B, Al-Johani I, Al-Shamrani JM, Musamed Alshamrani H, Al-Otaibi BG, Almazmomi K, et al.
    Saudi J Biol Sci, 2023 Apr;30(4):103604.
    PMID: 36936699 DOI: 10.1016/j.sjbs.2023.103604
    In the medical community, antibiotics are revered as a miracle because they stop diseases brought on by pathogenic bacteria. Antibiotics have become the cornerstone of contemporary medical advancements ever since penicillin was discovered. Antibiotic resistance developed among germs quickly, placing a strain in the medical field. Methicillin-resistant Staphylococcus aureus (MRSA), Since 1961, has emerged as the major general antimicrobial resistant bacteria (AMR) worldwide. MRSA can easily transmit across the hospital system and has mostly gained resistance to medications called beta-lactamases. This enzyme destroys the cell wall of beta-lactam antibiotics resulting in resistance against that respective antibiotic. Daptomycin, linezolid and vancomycin were previously used to treat MRSA infections. However, due to mutations and Single nucleotide polymorphisms (SNPs) in Open reading frames (ORFs) and SCCmec machinery of respective antibody, MRSA developed resistance against those antibiotics. The MRSA strains (USA300, CC398, CC130 etc.), when their pan-genomes were analyzed were found the genes involved in invoking resistance against the antibiotics as well as the epidemiology of that respective strain. PENC (penicillin plus potassium clavulanate) is the new antibiotic showing potential in treatment of MRSA though it is itself resistant against penicillin alone. In this review, our main focus is on mechanism of development of AMR in MRSA, how different ORFs are involved in evoking resistance in MRSA and what is the core-genome of different antimicrobial resistant MRSA.
  12. Fulltext A review of the potential of conventional and advanced membrane technology in the removal of pathogens from wastewater
    Nasir AM, Adam MR, Mohamad Kamal SNEA, Jaafar J, Othman MHD, Ismail AF, et al.
    Sep Purif Technol, 2022 Apr 01;286:120454.
    PMID: 35035270 DOI: 10.1016/j.seppur.2022.120454
    Consumption of pathogenic contaminated water has claimed the lives of many people. Hence, this scenario has emphasized the urgent need for research methods to avoid, treat and eliminate harmful pathogens in wastewater. Therefore, effective water treatment has become a matter of utmost importance. Membrane technology offers purer, cleaner, and pathogen-free water through the water separation method via a permeable membrane. Advanced membrane technology such as nanocomposite membrane, membrane distillation, membrane bioreactor, and photocatalytic membrane reactor can offer synergistic effects in removing pathogen through the integration of additional functionality and filtration in a single chamber. This paper also comprehensively discussed the application, challenges, and future perspective of the advanced membrane technology as a promising alternative in battling pathogenic microbial contaminants, which will also be beneficial and valuable in managing pandemics in the future as well as protecting human health and the environment. In addition, the potential of membrane technology in battling the ongoing global pandemic of coronavirus disease 2019 (COVID-19) was also discussed briefly.
  13. Fulltext Rare but Potentially Fatal Presentations of Diffuse Large B-cell Lymphoma: Leukemic Phase or Hemophagocytic Syndrome in Bone Marrow
    Wan Mohd Zohdi WA, Ismail AZ, Yusof N, Ithnin A, Shuib S, Masir N, et al.
    Clin Pathol, 2022 01 09;15:2632010X211070774.
    PMID: 35036912 DOI: 10.1177/2632010X211070774
    Diffuse large B-cell lymphoma (DLBCL) is a type of non-Hodgkin Lymphoma commonly presenting as a solid tumor either by nodal or extra-nodal manifestations. Here we describe two atypical presentations of lymphoma, finally resulting in the diagnosis of DLBCL. Case 1: A 53-year-old man with a previous history of nasopharyngeal carcinoma presented with a two-week history of B-symptoms and hyperleukocytosis. Peripheral blood film showed 78% abnormal mononuclear cells. Immunohistochemical stain showing Ki-67 of 90%, negative c-myc, BCL2 and BCL6, and negative c-MYC with fluorescence in-situ hybridization studies on the trephine biopsy, concluded the diagnosis of CD5+ DLBCL of ABC subtype. He received intravenous cyclophosphamide and oral prednisolone for cytoreduction, followed by 6 cycles of chemo-immunotherapy. However, he succumbed due to severe sepsis after the completion of therapy. Case 2: A 56-year-old lady who was initially investigated for pyrexia of unknown origin was noted to have hemophagocytosis upon bone marrow aspirate examination. The bone marrow trephine biopsy revealed some atypical clusters of B-cells positive for CD20 which was inconclusive. PET-CT scan noted an enlarged hypermetabolic spleen without lymphadenopathy. Splenic biopsy with immunohistochemical studies revealed DLBCL of ABC subtype. The diagnosis was consistent with primary splenic DLBCL. She became unwell post splenic biopsy and was admitted to the intensive care unit where she passed away 2 weeks later from Candida and Sternotrophomonas septicemia. These cases highlight the atypical presentations of a common subtype of NHL in our center. Arriving at the definitive diagnosis can be difficult especially when patients are acutely ill, hampering the necessary invasive procedures for diagnosis. The outcomes of both cases are briefly discussed hoping to spread awareness among clinicians on the rare and acutely critical presentations of DLBCL.
  14. Investigation of highly unsaturated fatty acid metabolism in the Asian sea bass, Lates calcarifer
    Mohd-Yusof NY, Monroig O, Mohd-Adnan A, Wan KL, Tocher DR
    Fish Physiol Biochem, 2010 Dec;36(4):827-43.
    PMID: 20532815 DOI: 10.1007/s10695-010-9409-4
    Lates calcarifer, commonly known as the Asian sea bass or barramundi, is an interesting species that has great aquaculture potential in Asia including Malaysia and also Australia. We have investigated essential fatty acid metabolism in this species, focusing on the endogenous highly unsaturated fatty acid (HUFA) synthesis pathway using both biochemical and molecular biological approaches. Fatty acyl desaturase (Fad) and elongase (Elovl) cDNAs were cloned and functional characterization identified them as ∆6 Fad and Elovl5 elongase enzymes, respectively. The ∆6 Fad was equally active toward 18:3n-3 and 18:2n-6, and Elovl5 exhibited elongation activity for C18-20 and C20-22 elongation and a trace of C22-24 activity. The tissue profile of gene expression for ∆6 fad and elovl5 genes, showed brain to have the highest expression of both genes compared to all other tissues. The results of tissue fatty acid analysis showed that the brain contained more docosahexaenoic acid (DHA, 22:6n-3) than flesh, liver and intestine. The HUFA synthesis activity in isolated hepatocytes and enterocytes using [1-(14)C]18:3n-3 as substrate was very low with the only desaturated product detected being 18:4n-3. These findings indicate that L. calcarifer display an essential fatty acid pattern similar to other marine fish in that they appear unable to synthesize HUFA from C18 substrates. High expression of ∆6 fad and elovl5 genes in brain may indicate a role for these enzymes in maintaining high DHA levels in neural tissues through conversion of 20:5n-3.
  15. Fulltext Prevalence of Plasmodium falciparum Molecular Markers of Antimalarial Drug Resistance in a Residual Malaria Focus Area in Sabah, Malaysia
    Norahmad NA, Mohd Abd Razak MR, Abdullah NR, Sastu UR, Imwong M, Muniandy PK, et al.
    PLoS One, 2016;11(10):e0165515.
    PMID: 27788228 DOI: 10.1371/journal.pone.0165515
    Chloroquine (CQ) and fansidar (sulphadoxine-pyrimethamine, SP) were widely used for treatment of Plasmodium falciparum for several decades in Malaysia prior to the introduction of Artemisinin-based Combination Therapy (ACT) in 2008. Our previous study in Kalabakan, located in south-east coast of Sabah showed a high prevalence of resistance to CQ and SP, suggesting the use of the treatment may no longer be effective in the area. This study aimed to provide a baseline data of antimalarial drug resistant markers on P. falciparum isolates in Kota Marudu located in the north-east coast of Sabah. Mutations on genes associated with CQ (pfcrt and pfmdr1) and SP (pfdhps and pfdhfr) were assessed by PCR amplification and restriction fragment length polymorphism. Mutations on the kelch13 marker (K13) associated with artemisinin resistance were determined by DNA sequencing technique. The assessment of pfmdr1 copy number variation associated with mefloquine resistant was done by real-time PCR technique. A low prevalence (6.9%) was indicated for both pfcrt K76T and pfmdr1 N86Y mutations. All P. falciparum isolates harboured the pfdhps A437G mutation. Prevalence of pfdhfr gene mutations, S108N and I164L, were 100% and 10.3%, respectively. Combining the different resistant markers, only two isolates were conferred to have CQ and SP treatment failure markers as they contained mutant alleles of pfcrt and pfmdr1 together with quintuple pfdhps/pfdhfr mutation (combination of pfdhps A437G+A581G and pfdhfr C59R+S108N+I164L). All P. falciparum isolates carried single copy number of pfmdr1 and wild type K13 marker. This study has demonstrated a low prevalence of CQ and SP resistance alleles in the study area. Continuous monitoring of antimalarial drug efficacy is warranted and the findings provide information for policy makers in ensuring a proper malaria control.
  16. Fulltext Mutations of pvdhfr and pvdhps genes in vivax endemic-malaria areas in Kota Marudu and Kalabakan, Sabah
    Sastu UR, Abdullah NR, Norahmad NA, Saat MN, Muniandy PK, Jelip J, et al.
    Malar J, 2016;15:63.
    PMID: 26850038 DOI: 10.1186/s12936-016-1109-9
    Malaria cases persist in some remote areas in Sabah and Sarawak despite the ongoing and largely successful malaria control programme conducted by the Vector Borne Disease Control Programme, Ministry Of Health, Malaysia. Point mutations in the genes that encode the two enzymes involved in the folate biosynthesis pathway, dihydrofolate reductase (DHFR) and dihydropteroate synthase (DHPS) enzymes confer resistance to pyrimethamine and sulfadoxine respectively, in both Plasmodium falciparum and P. vivax. The aim of the current study was to determine the mutation on both pvdhfr at codon 13, 33, 57, 58, 61, 117, and 173 and pvdhps genes at codon 383 and 553, which are potentially associated with resistance to pyrimethamine and sulfadoxine in P. vivax samples in Sabah.
  17. Myelodysplastic syndrome with fibrosis and complex karyotype arising in a patient with essential thrombocythaemia
    Mansor NA, Yusof N, Tang YL, Ithnin A, Azma RZ, Tumian NR, et al.
    Malays J Pathol, 2018 Aug;40(2):191-197.
    PMID: 30173238 MyJurnal
    INTRODUCTION: Essential thrombocythaemia (ET) is a chronic myeloproliferative neoplasm (MPN) characterised by persistent thombocytosis. It is an indolent disorder but transformation to myelofibrosis (MF), acute myeloid leukaemia (AML) or myelodyplastic syndrome (MDS) has been reported.

    CASE REPORT: We described a patient with ET whose disease evolved into MDS with fibrosis and complex karyotype after 15 years of stable disease. She was asymptomatic and was on hydroxyurea (HU) treatment until recently when she presented with worsening anaemia. Physical examination showed mild splenomegaly. Full blood picture showed leukoerythroblastic picture with presence of 3% circulating blasts and background of dysplastic features such as hypogranular cytoplasm and nuclear hyposegmentation of neutrophils. The bone marrow aspiration was haemodiluted but revealed presence of 6% blast cells, trilineage dysplasia and predominant erythroid precursors (60%). Trephine biopsy showed no excess of blast cells and normal quantity of erythroid precursors, but there was increased in fibrosis (WHO grade 2) and presence of dysmegakaryopoeisis such as nuclear hypolobation, multinucleation and micromegakaryocytes. Cytogenetic study showed complex karyotype; monosomy of chromosome 2, chromosome 5, chromosome 18 and presence of a marker chromosome (42~44, XX,-2,-5,-18,+mar). Fluorescence in situ hybridisation (FISH) showed 5q deletion (CSF1R and EGR1).

    CONCLUSION: The findings were consistent with transformation of ET to MDS with fibrosis and complex karyotype. ET progression to MDS is considered rare. The presence of complex karyotype and fibrosis in MDS are associated with unfavourable outcome.

  18. Nitrification of high-strength ammonium landfill leachate with microbial community analysis using fluorescence in situ hybridization (FISH)
    Yusof N, Hassan MA, Yee PL, Tabatabaei M, Othman MR, Mori M, et al.
    Waste Manag Res, 2011 Jun;29(6):602-11.
    PMID: 21447612 DOI: 10.1177/0734242X10397581
    Nitrification of mature sanitary landfill leachate with high-strength of N-NH(4) + (1080-2350 mg L(-1)) was performed in a 10 L continuous nitrification activated sludge reactor. The nitrification system was acclimatized with synthetic leachate during feed batch operation to avoid substrate inhibition before being fed with actual mature leachate. Successful nitrification was achieved with an approximately complete ammonium removal (99%) and 96% of N-NH(4) + conversion to N-NO(-) (3) . The maximum volumetric and specific nitrification rates obtained were 2.56 kg N-NH(4) (+) m(-3) day(-1) and 0.23 g N-NH(4) ( +) g(-1) volatile suspended solid (VSS) day(-1), respectively, at hydraulic retention time (HRT) of 12.7 h and solid retention time of 50 days. Incomplete nitrification was encountered when operating at a higher nitrogen loading rate of 3.14 kg N-NH(4) (+) m(-3) day(-1). The substrate overloading and nitrifiers competition with heterotrophs were believed to trigger the incomplete nitrification. Fluorescence in situ hybridization (FISH) results supported the syntrophic association between the ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria. FISH results also revealed the heterotrophs as the dominant and disintegration of some AOB cell aggregates into single cells which further supported the incomplete nitrification phenomenon.
  19. Measuring organic carbon, nutrients and heavy metals in rivers receiving leachate from controlled and uncontrolled municipal solid waste (MSW) landfills
    Yusof N, Haraguchi A, Hassan MA, Othman MR, Wakisaka M, Shirai Y
    Waste Manag, 2009 Oct;29(10):2666-80.
    PMID: 19564103 DOI: 10.1016/j.wasman.2009.05.022
    Since landfilling is the common method of waste disposal in Malaysia, river water is greatly exposed to the risk of contamination from leachate unless proper leachate management is carried out. In this study, leachates from three different types of landfills, namely active uncontrolled, active controlled and closed controlled, were characterized, and their relationships with river water chemistry were examined monthly for a year. The influence of leachate on river water chemistry from each type of landfill depended on many factors, including the presence of a leachate control mechanism, leachate characteristics, precipitation, surface runoff and the applied treatment. The impact of leachate from an active uncontrolled landfill was the highest, as the organic content, NH(4)(+)-N, Cd and Mn levels appeared high in the river. At the same time, influences of leachate were also observed from both types of controlled landfills in the form of inorganic nitrogen (NH(4)(+)-N, NO(3)(-)-N and NO(2)(-)-N) and heavy metals (Fe, Cr, Ni and Mn). Improper treatment practice led to high levels of some contaminants in the stream near the closed controlled landfill. Meanwhile, the active controlled landfill, which was located near the coastline, was exposed to the risk of contamination resulting from the pyrite oxidation of the surrounding area.
  20. Fulltext Thermal Properties and Drying Shrinkage Performance of Palm Kernel Shell Ash and Rice Husk Ash-Based Geopolymer Concrete
    Abdullah MN, Mustapha F, Yusof N', Khan T, Sebaey TA
    Materials (Basel), 2024 Mar 11;17(6).
    PMID: 38541452 DOI: 10.3390/ma17061298
    This study aims to develop suitable formulations of geopolymer concrete (GPC) by varying the percentages of the geopolymer with aggregates and evaluating the performances in thermal and mechanical properties of palm kernel shell ash (PKSA)-GPC compared to rice husk ash (RHA)-GPC and ordinary Portland cement concrete (OPCC). Preliminary tests were conducted to select the best mix design ratios before casting the specimens. Then, the performance of the PKSA-GPC, RHA-GPC and OPCC specimens was evaluated based on their thermal performance and drying shrinkage. The mix designs of PKSA-GPC 70:30, PKSA-GPC 60:40, PKSA-GPC 50:50 and PKSA-GPC 66.6:33.3 were found to produce an acceptable consistency, rheological and thixotropic behaviour for the development of the GPC. PKSA-GPC showed a better thermal performance than the RHA-GPC and OPCC due to their strong and dense intumescent layers and slow temperature increment upon exposure to a high flame temperature from ambient temperature to 169 °C. The low molar ratio of the Si/Al present in the PKSA-GPC created a thermally stable intumescent layer. In the drying shrinkage test, PKSA-GPC 60:40 and RHA-GPC 60:40 shared an equal drying shrinkage performance (5.040%) compared to the OPCC (8.996%). It was observed that microcrack formation could significantly contribute to the high shrinkage in the PKSA-GPC 50:50 and RHA-GPC 70:30 specimens. The findings of this study show that PKSA could be incorporated into GPC as a fire-retardant material due to its capability of prolonging the spread of fire upon ignition and acting as an alternative to the conventional OPCC.
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