Displaying all 16 publications

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  1. Yusop Z, Chan CH, Katimon A
    Water Sci Technol, 2007;56(8):41-8.
    PMID: 17978431
    Rainfall-runoff processes in a small oil palm catchment (8.2 ha) in Johor, Malaysia were examined. Storm hydrographs show rapid responses to rainfall with a short time to peak. The estimated initial hydrologic loss for the oil palm catchment is 5 mm. Despite the low initial loss, the catchment exhibits a high proportion of baseflow, approximately 54% of the total runoff. On an event basis, the stormflow response factor and runoff coefficient ranges from 0.003 to 0.21, and 0.02 to 0.44, respectively. Peakflow and stormflow volume were moderately correlated with rainfall. The hydrographs were satisfactorily modelled using the Hydrologic Engineering Centre-Hydrologic Modelling System (HEC-HMS). The efficiency indexes of the calibration and validation exercises are 0.81 and 0.82, respectively. Based on these preliminary findings, it could be suggested that an oil palm plantation would be able to serve reasonably well in regulating basic hydrological functions.
  2. Chan CH, Lim PE
    Bioresour Technol, 2007 May;98(7):1333-8.
    PMID: 16822665
    Performance of the sequencing batch reactor (SBR) treating synthetic phenolic wastewater at influent phenol concentrations from 100 to 1000 mg/L was evaluated. Two identical SBRs were built and operated with FILL, REACT, SETTLE and DRAW periods in the ratio of 4:6:1:1 for a cycle time of 12h. One of the reactors was operated with aerated FILL (R1) and the other with unaerated FILL (R2). The treated effluent quality and the rate of degradation during REACT were the criteria for evaluating performance of the two reactors. The results showed that the FILL mode had no significant influence on the treatment efficiency of phenol and COD for the entire range of influent phenol concentrations investigated. However, reactor R1 required a relatively shorter REACT time for phenol removal as compared to R2. This meant that R1 had the advantage of providing treatment at a higher organic loading rate.
  3. Chan CH, Yusoff R, Ngoh GC
    Food Chem, 2013 Sep 1;140(1-2):147-53.
    PMID: 23578626 DOI: 10.1016/j.foodchem.2013.02.057
    A modeling technique based on absorbed microwave energy was proposed to model microwave-assisted extraction (MAE) of antioxidant compounds from cocoa (Theobroma cacao L.) leaves. By adapting suitable extraction model at the basis of microwave energy absorbed during extraction, the model can be developed to predict extraction profile of MAE at various microwave irradiation power (100-600 W) and solvent loading (100-300 ml). Verification with experimental data confirmed that the prediction was accurate in capturing the extraction profile of MAE (R-square value greater than 0.87). Besides, the predicted yields from the model showed good agreement with the experimental results with less than 10% deviation observed. Furthermore, suitable extraction times to ensure high extraction yield at various MAE conditions can be estimated based on absorbed microwave energy. The estimation is feasible as more than 85% of active compounds can be extracted when compared with the conventional extraction technique.
  4. Chan CH, Ngoh GC, Yusoff R
    Pharmacogn Rev, 2012 Jan;6(11):22-8.
    PMID: 22654401 DOI: 10.4103/0973-7847.95854
    A study has been conducted with the aim to provide researchers with general information on anti diabetic extracts based on relevant research articles collected from 34 reliable medical journals. The study showed that Asian and African continents have 56% and 17% share of the worldwide distribution of therapeutic herbal plants, respectively. In Asia, India and China are the leading countries in herbal plants research, and there has been an increase in medicinal research on plants extract for diabetes treatment since 1995 in these regions. The information collected shows that plant leaves are about 20% more favorable for storing active ingredients, as compared to other parts of herbal plants. A brief review on the extraction techniques for the mentioned parts is also included. Furthermore, the acting mechanisms for the anti diabetic activity were described, and the related active ingredients were identified. The findings reveal that most of the anti diabetic research is focused on the alteration of glucose metabolism to prevent diabetes.
  5. Abdul Halim SI, Chan CH, Kressler J
    Polymers (Basel), 2020 Dec 11;12(12).
    PMID: 33322501 DOI: 10.3390/polym12122963
    The studies of phase behavior, dielectric relaxation, and other properties of poly(ethylene oxide) (PEO)/poly(methyl acrylate) (PMA) blends with the addition of lithium perchlorate (LiClO4) were done for different blend compositions. Samples were prepared by a solution casting technique. The binary PEO/PMA blends exhibit a single and compositional-dependent glass transition temperature (Tg), which is also true for ternary mixtures of PEO/PMA/LiClO4 when PEO was in excess with low content of salt. These may indicate miscibility of the constituents for the molten systems and amorphous domains of the systems at room temperature from the macroscopic point of view. Subsequently, the morphology of PEO/PMA blends with or without salt are correlated to the phase behavior of the systems. Phase morphology and molecular interaction of polymer chains by salt ions of the systems may rule the dielectric or electric relaxation at room temperature, which was estimated using electrochemical impedance spectroscopy (EIS). The frequency-dependent impedance spectra are of interest for the elucidation of polarization and relaxation of the charged entities for the systems. Relaxation can be noted only when a sufficient amount of salt is added into the systems.
  6. Chan CH, Ziyadi GM, Zuhdi MA
    Malays J Med Sci, 2019 May;26(3):49-63.
    PMID: 31303850 MyJurnal DOI: 10.21315/mjms2019.26.3.4
    BACKGROUND: Perioperative red blood cell (RBC) transfusion in coronary artery bypass grafting (CABG) has both benefits and harms. Our aim was to study the association between perioperative RBC transfusion and its adverse outcomes.

    METHODS: This was a retrospective study of patients who underwent isolated CABG in Hospital Universiti Sains Malaysia, Kelantan, Malaysia, from 1 January 2013 until 31 December 2017. Data were collected from medical records, and comparisons were made between patients who received perioperative RBC transfusions and those who did not have adverse outcomes after CABG.

    RESULTS: A total of 108 patients who underwent isolated CABG were included in our study, and 78 patients received perioperative RBC transfusions. Patients who received perioperative RBC transfusions compared to those who did not were significantly more likely to develop prolonged ventilatory support (21.8% versus 0%, P = 0.003), cardiac morbidity (14.1% versus 0%, P = 0.032), renal morbidity (28.2% versus 3.3%, P = 0.005) and serious infection (20.5% versus 3.3%, P = 0.037). With each unit of packed RBC transfusions, there was a significantly increased risk of prolonged ventilatory support (adjusted odds ratio [AOR] = 1.45; 95% confidence interval [CI] = 1.20-1.77; P < 0.001), cardiac morbidity (AOR =1.40; 95%CI = 1.01-1.79; P = 0.007), renal morbidity (AOR = 1.23; 95%CI = 1.03-1.45; P = 0.019) and serious infection (AOR = 1.31; 95%CI = 1.07-1.60; P = 0.009).

    CONCLUSION: Perioperative RBC transfusion in isolated CABG patients is associated with increased risks of developing adverse events such as prolonged ventilatory support, cardiac morbidity, renal morbidity and serious infection.

  7. Chan CH, Yusoff R, Ngoh GC, Kung FW
    J Chromatogr A, 2011 Sep 16;1218(37):6213-25.
    PMID: 21820119 DOI: 10.1016/j.chroma.2011.07.040
    Microwave-assisted extraction (MAE) is widely employed in the analysis and the extraction of active compounds from plants. This review summarizes the research done during the last decade on the MAE of active ingredients from plants. Advances and modifications to improve the performance of MAE are presented and discussed in detail. Modified MAE such as vacuum microwave-assisted extraction (VMAE), nitrogen-protected microwave-assisted extraction (NPMAE), ultrasonic microwave-assisted extraction (UMAE), dynamic microwave-assisted extraction (DMAE) and other advancements in MAE are also detailed in this article. In addition, the microwave extraction procedures and the important parameters influencing its performance are also included, together with the advantages and the drawbacks of each MAE techniques.
  8. Sim LH, Gan SN, Chan CH, Yahya R
    Spectrochim Acta A Mol Biomol Spectrosc, 2010 Aug;76(3-4):287-92.
    PMID: 20444642 DOI: 10.1016/j.saa.2009.09.031
    The interaction behaviours between components of polyacrylate (PAc)/poly(ethylene oxide) (PEO) and lithium perchlorate (LiClO(4)) were investigated in detail by Attenuated Total Reflectance (ATR)-Fourier Transformed Infrared (FTIR) spectroscopy. Solution cast films of the PAc/PEO and PAc/PEO/LiClO(4) were examined. No obvious shifting of the characteristic ether and ester group stretching modes of PEO and PAc was observed, indicating incompatibility of the binary PAc/PEO blend. The spectroscopic studies on the PAc/PEO/LiClO(4) blends reveal that Li(+) ions coordinate individually to the polymer components at the ether oxygen of PEO and the C-O of the ester group of PAc. Frequency changes observed on the nu(C-O-C) and omega(CH(2)) of PEO confirm the coordination between PEO and Li(+) ions resulting in crystallinity suppression of PEO. The absence of experimental evidence on the formation of PEO-Li(+)-PAc complexes suggests that LiClO(4) does not enhance the compatibility of PAc/PEO blend.
  9. Williams JD, Moosdeen F, Teoh-Chan CH, Lim VK, Jayanetra P
    Eur J Epidemiol, 1989 Jun;5(2):207-13.
    PMID: 2504618
    Antibiotic resistance in Gram-negative bacteria, particularly Salmonella and Shigella, requires surveillance worldwide. This study describes results of surveys in Hong Kong, Bangkok and Kuala Lumpur. All strains were isolated in hospitals which have large community catchment areas in addition to specialised hospital units. The prevalence of resistant strains was high in all areas. Gram-negative bacteria such as Enterobacter associated with hospital infections were resistant to penicillins and cephalosporins, with gentamicin resistance ranging from about 20% in Kuala Lumpur and Hong Kong, to 35% in Bangkok. Ninety-seven percent of Shigella isolated in Thailand were resistant to ampicillin. About 10% of Salmonella were resistant to chloramphenicol in all three centres.
  10. Chng SL, Krishnan MM, Ramachandran, Chan CH, Zain Z
    Singapore Med J, 1990 Feb;31(1):83-4.
    PMID: 2333552
    A 31-year old male presented with bone pain, polyuria and a palpable nodule in the neck. Radiological examination showed generalised osteopenia, subperiosteal erosion and presence of bilateral renal stones. The essential chemical pathological changes were increased plasma calcium, mid-molecule immuno-reactive parathyroid hormone (iPTH), human chorionic gonadotrophin (hCG) levels. Surgical excision of the nodule revealed a parathyroid carcinoma. The uniqueness of this case is the steroid-suppressible plasma calcium, iPTH, and hCG levels. The diagnostic implications of the findings are discussed.
  11. Chan CH, Tiwari A, Fong DY, Ho PC
    Int J Nurs Stud, 2010 Jul;47(7):918-25.
    PMID: 20303490 DOI: 10.1016/j.ijnurstu.2010.01.003
    BACKGROUND: Post-traumatic stress disorder is one of the most prevalent mental health sequelae of intimate partner violence, and as a result, it has been extensively documented in Western literature. However, whether abused women from non-Western cultures experience similar post-traumatic responses to intimate partner violence is less documented.

    OBJECTIVES: The objectives of this paper were (1) to review the literature for information about post-traumatic stress disorder among Chinese women survivors of intimate partner violence; (2) to provide a synthesis of the literature on post-traumatic stress disorder among abused Chinese women; and (3) to identify implications for practice and to suggest directions for research relating to post-traumatic stress disorder among abused Chinese women.

    DESIGN: A systematic review of the literature.

    DATA SOURCES: Following a systematic search for relevant literature in computerized databases and manual searches of English and Chinese language publications, five papers reporting on four studies conducted in China, Taiwan, Malaysia, and the United States were included in the review.

    REVIEW METHODS: Abstracts meeting the inclusion criteria were reviewed independently by two of the authors and any discrepancies were resolved by discussion. Full papers for selected abstracts were then retrieved and assessed independently by the same reviewers.

    RESULTS: The present literature review revealed a paucity of information relating to post-traumatic stress disorder symptoms or diagnoses in abused Chinese women. Nevertheless, a link between post-traumatic stress disorder and intimate partner violence was demonstrated by the reviewed papers.

    CONCLUSIONS: Caution should be exercised when making comparison of the findings across the four studies because of the inherent methodological differences. Also, as the assessment tools have not been validated for culture-bound interpretation of trauma and symptom manifestation, comparisons of findings for Chinese women to women in Western literature should be undertaken with due consideration. Implications for practice and recommendations for future research are discussed.

  12. Siva SP, Kow KW, Chan CH, Tang SY, Ho YK
    Ultrason Sonochem, 2019 Jul;55:348-358.
    PMID: 30871878 DOI: 10.1016/j.ultsonch.2018.12.040
    The dynamics of droplet breakup during emulsification is a complicated process due to the interplay between multiple physico-chemical and hydrodynamic factors, especially in an energy-intensive ultrasound-assisted emulsification process. In this work, by mapping the physical processing parameters of ultrasound emulsification into a reduced domain that is governed by the power density and the initial average droplet diameter, a dimensionless parameter that resembles the dynamic breakup potential (η) was established via dimensional analysis. In addition to shedding important insights into the emulsification process, η further facilitates the establishment of a transient scaling relationship that is a function of the characteristic value (a) of the emulsion system. Experimental case study on a cellulose nanocrystals (CNC)-based olein-in-water emulsion system prepared via ultrasound cavitation confirmed the validity of the scaling relationship and sub-universal self-similarity was observed. Using the proposed model, good predictions of the transient of droplet size evolution were attained where the value of η, i.e. the proportionality constant, can be conveniently computed using data from a single time point. Application on other emulsion systems further suggested that the value of a possibly indicates the relative minimum size limit of a particular fluids-emulsifier system. Our approach is general, which encourages widespread adoption for emulsification related studies.
  13. Chan CH, See TY, Yusoff R, Ngoh GC, Kow KW
    Food Chem, 2017 Apr 15;221:1382-1387.
    PMID: 27979103 DOI: 10.1016/j.foodchem.2016.11.016
    This work demonstrated the optimization and scale up of microwave-assisted extraction (MAE) and ultrasonic-assisted extraction (UAE) of bioactive compounds from Orthosiphon stamineus using energy-based parameters such as absorbed power density and absorbed energy density (APD-AED) and response surface methodology (RSM). The intensive optimum conditions of MAE obtained at 80% EtOH, 50mL/g, APD of 0.35W/mL, AED of 250J/mL can be used to determine the optimum conditions of the scale-dependent parameters i.e. microwave power and treatment time at various extraction scales (100-300mL solvent loading). The yields of the up scaled conditions were consistent with less than 8% discrepancy and they were about 91-98% of the Soxhlet extraction yield. By adapting APD-AED method in the case of UAE, the intensive optimum conditions of the extraction, i.e. 70% EtOH, 30mL/g, APD of 0.22W/mL, AED of 450J/mL are able to achieve similar scale up results.
  14. Lo FF, Kow KW, Kung F, Ahamed F, Kiew PL, Yeap SP, et al.
    Sci Total Environ, 2021 Aug 01;780:146337.
    PMID: 33770606 DOI: 10.1016/j.scitotenv.2021.146337
    Nano-magnetites are widely researched for its potential as an excellent adsorbent in many applications. However, the efficiency of the nano-magnetites are hindered by their tendency to agglomerate. In this work, we dispersed and embedded the nano-magnetites in a porous silica gel matrix to form a nanocomposite to reduce the extent of agglomeration and to enhance the adsorption performance. Our experimental results showed that the removal efficiency of Cu2+ ion has improved by 46% (22.4 ± 2.2%) on the nano-magnetite-silica-gel (NMSG) nanocomposite as compared to pure nano-magnetites (15.3 ± 0.6%). The adsorption capacity is further enhanced by 39% (from 11.2 ± 1.1 to 15.6 ± 1.6 mg/g) by subjecting the NMSG to a magnetic field prior to adsorption. We infer that the magnetic field aligned the magnetic domains within the nano-magnetites, resulting in an increased Lorentz force during adsorption. Similar alignment of magnetic domains is near to impossible in pure nano-magnetites due to severe agglomeration. We further found that the adsorption capacity of the NMSG can be manipulated with an external magnetic field by varying the strength and the configurations of the field. Equipped with proper process design, our finding has great potentials in processes that involve ion-adsorptions, for example, NMSG can: (i) replace/reduce chemical dosing in controlling adsorption kinetics, (ii) replace/reduce complex chemicals required in ion-chromatography columns, and (iii) reduce wastage of nano-adsorbents by immobilizing it in a porous matrix.
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