Displaying publications 1 - 20 of 26 in total

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  1. Fulltext Harnessing Reliable Evidence in the Post-COVID Era: A Practice Guide to Navigating the Ocean of Medical Literature
    Ooi C, Nalliah S
    Cureus, 2024 Jan;16(1):e52746.
    PMID: 38384650 DOI: 10.7759/cureus.52746
    The reliability and relevance of medical literature are significant concerns in the post-COVID-19 era, where misinformation and disinformation are serious threats. This practice guide provides an overview of practical strategies to appraise the reliability of research publications critically. These strategies include critically appraising the effectiveness and constraints of various approaches to disseminating medical information, choosing appropriate medical literature resources, navigating library databases, screening the literature from the search, and screening individual publications. We also discuss the importance of considering study limitations and the relevance of the results in research or use in the medical arena. In-depth, critical appraisal of medical or clinical research evidence requires expertise, insight into research methodologies, and a grasp of issues in each field. By harnessing the wealth of reliable and relevant information available in medical literature through the above steps, we can alleviate potentially misleading information and stay at the forefront of our respective fields.
  2. Colesevelam for Type 2 diabetes mellitus: an abridged Cochrane review
    Ooi CP, Loke SC
    Diabet Med, 2014 Jan;31(1):2-14.
    PMID: 24024701 DOI: 10.1111/dme.12295
    Colesevelam, a second-generation bile acid sequestrant, may be beneficial in controlling both glycaemia and lipids simultaneously. Our goal was to evaluate the systemic effects of colesevelam on Type 2 diabetes mellitus.
  3. Probing infinity in bounded two-dimensional electrostatic systems
    Abutalib M, Batle J, Ooi CH
    Chaos, 2016 Jul;26(7):073113.
    PMID: 27475073 DOI: 10.1063/1.4959138
    The total electrostatic energy of systems of identical particles of equal charge is studied in configurations bounded in space, but divergent in the number of charges. This approach shall guide us to unveil a non-linear, functional form specifying the divergent nature of system energy. We consider fractals to be physical entities, with charges located in their vertices or nodes. This description is interesting since features, such as the corresponding fractal dimension, can characterize the total energy EN. Finally, at local length scales, we describe how energy diverges at charge accumulation points in the fractal, that is, almost everywhere by definition.
  4. Fulltext Intricate Plasma-Scattered Images and Spectra of Focused Femtosecond Laser Pulses
    Ooi CH, Talib MR
    Sci Rep, 2016 Aug 30;6:32056.
    PMID: 27571644 DOI: 10.1038/srep32056
    We report on some interesting phenomena in the focusing and scattering of femtosecond laser pulses in free space that provide insights on intense laser plasma interactions. The scattered image in the far field is analyzed and the connection with the observed structure of the plasma at the focus is discussed. We explain the physical mechanisms behind the changes in the colorful and intricate image formed by scattering from the plasma for different compressions, as well as orientations of plano-convex lens. The laser power does not show significant effect on the images. The pulse repetition rate above 500 Hz can affect the image through slow dynamics The spectrum of each color in the image shows oscillatory peaks due to interference of delayed pulse that correlate with the plasma length. Spectral lines of atomic species are identified and new peaks are observed through the white light emitted by the plasma spot. We find that an Ar gas jet can brighten the white light of the plasma spot and produce high resolution spectral peaks. The intricate image is found to be extremely sensitive and this is useful for applications in sensing microscale objects.
  5. Fulltext Open total talus dislocation: a case report
    Tan E, Chua H, Ooi C, Zulkiflee O
    Malays Orthop J, 2012 Nov;6(3):60-2.
    PMID: 25279062 MyJurnal DOI: 10.5704/MOJ.1207.009
    Total talus dislocation is a rare injury and is commonly accompanied by associated fractures. Common worrisome sequelae are infection, avascular necrosis and post-traumatic arthritis. We report here on a patient who sustained an open total talus dislocation with an ipsilateral medial malleolus fracture. Following early debridement, reduction and a combination of internal and external fixations, early recovery was good with no evidence of avascular necrosis.
  6. Fulltext Coherently Tunable Triangular Trefoil Phaseonium Metamaterial
    Nguyen DM, Soci C, Ooi CH
    Sci Rep, 2016;6:21083.
    PMID: 26879520 DOI: 10.1038/srep21083
    Phaseonium is a three-level Λ quantum system, in which a coherent microwave and an optical control (pump) beams can be used to actively modulate the dielectric response. Here we propose a new metamaterial structure comprising of a periodic array of triangular phaseonium metamolecules arranged as a trefoil. We present a computational study of the spatial distribution of magnetic and electric fields of the probe light and the corresponding transmission and reflection, for various parameters of the optical and microwave beams. For specific values of the probing frequencies and control fields, the phaseonium can display either metallic or dielectric optical response. We find that, in the metallic regime, the phaseonium metamaterial structure supports extremely large transmission, with optical amplification at large enough intensity of the microwave thanks to strong surface plasmon coupling; while, in the dielectric regime without microwave excitation, the transmission bandwidth can be tuned by varying the control beam intensity. Implementation of such phaseonium metamaterial structure in solid-state systems, such as patterned crystals doped with rare-earth elements or dielectric matrices embedded with quantum dots, could enable a new class of actively tunable quantum metamaterials.
  7. Fulltext Non-locality Correlation in Two Driven Qubits Inside an Open Coherent Cavity: Trace Norm Distance and Maximum Bell Function
    Mohamed A-A, Eleuch H, Ooi CHR
    Sci Rep, 2019 Dec 23;9(1):19632.
    PMID: 31873086 DOI: 10.1038/s41598-019-55548-2
    We analytically investigate two separated qubits inside an open cavity field. The cavity is initially prepared in a superposition coherent state. The non-locality correlations [including trace norm measurement induced non-locality, maximal Bell-correlation, and concurrence entanglement] of the two qubits are explored. It is shown that, the generated non-locality correlations crucially depend on the decay and the initial coherence intensity of the cavity field. The enhancement of the initial coherence intensity and its superposition leads to increasing the generated non-locality correlations. The phenomena of sudden birth and death entanglement are found.
  8. Light absorption by interacting atomic gas in quantum optical regime
    Sizhuk AS, Dorfman K, Ooi CHR
    J Chem Phys, 2021 Jul 28;155(4):044105.
    PMID: 34340365 DOI: 10.1063/5.0054189
    Quantum optical theory of absorption properties of interacting atoms is developed. The concept of local absorptance is introduced as a derivative of the logarithm of intensity with respect to the distance in the vicinity of a given spatial point and a moment of time. The intensity is represented by the quantum and statistically averaged normal product of creation and annihilation operators of the electromagnetic field. The development of an analytical method of the estimation for the kinetic and optical parameters for the system is proposed here. The calculation method of the absorption coefficient includes thermal atomic motion, Doppler effect, and the short-range interaction between atoms. The absorption coefficient explicitly takes into account the quantum nature of the optical field. The ability of the system to absorb or emit quanta is quantitatively expressed through the special form of interaction integrals. The specific form of integrals results from the structure of the quantum brackets. The interplay between the collective (virtual photon exchange) and binary (optically induced inter-particle bonding) processes determines the system behavior. The spectral profile of the local absorption coefficient for different atomic densities and time intervals is simulated for realistic parameters.
  9. Fulltext Unified master equation for molecules in phonon and radiation baths
    Ooi CHR, Chia KJC
    Sci Rep, 2022 Nov 21;12(1):20015.
    PMID: 36414663 DOI: 10.1038/s41598-022-22732-w
    We have developed a unified quantum optical master equation that includes the dissipative mechanisms of an impurity molecule in crystals. Our theory applies generally to polyatomic molecules where several vibrational modes give rise to intramolecular vibrational redistributions. The usual assumption on identical shapes of the nuclear potentials in ground and excited electronic states and the rotating wave approximation have been relaxed, i.e. the vibrational coordinates are different in the ground and excited states, with counter-rotating terms included for generality. Linear vibrational coupling to the lattice phonons accounts for dissipations via non-radiative transitions. The interaction of a molecule with photons includes Herzberg-Teller coupling as the first order non-Condon interaction where the transition dipole matrix elements depend linearly on vibrational coordinates. We obtain new cross terms as the result of mixing the terms from the zeroth-order (Condon) and first-order (non-Condon) approximations. The corresponding Lamb shifts for all Liouvilleans are derived explicitly including the contributions of counter-rotating terms. The computed absorption and emission spectra for carbon monoxide is in good agreement with experimental data. We use our unified model to obtain the spectra for nitrogen dioxide, demonstrating the capability of our theory to incorporate all typical dissipative relaxation and decoherence mechanisms for polyatomic molecules. The molecular quantum master equation is a promising theory for studying molecular quantum memory.
  10. Fulltext Pilomatrixoma of left shoulder in an elderly female: a case report
    Tan L, Ooi C, Chua H, Zulkiflee O
    Malays Orthop J, 2013 Jul;7(2):48-50.
    PMID: 25722828 MyJurnal DOI: 10.5704/MOJ.1307.005
    We report a huge pilomatrixoma of the left shoulder in an elderly female, raising fear of malignancy. Magnetic Resonance Imaging delineated the swelling and wide surgical excision was performed. Post operative recovery was uneventful. Long term follow up is necessary in view of the possibility of recurrence and malignant transformation.

    KEY WORDS: Pilomatrixoma, Pilomatricoma, Calcifying Epithelioma of Malherbe, Shoulder, Upper Limb, Elderly, Female.

  11. Fulltext Arthroscopic resection of the distal clavicle with concomitant subacromial decompression: a case series
    Chan H, Ooi C, Lim M, Ong E, Zulkiflee O
    Malays Orthop J, 2014 Jul;8(2):59-62.
    PMID: 25279097 MyJurnal DOI: 10.5704/MOJ.1407.007
    Shoulder impingement syndrome and acromioclavicular joint osteoarthritis often occur simultaneously and easily missed. Kay et al. reported excellent results with combined arthroscopic subacromial decompression and resection of the distal end of the clavicle in patients with both disorders(1). Arthroscopic treatment of these disorders produces more favourable results than open procedures. We report two patients who were not responding to conservative management and were treated with direct arthroscopic distal clavicle excision and subacromial decompression in single setting. Both patients gained good postoperative outcome in terms of pain score, function and strength improvement assessed objectively with visual analogue score (VAS) and University of California Los Angeles Score (UCLA).
  12. Fulltext Cross-sectional study of older adults with type 2 diabetes mellitus in two rural public primary healthcare facilities in Malaysia
    Ooi CP, Loke SC, Zaiton A, Tengku-Aizan H, Zaitun Y
    Med J Malaysia, 2011 Jun;66(2):108-12.
    PMID: 22106688 MyJurnal
    Knowledge of the characteristics of older adults with type 2 diabetes mellitus (T2DM) is indispensible for improvement of their care. A cross-sectional study in two rural public primary healthcare centres in Malaysia identified 170 actively engaged older patients with T2DM, with suboptimal glycaemic control and frequent hypoglycaemia. The prevalence of multiple co-morbidities, complications of T2DM, high cardiovascular risk, neurological, musculoskeletal and visual deficits suggested high risk of disabilities and dependency but not yet disabled. This short window for interventions presents as an opportunity for development of a more comprehensive approach extending beyond glycaemia control to risk management, preventing functional loss and continuity of social participation.
    Study site: Klinik Kesihatan, Selangor, Malaysia
  13. The utility of immature reticulocyte fraction as an indicator of erythropoietic response to altitude training in elite cyclists
    Nadarajan VS, Ooi CH, Sthaneshwar P, Thompson MW
    Int J Lab Hematol, 2010 Feb;32(1 Pt 2):82-7.
    PMID: 19170774 DOI: 10.1111/j.1751-553X.2008.01132.x
    Altitude training is sometimes employed by elite endurance athletes to improve their sea level performance. This improvement results from the increased red cell mass consequent upon the boost in erythropoietin (EPO) level that occurs as a response to the relatively hypoxic environment at high altitudes. We measured serum EPO levels together with various red cell and reticulocyte parameters including immature reticulocyte fraction (IRF) in eight national track-endurance cyclists, resident at sea-level, prior to and upon return from an altitude of approximately 1905 m. Reticulocytes and soluble transferrin receptor (sTfR) were significantly increased with reduction in ferritin levels immediately on return from high altitude indicating increased erythropoietic activity. IRF in particular showed a significant peak immediately on return but decline to sub-baseline levels by day 9, and recovery to baseline by day 16. Our results indicate that IRF is a sensitive marker of erythropoietic status in athletes undergoing altitude training and subsequent loss of EPO stimuli on return to sea level.
  14. Genetic variation in the malaria mosquito vector Anopheles maculatus from Peninsular Malaysia
    Yong HS, Chiang GL, Loong KP, Ooi CS
    Southeast Asian J. Trop. Med. Public Health, 1988 Dec;19(4):681-7.
    PMID: 3238481
    Starch-gel electrophoretic studies on nine gene-enzyme systems comprising 14 loci revealed a fair level of genetic variation in two population samples of Anopheles maculatus from Peninsular Malaysia. The proportion of polymorphic loci was 0.36 for the Fort Bertau sample and 0.29 for the Gua Musang sample, while the mean heterozygosity value was 0.09 for Fort Bertau and 0.07 for Gua Musang. The values of genetic similarity (I = 0.98) and genetic distance (D = 0.02) were of the rank of geographical populations.
  15. General and specific combining abilities for different economic traits in broiler chickens
    Ooi CS, Mukherjee TK, Wong WC, Jalaludin S
    Theor Appl Genet, 1975 Jan;46(3):149-55.
    PMID: 24419868 DOI: 10.1007/BF00264870
    A complete diallel cross of four broiler breeds was made to investigate whether there are breed differences in the combining abilities for the traits, body weight, weight gain and feed efficiency, measured during the growing period from 4 to 12 weeks of age. Data collected from male and female birds were analysed separately. General combining ability (GCA) was found to be the largest and most significant source of variation contributing to differences between crosses for all the traits, in both male and female birds. Specific combining ability (SCA) was important for body weight in both sexes and for weight gain in females. Feed efficiency in both sexes did not appear to be influenced by SCA effects. Reciprocal effects (RE) were generally absent in both sexes for all the traits, except possibly for feed efficiency.
  16. Fulltext Effects of ultrashort laser pulses on angular distributions of photoionization spectra
    Ooi CHR, Ho WL, Bandrauk AD
    Sci Rep, 2017 07 27;7(1):6739.
    PMID: 28751648 DOI: 10.1038/s41598-017-05915-8
    We study the photoelectron spectra by intense laser pulses with arbitrary time dependence and phase within the Keldysh framework. An efficient semianalytical approach using analytical transition matrix elements for hydrogenic atoms in any initial state enables efficient and accurate computation of the photoionization probability at any observation point without saddle point approximation, providing comprehensive three dimensional photoelectron angular distribution for linear and elliptical polarizations, that reveal the intricate features and provide insights on the photoionization characteristics such as angular dispersions, shift and splitting of photoelectron peaks from the tunneling or above threshold ionization(ATI) regime to non-adiabatic(intermediate) and multiphoton ionization(MPI) regimes. This facilitates the study of the effects of various laser pulse parameters on the photoelectron spectra and their angular distributions. The photoelectron peaks occur at multiples of 2ħω for linear polarization while  odd-ordered peaks are suppressed in the direction perpendicular to the electric field. Short pulses create splitting and angular dispersion where the peaks are strongly correlated to the angles. For MPI and elliptical polarization with shorter pulses the peaks split into doublets and the first peak vanishes. The carrier envelope phase(CEP) significantly affects the ATI spectra while the Stark effect shifts the spectra of intermediate regime to higher energies due to interference.
  17. Real-time path-integral approach for dissipative quantum dot-cavity quantum electrodynamics: impure dephasing-induced effects (2017J. Phys.: Condens. Matter29055701)
    Nahri DG, Mathkoor FHA, Raymond Ooi CH
    J Phys Condens Matter, 2017 Dec 07;30(1).
    PMID: 29143756 DOI: 10.1088/1361-648X/aa9b00
    We have noticed one ambiguity and two minor errors in our original published paper [1], which we modify in this corrigendum. However, the errors do not affect the results and discussion of the original paper.
  18. Real-time path-integral approach for dissipative quantum dot-cavity quantum electrodynamics: impure dephasing-induced effects
    Nahri DG, Mathkoor FH, Raymond Ooi CH
    J Phys Condens Matter, 2017 Feb 08;29(5):055701.
    PMID: 27966466 DOI: 10.1088/1361-648X/29/5/055701
    A dissipative quantum dot (QD)-cavity system, where the QD is initially prepared in the excited state with no photon in the cavity, coupled to a longitudinal acoustic (LA) phonon reservoir is studied using a numerically exact real-time path-integral approach. Three distinct dynamical regimes of weak (WC), strong (SC), and coherent coupling (CC) are discussed and more accurate conditions identifying them are presented. Our results show that to have the CC regime, which is characterized by clear vacuum Rabi oscillation (VRO), vacuum Rabi splitting (VRS) should be larger than the sum of the widths of the corresponding peaks. In order to distinguish between contributions of population decay and impure dephasing, induced by LA phonon bath and the dissipations, we propose a two-part phenomenological expression, corresponding to the population decay and impure dephasing, which fits the QD-cavity decay curves perfectly and is used to calculate the corresponding spectra. We demonstrate that the effective population decay rate (the emission rate) increases from the carrier recombination rate to a maximum value, which is the mean of the QD and cavity dissipation rates, with QD-cavity coupling strength. To study the role of the effective impure dephasing rate on the width of the central peak of the spectra we introduce a quantity that can also be applied in determining the distinct coupling regimes. This quantity enables us to identify the onset of the SC regime as the point where the impure dephasing term begins to contribute to the central band of the spectrum significantly, as a result of the existence of VRO with a very small frequency (unclear VRO) at the corresponding decay curve. Its contribution to the width of the central peak increases with the coupling strength up to the onset of the CC regime, then reduces as a result of the appearance of sidebands in the spectra, which originates from clear VRO. The effective population decay and impure dephasing rate contribute solely to the width-of the central and sideband peaks of the triplet spectra respectively-only beyond a very large coupling strength which is the same across the considered temperature range. For higher temperatures, the maximum achievable emission rate can be obtained at larger coupling strengths.
  19. Corrosion and bioactivity performance of graphene oxide coating on TiNb shape memory alloys in simulated body fluid
    Saud SN, Hosseinian S R, Bakhsheshi-Rad HR, Yaghoubidoust F, Iqbal N, Hamzah E, et al.
    Mater Sci Eng C Mater Biol Appl, 2016 Nov 01;68:687-694.
    PMID: 27524069 DOI: 10.1016/j.msec.2016.06.048
    In the present work, the microstructure, corrosion, and bioactivity of graphene oxide (GO) coating on the laser-modified and -unmodified surfaces of TiNb shape memory alloys (SMAs) were investigated. The surface morphology and chemical composition was examined using field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). The surface modification was carried out via a femtosecond laser with the aim to increase the surface roughness, and thus increase the adhesion property. FE-SEM analysis of the laser-treated Ti-30at.% Nb revealed the increase in surface roughness and oxygen/nitrogen containing groups on the Ti-30at.% Nb surface after being surface modified via a femtosecond laser. Furthermore, the thickness of GO was increased from 35μm to 45μm after the surface was modified. Potentiodynamic polarisation and electrochemical impedance spectroscopy studies revealed that both the GO and laser/GO-coated samples exhibited higher corrosion resistance than that of the uncoated TiNb SMA sample. However, the laser/GO-coated sample presented the highest corrosion resistance in SBF at 37°C. In addition, during soaking in the simulated body fluid (SBF), both the GO and laser/GO coating improved the formation of apatite layer. Based on the bioactivity results, the GO coating exhibited a remarkable antibacterial activity against gram-negative bacteria compared with the uncoated. In conclusion, the present results indicate that Ti-30at.% Nb SMAs may be promising alternatives to NiTi for certain biomedical applications.
  20. Fulltext Large-scale structure formation in ionic solution and its role in electrolysis and conductivity
    Yee CN, Ooi CHR, Tan LP, Misran M, Tang NT
    PLoS One, 2019;14(3):e0213697.
    PMID: 30913207 DOI: 10.1371/journal.pone.0213697
    That water may not be an inert medium was indicated by the presence at water's interfaces a negatively charged solute free zone of several hundred microns in thickness called the exclusion zone (EZ). Further evidence was demonstrated by Ovchinnikova's experiments (2009) showing that water can store and release substantial amount of charge. We demonstrate that the charge storage capacity of water arises from highly stable large-scale ionic structures with measurable charge imbalances and discrete levels of charge density. We also show evidence that the charge zones formation requires ionic solutes, and their formation correlate to large change in conductivity, by as much as 250%. Our experiments indicate that large-scale structuring plays a pivotal role in electrolysis and conductivity in ionic solution. We propose that water is an electrochemically active medium and present a new model of electrolysis and conductivity in ionic solution.
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