Displaying publications 1 - 20 of 57 in total

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  1. Wan Abas WA
    Biomed Mater Eng, 1995;5(2):59-63.
    PMID: 7655319
    The response of human skin to "stress relaxation" tests at low loads in vitro was investigated. A number of behaviours, other than those already well established and documented, were observed. The significant behaviours are pure recovery and relaxation-recovery. Other behaviours observed are temporary stress recovery during the relaxation process, and momentary sudden non-linear drop in stress value followed by a second relaxation. The pure recovery and relaxation-recovery responses are repeatable. The latter represents the transitional response between the well-known behaviour of stress relaxation and the behaviour of stress recovery.
  2. Wan Abas WA
    Biomed Mater Eng, 1994;4(7):473-86.
    PMID: 7881331
    The response of human skin to biaxial stretch tests in vivo was investigated and compared to the response to uniaxial tension. The results obtained illustrate the nonlinear, anisotropic, and viscoelastic (time-dependent) properties of skin under biaxial stretch. Preconditioning in the load-extension response was found not to be prominent. The results also suggest that the response of skin to a biaxial stretch in vivo is qualitatively similar to that in vitro. Values of the terminal stiffness and limit strain of skin under a biaxial stretch are found.
  3. Low WS, Wan Abas WA
    Biomed Res Int, 2015;2015:239362.
    PMID: 25977918 DOI: 10.1155/2015/239362
    Circulating tumor cells (CTCs) are tumor cells that have detached from primary tumor site and are transported via the circulation system. The importance of CTCs as prognostic biomarker is leveraged when multiple studies found that patient with cutoff of 5 CTCs per 7.5 mL blood has poor survival rate. Despite its clinical relevance, the isolation and characterization of CTCs can be quite challenging due to their large morphological variability and the rare presence of CTCs within the blood. Numerous methods have been employed and discussed in the literature for CTCs separation. In this paper, we will focus on label free CTCs isolation methods, in which the biophysical and biomechanical properties of cells (e.g., size, deformability, and electricity) are exploited for CTCs detection. To assess the present state of various isolation methods, key performance metrics such as capture efficiency, cell viability, and throughput will be reported. Finally, we discuss the challenges and future perspectives of CTC isolation technologies.
  4. Wan Abas WA, Asseli MR
    Biomed Mater Eng, 1994;4(7):463-71.
    PMID: 7881330
    Local strains acting across an area of skin loaded uniaxially in vivo are converted to stresses using the standard elastic formulae. The stress values are compared to those obtained using the classical Bossinesq and Michell stress functions. The results indicate that these functions are capable of describing the response of the skin, both in the low load and the high load regions.
  5. Low WS, Kadri NA, Abas WA
    ScientificWorldJournal, 2014;2014:961301.
    PMID: 25136701 DOI: 10.1155/2014/961301
    We propose a strategy for optimizing distribution of flow in a typical benchtop microfluidic chamber for dielectrophoretic application. It is aimed at encouraging uniform flow velocity along the whole analysis chamber in order to ensure DEP force is evenly applied to biological particle. Via the study, we have come up with a constructive strategy in improving the design of microfluidic channel which will greatly facilitate the use of DEP system in laboratory and primarily focus on the relationship between architecture and cell distribution, by resorting to the tubular structure of blood vessels. The design was validated by hydrodynamic flow simulation using COMSOL Multiphysics v4.2a software. Simulations show that the presence of 2-level bifurcation has developed portioning of volumetric flow which produced uniform flow across the channel. However, further bifurcation will reduce the volumetric flow rate, thus causing undesirable deposition of cell suspension around the chamber. Finally, an improvement of microfluidic design with rounded corner is proposed to encourage a uniform cell adhesion within the channel.
  6. Ali S, Osman NA, Razak A, Hussain S, Wan Abas WA
    Eur J Phys Rehabil Med, 2015 Feb;51(1):31-7.
    PMID: 24963603
    Lower limb amputee's are greatly affected in dealing with the environmental barriers such as ramps and stairs and reported high interface pressure between the residual limb and socket/liner. Interface pressure between the residual limb and socket/liner can affect the satisfaction and use of the prosthesis. Until now, little attention has been paid to interface pressure between socket and stump during ramp negotiation and its effect on amputee's satisfaction.
  7. Arifin N, Abu Osman NA, Ali S, Wan Abas WA
    Biomed Eng Online, 2014;13(1):23.
    PMID: 24597518 DOI: 10.1186/1475-925X-13-23
    Achieving independent upright posture has known to be one of the main goals in rehabilitation following lower limb amputation. The purpose of this study was to compare postural steadiness of below knee amputees with visual alterations while wearing three different prosthetic feet.
  8. Ku PX, Abu Osman NA, Wan Abas WA
    Gait Posture, 2014 Feb;39(2):672-82.
    PMID: 24331296 DOI: 10.1016/j.gaitpost.2013.07.006
    Postural control has been widely evaluated for the normal population and different groups over the past 20 years. Numerous studies have investigated postural control in quiet standing posture among amputees. However, a comprehensive analysis is lacking on the possible contributing factors to balance. The present systematic review highlights the current findings on variables that contribute to balance instability for lower extremity amputees. The search strategy was performed on PubMed, Web of Science, Medline, Scopus, and CINAHL and then followed by additional manual searching via reference lists in the reviewed articles. The quality of the articles was evaluated using a methodological quality assessment tool. This review included and evaluated a total of 23 full-text articles. Despite the inconsistencies in the methodological design of the studies, all articles scored above the acceptable level in terms of quality. A majority of the studies revealed that lower extremity amputees have increased postural sway in the standing posture. Asymmetry in body weight, which is mainly distributed in the non-amputated leg, was described. Aside from the centre of pressure in postural control, sensory inputs may be a related topic for investigation in view of evidence on their contribution, particularly visual input. Other balance-related factors, such as stump length and patients' confidence level, were also neglected. Further research requires examination on the potential factors that affect postural control as the information of standing postural is still limited.
  9. Arifin N, Abu Osman NA, Wan Abas WA
    J Appl Biomech, 2014 Apr;30(2):300-4.
    PMID: 23878204 DOI: 10.1123/jab.2013-0130
    The measurements of postural balance often involve measurement error, which affects the analysis and interpretation of the outcomes. In most of the existing clinical rehabilitation research, the ability to produce reliable measures is a prerequisite for an accurate assessment of an intervention after a period of time. Although clinical balance assessment has been performed in previous study, none has determined the intrarater test-retest reliability of static and dynamic stability indexes during dominant single stance. In this study, one rater examined 20 healthy university students (female=12, male=8) in two sessions separated by 7 day intervals. Three stability indexes--the overall stability index (OSI), anterior/posterior stability index (APSI), and medial/ lateral stability index (MLSI) in static and dynamic conditions--were measured during single dominant stance. Intraclass correlation coefficient (ICC), standard error measurement (SEM) and 95% confidence interval (95% CI) were calculated. Test-retest ICCs for OSI, APSI, and MLSI were 0.85, 0.78, and 0.84 during static condition and were 0.77, 0.77, and 0.65 during dynamic condition, respectively. We concluded that the postural stability assessment using Biodex stability system demonstrates good-to-excellent test-retest reliability over a 1 week time interval.
  10. Ku PX, Abu Osman NA, Yusof A, Wan Abas WA
    J Biomech, 2012 Jun 1;45(9):1638-42.
    PMID: 22507349 DOI: 10.1016/j.jbiomech.2012.03.029
    Postural stability is crucial in maintaining body balance during quiet standing, locomotion, and any activities that require a high degree of balance performance, such as participating in sports and dancing. Research has shown that there is a relationship between stability and body mass. The aims of this study were to examine the impact that two variables had on static postural control: body mass index (BMI) and gender. Eighty healthy young adults (age=21.7±1.8 yr; height=1.65±0.09 m; mass=67.5±19.0 kg) participated in the study and the static postural control was assessed using the Biodex Balance System, with a 20 Hz sampling rate in the bipedic stance (BLS) and unipedic stance (ULS) for 30s. Five test evaluations were performed for each balance test. Postural control was found to be negatively correlated with increased adiposity, as the obese BMI group performed significantly poorer than the underweight, normal weight and overweight groups during BLS and ULS tests. The underweight, normal weight and overweight groups exhibited greater anterior-posterior stability in postural control during quiet stance. In addition, female displayed a trend of having a greater postural sway than male young adults, although it was evidenced in only some BMI groups. This study revealed that BMI do have an impact on postural control during both BLS and ULS. As such, BMI and gender-specific effects should be taken into consideration when selecting individuals for different types of sporting activities, especially those that require quiet standing.
  11. Abd Razak NA, Abu Osman NA, Wan Abas WA
    Disabil Rehabil Assist Technol, 2013 May;8(3):255-60.
    PMID: 22830946 DOI: 10.3109/17483107.2012.704654
    This study examined the kinematic differences between a body-powered prosthesis and a biomechatronics prosthesis as a transradial amputee performed activities that involve flexion/extension and supination/pronation of the wrist.
  12. Ibrahim F, Ismail NA, Taib MN, Wan Abas WA
    Physiol Meas, 2004 Jun;25(3):607-15.
    PMID: 15253113 DOI: 10.1088/0967-3334/25/3/002
    This paper describes a model for predicting hemoglobin (Hb) by using bioelectrical impedance analysis (BIA) in dengue patients in the Hospital Universiti Kebangsaan Malaysia (HUKM). Bioelectrical impedance measurements were conducted on 83 (47 males and 36 females) serologically confirmed dengue fever (DF) and dengue hemorrhagic fever (DHF) patients during their hospitalization. The predictive equation for Hb was derived using multivariate analysis. We investigated all the parameters in BIA, patients' symptom and demographic data. In this developed model, four predictors (reactance (XC), sex, weight and vomiting) were found to be the best predictive factors for modeling Hb in dengue patients. However, the model can only explain approximately 42% of the variation in Hb status, thus single frequency bio-impedance stand-alone technique is insufficient to monitor Hb for the DF and DHF patients. Further investigation using multi-frequency BIA is recommended in modeling Hb to achieve the most parsimonious model.
  13. Choi JR, Hu J, Feng S, Wan Abas WA, Pingguan-Murphy B, Xu F
    Biosens Bioelectron, 2016 May 15;79:98-107.
    PMID: 26700582 DOI: 10.1016/j.bios.2015.12.005
    Lateral flow assays (LFAs) have currently attracted broad interest for point-of-care (POC) diagnostics, but their application has been restricted by poor quantification and limited sensitivity. While the former has been currently solved to some extent by the development of handheld or smartphone-based readers, the latter has not been addressed fully, particularly the potential influences of environmental conditions (e.g., temperature and relative humidity (RH)), which have not yet received serious attention. The present study reports the use of a portable temperature-humidity control device to provide an optimum environmental requirement for sensitivity improvement in LFAs, followed by quantification by using a smartphone. We found that a RH beyond 60% with temperatures of 55-60°C and 37-40°C produced optimum nucleic acid hybridization and antigen-antibody interaction in LFAs, respectively representing a 10-fold and 3-fold signal enhancement over ambient conditions (25°C, 60% RH). We envision that in the future the portable device could be coupled with a fully integrated paper-based sample-to-answer biosensor for sensitive detection of various target analytes in POC settings.
  14. Khalaj N, Abu Osman NA, Mokhtar AH, George J, Abas WA
    ScientificWorldJournal, 2014;2014:815184.
    PMID: 25136689 DOI: 10.1155/2014/815184
    Knee osteoarthritis is a common cause of disability which influences the quality of life. It is associated with impaired knee joint proprioception, which affects postural stability. Postural stability is critical for mobility and physical activities. Different types of treatment including nonsurgical and surgical are used for knee osteoarthritis. Hyaluronic acid injection is a nonsurgical popular treatment used worldwide. The aim of this study was to demonstrate the effect of hyaluronic acid injections on postural stability in individuals with bilateral knee osteoarthritis. Fifty patients aged between 50 and 70 years with mild and moderate bilateral knee osteoarthritis participated in our study. They were categorized into treatment (n = 25) and control (n = 25) groups. The treatment group received five weekly hyaluronic acid injections for both knees, whereas the control group did not receive any treatment. Postural stability and fall risk were assessed using the Biodex Stability System and clinical "Timed Up and Go" test. All the participants completed the study. The treatment group showed significant decrease in postural stability and fall risk scores after five hyaluronic acid injections. In contrast, the control group showed significant increase. This study illustrated that five intra-articular hyaluronic acid injections could significantly improve postural stability and fall risk in bilateral knee osteoarthritis patients. This trial is registered with: NCT02063373.
  15. Ali S, Abu Osman NA, Arifin N, Gholizadeh H, Abd Razak NA, Abas WA
    ScientificWorldJournal, 2014;2014:769810.
    PMID: 25184154 DOI: 10.1155/2014/769810
    This study aimed to compare the effect of satisfaction and perceived problems between Pelite, Dermo with shuttle lock, and Seal-In X5 liners on the transtibial amputees.
  16. Pirouzi G, Abu Osman NA, Oshkour AA, Ali S, Gholizadeh H, Abas WA
    Sensors (Basel), 2014;14(9):16754-65.
    PMID: 25207872 DOI: 10.3390/s140916754
    The suspension system and socket fitting of artificial limbs have major roles and vital effects on the comfort, mobility, and satisfaction of amputees. This paper introduces a new pneumatic suspension system that overcomes the drawbacks of current suspension systems in donning and doffing, change in volume during daily activities, and pressure distribution in the socket-stump interface. An air pneumatic suspension system (APSS) for total-contact sockets was designed and developed. Pistoning and pressure distribution in the socket-stump interface were tested for the new APSS. More than 95% of the area between each prosthetic socket and liner was measured using a Tekscan F-Scan pressure measurement which has developed matrix-based pressure sensing systems. The variance in pressure around the stump was 8.76 kPa. APSS exhibits less pressure concentration around the stump, improved pressure distribution, easy donning and doffing, adjustability to remain fitted to the socket during daily activities, and more adaptability to the changes in stump volume. The volume changes were adjusted by utility of air pressure sensor. The vertical displacement point and reliability of suspension were assessed using a photographic method. The optimum pressure in every level of loading weight was 55 kPa, and the maximum displacement was 6 mm when 90 N of weight was loaded.
  17. Arifin N, Abu Osman NA, Ali S, Gholizadeh H, Abas WA
    ScientificWorldJournal, 2014;2014:856279.
    PMID: 25003155 DOI: 10.1155/2014/856279
    This study aimed to evaluate the effects of prosthetic foot types on the postural stability among transtibial amputees when standing on different support surfaces.
  18. Pirouzi G, Abu Osman NA, Eshraghi A, Ali S, Gholizadeh H, Wan Abas WA
    ScientificWorldJournal, 2014;2014:849073.
    PMID: 25197716 DOI: 10.1155/2014/849073
    Socket is an important part of every prosthetic limb as an interface between the residual limb and prosthetic components. Biomechanics of socket-residual limb interface, especially the pressure and force distribution, have effect on patient satisfaction and function. This paper aimed to review and evaluate studies conducted in the last decades on the design of socket, in-socket interface pressure measurement, and socket biomechanics. Literature was searched to find related keywords with transtibial amputation, socket-residual limb interface, socket measurement, socket design, modeling, computational modeling, and suspension system. In accordance with the selection criteria, 19 articles were selected for further analysis. It was revealed that pressure and stress have been studied in the last decaeds, but quantitative evaluations remain inapplicable in clinical settings. This study also illustrates prevailing systems, which may facilitate improvements in socket design for improved quality of life for individuals ambulating with transtibial prosthesis. It is hoped that the review will better facilitate the understanding and determine the clinical relevance of quantitative evaluations.
  19. Eshraghi A, Abu Osman NA, Gholizadeh H, Ali S, Abas WA
    Am J Phys Med Rehabil, 2015 Jan;94(1):1-10.
    PMID: 24919079 DOI: 10.1097/PHM.0000000000000134
    This study aimed to compare the effects of different suspension methods on the interface stress inside the prosthetic sockets of transtibial amputees when negotiating ramps and stairs.
  20. Khalaj N, Abu Osman NA, Mokhtar AH, Mehdikhani M, Wan Abas WA
    PLoS One, 2014;9(3):e92270.
    PMID: 24642715 DOI: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC39584
    Balance is essential for mobility and performing activities of daily living. People with knee osteoarthritis display impairment in knee joint proprioception. Thus, the aim of this study was to evaluate balance and risk of fall in individuals with bilateral mild and moderate knee osteoarthritis. Sixty subjects aged between 50 and 70 years volunteered in this study. They were categorized into three groups which were healthy (n = 20), mild (n = 20) and moderate (n = 20) bilateral knee osteoarthritis groups. Dynamic and static balance and risk of fall were assessed using Biodex Stability System. In addition, Timed Up and Go test was used as a clinical test for balance. Results of this study illustrated that there were significant differences in balance (dynamic and static) and risk of fall between three groups. In addition, the main (most significant) difference was found to be between healthy group and moderate group. Furthermore, on clinical scoring of balance, the "Timed Up and Go" test, all three groups showed significant difference. In conclusion, bilateral knee osteoarthritis impaired the balance and increased the risk of fall, particularly in people with moderate knee osteoarthritis.
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