Displaying publications 61 - 80 of 110 in total

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  1. Fulltext Multiphasic Reaction Modeling for Polypropylene Production in a Pilot-Scale Catalytic Reactor
    Jakir Hossain Khan M, Azlan Hussain M, Mujtaba IM
    Polymers (Basel), 2016 Jun 14;8(6).
    PMID: 30979325 DOI: 10.3390/polym8060220
    In this study, a novel multiphasic model for the calculation of the polypropylene production in a complicated hydrodynamic and the physiochemical environments has been formulated, confirmed and validated. This is a first research attempt that describes the development of the dual-phasic phenomena, the impact of the optimal process conditions on the production rate of polypropylene and the fluidized bed dynamic details which could be concurrently obtained after solving the model coupled with the CFD (computational fluid dynamics) model, the basic mathematical model and the moment equations. Furthermore, we have established the quantitative relationship between the operational condition and the dynamic gas⁻solid behavior in actual reaction environments. Our results state that the proposed model could be applied for generalizing the production rate of the polymer from a chemical procedure to pilot-scale chemical reaction engineering. However, it was assumed that the solids present in the bubble phase and the reactant gas present in the emulsion phase improved the multiphasic model, thus taking into account that the polymerization took place mutually in the emulsion besides the bubble phase. It was observed that with respect to the experimental extent of the superficial gas velocity and the Ziegler-Natta feed rate, the ratio of the polymer produced as compared to the overall rate of production was approximately in the range of 9%⁻11%. This is a significant amount and it should not be ignored. We also carried out the simulation studies for comparing the data of the CFD-dependent dual-phasic model, the emulsion phase model, the dynamic bubble model and the experimental results. It was noted that the improved dual-phasic model and the CFD model were able to predict more constricted and safer windows at similar conditions as compared to the experimental results. Our work is unique, as the integrated developed model is able to offer clearer ideas related to the dynamic bed parameters for the separate phases and is also capable of computing the chemical reaction rate for every phase in the reaction. Our improved mutiphasic model revealed similar dynamic behaviour as the conventional model in the initial stages of the polymerization reaction; however, it diverged as time progressed.
    Matched MeSH terms: Hydrodynamics
  2. Electrokinetic supercharging in nonaqueous capillary electrophoresis for online preconcentration and determination of tamoxifen and its metabolites in human plasma
    Thang LY, Breadmore MC, See HH
    J Chromatogr A, 2016 Jul 27.
    PMID: 27485148 DOI: 10.1016/j.chroma.2016.07.067
    An online preconcentration method, namely electrokinetic supercharging (EKS), was evaluated for the determination of tamoxifen and its metabolites in human plasma in nonaqueous capillary electrophoresis with ultraviolet detection (NACE-UV). This method was comprehensively optimized in terms of the leading electrolyte (LE) and terminating electrolyte (TE) injection lengths, as well as electrokinetic sample injection time. The optimized EKS conditions employed were as follows: hydrodynamic injection (HI) of 10mM potassium chloride as LE at 150mbar for 36s (4% of total capillary volume). The sample was injected at 10kV for 300s, followed by HI of 10mM pimozide as TE at 150mbar for 36s (4% of total capillary volume). Separation was performed in 7.5mM deoxycholic acid sodium salt, 15mM acetic acid and 1mM 18-crown-6 in 100% methanol at +25kV with UV detection at 205nm. Under optimized conditions, the sensitivity was enhanced between 160- and 600-fold when compared with our previously developed method based on HI at 150mbar for 12s. The detection limit of the method for tamoxifen and its metabolites were 0.05-0.25ng/mL, with RSDs between 2.1% and 3.5%. Recoveries in spiked human plasma were 95.6%-99.7%. A comparison was also made between the proposed EKS approach and the standard field-amplified sample injection (FASI) technique. EKS proved to be 3-5 times more sensitive than the FASI. The new EKS method was applied to the analysis of tamoxifen and its metabolites in plasma samples from breast cancer patients after liquid-liquid extraction.
    Matched MeSH terms: Hydrodynamics
  3. Effects of aqueous humor hydrodynamics on human eye heat transfer under external heat sources
    Tiang KL, Ooi EH
    Med Eng Phys, 2016 Aug;38(8):776-84.
    PMID: 27340100 DOI: 10.1016/j.medengphy.2016.05.011
    The majority of the eye models developed in the late 90s and early 00s considers only heat conduction inside the eye. This assumption is not entirely correct, since the anterior and posterior chambers are filled aqueous humor (AH) that is constantly in motion due to thermally-induced buoyancy. In this paper, a three-dimensional model of the human eye is developed to investigate the effects AH hydrodynamics have on the human eye temperature under exposure to external heat sources. If the effects of AH flow are negligible, then future models can be developed without taking them into account, thus simplifying the modeling process. Two types of external thermal loads are considered; volumetric and surface irradiation. Results showed that heat convection due to AH flow contributes to nearly 95% of the total heat flow inside the anterior chamber. Moreover, the circulation inside the anterior chamber can cause an upward shift of the location of hotspot. This can have significant consequences to our understanding of heat-induced cataractogenesis.
    Matched MeSH terms: Hydrodynamics*
  4. The influence of artery wall curvature on the anatomical assessment of stenosis severity derived from fractional flow reserve: a computational fluid dynamics study
    Govindaraju K, Viswanathan GN, Badruddin IA, Kamangar S, Salman Ahmed NJ, Al-Rashed AA
    Comput Methods Biomech Biomed Engin, 2016 Nov;19(14):1541-9.
    PMID: 27052093 DOI: 10.1080/10255842.2016.1170119
    This study aims to investigate the influence of artery wall curvature on the anatomical assessment of stenosis severity and to identify a region of misinterpretation in the assessment of per cent area stenosis (AS) for functionally significant stenosis using fractional flow reserve (FFR) as standard. Five artery models of different per cent AS severity (70, 75, 80, 85 and 90%) were considered. For each per cent AS severity, the angle of curvature of the arterial wall varied from straight to an increasingly curved model (0°, 30°, 60°, 90° and 120°). Computational fluid dynamics was performed under transient physiologic hyperemic flow conditions to investigate the influence of artery wall curvature on the pressure drop and the FFR. The findings in this study may be useful in in vitro anatomical assessment of functionally significant stenosis. The FFR decreased with increasing stenosis severity for a given curvature of the artery wall. Moreover, a significant decrease in FFR was found between straight and curved models discussed for a given severity condition. These findings indicate that the curvature effect was included in the FFR assessment in contrast to minimum lumen area (MLA) or per cent AS assessment. The MLA or per cent AS assessment may lead to underestimation of stenosis severity. From this numerical study, an uncertainty region could be evaluated using the clinical FFR cutoff value of 0.8. This value was observed at 81.98 and 79.10% AS for arteries with curvature angles of 0° and 120° respectively. In conclusion, the curvature of the artery should not be neglected in in vitro anatomical assessment.
    Matched MeSH terms: Hydrodynamics*
  5. Evaluation of the carotid artery stenosis based on minimization of mechanical energy loss of the blood flow
    Sia SF, Zhao X, Li R, Zhang Y, Chong W, He L, et al.
    Proc Inst Mech Eng H, 2016 Nov;230(11):1051-1058.
    PMID: 28095764 DOI: 10.1177/0954411916671752
    BACKGROUND: Internal carotid artery stenosis requires an accurate risk assessment for the prevention of stroke. Although the internal carotid artery area stenosis ratio at the common carotid artery bifurcation can be used as one of the diagnostic methods of internal carotid artery stenosis, the accuracy of results would still depend on the measurement techniques. The purpose of this study is to propose a novel method to estimate the effect of internal carotid artery stenosis on the blood flow based on the concept of minimization of energy loss.

    METHODS: Eight internal carotid arteries from different medical centers were diagnosed as stenosed internal carotid arteries, as plaques were found at different locations on the vessel. A computational fluid dynamics solver was developed based on an open-source code (OpenFOAM) to test the flow ratio and energy loss of those stenosed internal carotid arteries. For comparison, a healthy internal carotid artery and an idealized internal carotid artery model have also been tested and compared with stenosed internal carotid artery in terms of flow ratio and energy loss.

    RESULTS: We found that at a given common carotid artery bifurcation, there must be a certain flow distribution in the internal carotid artery and external carotid artery, for which the total energy loss at the bifurcation is at a minimum; for a given common carotid artery flow rate, an irregular shaped plaque at the bifurcation constantly resulted in a large value of minimization of energy loss. Thus, minimization of energy loss can be used as an indicator for the estimation of internal carotid artery stenosis.

    Matched MeSH terms: Hydrodynamics
  6. Transient electro-magneto-hydrodynamic two-phase blood flow and thermal transport through a capillary vessel
    Mirza IA, Abdulhameed M, Vieru D, Shafie S
    Comput Methods Programs Biomed, 2016 Dec;137:149-166.
    PMID: 28110721 DOI: 10.1016/j.cmpb.2016.09.014
    Therapies with magnetic/electromagnetic field are employed to relieve pains or, to accelerate flow of blood-particles, particularly during the surgery. In this paper, a theoretical study of the blood flow along with particles suspension through capillary was made by the electro-magneto-hydrodynamic approach. Analytical solutions to the non-dimensional blood velocity and non-dimensional particles velocity are obtained by means of the Laplace transform with respect to the time variable and the finite Hankel transform with respect to the radial coordinate. The study of thermally transfer characteristics is based on the energy equation for two-phase thermal transport of blood and particles suspension with viscous dissipation, the volumetric heat generation due to Joule heating effect and electromagnetic couple effect. The solution of the nonlinear heat transfer problem is derived by using the velocity field and the integral transform method. The influence of dimensionless system parameters like the electrokinetic width, the Hartman number, Prandtl number, the coefficient of heat generation due to Joule heating and Eckert number on the velocity and temperature fields was studied using the Mathcad software. Results are presented by graphical illustrations.
    Matched MeSH terms: Hydrodynamics*
  7. Fulltext Synthesis, characterization, and efficacy of antituberculosis isoniazid zinc aluminum-layered double hydroxide based nanocomposites
    Saifullah B, El Zowalaty ME, Arulselvan P, Fakurazi S, Webster TJ, Geilich BM, et al.
    Int J Nanomedicine, 2016;11:3225-37.
    PMID: 27486322 DOI: 10.2147/IJN.S102406
    The chemotherapy for tuberculosis (TB) is complicated by its long-term treatment, its frequent drug dosing, and the adverse effects of anti-TB drugs. In this study, we have developed two nanocomposites (A and B) by intercalating the anti-TB drug isoniazid (INH) into Zn/Al-layered double hydroxides. The average size of the nanocomposites was found to bê164 nm. The efficacy of the Zn/Al-layered double hydroxides intercalated INH against Mycobacterium tuberculosis was increased by approximately three times more than free INH. The nanocomposites were also found to be active against Gram-positive and -negative bacteria. Compared to the free INH, the nanodelivery formulation was determined to be three times more biocompatible with human normal lung fibroblast MRC-5 cells and 3T3 fibroblast cells at a very high concentration of 50 µg/mL for up to 72 hours. The in vitro release of INH from the Zn/Al-layered double hydroxides was found to be sustained in human body-simulated buffer solutions of pH 4.8 and 7.4. This research is a step forward in making the TB chemotherapy patient friendly.
    Matched MeSH terms: Hydrodynamics
  8. Influence of stenosis on hemodynamic parameters in the realistic left coronary artery under hyperemic conditions
    Kamangar S, Badruddin IA, Badarudin A, Nik-Ghazali N, Govindaraju K, Salman Ahmed NJ, et al.
    Comput Methods Biomech Biomed Engin, 2017 Mar;20(4):365-372.
    PMID: 27612619 DOI: 10.1080/10255842.2016.1233402
    The current study investigates the hyperemic flow effects on heamodynamics parameters such as velocity, wall shear stress in 3D coronary artery models with and without stenosis. The hyperemic flow is used to evaluate the functional significance of stenosis in the current era. Patients CT scan data of having healthy and coronary artery disease was chosen for the reconstruction of 3D coronary artery models. The diseased 3D models of coronary artery shows a narrowing of >50% lumen area. Computational fluid dynamics was performed to simulate the hyperemic flow condition. The results showed that the recirculation zone was observed immediate to the stenosis and highest wall shear stress was observed across the stenosis. The decrease in pressure was found downstream to the stenosis as compared to the coronary artery without stenosis. Our analysis provides an insight into the distribution of wall shear stress and pressure drop, thus improving our understanding of hyperemic flow effect under both conditions.
    Matched MeSH terms: Hydrodynamics
  9. Fulltext A Facile and Flexible Method for On-Demand Directional Speed Tunability in the Miniaturised Lab-on-a-Disc
    Tan MK, Siddiqi A, Yeo LY
    Sci Rep, 2017 07 27;7(1):6652.
    PMID: 28751783 DOI: 10.1038/s41598-017-07025-x
    The Miniaturised Lab-on-a-Disc (miniLOAD) platform, which utilises surface acoustic waves (SAWs) to drive the rotation of thin millimeter-scale discs on which microchannels can be fabricated and hence microfluidic operations can be performed, offers the possibility of miniaturising its larger counterpart, the Lab-on-a-CD, for true portability in point-of-care applications. A significant limitation of the original miniLOAD concept, however, is that it does not allow for flexible control over the disc rotation direction and speed without manual adjustment of the disc's position, or the use of multiple devices to alter the SAW frequency. In this work, we demonstrate the possibility of achieving such control with the use of tapered interdigitated transducers to confine a SAW beam such that the localised acoustic streaming it generates imparts a force, through hydrodynamic shear, at a specific location on the disc. Varying the torque that arises as a consequence by altering the input frequency to the transducers then allows the rotational velocity and direction of the disc to be controlled with ease. We derive a simple predictive model to illustrate the principle by which this occurs, which we find agrees well with the experimental measurements.
    Matched MeSH terms: Hydrodynamics
  10. Pilot scale intensification of rubber seed (Hevea brasiliensis) oil via chemical interesterification using hydrodynamic cavitation technology
    Bokhari A, Yusup S, Chuah LF, Klemeš JJ, Asif S, Ali B, et al.
    Bioresour Technol, 2017 Oct;242:272-282.
    PMID: 28341378 DOI: 10.1016/j.biortech.2017.03.046
    Chemical interesterification of rubber seed oil has been investigated for four different designed orifice devices in a pilot scale hydrodynamic cavitation (HC) system. Upstream pressure within 1-3.5bar induced cavities to intensify the process. An optimal orifice plate geometry was considered as plate with 1mm dia hole having 21 holes at 3bar inlet pressure. The optimisation results of interesterification were revealed by response surface methodology; methyl acetate to oil molar ratio of 14:1, catalyst amount of 0.75wt.% and reaction time of 20min at 50°C. HC is compared to mechanical stirring (MS) at optimised values. The reaction rate constant and the frequency factor of HC were 3.4-fold shorter and 3.2-fold higher than MS. The interesterified product was characterised by following EN 14214 and ASTM D 6751 international standards.
    Matched MeSH terms: Hydrodynamics
  11. Refined energy-conserving dissipative particle dynamics model with temperature-dependent properties and its application in solidification problem
    Ng KC, Sheu TWH
    Phys Rev E, 2017 Oct;96(4-1):043302.
    PMID: 29347538 DOI: 10.1103/PhysRevE.96.043302
    It has been observed previously that the physical behaviors of Schmidt number (Sc) and Prandtl number (Pr) of an energy-conserving dissipative particle dynamics (eDPD) fluid can be reproduced by the temperature-dependent weight function appearing in the dissipative force term. In this paper, we proposed a simple and systematic method to develop the temperature-dependent weight function in order to better reproduce the physical fluid properties. The method was then used to study a variety of phase-change problems involving solidification. The concept of the "mushy" eDPD particle was introduced in order to better capture the temperature profile in the vicinity of the solid-liquid interface, particularly for the case involving high thermal conductivity ratio. Meanwhile, a way to implement the constant temperature boundary condition at the wall was presented. The numerical solutions of one- and two-dimensional solidification problems were then compared with the analytical solutions and/or experimental results and the agreements were promising.
    Matched MeSH terms: Hydrodynamics
  12. The influence of geometrical shapes of stenosis on the blood flow in stenosed artery
    Kamangar S, Nik-Ghazali N, Badarudin A, Ameer Ahamad N, Irfan Anjum Badruddin, Govindaraju K, et al.
    Sains Malaysiana, 2017;46:1923-1933.
    The present work was carried out to investigate the blood flow behavior and the severity of blockage caused in the
    arterial passage due to the different geometries such as elliptical, trapezium and triangular shapes of stenosis. The study
    was conducted with respect to various sizes of stenosis in terms of 70%, 80% and 90% area blockage of the arterial
    blood flow. The study was carried out numerically with the help of advance computational fluid dynamic software. It
    was found that the shape of the stenosis plays an important role in overall pressure drop across the blockage region
    of artery. The highest level of pressure drop was observed for trapezoidal shape of stenosis followed by elliptical and
    then by triangular shaped stenosis. The wall shear stress across the stenosis is great for trapezoidal shape followed by
    triangular and elliptical stenosis for same blockage area in the artery.
    Matched MeSH terms: Hydrodynamics
  13. A facile, bio-based, novel approach for synthesis of covalently functionalized graphene nanoplatelet nano-coolants toward improved thermo-physical and heat transfer properties
    Sadri R, Hosseini M, Kazi SN, Bagheri S, Abdelrazek AH, Ahmadi G, et al.
    J Colloid Interface Sci, 2018 Jan 01;509:140-152.
    PMID: 28898734 DOI: 10.1016/j.jcis.2017.07.052
    In this study, we synthesized covalently functionalized graphene nanoplatelet (GNP) aqueous suspensions that are highly stable and environmentally friendly for use as coolants in heat transfer systems. We evaluated the heat transfer and hydrodynamic properties of these nano-coolants flowing through a horizontal stainless steel tube subjected to a uniform heat flux at its outer surface. The GNPs functionalized with clove buds using the one-pot technique. We characterized the clove-treated GNPs (CGNPs) using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). We then dispersed the CGNPs in distilled water at three particle concentrations (0.025, 0.075 and 0.1wt%) in order to prepare the CGNP-water nanofluids (nano-coolants). We used ultraviolet-visible (UV-vis) spectroscopy to examine the stability and solubility of the CGNPs in the distilled water. There is significant enhancement in thermo-physical properties of CGNPs nanofluids relative those for distilled water. We validated our experimental set-up by comparing the friction factor and Nusselt number for distilled water obtained from experiments with those determined from empirical correlations, indeed, our experimental set-up is reliable and produces results with reasonable accuracy. We conducted heat transfer experiments for the CGNP-water nano-coolants flowing through the horizontal heated tube in fully developed turbulent condition. Our results are indeed promising since there is a significant enhancement in the Nusselt number and convective heat transfer coefficient for the CGNP-water nanofluids, with only a negligible increase in the friction factor and pumping power. More importantly, we found that there is a significant increase in the performance index, which is a positive indicator that our nanofluids have potential to substitute conventional coolants in heat transfer systems because of their overall thermal performance and energy savings benefits.
    Matched MeSH terms: Hydrodynamics
  14. Modification of Aortic Cannula With an Inlet Chamber to Induce Spiral Flow and Improve Outlet Flow
    Darlis N, Osman K, Padzillah MH, Dillon J, Md Khudzari AZ
    Artif Organs, 2018 May;42(5):493-499.
    PMID: 29280161 DOI: 10.1111/aor.13021
    Physiologically, blood ejected from the left ventricle in systole exhibited spiral flow characteristics. This spiral flow has been proven to have several advantages such as lateral reduction of directed forces and thrombus formation, while it also appears to be clinically beneficial in suppressing neurological complications. In order to deliver spiral flow characteristics during cardiopulmonary bypass operation, several modifications have been made on an aortic cannula either at the internal or at the outflow tip; these modifications have proven to yield better hemodynamic performances compared to standard cannula. However, there is no modification done at the inlet part of the aortic cannula for inducing spiral flow so far. This study was carried out by attaching a spiral inducer at the inlet of an aortic cannula. Then, the hemodynamic performances of the new cannula were compared with the standard straight tip end-hole cannula. This is achieved by modeling the cannula and attaching the cannula at a patient-specific aorta model. Numerical approach was utilized to evaluate the hemodynamic performance, and a water jet impact experiment was used to demonstrate the jet force generated by the cannula. The new spiral flow aortic cannula has shown some improvements by reducing approximately 21% of impinging velocity near to the aortic wall, and more than 58% reduction on total force generated as compared to standard cannula.
    Matched MeSH terms: Hydrodynamics
  15. Evaluation of Alkylamine Modified Pt Nanoparticles as Oxygen Reduction Reaction Electrocatalyst for Fuel Cells via Electrochemical Impedance Spectroscopy
    Joshi P, Okada T, Miyabayashi K, Miyake M
    Anal Chem, 2018 May 15;90(10):6116-6123.
    PMID: 29613775 DOI: 10.1021/acs.analchem.8b00247
    Organically (octyl amine, OA) surface modified electrocatalyst (OA-Pt/CB) was studied for its oxygen reduction reaction (ORR) activity via dc methods and its charge and mass transfer properties were studied via electrochemical impedance spectroscopy (EIS). Comparison with a commercial catalyst (TEC10V30E) with similar Pt content was also carried out. In EIS, both the catalysts showed a single time-constant with an emerging high-frequency semicircle of very small diameter which was fitted using suitable equivalent circuits. The organically modified catalyst showed lower charge-transfer resistance and hence, low polarization resistance in high potential region as compared to the commercial catalyst. The dominance of kinetic processes was observed at 0.925-1.000 V, whereas domination of diffusion based processes was observed at lower potential region for the organic catalyst. No effect due to the presence of carbon was observed in the EIS spectra. Using the hydrodynamic method, higher current penetration depth was obtained for the organically modified catalyst at 1600 rpm. Exchange current density and Tafel slopes for both the electrocatalysts were calculated from the polarization resistance obtained from EIS which was in correlation with the results obtained from dc methods.
    Matched MeSH terms: Hydrodynamics
  16. Fulltext The global flood protection savings provided by coral reefs
    Beck MW, Losada IJ, Menéndez P, Reguero BG, Díaz-Simal P, Fernández F
    Nat Commun, 2018 06 12;9(1):2186.
    PMID: 29895942 DOI: 10.1038/s41467-018-04568-z
    Coral reefs can provide significant coastal protection benefits to people and property. Here we show that the annual expected damages from flooding would double, and costs from frequent storms would triple without reefs. For 100-year storm events, flood damages would increase by 91% to $US 272 billion without reefs. The countries with the most to gain from reef management are Indonesia, Philippines, Malaysia, Mexico, and Cuba; annual expected flood savings exceed $400 M for each of these nations. Sea-level rise will increase flood risk, but substantial impacts could happen from reef loss alone without better near-term management. We provide a global, process-based valuation of an ecosystem service across an entire marine biome at (sub)national levels. These spatially explicit benefits inform critical risk and environmental management decisions, and the expected benefits can be directly considered by governments (e.g., national accounts, recovery plans) and businesses (e.g., insurance).
    Matched MeSH terms: Hydrodynamics
  17. Effects of thermal radiation on mixed convection flow over a permeable vertical shrinking flat plate in an oldroyd-b fluid
    Kohilavani Naganthran, Roslinda Nazar, Ioan Pop
    Sains Malaysiana, 2018;47:1069-1076.
    This study offers the numerical solutions for the problem of mixed convection stagnation-point flow along a permeable
    vertical flat plate in an Oldroyd-B fluid. The present investigation considers the effects of thermal radiation and heat
    generation/absorption in the fluid flow. The similarity transformation simplifies the complex model and the bvp4c function
    generates the numerical solutions according to the variations in the governing parameters. A higher degree of shrinking
    hastens flow separations. The dual solutions are visible in the range of buoyancy opposing flow. The results from this study
    may be useful for the scientist to understand the behaviour of the dilute polymer solutions in the industrial applications,
    for example, the drag reduction in pipe flows.
    Matched MeSH terms: Hydrodynamics
  18. Ingham problem for mixed convection flow of a nanofluid over a moving vertical plate with suction and injection effects
    Anuar Jamaludin, Roslinda Nazar, Ioan Pop
    Sains Malaysiana, 2018;47:2213-2221.
    In this study, the effects of suction and injection on the mixed convection flow of a nanofluid, over a moving permeable
    vertical plate were discussed. A similarity variable was used to transform the governing equations to the ordinary
    differential equations, which were then solved numerically using the bvp4c programme from MATLAB. Dual solutions
    (upper and lower branches) were found within a certain range of the mixed convection parameter in assisting and
    opposing flow regions. A stability analysis was implemented to confirm that the upper branch solution was stable, while
    the lower branch solution was unstable.
    Matched MeSH terms: Hydrodynamics
  19. Effect of gamma irradiation on the physical stability of dppc liposomes
    Liyana Mohd Ali Napia, Faizal Mohamed, Hur Munawar Kabir Mohd, Intan Syakeela Ahmad Bastamam, Shamellia Sharin, Norsyahidah Mohd Hidzir, et al.
    Sains Malaysiana, 2018;47:1235-1240.
    Unilamellar liposomes composed of dipalmitoylphosphatidylcholine (DPPC) were prepared by the reverse-phase
    evaporation method and extrusion through a polycarbonate membrane filter. Liposomes at 0.7 mg/mL lipid concentration
    in deionized water were exposed to gamma irradiation at a dose in the range 0.5 to 25 kGy. Gamma irradiation of
    liposomes resulted in the degradation of DPPC lipids into free fatty acids, lysophosphatidylcholine and 1,2-palmitoylphosphatidic
    acid (DPPA). The effect of gamma irradiation towards the physical stability of liposomes was investigated
    by means of dynamic light scattering (DLS), transmission electron microscopy (TEM) and zeta potential analysis. From
    the DLS analysis, no significant changes were observed in the hydrodynamic size of liposomes. TEM images indicate that
    the liposomes surface became smoother and rounder as higher irradiation doses were applied. Zeta potential analysis
    showed that gamma irradiation of DPPC liposomes at radiation doses as low as 0.5 kGy resulted in a drastic rise in the
    magnitude of the zeta potential. The results also demonstrate that gamma irradiation of liposomes suspension enhanced
    the overall stability of liposomes. Hence, it can be concluded that gamma irradiation on DPPC liposomes may potentially
    produce liposomes with higher stability.
    Matched MeSH terms: Hydrodynamics
  20. Fulltext Mathematical Model for Steady State Subsea Cable Laying Problem
    Ahmad Razin Zainal Abidin, Shaymaa Mustafa, Zainal Abdul Aziz and, Kamarudin Ismail
    MATEMATIKA, 2018;34(2):173-186.
    MyJurnal
    Subsea cable laying process is a difficult task for an engineer due to many
    uncertain situations which occur during the operation. It is very often that the cable being
    laid out is not perfectly fit on the route being planned, which results in the formation of
    slack. In order to control wastages during installation, the slack needs to be minimized
    and the movement of a ship/vessel needs to be synchronized with the cable being laid out.
    The current problem was addressed using a mathematical model by considering a number
    of defining parameters such as the external forces, the cable properties and geometry. Due
    to the complexity, the model is developed for a steady-state problem assuming velocity
    of the vessel is constant, seabed is flat and the effect of wind and wave is insignificant.
    Non-dimensional system is used to scale the engineering parameters and grouped them
    into only two main parameters which are the hydrodynamic drag of the fluid and the
    bending stiffness of the cable. There are two solutions generated in this article; numerical
    and asymptotic solutions. The result of these solutions suggests that the percentage of
    slack can be reduced by the increase of the prescribed cable tension, and also the increase
    in either the drag coefficient of the sea water or the bending stiffness of the cable, similarly
    will result in lower slack percentage
    Matched MeSH terms: Hydrodynamics
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