Biological, chemical and mathematical sciences

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    Maghemite filled poly-vinyl alcohol nanofibres for tissue engineering scaffold.
    (Universiti Teknologi Malaysia, 2016) Ngadiman, Nor Hasrul Akhmal
    Maghemite (y-Fe2O3) nanoparticle with its unique magnetic properties has the potential to be used in biomedical applications. In this study, y-Fe2O3 was mixed with polyvinyl alcohol (PVA) in order to enhance cell growth which is required for tissue engineering (TE) scaffold. Electrospinning was chosen to be the main process in this study due to its ability to form fibers at nanometer scale and it can mimic the dimensions of the extracellular matrix (ECM) of human tissue. However, the major challenge faced is the limitation on its thickness of the electrospun mats produced. Thus in this study a 3D TE scaffold was fabricated from a novel biomaterial (PVA/y- Fe2O3) using a combined 3D printing with thermally induced phase separation (TIPS) and electrospinning processes. Design of experiments (DOE) was used to determine the optimum parameter settings for the electrospinning process so as to produce electrospun mats with good mechanical properties and porosity. The input factors of the electrospinnning process were the nanoparticles content, voltage, flow rate, spinning distance (tip to collector) and the rotating speed while the responses considered were Young’s Modulus and porosity. Maximum Young’s Modulus achieved was 273.51 MPa while maximum percentage of porosity achieved was 90.85%. The layer of electrospun nanofibers was then wrapped around the 3D PVA/y- Fe2O3 TE scaffold which was developed by combining 3D printing with TIPS. The characteristics and biocompatibility performance of the optimum PVA/y-Fe2O3 electrospun nanofiber mat and 3D structure were investigated. The developed 3D structure scaffold was again tested for its Young’s Modulus and was found to be 1.74 ± 0.17 GPa. Results also showed that the material developed has good biocompatibility properties. The rate of cells growth for the novel material (PVA/y- Fe2O3) was faster than the controlled material (only PVA) indicating that it is biocompatible. In conclusion, the developed 3D PVA/y-Fe2O3 nanofibrous scaffold has good mechanical and biocompatibility properties suitable for TE scaffold.
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    Mechanical, impact and post-impact characteristics of filament wound basalt composite tubes
    (Universiti Teknologi Malaysia, 2016) Mokhtar, Iqbal
    Basalt fiber has been proposed as an environmentally friendly alternative to traditional petroleum-derived fibers such as E-glass and carbon. Composite tubular structures are commonly used E-glass or carbon as a reinforcement materials have led to several effects, such as the substance being non-recyclable and nonbiodegradable. The durability of composite tubular structure is relying on damage resistance and damage tolerance. The primary aim of this research is to investigate the characteristics of Basalt reinforced epoxy composite tubes based on mechanical, impact and post-impact performances. Four different tube winding angles, [±45°]3, [±55°]3, [±65°]3 and [±75°]3 with an average of 3 mm thickness and 50 mm of inner diameter were selected. Hoop tensile and longitudinal tensile tests were conducted on carbon and three hybrid tubes for comparison purposes. Drop-weight impact tests were performed at different energy levels, which are 4, 6, 8 and 10 Joules using hemispherical tip impactor with different diameters of 6.3, 10, 12.7 and 15.9 mm. Compression after impact tests were carried out to determine the damage tolerance based on different parameters, including impact energy, shape of impactor tip, tubes’ reinforcement materials, tubes’ winding angles and compression loading rates. The results show that Basalt tubes produced up to 19.7% and 13.8% higher hoop and longitudinal strength respectively, have 3.8% higher damage resistance and up to 44% higher damage tolerance when compared to E-glass tubes. Scanning Electron Microscope was used to analyze the surface and texture morphology for both normal and damaged modes. There was evidence that matrix cracking and fiber fractures obtained from impact loads has affected up to 47% compressive strength of Basalt composite tubes. In overall, Basalt filament wound tubes show promising characteristics under mechanical, impact and post-impact loads
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    Deformation and fracture behaviour of cortical bone based on anisotropic yield criteria using finite element method.
    (Universiti Teknologi Malaysia, 2016) Ng, Theng Pin
    Bone fractures have long been studied by clinicians and biomedical engineering researchers. Despite the widespread use of different fracture criteria to evaluate the fracture behaviour of bone, yet the proposed models mostly consider the ultimate load as the failure point which is not practical and realistic for the natural quasi brittle behaviour of bone. In this study, a finite element based anisotropic failure criterion coupled with quasi brittle damage law model was proposed. The developed model aims to analyse the progressive failure of bone under different loading modes and to improve the prediction of both deformation and failure of cortical bone. Both experimental works and computational simulation were carried out under two type of loading modes: compression and bending. To validate the nature of quasi brittle bone behaviour and the experimental works, an available isotropic Brittle Damaged Plasticity (BDP) model in finite element software (ABAQUS) was implemented and the comparison was made with the experimental data. Then, anisotropic Liu-Huang-Stout (LHS) yield criterion and quasi brittle damage model were implemented through user subroutine code: user subroutine to define material behaviour (VUMAT) to display a complete force displacement curve as well as to characterise the damage and failure of full femur bovine bone. Experimental results showed that the trend of force-displacement exhibits the same trend with finite element BDP model. It also highlighted the damage propagation was corresponded to the accumulation of plastic strain. From the developed model, the force-displacement curve, the damage evolution and plastic strain distribution were in good agreement with the experimental works and the previous literatures. The accuracy of the proposed model is achieved up to 15% over the BDP model. This indicates that the proposed model could be more accurate in the prediction of bone deformation and fracture behaviour. Therefore, this model will provide better analysis in designing orthopaedic implants that will attach to the bone.
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    Treatment of poultry slaughterhouse wastewater using integrated anaerobic-aerobic sequencing batch reactor
    (Universiti Teknologi Malaysia, 2018) Rajab, Ahmed Rahomi
    Poultry slaughterhouse industries produce relatively high quantity of wastewater. This effluent is classified as a high-strength wastewater causing environmental deterioration if it is discharged without proper treatment especially for organics, ammoniacal nitrogen (NH3-N), including fat, oil, and grease (FOG) contaminants. A review was carried out to determine the research gap and to gain more insight on treatment system using two regimes (anaerobic and aerobic) processes in sequence for high-rate bioreactors which act as one unit in an integrated manner with physical separation and utilizing merely suspended growth system. Thus, a new configuration bioreactor called integrated anaerobic-aerobic sequencing batch reactor (IAASBR) was proposed and investigated to achieve the aforementioned targets. This study comprises of four parts: the first part characterized the poultry slaughterhouse wastewater (PSW) generated in Malaysia by selection of three poultry slaughterhouses. The second part dealt with choosing the best volumetric anaerobic/aerobic ratio (Van/Va) for the proposed IAASBR that has achieved the best organics and NH3-N removal efficiencies. Subsequently, the third part investigated the IAASBR’s endurance for maximum organic loading rate (OLR). Lastly, the ability of the proposed configuration for the simultaneous biological total nitrogen (TN) and phosphate (PO43-) removal from PSW was investigated. The characteristics of PSWs displayed high fluctuation in their pollution levels between the three selected factories and within the same plant itself (for example total chemical oxygen demand (TCOD) concentration was in the range of 940-3400 mg/L with an average 1940 ± 680 mg/L). The average removal efficiency for the best ratio (Van/Va = 2) measured as the TCOD, soluble chemical oxygen demand (SCOD), NH3-N, FOG, and total suspended solids were 97% ± 2%, 95% ± 3%, 98% ± 1.3%, 90% ± 11%, and 96% ± 3% respectively. The laboratory comparison test revealed that IAASBR configuration has enhanced the sludge settleability for aerobic sequencing batch reactor (SBR) more than the conventional SBR by emerging a new phenomenon called “Water Inflation Phenomenon (WIPh)”. IAASBR could tolerate the shock loading occurrence and handle OLR up to 4.5 kg(TCOD)/m3 d, producing a high-quality effluent complying with the standards for industrial’s effluents. In the aspect of renewable energy, the anaerobic SBR produced a reasonable quantity of biogas 0.10-0.21 L/d Lr (26-28°C) with methane (CH4) composition of 69%. This configuration exhibited low overall removal efficiencies for TN and PO43- by 38% and 6%, respectively. Furthermore, the main features of this IAASBR configuration are elimination of the inhibitory effect for FOG constituent’s concentration up to 370 mg/L and high removal efficiencies of organics and NH3-N with less aeration exertion (economical aspect) in addition of biogas production. In conclusion, the proposed bioreactor configuration exhibits a high performance, steady, and flexibility under different operation conditions along the 17 months period of this research
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    Development and characterization of sago based pervaporation membranes for the recovery of mixed cesium and potassium formate brines
    (Universiti Teknologi Malaysia, 2018) Zamrud, Zafifah
    Natural polymeric membranes being low cost, environmentally friendly and abundant in nature have proven their potential in pervaporative dehydration of organics. In this study, the efficiency of separation of mixed cesium and potassium (CsKFo) brines was evaluated at different membrane preparation conditions using sago starch (SS) and pervaporation (PV) operation conditions. Response surface methodology (RSM) was used to optimize the membrane preparation conditions and pervaporation operating conditions on flux and pervaporation separation index (PSI). Sago based pervaporation membranes showed excellent physicochemical properties after poly(vinyl) alcohol (PVA) blending, glutaraldehyde (GTA) crosslinking and heat treatment. The optimum preparation conditions for sago based membranes were found to be at 50 wt. % of SS in the blend, crosslinked with 1.0 wt. % GTA and heat treated at 150 °C with the highest flux and PSI of 228.03 g/m²h and 79.30 x 104, respectively. The optimum PV operating conditions were at 98% of CsKFo in feed and operated at 53 °C of feed temperature with the highest flux and PSI being 261.38 g/m²h and 277.42 x 105, respectively. The apparent activation energy for permeation (Ep) and activated diffusion (ED) calculated from the Arrhenius equation for water were smaller (Ep = 22.06 kJ/mol,ED = 22.17 kJ/mol) than CsKFo (Ep = 48.99 kJ/mol, ED = 48.98 kJ/mol) suggesting that the water molecules were easily permeated across the membrane and required less energy to diffuse through. The findings demonstrated that PV has potential for the complete recovery of CsKFo brines, which in turn benefits the oil and gas industry. This research also provides findings for extended application of SS biocomposite particularly as hydrophilic membranes