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- PublicationBioassay-guided profiling of quercus infectoria gall extracts using HPLC and their antimalarial activity(2025-01)Malaria is a public health concern as the emergence of drug-resistant malaria parasites causes significant morbidity and mortality annually. The discovery of potent antimalarial drugs derived from medicinal plants is believed to be a crucial strategy for addressing the antimalarial drug resistance crisis. Therefore, the antimalarial properties of crude extracts from Quercus infectoria (QI) galls were investigated through bioassay-guided fractionation. Acetone (QIA) and methanol (QIM) crude extracts have been reported to exhibit promising antimalarial activity against Plasmodium falciparum (3D7 strain) with IC50 values of 5.85 ± 1.64 μg/mL and 10.31 ± 1.90 μg/mL, respectively. These extracts were subjected to fractionation using automated preparative high-performance liquid chromatography (prep-HPLC) to identify the most active fractions. Nine fractions were separated from each extract, of which the fractions QIA6 and QIM6 showed potent antimalarial activity, with IC50 values of 17.65 ± 1.82 μg/mL and 24.21 ± 1.88 μg/mL, respectively. In comparison, the standard antimalarial drug artemisinin had an IC50 value of 0.004 ± 0.001 μg/mL. The fractions of the Quercus infectoria galls exhibited antimalarial activity, which could be attributed to the presence of various secondary metabolites, particularly phenolic compounds such as ellagic acid. The high-performance liquid chromatography (HPLC) analytical method was established for the quantification of ellagic acid as a marker in the Quercus infectoria gall crude extract. All parameters including specificity, precision, accuracy, linearity, limit of detection (LOD) and limit of quantitation (LOQ), were found to be in the acceptable criteria of the ICH guideline. Targeted phenolic compound analysis of the most active fraction was performed by high-resolution liquid chromatography coupled with mass spectrometry (HR-LCMS). HR-LCMS analysis was conducted on the active fractions, QIA6 and QIM6, and revealed that kaempferol-3-O-glucoside, quercetin-3-glucoside, and syringic acid were among the major compounds identified in QIA6, while syringic acid and 3,4-dihydroxybenzoic acid were predominant in QIM6. The correlation between antimalarial activity and phenolic compounds in fractions QIA6 and QIM6 led to the quantitation of four targeted phenolic compounds. Thus, this study showed promising antimalarial activity of Quercus infectoria (QI) galls when fractionation was performed, which can be used as a guideline for future investigations on the molecular mechanism underlying the antimalarial action and further reflect the importance of an in-depth antimalarial investigation.
- PublicationValidation of plasma probe hardware platform for in-situ measurement and monitoring of atmospheric parameters using sounding rocket(2024-04-01)This thesis presents the validation of a plasma probe hardware platform for insitu measurement, accompanied by a real-time communication system. The objective is to create an integrated system that combines a plasma probe hardware platform with a reliable and efficient real-time communication infrastructure. The hardware platform incorporates multiple sensors, including temperature, magnetic, accelerometer, camera, pressure, and GPS, to enhance the understanding of the relationship between in-situ plasma probe measurements and environmental parameters. The real-time communication system ensures seamless data transmission between the platform and the ground station operator during the data collection process, providing valuable realtime access to the collected data. This feature also serves as a redundancy solution in the event of recovery failure, ensuring that data can still be transmitted and monitored even if the platform cannot be recovered. Through this integrated approach, researchers can monitor, analyse, and make informed decisions based on the collected data in real-time, even in challenging recovery scenarios. The validation of the plasma probe hardware platform, coupled with the real-time communication system, advances our capability to study plasma phenomena, offering significant implications for space exploration, atmospheric research, and related scientific endeavours.
- PublicationSynthesis of molecularly imprinted polymer-ordered mesoporous silica adsorbent for batch and fixed-bed column adsorption of chloramphenicol(2024-09-01)This study describes a novel synthesis of a surface-imprinted polymer-ordered mesoporous silica adsorbent for highly selective chloramphenicol (CAP) adsorption using activator regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP). Initially, ordered mesoporous silica was synthesized by the sol-gel method and functionalized to prepare a silica-ATRP initiator (SiO2@Br) for polymer grafting. CAP was used as the template molecule for imprinting via precipitation polymerization. The effects of varying polymerization reaction parameters, such as template to functional monomer molar ratio (1:2 – 1:10), template to cross-linker molar ratio (1:4 – 1:20), solvent types (acetonitrile and toluene) and their mixtures (0 – 100%), catalyst to ligand ratio (1:2 – 1:10), catalyst to reducing agent ratio (1:2 – 1:10), reaction temperature (313 – 353 K), and reaction time (6 – 30 h) on imprinting factor (IF) values and adsorption capacities (Qt) were studied. The physical and chemical properties of the resulting adsorbent were analyzed using FTIR, TGA, EDX, SEM, HRTEM, and nitrogen sorption techniques. The SiO2@Br had a specific surface area of 638.31 m².g-1 and a total pore volume of 0.4152 cm³.g-1. Post-polymerization, the specific surface area and pore volume of the adsorbent (SiO2@MIPs-CAPcr) decreased to 11.91 m².g-1 and 0.019 cm³.g-1, indicating successful grafting. Adsorption performance was investigated through batch and fixed-bed column studies. Batch experiments investigated the effects of initial solute concentration (10 – 50 mg.L-1), adsorbent dosage (5 – 25 mg), temperature (293 – 313 K), and initial pH (3 – 11) on CAP adsorption. The adsorption equilibrium data for SiO2@MIPs-CAPcr were well fitted by the Sips models, with a maximum adsorption capacity (Qs) of 19.68 mg.g-1. The adsorption kinetic followed pseudo second-order behaviour. Thermodynamic analysis indicated an exothermic process with entropy change due to reduced molecule movement. Selectivity studies involved antibiotics ciprofloxacin (CIP) and thiamphenicol (TAP) as model adsorbates. Fixed-bed column experiments tested initial concentrations (10 – 50 mg.L-1), volumetric inlet flow rates (0.1 – 0.5 mL.min-1), and bed heights (0.5 – 1.0 cm). The Thomas model best described the fixed-bed column adsorption behaviour. The SiO2@MIPs-CAPcr adsorbent demonstrated remarkable selectivity for CAP and excellent adsorption capabilities in both batch and fixed-bed operations.
- PublicationFuzzy-based vector control system for permanent magnet synchronous motor(2024-12-01)Permanent Magnet Synchronous Motor (PMSM) is highly regarded for its efficiency, power density, and dynamic performance, making it integral in industrial automation and electric vehicles. However, traditional PI controllers often struggle with parameter variations, nonlinear characteristics, and load disturbances, affecting steady-state and dynamic performance. This thesis addresses these challenges by proposing a Fuzzy PI control strategy that combines Field-Oriented Control (FOC) with Fuzzy logic, enabling adaptive adjustments of PI parameters for enhanced stability, robustness, and responsiveness. MATLAB/Simulink simulations show that the Fuzzy PI controller achieves faster steady-state response, reduces steady-state error, and minimizes overshoot across various speeds, including 500 and 1200 r/min. During a load disturbance test with a drop from 50% (5 Nm) to zero at 2.5 seconds, both controllers reached a similar overshoot peak (about 600 rpm); however, the Fuzzy PI controller stabilized back to 500 rpm within 0.3 seconds, significantly faster than the 0.8 seconds of the conventional PI controller. Additionally, the Fuzzy PI controller reduced current oscillations (±4 A versus ±6 A), further affirming its superior dynamic response and precision. These results validate the Fuzzy PI control strategy's effectiveness in optimizing PMSM performance, offering a robust framework for advanced control applications.
- PublicationCopper oxide nanocrystals based electrospun nanofibrous membrane for solar water evaporation(2024-03-01)Solar water evaporation has attracted widespread research, which narrowed the huge gap between inadequate clean water supply and human needs. For membrane evaporators, improving the solar absorption, water supply ability, and thermal management are critical to photothermal performance. Developing a suitable structure of light absorbing material could be a feasible approach to address these problems and to enhance evaporation performance. Yet there is limited research focus on this topic. In this study, three different structural CuO-based membrane evaporators were developed to adjust the membrane properties for improving solar evaporation performance. First of all, a triple-layer P/CuO-nanocluster nanofibrous membrane was fabricated through electrospinning, heating and hydrothermal processes. The top and bottom hydrophilic layers of CuO-nanocluster can effectively absorb sunlight, transport water, and suppress salt accumulation on the membrane surface. The middle layer of nanofibrous PVDF-HFP thin-film can support the whole system. The resultant membrane showed an evaporation rate of 1.21 kgm−2h−1 and efficiency of 83.57% for 3.5 wt.% saline water, which is higher than control group without membrane of 0.24 kgm−2h−1 and 16.26%, respectively. The next membrane structure design was core-shell structural P/CuO-Ag NPs nanofibrous membrane. During the electrospinning process, hydrophilic PVP was introduced to help more CuO growth media penetrating into the membrane interior during hydrothermal process. The Ag NPs incorporation enhanced membrane light absorption and wettability. The resultant core-shell P/CuO-Ag membrane achieved better evaporation rates of 1.31 kgm−2h−1 and efficiency of 90.77% for 3.5 wt.% saline water. The final membrane structure was hollow structural P/CuO-C nanofibrous membrane synthesized through coaxial electrospinning. During the fabrication process, the spinning precursor mixed with C NPs in the shell layer to enhance the light absorption while the hydrophilic PVP in the core layer was removed in the hydrothermal step to form a hollow structure. The formation of the hollow structure not only enhanced light absorption but also improved thermal management capacity of the membrane. As a result, the hollow structural P/CuO-C membrane achieved the best evaporation rate of 1.36 kgm−2h−1 and efficiency of 93.07% for 3.5 wt.% saline water as compared to the previous two structures. The outcome of this work will inspire subsequent research to construct of suitable architecture materials for potential applications in water treatment, thermal insulation, energy generation, energy storage, and other related fields.
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- PublicationDesign of a retrofit inferarm cruthes(2008-04-01)The walking stick is a great aid when the person had an accident and his walking is impaired. It provides steadiness and stability, allowing the user to get around pretty well. By the way, for a person that unable to walk, the easiest way to help them to get around is using a wheelchair. It would help them hanging around easily with no burden to walk. But, wheelchair is not able to use in all aspect. For example, the user can't use the wheelchair to go up the staircase. Furthermore, if a person always sits on the wheelchair s without exercise, the bones of legs will get weaker. The main objective of this project is to design a crutch that can assist the disable or leg's injury person to climb up the staircase. It would help to prevent further damage or accidents when the user climbs up the staircase. Besides, the user is able to maintain proper posture, relieves damaging. stress, and reduces the overall chance of injury when climbing staircase. The project has completed with 3D solid modeling of the designed crutches with SolidWork 2007. Furthermore. COSMOS analysis was done on the critical parts of the designed crutches to make sure the factor of safety required was achieved.
- ItemMST 564 - Statistical Reliability - Oktober 2004(Universiti Sains Malaysia, 2004-10)
- PublicationIn vitro evaluation of the antioxidant and antimicrobial activities of tualang honey samples and purified 5-hydroxymethylfurfural(2025-01)Aged tualang honey (ATH) remains a favoured choice due to its superior health benefits, despite many people being unaware that it contains elevated concentrations of 5-hydroxymethylfurfural (HMF). This study aimed to assess the therapeutic properties of TH samples of varying ages (FTH, ATH-24 and ATH-48) containing natural HMF in comparison with purified HMF (HMF low, medium and high doses). The antioxidant property was evaluated through a DPPH radical scavenging assay to calculate IC50. Further, the antimicrobial activity of the TH samples was assessed based on the zone of inhibition by the agar well diffusion method. According to the findings, all TH samples demonstrated higher free radical scavenging activities (ATH-48 exhibited the highest) compared to purified HMF groups. The calculated IC50 values of TH samples were lower than the IC50 values of purified HMF, indicating their superior antioxidant potential. Apart from that, TH samples exhibited antimicrobial activity against all tested bacteria. The greatest antimicrobial activity, indicated by the largest inhibition zone of each TH sample, was observed against S. aureus. ATH-24 has the highest antimicrobial efficacy with better zones of inhibition for both Gram-positive and Gram-negative bacteria compared to FTH and ATH-48. Purified HMF groups demonstrated dose-dependent antioxidant effects without any antimicrobial activities. Taking all data together, ATH-24 with a medium level of HMF demonstrated good antioxidant and antimicrobial properties. As we uncover the advantages of TH samples containing natural HMF, these findings suggest that HMF may synergistically enhance the antioxidant effects in TH samples but not the antimicrobial effects. This study contributes to expanding new insights in apitherapy research
- ItemEffects Of Repetitive Uncontrolled Temperature Exposure On The Quality Of Packed Red Blood Cells(Universiti Sains Malaysia, 2019)Packed Red Blood Cells (PRBC) must be transfused within 30 minutes upon removal from blood refrigerator and the PRBC should not be hold in the ward where the storage temperature is not controlled. Untransfused blood which returned to the blood bank shall be discarded unless it is kept in an appropriate condition and temperature. Intermittent storage outside allowable temperature range often leads to destruction of the PRBC unit. This was a cross sectional study performed to determine the PRBC warming rates and the quality of PRBC upon repetitive exposure to uncontrolled temperature after 30 minutes and 4 hours. In this study four PRBC units (228 mL ± 37mL) collected from eligible volunteer subjects were equivalently split into two units, producing eight smaller units PRBC (±130mL) which then assigned into two groups; control and experimental group. Eight units of PRBC from both control and experimental group were tested on day 1, day 7, day 14 and day 35 of storage for haemoglobin level, haematocrit, haemolysis rate, potassium, lactate dehydrogenase (LDH), pH and sterility. The PRBC warming rate upon exposure to uncontrolled temperature were monitored and recorded. All PRBCs achieved desired quality requirement from national guideline from day 1 to day 35 for haematocrit, haemolysis rate, and sterility. However, none of the PRBC units met the standard requirement (>45g/unit) for haemoglobin starting day 14 to day 35. No significant changes observed for all PRBC’s quality over repetitive exposure to uncontrolled temperature in 35 days in experimental group (P<0.05). There was also no evidence of bacterial contamination in PRBC at the end of their shelf life.
- ItemSynthesis And Characterization Of Black Silicon By Silver-Assisted Chemical Etching For Solar Cell(Universiti Sains Malaysia, 2021-03)Crystalline silicon (c-Si) suffers from poor light absorption due to its indirect band gap and high reflection from its surface (about 35% in the visible region). This problem can be solved by texturing the surface of c-Si wafer to reduce its broadband reflection. Black silicon (b-Si) or nanotextured c-Si, has a huge potential for applications in solar cell due to its superior broadband light absorption within 300-1100 nm wavelength region. In this work, two-step metal-assisted chemical etching (MACE) is used to synthesize b-Si by combining low-annealing temperature of silver (Ag) film and short duration of etching of the c-Si wafer. For the b-Si fabrication, p-type (100) c-Si wafers are deposited with 15 nm Ag film using radio frequency (RF) sputtering process. Subsequently, the Ag film is annealed at low temperatures (200-230ᵒC) for 40 min in nitrogen (N2) ambient, producing Ag nanoparticles (NPs). Then, the c-Si wafers with the Ag NPs are etched in a solution containing hydrofluoric acid:hydrogen peroxide:deionized water (HF:H2O2:DI H2O) for a short duration (35-180 s). Effects of etching time, etchant volume ratio and annealing temperature towards surface morphological and optical properties by using atomic force microscope (AFM), field emission scanning electron microscope (FESEM) and UV-Vis-NIR (within 300-1100 nm wavelength region) of b-Si are then investigated. From the investigation, the b-Si with the lowest broadband reflection is produced by annealing at 230ᵒC for 40 min and etched for 70 s using HF:H2O2:DI H2O (1:5:10 by volume). The lowest reflection of the b-Si wafer is 3% at wavelength of 600 nm, with weighted average reflection (WAR) of 8%. The b-Si demonstrates average width and height of about 50-100 nm and 300-400 nm respectively for the nanotextures. For solar cell fabrication, the b-Si is diffused with phosphoric acid (H3PO4) and 2-butanol using temperatures between 850 to 950oC for 20 min to form front n+ emitter. The emitter is characterized using Hall effect measurement. Ag and aluminium (Al) are thermally evaporated on the front and rear surfaces respectively to form electrical contacts. From current-voltage measurement, the b-Si solar cells demonstrate short-circuit current density (Jsc) of 20 mA/cm2, open-circuit voltage (Voc) of 423 mV and fill factor (FF) of 25.4%. This corresponds to conversion efficiency (η) of 5.2%. On the other hand, the planar c-Si reference solar cells exhibit Jsc of 7 mA/cm2, Voc of 390 mV and FF of 21.7%. The low conversion efficiency of the solar cells is contributed by high shading loss due to the front metal fingers and poor quality of p-n junction formation.