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Suspended carbon nanowire biosensor for rapid and label-free salmonella detection / Aung Thiha
Get PDFCarbon, the building block life, is rapidly becoming the building block of nextgeneration electronics and sensor materials. Of many ways to handle nanocarbon materials, Carbon Microelectromechanical Systems (C-MEMS) emerges as a unique way for top-down fabrication of three-dimensional carbon micro to nanostructures. In this work, the use of C-MEMS techniques in nanowire biosensor fabrication is explored. Two main hindrances in the use of C-MEMS carbon structures for biosensing lie in miniaturization to nanoscale sensor material and inertness of as-fabricated carbon. This dissertation presents ways to overcome these limitations. First, miniaturization to patterned sub-100 nm carbon nanowires was achieved by optimization of ectrospinning properties and integration of electrospinning photoresist polymer with photolithographic pelatterning. Secondly, a microplasma direct writing technique was developed as a novel non-destructive technique for selective surface functionalization of C-MEMS manufactured carbon electrodes. This method uses a simple setup to pattern carboxylic functional groups on the carbon surface at atmospheric conditions. Surface oxygen percentage as high as 27% has been observed. The fabricated suspended carbon nanowires were integrated with microfluidics and immobilized with biomolecular probes for biosensing. Nanowire biosensing was demonstrated by developing an aptamer-based assay that can detect whole-cell Salmonella. The carbon nanowire biosensor used chemiresistive biosensing to achieve rapid detection of the pathogen with high sensitivity and specificity with a detection limit of 10 CFU/mL, which is more sensitive than conventional methods of detecting bacteria
Synthesis of polyaniline modified with palm oil based Alkyd as counter electrode in solar cell application / Mariam Fadzlina Ramli
Get PDFPresently, shortage of sustainable and environmental friendly energy resources has become an important global concern. Dye-sensitized solar cell (DSSC) has widely been used as a clean energy conversion device that can solve this problem. Platinum (Pt) has commonly been used as counter electrode (CE) in DSSC due to its good redox property. However, Pt is expensive and could be easily corroded in tri-iodide solution. Recently, polyaniline (PAni) has shown promising performance in DSSC, but PAni exhibit poor adhesion on fluorine-doped tin oxide (FTO) substrate. In this study, an environmental friendly CE was developed by modifying PAni using titanium dioxide (TiO2) and a palm oil-based (POB) alkyd to improve both the electrocatalytic activity and adhesion on FTO without using any toxic organic solvent like m-Cresol. A series of PAni and PAni-TiO2 with different TiO2 content (10%, 20% and 40%) were synthesized via chemical oxidative polymerization. POB alkyd was synthesized through alcoholysis and esterification reactions. Chemical structures of PAni, PAni-TiO2 and POB alkyd were confirmed by FTIR, UV-Vis, XRD and 1H NMR analyses. Result obtained showed that PAni exist as emeraldine salt phase with electrical conductivity of 1.23×103 to 1.31×103 Scm-1. The preparation of PAni modified with POB alkyd (PAni/Alkyd) films were investigated by different PAni:Alkyd ratios (1:0.5, 1:0.75 and 1:1), different acid number (AN) of POB alkyd (5.66, 14.74 and 17.60 mgKOH/g) and different reactive diluents such as methyl acrylate (MA), methyl methacrylate (MMA) and cyclohexyl methacrylate (CMA) under UV curing method. Among all PAni/Alkyd films, PAni/Alkyd using ratio 1:0.5 with alkyd having AN of 5.66 mgKOH/g and CMA as diluent give the lowest curing time of 5 min to give adhesion of 5B. Besides, PAni-TiO2 modified with POB alkyd (PAni-TiO2/Alkyd) films were prepared using similar ratio as discussed earlier. The results showed that all PAni/Alkyd and PAni-TiO2/Alkyd films exhibit high conductivity range of 6.11×102 to 6.49×102 Scm-1 with good adhesion on FTO substrate. The adhesion of PAni on FTO is significantly contributed by the reactive C=C of the POB alkyd that undergo crosslinking in the PAni/Alkyd coating during UV curing. Conductivity and adhesion are two main crucial factors that will contribute to high power conversion efficiency (PCE) of DSSC. In this research, the fabrications of DSSC were prepared using TiO2 photoanode, ruthenium dye, PAni/Alkyd and PAni-TiO2/Alkyd as CE and iodolyte AN50 electrolyte. The highest PCE was shown by PAni/Alkyd with 0.60% while PAni-TiO2/Alkyd showed lower PCE range of 0.20% to 0.30%. This is because PAni/Alkyd possessed higher conductivity of 6.49×102 Scm-1 compared with PAni-TiO2/Alkyd (6.11×102 to 6.32×102 Scm-1). As a result, an environmentally POB alkyd modified PAni as CE with high electrical conductivity of 6.11×102 to 6.49×102 Scm-1, excellent adhesion of 5B and moderate PCE of 0.20% to 0.60% in DSSC were successfully obtained. This research results confirmed that PAni modified with POB alkyd can be potentially applied as cost-effective and environmental friendly materials used for DSSC study
Genotoxic and hematological effects of endocrine disruptive chemicals, bisphenol a and nonylphenol, on Nile tilapia (Oreochromis niloticus) / Muhammad Faris Sahardin
Get PDFThis study was performed to evaluate the genotoxicity and hematology effects of single
and binary exposure of bisphenol A and nonylphenol towards Oreochromis niloticus. O.
niloticus was singly exposed to bisphenol A at concentration of 2 mg/l and nonylphenol
at concentration of 0.04 mg/l in 16 L glass tank. O. niloticus was also synergistically
exposed to the both concentration of 2 mg/l of bisphenol A and 0.04 mg/l of nonylphenol.
Four fishes were randomly used for four exposures after two weeks acclimatization. All
of them were exposed to the compound for 96 hours without water change prior
observation. Fishes were anaesthetized and sacrificed for blood for the analysis of
micronucleus, comet assay and hematology. The observation showed significant
difference in the micronuclei frequency and nuclear abnormalities frequency in
micronucleus test when they were singly exposed to 0.04 mg/l of nonylphenol. The
obvious strand breakage of supercoiled duplex DNA had been determined in the comet
assay analysis in single exposure of 0.04 mg/l of nonylphenol compared to others. Result
from complete blood count also showed nonylphenol exposure at concentration 0.04 mg/l
caused significant difference in some blood parameters when compared to the control.
Based on this study, it was proved that single exposure of nonylphenol contributed
stronger effect to O. niloticus compared to single exposure of bisphenol A and binary exposure of both chemicals
Intermediary roles of public research institutions in social innovation: The case of Malaysian Agricultural Research And Development Institute / Nur Hanis Mohamad Noor
Get PDFStudies on Public Research Institutions (PRIs) have been extensively explored by scholars in recent decades. The significant role of the PRIs in ensuring scientific discoveries to accommodate societal needs is very critical. Although PRIs are vital for the government to implement policy and regulation, studies on the institutions are still limited especially when it comes to the context of social innovation. Like any other public-driven institutions, PRIs have limited resources such as capital and labour. Yet, they are expected to perform multiple roles ranged from research and development (R&D) to social development that includes capacity building, knowledge generation and technology dissemination. Thus, the main objective of this study is to explore the intermediary roles of Malaysian Agricultural Research and Development Institute (MARDI) as social innovator in performing the elements of social innovation in Malaysia’s agriculture sector. It also attempts to determine the issues and challenges of MARDI in performing social innovation and proposing policy directions to strengthening the institution’s roles. This is an empirical study by using a single-case design. Interviews, focus group discussions and observations were performed and 30 interview sessions were conducted during the period of seven months from May 2018 until December 2018. The study applied inductive approach to interpret data obtained from the interviews. For data validation, the preliminary findings were validated by using triangulation method. This includes comparing the findings with other sources of empirical evidence such as archival record and observation. The study also consulted and integrated the insights of MARDI’s top management on the findings. The study found that MARDI’s intermediary roles in performing social objectives of social innovation are achieved through the mandated MARDI Act 1969. Through its varietal R&D activities, MARDI is the producer of innovation that has successfully increased the potential rice yield output and reduced maturation period of paddy. Besides, MARDI acts as a bridging organisation that connects private industry with the end user through its public-private partnership with Baden Aniline and Soda Factory (BASF) – a multinational herbicide company. The partnership has successfully provided a solution to weedy rice problem by introducing Clearfield Production System (CPS). However, a main challenge in performing social mechanism of social innovation is the lack of researcher-farmer partnership between MARDI and farmers. Currently, the collaborative engagement is heavily depending on agricultural extension agencies such as Department of Agriculture (DoA) and other regional agencies. The study also found the potential of social media and civil society organisations (CSOs) to transform Malaysian farmers into more an active innovation actor in agricultural innovation system. Based on the findings, the study proposed several policy directions to revise the conventional Triple Helix innovation model to the Quadruple Helix innovation model that emphasize on the synergy of four entities, namely government, industry, academia and civil society. As a conclusion, for a sustainable agriculture to be achieved in Malaysia, it needs (a) quality research by PRIs, (b) efficient extension agencies in disseminating knowledge to the farmers, (c) productive farmers in delivering high yield farming, and (d) communal support by CSOs and media
Multimode-interference based optical fiber sensor for civil structures monitoring / Chew Sue Ping
Get PDFThe thesis describes the experimental investigations on the multimode interferencebased fiber sensors using single mode multimode single mode (SMS) and multimode single mode multimode (MSM) structures as a sensing device for structural health monitoring (SHM) applications. Both sensor structures were fabricated, characterized and tested for detecting strain and vibration in civil infrastructures. The proposed SMS structure comprises of a short segment of multimode fiber (MMF), which were fusionspliced by two single mode fibers (SMFs) at both terminals. On the other hand, MSM was fabricated by splicing SMF with MMF at both ends. A new packaging technique for the SMS structure was successfully developed to use as water level gauge. The SMS structure was also used to measure the strain in a reinforced concrete beam. The results indicated that the SMS fiber sensor provides sensitivity of 3.7781 nm/(mm/mm) and linearity of 0.96606 in compressive strain measurements to a maximum of 0.116 mm/mm. It was also found that the packaged SMS has much better temperature stability up to 0.0904 nm/°C as compared to unpackaged SMS. On the other hand, the developed MSM based sensor was successfully used to demonstrate a vibration frequency measurement of the mechanical vibration. The structure was capable of detecting wide range of vibration frequency, ranging from 20 Hz up to 6 kHz with high accuracy
Optimized transconductance designs to enhance the linearity performance of RF front-end receiver circuits in 130 NM CMOS technology / Nandini Vitee
Get PDFHighly linear front-end circuits are greatly desired for wireless receivers to improve the dynamic range. However, intermodulation distortions caused by the non-linear transconductor current limits the linearity of the front-end receiver circuit in CMOS technologies. In addition to the inherent nonlinear effect, the downscaling of CMOS further exacerbates the linearity of the circuit due to lower voltage headroom and high-field mobility. Thus, it is essential to develop effective circuit techniques that can aid linearity enhancement without jeopardizing other preferred performances such as low noise, high conversion gain, and low-power consumption. In this thesis, two different high linear transconductors are presented which are designed and fabricated in 130 nm CMOS technology. The first circuit is a low-voltage high linearity differential-folded mixer with multiple-feedback techniques for performance enhancement. The capacitor cross-coupled (CCC) common-gate transconductance stage is implemented to improve the noise figure (NF) at low power by boosting the effective transconductance while enhancing the linearity via suppressing the 2nd-order harmonic distortion. However, the created loop gain of the CCC can raise the 3rd-order intermodulation (IM3) distortion, penalizing the input referred 3rd-order intercept point (IIP3) performance. Therefore, a positive and a 2nd capacitive feedback are implemented into the CCC common-gate transconductor, not only to suppress the IM3 distortion current, but also to add design flexibility to the input transistors. Furthermore, the positive feedback also improves the input impedance matching, conversion gain and NF through a flexible design criterion. The proposed mixer operating at 900 MHz dissipates 4 mW at 1.0 V. The measured NF is 8.5 dB, the conversion gain is 18.4 dB and the IIP3 is +12.5 dBm. The second circuit is a high conversion gain and high linearity inductively source degenerated balun-low noise amplifier (LNA)-mixer with integrated transformer-based gate inductor and 2nd-order intermodulation (IM2) injection technique. In this work, two linearization techniques are proposed to improve the IIP3 of the balun-LNA-mixer. The intrinsic IM3 product of the inductively source degenerated (ISD) transconductor from the 2nd-order derivative transconductance component ( ) is reduced by tailoring towards optimum biasing point at moderate-inversion region. While, the generated IM3 current by the 1st-order derivative transconductance ( ) due to the interaction with the feedback component in the ISD transconductor is attenuated by 2nd harmonic injection via the bulk of the ISD transconductor. Further, a transformer-based gate inductor and a transformer-based balun are applied to improve the input impedance matching and produce a balanced differential input signal. Measured results show a high IIP3 of +16 dBm and a conversion gain of 22 dB at 2.4 GHz. The double sideband (DSB) NFDSB is 7.2 dB and the power consumption is 3.15 mW at 1.2 V. m g m
Process improvement and microbial characterisation of biological nitrogen removal for tropical wastewater with low chemical oxygen demand/nitrogen ratio / How Seow Wah
Get PDFMalaysia has one of the most established biological nitrogen removal in wastewater treatment plants (WWTPs) among the developing Southeast Asian countries. The current WWTPs’ design and operating guidelines in Malaysia are mainly derived from other developed countries with more experiences in operating biological nitrogen removal. These design guidelines are good practices for WWTPs in the temperate climate region, but may not be optimal for the local wastewater characteristics and tropical climate in Malaysia. The local wastewater industry is keen to improve the design and operation of WWTPs to reduce the energy consumption and operating cost, which helps to foster a more cost-effective and sustainable industry. However, a complete understanding on the local wastewater conditions, such as the detailed characteristics and microbiology of tropical systems, are still lacking. This project aimed to develop an improved biological nitrogen removal in treating local wastewater. To achieve this aim, detailed wastewater characterisation were performed to formulate operating strategies for a low-cost biological nitrogen removal. The operating strategies were tested in lab-scale reactors. The microbial community were also investigated to understand the effects of these operating strategies on the microorganisms.
In the wastewater characterisation study, wastewater from six WWTPs in Kuala Lumpur was sampled to characterise their organic and nitrogen content. The results showed that soluble fraction of the tropical wastewater samples had low chemical oxygen demand-to-nitrogen ratio (COD/N). COD fractionation experiment further revealed that the readily-biodegradable COD (rbCOD) content was low, while slowly-biodegradable COD (sbCOD) from particulate settleable solids (PSS) in the wastewater was the main source of biodegradable COD. The hydrolysis rate of PSS was accelerated in tropical temperatures (30 ± 2°C) to provide sbCOD for denitrification. Based on these wastewater characteristics, the low rbCOD content may be conducive for nitrification under low-dissolved-oxygen (low-DO) condition (< 1 mg O2/L) to reduce aeration energy. Also, sbCOD in the wastewater may be utilised to enhance the denitrification performance.
Batch experiments demonstrated active nitrification at low-DO concentration (1 mg O2/L). When low-DO nitrification (0.9 ± 0.1 mg O2/L) was applied in a reactor, high ammonia removal efficiency (93 ± 6%) was achieved. Furthermore, utilising sbCOD in the post-anoxic stage of an oxic-anoxic (OA) reactor reduced the effluent nitrate concentration below the discharge limit in Malaysia. The recommended hydraulic retention time and sludge retention time (SRT) of the low-DO OA reactor developed in this study was 16 h and 20 d, respectively. Microbial analyses of the low-DO OA reactor showed that long SRT (20 d) promoted the growth of nitrifiers affiliated with Nitrospira to achieve a stable low-DO nitrification performance. Operating a low-DO OA process could reduce the WWTPs’ energy consumption by 20% when compared with the existing process design.
A better understanding on the local wastewater conditions in this study, such as detailed characteristics and process microbiology, led to the development of a low-DO OA process. The low-DO OA process was an improved biological nitrogen removal in treating low COD/N tropical wastewater, which could help to encourage a more energy-efficient and cost-effective wastewater industry in Malaysia
A learner corpus study of the article system / Siti Fatimah Yusof
Get PDFStudies on learner language tend to compare learners’ second language with a target language. Informed by recent reconceptualization of language learning in which bilingual minds are viewed as fundamentally different from monolingual minds (see, e.g., the notion of multicompetence by Cook, 1991, 2013), the present study explores how learner language is studied as a separate and independent linguistic system. By using Antconc 3.4.4w, this study analysed a recently developed learner corpus of written data by a group of secondary school students in Malaysia, examining how language development takes place over time. Participants composed essays based on a picture prompt and changes in their language use through the study of the articles (a, an and the) were tracked over time. Findings suggest that there were changes in the way the students used language as evidenced in their texts, from the frequency of use, the distribution of patterns as well as senses
In vitro regeneration of Dioscorea alata with anthocyanin and antimicrobial activity / Sakinah Abdullah
Get PDFAn efficient protocol was developed for rapid propagation and regeneration of the Dioscorea alata L. locally known as ‘ubi badak’ because of their rhinoceros-shaped tubers. In the present study, direct and indirect regeneration were induced to produce plantlets of Dioscorea alata L. For direct regeneration explants (leave, stem and node) were cultured on MS media supplemented with various combinations and concentrations of BAP and NAA to induce microshoots and roots formation. The optimum medium for microshoots formation was MS medium supplemented with 1.0 mg/l BAP and 0.5 mg/l NAA with the number of microshoot is 23.07±0.44 from node explant. While for root formation, MS medium supplemented with 2.0 mg/l NAA is the optimum medium with mean number of roots formation 17.40±0.58. For indirect regeneration, microtubers formation, callus induction, somatic embryogenesis and synthetic seeds production were studied. MS medium supplemented with 1.0 mg/l NAA and1.0 mg/l BAP, is the best medium for microtubers formation with 15.57±0.18 mean number of microtubers. MS medium supplemented with 1.0 mg/l BAP and mg/l 1.0 NAA was the best medium for microtubers germination with percentage of germination 76.67±0.08 %. Callus induction was obtained on MS media supplemented with various concentration of 2,4-D, NAA, TDZ, BAP, myo-inositol and activated charcoal. Node explant cultured in MS medium supplemented with 2.0 mg/l 2,4-D and 1.0 mg/l BAP added with 0.5 mg/l myo-inositol was the best condition for optimum callus production. Callus were then identified whether it is embryogenic or non embryogenic using double staining method. Embryogenic callus was stained in red and non embryogenic callus was stained in blue. Embryogenic callus was then subculture onto solid and liquid somatic embryos induction medium. MS medium supplemented with 2.5 mg/l 2,4-D combine with 1.0 mg/l BAP is the best medium for somatic embryos formation from 0.5 cm of embryogenic callus. Synthetic seeds were created by encapsulated propagules (microshoots, node and stem) with 16 different solution of sodium alginate and Calcium chloride dehydrate. In this study, propagules were successfully encapsulated in 2.0 to 5.0 % sodium alginate solution and harden in 25.0 to 100.0 mM Calcium chloride dehydrate solution. The beads varied morphologically with respect to texture, shape and transparency with different combinations of sodium alginate solution and calcium chloride. 3% sodium alginate harden in 100 µM Calcium chloride dehydrate was found to be the best encapsulation solution. Complete plantlets obtained from direct and indirect regeneration were then transferred to greenhouse. Plantlets response positively when acclimatized in garden soil (combination of black soil and red soil at ratio 2 to 1) with 93.33±0.09 % of survival rate. Callus exposed to different photoperiod produced different amount of anthocyanin. The total anthocyanin content was calculated using pH differential method. The highest (295.21 ± 0.20 mg cya-3-glu / 100 g FW) anthocyanin content was obtained from callus exposed to 16 hours light and 8 hours dark. Antimicrobial activity studies reveal that this plant response positively against bacteria (Staphylococcus aureus, Staphylococcus epidermis, Escherichia coli and Salmonella sp.) and fungi (Penicillium sp., and Mucor sp.) negative effect against Aspergilus nigerand Fusarium sp
A multimodal study of the legitimization of violence in Rumiyah / Nazri Mohd Noor
Get PDFThis study explored the process of legitimization of violence in Rumiyah magazine produced by al-Hayat Media Center (ISIS). It employs a multimodal approach consists of van Leeuwen (2008) legitimization strategies and Kress and van Leeuwen (2006) visual social semiotics to analyse texts and semiotic resources found in the selected articles. The qualitative method used is an inductive thematic analysis which reveals several thematic categorizations, i.e., (1) the impersonalisation of ‘others’, (2) the legitimization of jihad value, and (3) the (de)legitimization of ‘fasiq’ scholars. The analysis conducted highlights the recurring use of legitimation strategies and visual social semiotic metafunctions to justify violence in the Rumiyah magazine. The overall analysis indicates a complex interaction between the discursive and semiotics aspects of the study that are governed by ISIS’s ideological goals. Keywords: ISIS, discursive legitimization, social semiotics, terrorism, Rumiya