13474 research outputs found
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Study on the responses of glutathione S-transferase Acidovorax sp. KKS102 towards antibiotics / Rosalia Rani
No full textBeta class glutathione S-transferase (GST) activity is known to be associated with antibiotic resistance, one of the most serious threats to global health. In this research, the study of antibiotic resistance developed by beta class GST was conducted using KKSG6, one of the GST isozymes found in Acidovorax sp. KKS102. The KKSG6 gene has been successfully expressed in Escherichia coli BL21 Star™ (DE3) using pET101/D-TOPO®-KKSG6 as an expression vector, resulting in the presence of a protein band around 20 kDa. KKSG6 protein has also been successfully purified using GSTrap™ HP column. Optimisation expression showed that KKSG6 exhibits its optimum activity when the culture was incubated 5 hours after the addition of 0.1 mM IPTG. Over-expression of KKSG6 made Escherichia coli BL21 Star™ (DE3) to be less susceptible towards kanamycin, streptomycin, gentamycin, tetracycline and chloramphenicol, suggesting the antibiotics binding with KKSG6. Our study has shown that chloramphenicol inhibited the conjugation activity of the enzyme towards CDNB. An in-silico study using protein-ligand docking predicted that antibiotics binding could take place at the protein dimer interface and H-site depending on their properties
QoS enabled cross-layered clustering for mitigating flooding queries in internet of thing networks / Fawad Ali Khan
No full textThe Internet of Things (IoT) has received a lot of attention in recent years since it connects everyday things across a wide range of applications and domains. The IoT is intended to improve human lives through the rapid creation of resource-constrained gadgets and the rising connectivity of physical embedded devices that interact using present Internet infrastructure. To exchange queries among heterogeneous IoT networks, numerous sensors require bandwidth and network resources. Network flooding is a vital method for successful query exchange. However, the risk of the intended flooding queries is that they will result in unwanted and redundant network queries, resulting in increased network traffic. The leading cause of inefficient resources utilization is redundant, unwanted and flooding queries. Therefore, in this interconnected world of resource-controlled gadgets, the key issues are to mitigate redundant, unwanted and flooding queries. In this way, IoT devices need a lot of energy and take a long time to compute. More queries lead to increased bandwidth consumption and poor Quality-of-Service (QoS). Existing techniques are primarily concerned with how to speed up fundamental routing, have limited features, and only give QoS solutions to particular IoT layers. However, a sole QoS enabled cross-layered solutions for flooding suitable for both physical and network layers devices have not been studied yet. In this research, A QoS enabled cross-layered clustering (Cluster Based Flooding) an interoperable solution for network and sensor layer devices is proposed. The proposed system can minimize energy consumption, delay, network flooding, detect and eliminate redundant flooding queries by using a query control mechanism (QCM). The core idea behind the Cluster based flooding (CBF) is to split the network into various clusters. Inside the cluster Intralayer cluster (IALC) is responsible to maintain the local query information proactively. While outside the cluster Interlayer cluster (IELC) is used to reactively transfer the routing queries outside the cluster. The CBF is a hybrid method that can be more effective compared to conventional systems in terms of query traffic generation. However, if proper redundant query detection and termination mechanisms are not used, the CBF may generate more control traffic than typical flooding techniques. In this study, we employed the Cooja network simulator to assess the QoS performance of the proposed CBF. Based on the simulation results, the proposed technique is superior to traditional flooding and state-of-the-art in terms of traffic delays, network throughput and energy consumption under various performance metrics. Further, this study also contributes a testbed that is based on real-time scenarios
Development of holmium oxide thin film as high-K gate dielectric based on silicon carbide substrate / Odesanya Kazeem Olabisi
No full textThis thesis investigates the formation of holmium oxide (Ho2O3) thin film on silicon carbide (SiC) substrate by sputtering and thermal oxidation. The effects of thermal oxidation on the physical, chemical and electrical features of the resulting Ho2O3 layers were evaluated experimentally at various temperatures from (800 – 1100 °C). The crystallinity of the Ho2O3 films was detected by X-ray diffraction (XRD), while Fourier transform infrared (FTIR), High-Resolution Transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS) analysis were used to investigate the chemical working atoms, atomic structures, and the elemental composition of the samples, respectively. The results of electrical characterization showed that thermally oxidized samples at 900 °C have the best electrical properties, which could be attributed to the thinnest oxide and absence of interfacial layer that was recorded at that temperature. For the oxynitridated samples, the impact of flow concentration of oxynitridation gas on the structural and electrical performance of the high-κ Ho2O3 dielectric on the SiC substrate was studied. The Ho2O3 films were grown using the PVD RF magnetron sputtering at various O2 and N2 gas flow concentrations from (25 – 100 %), and at a constant temperature and period of 900 °C and 15 mins, respectively. The results of FTIR and XRD analysis showed that cubic c-Ho2O3 and monoclinic-(b) SiO2 crystal structures were formed in between the SiC substrate and the Ho2O3 thin films during thermal oxynitridation. The microstrain and crystallite size were obtained by Williamson-Hall (W-H) plot. The electrical measurements from the MOS capacitor revealed that 50 % oxynitridation exhibited the most encouraging electrical results, with the smallest leakage current density of 6.05 × 10-2 A/cm2 at a breakdown field of 7.52 MV/cm and barrier height value of 18.5 eV. These results provide potential and important implications for using Ho2O3/SiC gate stack, validating the usefulness of leakage current density–breakdown electric field measurement in understanding the operation of the gate dielectric in MOS-based devices. Owing to variation in temperature during thermal applications, the thin film layers and substrates in complementary metal oxide semiconductor (CMOS) structures undergo high thermal stresses, which can result in large deformation and failure. Consequently, thermal characterization and stress analysis are necessary for the reliability and durability of the electronic structures. Furthermore, the distribution of heat and thermal stress between the Ho2O3 thin film and the SiC substrate was simulated numerically using finite element modelling and analysis software (ANSYS). This is necessary to emulate the thermal behaviour of the structure under different thermal loadings, and for each temperature loading, the effects of thermal stress and deformation on the structure were also investigated. Based on the results of the simulation, an optimum temperature was suggested. The thermal stability and characteristics of the thin film layer/SiC structure were evaluated and validated for better electrical performance
Neuroprotective properties of Sanguinoderma rugosum extracts against glutamate-induced hippocampal cells / Sam Si Enn
No full textOxidative stress and neuroinflammation are two intertwined pathologic factors in a wide range of neurological diseases. With heightening prevalence of neurological diseases due to rising life expectancy around the globe, searching for novel and alternative therapeutic candidates is urgently needed. Sanguinoderma rugosum (synonym: Amauroderma rugosum) has been traditionally used as a natural remedy to reduce inflammation, prevent unceasing crying, cancer and epileptic fits in China and Malaysia. However, the potential neuroprotective and neurorescue effects of S. rugosum against glutamate-induced neurotoxicity remain largely unexplored. In the present study, extracts from S. rugosum were evaluated for their neuroprotective and neurorescue properties using in vitro HT-22 mouse hippocampal neuronal cells. The mycelia of S. rugosum were cultivated in submerged liquid culture and freeze-dried prior to solvent extraction. MTT cell viability assay was performed to determine the neurotoxicity, neuroprotective and neurorescue activities of S. rugosum extracts at 24 and 48 h. Flow cytometric analysis was conducted to investigate the effects of S. rugosum extracts on the intracellular reactive oxygen species (ROS) production and cell death induced by glutamate. The constituents present in SR-HF fraction were identified through GC/MS analysis. The preliminary findings showed that all extracts did not exhibit cytotoxic effect on HT-22 cells. Upon 24 h incubation, pre-treatment with both SR-EE (12.5 μg/mL) and SR-HF (100 μg/mL) markedly (P<0.05) restored the loss of cell viability to 65.80 ± 1.85% and 89.76 ± 9.50%, respectively. The glutamate-induced ROS generation was effectively declined by SR-EE and SR-HF to 13.8% and 8.0%, respectively. The population of late apoptotic/early necrotic cells showed reduction after pre-treatment with SR-HF, with value of 13.3%. However, an increase in the percentage of late apoptotic/early necrotic cells were shown in the glutamate-induced cells after pre-treatment with SR-EE, with value of 26.6%. In general, all extracts demonstrated neurorescue effect against glutamate-induced cells at 24 and 48 h. Eleven compounds were identified in SR-HF by GC/MS analysis, of which the linoleic acid, ergosterol and ethyl linoleate are the major chemical compounds. In short, these results demonstrated that SR-HF may be considered as a potent therapeutic agent to be used in treating neurological disorders related to oxidative stress and neuroinflammation
Properties of zinc doped hydroxyapatite bioceramic developed by using calcium precursor derived from biogenic waste / Mardziah Che Murad
No full textThe calcium derived from biogenic wastes materials is an inexpensive and innovative
alternative to using commercial calcium reagents for producing various types of calcium
phosphate bioceramics suitable for clinical applications. This research aims to synthesize
zinc-substituted hydroxyapatite using calcium oxide derived from waste eggshells
(ZnHA-Es) via chemical precipitation method and to evaluate its chemical, physical and
mechanical properties as well as the cytotoxicity behaviour of the derived bioceramics.
The performance of the ZnHA-Es was also compared with ZnHA that were synthesized
using commercial calcium reagent. The concentration of Zn was set at 1 mol% (1ZnHAEs),
3 mol% (3ZnHA-Es) and 5 mol% (5ZnHA-Es). The derived powders were calcined
at 700 °C and presureless sintered at various temperatures (1100 to 1300°C). Brunauer-
Emmett-Teller (BET) specific surface area measurement of all synthesized powders were
above 90 m2/g and composed of hydroxyapatite as the major crystalline phase.
Transmission electron microscopy (TEM) micrographs showed that the zinc-free HA
(HA-Es) and ZnHA-Es particles have nano-rod shape and were highly agglomerated. For
densification study, it was found that sintering at 1250 °C resulted in an improvement in
the mechanical properties of the ZnHA-Es when compared to the ZnHA samples. In
particular, it was revealed that sintering at this temperature, the 5ZnHA-Es exhibited the
highest fracture toughness of 1.55 ± 0.06 MPa.m1/2, grain size of 1.64 ± 0.20 μm, Vickers
hardness of 3.01 ± 0.08 GPa and relative density of 94.6 ± 0.06%. This enhancement of
the fracture toughness was attributed to the presence of minor β-TCP phase when 5 mol%
zinc ion was incorporated into HA, combined with enhanced densification at 1250°C.
Cytotoxicity analysis through methyl thiazole tetrazolium (MTT) assay indicated that
both HA-Es and 5ZnHA-Es were non-toxic. Nevertheless, the 5ZnHA-Es specimen
showed more than 90% of cell viability after 24 h exposure in the MTT assay solution, compared to only 81% for HA-Es sample. This finding inferred that the presence of Zn
ion promoted cells proliferation more effectively than HA-Es. This work had provided an
insight on the feasibility of using natural calcium extracted from waste eggshells as
starting material in the preparation of Zn-substituted HA, suitable for biomedical
applications
Growth of non-polar (11-20) a-plane GaN based leds grown on (1-120) r-plane sapphire substrate via MOCVD / Anas Kamarundzaman
No full textConventional gallium nitride (GaN)-based light-emitting diodes (LEDs), commonly grown in the c-plane direction suffer from the huge built-in electric field from spontaneous and piezoelectric polarisation, which cause the energy-band bending in the energy band diagram. Motivated to avoid the undesirable polarisation effect, this study explored the growth of the non-polar (11–20) a-plane GaN. In this study, the full structure of the a-plane InGaN/GaN LED epitaxial was grown on a two-inch r-plane sapphire substrate using Taiyo Nippon Sanso SR-2000 metal-organic chemical vapour deposition (MOCVD). The LED’s structure consisted of four main layers, which were undoped gallium nitride (ud-GaN), n-type GaN, p-type GaN and the active region of InGaN/GaN multi-quantum well (MQW). Several optimisations were employed in the epitaxial growth of ud-GaN, which were the GaN nucleation layer, the V/III ratio and the insertion of the periodic AlN/GaN multilayers (MLs) at different positions, as well as the number of AlN/GaN ML pairs. The a-plane ud-GaN with a low-temperature nucleation layer (NL), a low V/III ratio and 120 pairs of AlN/GaNMLs showed the best crystalline quality with the full width at half maximum (FWHM) value of 756 arcsec and surface roughness of 2.15 nm from the X-ray rocking curve (XRC) scan. The n- and p-type GaN were tuned by varying the flow rates of disilane and Cp2Mg, respectively. Both n- and p-type GaN showed the best electrical properties at the highest doping flow rate, with carrier concentration and mobility of 4.94 × 1019 cm-³ and 58.39 cm2/V•s for the n-GaN, respectively, and 2.13 × 1018 cm-³ and 20.46 cm2/V•s for the p-GaN, respectively. The full a-plane InGaN/GaN LED was grown on top of different ud-GaN structures, while utilising the suitable n- and p-type GaN. Significant improvements in light output power from 10 μW at 100 mA to 70 μW were recorded when the growth of the InGaN/GaN LED utilised 120 pairs of AlN/GaN MLs
A speech act analysis of Tun Mahathir’s political speeches / Nur Dinah Mohamed Hafidz
No full textTun Mahathir is undeniably one of the most prominent political figures in Malaysia. During his tenure as the prime minister, he had transformed Malaysia’s economy into becoming one of the most rapid developing nations in the South East Asian region. Despite Tun Mahathir’s numerous successes, very few studies were conducted on his political speeches. In order to bridge the gap in literature, this study directed its focus on Tun Mahathir’s language use as an important tool in his political speeches. Speeches are a prominent form of communication. It allows a speaker to convey his/her ideologies in a larger crowd and gain more attention from the hearers. Language also plays a crucial role in assuring the speeches are delivered with great clarity to the audience particularly in political speeches. It is therefore pivotal for a political leader to understand the power on the correct use of language in his/her political speeches. This study focused on Tun Mahathir’s language use in performing the speech acts to convey his messages. The study adapted Searle’s (1969) Speech Act Theory (SAT) to analyze the utterances of Tun Mahathir’s political speeches. Moreover, the objectives of the study are to identify the types and classification of speech acts and to illustrate how the speech acts are realized in his utterances. Overall, the results show that the representative act recorded the highest frequency with 81.4%. Meanwhile, the commissive act showed the lowest frequency with 1.2% from all the five speeches
Genetic variant discovery in a patient suspected with inborn errors of immunity by computational analyses / Chear Chai Teng
No full textThe NLR family caspase recruitment domain-containing protein 4 (NLRC4) is involved in mediating innate inflammatory response. Mutations in NLRC4 have been shown to cause autoinflammatory disorder (AID). In this study, a twelve-year-old girl suspected of having AID was investigated. To investigate the causative genetic defect and its structural impact, both experimental and computational methods were performed. Whole-exome sequencing and subsequent Sanger sequencing confirmed a heterozygous missense mutation in NLRC4 (c.1970A>T, p.Q657L). The change in this highly conserved residue was predicted to be damaging by in silico predictions. Increased pro-inflammatory cytokines were also observed in this patient. Yet, the exact molecular mechanism of Q657L mutation causing inflammasome activation remains unclear. Therefore, human full-length NLRC4 structure of the resting and activated state were homology modelled. The Q657L mutant structures of both states were then constructed using computational mutagenesis. All structures were subjected to molecular dynamics (MD) simulations to investigate the structural and dynamics changes of NLRC4 protein due to Q657L mutation. The MD simulation results revealed the mutation leads to conformational and dynamics changes in the resting and activated state. These changes might disrupt the autoinhibitory mechanism required to prevent inflammasome activation in the resting state. In the activated state, the MD simulation results also suggested that the mutant structure might favour oligomerization. Therefore, these findings demonstrated the structural impact of Q657L mutation in the NLRC4 inflammasome activation
Microbiota associated with oyster mushroom substrates using culture dependent and targeted-metagenomics methods / Ameertha Ponnusamy
No full textThe globally mushroom cultivation industry is challenged with frequent green mold contamination that is often thought to be caused by the green mold - Trichoderma spp. However, the farmers and researchers do not have much insight on the possible factors that lead to the frequent but random green mold contamination in the mushroom cultivation industry. Therefore, this study aims to investigate the possible role of the natural microbiota present in the mushroom substrate has on green mold contamination. To do so, both culture-dependent and culture independent (16 srRNA targeted- metagenomic) approaches were used in this study to identify and compare the diversity of microbiota found in both healthy and contaminated mushroom substrates collected from a local mushroom farm at different stages of harvest. The study found that the green mold contaminated mushroom substrates had the highest total heterophilic bacteria count, 9.5×10⁷cfu/g. In general, the total heterophilic bacteria count in mushroom substrates increased from after sterilization stage (<10cfu/g) to reach the maximum count in contaminated stage (9.5×10⁷cfu/g) of harvest. The findings revealed that bacterial community from the Proteobacteria phylum was the most abundant in both final harvest (healthy) and green mold contaminated substrates. However, there was a shift in the bacterial diversity in the cultured bacterial populations with the increase of Gammaproteobacteria and the decrease of Bacilli after sterilisation of substrate along the cultivation stages. Gammaproteobacteria, the highest occurring class of bacteria in contaminated substrate with Enterobacteriaceae being the largest community indicates possible unhygienic practices during cultivation process. High abundance of Pseudomonas, Enterobacter and Stenotrophomonas in contaminated substrate from the cultured population and metagenomic data may also be contributing to Trichoderma colonisation
Biochemical and genetic analyses of immune response towards acute hepatopancreatic necrosis in disease tolerant Penaeus monodon / Christie Soo Tze Chiew
No full textShrimp aquaculture industry has long overtaken wild capture fisheries as the main supplier of freshwater and marine shrimps globally. However, even until now, disease has remained the top concern of shrimp aquaculture farmers as it has significantly reduced the growth of production in aquaculture industry. There exists a shrimp bacterial disease, known as Acute Hepatopancreatic Necrosis Disease (AHPND) by which the pathogen involved is a unique Vibrio parahaemolyticus bacteria strain (VpAHPND). This disease can lead to mass mortalities in shrimp ponds within early post-stocking days. Intriguingly, different shrimp species demonstrated different levels of immune tolerance or resistance towards AHPND infection. For better understanding of this matter, this study was conducted to identify the immune response triggered in disease tolerant Penaeus monodon upon AHPND infection and the underlying genetic factors or forces that resulted in differing immune tolerance between shrimp species. The disease tolerant P. monodon shrimps were exposed to VpAHPND bacteria through immersion method and sampled at time points of 0, 3, 6, 12, 24, 36, and 48 hours post-infection (hpi). The physiological and immunological changes of disease tolerant P. monodon after AHPND infection were observed and validated. Biochemical tests, including Phenoloxidase, Respiratory Burst, Superoxide Dismutase, Nitrite Concentration, Calcium Concentration, Total Haemocyte Count, and Bradford Assay were conducted. This was followed by 16S amplicon sequencing of P. monodon gut samples. In addition, important immune-related Differentially Expressed Genes (DEGs) were determined through transcriptome analysis of P. monodon hepatopancreas samples at 3, 6, and 24 hpi together with uninfected control. The gene expressions were further determined and validated using qPCR analysis. Subsequently, nucleotide sequences of selected immune-related genes were obtained through PCR and Sanger Sequencing. The trimmed sequences were then analysed using various genetics software for evolutionary genetics, phylogenetic, and molecular clock tracing analyses. Gross clinical symptoms of AHPND disease such as empty stomach, empty gut, and damaged hepatopancreas were observed. The biochemical tests validated the immunological activation of VpAHPND-infected P. monodon especially at 6 and 12 hpi. The gut microbiome changes of P. monodon caused by AHPND infection were determined at phylum, family, and genus levels. Based on the gene expression analysis results, an interactive innate immune response pattern was deduced to be activated at hepatopancreas of VpAHPND-infected P. monodon. Pathogen-Associated Molecular Patterns (PAMPs) were detected by Pattern Recognition Receptors (PRRs) which then led to downstream immune cascade reactions mainly involving immune signalling genes, antimicrobial peptides, antioxidants, and Damage-Associated Molecular Patterns (DAMPs). From the evolutionary genetic analysis, significant genetic divergence between the compared gene group sequences was identified. Purifying selection was uncovered to be the main evolutionary force acting on M. rosenbergii and disease tolerant P. monodon. Balancing selection was deduced to have occurred during AHPND infection. The divergence times for selected immune genes were estimated to be within the Paleozoic era which was after the famous Cambrian explosion. In conclusion, the information obtained in this study can provide insights for future shrimp functional and evolutionary genomics studies