Pusat Pengajian Sains Kajihayat - Tesis
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- PublicationCompatibility And Biodegradability Of Biopolyester-Based Blends With Poly(3-Hydroxybutyrate-Co-3-Hydroxyhexanoate) (Phbh) As A Blend Matrix(2024-07)Jeepery, Iffa FarahinPoly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (phbh) has been evaluated to have excellent degradability in marine environment. However, its performance for application is still limited. A series of properties enhancement is deemed necessary to improve the potential of phbh being both a high-performance material and readily biodegradable. In this study, phbh containing 5 and 17 mol% 3-hydroxyhexanoate (3hh) were blended with atactic poly(3-hydroxybutyrate) (phb), polycaprolactone (pcl), and polybutylene succinate (pbs) at different ratios by the solvent-casting method. Phbh-5%/atactic phb and phbh-17%/atactic phb showed a single glass-transition temperature (tg), indicating miscibility in the amorphous state. Immiscibility was observed in the phbh-5%/pcl and phbh-17%/pcl blends based on the non-transitioning tg of the phbh component, presence of two distinct tg values for some of the blend films, and individual crystallization manner. The thermal properties and spherulitic morphologies of the phbh-5%/pbs blend films suggested partial miscibility. The enzymatic degradability of the three types of blends by ralstonia pickettii t1 phb depolymerase and burkholderia cepacia lipase was investigated. Depending on the enzyme–substrate specificity, miscibility, and phase structure of the blend, the enzymatic erosion rate was different among the three types of blends.
- PublicationPolyhydroxyalkanoates Production By Cupriavidus Necator Transformants Harboring Polyhydroxyalkanoate Synthase Of Chromobacterium Sp. Usm2 (Phaccs) And Its Potential Application For Lipase Assay Kit(2024-05)Tang, Hui JiaPolyhydroxyalkanoates (phas) are biopolyesters produced by microorganisms as carbon storage in the presence of abundant carbon sources and the limitation of growth nutrients. Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [p(3hb-co-4hb)] has been used for industrial applications, including packaging, biodegradable plastics, medical devices, and biomedical applications, owing to its biodegradability properties. Chromobacterium sp. Usm2 was isolated in langkawi, malaysia, and was able to accumulate pha. Pha synthase of chromobacterium sp. Usm2 (phaccs) was able to polymerize various monomers such as 3-hydroxybutyrate (3hb), 3-hydroxyvalerate (3hv), and 3-hydroxyhexanoate (3hhx) from carbon sources or precursors due to its broad substrate specificity. To date, there is no report on the potential of phaccs to produce p(3hb-co-4hb) copolymer. In this study, a series of optimization tests and pha biosynthesis were performed to investigate the potential of the heterologous expression of phaccs in c. Necator transformants to produce p(3hb-co-4hb) using 4hb-structurally related precursors such as 1,6-hexanediol, 1,4-butanediol, γ-butyrolactone, and sodium 4-hydroxybutyrate. The polymers obtained were then further characterized to determine their monomer compositions, thermal properties, and lipase depolymerizing activity.
- PublicationOverexpression Of Mirna-975 Induced Immune Genes And Abnormal Spermatogenesis In Drosophila Melanogaster(2024-06)Manickam, SharvinHomeostasis is the measure of an organism’s evolutionary adaptation. Any oddities to the organism’s phenotype signal a system at disarray, with the full force of immune systems in response. When mir-975 was overexpressed, the apical tip of the d. Melanogaster’s testis was bulged, mirroring a tumour-like appearance, suggesting its homeostasis were ‘knocked off’ balance. Thence, the associations between mir-975, spermatogenesis and its innate immunity is to be investigated in this manuscript. To understand the bulged phenotype of the testis’s apical tip, the developmental stages of spermatogenesis had to be characterised, from the onset till late spermatocyte stage, whilst mir-975’s transcriptomics identifies which of the immune genes were in response to the said imbalanced homeostasis. To characterise the spermatogenesis of the bulged testis, antibodies complimentary to the aforesaid stages, matched to its appropriate markers each were incubated with dissected testes from control (actin5c-gal4 > oregon r) and transgenic progenies (actin5c-gal4 > uas-mir-975) respectively, using confocal microscopy. On the other hand, to elucidate the transcriptomics’ data, genes that were upregulated were singled out and validated using qpcr. The bulges apical tips were found to have shorter transit amplification (ta), more of coilin-positive (spermatocyte) cells’ number, and fewer elongating spermatids. Upregulated immune genes were validated as per suggested by the transcriptomics. The research models proposed to discuss the bulged apical tips are early differentiations, cell competition, rogue asymmetrical cell division, apoptosis aversion, and meiosis entry defects.
- PublicationThe Effects Of Photoperiods And Light Emitting Diodes (Leds) On Cell Suspension And Hairy Root Cultures Of Eurycoma Longifolia Jack(2024-09)Sani, SaleIn recent years, the issue of earnings management has garnered significant attention from researchers and academics due to its consequences on the quality of financial reports and its impact on investors' decision-making. This study aims to provide evidence on the influence of COVID-19, CEO characteristics, and ownership concentration on two forms of earnings management (EM), namely accruals-based earnings management (AEM) and real earnings management (REM) in Jordan. Additionally, the study explores the role of ownership concentration (family and foreign ownership) as a moderating variable in the relationship between CEO characteristics and earnings management. The study sample included all service and industrial companies listed on the Amman Stock Exchange (ASE) after the update of the Jordanian Corporate Governance Code (JCGC) 2017, covering the period from 2017 to 2021. The theoretical basis for understanding this relationship draws upon the agency, upper-echelons theories and the entrenchment and alignment effects. The hypotheses were tested using the feasible generalized least squares (FGLS) method to address heteroskedasticity and autocorrelation issues, as it provides a suitable approach for controlling these problems in the analysis. The results reveal a negative relationship between COVID-19, CEO tenure, and AEM practices in Jordanian companies. A negative relationship exists between CEO non-duality, CEO age, and REM practices. However, the study uncovers a positive relationship between CEO gender, CEO experience, CEO age, and AEM.
- PublicationThe Effect Of Chitin Synthesis Inhibitors (Csi) On Three Subterranean Termite Species (Blattodea: Rhinotermitidae, Termitidae) Towards The Termite Gut Symbionts(2024-06)Shamsuri, Qurratu’Aini SyasyaThe infestation subterranean termites were first encountered after establishment of rubber plantation during 20st century in peninsular of malaysia. Subsequently, interest has been devoted in termite research and chitin synthesis inhibitors (csi) has been introduced as one of numerous agents to against lower and higher termite infestation. Majority of published studies focused on efficacy and considering colony elimination in the absence of termites in the bait and monitoring station. However, there was dearth of studies assessing the impact on the feeding activity and mortality in laboratory bioassay, and the bait influence towards gut symbiont composition. Therefore, this study was performed on the lower (coptotermes gestroi) and higher termites (globitermes sulphureus and macrotermes gilvus), using three csi baits through ‘no-choice’ bioassay. Each of these baits also contained respective active ingredients which is widely used by pest companies in malaysia, and they are chlorfluazuron, bistrifluron, and hexaflumuron. The feeding activity was initially detected in c. Gestroi, followed by g. Sulphureus, and lastly m. Gilvus. The results determined that there were substantial differences (p < 0.05) in the feeding activity among the treated termites. However, unlike chlorfluazuron, only c. Gestroi was differed significantly from the other treated species. In response to all baits, m. Gilvus exhibited the highest mean mortality,