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Publication A DESIGN METHODOLOGY FOR REMANUFACTURING AND REMANUFACTURABILITY ASSESSMENT(2015-08-20) YANG SHANSHAN; NUS GRAD SCH FOR INTEGRATIVE SCI & ENGG; NEE YEH CHING, ANDREW; ONG SOH KHIMREMANUFACTURING IS A KEY ENABLER FOR SUSTAINABLE PRODUCTION DUE TO ITS EFFECTIVENESS IN CLOSING THE LOOP ON MATERIAL FLOW, EXTENDING PRODUCT LIFE CYCLE AND REDUCING PRODUCTION WASTE AND EMISSION. IT IS THE PROCESS OF RETURNING AN END OF LIFE (EOL) PRODUCT TO `AS-NEW? CONDITION, THROUGH THE PROCESSES OF DISASSEMBLING, CLEANING, INSPECTING, RECONDITIONING, REPLACING AND REASSEMBLING THE COMPONENTS OF A PART OR PRODUCT AND THUS PROVIDES A MATERIAL RECIRCULATION LOOP WITHIN THE PRODUCT SYSTEM. THIS DISSERTATION PRESENTS A DESIGN FOR REMANUFACTURING AND REMANUFACTURABILITY ASSESSMENT (DRRA) TOOL, TO BE USED AT THE EARLY PRODUCT DEVELOPMENT STAGE TO ASSESS THE SUITABILITY OF A PRODUCT AND ITS COMPONENTS FOR REMANUFACTURING AND TO MAKE SUITABLE MODIFICATION OF THE DESIGN TO IMPROVE THE POTENTIAL OF PRODUCT FOR REMANUFACTURING. THE DRRA TOOL CAN ALSO BE USED DURING THE PRODUCT RETURN/SERVICE STAGE, TO ASSIST GENERATING THE RECOVERY PLAN OF THE RETURNED PRODUCTS TAKEN INTO ACCOUNT THEIR QUALITYPublication APPLICATION OF CARBON NANOTUBES IN DRUG DELIVERY: TARGETING MITOCHONDRIA FOR CANCER THERAPY(2014-08-21) YOONG SIA LEE; NUS GRAD SCH FOR INTEGRATIVE SCI & ENGG; PASTORIN, GIORGIA; YU CHUN KONG, VICTORMitochondria emerge as intriguing targets as their physiological functions are altered in cancer. Numerous studies have illustrated potential of nanocarriers in delivering mitochondria-acting compounds. Carbon nanotubes (CNTs) are becoming prominent for drug delivery due to their unique shape which promotes cellular-uptake and large aspect-ratio that facilitates surface functionalization of bioactive molecules. In first part of the project, multi-walled carbon nanotubes (MWCNTs) were functionalized with mitochondria-targeting Rhodamine-110, yielding MWCNT-Rho. MWCNT-Rho was found to co-localize with mitochondria and potentiate the activity of its encapsulated cargo drug molecules. In second part of the project, MWCNTs was engineered to deliver an anti-cancer peptide targeting hexokinase II on mitochondria. All MWCNT-peptide conjugates were internalized intracellularly and found to be in the vicinity of mitochondria. Importantly, MWCNT-peptide conjugates induced hexokinase II release from mitochondria that resulted in apoptosis. In conclusion, MWCNTs could be a versatile nanocarrier for targeted delivery.Publication MAGNETISM AND MAGNETOTRANSPORT STUDIES OF IV-VI FERROMAGNETIC SEMICONDUCTOR(2011-12-06) LIM SZE TER; NUS GRAD SCH FOR INTEGRATIVE SCI & ENGG; TEO KIE LEONGAmong the IV-VI ferromagnetic semiconductors, GeMnTe reveals relatively high Curie temperature (Tc) of 200 K under appropriate growth conditions. This makes it a promising material for spintronic applications and warrants much research interests. This thesis focuses on the study of magnetic and transport properties of GeMnTe thin films grown by molecular beam epitaxy. Anomalous Hall effect is clearly observed in the samples which can be attributed to extrinsic skew scattering. The interplay between localized magnetic moments from the Mn ions and the free carriers resulting from the presence of both Ge vacancy and Ge-Te disorder type of defects determine the ferromagnetic properties in GeMnTe. This interaction is investigated by means of magnetotransport studies in GeMnTe under the effect of hydrostatic pressure (P). The Tc is observed to change with P which is due to the increase in carrier concentration responsible for the interactions between Mn ions. A two valence model as well as RKKY interaction are invoked to explain these results. Magnetoresistance (MR) measurements have been used to investigate the localization and antilocalization effects. The spin-orbit, elastic and inelastic scattering times as well as coherence length as a function of pressure are obtained from the fitting of MR results. Additionally, exchange bias effect (EB) of GeMnTe with antiferromagnetic MnTe and MnO materials has been investigated. While GeMnTe-MnTe system only leads to a modification of coercivity field, a negative EB shift in the hysteresis loop is observed for GeMnTe-MnO bilayer when it is cooled in applied field. Our findings pose challenges as well as opportunities for future studies of GeMnTe for spintronic applications.Publication Surface Passivation for Heterojunction Silicon Wafer Solar Cells(2014-07-31) GE JIA; NUS GRAD SCH FOR INTEGRATIVE SCI & ENGG; ABERLE, ARMIN GERHARD; THOMAS MUELLERThis thesis focuses on the development and analysis of surface passivating silicon alloys for heterojunction silicon wafer solar cell applications. As the narrow process window of conventional intrinsic amorphous silicon limits its industrial applicability, an alternative material that excels in both passivation quality and industrial compatibility is required. By using a new structure that consists of remote inductively coupled plasma deposited amorphous silicon suboxide thin films on low-resistivity n-type Czochralski silicon wafers, a state-of-the-art passivation quality with an extremely wide process window is demonstrated compared to other high-quality passivation schemes. A detailed understanding of the film properties and the deposition mechanisms is obtained by a sequence of electrical and structural measurements as well as computer simulations. A comparison between films deposited with capacitively and inductively coupled plasmas is also performed to demonstrate the advantage of the inductive method for passivation layer deposition of heterojunction solar cells.Publication Single-molecule Studies on the Role of Nucleoid-associated Proteins in Bacterial Chromatin(2014-08-05) RICKSEN SURYA WINARDHI; NUS GRAD SCH FOR INTEGRATIVE SCI & ENGG; YAN JIE; WOHLAND, THORSTENBacterial chromatin contains the genetic code of bacteria, assembled by many factors into a compact structure called nucleoid. Single-molecule manipulation by magnetic tweezers and single-molecule imaging by atomic force microscopy are performed to gain insight into the molecular mechanism of nucleoid-associated proteins in shaping the bacterial nucleoid and regulating the gene expression. We investigate the role of gene silencing protein MvaT and MvaU in Pseudomonas aeruginosa, an important pathogens that can cause chronic infections, showing for the first time the direct evidence on the importance of nucleoprotein filaments formation for achieving gene silencing function in vivo. In addition, to better understand the process of gene anti-silencing, the DNA binding properties of Ler from pathogenic Escherichia coli and its competition with H-NS nucleoprotein filaments are studied. The works done in this thesis will provide insight and extend our understanding on the role of nucleoid-associated proteins in bacterial chromatin.Publication Spin-Orbit Interaction Induced Spin-Separation In Platinum Nanostructures(2009-09-04) KOONG CHEE WENG; NUS GRAD SCH FOR INTEGRATIVE SCI & ENGG; ENGLERT, BERTHOLD-GEORG; CHANDRASEKHAR NATARAJANWe have demonstrated electrical generation and detection of spin polarization by the spin Hall effect in platinum. The spin Hall effect refers to the generation of a transverse spin current, and the subsequent non-equilibrium spin accumulation near sample boundaries. This occurs when a longitudinal electrical current is applied to materials with spin-orbit interaction. Spin polarization in metals is usually small and requires ferromagnetic metals to create and detect spin polarization. This ferromagnetic-based approach is suitable to be used as a laboratory investigation of spin transport phenomenon, but it limits the performance and scalability of the spintronics devices. Therefore, we designed and experimentally demonstrated using a non-local lateral geometry structure to investigate the generation and detection of spin polarization based on the spin Hall effect, without the need for magnetic materials, external magnetic field, or bulky optical systems. The geometry made use of the spin Hall effect effect to generate spin polarization and its reciprocal effect, the inverse spin Hall effect, to detect spin polarization. A large spin Hall effect signal was observed from 10 K up to room temperature, which was the largest value reported so far in the literature. The measurements were also done using gold and aluminum samples. Aluminum failed to demonstrate any signal while gold showed weak signals compared to platinum in spite of similar atomic number. This suggested that the spin Hall effect in platinum was unusual. The drift-diffusion model was found to be adequate to model the spin transport in platinum. Based on the experimental results, the spin Hall effect in platinum was expected to be extrinsic. However, the extrinsic contribution to the observed effect was not fully understood and further investigation is needed.Publication DEVELOPMENT OF MICROBIAL FUEL CELL BASED SENSOR FOR ON-LINE MEASUREMENT OF BOD IN WASTE WATER(2014-01-24) SHAILESH KHARKWAL; NUS GRAD SCH FOR INTEGRATIVE SCI & ENGG; NG HOW YONG; LI FONG YAU, SAMTo ensure the efficient operation of wastewater treatment processes, continuous monitoring of biochemical oxygen demand (BOD) of the treated effluent is essential. However, the conventional 5-day BOD (BOD5) test is laborious, sometimes poorly reproducible and inaccurate, particularly at low concentrations. These issues supported the development of several microbial biosensors for BOD measurement. In this study, microbial fuel cell (MFC) was developed as an alternative BOD sensing device for online measurement of BOD in wastewater. The performance of MFC-BOD sensor was investigated in terms of various parameters such as BOD measurement range, response time, sensitivity and long term stability. With a view to implement MFC-BOD sensor in wastewater treatment plants, a sequential optimization strategy was applied to lower the response time and increase the sensitivity of the MFC-BOD sensor. The behaviour of the electrochemically-active biofilm of MFC-BOD sensor was studied.Publication SYNTHESIS AND ARCHITECTURES OF METAL-ORGANIC FRAMEWORKS NANOPARTICLES(2013-08-21) LI ZHENG; NUS GRAD SCH FOR INTEGRATIVE SCI & ENGG; ZENG HUA CHUNThe main focus of this thesis is about the control over the size and morphologies of Metal-organic Frameworks (MOFs) nanocrystals, as well as the synthesis of hybrid structures composed of MOFs nanocrystals and other functional materials. The integration of metal nanoparticles with MOFs nanocrystals, with controlled distribution and size limitation of metal nanoparticles, could be well-obtained and the catalytic properties of the products were well-examined. Meanwhile, the mechanical properties enhancement of MOFs nanocrystals with controlled size and morphologies have be achieved through the wet chemistry approach to form the complicated core-shell architectures. Moreover, an unique growth pathway of MOFs nanocrystals on the template composed of 2-dimensional gold nanowires located at the interface was developed, resulting the hybrid structures of MOFs@Au at the interface as well. Last but not least, an interesting precursor-induced transition pathway has been developed to prepare the 2-dimensional MOFs microplates.Publication ELUCIDATING THE FUNCTIONS OF GPR43 AND GPR41 IN MONOCYTES(2015-01-22) ANG ZHIWEI; NUS GRAD SCH FOR INTEGRATIVE SCI & ENGG; DING JEAK LINGThe fermentation of dietary fiber by the gut microbiota produces short-chain fatty acids (SCFAs), namely acetate, propionate and butyrate. These SCFAs activate the human G protein-coupled receptors: GPR41 and GPR43. Here, we fully characterize the human GPR43 promoter, identifying XBP1 as a core cis element which is activated by stimuli such as LPS, GM-CSF and TNF to induce GPR43 expression in monocytes. Next, we defined the role of GPR43 and the related SCFA receptor, GPR41, in monocytes. Wildtype and GPR43/41 knockout monocytes were cultured ex vivo and treated with synthetic GPR43/41 agonists. These assays confirmed that the SCFA, acetate, acts via GPR43 and GPR41 to repress inflammatory cytokine expression and signaling in human monocytes. Surprisingly, these GPR43/41 inhibition pathways were absent in mice monocytes, resulting in a distinct response to acetate. Collectively, we reveal that GPR41 and GPR43 modulate human monocytes cytokine expression.Publication Ultrafast Phase-Change for Data Storage Applications(2012-09-03) LOKE KOK LEONG DESMOND; NUS GRAD SCH FOR INTEGRATIVE SCI & ENGG; YEO YEE CHIA; CHONG TOW CHONG; SHI LUPINGPhase-change random access memory (PCRAM) is one of the leading candidates for next-generation data-storage devices, but the trade-off between crystallization speed and amorphous-phase stability presents a key challenge. In this thesis, nanoscale effects in phase-change (PC) materials and functional materials were exploited to achieve fast-speed, low-power, and high-endurance in PCRAM cells. Incubations of nanostructural units in PC materials were studied to control the crystallization kinetics by the application of a constant low-voltage. To change the PC mechanisms, nanostructured PC materials were also investigated by controlling feature sizes. Thermal effects in nanoscale PC materials with superlattice-like (SLL) structures were further examined to control the thermal-confinement properties by varying device sizes. To enhance thermal-confinement, thermal properties of nanoscale SLL dielectric materials were studied by varying the number of periods in SLL dielectric. These studies pave the way for achieving a broadly applicable memory device, capable of non-volatile operations beyond GHz data-transfer rates.