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Publication Beyond the 'Himalayan Pearl Harbor'(2012-11) Kudaisya, G.; SOUTH ASIAN STUDIES PROGRAMMEPublication Analysis of the peanut agglutinin molten globule-like intermediate by limited proteolysis(2005-10-10) Mitra, N.; Sinha, S.; Kini, R.M.; Surolia, A.; BIOLOGICAL SCIENCESThese studies attempt to characterize the molten globule-like intermediate in the unfolding pathway of peanut agglutinin (PNA). PNA is the only known example of a homotetrameric protein that lacks the 2,2,2 or the fourfold symmetry. Previous studies have shown that PNA describes a non two-state unfolding process populated with a clearly defined intermediate. The intermediate is monomeric and has lost most of its tertiary structure and has a substantial amount of secondary structure still intact, thus described as a molten-globule (MG)-like intermediate. It was also shown by isothermal titration calorimetry to bind to lactose and some other ligands with an affinity similar to that of the native protein. This paper describes limited protease cleavage experiments on the intermediate using trypsin and protease V8 for its structural characterization. There are two hydrophobic cores in the PNA subunit. These experiments suggest that in the MG-like intermediate, the second hydrophobic core, near the sugar-binding loop of the protein loosens up. This effect is significantly reduced by the presence of 90% saturating lactose, as deduced by a reduction in cleavage propensity. This is also supported by the gain in the tertiary structure as observed by near-UV CD. © 2005 Elsevier B.V. All rights reserved.Publication Power allocation for OFDM-based cognitive radio systems with hybrid protection to primary users(2009) Kang, X.; Garg, H.K.; Liang, Y.-C.; Zhang, R.; ELECTRICAL & COMPUTER ENGINEERINGThis paper considers a spectrum sharing wireless environment, where an OFDM-based cognitive radio system is allowed to access the spectrum originally licensed to an OFDMA primary system. A new criterion referred to as the rate loss constraint, in the form of an upper bound on the maximum rate loss of the primary user due to the secondary transmission, is proposed for primary transmission protection. In addition, assuming that some PUs are protected by the rate loss constraint, and some PUs are protected by the interference power constraint, the optimal power allocation strategy to maximize the rate of the cognitive radio system under such a hybrid protection to PUs together with a transmit power constraint is derived. Then, the relationship between the rate loss constraint and the interference power constraint is investigated, and it is shown by simulation that the cognitive radio system can achieve a significant rate gain under the proposed constraint compared with that under the conventional interference power constraint.Publication Constructed tropical wetlands with integrated submergent-emergent plants for sustainable water quality management(2006-10-01) Tanaka, N.; Jinadasa, K.B.S.N.; Werellagama, D.R.I.B.; Mowjood, M.I.M.; Ng, W.J.; DIVISION OF ENVIRONMENTAL SCIENCE & ENGGImprovement of primary effluent quality by using an integrated system of emergent plants (Scirpus grossus in the leading subsurface flow arrangement) and submergent plants (Hydrilla verticillata in a subsequent channel) was investigated. The primary effluent was drawn from a septic tank treating domestic sewage from a student dormitory at the University of Peradeniya, Sri Lanka. Influent and effluent samples were collected once every 2 weeks from May 2004 through July 2005 and analyzed to determine water quality parameters. Both the emergent and submergent plants were harvested at predetermined intervals. The results suggested that harvesting prolonged the usefulness of the system and the generation of a renewable biomass with potential economic value. The mean overall pollutant removal efficiencies of the integrated emergent and submergent plant system were biological oxygen demand (BOD5), 65.7%; chemical oxygen demand (COD), 40.8%; ammonium (NH4 +-N), 74.8%; nitrate (NO3 --N), 38.8%; phosphate (PO4 3-), 61.2%; total suspended solids (TSS), 65.8%; and fecal coliforms, 94.8%. The submergent plant subsystem improved removal of nutrients that survived the emergent subsystem operated at low hydraulic retention times. The significant improvement in effluent quality following treatment by the submergent plant system indicates the value of incorporating such plants in wetland systems. Copyright © Taylor & Francis Group, LLC.Publication A Monte Carlo model for trapped charge distribution in electron-irradiated α-quartz(1993) Oh, K.H.; Ong, C.K.; Tan, B.T.G.; Le Gressus, G.; PHYSICSThe space dependence of charge carriers trapped in α-quartz under electron-beam bombardment is investigated using a Monte Carlo algorithm. The average energy of the electron after being detrapped from a trap site is first calculated by considering both the polar and nonpolar phonon scatterings. Later, the detrapping and trapping rates are also included in the model to obtain a stable trapped charge distribution, which is found to be dependent on the size as well as the temperature of the sample. Comparisons with experimental results of the size effect on the dielectric strength obtained from a scanning electron microscope are also made.Publication Determination of strategic adaptation actions for public housing in Singapore(2011-07) Teo, E.A.L.; Lin, G.; BUILDINGAlthough building adaptation finds it significant in combating building deterioration and delivering building sustainability, what level of adaptation a building shall receive always seems puzzling to property portfolio managers. This research aims to provide policy makers with a theoretical approach to choose strategically desired adaptation actions for buildings. Personal interviews with policy makers in Singapore public housing sector gave rise to the construction of an Attribute-Action database; this database was used to derive an Attribute-Action Matrix, which consists of a set of preference values for each adaptation action (i.e. retaining, renovating and rebuilding). This approach was then applied to a real public residential building in Singapore. The results show that the total preference values for the actions of retaining, renovating and rebuilding are 157.849, 111.609, and 90.575, respectively; the action of retaining with minor maintenance of building facades is found to be the most desired adaptation strategy for the case building, because compared with the other two, retaining has the maximum total preference value. The presented approach would therefore extend the understanding of how strategic adaptation actions can be made for existing buildings that require adaptation. Lessons learnt in Singapore public housing context may be useful for many other cities in face of similar problems. © 2011 Elsevier Ltd.Publication Introduction(2004) Ravi, S.; Goh, B.-L.; Rutten, M.; SOUTHEAST ASIAN STUDIESPublication Level crossings in complex two-dimensional potentials(2009-08) Wang, Q.-H.; PHYSICSTwo-dimensional PT -symmetric quantum-mechanical systems with the com-plex cubic potential V12 = x2 + y2 + igxy 2 and the complex Hénon-Heiles potential VHH = x2 +y2 +ig(xy2 -x3/3) are investigated. Using numerical and perturbative meth ods, energy spectra are obtained to high levels. Although both potentials respect the PT symmetry, the complex energy eigenvalues appear when level crossing happens between same parity eigenstates. © Indian Academy of Sciences.Publication Drug-induced permeabilization of parasite's digestive vacuole is a key trigger of programmed cell death in Plasmodium falciparum(2011-10) Ch'ng, J.-H.; Liew, K.; Goh, A.S.-P.; Sidhartha, E.; Tan, K.S.-W.; MICROBIOLOGYHaving previously characterized chloroquine (CQ)-induced programmed cell death (PCD) hallmarks in the malaria parasite Plasmodium falciparum and delineating a pathway linking these features, the roles of non-classical mediators were investigated in this paper. It was shown that the later stages of this pathway are Ca2 +-dependent and transcriptionally regulated. Moreover, it was demonstrated for the first time that micromolar concentrations of CQ partially permeabilized the parasite's digestive vacuole (DV) membrane and that this important upstream event appears to precede mitochondrial dysfunction. This permeabilization of the DV occurred without rupture of the DV membrane and was reminiscent of lysosome-mediated cell death in mammalian cells. As such micromolar concentrations of CQ are found in the patient's plasma after initial CQ loading, this alludes to a clinically relevant antimalarial mechanism of the drug which has yet to be recognized. Furthermore, other 'non-antimalarial' lysosomotropic compounds were also shown to cause DV permeabilization, triggering PCD in both CQ-sensitive and -resistant parasites. These findings present new avenues for antimalarial developments, which induce DV destabilization to kill parasites. © 2011 Macmillan Publishers Limited.Publication Polarization conversion of electromagnetic waves by Faraday chiral media(2010) Meng, F.-Y.; Zhang, K.; Wu, Q.; Li, L.-W.; ELECTRICAL & COMPUTER ENGINEERINGThe reflection of a normally incident plane wave due to the interface between vacuum and a Faraday chiral medium (FCM) supported by a perfect electric conductor was rigorously derived. Numerical results strongly indicated that arbitrary polarization conversions are realizable from the incident plane wave to the reflected plane wave by properly choosing the constitutive parameters of the FCM. © 2010 American Institute of Physics.