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Search Results: 1 - 10 of 229640 matches for " David K. Y. Lim "
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Microalgal biofactories: a promising approach towards sustainable omega-3 fatty acid production
Adarme-Vega T,Lim David K Y,Timmins Matthew,Vernen Felicitas
Microbial Cell Factories , 2012, DOI: 10.1186/1475-2859-11-96
Abstract: Omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) provide significant health benefits and this has led to an increased consumption as dietary supplements. Omega-3 fatty acids EPA and DHA are found in animals, transgenic plants, fungi and many microorganisms but are typically extracted from fatty fish, putting additional pressures on global fish stocks. As primary producers, many marine microalgae are rich in EPA (C20:5) and DHA (C22:6) and present a promising source of omega-3 fatty acids. Several heterotrophic microalgae have been used as biofactories for omega-3 fatty acids commercially, but a strong interest in autotrophic microalgae has emerged in recent years as microalgae are being developed as biofuel crops. This paper provides an overview of microalgal biotechnology and production platforms for the development of omega-3 fatty acids EPA and DHA. It refers to implications in current biotechnological uses of microalgae as aquaculture feed and future biofuel crops and explores potential applications of metabolic engineering and selective breeding to accumulate large amounts of omega-3 fatty acids in autotrophic microalgae.
Isolation and Evaluation of Oil-Producing Microalgae from Subtropical Coastal and Brackish Waters
David K. Y. Lim, Sourabh Garg, Matthew Timmins, Eugene S. B. Zhang, Skye R. Thomas-Hall, Holger Schuhmann, Yan Li, Peer M. Schenk
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0040751
Abstract: Microalgae have been widely reported as a promising source of biofuels, mainly based on their high areal productivity of biomass and lipids as triacylglycerides and the possibility for cultivation on non-arable land. The isolation and selection of suitable strains that are robust and display high growth and lipid accumulation rates is an important prerequisite for their successful cultivation as a bioenergy source, a process that can be compared to the initial selection and domestication of agricultural crops. We developed standard protocols for the isolation and cultivation for a range of marine and brackish microalgae. By comparing growth rates and lipid productivity, we assessed the potential of subtropical coastal and brackish microalgae for the production of biodiesel and other oil-based bioproducts. This study identified Nannochloropsis sp., Dunaniella salina and new isolates of Chlorella sp. and Tetraselmis sp. as suitable candidates for a multiple-product algae crop. We conclude that subtropical coastal microalgae display a variety of fatty acid profiles that offer a wide scope for several oil-based bioproducts, including biodiesel and omega-3 fatty acids. A biorefinery approach for microalgae would make economical production more feasible but challenges remain for efficient harvesting and extraction processes for some species.
Diversity and Adaptation in Large Population Games
K. Y. Michael Wong,S. W. Lim,Peixun Luo
Physics , 2003, DOI: 10.1142/S0217979204025464
Abstract: We consider a version of large population games whose players compete for resources using strategies with adaptable preferences. The system efficiency is measured by the variance of the decisions. In the regime where the system can be plagued by the maladaptive behavior of the players, we find that diversity among the players improves the system efficiency, though it slows the convergence to the steady state. Diversity causes a mild spread of resources at the transient state, but reduces the uneven distribution of resources in the steady state.
Dynamical Mechanisms in Multi-agent Systems: Minority Games
K. Y. Michael Wong,S. W. Lim,Zhuo Gao
Physics , 2003,
Abstract: We consider a version of large population games whose agents compete for resources using strategies with adaptable preferences. Diversity among the agents reduces their maladpative behavior. We find interesting scaling relations with diversity for the variance of decisions. When diversity increases, the scaling dynamics is modified by kinetic sampling and waiting mechanisms.
Effects of Diversity on Multi-agent Systems: Minority Games
K. Y. Michael Wong,S. W. Lim,Zhuo Gao
Physics , 2005, DOI: 10.1103/PhysRevE.71.066103
Abstract: We consider a version of large population games whose agents compete for resources using strategies with adaptable preferences. The games can be used to model economic markets, ecosystems or distributed control. Diversity of initial preferences of strategies is introduced by randomly assigning biases to the strategies of different agents. We find that diversity among the agents reduces their maladaptive behavior. We find interesting scaling relations with diversity for the variance and other parameters such as the convergence time, the fraction of fickle agents, and the variance of wealth, illustrating their dynamical origin. When diversity increases, the scaling dynamics is modified by kinetic sampling and waiting effects. Analyses yield excellent agreement with simulations.
Integrity Assessment of Pipe System in a Full-Scale Membrane Water Treatment Plant  [PDF]
H. K. Oh, J. Y. Eom, S. H. Kang, H. C. Yoo, Y. J. Kim, D. M. Yoon, J. H. Lim
Journal of Water Resource and Protection (JWARP) , 2014, DOI: 10.4236/jwarp.2014.64038

The pipe system roles as a main bridge between membrane modules and pumps in membrane water treatment plants. Membrane operation modes generally consist of filtration and backwash processes in a normal mode, a pressure decay test as an integrity test and a chemical circulation through pipe system in a cleaning mode. Thus factors effecting on membrane performance should be sufficiently considered before design and operation. This study evaluated flow analysis for vibration diagnostic and evaluation of the fatigue lifetime in the microfiltration system applied for a drinking water treatment plant. Vibration of main membrane pipelines was measured to identify the source of vibration. Also natural frequency and fluid dynamics was calculated by computational fluid dynamics. It showed that maximum magnitude frequencies were at 12 Hz and 22 Hz, respectively at water and air pipeline during filtration and backwash. Backwash process caused mainly vibration on the backwash water pipe. The calculated frequency from analysis of frequency response and CFD was in a good agreement with the measured frequency. Fatigue analysis showed that pipelines were getting little damage caused by vibration. Fatigue lifetime was predicted more than 15 years under the operation condition of daily filtration, and more than 27 years under the operation condition of a daily backwash mode, resulting in minor damage on the pipe lifetime.

Diffuse Sclerosing Variant of Papillary Thyroid Carcinoma with Concomitant Thyrotoxicosis: A Case Report and Literature Review  [PDF]
Jessie Y. W. Chan, David K. K. Tsui, Polly Tsui, Tang Chung Ngai
Surgical Science (SS) , 2014, DOI: 10.4236/ss.2014.53021

Diffuse sclerosing variant of papillary thyroid carcinoma (DSVPC) is a rare variant of conventional papillary thyroid carcinoma which was first reported in 1985. It appears to be more aggressive than conventional type of papillary thyroid carcinoma. We present a case in a 14-year-old girl who initially presented with thyrotoxicosis and was later diagnosed with DSVPC on subsequent ultrasound and fine need leaspiration when cervicallymph node was evident on clinical examination. Concomitant thyrotoxicosis in thyroid carcinoma is uncommon. The prevalence, clinical presentation, characteristic radiological and histological features, management and prognosis of DSVPC are discussed with literature review. We also hope to illustrate through this case that ultrasound as a non-invasive imaging modality is an invaluable tool for workup in functional thyroid problems and concomitant malignancy may not be that uncommon, so that we could provide prompt treatment to our patients.

Mechanisms leading to oligomers and SOA through aqueous photooxidation: insights from OH radical oxidation of acetic acid and methylglyoxal
Y. Tan, Y. B. Lim, K. E. Altieri, S. P. Seitzinger,B. J. Turpin
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2012,
Abstract: Previous experiments have demonstrated that the aqueous OH radical oxidation of methylglyoxal produces low volatility products including pyruvate, oxalate and oligomers. These products are found predominantly in the particle phase in the atmosphere, suggesting that methylglyoxal is a precursor of secondary organic aerosol (SOA). Acetic acid plays a central role in the aqueous oxidation of methylglyoxal and it is a ubiquitous product of gas phase photochemistry, making it a potential "aqueous" SOA precursor in its own right. However, the fate of acetic acid upon aqueous-phase oxidation is not well understood. In this research, acetic acid (20 μM–10 mM) was oxidized by OH radicals, and pyruvic acid and methylglyoxal experimental samples were analyzed using new analytical methods, in order to better understand the formation of SOA from acetic acid and methylglyoxal. Glyoxylic, glycolic, and oxalic acids formed from acetic acid and OH radicals. In contrast to the aqueous OH radical oxidation of methylglyoxal, the aqueous OH radical oxidation of acetic acid did not produce succinic acid and oligomers. This suggests that the methylgloxal-derived oligomers do not form through the acid catalyzed esterification pathway proposed previously. Using results from these experiments, radical mechanisms responsible for oligomer formation from methylglyoxal oxidation in clouds and wet aerosols are proposed. The importance of acetic acid/acetate as an SOA precursor is also discussed. We hypothesize that this and similar chemistry is central to the daytime formation of oligomers in wet aerosols.
Embolisation of Bleeding Renal Angiomyolipoma in Pregnancy  [PDF]
Chin Hong Lim, David Mulvin
Open Journal of Urology (OJU) , 2011, DOI: 10.4236/oju.2011.13007
Abstract: Bleeding from renal angiomyolipoma in pregnancy can be catastrophic to both mother and fetus. Selective arterial embolisation is considered more superior than conventional surgery in these patients. Our case report exemplifies how a bleeding angiomyolipoma was halted with embolisation in our pregnant patient.
Optical studies of carrier and phonon dynamics in Ga_{1-x}Mn_{x}As
K. J. Yee,D. Lee,X. Liu,W. L. Lim,M. Dobrowolska,J. K. Furdyna,Y. S. Lim,K. G. Yee,D. S. Kim
Physics , 2005, DOI: 10.1063/1.2137889
Abstract: We present a time-resolved optical study of the dynamics of carriers and phonons in Ga_{1-x}Mn_{x}As layers for a series of Mn and hole concentrations. While band filling is the dominant effect in transient optical absorption in low-temperature-grown (LT) GaAs, band gap renormalization effects become important with increasing Mn concentration in Ga_{1-x}Mn_{x}As, as inferred from the sign of the absorption change. We also report direct observation on lattice vibrations in Ga1-xMnxAs layers via reflective electro-optic sampling technique. The data show increasingly fast dephasing of LO phonon oscillations for samples with increasing Mn and hole concentration, which can be understood in term of phonon scattering by the holes.
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