新加坡

The process of gene targeting via Chimeraplasty is achieved by using a RNA-DNA oligonucleotide homologous to a gene of interest ,to introduce a single base pair or frameshift mutation in genomic DNA .The extensive use of chimeraplasty is currently limited by wide variation in its gene conversion rates(.01-40%) and its mechanism of action remains to be fully understood. For cell studies, chimeraplasty is an alternative strategy to homeologus recombination in generating gene knockout models.

Size-exclusion chromatography (SEC) is often used to determine the molecular weights of and separate polymers and proteins. The porous packing of the SEC column effects the separation of molecules, with larger molecules eluting earlier. Interest in high-speed SEC for larger molecules has been building, especially for combinatorial polymerization reactions and online SEC-MS applications. Mechanical stability of the packing, which siliceous materials have more of than polymeric ones, therefore needs to be improved. Several silicas have been explored but limited pore sizes and pore volumes have restricted their usage to separating small molecules. Siliceous MCF templated using oil-in-water microemulsions has good potential for SEC packing because it has ultralarge pore size (20-50 nm), high porosity and sturdy skeleton. However conventional MCF consists of highly irregular particles and hence cannot be used as packing.

The skin of amphibians can secrete poisons from glands which reduces Palatability or sometimes result in rejection by predators. My research serves to confim the hypothesis that the pair of glands located on the ventral side of Rana Chalconota Tadpoles acts as an anti-presatory structure. Their palatability was measured by the consumption of them at developmental stages intermediate and post-metamorphic by Channa gachua and Giant Dragonfly Nymph. A known-palatable tadpole, Rana malesiana, was used as a control.

"Nitrates and phosphates cause eutrophication when present in high concentrations.\r This project aims to employ macrophytes to reduce such macronutrients in water bodies via growth and kinetic studies, which is a unique fusion of methodologies. It also involves a novel design and analysis of several enclosure prototypes to introduce macrophytes into waterways and their effects on the waterway’s ability to convey storm water rapidly away from flood-prone areas.\r Tropical macrophytes (emergent macrophytes Typha angustifolia and Cyperus haspan, submerged macrophytes Hydrilla verticillata and Cabomba aquatica, floating macrophytes Lemna minor) were grown in simulated wastewater with high nitrate and phosphate concentrations. Analysis of the growth and uptake kinetics of the macrophytes showed a correlation between high growth rate and high nitrates and phosphates uptake. C. aquatica had the highest uptake rate for nitrates and phosphates as well as the highest growth rate of 6.11 ± 1.2 % day-1 . The remaining macrophytes were proven to exhibit good phytoremediative properties, with emergent macrophytes C. haspan and T. angustifolia having great affinity (as indicated by a low Km value) for phosphate and nitrate respectively. An analysis of the phytoremediative abilities of each macrophyte was done to provide recommendations for growth in different aquatic areas.\r A total of eight nettings, made from different materials-linen and plastic, and pore sizes were used to design the enclosure prototypes. These enclosures possess a metal skeletal structure for greater stability. Results show that a combination of 2 different nettings provided the best trade-off between ensuring that the macrophytes were contained within the enclosures and minimising the enclosure’s impact on the flow velocity of the waterways. Enclosures could then be attached to existing infrastructure like the float booms as a platform for large scale phytoremediation locally."

Neuroinflammation is implicated as a contributive factor to neurodegeneration in Parkinson’s disease (PD). Increased iron accumulation and deposition of -synuclein within Lewy Bodies in PD brains have been observed. It has been hypothesized that unbound iron is able to react with H2O2 to generate free radicals. Using the Divalent Metal Transporter-1 (DMT1) as a vehicle to transport iron into the brain, a DMT1 transgenic mouse model (DTg) was generated to recapitulate iron deposition in PD. The DTg was crossbred with the SNCA (synuclein) transgenic mouse to produce a DMT1_SNCA (BTg) mouse model to study the link between iron, -synuclein and neuroinflammation in PD. Our hypothesis predicts that iron exacerbates -synuclein toxicity by inducing larger inflammatory responses and consequently compromising functions of biomolecules. Our study shows that –synuclein triggers a low-grade inflammatory response by microglia and astrocytes while iron exacerbates -synuclein toxicity by eliciting immunological responses mediated by glia cells in the brain observed both in the DTg and BTg mice. Elevated levels of nitrated proteins were observed in the DTg, suggesting the role of iron in inducing nitrosative stress via upregulation of iNOS in glia cells. With the BTg mice, we hope to understand the effect of iron accumulation as an environmental stressor in aggravating -synuclein toxicity which may lead to the selective demise of dopaminergic neurons.

Background:\r Delivery of anticancer drugs in vivo can be achieved by using targetspecific\r drug carriers of various types – e.g. microspheres and liposomes –\r which can be applied intravenously, or subcutaneously via a hypodermal\r patch, etc. as appropriate to the type of drug carrier employed. Recently,\r interest has surged in the usage of amphiphilic polymeric micelles for this\r purpose, as they prove superior to other drug carriers in many ways. They\r have highly-hydrated hydrophilic shells, and hydrophobic cores wherein\r hydrophobic anticancer drugs such as adriamycin can be encapsulated\r during transport in the blood. Their main advantages include their\r smallness of size – enabling them to elude capture by the\r reticuloendothelial system (RES) – their stability in the bloodstream as\r shown in their low critical micelle concentration (CMC) values, their\r passive targeting of tumour sites via the enhanced permeability and\r retention (EPR) effect, and their ability to integrate an active targeting\r mechanism, e.g. antibody-antigen recognition, pH-sensitivity, etc.

Many biological processes in the human body take place in intracellular environments under crowded conditions. This means that such cellular activities occur in the presence of inert macromolecules. These macromolecules are thought to have large effects on reaction rates and equilibria. However, under conventional conditions, these same processes are studied in vitro under uncrowded conditions in dilute buffers and therefore not reflective of physiological conditions. Hence, this project aims to study the effect of macromolecular crowding on antigen-antibody reactions in an attempt to mimic intracellular environments. It also aims to highlight the importance of introducing crowders as a factor of study in conventional in vitro experiments involving cellular reactions. The model reaction investigated involves human collagen type 1 on skin samples and specific antibodies against these antigens. Inert macromolecules of defined hydrodynamic radius and charge were added into the reaction media while quantitative tests are conducted to determine the effect of crowding on the rate and extent of reaction. The macromolecular crowders used were Dextran Sulphate, Ficol170, Ficol1400 and Polyvinylpyrrolidone360. Results were than analysed with the Metamorph 7 imaging system to determine signal strength under crowded and non-crowded conditions. At high primary antibody dilutions, skin samples incubated with a primary antibody solution crowded with a combination of inert macromolecules showed improve signal strength. This could be because crowding tends to shift reaction equilibria such as to minimise the amount of excluded volume, leading to association of the antigen and its specific antibody. This is known as the excluded volume effect. In addition, crowding the primary antibody solution helped increase the rate of reaction. The results also suggest that the addition of crowders may reduce the amount of antibodies needed per sample and decrease the necessary incubation time. Therefore, antigen-antibody reactions can be done more cost-effectively, However, the presence of charged macromolecules such as Dextran Sulphate has an inhibitory effect. Further work is also needed to establish whether macromolecular crowding enhances specificity and thereby reduce autoflourescence of the skin sample.

It is extremely costly to care for elderly people who have suffered a serious fall. Thus, doctors welcome a device or method to identify people prone to falling, to reduce elderly health costs and enable those identified as “fallers” to take precautions. Recently, a Sound Wave Assessment (SWA) device was developed to determine if tested human subjects were prone to falling. It is based on the concept that all humans exhibit postural sway while standing stationarily. The device employs two sonar transducers, which emit and receive ultrasonic pulse signals. The first transducer is positioned on a tripod, while the second is attached to the lower back of the human subject. Each transducer emits ultrasonic modulation pulses, which are detected by the other transducer. The distance between the two transducers is calculated from the time taken for the pulses to travel from the sender to the receiver. Hence, we can measure the small displacement fluctuations of the standing human subject, both approaching and receding from a static transducer, as a function of time.

An exact solution to many current computational problems, such as the famous Travelling Salesman Problem (TSP), require a complete tree traversal in order to determine. This is often unfeasible, as the time complexity of the tree traversal grows exponentially with the size of the input, thus leading to an essentially computationally intractable problem. The branch and bound technique is an approach commonly used to speed this process. It entails dynamically pruning off branches of the tree in which the answer is probably not found in, hence reducing the amount of data that is needed to be traversed and the total time and resources required to perform the computation. In this paper, we introduce a new load-balancing strategy for the execution of such a branch and bound algorithm in parallel, using a three-tiered hierarchical approach, to perform fractal image compression, which is essentially a complete tree traversal problem. This novel heuristic is aimed at achieving optimal load-balancing and minimising unnecessary network traffic and bottlenecking, which functions by predicting the optimum search depth and hence controlling the coarseness of the input that is assigned to each worker node. Our scheme additionally enables us to tailor to the specifications of different clusters, as the heuristic is adjusted based on network speed and processor speed, which vary appreciably from cluster to cluster. We further discuss how to apply our method to other large tree search problems, such as the TSP and other NP-complete problems. We have also enhanced an existing load-balancing strategy outlined in Crivelli et. al. (2004, IBM Journal of Research and Development), by prioritising the reallocation of idle worker nodes such that supervisors who are in need of more help receive a larger share of the free workers.