[1] Many Southeast Asian countries have been constantly plagued by recurring smoke haze episodes as a result of traditional slash-and-burn practices in agricultural areas to clear crop lands or uncontrolled forest fires. However, our current knowledge on the physiochemical and optical properties of ambient aerosols associated with regional haze phenomenon is still fairly limited. Therefore a comprehensive field study was carried out in Singapore from March 2001 to March 2002 under varying weather conditions to gain a better understanding of the characteristics. The physical (size distribution of mass and number concentrations), chemical (mass concentrations of chemical components: 14 ions, 24 metals, elemental carbon (EC) and organic carbon (OC)), and optical (light absorption (b ap ) and scattering (b sp ) by particles) characteristics of ambient aerosol particles were investigated. The results are reported separately for clear and hazy days by categorizing the days as clear or hazy on the basis of visibility data. It was observed that the average concentrations of PM 2.5 and most chemical components increased approximately by a factor of 2 on hazy days. Backward air trajectories together with the hot spot distributions in the region indicated that the degradation in Singapore's air quality on hazy days was attributable to large-scale forest fires in Sumatra. This visibility degradation was quantitatively measured on the basis of the light absorption and scattering by particles. As expected, scattering rather than absorption controlled atmospheric visibility, and PM 2.5 particles present on hazy days were more efficient at scattering light than those found on clear days.

Magnetic resonance imaging (MRI) is emerging as a powerful tool for in vivo noninvasive tracking of magnetically labeled stem cells. In this work, we present an efficient cell-labeling approach using (carboxymethyl)chitosan-modified superparamagnetic iron oxide nanoparticles (CMCS-SPIONs) as contrast agent in MRI. The CMCS-SPIONs were prepared by conjugating (carboxymethyl)chitosan to (3-aminopropyl)trimethoxysilane-treated SPIONs. These nanoparticles were internalized into human mesenchymal stem cells (hMSCs) via endocytosis as confirmed by Prussian Blue staining and electron microscopy investigation and quantified by inductively coupled plasma mass spectrometry. A MTT assay of the labeled cells showed that CMCS-SPIONs did not possess significant cytotoxicity. In addition, the osteogenic and adipogenic differentiations of the hMSCs were not influenced by the labeling process. The in vitro detection threshold of cells after incubation with 0.05 mg/mL of CMCS-SPIONs for 24 h was estimated to be about 40 cells. The results from this study indicate that the biocompatible CMCS-SPIONs show promise for use with MRI in visualizing hMSCs.

Polymer axial drawing enables the design of optimal microarchitectured scaffolds for tendon regeneration.

Strategies for nursing recruitment in Singapore must include creating more opportunities for exposure to nursing in early school years, reviewing the admission policies for nursing programmes to attract academically abled students, ensuring that nursing graduates' salaries are comparable with other healthcare graduates, promoting a better understanding on the role of a registered nurse and its career developments, and providing support for those who are interested in nursing but are faced with career decision-making difficulties due to their families.