In Situ Quantitative Study of Single-Molecule Photoreduction Activities and Kinetics on 1D-1D Heterostructure.

Understanding the underlying catalytic mechanisms with nanometer resolution is of critical importance to the rational design of 1D heterogeneous catalysts. However, a fundamental investigation of photocatalytic activities and kinetics at their individual sites is still challenging. Herein, in situ single-molecule fluorescence microscopy is employed to study the site-specific catalytic activities and dynamics on 1D-1D heterostructure for the first time. For carbon nanotube (CNT)/CdS nanorod composites, it is found that the CdS end with heterojunction exhibits the highest catalytic conversion rate constant of resazurin photoreduction, which is 30%, 7%, and 19% higher than those of the middle segment and the bare end of CdS, and the CNT end with heterojunction, respectively. A similar trend of adsorption abilities is observed in these structures. Such phenomena can be attributed to the different content of defects in these structures. Regarding the dissociation behaviors, the dissociation rate constants of all structures exhibit an opposite trend to those of adsorption and conversion. The direct and indirect dissociation are found to be predominant on CdS and CNT, respectively. Such investigation provides a deep insight into the understanding of site-specific properties on 1D heterogeneous catalysts and helps construct the "structure-dynamics" correlations at the nanoscale.

Characterization of epithelial cell adhesion molecule as a surface marker on undifferentiated human embryonic stem cells.

Human embryonic stem cells (hESCs) have the capacity to remain pluripotent and self-renew indefinitely. To discover novel players in the maintenance of hESCs, we have previously reported the generation of monoclonal antibodies that bind to cell surface markers on hESCs, and not to mouse embryonic stem cells or differentiated embryoid bodies. In this study, we have identified the antigen target of one such monoclonal antibody as the epithelial cell adhesion molecule (EpCAM). In undifferentiated hESCs, EpCAM is localized to Octamer 4 (OCT4)-positive pluripotent cells, and its expression is down-regulated upon differentiation. To further understand its biological function in hESCs, endogenous EpCAM expression was silenced using small interfering RNA. EpCAM knockdown had marginal negative effects on OCT4 and TRA-1-60 expression, however cell proliferation was decreased by >40%. Examination of lineage marker expression showed marked upregulation of endoderm and mesoderm genes in EpCAM-silenced cells, under both pluripotent and differentiating conditions. These results were validated using a hESC line whose EpCAM expression has been stably knocked down. Data from the stable line confirmed that downregulation of EpCAM decreases cell growth and increases gene expression in the endoderm and mesoderm lineages. In vivo, hESCs lacking EpCAM were able to form teratomas containing tissues representing the three germ layers, and gene expression analysis yielded marked increase in the endoderm marker alpha fetoprotein compared with control. Together these data demonstrate that EpCAM is a surface marker on undifferentiated hESCs and plays functional roles in proliferation and differentiation.

Effect of Nanofillers on Tribological Properties of Polymer Nanocomposites: A Review on Recent Development.

Polymer nanocomposites with enhanced performances are becoming a trend in the current research field, overcoming the limitations of bulk polymer and meeting the demands of market and society in tribological applications. Polytetrafluoroethylene, poly(ether ether ketone) and ultrahigh molecular weight polyethylene are the most popular polymers in recent research on tribology. Current work comprehensively reviews recent advancements of polymer nanocomposites in tribology. The influence of different types of nanofiller, such as carbon-based nanofiller, silicon-based nanofiller, metal oxide nanofiller and hybrid nanofiller, on the tribological performance of thermoplastic and thermoset nanocomposites is discussed. Since the tribological properties of polymer nanocomposites are not intrinsic but are dependent on sliding conditions, direct comparison between different types of nanofiller or the same nanofiller of different morphologies and structures is not feasible. Friction and wear rate are normalized to indicate relative improvement by different fillers. Emphasis is given to the effect of nanofiller content and surface modification of nanofillers on friction, wear resistance, wear mechanism and transfer film formation of its nanocomposites. Limitations from the previous works are addressed and future research on tribology of polymer nanocomposites is proposed.

Intubation with channeled versus non-channeled video laryngoscopes in simulated difficult airway by junior doctors in an out-of-hospital setting: A crossover manikin study.

Failure to secure the airway is an important cause of morbidity and mortality during resuscitations. We compared the rate of successful intubation of the King Vision™ aBlade™ channeled and non-channeled video laryngoscopes, and McGRATH™ MAC video laryngoscope when used by junior doctors to intubate a simulated difficult airway in an out-of-hospital setting. 105 junior doctors were recruited in a crossover study to perform tracheal intubation with the three video laryngoscopes on a simulated difficult airway using the SimMan® 3G manikin. Primary outcome was the rate of successful intubations. Secondary outcomes were time-to-visualization, time-to-intubation and ease of use. Rates of successful intubations were higher for King Vision channeled and McGrath compared to the King Vision non-channeled (85.7% and 82.9% respectively versus 24.8%; p<0.001). Amongst the participants who had successful intubations, King Vision channeled and McGrath had shorter mean time-to-intubation compared to the King Vision non-channeled (41.3±20.3s and 38.5±18.7s respectively versus 53.8±23.8s, p<0.004;). There was no significant difference in the rate of successful intubation and mean time-to-intubation between King Vision channeled and McGrath. The King Vision channeled and McGrath video laryngoscopes demonstrated superior intubation success rates compared to King Vision non-channeled laryngoscope when used by junior doctors for intubating simulated difficult airway in an out-of-hospital setting. We postulated that the presence of a guidance channel in the King Vision channeled laryngoscope and the familiarity of the blade curvature and handling of the McGrath could have accounted for their improved intubation success rates.

Toy safety in Singapore: where are we now?

INTRODUCTION: Toy-related injuries, a common reason for emergency department visits in the paediatric population, constitute a significant health burden in Singapore. Although government regulations imposed on toys and childcare-related items are in place, parents and caregivers still play a pivotal role in ensuring toy safety in children. We hypothesised that deficiencies in knowledge surrounding toy safety issues exist in our adult population. METHODS: We conducted a cross-sectional questionnaire study at KK Women's and Children's Hospital, Singapore, to examine the current attitudes, knowledge and practices of the local population regarding toy safety. Hypothetical questions on toy selection were included in the questionnaire to assess respondents' ability to identify appropriate toys and discern potentially dangerous toys for a specified age group. RESULTS: The scores of the 93 respondents showed that they were less able to identify appropriate toys for children in the 1-2 years (66.7%; 95% confidence interval [CI] 61.4%-72.0%) and 2-3 years age groups (69.9%; 95% CI 65.5%-74.3%) than for children in the 0-1 year (82.8%; 95% CI 79.9%-85.7%) and 3-5 years age groups (85.2%; 95% CI 81.2%-89.2%). Our survey also identified key areas for improvement (e.g. educational efforts and government regulation) in current practices in order to attain a higher level of toy safety. CONCLUSION: Our study highlights the current knowledge deficit in toy safety issues and the need for improvements in regulation, education and surveillance in order to minimise the risk of toy-related injuries in children.

Fragmented QRS complexes predict right ventricular dysfunction and outflow tract aneurysms in patients with repaired tetralogy of Fallot.

BACKGROUND: Fragmented QRS complexes (fQRS) correlate with myocardial scar, and may predict arrhythmias in patients with repaired tetralogy of Fallot (TOF). We investigated the relationship between fQRS in operated TOF patients with right ventricular (RV) dysfunction and RV outflow tract (RVOT) aneurysm. METHODS: We studied 56 operated TOF patients with moderate/severe pulmonary regurgitation, referred for cardiac magnetic resonance imaging (MRI) over a 4.5 year period. The presence of fQRS (additional notches in the R/S wave in ≥ 2 contiguous leads on the ECG) was correlated with MRI findings. RESULTS: fQRS was observed in 44 (78.6%) patients. Patients with fQRS had significantly larger RV end diastolic volume index (RVEDVi; 162 ml vs 141 ml, p=0.028) and RV end systolic volume index (RVESVi; 88 ml vs 70 ml, p=0.031). Increasing number of leads with fragmentation was independently associated with increasingly lower RV ejection fraction (adjusted co-efficient -0.97, 95%CI -1.83 to -0.12, p=0.026), greater pulmonary regurgitation fraction (1.65, 0.28 to 3.01, p=0.019), larger RVEDVi (6.78, 2.00 to 11.56, p=0.006) and RVESVi (5.41, 1.66 to 9.15, p=0.005). Anterior fragmentation correlated most significantly with RV dysfunction (p<0.05). fQRS had no significant association with LV dysfunction. Presence of any fQRS (OR 17.5, 95%CI 2.1-147.8, p=0.009) and inferior fQRS (OR 9.0, 95%CI 2.7-30.1, p<0.001) were found to be significant predictors for RVOT aneurysm. CONCLUSIONS: The presence of fQRS on the ECG is significantly associated with RV dysfunction and RVOT aneurysms in repaired TOF patients. Increasing burden of fragmentation, especially in the anterior leads, is associated with increasing RV dysfunction.