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Toluene, one of many volatile organic compounds existing in the atmosphere, was studied as an impurity or contaminant in the airstream of proton exchange membrane ͑PEM͒ fuel cells. The effects of toluene contamination on fuel cell performance were investigated with constant-current polarization discharge under various operating conditions, including current density, back pressure, and air stoichiometry. The severity of the contamination increased with increasing current density, toluene concentration, and air stoichiometry, but decreased with increasing back pressure. The effect of toluene contamination on current dynamic operation was also studied by cycling the current density from 0.0 to 0.2 A cm −2 and then to 1.0 A cm −2 in the presence of toluene. Cell performance degradation during current dynamic operation was accelerated by the presence of toluene. Electrochemical impedance measurements and analysis revealed that both kinetic resistance and mass transfer resistance were increased as a result of toluene contamination, but the increase in kinetic resistance was dominant.Proton exchange membrane ͑PEM͒ fuel cells are considered promising clean-energy converting devices due to their high efficiency, high power density, and low/zero emissions in portable, residential, and automobile applications. However, major technical challenges, such as high cost and unsatisfactory durability/reliability, are hindering the commercialization of this technology.With respect to the issue of durability/reliability, great efforts have been made in recent years to identify failure modes and develop corresponding mitigation strategies. Fuel cell contamination caused by impurities or contaminants in the feed streams or from fuel cell components has been identified as one of the significant factors contributing to the failure modes of PEM fuel cells. 1-5 Impurities damage the membrane electrode assembly ͑MEA͒ by affecting both anode and cathode catalyst layers ͑CLs͒, the gas diffusion layers ͑GDLs͒, as well as the membrane, causing MEA degradation or even fuel cell failure. Correspondingly, the contamination effects of impurities on a PEM fuel cell fall into three categories: kinetic effect, caused by the poisoning of both anode and cathode catalyst sites; mass transfer effect, due to changes in the structure and hydrophobility of the CLs or GDLs; and conductivity effect, caused by the increase in resistance of the membrane and ionomer.Extensive research has been done on contamination caused by fuel-side impurities, such as CO, H 2 S, and NH 3 . 2,3,6-10 However, there has been much less research on the impact of air-side impurities, including NO x , SO x , CO x , and volatile organic compounds ͑VOCs͒. 11-13 Studying the effect of atmospheric impurities on the durability of the fuel cell is an effort toward overcoming fuel cell contamination problems and developing mitigation strategies to improve the environmental adaptability of the fuel cell system.Our previous paper is the first reported study of the contamination effect of tol...

was injected into the cathode air stream, and Co 2+ contamination became more severe with decreasing temperature. To investigate in detail the mechanism of Co 2+ poisoning, AC impedance was monitored before and during Co 2+ injection, revealing that both charge transfer and mass transport related processes deteriorated significantly in the presence of Co 2+ , whereas membrane conductivity decreased to a lesser extent. Surface cyclic voltammetry and contact angle measurements further revealed changes in physical properties, such as active Pt surface area and hydrophilicity, furthering our understanding of the contamination process.Crown

Squamous cell carcinoma (SCC) of the larynx is extremely rare in adolescents and typically has an aggressive nature. The mechanism of laryngeal oncogenesis is complex and little is known about the role that human papillomavirus (HPV) plays in SCC in adolescents. We report a case of invasive laryngeal SCC that co-expressed HPV DNA subtypes 16 and 18 in a 13 year-old boy. Detection of HPV DNA types 6, 11, 16, 18, 31, 33, and 51 was performed by in situ hybridization, with confirmation by polymerase chain reaction. Immunohistochemical staining with p16 and HPV 16/18 revealed diffusely positive staining in the tumor cells. Coinfection by HPV DNA types 16 and 18 has not been previously reported, but our case suggests that HPV is a risk factor in developing laryngeal SCC in children and adolescents. Future studies evaluating HPV in the pathogenesis of these lesions is recommended to determine its prognostic significance.