Behavioural and ERP evidence of a contrary effect between active and passive suppression of facial expressions.

There has been disagreement regarding the relationship among the three components (subjective experience, external performance, and physiological response) of emotional responses. To investigate this issue further, this study compared the effects of active and passive suppression of facial expressions on subjective experiences and event-related potentials (ERPs) through two experiments. The two methods of expression suppression produced opposite patterns of ERPs for negative emotional stimuli: compared with the free-viewing condition, active suppression of expression decreased, while passive suppression increased the amplitude of the late positive potential (LPP) when viewing negative emotional stimuli. Further, while active suppression had no effect on participants' emotional experience, passive suppression enhanced their emotional experience. Among the three components of emotional responses, facial expressions are more closely related to the physiological response of the brain than to subjective experience, and whether the suppression was initiated by participants determines the decrease or increase in physiological response of the brain (i.e. LPP). The findings revealed the important role of individual subjective initiative in modulating the relationship among the components of emotional response, which provides new insights into effectively emotional regulation.

[Method development for analysis of short-and long-chain perfluorocarboxylates in sewage].

A method using weak anion exchange cartridge for solid phase extraction before high performance liquid chromatography-negative electronspray ionization-tandem mass spectrometry [WAX-SPE + HPLC-ESI(-)-MS/MS] detection has been developed to measure C2-C14 perfluorocarboxylates (PFCAs) in sewages. When the weak anion exchange (WAX) cartridges were used for solid phase extraction (SPE), the better recoveries of short- and long-chain PFCAs (C2-C14) were achieved as the sewage samples were acidified to pH = 3.0 by formic acid, 2% formic acid was used for washing solvent and 1% ammonium hydroxide in methanol was used for elution solvent. The WAX cartridges used for SPE overcame the disadvantages of reverse phase solid phase extraction cartridges, i.e. the recoveries of short-chain PFCAs (C2-C5) were very low. The validity of this method was demonstrated by determination of short- and long-chain PFCAs (C2-C14) in influent of municipal wastewater treatment plant A and B in Shanghai, China. The results indicate that the recoveries of all PFCAs in influent of plant A and B are 56%-121% and 54%-120%, respectively; the recovery relative standard deviations (RSD) of plant A and B are < 11% and < 14%, respectively; and the method detection limits (MDL) and method quantitation limits (MQL) are 0.2-1.0 ng/L and 1.0-5.0 ng/L, respectively. In addition, the perfluorooctanoate (743 ng/L and 837 ng/L, respectively) and trifluoroacetic acid (139 ng/L and 489 ng/L, respectively) are the most and the second most PFCAs found in both plant A and B.