In China, many studies have been carried out on pesticide residues in human milk, yet all of them are on organochlorine pesticides (OCPs) and mostly focused on large, economically developed cities. In this study, 27 pesticides including OCPs, pyrethroid pesticides (PYRs) and organophosphate pesticides (OPPs) in human milk were investigated in Jinhua, an inland and medium sized city in China. Method based on QuEChERS extraction and gas chromatography-mass spectrometer (GC-MS) determination was adopted to analyze the above pesticide residues. The influencing factors as well as the health risks were also evaluated. Results show that PYRs and OPPs in human milk samples were both undetectable. Regarding OCPs, the detection rate of hexachlorobenzene (HCB), β-hexachlorocyclohexane (β-HCH) and p,p'-dichlorodiphenyl-dichloroethylene (p,p'-DDE) were 83.6%, 36.4% and 58.2%, respectively, and their mean value were 29.4, 32.0 and 85.2 ng/g lipid, respectively. p,p'-DDE levels in human milk was significantly (p < 0.05) related to maternal age, but no association was detected between OCPs residues and other factors (living environment, dietary habit, living style, etc.), suggesting that OCPs in human milk in Jinhua were originated from nonspecific source. All estimated daily intake of pesticides (EDIpesticides) by infants were under the guideline suggested by Food and Agriculture Organization (FAO) and China Ministry of Health (CMH). Yet 9% of EDIsHCB and 16% of EDIsHCHs exceeded the guideline recommended by Health Canada. The associations between DDE residues and the delivery way as well as HCBs residues and the birth weight were seemly significant, yet the significance disappeared when consider age or gestational age as a cofounder, indicating that OCPs residue in mother's body in Jinhua has no obvious influence on fetus development and the delivery way.
The selection of suitable shed profiles for station insulators with silicone rubber housings is an important subject for the successful operation of the HVDC and UHVDC systems. This subject has been discussed on a Seminar with a group of invited experts on external insulation. The participants recognized the lack of research results in this area. However, considering the urgent engineering needs for the coming UHVDC projects, after a review of the operational experiences of the existing 500-600 kV HVDC stations, especially the stations in China, the participants concluded the Seminar with preliminary recommendations on the decisive parameters of suitable shed profiles and a test method for shed profile selection. These recommendations are considered to be applicable to vertically installed HVDC station insulators with silicone rubber housing and with relative large diameters. At the same time, the participants encourage and invite utilities, manufacturers, and research institutes to be active on this subject and to provide more reliable test results.
Bi-axially oriented PEN film has superior performance in terms of dielectric strength, mechanical strength, heat resistance, anti-hydrolysis, etc. Thus, it has been widely used for energy storage applications, such as capacitors and batteries. In this paper, we attempted to increase the dielectric strength of PEN films by electron beam irradiation. PEN films of two different thickness, 6 µm and 12 µm, were exposed to an electron beam of 10 MeV energy. Improvement of breakdown strength was observed for both 6 µm and 12 µm PEN films. The largest increase was 13% for 12 µm PEN films with dosage of 100 kGy. The distribution of breakdown test results also improved upon irradiation as the increase of the shape parameter of Weilbull distribution. Post heat treatment slightly increased the dielectric strength for 12 µm but decreased the shape parameter of the breakdown test results for 6 µm.
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