Aflatoxin B 1 (AFB 1) contamination in foods is an important health challenge for low-and middle-income countries in subtropical regions. AFB 1 has been detected in a variety of foodsin Guangzhou, while the risk of dietary exposure is unknown. this study aimed to assess the probabilistic risk of dietary exposure to AFB 1 contamination in food stuffs in Guangzhou by using margin of exposure (MOE) and quantitative liver cancer risk approaches. A total of1854 AFB 1-contaminated foodstuffs were sampled in supermarkets, agricultural markets, retail shops, and family workshops from 11 districts of Guangzhou, and AFB 1 content was determined by HPLC-fluorescence detector. In total, 9.9% (184/1854) of the test samples had AFB 1 concentrations above the limit of detection. Home-made peanut oil had the highest AFB 1 concentration, with a mean value of 38.74 ± 47.45 μg kg −1. The average MOE levels of Guangzhou residents ranged from 100 to 1000. The risk of liver cancer was 0.0264 cancers (100,000 population year) −1. the health risks of suburban people were higher than those of urban people, and home-made peanut oil was the main contributorto dietary exposure to AFB 1 among suburban residents in Guangzhou. The production of home-made peanut oil should be supervised to reduce the risk of AFB 1 exposure. Aflatoxins (AFs) are mycotoxins produced by the common fungi Aspergillus flavusand Aspergillus parasiticus 1 and have been found in a wide range of crops such as maize, peanut, and walnut and their derived products 2. There are four major aflatoxins (AFB 1 , AFB2, AFG1, and AFG2) produced by the two fungi that commonly found in contaminated crops 3-5. AFB 1 and AFB 2 can be produced by A. flavus (both S and L strains) and A. parasiticus, whileAFG 1 and AFG 2 can be produced by A. flavus S strains and A. parasiticus 5,6. AFB 1 is considered the most toxic carcinogenwhich is classified as Group 1 human carcinogen by the International Agency for Research on Cancer (IARC)that induces mainly liver cancer 7-9 and to a lesser degree rectal cancer 10. AFB 1 is commonly found in cereals and nuts 11 , and it has attracted concern in lessdeveloped tropical regions 12-15. Previous studies showed that AFs were found in 5%-30%of raw peanuts and peanut products in major peanut-producing regions in China 16. Since some crops susceptible to AFs contamination, such as peanuts, are commonly consumed, it is hard to achieve zero exposure to AFs. Therefore, it is important to reduce the exposure to total AFsby establishing regulatory limits to AFs.The Codex Alimentarius Commission, the Joint Food and Agriculture Organization (FAO), and the World Health Organization (WHO) Food Standards Program jointly adopted a maximum level of 15 μg kg − 1 for total AFsin unprocessed peanuts 17. The European Commission regulation (EC) No. 1881/2006 set a maximum limit for AFB 1 of 2 μg kg −1 for peanuts and cereals that are intended for direct consumption 18. In China, the National Food Safety Standard set the limit of 20 µg kg −1 for AFB 1 in peanut and its pro...

A compact dual-band bandpass filter implemented with an embedded coplanar waveguide (ECPW) resonator and a capacitively loaded resonator (CLR) in substrate integrated waveguide (SIW) cavity is presented and analyzed in this paper. Three transmission zeroes (TZs), of which two are located in the middle of the two passbands and one located in the upper stopband, are obtained to improve the inner-band isolation and the selectivity of the filter. The center frequencies and bandwidths of the two passbands can be easily tuned by changing the geometrical parameters of the two resonators. The proposed dual-band SIW filter is demonstrated with center frequencies located at 8.41/14.29 GHz. The measured insertion loss is −1.28/ − 1.91 dB with the corresponding fractional bandwidth (FBW) of 21.2%/7.3%. The measured results are in good agreement with the simulated ones.

The appearance of unconventional vacuum properties in intense fields has long been an active field of research. In this paper the vacuum polarization effect is investigated via a pump probe scheme of a probe light propagating in the vacuum excited by two counter-propagating laser beams. The modified light cone condition of the probe light is derived analytically for the situation that it passes through the electric/magnetic antinode plane of the pump field. The derivation does not follow the commonly adopted assumption of treating the pump field as a constant field. Differences from the conventional light cone conditions are identified. The implications of the result are discussed with a consideration of the vacuum birefringence measurement.

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Nonperturbative calculation of QED processes participated by a strong electromagnetic field, especially provided by strong laser facilities at present and in the near future, generally resorts to the Furry picture with the usage of analytical solutions of the particle dynamical equation, such as the Klein-Gordon equation and Dirac equation. However only for limited field configurations such as a plane-wave field could the equations be solved analytically. Studies have shown significant interests in QED processes in a strong field composed of two counter-propagating laser waves, but the exact solutions in such a field is out of reach. In this paper, inspired by the observation of the structure of the solutions in a plane-wave field, we develop a new method and obtain the analytical solution for the Klein-Gordon equation and equivalently the action function of the solution for the Dirac equation in this field, under a largest dynamical parameter condition that there exists an inertial frame in which the particle free momentum is far larger than the other field dynamical parameters. The applicable range of the new solution is demonstrated and its validity is proven clearly. The result has the advantage of Lorentz covariance, clear structure and close similarity to the solution in a plane-wave field, and thus favors convenient application.

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