Nanograting inscription with a tightly focused femtosecond beam on the surface of fused silica was studied. The width and spacing of grooves are shown to decrease with the increase of the number of overlapped shots in both stationary and scanning cases. We propose a model to explain this behavior, based on both the so-called nanoplasmonic model and the incubation effect.

Lead (Pb) is a highly toxic element to the human body. After phasing out of leaded gasoline we find that the blood lead level of children strongly correlates with the lead concentration in atmospheric particles, and the latter correlates with the coal consumption instead of leaded gasoline. Combined with the (207)Pb/(206)Pb ratio measurements, we find that the coal consumption fly ash is a dominate source of Pb exposure to children in Shanghai, rather than vehicle exhaust, metallurgic dust, paint dust, and drinking water. Those particles are absorbed to children's blood via breathing and digesting their deposition on ground by hand-to-mouth activities. Probably the same situation occurs in other large cities of developing countries where the structure of energy supply is mainly based on coal-combustion.

Although the need for policy development on arsenic (As) in rice has been recognized and a legally enforceable maximum contaminant level (MCL) for inorganic arsenic (As(i)) in rice has been established in China, evidence reported in this article indicates that the risk of exposure to As for the Chinese population through rice is still underestimated. Polished rice from various production regions of China was analyzed for total As and arsenic species using HPLC-ICPMS. Total As concentration ranged 65.3-274.2 ng g(-1), with an average value of 114.4 ng g(-1). Four arsenic species, including arsenite (As(III)), arsenate (As(V)), dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA), were detected in most rice samples. The As(i) (As(III) + As(V)) species was predominant, accounting for approximately 72% of the total As in rice, with a mean concentration of 82.0 ng g(-1). In assessing the risk from As in rice, we found that As intake for the Chinese population through rice is higher than from drinking water, with a 37.6% contribution to the maximum tolerable daily intake (MTDI) of As recommended by World Health Organization (WHO), compared with 1.5% from drinking water. Compared to other countries, the risk for the Chinese from exposure to As through rice is more severe due to the large rice consumption in China. Therefore, not only the scientific community but also local authorities should take this risk seriously. Furthermore, more stringent legislation of the MCL for rice should be enacted to protect the Chinese consumer from a high intake of As.

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We have investigated the formation of nanogratings induced by femtosecond laser pulses on the surface of silica glass blocks. The nanograting period ranges between 170 and 340 nm, depending on the pulse-to-pulse spacing, whereas for a given spacing the period remains constant upon changing the laser pulse energy. Intensity clamping is proposed as the mechanism that is responsible for such independence of the grating period from pulse energy.

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Cytochrome P450 (CYP) 3A5 characterized with polymorphic and extensive expression in multiple tissues is the most important P450 enzyme among the minor CYP3A isoforms. However, a selective and sensitive probe for CYP3A5 remains unavailable. In this study, we identified and characterized a naturally occurring lignan 12 (schisantherin E) as an isoform-specific probe for selective detection of CYP3A5 activity in complex biological samples. With thorough characterization including LC-MS and NMR, we found that 12 can be metabolized by CYP3A5 to generate a major metabolite 2-O-demethylated 12. Meanwhile, both reaction phenotyping and chemical inhibition experiments further revealed that CYP3A5 selectively catalyzed the 2-O-demethylation of 12. Specifically, the interactions between the Phe210 residue of CYP3A5 and methyl benzoate of 12 might play key roles in 12-O-demethylation, which was revealed by docking simulation and site-directed mutagenesis studies. These findings are beneficial for exploring the role of CYP3A5 in drug metabolism and pathologic process.

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