Pesticide Residue Content in Vegetable Bases of Lhasa City

[Objectives]To understand the quality safety of vegetables produced in vegetable planting bases around Lhasa City.[Methods]Four vegetable planting bases in the east,west,south,and north of Lhasa City were randomly selected for testing using rapid measuring instrument for agricultural residues and solid-phase microextraction-gas chromatography-mass spectrometer,with 120 vegetable samples selected.The testing samples included seven categories:green leafy vegetables,eggplants,melons,onions and garlic,root vegetables,beans,and fungi,totaling 29 types of vegetables.The samples were tested for 8 common prohibited and restricted pesticides in organic phosphorus and carbamate esters,including methamidophos,parathion,methyl parathion,monocrotophos,isocarbophos,methamidophos,aldicarb,and carbofuran.[Results]The pesticide inhibition rate of 6 kinds of vegetables detected by the rapid measuring instrument for agricultural residues was relatively high,with green leafy vegetables being the majority,reaching over 25%.By further establishing a solid-phase microextraction-gas chromatography-tandem mass spectrometry method,the accuracy of the data was verified experimentally.The experimental results indicated that the inhibition rate of vegetable samples in this experiment did not exceed 15%,and it was determined as a pollution-free vegetable.[Conclusions]According to the restriction standard of national pesticide use,the inhibition rate of vegetable samples was less than or equal to 40%,indicating that the quality of vegetables was qualified.

A wideband,high-resolution vector spectrum analyzer for integrated photonics

The analysis of optical spectra—emission or absorption—has been arguably the most powerful approach for discovering and understanding matter.The invention and development of many kinds of spectrometers have equipped us with versatile yet ultra-sensitive diagnostic tools for trace gas detection,isotope analysis,and resolving hyperfine structures of atoms and molecules.With proliferating data and information,urgent and demanding requirements have been placed today on spectrum analysis with ever-increasing spectral bandwidth and frequency resolution.These requirements are especially stringent for broadband laser sources that carry massive information and for dispersive devices used in information processing systems.In addition,spectrum analyzers are expected to probe the device’s phase response where extra information is encoded.Here we demonstrate a novel vector spectrum analyzer(VSA)that is capable of characterizing passive devices and active laser sources in one setup.Such a dual-mode VSA can measure loss,phase response,and dispersion properties of passive devices.It also can coherently map a broadband laser spectrum into the RF domain.The VSA features a bandwidth of 55.1 THz(1260–1640 nm),a frequency resolution of 471 kHz,and a dynamic range of 56 dB.Meanwhile,our fiber-based VSA is compact and robust.It requires neither high-speed modulators and photodetectors nor any active feedback control.Finally,we employ our VSA for applications including characterization of integrated dispersive waveguides,mapping frequency comb spectra,and coherent light detection and ranging(LiDAR).Our VSA presents an innovative approach for device analysis and laser spectroscopy,and can play a critical role in future photonic systems and applications for sensing,communication,imaging,and quantum information processing.

Selective catalytic reduction of NO_(x) with NH_(3) over core-shell Ce@W catalyst

An environmentally benign WO_(3) wrapped cubic CeO_(2) core-shell catalyst(Ce@W)was developed for the selective catalytic reduction of NO_(x) with NH_(3).Compared with CeW particles prepared via the conventional co-precipitation method,this core-shell catalyst not only displays higher tolerance to SO_(2) and H_(2)O,but also exhibits a wider activity tempe rature window of 250-450℃,in which NO_(x)conversion and N_(2) selectivity reaches 100%.The improved performance of Ce@W catalysts can be contributed to the strong interactions between CeO_(2)(100) and WO_(3),which generates more Ce^(3+) and surface chemisorbed oxygen.In situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTs)reveal that the more thermally stable Br?nsted acid sites on Ce@W lead to its excellent high-temperature activity.

Homologous analysis on centromeric region sequences of A and B chromosomes from rye by FISH

Four centromeric segments from B chromosomes (Bs) of rye have been microdis-sected and amplified by linker adapter PCR (LA-PCR). The PCR products ranged from 100 to 2 000 bp. Fluorescence in situ hybridization (FISH) experiment has been carried out using PCR products as the probe, which was labeled by DIG-11-dUTP. The result confirms that these PCR products from Bs centromeric region are homologous with that of A chromosomes (As) in rye. It also proves that Bs are originated from As.