Soot, mainly derived from incomplete combustion of fossil fuel and biomass, exists ubiquitously in different environmental matrixes. To study the detrimental effects of soot on climate, air quality, and human health, accurate quantification of soot is an important prerequisite. However, until now, quantification of soot in environmental media, especially in carbonaceous media, is still very challenging. Here, we report a matrix-free laser desorption/ionization mass spectrometry (LDI-MS) method for in situ imaging of soot particles in size-segregated aerosol samples collected on filter membranes. A series of round-shaped sample spots in filter membranes were selected and subjected to MS imaging analysis, enabling direct in situ quantification of soot without solvent extraction or separation. Especially, the MS imaging with serial sample spots can overcome the problems of sweet-spot in LDI-MS and inhomogeneous distribution of soot in the filter membrane, thus greatly improving the precision of quantification. The limit of detection of soot was 4 ng/m2 and the recovery was 84.4–126%. By using this method, we found that a higher soot content was present in larger-sized particulate matter than smaller-sized particles, suggesting that aerosol soot was mainly derived from primary emission sources. Furthermore, this method also shows the potential to analyze nitrate and sulfate species in PM2.5. To the best of our knowledge, it is the first method capable of simultaneous analysis of inorganic salts and soot in air samples. It represents a novel strategy for in situ quantification of aerosol soot with the advantages of high specificity, high sensitivity, separation-, solvent- and matrix-free.
The effects of surface-induced evaporative cooling on an atom chip are investigated. The evolutions of temperature, number and phase-space density of the atom cloud are measured when the atom cloud is brought close to the surface. Rapid decrease of the temperature and number of the atoms is found when the atom-surface distance is 8 ms. It is important that the surface-induced evaporative cooling offers novel possibilities for the realization of a continuous condensation, where a spatially varying evaporative cooling is required.
The research progress of glyphosate production by the oxidation of N-(phosphonomethyl)iminodiacetic acid with oxygen or oxygen-containing gas as oxidizing agent in the presence of catalysts was reviewed.
3D printing, a technology that allows the layer-by-layer construction of complex 3D structures from a range of precursor materials, has shown promising applicability in construction and in the automotive, aerospace, defense, biomedicine, and consumer electronics industries. A key concern, however, is the health effects and safety problems due to its emission of fine particles (PM2.5, particles with aerodynamic diameters of <2.5 μm) and volatile organic compounds (VOCs). Understanding the characteristics and relevant toxicological effects of 3D printing-emitted PM2.5 and VOCs is important for its health risk assessment and safe application. Here, we thoroughly review the emission levels of PM2.5 and VOCs in workplaces, the simulation tests of laboratory environment, and the in vitro and in vivo evaluation of 3D printing-emitted PM2.5 and VOCs. Meanwhile, standard protocols are recommended in the assessment of hazard risks of 3D printers to obtain better comparability of the results. Some safety guidance for 3D printer users is also provided. Finally, we point out the current research gaps and discuss the challenges encountered in this field. This review will be beneficial for the understanding of the health risks of emitted PM2.5 and VOCs from 3D printing for the development of safer 3D printing technologies.
We propose a scheme to implement single-qubit operations for singlet-triplet qubits located in an isolated double-well potential with fixed inter-site tunneling when superexchange interactions predominate. Arbitrary single-qubit gates can be realized by a sequence composed of two elementary operations which can be switched between different parameter regimes by adjusting slightly the relative energy bias of trapped atoms in each sub-well site. The experimental feasibility of the strategy and the fidelity of basic rotation operations are also analyzed.
We propose a tailored-waveguide based photonic chip with the functions of trapping, coherently manipulating, detecting and individually addressing an array of single neutral atoms. Such photonic chip consists of an array of independent functional units spaced by a few micrometers, each of which is comprised of one silica-on-silicon optical waveguide and one phase Fresnel microlens etched in the middle of the output interface of the optical waveguide. We fabricated a number of photonic chips with 7 functional units and measured optical characteristics of these chips. We further propose feasible schemes to realize the functions of such photonic chip. The photonic chip is stable, scalable and can be combined with other integrated devices, such as atom chips, and can be used in the future hybrid quantum system and photonic quantum devices.
With the increasing use of metal–organic frameworks (MOFs), they will inevitably enter the environment intentionally or unintentionally. However, the effects of MOFs on plant growth are poorly understood. Here, we investigated the effects of exposure of the rhizosphere to MOFs on plant growth. MIL-101(Cr) was selected as a research model due to its commercial availability and wide use. Soybean plants at the two-leaf stage were subjected to various durations (1–7 days) and concentrations (0–1000 mg/L) of exposure in hydroculture with a control group treated with ultrapure water. We found that MIL-101(Cr) had a positive effect on soybean growth at a lower dose (i.e., 200 mg/L); however, at higher doses (i.e., 500 and 1000 mg/L), it exhibited significant toxicity to plant growth, which is evidenced by leaf damage. To investigate the mechanism of this effect, we used Cr as an indicator to quantify, track, and image MIL-101(Cr) in the plant with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Results indicated that MIL-101(Cr) primarily accumulated in the cortex of roots (up to 40 times higher than that in stems), with limited translocation to stems and negligible presence in leaves and cotyledons. In addition, metabolomic analysis of soybeans indicated that low-dose MIL-101(Cr) could increase the sucrose content of soybean roots to promote plant growth, while a high dose could induce lipid oxidation in roots. This study provides valuable insights into the ecological toxicology of MOFs and underscores the importance of assessing their environmental impact for sustainable agricultural practices.
The quantitative analysis of glyphosate and N-(phosphonomethyl)iminodiacetic acid was conducted using HPLC with potassium dihydrogen phosphate buffer solution as mobile phase, Hypersil SAX column, flow rate: 0.8 mL/min, using UV detector at 195 nm wavelength to quantitative analysis glyphosate and N-(phosphonomethyl)iminodiacetic acid at the same column. The results showed that linear correlation for glyphosate and N-(phosphonomethyl)iminodiacetic acid were 0.999 9 and 0.998 4, the standard deviation were 0.089 9 and 0.770 1, the variation coefficient were 0.162 0% and 0.966 0%, respectively.
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