科研成果

Traditional chemical disinfectants are becoming increasingly defective due to the generation of carcinogenic disinfection byproducts and the emergence of antibiotic-resistant bacterial strains. Functionalized magnetic nanoparticles yet have shown great application potentials in water treatment processes especially for bacterial removal. In this study, three types of amino acids (arginine, lysine, and poly-l-lysine) functionalized Fe3O4 nanoparticles (Fe3O4@Arg, Fe3O4@Lys, and Fe3O4@PLL) were prepared through a facile and inexpensive two-step process. The amino acid modified Fe3O4 nanoparticles (Fe3O4@AA) showed rapid and efficient capture and removal properties for both Gram-positive Bacillus subtilis (B. subtilis) and Gram-negative Escherichia coli 15597 (E. coli). For both strains, more than 97% of bacteria (initial concentration of 1.5 × 107 CFU mL−1) could be captured by all three types of magnetic nanoparticles within 20 min. With E. coli as a model strain, Fe3O4@AA could remove more than 94% of cells from solutions over a broad pH range (from 4 to 10). Solution ionic strength did not affect cell capture efficiency. The co-presence of sulfate and nitrate in solutions did not affect the capture efficiency, whereas, the presence of phosphate and silicate slightly decreased the removal rate. However, around 90% and 80% of cells could be captured by Fe3O4@AA even at 10 mM of silicate and phosphate, respectively. Bacterial capture efficiencies were over 90% and 82% even in the present of 10 mg L−1 of humic acid and alginate, respectively. Moreover, Fe3O4@AA nanoparticles exhibited good reusability, and greater than 90% of E. coli cells could be captured even in the fifth regeneration cycle. The results showed Fe3O4@AA fabricated in this study have great application potential for bacteria removal from water.

We present experimental studies on the conversion efficiency of fusion neutrons generated from Coulomb explosion of cryogenically cooled heteronuclear deuterated methane (CD 4 ) clusters irradiated by intense femtosecond laser pulses. A stronger nonlinear relationship between the cluster size and the stagnation temperature for CD 4 clusters than that for monoatomic or diatomic clusters is revealed, resulting in marked increases in the average kinetic energy of deuterons and the fusion neutron yield. Finally, a significantly enhanced conversion efficiency of 1.9 × 10 7 neutrons/J of incident laser energy is achieved by lowering the stagnation temperature to 217 K under a backing pressure of 80 bars.

A highly efficient recognition phenomenon was observed between alkoxylated arylene-ethynylene macrocycles bearing identical side chains but different core size, which is based on van der Waals interactions between alkoxy chains. The ratio of both molecules and the environment of each molecule have been statistically analyzed to quantify the recognition efficiency.

As the world's second largest economy, China has experienced severe haze pollution, with fine particulate matter ( PM) recently reaching unprecedentedly high levels across many cities, and an understanding of the PM formation mechanism is critical in the development of efficient mediation policies to minimize its regional to global impacts. We demonstrate a periodic cycle of PM episodes in Beijing that is governed by meteorological conditions and characterized by two distinct aerosol formation processes of nucleation and growth, but with a small contribution from primary emissions and regional transport of particles. Nucleation consistently precedes a polluted period, producing a high number concentration of nano-sized particles under clean conditions. Accumulation of the particle mass concentration exceeding several hundred micrograms per cubic meter is accompanied by a continuous size growth from the nucleation-mode particles over multiple days to yield numerous larger particles, distinctive from the aerosol formation typically observed in other regions worldwide. The particle compositions in Beijing, on the other hand, exhibit a similarity to those commonly measured in many global areas, consistent with the chemical constituents dominated by secondary aerosol formation. Our results highlight that regulatory controls of gaseous emissions for volatile organic compounds and nitrogen oxides from local transportation and sulfur dioxide from regional industrial sources represent the key steps to reduce the urban PM level in China.

As the world's second largest economy, China has experienced severe haze pollution, with fine particulate matter ( PM) recently reaching unprecedentedly high levels across many cities, and an understanding of the PM formation mechanism is critical in the development of efficient mediation policies to minimize its regional to global impacts. We demonstrate a periodic cycle of PM episodes in Beijing that is governed by meteorological conditions and characterized by two distinct aerosol formation processes of nucleation and growth, but with a small contribution from primary emissions and regional transport of particles. Nucleation consistently precedes a polluted period, producing a high number concentration of nano-sized particles under clean conditions. Accumulation of the particle mass concentration exceeding several hundred micrograms per cubic meter is accompanied by a continuous size growth from the nucleation-mode particles over multiple days to yield numerous larger particles, distinctive from the aerosol formation typically observed in other regions worldwide. The particle compositions in Beijing, on the other hand, exhibit a similarity to those commonly measured in many global areas, consistent with the chemical constituents dominated by secondary aerosol formation. Our results highlight that regulatory controls of gaseous emissions for volatile organic compounds and nitrogen oxides from local transportation and sulfur dioxide from regional industrial sources represent the key steps to reduce the urban PM level in China.

The purpose of this study is to analyze the recent development of Chinese vocational colleges from two perspectives: the adoption of employability as a new institutional mission and organizational changes in six areas. The analysis is based on a multiple-case study. The analytical frameworks are developed from sociological theory and organizational theory. This study argues that vocational colleges in China are experiencing substantial transformations. At the macro level, they are transforming from a social institution to industry under the neoliberal argument for globalization. Colleges adopt employability as their new mission. At the micro level, there are considerable changes under the influence of the new mission, in terms of program goal, program development, curriculum development, dominant pedagogy, faculty development, and internal management. The changes fit the rhetoric of employability as a core competency. There is a tendency that Chinese vocational higher education institutions will degenerate into training organizations for employment.