科研成果

We derive the definition of the Berry phase for the adiabatic transport of a composite fermion (CF) in a half-filled composite Fermi liquid (CFL). It is found to be different from that adopted in previous investigations by Geraedts et al. For the standard CFL wave function, we analytically show that the Berry curvature is uniformly distributed in the momentum space. For the Jain-Kamilla wave function, we numerically show that its Berry curvature has a continuous distribution inside the Fermi sea and vanishes outside. We conclude that the CF with respect to both the microscopic wave functions is not a massless Dirac particle.

Ambient particulate matter (PM) is often used as a proxy of personal exposure in epidemiological studies of PM-induced health effects, yet whether this proxy biases the estimates of health effects is still unknown. On the basis of a panel study in Beijing, China, we investigated the dependence of 24 h personal exposure concentration to fine particles (PM2.5) and its carbonaceous components on the corresponding 24 h ambient concentration. The associated changes in inflammatory biomarkers with personal and ambient exposure were further examined using linear mixed-effect models. At ambient PM2.5 levels of \textless25 $μ$g m–3, personal exposure to PM2.5 was often several times higher, with a median personal/ambient ratio of ∼3. The ratio declined with an increase in ambient concentration, approaching ∼1 at ambient PM2.5 levels of \textgreater75 $μ$g m–3. Similar trends were also observed for organic carbon and elemental carbon. Personal exposures were significantly associated with both respiratory and systemic inflammatory biomarkers, such as fractional exhaled nitric oxide and white blood cell count. When ambient data were used, the association with systemic inflammation weakened. Our findings imply that the use of the ambient pollutant concentration as a proxy for personal exposure may be inaccurate and could bias the estimates of PM-induced health effects.

This article considers a bilinear model that includes two different latent effects. The first effect has a direct influence on the response variable, whereas the second latent effect is assumed to first influence other latent variables, which in turn affect the response variable. In this article, latent variables are modelled via rank restrictions on unknown mean parameters and the models which are used are often referred to as reduced rank regression models. This article presents a likelihood-based approach that results in explicit estimators. In our model, the latent variables act as covariates that we know exist, but their direct influence is unknown and will therefore not be considered in detail. One example is if we observe hundreds of weather variables, but we cannot say which or how these variables affect plant growth.

Heavy metal contamination poses considerable threats to various ecosystems, yet little is known about the assembly and adaptation of microbial communities at sites with combined heavy metal(loid) pollution. Here, we examined metal(loid) pollutants and bacterial communities in three zones (Zones I, II, and III) of an abandoned sewage reservoir with different usage years. The contamination level of multiple metal(loid)s was higher in Zone I than in the other zones, and arsenic (As), zinc (Zn), selenium (Se), copper (Cu), tin (Sn), molybdenum (Mo), antimony (Sb), cadmium (Cd), lead (Pb), thallium (TI), and nickel (Ni) were the major contaminants (pollution load index > 1). Bioavailable forms of titanium (Ti), chromium (Cr), Sn, and cobalt (Co) played essential roles in shaping the microbial structure, and physicochemical properties, especially organic matter (OM) and pH, also mediated the microbial diversity and composition in the metal(loid) contaminated zones. Metal-microbe interactions and heatmap analysis revealed that the bioavailability of metal(loid)s promoted the niche partitioning of microbial species. Metal-resistant species were abundant in Zone I that had the highest metal-contaminated level, whereas metal-sensitive species prevailed in Zone III that had the lowest pollution level. The bioavailable metal(loid)s rather than physicochemical and spatial variables explained a larger portion of the variance in the microbial community, and the homogeneous selection was the dominant ecological process driving the assembly of the microbial community. Overall, our study highlighted the importance of metal(loid) bioavailability in shaping microbial structure, future bioremediation, and environmental management of metal(loid) contaminated sites. (C) 2020 Elsevier Ltd. All rights reserved.

Bioorthogonal chemistry capable of operating in live animals is needed to investigate biological processes such as cell death and immunity. Recent studies have identified a gasdermin family of pore-forming proteins that executes inflammasome-dependent and -independent pyroptosis1,2,3,4,5. Pyroptosis is proinflammatory, but its effect on antitumour immunity is unknown. Here we establish a bioorthogonal chemical system, in which a cancer-imaging probe phenylalanine trifluoroborate (Phe-BF3) that can enter cells desilylates and ‘cleaves’ a designed linker that contains a silyl ether. This system enabled the controlled release of a drug from an antibody–drug conjugate in mice. When combined with nanoparticle-mediated delivery, desilylation catalysed by Phe-BF3 could release a client protein—including an active gasdermin—from a nanoparticle conjugate, selectively into tumour cells in mice. We applied this bioorthogonal system to gasdermin, which revealed that pyroptosis of less than 15% of tumour cells was sufficient to clear the entire 4T1 mammary tumour graft. The tumour regression was absent in immune-deficient mice or upon T cell depletion, and was correlated with augmented antitumour immune responses. The injection of a reduced, ineffective dose of nanoparticle-conjugated gasdermin along with Phe-BF3 sensitized 4T1 tumours to anti-PD1 therapy. Our bioorthogonal system based on Phe-BF3 desilylation is therefore a powerful tool for chemical biology; our application of this system suggests that pyroptosis-induced inflammation triggers robust antitumour immunity and can synergize with checkpoint blockade.

DNA methylation has fundamental roles in gene programming and aging that may help predict mortality. However, no large-scale study has investigated whether site-specific DNA methylation predicts all-cause mortality. We used the Illumina-HumanMethylation450-BeadChip to identify blood DNA methylation sites associated with all-cause mortality for 12, 300 participants in 12 Cohorts of the Heart and Aging Research in Genetic Epidemiology (CHARGE) Consortium. Over an average 10-year follow-up, there were 2,561 deaths across the cohorts. Nine sites mapping to three intergenic and six gene-specific regions were associated with mortality (P < 9.3x10(-7)) independently of age and other mortality predictors. Six sites (cg14866069, cg23666362, cg20045320, cg07839457, cg07677157, cg09615688)-mapping respectively to BMPR1B, MIR1973, IFITM3, NLRC5, and two intergenic regions-were associated with reduced mortality risk. The remaining three sites (cg17086398, cg12619262, cg18424841)-mapping respectively to SERINC2, CHST12, and an intergenic region-were associated with increased mortality risk. DNA methylation at each site predicted 5%-15% of all deaths. We also assessed the causal association of those sites to age-related chronic diseases by using Mendelian randomization, identifying weak causal relationship between cg18424841 and cg09615688 with coronary heart disease. Of the nine sites, three (cg20045320, cg07839457, cg07677157) were associated with lower incidence of heart disease risk and two (cg20045320, cg07839457) with smoking and inflammation in prior CHARGE analyses. Methylation of cg20045320, cg07839457, and cg17086398 was associated with decreased expression of nearby genes (IFITM3, IRF, NLRC5, MT1, MT2, MARCKSL1) linked to immune responses and cardiometabolic diseases. These sites may serve as useful clinical tools for mortality risk assessment and preventative care.

The stochastic solutions to the Wigner equation, which explain the nonlocal oscillatory integral operator $\Theta_V$ with an anti-symmetric kernel as the generator of two branches of jump processes,  are analyzed. All existing branching random walk solutions are formulated based on the Hahn-Jordan decomposition $\Theta_V=\Theta^+_V-\Theta^-_V$, i.e., treating $\Theta_V$ as the difference of two positive operators $\Theta^\pm_V$, each of which characterizes the transition of states for one branch of particles. Despite the fact that the first moments of such models solve the Wigner equation, we prove that the bounds of corresponding variances grow exponentially in time with the rate depending on the upper bound of $\Theta^\pm_V$, instead of $\Theta_V$. In other words, the decay of high-frequency components is totally ignored, resulting in a severe numerical sign problem. To fully utilize such decay property, we have recourse to the stationary phase approximation for $\Theta_V$, which captures essential contributions from the stationary phase points as well as the near-cancelation of positive and negative weights. The resulting branching random walk solutions are then proved to asymptotically solve the Wigner equation, but gain a substantial reduction in variances, thereby ameliorating the sign problem. Numerical experiments in 4-D phase space validate our theoretical findings. 

This paper aims at characterizing the bypass transition in boundary layers subject to strong pressure gradient and curvature effects. A series of highly resolved large-eddy simulations of a high-pressure turbine vane are performed, and the primary focus is on the effects of free-stream turbulence (FST) states on transition mechanisms. The turbulent fluctuations that have convected from the inlet first interact with the blunt blade leading edge, forming vortical structures wrapping around the blade. For cases with relatively low-level FST, streamwise streaks are observed in the suction-side boundary layer, and the instabilities of the streaks cause the breakdown to turbulence. Moreover, the varicose mode of streak instability is predominant in the adverse pressure gradient region, while the sinuous mode is more common in the (weak) favourable pressure gradient region. On the other hand, for cases with higher levels of FST, the leading-edge structures are more irregularly distributed and no obvious streak instability is observed. Accordingly, the transition onset occurs much earlier, through the breakdown caused by interactions between vortical structures. Comparing between different cases, it is the competing effect between the FST intensity and the stabilizing pressure gradient that decides the path to transition and also the transition onset, whereas the integral length scale of FST affects the scales of the streamwise streaks in the boundary layer. Furthermore, while the streaks in the low-level FST cases are mainly induced by leading-edge vortical structures, the corresponding fluctuations show a stage of algebraic growth despite the weak favourable pressure gradient and curvature.

A novel tubular graphitic carbon nitride (g-C3N4) modified with carbon quantum dots (CQDs) was fabricated and employed for the elimination of carbamazepine (CBZ) under visible light irradiation. The as-fabricated metal-free catalysts exhibited tubular morphologies due to the preforming of tubular protonated melamine with CQDs surface adsorption as the polymerization precursors. The surface bonded CQDs did not alter the band gap structure of g-C3N4, but greatly inhibited the charge recombination. Therefore, the CBZ degradation kinetics of tubular g-C3N4 were increased by over 5 times by the incorporation of CQDs. The main active species for CBZ degradation were found to be superoxide radical (O2−) and photo-generated holes (h+), which were further confirmed by electron spin resonance (ESR) analysis. In addition, the degradation pathways of CBZ were clarified via intermediates identification and quantum chemical computation using density functional theory (DFT) and wave function analysis. The olefinic double bond with the highest condensed Fukui index (f 0 = 0.108) in CBZ molecule was found to be the most preferable sites for radical attack. Moreover, good stability of the as-prepared photocatalysts was observed in the consecutive recycling cycles, while the slight decline of photocatalytic activity was attributed to the minimal surface oxidation.

Regional higher education growth in non-federal states has not attracted much academic attention. This paper is one of the first attempts to explore China's latest higher education expansion and its systematic and regional impact from the perspective of multi-level governance. This article argues that the state had explicitly utilized the Commanding Heights Strategy to diffuse the higher education authority to sub-national level and promote regional growth. The Central authorities allowed the Ministry of Education establishing a vertical elite coalition to command the heights of tertiary institutional hierarchy and key resources for tertiary development. In addition, the state used both financial incentives and sectoral incentives to mobilize resources for regional expansion. The Commanding Heights Strategy shapes China's response to the higher education trilemma of costs, access, and quality. Under this strategy, the unprecedented tertiary expansion has expanded college access, but at the expense of affordability, quality, and a large and increasing regional variation.

Downward feed injection scheme is more promising than traditionally upper feed injection scheme for FCC riser reactors, however, its effects on the whole riser performance have not been elaborated. This study aims at CFD modeling of hydrodynamics and chemical reactions in an industrial-scale riser reactor, with focus on the influence of downward feed injection scheme. For this purpose, a CFD model, verified earlier in a real industrial riser reactor, is extended to the present work. The hydrodynamics, temperature profile and species concentration distribution in the riser reactor with the downward feed injection scheme are numerically studied and compared to those in the upper feed injection scheme. The results indicate that different from the smooth evolution in the upward feed injection scheme, the gas velocity, particle content and riser temperature in the downward injection scheme exhibit local maximum value in the feed injection zone. In the middle and upper zones of the riser reactor, the downward 45° and 60° injections show lower gas velocity and riser temperature than the upward 60° injection while the downward 30° injection shows an opposite trend. The downward feed injection scheme with an angle of 45° and a velocity of 60 m/s is optimal for the present industrial-scale riser reactor. Compared to the traditionally upper feed injection scheme, the new downward feed injection scheme could enhance the yields of the diesel and gasoline species by 0.93 and 0.29% point and reduce the yields of the dry gas and coke species by 0.61 and 0.96 unit.