The K\"ahler-Ricci flow on surfaces of positive Kodaira dimension

The existence of K\"ahler-Einstein metrics on a compact K\"ahler manifold has been the subject of intensive study over the last few decades, following Yau's solution to Calabi's conjecture. The Ricci flow, introduced by Richard Hamilton has become one of the most powerful tools in geometric analysis. We study the K\"ahler-Ricci flow on minimal surfaces of Kodaira dimension one and show that the flow collapses and converges to a unique canonical metric on its canonical model. Such a canonical is a generalized K\"ahler-Einstein metric. Combining the results of Cao, Tsuji, Tian and Zhang, we give a metric classification for K\"aher surfaces with a numerical effective canonical line bundle by the K\"ahler-Ricci flow. In general, we propose a program of finding canonical metrics on canonical models of projective varieties of positive Kodaira dimension

Engineering d-band center of FeN<inf>4</inf> moieties for efficient oxygen reduction reaction electrocatalysts

Atomically-dispersed FeN4 moieties are emerging as low-cost electrocatalysts for oxygen reduction reaction (ORR), which can be applied in fuel cells and metal-air batteries. Whereas, the unsatisfactory position of the d-band center from the metal sites offered by FeN4 affects the adsorption-desorption behaviors of oxygenated intermediates, further impeding the improvement of their ORR performances. Herein, we report a well-designed diatomic Fe/Zn-CNHC catalyst on a microporous hollow support. This strategy drives the position of the d-band center of Fe upward, thus making FeN4 active sites more favorable and stable during the ORR kinetic processes. The material exhibits an excellent ORR activity with a half-wave potential of 0.91 V and excellent stability (insignificant attenuation after 5,000 cycles), surpassing commercial Pt/C and many other single-atom catalysts. DFT calculations further indicate that the tuning effect of Zn on the d-orbital electron distribution of Fe facilitates the stretching and cleavage of Fe-O, thus accelerating the rate-determining step. This work presents a simple strategy to fabricate well-defined diatomic coordination in single-atom ORR electrocatalysts and inspires future research on developing new syntheses to control the coordination of single-atom electrocatalysts

Potent Charge-Trapping for Boosted Electrocatalytic Oxygen Reduction

Metal-free carbon-based materials are considered to be one of the most promising alternatives to precious metal Pt-based electrocatalysts. However, the electrocatalytic activity of heteroatom-modulated carbon rarely reaches the level of metal-based electrocatalysts. Here, electron-rich carbon and abundant pyridinic-N adjacent to C vacancies decorated with carbon nanosheets (E-NC-V) are synthesized and used as the host for boosting efficient oxygen reduction reaction. Rich pyridinic-N structures adjacent to C vacancies work in synergy with electron-rich carbon, which promotes the sharp decrease of |ΔGO*|, resulting in the balanced adsorption and dissociation of oxygen intermediates, and thus activating OO. This can be attributed to the abundant vacancies and d–p orbital hybridization between Zn and N/C. The E-NC-V catalyst drives the oxygen reduction reaction (ORR) via a 4e− transfer-dominated pathway with a half-wave potential of 0.87 V versus RHE in the alkaline solution, even superior to Pt/C. The assembled Al–air battery exhibits a high peak power density of 113 mW cm^{−2}. This promising strategy sheds light on the design and fabrication of robust, rich-density, and high-performance active sites for the ORR. The work is expected to inspire future work on the role of electronic structure modulation and defect engineering for enhanced reaction kinetics

Birational cobordism invariance of uniruled symplectic manifolds

A symplectic manifold $(M,\omega)$ is called {\em (symplectically) uniruled} if there is a nonzero genus zero GW invariant involving a point constraint. We prove that symplectic uniruledness is invariant under symplectic blow-up and blow-down. This theorem follows from a general Relative/Absolute correspondence for a symplectic manifold together with a symplectic submanifold. A direct consequence is that symplectic uniruledness is a symplectic birational invariant. Here we use Guillemin and Sternberg's notion of cobordism as the symplectic analogue of the birational equivalence.Comment: To appear in Invent. Mat

Association of 6-Minute Walk Performance and Physical Activity With Incident Ischemic Heart Disease Events and Stroke in Peripheral Artery Disease.

BackgroundWe determined whether poorer 6-minute walk performance and lower physical activity levels are associated with higher rates of ischemic heart disease (IHD) events in people with lower extremity peripheral artery disease (PAD).Methods and resultsFive hundred ten PAD participants were identified from Chicago-area medical centers and followed prospectively for 19.0±9.5 months. At baseline, participants completed the 6-minute walk and reported number of blocks walked during the past week (physical activity). IHD events were systematically adjudicated and consisted of new myocardial infarction, unstable angina, and cardiac death. For 6-minute walk, IHD event rates were 25/170 (14.7%) for the third (poorest) tertile, 10/171 (5.8%%) for the second tertile, and 6/169 (3.5%) for the first (best) tertile (P=0.003). For physical activity, IHD event rates were 21/154 (13.6%) for the third (poorest) tertile, 15/174 (8.6%) for the second tertile, and 5/182 (2.7%) for the first (best) tertile (P=0.001). Adjusting for age, sex, race, smoking, body mass index, comorbidities, and physical activity, participants in the poorest 6-minute walk tertile had a 3.28-fold (95% CI 1.17 to 9.17, P=0.024) higher hazard for IHD events, compared with those in the best tertile. Adjusting for confounders including 6-minute walk, participants in the poorest physical activity tertile had a 3.72-fold (95% CI 1.24 to 11.19, P=0.019) higher hazard for IHD events, compared with the highest tertile.ConclusionsSix-minute walk and physical activity predict IHD event rates in PAD. Further study is needed to determine whether interventions that improve 6-minute walk, physical activity, or both can reduce IHD events in PAD

FOXO1 Regulates Bacteria-Induced Neutrophil Activity

Neutrophils play an essential role in the innate immune response to microbial infection and are particularly important in clearing bacterial infection. We investigated the role of the transcription factor FOXO1 in the response of neutrophils to bacterial challenge with Porphyromonas gingivalis in vivo and in vitro. In these experiments, the effect of lineage-specific FOXO1 deletion in LyzM.Cre+FOXO1L/L mice was compared with matched littermate controls. FOXO1 deletion negatively affected several critical aspects of neutrophil function in vivo including mobilization of neutrophils from the bone marrow (BM) to the vasculature, recruitment of neutrophils to sites of bacterial inoculation, and clearance of bacteria. In vitro FOXO1 regulated neutrophil chemotaxis and bacterial killing. Moreover, bacteria-induced expression of CXCR2 and CD11b, which are essential for several aspects of neutrophil function, was dependent on FOXO1 in vivo and in vitro. Furthermore, FOXO1 directly interacted with the promoter regions of CXCR2 and CD11b. Bacteria-induced nuclear localization of FOXO1 was dependent upon toll-like receptor (TLR) 2 and/or TLR4 and was significantly reduced by inhibitors of reactive oxygen species (ROS and nitric oxide synthase) and deacetylases (Sirt1 and histone deacetylases). These studies show for the first time that FOXO1 activation by bacterial challenge is needed to mobilize neutrophils to transit from the BM to peripheral tissues in response to infection as well as for bacterial clearance in vivo. Moreover, FOXO1 regulates neutrophil function that facilitates chemotaxis, phagocytosis, and bacterial killing