Unconventional exciton evolution from the pseudogap to superconducting phases in cuprates.

Electron quasiparticles play a crucial role in simplifying the description of many-body physics in solids with surprising success. Conventional Landau's Fermi-liquid and quasiparticle theories for high-temperature superconducting cuprates have, however, received skepticism from various angles. A path-breaking framework of electron fractionalization has been established to replace the Fermi-liquid theory for systems that show the fractional quantum Hall effect and the Mott insulating phenomena; whether it captures the essential physics of the pseudogap and superconducting phases of cuprates is still an open issue. Here, we show that excitonic excitation of optimally doped Bi2Sr2CaCu2O8+δ with energy far above the superconducting-gap energy scale, about 1 eV or even higher, is unusually enhanced by the onset of superconductivity. Our finding proves the involvement of such high-energy excitons in superconductivity. Therefore, the observed enhancement in the spectral weight of excitons imposes a crucial constraint on theories for the pseudogap and superconducting mechanisms. A simple two-component fermion model which embodies electron fractionalization in the pseudogap state provides a possible mechanism of this enhancement, pointing toward a novel route for understanding the electronic structure of superconducting cuprates.

Prognostic relevance and therapeutic implications of centromere protein F expression in patients with esophageal squamous cell carcinoma.

Centromere protein F (CENP-F), a cell cycle-regulated centromere protein, has been shown to affect numerous tumorigenic processes. This study aimed to clarify the prognostic significance of CENP-F expression in patients with esophageal squamous cell carcinoma (ESCC). The levels of CENP-F messenger RNA and protein were higher in ESCC cell lines than in the normal tissues. An immunohistochemical analysis of paired tissue specimens showed that the CENP-F expression was higher in tumorous tissues than in the adjacent non-tumorous tissues (P < 0.001). Moreover, there was a significant correlation between CENP-F expression and gender (P = 0.012), clinical stage (P = 0.039), and T classification (P = 0.026). Patients with higher CENP-F expression had shorter overall survival than those with lower CENP-F expression (P = 0.009). Multivariate Cox analysis indicated that CENP-F expression is an independent prognostic factor for overall survival (hazard ratio = 0.582, 95% confidence interval = 0.397-0.804, P = 0.041). Importantly, it was found that zoledronic acid (ZOL) could significantly enhance the chemotherapeutic sensitivity of ESCC cell lines with high CENP-F expression to cisplatin, although ZOL alone only exhibited a minor inhibitory effect to ESCC cells. In summary, these findings demonstrate that CENP-F may serve as a valuable molecular marker for predicting the prognosis of ESCC patients. In addition, the data indicate a potential benefit of combining ZOL with cisplatin in ESCC, suggesting that CENP-F expression may have therapeutic implications.