Hot-carrier transfer at photocatalytic silicon/platinum interfaces.

Interfacial charge transfer from silicon to heterogeneous catalysts plays a key role in silicon-based photoelectrochemical systems. In general, prior to interfacial charge transfer, carriers that are generated by photons with energies above the bandgap dissipate the excess kinetic energy via hot-carrier cooling, and such energy loss limits the maximum power conversion efficiency. The excess energy of hot-carriers, however, could be utilized through hot-carrier transfer from silicon to the catalysts, but such hot-carrier extraction has not yet been demonstrated. Here, we exploit transient reflection spectroscopy to interrogate charge transfer at the interface between silicon and platinum. Quantitative modeling of the surface carrier kinetics indicates that the velocity of charge transfer from silicon to platinum exceeds 2.6 × 107 cm s-1, corresponding to an average carrier temperature of extracted carriers of ∼600 K, two times higher than the lattice temperature. The charge transfer velocity can be controllably reduced by inserting silica spacing layers between silicon and platinum.

Identification of candidate genes simultaneously shared by adipogenesis and osteoblastogenesis from human mesenchymal stem cells.

INTRODUCTION: In osteoporosis field, it had been clinically well established a given relationship between bone formation and lipid accumulation. Although numerous molecules had been well documented for adipogenesis and osteoblastogenesis (adipo-osteoblastogenesis), the reciprocal transcriptional regulation still remains to be explored. MATERIAL AND METHODS: Here, we tried to identify the common candidate genes of adipocyte/osteoblastocyte differentiation at 3, 5, and 7 days using human mesenchymal stem cells (hMSCs) via RNA-Seq technique. By using RNA interference (RNAi), we further confirmed the function of candidate genes during adipo-osteoblastogenesis through Oil Red/Alizarin Red/alkaline phosphatase (ALPL) staining and qRT-PCR (quantitative real-time PCR). RESULTS: The identified 275 significantly differentially expressed genes (DEGs), especially with the down-regulated genes most prevalent and PI3K-AKT signaling pathway mostly enriched, were simultaneously shared by both differentiation events. Using lentiviral system, we further confirmed that ANKRD1 (ankyrin repeat domain 1) promoted adipogenesis and inhibited osteoblastogenesis via RNA interference (RNAi), and IGF1 (insulin like growth factor 1) simultaneously facilitated adipo-osteoblastogenesis on the base of gene expression of biomarkers and cellular phenotype property. CONCLUSION: This study would provide the potential molecular switches to control the adipocyte/osteoblastocyte balance or hMSCs fate choices and clues to screen the study and therapy targets of metabolic bone disease osteoporosis.

Recombination of Polaronic Electron-Hole Pairs in Hematite Determined by Nuclear Quantum Tunneling.

Here, we investigate the intrinsic nonradiative recombination mechanism in hematite single crystals that decides the photocarrier lifetime under solar illumination. On the basis of the small polaron theory, we propose that the photogenerated electron-hole pair along with its induced lattice deformation in hematite could be treated as a pseudocoordination-complex (PCC) dispersed in a solid medium. We demonstrate that the nonradiative recombination rate at different temperatures determined from the transient absorption spectroscopy can be excellently described by the nonradiative transition theory developed previously for parallels of the PCC model. Our finding suggests that at room temperature the nonradiative recombination in hematite substantially depends on the probability of quantum tunneling of the nuclear configuration.

Micro-Heterogeneous Annihilation Dynamics of Self-Trapped Excitons in Hematite Single Crystals.

The Auger recombination in bulk semiconductors can quickly depopulate the charge carriers in a nonradiative way, which, fortunately, only has a detrimental impact on optoelectronic device performance under the condition of high carrier density because the restriction arising from concurrent momentum and energy conservation limits the Auger rate. Here, we surprisingly observed enhanced Auger recombination in an α-Fe2O3 single crystal, a wide bandgap semiconductor with low carrier mobility. The Auger process was ascribed to the Coulombically coupled self-trapped excitons (STEs), and the relaxation of momentum conservation due to the strong spatial localization of these STEs should account for the enhancement. The STE-density dependent kinetics suggested that the strong polaronic effect could cause a micro-heterogeneous distribution of STEs in a high-quality bulk single crystal, which also gave rise to the micro-heterogeneous annihilation dynamics, and a stochastic recombination model was developed and successfully described the STE annihilation dynamics.

Large-scale expressed sequence tag analysis for the chestnut blight fungus Cryphonectria parasitica.

Cryphonectria parasitica is the causal fungal agent responsible for the chestnut blight disease. We report the generation of 14,263 expressed sequence tags representing 6318 unisequences for the fungus. Functional annotation of these unisequences revealed different gene expression patterns for wild-type and hypovirus-infected cultures at the sporulation stage and allowed the reconstruction of key C. parasitica signal transduction pathways conserved in the Sorbidaryomycetes. A list of homologous genes implicated in pathogenicity, sporulation, and virus replication in other fungi were also identified. A large-scale gene comparison indicated that C. parasitica is most closely related to the plant pathogen Fusarium graminearum but more closely related to the non-pathogen Neurospora crassa than to the rice pathogen Magnaporthe grisea. This transcriptional information lays a new and solid ground for further investigation of both the biology of the fungus and interaction between a hypovirus and the host fungus.

A systematic molecular pathology study of a laboratory confirmed H5N1 human case.

Autopsy studies have shown that human highly pathogenic avian influenza virus (H5N1) can infect multiple human organs other than just the lungs, and that possible causes of organ damage are either viral replication and/or dysregulation of cytokines and chemokines. Uncertainty still exists, partly because of the limited number of cases analysed. In this study, a full autopsy including 5 organ systems was conducted on a confirmed H5N1 human fatal case (male, 42 years old) within 18 hours of death. In addition to the respiratory system (lungs, bronchus and trachea), virus was isolated from cerebral cortex, cerebral medullary substance, cerebellum, brain stem, hippocampus ileum, colon, rectum, ureter, aortopulmonary vessel and lymph-node. Real time RT-PCR evidence showed that matrix and hemagglutinin genes were positive in liver and spleen in addition to positive tissues with virus isolation. Immunohistochemistry and in-situ hybridization stains showed accordant evidence of viral infection with real time RT-PCR except bronchus. Quantitative RT-PCR suggested that a high viral load was associated with increased host responses, though the viral load was significantly different in various organs. Cells of the immunologic system could also be a target for virus infection. Overall, the pathogenesis of HPAI H5N1 virus was associated both with virus replication and with immunopathologic lesions. In addition, immune cells cannot be excluded from playing a role in dissemination of the virus in vivo.