A high resolution electron energy loss spectroscopy study of the Fermi resonance of CO₂ adsorbed on a Ag(110)/CO₃ layer

The adsorption of CO2 on a Ag(110) surface precovered with a saturated CO3 layer has been studied by high resolution electron energy loss spectroscopy (HREELS). A weakly bound state of CO2 is stabilized by the presence of carbonate. In addition to the losses of the bend (658 cm−1) and the antisymmetric stretch (2343 cm−1) fundamental modes, the presence of two peaks in the frequency region of the symmetric stretch mode have been observed. Such a loss pair is characteristic for the existence of a Fermi resonance, between the overtone of the bend and the symmetric stretch vibration, which had been studied in detail for the gas phase CO2 molecule. By use of three CO2 isotopomers the existence of the Fermi resonance in the adsorbed state has been verified and the Fermi constant and the energy of the unperturbed vibrations have been determined from the isotopic shifts. The character of the CO2 molecule is almost unaffected by the bonding and it adsorbs in a tilted geometry

Characteristics of phonon transmission across epitaxial interfaces: a lattice dynamic study

Phonon transmission across epitaxial interfaces is studied within the lattice dynamic approach. The transmission shows weak dependence on frequency for the lattice wave with a fixed angle of incidence. The dependence on azimuth angle is found to be related to the symmetry of the boundary interface. The transmission varies smoothly with the change of the incident angle. A critical angle of incidence exists when the phonon is incident from the side with large group velocities to the side with low ones. No significant mode conversion is observed among different acoustic wave branches at the interface, except when the incident angle is near the critical value. Our theoretical result of the Kapitza conductance $G_{K}$ across the Si-Ge (100) interface at temperature $T=200$K is 4.6\times10^{8} {\rm WK}^{-1}{\rmm}^{-2}. A scaling law $G_K \propto T^{2.87}$ at low temperature is also reported. Based on the features of transmission obtained within lattice dynamic approach, we propose a simplified formula for thermal conductanceacross the epitaxial interface. A reasonable consistency is found between the calculated values and the experimentally measured ones.Comment: 8 figure

Registration of 'Ok102' wheat

Peer reviewedPlant and Soil SciencesEntomology and Plant PathologyBiochemistry and Molecular Biolog

Deep learning for detection and segmentation of artefact and disease instances in gastrointestinal endoscopy

The Endoscopy Computer Vision Challenge (EndoCV) is a crowd-sourcing initiative to address eminent problems in developing reliable computer aided detection and diagnosis endoscopy systems and suggest a pathway for clinical translation of technologies. Whilst endoscopy is a widely used diagnostic and treatment tool for hollow-organs, there are several core challenges often faced by endoscopists, mainly: 1) presence of multi-class artefacts that hinder their visual interpretation, and 2) difficulty in identifying subtle precancerous precursors and cancer abnormalities. Artefacts often affect the robustness of deep learning methods applied to the gastrointestinal tract organs as they can be confused with tissue of interest. EndoCV2020 challenges are designed to address research questions in these remits. In this paper, we present a summary of methods developed by the top 17 teams and provide an objective comparison of state-of-the-art methods and methods designed by the participants for two sub-challenges: i) artefact detection and segmentation (EAD2020), and ii) disease detection and segmentation (EDD2020). Multi-center, multi-organ, multi-class, and multi-modal clinical endoscopy datasets were compiled for both EAD2020 and EDD2020 sub-challenges. The out-of-sample generalization ability of detection algorithms was also evaluated. Whilst most teams focused on accuracy improvements, only a few methods hold credibility for clinical usability. The best performing teams provided solutions to tackle class imbalance, and variabilities in size, origin, modality and occurrences by exploring data augmentation, data fusion, and optimal class thresholding techniques

Conjunctival Reconstruction with Progenitor Cell-Derived Autologous Epidermal Sheets in Rhesus Monkey

Severe ocular surface diseases are some of the most challenging problems that the clinician faces today. Conventional management is generally unsatisfactory, and the long-term ocular consequences of these conditions are devastating. It is significantly important to find a substitute for conjunctival epithelial cells. This study was to explore the possibility of progenitor cell-derived epidermal sheets on denuded amniotic membrane to reconstruct ocular surface of conjunctiva damaged monkeys. We isolated epidermal progenitor cells of rhesus monkeys by type IV collagen adhesion, and then expanded progenitor cell-derived epidermal sheets on denuded amniotic membrane ex vivo. At 3 weeks after the conjunctiva injury, the damaged ocular surface of four monkeys was surgically reconstructed by transplanting the autologous cultivated epidermal progenitor cells. At 2 weeks after surgery, transplants were removed and examined with Hematoxylin-eosin staining, Periodic acid Schiff staining, immunofluorescent staining, scanning and transmission electron microscopy. Histological examination of transplanted sheets revealed that the cell sheets were healthy alive, adhered well to the denuded amniotic membrane, and had several layers of epithelial cells. Electron microscopy showed that the epithelial cells were very similar in appearance to those of normal conjunctival epithelium, even without goblet cell detected. Epithelial cells of transplants had numerous desmosomal junctions and were attached to the amniotic membrane with hemidesmosomes. Immunohistochemistry confirmed the presence of the conjunctival specific markers, mucin 4 and keratin 4, in the transplanted epidermal progenitor cells. In conclusion, our present study successfully reconstructed conjunctiva with autologous transplantation of progenitor cell-derived epidermal sheets on denuded AM in conjunctival damaged monkeys, which is the first step toward assessing the use of autologous transplantation of progenitor cells of nonocular surface origin. Epidermal progenitor cells could be provided as a new substitute for conjunctival epithelial cells to overcome the problems of autologous conjunctiva shortage

Kallikrein-related peptidase 6 regulates epithelial-to-mesenchymal transition and serves as prognostic biomarker for head and neck squamous cell carcinoma patients

Background: Dysregulated expression of Kallikrein-related peptidase 6 (KLK6) is a common feature for many human malignancies and numerous studies evaluated KLK6 as a promising biomarker for early diagnosis or unfavorable prognosis. However, the expression of KLK6 in carcinomas derived from mucosal epithelia, including head and neck squamous cell carcinoma (HNSCC), and its mode of action has not been addressed so far. Methods: Stable clones of human mucosal tumor cell lines were generated with shRNA-mediated silencing or ectopic overexpression to characterize the impact of KLK6 on tumor relevant processes in vitro. Tissue microarrays with primary HNSCC samples from a retrospective patient cohort (n = 162) were stained by immunohistochemistry and the correlation between KLK6 staining and survival was addressed by univariate Kaplan-Meier and multivariate Cox proportional hazard model analysis. Results: KLK6 expression was detected in head and neck tumor cell lines (FaDu, Cal27 and SCC25), but not in HeLa cervix carcinoma cells. Silencing in FaDu cells and ectopic expression in HeLa cells unraveled an inhibitory function of KLK6 on tumor cell proliferation and mobility. FaDu clones with silenced KLK6 expression displayed molecular features resembling epithelial-to-mesenchymal transition, nuclear β-catenin accumulation and higher resistance against irradiation. Low KLK6 protein expression in primary tumors from oropharyngeal and laryngeal SCC patients was significantly correlated with poor progression-free (p = 0.001) and overall survival (p < 0.0005), and served as an independent risk factor for unfavorable clinical outcome. Conclusions: In summary, detection of low KLK6 expression in primary tumors represents a promising tool to stratify HNSCC patients with high risk for treatment failure. These patients might benefit from restoration of KLK6 expression or pharmacological targeting of signaling pathways implicated in EMT

Circuit-based interrogation of sleep control.

Sleep is a fundamental biological process observed widely in the animal kingdom, but the neural circuits generating sleep remain poorly understood. Understanding the brain mechanisms controlling sleep requires the identification of key neurons in the control circuits and mapping of their synaptic connections. Technical innovations over the past decade have greatly facilitated dissection of the sleep circuits. This has set the stage for understanding how a variety of environmental and physiological factors influence sleep. The ability to initiate and terminate sleep on command will also help us to elucidate its functions within and beyond the brain

Carbonate formation by reacting CO₂ with an O₂ layer on Ag(110) studied by high resolution electron energy loss spectroscopy

The coadsorption and reaction of CO2 with a layer of molecular oxygen preadsorbed on a Ag(110) surface have been studied with high resolution electron energy loss spectroscopy (HREELS). Clear evidence has been found for a direct reaction of CO2 and O2 to CO3 at 100 K, resulting in a product coverage higher than attainable with atomic oxygen in the (2×1)O reconstruction. All internal modes of CO3 have been detected, including the in-plane bend and the asymmetric stretch modes, which are degenerate at intermediate but split at saturation coverages. An intermediate species has been observed to be stable only in coadsorption with molecular oxygen, and has been tentatively assigned to a CO-4 anion. The quantitative analysis of the isotopic shift observed with 13C16O2, 12C18O2 and 18O2 is consistent with a planar adsorption geometry of a structurally unmodified CO3 anion bound via the central carbon atom

The formation of carbonate on Ag(100) studied by high-resolution EELS

The formation of carbonate species (CO3) on Ag(100) by exposure of the (4×1) oxygen-reconstructed surface to CO2 has been studied with high-resolution electron energy loss spectroscopy (HREELS). The position and shape of the CO3-related loss peaks were found to depend on the long-range order in the carbonate layer, as observed with LEED. In addition to the γ, νs and νas modes of CO3 at 833, 1050 and 1343 cm−1, two separate peaks in the Ag–CO3 frequency region occur at 277 and 239 cm−1. The latter is particularly sensitive to disorder. Coadsorbed CO2, which is stabilized by the CO3, exhibits vibrations that are almost unchanged compared to the gas phase values, although the Fermi resonance appears to be largely suppressed