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The thermal stability and reduction kinetics of graphene oxide were studied by measuring the electrical resistivity of single-layer graphene films at various stages of reduction in high vacuum and by performing temperature programmed desorption (TPD) measurements of multilayer films in ultrahigh vacuum. The graphene oxide was exfoliated from the graphite oxide source material by slow-stirring in aqueous solution, which produces single-layer platelets with an average lateral size of ∼10 μm. From the TPD measurements, it was determined that the primary desorption products of the graphene oxide films for temperatures up to 300 °C are H2O, CO2, and CO, with only trace amounts of O2 being detected. Resistivity measurements on individual single-layer graphene oxide platelets resulted in an activation energy of 37 ± 1 kcal/mol. The TPD measurements of multilayer films of graphene oxide platelets give an activation energy of 32 ± 4 kcal/mol.

We report plasmon-enhanced Raman scattering in graphene coupled to a single plasmonic hotspot measured as a function of laser energy. The enhancement profiles of the G peak show strong enhancement (up to $10^5$) and narrow resonances (30 meV) that are induced by the localized surface plasmon of a gold nanodimer. We observe the evolution of defect-mode scattering in a defect-free graphene lattice in resonance with the plasmon. We propose a quantum theory of plasmon-enhanced Raman scattering, where the plasmon forms an integral part of the excitation process. Quantum interferences between scattering channels explain the experimentally observed resonance profiles, in particular, the marked difference in enhancement factors for incoming and outgoing resonance and the appearance of the defect-type modes., Keywords: plasmon-enhanced Raman scattering, SERS, graphene, quantum interferences, microscopic theory of Raman scattering. Content: 22 pages including 5 figures + 11 pages supporting information

Twisted-bilayer graphene (tBLG) exhibits van Hove singularities in the density of states that can be tuned by changing the twisting angle $\theta$. A $\theta$-defined tBLG has been produced and characterized with optical reflectivity and resonance Raman scattering. The $\theta$-engineered optical response is shown to be consistent with persistent saddle-point excitons. Separate resonances with Stokes and anti-Stokes Raman scattering components can be achieved due to the sharpness of the two-dimensional saddle-point excitons, similar to what has been previously observed for one-dimensional carbon nanotubes. The excitation power dependence for the Stokes and anti-Stokes emissions indicate that the two processes are correlated and that they share the same phonon., Comment: 5 pages, 6 figures

We report the electrochemical characterisation of well-defined graphene samples, prepared by mechanical exfoliation. Mechanical exfoliation is the method of choice for high purity graphene samples, despite the inherent complexity of the approach and the small scale of the resultant flakes. However, one important, yet presently unclear area, is the role of adsorbates such as processing residue, on the properties of the graphene layer. We report high resolution microscopic and electrochemical characterisation of a variety of poly(methyl methacrylate) (PMMA) transferred graphene samples, with the explicit aim of investigating the relationship between electrochemical activity and sample purity.

BackgroundThe control of vascular tissue development in plants is influenced by diverse hormonal signals, but their interactions during this process are not well understood. Wild-type sterol profiles are essential for growth, tissue patterning and signalling processes in plant development, and are required for regulated vascular patterning.Methodology/principal findingsHere we investigate the roles of sterols in vascular tissue development, through an analysis of the Arabidopsis mutants hydra1 and fackel/hydra2, which are defective in the enzymes sterol isomerase and sterol C-14 reductase respectively. We show that defective vascular patterning in the shoot is associated with ectopic cell divisions. Expression of the auxin-regulated AtHB8 homeobox gene is disrupted in mutant embryos and seedlings, associated with variably incomplete vascular strand formation and duplication of the longitudinal axis. Misexpression of the auxin reporter proIAA2ratioGUS and mislocalization of PIN proteins occurs in the mutants. Introduction of the ethylene-insensitive ein2 mutation partially rescues defective cell division, localization of PIN proteins, and vascular strand development.ConclusionsThe results support a model in which sterols are required for correct auxin and ethylene crosstalk to regulate PIN localization, auxin distribution and AtHB8 expression, necessary for correct vascular development.

The control of goal-directed reaching movements is thought to rely upon egocentric visual information derived from the visuomotor networks of the dorsal visual pathway. However, recent research (Krigolson and Heath, 2004) suggests it is also possible to make allocentric comparisons between a visual background and a target object to facilitate reaching accuracy. Here we sought to determine if the effectiveness of these allocentric comparisons is reduced as distance between a visual background and a target object increases. To accomplish this, participants completed memory-guided reaching movements to targets presented in an otherwise empty visual background or positioned within a proximal, medial, or distal visual background. Our results indicated that the availability of a proximal or medial visual background reduced endpoint variability relative to reaches made without a visual background. Interestingly, we found that endpoint variability was not reduced when participants reached to targets framed within a distal visual background. Such findings suggest that allocentric visual information is used to facilitate reaching performance; however, the fidelity by which such cues are used appears linked to the proximity of veridical target location. Importantly, these data also suggest that information from both the dorsal and ventral visual streams can be integrated to facilitate the online control of reaching movements.

We examine the near-IR light-matter interaction for graphene integrated cavity ring resonators based on silicon-on-insulator (SOI) race-track waveguides. Fitting of the cavity resonances from quasi-TE mode transmission spectra reveal the real part of the effective refractive index for graphene, neff = 2.23 ± 0.02 and linear absorption coefficient, αgTE = 0.11 ± 0.01dBµm-1. The evanescent nature of the guided mode coupling to graphene at resonance depends strongly on the height of the graphene above the cavity, which places limits on the cavity length for optical sensing applications.

Background & Aims The level of fecal calprotectin (FC) can predict the onset of inflammatory bowel disease (IBD) with high accuracy and precision. We evaluated the cost-effectiveness of using measurements of FC to identify adults and children who require endoscopic confirmation of IBD. Methods We constructed a decision analytic tree to compare the cost-effectiveness of measuring FC before endoscopy examination with that of direct endoscopic evaluation alone. A second decision analytic tree was constructed to evaluate the cost-effectiveness of FC cutoff levels of 100 μg/g vs 50 μg/g (typically used to screen for intestinal inflammation). The primary outcome measure was the incremental cost required to avoid 1 false-negative result by using FC level to diagnose new-onset IBD. Results In adults, FC screening saved $417/patient but delayed diagnosis for 2.2/32 patients with IBD among 100 screened patients. In children, FC screening saved $300/patient but delayed diagnosis for 4.8/61 patients with IBD among 100 screened patients. If endoscopic biopsy analysis remained the standard for diagnosis, direct endoscopic evaluation would cost an additional $18,955 in adults and $6250 in children to avoid 1 false-negative result from FC screening. Sensitivity analyses showed that cost-effectiveness of FC screening varied with the sensitivity of the test and the pre-test probability of IBD in adults and children. Pre-test probabilities for IBD of ≤75% in adults and ≤65% in children made FC screening cost-effective, but it was cost-ineffective if the probabilities were ≥85% and ≥78% in adults and children, respectively. Compared with the FC cutoff level of 100 μg/g, the cutoff level of 50 μg/g cost an additional $55 and $43 for adults and children, respectively, but it yielded 2.4 and 6.1 additional accurate diagnoses of IBD per 100 screened adults and children, respectively. Conclusions Screening adults and children to measure fecal levels of calprotectin is effective and cost-effective in identifying those with IBD on a per-case basis when the pre-test probability is ≤75% for adults and ≤65% for children. The utility of the test is greater for adults than children. Increasing the FC cutoff level to ≥50 μg/g increases diagnostic accuracy without substantially increasing total cost.