792 research outputs found
Interacting Dirac Materials
We investigate the extent to which the class of Dirac materials in
two-dimensions provides general statements about the behavior of both fermionic
and bosonic Dirac quasiparticles in the interacting regime. For both
quasiparticle types, we find common features for the interaction induced
renormalization of the conical Dirac spectrum. We perform the perturbative
renormalization analysis and compute the self-energy for both quasiparticle
types with different interactions and collate previous results from the
literature whenever necessary. Guided by the systematic presentation of our
results in Table~\ref{Summary}, we conclude that long-range interactions
generically lead to an increase of the slope of the single-particle Dirac cone,
whereas short-range interactions lead to a decrease. The quasiparticle
statistics does not qualitatively impact the self-energy correction for
long-range repulsion but does affect the behavior of short-range coupled
systems, giving rise to different thermal power-law contributions. The
possibility of a universal description of the Dirac materials based on these
features is also mentioned.Comment: 19 pages and 12 Figures; Contains 6 Appendice
Fluorescence-based measurements of membrane-bound angiotensin converting enzyme 2 activity using Xenopus Laevis Oocytes
Functional investigations of enzymes involving cellular expression systems are important for pharmacological studies. The precise control of expression is challenging in transiently transfected mammalian cell lines. Here, we explored the ability of Xenopus laevis oocytes to express a membrane-bound enzyme for functional characterization using standard 96-well plates and a fluorescence-based plate reader assay. We microinjected oocytes with cRNA encoding the angiotensin converting enzyme 2 (ACE2) and measured the enzymatic activity in single oocytes using a commercial fluorescence-based assay. The injected oocytes showed up to a 50-fold increase in fluorescence compared to uninjected oocytes. This fluorescence intensity was dose-dependent on the amount of ACE2 cRNA. These results suggest that Xenopus oocytes can be used for the functional evaluation of membrane-bound enzymes, decreasing the experimental workload
Surveillance of Echinococcus multilocularis in rodents in the vicinity of the finding of the first infected red fox (Vulpes vulpes) in Sweden
Olsson, G.E., Hörnfeldt, B., Ågren, E., Wahlström, H
Estimating Discharge in Low-Order Rivers With High-Resolution Aerial Imagery
Remote sensing of river discharge promises to augment in situ gauging stations, but the majority of research in this field focuses on large rivers (\u3e50 m wide). We present a method for estimating volumetric river discharge in low-order (wide) rivers from remotely sensed data by coupling high-resolution imagery with one-dimensional hydraulic modeling at so-called virtual gauging stations. These locations were identified as locations where the river contracted under low flows, exposing a substantial portion of the river bed. Topography of the exposed river bed was photogrammetrically extracted from high-resolution aerial imagery while the geometry of the remaining inundated portion of the channel was approximated based on adjacent bank topography and maximum depth assumptions. Full channel bathymetry was used to create hydraulic models that encompassed virtual gauging stations. Discharge for each aerial survey was estimated with the hydraulic model by matching modeled and remotely sensed wetted widths. Based on these results, synthetic width-discharge rating curves were produced for each virtual gauging station. In situ observations were used to determine the accuracy of wetted widths extracted from imagery (mean error 0.36 m), extracted bathymetry (mean vertical RMSE 0.23 m), and discharge (mean percent error 7% with a standard deviation of 6%). Sensitivity analyses were conducted to determine the influence of inundated channel bathymetry and roughness parameters on estimated discharge. Comparison of synthetic rating curves produced through sensitivity analyses show that reasonable ranges of parameter values result in mean percent errors in predicted discharges of 12%–27%
The electronic structure of poly(pyridine-2,5-diyl) investigated by soft x-ray absorption and emission spectroscopies
The electronic structure of the poly-pyridine conjugated polymer has been
investigated by resonant and nonresonant inelastic X-ray scattering and X-ray
absorption spectroscopies using synchrotron radiation. The measurements were
made for both the carbon and nitrogen contents of the polymer. The analysis of
the spectra has been carried out in comparison with molecular orbital
calculations taking the repeat-unit cell as a model molecule of the polymer
chain. The simulations indicate no significant differences in the absorption
and in the non-resonant X-ray scattering spectra for the different isomeric
geometries, while some isomeric dependence of the resonant spectra is
predicted. The resonant emission spectra show depletion of the {\pi} electron
bands in line with symmetry selection and momentum conservation rules. The
effect is most vizual for the carbon spectra; the nitrogen spectra are
dominated by lone pair n orbital emission of {\sigma} symmetry and are less
frequency dependent.Comment: 11 pages, 7 figures, 1 table,
http://www.sciencedirect.com/science/article/pii/S030101049800262
Competition between decay and dissociation of core-excited OCS studied by X-ray scattering
We show the first evidence of dissociation during resonant inelastic soft
X-ray scattering. Carbon and oxygen K-shell and sulfur L-shell resonant and
non-resonant X-ray emission spectra were measured using monochromatic
synchrotron radiation for excitation and ionization. After sulfur, L2,3 ->
{\pi}*, {\sigma}* excitation, atomic lines are observed in the emission spectra
as a consequence of competition between de-excitation and dissociation. In
contrast the carbon and oxygen spectra show weaker line shape variations and no
atomic lines. The spectra are compared to results from ab initio calculations
and the discussion of the dissociation paths is based on calculated potential
energy surfaces and atomic transition energies.Comment: 12 pages, 6 pictures, 2 tables,
http://link.aps.org/doi/10.1103/PhysRevA.59.428
Resonant inelastic soft-x-ray scattering spectra at the N1s and C1s edges of poly(pyridine-2,5-diyl)
Resonant inelastic scattering measurements of poly(pyridine-2,5-diyl) have
been performed at the N1s and C1s edges using synchrotron radiation. For
comparison, molecular orbital calculations of the spectra have been carried out
with the repeat unit as a model molecule of the polymer chain. The resonant
emission spectra show depletion of the p electron bands which is consistent
with symmetry selection and momentum conservation rules. The depletion is most
obvious in the resonant inelastic scattering spectra of carbon while the
nitrogen spectra are dominated by lone pair n orbital emission of s symmetry
and are less excitation energy dependent. By comparing the measurements to
calculations an isomeric dependence of the resonant spectra is found giving
preference to two of the four possible isomers in the polymer.Comment: 6 pages, 3 figures,
http://www.sciencedirect.com/science/article/pii/S036820489800354
Solar cycle modulation of Titan's ionosphere
This is the publisher's version, also available electronically from http://onlinelibrary.wiley.com/doi/10.1002/jgra.50463/abstractDuring the six Cassini Titan flybys T83–T88 (May 2012 to November 2012) the electron density in the ionospheric peak region, as measured by the radio and plasma wave science instrument/Langmuir probe, has increased significantly, by 15–30%, compared to previous average. These measurements suggest that a long‒term change has occurred in the ionosphere of Titan, likely caused by the rise to the new solar maximum with increased EUV fluxes. We compare measurements from TA, TB, and T5, from the declining phase of solar cycle 23 to the recent T83–T88 measurements during cycle 24, since the solar irradiances from those two intervals are comparable. The peak electron densities normalized to a common solar zenith angle Nnorm from those two groups of flybys are comparable but increased compared to the solar minimum flybys (T16–T71). The integrated solar irradiance over the wavelengths 1–80nm, i.e., the solar energy flux, Fe, correlates well with the observed ionospheric peak density values. Chapman layer theory predicts that inline image, with k=0.5. We find observationally that the exponent k=0.54±0.18. Hence, the observations are in good agreement with theory despite the fact that many assumptions in Chapman theory are violated. This is also in good agreement with a similar study by Girazian and Withers (2013) on the ionosphere of Mars. We use this power law to estimate the peak electron density at the subsolar point of Titan during solar maximum conditions and find it to be about 6500cm−3, i.e., 85–160% more than has been measured during the entire Cassini mission
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