545 research outputs found
Compressibility of graphene
We develop a theory for the compressibility and quantum capacitance of
disordered monolayer and bilayer graphene including the full hyperbolic band
structure and band gap in the latter case. We include the effects of disorder
in our theory, which are of particular importance at the carrier densities near
the Dirac point. We account for this disorder statistically using two different
averaging procedures: first via averaging over the density of carriers
directly, and then via averaging in the density of states to produce an
effective density of carriers. We also compare the results of these two models
with experimental data, and to do this we introduce a model for inter-layer
screening which predicts the size of the band gap between the low-energy
conduction and valence bands for arbitary gate potentials applied to both
layers of bilayer graphene. We find that both models for disorder give
qualitatively correct results for gapless systems, but when there is a band gap
at charge neutrality, the density of states averaging is incorrect and
disagrees with the experimental data.Comment: 10 pages, 7 figures, RevTe
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
Optical and transport gaps in gated bilayer graphene
We discuss the effect of disorder on the band gap measured in bilayer
graphene in optical and transport experiments. By calculating the optical
conductivity and density of states using a microscopic model in the presence of
disorder, we demonstrate that the gap associated with transport experiments is
smaller than that associated with optical experiments. Intrinsic bilayer
graphene has an optical conductivity in which the energy of the peaks
associated with the interband transition are very robust against disorder and
thus provide an estimate of the band gap. In contrast, extraction of the band
gap from the optical conductivity of extrinsic bilayer graphene is almost
impossible for significant levels of disorder due to the ambiguity of the
transition peaks. The density of states contains an upper bound on the gap
measured in transport experiments, and disorder has the effect of reducing this
gap which explains why these experiments have so far been unable to replicate
the large band gaps seen in optical measurements.Comment: 5 pages, 5 figures, RevTeX. Published versio
Over-the-Scope Clip to the Rescue! A Novel Tool for Refractory Acute Nonvariceal Upper Gastrointestinal Hemorrhage
© 2020 © 2020 The Author(s). Published by S. Karger AG, Basel. Nonvariceal upper gastrointestinal hemorrhage (NVUGIH) is more prevalent than lower gastrointestinal hemorrhage and carries a high risk of mortality in the elderly, especially those with significant cardiovascular comorbidities. Traditional endoscopic methods, such as through-the-scope clips, electrocautery, and epinephrine injection, are frequently used to control these bleeds; however, they carry a 10% risk of rebleeding, and this itself carries a mortality risk of 36%. The larger over-the-scope clips (OTSC) that were initially used for the closure of fistulas and perforations are now gradually being implemented to manage NVUGIH. To our knowledge, we present the first cases to be reported in the literature where OTSC was successfully used as salvage therapy for refractory acute upper gastrointestinal bleeders who failed traditional endoscopic management and interventional radiology-guided embolization of the bleeding artery. We also provide an up-to-date literature review on the use of OTSC and its superiority to traditional endoscopic interventions in the management of complicated NVUGIH
Opportunities for financing sustainable development using complementary local currencies
Financing building retrofit projects that contribute to climate change mitigation has always represented a significant barrier. With 28% of global emissions coming from existing buildings, it is of paramount importance to carry out retrofit measures that lead to significant reduction of these emissions. Whilst this is perfectly possible to achieve with current methods and current technology, there is no sufficient conventional finance to carry out zero carbon retrofit at scale required for climate change mitigation. The article introduces an alternative and sustainable business model that creates new opportunities for financing zero carbon retrofit of buildings. It demonstrates that the value of solar energy falling on roofs of buildings can become a driver for new local economic systems, and discusses the requirements for practical application.Peer reviewedFinal Published versio
Acute Liver Failure in a COVID-19 Patient Without any Preexisting Liver Disease.
In December 2019, an outbreak of novel coronavirus started in Wuhan, China, which gradually spread to the entire world. The World Health Organization (WHO) on February 11, 2020, officially announced the name for the disease as coronavirus disease 2019, abbreviated as COVID-19. It is caused by severe respiratory distress syndrome coronavirus 2 (SARS-CoV-2). The WHO declared SARS-CoV-2 as a pandemic on March 11, 2020. SARS-CoV-2 mainly causes fever as well as respiratory symptoms such as cough and shortness of breath. Gastrointestinal/hepatic sequelae such as diarrhea, nausea, vomiting, and elevated liver enzymes have been reported as well. Studies and data so far on coronavirus infections from China, Singapore, and other countries showed that liver enzymes elevation could be seen in 20-50% of cases. More severe disease can correlate with the worsening of liver enzymes. However, acute liver failure in patients with COVID-19 has not been described. Herein we report a case of acute liver failure in an elderly patient with COVID-19 infection who did not have a history of preexisting liver disease
Spontaneous Chelation-Driven Reduction of the Neptunyl Cation in Aqueous Solution.
Octadentate hydroxypyridinone (HOPO) and catecholamide (CAM) siderophore analogues are known to be efficacious chelators of the actinide cations, and these ligands are also capable of facilitating both activation and reduction of actinyl species. Utilizing X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopies, as well as cyclic voltammetry measurements, herein, we elucidate chelation-based mechanisms for driving reactivity and initiating redox processes in a family of neptunyl-HOPO and CAM complexes. Based on the selected chelator, the ability to control the oxidation state of neptunium and the speed of reduction and concurrent oxo group activation was demonstrated. Most notably, reduction kinetics for the NpV O2 +/ /NpIV redox couple upon chelation by the ligands 3,4,3-LI(1,2-HOPO) and 3,4,3-LI(CAM)2 (1,2-HOPO)2 was observed to be faster than ever reported, and in fact quicker than we could measure using either X-ray absorption spectroscopy or electrochemical techniques
A Case of Wernicke\u27s Encephalopathy in a Pregnant Woman With a History of Sleeve Gastrectomy.
Wernicke\u27s encephalopathy (WE) is a neurological complication of thiamine deficiency characterized by a triad of acute confusion, ataxia, and ophthalmoplegia. Even though it is most common in chronic alcoholism, an increase in prevalence has been reported recently due to the increased popularity of bariatric surgeries. WE is a known neurological complication after gastric bypass surgery but rarely reported after sleeve gastrectomy. We present a unique case of WE in pregnant women four months after sleeve gastrectomy
Super-resolution in map-making based on a physical instrument model and regularized inversion. Application to SPIRE/Herschel
We investigate super-resolution methods for image reconstruction from data
provided by a family of scanning instruments like the Herschel observatory. To
do this, we constructed a model of the instrument that faithfully reflects the
physical reality, accurately taking the acquisition process into account to
explain the data in a reliable manner. The inversion, ie the image
reconstruction process, is based on a linear approach resulting from a
quadratic regularized criterion and numerical optimization tools. The
application concerns the reconstruction of maps for the SPIRE instrument of the
Herschel observatory. The numerical evaluation uses simulated and real data to
compare the standard tool (coaddition) and the proposed method. The inversion
approach is capable to restore spatial frequencies over a bandwidth four times
that possible with coaddition and thus to correctly show details invisible on
standard maps. The approach is also applied to real data with significant
improvement in spatial resolution.Comment: Astronomy & Astrophysic
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