676 research outputs found
Ground-state of graphene in the presence of random charged impurities
We calculate the carrier density dependent ground state properties of
graphene in the presence of random charged impurities in the substrate taking
into account disorder and interaction effects non-perturbatively on an equal
footing in a self-consistent theoretical formalism. We provide detailed
quantitative results on the dependence of the disorder-induced spatially
inhomogeneous two-dimensional carrier density distribution on the external gate
bias, the impurity density, and the impurity location. We find that the
interplay between disorder and interaction is strong, particularly at lower
impurity densities. We show that for the currently available typical graphene
samples, inhomogeneity dominates graphene physics at low (
cm) carrier density with the density fluctuations becoming larger than
the average density.Comment: Final version, accepted for publication in Phys. Rev. Let
Functional microperimetry and SD-OCT confirm consecutive retinal atrophy from optic nerve pit
A congenital anomaly, optic nerve pit is often associated with serous retinal detachment involving macula. Long standing serous detachment leads to outer retinal atrophy and decrease in visual sensitivity. Recently, spectral-domain optical coherence tomography (OCT) has been reported to demonstrate a communication between the optic nerve sheath and the subretinal space. Vitreous cavity is proposed as an alternate source of fluid for accumulation in the subretinal space. We imaged a patient with optic nerve pit with Spectralis OCT and report the findings seen including the presence of an area of peripapapillary retinal atrophy, due to the spontaneous resolution of associated long-standing retinal detachment
Spectral domain optical coherence tomography guided photodynamic therapy for choroidal hemangioma: a case report
Major and minor fisheries harbours of India. 8. Fisherries harbours along the coasts of North Andhra Pradesh, Orissa and West Bengal
The present account gives information about the three major and five minor fisheries harbours along the coasts of north Andhra Pradesh, Orissa and West Benga
Infrared imaging and spectral-domain optical coherence tomography findings correlate with microperimetry in acute macular neuroretinopathy: a case report
<p>Abstract</p> <p>Introduction</p> <p>Spectral-domain optical coherence tomography findings in a patient with acute macular neuroretinopathy, and correlation with functional defects on microperimetry, are presented.</p> <p>Case presentation</p> <p>A 25-year old Caucasian woman presented with bitemporal field defects following an upper respiratory tract infection. Her visual acuity was 20/20 in both eyes and a dilated fundus examination revealed bilateral hyperpigmentary changes in the papillomacular bundle. Our patient underwent further evaluation with spectral-domain optical coherence tomography, infrared and fundus autofluorescence imaging. Functional changes were assessed by microperimetry. Infrared imaging showed the classic wedge-shaped defects and spectral-domain optical coherence tomography exhibited changes at the inner segment-outer segment junction, with a thickened outer plexiform layer overlying these areas. Fluorescein and indocyanine green angiography did not demonstrate any perfusion defects or any other abnormality. Microperimetry demonstrated focal elevation in threshold correlating with the wedge-shaped defects in both eyes.</p> <p>Conclusion</p> <p>Spectral-domain optical coherence tomography findings provide new evidence of the involvement of the outer plexiform layer of the retina in acute macular neuroretinopathy.</p
Local density of states and scanning tunneling currents in graphene
We present exact analytical calculations of scanning tunneling currents in
locally disordered graphene using a multimode description of the microscope
tip. Analytical expressions for the local density of states (LDOS) are given
for energies beyond the Dirac cone approximation. We show that the LDOS at the
and sublattices of graphene are out of phase by implying that the
averaged LDOS, as one moves away from the impurity, shows no trace of the
(with the Fermi momentum) Friedel modulation. This means that a
STM experiment lacking atomic resolution at the sublattice level will not be
able of detecting the presence of the Friedel oscillations [this seems to be
the case in the experiments reported in Phys. Rev. Lett. {\bf 101}, 206802
(2008)]. The momentum maps of the LDOS for different types of impurities are
given. In the case of the vacancy, features are seen in these maps. In
all momentum space maps, and features are seen. The
features are different from what is seen around zero momentum. An
interpretation for these features is given. The calculations reported here are
valid for chemical substitution impurities, such as boron and nitrogen atoms,
as well as for vacancies. It is shown that the density of states close to the
impurity is very sensitive to type of disorder: diagonal, non-diagonal, or
vacancies. In the case of weakly coupled (to the carbon atoms) impurities, the
local density of states presents strong resonances at finite energies, which
leads to steps in the scanning tunneling currents and to suppression of the
Fano factor.Comment: 21 pages. Figures 6 and 7 are correctly displayed in this new versio
Second-order harmonic and combination modes in graphite, single-wall carbon nanotube bundles, and isolated single-wall carbon nanotubes
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