A two-dimensional semimetal is discovered in the (013) HgTe quantum well with a thickness of
d
= 14 nm, which is much smaller than those previously studied. It is found that such semimetal is ...characterized by the same band overlap as the wells with
d
=18−22 nm having the same orientation, but here the impurity scattering of both electrons and holes is much more pronounced. The electron cyclotron photoresistance is measured as a function of the electron density (
N
s
) and it is shown that the amplitude of the electron cyclotron photoresistance decreases with decreasing density, and the electron cyclotron photoresistance is not detected at
N
s
< 5 × 10
9
cm
−2
. Thus, the two-dimensional semimetal under study does not exhibit the
N
s
-independent electron cyclotron photoresistance, which was earlier observed in the two-dimensional semimetal arising near the (100) surface. This is assumingly due to a significantly lower (by more than an order of magnitude) electron mobility in the system under study.
A
bstract
We present analytical results for massless correlators of two vector, tensor, and scalar composite vertices with the Bjorken fractions
x
and
y
of order
α
s
2
β
0
of QCD. The structure of ...these correlators Π
V,T,S
(
x, y
;
p
2
) and properties of its main elements are discussed in detail. Special attention is paid to verifying the results and comparing them with known particular cases. We apply the correlators to evaluate radiative corrections to the distribution amplitudes of light mesons within the QCD sum rules.
Introduction
Anti-NMDA-receptor encephalitis is a severe rare acute form of encephalitis caused by an autoimmune process with the synthesis of autoantibodies to the glutamate receptors. The average ...age of onser is estimated to be 23-25 years. A typical clinical picture consist of prodromal, psychotic, areactive, hyperkinetic phases, and a phase of gradual regression of symptoms. The disease usually lasts for a several weeks with spontaneous recovery or fatal outcome and caused by neoplastic process. Our case demonstrates that the course of anti-NMDAR encephalitis is possible at more mature age in the form of a long process with cultural features, without significant catadrome, inflammation and associated neoplastic process.
Objectives
50-year-old woman complained about hypomnesia, anosmia and dissomnia. The disease began with impaired consciousness, disorientation, seizures and memory loss 4 years ago. After 3 weeks IgG to the herpes simplex and cytomegalovirus were detected. Then after a discharge with no improvement and visit of Lama, the symtoms described above spontaneously reduced and schizophrenia-like psychosis developed, accompanied by mild neurological and severe neurocognitive symptoms, weight loss, intolerance to antipsychotics in minimal daily doses. This state was mantained till 2020.
Methods
Examination included: CBC, metabolic panel, coagulogram, tumor markers, CSF, MRI, PET, specialists.
Results
CBC, metabolic blood analysis, tumor markers - within the reference values. CSF: cytosis 9/3, glucose 5.5 mmol/l, Pandi++, Nonnet-Apeltau+, antibodies to the NMDA receptor - 8. MRI: signs of the consequences of encephalitis. PET: no signs of metabolic activity of the malignant process.
Conclusions
This case brings additional data about a couse, age of onset, duration and trigger factors for anti-NMDAR encephalitis.
Introduction
Anti-NMDA-receptor encephalitis is a severe rare acute form of encephalitis caused by an autoimmune process with the synthesis of autoantibodies to the glutamate receptors. The average ...age of onser is estimated to be 23-25 years. A typical clinical picture consist of prodromal, psychotic, areactive, hyperkinetic phases, and a phase of gradual regression of symptoms. The disease usually lasts for a several weeks with spontaneous recovery or fatal outcome and caused by neoplastic process. Our case demonstrates that the course of anti-NMDAR encephalitis is possible at more mature age in the form of a long process with cultural features, without significant catadrome, inflammation and associated neoplastic process.
Objectives
50-year-old Buddhist Buryat woman with complaints about hypomnesia, anosmia and dissomnia. The disease began with impaired consciousness, disorientation, seizures and memory loss 4 years ago. Then after a visit of Lama, the symtoms described above spontaneously reduced and schizophrenia-like psychosis developed (voice of Lama in the head, a belief in the existence of super-powers, disorganized behavior), mild neurological and severe neurocognitive symptoms, weight loss, intolerance to antipsychotics in minimal daily doses.
Methods
Examination included: CBC, metabolic panel, coagulogram, tumor markers, CSF, MRI, PET, specialists.
Results
CBC, metabolic blood analysis, tumor markers - within the reference values. CSF: cytosis 9/3, glucose 5.5 mmol/l, Pandi++, Nonnet-Apeltau+, antibodies to the NMDA receptor - 8. MRI: signs of the consequences of encephalitis. PET: no signs of metabolic activity of the malignant process.
Conclusions
The diagnosis of anti-NMDA-receptor-encephalitis was confirmed by the laboratory and clinical criteria despite unususal course and age. The trigger role of herpes is possible, but not verified.
Disclosure
No significant relationships.
Since the emergence of graphene, we have seen several proposals for the realization of Landau lasers tunable over the terahertz frequency range. The hope was that the non-equidistance of the Landau ...levels from Dirac fermions would suppress the harmful non-radiative Auger recombination. Unfortunately, even with this non-equidistance, an unfavourable non-radiative process persists in Landau-quantized graphene, and so far no cyclotron emission from Dirac fermions has been reported. One way to eliminate this last non-radiative process is to sufficiently modify the dispersion of the Landau levels by opening a small gap in the linear band structure. HgTe quantum wells close to the topological phase transition are a proven example of such gapped graphene-like materials. In this work we experimentally demonstrate Landau emission from Dirac fermions in such HgTe quantum wells, where the emission is tunable by both the magnetic field and the carrier concentration. Consequently, these results represent an advance in the realization of terahertz Landau lasers tunable by a magnetic field and gate voltage.Two-dimensional massive and massless Dirac fermions in HgTe/CdHgTe quantum wells yield terahertz Landau emission. The emission frequency is continuously tunable with magnetic field or carrier concentration, over the range from 0.5 to 3 THz.
Quantum wells formed by layers of HgTe between HgFormula: see textCdFormula: see textTe barriers lead to two-dimensional (2D) topological insulators, as predicted by the BHZ model. Here, we ...theoretically and experimentally investigate the characteristics of triple HgTe quantum wells. We describe such heterostructure with a three dimensional Formula: see text Kane model, and use its eigenstates to derive an effective 2D Hamiltonian for the system. From these we obtain a phase diagram as a function of the well and barrier widths and we identify the different topological phases composed by zero, one, two, and three sets of edge states hybridized along the quantum wells. The phase transitions are characterized by a change of the spin Chern numbers and their corresponding band inversions. Complementary, transport measurements are experimentally investigated on a sample close to the transition line between the phases with one and two sets of edges states. Accordingly, for this sample we predict a gapless spectrum with low energy bulk conduction subbands given by one parabolic and one Dirac subband, and with edge states immersed in the bulk valence subbands. Consequently, we show that under these conditions, local and non-local transport measurements are inconclusive to characterize a sole edge state conductivity due to bulk conductivity. On the other hand, Shubnikov-de Haas (SdH) oscillations show an excellent agreement with our theory. Particularly, we show that the measured SdH oscillation frequencies agrees with our model and show clear signatures of the coexistence of a parabolic and Dirac subbands.
We report the first results on a direct search for a new 16.7 MeV boson (X) which could explain the anomalous excess of e^{+}e^{-} pairs observed in the excited ^{8}Be^{*} nucleus decays. Because of ...its coupling to electrons, the X could be produced in the bremsstrahlung reaction e^{-}Z→e^{-}ZX by a 100 GeV e^{-} beam incident on an active target in the NA64 experiment at the CERN Super Proton Synchrotron and observed through the subsequent decay into a e^{+}e^{-} pair. With 5.4×10^{10} electrons on target, no evidence for such decays was found, allowing us to set first limits on the X-e^{-} coupling in the range 1.3×10^{-4}≲ε_{e}≲4.2×10^{-4} excluding part of the allowed parameter space. We also set new bounds on the mixing strength of photons with dark photons (A^{'}) from nonobservation of the decay A^{'}→e^{+}e^{-} of the bremsstrahlung A^{'} with a mass ≲23 MeV.
Topological states of matter have attracted a lot of attention due to their many intriguing transport properties. In particular, two-dimensional topological insulators (2D TI) possess gapless counter ...propagating conducting edge channels, with opposite spin, that are topologically protected from backscattering. Two basic features are supposed to confirm the existence of the ballistic edge channels in the submicrometer limit: the 4-terminal conductance is expected to be quantized at the universal value 2e2/h, and a nonlocal signal should appear due to a net current along the sample edge, carried by the helical states. On the other hand for longer channels the conductance has been found to deviate from the quantized value. This article reviewer the experimental and theoretical work related to the transport in two-dimensional topological insulators (2D-TI), based on HgTe quantum wells in zero magnetic field. We provide an overview of the basic mechanisms predicting a deviation from the quantized transport due to backscattering (accompanied by spin-flips) between the helical channels. We discuss the details of the model, which takes into account the edge and bulk contribution to the total current and reproduces the experimental results.
•Two-dimensional topological insulators possess counter propagating edge channels protected from backscattering.•This article reviews work related to the transport in two-dimensional topological insulators, based on HgTe quantum wells.•Basic mechanisms of scattering between the edge states responsible for the deviation from quantized resistance are discussed.
Protons and helium nuclei are the most abundant components of the cosmic radiation. Precise measurements of their fluxes are needed to understand the acceleration and subsequent propagation of cosmic ...rays in our Galaxy. We report precision measurements of the proton and helium spectra in the rigidity range 1 gigavolt to 1.2 teravolts performed by the satellite-borne experiment PAMELA (payload for antimatter matter exploration and light-nuclei astrophysics). We find that the spectral shapes of these two species are different and cannot be described well by a single power law. These data challenge the current paradigm of cosmic-ray acceleration in supernova remnants followed by diffusive propagation in the Galaxy. More complex processes of acceleration and propagation of cosmic rays are required to explain the spectral structures observed in our data.
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