Kagome Quantum Oscillations in Graphene Superlattices.

Electronic spectra of solids subjected to a magnetic field are often discussed in terms of Landau levels and Hofstadter-butterfly-style Brown-Zak minibands manifested by magneto-oscillations in two-dimensional electron systems. Here, we present the semiclassical precursors of these quantum magneto-oscillations which appear in graphene superlattices at low magnetic field near the Lifshitz transitions and persist at elevated temperatures. These oscillations originate from Aharonov-Bohm interference of electron waves following open trajectories that belong to a kagome-shaped network of paths characteristic for Lifshitz transitions in the moire superlattice minibands of twistronic graphenes.

Mixed-Stacking Few-Layer Graphene as an Elemental Weak Ferroelectric Material.

Ferroelectricity (Valasek, J. Phys. Rev. 1921, 17, 475), a spontaneous formation of electric polarization, is a solid state phenomenon, usually, associated with ionic compounds or complex materials. Here we show that, atypically for elemental solids, few-layer graphenes can host an equilibrium out-of-plane electric polarization, switchable by sliding the constituent graphene sheets. The systems hosting such effect include mixed-stacking tetralayers and thicker (5-9 layers) rhombohedral graphitic films with a twin boundary in the middle of a flake. The predicted electric polarization would also appear in marginally (small-angle) twisted few-layer flakes, where lattice reconstruction would give rise to networks of mesoscale domains with alternating value and sign of out-of-plane polarization.

ARPES Signatures of Few-Layer Twistronic Graphenes.

Diverse emergent correlated electron phenomena have been observed in twisted-graphene layers. Many electronic structure predictions have been reported exploring this new field, but with few momentum-resolved electronic structure measurements to test them. We use angle-resolved photoemission spectroscopy to study the twist-dependent (1° < θ < 8°) band structure of twisted-bilayer, monolayer-on-bilayer, and double-bilayer graphene (tDBG). Direct comparison is made between experiment and theory, using a hybrid k·p model for interlayer coupling. Quantitative agreement is found across twist angles, stacking geometries, and back-gate voltages, validating the models and revealing field-induced gaps in twisted graphenes. However, for tDBG at θ = 1.5 ± 0.2°, close to the magic angle θ = 1.3°, a flat band is found near the Fermi level with measured bandwidth Ew = 31 ± 5 meV. An analysis of the gap between the flat band and the next valence band shows deviations between experiment (Δh = 46 ± 5 meV) and theory (Δh = 5 meV), indicative of lattice relaxation in this regime.

Band Gap Opening in Bilayer Graphene-CrCl3/CrBr3/CrI3 van der Waals Interfaces.

We report experimental investigations of transport through bilayer graphene (BLG)/chromium trihalide (CrX3; X = Cl, Br, I) van der Waals interfaces. In all cases, a large charge transfer from BLG to CrX3 takes place (reaching densities in excess of 1013 cm-2), and generates an electric field perpendicular to the interface that opens a band gap in BLG. We determine the gap from the activation energy of the conductivity and find excellent agreement with the latest theory accounting for the contribution of the σ bands to the BLG dielectric susceptibility. We further show that for BLG/CrCl3 and BLG/CrBr3 the band gap can be extracted from the gate voltage dependence of the low-temperature conductivity, and use this finding to refine the gap dependence on the magnetic field. Our results allow a quantitative comparison of the electronic properties of BLG with theoretical predictions and indicate that electrons occupying the CrX3 conduction band are correlated.

Scattering between Minivalleys in Twisted Double Bilayer Graphene.

A unique feature of the complex band structures of moiré materials is the presence of minivalleys, their hybridization, and scattering between them. Here, we investigate magnetotransport oscillations caused by scattering between minivalleys-a phenomenon analogous to magnetointersubband oscillations-in a twisted double bilayer graphene sample with a twist angle of 1.94°. We study and discuss the potential scattering mechanisms and find an electron-phonon mechanism and valley conserving scattering to be likely. Finally, we discuss the relevance of our findings for different materials and twist angles.

Out-of-Plane Dielectric Susceptibility of Graphene in Twistronic and Bernal Bilayers.

We describe how the out-of-plane dielectric polarizability of monolayer graphene influences the electrostatics of bilayer graphene-both Bernal (BLG) and twisted (tBLG). We compare the polarizability value computed using density functional theory with the output from previously published experimental data on the electrostatically controlled interlayer asymmetry potential in BLG and data on the on-layer density distribution in tBLG. We show that monolayers in tBLG are described well by polarizability αexp = 10.8 Å3 and effective out-of-plane dielectric susceptibility ϵz = 2.5, including their on-layer electron density distribution at zero magnetic field and the interlayer Landau level pinning at quantizing magnetic fields.

Coherent Jetting from a Gate-Defined Channel in Bilayer Graphene.

Graphene has evolved as a platform for quantum transport that can compete with the best and cleanest semiconductor systems. Here, we report on the observation of distinct electronic jets emanating from a narrow split-gate-defined channel in bilayer graphene. We find that these jets, which are visible via their interference patterns, occur predominantly with an angle of 60° between each other. This observation is related to the trigonal warping in the band structure of bilayer graphene, which, in conjunction with electron injection through a constriction, leads to a valley-dependent selection of momenta. This experimental observation of electron jetting has consequences for carrier transport in two-dimensional materials with a trigonally warped band structure in general, as well as for devices relying on ballistic and valley-selective transport.

Spectroscopic Signatures of Electronic Excitations in Raman Scattering in Thin Films of Rhombohedral Graphite.

Rhombohedral graphite features peculiar electronic properties, including persistence of low-energy surface bands of a topological nature. Here, we study the contribution of electron-hole excitations toward inelastic light scattering in thin films of rhombohedral graphite. We show that, in contrast to the featureless electron-hole contribution toward Raman spectrum of graphitic films with Bernal stacking, the inelastic light scattering accompanied by electron-hole excitations in crystals with rhombohedral stacking produces distinct features in the Raman signal which can be used both to identify the stacking and to determine the number of layers in the film.

Impact of a tire fire accident on soil pollution and the use of clay minerals as natural geo-indicators.

Following the occurrence of a fire at a tire landfill in the surrounding area of Madrid City (Spain), polycyclic aromatic hydrocarbons (PAHs) and trace elements present in soils were analyzed to assess the impact of the fire. The capacity of the soils' clay mineral fraction to reflect this air pollution incident was studied. Fourteen soil samples were collected at different distances under the smoke plume, and they were subjected to high-performance liquid chromatography-photodiode array detection, inductively coupled plasma mass spectrometry and X-ray diffraction analyses. Clay minerals content showed a strong correlation with the pollutants potentially released in the tire fire, acenaphthene, pyrene, benzo(a)pyrene and benzo(a)fluoranthene. Trace metals Zn and Se were related to the proximity of the tire fire without any relationship with clay minerals content. This work suggests the use of natural clay minerals as potential PAHs geo-indicators in response to air pollution, complementary to current air and biological analyses.

White matter involvement on DTI-MRI in Cushing's syndrome relates to mood disturbances and processing speed: a case-control study.

PURPOSE: Cushing's syndrome (CS) is an endocrine disorder due to prolonged exposure to cortisol. Recently, microstructural white matter (WM) alterations detected by diffusion tensor imaging (DTI) have been reported in CS patients, and related to depression, but other functional significances. remain otherwise unclear. We aimed at investigating in more depth mood symptoms in CS patients, and how these relate to cognition (information processing speed), and to WM alterations on DTI. METHODS: The sample comprised 35 CS patients and 35 healthy controls. Beck Depression Inventory-II (BDI-II) was used to measure depressive symptoms, State-Trait Anxiety Inventory (STAI) to assess anxiety, and processing speed was measured by the Symbol Digit Modalities Test (SDMT). DTI studies were acquired using a 3-Tesla Philips-Achieva MR-facility. Voxelwise statistical analysis of fractional anisotropy (FA), mean, axial and radial diffusivities (MD, AD, RD) data were performed using FMRIB Software Library. Correlation analysis were obtained between mood and processing speed variables, and FA, MD, AD and RD values, taking both CS patients and healthy controls. RESULTS: Active, controlled and cured CS patients showed greater depression (F = 12.4, p < 0.001), anxious state (F = 4.8, p = 0.005) and anxious trait (F = 9.6, p < 0.001) scores, than controls. Using the entire sample, depression scores correlated negatively to FA and positively to RD values. Although there were no differences in processing speed between groups, SDMT scores correlated positively to both FA and AD values. CONCLUSIONS: There were greater depressive and anxious symptoms in CS patients than in healthy controls, but no difference in processing speed. However, DTI is related to depression and information processing speed in CS.

Parametric characterization of surface plasmon polaritons at a lossy interface.

Using exact solutions of Maxwell's equations, we investigate the evolution of the transversal profile of a surface plasmon polariton (SPP) packet propagating along a planar interface between a dielectric and a lossy metal. We introduce a parameter to measure the propagation length of the SPP packet and analyze its behavior with respect to the shape of the packet and the dielectric characteristics of the interface. Furthermore, we study the polarization properties of the SPP packet and define two parameters to quantify the fraction of the irradiance contained in the s- and p-polarization components of the associated field. Our results help to advance in the understanding of the SPP optics beyond the single-mode description.

Natalizumab: safety and risk in patients with relapsing-remitting multiple sclerosis.

OBJECTIVE: To estimate the risk of progressive multifocal leukoencephalopathy (PML) and the safety of natalizumab administration in patients with relapsing-remitting multiple sclerosis (RRMS). METHODS: A descriptive retrospective observational study including all patients with RRMS treated with natalizumab followed-up after 10 years.The likelihood of developing PML was estimated based on three risk factors: anti-John Cunningham virus antibody index, previous immunosuppressive therapy, and duration of treatment. Patients were classified into five categories: minimum probability (<0.1/1000); low (0.1/1000); medium-low (0.2-0.6/1000); medium-high (0.8-3/1000); high probability (3-10/1000). RESULTS: 34 patients were included. The probability of PML in the last cycle was: 55.9% minimum, 8.8% low, 11.8% medium-low, 3% medium-high, and 20.5% high. 12 patients continue with active treatment with natalizumab. No cases of PML have been confirmed. Adverse effects were detected in 50% of patients. CONCLUSIONS: Quantifying risk factors allows us to estimate the probability of PML appearance, thus assessing the maintenance or suspension of natalizumab.

Alemtuzumab for relapsing multiple sclerosis in clinical practice: A four-year retrospective one-center study.

BACKGROUND: Disease-modifying therapies for multiple sclerosis have been developed tremendously over the last two decades. OBJECTIVE: The aim of this study was to review the short-, medium-, and long-term safety of alemtuzumab in relapsing remitting multiple sclerosis (RRMS). METHOD: This retrospective observational study (2015-2019) included all patients with highly active or rapidly progressing and aggressive RRMS who were treated with alemtuzumab at the Cabueñes University Hospital. The short-, medium-, and long-term adverse effects were evaluated following the risk management program of the European Medicines Agency. RESULTS: 39 patients were included, 23 of them received at least two cycles of treatment. Most patients showed at least one adverse event. The following adverse reactions were reported: infusional reactions (17), urinary tract infections (six), thrombopenia (five), and thyroid dysfunction (six). CONCLUSION: In clinical practice alemtuzumab showed an acceptable safety profile in selected patients even if all of them suffered at least one adverse effect. Thorough and prolonged follow-up is required to further confirm the safety of this drug.

Heparin-induced thrombocytopenia in haemodialysis treated with argatroban.

We present the case of a patient diagnosed with likely immune heparin-induced thrombocytopenia (HIT II) based on clinical criteria and a positive ELISA test, in which emergency treatment was crucial, given the seriousness of the process. The discontinuation of heparin and administration of argatroban resolved inefficiency of dialysis resulting from repeated coagulation of the circuit and catheter, allowing peritoneal dialysis without further setbacks. We consider decision-making to be a priority before certifying diagnostic confidence.