1,682 research outputs found

    Mirror-protected Majorana zero modes in ff-wave multilayer graphene superconductors

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    Inspired by recent experimental discoveries of superconductivity in chirally-stacked and twisted multilayer graphene, we study models of ff-wave superconductivity on the honeycomb lattice with arbitrary numbers of layers. These models respect a mirror symmetry that allows classification of the bands by a mirror-projected winding number Μ±\nu_\pm. For odd numbers of layers, the systems are topologically nontrivial with Μ±=±1\nu_\pm = \pm 1. Along each mirror-preserving edge in armchair nanoribbons, there are two protected Majorana zero modes. These modes are present even if the sample is finite in both directions, such as in rectangular and hexagonal flakes. Crucially, zero modes can also be confined to vortex cores, which can be created by a magnetic field or localized magnetic impurities and accessed by local scanning probes. Finally, we apply these models to twisted bilayer and trilayer systems, which also feature boundary-projected and vortex-confined zero modes. Since vortices are experimentally accessible, our study suggests that superconducting multilayer graphene systems are promising platforms to create and manipulate Majorana zero modes.Comment: Comments are greatly appreciated. 8 + 22 pages with 4 + 15 figure

    The Traspena meteorite: heliocentric orbit, atmospheric trajectory, strewn field, and petrography of a new L5 ordinary chondrite

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    The Traspena meteorite fell on 2021 January 18 about 20 km south-east of the city of Lugo (Galiza, Spain), shortly after a huge and bright fireball crossed the sky for 4.84 s. Astrometric measurements obtained from the fireball cameras of the Universidade de Santiago de Compostela (USC) as well as from many casual videos were used to determine the atmospheric trajectory of this meteoroid which penetrated the atmosphere and generated sound waves that were detected at three seismic stations. The original meteoroid had a diameter of about 1.15 m and a mass around 2620 kg. It impacted the Earth’s atmosphere with a steep entry angle of about 76∘.7 from a height of 75.10 km until fading away at 15.75 km with a velocity of 2.38 km s−1. Before the impact, this small asteroid was orbiting the Sun with a semimajor axis of 1.125 au, a moderate eccentricity of 0.386, and a low inclination of 4∘.55. A weak evidence of dynamic link with the PHA (Potential Hazardous Asteroid) Minos was investigated. During the atmospheric entry, two major fragmentation events occurred between heights of 35 and 29 km at aerodynamic pressures between 1 and 5 MPa. The strewn field was computed after calculating the individual dark flights of the main body along with two smaller fragments. Fortunately, 2 month after the superbolide, a 527-g meteorite was found. It was examined using several geochemical and petrographic analyses which allowed us to classify it as a moderately shocked (S3) L5 ordinary chondrite with a bulk density of 3.25 g cm−3This paper was supported by the Xunta de Galicia (Spain) under the ED431B 2020/38 grantS

    Thermo-optical detection of defects and decarbonation in natural smithsonite

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    Natural hydrothermal ZnCO3 crystal aggregates are nominally anhydrous phases with interfacial water, with substitutional divalent cations and decarbonation c. 300°C. All these common features must be involved during the experimental heating of a thermoluminescence (TL) glow curve up to 500°C: dehydration–dehydroxylation, phase transition and ion transition of point defects in Zn2+ positions. A representative specimen of natural smithsonite was analysed by X-ray fluorescence spectrometry, field emission scanning electron microscopy (FESEM) with a chemical probe of energy dispersive spectrometer, high temperature in situ X-ray diffraction, differential scanning calorimetry, differential thermal analyses coupled to thermogravimetry, TL, radioluminescence and high resolution spectra thermoluminescence (3DTL), to gain an overview of the spectra emission and defects linkages modified by heating from room temperature up to 500°C. The ZnCO3 specimen contains minor amounts of Ca, Cu, Cr, Cd, Pb, Ce, Co, Ni, Mn and Fe. Under FESEM, it displays CaCO3 clusters and oscillatory zoning distribution with lamellae ranging from Ca0.11Zn0.89 to Ca0.19Zn0.81. The analytical results suggest assignments of defects and processes to measured 3DTL emission bands, as follows: (1) peak at ~260°C, ~360 nm bonds, breaking during the thermal decarbonation process; (2) peak ~120°C, ~340 nm: non-bridging oxygen centres associated to a complex dehydration–dehydroxylation process and (3) peak at ~170°C, ~650 nm, crystal field effects on the thermoluminescence of Mn2+ centres and associated transitional elements in the ZnCO3 phase.This work was supported in part by PROJETS: C·I.C.Y.T. CGL2008-03842, Comunidad AutĂłnoma de Madrid MATERNAS (CAM) S0505/MAT/0094, CTQ2007-60895/BQU and a Contract Post-PhD CSIC JAE-DOC

    Aspergillus endocarditis in the recent years, report of cases of a multicentric national cohort and literature review

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    OBJECTIVES: (1) To describe the incidence, clinical characteristics, treatment and outcome of Aspergillus Endocarditis (AE) in a nationwide multicentric cohort (GAMES). (2) To compare the AE cases of the GAMES cohort, with the AE cases reported in the literature since 2010. (3) To identify variables related to mortality. METHODS: We recruited 10 AE cases included in the GAMES cohort (January 2008-December 2018) and 51 cases from the literature published from January 2010 to July 2019. RESULTS: 4528 patients with infectious endocarditis (IE) were included in the GAMES cohort, of them 10 (0.2%) were AE. After comparing our 10 cases with the 51 of the literature, no differences were found. Analysing the 61 AE cases together, 55.7% were male, median age 45 years. Their main underlying conditions were as follows: prosthetic valve surgery (34.4%) and solid organ transplant (SOT) (19.7%). Mainly affecting mitral (36.1%) and aortic valve (29.5%). Main isolated species were as follows: Aspergillus fumigatus (47.5%) and Aspergillus flavus (24.6%). Embolisms occurred in 54%. Patients were treated with antifungals (90.2%), heart surgery (85.2%) or both (78.7%). Overall, 52.5% died. A greater mortality was observed in immunosuppressed patients (59.4% vs. 24.1%, OR = 4.09, 95%CI = 1.26-13.19, p = .02), and lower mortality was associated with undergoing cardiac surgery plus azole therapy (28.1% vs. 65.5%, OR = 0.22, 95%CI = 0.07-0.72, p = .01). CONCLUSIONS: AE accounts for 0.2% of all IE episodes of a national multicentric cohort, mainly affecting patients with previous valvular surgery or SOT recipients. Mortality remains high especially in immunosuppressed hosts and azole-based treatment combined with surgical resection are related to a better outcome

    Structural and temperature-dependent luminescence of Terbium doped YAl3(BO3)4 phosphor synthesized by the combustion method

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    A series of Y1-xAl3(BO3)4:x Tb3+ (x = 0.5 to 7 wt%) phosphors synthesized by a gel combustion method have been systemically investigated by X-ray diffraction (XRD), Fourier transform infrared (FTIR), energy dispersive spectroscopy (EDS), and photoluminescence (PL) as a function of temperature from 300 K to 10 K and 300 K-550 K. An XRD analysis confirms that the phosphors crystallized, and its crystal structure was analysed. The synthesized phosphor matches the XRD pattern provided in the ICSD File No 96-152-6006. The FTIR analysis indicates that nitrates and organic matter have been completely removed and the BO3 groups are present. The broad PL band peaked at 420 nm with a shoulder circa 460 nm of YAl3(BO3)4 is associated with hydrous components which attached to the sample in environmental conditions after synthesis. The PL spectra of YAl3(BO3):Tb3+ phosphors exhibit a bright and narrow green main emission peak at 543 nm corresponding to the 5D4 -> 7F5 transition under 359 nm excitation. The PL intensity increases with increasing Tb3+ ion concentration up to 5 wt %, followed by evidence for concentration quenching. There is a possibility that higher concentration quenching could be from confinement effects of localised resonant energy transfer. PL data revealed that acti-vation energies for thermal quenching at 485 nm and 543 nm were found to be 0.659 and 0.092 eV, and 0.585 and 0.087 eV, respectively

    Relationship between Arterial Calcifications on Mammograms and Cardiovascular Events: A Twenty-Three Year Follow-Up Retrospective Cohort Study

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    Purpose: Breast arterial calcifications (BAC) have been associated with cardiovascular diseases. We aimed to examine whether the presence of BAC could predict the development of cardiovascular events in the very long term, as evidence has suggested. Patients and Methods: We conducted a 23-year follow-up retrospective cohort study considering women specifically studied for breast cancer. After reviewing the mammograms of 1759 women, we selected 128 patients with BAC and an equal number of women without BAC. Results: Women with BAC had higher relative risk (RR) for cardiovascular events, globally 1.66 (95% CI): 1.31–2.10 vs. 0.53 (0.39–0.72), and individually for ischemic heart disease 3.25 (1.53–6.90) vs. 0.85 (0.77–0.94), hypertensive heart disease 2.85 (1.59–5.09) vs. 0.79 (0.69–0.89), valvular heart disease 2.19 (1.28–3.75) vs. 0.83 (0.73–0.94), congestive heart failure 2.06 (1.19–3.56) vs. 0.85 (0.75–0.96), peripheral vascular disease 2.8 (1.42–5.52) vs. 0.85 (0.76–0.94), atrial fibrillation 1.83 (1.09–3.08) vs. 0.86 (0.76–0.98), and lacunar infarction 2.23 (1.21–4.09) vs. 0.86 (0.77–0.96). Cox’s multivariate analysis, also considering classical risk factors, indicated that this BAC was significantly and independently associated with survival (both cardiovascular event-free and specific survival; 1.94 (1.38–2.73) and 6.6 (2.4–18.4)). Conclusions: Our data confirm the strong association of BAC on mammograms and the development cardiovascular events, but also evidence the association of BAC with cardiovascular event-free and specific survival