In: Proceedings of the Estonian Academy of Sciences: official publication of Tallinn Technical University and the Estonian Academy of Sciences = Eesti Teaduste Akadeemia toimetised = Izvestija Akademii Nauk Ėstonii. Engineering = tehnikateadused = techničeskie nauki, Volume 7, Issue 1, p. 35
Owing to its array of unique properties, graphene is a promising material for a wide variety of applications. Being two-dimensional, the properties of graphene are also easily tuned via proximity to other materials. In this work, we investigate the possibility of inducing electrical and optical anisotropy in graphene by interfacing it with other anisotropic carbon systems, including nanoporous graphene and arrays of graphene nanoribbons. We find that such materials do indeed induce such anisotropy in graphene while also preserving the unique properties offered by graphene's Dirac band structure, namely, its superior charge transport and long-wavelength optical absorption. The optical anisotropy makes such heterostructures interesting for their use in applications related to long-wavelength polarimetry, while the electrical anisotropy may be valuable for enhancing the performance of graphene photothermoelectric detectors. ; ICN2 is supported by the Severo Ochoa Centers of Excellence Program, funded by the Spanish State Research Agency (AEI, Grant No. SEV-2017-0706). ICN2 is also supported by the CERCA Program of the Generalitat de Catalunya. This work received funding from the European Union's Horizon 2020 Research and Innovation Program under Grant Agreement No. 825272 (ULISSES) and from the project "Waveguide-Integrated Mid-Infrared Graphene Detectors for Optical Gas Sensor Systems," Reference No. PCI2018-093128, funded by the Spanish Ministry of Science and Innovation—AEI.
The origin of power asymmetry and other measures of statistical anisotropy on the largest scales of the universe, as manifested in cosmic microwave background (CMB) and large-scale structure data, is a long-standing open question in cosmology. In this paper, we analyse the Planck Legacy temperature anisotropy data and find strong evidence for a violation of the Cosmological principle of isotropy, with a probability of being a statistical fluctuation of the order of ∼10-9. The detected anisotropy is related to large-scale directional ΛCDM cosmological parameter variations across the CMB sky, which are sourced by three distinct patches in the maps with circularly averaged sizes between 40° and 70° in radius. We discuss the robustness of our findings to different foreground separation methods and analysis choices, and find consistent results from WMAP data when limiting the analysis to the same scales. We argue that these well-defined regions within the cosmological parameter maps may reflect finite and casually disjoint horizons across the observable universe. In particular, we show that the observed relation between horizon size and mean dark energy density within a given horizon is in good agreement with expectations from a recently proposed model of the universe that explains cosmic acceleration and cosmological parameter tensions between the high- and low-redshift universe from the existence of casual horizons within our universe. ; This work is dedicated to the memory of my father, Marcelo. PF is specially grateful to K. Benabed and O. Doré for useful comments on the draft, I. Tutusaus for advice with iMinuit, and J. Guerrero for help with the Hidra computing cluster at ICE. Hidra is funded by CSIC project EQC2019-005664-P, with European FEDER funds. The development of this project required 800 000+ CPU hours at Hidra. Some of the results in this paper have been derived using the HEALPY (Zonca et al. 2019), HEALPIX (Górski et al. 2005), and CAMB (Lewis, Challinor & Lasenby 2000) packages. We acknowledge support from MINECO through grants ESP2017-89838-C3-1-R and PGC2019-102021-B-100, the H2020 European Union grants LACEGAL 734374 and EWC 776247 with ERDF funds, and Generalitat de Catalunya through CERCA to grant 2017-SGR-885 and funding to IEEC.
This work was supported by the European Union's Horizon2020 Research and Innovation Programme under grant agreement No. 731976 (MAGENTA). G. Muscas acknowledges financial support from the Swedish Research Council (VR) and the Olle Engkvist Byggmästare foundation.
Publisher's version (útgefin grein) ; We investigate the effect of atomic ordering on the magnetic anisotropy of Ni80Fe20 at.% (Py). To this end, Py films were grown epitaxially on MgO(001) using dc magnetron sputtering (dcMS) and high power impulse magnetron sputtering (HiPIMS). Aside from twin boundaries observed in the latter case, both methods present high quality single crystals with cube-on-cube epitaxial relationship as verified by the polar mapping of important crystal planes. However, X-ray diffraction results indicate higher order for the dcMS deposited film towards L12 Ni3Fe superlattice. This difference can be understood by the very high deposition rate of HiPIMS during each pulse which suppresses adatom mobility and ordering. We show that the dcMS deposited film presents biaxial anisotropy while HiPIMS deposition gives well defined uniaxial anisotropy. Thus, higher order achieved in the dcMS deposition behaves as predicted by magnetocrystalline anisotropy i.e. easy axis along the [111] direction that forced in the plane along the [110] direction due to shape anisotropy. The uniaxial behaviour in HiPIMS deposited film then can be explained by pair ordering or more recent localized composition non-uniformity theories. Further, we studied magnetoresistance of the films along the [100] directions using an extended van der Pauw method. We find that the electrical resistivities of the dcMS deposited film are lower than in their HiPIMS counterparts verifying the higher order in the dcMS case. ; This work was partially supported by the Icelandic Research Fund (Rannis) Grant Nos. 196141, 130029 and 120002023, and the Swedish Government Agency for Innovation Systems (VINNOVA) contract No. 2014-04876. ; Peer Reviewed
UHECR (Ultra High Energy Cosmic Rays) were expected to be protons, to fly straight and to suffer of a GZK (opacity on CMB radiation) cut off. AUGER did suggest on 2007 that such early UHECR anisotropy was compatible with the foreseen Super-Galactic plane while both HIRES and AUGER confirmed such apparent GZK cut-off in the spectra. However the same AUGER composition since 2007 was favoring nuclei (and not nucleon). The recent absence of narrow angle clustering in UHECR maps, as it should be expected by protons, the missing of events along nearest Cluster Virgo, the wide spread (16°) angle of UHECR along CenA are in disagreement with first proton–UHECR AUGER understanding. We claimed since 2008 a light nuclei role for CenA crowded area. On the other side the ICECUBE absence of TeVs neutrino clustering or anisotropy, its spectra steepening is favoring mostly a ruling atmospheric neutrino noise up to tens TeV. However recent two PeV neutrino event cannot easily coexist or being extrapolate with such atmospheric ruling scenario, nor with GZK (either nucleon or nuclei) secondaries expected spectra. Finally tens TeV gamma anisotropy in ARGO–MILAGRO–ICECUBE maps may hardly be associated with known hadronic sources. We<br />imagine such anisotropy ruled by diffused gamma secondaries, being shine along UHECR bending and flight: radioactive light and heavy UHECR nuclei, while decaying in flight, may paint in the sky (by gamma, electrons and neutrinos) their trajectories and bending, connecting UHECR spread events with TeV anisotropy, as well offering a very realistic source of first, otherwise puzzling, observed PeV neutrinos.
Anisotropy of attenuation of acoustic waves in photorefractive BSO and BGO crystals has been studied in the frequency range of 0.4−1.6 GHz. The anisotropy parameters determined by the imaginary constants of BSO and BGO crystals are equal 0.58 and 0.52, respectively. It is shown that the most contribution of dielectric loss to the attenuation of acoustic waves is observed for the piezoactive transversal waves propagating in the (100) plane.