1,723 research outputs found
Designed intramolecular blocking of the spin crossover of an Fe(II) complex
A ligand derived from 1,3bpp (2-(pyrazol-1-yl)-6-(pyrazol-3-yl)- pyridine) has been prepared to prove that the spin crossover (SCO) of an Fe(II) complex can be blocked by means of intramolecular interactions not related to the crystal field. Calculations show that the blocking is caused by the energy penalty incurred by the rotation of a phenyl ring, needed to avoid steric hindrance upon SCO
Method to preserve the chiral-symmetry protection of the zeroth Landau level on a two-dimensional lattice
The spectrum of massless Dirac fermions on the surface of a topological
insulator in a perpendicular magnetic field contains a -independent
"zeroth Landau level", protected by chiral symmetry. If the Dirac equation is
discretized on a lattice by the method of "Wilson fermions", the chiral
symmetry is broken and the zeroth Landau level is broadened when has
spatial fluctuations. We show how this lattice artefact can be avoided starting
from an alternative nonlocal discretization scheme introduced by Stacey. A key
step is to spatially separate the states of opposite chirality in the zeroth
Landau level, by adjoining and regions.Comment: Contribution to a special issue of Annals of Physics in memory of
Kostya Efeto
Dynamical simulation of the injection of vortices into a Majorana edge mode
The chiral edge modes of a topological superconductor can transport fermionic
quasiparticles, with Abelian exchange statistics, but they can also transport
non-Abelian anyons: Majorana zero-modes bound to a {\pi}-phase domain wall that
propagates along the boundary. Such an edge vortex is injected by the
application of an h/2e flux bias over a Josephson junction. Existing
descriptions of the injection process rely on the instantaneous scattering
approximation of the adiabatic regime, where the internal dynamics of the
Josephson junction is ignored. Here we go beyond that approximation in a
time-dependent many-body simulation of the injection process, followed by a
braiding of the mobile edge vortex with an immobile Abrikosov vortex in the
bulk of the superconductor. Our simulation sheds light on the properties of the
Josephson junction needed for a successful implementation of a flying Majorana
qubit.Comment: 13 pages 12 figure
Tangent fermions: Dirac or Majorana fermions on a lattice without fermion doubling
I. Introduction
II. Two-dimensional lattice fermions
III. Methods to avoid fermion doubling (sine dispersion, sine plus cosine
dispersion, staggered lattice dispersion, linear sawtooth dispersion, tangent
dispersion)
IV. Topologically protected Dirac cone
V. Application: Klein tunneling (tangent fermions on a space-time lattice,
wave packet propagation)
VI. Application: Strong antilocalization (transfer matrix of tangent
fermions, topological insulator versus graphene)
VII. Application: Anomalous quantum Hall effect (gauge invariant tangent
fermions, topologically protected zeroth Landau level)
VIII. Application: Majorana metal (Dirac versus Majorana fermions, phase
diagram)
IX. OutlookComment: review article, 26 pages, 13 figures; V2: added three appendices, and
provided code for the various implementation
Magnetic breakdown spectrum of a Kramers-Weyl semimetal
We calculate the Landau levels of a Kramers-Weyl semimetal thin slab in a
perpendicular magnetic field . The coupling of Fermi arcs on opposite
surfaces broadens the Landau levels with a band width that oscillates
periodically in . We interpret the spectrum in terms of a one-dimensional
superlattice induced by magnetic breakdown at Weyl points. The band width
oscillations may be observed as -periodic magnetoconductance oscillations,
at weaker fields and higher temperatures than the Shubnikov-de Haas
oscillations due to Landau level quantization. No such spectrum appears in a
generic Weyl semimetal, the Kramers degeneracy at time-reversally invariant
momenta is essential.Comment: 13 pages, 18 figure
Effect of antibiotics on mechanical properties of Bordetella pertussis examined by atomic force microscopy.
In recent years, the coevolution of microorganisms with current antibiotics has increased the mechanisms of bacterial resistance, generating a major health problem worldwide. Bordetella pertussis is a bacterium that causes whooping cough and is capable of adopting different states of virulence, i.e. virulent or avirulent states. In this study, we explored the nanomechanical properties of both virulent and avirulent B. pertussis as exposed to various antibiotics. The nanomechanical studies highlighted that only virulent B. pertussis cells undergo a decrease in their cell elastic modulus and height upon antimicrobial exposure, whereas their avirulent counterparts remain unaffected. This study also permitted to highlight different mechanical properties of individual cells as compared to those growing in close contact with other individuals. In addition, we analyzed the presence on the bacterial cell wall of Filamentous hemagglutinin adhesin (FHA), the major attachment factor produced by virulent Bordetella spp., under different virulence conditions by Force Spectroscopy
Psychometric properties of the Caregiver Preparedness Scale in caregivers of stroke survivors
Objective: To evaluate the psychometric characteristics of the Caregiver Preparedness Scale (CPS) in
caregivers of stroke survivors.
Background: Caregiver preparedness can have an important impact on both the caregiver and the stroke
survivor. The validity and reliability of the CPS has not been tested for the stroke-caregiver population.
Methods: We used a cross-sectional design to study a sample of 156 caregivers of stroke survivors.
Construct validity of the CPS was evaluated by confirmatory factor analysis (CFA). Internal consistency
and test-retest reliability were also evaluated.
Results: Caregivers were, on average, 54 year old (SD ¼ 13.2) and most were women (64.7%). CFA supported
the unidimensionality of the scale (comparative fit index ¼ 0.98). Reliability was also supported:
item-reliability index and itemetotal correlations above 0.30; composite reliability index ¼ 0.93;
Cronbach’s alpha ¼ 0.94; factor score determinacy ¼ 0.97; and test-retest reliability ¼ 0.92.
Conclusion: The CPS is valid and reliable in caregivers of stroke survivors. Scores on this scale may assist
health-care providers in identifying caregivers with less preparedness to provide specific interventions
The Libyan collections in FI (Herbarium Centrale Italicum and Webb Herbarium) and studies on the Libyan Flora by R. Pampanini - Part 2
This work is the continuation of Part 1, published in 2015, and comprises the reconstruction of the original collections of new taxa described by R. Pampanini and other botanists and, where possible, typification of the new names and taxonomical updating. The material studied for the most part concerns Libyan specimens held in the FI and FI-W herbaria but in some case also K, LD, MPU, P, PAD, PAL, ULT. Other material, which Pampanini studied in Florence was subsequently conserved in other herbaria. Specimens belonging to 21 families have been examined, from the Najadaceae to Zygophyllaceae. As well as typification, bibliographical data have been provided for those already typified. In this second part, a total of 113 names have been indexed and 91 typified, taking the names validly published in the entire work to 353, of which 286 are typified. Also on this occasion, we have provided taxonomic updates for each taxon. The Conclusions present a synthetic sum of the taxa still recognised taxonomically (entirely, in new combinations, or with a new status) in recent works on the Flora of N. Africa, in general revisions of various systematic groups, or reconsidered by the authors of this present work. We have also investigated the phyto-geographic origins of the taxa [according to the dominions proposed by Quézel (1978) for N. Africa]. Finally we have very briefly indicated the presence of material of the R. Pampanini collections (for Cyrenaica, together with R. E. G. Pichi Sermolli in 1934) in the most important herbaria. The paragraph "Addenda et Corrigenda" has been added to the final part of the treatise and relates chiefly to taxa omitted from the first part, either on account of new information or as a result of errors which came to light after publication
The UHECR-FR0 Radio Galaxy Connection: A Multi-Messenger Study of Energy Spectra/Composition Emission and Intergalactic Magnetic Field Propagation
This study investigates low luminosity Fanaroff-Riley Type 0 (FR0) radio
galaxies as a potentially significant source of ultra-high energy cosmic rays
(UHECRs). Due to their much higher prevalence in the local universe compared to
more powerful radio galaxies (about five times more than FR-1s), FR0s may
provide a substantial fraction of the total UHECR energy density. To determine
the nucleon composition and energy spectrum of UHECRs emitted by FR0 sources,
simulation results from CRPropa3 are fit to Pierre Auger Observatory data. The
resulting emission spectral indices, rigidity cutoffs, and nucleon fractions
are compared to recent Auger results. The FR0 simulations include the
approximately isotropic distribution of FR0 galaxies and various intergalactic
magnetic field configurations (including random and structured fields) and
predict the fluxes of secondary photons and neutrinos produced during UHECR
propagation through cosmic photon backgrounds. This comprehensive simulation
allows for investigating the properties of the FR0 sources using observational
multi-messenger data.Comment: PoS 444 (38th ICRC) 151
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