Generalized effective hamiltonian for graphene under non-uniform strain

We use a symmetry approach to construct a systematic derivative expansion of the low energy effective Hamiltonian modifying the continuum Dirac description of graphene in the presence of non-uniform elastic deformations. We extract all experimentally relevant terms and describe their physical significance. Among them there is a new gap-opening term that describes the Zeeman coupling of the elastic pseudomagnetic field and the pseudospin. We determine the value of the couplings using a generalized tight binding model.Comment: 13 pages, 1 figure. Matches published version + 1 footnote added, typos correcte

Fiber optic strain gages for stress analysis by means of the hole drilling technique

ABSTRACT: The article deals with the application of the hole drilling technique on structural elements of architectural heritage constructions by using eight fiber optic strain gages. The objective of the research is the on site deduction of the stress state on stone masonry of architectural heritage constructions. The hole drilling method is a Minor Destructive Testing (MDT) giving information about the Principal Stresses of the local stress state around the measured zone and, in consequence, it favours the estimation of the stresses associated with a certain direction, for example the vertical stress of a stone masonry element. Fiber optic technology allows the storage of the strains in the strain gages even when the unit of measure is temporarily not connected. Thus it will be able to monitor the stress measurements as a time function. The tests carried out have compared the applied loads in a laboratory machine with the results obtained by the hole drilling technique through fiber optic strain gages. Until now only resistive strain gages have been used. In this sense the contribution is innovative with an evident advance towards the complete structural characterisation of stone masonry structural elements

Existence and topological stability of Fermi points in multilayered graphene

We study the existence and topological stability of Fermi points in a graphene layer and stacks with many layers. We show that the discrete symmetries (spacetime inversion) stabilize the Fermi points in monolayer, bilayer and multilayer graphene with orthorhombic stacking. The bands near $k=0$ and $\epsilon=0$ in multilayers with the Bernal stacking depend on the parity of the number of layers, and Fermi points are unstable when the number of layers is odd. The low energy changes in the electronic structure induced by commensurate perturbations which mix the two Dirac points are also investigated.Comment: 6 pages, 6 figures. Expanded version as will appear in PR

Space dependent Fermi velocity in strained graphene

We resolve some apparent discrepancies between two different models for curved graphene: the one based on tight binding and elasticity theory, and the covariant approach based on quantum field theory in curved space. We demonstrate that strained or corrugated samples will have a space dependent Fermi velocity in either approach that can affect the interpretation of some experiments.Comment: Revised version as will appear in Phys. Rev. Let

Low risk perception about ticks and tick-borne diseases in an area recently invaded by ticks in northwestern italy

Risk perception, together with the adoption of measures to prevent tick bites, may strongly influence human exposure to ticks and transmitted pathogens. We created a questionnaire to evaluate how people perceive the health risk posed by ticks in an area recently invaded by these arthropods, in the western Italian Alps. Moreover, through a collaborative effort with park rangers and physicians, we investigated which tick species bite humans and their infection with pathogens (Borrelia burgdorferi s.l., Anaplasma phagocytophilum, and spotted-fever group Rickettsiae). Apart from two Dermacentor marginatus bites, we identified Ixodes ricinus (n = 124) as the main species responsible for tick bites. The investigated pathogens infected 25.4% of tested I. ricinus. The evaluation of the engorgement rate of biting I. ricinus revealed that they had been likely feeding on humans for 24 h or more, suggesting a high probability of pathogen transmission. Indeed, the questionnaires revealed that people infrequently adopt preventive measures, such as inspecting the body for ticks, although most respondents claimed that ticks are a threat to human health. Having suffered from previous tick bites was positively associated with the adoption of personal protection measures. Given the increasing incidence of tick-borne diseases in the region, the public should be better informed about the possibility of being bitten by infected ticks in order to mitigate the risk

Electronic interactions in fullerene spheres

The electron-phonon and Coulomb interactions inC$_{60}$, and larger fullerene spheres are analyzed. The coupling between electrons and intramolecular vibrations give corrections $\sim 1 - 10$ meV to the electronic energies for C$_{60}$, and scales as $R^{-4}$ in larger molecules. The energies associated with electrostatic interactions are of order $\sim 1 - 4$ eV, in C$_{60}$ and scale as $R^{-1}$. Charged fullerenes show enhanced electron-phonon coupling, $\sim 10$ meV, which scales as $R^{-2}$. Finally, it is argued that non only C$_{60}^{-}$, but also C$_{60}^{--}$ are highly polarizable molecules. The polarizabilities scale as $R^3$ and $R^4$, respectively. The role of this large polarizability in mediating intermolecular interactions is also discussed.Comment: 12 pages. No figure