We study the effect of Coulomb interaction between charge carriers on the properties of graphene monolayer, assuming that the strength of the interaction is controlled by the dielectric permittivity ...of the substrate on which the graphene layer is placed. To this end, we consider the tight-binding model on the hexagonal lattice coupled to the noncompact gauge field. The action of the latter is also discretized on the hexagonal lattice. Equilibrium ensembles of gauge field configurations are obtained using the hybrid Monte Carlo algorithm. Our numerical results indicate that at sufficiently strong coupling, that is, at sufficiently small substrate dielectric permittivities epsilon lap 4 and at sufficiently small temperatures T lap 1 x 10 super(4) K, the symmetry between simple sublattices of hexagonal lattice breaks down spontaneously and the low-frequency conductivity gradually decreases down to 20- 30% of its weak-coupling value. On the other hand, in the weak-coupling regime (with epsilon gap 4), the conductivity practically does not depend on epsilon and is close to the universal value sigma sub(0) = 1/4.
We report on the results of the first-principles numerical study of spontaneous breaking of chiral (sublattice) symmetry in suspended monolayer graphene due to electrostatic interaction, which takes ...into account the screening of Coulomb potential by electrons on σ orbitals. In contrast to the results of previous numerical simulations with unscreened potential, we find that suspended graphene is in the conducting phase with unbroken chiral symmetry. This finding is in agreement with recent experimental results by the Manchester group D. C. Elias et al., Nat. Phys. 7, 701 (2011); A. S. Mayorov et al., Nano Lett. 12, 4629 (2012). Further, by artificially increasing the interaction strength, we demonstrate that suspended graphene is quite close to the phase transition associated with spontaneous chiral symmetry breaking, which suggests that fluctuations of chirality and nonperturbative effects might still be quite important.
The first observation of two excited states of the
is presented together with the measurements of the
mass and the mass difference
. Additionally, we present a study of
-baryon excited states, ...namely,
,
,
, and
, decaying into
. The two analyses are carried out using the data collected in proton-proton collisions at a centre-of-mass energy of 13 TeV by the CMS experiment and corresponding to an integrated luminosity of about 140 fb
.
The axial magnetic effect is the generation of an equilibrium dissipationless energy flow of chiral fermions in the direction of the axial (chiral) magnetic field. At finite temperature the ...dissipationless energy transfer may be realized in the absence of any chemical potentials. We numerically study the temperature behavior of the axial magnetic effect in quenched SU(2) lattice gauge theory. We show that in the confinement (hadron) phase the effect is absent. In the deconfinement transition region the conductivity quickly increases, reaching the asymptotic T super(2) behavior in a deep deconfinement (plasma) phase. Apart from an overall proportionality factor, our results qualitatively agree with theoretical predictions for the behavior of the energy flow as a function of temperature and strength of the axial magnetic field.
We study the correlator of two vector currents in quenched SU(2) lattice gauge theory with a chirally invariant lattice Dirac operator with a constant external magnetic field. It is found that in the ...confinement phase the correlator of the components of the current parallel to the magnetic field decays much slower than in the absence of a magnetic field, while for other components the correlation length slightly decreases. We apply the maximal entropy method to extract the corresponding spectral function. In the limit of zero frequency this spectral function yields the electric conductivity of quenched theory. We find that in the confinement phase the external magnetic field induces nonzero electric conductivity along the direction of the field, transforming the system from an insulator into an anisotropic conductor. In the deconfinement phase the conductivity does not exhibit any sizable dependence on the magnetic field.
Breast cancer is the most common type of cancer worldwide. Diagnosing breast cancer relies on clinical examination, imaging and biopsy. A core-needle biopsy enables a morphological and biochemical ...characterization of the cancer and is considered the gold standard for breast cancer diagnosis. A histopathological examination uses high-resolution microscopes with outstanding contrast in the 2D plane, but the spatial resolution in the third, Z-direction, is reduced. In the present paper, we propose two high-resolution table-top systems for phase-contrast X-ray tomography of soft-tissue samples. The first system implements a classical Talbot-Lau interferometer and allows to perform ex-vivo imaging of human breast samples with a voxel size of 5.57 μm. The second system with a comparable voxel size relies on a Sigray MAAST X-ray source with structured anode. For the first time, we demonstrate the applicability of the latter to perform X-ray imaging of human breast specimens with ductal carcinoma in-situ. We assessed image quality of both setups and compared it to histology. We showed that both setups made it possible to target internal features of breast specimens with better resolution and contrast than previously achieved, demonstrating that grating-based phase-contrast X-ray CT could be a complementary tool for clinical histopathology.
The present work demonstrates the potential applicability of additive manufacturing to X-Ray refractive nano-lenses. A compound refractive lens with a radius of 5 µm was produced by the two-photon ...polymerization induced lithography. It was successfully tested at the X-ray microfocus laboratory source and a focal spot of 5 μm was measured. An amorphous nature of polymer material combined with the potential of additive technologies may result in a significantly enhanced focusing performance compared to the best examples of modern X-ray compound refractive lenses.
We highlight the progress, current status, and open challenges of QCD-driven physics, in theory and in experiment. We discuss how the strong interaction is intimately connected to a broad sweep of ...physical problems, in settings ranging from astrophysics and cosmology to strongly coupled, complex systems in particle and condensed-matter physics, as well as to searches for physics beyond the Standard Model. We also discuss how success in describing the strong interaction impacts other fields, and, in turn, how such subjects can impact studies of the strong interaction. In the course of the work we offer a perspective on the many research streams which flow into and out of QCD, as well as a vision for future developments.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
An extreme bottom-up filling variant of superconformal Au electrodeposition yielding void-free filling of recessed features is demonstrated with diffraction gratings composed of a two-dimensional ...patterned "chessboard" array of square vias of aspect ratio (depth/width) ≈ 23 as well as one-dimensional arrays of trenches having aspect ratios exceeding 50 and 65. Deposition on planar and patterned substrates is examined in several near-neutral x mol·L
Na
Au(SO
)
+ 0.64 mol·L
Na
SO
electrolytes (x = 0.08, 0.16, 0.32) containing ≈ 50 μmol·L
Bi
additive. The electrolytes are similar to those used in earlier work, although the upper bound on Au(SO
)
concentration is twofold greater than previously described. Filling results are complemented by associated current and deposition charge transients whose features, particularly with well controlled pH, exhibit repeatable behaviors and timescales for incubation of passive deposition followed by bottom-up, void-free filling. While incompletely filled features can exhibit substantial via-to-via variation in fill height, self-passivation that follows complete bottom-up filling results in highly uniform filling profiles across the substrates. Visibility measurements capture the quality and uniformity of the as-formed wafer scale gratings. X-ray phase contrast imaging demonstrates their potential for imaging applications.
The study analyzes the major adverse factors that caused destruction of forest stands in Novgorod region over the past 10 years based on the data on monitoring the state of forest ecosystems. Adverse ...effects such as weather conditions, fires, forest diseases, and insect forest pests were considered. The crucial reason of forest stand mortality in the region over the period under study was revealed. The features and patterns of the mortality of forest stands were studied with regard to their taxation characteristics and confinement to the natural landscapes of the region.
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