1,459 research outputs found
Representation of the space in the early XX century poetic discourse
Analysis of the representatives of outer space in the poetic texts of the authors representing different literary directions (K. Balmont - impressionism, V. Bryusov, M. Voloshin - symbolism, N. Gumilev -acmeism) allowed to present a holistic impression of the image of outer space in the poetry of a certain period of time. The Space in the poetic discourse of the early XX century is synthetic, it is created by a comprehensive perception of reality in which the second plan is forming on the basis of perceptual data (especially on the visual impressions) reinterpreted in the literary textsyesBelgorod State Universit
Superconductivity in the Cuprates as a Consequence of Antiferromagnetism and a Large Hole Density of States
We briefly review a theory for the cuprates that has been recently proposed
based on the movement and interaction of holes in antiferromagnetic (AF)
backgrounds. A robust peak in the hole density of states (DOS) is crucial to
produce a large critical temperature once a source of hole attraction is
identified. The predictions of this scenario are compared with experiments. The
stability of the calculations after modifying some of the original assumptions
is addressed. We find that if the dispersion is changed from an
antiferromagnetic band at half-filling to a tight binding
narrow band at , the main conclusions of the approach remain
basically the same i.e. superconductivity appears in the -channel and is enhanced by a large DOS. The main features
distinguishing these ideas from more standard theories based on
antiferromagnetic correlations are here discussed.Comment: RevTex, 7 pages, 5 figures are available on reques
Ordered droplet structures at the liquid crystal surface and elastic-capillary colloidal interactions
We demonstrate a variety of ordered patterns, including hexagonal structures
and chains, formed by colloidal particles (droplets) at the free surface of a
nematic liquid crystal (LC). The surface placement introduces a new type of
particle interaction as compared to particles entirely in the LC bulk. Namely,
director deformations caused by the particle lead to distortions of the
interface and thus to capillary attraction. The elastic-capillary coupling is
strong enough to remain relevant even at the micron scale when its
buoyancy-capillary counterpart becomes irrelevant.Comment: 10 pages, 3 figures, to be published in Physical Review Letter
Surface alignment and anchoring transitions in nematic lyotropic chromonic liquid crystal
The surface alignment of lyotropic chromonic liquid crystals (LCLCs) can be
not only planar (tangential) but also homeotropic, with self-assembled
aggregates perpendicular to the substrate, as demonstrated by mapping optical
retardation and by three-dimensional imaging of the director field. With time,
the homeotropic nematic undergoes a transition into a tangential state. The
anchoring transition is discontinuous and can be described by a double-well
anchoring potential with two minima corresponding to tangential and homeotropic
orientation.Comment: Accepted for publication in Phys. Rev. Lett. (Accepted Wednesday Jun
02, 2010
Single Hole Green's Functions in Insulating Copper Oxides at Nonzero Temperature
We consider the single hole dynamics in a modified model at finite
temperature. The modified model includes a next nearest () and next-next
nearest () hopping. The model has been considered before in the zero
temperature limit to explain angle resolved photo-emission measurements. We
extend this consideration to the case of finite temperature where long-range
anti-ferromagnetic order is destroyed, using the self-consistent Born
approximation. The Dyson equation which relates the single hole Green's
functions for a fixed pseudo-spin and for fixed spin is derived. The Green's
function with fixed pseudo-spin is infrared stable but the Green's function
with fixed spin is close to an infrared divergency. We demonstrate how to
renormalize this Green's function in order to assure numerical convergence. At
non-zero temperature the quasi-particle peaks are found to shift down in energy
and to be broadened.Comment: 7 pages, RevTex, 5 Postscript figure
Comparison of 32-site exact diagonalization results and ARPES spectral functions for the AFM insulator
We explore the success of various versions of the one-band t-J model in
explaining the full spectral functions found in angle-resolved photoemission
spectra for the prototypical, quasi two-dimensional, tetragonal,
antiferromagnetic insulator . After presenting arguments
justifying our extraction of from the experimental data, we rely
on exact-diagonalization results from studies of a square 32-site lattice, the
largest cluster for which such information is presently available, to perform
this comparison. Our work leads us to believe that (i) a one-band model that
includes hopping out to third-nearest neighbours, as well three-site,
spin-dependent hopping, can indeed explain not only the dispersion relation,
but also the quasiparticle lifetimes -- only in the neighbourhood of do we find disagreement; (ii) an energy-dependent broadening
function, , is important in accounting for the
incoherent contributions to the spectral functions.Comment: 8 pages, Revtex
Evidence for Quasiparticle Decay in Photoemission from Underdoped Cuprates
I argue that the ``gap'' recently observed at the Brillouin zone face of
cuprate superconductors in photoemission by Marshall et al [Phys. Rev. Lett.
76, 4841 (1996)] and Ding et al [Nature 382, 54 (1996)] is evidence for the
decay of the injected hole into a spinon-holon pair.Comment: 4 pages of ReVTeX, 3 eps figure
Thermal and Mechanical Characteristics of Polymer Composites Based on Epoxy Resin, Aluminium Nanopowders and Boric Acid
The epoxy polymers are characterized by low thermal stability and high flammability. Nanoparticles are considered to be effective fillers of polymer composites for improving their thermal and functional properties. In this work, the epoxy composites were prepared using epoxy resin ED-20, polyethylene polyamine as a hardener, aluminum nanopowder and boric acid fine powder as flame-retardant filler. The thermal characteristics of the obtained samples were studied using thermogravimetric analysis and differential scanning calorimetry. The mechanical characteristics of epoxy composites were also studied. It was found that an addition of all fillers enhances the thermal stability and mechanical characteristics of the epoxy composites. The best thermal stability showed the epoxy composite filled with boric acid. The highest flexural properties showed the epoxy composite based on the combination of boric acid and aluminum nanopowder
Hole photoproduction in insulating copper oxide
Basing on t-J model we calculate the k-dependence of a single hole
photoproduction probability for CuO2 plane at zero doping. We also discuss the
radiation of spin-waves which can substantially deform the shape of
photoemission spectra.Comment: latex 8 pages, 3 figure
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