1,800 research outputs found
Giant vortices, vortex rings and reentrant behavior in type-1.5 superconductors
We predict that in a bulk type-1.5 superconductor the competing magnetic
responses of the two components of the order parameter can result in a vortex
interaction that generates group-stabilized giant vortices and unusual vortex
rings in the absence of any extrinsic pinning or confinement mechanism. We also
find within the Ginzburg-Landau theory a rich phase diagram with successions of
behaviors like type-1 -> type-1.5 -> type-2 -> type-1.5 as temperature
decreases.Comment: 5 pages, 4 figure
CEMENT SELECTION IN DENTAL PRACTICE
The cementation procedure is considered to be the most important stage of fixed prosthodontics, while the correct selection of cement is the guarantee of successful restoration which is conditioned by the its durability. Over the recent years, numerous cementing substances have been introduced to the dental practice that differ greatly from conventional cements with their properties and application methods and that is why even experienced dentists often have certain difficulties in the variety of cements to choose the one that is right for each clinical case. The selection of cement depends on a number of factors, such as the type of resorption substance, the shape of prepared tooth, the possibility to isolate the area, subject to cementation in the oral cavity as well as the patient’s aesthetic requirements. Thus, the objective of the article is to analyze currently used dental cements in order to help the dentists make the right selection of cement for different clinical cases.The cementation procedure is considered to be the most important stage of fixed prosthodontics, while the correct selection of cement is the guarantee of successful restoration which is conditioned by the its durability. Over the recent years, numerous cementing substances have been introduced to the dental practice that differ greatly from conventional cements with their properties and application methods and that is why even experienced dentists often have certain difficulties in the variety of cements to choose the one that is right for each clinical case. The selection of cement depends on a number of factors, such as the type of resorption substance, the shape of prepared tooth, the possibility to isolate the area, subject to cementation in the oral cavity as well as the patient’s aesthetic requirements. Thus, the objective of the article is to analyze currently used dental cements in order to help the dentists make the right selection of cement for different clinical cases
Fermionic vacuum currents in topologically nontrivial braneworlds: Two-brane geometry
The vacuum expectation value (VEV) of the fermionic current density is
investigated in the geometry of two parallel branes in locally AdS spacetime
with a part of spatial dimensions compactified to a torus. Along the toral
dimensions quasiperiodicity conditions are imposed with general phases and the
presence of a constant gauge field is assumed. Different types of boundary
conditions are discussed on the branes, including the bag boundary condition
and the conditions arising in -symmetric braneworld models. Nonzero
vacuum currents appear along the compact dimensions only. In the region between
the branes they are decomposed into the brane-free and brane-induced
contributions. Both these contributions are periodic functions of the magnetic
flux enclosed by compact dimensions with the period equal to the flux quantum.
Depending on the boundary conditions, the presence of the branes can either
increase or decrease the vacuum current density. For a part of boundary
conditions, a memory effect is present in the limit when one of the branes
tends to the AdS boundary. Unlike to the fermion condensate and the VEV of the
energy-momentum tensor, the VEV of the current density is finite on the branes.
Applications are given to higher-dimensional generalizations of the
Randall-Sundrum models with two branes and with toroidally compact subspace.
The features of the fermionic current are discussed in odd-dimensional parity
and time-reversal symmetric models. The corresponding results for
three-dimensional spacetime are applied to finite length curved graphene tubes
threaded by a magnetic flux. It is shown that a nonzero current density can
also appear in the absence of the magnetic flux if the fields corresponding to
two different points of the Brillouin zone obey different boundary conditions
on the tube edges.Comment: 33 pages, 7 figures, PACS numbers: 04.62.+v, 03.70.+k, 98.80.-k,
61.46.F
Flux tubes and the type-I/type-II transition in a superconductor coupled to a superfluid
We analyze magnetic flux tubes at zero temperature in a superconductor that
is coupled to a superfluid via both density and gradient (``entrainment'')
interactions. The example we have in mind is high-density nuclear matter, which
is a proton superconductor and a neutron superfluid, but our treatment is
general and simple, modeling the interactions as a Ginzburg-Landau effective
theory with four-fermion couplings, including only s-wave pairing. We
numerically solve the field equations for flux tubes with an arbitrary number
of flux quanta, and compare their energies. This allows us to map the
type-I/type-II transition in the superconductor, which occurs at the
conventional kappa = 1/sqrt(2) if the condensates are uncoupled.
We find that a density coupling between the condensates raises the critical
kappa and, for a sufficiently high neutron density, resolves the type-I/type-II
transition line into an infinite number of bands corresponding to
``type-II(n)'' phases, in which n, the number of quanta in the favored flux
tube, steps from 1 to infinity. For lower neutron density, the coupling creates
spinodal regions around the type-I/type-II boundary, in which metastable flux
configurations are possible. We find that a gradient coupling between the
condensates lowers the critical kappa and creates spinodal regions. These
exotic phenomena may not occur in nuclear matter, which is thought to be deep
in the type-II region, but might be observed in condensed matter systems.Comment: 14 pages, improved discussion of the effects of varying the
neutron/proton condensate ratio; added reference
Oscillations of General Relativistic Multi-fluid/Multi-layer Compact Stars
We develop the formalism for determining the quasinormal modes of general
relativistic multi-fluid compact stars in such a way that the impact of
superfluid gap data can be assessed. Our results represent the first attempt to
study true multi-layer dynamics, an important step towards considering
realistic superfluid/superconducting compact stars. We combine a relativistic
model for entrainment with model equations of state that explicity incorporate
the symmetry energy. Our analysis emphasises the many different parameters that
are required for this kind of modelling, and the fact that standard tabulated
equations of state are grossly incomplete in this respect. To make progress,
future equations of state need to provide the energy density as a function of
the various nucleon number densities, the temperature (i.e. entropy), and the
entrainment among the various components
Nonequilibrium electrons in tunnel structures under high-voltage injection
We investigate electronic distributions in nonequilibrium tunnel junctions
subject to a high voltage bias under competing electron-electron and
electron-phonon relaxation processes. We derive conditions for reaching
quasi-equilibrium and show that, though the distribution can still be thermal
for low energies where the rate of the electron-electron relaxation exceeds
significantly the electron-phonon relaxation rate, it develops a power-law tail
at energies of order of . In a general case of comparable electron-electron
and electron-phonon relaxation rates, this tail leads to emission of
high-energy phonons which carry away most of the energy pumped in by the
injected current.Comment: Revised versio
The probable evidence of leprosy in a male individual unearthed in medieval Armenia (Angeghakot)
The objective of this study is to present the paleopathological lesions relevant to the discussion of the differential diagnosis of leprosy. Macroscopic, histological and X-ray observation of the bones and scrutiny of lesions according to the paleopathological literature allowed the identification of a probable case of leprosy in an adult male from Angeghakot (Early Middle Age, skeleton 4). The skeleton of a male (50–55 years) revealed several bony changes indicative of leprosy with clear rhino-maxillary syndrome. There is a scarcity of information in the osteoarchaeological literature of leprosy in ancient Armenia. The significance of this case is that it adds to an understanding of the history of the disease in Armenia and to the data set necessary to understand the epidemiological dynamics in the South Caucasus during the Early Middle Ages
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