21,477 research outputs found
The adaptive nature of the bone-periodontal ligament-cementum complex in a ligature-induced periodontitis rat model.
The novel aspect of this study involves illustrating significant adaptation of a functionally loaded bone-PDL-cementum complex in a ligature-induced periodontitis rat model. Following 4, 8, and 15 days of ligation, proinflammatory cytokines (TNF- α and RANKL), a mineral resorption indicator (TRAP), and a cell migration and adhesion molecule for tissue regeneration (fibronectin) within the complex were localized and correlated with changes in PDL-space (functional space). At 4 days of ligation, the functional space of the distal complex was widened compared to controls and was positively correlated with an increased expression of TNF- α. At 8 and 15 days, the number of RANKL(+) cells decreased near the mesial alveolar bone crest (ABC) but increased at the distal ABC. TRAP(+) cells on both sides of the complex significantly increased at 8 days. A gradual change in fibronectin expression from the distal PDL-secondary cementum interfaces through precementum layers was observed when compared to increased and abrupt changes at the mesial PDL-cementum and PDL-bone interfaces in ligated and control groups. Based on our results, we hypothesize that compromised strain fields can be created in a diseased periodontium, which in response to prolonged function can significantly alter the original bone and apical cementum formations
The fluctuation spectra around a Gaussian classical solution of a tensor model and the general relativity
Tensor models can be interpreted as theory of dynamical fuzzy spaces. In this
paper, I study numerically the fluctuation spectra around a Gaussian classical
solution of a tensor model, which represents a fuzzy flat space in arbitrary
dimensions. It is found that the momentum distribution of the low-lying
low-momentum spectra is in agreement with that of the metric tensor modulo the
general coordinate transformation in the general relativity at least in the
dimensions studied numerically, i.e. one to four dimensions. This result
suggests that the effective field theory around the solution is described in a
similar manner as the general relativity.Comment: 29 pages, 13 figure
Gutzwiller density functional theory for correlated electron systems
We develop a new density functional theory (DFT) and formalism for correlated
electron systems by taking as reference an interacting electron system that has
a ground state wavefunction which obeys exactly the Gutzwiller approximation
for all one particle operators. The solution of the many electron problem is
mapped onto the self-consistent solution of a set of single particle
Schroedinger equations analogous to standard DFT-LDA calculations.Comment: 4 page
Particle abundance in a thermal plasma: quantum kinetics vs. Boltzmann equation
We study the abundance of a particle species in a thermalized plasma by
introducing a quantum kinetic description based on the non-equilibrium
effective action. A stochastic interpretation of quantum kinetics in terms of a
Langevin equation emerges naturally. We consider a particle species that is
stable in the vacuum and interacts with \emph{heavier} particles that
constitute a thermal bath in equilibrium and define of a fully renormalized
single particle distribution function. The distribution function thermalizes on
a time scale determined by the \emph{quasiparticle} relaxation rate. The
equilibrium distribution function depends on the full spectral density and
features off-shell contributions to the particle abundance. A model of a
bosonic field in interaction with two \emph{heavier} bosonic fields is
studied. We find substantial departures from the Bose-Einstein result both in
the high temperature and the low temperature but high momentum region. In the
latter the abundance is exponentially suppressed but larger than the
Bose-Einstein result. We obtain the Boltzmann equation in renormalized
perturbation theory and highlight the origin of the differences. We argue that
the corrections to the abundance of cold dark matter candidates are
observationally negligible and that recombination erases any possible spectral
distortions of the CMB. However we expect that the enhancement at high
temperature may be important for baryogenesis.Comment: 39 pages, 11 figures. Clarifying remarks. To appear in Physical
Review
Superconductivity and the high field ordered phase in the heavy fermion compound PrOsSb
Superconductivity is observed in the filled skutterudite compound \PrOsSb{}
below a critical temperature temperature K and appears to
develop out of a nonmagnetic heavy Fermi liquid with an effective mass , where is the free electron mass.
Features associated with a cubic crystalline electric field are present in
magnetic susceptibility, specific heat, electrical resistivity, and inelastic
neutron scattering measurements, yielding a Pr energy level scheme
consisting of a nonmagnetic doublet ground state, a low lying
triplet excitied state at K, and much higher temperature
triplet and singlet excited states. Measurements also
indicate that the superconducting state is unconventional and consists of two
distinct superconducting phases. At high fields and low temperatures, an
ordered phase of magnetic or quadrupolar origin is observed, suggesting that
the superconductivity may occur in the vicinity of a magnetic or quadrupolar
quantum critical point.Comment: 11 pages, 4 figures, presented at the 3rd international symposium on
Advance Science Research (ASR 2002), JAERI Tokai, Ibaraki, Japa
The role of electron-electron interactions in two-dimensional Dirac fermions
The role of electron-electron interactions on two-dimensional Dirac fermions
remains enigmatic. Using a combination of nonperturbative numerical and
analytical techniques that incorporate both the contact and long-range parts of
the Coulomb interaction, we identify the two previously discussed regimes: a
Gross-Neveu transition to a strongly correlated Mott insulator, and a
semi-metallic state with a logarithmically diverging Fermi velocity accurately
described by the random phase approximation. Most interestingly, experimental
realizations of Dirac fermions span the crossover between these two regimes
providing the physical mechanism that masks this velocity divergence. We
explain several long-standing mysteries including why the observed Fermi
velocity in graphene is consistently about 20 percent larger than the best
values calculated using ab initio and why graphene on different substrates show
different behavior.Comment: 11 pages, 4 figure
The lowest modes around Gaussian solutions of tensor models and the general relativity
In the previous paper, the number distribution of the low-lying spectra
around Gaussian solutions representing various dimensional fuzzy tori of a
tensor model was numerically shown to be in accordance with the general
relativity on tori. In this paper, I perform more detailed numerical analysis
of the properties of the modes for two-dimensional fuzzy tori, and obtain
conclusive evidences for the agreement. Under a proposed correspondence between
the rank-three tensor in tensor models and the metric tensor in the general
relativity, conclusive agreement is obtained between the profiles of the
low-lying modes in a tensor model and the metric modes transverse to the
general coordinate transformation. Moreover, the low-lying modes are shown to
be well on a massless trajectory with quartic momentum dependence in the tensor
model. This is in agreement with that the lowest momentum dependence of metric
fluctuations in the general relativity will come from the R^2-term, since the
R-term is topological in two dimensions. These evidences support the idea that
the low-lying low-momentum dynamics around the Gaussian solutions of tensor
models is described by the general relativity. I also propose a renormalization
procedure for tensor models. A classical application of the procedure makes the
patterns of the low-lying spectra drastically clearer, and suggests also the
existence of massive trajectories.Comment: 31 pages, 8 figures, Added references, minor corrections, a
misleading figure replace
Resolving Molecular Line Emission from Protoplanetary Disks: Observational Prospects for Disks Irradiated by Infalling Envelopes
Molecular line observations that could resolve protoplanetary disks of ~100
AU both spatially and kinematically would be a useful tool to unambiguously
identify these disks and to determine their kinematical and physical
characteristics. In this work we model the expected line emission from a
protoplanetary disk irradiated by an infalling envelope, addressing the
question of its detectability with subarcsecond resolution. We adopt a
previously determined disk model structure that gives a continuum spectral
energy distribution and a mm intensity spatial distribution that are consistent
with observational constraints of HL Tau. An analysis of the capability of
presently working and projected interferometers at mm and submm wavelengths
shows that molecular transitions of moderate opacity at these wavelengths
(e.g., C17O lines) are good candidates for detecting disk lines at subarcsecond
resolution in the near future. We suggest that, in general, disks of typical
Class I sources will be detectable.Comment: 41 pages, 16 figures. To be published in The Astrophysical Journa
Nambu-Poisson Bracket and M-Theory Branes Coupled to Antisymmetric Fluxes
By using the recently proposed prescription arXiv:0804.3629 for obtaining the
brane action from multiple branes action in BLG theory, we examine
such transition when 11 Dimensional background antisymmetric fluxes couple to
the brane world volume. Such couplings was suggested in arXiv:0805.3427
where it was used the fact that various fields in BLG theory are valued in a
Lie 3-algebra. We argue that this action and promoting it by Nambu-Poisson
bracket gives the expected coupling of fluxes with brane at least at weak
coupling limit. We also study some other aspects of the action for example, the
gauge invariance of the theory.Comment: 14 page
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