7,541 research outputs found
Non-chaotic dynamics in general-relativistic and scalar-tensor cosmology
In the context of scalar-tensor models of dark energy and inflation, the
dynamics of vacuum scalar-tensor cosmology are analysed without specifying the
coupling function or the scalar field potential. A conformal transformation to
the Einstein frame is used and the dynamics of general relativity with a
minimally coupled scalar field are derived for a generic potential. It is shown
that the dynamics are non-chaotic, thus settling an existing debate.Comment: 20 pages, LaTeX, to appear in Class. Quantum Gra
Nanofat 2.0: experimental evidence for a fat grafting rich in mesenchymal stem cells.
Different strategies have been developed in the last decade to obtain fat grafts as rich as possible of mesenchymal stem cells, so exploiting their regenerative potential. Recently, a new kind of fat grafting, called "nanofat", has been obtained after several steps of fat emulsification and filtration. The final liquid suspension, virtually devoid of mature adipocytes, would improve tissue repair because of the presence of adipose mesenchymal stem cells (ASCs). However, since it is probable that many ASCs may be lost in the numerous phases of this procedure, we describe here a novel version of fat grafting, which we call "nanofat 2.0", likely richer in ASCs, obtained avoiding the final phases of the nanofat protocol. The viability, the density and proliferation rate of ASCs in nanofat 2.0 sample were compared with samples of nanofat and simple lipoaspirate. Although the density of ASCs was initially higher in lipoaspirate sample, the higher proliferation rate of cells in nanofat 2.0 virtually filled the gap within 8 days. By contrast, the density of ASCs in nanofat sample was the poorest at any time. Results show that nanofat 2.0 emulsion is considerably rich in stem cells, featuring a marked proliferation capability
Phenomenology of a realistic accelerating universe using only Planck-scale physics
Modern data is showing increasing evidence that the Universe is accelerating.
So far, all attempts to account for the acceleration have required some
fundamental dimensionless quantities to be extremely small. We show how a class
of scalar field models (which may emerge naturally from superstring theory) can
account for acceleration which starts in the present epoch with all the
potential parameters O(1) in Planck units.Comment: 4 pages including 4 figures. Final version accepted for publication
in PRL with expanded discussion of the relationship to other quintessence
research. No changes to our own wor
Toll-like receptor 4 expression in the epithelium of inflammatory periapical lesions. An immunohistochemical study
Toll-like receptors (TLR) are essential for the innate immune response against invading pathogens and have been described in immunocompetent cells of areas affected by periapical disease. Besides initiating the inflammatory response, they also directly regulate epithelial cell proliferation and survival in a variety of settings. This study evaluates the in situ expression of TLR4 in periapical granulomas (PG) and radicular cysts, focusing on the epithelial compartment. Twenty-one periapical cysts (PC) and 10 PG were analyzed; 7 dentigerous non-inflamed follicular cyst (DC) served as control. TLR4 expression was assessed by immunohistochemistry. TLR4 immunoreaction products were detected in the epithelium of all specimens, with a higher percentage of immunostained cells in PG. Although TLR4 overexpression was detected in both PG and PC, there were differences that seemed to be related to the nature of the lesion, since in PG all epithelial cells of strands, islands and trabeculae were strongly immunoreactive for TLR4, whereas in PC only some areas of the basal and suprabasal epithelial layers were immunostained. This staining pattern is consistent with the action of TLR4: in PG it could promote formation of epithelial cell rests of Malassez and in epithelial strands and islands the enhancement of cell survival, proliferation and migration, whereas in PC TLR4 could protect the lining epithelium from extensive apoptosis. These findings go some way towards answering the intriguing question of why many epithelial strands or islands in PG and the lining epithelium of apical cysts regress after non-surgical endodontic therapy, and suggest that TLR4 plays a key role in the pathobiology of the inflammatory process related to periapical disease
Remission in ankylosing spondylitis treated with anti-TNF-α drugs: a national multicentre study
Objective: The primary objective of this retrospective study was to investigate the possibility of achieving partial remission (PR) in AS patients treated with anti-TNF-α antagonists, such as adalimumab (ADA), etanercept (ETA) and infliximab (INF), in a real clinical practice setting. Predictors of PR were also evaluated. Methods: A retrospective study was conducted in patients with AS treated with ADA, ETA and INF from 2000 to 2012. Kaplan-Meier survival curves were plotted to determine the rates of PR during the treatment with anti-TNF-α drugs. Results: A total of 283 patients with AS were treated with ADA (18.7%), ETA (26.8%) and INF (54.4%) as first anti-TNF-α drugs, with a PR rate of 57.6%. The probability of obtaining PR with ADA, ETA or INF was not significantly different among all anti-TNF-α patients. AS patients treated with a second anti-TNF-α drug had a PR rate of 40.5%, but after switching for lack of response, the probability of obtaining PR with a second anti-TNF-α drug was significantly lower from that of the first anti-TNF-α drug (P = 0.0039). The probability of obtaining PR in patients with enthesitis (P = 0.04) or psoriasis (P = 0.0016) or low levels of CRP (P = 0.0225) was significantly lower compared with that of patients without these manifestations at baseline. Conclusion: Our real-life study on PR confirmed the effectiveness of ADA, ETA or INF as first or second anti-TNF-α drugs. The presence at baseline of enthesitis or psoriasis or low CRP values yielded a lower probability of obtaining PR. © The Author 2013. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved
Constraining the dark energy dynamics with the cosmic microwave background bispectrum
We consider the influence of the dark energy dynamics at the onset of cosmic
acceleration on the Cosmic Microwave Background (CMB) bispectrum, through the
weak lensing effect induced by structure formation. We study the line of sight
behavior of the contribution to the bispectrum signal at a given angular
multipole : we show that it is non-zero in a narrow interval centered at a
redshift satisfying the relation , where the
wavenumber corresponds to the scale entering the non-linear phase, and is
the cosmological comoving distance. The relevant redshift interval is in the
range 0.1\lsim z\lsim 2 for multipoles 1000\gsim\ell\gsim 100; the signal
amplitude, reflecting the perturbation dynamics, is a function of the
cosmological expansion rate at those epochs, probing the dark energy equation
of state redshift dependence independently on its present value. We provide a
worked example by considering tracking inverse power law and SUGRA Quintessence
scenarios, having sensibly different redshift dynamics and respecting all the
present observational constraints. For scenarios having the same present
equation of state, we find that the effect described above induces a projection
feature which makes the bispectra shifted by several tens of multipoles, about
10 times more than the corresponding effect on the ordinary CMB angular power
spectrum.Comment: 15 pages, 7 figures, matching version accepted by Physical Review D,
one figure improve
Quintessence, scalar-tensor theories and non-Newtonian gravity
We discuss some of the issues which we encounter when we try to invoke the
scalar-tensor theories of gravitation as a theoretical basis of quintessence.
One of the advantages of appealing to these theories is that they allow us to
implement the scenario of a ``decaying cosmological constant,'' which offers a
reasonable understanding of why the observed upper bound of the cosmological
constant is smaller than the theoretically natural value by as much as 120
orders of magnitude. In this context, the scalar field can be a candidate of
quintessence in a broader sense. We find, however, a serious drawback in the
prototype Brans-Dicke model with added; a static universe in the
physical conformal frame which is chosen to have constant particle masses. We
propose a remedy by modifying the matter coupling of the scalar field taking
advantage of scale invariance and its breakdown through quantum anomaly. By
combining this with a conjecture on another cosmological constant problem
coming from the vacuum energy of matter fields, we expect a possible link
between quintessence and non-Newtonian gravity featuring violation of Weak
Equivalence Principle and intermediate force range, likely within the
experimental constraints. A new prediction is also offered on the
time-variability of the gravitational constant.Comment: 12 pages LaTex including 1 eps figur
Spatial Periodicity of Galaxy Number Counts, CMB Anisotropy, and SNIa Hubble Diagram Based on the Universe Accompanied by a Non-Minimally Coupled Scalar Field
We have succeeded in establishing a cosmological model with a non-minimally
coupled scalar field that can account not only for the spatial
periodicity or the {\it picket-fence structure} exhibited by the galaxy -
relation of the 2dF survey but also for the spatial power spectrum of the
cosmic microwave background radiation (CMB) temperature anisotropy observed by
the WMAP satellite. The Hubble diagram of our model also compares well with the
observation of Type Ia supernovae. The scalar field of our model universe
starts from an extremely small value at around the nucleosynthesis epoch,
remains in that state for sufficiently long periods, allowing sufficient time
for the CMB temperature anisotropy to form, and then starts to grow in
magnitude at the redshift of , followed by a damping oscillation
which is required to reproduce the observed picket-fence structure of the
- relation. To realize such behavior of the scalar field, we have found
it necessary to introduce a new form of potential , with being a constant. Through this parameter ,
we can control the epoch at which the scalar field starts growing.Comment: 19 pages, 18 figures, Accepted for publication in Astrophysics &
Space Scienc
Dark energy and dark matter from an inhomogeneous dilaton
A cosmological scenario is proposed where the dark matter (DM) and dark
energy (DE) of the universe are two simultaneous manifestations of an
inhomogenous dilaton. The equation of state of the field is scale-dependent and
pressureless at galactic and larger scales and it has negative pressure as a DE
at very large scales. The dilaton drives an inflationary phase followed by a
kinetic energy-dominated one, as in the "quintessential inflation" model
introduced by Peebles & Vilenkin, and soon after the end of inflation particle
production seeds the first inhomogeneities that lead to galaxy formation. The
dilaton is trapped near the minimum of the potential where it oscillates like a
massive field, and the excess of kinetic energy is dissipated via the mechanism
of "gravitational cooling" first introduced by Seidel & Suen. The
inhomogeneities therefore behave like solitonic oscillations around the minimum
of the potential, known as "oscillatons", that we propose account for most DM
in galaxies. Those regions where the dilaton does not transform enough kinetic
energy into reheating or carry an excess of it from regions that have cooled,
evolve to the tail of the potential as DE, driving the acceleration of the
universe.Comment: 9 pages, 8 figures, uses revtex, submitted PR
Photochemistry of Furyl- and Thienyldiazomethanes: Spectroscopic Characterization of Triplet 3-Thienylcarbene
Photolysis (λ \u3e 543 nm) of 3-thienyldiazomethane (1), matrix isolated in Ar or N2 at 10 K, yields triplet 3-thienylcarbene (13) and α-thial-methylenecyclopropene (9). Carbene 13 was characterized by IR, UV/vis, and EPR spectroscopy. The conformational isomers of 3-thienylcarbene (s-E and s-Z) exhibit an unusually large difference in zero-field splitting parameters in the triplet EPR spectrum (|D/hc| = 0.508 cmâ1, |E/hc| = 0.0554 cmâ1; |D/hc| = 0.579 cmâ1, |E/hc| = 0.0315 cmâ1). Natural Bond Orbital (NBO) calculations reveal substantially differing spin densities in the 3-thienyl ring at the positions adjacent to the carbene center, which is one factor contributing to the large difference in D values. NBO calculations also reveal a stabilizing interaction between the sp orbital of the carbene carbon in the s-Z rotamer of 13 and the antibonding Ï orbital between sulfur and the neighboring carbonâan interaction that is not observed in the s-E rotamer of 13. In contrast to the EPR spectra, the electronic absorption spectra of the rotamers of triplet 3-thienylcarbene (13) are indistinguishable under our experimental conditions. The carbene exhibits a weak electronic absorption in the visible spectrum (λmax = 467 nm) that is characteristic of triplet arylcarbenes. Although studies of 2-thienyldiazomethane (2), 3-furyldiazomethane (3), or 2-furyldiazomethane (4) provided further insight into the photochemical interconversions among C5H4S or C5H4O isomers, these studies did not lead to the spectroscopic detection of the corresponding triplet carbenes (2-thienylcarbene (11), 3-furylcarbene (23), or 2-furylcarbene (22), respectively)
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