75 research outputs found
Signals of primordial phase transitions on CMB maps
The analysis of the CMB anisotropies is a rich source of cosmological
informations. In our study, we simulated the signals produced by the relics of
a first order phase transition occured during an inflationary epoch in the
early Universe. These relics are bubbles of true vacuum that leave a
characteristic non-Gaussian imprint on the CMB. We use different statistical
estimators in order to evaluate this non-Gaussianity. We obtain some limits on
the allowed values of the bubble parameters comparing our results with the
experimental data.
We also predict the possibility to detect this signal with the next high
resolution experiments.Comment: 2 pages, submitted to Proceedings of 9th Marcel Grossmann meetin
Imprints of Primordial Voids on the CMB
We generalize in several ways the results existing in the literature: a) we
make use of an exact general relativistic solution for a spherical, nearly
empty cavity in the matter dominated era to evaluate the null geodesics and the
Sachs-Wolfe effect; b) we evaluate the magnitude of the adiabatic fluctuations
of the photon-baryon plasma; c) we study the influence of the shell profile;
and d) we take into account the finite thickness of the last scattering surface
(LSS) and the influence of its position with respect to the void center. We
find empirically an analytic approximation to the Sachs-Wolfe effect for all
crossing geometries and we derive an upper limit of 25 Mpc
for the comoving radii of voids sitting on the LSS in order to achieve
compatibility with COBE's data. As a nearly empty void has an overcomoving
expansion of a factor of 4 between decoupling and the present, the
maximum allowed size at present is 100 Mpc. On the other
hand, the smallness of the comoving size relative to the sound horizon reduces
strongly the adiabatic effect by Silk damping and makes it negligible. Most of
the signature of primordial voids comes therefore from metric effects and
consists of subdegree spots blue or red depending on whether the center lies
beyond or within the LSS. In conclusion we refine and confirm earlier
constraints on a power law void spectrum originated in an inflationary phase
transition and capable of generating the observed large scale structure.Comment: 14 pages, 5 figures, submitted to Montly Notice
Understanding regional activation of thoraco-lumbar muscles in chronic low back pain and its relationship to clinically relevant domains
Background: Altered regional activation of the lumbar extensors has been previously observed in individuals with low back pain (LBP) performing high-effort and fatiguing tasks. It is currently unknown whether similar alterations can be observed during low-effort functional tasks. Similarly, previous studies did not investigate whether side differences in regional activation are present in individuals with LBP. Finally, there is limited evidence of whether the extent of the alteration of regional activation is associated with clinical factors. Therefore, the aim of this study was to investigate whether individuals with LBP exhibit asymmetric regional activation of the thoraco-lumbar extensor muscles during functional tasks, and if the extent of neuromuscular control alteration is associated with clinical and psychosocial outcome domains. Methods: 21 participants with and 21 without LBP performed five functional tasks (gait, sit-to-stand, forward trunk flexion, shoulder flexion and anterior pelvic tilt). The spatial distribution of activation of the thoraco-lumbar extensor muscles was assessed bilaterally using high-density electromyography. For each side, the distribution of electromyographic (EMG) amplitude was characterized in terms of intensity, location and size. Indices of asymmetry were calculated from these features and comparisons between groups and tasks were performed using ANOVA. The features that significantly differed between groups were correlated with self-reported measures of pain intensity and other outcome domains. Results: Indices of asymmetry did not differ between participants with and without LBP (p > 0.11). The cranio-caudal location of the activation differed between tasks (p < 0.05), but not between groups (p = 0.64). Participants with LBP showed reduced EMG amplitude during anterior pelvic tilt and loading response phase during gait (both p < 0.05). Pearson correlation revealed that greater pain intensity was associated with lower EMG amplitude for both tasks (R<-0.5, p < 0.05). Conclusions: Despite clear differences between tasks, individuals with and without LBP exhibited similar distributions of EMG amplitude during low-effort functional activities, both within and between sides. However, individuals with LBP demonstrated lower activation of the thoraco-lumbar muscles during gait and anterior pelvic tilt, especially those reporting higher pain intensity. These results have implications in the development or refinement of assessment and intervention strategies focusing on motor control in patients with chronic LBP
Sufficient conditions for curvature invariants to avoid divergencies in Hyperextended Scalar Tensor theory for Bianchi models
We look for sufficient conditions such that the scalar curvature, Ricci and
Kretchmann scalars be bounded in Hyperextended Scalar Tensor theory for Bianchi
models. We find classes of gravitation functions and Brans-Dicke coupling
functions such that the theories thus defined avoid the singularity. We compare
our results with these found by Rama in the framework of the Generalised Scalar
Tensor theory for the FLRW models.Comment: 13 page
Anticancer activity of "Trigno M", extract of Prunus spinosa drupes, against in vitro 3D and in vivo colon cancer models
Abstract In 2018 there were over 1.8 million new cases worldwide of colorectal cancer and relapses after clinical treatments. Many studies ascribe the risk of the appearance of this cancer to the Western life style : a sedentary life, obesity, and low -fiber, high -fat diets can promote the onset of disease. Several studies have shown supplement phytochemicals to have an inhibiting effect on the growth of various cancers through the activation of apoptosis. Our goal was to prove the effectiveness of a natural compound in the combined therapy of colorectal cancer. Trigno M supplement was an optimal candidate as anticancer product for its high concentrations of phenolic acids, flavonoids and anthocyanins. Our work showed the antitumor activity of Trigno M, extract of Prunus spinosa drupes combined with the nutraceutical activator complex (NAC), in 2D, 3D and in vivo colorectal cancer models. The cellular model we used both in vitro and in vivo was the HCT116 cell line, particularly suitable for engraftment after inoculation in mice. Trigno M inhibited the growth and colony formation of HCT116 cells (35%) as compared to the chemotherapy treatment with 5-fluorouracil (80%) used in clinical therapy. The reduction of the morphological dimensions in the spheroid cells after Trigno M, was compared with 5-fluorouracil demonstrating the efficacy of the Trigno M compound also in 3D models. Flow cytometric analysis on 3D cells showed a significant increase in the apoptotic cell fraction after Trigno M treatment (44.8%) and a low level of necrotic fraction (6.7%) as compared with control cells. Trigno M and 5-fluorouracil induced the apoptosis in a comparable percentage. Monotherapy with Trigno M in severely immunodeficient mice, carrying colon rectal cancer xenografts, significantly reduced tumor growth. The histopatological analysis of the ectopic tumors showed a lower level of necrosis after Trigno M treatment compared with the control. We conclude that Trigno M is well tolerated by mice, delays colorectal cancer growth in these animals and should be weighed up for integration of the current multi-drug protocols in the treatment of colon carcinoma
Cosmic microwave background: polarization and temperature anisotropies from symmetric structures
I consider the case of anisotropies in the Cosmic Microwave Background (CMB)
from one single ordered perturbation source, or seed, existing well before
decoupling between matter and radiation. Such structures could have been left
by high energy symmetries breaking in the early universe.
I focus on the cases of spherical and cylindrical symmetry of the seed. I
give general analytic expressions for the polarization and temperature linear
perturbations, factoring out of the Fourier integral the dependence on the
photon propagation direction and on the geometric coordinates describing the
seed. I show how the CMB perturbations manifestly reflect the symmetries of
their seeds. CMB anisotropies are obtained with a line of sight integration.
This treatment highlights the undulatory properties of the CMB. I show with
numerical examples how the polarization and temperature perturbations propagate
beyond the size of their seeds, reaching the CMB sound horizon at the time
considered. Just like the waves from a pebble thrown in a pond, CMB anisotropy
from a seed intersecting the last scattering surface appears as a series of
temperature and polarization waves surrounding the seed, extending on the scale
of the CMB sound horizon at decoupling, roughly in the sky. Each wave
is characterized by its own value of the CMB perturbation, with the same mean
amplitude of the signal coming from the seed interior.
These waves could allow to distinguish relics from high energy processes of
the early universe from point-like astrophysical sources, because of their
angular extension and amplitude. Also, the marked analogy between polarization
and temperature signals offers cross correlation possibilities for the future
Planck Surveyor observations.Comment: 21 pages, seven postscript figures, final version accepted for
publication in Phys.Rev.
Clumps into Voids
We consider a spherically symmetric distribution of dust and show that it is
possible, under general physically reasonable conditions, for an overdensity to
evolve to an underdensity (and vice versa). We find the conditions under which
this occurs and illustrate it on a class of regular Lemaitre-Tolman-Bondi
solutions. The existence of this phenomenon, if verified, would have the result
that the topology of density contours, assumed fixed in standard structure
formation theories, would have to change and that luminous matter would not
trace the dark matter distribution so well.Comment: LaTeX, 17 pages, 4 figures. Submitted to GRG 20/4/200
Evolution of radial profiles in regular Lemaitre-Tolman-Bondi dust models
We undertake a comprehensive and rigorous analytic study of the evolution of
radial profiles of covariant scalars in regular Lemaitre-Tolman-Bondi dust
models. We consider specifically the phenomenon of "profile inversions" in
which an initial clump profile of density, spatial curvature or the expansion
scalar, might evolve into a void profile (and vice versa). Previous work in the
literature on models with density void profiles and/or allowing for density
profile inversions is given full generalization, with some erroneous results
corrected. We prove rigorously that if an evolution without shell crossings is
assumed, then only the 'clump to void' inversion can occur in density profiles,
and only in hyperbolic models or regions with negative spatial curvature. The
profiles of spatial curvature follow similar patterns as those of the density,
with 'clump to void' inversions only possible for hyperbolic models or regions.
However, profiles of the expansion scalar are less restrictive, with profile
inversions necessarily taking place in elliptic models. We also examine radial
profiles in special LTB configurations: closed elliptic models, models with a
simultaneous big bang singularity, as well as a locally collapsing elliptic
region surrounded by an expanding hyperbolic background. The general analytic
statements that we obtain allow for setting up the right initial conditions to
construct fully regular LTB models with any specific qualitative requirements
for the profiles of all scalars and their time evolution. The results presented
can be very useful in guiding future numerical work on these models and in
revising previous analytic work on all their applications.Comment: Final version to appear in Classical and Quantum Gravity. Readers
eager to know the results and implications without having to go through the
technical detail are recommended to go directly to the summary and discussion
in the final section (section 11). Typos have been corrected and an important
reference has been adde
Graviton Spectra in String Cosmology
We propose to uncover the signature of a stringy era in the primordial
Universe by searching for a prominent peak in the relic graviton spectrum. This
feature, which in our specific model terminates an increase and
initiates an decrease, is induced during the so far overlooked
bounce of the scale factor between the collapsing deflationary era (or pre-Big
Bang) and the expanding inflationary era (or post-Big Bang). We evaluate both
analytically and numerically the frequency and the intensity of the peak and we
show that they may likely fall in the realm of the new generation of
interferometric detectors. The existence of a peak is at variance with
ordinarily monotonic (either increasing or decreasing) graviton spectra of
canonical cosmologies; its detection would therefore offer strong support to
string cosmology.Comment: 14 pages, RevTex source and 6 figures.p
Low-Temperature Sintering of Alumina with Liquid-Forming Additives
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66046/1/j.1151-2916.1991.tb07825.x.pd
- …