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Search Results: 1 - 10 of 544 matches for " Tiziana Notari "
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D-Aspartate, a Key Element for the Improvement of Sperm Quality  [PDF]
Gemma D’Aniello, Salvatore Ronsini, Tiziana Notari, Natascia Grieco, Vincenzo Infante, Nicola D’Angel, Fara Mascia, Maria Maddalena Di Fiore, George Fisher, Antimo D’Aniello
Advances in Sexual Medicine (ASM) , 2012, DOI: 10.4236/asm.2012.24008
Abstract: Introduction: D-Aspartate is an endogenous amino acid involved in LH and testosterone release in humans. In this study we investigate the impact of nutritional supplementation of sodium D-aspartate on the improvement of sperm quality in sub-fertile patients and the rate of pregnancies that occurred with their partners. Materials and Methods: A group of 30 patients affected by oligo-asthenozoospermia and a group of 30 patients affected by asthenozoospermia were treated with a daily dose of sodium D-aspartate for 90 days. After which, the change in spermatozoa concentration and their motility and the pregnancies that occurred with their partners were recorded. Results: We found that the supplementation of D-aspartate significantly increased the concentration and the motility of spermatozoa. In oligo- asthenozoospermic patients the increase of sperm concentration was found to be 2.0-fold, P < 0.001 (from a mean of 8.2 ± 4.5 million spermatozoa/ml of seminal plasma before treatment to a mean of 16.5 ± 5.5 million after treatment). In asth- enozoospermic patients, the increase of spermatozoa was 1.6-fold, P < 0.001 (from a mean of 29.9 ± 5.7 million spermatozoa/ml before treatment to a mean of 48.7 ± 12.8 after treatment). The same positive effects also occurred for sperm motility. Oligo-asthenozoospermic patients showed an increase of rapid progressive spermatozoa motility from a mean of 15.5% ± 4.4% before treatment to a mean of 23.1% ± 4.7% after D-aspartate treatment (1.49-fold increased, P < 0.001). The same effects occurred in oligo-asthenozoospermic patients. In these subjects the increase of rapid pro- gressive spermatozoa motility was 1.86-fold (from 11.6% ± 3.9% before treatment to 21.6 ± 7.5 after treatment, P < 0.001). In addition, the treatment of D-aspartate in these patients consequently led to a significantly increased number of pregnancies occurring in the partners of the treated patients. Conclusions:Treatment of sub-fertile patients with sodium D-aspartate improved the number and the motility of the spermatozoa and consequently improved the rate of pregnancies of their partners.
Late time failure of Friedmann equation
Alessio Notari
Physics , 2005, DOI: 10.1142/S0217732306021852
Abstract: It is widely believed that the assumption of homogeneity is a good zero{\it th} order approximation for the expansion of our Universe. We analyze the correction due to subhorizon inhomogeneous gravitational fields. While at early times this contribution (which may act as a negative pressure component) is perturbatively subdominant, we show that the perturbative series is likely to diverge at redshift of order 1, due to the growth of perturbations. So, the homogeneous Friedmann equation can not be trusted at late times. We suggest that the puzzling observations of a present acceleration of the Universe, may just be due to the unjustified use of the Friedmann equation and not to the presence of a Dark Energy component. This would completely solve the coincidence problem.
Imprints on CMB Angular Power Spectrum Modes from Cosmological Reionization  [PDF]
Tiziana Trombetti, Carlo Burigana
Journal of Modern Physics (JMP) , 2012, DOI: 10.4236/jmp.2012.312242
Abstract: The accurate understanding of the ionization history of the Universe plays a fundamental role in modern cosmology. It includes a phase of cosmological reionization after the standard recombination epoch, possibly associated to the early stages of structure and star formation. While the simple “τ-parametrization” of the reionization process and, in particular, of its imprints on the Cosmic Microwave Background (CMB) anisotropy likely represents a sufficiently accurate modelling for the interpretation of current CMB data, a great attention has been recently posed on the accurate computation of the reionization signatures in the CMB for a large variety of astrophysical scenarios and physical processes. The amplitude and shape of the B-mode Angular Power Spectrum (APS) depends, in particular, on the tensortoscalar ratio, r, related to the energy scale of inflation, and on the reionization history, thus an accurate modeling of the reionization process will have implications for the precise determination of r or to set more precise constraints on it through the joint analysis of E and B-mode polarization data available in the next future and from a mission of next generation. In this work we review some classes of astrophysical and phenomenological reionization histories, beyond the simpleτ-parametrization, a present a careful characterization of the imprints introduced in all the CMB APS modes. We have implemented a modified version of CAMB, the Cosmological Boltzmann code for computing the CMB anisotropy APS, to introduce the predicted hydrogen and helium ionization fractions. We compared the results obtained for these models for all the non-vanishing (in the assumed scenarios) modes of the CMB APS. Considering also the limitation from potential residuals of astrophysical foregrounds, we discussed the capability of next data to disentangle between different reionization scenarios in a wide range of tensor-to-scalar ratios.
The Cold Spot as a Large Void: Rees-Sciama effect on CMB Power Spectrum and Bispectrum
Masina, Isabella;Notari, Alessio
High Energy Physics - Phenomenology , 2008, DOI: 10.1088/1475-7516/2009/02/019
Abstract: The detection of a "Cold Spot" in the CMB sky could be explained by the presence of an anomalously large spherical underdense region (with radius of a few hundreds Mpc/h) located between us and the Last Scattering Surface. Modeling such an underdensity with an LTB metric, we investigate whether it could produce significant signals on the CMB power spectrum and bispectrum, via the Rees-Sciama effect. We find that this leads to a bump on the power spectrum, that corresponds to an O(5%-25%) correction at multipoles 5 < l < 50; in the cosmological fits, this would modify the \chi^2 by an amount of order unity. We also find that the signal should be visible in the bispectrum coefficients with a signal-to-noise S/N ~ O (1-10), localized at 10 < l < 40. Such a signal would lead to an overestimation of the primordial f_{NL} by an amount \Delta f_{NL} ~ 1 for WMAP and by \Delta f_{NL} ~ 0.1 for Planck.
The Cold Spot as a Large Void: Lensing Effect on CMB Two and Three Point Correlation Functions
Isabella Masina,Alessio Notari
Physics , 2009, DOI: 10.1088/1475-7516/2009/07/035
Abstract: The "Cold Spot" in the CMB sky could be due to the presence of an anomalous huge spherical underdense region - a "Void" - of a few hundreds Mpc/h radius. Such a structure would have an impact on the CMB two-point (power spectrum) and three-point (bispectrum) correlation functions not only at low-l, but also at high-l through Lensing, which is a unique signature of a Void. Modeling such an underdensity with an LTB metric, we show that for the power spectrum the effect should be visible already in the WMAP data only if the Void radius is at least L \gtrsim 1 Gpc/h, while it will be visible by the Planck satellite if L \gtrsim 500 Mpc/h. We also speculate that this could be linked to the high-l detection of an hemispherical power asymmetry in the sky. Moreover, there should be non-zero correlations in the non-diagonal two-point function. For the bispectrum, the effect becomes important for squeezed triangles with two very high l's: this signal can be detected by Planck if the Void radius is at least L \gtrsim 300 Mpc/h, while higher resolution experiments should be able to probe the entire parameter space. We have also estimated the contamination of the primordial non-Gaussianity f_NL due to this signal, which turns out to be negligible.
"Swiss-Cheese" Inhomogeneous Cosmology & the Dark Energy Problem
Tirthabir Biswas,Alessio Notari
Physics , 2007, DOI: 10.1088/1475-7516/2008/06/021
Abstract: We study an exact swiss-cheese model of the Universe, where inhomogeneous LTB patches are embedded in a flat FLRW background, in order to see how observations of distant sources are affected. We find negligible integrated effect, suppressed by (L/R_{H})^3 (where L is the size of one patch, and R_{H} is the Hubble radius), both perturbatively and non-perturbatively. We disentangle this effect from the Doppler term (which is much larger and has been used recently \cite{BMN} to try to fit the SN curve without dark energy) by making contact with cosmological perturbation theory.
Inflation from the Higgs field false vacuum with hybrid potential
Isabella Masina,Alessio Notari
Physics , 2012, DOI: 10.1088/1475-7516/2012/11/031
Abstract: We have recently suggested [1,2] that Inflation could have started in a local minimum of the Higgs potential at field values of about $10^{15}-10^{17}$ GeV, which exists for a narrow band of values of the top quark and Higgs masses and thus gives rise to a prediction on the Higgs mass to be in the range 123-129 GeV, together with a prediction on the the top mass and the cosmological tensor-to-scalar ratio $r$. Inflation can be achieved provided there is an additional degree of freedom which allows the transition to a radiation era. In [1] we had proposed such field to be a Brans-Dicke scalar. Here we present an alternative possibility with an additional subdominant scalar very weakly coupled to the Higgs, realizing an (inverted) hybrid Inflation scenario. Interestingly, we show that such model has an additional constraint $m_H<125.3 \pm 3_{th}$, where $3_{th}$ is the present theoretical uncertainty on the Standard Model RGEs. The tensor-to-scalar ratio has to be within the narrow range $10^{-4}\lesssim r<0.007$, and values of the scalar spectral index compatible with the observed range can be obtained. Moreover, if we impose the model to have subplanckian field excursion, this selects a narrower range $10^{-4} \lesssim r<0.001$ and an upper bound on the Higgs mass of about $m_H <124 \pm 3_{th}$.
Observational constraints on inhomogeneous cosmological models without dark energy
Valerio Marra,Alessio Notari
Physics , 2011, DOI: 10.1088/0264-9381/28/16/164004
Abstract: It has been proposed that the observed dark energy can be explained away by the effect of large-scale nonlinear inhomogeneities. In the present paper we discuss how observations constrain cosmological models featuring large voids. We start by considering Copernican models, in which the observer is not occupying a special position and homogeneity is preserved on a very large scale. We show how these models, at least in their current realizations, are constrained to give small, but perhaps not negligible in certain contexts, corrections to the cosmological observables. We then examine non-Copernican models, in which the observer is close to the center of a very large void. These models can give large corrections to the observables which mimic an accelerated FLRW model. We carefully discuss the main observables and tests able to exclude them.
Detecting the Cold Spot as a Void with the Non-Diagonal Two-Point Function
Isabella Masina,Alessio Notari
Physics , 2010, DOI: 10.1088/1475-7516/2010/09/028
Abstract: The anomaly in the Cosmic Microwave Background known as the "Cold Spot" could be due to the existence of an anomalously large spherical (few hundreds Mpc/h radius) underdense region, called a "Void" for short. Such a structure would have an impact on the CMB also at high multipoles l through Lensing. This would then represent a unique signature of a Void. Modeling such an underdensity with an LTB metric, we show that the Lensing effect leads to a large signal in the non-diagonal two-point function, centered in the direction of the Cold Spot, such that the Planck satellite will be able to confirm or rule out the Void explanation for the Cold Spot, for any Void radius with a Signal-to-Noise ratio of at least O(10).
Improving Planck calibration by including frequency-dependent relativistic corrections
Miguel Quartin,Alessio Notari
Physics , 2015, DOI: 10.1088/1475-7516/2015/09/050
Abstract: The Planck satellite detectors are calibrated in the 2015 release using the "orbital dipole", which is the time-dependent dipole generated by the Doppler effect due to the motion of the satellite around the Sun. Such an effect has also relativistic time-dependent corrections of relative magnitude 10^(-3), due to coupling with the "solar dipole" (the motion of the Sun compared to the CMB rest frame), which are included in the data calibration by the Planck collaboration. We point out that such corrections are subject to a frequency-dependent multiplicative factor. This factor differs from unity especially at the highest frequencies, relevant for the HFI instrument. Since currently Planck calibration errors are dominated by systematics, to the point that polarization data is currently unreliable at large scales, such a correction can in principle be highly relevant for future data releases.
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