324 research outputs found
Propagator poles and an emergent stable state below threshold: general discussion and the E(38) state
In the framework of a simple quantum field theory describing the decay of a
scalar state into two (pseudo)scalar ones we study the pole(s) motion(s) of its
propagator: besides the expected pole on the second Riemann sheet, we find --
for a large enough coupling constant -- a second, additional pole on the first
Riemann sheet below threshold, which corresponds to a stable state. We then
perform a numerical study for a hadronic system in which a scalar particle
couples to pions. We investigate under which conditions a stable state below
the two-pion threshold can emerge. In particular, we study the case in which
this stable state has a mass of 38 MeV, which corresponds to the recently
claimed novel scalar state E(38). Moreover, we also show that the resonance
and the stable state E(38) could be two different manifestation of
the same `object'. Finally, we also estimate the order of magnitude of its
coupling to photons.Comment: 9 pages, 4 figure
Increase in environmental temperature affects exploratory behaviour, anxiety and social preference in Danio rerio
The aim of this work is to investigate the effect of a temperature increase on the behaviour of adult zebrafish (Danio rerio) maintained for 21 days at 34 °C (treatment) and 26 °C (control). The temperatures chosen are within the vital range of zebrafish and correspond to temperatures that this species encounters in the natural environment. Previous results showed that the same treatment affects the brain proteome and the behaviour of adult zebrafish by producing alterations in the proteins involved in neurotransmitter release and synaptic function and impairing fish exploratory behaviour. In this study, we have investigated the performance of treated and control zebrafish during environmental exploration by using four behavioural tests (novel tank diving, light and dark preference, social preference and mirror biting) that are paradigms for assessing the state of anxiety, boldness, social preference and aggressive behaviour, respectively. The results showed that heat treatment reduces anxiety and increases the boldness of zebrafish, which spent more time in potentially dangerous areas of the tank such as the top and the uncovered bright area and at a distance from the social group, thus decreasing protection for the zebrafish. These data suggest that the increase in ambient temperature may compromise zebrafish survival rate in the natural environment
Quiescent times in Gamma-Ray-Bursts: hints of a dormant inner engine
We perform a statistical analysis of the temporal structure of long
Gamma-Ray-Bursts (GRBs). First we consider a sample of bursts in which a long
quiescent time is present. Comparing the pre-quiescence with the
post-quiescence emission we show that they display similar temporal structures,
hardness ratios and emitted powers, but, on the average, the post-quiescence
emission is roughly twice as long as the pre-quiescence emission. We then
consider a sample of long and bright GRBs. We show that the duration of each
emission period is compatible with the duration of an active period computed in
various inner engine models. At the contrary, if the inner engine is assumed to
be always active, i.e. also during the quiescent times, in several cases the
total duration of the burst largely exceeds the theoretical durations. Our
analysis therefore does not support the interpretation of long quiescent times
in terms of stochastic modulation of a continuous wind. Instead the quiescent
times can be interpreted as dormancy periods of the inner engine. Before and
after a dormancy period the inner engine produces similar emissions.Comment: 17 pages, 7 figures. New version after referee's comments. Two
figures adde
Neutron stars within the SU(2) parity doublet model
The equation of state of beta-stable and charge neutral nucleonic matter is
computed within the SU(2) parity doublet model in mean field and in the
relativistic Hartree approximation. The mass of the chiral partner of the
nucleon is assumed to be 1200 MeV. The transition to the chiral restored phase
turns out to be a smooth crossover in all the cases considered, taking place at
a baryon density of just . The mass-radius relations of compact stars
are calculated to constrain the model parameters from the maximum mass limit of
neutron stars. It is demonstrated that chiral symmetry starts to be restored,
which in this model implies the appearance of the chiral partners of the
nucleons, in the center of neutron stars. However, the analysis of the decay
width of the assumed chiral partner of the nucleon poses limits on the validity
of the present version of the model to describe vacuum properties.Comment: 14 pages, 9 figures, 2 tables, version accepted for publication in
EJP
Is contrast-enhanced US alternative to spiral CT in the assessment of treatment outcome of radiofrequency ablation in hepatocellular carcinoma?
Purpose: The present study was conducted to assess the efficacy of contrast-enhanced ultrasound with low mechanical index in evaluating the response of percutaneous radiofrequency ablation treatment of hepatocellular carcinoma by comparing it with 4-row spiral computed tomography. Materials and Methods: 100 consecutive patients (65 men and 35 women; age range: 62 – 76 years) with solitary hepatocellular carcinomas (mean lesion diameter: 3.7cm± 1.1cm SD) underwent internally cooled radiofrequency ablation. Therapeutic response was evaluated at one month after the treatment with triple-phasic contrast-enhanced spiral CT and low-mechanical index contrast-enhanced ultrasound following bolus injection of 2.4 ml of Sonovue (Bracco, Milan). 60 out of 100 patients were followed up for another 3 months. Contrast-enhanced sonographic studies were reviewed by two blinded radiologists in consensus. Sensitivity, specificity, NPV and PPV of contrast-enhanced ultrasound examination were determined. Results: After treatment, contrast-enhanced ultrasound identified persistent signal enhancement in 24 patients (24%), whereas no intratumoral enhancement was detected in the remaining 76 patients (76%). Using CT imaging as gold standard, the sensitivity, specificity, NPV, and PPV of contrast enhanced ultrasound were 92.3% (95% CI = 75.9 – 97.9%), 100% (95% CI = 95.2 – 100%), 97.4% (95% CI = 91.1 – 99.3%), and 100% (95% CI = 86.2 – 100%). Conclusion: Contrast-enhanced ultrasound with low mechanical index using Sonovue is a feasible tool in evaluating the response of hepatocellular carcinoma to radiofrequency ablation. Accuracy is comparable to 4-row spiral CT
Not All Children with Under-Control Asthma are Controlled
Subclinical lung function alterations can sometimes be discovered in asthmatic patients under clinical control. This study aimed to identify the burden of asthmatic children with subclinical airways abnormalities who may benefit from an adjustment in asthma therapy. 134 6-to-17-year-old asthmatic children were enrolled. Of them, 98 presented apparently under clinical control disease and all performed spirometry before and after bronchodilation: 17 (17.3%) had a positive bronchodilation test, in addition to significantly lower lung function indexes as compared to those with under-control asthma who had a negative bronchodilation test. These patients were randomized and re-evaluated: patients (n=8) receiving an adjustment in their therapy showed an improvement in lung function tests and quality of life indexes as compared to 7 without therapy adjustment. In conclusion, a substantial number of apparently-under-control asthmatic children show airways alterations that can be improved by adjusting their therapy, which also seems to enhance their quality of life
5-FU targets rpL3 to induce mitochondrial apoptosis via cystathionine-b-synthase in colon cancer cells lacking p53
Recent findings revealed in cancer cells novel stress response pathways, which in response to many chemotherapeutic drugs causing nucleolar stress, will function independently from tumor protein p53 (p53) and still lead to cell cycle arrest and/or apoptosis. Since it is known that most cancers lack functional p53, it is of great interest to explore these emerging molecular mechanisms. Here, we demonstrate that nucleolar stress induced by 5-fluorouracil (5-FU) in colon cancer cells devoid of p53 leads to the activation of ribosomal protein L3 (rpL3) as proapoptotic factor. rpL3, as ribosome-free form, is a negative regulator of cystathionine-β-synthase (CBS) expression at transcriptional level through a molecular mechanism involving Sp1. The rpL3-CBS association affects CBS stability and, in addition, can trigger CBS translocation into mitochondria. Consequently apoptosis will be induced through the mitochondrial apoptotic cell death pathway characterized by an increased ratio of Bax to Bcl-2, cytochrome c release and subsequent caspase activation. It is noteworthy that silencing of CBS is associated to a strong increase of 5-FU-mediated inhibition of cell migration and
proliferation. These data reveal a novel mechanism to accomplish p53-independent apoptosis and suggest a potential therapeutic approach aimed at upregulating rpL3 for treating cancers lacking p53
Strangeness in Astrophysics and Cosmology
Some recent developments concerning the role of strange quark matter for
astrophysical systems and the QCD phase transition in the early universe are
addressed. Causality constraints of the soft nuclear equation of state as
extracted from subthreshold kaon production in heavy-ion collisions are used to
derive an upper mass limit for compact stars. The interplay between the
viscosity of strange quark matter and the gravitational wave emission from
rotation-powered pulsars are outlined. The flux of strange quark matter nuggets
in cosmic rays is put in perspective with a detailed numerical investigation of
the merger of two strange stars. Finally, we discuss a novel scenario for the
QCD phase transition in the early universe, which allows for a small
inflationary period due to a pronounced first order phase transition at large
baryochemical potential.Comment: 8 pages, invited talk given at the International Conference on
Strangeness in Quark Matter (SQM2009), Buzios, Brasil, September 28 - October
2, 200
Erratum to: A study of vorticity formation in high energy nuclear collisions
Due to an oversight of ours in proofreading and a communication problem with the publisher, the figures published in F. Becattini et al. Eur. Phys. J. C (2015) 75: 406 were not correct. This Erratum contains the correct figures as in arXiv 1501.04468v2, submitted on March 12 2015, and the post-publication version arXiv 1501.04468v3, submitted on August 17 2015
Relativistic viscous hydrodynamics for heavy-ion collisions with ECHO-QGP
We present ECHO-QGP, a numerical code for -dimensional relativistic
viscous hydrodynamics designed for the modeling of the space-time evolution of
the matter created in high energy nuclear collisions. The code has been built
on top of the \emph{Eulerian Conservative High-Order} astrophysical code for
general relativistic magneto-hydrodynamics [\emph{Del Zanna et al., Astron.
Astrophys. 473, 11, 2007}] and here it has been upgraded to handle the physics
of the Quark-Gluon Plasma. ECHO-QGP features second-order treatment of causal
relativistic viscosity effects in both Minkowskian or Bjorken coordinates;
partial or complete chemical equilibrium of hadronic species before kinetic
freeze-out; initial conditions based on the optical Glauber model, including a
Monte-Carlo routine for event-by-event fluctuating initial conditions; a
freeze-out procedure based on the Cooper-Frye prescription. The code is
extensively validated against several test problems and results always appear
accurate, as guaranteed by the combination of the conservative
(shock-capturing) approach and the high-order methods employed. ECHO-QGP can be
extended to include evolution of the electromagnetic fields coupled to the
plasma.Comment: 25 pages, two column, Final version: accepted for publication in
European Physical Journal
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