Prion expression is activated by Adenovirus 5 infection and affects the adenoviral cycle in human cells

The prion protein is a cell surface glycoprotein whose physiological role remains elusive, while its implication in transmissible spongiform encephalopathies (TSEs) has been demonstrated. Multiple interactions between the prion protein and viruses have been described: viruses can act as co-factors in TSEs and life cycles of different viruses have been found to be controlled by prion modulation. We present data showing that human Adenovirus 5 induces prion expression. Inactivated Adenovirus did not alter prion transcription, while variants encoding for early products did, suggesting that the prion is stimulated by an early adenoviral function. Down-regulation of the prion through RNA interference showed that the prion controls adenovirus replication and expression. These data suggest that the prion protein could play a role in the defense strategy mounted by the host during viral infection, in a cell autonomous manner. These results have implications for the study of the prion protein and of associated TSEs

Modeling cardiac muscle fibers in ventricular and atrial electrophysiology simulations

Since myocardial fibers drive the electric signal propagation throughout the myocardium, accurately modeling their arrangement is essential for simulating heart electrophysiology (EP). Rule-Based-Methods (RBMs) represent a commonly used strategy to include cardiac fibers in computational models. A particular class of such methods is known as Laplace-Dirichlet-Rule-Based-Methods (LDRBMs) since they rely on the solution of Laplace problems. In this work we provide a unified framework, based on LDRBMs, for generating full heart muscle fibers. First, we review existing ventricular LDRBMs providing a communal mathematical description and introducing also some modeling improvements with respect to the existing literature. We then carry out a systematic comparison of LDRBMs based on meaningful biomarkers produced by numerical EP simulations. Next we propose, for the first time, a LDRBM to be used for generating atrial fibers. The new method, tested both on idealized and realistic atrial models, can be applied to any arbitrary geometries. Finally, we present numerical results obtained in a realistic whole heart where fibers are included for all the four chambers using the discussed LDRBMs

The elusive nature of the r-stars

R stars are carbon stars, less luminous and hotter than the carbon stars evolving along the AGB phase. Thus, their carbon enrichment cannot be a consequence of the third dredge-up, a fact also in agreement with the lack of s-element enhancements in their envelopes. Since their discovery the absence of binaries has lead to the conclusion that a previous merger might play a fundamental role in the observed chemical composition, likely through non-standard mixing at the time of the He-flash. On the other hand numerical simulations, in which the He-flash is artificially located close to the edge of a degenerate He core, have successfully induced mixing of carbon into the envelope. In this context it has been suggested that the merger of a degenerate He core with that of a normal red giant star could lead to the formation of a rapidly rotating core undergoing o -centre He ignition in highly degenerate conditions. This scenario is also supported by statistical analysis of the potential mergers that could explain the number, and location in the Galaxy, of observed R stars. Basing on detailed stellar models we will show the evolution of these mergers, that are very common in nature, and do not seem to be the progenitors of (hot) R stars.Postprint (published version

On the evolution of rapidly rotating massive white dwarfs towards supernovae or collapses

A recent study by Yoon & Langer (2004a) indicated that the inner cores of rapidly accreting (Mdot > 10^{-7} M_sun/yr) CO white dwarfs may rotate differentially, with a shear rate near the threshold value for the onset of the dynamical shear instability. Such differentially rotating white dwarfs obtain critical masses for thermonuclear explosion or electron-capture induced collapse which significantly exceed the canonical Chandrasekhar limit. Here, we construct two-dimensional differentially rotating white dwarf models with rotation laws resembling those of the one-dimensional models of Yoon & Langer (2004a). We derive analytic relations between the white dwarf mass, its angular momentum, and its rotational-, gravitational- and binding energy. We show that these relations are applicable for a wide range of angular velocity profiles, including solid body rotation. We demonstrate that pre-explosion and pre-collapse conditions of both, rigidly and differentially rotating white dwarfs are well established by the present work, which may facilitate future multi-dimensional simulations of Type Ia supernova explosions and studies of the formation of millisecond pulsars and gamma-ray bursts from collapsing white dwarfs.Our results lead us to suggest various possible evolutionary scenarios for progenitors of Type Ia supernovae, leading to a new paradigm of a variable mass of exploding white dwarfs, at values well above the classical Chandrasekhar mass. Based on our 2D-models, we argue for the supernova peak brightness being proportional to the white dwarf mass, which could explain various aspects of the diversity of Type Ia supernovae, such as their variation in brightness, the dependence of their mean luminosity on the host galaxy type, and the weak correlation between ejecta velocity and peak brightness.Comment: Based on 2-D white dwarf models: 19 pages, 13 figures, A&A, accepte

Impact of a revised 25^{25}Mg(p,γ\gamma)26^{26}Al reaction rate on the operation of the Mg-Al cycle

Proton captures on Mg isotopes play an important role in the Mg-Al cycle active in stellar H-burning regions. In particular, low-energy nuclear resonances in the $^{25}$Mg(p,$\gamma$)$^{26}$Al reaction affect the production of radioactive $^{26}$Al$^{gs}$ as well as the resulting Mg/Al abundance ratio. Reliable estimations of these quantities require precise measurements of the strengths of low-energy resonances. Based on a new experimental study performed at LUNA, we provide revised rates of the $^{25}$Mg(p,$\gamma$)$^{26}$Al$^{gs}$ and the $^{25}$Mg(p,$\gamma$)$^{26}$Al$^{m}$ reactions with corresponding uncertainties. In the temperature range 50 to 150 MK, the new recommended rate of the $^{26}$Al$^{m}$ production is up to 5 times higher than previously assumed. In addition, at T$=100$ MK, the revised total reaction rate is a factor of 2 higher. Note that this is the range of temperature at which the Mg-Al cycle operates in an H-burning zone. The effects of this revision are discussed. Due to the significantly larger $^{25}$Mg(p,$\gamma$)$^{26}$Al$^{m}$ rate, the estimated production of $^{26}$Al$^{gs}$ in H-burning regions is less efficient than previously obtained. As a result, the new rates should imply a smaller contribution from Wolf-Rayet stars to the galactic $^{26}$Al budget. Similarly, we show that the AGB extra-mixing scenario does not appear able to explain the most extreme values of $^{26}$Al/$^{27}$Al, i.e. $>10^{-2}$, found in some O-rich presolar grains. Finally, the substantial increase of the total reaction rate makes the hypothesis of a self-pollution by massive AGBs a more robust explanation for the Mg-Al anticorrelation observed in Globular-Cluster stars

Extended calibration range for prompt photon emission in ion beam irradiation

Monitoring the dose delivered during proton and carbon ion therapy is still a matter of research. Among the possible solutions, several exploit the measurement of the single photon emission from nuclear decays induced by the irradiation. To fully characterize such emission the detectors need development, since the energy spectrum spans the range above the MeV that is not traditionally used in medical applications. On the other hand, a deeper understanding of the reactions involving gamma production is needed in order to improve the physic models of Monte Carlo codes, relevant for an accurate prediction of the prompt-gamma energy spectrum.This paper describes a calibration technique tailored for the range of energy of interest and reanalyzes the data of the interaction of a 80MeV/u fully stripped carbon ion beam with a Poly-methyl methacrylate target. By adopting the FLUKA simulation with the appropriate calibration and resolution a significant improvement in the agreement between data and simulation is reported.Comment: 4 pages, 7 figures, Submitted to JINS

LIFE Med Hiss: An innovative cohort design for public health

The aim of MED HISS methodology was to test the effectiveness of a low-cost approach to study long-term effects of air pollution, applicable in all European countries. This approach is potentially exportable to other environmental issues where a cohort representative of the country population is needed. The cohort is derived from the National Health Interview Survey, compulsory in European countries, which has information on individual lifestyle factors. In Life Med Hiss approach, subjects recruited have been linked at individual level with health data and have been then followed-up for mortality and hospital admissions outcomes. Exposure values of air pollution (PM2.5 and NO 2 ) have been assigned using national dispersion models, enhanced by the information derived from monitoring station with data fusion techniques, and then upscaled at municipality level (highest level of detail achievable for the Italian Survey). Results for mortality have been used to test the effectiveness of this methodology and are encouraging if compared with European ones. The advantages of this technique are summarized below: • It uses a cohort already available and compulsory in European countries• It uses air quality modelling data, available for most of the countries• It permits to implement versatile environmental surveillance system