Preasymptotic multiscaling in the phase-ordering dynamics of the kinetic Ising model

The evolution of the structure factor is studied during the phase-ordering dynamics of the kinetic Ising model with conserved order parameter. A preasymptotic multiscaling regime is found as in the solution of the Cahn-Hilliard-Cook equation, revealing that the late stage of phase-ordering is always approached through a crossover from multiscaling to standard scaling, independently from the nature of the microscopic dynamics.Comment: 11 pages, 3 figures, to be published in Europhys. Let

Breaking degeneracy in jet dynamics: multi-epoch joint modelling of the BL Lac PKS 2155-304

Supermassive black holes can launch powerful jets which can be some of the most luminous multi-wavelength sources; decades after their discovery their physics and energetics are still poorly understood. The past decade has seen a dramatic improvement in the quality of available data, but despite this improvement the semi-analytical modelling of jets has advanced slowly: simple one-zone models are still the most commonly employed method of interpreting data, in particular for AGN jets. These models can roughly constrain the properties of jets but they cannot unambiguously couple their emission to the launching regions and internal dynamics, which can be probed with simulations. However, simulations are not easily comparable to observations because they cannot yet self-consistently predict spectra. We present an advanced semi-analytical model which accounts for the dynamics of the whole jet, starting from a simplified parametrization of Relativistic Magnetohydrodynamics in which the magnetic flux is converted into bulk kinetic energy. To benchmark the model we fit six quasisimultaneous, multi-wavelength spectral energy distributions of the BL Lac PKS 2155-304 obtained by the TANAMI program, and we address the degeneracies inherent to such a complex model by employing a state-of-the-art exploration of parameter space, which so far has been mostly neglected in the study of AGN jets. We find that this new approach is much more effective than a single-epoch fit in providing meaningful constraints on model parameters.Comment: Accepted for publication on MNRA

Serotonin signaling contribution to an evolutionary success: the jaw joint of vertebrates

Serotonin (5-HT) is an ancient molecule that appeared very early during evolution, and it is present in different phyla. The 5-HT signaling system includes several G-coupled receptors and it is widely conserved in vertebrates. 5-HT is implicated in an astonishing number of biological processes and it has a key role as a morphogen in several complex networks during development before it can act as a neurotransmitter. Recent advances on how serotonin signaling can influence early development and its role in vertebrate morphogenesis come from mice and Xenopus. The emergence of jawed vertebrates (gnathostomes) from jawless vertebrates (agnathans) represents a major event in the evolution of vertebrates. The acquisition of a jaw is assumed to have occurred after the split between gnathostomes and jawless vertebrates. A crucial question concerns what changes were introduced in the developmental patterning programme to obtain a jaw joint that is one of the most innovative inventions in the history of vertebrates. Molecular and developmental studies performed in Xenopus revealed for the first time that serotonin, through the 5-HT2B receptor signaling, is both sufficient and necessary to modulate the shape and functionality of the jaw, including the jaw joint. Accordingly, serotonin can be added to the complex interactive network of extrinsic factors that regulates mandibular arch development, thus contributing to one of the major vertebrate successes in evolution

Retrofitting unreinforced masonry by steel fiber reinforced mortar coating: uniaxial and diagonal compression tests

AbstractThin layers of mortar reinforced with steel fibers can be applied on one or both sides of bearing walls as an effective seismic strengthening of existing masonry buildings. To assess the effectiveness of this technique, an experimental study on masonry sub-assemblages was carried out at the University of Brescia. This paper summarizes and discusses the main results of the investigation, which included mechanical characterization tests on masonry and its components as well as on the Steel Fiber Reinforced Mortar (SFRM) used to retrofit the masonry samples. Uniaxial and diagonal compression tests were carried out on both unstrengthened wallets and masonry samples retrofitted with 25 mm thick SFRM coating. Both single-sided and double-sided retrofitting configurations for application on wall surfaces were considered. The results highlighted the ability of the technique to improve the compressive and the shear behavior of masonry, even in case of single-sided strengthening. Moreover, no premature debonding of coating was observed. Lastly, the manuscript presents the results of a numerical investigation that was performed both to simulate the diagonal compression tests described in the first part of the paper and to predict the response of panels with different strengthening configurations

Effects of fuel cetane number on the structure of diesel spray combustion: An accelerated Eulerian stochastic fields method

An Eulerian stochastic fields (ESF) method accelerated with the chemistry coordinate mapping (CCM) approach for modelling spray combustion is formulated, and applied to model diesel combustion in a constant volume vessel. In ESF-CCM, the thermodynamic states of the discretised stochastic fields are mapped into a low-dimensional phase space. Integration of the chemical stiff ODEs is performed in the phase space and the results are mapped back to the physical domain. After validating the ESF-CCM, the method is used to investigate the effects of fuel cetane number on the structure of diesel spray combustion. It is shown that, depending of the fuel cetane number, liftoff length is varied, which can lead to a change in combustion mode from classical diesel spray combustion to fuel-lean premixed burned combustion. Spray combustion with a shorter liftoff length exhibits the characteristics of the classical conceptual diesel combustion model proposed by Dec in 1997 (http://dx.doi.org/10.4271/970873), whereas in a case with a lower cetane number the liftoff length is much larger and the spray combustion probably occurs in a fuel-lean-premixed mode of combustion. Nevertheless, the transport budget at the liftoff location shows that stabilisation at all cetane numbers is governed primarily by the auto-ignition process

Prolactin Changes as a Consequence of Chemical Exposure

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Exploring the role of composition and mass loading on the properties of hadronic jets

Astrophysical jets are relativistic outflows that remain collimated for remarkably many orders of magnitude. Despite decades of research, the origin of cosmic rays (CRs) remains unclear, but jets launched by both supermassive black holes in the centre of galaxies and stellar-mass black holes harboured in X-ray binaries (BHXBs) are among the candidate sources for CR acceleration. When CRs accelerate in astrophysical jets, they initiate particle cascades that form gamma-rays and neutrinos. In the so-called hadronic scenario, the population of accelerated CRs requires a significant amount of energy to properly explain the spectral constraints, similarly to a purely leptonic scenario. The amount of energy required often exceeds the Eddington limit or even the total energy available within the jets. The exact energy source for the accelerated protons is unclear, but due to energy conservation along the jets, it is believed to come from the jet itself via transfer of energy from the magnetic fields or kinetic energy from the outflow. To address this hadronic energy issue and to self-consistently evolve the energy flux along the flows, we explore a novel treatment for including hadronic content, in which instabilities along the jet/wind border play a critical role. We discuss the impact of the different jet compositions on the jet dynamics for a pair dominated and an electron-proton jet and, consequently, the emitted spectrum, accounting for both leptonic and hadronic processes. Finally, we discuss the implications of this mass-loading scenario to address the proton energy issue

Food groups and colorectal cancer risk

Most studies of diet and colorectal cancer have considered nutrients and micronutrients, but the role of foods or food groups remains open to debate. To elucidate the issue, we examined data from a case–control study conducted between 1992 and 1997 in the Swiss canton of Vaud. Cases were 223 patients (142 men, 81 women) with incident, histologically confirmed colon (n = 119) or rectal (n = 104) cancer (median age 63 years), linked with the Cancer Registry of the Swiss Canton of Vaud, and controls were 491 subjects (211 men, 280 women, median age 58 years) admitted to the same university hospital for a wide spectrum of acute non-neoplastic conditions unrelated to long-term modifications of diet. Odds ratios (OR) were obtained after allowance for age, sex, education, smoking, alcohol, body mass index, physical activity and total energy intake. Significant associations were observed for refined grain (OR = 1.32 for an increase of one serving per day), and red meat (OR = 1.54), pork and processed meat (OR = 1.27), alcohol (OR = 1.28), and significant protections for whole grain (OR = 0.85), raw (OR = 0.85) and cooked vegetables (OR = 0.69), citrus (OR = 0.86) and other fruits (OR = 0.85), and for coffee (OR = 0.73). Garlic was also protective (OR = 0.32 for the highest tertile of intake). These findings in a central European population support the hypothesis that a diet rich in refined grains and red meat increases the risk of colorectal cancer; they, therefore, support the recommendation to substitute whole grains for refined grain, to limit meat intake, and to increase fruit and vegetable consumption. © 1999 Cancer Research Campaig