On the radial distribution of Galactic cosmic rays

The spectrum and morphology of the diffuse Galactic gamma-ray emission carries valuable information on cosmic ray (CR) propagation. Recent results obtained by analyzing Fermi-LAT data accumulated over seven years of observation show a substantial variation of the CR spectrum as a function of the distance from the Galactic Center. The spatial distribution of the CR density in the outer Galaxy appears to be weakly dependent upon the galactocentric distance, as found in previous studies as well, while the density in the central region of the Galaxy was found to exceed the value measured in the outer Galaxy. At the same time, Fermi-LAT data suggest a gradual spectral softening while moving outward from the center of the Galaxy to its outskirts. These findings represent a challenge for standard calculations of CR propagation based on assuming a uniform diffusion coefficient within the Galactic volume. Here we present a model of non-linear CR propagation in which transport is due to particle scattering and advection off self-generated turbulence. We find that for a realistic distribution of CR sources following the spatial distribution of supernova remnants and the space dependence of the magnetic field on galactocentric distance, both the spatial profile of CR density and the spectral softening can easily be accounted for.Comment: 6 pages, 3 figures. Accepted for publivation to MNRAS letter

Authorising humanitarian intervention: A five-point defence of existing multilateral procedures

AbstractEven scholars who support multilateralism in principle frequently question the value of securing approval from existing multilateral bodies for humanitarian intervention. The United Nations (UN) and regional organisations such as NATO, the argument goes, are far from democratic; furthermore, multilateralism is often a recipe for doing nothing; therefore, unauthorised intervention should be permissible in circumstances of ‘humanitarian necessity’. This article maintains that although today’s multilateral organisations and related procedures for authorising armed intervention may be suboptimal, they have significant output legitimacy. First, existing authorisation procedures reduce the risk of destabilising conflict spirals among powerful states. Second, they diminish the likelihood that humanitarianism will be used as a pretext. Third, they reduce epistemic problems concerning the identification of a just cause for intervention and thus the risk of accidental abuse. Fourth, they minimise the ‘moral hazard’ of humanitarian intervention. Finally, compliance with multilateral procedures is increasingly required for successful peacebuilding. This leads me to conclude that humanitarian warfare should always be authorised by the UN or regional multilateral organisations.This is the final version of the article. It first appeared from Cambridge University Press via http://dx.doi.org/10.1017/S026021051600027

Cosmic ray driven Galactic winds

The escape of cosmic rays from the Galaxy leads to a gradient in the cosmic ray pressure that acts as a force on the background plasma, in the direction opposite to the gravitational pull. If this force is large enough to win against gravity, a wind can be launched that removes gas from the Galaxy, thereby regulating several physical processes, including star formation. The dynamics of these cosmic ray driven winds is intrinsically non-linear in that the spectrum of cosmic rays determines the characteristics of the wind (velocity, pressure, magnetic field) and in turn the wind dynamics affects the cosmic ray spectrum. Moreover, the gradient of the cosmic ray distribution function causes excitation of Alfven waves, that in turn determine the scattering properties of cosmic rays, namely their diffusive transport. These effects all feed into each other so that what we see at the Earth is the result of these non-linear effects. Here we investigate the launch and evolution of such winds, and we determine the implications for the spectrum of cosmic rays by solving together the hydrodynamical equations for the wind and the transport equation for cosmic rays under the action of self-generated diffusion and advection with the wind and the self-excited Alfven waves.Comment: 14 pages, 15 figures. Accepted for publication to MNRAS main journa

Soldiers, Civilians, and Multilateral Humanitarian Intervention

Approval from the United Nations or NATO appears to have become a necessary condition for US humanitarian military intervention. Conventional explanations emphasizing the pull of legitimacy norms cannot fully account for this given that US policymakers vary considerably in their attachment to multilateralism. This article argues that America’s military leaders, who are consistently skeptical about humanitarian intervention and tend to emphasize its costs, play a central role in making multilateral approval necessary. As long as the top-ranking generals express strong reservations about intervention and no clear threat to US national security exists, they can veto the use of force. In such circumstances, even heavyweight “humanitarian hawks” among the civilian leadership, who initially may have wanted to bypass multilateral bodies to maximize US freedom of action, can be expected to recognize the need for UN or NATO approval—if only as a means of mollifying the generals by reassuring them about the prospect of sustained multilateral burden sharing. Two case studies drawing on interviews with senior civilian and military officials illustrate and probe the plausibility of the argument.Research on this article was supported by a fellowship in foreign policy that the author held at the Brookings Institution in Washington, D.C.http://dx.doi.org/10.1080/09636412.2015.1036626This is the final version of the article. It first appeared from Taylor & Franics via http://dx.doi.org/10.1080/09636412.2015.103662

Spin Echo Decay in a Stochastic Field Environment

We derive a general formalism with which it is possible to obtain the time dependence of the echo size for a spin in a stochastic field environment. Our model is based on ``strong collisions''. We examine in detail three cases where: (I) the local field is Ising-like, (II) the field distribution is continuous and has a finite second moment, and (III) the distribution is Lorentzian. The first two cases show a T2 minimum effect and are exponential in time cubed for short times. The last case can be approximated by a phenomenological stretched exponential.Comment: 11 pages + 3 postscript figure

Effects of miRNA-15 and miRNA-16 expression replacement in chronic lymphocytic leukemia : implication for therapy

This work was supported by: Associazione Italiana Ricerca sul Cancro (AIRC) Grant 5 x mille n.9980, (to M.F., F.M. A. N., P.T. and M.N.) ; AIRC I.G. n. 14326 (to M.F.), n.10136 and 16722 (A.N.), n.15426 (to F.F.). AIRC and Fondazione CaRiCal co-financed Multi Unit Regional Grant 2014 n.16695 (to F.M.). Italian Ministry of Health 5x1000 funds (to S.Z. and F.F). A.G R. was supported by Associazione Italiana contro le Leucemie-Linfomi-Mielomi (AIL) Cosenza - Fondazione Amelia Scorza (FAS). S.M. C.M., M.C., L.E., S.B. were supported by AIRC.Peer reviewedPostprin

Identification and rejection of scattered neutrons in AGATA

Gamma rays and neutrons, emitted following spontaneous fission of 252Cf, were measured in an AGATA experiment performed at INFN Laboratori Nazionali di Legnaro in Italy. The setup consisted of four AGATA triple cluster detectors (12 36-fold segmented high-purity germanium crystals), placed at a distance of 50 cm from the source, and 16 HELENA BaF2 detectors. The aim of the experiment was to study the interaction of neutrons in the segmented high-purity germanium detectors of AGATA and to investigate the possibility to discriminate neutrons and gamma rays with the gamma-ray tracking technique. The BaF2 detectors were used for a time-of-flight measurement, which gave an independent discrimination of neutrons and gamma rays and which was used to optimise the gamma-ray tracking-based neutron rejection methods. It was found that standard gamma-ray tracking, without any additional neutron rejection features, eliminates effectively most of the interaction points due to recoiling Ge nuclei after elastic scattering of neutrons. Standard tracking rejects also a significant amount of the events due to inelastic scattering of neutrons in the germanium crystals. Further enhancements of the neutron rejection was obtained by setting conditions on the following quantities, which were evaluated for each event by the tracking algorithm: energy of the first and second interaction point, difference in the calculated incoming direction of the gamma ray, figure-of-merit value. The experimental results of tracking with neutron rejection agree rather well with Geant4 simulations