Dual Maxwellian-Kappa modelling of the solar wind electrons: new clues on the temperature of Kappa populations

Context. Recent studies on Kappa distribution functions invoked in space plasma applications have emphasized two alternative approaches which may assume the temperature parameter either dependent or independent of the power-index $\kappa$. Each of them can obtain justification in different scenarios involving Kappa-distributed plasmas, but direct evidences supporting any of these two alternatives with measurements from laboratory or natural plasmas are not available yet. Aims. This paper aims to provide more facts on this intriguing issue from direct fitting measurements of suprathermal electron populations present in the solar wind, as well as from their destabilizing effects predicted by these two alternating approaches. Methods. Two fitting models are contrasted, namely, the global Kappa and the dual Maxwellian-Kappa models, which are currently invoked in theory and observations. The destabilizing effects of suprathermal electrons are characterized on the basis of a kinetic approach which accounts for the microscopic details of the velocity distribution. Results. In order to be relevant, the model is chosen to accurately reproduce the observed distributions and this is achieved by a dual Maxwellian-Kappa distribution function. A statistical survey indicates a $\kappa$-dependent temperature of the suprathermal (halo) electrons for any heliocentric distance. Only for this approach the instabilities driven by the temperature anisotropy are found to be systematically stimulated by the abundance of suprathermal populations, i.e., lowering the values of $\kappa$-index.Comment: Submitted to A&

Antigen recognition by human γδ T cells: one step closer to knowing

Sensing of self and non‐self phosphoantigens by human Vγ9/Vδ2 T cells in the context of the butyrophilin family members BTN2A1 and BTN3A1

Retirement Saving and Decumulation in a Persistent Low-Return Environment

Recent economic conditions have vastly changed the retirement landscape as a lengthy period of low interest rates have made building wealth for retirement harder and the risk of depleting wealth during the decumulation phase of retirement greater than at any time in recent history. The retirement environment presents challenges, over (i) the period for which interest rate remain low, and (ii) once interest rates appreciably increase--as fixed income assets then decrease in value. This paper addresses two related topics: first, how have households responded to the current low interest rate environment and second, are there alternative responses or investments which households might do well to consider? Beginning with the first topic: we employ the HRS to first investigate impacts of the 2008 – 2014 low interest rate impacts on savings, wealth and asset allocation both ahead of and while in retirement. As well as employing a full sample we report on the responses of the subset of households who have been relatively successful at building and preserving wealth over this period. Following this analytic work we consider alternative portfolio and wealth management strategies targeting increases in equities and delayed participation in Social Security in terms of their potential to add value in persistent low return environments

Role of dipolar interactions in a system of Ni nanoparticles studied by magnetic susceptibility measurements

The role of dipolar interactions among Ni nanoparticles (NP) embedded in an amorphous SiO2/C matrix with different concentrations has been studied performing ac magnetic susceptibility Chi_ac measurements. For very diluted samples, with Ni concentrations < 4 wt % Ni or very weak dipolar interactions, the data are well described by the Neel-Arrhenius law. Increasing Ni concentration to values up to 12.8 wt % Ni results in changes in the Neel-Arrhenius behavior, the dipolar interactions become important, and need to be considered to describe the magnetic response of the NPs system. We have found no evidence of a spin-glasslike behavior in our Ni NP systems even when dipolar interactions are clearly present.Comment: 7 pages, 5 figures, 3 table