1,486 research outputs found
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
. 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
-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
-index.Comment: Submitted to A&
On the entropy of plasmas described with regularized -distributions
In classical thermodynamics the entropy is an extensive quantity, i.e.\ the
sum of the entropies of two subsystems in equilibrium with each other is equal
to the entropy of the full system consisting of the two subsystems. The
extensitivity of entropy has been questioned in the context of a theoretical
foundation for the so-called -distributions, which describe plasma
constituents with power-law velocity distributions. We demonstrate here, by
employing the recently introduced {\it regularized -distributions},
that entropy can be defined as an extensive quantity even for such
power-law-like distributions that truncate exponentially.Comment: Preprint accepted for publication in Phys. Rev.
Uncovering Offshore Financial Centers: Conduits and Sinks in the Global Corporate Ownership Network
Multinational corporations use highly complex structures of parents and
subsidiaries to organize their operations and ownership. Offshore Financial
Centers (OFCs) facilitate these structures through low taxation and lenient
regulation, but are increasingly under scrutiny, for instance for enabling tax
avoidance. Therefore, the identification of OFC jurisdictions has become a
politicized and contested issue. We introduce a novel data-driven approach for
identifying OFCs based on the global corporate ownership network, in which over
98 million firms (nodes) are connected through 71 million ownership relations.
This granular firm-level network data uniquely allows identifying both
sink-OFCs and conduit-OFCs. Sink-OFCs attract and retain foreign capital while
conduit-OFCs are attractive intermediate destinations in the routing of
international investments and enable the transfer of capital without taxation.
We identify 24 sink-OFCs. In addition, a small set of five countries -- the
Netherlands, the United Kingdom, Ireland, Singapore and Switzerland -- canalize
the majority of corporate offshore investment as conduit-OFCs. Each conduit
jurisdiction is specialized in a geographical area and there is significant
specialization based on industrial sectors. Against the idea of OFCs as exotic
small islands that cannot be regulated, we show that many sink and conduit-OFCs
are highly developed countries
The Science with the Interstellar Heliopause Probe
International audienceAfter the exciting in-situ observations of the termination shock and the entry of the Voyager 1 spacecraft in the heliosheath, there is a growing awareness of the significance of the physics of the outer heliosphere. Its understanding helps to clarify the structure of our immediate interstellar neighbourhood, contributes to the clarification of fundamental astrophysical processes like the acceleration of charged particles at a steller wind termination shock, and also sheds light on the question to what extent interstellar-terrestrial relations are important for the environment of and on the Earth. Consequently, there are new seriously discussed suggestions for sending a modern spacecraft into the heliosheath and beyond. One of those candidates is the Interstellar Heliopause Probe (IHP) that has been studied in a Technology Reference Study by ESA/ESTEC. Here, we discuss the science objectives and expected scientific performance of this mission
Electrochemical synthesis of carbon-metal fluoride nanocomposites as cathode materials for lithium batteries
Herein we have demonstrated an electrochemical method for the synthesis of carbon-metal fluoride nanocomposites (CMFNCs). Electrochemical intercalation of transition metal ions into graphite fluoride (CF) resulted in the formation of CMFNCs. As a proof-of-concept, we have synthesized C-FeF and C-NiF nanocomposites by the electrochemical intercalation of Fe and Ni into CF from corresponding non-aqueous electrolytes. The C-FeF and C-NiF nanocomposites synthesized by this method showed high reversible capacity and cycling stability compared to chemically synthesized analogs as cathode materials for lithium batteries. The reversible capacity of chemically synthesized C-FeF is 181 mAh g, whereas electrochemically synthesized material is 349 mAh g after 20 cycles. The better cycling performance of electrochemically synthesized C-FeF was attributed to the homogeneous distribution of FeF nanoparticles within the carbon matrix enabled by the electrochemical intercalation of Fe. The electrochemical method described here is emission-free, cost-effective, occurs at room temperature, and extendable to the synthesis of several other CMFNCs. Moreover, it might provide new avenues for the synthesis of advanced functional materials
- …