85 research outputs found
Dynamical chaos in the problem of magnetic jet collimation
We investigate dynamics of a jet collimated by magneto-torsional
oscillations. The problem is reduced to an ordinary differential equation
containing a singularity and depending on a parameter. We find a parameter
range for which this system has stable periodic solutions and study
bifurcations of these solutions. We use Poincar\'e sections to demonstrate
existence of domains of regular and chaotic motions. We investigate transition
from periodic to chaotic solutions through a sequence of period doublings.Comment: 11 pages, 29 figures, 1 table, MNRAS (published online
Methods of improvement of forecasting of development of mineral deposits' power supply
Mineral deposits (among which non-ferrous metals take a leading place) are situated on the territory of our planet rather unevenly, and often in out-of-the-way places. Nuclear power (particularly, transportable nuclear power plants) provides the new possibilities of power supply, which is very important for deposits' development. This article shares the economic aspects of forecasting in the field of power development (in particular, nuclear power on the basis of transportable nuclear power plants). Economic barriers of development of innovative nuclear technologies are considered on the example of transportable nuclear power plants. At the same time, there are given the ways of elimination of such barrier to development of this technology as methodical absence of investigation of a question of distribution of added cost between producers of innovative equipment and final product. Addition of new analytical tool (“business diagonal”) is offered for a method of definition of economically efficient distribution of added cost (received as a result of introduction of innovative technologies) between participants of production and consumption of atomic energy within the “economic cross” model. There is offered the order of use of method of cash flows discounting at calculations between nuclear market participants. Economic methods, offered in this article, may be used in forecasting of development of other energy technologies and introduction of prospective energy equipment
A Tale of Two Current Sheets
I outline a new model of particle acceleration in the current sheet
separating the closed from the open field lines in the force-free model of
pulsar magnetospheres, based on reconnection at the light cylinder and
"auroral" acceleration occurring in the return current channel that connects
the light cylinder to the neutron star surface. I discuss recent studies of
Pulsar Wind Nebulae, which find that pair outflow rates in excess of those
predicted by existing theories of pair creation occur, and use those results to
point out that dissipation of the magnetic field in a pulsar's wind upstream of
the termination shock is restored to life as a viable model for the solution of
the "" problem as a consequence of the lower wind 4-velocity implied by
the larger mass loading.Comment: 17 pages, 6 figures, Invited Review, Proceedings of the "ICREA
Workshop on The High-Energy Emission from Pulsars and their Systems", Sant
Cugat, Spain, April 12-16, 201
Electric current circuits in astrophysics
Cosmic magnetic structures have in common that they are anchored
in a dynamo, that an external driver converts kinetic energy into internal
magnetic energy, that this magnetic energy is transported as Poynting fl ux across the magnetically dominated structure, and that the magnetic energy
is released in the form of particle acceleration, heating, bulk motion,
MHD waves, and radiation. The investigation of the electric current system is
particularly illuminating as to the course of events and the physics involved.
We demonstrate this for the radio pulsar wind, the solar flare, and terrestrial
magnetic storms
The theory of pulsar winds and nebulae
We review current theoretical ideas on pulsar winds and their surrounding
nebulae. Relativistic MHD models of the wind of the aligned rotator, and of the
striped wind, together with models of magnetic dissipation are discussed. It is
shown that the observational signature of this dissipation is likely to be
point-like, rather than extended, and that pulsed emission may be produced. The
possible pulse shapes and polarisation properties are described. Particle
acceleration at the termination shock of the wind is discussed, and it is
argued that two distinct mechanisms must be operating, with the first-order
Fermi mechanism producing the high-energy electrons (above 1 TeV) and either
magnetic annihilation or resonant absorption of ion cyclotron waves responsible
for the 100 MeV to 1 TeV electrons. Finally, MHD models of the morphology of
the nebula are discussed and compared with observation.Comment: 33 pages, to appear in Springer Lecture Notes on "Neutron stars and
pulsars, 40 years after the discovery", ed W.Becke
New Phase-coherent Measurements of Pulsar Braking Indices
Pulsar braking indices offer insight into the physics that underlies pulsar
spin-down. Only five braking indices have been measured via phase-coherent
timing; all measured values are less than 3, the value expected from magnetic
dipole radiation. Here we present new measurements for three of the five pulsar
braking indices, obtained with phase-coherent timing for PSRs J1846-0258
(n=2.65+/-0.01), B1509-58 (n=2.839+/-0.001) and B0540-69 (n=2.140+/-0.009). We
discuss the implications of these results and possible physical explanations
for them.Comment: 7 pages, 5 figures. To be published in the proceedings of the
conference "Isolated Neutron Stars: from the Interior to the Surface" (April
24-28, 2006, London, UK), eds. D. Page, R. Turolla, & S. Zan
Upgrade of Biomass-Derived Levulinic Acid via Ru/C-Catalyzed Hydrogenation to γ‑Valerolactone in Aqueous−Organic−Ionic Liquids Multiphase Systems
A liquid triphase system made by an aqueous phase, an
organic phase, and an ionic liquid was designed and applied to the
catalytic hydrogenation/dehydration of biomass-derived levulinic acid to
γ-valerolactone. This paper demonstrates that, by operating at 100−150
°C and 35 atm of H2, both in the presence of Ru/C or of a homogeneous
Ru precursor, the use of the triphase system designed to match the
investigated reaction allows the following: (1) to obtain up to quantitative
conversions and 100% selectivity toward the desired product; (2) to
recover the product by simple phase separation; and (3) to preserve the
catalyst activity for in situ recycles without loss of metal. Globally the
investigated reaction proves the concept that a cradle-to-grave approach
to the design of a catalytic reaction system can improve the global sustainability of a chemical transformation by improving
efficiency, product isolation, and catalyst recycle
Modelling Jets, Tori and Flares in Pulsar Wind Nebulae
In this contribution we review the recent progress in the modelling of Pulsar Wind Nebulae (PWN). We start with a brief overview of the relevant physical processes in the magnetosphere, the wind-zone and the inflated nebula bubble. Radiative signatures and particle transport processes obtained from 3D simulations of PWN are discussed in the context of optical and X-ray observations. We then proceed to consider particle acceleration in PWN and elaborate on what can be learned about the particle acceleration from the dynamical structures called GwispsG observed in the Crab nebula. We also discuss recent observational and theoretical results of gamma-ray flares and the inner knot of the Crab nebula, which had been proposed as the emission site of the flares. We extend the discussion to GeV flares from binary systems in which the pulsar wind interacts with the stellar wind from a companion star. The chapter concludes with a discussion of solved and unsolved problems posed by PWN
The first case of mass catch of a rare frill shark Chlamydoselachus anguineus over a seamount of the Mid-Atlantic Ridge
Control of the energy distribution and safety of a VV�R-1000 reactor when operating in the variable mode
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