288 research outputs found
Cosmic ray driven dynamo in barred and ringed galaxies
We study the global evolution of the magnetic field and interstellar medium (ISM) of the barred and ringed galaxies in the presence of non-axisymmetric components of the potential, i.e. the bar and/or the oval perturbations. The magnetohydrodynamical dynamo is driven by cosmic rays (CR), which are continuously supplied to the disk by supernova (SN) remnants. Additionally, weak, dipolar and randomly oriented magnetic field is injected to the galactic disk during SN explosions. To compare our results directly with the observed properties of galaxies we construct realistic maps of high-frequency polarized radio emission. The main result is that CR driven dynamo can amplify weak magnetic fields up to few G within few Gyr in barred and ringed galaxies. What is more, the modelled magnetic field configuration resembles maps of the polarized intensity observed in barred and ringed galaxies
The role of accelerated hyperfractionated radiotherapy in the treatment of inoperable non-small celi lung cancer: a controlled clinical trial
Formation of gaseous arms in barred galaxies with dynamically important magnetic field : 3D MHD simulations
We present results of three-dimensional nonlinear MHD simulations of a
large-scale magnetic field and its evolution inside a barred galaxy with the
back reaction of the magnetic field on the gas. The model does not consider the
dynamo process. To compare our modeling results with observations, we construct
maps of the high-frequency (Faraday-rotation-free) polarized radio emission on
the basis of simulated magnetic fields. The model accounts for the effects of
projection and the limited resolution of real observations. We performed 3D MHD
numerical simulations of barred galaxies and polarization maps. The main result
is that the modeled magnetic field configurations resemble maps of the
polarized intensity observed in barred galaxies. They exhibit polarization
vectors along the bar and arms forming coherent structures similar to the
observed ones. In the paper, we also explain the previously unsolved issue of
discrepancy between the velocity and magnetic field configurations in this type
of galaxies. The dynamical influence of the bar causes gas to form spiral waves
that travel outwards. Each gaseous spiral arm is accompanied by a magnetic
counterpart, which separates and survives in the inter-arm region. Because of a
strong compression, shear of non-axisymmetric bar flows and differential
rotation, the total energy of modeled magnetic field grows constantly, while
the azimuthal flux grows slightly until 0.05\Gyr and then saturates.Comment: 4 pages, 4 figure
Simulations of galactic dynamos
We review our current understanding of galactic dynamo theory, paying
particular attention to numerical simulations both of the mean-field equations
and the original three-dimensional equations relevant to describing the
magnetic field evolution for a turbulent flow. We emphasize the theoretical
difficulties in explaining non-axisymmetric magnetic fields in galaxies and
discuss the observational basis for such results in terms of rotation measure
analysis. Next, we discuss nonlinear theory, the role of magnetic helicity
conservation and magnetic helicity fluxes. This leads to the possibility that
galactic magnetic fields may be bi-helical, with opposite signs of helicity and
large and small length scales. We discuss their observational signatures and
close by discussing the possibilities of explaining the origin of primordial
magnetic fields.Comment: 28 pages, 15 figure, to appear in Lecture Notes in Physics "Magnetic
fields in diffuse media", Eds. E. de Gouveia Dal Pino and A. Lazaria
Distributed physical sensors network for the protection of critical infrastractures against physical attacks
The SCOUT project is based on the use of multiple innovative and low impact technologies for the protection of space control ground stations and the satellite links against physical and cyber-attacks, and for intelligent reconfiguration of the ground station network (including the ground node of the satellite link) in the case that one or more nodes fail. The SCOUT sub-system devoted to physical attacks protection, SENSNET, is presented. It is designed as a network of sensor networks that combines DAB and DVB-T based passive radar, noise radar, Ku-band radar, infrared cameras, and RFID technologies. The problem of data link architecture is addressed and the proposed solution described
Nucleon density of 172Yb and 176Yb at the nuclear periphery determined with antiprotonic x rays
Towards transnational feminist queer methodologies
This article introduces the possibilities of transnational feminist queer research as seeking to conceptualise the transnational as a methodology composed of a series of flows that can augment feminist and queer research. Transnational feminist queer methodologies can contest long-standing configurations of power between researcher and researched, subject and object, academics and activists across places, typically those which are embedded in the hierarchies of the Global North/Global South. Beginning with charting our roots in, and routes through, the diverse arenas of transnational, feminist, participatory and queer methodologies, the article uses a transcribed and edited conversation between members of the Liveable Lives research team in Kolkata and Brighton, to start an exploration of transnational feminist queer methodologies. Understanding the difficult, yet constructive moments of collaborative work and dialogue, we argue for engagements with the multiplicities of ‘many-many' lives that recognise local specificities, and the complexities of lives within transnational research, avoiding creating a currency of comparison between places. We seek to work toward methodologies that take seriously the politics of place, namely by creating research that answers the same question in different places, using methods that are created in context and may not be ‘comparable'. Using a dialogue across the boundaries of activism/academia, as well as across geographical locations, the article contends that there are potentials, as well as challenges, in thinking ourselves through transnational research praxis. This seeks complexities and spatial nuances within as well as between places
Attitudes towards the ‘stranger’: negotiating encounters with difference in the UK and Poland
Due to recent intensification in international mobility in Europe, its citizens are exposed to a much wider range of lifestyles and competing attitudes towards difference. Individuals are, therefore, increasingly likely to encounter ‘strangers’ and are, therefore, required to negotiate discontinuities and contradictions between the values that are transmitted through different sites. In response, the article explores the concept of the ‘stranger’ through original data collected in the UK and Poland. The article highlights that the construction of who is a stranger depends on national historical contexts, core values and related visions of the society. The UK and Poland have very different histories and experiences with social diversity, impacting on the ways in which individuals negotiate strange encounters. In both countries, the ‘stranger’ is often seen in a negative way and in relation to the minority groups that are perceived to be visibly different, distinct or ‘unknown’ in contemporary times. In Poland, this is now largely articulated through sexual prejudice (homophobia), whilst in the UK, attitudes towards the ‘stranger’ are largely conveyed through religious prejudice (Islamophobia). As such, the article offers a means of understanding how encounters with difference ‘produce’ strangers in different contexts
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