48,486 research outputs found
Polarization characteristics of the Crab pulsar's giant radio pulses at HFCs phases
We discuss our recent discovery of the giant radio emission from the Crab
pulsar at its high frequency components (HFCs) phases and show the polarization
characteristic of these pulses. This leads us to a suggestion that there is no
difference in the emission mechanism of the main pulse (MP), interpulse (IP)
and HFCs. We briefly review the size distributions of the Crab giant radio
pulses (GRPs) and discuss general characteristics of the GRP phenomenon in the
Crab and other pulsars.Comment: AIP Conference Proceedings "Astrophysical Sources of High Energy
Particles and Radiation", eds. T. Bulik et al. (NY:AIP), Volume 801, 2005,
pp. 324-32
Comparison of giant radio pulses in young pulsars and millisecond pulsars
Pulse-to-pulse intensity variations are a common property of pulsar radio
emission. For some of the objects single pulses are often 10-times stronger
than their average pulse. The most dramatic events are so-called giant radio
pulses (GRPs). They can be thousand times stronger than the regular single
pulses from the pulsar. Giant pulses are a rare phenomenon, occurring in very
few pulsars which split into two groups. The first group contains very young
and energetic pulsars like the Crab pulsar, and its twin (PSR B0540-69) in the
Large Magellanic Cloud (LMC), while the second group is represented by old,
recycled millisecond pulsars like PSR B1937+21, PSR B1821-24, PSR B1957+20 and
PSR J0218+4232 (the only millisecond pulsar detected in gamma-rays). We compare
the characteristics of GRPs for these two pulsar groups. Moreover, our latest
findings of new features in the Crab GRPs are presented. Analysis of our
Effelsberg data at 8.35 GHz shows that GRPs do occur in all phases of its
ordinary radio emission, including the phases of the two high frequency
components (HFCs) visible only between 5 and 9 GHz.Comment: Proceedings of the 363. WE-Heraeus Seminar on: Neutron Stars and
Pulsars (Posters and contributed talks) Physikzentrum Bad Honnef, Germany,
May.14-19, 2006, eds. W.Becker, H.H.Huang, MPE Report 291, pp.64-6
Jet reconstruction and jet background classification with the ALICE experiment in PbPb collisions at the LHC
For a quantitative interpretation of reconstructed jet properties in
heavy-ion collisions it is paramount to characterize the contribution from the
underlying event and the influence of background fluctuations on the jet
signal. In addition to the pure number fluctuations, region-to-region
correlated background within one event can enhance or deplete locally the level
of background and modify the jet energy. We show a first detailed assessment of
background effects using different probes embedded into heavy-ion data and
quantify their influence on the reconstructed jet spectrum.Comment: 4 pages, 2 figures, Proceedings for the XXII International Conference
on Ultra-Relativistic Nucleus-Nucleus Collisions, Quark Matter 2011, Annec
Choosing Prevention Products: Questions to Ask When Considering Sexual and Relationship Violence and Stalking Prevention Products
The purpose of this white paper is to provide guidance to university and college leaders on how to choose products that address concerns of sexual and relationship violence and stalking from the perspective of prevention
Predictions for the First Parker Solar Probe Encounter
We examine Alfv\'en Wave Solar atmosphere Model (AWSoM) predictions of the
first Parker Solar Probe (PSP) encounter. We focus on the 12-day closest
approach centered on the 1st perihelion. AWSoM (van der Holst et al., 2014)
allows us to interpret the PSP data in the context of coronal heating via
Alfv\'en wave turbulence. The coronal heating and acceleration is addressed via
outward-propagating low-frequency Alfv\'en waves that are partially reflected
by Alfv\'en speed gradients. The nonlinear interaction of these
counter-propagating waves results in a turbulent energy cascade. To apportion
the wave dissipation to the electron and anisotropic proton temperatures, we
employ the results of the theories of linear wave damping and nonlinear
stochastic heating as described by Chandran et al. (2011). We find that during
the first encounter, PSP was in close proximity to the heliospheric current
sheet (HCS) and in the slow wind. PSP crossed the HCS two times, namely at
2018/11/03 UT 01:02 and 2018/11/08 UT 19:09 with perihelion occuring on the
south of side of the HCS. We predict the plasma state along the PSP trajectory,
which shows a dominant proton parallel temperature causing the plasma to be
firehose unstable.Comment: 16 pages, 5 figures; accepted for publication in the Astrophysical
Journal Letter
Electrolytically regenerative hydrogen-oxygen fuel cell Patent
Electrolytically regenerative hydrogen-oxygen fuel cell
Mathematical modelling of the pathogenesis of multiple myeloma-induced bone disease
Multiple myeloma (MM) is the second most common haematological malignancy and results in destructive bone lesions. The interaction between MM cells and the bone microenvironment plays an important role in the development of the tumour cells and MM-induced bone disease and forms a 'vicious cycle' of tumour development and bone destruction, intensified by suppression of osteoblast activity and promotion of osteoclast activity. In this paper, a mathematical model is proposed to simulate how the interaction between MM cells and the bone microenvironment facilitates the development of the tumour cells and the resultant bone destruction. It includes both the roles of inhibited osteoblast activity and stimulated osteoclast activity. The model is able to mimic the temporal variation of bone cell concentrations and resultant bone volume after the invasion and then removal of the tumour cells and explains why MM-induced bone lesions rarely heal even after the complete removal of MM cells. The behaviour of the model compares well with published experimental data. The model serves as a first step to understand the development of MM-induced bone disease and could be applied further to evaluate the current therapies against MM-induced bone disease and even suggests new potential therapeutic targets
M82 - A radio continuum and polarisation study II. Polarisation and rotation measures
The composition and morphology of the interstellar medium in starburst
galaxies has been well investigated, but the magnetic field properties are
still uncertain. The nearby starburst galaxy M82 provides a unique opportunity
to investigate the mechanisms leading to the amplification and reduction of
turbulent and regular magnetic fields. Possible scenarios of the contribution
of the magnetic field to the star-formation rate are evaluated. Archival data
from the VLA and WSRT were combined and re-reduced to cover the wavelength
regime between 3cm and 22cm. All observations revealed polarised emission in
the inner part of the galaxy, while extended polarised emission up to a
distance of 2kpc from the disk was only detected at 18cm and 22cm. The
observations hint at a magnetised bar in the inner part of the galaxy. We
calculate the mass inflow rate due to magnetic stress of the bar to 7.1 solar
masses per year, which can be a significant contribution to the star-formation
rate of M82 of approximately 13 solar masses per year. The halo shows polarised
emission, which might be the remnant of a regular disk field. Indications for a
helical field in the inner part of the outflow cone are provided. The coherence
length of the magnetic field in the centre is similar to the size of giant
molecular clouds. Using polarisation spectra more evidence for a close coupling
of the ionised gas and the magnetic field as well as a two-phase magnetic field
topology were found. Electron densities in the halo are similar to the ones
found in the Milky Way. The magnetic field morphology is similar to the one in
other nearby starburst galaxies with possible large-scale magnetic loops in the
halo and a helical magnetic field inside the outflow cones. The special
combination of a magnetic bar and a circumnuclear ring are able to
significantly raise the star-formation rate in this galaxy by magnetic braking
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