1,802 research outputs found
The Dynamic Formation of Prominence Condensations
We present simulations of a model for the formation of a prominence
condensation in a coronal loop. The key idea behind the model is that the
spatial localization of loop heating near the chromosphere leads to a
catastrophic cooling in the corona (Antiochos & Klimchuk 1991). Using a new
adaptive grid code, we simulate the complete growth of a condensation, and find
that after approx. 5,000 s it reaches a quasi-steady state. We show that the
size and the growth time of the condensation are in good agreement with data,
and discuss the implications of the model for coronal heating and SOHO/TRACE
observations.Comment: Astrophysical Journal latex file, 20 pages, 7 b-w figures (gif files
Higher analogues of the discrete-time Toda equation and the quotient-difference algorithm
The discrete-time Toda equation arises as a universal equation for the
relevant Hankel determinants associated with one-variable orthogonal
polynomials through the mechanism of adjacency, which amounts to the inclusion
of shifted weight functions in the orthogonality condition. In this paper we
extend this mechanism to a new class of two-variable orthogonal polynomials
where the variables are related via an elliptic curve. This leads to a `Higher
order Analogue of the Discrete-time Toda' (HADT) equation for the associated
Hankel determinants, together with its Lax pair, which is derived from the
relevant recurrence relations for the orthogonal polynomials. In a similar way
as the quotient-difference (QD) algorithm is related to the discrete-time Toda
equation, a novel quotient-quotient-difference (QQD) scheme is presented for
the HADT equation. We show that for both the HADT equation and the QQD scheme,
there exists well-posed -periodic initial value problems, for almost all
\s\in\Z^2. From the Lax-pairs we furthermore derive invariants for
corresponding reductions to dynamical mappings for some explicit examples.Comment: 38 page
Impulsive phase flare energy transport by large-scale Alfven waves and the electron acceleration problem
The impulsive phase of a solar flare marks the epoch of rapid conversion of
energy stored in the pre-flare coronal magnetic field. Hard X-ray observations
imply that a substantial fraction of flare energy released during the impulsive
phase is converted to the kinetic energy of mildly relativistic electrons
(10-100 keV). The liberation of the magnetic free energy can occur as the
coronal magnetic field reconfigures and relaxes following reconnection. We
investigate a scenario in which products of the reconfiguration - large-scale
Alfven wave pulses - transport the energy and magnetic-field changes rapidly
through the corona to the lower atmosphere. This offers two possibilities for
electron acceleration. Firstly, in a coronal plasma with beta < m_e/m_p, the
waves propagate as inertial Alfven waves. In the presence of strong spatial
gradients, these generate field-aligned electric fields that can accelerate
electrons to energies on the order of 10 keV and above, including by repeated
interactions between electrons and wavefronts. Secondly, when they reflect and
mode-convert in the chromosphere, a cascade to high wavenumbers may develop.
This will also accelerate electrons by turbulence, in a medium with a locally
high electron number density. This concept, which bridges MHD-based and
particle-based views of a flare, provides an interpretation of the
recently-observed rapid variations of the line-of-sight component of the
photospheric magnetic field across the flare impulsive phase, and offers
solutions to some perplexing flare problems, such as the flare "number problem"
of finding and resupplying sufficient electrons to explain the impulsive-phase
hard X-ray emission.Comment: 31 pages, 6 figure
Freelance networks, trade unions and below-the-line solidarity in regional film and television clusters: An interview with the Bristol editors network
This article consists of an introduction and extended interview transcript conducted with several members of the Bristol Editorsâ Network (BEN), an organization established in May 2015 to support the large community of editors that work in and around Bristol and the South West of England. The interview transcript is significant for several reasons. First and foremost, it provides a rich account of what it is like to freelance within the third-largest film and television production cluster in the UK, after London and Manchester. In doing so, the transcript also offers an insight into the sometimes-fraught state of contemporary industrial relations between the regionâs employers and its largely freelance workforce. Moreover, the transcript provides an account of how, by establishing BEN, Bristol editors are working to defend themselves against exploitative practices in the cluster, fostering a mutually-supportive freelance community and contributing to a more effective, equitable production culture in the city
The Politics of Commerce : The Congress of Chambers of Commerce of the Empire, 1886-1914
Peer reviewedPublisher PD
Preparing to work: dramaturgy, cynicism and normative âremoteâ control in the socialization of graduate recruits in management consulting
online) This paper examines the socialization of graduate recruits into a knowledge intensive labour
process and organizational culture. Theoretically the paper draws upon the idea of âpreparing
for workâ to position this early socialization as a crucial moment in the production of
subjectivities suited (and booted) for the labour process of management consulting. Empirically
the paper reports on a two-day induction session for new graduate recruits joining a global
management consultancy and their responses to this training. Particular attention is given to
the use of role-play and a dramaturgical workshop used in part of the training process. The paper
argues that the utilization of dramaturgy in training is consistent with the overall approach to
control developed in the firm in response to the fact that the labour process of consulting is
often conducted on client sites, away from any direct supervisory gaze. As such, the consultants
were subjected to a form of cultural control that was designed to function independently of
direct supervision. This control did not operate directly upon the new employees professed
values, however, but at one step removed so that a âcynical distanceâ from the content of the
organizationâs culture was accepted so long as a professional âethic of behaviourâ was
established. By focusing on an âethic of behaviourâ these young professionals were encouraged
to internalize a self-control akin to that of an actor, rather than internalizing the corporate values
entirely
The proteome of extracellular vesicles released by clastic cells differs based on their substrate
Extracellular vesicles (EVs) from osteoclasts are important regulators in intercellular communication. Here, we investigated the proteome of EVs from clastic cells plated on plastic
(clasts), bone (osteoclasts) and dentin (odontoclasts) by two-dimensional high performance
liquid chromatography mass spectrometry seeking differences attributable to distinct mineralized matrices. A total of 1,952 proteins were identified. Of the 500 most abundant proteins
in EVs, osteoclast and odontoclast EVs were 83.3% identical, while clasts shared 70.7% of
the proteins with osteoclasts and 74.2% of proteins with odontoclasts. For each protein, the
differences between the total ion count values were mapped to an expression ratio histogram (Z-score) in order to detect proteins differentially expressed. Stabilin-1 and macrophage mannose receptor-1 were significantly-enriched in EVs from odontoclasts compared
with osteoclasts (Z = 2.45, Z = 3.34) and clasts (Z = 13.86, Z = 1.81) and were abundant in
odontoclast EVs. Numerous less abundant proteins were differentially-enriched. Subunits of
known protein complexes were abundant in clastic EVs, and were present at levels consistent with them being in assembled protein complexes. These included the proteasome,
COP1, COP9, the T complex and a novel sub-complex of vacuolar H+
-ATPase (V-ATPase),
which included the (pro) renin receptor. The (pro) renin receptor was immunoprecipitated
using an anti-E-subunit antibody from detergent-solubilized EVs, supporting the idea that
the V-ATPase subunits present were in the same protein complex. We conclude that the
protein composition of EVs released by clastic cells changes based on the substrate. Clastic
EVs are enriched in various protein complexes including a previously undescribed VATPase sub-complex
Noise storm continua: power estimates for electron acceleration
We use a generic stochastic acceleration formalism to examine the power
() input to nonthermal electrons that cause
noise storm continuum emission. The analytical approach includes the derivation
of the Green's function for a general second-order Fermi process, and its
application to obtain the particular solution for the nonthermal electron
distribution resulting from the acceleration of a Maxwellian source in the
corona. We compare with the power observed in noise
storm radiation. Using typical values for the various parameters, we find that
, yielding an efficiency
estimate in the range 10^{-10} \lsim \eta
\lsim 10^{-6} for this nonthermal acceleration/radiation process. These
results reflect the efficiency of the overall process, starting from electron
acceleration and culminating in the observed noise storm emission.Comment: Accepted for publication in Solar Physic
Electronic structure of monoclinic BaBiO3
We present the results of photoemission studies of ââvalence disorderedââ monoclinic BaBiO3 in the photon energy range 15â120 eV. The lineâshapes of the valence band photoemission spectra and the Ba contributions to the valence band are very similar to the line shapes of the total density of states and Ba partial density of states, respectively. Oxygen resonance is observed, demonstrating the existence of empty O 2p states. These results support a more covalent rather than a simple ionic picture for the electronic states of BaBiO3.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87627/2/30_1.pd
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