2,810 research outputs found
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Intermittent release of transients in the slow solar wind: 2. In situ evidence
In paper 1, we showed that the Heliospheric Imager (HI) instruments on the pair of NASA STEREO spacecraft can be used to image the streamer belt and, in particular, the variability of the slow solar wind which originates near helmet streamers. The observation of intense intermittent transient outflow by HI implies that the corresponding in situ observations of the slow solar wind and corotating interaction regions (CIRs) should contain many signatures of transients. In the present paper, we compare the HI observations with in situ measurements from the STEREO and ACE spacecraft. Analysis of the solar wind ion, magnetic field, and suprathermal electron flux measurements from
the STEREO spacecraft reveals the presence of both closed and partially disconnected interplanetary magnetic field lines permeating the slow solar wind. We predict that one of the transients embedded within the second CIR (CIR‐D in paper 1) should impact the near‐Earth ACE spacecraft. ACE measurements confirm the presence of a transient at the time of CIR passage; the transient signature includes helical magnetic fields and bidirectional suprathermal electrons. On the same day, a strahl electron dropout is observed at STEREO‐B, correlated with the passage of a high plasma beta structure. Unlike ACE, STEREO‐B observes the transient a few hours ahead of the CIR. STEREO‐A, STEREO‐B, and ACE spacecraft observe very different slow solar wind properties ahead of and during the CIR analyzed in this paper, which we associate with the intermittent release of transients
Surface plasmon resonance imaging detection of silver nanoparticle-tagged immunoglobulin
This article is available open access through the publisher’s website at the link below. Copyright @ 2011 The Royal Society.The detection sensitivity of silver nanoparticle (AgNP)-tagged goat immunoglobulin G (gIgG) microarrays was investigated by studying surface plasmon resonance (SPR) images captured in the visible wavelength range with the help of a Kretchmann-configured optical coupling set-up. The functionalization of anti-gIgG molecules on the AgNP surface was studied using transmission electron microscopy, photon correlation measurements and UV–visible absorption spectroscopy. A value of 1.3 × 107 M−1 was obtained for the antibody–antigen binding constant by monitoring the binding events at a particular resonance wavelength. The detection limit of this SPR imaging instrument is 6.66 nM of gIgG achieved through signal enhancement by a factor of larger than 4 owing to nanoparticle tagging with the antibody.The European Commissio
On the Cause of Supra-Arcade Downflows in Solar Flares
A model of supra-arcade downflows (SADs), dark low density regions also known
as tadpoles that propagate sunward during solar flares, is presented. It is
argued that the regions of low density are flow channels carved by
sunward-directed outflow jets from reconnection. The solar corona is
stratified, so the flare site is populated by a lower density plasma than that
in the underlying arcade. As the jets penetrate the arcade, they carve out
regions of depleted plasma density which appear as SADs. The present
interpretation differs from previous models in that reconnection is localized
in space but not in time. Reconnection is continuous in time to explain why
SADs are not filled in from behind as they would if they were caused by
isolated descending flux tubes or the wakes behind them due to temporally
bursty reconnection. Reconnection is localized in space because outflow jets in
standard two-dimensional reconnection models expand in the normal (inflow)
direction with distance from the reconnection site, which would not produce
thin SADs as seen in observations. On the contrary, outflow jets in spatially
localized three-dimensional reconnection with an out-of-plane (guide) magnetic
field expand primarily in the out-of-plane direction and remain collimated in
the normal direction, which is consistent with observed SADs being thin.
Two-dimensional proof-of-principle simulations of reconnection with an
out-of-plane (guide) magnetic field confirm the creation of SAD-like depletion
regions and the necessity of density stratification. Three-dimensional
simulations confirm that localized reconnection remains collimated.Comment: 16 pages, 5 figures, accepted to Astrophysical Journal Letters in
August, 2013. This version is the accepted versio
A Review of Leadership Theory and Competency Frameworks
This report presents a review of leadership theory and competency frameworks that was commissioned to assist the development of the new National Occupational Standards in Management and Leadership.
The report begins with a review of leadership theories and tracks their evolution over the past 70 years from the “great man” notion of heroic leaders, through trait theories, behaviourist theories, situational leadership, contingency theory and on to transactional and transformational leadership. Each of these offers some insights into the qualities of successful leaders, but there has been a shift in focus from the generic characteristics and behaviours of the individual to a recognition of the importance of responding to different situations and contexts and the leaders’ role in relation to followers. The review concludes with an introduction to the notion of “dispersed leadership” and a distinction between the process of “leadership” and the socially-constructed role of “leader”.
The next section, on Leadership Models and Competency Frameworks, presents a range of leadership and management frameworks currently being used in organisations. These define the qualities required of people in leadership positions and help to inform the leadership development process. Seven private-sector, nine public sector and eight generic frameworks are discussed and web links to the full models included where available.
The following section gives a brief overview of a selection of leadership development initiatives both associated with, and as alternatives to, a leadership competencies framework. The aim of this is to give an indication of how different techniques can be used to develop leadership capability within individuals and organisations and how this relates to the underlying philosophy of the programme.
The section on Providing Governance, describes the key legal and ethical responsibilities of Directors and an indication of the kinds of skills, behaviours and values required to achieve these.
The report concludes with a discussion of the competency framework approach to leadership and leadership development and a proposal as to alternative ways of addressing these issues. It is concluded that whilst this approach has its strengths, it leads to a particularly individualistic notion of leadership and a relatively prescribed approach to leadership development. The changing nature of work and society, it is argued, may demand new approaches that encourage a more collective and emergent view of leadership and leadership development and of sharing the role of “leader” more widely within organisations.Chase Consulting; Management Standards Centr
Can Streamer Blobs prevent the Buildup of the Interplanetetary Magnetic Field?
Coronal Mass Ejections continuously drag closed magnetic field lines away
from the Sun, adding new flux to the interplanetary magnetic field (IMF). We
propose that the outward-moving blobs that have been observed in helmet
streamers are evidence of ongoing, small-scale reconnection in streamer current
sheets, which may play an important role in the prevention of an indefinite
buildup of the IMF. Reconnection between two open field lines from both sides
of a streamer current sheet creates a new closed field line, which becomes part
of the helmet, and a disconnected field line, which moves outward. The blobs
are formed by plasma from the streamer that is swept up in the trough of the
outward moving field line. We show that this mechanism is supported by
observations from SOHO/LASCO. Additionally, we propose a thorough statistical
study to quantify the contribution of blob formation to the reduction of the
IMF, and indicate how this mechanism may be verified by observations with
SOHO/UVCS and the proposed NASA STEREO and ESA Polar Orbiter missions.Comment: 7 pages, 2 figures; accepted by The Astrophysical Journal Letters;
uses AASTe
The Path to Buried Treasure: Paving the Way to the FLAMINGOS-2 Galactic Center Survey with IR and X-ray Observations
I describe the IR and X-ray campaign we have undertaken to determine the
nature of the faint discrete X-ray source population discovered by Chandra in
the Galactic Center. These results will provide the input to the FLAMINGOS-2
Galactic Center Survey (F2GCS). With FLAMINGOS-2's multi-object IR spectrograph
we will obtain 1000s of IR spectra of candidate X-ray source counterparts,
allowing us to efficiently identify the nature of these sources, and thus
dramatically increase the number of known X-ray binaries and CVs in the Milky
Way.Comment: To be published in Proceedings of 'A Population Explosion: The Nature
and Evolution of X-ray Binaries in Diverse Environments', 28 Oct - 2 Nov, St.
Pete Beach, FL; eds. R.M. Bandyopadhyay, S. Wachter, D. Gelino, C.R. Gelino;
AIP Conference Proceedings Serie
Peer observation of teaching: A decoupled process
This article details the findings of research into the academic teaching staff experience of peer observation of their teaching practice. Peer observation is commonly used as a tool to enhance a teacher’s continuing professional development. Research participants acknowledged its ability to help develop their teaching practice, but they also reported that it could operate superficially as a tick box exercise, that its outcomes were frequently decoupled from formal staff development processes, and that its purpose and usefulness therefore seemed unclear. This article argues that the presence of decoupling reinforces the need to account for structural factors that can interact with peer observation of teaching to ensure it is a meaningful exercise for all teaching staff. It concludes that the published academic literature is perhaps guilty of overplaying the role of personal choice and individual tutor characteristics when addressing the complex issue that is staff disengagement with peer observation of teaching
Ion heating resulting from pickup in magnetic reconnection exhausts
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95415/1/jgra19672.pd
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Contrasting arbuscular mycorrhizal communities colonizing different host plants show a similar response to a soil phosphorus concentration gradient
High soil phosphorus (P) concentration is frequently shown to reduce root colonization by arbuscular mycorrhizal (AM) fungi, but the influence of P on the diversity of colonizing AM fungi is uncertain.
We used terminal restriction fragment length polymorphism (T-RFLP) of 18S rDNA and cloning to assess diversity of AM fungi colonizing maize (Zea mays), soybean (Glycene max) and field violet (Viola arvensis) at three time points in one season along a P gradient of 10–280 mg l−1 in the field.
Percentage AM colonization changed between sampling time points but was not reduced by high soil P except in maize. There was no significant difference in AM diversity between sampling time points. Diversity was reduced at concentrations of P > 25 mg l−1, particularly in maize and soybean. Both cloning and T-RFLP indicated differences between AM communities in the different host species. Host species was more important than soil P in determining the AM community, except at the highest P concentration.
Our results show that the impact of soil P on the diversity of AM fungi colonizing plants was broadly similar, despite the fact that different plants contained different communities. However, subtle differences in the response of the AM community in each host were evident
Exploring a New Population of Compact Objects: X-ray and IR Observations of the Galactic Centre
I describe the IR and X-ray observational campaign we have undertaken for the
purpose of determining the nature of the faint discrete X-ray source population
discovered by Chandra in the Galactic Center (GC). Data obtained for this
project includes a deep Chandra survey of the Galactic Bulge; deep, high
resolution IR imaging from VLT/ISAAC, CTIO/ISPI, and the UKIDSS Galactic Plane
Survey (GPS); and IR spectroscopy from VLT/ISAAC and IRTF/SpeX. By
cross-correlating the GC X-ray imaging from Chandra with our IR surveys, we
identify candidate counterparts to the X-ray sources via astrometry. Using a
detailed IR extinction map, we are deriving magnitudes and colors for all the
candidates. Having thus established a target list, we will use the multi-object
IR spectrograph FLAMINGOS-2 on Gemini-South to carry out a spectroscopic survey
of the candidate counterparts, to search for emission line signatures which are
a hallmark of accreting binaries. By determining the nature of these X-ray
sources, this FLAMINGOS-2 Galactic Center Survey will have a dramatic impact on
our knowledge of the Galactic accreting binary population.Comment: 4 pages, 2 figures, to appear in the Proceedings of The Second
Kolkata Conference on Observational Evidence for Black Holes in the
Universe'', ed. S. Charkrabarti, Kolkata, India; AIP Conf. Serie
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