5,379 research outputs found
Systematic Examination of Stardust Bulbous Track Wall Materials
Analyses of Comet Wild-2 samples returned by NASA's Stardust spacecraft have focused primarily on terminal particles (TPs) or well-preserved fine-grained materials along the track walls [1,2]. However much of the collected material was melted and mixed intimately with the aerogel by the hypervelocity impact [3,4]. We are performing systematic examinations of entire Stardust tracks to establish the mineralogy and origins of all comet Wild 2 components [7,8]. This report focuses on coordinated analyses of indigenous crystalline and amorphous/melt cometary materials along the aerogel track walls, their interaction with aerogel during collection and comparisons with their TPs
Parton Distributions Working Group
The main focus of this working group was to investigate the different issues
associated with the development of quantitative tools to estimate parton
distribution functions uncertainties. In the conclusion, we introduce a
"Manifesto" that describes an optimal method for reporting data.Comment: Report of the Parton Distributions Working Group of the 'QCD and Weak
Boson Physics workshop in preparation for Run II at the Fermilab Tevatron'.
Co-Conveners: L. de Barbaro, S.A. Keller, S. Kuhlmann, H. Schellman, and
W.-K. Tun
Small-scale solar magnetic fields
As we resolve ever smaller structures in the solar atmosphere, it has become
clear that magnetism is an important component of those small structures.
Small-scale magnetism holds the key to many poorly understood facets of solar
magnetism on all scales, such as the existence of a local dynamo, chromospheric
heating, and flux emergence, to name a few. Here, we review our knowledge of
small-scale photospheric fields, with particular emphasis on quiet-sun field,
and discuss the implications of several results obtained recently using new
instruments, as well as future prospects in this field of research.Comment: 43 pages, 18 figure
Post-traumatic stress disorder following patient assaults among staff members of mental health hospitals: a prospective longitudinal study
BACKGROUND: Violence by patients against staff members in mental health institutions has become an important challenge. Violent attacks may not only cause bodily injuries but can also have posttraumatic consequences with high rates of stress for mental health staff. This study prospectively assessed posttraumatic stress disorder (PTSD) in employees who were severely assaulted by patients in nine German state mental health institutions. METHODS: During the study period of six months 46 assaulted staff members were reported. Each staff member was interviewed three times after the violent incident, using the Impact of Event Scale-Revised (IES-R), a widely used PTSD research tool, as well as the Posttraumatic Stress Disorder Checklist – Civilian (PCL-C). RESULTS: In the baseline assessment following an assault by a patient, eight subjects (17%) met the criteria for PTSD. After two and six months, three and four subjects respectively still met diagnosis criteria. CONCLUSION: A small minority of assaulted employees suffer from PTSD for several months after a patient assault
Disenchanting secularism (or the cultivation of soul) as pedagogy in resistance to populist racism and colonial structures in the academy
This paper explores pedagogic strategies for resisting the racism of contemporary populism and age-old coloniality through challenging secularism in the academy, especially in social theory. Secularism sustains racism and imperialism in the contemporary academy and is inscribed, in part, through the norms of social theory. Post-secular social theory has been positioned by some as the decolonial answer, but often replicates the most problematic aspects of secularism. Whereas post-secularism affirms the previously denigrated side of the secular vs religious dualism, I am more interested in unworking those classificatory schemas, setting the critical thought of religious teachers in relation with ‘secular’ social and political theorists such that boundaries erode. The ambition in this is to resist the hierarchical orderings of knowledge that pit Islamic, indigenous, and feminised subjectivity as backwards, dangerous or intrinsically inferior to secular, Christian, rational knowledge. It is also to disenchant the secular Gods (progress, money, growth, health) and hold open space for critical play in relation to the transcendental - to create a permissive, legitimising, space for students’ spiritual dimension, conocimiento, or the cultivation of soul. The paper draws theoretical inspiration from Gloria Anzaldúa, Gayatri Chakravorty Spivak, and Sylvia Wynter. It also draws on a practical experiment in disenchanting secularism through teaching an undergraduate module in social theory called Capitalism and Religion
Electromagnetic Counterparts of Compact Object Mergers Powered by the Radioactive Decay of R-process Nuclei
The most promising astrophysical sources of kHz gravitational waves (GWs) are
the inspiral and merger of binary neutron star(NS)/black hole systems.
Maximizing the scientific return of a GW detection will require identifying a
coincident electro-magnetic (EM) counterpart. One of the most likely sources of
isotropic EM emission from compact object mergers is a supernova-like transient
powered by the radioactive decay of heavy elements synthesized in ejecta from
the merger. We present the first calculations of the optical transients from
compact object mergers that self-consistently determine the radioactive heating
by means of a nuclear reaction network; using this heating rate, we model the
light curve with a one dimensional Monte Carlo radiation transfer calculation.
For an ejecta mass ~1e-2 M_sun[1e-3 M_sun] the resulting light curve peaks on a
timescale ~ 1 day at a V-band luminosity nu L_nu ~ 3e41[1e41] ergs/s (M_V =
-15[-14]); this corresponds to an effective "f" parameter ~3e-6 in the
Li-Paczynski toy model. We argue that these results are relatively insensitive
to uncertainties in the relevant nuclear physics and to the precise early-time
dynamics and ejecta composition. Due to the rapid evolution and low luminosity
of NS merger transients, EM counterpart searches triggered by GW detections
will require close collaboration between the GW and astronomical communities.
NS merger transients may also be detectable following a short-duration
Gamma-Ray Burst or "blindly" with present or upcoming optical transient
surveys. Because the emission produced by NS merger ejecta is powered by the
formation of rare r-process elements, current optical transient surveys can
directly constrain the unknown origin of the heaviest elements in the Universe.Comment: 14 pages, 7 figures; accepted to MNRAS; title changed to highlight
r-process connection and new figure added
Magnetic Coupling in the Quiet Solar Atmosphere
Three kinds of magnetic couplings in the quiet solar atmosphere are
highlighted and discussed, all fundamentally connected to the Lorentz force.
First the coupling of the convecting and overshooting fluid in the surface
layers of the Sun with the magnetic field. Here, the plasma motion provides the
dominant force, which shapes the magnetic field and drives the surface dynamo.
Progress in the understanding of the horizontal magnetic field is summarized
and discussed. Second, the coupling between acoustic waves and the magnetic
field, in particular the phenomenon of wave conversion and wave refraction. It
is described how measurements of wave travel times in the atmosphere can
provide information about the topography of the wave conversion zone, i.e., the
surface of equal Alfv\'en and sound speed. In quiet regions, this surface
separates a highly dynamic magnetic field with fast moving magnetosonic waves
and shocks around and above it from the more slowly evolving field of high-beta
plasma below it. Third, the magnetic field also couples to the radiation field,
which leads to radiative flux channeling and increased anisotropy in the
radiation field. It is shown how faculae can be understood in terms of this
effect. The article starts with an introduction to the magnetic field of the
quiet Sun in the light of new results from the Hinode space observatory and
with a brief survey of measurements of the turbulent magnetic field with the
help of the Hanle effect.Comment: To appear in "Magnetic Coupling between the Interior and the
Atmosphere of the Sun", eds. S.S. Hasan and R.J. Rutten, Astrophysics and
Space Science Proceedings, Springer-Verlag, Heidelberg, Berlin, 200
The formation of sunspot penumbra. I. Magnetic field properties
We study the formation of a sunspot penumbra in the active region NOAA11024.
We simultaneously observed the Stokes parameters of the photospheric iron lines
at 1089.6 nm with the TIP and 617.3 nm with the GFPI spectropolarimeters along
with broad-band images using G-band and CaIIK filters at the German VTT. The
formation of the penumbra is intimately related to the inclined magnetic field.
Within 4.5 h observing time, the magnetic flux of the penumbra increases from
9.7E+20 to 18.2E+20 Mx, while the magnetic flux of the umbra remains constant
at about 3.8E+20 Mx. Magnetic flux in the immediate surroundings is
incorporated into the spot, and new flux is supplied via small flux patches
(SFPs), which on average have a flux of 2-3E+18 Mx. The spot's flux increase
rate of 4.2E+16 Mx/s corresponds to the merging of one SFP per minute. We also
find that during the formation of the spot penumbra: a) the maximum magnetic
field strength of the umbra does not change, b) the magnetic neutral line keeps
the same position relative to the umbra, c) the new flux arrives on the
emergence side of the spot while the penumbra forms on the opposite side, d)
the average LRF inclination of the light bridges decreases from 50 to 37 deg,
and e) as the penumbra develops, the mean magnetic field strength at the spot
border decreases from 1.0 to 0.8 kG. The SFPs associated with elongated
granules are the building blocks of structure formation in active regions.
During the sunspot formation, their contribution is comparable to the
coalescence of pores. A quiet environment in the surroundings is important for
penumbral formation. As remnants of trapped granulation between merging pores,
the light bridges are found to play a crucial role in the formation process.
They seem to channel the magnetic flux through the spot during its formation.
Light bridges are also the locations where the first penumbral filaments form.Comment: 14 pages, 12 figures, accepted by A&
QCD
We discuss issues of QCD at the LHC including parton distributions, Monte
Carlo event generators, the available next-to-leading order calculations,
resummation, photon production, small x physics, double parton scattering, and
backgrounds to Higgs production.Comment: 115 pages, Latex, 47 figures, to appear in the Report of the ``1999
CERN Workshop on SM Physics (and more) at the LHC'', S. Catani, M. Dittmar,
D. Soper, W.J. Stirling, S. Tapprogge (convenors
Control of intestinal stem cell function and proliferation by mitochondrial pyruvate metabolism.
Most differentiated cells convert glucose to pyruvate in the cytosol through glycolysis, followed by pyruvate oxidation in the mitochondria. These processes are linked by the mitochondrial pyruvate carrier (MPC), which is required for efficient mitochondrial pyruvate uptake. In contrast, proliferative cells, including many cancer and stem cells, perform glycolysis robustly but limit fractional mitochondrial pyruvate oxidation. We sought to understand the role this transition from glycolysis to pyruvate oxidation plays in stem cell maintenance and differentiation. Loss of the MPC in Lgr5-EGFP-positive stem cells, or treatment of intestinal organoids with an MPC inhibitor, increases proliferation and expands the stem cell compartment. Similarly, genetic deletion of the MPC in Drosophila intestinal stem cells also increases proliferation, whereas MPC overexpression suppresses stem cell proliferation. These data demonstrate that limiting mitochondrial pyruvate metabolism is necessary and sufficient to maintain the proliferation of intestinal stem cells
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