1,268 research outputs found
WLM-1: A Non-Rotating, Gravitationally Unperturbed, Highly Elliptical Extragalactic Globular Cluster
Globular clusters have long been known for presenting (at times) significant
deviations from spherical symmetry. While rotation has been the main proposed
explanation, other complicating factors such as their constant interaction with
the strong gravitational potential of their host galaxy have made it difficult
for a consensus to be reached. To address this question we have obtained
high-resolution spectra of WLM-1, the lone globular cluster associated with the
isolated, low-mass dwarf irregular galaxy WLM. Using archival HST WFPC2 data,
we measure the radial ellipticity profile of WLM-1, finding it to be highly
elliptical, with a mean value of 0.17 in the region 0.5-5" -- which is
comparable to what is found in our Galaxy for the most elliptical globular
clusters. There is no evidence of isophote twisting, except for the innermost
regions of the cluster (r < 0.5"). To investigate whether the observed
flattening can be ascribed to rotation, we have obtained long-slit
high-resolution VLT/UVES spectra of this cluster along and perpendicular to the
axis of flattening. Using cross-correlation we find that the velocity profile
of the cluster is consistent with zero rotation along either axis. Thus neither
cluster rotation nor galactic tides can be responsible for the flattened
morphology of WLM-1. We argue that the required velocity dispersion anisotropy
between the semi-major and semi-minor axes that would be required to account
for the observed flattening is relatively small, of order 1 km/s. Even though
our errors preclude us from conclusively establishing that such a difference
indeed exists, velocity anisotropy remains at present the most plausible
explanation for the shape of this cluster.Comment: 11 pages, 10 figures, submitted to the A
Phase separation transition in liquids and polymers induced by electric field gradients
Spatially uniform electric fields have been used to induce instabilities in
liquids and polymers, and to orient and deform ordered phases of
block-copolymers. Here we discuss the demixing phase transition occurring in
liquid mixtures when they are subject to spatially nonuniform fields. Above the
critical value of potential, a phase-separation transition occurs, and two
coexisting phases appear separated by a sharp interface. Analytical and
numerical composition profiles are given, and the interface location as a
function of charge or voltage is found. The possible influence of demixing on
the stability of suspensions and on inter-colloid interaction is discussed.Comment: 7 pages, 3 figures. Special issue of the J. Phys. Soc. Ja
Recommended from our members
Pulmonary environmental cues drive group 2 innate lymphoid cell dynamics in mice and humans
Group 2 innate lymphoid cells (ILC2s) are enriched in mucosal tissues (e.g., lung) and respond to epithelial cellâderived cytokines initiating type 2 inflammation. During inflammation, ILC2 numbers are increased in the lung. However, the mechanisms controlling ILC2 trafficking and motility within inflamed lungs remain unclear and are crucial for understanding ILC2 function in pulmonary immunity. Using several approaches, including lung intravital microscopy, we demonstrate that pulmonary ILC2s are highly dynamic, exhibit amoeboid-like movement, and aggregate in the lung peribronchial and perivascular spaces. They express distinct chemokine receptors, including CCR8, and actively home to CCL8 deposits located around the airway epithelium. Within lung tissue, ILC2s were particularly motile in extracellular matrixâenriched regions. We show that collagen-I drives ILC2 to markedly change their morphology by remodeling their actin cytoskeleton to promote environmental exploration critical for regulating eosinophilic inflammation. Our study provides previously unappreciated insights into ILC2 migratory patterns during inflammation and highlights the importance of environmental guidance cues in the lung in controlling ILC2 dynamics
Military deployment, masculinity and trauma : reviewing the connections
This article reviews the literature on deployment trauma and examines the limitations
of conventional understandings of trauma as they relate to veteransâ experiences.
It suggests that the failure to take into account social influences and social
relationships limits the usefulness of conventional approaches to trauma. The article
considers the role that masculinity plays in male veteransâ experience of and
sense making about trauma. It is suggested that while formal recognition of posttraumatic
stress disorder in the DSM has provided a helpful language for veterans,
it is an incomplete response. A new model of masculinity that better enables the male
veteran to speak about trauma and to reconnect with others has implications for
counselling practice with veterans
Whatever happened to repeat victimisation?
Crime is concentrated at the individual level (hot dots) as well as at area level (hot spots). Research on repeat victimisation affords rich prevention opportunities but has been increasingly marginalised by policy makers and implementers despite repeat victims accounting for increasing proportions of total crime. The present paper seeks to trigger a resurgence of interest in research and initiatives based on the prevention of repeat victimisation.N/
Multimodal database of emotional speech, video and gestures
People express emotions through different modalities. Integration of verbal and non-verbal communication channels creates a system in which the message is easier to understand. Expanding the focus
to several expression forms can facilitate research on emotion recognition as well as human-machine interaction. In this article, the authors
present a Polish emotional database composed of three modalities: facial expressions, body movement and gestures, and speech. The corpora
contains recordings registered in studio conditions, acted out by 16 professional actors (8 male and 8 female). The data is labeled with six basic
emotions categories, according to Ekmanâs emotion categories. To check
the quality of performance, all recordings are evaluated by experts and
volunteers. The database is available to academic community and might
be useful in the study on audio-visual emotion recognition
Graphite and Hexagonal Boron-Nitride Possess the Same Interlayer Distance. Why?
Graphite and hexagonal boron nitride (h-BN) are two prominent members of the
family of layered materials possessing a hexagonal lattice. While graphite has
non-polar homo-nuclear C-C intra-layer bonds, h-BN presents highly polar B-N
bonds resulting in different optimal stacking modes of the two materials in
bulk form. Furthermore, the static polarizabilities of the constituent atoms
considerably differ from each other suggesting large differences in the
dispersive component of the interlayer bonding. Despite these major differences
both materials present practically identical interlayer distances. To
understand this finding, a comparative study of the nature of the interlayer
bonding in both materials is presented. A full lattice sum of the interactions
between the partially charged atomic centers in h-BN results in vanishingly
small monopolar electrostatic contributions to the interlayer binding energy.
Higher order electrostatic multipoles, exchange, and short-range correlation
contributions are found to be very similar in both materials and to almost
completely cancel out by the Pauli repulsions at physically relevant interlayer
distances resulting in a marginal effective contribution to the interlayer
binding. Further analysis of the dispersive energy term reveals that despite
the large differences in the individual atomic polarizabilities the
hetero-atomic B-N C6 coefficient is very similar to the homo-atomic C-C
coefficient in the hexagonal bulk form resulting in very similar dispersive
contribution to the interlayer binding. The overall binding energy curves of
both materials are thus very similar predicting practically the same interlayer
distance and very similar binding energies.Comment: 18 pages, 5 figures, 2 table
Towards mathematical AI via a model of the content and process of mathematical question and answer dialogues
This paper outlines a strategy for building semantically meaningful representations and carrying out effective reasoning in technical knowledge domains such as mathematics. Our central assertion is that the semi-structured Q and A format, as used on the popular Stack Exchange network of websites, exposes domain knowledge in a form that is already reasonably close to the structured knowledge formats that computers can reason about. The knowledge in question is not only facts - but discursive, dialectical, argument for purposes of proof and pedagogy. We therefore assert that modelling the Q and A process computationally provides a route to domain understanding that is compatible with the day-to-day practices of mathematicians and students. This position is supported by a small case study that analyses one question from Mathoverflow in detail, using concepts from argumentation theory. A programme of future work, including a rigorous evaluation strategy, is then advanced
Multi-Wavelength Observations of the Blazar 1ES 1011+496 in Spring 2008
The BL Lac object 1ES 1011+496 was discovered at Very High Energy gamma-rays
by MAGIC in spring 2007. Before that the source was little studied in different
wavelengths. Therefore a multi-wavelength (MWL) campaign was organized in
spring 2008. Along MAGIC, the MWL campaign included the Metsahovi radio
observatory, Bell and KVA optical telescopes and the Swift and AGILE
satellites. MAGIC observations span from March to May, 2008 for a total of 27.9
hours, of which 19.4 hours remained after quality cuts. The light curve showed
no significant variability. The differential VHE spectrum could be described
with a power-law function. Both results were similar to those obtained during
the discovery. Swift XRT observations revealed an X-ray flare, characterized by
a harder when brighter trend, as is typical for high synchrotron peak BL Lac
objects (HBL). Strong optical variability was found during the campaign, but no
conclusion on the connection between the optical and VHE gamma-ray bands could
be drawn. The contemporaneous SED shows a synchrotron dominated source, unlike
concluded in previous work based on nonsimultaneous data, and is well described
by a standard one zone synchrotron self Compton model. We also performed a
study on the source classification. While the optical and X-ray data taken
during our campaign show typical characteristics of an HBL, we suggest, based
on archival data, that 1ES 1011+496 is actually a borderline case between
intermediate and high synchrotron peak frequency BL Lac objects.Comment: 13 pages, accepted for publication in MNRA
- âŠ