7,328 research outputs found
The nature of Ho magnetism in multiferroic HoMnO3
Using x-ray resonant magnetic scattering and x-ray magnetic circular
dichroism, techniques that are element specific, we have elucidated the role of
Ho3+ in multiferroic HoMnO3. In zero field, Ho3+ orders antiferromagnetically
with moments aligned along the hexagonal c direction below 40 K, and undergoes
a transition to another magnetic structure below 4.5 K. In applied electric
fields of up to 1x10^7 V/m, the magnetic structure of Ho3+ remains unchanged.Comment: 4 pages, 3 figures Manuscript accepted for publication in Phys. Rev.
Lett. 200
Extinction toward the Compact HII Regions G-0.02-0.07
The four HII regions in the Sgr A East complex: A, B, C, and D, represent
evidence of recent massive star formation in the central ten parsecs. Using
Paschen-alpha images taken with HST and 8.4 GHz VLA data, we construct an
extinction map of A-D, and briefly discuss their morphology and location.Comment: 2 pages, 1 figure. To be published in the Astronomical Society of the
Pacific Conference Series Proceedings of the Galactic Center Workshop 2009,
Shangha
HST Palpha Survey of the Galactic Center -- Searching the missing young stellar populations within the Galactic Center
We present preliminary results of our \hst Pa survey of the Galactic
Center (\gc), which maps the central 0.650.25 degrees around Sgr A*.
This survey provides us with a more complete inventory of massive stars within
the \gc, compared to previous observations. We find 157 Pa emitting
sources, which are evolved massive stars. Half of them are located outside of
three young massive star clusters near Sgr A*. The loosely spatial distribution
of these field sources suggests that they are within less massive star
clusters/groups, compared to the three massive ones. Our Pa mosaic not
only resolves previously well-known large-scale filaments into fine structures,
but also reveals many new extended objects, such as bow shocks and H II
regions. In particular, we find two regions with large-scale Pa diffuse
emission and tens of Pa emitting sources in the negative Galactic
longitude suggesting recent star formation activities, which were not known
previously. Furthermore, in our survey, we detect 0.6 million stars, most
of which are red giants or AGB stars. Comparisons of the magnitude distribution
in 1.90 m and those from the stellar evolutionary tracks with different
star formation histories suggest an episode of star formation process about 350
Myr ago in the \gc .Comment: 10 pages, 6 figures, Proceedings of the Galactic Center Workshop
2009, Shangha
Isotopic (ÎŽ13C, Î14C) Analysis of Organic Acids in Marine Samples Using Wet Chemical Oxidation
We present a method for the isolation and off-line isotope analysis of formate and acetate in marine samples. Organic acids are separated by high performance liquid chromatography and collected in glass ExetainerŸ screw-capped vials that have been prespiked with an oxidant and flushed with helium. The vials are subsequently heated to convert the organic compounds to CO2 for radiocarbon and Ύ13C analysis. Small aliquots are sampled for measurement of Ύ13C by isotope ratio mass spectrometry, whereas the majority of the CO2 is saved for radiocarbon analysis by accelerator mass spectrometry using a gas ion source. Accurate Ύ13C and radiocarbon values were obtained for formate and acetate standards spiked into deep seawater and saline Milli-Q water at concentrations of 25 to 1000 ”M C. The process blank associated with the isolation of formate for radiocarbon analysis was ~1.5 ”g C and stable over time. Accurate results could be obtained for marine samples with only 25 ”M formate. The radiocarbon analysis of acetate showed significantly higher and more variable extraneous carbon contributions, particularly for samples spiked into seawater. Potential improvements that may make the method appropriate for the radiocarbon analysis of acetate in seawater are discussed. The blanks associated with the wet chemical oxidation were assessed independently and found to be small and consistent (\u3c0.3 ”g C), potentially making this approach feasible for a broader set of compounds separated by HPLC for radiocarbon analysis
The Expression and Roles of Nde1 and Ndel1 in the Adult Mammalian Central Nervous System
Open Access funded by Wellcome Trust Under a Creative Commons license Acknowledgments We thank Prof Angelo Sementilli, Department of Pathology, Universidade Metropolitana de Santos, SP, Brazil, for the human sample collection. This study is funded by Scottish Universities Life Sciences Alliance (HR07019 to S. Shen and C.D. McCaig), Medical Research Scotland (384 FRG to B. Lang, United Kingdom), Tenovus Scotland (G12/25 to B. Lang), Sino-UK Higher Education Research Partnership for PhD Studies (C.D. McCaig and Y.Q. Ding) and Wellcome Trust (WT081633MA-NCE to P.J.A. McCaffery, United Kingdom).Peer reviewedPublisher PD
Design and analysis of fractional factorial experiments from the viewpoint of computational algebraic statistics
We give an expository review of applications of computational algebraic
statistics to design and analysis of fractional factorial experiments based on
our recent works. For the purpose of design, the techniques of Gr\"obner bases
and indicator functions allow us to treat fractional factorial designs without
distinction between regular designs and non-regular designs. For the purpose of
analysis of data from fractional factorial designs, the techniques of Markov
bases allow us to handle discrete observations. Thus the approach of
computational algebraic statistics greatly enlarges the scope of fractional
factorial designs.Comment: 16 page
Properties of the Compact HII Region Complex G-0.02-0.07
We present new extinction maps and high-resolution Paschen alpha images of
G-0.02-0.07, a complex of compact HII regions located adjacent to the
M-0.02-0.07 giant molecular cloud, 6 parsecs in projection from the center of
the Galaxy. These HII regions, which lie in projection just outside the
boundary of the Sgr A East supernova remnant, represent one of the most recent
episodes of star formation in the central parsecs of the Galaxy. The 1.87
micron extinctions of regions A, B and C are almost identical, approximately
1.5 magnitudes. Region D, in contrast, has a peak 1.87 micron extinction of 2.3
magnitudes. Adopting the Nishiyama et al. (2008) extinction law, we find these
extinctions correspond to visual extinctions of A_V = 44.5 and A_V = 70,
respectively. The similar and uniform extinctions of regions A, B and C are
consistent with that expected for foreground extinction in the direction of the
Galactic center, suggesting that they lie at the front side of the M-0.02-0.07
molecular cloud. Region D is more compact, has a higher extinction and is thus
suspected to be younger and embedded in a dense core in a compressed ridge on
the western edge of this cloud.Comment: 21 pages, 11 figures, submitted to ApJ, comments welcom
Visual Affect Around the World: A Large-scale Multilingual Visual Sentiment Ontology
Every culture and language is unique. Our work expressly focuses on the
uniqueness of culture and language in relation to human affect, specifically
sentiment and emotion semantics, and how they manifest in social multimedia. We
develop sets of sentiment- and emotion-polarized visual concepts by adapting
semantic structures called adjective-noun pairs, originally introduced by Borth
et al. (2013), but in a multilingual context. We propose a new
language-dependent method for automatic discovery of these adjective-noun
constructs. We show how this pipeline can be applied on a social multimedia
platform for the creation of a large-scale multilingual visual sentiment
concept ontology (MVSO). Unlike the flat structure in Borth et al. (2013), our
unified ontology is organized hierarchically by multilingual clusters of
visually detectable nouns and subclusters of emotionally biased versions of
these nouns. In addition, we present an image-based prediction task to show how
generalizable language-specific models are in a multilingual context. A new,
publicly available dataset of >15.6K sentiment-biased visual concepts across 12
languages with language-specific detector banks, >7.36M images and their
metadata is also released.Comment: 11 pages, to appear at ACM MM'1
Reentrant charge ordering caused by polaron formation
Based on a two-dimensional extended Hubbard model with electron-phonon
interaction, we have studied the effect of polaron formation on the charge
ordering (CO) transition. It is found that for fully ferromagnetically ordered
spins the CO state may go through a process of appearance, collapse and
reappearance with decreasing temperature. This is entirely due to a
emperature-dependent polaron bandwidth. On the other hand, when a paramagnetic
spin state is considered, only a simple reentrant behavior of the CO transition
is found, which is only partly due to polaron effect. This model is proposed as
an explanation of the observed reentrant behavior of the CO transition in the
layered manganite LaSrMnO.Comment: 4 pages, 2 eps figures, revised version accepted by Phys. Rev. Let
- âŠ