12,151 research outputs found
On transversally elliptic operators and the quantization of manifolds with -structure
An -structure on a manifold is an endomorphism field
\phi\in\Gamma(M,\End(TM)) such that . Any -structure
determines an almost CR structure E_{1,0}\subset T_\C M given by the
-eigenbundle of . Using a compatible metric and connection
on , we construct an odd first-order differential operator ,
acting on sections of , whose principal symbol is of the
type considered in arXiv:0810.0338. In the special case of a CR-integrable
almost -structure, we show that when is the generalized
Tanaka-Webster connection of Lotta and Pastore, the operator is given by D
= \sqrt{2}(\dbbar+\dbbar^*), where \dbbar is the tangential Cauchy-Riemann
operator.
We then describe two "quantizations" of manifolds with -structure that
reduce to familiar methods in symplectic geometry in the case that is a
compatible almost complex structure, and to the contact quantization defined in
\cite{F4} when comes from a contact metric structure. The first is an
index-theoretic approach involving the operator ; for certain group actions
will be transversally elliptic, and using the results in arXiv:0810.0338,
we can give a Riemann-Roch type formula for its index. The second approach uses
an analogue of the polarized sections of a prequantum line bundle, with a CR
structure playing the role of a complex polarization.Comment: 31 page
The Magellanic System: What have we learnt from FUSE?
I review some of the findings on the Magellanic System produced by the Far
Ultraviolet Spectroscopic Explorer (FUSE) during and after its eight years of
service. The Magellanic System with its high-velocity complexes provides a
nearby laboratory that can be used to characterize phenomena that involve
interaction between galaxies, infall and outflow of gas and metals in galaxies.
These processes are crucial for understanding the evolution of galaxies and the
intergalactic medium. Among the FUSE successes I highlight are the coronal gas
about the LMC and SMC, and beyond in the Stream, the outflows from these
galaxies, the discovery of molecules in the diffuse gas of the Stream and the
Bridge, an extremely sub-solar and sub-SMC metallicity of the Bridge, and a
high-velocity complex between the Milky Way and the Clouds.Comment: A contributed paper to the FUSE Annapolis Conference "Future
Directions in Ultraviolet Spectroscopy.", 5 pages. To appear as an AIP
Conference Proceedin
Isotopic composition of Murchison organic compounds: Intramolecular carbon isotope fractionation of acetic acid. Simulation studies of cosmochemical organic syntheses
Recently, in our laboratories, samples of Murchison acetic acid were decarboxylated successfully and the carbon isotopic composition was measured for the methane released by this procedure. These analyses showed significant differences in C-13/C-12 ratios for the methyl and carboxyl carbons of the acetic acid molecule, strongly suggesting that more than one carbon source may be involved in the synthesis of the Murchison organic compounds. On the basis of this finding, laboratory model systems simulating cosmochemical synthesis are being studied, especially those processes capable of involving two or more starting carbon sources
Validity and practical utility of accelerometry for the measurement of in-hand physical activity in horses
Background:
Accelerometers are valid, practical and reliable tools for the measurement of habitual physical activity (PA). Quantification of PA in horses is desirable for use in research and clinical settings. The objective of this study was to evaluate a triaxial accelerometer for objective measurement of PA in the horse by assessment of their practical utility and validity.
Horses were recruited to establish both the optimal site of accelerometer attachment and questionnaire designed to explore owner acceptance. Validity and cut-off values were obtained by assessing PA at various gaits. Validation study- 20 horses wore the accelerometer while being filmed for 10Â min each of rest, walking and trotting and 5 mins of canter work. Practical utility study- five horses wore accelerometers on polls and withers for 18Â h; compliance and relative data losses were quantified.
Results:
Accelerometry output differed significantly between the four PA levels (Pâ<0âą001) for both wither and poll placement. For withers placement, ROC analyses found optimal sensitivity and specificity at a cut-off of <47 counts per minute (cpm) for rest (sensitivity 99.5Â %, specificity 100Â %), 967â2424Â cpm for trotting (sensitivity 96.7Â %, specificity 100Â %) and ≥2425Â cpm for cantering (sensitivity 96.0Â %, specificity 97.0Â %). Attachment at the poll resulted in optimal sensitivity and specificity at a cut-off of <707 counts per minute (cpm) for rest (sensitivity 97.5Â %, specificity 99.6Â %), 1546â2609Â cpm for trotting (sensitivity 90.33Â %, specificity 79.25Â %) and ≥2610Â cpm for cantering (sensitivity 100Â %, specificity 100Â %) In terms of practical utility, accelerometry was well tolerated and owner acceptance high.
Conclusion:
Accelerometry data correlated well with varying levels of in-hand equine activity. The use of accelerometers is a valid method for objective measurement of controlled PA in the horse
Sand in the wheels, or oiling the wheels, of international finance? : New Labour's appeal to a 'new Bretton Woods'
Tony Blairâs political instinct typically is to associate himself only with the future. As such, his explicit appeal to âthe pastâ in his references to New Labourâs desire to establish a ânew Bretton Woodsâ is sufficient in itself to arouse some degree of analytical curiosity (see Blair 1998a). The fact that this appeal was made specifically in relation to Bretton Woods is even more interesting. The resonant image of the international economic context established by the original Bretton Woods agreements invokes a style and content of policy-making which Tony Blair typically dismisses as neither economically nor politically consistent with his preferred vision of the future (see Blair 2000c, 2001b)
A Comparison of Ultraviolet, Optical, and X-Ray Imagery of Selected Fields in the Cygnus Loop
During the Astro-1 and Astro-2 Space Shuttle missions in 1990 and 1995, far
ultraviolet (FUV) images of five 40' diameter fields around the rim of the
Cygnus Loop supernova remnant were observed with the Ultraviolet Imaging
Telescope (UIT). These fields sampled a broad range of conditions including
both radiative and nonradiative shocks in various geometries and physical
scales. In these shocks, the UIT B5 band samples predominantly CIV 1550 and the
hydrogen two-photon recombination continuum. Smaller contri- butions are made
by emission lines of HeII 1640 and OIII] 1665. We present these new FUV images
and compare them with optical Halpha and [OIII], and ROSAT HRI X-ray images.
Comparing the UIT images with those from the other bands provides new insights
into the spatial variations and locations of these different types of emission.
By comparing against shock model calculations and published FUV spectroscopy at
select locations, we surmise that resonance scattering in the strong FUV
permitted lines is widespread in the Cygnus Loop, especially in the bright
optical filaments typically selected for observation in most previous studies.Comment: 21 pages with 10 figures. See http://www.pha.jhu.edu/~danforth/uit/
for full-resolution figure
National registry for sudden unexpected deaths of infants and children in England: why do we need one and do families want one?
The sudden and unexpected death of an infant or child is devastating. An inability to explain why an infant or child died is difficult to accept for both families and professionals. No reliable national dataset exists to estimate precisely how many infants and children die unexpectedly each year in England. This lack of accurate epidemiological data belies the scale of this public health problem. Detailed controlled observational studies of infant deaths identifying risk factors and providing evidence-based advice for parents has seen a dramatic reduction in incidence over the last 30 years by almost 80% but greater knowledge is needed if future deaths of infants and older children are to be prevented and families optimally supported. We propose that a national registry of sudden unexpected deaths in infancy and childhood would accurately determine incidence, identify unknown risk factors and highlight good care practices, ensuring these can be standardised nationally. For such a project to be successful, however, parents must be at the heart of it. We held a consultation day between families, professionals and supporting charities (The Lullaby Trust, Child Bereavement UK, SUDC UK and CRY) to seek opinion on the desire for a registry and how best to ensure families are engaged. Here, we summarise our rationale for a registry and the feedback we received from attendees regarding their views of the proposal and the practical aspects of administering it
Statewide Collaboration to Improve ASD Initiatives in Montana
The Montana Autism Center, funded by a small state grant from AMCHP, is part of the national Act Early Network. This poster highlights initial outcomes from the first 18 months of grant funding. It describes the âfast factsâ related to ASD service provision (screening and monitoring) in Montana
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