683 research outputs found
Higher first-pass extraction of 99mTc-N-NOET enhances magnitude of reversible defects: Validation of animal model in humans
Energy gap in superconducting fullerides: optical and tunneling studies
Tunneling and optical transmission studies have been performed on
superconducting samples of Rb3C60. At temperatures much below the
superconducting transition temperature Tc the energy gap is 2 Delta=5.2 +-
0.2meV, corresponding to 2 Delta/kB Tc = 4.2. The low temperature density of
states, and the temperature dependence of the optical conductivity resembles
the BCS behavior, although there is an enhanced ``normal state" contribution.
The results indicate that this fulleride material is an s-wave superconductor,
but the superconductivity cannot be described in the weak coupling limit.Comment: RevTex file with four .EPS figures. Prints to four pages. Also
available at http://buckminster.physics.sunysb.edu/papers/pubrece.htm
Physical Properties and Galactic Distribution of Molecular Clouds identified in the Galactic Ring Survey
We derive the physical properties of 580 molecular clouds based on their 12CO
and 13CO line emission detected in the University of Massachusetts-Stony Brook
(UMSB) and Galactic Ring surveys. We provide a range of values of the physical
properties of molecular clouds, and find a power-law correlation between their
radii and masses, suggesting that the fractal dimension of the ISM is around
2.36. This relation, M = (228 +/- 18) R^{2.36+/-0.04}, allows us to derive
masses for an additional 170 GRS molecular clouds not covered by the UMSB
survey. We derive the Galactic surface mass density of molecular gas and
examine its spatial variations throughout the Galaxy. We find that the
azimuthally averaged Galactic surface density of molecular gas peaks between
Galactocentric radii of 4 and 5 kpc. Although the Perseus arm is not detected
in molecular gas, the Galactic surface density of molecular gas is enhanced
along the positions of the Scutum-Crux and Sagittarius arms. This may indicate
that molecular clouds form in spiral arms and are disrupted in the inter-arm
space. Last, we find that the CO excitation temperature of molecular clouds
decreases away from the Galactic center, suggesting a possible decline in the
star formation rate with Galactocentric radius. There is a marginally
significant enhancement in the CO excitation temperature of molecular clouds at
a Galactocentric radius of about 6 kpc, which in the longitude range of the GRS
corresponds to the Sagittarius arm. This temperature increase could be
associated with massive star formation in the Sagittarius spiral arm
Metallicity in the merger Seyfert galaxy NGC 6240
We have calculated the physical conditions throughout the NLR of the merger
Seyfert galaxy NGC 6240 by modelling the observed optical and infrared line
ratios. We have found that the optical spectra are emitted by clouds
photoionised by the power-law radiation flux from the AGN (or AGNs), and heated
mainly by the shock accompanying the propagation of the clouds outwards. The
infrared line ratios are emitted from clouds ejected from a starburst which
photoionises the gas by the black-body radiation flux corresponding to a
stellar colour temperature of about 50,000 K. Both the flux from the AGN and
the ionization parameters are low. The most characteristic physical parameters
are the relatively high shock velocities (>400 km/s) and low preshock densities
(about 40-60 cm-3) of the gas. The C/H, N/H, O/H relative abundances are higher
than solar by a factor lower or about 1.5. We suggest that those high relative
abundances indicate trapping of H into H2 molecules rather than high
metallicities. Adopting an initial grain radius of 1 micron, the dust
temperatures calculated in the clouds reached by the power-law radiation flux
and by the black-body radiation flux are 81 K and 68 K, respectively.Comment: 14 pages, 5 figures, accepted for publication in MNRA
Sensitivity and Insensitivity of Galaxy Cluster Surveys to New Physics
We study the implications and limitations of galaxy cluster surveys for
constraining models of particle physics and gravity beyond the Standard Model.
Flux limited cluster counts probe the history of large scale structure
formation in the universe, and as such provide useful constraints on
cosmological parameters. As a result of uncertainties in some aspects of
cluster dynamics, cluster surveys are currently more useful for analyzing
physics that would affect the formation of structure than physics that would
modify the appearance of clusters. As an example we consider the Lambda-CDM
cosmology and dimming mechanisms, such as photon-axion mixing.Comment: 24 pages, 8 eps figures. References added, discussion of scatter in
relations between cluster observables lengthene
Dog Burials Associated with Human Burials in the West Indies during the Early Pre-Columbian Ceramic Age (500 BC-600 AD)
Across the Caribbean, the widespread presence of canine remains at archaeological sites from the Saladoid period raises questions about the role of “man’s best friend.” Dog (Canis familiaris) remains have been found located in both refuse middens and burials adjacent to human graves in a number of sites in the French Antilles and Barbuda, West Indies. This paper will critically examine dog remains and discuss the varied duality of the dog’s role in the Saladoid world: from food source to lifelong companion. The importance of dogs within Amerindian sites from Saint Martin, the Guadeloupe archipelago, Martinique and Barbuda will be explored from a zooarchaeological perspective, concluding with a critical discussion of changes in cultural patterns, as seen through the decline in dog remains during the Troumassoid and Suazoid period at the sites in the French Antilles.
Résumé
Sépultures de chiens associées à des sépultures humaines dans les Petites Antilles à l’Âge du Néoindien ancien (500 av. – 600 ap. J.-C.). Dans les Antilles, la présence généralisée de restes de chiens sur les sites de la période céramique ancienne Saladoïde soulève des questions sur le rôle de ce « meilleur ami de l’homme ». En effet, des chiens (Canis familiaris) ont été trouvés aussi bien dans des zones de rejets, qu’enterrés aux côtés de sépultures humaines dans un certain nombre de sites des Petites Antilles. Ce document examinera ces restes de chiens de façon critique et décrira les morphologies particulières des chiens des sites amérindiens de l’île de Saint-Martin, l\u27archipel de la Guadeloupe, la Martinique et de l’île de Barbuda, dans une perspective archéozoologique. Une discussion critique portera sur l\u27évolution des changements des modèles culturels, comme celui de la chute drastique des chiens enterrés pendant les périodes archéologiques plus tardives, Troumassoïde et Suazoïde, des sites des Antilles françaises. Enfin, la discussion portera sur la dualité du rôle du chien dans le monde Saladoïde, à la fois source de nourriture et compagnon de vie
Identification and functional characterisation of CRK12:CYC9, a novel cyclin-dependent kinase (CDK)-cyclin complex in Trypanosoma brucei
The protozoan parasite, Trypanosoma brucei, is spread by the tsetse fly and causes trypanosomiasis in humans and animals. Both the life cycle and cell cycle of the parasite are complex. Trypanosomes have eleven cdc2-related kinases (CRKs) and ten cyclins, an unusually large number for a single celled organism. To date, relatively little is known about the function of many of the CRKs and cyclins, and only CRK3 has previously been shown to be cyclin-dependent in vivo. Here we report the identification of a previously uncharacterised CRK:cyclin complex between CRK12 and the putative transcriptional cyclin, CYC9. CRK12:CYC9 interact to form an active protein kinase complex in procyclic and bloodstream T. brucei. Both CRK12 and CYC9 are essential for the proliferation of bloodstream trypanosomes in vitro, and we show that CRK12 is also essential for survival of T. brucei in a mouse model, providing genetic validation of CRK12:CYC9 as a novel drug target for trypanosomiasis. Further, functional characterisation of CRK12 and CYC9 using RNA interference reveals roles for these proteins in endocytosis and cytokinesis, respectively
First narrow-band search for continuous gravitational waves from known pulsars in advanced detector data
Spinning neutron stars asymmetric with respect to their rotation axis are potential sources of
continuous gravitational waves for ground-based interferometric detectors. In the case of known pulsars a
fully coherent search, based on matched filtering, which uses the position and rotational parameters
obtained from electromagnetic observations, can be carried out. Matched filtering maximizes the signalto-
noise (SNR) ratio, but a large sensitivity loss is expected in case of even a very small mismatch
between the assumed and the true signal parameters. For this reason, narrow-band analysis methods have
been developed, allowing a fully coherent search for gravitational waves from known pulsars over a
fraction of a hertz and several spin-down values. In this paper we describe a narrow-band search of
11 pulsars using data from Advanced LIGO’s first observing run. Although we have found several initial
outliers, further studies show no significant evidence for the presence of a gravitational wave signal.
Finally, we have placed upper limits on the signal strain amplitude lower than the spin-down limit for 5 of
the 11 targets over the bands searched; in the case of J1813-1749 the spin-down limit has been beaten for
the first time. For an additional 3 targets, the median upper limit across the search bands is below the
spin-down limit. This is the most sensitive narrow-band search for continuous gravitational waves carried
out so far
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