6,010 research outputs found
Tentative Detection of the Rotation of Eris
We report a multi-week sequence of B-band photometric measurements of the
dwarf planet Eris using the {\it Swift} satellite. The use of an observatory in
low-Earth orbit provides better temporal sampling than is available with a
ground-based telescope. We find no compelling evidence for an unusually slow
rotation period of multiple days, as has been suggested previously. A
1.08 day rotation period is marginally detected at a modest level of
statistical confidence (97%). Analysis of the combination of the
data with the ground-based B-band measurements of \citet{2007AJ....133...26R}
returns the same period (1.08 day) at a slightly higher statistical
confidence (99%).Comment: Accepted to Icarus 2008-Aug-19. 19 pages total, including 4 figures
and 1 tabl
On the Localization of One-Photon States
Single photon states with arbitrarily fast asymptotic power-law fall-off of
energy density and photodetection rate are explicitly constructed. This goes
beyond the recently discovered tenth power-law of the Hellwarth-Nouchi photon
which itself superseded the long-standing seventh power-law of the Amrein
photon.Comment: 7 pages, tex, no figure
Hysteresis loops of Co-Pt perpendicular magnetic multilayers
We develop a phenomenological model to study magnetic hysteresis in two
samples designed as possible perpendicular recording media. A stochastic
cellular automata model captures cooperative behavior in the nucleation of
magnetic domains. We show how this simple model turns broad hysteresis loops
into loops with sharp drops like those observed in these samples, and explains
their unusual features. We also present, and experimentally verify, predictions
of this model, and suggest how insights from this model may apply more
generally.Comment: 4.5 pages, 5 figure
Cosmological Parameters from the Comparison of the 2MASS Gravity Field with Peculiar Velocity Surveys
We compare the peculiar velocity field within 65 Mpc predicted from
2MASS photometry and public redshift data to three independent peculiar
velocity surveys based on type Ia supernovae, surface brightness fluctuations
in ellipticals, and Tully-Fisher distances to spirals. The three peculiar
velocity samples are each in good agreement with the predicted velocities and
produce consistent results for \beta_{K}=\Omega\sbr{m}^{0.6}/b_{K}. Taken
together the best fit . We explore the effects of
morphology on the determination of by splitting the 2MASS sample into
E+S0 and S+Irr density fields and find both samples are equally good tracers of
the underlying dark matter distribution, but that early-types are more
clustered by a relative factor b\sbr{E}/b\sbr{S} \sim 1.6. The density
fluctuations of 2MASS galaxies in Mpc spheres in the local volume is
found to be \sigma\sbr{8,K} = 0.9. From this result and our value of
, we find \sigma_8 (\Omega\sbr{m}/0.3)^{0.6} = 0.91\pm0.12. This
is in excellent agreement with results from the IRAS redshift surveys, as well
as other cosmological probes. Combining the 2MASS and IRAS peculiar velocity
results yields \sigma_8 (\Omega\sbr{m}^/0.3)^{0.6} = 0.85\pm0.05.Comment: 11 pages, ApJ accepte
Is There a Doctor in the House? Medical Ethics and the Doctoral Honorific
The proliferation of professional doctorates has reinvigorated debate over the use of the doctoral honorific. Doctorate holders are often addressed as “doctor” in academic contexts, but idiomatic American English associates “doctor” with physicians—licensed clinicians with doctoral degrees in medicine. The possibility of patient confusion has historically justified proscription of the doctoral honorific by others, including nurses, but recently such proscriptions have been withdrawn. An examination of history, language, and ethical reasoning leads us to conclude that, in the context of patient interaction, clinicians should eschew the doctoral honorific entirely. We think it appropriate for professionals to rely on training-pathway titles as part of their professional duty to inform. In particular, we argue that licensed clinicians with doctoral degrees in medicine should embrace the title of “physician.
Exploitation of Phosphoinositides by the Intracellular Pathogen, <em>Legionella pneumophila</em>
Manipulation of host phosphoinositide lipids has emerged as a key survival strategy utilized by pathogenic bacteria to establish and maintain a replication-permissive compartment within eukaryotic host cells. The human pathogen, Legionella pneumophila, infects and proliferates within the lung’s innate immune cells causing severe pneumonia termed Legionnaires’ disease. This pathogen has evolved strategies to manipulate specific host components to construct its intracellular niche termed the Legionella-containing vacuole (LCV). Paramount to LCV biogenesis and maintenance is the spatiotemporal regulation of phosphoinositides, important eukaryotic lipids involved in cell signaling and membrane trafficking. Through a specialized secretion system, L. pneumophila translocates multiple proteins that target phosphoinositides in order to escape endolysosomal degradation. By specifically binding phosphoinositides, these proteins can anchor to the cytosolic surface of the LCV or onto specific host membrane compartments, to ultimately stimulate or inhibit encounters with host organelles. Here, we describe the bacterial proteins involved in binding and/or altering host phosphoinositide dynamics to support intracellular survival of L. pneumophila
Further studies of space-time clustering of Burkitt's lymphoma in Uganda.
All hospital-treated cases of Burkitt's lymphoma (BL), with onset of symptoms in the period 1963-68 and resident in the Lango and Acholi districts of Uganda, were identified. The average annual incidence of BL in the 6-year period was 1-87 X 10(-5), similar to that in the adjacent West Nile district. Contrary to findings in other areas of Uganda, there was no evidence of seasonal variation in the onset of cases, nor of space-time clustering, nor of a decline in the incidence of BL in the study period. An inverse relationship was noted between the median age at onset of BL and the incidence of the disease in different areas of Uganda, a finding consistent with intense malarial infection being a precipitating factor for BL. The variable observations with respect to space-time clustering of BL and seasonal variation in incidence in different areas remains unexplained, but it is suggested that a closer study of the patterns of malarial infection in these areas may help to account for the findings
Elasticity of Stiff Polymer Networks
We study the elasticity of a two-dimensional random network of rigid rods
(``Mikado model''). The essential features incorporated into the model are the
anisotropic elasticity of the rods and the random geometry of the network. We
show that there are three distinct scaling regimes, characterized by two
distinct length scales on the elastic backbone. In addition to a critical
rigidiy percolation region and a homogeneously elastic regime we find a novel
intermediate scaling regime, where elasticity is dominated by bending
deformations.Comment: 4 pages, 4 figure
Low-Temperature Permittivity of Insulating Perovskite Manganites
Measurements of the low-frequency (f<=100 kHz) permittivity and conductivity
at T<= 150 K are reported for La(1-x)Ca(x)MnO(3) (0<=x<=1) and
Ca(1-y)Sr(y)MnO(3) (0<=y<=0.75) having antiferromagnetic, insulating ground
states covering a broad range of Mn valencies from Mn(3+) to Mn(4+). Static
dielectric constants are determined from the low-T limiting behavior. With
increasing T, relaxation peaks associated with charge-carrier hopping are
observed in the real part of the permittivities and analyzed to determine
dopant binding energies. The data are consistent with a simple model of
hydrogenic impurity levels and imply effective masses m*/m_e~3 for the Mn(4+)
compounds. Particularly interesting is a large dielectric constant (~100)
associated with the C-type antiferromagnetic state near the composition
La(0.2)Ca(0.8)MnO(3).Comment: 6 pages, 8 figures, PRB in pres
MS4 SOCIETAL COST OF RHEUMATOID ARTHRITIS (RA) IN THE UNITED STATES: METHODOLOGY FOR INCORPORATING INTANGIBLE COSTS
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