3,168 research outputs found
The cost of anchoring on credit-card minimum repayments
About three quarters of credit card accounts attract interest charges. In the US, credit card debt is 2,539.7 billion of consumer credit. In the UK, credit card debt is £55.1 billion of £174.4 billion of consumer credit. The 2005 US Bankruptcy Abuse Prevention and Consumer Protection Act and the 2003 UK Treasury Select Committee's report require lenders to collect a minimum payment of at least the interest accrued each month. Thus people are protected from the effects of compounding interest. But including minimum payment information has an unintended negative effect, because minimum payments act as psychological anchors
RXTE Hard X-ray Observation of A754: Constraining the Hottest Temperature Component and the Intracluster Magnetic Field
Abell 754, a cluster undergoing merging, was observed in hard X-rays with the
Rossi X-ray Timing Explorer (RXTE) in order to constrain its hottest
temperature component and search for evidence of nonthermal emission.
Simultaneous modeling of RXTE data and those taken with previous missions
yields an average intracluster temperature of keV in the 1-50 keV
energy band. A multi-temperature component model derived from numerical
simulations of the evolution of a cluster undergoing a merger produces similar
quality of fit, indicating that the emission measure from the very hot gas
component is sufficiently small that it renders the two models
indistinguishable. No significant nonthermal emission was detected. However,
our observations set an upper limit of
(90% confidence limit) to the nonthermal emission flux at 20 keV. Combining
this result with the radio synchrotron emission flux we find a lower limit of
0.2 G for the intracluster magnetic field. We discuss the implications of
our results for the theories of magnetic field amplifications in cluster
mergers.Comment: Accepted for Publication in the Astrophysical Journal, 22 pages, 5
figure
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Bragging Through an Intermediary
The use of an intermediary to convey positive information about a target person is received more favorably and is more effective than direct self -promotion by the target person . These effects persist irrespective of whether the intermediary is motivated by self-interest . However, intermediation may carry image costs for the intermediary
Assessing the progression of mild cognitive impairment to Alzheimer's disease: current trends and future directions
With the advent of advances in biomarker detection and neuropsychological measurement, prospects have improved for identifying and tracking the progression of Alzheimer's disease (AD) from its earliest stages through dementia. While new diagnostic techniques have exciting implications for initiating treatment earlier in the disease process, much work remains to be done to optimize the contributions of the expanding range of tools at the disposal of researchers and clinicians. The present paper examines recent work in cerebrospinal fluid biomarkers, magnetic resonance imaging, positron emission tomography, neuropsychological measures, and functional assessment. The strengths and weaknesses of current methodologies are explored and discussed. It is concluded that AD from its mild cognitive impairment state through dementia represents a continuous process, and that progression over time can best be accomplished by interval-level variables. Biomarkers that are most sensitive to early AD may not be the most optimal for monitoring longitudinal change, and it is likely that multivariate models incorporating cognitive measures, functional variables and biomarker data will be the most fruitful avenues for future research
Search For Unresolved Sources In The COBE-DMR Two-Year Sky Maps
We have searched the temperature maps from the COBE Differential Microwave
Radiometers (DMR) first two years of data for evidence of unresolved sources.
The high-latitude sky (|b| > 30\deg) contains no sources brighter than 192 uK
thermodynamic temperature (322 Jy at 53 GHz). The cumulative count of sources
brighter than threshold T, N(> T), is consistent with a superposition of
instrument noise plus a scale-invariant spectrum of cosmic temperature
fluctuations normalized to Qrms-PS = 17 uK. We examine the temperature maps
toward nearby clusters and find no evidence for any Sunyaev-Zel'dovich effect,
\Delta y < 7.3 x 10^{-6} (95% CL) averaged over the DMR beam. We examine the
temperature maps near the brightest expected radio sources and detect no
evidence of significant emission. The lack of bright unresolved sources in the
DMR maps, taken with anisotropy measurements on smaller angular scales, places
a weak constraint on the integral number density of any unresolved
Planck-spectrum sources brighter than flux density S, n(> S) < 2 x 10^4 (S/1
Jy)^{-2} sr^{-1}.Comment: 16 pages including 2 figures, uuencoded PostScript, COBE preprint
94-0
First Results from SPARO: Evidence for Large-Scale Toroidal Magnetic Fields in the Galactic Center
We have observed the linear polarization of 450 micron continuum emission
from the Galactic center, using a new polarimetric detector system that is
operated on a 2 m telescope at the South Pole. The resulting polarization map
extends ~ 170 pc along the Galactic plane and ~ 30 pc in Galactic latitude, and
thus covers a significant fraction of the central molecular zone. Our map shows
that this region is permeated by large-scale toroidal magnetic fields. We
consider our results together with radio observations that show evidence for
poloidal fields in the Galactic center, and with Faraday rotation observations.
We compare all of these observations with the predictions of a magnetodynamic
model for the Galactic center that was proposed in order to explain the
Galactic Center Radio Lobe as a magnetically driven gas outflow. We conclude
that the observations are basically consistent with the model.Comment: 11 pages, 2 figures, 1 table, submitted to ApJ Let
Thermal conduction and particle transport in strong MHD turbulence, with application to galaxy-cluster plasmas
We investigate field-line separation in strong MHD turbulence analytically
and with direct numerical simulations. We find that in the
static-magnetic-field approximation the thermal conductivity in galaxy clusters
is reduced by a factor of about 5-10 relative to the Spitzer thermal
conductivity of a non-magnetized plasma. We also estimate how the thermal
conductivity would be affected by efficient turbulent resistivity.Comment: Major revision: higher resolution simulations lead to significantly
different conclusions. 26 pages, 10 figure
Convection and AGN Feedback in Clusters of Galaxies
A number of studies have shown that the convective stability criterion for
the intracluster medium (ICM) is very different from the Schwarzchild criterion
due to the effects of anisotropic thermal conduction and cosmic rays. Building
on these studies, we develop a model of the ICM in which a central active
galactic nucleus (AGN) accretes hot intracluster plasma at the Bondi rate and
produces cosmic rays that cause the ICM to become convectively unstable. The
resulting convection heats the intracluster plasma and regulates its
temperature and density profiles. By adjusting a single parameter in the model
(the size of the cosmic-ray acceleration region), we are able to achieve a good
match to the observed density and temperature profiles in a sample of eight
clusters. Our results suggest that convection is an important process in
cluster cores. An interesting feature of our solutions is that the cooling rate
is more sharply peaked about the cluster center than is the convective heating
rate. As a result, in several of the clusters in our sample, a compact cooling
flow arises in the central region with a size R that is typically a few kpc.
The cooling flow matches onto a Bondi flow at smaller radii. The mass accretion
rate in the Bondi flow is equal to, and controlled by, the rate at which mass
flows in through the cooling flow. Our solutions suggest that the AGN regulates
the mass accretion rate in these clusters by controlling R: if the AGN power
rises above the equilibrium level, R decreases, the mass accretion rate drops,
and the AGN power drops back down to the equilibrium level.Comment: 41 pages, 7 figures, accepted for publication in ApJ. Changes in this
version: extended discussion of Bondi accretion in clusters, better mass
model, new numerical solution
Incentives in Health: Different Prescriptions for Physicians and Patients
Financial incentives abound in health care. They are found in the ways physicians are paid and in the ways health insurance coverage, co-payments, and deductibles are structured for patients. The effects of these incentives are often understood through conventional economic principles, with the assumption that individuals are self-interest maximizers who respond directly to changes in incentives. In contrast, behavioral economics imports insights from psychology and recognizes that individuals often do not respond to incentives as rationally as they might. In some cases, individuals lack information, but in others, they just seem to act contrary to their own known interests, for example, when they overeat, fail to take medication, or neglect to wear seat belts
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