142,151 research outputs found
High field magnetotransport in composite conductors: the effective medium approximation revisited
The self consistent effective medium approximation (SEMA) is used to study
three-dimensional random conducting composites under the influence of a strong
magnetic field {\bf B}, in the case where all constituents exhibit isotropic
response. Asymptotic analysis is used to obtain almost closed form results for
the strong field magnetoresistance and Hall resistance in various types of two-
and three-constituent isotropic mixtures for the entire range of compositions.
Numerical solutions of the SEMA equations are also obtained, in some cases, and
compared with those results. In two-constituent
free-electron-metal/perfect-insulator mixtures, the magnetoresistance is
asymptotically proportional to at {\em all concentrations above the
percolation threshold}. In three-constituent metal/insulator/superconductor
mixtures a line of critical points is found, where the strong field
magnetoresistance switches abruptly from saturating to non-saturating
dependence on , at a certain value of the
insulator-to-superconductor concentration ratio. This transition appears to be
related to the phenomenon of anisotropic percolation.Comment: 16 pages, 3 figure
The Impact of Contaminated RR Lyrae/Globular Cluster Photometry on the Distance Scale
RR Lyrae variables and the stellar constituents of globular clusters are
employed to establish the cosmic distance scale and age of the universe.
However, photometry for RR Lyrae variables in the globular clusters M3, M15,
M54, M92, NGC2419, and NGC6441 exhibit a dependence on the clustercentric
distance. For example, variables and stars positioned near the crowded
high-surface brightness cores of the clusters may suffer from photometric
contamination, which invariably affects a suite of inferred parameters (e.g.,
distance, color excess, absolute magnitude, etc.). The impetus for this study
is to mitigate the propagation of systematic uncertainties by increasing
awareness of the pernicious impact of contaminated and radial-dependent
photometry.Comment: To appear in ApJ
Antidepressants and age
Antidepressants as a commodity have been remarkably little-studied by economists.
This study shows in new data for 27 European countries that 8% of people (and
10% of those middle-aged) take antidepressants each year. The probability of
antidepressant use is greatest among those who are middle-aged, female,
unemployed, poorly educated, and divorced or separated. A hill-shaped age pattern
is found. The adjusted probability of using antidepressants reaches a peak --
approximately doubling -- in people‟s late 40s. This finding is consistent with, and
provides a new and independent form of corroboration of, recent claims in the
research literature that human well-being follows a U-shape through life
International happiness
This paper describes the findings from a new, and intrinsically interdisciplinary, literature on happiness
and human well-being. The paper focuses on international evidence. We report the patterns in modern
data; we discuss what has been persuasively established and what has not; we suggest paths for future
research. Looking ahead, our instinct is that this social-science research avenue will gradually merge
with a related literature -- from the medical, epidemiological, and biological sciences -- on biomarkers
and health. Nevertheless, we expect that intellectual convergence to happen slowly
- …