4,761 research outputs found
Reasons to Care about Reasons for Action: A Response to Paul S. Davies
In eschewing the specialty-standards of neuro-babble and philosophical neologism, Paul S. Davies (2016) argues with courageous clarity. He connects issues in neuroscience and epistemology to problems surrounding agency. I agree with many of his claims, but I think they need more context and precision for application. This is because his argument as it stands now affects only a limited set of theories, and a hidden modality in thesis 3 tempers his argument further. And perhaps most urgently, if his theory fails to address âtop-downâ1 mental processes or social dimensions of knowledge, his argument fails to meet even his own goals set out in the paper
Topological Ramsey spaces from Fra\"iss\'e classes, Ramsey-classification theorems, and initial structures in the Tukey types of p-points
A general method for constructing a new class of topological Ramsey spaces is
presented. Members of such spaces are infinite sequences of products of
Fra\"iss\'e classes of finite relational structures satisfying the Ramsey
property. The Product Ramsey Theorem of Soki\v{c} is extended to equivalence
relations for finite products of structures from Fra\"iss\'e classes of finite
relational structures satisfying the Ramsey property and the Order-Prescribed
Free Amalgamation Property. This is essential to proving Ramsey-classification
theorems for equivalence relations on fronts, generalizing the Pudl\'ak-R\"odl
Theorem to this class of topological Ramsey spaces.
To each topological Ramsey space in this framework corresponds an associated
ultrafilter satisfying some weak partition property. By using the correct
Fra\"iss\'e classes, we construct topological Ramsey spaces which are dense in
the partial orders of Baumgartner and Taylor in \cite{Baumgartner/Taylor78}
generating p-points which are -arrow but not -arrow, and in a partial
order of Blass in \cite{Blass73} producing a diamond shape in the Rudin-Keisler
structure of p-points. Any space in our framework in which blocks are products
of many structures produces ultrafilters with initial Tukey structure
exactly the Boolean algebra . If the number of Fra\"iss\'e
classes on each block grows without bound, then the Tukey types of the p-points
below the space's associated ultrafilter have the structure exactly
. In contrast, the set of isomorphism types of any product
of finitely many Fra\"iss\'e classes of finite relational structures satisfying
the Ramsey property and the OPFAP, partially ordered by embedding, is realized
as the initial Rudin-Keisler structure of some p-point generated by a space
constructed from our template.Comment: 35 pages. Abstract and introduction re-written to make very clear the
main points of the paper. Some typos and a few minor errors have been fixe
A Correlation Between Inclination and Color in the Classical Kuiper Belt
We have measured broadband optical BVR photometry of 24 Classical and
Scattered Kuiper belt objects (KBOs), approximately doubling the published
sample of colors for these classes of objects. We find a statistically
significant correlation between object color and inclination in the Classical
Kuiper belt using our data. The color and inclination correlation increases in
significance after the inclusion of additional data points culled from all
published works. Apparently, this color and inclination correlation has not
been more widely reported because the Plutinos show no such correlation, and
thus have been a major contaminant in previous samples. The color and
inclination correlation excludes simple origins of color diversity, such as the
presence of a coloring agent without regard to dynamical effects.
Unfortunately, our current knowledge of the Kuiper belt precludes us from
understanding whether the color and inclination trend is due to environmental
factors, such as collisional resurfacing, or primordial population effects. A
perihelion and color correlation is also evident, although this appears to be a
spurious correlation induced by sampling bias, as perihelion and inclination
are correlated in the observed sample of KBOs.Comment: Accepted to Astrophysical Journal Letter
Health inequalities and development plans in Iran: An analysis of the past three decades (1984â2010)
Introduction: Reducing inequalities in health care is one of the main challenges in all countries. In Iran as in other oil-exporting upper middle income countries, we expected to witness fewer inequalities especially in the health sector with the increase in governmental revenues.
Methods: This study presents an inequalities assessment of health care expenditures in Iran. We used data from the Household Income and Expenditure Survey (HIES) in Iran from 1984â2010. The analysis included 308,735 urban and 342,532 rural households.
Results: The results suggest heightened inequality in health care expenditures in Iran over the past three decades, including an increase in the gap between urban and rural areas. Furthermore, inflation has affected the poor more than the rich. The Kakwani progressivity index in all years is positive, averaging 0.436 in rural and 0.470 in urban areas during the time period of analysis. Compared to inequality in income distribution over the last 30 years, health expenditures continuously show more inequality and progressivity over the same period of time.
Conclusions: According to the result of our study, during this period Iran introduced four National Development Plans (NDPs); however, the NDPs failed to provide sustainable strategies for reducing inequalities in health care expenditures. Policies that protect vulnerable groups should be prioritized
A correlation between light profile and [Mg/Fe] abundance ratio in early-type galaxies
We explore possible correlations between light profile shapes, as
parameterized by the Sersic index or the concentration index C_re(1/3), and
relevant stellar population parameters in early-type galaxies. Mean luminosity
weighted ages, metallicities and abundance ratios were obtained from spectra of
very high signal-to-noise and stellar population models that synthesize galaxy
spectra at the resolution given by their velocity dispersions, in combination
with an age indicator that is virtually free of the effects of metallicity. We
do not find any significant correlation between the Sersic index (or C_re(1/3))
and mean age or metallicity, but a strong positive correlation of the shape
parameters with [Mg/Fe] abundance ratio. This dependence is as strong as the
[Mg/Fe] vs. velocity dispersion and C_re(1/3) vs. velocity dispersion
relations. We speculate that early-type galaxies settle up their structure on
time-scales in agreement with those imposed by their [Mg/Fe] ratios. This
suggest that the global structure of larger galaxies, with larger [Mg/Fe]
ratios and shorter time-scales, was already at place at high z, without
experiencing a significant time evolution.Comment: 5 pages, 3 figures (to appear in The Astrophysical Journal Letters
Exploring the evolutionary paths of the most massive galaxies since z~2
We use Spitzer MIPS data from the FIDEL Legacy Project in the Extended Groth
Strip to analyze the stellar mass assembly of massive (M>10^11 M_sun) galaxies
at z<2 as a function of structural parameters. We find 24 micron emission for
more than 85% of the massive galaxies morphologically classified as disks, and
for more than 57% of the massive systems morphologically classified as
spheroids at any redshift, with about 8% of sources harboring a bright X-ray
and/or infrared emitting AGN. More noticeably, 60% of all compact massive
galaxies at z=1-2 are detected at 24 micron, even when rest-frame optical
colors reveal that they are dead and evolving passively. For spheroid-like
galaxies at a given stellar mass, the sizes of MIPS non-detections are smaller
by a factor of 1.2 in comparison with IR-bright sources. We find that disk-like
massive galaxies present specific SFRs ranging from 0.04 to 0.2 Gyr^-1 at z<1
(SFRs ranging from 1 to 10 M_sun/yr), typically a factor of 3-6 higher than
massive spheroid-like objects in the same redshift range. At z>1, and more
pronouncedly at z>1.3, the median specific SFRs of the disks and spheroids
detected by MIPS are very similar, ranging from 0.1 to 1 Gyr^-1 (SFR=10-200
M_sun/yr). We estimate that massive spheroid-like galaxies may have doubled (at
the most) their stellar mass from star-forming events at z<2: less than 20%
mass increase at 1.7<z<2.0, up to 40% more at 1.1<z<1.7, and less than 20%
additional increase at z<1. Disk-like galaxies may have tripled (at the most)
their stellar mass at z<2 from star formation alone: up to 40% mass increase at
1.7<z<2.0, and less than 180% additional increase below z=1.7 occurred at a
steady rate.Comment: Accepted for publication in ApJ; 10 pages, 5 figures, 1 tabl
Discovery of Temperate Latitude Clouds on Titan
Until now, all the clouds imaged in Titan's troposphere have been found at far southern latitudes (60°-90° south). The occurrence and location of these clouds is thought to be the result of convection driven by the maximum annual solar heating of Titan's surface, which occurs at summer solstice (2002 October) in this south polar region. We report the first observations of a new recurring type of tropospheric cloud feature, confined narrowly to ~40° south latitude, which cannot be explained by this simple insolation hypothesis. We propose two classes of formation scenario, one linked to surface geography and the other to seasonally evolving circulation, which will be easily distinguished with continued observations over the next few years
The influence of coronal EUV irradiance on the emission in the He I 10830 A and D3 multiplets
Two of the most attractive spectral windows for spectropolarimetric
investigations of the physical properties of the plasma structures in the solar
chromosphere and corona are the ones provided by the spectral lines of the He I
10830 A and 5876 A (or D3) multiplets, whose polarization signals are sensitive
to the Hanle and Zeeman effects. However, in order to be able to carry out
reliable diagnostics, it is crucial to have a good physical understanding of
the sensitivity of the observed spectral line radiation to the various
competing driving mechanisms. Here we report a series of off-the-limb non-LTE
calculations of the He I D3 and 10830 A emission profiles, focusing our
investigation on their sensitivity to the EUV coronal irradiation and the model
atmosphere used in the calculations. We show in particular that the intensity
ratio of the blue to the red components in the emission profiles of the He I
10830 A multiplet turns out to be a good candidate as a diagnostic tool for the
coronal irradiance. Measurements of this observable as a function of the
distance to the limb and its confrontation with radiative transfer modeling
might give us valuable information on the physical properties of the solar
atmosphere and on the amount of EUV radiation at relevant wavelengths
penetrating the chromosphere from above.Comment: 19 pages, 11 figures (pre-print format). Accepted for publication in
Ap
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