102 research outputs found
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Evidence of a Causal Association Between Cancer and Alzheimer’s Disease: a Mendelian Randomization Analysis
Abstract: While limited observational evidence suggests that cancer survivors have a decreased risk of developing Alzheimer’s disease (AD), and vice versa, it is not clear whether this relationship is causal. Using a Mendelian randomization approach that provides evidence of causality, we found that genetically predicted lung cancer (OR 0.91, 95% CI 0.84–0.99, p = 0.019), leukemia (OR 0.98, 95% CI 0.96–0.995, p = 0.012), and breast cancer (OR 0.94, 95% CI 0.89–0.99, p = 0.028) were associated with 9.0%, 2.4%, and 5.9% lower odds of AD, respectively, per 1-unit higher log odds of cancer. When genetic predictors of all cancers were pooled, cancer was associated with 2.5% lower odds of AD (OR 0.98, 95% CI 0.96–0.988, p = 0.00027) per 1-unit higher log odds of cancer. Finally, genetically predicted smoking-related cancers showed a more robust inverse association with AD than non-smoking related cancers (OR 0.95, 95% CI 0.92–0.98, p = 0.0026, vs. OR 0.98, 95% CI 0.97–0.995, p = 0.0091)
Word reading and translation in bilinguals: the impact of formal and informal translation expertise
Studies on bilingual word reading and translation have examined the effects of lexical variables (e.g., concreteness, cognate status) by comparing groups of non-translators with varying levels of L2 proficiency. However, little attention has been paid to another relevant factor: translation expertise (TI). To explore this issue, we administered word reading and translation tasks to two groups of non-translators possessing different levels of informal TI (Experiment 1), and to three groups of bilinguals possessing different levels of translation training (Experiment 2). Reaction-time recordings showed that in all groups reading was faster than translation and unaffected by concreteness and cognate effects. Conversely, in both experiments, all groups translated concrete and cognate words faster than abstract and non-cognate words, respectively. Notably, an advantage of backward over forward translation was observed only for low-proficiency non-translators (in Experiment 1). Also, in Experiment 2, the modifications induced by translation expertise were more marked in the early than in the late stages of training and practice. The results suggest that TI contributes to modulating inter-equivalent connections in bilingual memory.Fil: García, Adolfo Martín. Universidad Nacional de Córdoba; Argentina. Universidad Diego Portales; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencia Cognitiva. Fundación Favaloro. Instituto de Neurociencia Cognitiva; ArgentinaFil: Ibáñez Barassi, Agustín Mariano. Universidad Diego Portales; Chile. Universidad Autónoma del Caribe; Colombia. Australian Research Council; Australia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencia Cognitiva. Fundación Favaloro. Instituto de Neurociencia Cognitiva; ArgentinaFil: Huepe, David. Universidad Diego Portales; ChileFil: Houck, Alexander L.. University of Tennessee; Estados UnidosFil: Michon, Maeva. Universidad Diego Portales; ChileFil: Gelormini Lezama, Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencia Cognitiva. Fundación Favaloro. Instituto de Neurociencia Cognitiva; ArgentinaFil: Chadha, Sumeer. Universidad Diego Portales; ChileFil: Rivera Rei, Álvaro. Universidad Diego Portales; Chil
[CII] 158 micron Luminosities and Star Formation Rate in Dusty Starbursts and AGN
Results are presented for [CII] 158 micron line fluxes observed with the
Herschel PACS instrument in 112 sources with both starburst and AGN
classifications, of which 102 sources have confident detections. Results are
compared with mid-infrared spectra from the Spitzer Infrared Spectrometer and
with L(IR) from IRAS fluxes; AGN/starburst classifications are determined from
equivalent width of the 6.2 micron PAH feature. It is found that the [CII] line
flux correlates closely with the flux of the 11.3 micron PAH feature
independent of AGN/starburst classification, log [f([CII] 158 micron)/f(11.3
micron PAH)] = -0.22 +- 0.25. It is concluded that [CII] line flux measures the
photodissociation region associated with starbursts in the same fashion as the
PAH feature. A calibration of star formation rate for the starburst component
in any source having [CII] is derived comparing [CII] luminosity L([CII]) to
L(IR) with the result that log SFR = log L([CII)]) - 7.08 +- 0.3, for SFR in
solar masses per year and L([CII]) in solar luminosities. The decreasing ratio
of L([CII]) to L(IR) in more luminous sources (the "[CII] deficit") is shown to
be a consequence of the dominant contribution to L(IR) arising from a luminous
AGN component because the sources with largest L(IR) and smallest
L([CII])/L(IR) are AGN.Comment: Accepted for publication in The Astrophysical Journa
Detections of CO Molecular Gas in 24um-Bright ULIRGs at z~2 in the Spitzer First Look Survey
We present CO observations of 9 ULIRGs at z~2 with S(24\mu m)>1mJy,
previously confirmed with the mid-IR spectra in the Spitzer First Look Survey.
All targets are required to have accurate redshifts from Keck/GEMINI near-IR
spectra. Using the Plateau de Bure millimeter-wave Interferometer (PdBI) at
IRAM, we detect CO J(3-2) [7 objects] or J(2-1) [1 object] line emission from 8
sources with integrated intensities Ic ~(5-9)sigma. The CO detected sources
have a variety of mid-IR spectra, including strong PAH, deep silicate
absorption and power-law continuum, implying that these molecular gas rich
objects at z~2 could be either starbursts or dust obscured AGNs. The measured
line luminosity L'[CO] is (1.28-3.77)e+10[K km/s pc^2]. The averaged molecular
gas mass M(H2) is 1.7e+10Msun, assuming CO-to-H2 conversion factor of
0.8Msun/[K km/s pc^2]. Three sources (33%) -- MIPS506, MIPS16144 & MIPS8342 --
have double peak velocity profiles. The CO double peaks in MIPS506 and
MIPS16144 show spatial separations of 45kpc and 10.9kpc, allowing the estimates
of the dynamical masses of 3.2e+11*sin^(-2)(i)Msun and 5.4e+11*sin^{-2}(i)Msun
respectively. The implied gas fraction, M(gas)/M(dyn), is 3% and 4%, assuming
an average inclination angle. Finally, the analysis of the HST/NIC2 images,
mid-IR spectra and IR SED revealed that most of our sources are mergers,
containing dust obscured AGNs dominating the luminosities at (3-6)um. Together,
these results provide some evidence suggesting SMGs, bright 24um z~2 ULIRGs and
QSOs could represent three different stages of a single evolutionary sequence,
however, a complete physical model would require much more data, especially
high spatial resolution spectroscopy.Comment: 15 pages, 8 figures, accepted for publication in ApJ
Black Hole Masses and Star Formation Rates of z >1 Dust Obscured Galaxies (DOGs): Results from Keck OSIRIS Integral Field Spectroscopy
We have obtained high spatial resolution Keck OSIRIS integral field
spectroscopy of four z~1.5 ultra-luminous infrared galaxies that exhibit broad
H-alpha emission lines indicative of strong AGN activity. The observations were
made with the Keck laser guide star adaptive optics system giving a spatial
resolution of 0.1", or <1 kpc at these redshifts. These high spatial resolution
observations help to spatially separate the extended narrow-line regions ---
possibly powered by star formation --- from the nuclear regions, which may be
powered by both star formation and AGN activity. There is no evidence for
extended, rotating gas disks in these four galaxies. Assuming dust correction
factors as high as A(H-alpha)=4.8 mag, the observations suggest lower limits on
the black hole masses of (1 - 9) x 10^8 solar masses, and star formation rates
<100 solar masses per year. The black hole masses and star formation rates of
the sample galaxies appear low in comparison to other high-z galaxies with
similar host luminosities. We explore possible explanations for these
observations including, host galaxy fading, black hole growth, and the shut
down of star formation.Comment: Accepted for publication in the Astronomical Journal. 12 pages, 6
figures, 5 table
Paschen-alpha Emission in the Gravitationally Lensed Galaxy SMM J163554.2+661225
We report the detection of the Paschen-alpha emission line in the z=2.515
galaxy SMM J163554.2+661225 using Spitzer spectroscopy. SMM J163554.2+661225 is
a sub-millimeter-selected infrared (IR)-luminous galaxy maintaining a high
star-formation rate (SFR), with no evidence of an AGN from optical or infrared
spectroscopy, nor X-ray emission. This galaxy is lensed gravitationally by the
cluster Abell 2218, making it accessible to Spitzer spectroscopy. Correcting
for nebular extinction derived from the H-alpha and Pa-alpha lines, the
dust-corrected luminosity is L(Pa-alpha) = (2.57+/-0.43) x 10^43 erg s^-1,
which corresponds to an ionization rate, Q = (1.6+/-0.3) x 10^55 photons s^-1.
The instantaneous SFR is 171+/-28 solar masses per year, assuming a
Salpeter-like initial mass function. The total IR luminosity derived using 70,
450, and 850 micron data is L(IR) = (5-10) x 10^11 solar luminosities,
corrected for gravitational lensing. This corresponds to a SFR=90-180 solar
masses per year, where the upper range is consistent with that derived from the
Paschen-alpha luminosity. While the L(8 micron) / L(Pa-alpha) ratio is
consistent with the extrapolated relation observed in local galaxies and
star-forming regions, the rest-frame 24 micron luminosity is significantly
lower with respect to local galaxies of comparable Paschen-alpha luminosity.
Thus, SMM J163554.2+661225 arguably lacks a warmer dust component (T ~ 70 K),
which is associated with deeply embedded star formation, and which contrasts
with local galaxies with comparable SFRs. Rather, the starburst is consistent
with star-forming local galaxies with intrinsic luminosities, L(IR) ~ 10^10
solar luminosities, but "scaled-up" by a factor of 10-100.Comment: Published in the Astrophysical Journal. 14 pages in emulateapj
format, 9 figures (many in color
Statistical Characterization of the Chandra Source Catalog
The first release of the Chandra Source Catalog (CSC) contains ~95,000 X-ray
sources in a total area of ~0.75% of the entire sky, using data from ~3,900
separate ACIS observations of a multitude of different types of X-ray sources.
In order to maximize the scientific benefit of such a large, heterogeneous
data-set, careful characterization of the statistical properties of the
catalog, i.e., completeness, sensitivity, false source rate, and accuracy of
source properties, is required. Characterization efforts of other, large
Chandra catalogs, such as the ChaMP Point Source Catalog (Kim et al. 2007) or
the 2 Mega-second Deep Field Surveys (Alexander et al. 2003), while
informative, cannot serve this purpose, since the CSC analysis procedures are
significantly different and the range of allowable data is much less
restrictive. We describe here the characterization process for the CSC. This
process includes both a comparison of real CSC results with those of other,
deeper Chandra catalogs of the same targets and extensive simulations of
blank-sky and point source populations.Comment: To be published in the Astrophysical Journal Supplement Series (Fig.
52 replaced with a version which astro-ph can convert to PDF without issues.
A backward evolution model for infrared surveys: the role of AGN- and Color-L_TIR distributions
Empirical "backward" galaxy evolution models for infrared bright galaxies are
constrained using multi-band infrared surveys. We developed a new Monte-Carlo
algorithm for this task, implementing luminosity dependent distribution
functions for the galaxies' infrared spectral energy distributions (SEDs) and
for the AGN contribution, allowing for evolution of these quantities. The
adopted SEDs take into account the contributions of both starbursts and AGN to
the infrared emission, for the first time in a coherent treatment rather than
invoking separate AGN and star-forming populations. In the first part of the
paper we consider the quantification of the AGN contribution for local universe
galaxies, as a function of total infrared luminosity. It is made using a large
sample of LIRGs and ULIRGs for which mid-infrared spectra are available in the
Spitzer archive. In the second part we present the model. Our best-fit model
adopts very strong luminosity evolution, , up to , and
density evolution, , up to , for the population of
infrared galaxies. At higher , the evolution rates drop as and
respectively. To reproduce mid-infrared to submillimeter number
counts and redshift distributions, it is necessary to introduce both an
evolution in the AGN contribution and an evolution in the
luminosity-temperature relation. Our models are in plausible agreement with
current photometry-based estimates of the typical AGN contribution as a
function of mid-infrared flux, and well placed to be compared to upcoming
Spitzer spectroscopic results. As an example of future applications, we use our
best-fitting model to make predictions for surveys with Herschel.Comment: Model available at: (http://www.physics.ubc.ca/~valiante/model) ApJ
accepte
On the origin of [Ne II] emission in young stars: mid-infrared and optical observations with the Very Large Telescope
{Abridged version for ArXiv}. We provide direct constraints on the origin of
the [Ne II] emission in 15 young stars using high-spatial and spectral
resolution observations with VISIR at the VLT that allow us to study the
kinematics of the emitting gas. In addition we compare the [Ne II] line with
optical forbidden lines observed for three stars with UVES. The [Ne II] line
was detected in 7 stars, among them the first confirmed detection of [Ne II] in
a Herbig Be star, V892 Tau. In four cases, the large blueshifted lines indicate
an origin in a jet. In two stars, the small shifts and asymmetric profiles
indicate an origin in a photo-evaporative wind. CoKu Tau 1, seen close to
edge-on, shows a spatially unresolved line centered at the stellar rest
velocity, although cross-dispersion centroids move within 10 AU from one side
of the star to the other as a function of wavelength. The line profile is
symmetric with wings extending up to about +-80 km/s. The origin of the [Ne II]
line could either be due to the bipolar jet or to the disk. For the stars with
VLT-UVES observations, in several cases, the optical forbidden line profiles
and shifts are very similar to the profile of the [Ne II] line, suggesting that
the lines are emitted in the same region. A general trend observed with VISIR
is a lower line flux when compared with the fluxes obtained with Spitzer. We
found no correlation between the line full-width at half maximum and the line
peak velocity. The [Ne II] line remains undetected in a large part of the
sample, an indication that the emission detected with Spitzer in those stars is
likely extended.Comment: Accepted for publication in Astronomy & Astrophysics; revised
version: corrected minor typos, corrected center values (col 3) for CoKuTau1
in Table
A New Population of High Redshift, Dusty Lyman-Alpha Emitters and Blobs Discovered by WISE
We report a new technique to select 1.6<z<4.6 dusty Lyman-alpha emitters
(LAEs), over a third of which are `blobs' (LABs) with emission extended on
scales of 30-100kpc. Combining data from the NASA Wide-field Infrared Survey
Explorer (WISE) mission with optical spectroscopy from the W.M. Keck telescope,
we present a color criteria that yields a 78% success rate in identifying rare,
dusty LAEs of which at least 37% are LABs. The objects have a surface density
of only ~0.1 per square degree, making them rare enough that they have been
largely missed in narrow surveys. We measured spectroscopic redshifts for 92 of
these WISE-selected, typically radio-quiet galaxies and find that the LAEs
(LABs) have a median redshift of 2.3 (2.5). The WISE photometry coupled with
data from Herschel reveals that these galaxies have extreme far-infrared
luminosities (L_IR>10^{13-14}L_sun) and warm colors, typically larger than
submillimeter-selected galaxies (SMGs) and dust-obscured galaxies (DOGs). These
traits are commonly associated with the dust being energized by intense AGN
activity. We hypothesize that the combination of spatially extended
Lyman-alpha, large amounts of warm IR-luminous dust, and rarity (implying a
short-lived phase) can be explained if the galaxies are undergoing strong
`feedback' transforming them from an extreme dusty starburst to a QSO.Comment: Submitted to ApJ Letters, 6 pages, 4 figures. Comments welcom
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