1,535 research outputs found
Stellar Population Properties and Evolution Analysis of NGC 628 with the Panchromatic Photometry
Panchromatic spectral energy distribution (SED) from the ultraviolet (UV),
optical to infrared (IR) photometry of NGC 628, combined with the evolutionary
stellar population synthesis, is used to derive the spatially resolved age,
metallicity and reddening maps. These parameter distributions show that the
bulge of this galaxy is a disk-like pseudobulge, which has the S{\'e}rsic index
close to the exponential law, rich gas, and a young circumnuclear ring
structure. We also discover the disk has two distinct regions with different
radial age and metallicity gradients. The inner region is older and has a much
steeper age gradient than the outer region of the disk. Both these two regions
and the central young structure can be seen in the radial profile of the
optical color. Based on the age and reddening distributions, we consider that
the pseudobulge and disk are likely to have grown via the secular evolution,
which is the redistribution of mass and energy through the angular momentum
transport caused by the non-axisymmetric potential of the spirals. However,
possible gas accretion events could affect the outer region of the disk, due to
abundant H{\sc i} gas accumulating in the outer disk.Comment: 9 figures, accepted for publication in A
Structural Mechanism for the Specific Assembly and Activation of the Extracellular Signal Regulated Kinase 5 (ERK5) Module
Mitogen-activated protein kinase (MAPK) activation depends on a linear binding motif found in all MAPK kinases (MKK). In addition, the PB1 (Phox and Bem1) domain of MKK5 is required for extracellular signal regulated kinase 5 (ERK5) activation. We present the crystal structure of ERK5 in complex with an MKK5 construct comprised of the PB1 domain and the linear binding motif. We show that ERK5 has distinct protein-protein interaction surfaces compared with ERK2, which is the closest ERK5 paralog. The two MAPKs have characteristically different physiological functions and their distinct protein-protein interaction surface topography enables them to bind different sets of activators and substrates. Structural and biochemical characterization revealed that the MKK5 PB1 domain cooperates with the MAPK binding linear motif to achieve substrate specific binding, and it also enables co-recruitment of the upstream activating enzyme and the downstream substrate into one signaling competent complex. Studies on present day MAPKs and MKKs hint on the way protein kinase networks may evolve. In particular, they suggest how paralogous enzymes with similar catalytic properties could acquire novel signaling roles by merely changing the way they make physical links to other proteins
ARC Newsletter Volume 1, Issue 3
https://digitalcommons.lasalle.edu/arc_newsletter/1002/thumbnail.jp
Direct Formation of Supermassive Black Holes via Multi-Scale Gas Inflows in Galaxy Mergers
Observations of distant bright quasars suggest that billion solar mass
supermassive black holes (SMBHs) were already in place less than a billion
years after the Big Bang. Models in which light black hole seeds form by the
collapse of primordial metal-free stars cannot explain their rapid appearance
due to inefficient gas accretion. Alternatively, these black holes may form by
direct collapse of gas at the center of protogalaxies. However, this requires
metal-free gas that does not cool efficiently and thus is not turned into
stars, in contrast with the rapid metal enrichment of protogalaxies. Here we
use a numerical simulation to show that mergers between massive protogalaxies
naturally produce the required central gas accumulation with no need to
suppress star formation. Merger-driven gas inflows produce an unstable, massive
nuclear gas disk. Within the disk a second gas inflow accumulates more than 100
million solar masses of gas in a sub-parsec scale cloud in one hundred thousand
years. The cloud undergoes gravitational collapse, which eventually leads to
the formation of a massive black hole. The black hole can grow to a billion
solar masses in less than a billion years by accreting gas from the surrounding
disk.Comment: 26 pages, 4 Figures, submitted to Nature (includes Supplementary
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Summary of technical information and agreements from Nuclear Management and Resources Council industry reports addressing license renewal
In about 1990, the Nuclear Management and Resources Council (NUMARC) submitted for NRC review ten industry reports (IRs) addressing aging issues associated with specific structures and components of nuclear power plants ad one IR addressing the screening methodology for integrated plant assessment. The NRC staff had been reviewing the ten NUMARC IRs; their comments on each IR and NUMARC responses to the comments have been compiled as public documents. This report provides a brief summary of the technical information and NUMARC/NRC agreements from the ten IRs, except for the Cable License Renewal IR. The technical information and agreements documented herein represent the status of the NRC staffs review when the NRC staff and industry resources were redirected to address rule implementation issues. The NRC staff plans to incorporate appropriate technical information and agreements into the draft standard review plan for license renewal
The Lyman-alpha forest at redshifts 0.1 -- 1.6: good agreement between a large hydrodynamic simulation and HST spectra
We give a comprehensive statistical description of the Lyman-alpha absorption
from the intergalactic medium in a hydrodynamic simulation at redshifts
0.1-1.6, the range of redshifts covered by HST spectra of QSOs. We use the ENZO
code to make a 76 comoving Mpc cube simulation using 75 kpc cells, for a Hubble
constant of 71 km/s/Mpc. The best prior work, by \citet{dave99},used an SPH
simulation in a 15.6 Mpc box with an effective resolution of 245 kpc and
slightly different cosmological parameters. At redshifts z=2 this simulation is
different from data. \citet{tytler07b} found that the simulated spectra at z=2
have too little power on large scales, Lyman-alpha lines are too wide, there is
a lack high column density lines, and there is a lack of pixels with low flux.
Here we present statistics at z<1.6, including the flux distribution, the mean
flux, the effective opacity, and the power and correlation of the flux. We also
give statistics of the lyman alpha lines including the line width distribution,
the column density distribution, the number of lines per unit equivalent width
and redshift, and the correlation between the line width and column density. We
find that the mean amount of absorption in the simulated spectra changes
smoothly with redshift with DA(z)=0.01(1+z)^{2.25}. Both the trend and absolute
values are close to measurements of HST spectra by \citet{kirkman07a}. The
column density and line width distributions are also close to those measured
from HST spectra by \citet{janknecht06a}, except for the mode of the line width
distribution which is smaller in the HST spectra. Although some differences
that we saw at z=2 are too subtle to be seen in existing HST spectra, overall,
the simulation gives an good description of HST spectra at 0.1<z<1.6
Antenatal influenza and pertussis vaccination in Western Australia: A cross-sectional survey of vaccine uptake and influencing factors
Background: Influenza and pertussis vaccines have been recommended in Australia for women during each pregnancy since 2010 and 2015, respectively. Estimating vaccination coverage and identifying factors affecting uptake are important for improving antenatal immunisation services.
Methods: A random sample of 800 Western Australian women ā„18 years of age who gave birth between 4th April and 4th October 2015 were selected. Of the 454 (57%) who were contactable by telephone, 424 (93%) completed a survey. Data were weighted by maternal age and area of residence to ensure representativeness. The proportion immunised against influenza and pertussis was the main outcome measure; multivariate logistic regression was used to identify factors significantly associated with antenatal vaccination. Results from the 2015 study were compared to similar surveys conducted in 2012ā2014.
Results: In 2015, 71% (95% CI 66ā75) of women received pertussis-containing vaccine and 61% (95% CI 56ā66) received influenza vaccine during pregnancy; antenatal influenza vaccine coverage was 18% higher than in 2014 (43%; 95% CI: 34ā46). Pertussis and influenza vaccine were co-administered for 68% of the women who received both vaccines. The majority of influenza vaccinations in 2015 were administered during the third trimester of pregnancy, instead of the second trimester, as was observed in prior years. Women whose care provider recommended both antenatal vaccinations had significantly higher odds of being vaccinated against both influenza and pertussis (OR 33.3, 95% CI: 15.15ā73.38). Of unvaccinated mothers, 53.6% (95% CI: 45.9ā61.3) and 78.3% (95% CI: 70.4ā85.3) reported that they would have been vaccinated against influenza and pertussis, respectively, if their antenatal care provider had recommended it.
Conclusions: Pertussis vaccination coverage was high in the first year of an antenatal immunisation program in Western Australia. Despite a substantial increase in influenza vaccination uptake between 2014 and 2015, coverage remained below that for pertussis. Our data suggest influenza and pertussis vaccination rates of 83% and 94%, respectively, are achievable if providers were to recommend them to all pregnant women
Chromatic Illumination Discrimination Ability Reveals that Human Colour Constancy Is Optimised for Blue Daylight Illuminations
The phenomenon of colour constancy in human visual perception keeps surface colours constant, despite changes in their reflected light due to changing illumination. Although colour constancy has evolved under a constrained subset of illuminations, it is unknown whether its underlying mechanisms, thought to involve multiple components from retina to cortex, are optimised for particular environmental variations. Here we demonstrate a new method for investigating colour constancy using illumination matching in real scenes which, unlike previous methods using surface matching and simulated scenes, allows testing of multiple, real illuminations. We use real scenes consisting of solid familiar or unfamiliar objects against uniform or variegated backgrounds and compare discrimination performance for typical illuminations from the daylight chromaticity locus (approximately blue-yellow) and atypical spectra from an orthogonal locus (approximately red-green, at correlated colour temperature 6700 K), all produced in real time by a 10-channel LED illuminator. We find that discrimination of illumination changes is poorer along the daylight locus than the atypical locus, and is poorest particularly for bluer illumination changes, demonstrating conversely that surface colour constancy is best for blue daylight illuminations. Illumination discrimination is also enhanced, and therefore colour constancy diminished, for uniform backgrounds, irrespective of the object type. These results are not explained by statistical properties of the scene signal changes at the retinal level. We conclude that high-level mechanisms of colour constancy are biased for the blue daylight illuminations and variegated backgrounds to which the human visual system has typically been exposed
Nanoscale Conductivity Imaging of Correlated Electronic States in WSe2/WS2 Moir\'e Superlattices
We report the nanoscale conductivity imaging of correlated electronic states
in angle-aligned WSe2/WS2 heterostructures using microwave impedance
microscopy. The noncontact microwave probe allows us to observe the Mott
insulating state with one hole per moir\'e unit cell that persists for
temperatures up to 150 K, consistent with other characterization techniques. In
addition, we identify for the first time a Mott insulating state at one
electron per moir\'e unit cell. Appreciable inhomogeneity of the correlated
states is directly visualized in the hetero-bilayer region, indicative of local
disorders in the moir\'e superlattice potential or electrostatic doping. Our
work provides important insights on 2D moir\'e systems down to the microscopic
level.Comment: 12 Pages, 4 figure
Robot rights? Towards a social-relational justification of moral consideration \ud
Should we grant rights to artificially intelligent robots? Most current and near-future robots do not meet the hard criteria set by deontological and utilitarian theory. Virtue ethics can avoid this problem with its indirect approach. However, both direct and indirect arguments for moral consideration rest on ontological features of entities, an approach which incurs several problems. In response to these difficulties, this paper taps into a different conceptual resource in order to be able to grant some degree of moral consideration to some intelligent social robots: it sketches a novel argument for moral consideration based on social relations. It is shown that to further develop this argument we need to revise our existing ontological and social-political frameworks. It is suggested that we need a social ecology, which may be developed by engaging with Western ecology and Eastern worldviews. Although this relational turn raises many difficult issues and requires more work, this paper provides a rough outline of an alternative approach to moral consideration that can assist us in shaping our relations to intelligent robots and, by extension, to all artificial and biological entities that appear to us as more than instruments for our human purpose
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