9,424 research outputs found
The Mass Growth and Stellar Ages of Galaxies: Observations versus Simulations
Using observed stellar mass functions out to , we measure the main
progenitor stellar mass growth of descendant galaxies with masses of
at using an evolving
cumulative number density selection. From these mass growth histories, we are
able to measure the time at which half the total stellar mass of the descendant
galaxy was assembled, , which, in order of decreasing mass corresponds
to redshifts of and . We compare this to the
median light-weighted stellar age ( and
) of a sample of low redshift SDSS galaxies (from the literature) and
find the timescales are consistent with more massive galaxies forming a higher
fraction of their stars ex-situ compared to lower mass descendants. We find
that both and strongly correlate with mass which is in contrast
to what is found in the EAGLE hydrodynamical simulation which shows a flat
relationship between and . However, the semi-analytic model of
\citet{henriques2015} is consistent with the observations in both and
with , showing the most recent semi-analytic models are better
able to decouple the evolution of the baryons from the dark matter in
lower-mass galaxies.Comment: 6 pages, 3 figures, accepted for publication in ApJ
Norms, Attitudes and Compliance
Reviewing Geoffrey Brennan, Lina Eriksson, Robert E. Goodin, and Nicholas Southwood, Explaining Norms
Norms, Attitudes and Compliance
Reviewing Geoffrey Brennan, Lina Eriksson, Robert E. Goodin, and Nicholas Southwood, Explaining Norms
Exploration Space Suit Architecture and Destination Environmental-Based Technology Development
This paper continues forward where EVA Space Suit Architecture: Low Earth Orbit Vs. Moon Vs. Mars [1] left off in the development of a space suit architecture that is modular in design and could be reconfigured prior to launch or during any given mission depending on the tasks or destination. This paper will address the space suit system architecture and technologies required based upon human exploration extravehicular activity (EVA) destinations, and describe how they should evolve to meet the future exploration EVA needs of the US human space flight program.1, 2, 3 In looking forward to future US space exploration to a space suit architecture with maximum reuse of technology and functionality across a range of mission profiles and destinations, a series of exercises and analyses have provided a strong indication that the Constellation Program (CxP) space suit architecture is postured to provide a viable solution for future exploration missions4. The destination environmental analysis presented in this paper demonstrates that the modular architecture approach could provide the lowest mass and mission cost for the protection of the crew given any human mission outside of low-Earth orbit (LEO). Additionally, some of the high-level trades presented here provide a review of the environmental and non-environmental design drivers that will become increasingly important the farther away from Earth humans venture. This paper demonstrates a logical clustering of destination design environments that allows a focused approach to technology prioritization, development, and design that will maximize the return on investment, independent of any particular program, and provide architecture and design solutions for space suit systems in time or ahead of need dates for any particular crewed flight program in the future. The approach to space suit design and interface definition discussion will show how the architecture is very adaptable to programmatic and funding changes with minimal redesign effort such that the modular architecture can be quickly and efficiently honed into a specific mission point solution if required. Additionally, the modular system will allow for specific technology incorporation and upgrade as required with minimal redesign of the system
High Redshift Massive Quiescent Galaxies are as Flat as Star Forming Galaxies: The Flattening of Galaxies and the Correlation with Structural Properties in CANDELS/3D-HST
We investigate the median flattening of galaxies at in all five
CANDELS/3D-HST fields via the apparent axis ratio . We separate the sample
into bins of redshift, stellar-mass, s\'ersic index, size, and UVJ determined
star-forming state to discover the most important drivers of the median
(). Quiescent galaxies at are
rounder than those at lower masses, consistent with the hypothesis that they
have grown significantly through dry merging. The massive quiescent galaxies at
higher redshift become flatter, and are as flat as star forming massive
galaxies at , consistent with formation through direct
transformations or wet mergers. We find that in quiescent galaxies,
correlations with and , and are driven by the
evolution in the s\'ersic index (), consistent with the growing accumulation
of minor mergers at lower redshift. Interestingly, does not drive these
trends fully in star-forming galaxies. Instead, the strongest predictor of
in star-forming galaxies is the effective radius, where larger galaxies are
flatter. Our findings suggest that is tracing bulge-to-total ()
galaxy ratio which would explain why smaller/more massive star-forming galaxies
are rounder than their extended/less massive analogues, although it is unclear
why s\'ersic index correlates more weakly with flattening for star forming
galaxies than for quiescent galaxies.Comment: 13 pages, 11 figures, accepted to Ap
Update on Electricity Customer Choice In Ohio: Competition Continues to Outperform Traditional Monopoly Regulation (Executive Summary)
Key Findings at a Glance:
Deregulated Markets Save Ohio Electricity Consumers Billions Since 2011, deregulation has saved Ohio consumers 3 billion per year. However, these savings may be lost, in whole or in part, if deregulated energy markets continue to be undermined by cross subsidies.
Competition Outperforms Monopoly Regulation Competition has driven down average electricity prices in deregulated Midwestern states while their regulated peers have seen a steady increase in price of generated electricity
Update on Electricity Customer Choice In Ohio: Competition Continues to Outperform Traditional Monopoly Regulation (Executive Summary)
Key Findings at a Glance:
Deregulated Markets Save Ohio Electricity Consumers Billions Since 2011, deregulation has saved Ohio consumers 3 billion per year. However, these savings may be lost, in whole or in part, if deregulated energy markets continue to be undermined by cross subsidies.
Competition Outperforms Monopoly Regulation Competition has driven down average electricity prices in deregulated Midwestern states while their regulated peers have seen a steady increase in price of generated electricity
Natural Theories of Ultra-Low Mass PNGB's: Axions and Quintessence
We consider the Wilson Line PNGB which arises in a U(1)^N gauge theory,
abstracted from a latticized, periodically compactified extra dimension U(1).
Planck scale breaking of the PNGB's global symmetry is suppressed, providing
natural candidates for the axion and quintessence. We construct an explicit
model in which the axion may be viewed as the 5th component of the U(1)_Y gauge
field in a 1+4 latticized periodically compactified extra dimension. We also
construct a quintessence PNGB model where the ultra-low mass arises from
Planck-scale suppressed physics itself.Comment: 20 pages, fixed typo and reference
Genomic insights into the Ixodes scapularis tick vector of Lyme disease
Ticks transmit more pathogens to humans and animals than any other arthropod. We describe the 2.1 Gbp nuclear genome of the tick, Ixodes scapularis (Say), which vectors pathogens that cause Lyme disease, human granulocytic anaplasmosis, babesiosis and other diseases. The large genome reflects accumulation of repetitive DNA, new lineages of retro-transposons, and gene architecture patterns resembling ancient metazoans rather than pancrustaceans. Annotation of scaffolds representing approximately 57% of the genome, reveals 20,486 protein-coding genes and expansions of gene families associated with tick-host interactions. We report insights from genome analyses into parasitic processes unique to ticks, including host \u27questing\u27, prolonged feeding, cuticle synthesis, blood meal concentration, novel methods of haemoglobin digestion, haem detoxification, vitellogenesis and prolonged off-host survival. We identify proteins associated with the agent of human granulocytic anaplasmosis, an emerging disease, and the encephalitis-causing Langat virus, and a population structure correlated to life-history traits and transmission of the Lyme disease agent
Enrichment of clinical trials in MCI due to AD using markers of amyloid and neurodegeneration
Objective:
To investigate the effect of enriching mild cognitive impairment (MCI) clinical trials using combined markers of amyloid pathology and neurodegeneration.
Methods:
We evaluate an implementation of the recent National Institute for Aging–Alzheimer's Association (NIA-AA) diagnostic criteria for MCI due to Alzheimer disease (AD) as inclusion criteria in clinical trials and assess the effect of enrichment with amyloid (A+), neurodegeneration (N+), and their combination (A+N+) on the rate of clinical progression, required sample sizes, and estimates of trial time and cost.
Results:
Enrichment based on an individual marker (A+ or N+) substantially improves all assessed trial characteristics. Combined enrichment (A+N+) further improves these results with a reduction in required sample sizes by 45% to 60%, depending on the endpoint.
Conclusions:
Operationalizing the NIA-AA diagnostic criteria for clinical trial screening has the potential to substantially improve the statistical power of trials in MCI due to AD by identifying a more rapidly progressing patient population
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