16,017 research outputs found
Evolutionary Analysis of Gaseous Sub-Neptune-Mass Planets with MESA
Sub-Neptune-sized exoplanets represent one of the most common types of
planets in the Milky Way, yet many of their properties are unknown. Here, we
present a prescription to adapt the capabilities of the stellar evolution
toolkit Modules for Experiments in Stellar Astrophysics (MESA) to model
sub-Neptune mass planets with H/He envelopes. With the addition of routines
treating the planet core luminosity, heavy element enrichment, atmospheric
boundary condition, and mass loss due to hydrodynamic winds, the evolutionary
pathways of planets with diverse starting conditions are more accurately
constrained. Using these dynamical models, we construct mass-composition
relationships of planets from 1 to 400 and investigate how
mass-loss impacts their composition and evolution history. We demonstrate that
planet radii are typically insensitive to the evolution pathway that brought
the planet to its instantaneous mass, composition and age, with variations from
hysteresis. We find that planet envelope mass loss timescales, , vary non-monotonically with H/He envelope mass fractions (at fixed
planet mass). In our simulations of young (100~Myr) low-mass
() planets with rocky cores, is
maximized at to . The resulting convergent mass loss
evolution could potentially imprint itself on the close-in planet population as
a preferred H/He mass fraction of . Looking ahead, we anticipate
that this numerical code will see widespread applications complementing both
3-D models and observational exoplanet surveys.Comment: 18 pages, 9 figures, and 4 tables. Accepted to the Astrophysical
Journal on August 29th, 201
From urban to national heat island: The effect of anthropogenic heat output on climate change in high population industrial countries
The project presented here sought to determine whether changes in anthropogenic thermal emission can have a measurable effect on temperature at the national level, taking Japan and Great Britain as type examples. Using energy consumption as a proxy for thermal emission, strong correlations (mean r2β=β0.90 and 0.89, respectively) are found between national equivalent heat output (HO) and temperature above background levels Ξt averaged over 5β to 8βyr periods between 1965 and 2013, as opposed to weaker correlations for CMIP5 model temperatures above background levels Ξmt (mean r2β=β0.52 and 0.10). It is clear that the fluctuations in Ξt are better explained by energy consumption than by present climate models, and that energy consumption can contribute to climate change at the national level on these timescales
Dynamic communicability and epidemic spread: a case study on an empirical dynamic contact network
We analyze a recently proposed temporal centrality measure applied to an
empirical network based on person-to-person contacts in an emergency department
of a busy urban hospital. We show that temporal centrality identifies a
distinct set of top-spreaders than centrality based on the time-aggregated
binarized contact matrix, so that taken together, the accuracy of capturing
top-spreaders improves significantly. However, with respect to predicting
epidemic outcome, the temporal measure does not necessarily outperform less
complex measures. Our results also show that other temporal markers such as
duration observed and the time of first appearance in the the network can be
used in a simple predictive model to generate predictions that capture the
trend of the observed data remarkably well.Comment: 31 pages, 15 figures, 11 tables; typos corrected; references added;
Figure 3 added; some changes to the conclusion and introductio
Combined SIRT3 and SIRT5 deletion is associated with inner retinal dysfunction in a mouse model of type 1 diabetes
Abstract Diabetic retinopathy (DR) is a major cause of blindness in working adults in the industrialized world. In addition to vision loss caused by macular edema and pathological angiogenesis, DR patients often exhibit neuronal dysfunction on electrophysiological testing, suggesting that there may be an independent neuronal phase of disease that precedes vascular disease. Given the tremendous metabolic requirements of the retina and photoreceptors in particular, we hypothesized that derangements in metabolic regulation may accelerate retinal dysfunction in diabetes. As such, we induced hyperglycemia with streptozotocin in mice with monoallelic Nampt deletion from rod photoreceptors, mice lacking SIRT3, and mice lacking SIRT5 and tested multiple components of retinal function with electroretinography. None of these mice exhibited accelerated retinal dysfunction after induction of hyperglycemia, consistent with normal-appearing retinal morphology in hyperglycemic Sirt3 β/β or Sirt5 β/β mice. However, mice lacking both SIRT3 and SIRT5 (Sirt3 β/β Sirt5 β/β mice) exhibited significant evidence of inner retinal dysfunction after induction of hyperglycemia compared to hyperglycemic littermate controls, although this dysfunction was not accompanied by gross morphological changes in the retina. These results suggest that SIRT3 and SIRT5 may be involved in regulating neuronal dysfunction in DR and provide a foundation for future studies investigating sirtuin-based therapies
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AZIP, audio compression system: Research on audio compression, comparison of psychoacoustic principles and genetic algorithms
The purpose of this project is to investigate the differences between psychoacoustic principles and genetic algorithms (GA0). These will be discussed separately. The review will also compare the compression ratio and the quality of the decompressed files decoded by these two methods
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