264 research outputs found
Comparing Simple Quasar Demographics Models
This paper explores several simple model variations for the connections among
quasars, galaxies, and dark matter halos for redshifts 1 < z < 6. A key
component of these models is that we enforce a self-consistent black hole (BH)
history by tracking both BH mass and BH growth rate at all redshifts. We
connect objects across redshift with a simple constant-number-density
procedure, and choose a fiducial model with a relationship between BH and
galaxy growth rates that is linear and evolves in a simple way with redshift.
Within this fiducial model, we find the quasar luminosity function (QLF) by
calculating an "intrinsic" luminosity based on either the BH mass or BH growth
rate, and then choosing a model of quasar variability with either a lognormal
or truncated power-law distribution of instantaneous luminosities. This gives
four model variations, which we fit to the observed QLF at each redshift. With
the best-fit models in hand, we undertake a detailed comparison of the four
fiducial models, and explore changes to our fiducial model of the BH-galaxy
relationship. Each model variation can successfully fit the observed QLF, the
shape of which is generally set by the "intrinsic" luminosity at the faint end
and by the scatter due to variability at the bright end. We focus on accounting
for the reasons that physically different models can make such similar
predictions, and on identifying what observational data or physical arguments
are most essential in breaking the degeneracies among models.Comment: 14 pages, 8 figures, 1 tabl
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Irs2 and Irs4 synergize in non-LepRb neurons to control energy balance and glucose homeostasis★
Insulin receptor substrates (Irs1, 2, 3 and Irs4) mediate the actions of insulin/IGF1 signaling. They have similar structure, but distinctly regulate development, growth, and metabolic homeostasis. Irs2 contributes to central metabolic sensing, partially by acting in leptin receptor (LepRb)-expressing neurons. Although Irs4 is largely restricted to the hypothalamus, its contribution to metabolic regulation is unclear because Irs4-null mice barely distinguishable from controls. We postulated that Irs2 and Irs4 synergize and complement each other in the brain. To examine this possibility, we investigated the metabolism of whole body Irs4−/y mice that lacked Irs2 in the CNS (bIrs2−/−·Irs4−/y) or only in LepRb-neurons (Lepr∆Irs2·Irs4−/y). bIrs2−/−·Irs4−/y mice developed severe obesity and decreased energy expenditure, along with hyperglycemia and insulin resistance. Unexpectedly, the body weight and fed blood glucose levels of Lepr∆Irs2·Irs4−/y mice were not different from Lepr∆Irs2 mice, suggesting that the functions of Irs2 and Irs4 converge upon neurons that are distinct from those expressing LepRb
Enhanced thermoelectricity in Bi-sprayed bismuth sulphide particles
Bismuth sulphide (Bi2S3), an n-type semiconductor that critically demonstrates the Seebeck effect with Seebeck coefficients of about 300 μVK−1. However, its poor electrical conductivity makes it unsuitable for thermoelectric applications. In this study, we present a facile preparation method for fabricating Bi-sprayed Bi2S3 particles that alters their thermoelectric properties. Samples were created with differing Bi concentrations into the Bi2S3 compound to test for enhanced thermoelectric properties of the resulting Bi/Bi2S3 composites. The incorporation of excess Bi into Bi2S3 significantly improves the compound's electrical conductivity and optimises overall thermoelectric performance. The electrical conductivity of the Bi/Bi2S3 composites improved from 6.5 Scm−1 (for pristine Bi2S3) to 154 Scm−1 (for highest Bi added Bi2S3). Although the Seebeck coefficient of samples decreased with Bi incorporation, a high power factor (∼390 μWm−1K−2) has been achieved for an optimised composition of the composite. Incorporation of metallic Bi has led to an increase in the thermal conductivity of the samples, but the increase is not significant for the optimised composition of the composites where a high thermoelectric performance has been observed. Therefore, enhanced power factor and moderate thermal conductivity have resulted in a peak ZT value of 0.11 at room temperature. The strategy proposed here improves the thermoelectricity in Bi2S3 and shows excellent potential for developing better-performing thermoelectric compounds with excess elemental contents
Evaluation of the angiotensin II receptor blocker azilsartan medoxomil in African-American patients with hypertension
The efficacy and safety of azilsartan medoxomil (AZL-M) were evaluated in African-American patients with hypertension in a 6-week, double-blind, randomized, placebo-controlled trial, for which the primary end point was change from baseline in 24-hour mean systolic blood pressure (BP). There were 413 patients, with a mean age of 52years, 57% women, and baseline 24-hour BP of 146/91mmHg. Treatment differences in 24-hour systolic BP between AZL-M 40mg and placebo (-5.0mmHg; 95% confidence interval, -8.0 to -2.0) and AZL-M 80mg and placebo (-7.8mmHg; 95% confidence interval, -10.7 to -4.9) were significant (P.001 vs placebo for both comparisons). Changes in the clinic BPs were similar to the ambulatory BP results. Incidence rates of adverse events were comparable among the treatment groups, including those of a serious nature. In African-American patients with hypertension, AZL-M significantly reduced ambulatory and clinic BPs in a dose-dependent manner and was well tolerated
Modeling Luminosity-Dependent Galaxy Clustering Through Cosmic Time
We employ high-resolution dissipationless simulations of the concordance LCDM
cosmology to model the observed luminosity dependence and evolution of galaxy
clustering through most of the age of the universe, from z~5 to z~0. We use a
simple, non-parametric model which monotonically relates galaxy luminosities to
the maximum circular velocity of dark matter halos (V_max) by preserving the
observed galaxy luminosity function in order to match the halos in simulations
with observed galaxies. The novel feature of the model is the use of the
maximum circular velocity at the time of accretion, V_max,acc, for subhalos,
the halos located within virial regions of larger halos. We argue that for
subhalos in dissipationless simulations, V_max,acc reflects the luminosity and
stellar mass of the associated galaxies better than the circular velocity at
the epoch of observation, V_max,now. The simulations and our model L-V_max
relation predict the shape, amplitude, and luminosity dependence of the
two-point correlation function in excellent agreement with the observed galaxy
clustering in the SDSS data at z~0 and in the DEEP2 samples at z~1 over the
entire probed range of projected separations, 0.1<r_p/(Mpc/h)<10.0. In
particular, the small-scale upturn of the correlation function from the
power-law form in the SDSS and DEEP2 luminosity-selected samples is reproduced
very well. At z~3-5, our predictions also match the observed shape and
amplitude of the angular two-point correlation function of Lyman-break galaxies
(LBGs) on both large and small scales, including the small-scale upturn.Comment: 16 pages 11 figures, ApJ in pres
LMRL Gym: Benchmarks for Multi-Turn Reinforcement Learning with Language Models
Large language models (LLMs) provide excellent text-generation capabilities,
but standard prompting and generation methods generally do not lead to
intentional or goal-directed agents and might necessitate considerable prompt
tuning. This becomes particularly apparent in multi-turn conversations: even
the best current LLMs rarely ask clarifying questions, engage in explicit
information gathering, or take actions now that lead to better decisions after
multiple turns. Reinforcement learning has the potential to leverage the
powerful modeling capabilities of LLMs, as well as their internal
representation of textual interactions, to create capable goal-directed
language agents. This can enable intentional and temporally extended
interactions, such as with humans, through coordinated persuasion and carefully
crafted questions, or in goal-directed play through text games to bring about
desired final outcomes. However, enabling this requires the community to
develop stable and reliable reinforcement learning algorithms that can
effectively train LLMs. Developing such algorithms requires tasks that can
gauge progress on algorithm design, provide accessible and reproducible
evaluations for multi-turn interactions, and cover a range of task properties
and challenges in improving reinforcement learning algorithms. Our paper
introduces the LMRL-Gym benchmark for evaluating multi-turn RL for LLMs,
together with an open-source research framework containing a basic toolkit for
getting started on multi-turn RL with offline value-based and policy-based RL
methods. Our benchmark consists of 8 different language tasks, which require
multiple rounds of language interaction and cover a range of tasks in
open-ended dialogue and text games
E-Data Quality: How Publishers and Libraries are Working Together to Improve Data Quality
High quality data is essential for discovery and access of e-resources, but in many cases low quality, inaccurate information leads to low usage and a poor return on library investment dollars. In this article, publishers, aggregators, librarians, and knowledge base providers talk about how they are working together to improve access to e-resources
Aquilegia, Vol. 40 No. 1 - Winter 2015-2016, Newsletter of the Colorado Native Plant Society
https://epublications.regis.edu/aquilegia/1188/thumbnail.jp
A Simple Model for Quasar Demographics
We present a simple model for the relationship between quasars, galaxies, and
dark matter halos from 0.5<z<6. In the model, black hole (BH) mass is linearly
related to galaxy mass, and galaxies are connected to dark matter halos via
empirically constrained relations. A simple "scattered" light bulb model for
quasars is adopted, wherein BHs shine at a fixed fraction of the Eddington
luminosity during accretion episodes, and Eddington ratios are drawn from a
lognormal distribution that is redshift-independent. This model has two free,
physically meaningful parameters at each redshift: the normalization of the
Mbh-Mgal relation and the quasar duty cycle; these parameters are fit to the
observed quasar luminosity function (LF) over the interval 0.5<z<6. This simple
model provides an excellent fit to the LF at all epochs, and also successfully
predicts the observed projected two-point correlation of quasars from
0.5<z<2.5. It is significant that a single quasar duty cycle at each redshift
is capable of reproducing the extant observations. The data are therefore
consistent with a scenario wherein quasars are equally likely to exist in
galaxies, and therefore dark matter halos, over a wide range in masses. The
knee in the quasar LF is a reflection of the knee in the stellar mass-halo mass
relation. Future constraints on the quasar LF and quasar clustering at high
redshift will provide strong constraints on the model. In the model, the
autocorrelation function of quasars becomes a strong function of luminosity
only at the very highest luminosities, and will be difficult to observe because
such quasars are so rare. Cross-correlation techniques may provide useful
constraints on the bias of such rare objects.Comment: 12 pages, 12 figures, ApJ accepte
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