41 research outputs found
Asymmetry, Gap Opening and High Accretion Rate on DM Tau: A Hypothesis Based on Interaction of Magnetized Disk Wind with Planet
Over two hundred protoplanetary disk systems have been resolved by ALMA, and
the vast majority suggest the presence of planets. The dust gaps in transition
disks are considered evidence of giant planets sculpting gas and dust under
appropriate disk viscosity. However, the unusually high accretion rates in many
T Tauri stars hosting transition disks challenge this theory. As the only disk
currently observed with high turbulence, the high accretion rate
() observed in DM Tau indicates the presence of
strong turbulence may within the system. Considering the recent theoretical
advancements in magnetized disk winds is challenging the traditional
gap-opening theories and viscosity-driven accretion models, our study presents
a pioneering simulation incorporating a simplified magnetized disk wind model
to explain the observed features in DM Tau. Employing multi-fluid simulations
with an embedded medium mass planet, we successfully replicate the gap
formation and asymmetric structures evident in ALMA Band 6 and the recently
JVLA 7 mm observations. Our results suggest that when magnetized disk wind
dominate the accretion mode of the system, it's entirely possible for a planet
with a medium mass to exist within the gap inside 20 au of DM Tau. This means
that DM Tau may not be as turbulence as imagined. However, viscosity within the
disk should also contribute a few turbulence to maintain disk stability.Comment: 13 pages, 4 figures, accepted by ApJ. Welcome any comments and
suggestions
Fertilizer Use in China: The Role of Agricultural Support Policies
Using a decomposition method, this paper proposes an analytical framework to investigate the mechanisms by which agricultural support policies affect farmersâ use of fertilizers in agriculture in China. The mechanisms are decomposed into âthree effectsâ (structural, scale, and technological effects). It is found that Chinaâs agricultural support polices have significantly contributed to the increased use of agricultural fertilizers through encouraging farmers to bring more land under cultivation (the scale effect). Meanwhile, some policies have also helped reduce fertilizer consumption when farmers were motivated to increase the area of grains crops (the structural effect). The role of technological progress in affecting fertilizer consumption (the technological effect) appears to be minimal and uncertain. Compared to direct subsidies, indirect subsidies play a much greater role in affecting farmersâ production decision making and are more environmentally consequential. This paper argues that some of Chinaâs agricultural support policies are not well aligned with one key objective of the countryâs rural policiesâimproving environmental sustainability. It is recommended that the government takes measures to reform agricultural support policies and to reconcile agricultural and rural policies in order to achieve sustainable rural development
Using planet migration and dust drift to weigh protoplanetary discs
ALMA has spatially resolved over 200 annular structures in protoplanetary
discs, many of which are suggestive of the presence of planets. Constraining
the mass of these putative planets is quite degenerate for it depends on the
disc physical properties, and for simplicity a steady-state is often assumed
whereby the planet position is kept fixed and there is a constant source of
dust at the outer edge of the disc. Here we argue against this approach by
demonstrating how the planet and dust dynamics can lift degeneracies of such
steady-state models. We take main disc parameters from the well-known
protoplanetary disc HD 163296 with a suspected planet at ~au as an
example. By running gas and dust hydrodynamical simulations post-processed with
dust radiative transfer calculations, we first find steady-state disc and
planet parameters that reproduce ALMA continuum observations fairly well. For
the same disc mass, but now allowing the planet to migrate in the simulation,
we find that the planet undergoes runaway migration and reaches the inner disc
in Myr. Further, decreasing the disc mass slows down planet
migration, but it then also increases the dust's radial drift, thereby
depleting the disc dust faster. We find that the opposing constraints of planet
migration and dust drift require the disc mass to be at most 0.025~\msun,
must less massive than previously estimated, and for the dust to be porous
rather than compact. We propose that similar analysis should be extended to
other sources with suspected planetary companions.Comment: 15 pages, 9 figures, resubmitted to MNRAS, version addressing
referee's comment
Chaotic Type I Migration in Turbulent Discs
By performing global hydrodynamical simulations of accretion discs with
driven turbulence models, we demonstrate that elevated levels of turbulence
induce highly stochastic migration torques on low-mass companions embedded in
these discs. This scenario applies to planets migrating within
gravito-turbulent regions of protoplanetary discs as well as stars and black
holes embedded in the outskirts of active galactic nuclei (AGN) accretion
discs. When the turbulence level is low, linear Lindblad torques persists in
the background of stochastic forces and its accumulative effect can still
dominate over relatively long timescales. However, in the presence of very
stronger turbulence, classical flow patterns around the companion embedded in
the disc are disrupted, leading to significant deviations from the expectations
of classical Type I migration theory over arbitrarily long timescales. Our
findings suggest that the stochastic nature of turbulent migration can prevent
low-mass companions from monotonically settling into universal migration traps
within the traditional laminar disc framework, thus reducing the frequency of
three-body interactions and hierarchical mergers compared to previously
expected. We propose a scaling for the transition mass ratio from classical to
chaotic migration , where is the Reynolds
viscosity stress parameter, which can be further tested and refined by
conducting extensive simulations over the relevant parameter space.Comment: 6 pages, 7 figures, accepted by MNRAS Letters. Welcome any comments
and suggestions
Network-Based Regularization for Generalized Linear Models
Network-based regularization has achieved success in variable selection for high-dimensional biological data due to its ability to incorporate correlations among genomic features. This package provides procedures of network-based variable selection for generalized linear models (Ren et al. (2017) and Ren et al.(2019) ). Continuous, binary, and survival response are supported. Robust network-based methods are available for continuous and survival responses
Uncertainty-Aware Unlikelihood Learning Improves Generative Aspect Sentiment Quad Prediction
Recently, aspect sentiment quad prediction has received widespread attention
in the field of aspect-based sentiment analysis. Existing studies extract
quadruplets via pre-trained generative language models to paraphrase the
original sentence into a templated target sequence. However, previous works
only focus on what to generate but ignore what not to generate. We argue that
considering the negative samples also leads to potential benefits. In this
work, we propose a template-agnostic method to control the token-level
generation, which boosts original learning and reduces mistakes simultaneously.
Specifically, we introduce Monte Carlo dropout to understand the built-in
uncertainty of pre-trained language models, acquiring the noises and errors. We
further propose marginalized unlikelihood learning to suppress the
uncertainty-aware mistake tokens. Finally, we introduce minimization entropy to
balance the effects of marginalized unlikelihood learning. Extensive
experiments on four public datasets demonstrate the effectiveness of our
approach on various generation templates1
Exposure assessment of dietary cadmium: findings from shanghainese over 40 years, China
BACKGROUND: Environmental exposure to cadmium causes renal dysfunction and bone damage. Cadmium contamination in food is regarded as the main environmental source of non-occupational exposure. The aim of this study was to assess the contribution of dietary cadmium exposure in environmental cadmium exposure and its health risk among adults in Shanghai, China. METHODS: A cross-sectional survey about food consumption was conducted in 2008 among 207 citizens aged over 40 years in Shanghai, China. The food frequency questionnaire was combined with food, tobacco and water cadmium exposure to estimate the daily environmental cadmium exposure in both point and probabilistic estimations. Urine and blood samples of the participants were analyzed for internal exposure to total cadmium. Correlation analysis was conducted between the internal cadmium exposure and environmental cadmium exposure. RESULTS: According to the point estimation, average daily environmental cadmium exposure of the participants was 16.7 ÎŒg/day and approached 33.8% of the provisional tolerable daily intake (PTDI). Dietary and tobacco cadmium exposure approached 25.8% and 7.9% of the PTDI, respectively. Males had higher levels of dietary cadmium exposure than females (p?=?0.002). The probabilistic model showed that 93.4% of the population did not have any health risks from dietary cadmium exposure. By sensitivity analysis, tobacco consumption, tobacco cadmium level, cadmium in vegetables and cadmium in rice accounted for 27.5%, 24.9%, 20.2% and 14.6% of the total cadmium exposure, respectively. The mean values of urinary and blood cadmium among the study population were 0.5 ÎŒg/L and 1.9 ÎŒg/L, respectively. Positive correlations were observed between environmental cadmium exposure and blood cadmium (R?=?0.52, P<0.01), tobacco cadmium intake and blood cadmium excluding non-smokers (R?=?0.26, P?=?0.049<0.05), and urine cadmium and age (R?=?0.15, P?=?0.037). CONCLUSIONS: It has been suggested that there is no increased health risk among adult residents in Shanghai, China because of recent total cadmium exposure. Vegetables and rice were the main sources of dietary cadmium intake. Tobacco cadmium exposure, which accounted for approximately 25% of the total dietary cadmium exposure, was another important source of non-occupational cadmium exposure
Factorized Inverse Path Tracing for Efficient and Accurate Material-Lighting Estimation
Inverse path tracing has recently been applied to joint material and lighting
estimation, given geometry and multi-view HDR observations of an indoor scene.
However, it has two major limitations: path tracing is expensive to compute,
and ambiguities exist between reflection and emission. Our Factorized Inverse
Path Tracing (FIPT) addresses these challenges by using a factored light
transport formulation and finds emitters driven by rendering errors. Our
algorithm enables accurate material and lighting optimization faster than
previous work, and is more effective at resolving ambiguities. The exhaustive
experiments on synthetic scenes show that our method (1) outperforms
state-of-the-art indoor inverse rendering and relighting methods particularly
in the presence of complex illumination effects; (2) speeds up inverse path
tracing optimization to less than an hour. We further demonstrate robustness to
noisy inputs through material and lighting estimates that allow plausible
relighting in a real scene. The source code is available at:
https://github.com/lwwu2/fiptComment: Updated experiment results; modified real-world section
Identification of Prognostic Genes and Pathways in Lung Adenocarcinoma Using a Bayesian Approach
Lung cancer is the leading cause of cancer-associated mortality in the United States and the world. Adenocarcinoma, the most common subtype of lung cancer, is generally diagnosed at the late stage with poor prognosis. In the past, extensive effort has been devoted to elucidating lung cancer pathogenesis and pinpointing genes associated with survival outcomes. As the progression of lung cancer is a complex process that involves coordinated actions of functionally associated genes from cancer-related pathways, there is a growing interest in simultaneous identification of both prognostic pathways and important genes within those pathways. In this study, we analyse The Cancer Genome Atlas lung adenocarcinoma data using a Bayesian approach incorporating the pathway information as well as the interconnections among genes. The top 11 pathways have been found to play significant roles in lung adenocarcinoma prognosis, including pathways in mitogen-activated protein kinase signalling, cytokine-cytokine receptor interaction, and ubiquitin-mediated proteolysis. We have also located key gene signatures such as RELB, MAP4K1, and UBE2C. These results indicate that the Bayesian approach may facilitate discovery of important genes and pathways that are tightly associated with the survival of patients with lung adenocarcinoma