115 research outputs found
Well-posedness for the incompressible magneto-hydrodynamic system on modulation spaces
AbstractWe study the Cauchy problem for an incompressible magneto-hydrodynamics (MHD) system in the modulation space Mq,σs(Rn) (n⩾2) with initial data (u0,b0)∈PMq,σs(Rn)×PMq,σs(Rn). We prove that this problem is locally well-posed in such a space when 1⩽q⩽∞, 1⩽σ<∞ and n(σ−1)σ−1⩽s, and globally well-posed when 1⩽q⩽n, nn−1⩽σ<∞ and max{n(σ−1)σ−1,n(σ−2)σ}<s<n(σ−1)σ
Observations of Magnetic Helicity Proxies in Solar Photosphere: Helicity with Solar Cycles
Observations of magnetic helicity transportation through the solar
photosphere reflect the interaction of turbulent plasma movements and magnetic
fields in the solar dynamo process. In this chapter, we have reviewed the
research process of magnetic helicity inferred from the observed solar magnetic
fields in the photosphere and also the solar morphological configurations with
solar cycles. After introducing some achievements in the study of magnetic
helicity, some key points would like to be summarized.
The magnetic (current) helicity in the solar surface layer presents a
statistical distribution similar to that of the sunspot butterfly diagram, but
its maximum value is delayed from the extreme value of the sunspot butterfly
diagram and corresponds in the phase with the statistical eruption of solar
flares. During the spatial transport of magnetic (current) helicity from the
interior of the sun into the interplanetary space at the time-space scale of
the solar cycle, it shows the statistical distribution and the fluctuation with
the hemispheric sign rule. These show that the current helicity and magnetic
helicity transport calculation methods are complementary to each other.
We also notice that the study of the inherent relationship between magnetic
helicity and the solar cycle still depends on the observed accuracy of the
solar magnetic field.Comment: 48 page,17 figure
BotMoE: Twitter Bot Detection with Community-Aware Mixtures of Modal-Specific Experts
Twitter bot detection has become a crucial task in efforts to combat online
misinformation, mitigate election interference, and curb malicious propaganda.
However, advanced Twitter bots often attempt to mimic the characteristics of
genuine users through feature manipulation and disguise themselves to fit in
diverse user communities, posing challenges for existing Twitter bot detection
models. To this end, we propose BotMoE, a Twitter bot detection framework that
jointly utilizes multiple user information modalities (metadata, textual
content, network structure) to improve the detection of deceptive bots.
Furthermore, BotMoE incorporates a community-aware Mixture-of-Experts (MoE)
layer to improve domain generalization and adapt to different Twitter
communities. Specifically, BotMoE constructs modal-specific encoders for
metadata features, textual content, and graphical structure, which jointly
model Twitter users from three modal-specific perspectives. We then employ a
community-aware MoE layer to automatically assign users to different
communities and leverage the corresponding expert networks. Finally, user
representations from metadata, text, and graph perspectives are fused with an
expert fusion layer, combining all three modalities while measuring the
consistency of user information. Extensive experiments demonstrate that BotMoE
significantly advances the state-of-the-art on three Twitter bot detection
benchmarks. Studies also confirm that BotMoE captures advanced and evasive
bots, alleviates the reliance on training data, and better generalizes to new
and previously unseen user communities.Comment: Accepted at SIGIR 202
Disease burden in patients with acute hepatic porphyria: experience from the phase 3 ENVISION study
Background: Acute hepatic porphyria (AHP) is a family of four rare genetic diseases, each involving deficiency in
a hepatic heme biosynthetic enzyme. Resultant overproduction of the neurotoxic intermediates δ-aminolevulinic
acid (ALA) and porphobilinogen (PBG) leads to disabling acute neurovisceral attacks and progressive neuropathy.
We evaluated the AHP disease burden in patients aged ≥ 12 years in a post hoc analysis of the Phase 3, randomized,
double-blind, placebo-controlled ENVISION trial of givosiran (NCT03338816), an RNA interference (RNAi) therapeutic
that targets the enzyme ALAS1 to decrease ALA and PBG production. We analyzed baseline AHP severity via chronic
symptoms between attacks, comorbidities, concomitant medications, hemin-associated complications, and quality
of life (QOL) and evaluated givosiran (2.5 mg/kg monthly) in patients with and without prior hemin prophylaxis on
number and severity of attacks and pain scores during and between attacks.
Results: Participants (placebo, n = 46; givosiran, n = 48) included patients with low and high annualized attack rates
(AARs; range 0–46). At baseline, patients reported chronic symptoms (52%), including nausea, fatigue, and pain;
comorbidities, including neuropathy (38%) and psychiatric disorders (47%); concomitant medications, including
chronic opioids (29%); hemin-associated complications (eg, iron overload); and poor QOL (low SF-12 and EuroQol
visual analog scale scores). A linear relationship between time since diagnosis and AAR with placebo suggested worsening
of disease over time without effective treatment. Givosiran reduced the number and severity of attacks, days
with worst pain scores above baseline, and opioid use versus placebo.
Conclusions: Patients with AHP, regardless of annualized attack rates, have considerable disease burden that may partly be alleviated with givosiran
A Multi-mode Waveguide Tunnel Channel Model for High-Speed Train Wireless Communication Systems
The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.The recent development of high-speed trains (HSTs) introduces new challenges to wireless communication systems for HSTs. For demonstrating the feasibility of these systems, accurate channel models which can mimic key characteristics of HST wireless channels are essential. In this paper, we focus on HST channel models for the tunnel scenario, which is different from other HST channel environments, such as rural area and
viaducts. Considering unique characteristics of tunnel channel environments, we extend the existing multi-mode waveguide tunnel channel model to be time dependent, obtain the channel impulse responses and then further investigate the certain key tunnel
channel characteristics such as temporal autocorrelation function (ACF) and power spectrum density (PSD). The impact of time on ACFs and PSDs, and the impact of frequency on the received power are revealed via numerical results
Association between total cholesterol and all-cause mortality in oldest old: a national longitudinal study
BackgroundA common sense is that lower serum cholesterol levels are better. However, a growing number of researches have questioned this especially for the oldest old. The current study was to assess the association between total cholesterol and all-cause mortality in a group of people aged 85 years old and over.MethodsWe selected 903 Chinese old participants who aged ≥85 years from the Chinese Longitudinal Healthy Longevity Survey(CLHLS) at baseline in 2012. The participants were followed up until death or until December 31, 2014. The outcome was all-cause mortality. The univariate and multivariate Cox regression analyses were used to estimate risk levels of all-cause mortality. We stratified the participants into three groups (<3.40, 3.40–4.39, ≥4.39 mmol/L) based on the restricted cubic splines methods. The survival probability according to total cholesterol category was calculated using the Kaplan-Meier curves, and the log-rank test was performed to analyze differences between the groups.ResultsDuring the follow-up of three years, 282 participants died, 497 survived and 124 lost to follow-up. There was significant relationship between the total cholesterol and lower risk of all-cause mortality in the multivariable Cox regression analysis (HR=0.88, 95% CI: 0.78–1.00). Based on the restricted cubic splines methods, the total cholesterol was converted from a continuous variable to a categorical variable. The populations were divided into three groups (<3.40, 3.40–4.39, ≥4.39 mmol/L) according to the total cholesterol categorized by cutoff values. Compared to the total cholesterol level of <3.40 mmol/L, populations in the total cholesterol level of 3.40–4.39 mmol/L (HR = 0.72, 95% CI: 0.53–0.97) and ≥4.39 mmol/L (HR = 0.71, 95% CI: 0.52–0.96) groups had lower all-cause mortality in multivariate Cox regression analysis and higher survival probability in survival analysis. When two groups were divided, similar results were found among the populations in the total cholesterol level of ≥3.40 mmol/L compared to the populations in the total cholesterol level of <3.40 mmol/L groups.ConclusionIn oldest old aged 85 and older, serum total cholesterol levels are inversely associated with all-cause mortality. This study suggested that total cholesterol should be maintained to acceptable levels (≥ 3.40 mmol/L) in oldest old to achieve longevity
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