1,025 research outputs found
Improving Convergence and Generalization Using Parameter Symmetries
In overparametrized models, different values of the parameters may result in
the same loss value. Parameter space symmetries are transformations that change
the model parameters but leave the loss invariant. Teleportation applies such
transformations to accelerate optimization. However, the exact mechanism behind
this algorithm's success is not well understood. In this paper, we show that
teleportation not only speeds up optimization in the short-term, but gives
overall faster time to convergence. Additionally, we show that teleporting to
minima with different curvatures improves generalization and provide insights
on the connection between the curvature of the minima and generalization
ability. Finally, we show that integrating teleportation into a wide range of
optimization algorithms and optimization-based meta-learning improves
convergence.Comment: 29 pages, 13 figure
DYffusion: A Dynamics-informed Diffusion Model for Spatiotemporal Forecasting
While diffusion models can successfully generate data and make predictions,
they are predominantly designed for static images. We propose an approach for
training diffusion models for dynamics forecasting that leverages the temporal
dynamics encoded in the data, directly coupling it with the diffusion steps in
the network. We train a stochastic, time-conditioned interpolator and a
backbone forecaster network that mimic the forward and reverse processes of
conventional diffusion models, respectively. This design choice naturally
encodes multi-step and long-range forecasting capabilities, allowing for highly
flexible, continuous-time sampling trajectories and the ability to trade-off
performance with accelerated sampling at inference time. In addition, the
dynamics-informed diffusion process imposes a strong inductive bias, allowing
for improved computational efficiency compared to traditional Gaussian
noise-based diffusion models. Our approach performs competitively on
probabilistic skill score metrics in complex dynamics forecasting of sea
surface temperatures, Navier-Stokes flows, and spring mesh systems.Comment: Code will be released at: https://github.com/Rose-STL-Lab/dyffusio
Spatial Domain Management and Massive MIMO Coordination in 5G SDN
In 5G mobile communication systems, massive multiple-input multiple-output (MIMO) and heterogeneous networks (HetNets) play crucial roles to achieve expected coverage and capacity across venues. This paper correspondingly addresses software-defined network (SDN) as the central controller of radio resource management in massive MIMO HetNets. In particular, we identify the huge spatial domain information management and complicated MIMO coordination as the grand challenges in 5G systems. Our work accordingly distinguishes itself by considering more network MIMO aspects, including flexibility and complexity of spatial coordination. In our proposed scheme, SDN controller first collects the user channel state information in an effective way, and then calculates the null-space of victim users and applies linear precoding to that null-space. Simulation results show that our design is highly beneficial and easy to be deployed, due to its high quality of service performance but low computation complexity
First Digit Distribution of Hadron Full Width
A phenomenological law, called Benford's law, states that the occurrence of
the first digit, i.e., , of numbers from many real world sources is
not uniformly distributed, but instead favors smaller ones according to a
logarithmic distribution. We investigate, for the first time, the first digit
distribution of the full widths of mesons and baryons in the well defined
science domain of particle physics systematically, and find that they agree
excellently with the Benford distribution. We also discuss several general
properties of Benford's law, i.e., the law is scale-invariant, base-invariant,
and power-invariant. This means that the lifetimes of hadrons follow also
Benford's law.Comment: 8 latex pages, 4 figures, final version in journal publicatio
Halpha-Derived Star-Formation Rates For Three z ~ 0.75 EDisCS Galaxy Clusters
We present Halpha-derived star-formation rates (SFRs) for three z ~ 0.75
galaxy clusters. Our 1 sigma flux limit corresponds to a star-formation rate of
0.10-0.24 solar mass per year, and our minimum reliable Halpha + [N II]
rest-frame equivalent width is 10\AA. We show that Halpha narrowband imaging is
an efficient method for measuring star formation in distant clusters. In two
out of three clusters, we find that the fraction of star-forming galaxies
increases with projected distance from the cluster center. We also find that
the fraction of star-forming galaxies decreases with increasing local galaxy
surface density in the same two clusters. We compare the median rate of star
formation among star-forming cluster galaxies to a small sample of star-forming
field galaxies from the literature and find that the median cluster SFRs are
\~50% less than the median field SFR. We characterize cluster evolution in
terms of the mass-normalized integrated cluster SFR and find that the z ~ 0.75
clusters have more SFR per cluster mass on average than the z <= 0.4 clusters
from the literature. The interpretation of this result is complicated by the
dependence of the mass-normalized SFR on cluster mass and the lack of
sufficient overlap in the mass ranges covered by the low and high redshift
samples. We find that the fraction and luminosities of the brightest starburst
galaxies at z ~ 0.75 are consistent with their being progenitors of the
post-starburst galaxies at z ~ 0.45 if the post-starburst phase lasts several
(~5) times longer than the starburst phase.Comment: Accepted for publication in ApJ, 20 pages, 24 figure
Use of electronic patient data overview with alerts in primary care increases prescribing of lipid-lowering medications in patients with type 2 diabetes
AIMS/HYPOTHESIS: We aimed to assess whether general practices (GPs) using an electronic disease management program (DMP) with population overviews, including alerts when patients failed to receive guideline-recommended prescription medications, increased prescriptions of lipid-lowering drugs for patients with type 2 diabetes with no history of lipid-lowering treatment. METHODS: This observational study included 165 GPs that reached a high level of use of the DMP in 2012 and a control group of 135 GPs who reached a high level of use in 2013 and, hence, who were less exposed to the DMP throughout 2012. A binary measure for having been prescribed and filled lipid-lowering drugs at any time within a 12-month exposure period was derived for all patients with type 2 diabetes who did not receive a prescription for lipid-lowering drugs in the baseline year prior to the study period (i.e. 2011). Results were derived using ORs from multivariate logistic regression analyses. Subgroup stratification based on age, sex, diabetes duration, deprivation status and Charlson Comorbidity Index (CCI) score was conducted and assessed. Placebo tests were carried out to assess bias from selection to treatment. RESULTS: Patients who did not receive a prescription of lipid-lowering drugs in the year prior to being listed with GPs that used the DMP had statistically significant greater odds of receiving a prescription of lipid-lowering medications when compared with individuals who attended control GPs (OR 1.23 [95% CI 1.09, 1.38]). When the analysis period was shifted back by 2 years, no significant differences in lipid-lowering drug prescription between the two groups were found to occur, which indicates that these results were not driven by selection bias. Subgroup analyses showed that the increase in lipid-lowering drug prescriptions was primarily driven by changes among male participants (OR 1.32 [95% CI 1.12, 1.54]), patients aged 60â70 years (OR 1.40 [95% CI 1.13, 1.74]), patients with a diabetes duration of â€5 years (OR 1.33 [95% CI 1.13, 1.56]), non-deprived patients (OR 1.25 [95% CI 1.08, 1.45]) and patients without comorbidities (CCI scoreâ=â0; OR 1.27 [95% CI 1.11, 1.45]). CONCLUSIONS/INTERPRETATION: Access to population overviews using a DMP with alerts of clinical performance measures with regard to adhering to guideline-recommended prescription of medications can increase GP prescriptions of lipid-lowering drugs. GRAPHICAL ABSTRACT: [Image: see text] SUPPLEMENTARY INFORMATION: The online version contains peer-reviewed but unedited supplementary material available at 10.1007/s00125-021-05598-x
The relation between star formation, morphology and local density in high redshift clusters and groups
We investigate how the [OII] properties and the morphologies of galaxies in
clusters and groups at z=0.4-0.8 depend on projected local galaxy density, and
compare with the field at similar redshifts and clusters at low-z. In both
nearby and distant clusters, higher-density regions contain proportionally
fewer star-forming galaxies, and the average [OII] equivalent width of
star-forming galaxies is independent of local density. However, in distant
clusters the average current star formation rate (SFR) in star-forming galaxies
seems to peak at densities ~15-40 galaxies Mpc^{-2}. At odds with low-z
results, at high-z the relation between star-forming fraction and local density
varies from high- to low-mass clusters. Overall, our results suggest that at
high-z the current star formation (SF) activity in star-forming galaxies does
not depend strongly on global or local environment, though the possible SFR
peak seems at odds with this conclusion. We find that the cluster SFR
normalized by cluster mass anticorrelates with mass and correlates with the
star-forming fraction. These trends can be understood given a) that the average
star-forming galaxy forms about 1 Msun/yr in all clusters; b) that the total
number of galaxies scales with cluster mass and c) the dependence of
star-forming fraction on cluster mass. We present the morphology-density (MD)
relation for our z=0.4-0.8 clusters, and uncover that the decline of the spiral
fraction with density is entirely driven by galaxies of types Sc or later. For
galaxies of a given Hubble type, we see no evidence that SF properties depend
on local environment. In contrast with recent findings at low-z, in our distant
clusters the SF-density relation and the MD-relation are equivalent, suggesting
that neither of the two is more fundamental than the other.(abr.)Comment: 21 pages, 14 figures, accepted for publication in Ap
The Significant Digit Law in Statistical Physics
The occurrence of the nonzero leftmost digit, i.e., 1, 2, ..., 9, of numbers
from many real world sources is not uniformly distributed as one might naively
expect, but instead, the nature favors smaller ones according to a logarithmic
distribution, named Benford's law. We investigate three kinds of widely used
physical statistics, i.e., the Boltzmann-Gibbs (BG) distribution, the
Fermi-Dirac (FD) distribution, and the Bose-Einstein (BE) distribution, and
find that the BG and FD distributions both fluctuate slightly in a periodic
manner around the Benford distribution with respect to the temperature of the
system, while the BE distribution conforms to it exactly whatever the
temperature is. Thus the Benford's law seems to present a general pattern for
physical statistics and might be even more fundamental and profound in nature.
Furthermore, various elegant properties of Benford's law, especially the
mantissa distribution of data sets, are discussed.Comment: 21 latex pages, 5 figures, final version in journal publicatio
The association between selected mid-trimester amniotic fluid candidate proteins and spontaneous preterm delivery
Objective: The aim of this study was to explore inflammatory response and identify early potential biomarkers in mid-trimester amniotic fluid associated with subsequent spontaneous preterm delivery (PTD). Methods: A cohort study was performed at Sahlgrenska University Hospital/
6stra, Gothenburg, Sweden, between 2008 and 2010. Amniotic fluid was collected from consecutive women undergoing mid-trimester transabdominal genetic amniocentesis at 14â19 gestational weeks. Clinical data and delivery outcome variables were obtained from medical records. The analysis included 19 women with spontaneous PTD and 118 women who delivered at term. A panel of 26 candidate proteins was analyzed using Luminex xMAP technology. Candidate protein concentrations were analyzed with ANCOVA and adjusted for plate effects. Results: The median gestational age at delivery was 35 + 3 weeks in women with spontaneous PTD and 40 + 0 weeks in women who delivered at term. Nominally significantly lower amniotic fluid levels of adiponectin (PTD: median 130,695 pg/mL (IQR 71,852â199,414) vs term: median 185,329 pg/mL (IQR (135,815â290,532)), granulocyte-macrophage colony stimulating factor (PTD: median 137 pg/mL (IQR 74â156) vs term: median 176 pg/mL (IQR 111â262)), and macrophage migration inhibitory factor (PTD: median 3025 pg/mL (IQR 1885â3891) vs term: median 3400 pg/mL (IQR 2181â5231)) were observed in the spontaneous PTD group, compared with the term delivery group, after adjusting for plate effects. No significant differences remained after Bonferroni correction for multiple comparisons. Conclusions: Our results are important in the process of determining the etiology behind spontaneous PTD but due to the non-significance after Bonferroni correction, the results should be interpreted with caution. Further analyses of larger sample size will be required to determine whether these results are cogent and to examine whether microbial invasion of the amniotic cavity or intra-amniotic inflammation occurs in asymptomatic women in the mid-trimester with subsequent spontaneous PTD
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