126 research outputs found
Relaxing the I.I.D. Assumption: Adaptively Minimax Optimal Regret via Root-Entropic Regularization
We consider sequential prediction with expert advice when data are generated
from distributions varying arbitrarily within an unknown constraint set. We
quantify relaxations of the classical i.i.d. assumption in terms of these
constraint sets, with i.i.d. sequences at one extreme and adversarial
mechanisms at the other. The Hedge algorithm, long known to be minimax optimal
in the adversarial regime, was recently shown to be minimax optimal for i.i.d.
data. We show that Hedge with deterministic learning rates is suboptimal
between these extremes, and present a new algorithm that adaptively achieves
the minimax optimal rate of regret with respect to our relaxations of the
i.i.d. assumption, and does so without knowledge of the underlying constraint
set. We analyze our algorithm using the follow-the-regularized-leader
framework, and prove it corresponds to Hedge with an adaptive learning rate
that implicitly scales as the square root of the entropy of the current
predictive distribution, rather than the entropy of the initial predictive
distribution.Comment: 71 pages, 2 figures. Blair Bilodeau and Jeffrey Negrea are
equal-contribution authors; order was determined randoml
Minimax optimal quantile and semi-adversarial regret via root-logarithmic regularizers
Quantile (and, more generally, KL) regret bounds, such as those achieved by
NormalHedge (Chaudhuri, Freund, and Hsu 2009) and its variants, relax the
goal of competing against the best individual expert to only competing against
a majority of experts on adversarial data. More recently, the semi-adversarial
paradigm (Bilodeau, Negrea, and Roy 2020) provides an alternative relaxation of
adversarial online learning by considering data that may be neither fully adversarial
nor stochastic (i.i.d.). We achieve the minimax optimal regret in both paradigms
using FTRL with separate, novel, root-logarithmic regularizers, both of which
can be interpreted as yielding variants of NormalHedge. We extend existing KL
regret upper bounds, which hold uniformly over target distributions, to possibly
uncountable expert classes with arbitrary priors; provide the first full-information
lower bounds for quantile regret on finite expert classes (which are tight); and
provide an adaptively minimax optimal algorithm for the semi-adversarial paradigm
that adapts to the true, unknown constraint faster, leading to uniformly improved
regret bounds over existing methods.https://arxiv.org/pdf/2110.14804.pdfPublished versio
Pairing and alpha-like quartet condensation in N=Z nuclei
We discuss the treatment of isovector pairing by an alpha-like quartet
condensate which conserves exactly the particle number, the spin and the
isospin. The results show that the quartet condensate describes accurately the
isovector pairing correlations in the ground state of systems with an equal
number of protons and neutronsComment: 4 pages, to appear in Journal of Physics: Conference Serie
Some Researches Concerning the Deep Drawing Process of the Rectangular Box
The deep drawing process of the rectangular boxes is difficult difficulties because of the complexity of the stress and strain states. This paper presents the results of the researches on the variation of the stamping force in function of some deformation factors and the variation of the micro-structure in the maximum deformation zone
Start spreading the news: A comparative experiment on the effects of populist communication on political engagement in sixteen European countries
A 2500-yr late holocenemulti-proxy record of vegetation and hydrologic changes from a cave guano-clay sequence in SW Romania
We provide sedimentological, geochemical, mineral magnetic, stable carbon isotope, charcoal, and pollen-based
evidence froma guano/clay sequence in Gaura cuMuscă Cave (SWRomania), fromwhichwe deduced that from
~1230 BC to ~AD 1240 climate oscillated betweenwet and dry. From ~1230 BC to AD 1000 the climate was wetter
than the present, prompting flooding of the cave, preventing bats fromroosting, and resulting in a slowrate of
clay accumulation. The second half of the MedievalWarm Period (MWP) was generally drier; the cave experienced
occasional flash flooding in between which maternity bat roosts established in the cave. One extremely
wet event occurred around AD 1170, when Fe/Mn and Ti/Zr ratios show the highest values coincident with a
substantial increase of sediment load in the underground stream. The mineral magnetic characteristics for the
second part of the MWP indicate the partial input of surface-sourced sediments reflecting agricultural development and forest clearance in the area. Pollen and microcharcoal studies confirm that the overall vegetation
cover and human land use have not changed much in this region since the medieval times
Accurate Prediction of Secreted Substrates and Identification of a Conserved Putative Secretion Signal for Type III Secretion Systems
The type III secretion system is an essential component for virulence in many Gram-negative bacteria. Though components of the secretion system apparatus are conserved, its substrates—effector proteins—are not. We have used a novel computational approach to confidently identify new secreted effectors by integrating protein sequence-based features, including evolutionary measures such as the pattern of homologs in a range of other organisms, G+C content, amino acid composition, and the N-terminal 30 residues of the protein sequence. The method was trained on known effectors from the plant pathogen Pseudomonas syringae and validated on a set of effectors from the animal pathogen Salmonella enterica serovar Typhimurium (S. Typhimurium) after eliminating effectors with detectable sequence similarity. We show that this approach can predict known secreted effectors with high specificity and sensitivity. Furthermore, by considering a large set of effectors from multiple organisms, we computationally identify a common putative secretion signal in the N-terminal 20 residues of secreted effectors. This signal can be used to discriminate 46 out of 68 total known effectors from both organisms, suggesting that it is a real, shared signal applicable to many type III secreted effectors. We use the method to make novel predictions of secreted effectors in S. Typhimurium, some of which have been experimentally validated. We also apply the method to predict secreted effectors in the genetically intractable human pathogen Chlamydia trachomatis, identifying the majority of known secreted proteins in addition to providing a number of novel predictions. This approach provides a new way to identify secreted effectors in a broad range of pathogenic bacteria for further experimental characterization and provides insight into the nature of the type III secretion signal
Impact of primary kidney disease on the effects of empagliflozin in patients with chronic kidney disease: secondary analyses of the EMPA-KIDNEY trial
Background: The EMPA KIDNEY trial showed that empagliflozin reduced the risk of the primary composite outcome of kidney disease progression or cardiovascular death in patients with chronic kidney disease mainly through slowing progression. We aimed to assess how effects of empagliflozin might differ by primary kidney disease across its broad population. Methods: EMPA-KIDNEY, a randomised, controlled, phase 3 trial, was conducted at 241 centres in eight countries (Canada, China, Germany, Italy, Japan, Malaysia, the UK, and the USA). Patients were eligible if their estimated glomerular filtration rate (eGFR) was 20 to less than 45 mL/min per 1·73 m2, or 45 to less than 90 mL/min per 1·73 m2 with a urinary albumin-to-creatinine ratio (uACR) of 200 mg/g or higher at screening. They were randomly assigned (1:1) to 10 mg oral empagliflozin once daily or matching placebo. Effects on kidney disease progression (defined as a sustained ≥40% eGFR decline from randomisation, end-stage kidney disease, a sustained eGFR below 10 mL/min per 1·73 m2, or death from kidney failure) were assessed using prespecified Cox models, and eGFR slope analyses used shared parameter models. Subgroup comparisons were performed by including relevant interaction terms in models. EMPA-KIDNEY is registered with ClinicalTrials.gov, NCT03594110. Findings: Between May 15, 2019, and April 16, 2021, 6609 participants were randomly assigned and followed up for a median of 2·0 years (IQR 1·5–2·4). Prespecified subgroupings by primary kidney disease included 2057 (31·1%) participants with diabetic kidney disease, 1669 (25·3%) with glomerular disease, 1445 (21·9%) with hypertensive or renovascular disease, and 1438 (21·8%) with other or unknown causes. Kidney disease progression occurred in 384 (11·6%) of 3304 patients in the empagliflozin group and 504 (15·2%) of 3305 patients in the placebo group (hazard ratio 0·71 [95% CI 0·62–0·81]), with no evidence that the relative effect size varied significantly by primary kidney disease (pheterogeneity=0·62). The between-group difference in chronic eGFR slopes (ie, from 2 months to final follow-up) was 1·37 mL/min per 1·73 m2 per year (95% CI 1·16–1·59), representing a 50% (42–58) reduction in the rate of chronic eGFR decline. This relative effect of empagliflozin on chronic eGFR slope was similar in analyses by different primary kidney diseases, including in explorations by type of glomerular disease and diabetes (p values for heterogeneity all >0·1). Interpretation: In a broad range of patients with chronic kidney disease at risk of progression, including a wide range of non-diabetic causes of chronic kidney disease, empagliflozin reduced risk of kidney disease progression. Relative effect sizes were broadly similar irrespective of the cause of primary kidney disease, suggesting that SGLT2 inhibitors should be part of a standard of care to minimise risk of kidney failure in chronic kidney disease. Funding: Boehringer Ingelheim, Eli Lilly, and UK Medical Research Council
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