1,013 research outputs found
Nesterov Meets Optimism: Rate-Optimal Separable Minimax Optimization
We propose a new first-order optimization algorithm --
AcceleratedGradient-OptimisticGradient (AG-OG) Descent Ascent -- for separable
convex-concave minimax optimization. The main idea of our algorithm is to
carefully leverage the structure of the minimax problem, performing Nesterov
acceleration on the individual component and optimistic gradient on the
coupling component. Equipped with proper restarting, we show that AG-OG
achieves the optimal convergence rate (up to a constant) for a variety of
settings, including bilinearly coupled strongly convex-strongly concave minimax
optimization (bi-SC-SC), bilinearly coupled convex-strongly concave minimax
optimization (bi-C-SC), and bilinear games. We also extend our algorithm to the
stochastic setting and achieve the optimal convergence rate in both bi-SC-SC
and bi-C-SC settings. AG-OG is the first single-call algorithm with optimal
convergence rates in both deterministic and stochastic settings for bilinearly
coupled minimax optimization problems.Comment: 44 pages. This version matches the camera-ready that appeared at ICML
2023 under the same titl
The Huntington's disease mutation impairs Huntingtin's role in the transport of NF-κB from the synapse to the nucleus
Expansion of a polyglutamine (polyQ) tract in the Huntingtin (Htt) protein causes Huntington's disease (HD), a fatal inherited neurodegenerative disorder. Loss of the normal function of Htt is thought to be an important pathogenetic component of HD. However, the function of wild-type Htt is not well defined. Htt is thought to be a multifunctional protein that plays distinct roles in several biological processes, including synaptic transmission, intracellular transport and neuronal transcription. Here, we show with biochemical and live cell imaging studies that wild-type Htt stimulates the transport of nuclear factor κ light-chain-enhancer of activated B cells (NF-κB) out of dendritic spines (where NF-κB is activated by excitatory synaptic input) and supports a high level of active NF-κB in neuronal nuclei (where NF-κB stimulates the transcription of target genes). We show that this novel function of Htt is impaired by the polyQ expansion and thus may contribute to the etiology of HD
Holistic Processing of Words Modulated by Reading Experience
Perceptual expertise has been studied intensively with faces and object categories involving detailed individuation. A common finding is that experience in fulfilling the task demand of fine, subordinate-level discrimination between highly similar instances is associated with the development of holistic processing. This study examines whether holistic processing is also engaged by expert word recognition, which is thought to involve coarser, basic-level processing that is more part-based. We adopted a paradigm widely used for faces – the composite task, and found clear evidence of holistic processing for English words. A second experiment further showed that holistic processing for words was sensitive to the amount of experience with the language concerned (native vs. second-language readers) and with the specific stimuli (words vs. pseudowords). The adoption of a paradigm from the face perception literature to the study of expert word perception is important for further comparison between perceptual expertise with words and face-like expertise
Coherent signature of warming-induced extreme sub-continental boreal wildfire activity 4800 and 1100 years BP
Climate changes are expected to progressively increase extreme wildfire frequency in forests. Finding past analogs for periods of extreme biomass burning would provide valuable insights regarding what the effects of warming might be for tree species distribution, ecosystem integrity, atmospheric greenhouse gas balance, and human safety. Here, we used a network of 42 lake-sediment charcoal records across a ~2000 km transect in eastern boreal North America to infer widespread periods of wildfire activity in association with past climate conditions. The reconstructed fluctuations in biomass burning are broadly consistent with variations in ethane concentration in Greenland polar ice cores. Biomass burning fluctuations also significantly co-varied with Greenland temperatures estimated from ice cores, at least for the past 6000 years. Our retrospective analysis of past fire activity allowed us to identify two fire periods centered around 4800 and 1100 BP, coinciding with large-scale warming in northern latitudes and having respectively affected an estimated ~71% and ~57% of the study area. These two periods co-occurred with widespread decreases in mean fire-return intervals. The two periods are likely the best analogs for what could be anticipated in terms of impacts of fire on ecosystem services provided by these forests in coming decades
Predicting successful prosthetic rehabilitation in major lower-limb amputation patients: a 15-year retrospective cohort study
Objective: To determine and compare specific factors that could be associated and predictive
with successful prosthetic rehabilitation in major lower-limb amputations.
Methods: A 15-year long (2000-2014) retrospective observational cohort study was conducted.
Two different criteria were used to define successful prosthetic rehabilitation: (1) the ability
to walk at least 45 m, regardless of assistive devices; and (2) walking >45 m without other
ambulatory aids than one cane (if required). Age, gender, comorbidities, cause and level of
amputation, stump characteristics, ulcers in the preserved limb, and time between surgery and
physical therapy were examined as predictors of successful prosthetic rehabilitation.
Results: A total of 169 patients (61.60±15.9 years) were included. Regarding walking ability
with or without walking aids, the presence of ulcers in the preserved limb was individually
associated with failed prosthetic rehabilitation (p < 0.001), while being male (OR = 0.21;
95%CI = 0.06-0.80) and transtibial level of amputation (OR = 6.73; 95%CI = 1.92-23.64) were
identified as independent predictors of failure and success, respectively. Regarding the criterion
of successful rehabilitation, a shorter time until rehabilitation was individually associated
with improved walking ability (p < 0.013), while failure could be predicted by comorbidities
(OR = 0.48; 95%CI = 0.29---0.78) and age groups of 65---75 years old (OR = 0.19; 95%CI = 0.05-0.78)
and over 75 years old (OR = 0.19; 95%CI = 0.04-0.91).
Conclusions: Regarding walking ability with or without walking aids, male gender and transtibiallevel of amputation are independently associated with failure and success respectively, whereasolder age and comorbidities can predict failed prosthetic rehabilitation when assistive walking devices are considered. Future prospective cohort studies are needed to confirm these findings
Frontotemporal lobar degeneration and social behaviour:Dissociation between the knowledge of its consequences and its conceptual meaning
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