76 research outputs found
EMO: Episodic Memory Optimization for Few-Shot Meta-Learning
Few-shot meta-learning presents a challenge for gradient descent optimization
due to the limited number of training samples per task. To address this issue,
we propose an episodic memory optimization for meta-learning, we call
\emph{EMO}, which is inspired by the human ability to recall past learning
experiences from the brain's memory. EMO retains the gradient history of past
experienced tasks in external memory, enabling few-shot learning in a
memory-augmented way. By learning to retain and recall the learning process of
past training tasks, EMO nudges parameter updates in the right direction, even
when the gradients provided by a limited number of examples are uninformative.
We prove theoretically that our algorithm converges for smooth, strongly convex
objectives. EMO is generic, flexible, and model-agnostic, making it a simple
plug-and-play optimizer that can be seamlessly embedded into existing
optimization-based few-shot meta-learning approaches. Empirical results show
that EMO scales well with most few-shot classification benchmarks and improves
the performance of optimization-based meta-learning methods, resulting in
accelerated convergence.Comment: Accepted by CoLLAs 202
Multi-Label Meta Weighting for Long-Tailed Dynamic Scene Graph Generation
This paper investigates the problem of scene graph generation in videos with
the aim of capturing semantic relations between subjects and objects in the
form of subject, predicate, object triplets. Recognizing the
predicate between subject and object pairs is imbalanced and multi-label in
nature, ranging from ubiquitous interactions such as spatial relationships (\eg
\emph{in front of}) to rare interactions such as \emph{twisting}. In
widely-used benchmarks such as Action Genome and VidOR, the imbalance ratio
between the most and least frequent predicates reaches 3,218 and 3,408,
respectively, surpassing even benchmarks specifically designed for long-tailed
recognition. Due to the long-tailed distributions and label co-occurrences,
recent state-of-the-art methods predominantly focus on the most frequently
occurring predicate classes, ignoring those in the long tail. In this paper, we
analyze the limitations of current approaches for scene graph generation in
videos and identify a one-to-one correspondence between predicate frequency and
recall performance. To make the step towards unbiased scene graph generation in
videos, we introduce a multi-label meta-learning framework to deal with the
biased predicate distribution. Our meta-learning framework learns a meta-weight
network for each training sample over all possible label losses. We evaluate
our approach on the Action Genome and VidOR benchmarks by building upon two
current state-of-the-art methods for each benchmark. The experiments
demonstrate that the multi-label meta-weight network improves the performance
for predicates in the long tail without compromising performance for head
classes, resulting in better overall performance and favorable
generalizability. Code: \url{https://github.com/shanshuo/ML-MWN}.Comment: ICMR 202
Learning to Learn Variational Semantic Memory
In this paper, we introduce variational semantic memory into meta-learning to
acquire long-term knowledge for few-shot learning. The variational semantic
memory accrues and stores semantic information for the probabilistic inference
of class prototypes in a hierarchical Bayesian framework. The semantic memory
is grown from scratch and gradually consolidated by absorbing information from
tasks it experiences. By doing so, it is able to accumulate long-term, general
knowledge that enables it to learn new concepts of objects. We formulate memory
recall as the variational inference of a latent memory variable from addressed
contents, which offers a principled way to adapt the knowledge to individual
tasks. Our variational semantic memory, as a new long-term memory module,
confers principled recall and update mechanisms that enable semantic
information to be efficiently accrued and adapted for few-shot learning.
Experiments demonstrate that the probabilistic modelling of prototypes achieves
a more informative representation of object classes compared to deterministic
vectors. The consistent new state-of-the-art performance on four benchmarks
shows the benefit of variational semantic memory in boosting few-shot
recognition.Comment: accepted to NeurIPS 2020; code is available in
https://github.com/YDU-uva/VS
Learning to Learn Kernels with Variational Random Features
In this work, we introduce kernels with random Fourier features in the
meta-learning framework to leverage their strong few-shot learning ability. We
propose meta variational random features (MetaVRF) to learn adaptive kernels
for the base-learner, which is developed in a latent variable model by treating
the random feature basis as the latent variable. We formulate the optimization
of MetaVRF as a variational inference problem by deriving an evidence lower
bound under the meta-learning framework. To incorporate shared knowledge from
related tasks, we propose a context inference of the posterior, which is
established by an LSTM architecture. The LSTM-based inference network can
effectively integrate the context information of previous tasks with
task-specific information, generating informative and adaptive features. The
learned MetaVRF can produce kernels of high representational power with a
relatively low spectral sampling rate and also enables fast adaptation to new
tasks. Experimental results on a variety of few-shot regression and
classification tasks demonstrate that MetaVRF delivers much better, or at least
competitive, performance compared to existing meta-learning alternatives.Comment: ICML'2020; code is available in:
https://github.com/Yingjun-Du/MetaVR
Wildfires enhance phytoplankton production in tropical oceans
Unidad de excelencia María de Maeztu CEX2019-000940-MWildfire magnitude and frequency have greatly escalated on a global scale. Wildfire products rich in biogenic elements can enter the ocean through atmospheric and river inputs, but their contribution to marine phytoplankton production is poorly understood. Here, using geochemical paleo-reconstructions, a century-long relationship between wildfire magnitude and marine phytoplankton production is established in a fire-prone region of Kimberley coast, Australia. A positive correlation is identified between wildfire and phytoplankton production on a decadal scale. The importance of wildfire on marine phytoplankton production is statistically higher than that of tropical cyclones and rainfall, when strong El Niño Southern Oscillation coincides with the positive phase of Indian Ocean Dipole. Interdecadal chlorophyll-a variation along the Kimberley coast validates the spatial connection of this phenomenon. Findings from this study suggest that the role of additional nutrients from wildfires has to be considered when projecting impacts of global warming on marine phytoplankton production
Multiple-relaxation-time lattice Boltzmann model for compressible fluids
We present an energy-conserving multiple-relaxation-time finite difference
lattice Boltzmann model for compressible flows. This model is based on a
16-discrete-velocity model. The collision step is first calculated in the
moment space and then mapped back to the velocity space. The moment space and
corresponding transformation matrix are constructed according to the group
representation theory. Equilibria of the nonconserved moments are chosen
according to the need of recovering compressible Navier-Stokes equations
through the Chapman-Enskog expansion. Numerical experiments showed that
compressible flows with strong shocks can be well simulated by the present
model. The used benchmark tests include (i) shock tubes, such as the Sod, Lax,
Sjogreen, Colella explosion wave and collision of two strong shocks, (ii)
regular and Mach shock reflections, and (iii) shock wave reaction on
cylindrical bubble problems. The new model works for both low and high speeds
compressible flows. It contains more physical information and has better
numerical stability and accuracy than its single-relaxation-time version.Comment: 11 figures, Revte
Wildfires enhance phytoplankton production in tropical oceans
Wildfire magnitude and frequency have greatly escalated on a global scale. Wildfire products rich in biogenic elements can enter the ocean through atmospheric and river inputs, but their contribution to marine phytoplankton production is poorly understood. Here, using geochemical paleo-reconstructions, a century-long relationship between wildfire magnitude and marine phytoplankton production is established in a fire-prone region of Kimberley coast, Australia. A positive correlation is identified between wildfire and phytoplankton production on a decadal scale. The importance of wildfire on marine phytoplankton production is statistically higher than that of tropical cyclones and rainfall, when strong El Niño Southern Oscillation coincides with the positive phase of Indian Ocean Dipole. Interdecadal chlorophyll-a variation along the Kimberley coast validates the spatial connection of this phenomenon. Findings from this study suggest that the role of additional nutrients from wildfires has to be considered when projecting impacts of global warming on marine phytoplankton production
SNX14 deficiency-induced defective axonal mitochondrial transport in Purkinje cells underlies cerebellar ataxia and can be reversed by valproate
共济失调是一类以运动协调性紊乱为主要特征的神经系统症状,临床表现包括步态不稳、丧失平衡、吞咽困难、眼球运动异常、肌张力受损等。厦门大学医学院神经科学研究所王鑫教授团队首次从轴突线粒体运输这一全新视角揭示了一类遗传性共济失调的发病机制,并发现抗癫痫药--丙戊酸大幅度减缓模型小鼠的疾病进程,具有较强的转化应用价值,有望为共济失调提供新的治疗手段。
该研究工作由王鑫教授指导完成,厦门大学医学院助理教授张洪峰和博士生洪育娟共同完成主要实验工作。Loss-of-function mutations in SNX14 cause autosomal recessive spinocerebellar ataxia 20, which is a form of early-onset cerebellar ataxia that lacks molecular mechanisms and mouse models. We generated Snx14-deficient mouse models and observed severe motor deficits and cell-autonomous Purkinje cell degeneration. SNX14 deficiency disrupted microtubule organization and mitochondrial transport in axons by destabilizing the microtubule-severing enzyme spastin, which is implicated in dominant hereditary spastic paraplegia with cerebellar ataxia, and compromised axonal integrity and mitochondrial function. Axonal transport disruption and mitochondrial dysfunction further led to degeneration of high-energy-demanding Purkinje cells, which resulted in the pathogenesis of cerebellar ataxia. The antiepileptic drug valproate ameliorated motor deficits and cerebellar degeneration in Snx14-deficient mice via the restoration of mitochondrial transport and function in Purkinje cells. Our study revealed an unprecedented role for SNX14-dependent axonal transport in cerebellar ataxia, demonstrated the convergence of SNX14 and spastin in mitochondrial dysfunction, and suggests valproate as a potential therapeutic agent.We thank Tim Huang for helpful discussion, Wei Mo for sharing mouse lines, Li Zhong
for sharing reagents, Aidong Han, Luming Yao, Caiming Wu, Mingxia Zhu, Qingfeng
Liu, Lin Zhu, Shuo Zhang, Haiping Zheng, and Changchuan Xie for technical
assistance, and Cui Li for providing bioinformatics software. We also thank Novogene
Co., Ltd. and PTM Biolab Co., Ltd. for technical assistance in the transcriptomic and
proteomic analyses, respectively.
厦门大学医学院许华曦、赵颖俊、张云武、杜丹教授在研究过程中给予大力帮助和支持。本研究工作得到国家重点研发计划项目、国家自然科学基金、福建省自然科学基金、厦门大学校长基金的资助和支持
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